WO2018078858A1 - Wireless base station, wireless terminal, wireless communication system, and wireless communication method - Google Patents

Abstract

A connection base station (110) makes it possible to set the length of an intermittent time interval during which a wireless terminal does not have to receive a signal from the connection base station, for each time inerval. The terminal (130) receives a signal from the connection base station (110) during an interval different from a time interval and receives a signal from a peripheral base station (120) during the time interval. Each time the peripheral base station (120) transmits an identical signal by use of a plurality of transmission antennas, the peripheral base station (120) can change at least one of the phase difference between the plurality of transmission antennas and the phase difference between the transmission streams of the identical signal.

Description

Wireless base station, wireless terminal, wireless communication system, and wireless communication method

The present invention relates to a wireless base station, a wireless terminal, a wireless communication system, and a wireless communication method that perform wireless communication.

Conventionally, in 3GPP, specifications of mobile communication systems such as the third generation mobile communication system (3G), LTE corresponding to the 3.9th generation mobile communication system, LTE-Advanced corresponding to the fourth generation mobile communication system have been studied. ing. 3GPP is an abbreviation for 3rd Generation Partnership Project. LTE is an abbreviation for Long Term Evolution. In addition, studies on technologies relating to the fifth generation mobile communication system (5G) have also started. In addition, a technique is known in which a base station apparatus changes a beam forming weight for a synchronization signal at a predetermined time interval (see, for example, Patent Document 1 below).

Japanese Patent Laying-Open No. 2015-041817

However, in the above-described conventional technique, for example, when a synchronization signal from a base station is transmitted by beam sweeping, it is required to efficiently detect the synchronization signal.

In one aspect, an object of the present invention is to provide a radio base station, a radio terminal, a radio communication system, and a radio communication method that can efficiently detect a synchronization signal transmitted by beam sweeping.

In order to solve the above-described problems and achieve the object, in one embodiment, the first radio base station sets the length of the intermittent time interval in which the radio terminal may not receive a signal from the own station. It is possible to set for each time interval, and the radio terminal receives a signal from the first radio base station in a different interval from the time interval, and is different from the first radio base station in the time interval. 2 radio base stations, each time the same signal is transmitted from the own station using a plurality of transmission antennas, the phase difference between the plurality of transmission antennas and the phase difference between the transmission streams of the same signal A radio base station, a radio terminal, a radio communication system, and a radio communication method that receive a signal from a second radio base station that can change at least one of them are proposed.

According to one aspect of the present invention, it is possible to efficiently detect a synchronization signal transmitted by beam sweeping.

FIG. 1 is a diagram illustrating an example of a communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of transmission of a synchronization signal by beam sweeping by a peripheral base station of a connection base station according to the embodiment. FIG. 3 is a diagram illustrating an example of the transmission timing of the synchronization signal by the peripheral base station of the connected base station according to the embodiment. FIG. 4 is a diagram illustrating an example of a configuration of a gap period according to the embodiment. FIG. 5 is a diagram illustrating an example of setting a measurement gap for each gap period by the connecting base station according to the embodiment. FIG. 6 is a diagram illustrating an example of an arrangement of measurement gaps within a gap period by a connecting base station according to the embodiment. FIG. 7 is a diagram illustrating another example of setting a measurement gap for each gap period by the connecting base station according to the embodiment. FIG. 8 is a sequence diagram illustrating an example of measurement gap parameter notification from the connected base station to the terminal according to the embodiment. FIG. 9 is a diagram illustrating an example of improvement in the maximum detection time versus loss rate by the connected base station according to the embodiment. FIG. 10 is a diagram of an example of the connection base station according to the embodiment. FIG. 11 is a diagram illustrating an example of a hardware configuration of a connection base station according to the embodiment. FIG. 12 is a diagram illustrating an example of a terminal according to the embodiment. FIG. 13 is a diagram illustrating an example of a hardware configuration of the terminal according to the embodiment. FIG. 14 is a flowchart illustrating an example of gap determination processing by the measurement gap control unit of the connected base station according to the embodiment. FIG. 15 is a flowchart illustrating an example of gap determination processing by the measurement gap control unit of the terminal according to the embodiment. FIG. 16 is a sequence diagram illustrating an example of processing in the wireless communication system according to the embodiment.

Hereinafter, embodiments of a radio base station, a radio terminal, a radio communication system, and a radio communication method according to the present invention will be described in detail with reference to the drawings.

(Embodiment)
(Communication system according to embodiment)
FIG. 1 is a diagram illustrating an example of a communication system according to an embodiment. As illustrated in FIG. 1, a wireless communication system 100 according to an embodiment includes a connection base station 110, a peripheral base station 120, and a terminal 130. The connection base station 110 is a radio base station to which the terminal 130 is connected. The terminal 130 is a wireless terminal that is connected to the cell of the connected base station 110 and performs wireless communication with the connected base station 110.

The peripheral base station 120 is a radio base station around the connection base station 110, for example, a radio base station that can be a handover destination of the terminal 130 connected to the connection base station 110. The connected base station 110 and the peripheral base station 120 are connected to each other by an inter-base station interface such as an X2 interface, and can transmit and receive information to and from each other.

In the wireless communication system 100, a TDD (Time Division Duplex) method in which amplifier link communication and downlink communication are performed in a time division manner is used. In the example illustrated in FIG. 1, the connecting base station 110 transmits a synchronization signal and a downlink signal (DL signal for the terminal) to the terminal (for example, the terminal 130) at the frequency # 1. The terminal 130 transmits an uplink signal (UL signal) to the connected base station 110 at the frequency # 1.

Peripheral base station 120 transmits a periodic synchronization signal at frequency # 2 different from frequency # 1. Also, the peripheral base station 120 transmits the synchronization signal by beam sweeping that transmits a signal while switching the beam angle. The beam 121 shown in FIG. 1 is a sync signal beam when the beam angle is angle # 1. The beam 122 shown in FIG. 1 is a sync signal beam when the beam angle is #x different from the angle # 1.

Terminal 130 detects the synchronization signal from neighboring base station 120 and measures the power of the detected synchronization signal. Then, the terminal 130 reports the measurement result of the synchronization signal power to the connecting base station 110 using an uplink signal. The connecting base station 110 sets a measurement gap for the terminal 130 so that the terminal 130 wirelessly measures the synchronization signal from the neighboring base station 120. In the measurement gap section, the connecting base station 110 does not transmit a downlink signal to the terminal 130. The terminal 130 detects the synchronization signal from the neighboring base station 120 in the measurement gap set by the connecting base station 110.

However, even if the measurement gap is set at the timing when the peripheral base station 120 transmits the synchronization signal, the synchronization signal beam is not always directed to the terminal 130 at that timing, so the terminal 130 can detect the synchronization signal. Not necessarily. For example, in the connecting base station 110 and the terminal 130, the synchronization signal from the neighboring base station 120 to be detected is known only in the transmission period, and the timing and beam angle are unknown.

On the other hand, the connecting base station 110 sets the measurement gap of the terminal 130 so that the synchronization signal transmitted from the neighboring base station 120 by beam sweeping can be detected efficiently.

(Transmission of synchronization signal by beam sweeping by peripheral base stations of connected base station according to embodiment)
FIG. 2 is a diagram illustrating an example of transmission of a synchronization signal by beam sweeping by a peripheral base station of a connection base station according to the embodiment. The peripheral base station 120 located in the vicinity of the connection base station 110 according to the embodiment transmits a synchronization signal by, for example, beam sweeping illustrated in FIG. In the example illustrated in FIG. 2, the neighboring base station 120 divides the cell 200 of the neighboring base station 120 into 16 beam angles, and wirelessly transmits a synchronization signal while sequentially switching the 16 divided angles # 1 to # 16. Beam sweeping (switching of the beam angle) can be realized, for example, by changing at least one of a phase difference between a plurality of transmission antennas of the neighboring base station 120 and a phase difference between transmission streams.

(Transmission timing of synchronization signal by peripheral base station of connected base station according to embodiment)
FIG. 3 is a diagram illustrating an example of the transmission timing of the synchronization signal by the peripheral base station of the connected base station according to the embodiment. In FIG. 3, the horizontal direction indicates time. The radio frame 300 is a radio frame for radio communication in the radio communication system 100. The length of the radio frame 300 is 10 [ms] as an example. Subframes # 0 to # 9 are 10 subframes included in radio frame 300. The length of each of the subframes # 0 to # 9 is 1 [ms] as an example.

PSS 311 and SSS 312 are synchronization signals wirelessly transmitted by neighboring base station 120 in subframe # 0. PSS is an abbreviation for Primary Synchronization Signal (primary synchronization signal). SSS is an abbreviation for Secondary Synchronization Signal (secondary synchronization signal).

PSS 321 and SSS 322 are synchronization signals that are wirelessly transmitted by neighboring base station 120 in subframe # 5. The peripheral base station 120 transmits the synchronization signal at a constant synchronization signal period 330 by transmitting the synchronization signal at the same timing in each of the subframes # 0 and # 5. As an example, the length of the synchronization signal period 330 is 5 [ms]. Then, the peripheral base station 120 performs beam sweeping to switch the beam angle of the synchronization signal at a constant period while wirelessly transmitting the synchronization signal at a constant synchronization signal period 330 (see, for example, FIG. 2).

(Configuration of gap period according to the embodiment)
FIG. 4 is a diagram illustrating an example of a configuration of a gap period according to the embodiment. The gap period 410 shown in FIG. 4 indicates the length of the period in which the measurement gap is set by the connecting base station 110. The period of the gap cycle 410 includes a measurement gap 411, a communication section 412, and a gap shift section 413.

The measurement gap 411 is a period during which the connected base station 110 does not perform wireless communication with the terminal 130 and the terminal 130 measures the power of the synchronization signal from the neighboring cell (for example, the neighboring base station 120). The communication section 412 is a period during which the connecting base station 110 performs wireless communication with the terminal 130. The gap shift section 413 is a period set in order to change the length of the gap period 410. In the gap shift section 413, the connected base station 110 performs wireless communication with the terminal 130 as in the communication section 412.

MGRP is the length of the gap period 410. MGL is the length of the measurement gap 411. MGST is the length of the gap shift section 413. For example, the connection base station 110 can set MGRP, MGL, and MMGST, respectively. MGST can be set to 0. In this case, the gap shift section 413 is eliminated.

The connecting base station 110 can set the measurement gap 411 having a different length for each gap period 410 in the terminal 130. As a result, in a situation where the sweep pattern (timing and beam angle) of the synchronization signal of the neighboring cell (for example, neighboring base station 120) is unknown, it is possible to achieve both optimization of the time required for detecting the synchronization signal and the loss rate. Become.

(Setting of measurement gap for each gap period by the connecting base station according to the embodiment)
FIG. 5 is a diagram illustrating an example of setting a measurement gap for each gap period by the connecting base station according to the embodiment. In FIG. 5, the horizontal direction indicates time. A beam 510 (Beam) illustrated in FIG. 5 is a beam transmitted by the peripheral base station 120. Beams # 1 to # 16 of the beam 510 are beams for one cycle of beam sweeping by the peripheral base station 120, and are beams having different beam angles. Beams # 1 to # 16 are beams corresponding to the beam angles # 1 to # 16 shown in FIG. 2, for example.

In the example shown in FIG. 5, it is assumed that the peripheral base station 120 transmits a synchronization signal having a period of 5 [ms] as in the LTE specification, and performs beam sweeping to divide the beam angle into 16 at a period of 640 [ms]. In this case, the beams # 1 to # 16 of the beam 510 each have a length of 640 [ms] / 16 = 40 [ms].

Also, the length Tsync of the synchronization signal detection section, which is the repetition period of the measurement gap arrangement, is set to MGRP * (8 * 2 + 8) = MGRP * 24. A method for determining the length Tsync of the synchronization signal detection section will be described later.

The gap periods 521 to 544 are 24 gap periods included in the synchronization signal detection section. Each of the gap periods 521 to 544 is the gap period 410 shown in FIG. That is, the connecting base station 110 sets the gap periods 521 to 544 shown in FIG. 5 for each synchronization signal detection period. A method for determining the synchronization signal detection period will be described later. In the example shown in FIG. 5, each of the gap periods 521 to 544 has the same length of 40 [ms] as the beam for each angle of the beam 510 (MGRP = 40 [ms]).

In the example shown in FIG. 5, a measurement gap (G) of 3 [ms] is set in the first eight gap periods 521 to 528 of the gap periods 521 to 544. In the next eight gap periods 529 to 536 after the gap periods 521 to 528, a measurement gap (G) of 6 [ms] is set. In the next eight gap periods 537 to 544 after the gap periods 529 to 536, a measurement gap (G) of 4 [ms] is set. In FIG. 5, the measurement gap (G) is illustrated as being arranged at the beginning of each gap period, but the position of the measurement gap (G) is not limited to the beginning of each gap period.

Thus, the connecting base station 110 can set a measurement gap having a different length for each gap period. The length of each measurement gap in the gap periods 521 to 528 is MGL (1). Further, the length of each measurement gap in the gap periods 529 to 536 is MGL (2). In addition, the length of each measurement gap in the gap periods 537 to 544 is MGL (3). MGL (1) to MGL (3) can be calculated by, for example, the following formulas (1) to (3).

MGL (2) = (Tss + Trf) (1)
MGL (1) = int ((Tss + Trf) / 2) (2)
MGL (3) = (Tss + Trf + Trf) −MGL (1) (3)

Tss is a transmission period of the synchronization signal in the peripheral base station 120, and is 5 [ms] as an example. Trf is a time for frequency switching of a radio unit (for example, radio reception unit 1202 shown in FIG. 12) of terminal 130, and is 1 [ms] as an example. Tss and Trf are defined in the wireless communication system 100, for example, and are included in the system information of the wireless communication system 100. int () is a function indicating fractional truncation of the quotient.

That is, MGL (2) is the length of the measurement gap that the terminal 130 can reliably receive the synchronization signal in one measurement gap, assuming that the neighboring base station 120 simultaneously transmits the synchronization signal into the cell 200. is there. In the example illustrated in FIG. 5, MGL (2) = (Tss + Trf) = 5 + 1 = 6 [ms].

MGL (1) and MGL (3) are shorter than MGL (2), respectively, but when MGL (1) and MGL (3) are combined, they are determined to be MGL (2) or more. In the example shown in FIG. 5, MGL (1) is MGL (1) = int ((Tss + Trf) / 2) = int ((5 + 1) / 2) = 3 [ms]. In the example shown in FIG. 5, MGL (3) is MGL (3) = (Tss + Trf + Trf) −MGL (1) = (5 + 1 + 1) −3 = 4 [ms].

The division search 550 is divided into a gap period including a measurement gap of MGL (1) and a gap including a measurement gap of MGL (2) in one synchronization signal detection period in each period of beam angles # 1 to # 16. Indicates the period during which the cycle is set. In the example shown in FIG. 5, in each period of beam angles # 1 to # 8, a gap period including a measurement gap of MGL (1) and a gap period including a measurement gap of MGL (2) are set, and the synchronization signal A split search is performed. The measurement gap of MGL (1) and the measurement gap of MGL (2) are different from each other in the start position (timing) within the gap period. For this reason, since the synchronization signal is searched at different timings in the divided search, it is possible to efficiently detect the synchronization signal transmitted by beam sweeping.

(Arrangement of measurement gaps within the gap period by the connecting base station according to the embodiment)
FIG. 6 is a diagram illustrating an example of an arrangement of measurement gaps within a gap period by a connecting base station according to the embodiment. In FIG. 6, the horizontal direction indicates time. A gap cycle 610 shown in FIG. 6 is a gap cycle in which a measurement gap 611 having a length of MGL (1) is set, and corresponds to each of the gap cycles 521 to 528 in the example shown in FIG. The connecting base station 110 makes the start position of the measurement gap 611 having a length of MGL (1) the same as the start position of the gap period 610. In the example shown in FIG. 6, MGST = 0 is set, and a period excluding the measurement gap 611 in the gap period 610 is a communication section 612 (communication section 412 shown in FIG. 4).

6 is a gap period in which the measurement gap 621 having a length of MGL (2) is set, and corresponds to each of the gap periods 529 to 536 in the example shown in FIG. The connecting base station 110 makes the start position of the measurement gap 621 having a length of MGL (2) the same as the start position of the gap period 620. In the example shown in FIG. 6, MGST = 0 is set, and a period excluding the measurement gap 621 in the gap period 620 is a communication section 622 (communication section 412 shown in FIG. 4).

The gap period 630 shown in FIG. 6 is a gap period in which the measurement gap 631 having a length of MGL (3) is set, and corresponds to each of the gap periods 537 to 544 in the example shown in FIG. The connecting base station 110 sets the start position of the measurement gap 631 having a length of MGL (3) as a position after MGL (1) −Trf from the start position of the gap period 630. In the example shown in FIG. 6, MGST = 0 is set, and the period excluding the measurement gap 631 in the gap period 630 is the communication sections 632 and 633 (communication section 412 shown in FIG. 4).

In the synchronization signal detection section, the number of measurement gaps 611 having a length of MGL (1) and the number of measurement gaps 631 having a length of MGL (3) are the same. Let Ndg be the total number of measurement gaps 611 and 631 set in the synchronization signal detection section. That is, in the synchronization signal detection section, Ndg / 2 measurement gaps 611 and 631 are set. In the example shown in FIG. 5, Ndg = 16.

In addition, the beam division number of the beam sweeping of the synchronization signal by the peripheral base station 120 is Nbeam (16 as an example). In addition, the period of beam sweeping of the synchronization signal by the peripheral base station 120 is Tbs (640 [ms] as an example). Further, the length of the synchronization signal detection section is assumed to be Tsync.

The connecting base station 110 determines the length MGRP of the gap period 410 (each of the gap periods 521 to 544) by, for example, the following equation (4). Here, N is a cycle adjustment coefficient and is an integer from 1 to Nbeam. A method for determining the cycle adjustment coefficient will be described later. MGRP_0 is a basic gap period.

MGRP_0 = Tbs / Nbeam * N
MGRP = MGRP_0
... (4)

In the example shown in FIG. 5, N = 1 and MGRP = MGRP — 0 = Tbs / Nbeam * N = 640/16 * 1 = 40 [ms]. Further, the connecting base station 110 determines the length Tsync of the synchronization signal detection section, for example, by the following equation (5). However, 0 ≦ Ndg / 2 ≦ Nbeam and Ndg is an even number.

Tsync = MGRP — 0 * ((Ndg / 2) * 2 + (Nbeam−Ndg / 2))
= MGRP_0 * (Ndg / 2 + Nbeam)
... (5)

That is, Tsync is the number of gap periods in which the measurement gaps of MGL (1) and MGL (3) are set in the length of the gap period, and the number of gap periods in which the measurement gap of MGL (2) is set. The length multiplied by the sum of The length of the gap period corresponds to MGRP_0, the number of gap periods in which the measurement gaps of MGL (1) and MGL (3) are set corresponds to (Ndg / 2) * 2, and the measurement gap of MGL (2) The number of gap periods for which is set corresponds to Nbeam-Ndg / 2.

In the example shown in FIG. 5, Tsync = MGRP — 0 * (Ndg / 2 + Nbeam) = 40 * (16/2 + 16) = 960 [ms]. Or, Tsync = MGRP — 0 * ((Ndg / 2) * 2 + (Nbeam−Ndg / 2)) = 40 * ((16/2) * 2 + (16−16 / 2)) = 960 [ms].

Also, the neighboring base station 120 sets the gap period 610 for setting the measurement gap 611 having a length of MGL (1) as a gap period of Ndg / 2 from the head gap period in the synchronization signal detection section. In the example shown in FIG. 6, the gap period 610 for setting the measurement gap 611 having a length of MGL (1) is 16/2 = 8 gap periods 521 to 528 from the head gap period 521.

Also, the neighboring base station 120 sets a gap period 620 for setting the measurement gap 621 having a length of MGL (2) to a gap period corresponding to Nbeam−Ndg / 2 from the Ndg / 2 + 1th gap period in the synchronization signal detection period. And In the example shown in FIG. 6, the gap period 620 for setting the measurement gap 621 having a length of MGL (2) is 16-16 / 2 = 8 gap periods 529 from the 16/2 + 1 = 9th gap period. ~ 536.

Also, the neighboring base station 120 sets the gap period 630 for setting the measurement gap 631 having a length of MGL (3) as the gap period for Ndg / 2 from the Nbeam + 1st gap period in the synchronization signal detection section. In the example shown in FIG. 5, the gap period 630 for setting the measurement gap 631 having a length of MGL (3) is 16/2 = 8 gap periods 537 to 544 from the 16 + 1 = 17th gap period. .

(Another example of measurement gap setting for each gap period by the connecting base station according to the embodiment)
FIG. 7 is a diagram illustrating another example of setting a measurement gap for each gap period by the connecting base station according to the embodiment. In FIG. 7, the same parts as those shown in FIG. In FIG. 7, a case where N ≧ 2 and MOD (Nbeam, N) = 0 is described. Note that the connecting base station 110 does not select N that satisfies, for example, N ≧ 2 and MOD (Nbeam, N)> 0. MOD () is a function indicating remainder calculation.

The gap periods 711 to 726 are 16 gap periods included in the synchronization signal detection section. Each of the gap periods 711 to 726 is the gap period 410 shown in FIG. That is, the connected base station 110 sets the gap periods 711 to 726 shown in FIG. 7 for each synchronization signal detection section when N ≧ 2. In the example shown in FIG. 7, each of the gap periods 711 to 717 and 719 to 725 has the same length of 40 [ms] as the beam for each angle of the beam 510. In the example shown in FIG. 7, each of the gap periods 718 and 726 is a total length of the beam length 40 [ms] for each angle of the beam 510 and MGST = Tbs / Nbeam. In the example shown in FIG. 7, a measurement gap (G) having a length of MGL (2) is set in all the gap periods 711 to 726.

When N ≧ 2, the connecting base station 110 sets Ndg = 0. That is, the connecting base station 110 sets a measurement gap having a length of MGL (2) in each gap period without setting a measurement gap having a length of MGL (1) or MGL (3).

Also, the connecting base station 110 determines the length MGST (n) of the gap shift section (for example, the gap shift section 413 shown in FIG. 4) in the n-th (n is 1 to Nbeam) gap period by the following equation (6): Decide like this.

If MOD (n, Nbeam / N) = 0 then
MGST (n) = MGRP_0
Else
MGST (n) = 0
... (6)

That is, the connecting base station 110 sets the length MGST (n) of the gap shift section in the nth gap period that satisfies MOD (n, Nbeam / N) = 0 as MGRP — 0 = Tbs / Nbeam. In addition, the connecting base station 110 sets the length MGST (n) of the gap shift section in the nth gap period not satisfying MOD (n, Nbeam / N) = 0 to 0. Further, the connecting base station 110 determines the length MGRP (n) of the n-th (n is 1 to Nbeam) gap period, for example, by the following equation (7).

MGRP_0 = Tbs / Nbeam
MGRP (n) = MGRP_0 * N + MGST (n)
... (7)

Further, the connecting base station 110 determines the length Tsync of the synchronization signal detection section by, for example, the following equation (8).

Tsync = ΣMGRP (n) (8)

That is, the connecting base station 110 determines the sum of the lengths MGRP (n) of the first to Nbeam gap periods as the length Tsync of the synchronization signal detection section. In the example shown in FIG. 7, the lengths of the gap periods 711 to 717 and 719 to 725 are MGRP_0 = Tbs / Nbeam = 40 [ms], and the lengths of the gap periods 718 and 726 are MGRP_0 + MGST (n). = 40 + 40 = 80 [ms]. Therefore, Tsync = 40 * 14 + 80 * 2 = 720 [ms].

In the case of N ≧ 2, for example, as in the case of Tbs / Nbeam = 10 [ms], the length of one step of beam sweeping of the peripheral base station 120 is as short as 10 [ms], and the synchronization signal transmission cycle Tss ( For example, it is close to 5 [ms]). In this case, for example, the length of the communication section 412 shown in FIG. 4 is shortened, and the period during which data communication between the connecting base station 110 and the terminal 130 is possible is shortened.

On the other hand, as in the example shown in FIG. 7, the communication period 412 is lengthened by periodically increasing the gap period length MGRP (n) and shifting the gap period. The period in which data communication between the terminal 130 and the terminal 130 is possible can be lengthened. In the example shown in FIG. 7, the gap period is shifted by increasing the multiple of 8 gap periods 718 and 726 so that the division search 550 does not occur.

This lengthens the period in which data communication between the connecting base station 110 and the terminal 130 is possible, and eliminates the redundant search that sets the measurement gap multiple times for the same beam angle in one synchronization signal detection section. be able to. For this reason, it is possible to efficiently detect a synchronization signal transmitted by beam sweeping.

(Notification of measurement gap parameter from connected base station to terminal according to embodiment)
FIG. 8 is a sequence diagram illustrating an example of measurement gap parameter notification from the connected base station to the terminal according to the embodiment. UE 810 shown in FIG. 8 is, for example, terminal 130. EUTRAN 820 shown in FIG. 8 is, for example, connected base station 110. EUTRAN 820 is an abbreviation for Evolved Universal Terrestrial Radio Access Network.

First, EUTRAN 820 transmits RRC connection reconfiguration (RRCConnectionReconfiguration) to UE 810 (step S801). Further, the EUTRAN 820 stores the measurement gap parameter in the RRC connection reconfiguration transmitted in step S801.

For example, EUTRAN 820 stores the measurement gap parameter in MeasGapConfig of RRC connection reconfiguration. The measurement gap parameters include, for example, the division measurement gap interval number Ndg, the beam division number Nbeam, the cycle adjustment coefficient N, the basic gap cycle MGRP_0, and the start offset gapOffset. However, the measurement gap parameters stored in the RRC connection reconfiguration are not limited to these measurement gap parameters, and may be other information that can specify these measurement gap parameters.

Next, the UE 810 transmits an RRC connection reconfiguration complete (RRCConnectionReconfigurationCompletion) to the EUTRAN 820 (step S802). The RRC connection reconfiguration complete transmitted at step S802 is a response signal to the RRC connection reconfiguration received at step S801.

Then, the UE 810 and the EUTRAN 820 set a common measurement gap according to the measurement gap parameter included in the RRC connection reconfiguration transmitted in step S801.

(Improvement of maximum detection time versus loss rate by connected base station according to embodiment)
FIG. 9 is a diagram illustrating an example of improvement in the maximum detection time versus loss rate by the connected base station according to the embodiment. In FIG. 9, the horizontal axis represents the maximum detection time [ms], and the vertical axis represents the loss rate [%]. The maximum detection time is the maximum time required for detecting the synchronization signal. The loss rate can be calculated by dividing the total length of each measurement gap in the synchronization signal detection section by the length of the synchronization signal detection section.

FIG. 9 shows an example of beam sweeping in which the peripheral base station 120 transmits a synchronization signal with a period of 5 [ms] and divides the beam angle into 16 with a period of 640 [ms] as in the LTE specification. The maximum detection time vs. loss rate 911 shows the characteristic of the loss rate with respect to the maximum detection time in the first method in which a long continuous measurement gap is set.

The maximum detection time versus loss rate 912 is a characteristic of the loss rate with respect to the maximum detection time in the second method in which a measurement gap having a fixed length (for example, 6 [ms]) is set with a constant gap period (for example, 40 [ms]). Is shown. The maximum detection time vs. loss rate 913 shows the characteristic of the loss rate with respect to the maximum detection time in the third method in which the length of the measurement gap is shortened and the timing of the measurement gap is slid for each gap period to perform multiple searches. Yes.

The minimum value MGL (min) of the length of the measurement gap in the first method and the second method can be calculated by, for example, the following formula (9) and the following formula (10), respectively.

MGL (min) = max (Tbs, Tss * Nbeam) + Trf (9)

MGL (min) = (Tss + Trf) * Nbeam (10)

Further, for example, regarding the above equation (10), the loss rate LG of data transmission / reception between the connected base station 110 and the terminal 130 during the period required for the detection of the synchronization signal can be expressed by the following equation (11), for example.

LG = MGL (min) / (MGRP * Nbeam)
= (Tss + Trf) / MGRP
... (11)

The total measurement gap length MGL (total) in the third method can be calculated by, for example, the following equation (12). Tg is the divided gap length [ms], Ndiv is the number of beam divisions, and Nbeam is the number of beams of the base station. However, Tg * Ndiv> Tss + Trf is satisfied.

MGL (total) = Tg * Ndiv * Nbeam (12)

Further, with regard to the equation (12), the loss rate LG of data transmission / reception between the connected base station 110 and the terminal 130 during the period required for the detection of the synchronization signal can be expressed by the following equation (13), for example.

LG = MGL (total) / (MGRP * Ndiv * Nbeam)
= Tg / MGRP
... (13)

The maximum detection time vs. loss rate 920 indicates the characteristic of the loss rate with respect to the maximum detection time in the gap determination method by the connecting base station 110 according to the embodiment.

As shown in the maximum detection time to loss ratios 911 to 913 and 920, according to the present method by the connecting base station 110, compared with the first to third systems, the loss rate is low at the same maximum detection time, and the same It can be seen that the maximum detection time is shortened in the loss rate.

As shown in FIG. 9, according to the connecting base station 110, by setting a plurality of time interval periods in one synchronization signal detection interval and searching the same beam in two, the beam sweeping period and the synchronization signal transmission period It is possible to eliminate the waste of duplicate search due to the mutual relationship. For this reason, the loss rate of data transmission / reception can be suppressed, and the number of selectable combinations can be increased. Further, unlike the third method, the number of beams for performing the divided search can be set, so that the number of combinations that can be selected for the search time request can be increased.

(Connection base station according to the embodiment)
FIG. 10 is a diagram of an example of the connection base station according to the embodiment. As shown in FIG. 10, the connection base station 110 according to the embodiment includes, for example, an inter-base station communication unit 1001, a beam sweep control unit 1002, a synchronization signal weight coefficient calculation unit 1003, and a synchronization signal generation unit 1004. A synchronization signal modulation unit 1005. The connected base station 110 includes a measurement gap control unit 1006, a transmission data generation unit 1007, an encoding / modulation unit 1008, a beamforming / radio transmission unit 1009, and an antenna group 1010. In addition, the connecting base station 110 includes a wireless reception unit 1011, a demodulation / decoding unit 1012, a reception data processing unit 1013, and a transmission signal weight coefficient calculation unit 1014.

The inter-base station communication unit 1001 performs communication with the peripheral base station 120 via an inter-base station interface such as an X2 interface. For example, the inter-base station communication unit 1001 receives the peripheral base station information of the peripheral base station 120 from the peripheral base station 120. The peripheral base station information of the peripheral base station 120 includes the beam division number Nbeam and the period Tbs in the beam sweeping of the synchronization signal by the peripheral base station 120. The inter-base station communication unit 1001 outputs the received neighboring base station information to the measurement gap control unit 1006.

In addition, the inter-base station communication unit 1001 may transmit the local station information output from the beam sweep control unit 1002 to the neighboring base stations 120. The local station information includes, for example, the beam division number Nbeam and the cycle Tbs in beam sweeping of the synchronization signal by the connecting base station 110. Further, for example, the beam division number Nbeam = 1 indicates that beam sweeping is not performed.

The beam sweep control unit 1002 controls beam sweeping of the synchronization signal by the connecting base station 110. For example, the beam sweep control unit 1002 controls the synchronization signal beam sweeping by the connecting base station 110 by controlling the calculation of the synchronization signal weight coefficient in the synchronization signal weight coefficient calculation unit 1003. Further, the beam sweep control unit 1002 may output the local station information including the beam division number Nbeam and the cycle Tbs in the beam sweeping of the synchronization signal by the connected base station 110 to the inter-base station communication unit 1001.

The synchronization signal weight coefficient calculation unit 1003 calculates a weight coefficient for the synchronization signal in the beamforming / radio transmission unit 1009 according to the control from the beam sweep control unit 1002. Then, the synchronization signal weight coefficient calculation unit 1003 outputs the calculated weight coefficient to the beamforming / radio transmission unit 1009. By calculating the weighting factor by the synchronization signal weighting factor calculation unit 1003, beam sweeping can be performed by controlling the phase difference between a plurality of transmission antennas and the phase difference between transmission streams.

The synchronization signal generator 1004 generates a synchronization signal such as PSS or SSS. Then, the synchronization signal generation unit 1004 outputs the generated synchronization signal to the synchronization signal modulation unit 1005. The synchronization signal modulation unit 1005 modulates the synchronization signal output from the synchronization signal generation unit 1004 and outputs the modulated synchronization signal to the beamforming / radio transmission unit 1009.

The measurement gap control unit 1006 selects the period adjustment coefficient N based on the number of beam divisions Nbeam and the period Tbs included in the neighboring base station information output from the inter-base station communication unit 1001. For example, the measurement gap control unit 1006 obtains the period adjustment coefficient N by searching for the minimum N that satisfies β <(Tss + Trf) / (Tbs / Nbeam) / N on the condition that N is a divisor of Nbeam. select. β is a parameter of the connecting base station 110 and satisfies 0 <β <1.0.

Further, the measurement gap control unit 1006 determines a gap shift section length MGST, a measurement gap length MGL, a measurement gap start offset gapOffset, a gap period length MGRP, and the like according to the selected period adjustment coefficient N. To do. Further, the measurement gap control unit 1006 determines the number Ndg of divided measurement gap sections. For example, when N = 1, the measurement gap control unit 1006 determines the number Ndg of divided measurement gap intervals by Ndg = 2 * int (α * Nbeam). However, α is a parameter of the connecting base station 110 and satisfies 0 ≦ α ≦ 1.0.

Then, the measurement gap control unit 1006 arranges the measurement gaps with a gap period of 1 to Nbeam + Ndg / 2 times or 1 to Nbeam times according to the determined divided measurement gap interval number Ndg. Further, the measurement gap control unit 1006 determines the start position of the first MGRP by the start offset gapOffset, and generates terminal notification information indicating each parameter related to the determined measurement gap.

The measurement gap control unit 1006 outputs the generated terminal notification information to the transmission data generation unit 1007. In addition, the measurement gap control unit 1006 controls setting of the measurement gap by the encoding / modulation unit 1008 based on each parameter related to the determined measurement gap. In addition, the measurement gap control unit 1006 may perform control to stop the demodulation and decoding processes in the demodulation / decoding unit 1012 in the determined measurement gap.

The transmission data generation unit 1007 generates transmission data to be transmitted to the terminal 130. For example, the transmission data generation unit 1007 generates transmission data including downlink user data for the terminal 130. Also, the transmission data generation unit 1007 generates transmission data including RRC connection reconfiguration in which the terminal notification information output from the measurement gap control unit 1006 is stored. Then, transmission data generation section 1007 outputs the generated transmission data to encoding / modulation section 1008.

The encoding / modulation unit 1008 encodes and modulates transmission data output from the transmission data generation unit 1007. Then, encoding / modulation section 1008 outputs the transmission signal obtained by the encoding and modulation to beamforming / radio transmission section 1009.

Also, the encoding / modulation unit 1008 sets a measurement gap for each terminal (for example, the terminal 130) that is the transmission destination of the transmission signal in accordance with control from the measurement gap control unit 1006. Then, the encoding / modulation section 1008 does not output the transmission signal to the target terminal in the set measurement gap. Thereby, the target terminal can measure a radio signal from another base station such as the neighboring base station 120.

The beamforming / radio transmission unit 1009 weights the synchronization signal output from the synchronization signal modulation unit 1005 with the weighting factor output from the synchronization signal weighting factor calculation unit 1003. The beamforming / radio transmission unit 1009 weights the transmission signal output from the encoding / modulation unit 1008 with the weighting coefficient output from the transmission signal weighting coefficient calculation unit 1014. Thereby, the beam forming (beam sweeping) of the synchronization signal and the beam forming of the transmission signal can be realized.

The beamforming / radio transmission unit 1009 performs radio transmission processing of a signal including the weighted synchronization signal and transmission signal. The wireless transmission processing includes, for example, conversion from a digital signal to an analog signal, frequency conversion from a baseband to a high frequency band, amplification, and the like. Beamforming / radio transmission section 1009 outputs a signal subjected to radio transmission processing to antenna group 1010.

The antenna group 1010 is a plurality of antennas that wirelessly transmit signals output from the beamforming / wireless transmission unit 1009 to other wireless communication devices (for example, the terminal 130). Further, the antenna group 1010 receives a signal wirelessly transmitted from another wireless communication device (for example, the terminal 130), and outputs the received signal to the wireless reception unit 1011.

The wireless reception unit 1011 performs wireless reception processing on the signals output from the antenna group 1010. The wireless reception processing includes, for example, amplification, frequency conversion from a high frequency band to a base band, conversion from an analog signal to a digital signal, and the like. Radio reception section 1011 outputs the signal subjected to radio reception processing to demodulation / decoding section 1012 and transmission signal weight coefficient calculation section 1014.

The demodulation / decoding unit 1012 demodulates and decodes the signal output from the wireless reception unit 1011. Demodulation / decoding section 1012 then outputs received data obtained by demodulation and decoding to received data processing section 1013. The reception data processing unit 1013 performs processing based on the reception data output from the demodulation / decoding unit 1012.

The transmission signal weighting factor calculation unit 1014 applies a transmission signal to the beamforming / radio transmission unit 1009 based on a control signal (feedback signal) from a terminal (for example, the terminal 130) included in the signal output from the radio reception unit 1011. Calculate the weighting factor. Then, transmission signal weight coefficient calculation section 1014 outputs the calculated weight coefficient to beamforming / radio transmission section 1009.

A setting unit that sets the length of an intermittent time interval (measurement gap) that does not require the wireless terminal to receive a signal from the own station can be realized by the measurement gap control unit 1006, for example. A generation unit that generates a signal including information related to the length of the time interval can be realized by, for example, the transmission data generation unit 1007 and the encoding / modulation unit 1008. A transmission unit that transmits the generated signal to the neighboring base station 120 can be realized by, for example, the wireless transmission unit 1209 (see, for example, FIG. 12) and the antenna group 1010.

Although the configuration of the connection base station 110 has been described, the peripheral base station 120 can also have the same configuration as the connection base station 110. Accordingly, the neighboring base station 120 can perform beam sweeping by controlling the phase difference between the plurality of transmission antennas and the phase difference between the transmission streams by calculating the weighting factor by the synchronization signal weighting factor calculating unit 1003. .

(Hardware configuration of connected base station according to embodiment)
FIG. 11 is a diagram illustrating an example of a hardware configuration of a connection base station according to the embodiment. 11, the same parts as those shown in FIG. 10 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 11, the inter-base station communication unit 1001, the beam sweep control unit 1002, the synchronization signal weight coefficient calculation unit 1003, the synchronization signal generation unit 1004, and the synchronization signal modulation unit 1005 can be realized by a digital circuit 1100, for example. it can.

The measurement gap control unit 1006, the transmission data generation unit 1007, the encoding / modulation unit 1008, the demodulation / decoding unit 1012, the reception data processing unit 1013, and the transmission signal weight coefficient calculation unit 1014 are realized by, for example, the digital circuit 1100. Can do. The digital circuit 1100 is, for example, a processor such as an FPGA (Field Programmable Gate Array) or a DSP (Digital Signal Processor).

The beamforming / radio transmission unit 1009 shown in FIG. 10 can be realized by a circuit such as a DAC (Digital / Analog Converter), a mixer, and an amplifier. 10 can be realized by a circuit such as an amplifier, a mixer, and an ADC (Analog / Digital Converter).

(Terminal according to the embodiment)
FIG. 12 is a diagram illustrating an example of a terminal according to the embodiment. As illustrated in FIG. 11, the terminal 130 according to the embodiment includes, for example, an antenna 1201, a radio reception unit 1202, a demodulation / decoding unit 1203, a reception data processing unit 1204, a synchronization signal detection / measurement unit 1205, And a measurement gap control unit 1206. The terminal 130 includes a transmission data generation unit 1207, an encoding / modulation unit 1208, and a wireless transmission unit 1209.

The antenna 1201 is a plurality of antennas that receive signals wirelessly transmitted from other wireless communication devices (for example, the connecting base station 110 and the neighboring base station 120) and output the received signals to the wireless receiving unit 1202. Further, the antenna 1201 wirelessly transmits the signal output from the wireless transmission unit 1209 to another wireless communication device (for example, the connection base station 110).

The wireless reception unit 1202 performs wireless reception processing on the signal output from the antenna 1201. The wireless reception processing includes, for example, amplification, frequency conversion from a high frequency band to a base band, conversion from an analog signal to a digital signal, and the like. Radio reception section 1202 outputs the signal subjected to the radio reception processing to demodulation / decoding section 1203 and synchronization signal detection / measurement section 1205.

For example, the radio reception unit 1202 performs radio reception processing on the signal component in the frequency band of the synchronization signal from the neighboring base station 120 in the measurement gap section set by the measurement gap control unit 1206. Radio reception section 1202 performs radio reception processing on signal components in the frequency band of a signal (for example, communication data) from connected base station 110 serving as a serving cell in a section other than the measurement gap set by measurement gap control section 1206. I do. The above Trf is a time for switching the target frequency (carrier frequency) of the wireless reception processing by the wireless reception unit 1202, for example.

The demodulation / decoding unit 1203 demodulates and decodes the signal output from the wireless reception unit 1202. Demodulation / decoding section 1203 outputs the reception data obtained by demodulation and decoding to reception data processing section 1204 and measurement gap control section 1206. The reception data processing unit 1204 performs processing based on the reception data output from the demodulation / decoding unit 1203.

The synchronization signal detection / measurement unit 1205 detects a synchronization signal included in the signal output from the wireless reception unit 1202 in the measurement gap set by the measurement gap control unit 1206. Then, the synchronization signal detection / measurement unit 1205 measures the power of the detected synchronization signal. Further, the synchronization signal detection / measurement unit 1205 notifies the transmission data generation unit 1207 of the measurement result of the power of the synchronization signal.

The measurement gap control unit 1206 acquires terminal notification information included in the reception data (for example, RRC connection reconfiguration) output from the demodulation / decoding unit 1203. Then, measurement gap control section 1206 sets a measurement gap for radio reception section 1202 and synchronization signal detection / measurement section 1205 based on each parameter indicated by the acquired terminal notification information. Further, the measurement gap control unit 1206 may perform control to stop the encoding and modulation by the encoding / modulation unit 1208 and the wireless transmission processing by the wireless transmission unit 1209 in the measurement gap section. In addition, the measurement gap control unit 1206 outputs a response signal (for example, RRC connection reconfiguration complete) to the connection base station 110 with respect to the terminal notification information to the transmission data generation unit 1207.

The transmission data generation unit 1207 generates transmission data to be transmitted to the connected base station 110. For example, the transmission data generation unit 1207 generates transmission data including uplink user data to the connected base station 110. Also, the transmission data generation unit 1207 generates transmission data including the measurement result (report information) of the power of the synchronization signal output from the synchronization signal detection / measurement unit 1205. Further, the transmission data generation unit 1207 generates transmission data including the RRC connection reconfiguration complete output from the measurement gap control unit 1206. Then, transmission data generating section 1207 outputs the generated transmission data to encoding / modulation section 1208.

The encoding / modulation unit 1208 encodes and modulates the transmission data output from the transmission data generation unit 1207. Then, encoding / modulation section 1208 outputs a transmission signal obtained by encoding and modulation to radio transmission section 1209.

Also, the encoding / modulation unit 1208 sets the measurement gap in accordance with the control from the measurement gap control unit 1206. Then, encoding / modulation section 1208 does not output a transmission signal to connected base station 110 in the set measurement gap.

The wireless transmission unit 1209 performs wireless transmission processing of the transmission signal output from the encoding / modulation unit 1208. The wireless transmission processing includes, for example, conversion from a digital signal to an analog signal, frequency conversion from a baseband to a high frequency band, amplification, and the like. The wireless transmission unit 1209 outputs the signal subjected to the wireless transmission process to the antenna 1201.

The first receiving unit that receives a signal including information related to the length of the time interval (measurement gap) from the connected base station 110 can be realized by the antenna 1201 and the wireless receiving unit 1202, for example. The second receiving unit that receives signals from the connecting base station 110 and the neighboring base station 120 can be realized by, for example, the antenna 1201, the wireless receiving unit 1202, the synchronization signal detecting / measuring unit 1205, and the measurement gap control unit 1206.

(Hardware configuration of terminal according to embodiment)
FIG. 13 is a diagram illustrating an example of a hardware configuration of the terminal according to the embodiment. In FIG. 13, the same parts as those shown in FIG. As illustrated in FIG. 13, the demodulation / decoding unit 1203, the reception data processing unit 1204, and the synchronization signal detection / measurement unit 1205 illustrated in FIG. 12 can be realized by a digital circuit 1300, for example.

Also, the measurement gap control unit 1206, the transmission data generation unit 1207, and the encoding / modulation unit 1208 can be realized by a digital circuit 1300, for example. The digital circuit 1300 is a processor such as an FPGA or a DSP, for example. The radio reception unit 1202 illustrated in FIG. 12 can be realized by a circuit such as a DAC, a mixer, and an amplifier. The radio transmission unit 1209 illustrated in FIG. 12 can be realized by a circuit such as an amplifier, a mixer, and an ADC.

(Gap determination process by measurement gap control unit of connected base station according to embodiment)
FIG. 14 is a flowchart illustrating an example of gap determination processing by the measurement gap control unit of the connected base station according to the embodiment. The measurement gap control unit 1006 of the connecting base station 110 according to the embodiment executes, for example, each step shown in FIG. 14 as the gap determination process.

First, the measurement gap control unit 1006 determines whether or not the cycle adjustment coefficient N is 1 (step S1401). The cycle adjustment coefficient N is an integer of 1 or more. For example, the measurement gap control unit 1006 sets the minimum integer satisfying β <(Tss + Trf) / (Tbs / Nbeam) / N as the period adjustment coefficient on condition that the period adjustment coefficient N is a divisor of the beam division number Nbeam. Calculate as N. β is a parameter of the connected base station 110 that satisfies 0 <β <1.0. The beam division number Nbeam and the period Tbs are included in the peripheral base station information from the peripheral base station 120, for example. The transmission cycle Tss and time Trf are included in the system information, for example.

In step S1401, when the cycle adjustment coefficient N is 1 (step S1401: Yes), the measurement gap control unit 1006 sets the length MGST of the gap shift section (for example, the gap shift section 413 shown in FIG. 4) to 0. Determination is made (step S1402). That is, the measurement gap control unit 1006 determines not to insert a gap shift section.

Also, the measurement gap control unit 1006 determines three types of lengths MGL (1) to MGL (3) of the measurement gap (for example, the measurement gap 411 shown in FIG. 4) (step S1403). For example, the measurement gap control unit 1006 determines MGL (2) from the above equation (1), MGL (1) from the above equation (2), and MGL (3) from the above equation (3). .

The measurement gap control unit 1006 determines the arrangement of the measurement gaps having lengths MGL (1) to MGL (3) within the gap period (for example, the gap period 410 shown in FIG. 4) (step S1404). ). For example, the measurement gap control unit 1006 determines the start position of the measurement gap having the lengths MGL (1) and MGL (2) as the start position of the gap period. In addition, the measurement gap control unit 1006 determines the start position of the measurement gap having a length of MGL (3) at a timing after MGL (1) −Trf from the start position of the gap period.

The measurement gap control unit 1006 also includes a gap period length MGRP, a divided measurement gap interval number Ndg, which is the number of measurement gaps whose length in the synchronization signal detection interval is MGL (1) or MGL (3), Is determined (step S1405). For example, the measurement gap control unit 1006 first calculates the basic gap period MGRP_0 from MGRP_0 = Tbs / Nbeam. Then, the measurement gap control unit 1006 determines the length MGRP of each gap period as the basic gap period MGRP_0. In this case, each gap period becomes the same MGRP_0 = Tbs / Nbeam. The measurement gap control unit 1006 determines Ndg according to Ndg = 2 * int (α * Nbeam). α is a parameter of the connected base station 110 that satisfies 0 ≦ α ≦ 1.0.

Further, the measurement gap control unit 1006 determines the arrangement of gap periods in the synchronization signal detection section (step S1406). For example, the measurement gap control unit 1006 determines the first to Ndg / 2nd gap cycle as a gap cycle including a measurement gap having a length of MGL (1). In addition, the measurement gap control unit 1006 determines the Ndg / 2 + 1-th to Nbeam-th gap period as a gap period including a measurement gap having a length of MGL (2). Further, the measurement gap control unit 1006 determines the Nbeam + 1-th to Nbeam + Ndg / 2nd gap cycle as a gap cycle including a measurement gap having a length of MGL (3).

Further, the measurement gap control unit 1006 determines the length Tsync of the synchronization signal detection section (step S1407). For example, the measurement gap control unit 1006 determines Tsync by Tsync = MGRP — 0 * (Ndg / 2 + Nbeam). However, 0 ≦ Ndg / 2 ≦ Nbeam and Ndg is an even number.

In step S1401, when the cycle adjustment coefficient N is 2 or more (step S1401: No), it may be determined that the length of one step of beam sweeping of the neighboring base station 120 is short and close to the synchronization signal transmission cycle Tss. it can. In this case, the measurement gap control unit 1006 determines the length MGST of the gap shift section to be inserted in each gap cycle (step S1408). For example, the measurement gap control unit 1006 first calculates the basic gap period MGRP_0 from MGRP_0 = Tbs / Nbeam.

Then, the measurement gap control unit 1006 determines the length MGST of the gap shift section in each of the first to Nbeam gap periods. For example, the measurement gap control unit 1006 determines the MGST (n) of the nth gap cycle as the basic gap cycle MGRP_0 when MOD (n, Nbeam / N) = 0, and MOD (n, Nbeam / N). If ≠ 0, 0 is determined. n is the number of the gap period and is an integer in the range of 1 to Nbeam. MOD () is a function indicating remainder calculation.

Also, the measurement gap control unit 1006 determines the length MGL of the measurement gap (step S1409). For example, the measurement gap control unit 1006 determines MGL by (Tss + Trf) in the above equation (1). In this case, the length of each measurement gap is all MGL (2). In addition, the measurement gap control unit 1006 determines the arrangement of the measurement gaps within the gap period (step S1410). For example, the measurement gap control unit 1006 determines the start position of each measurement gap as the start position of the gap period.

The measurement gap control unit 1006 also includes a gap period length MGRP, a divided measurement gap interval number Ndg, which is the number of measurement gaps whose length in the synchronization signal detection interval is MGL (1) or MGL (3), Is determined (step S1411). For example, the measurement gap control unit 1006 calculates the length MGRP (n) of the nth gap period by MGRP (n) = MGRP — 0 * N + MGMT (n) in the above equation (7). In this case, the measurement gap control unit 1006 determines that Ndg is 0 because the length of each measurement gap is MGL (2) and there is no measurement gap whose length is MGL (1) or MGL (3). To do.

In addition, the measurement gap control unit 1006 determines the arrangement of gap periods in the synchronization signal detection section (step S1412). For example, the measurement gap control unit 1006 arranges the above-described gap cycles from the first to the Nbeams in order. That is, the measurement gap control unit 1006 arranges the first gap cycle, the second gap cycle,..., The Nbeam-th gap cycle in this order.

In addition, the measurement gap control unit 1006 determines the length Tsync of the synchronization signal detection section (step S1413). For example, the measurement gap control unit 1006 determines Tsync by Tsync = ΣMGRP (n). That is, the measurement gap control unit 1006 determines the total of the gap period lengths MGRP (1) to MGRP (Nbeam) from the first to the Nbeamth as Tsync.

At Steps S1402 to S1407 or Steps S1408 to S1413, MGST, MGL, arrangement of measurement gaps in the gap period, MGRP, Ndg, arrangement of each gap period in the synchronization signal detection section, and Tsync are determined.

Next, the measurement gap control unit 1006 determines the start offset of the gap period, that is, the start position of the first gap period for each terminal (for example, terminal 130) connected to the own cell (step S1414). The determination of the start offset gapOffset is specified in, for example, 3GPP TS36.331. In this LTE regulation, the start offset gapOffset is determined by the following equation (14). FLOOR () is a floor function.

SFN mod T = FLOOR (gapOffset / 10);
subframe = gapOffset mod 10;
with T = MGRP / 10
... (14)

SFN in the above equation (14) is a system frame number shared by the connecting base station 110 and the terminal 130. T = MGRP / 10 is defined in TS36.133 of 3GPP, for example. The measurement gap control unit 1006 determines the start offset gapOffset based on, for example, the determined Tsync and the following equation (15). In the following formula (15), basicTime is a predetermined time as a reference, and is 10 [ms] in LTE.

SFN mod Ts = FLOOR (gapOffset / basicTime);
subframe = gapOffset mod basicTime;
with Ts = Tsync / basicTime
... (15)

Next, the measurement gap control unit 1006 generates terminal notification information for notifying the terminal 130 based on the information determined in steps S1402 to S1407 or steps S1408 to S1413 (step S1415), and ends the series of processes. To do. The terminal notification information includes, for example, a start offset gapOffset, a division measurement gap interval number Ndg, a beam division number Nbeam, a period adjustment coefficient N, and a basic gap period MGRP_0.

The measurement gap control unit 1006 transmits the terminal notification information generated in each step shown in FIG. 14 to the transmission data generation unit 1007 to transmit it to the terminal 130. In addition, the measurement gap control unit 1006 controls setting of the measurement gap by the encoding / modulation unit 1008 based on each parameter related to the determined measurement gap.

(Gap determination process by measurement gap control unit of terminal according to embodiment)
FIG. 15 is a flowchart illustrating an example of gap determination processing by the measurement gap control unit of the terminal according to the embodiment. The measurement gap control unit 1206 of the terminal 130 according to the embodiment performs, for example, FIG. 15 as a gap determination process based on the terminal notification information generated in step S1414 in FIG. 14 and transmitted from the connected base station 110 to the own terminal. The steps shown in FIG. The terminal notification information includes, for example, a start offset gapOffset, a division measurement gap interval number Ndg, a beam division number Nbeam, a period adjustment coefficient N, and a basic gap period MGRP_0.

First, the measurement gap control unit 1206 determines whether or not the cycle adjustment coefficient N included in the terminal notification information is 1 (step S1501). When the cycle adjustment coefficient N is 1 (step S1501: Yes), the process proceeds to step S1502.

Steps S1502 to S1507 by the measurement gap control unit 1206 are the same as steps S1402 to S1407 by the measurement gap control unit 1006 shown in FIG. However, in step S1505, the measurement gap control unit 1206 determines the length MGRP of each gap period as the basic gap period MGRP_0 included in the terminal notification information. In step S1505, the measurement gap control unit 1206 determines the divided measurement gap interval number Ndg based on the divided measurement gap interval number Ndg included in the terminal notification information.

Also, in step S1507, the measurement gap control unit 1206 determines Tsync based on the beam division number Nbeam and the division measurement gap interval number Ndg included in the terminal notification information.

In step S1501, when the cycle adjustment coefficient N is 2 or more (step S1501: No), the measurement gap control unit 1206 proceeds to step S1508. Steps S1508 to S1513 shown in FIG. 15 are the same as steps S1408 to S1413 shown in FIG. However, in step S1508, the measurement gap control unit 1206 determines the basic gap period MGRP_0 and the MGST (n) of the nth gap period based on the beam division number Nbeam included in the terminal notification information.

Also, in step S1511, the measurement gap control unit 1206 determines the length MGRP (n) of the nth gap cycle based on the basic gap cycle MGRP_0 and the cycle adjustment coefficient N included in the terminal notification information.

In steps S1502 to S1507 or S1508 to S1513, MGST, MGL, arrangement of measurement gaps in the gap period, MGRP, Ndg, arrangement of the gap periods in the synchronization signal detection section, and Tsync are determined. Next, the measurement gap control unit 1206 sets the start offset of the gap period included in the terminal notification information in the own terminal (step S1514), and ends the series of processes. For example, the measurement gap control unit 1206 sets a measurement gap for the radio reception unit 1202 and the synchronization signal detection / measurement unit 1205.

(Processing in Radio Communication System According to Embodiment)
FIG. 16 is a sequence diagram illustrating an example of processing in the wireless communication system according to the embodiment. In the wireless communication system 100, for example, each step shown in FIG. 16 is executed. First, the connecting base station 110 transmits / receives information regarding beam sweeping to / from the neighboring base station 120 as neighboring base station information (step S1601). The information related to beam sweeping includes a beam sweeping period (beam sweeping period) Tbs and a beam division number Nbeam.

The neighboring base station 120 transmits a synchronization signal by beam sweeping according to information related to beam sweeping included in the neighboring base station information transmitted to the connecting base station 110 in step S1601 (step S1602).

Also, the connecting base station 110 determines a measurement gap parameter (step S1603). Determination of the measurement gap parameter is, for example, determination of each parameter in steps S1401 to S1414 shown in FIG. Next, the connecting base station 110 sets a measurement gap based on the measurement gap parameter determined in step S1603 (step S1604).

Next, the connecting base station 110 transmits terminal notification information including the measurement gap parameter determined in step S1603 to the terminal 130 (step S1605). The terminal notification information is transmitted by, for example, MeasGapConfig of RRC connection reconfiguration. In addition to release, setup, and gapOffset defined in 3GPP, MeasGapConfig includes a division measurement gap interval number Ndg, a beam division number Nbeam, a period adjustment coefficient N, and a basic gap period MGRP_0 as measurement information.

Next, the terminal 130 sets a measurement gap based on the measurement gap parameter included in the terminal notification information transmitted from the connected base station 110 in step S1605 (step S1606). Thereby, a common measurement gap is set in the connecting base station 110 and the terminal 130, and radio measurement using the measurement gap is started.

First, the connecting base station 110 stops transmission / reception of communication data with the terminal 130 in the measurement gap section set in step S1404 (step S1607). On the other hand, when the measurement gap section set in step S1406 is reached, the terminal 130 performs radio measurement of the synchronization signal transmitted from the neighboring base station 120 in step S1602 (step S1608). Next, the terminal 130 switches the frequency of the radio unit (step S1609). For example, the terminal 130 switches the frequency received by the radio unit from the frequency used by the connecting base station 110 for communication data to the terminal 130 to the frequency used by the neighboring base station 120 for transmitting the synchronization signal.

Next, the connected base station 110 transmits downlink communication data to the terminal 130 when the communication period (including the gap shift period) other than the measurement gap period set in step S1404 is reached (step S1610). On the other hand, when the communication section (including the gap shift section) other than the measurement gap section set in step S1406 is entered, the terminal 130 transmits uplink communication data and the wireless measurement result in step S1608 to the connected base station 110 ( Step S1611).

Next, the terminal 130 switches the frequency of the radio unit (step S1612). For example, the terminal 130 switches the frequency received by the radio unit from the frequency used by the connecting base station 110 for communication data to the terminal 130 to the frequency used by the neighboring base station 120 for transmitting the synchronization signal.

Next, when the connecting base station 110 enters the section of the measurement gap set in step S1404, transmission / reception of communication data with the terminal 130 is stopped (step S1613). On the other hand, when the measurement gap section set in step S1406 is reached, the terminal 130 performs radio measurement of the synchronization signal transmitted from the neighboring base station 120 in step S1612 (step S1614).

As described above, according to the connection base station 110 according to the embodiment, the length of the intermittent time interval in which the terminal 130 does not have to receive the signal from the connection base station 110 is set for each time interval. A signal including information related to the length of the time interval can be transmitted to the terminal 130. Thereby, between the connecting base station 110 and the terminal 130, the length of the time interval in which the terminal 130 does not have to receive the signal from the connecting base station 110 is set for each time interval, and the synchronization is transmitted by beam sweeping. Signal detection can be performed efficiently.

The time section is a section in which no data signal is transmitted from the connecting base station 110 to the terminal 130, and is, for example, the above-described measurement gap. The length of the time interval is, for example, the above-described MGL, MGL (1) to MGL (3). The information related to the length of the time interval is information that enables the terminal 130 to specify the length of the time interval, and is the period adjustment coefficient N described above as an example.

For example, the connecting base station 110 sets, for the terminal 130, a period for setting a time interval of a first length, a period for setting a time interval of a second length, and a time interval of a short third length. The length of the time interval is determined for each time interval so that the set cycles are mixed. As an example, the first length is the above-described MGL (2). The second length is shorter than the first length, and is, for example, MGL (1) described above. The third length is shorter than the first length, and is, for example, the above-described MGL (3). Further, the third time period is a time period having a different timing from the second time period.

Thereby, for example, compared to a case where only the first length of the time interval is set and the first length of the time interval is lengthened, the measurement gap is determined at each timing when the beam angle of the synchronization signal is the same. The search time interval can be shortened. For this reason, it is possible to efficiently detect a synchronization signal transmitted by beam sweeping.

Also, the connecting base station 110 determines the length of the time interval based on the peripheral base station information received from the peripheral base station 120. Thereby, even if the beam sweep pattern of the synchronization signal in the neighboring base station 120 is unknown, the length of the time interval in which the neighboring base station 120 can efficiently detect the synchronization signal transmitted by beam sweeping is determined. it can. Each time the neighboring base station 120 transmits the same signal (synchronization signal) using a plurality of transmission antennas, the neighboring base station 120 calculates at least one of the phase difference between the plurality of transmission antennas and the phase difference between the transmission streams of the synchronization signals. It is a radio base station that can be changed.

Peripheral base station information is information related to changing at least one of the phase difference between a plurality of transmission antennas and the phase difference between transmission streams of synchronization signals. As an example, the peripheral base station information includes the number of beam divisions Nbeam and the period Tbs in beam sweeping of the synchronization signal by the peripheral base station 120.

Also, the connecting base station 110 may set a period length for setting a time interval (for example, a measurement gap) for each period and generate a signal including information on the set period length. The period for setting the time interval is, for example, the above-described gap period. The information on the length of the period for setting the time interval is, for example, the gap period length MGRP (n) described above. The information regarding the period length for setting the time interval is information that enables the terminal 130 to specify the gap period length MGRP (n), for example, and includes the period adjustment coefficient N and the number of beam divisions described above as an example. Nbeam and basic gap period MGRP_0.

Thereby, between the connecting base station 110 and the terminal 130, the length of the period for setting the time interval in which the terminal 130 does not need to receive the signal from the connecting base station 110 is set for each period, and transmitted by beam sweeping. The detected sync signal can be detected efficiently. For example, it is possible to eliminate the duplicate search in which the measurement gap is set a plurality of times for the same beam angle in one synchronization signal detection section. For this reason, it is possible to efficiently detect a synchronization signal transmitted by beam sweeping.

For example, the connecting base station 110 has a period length (for example, Tss) at which the neighboring base station 120 transmits a synchronization signal and a period length (for example, Tbs / Nbeam) at which the neighboring base station 120 switches the beam angle. Make a comparison. Then, the connecting base station 110 may perform processing for setting the length of the period for setting the time interval for each period in accordance with the comparison result. As an example, as described above, the connecting base station 110 calculates the minimum integer satisfying β <(Tss + Trf) / (Tbs / Nbeam) / N as the period adjustment coefficient N, and when N ≧ 2 is satisfied, A process for setting the length of the period for setting the time interval for each period is performed. As a result, it is possible to efficiently detect the synchronization signal transmitted by beam sweeping while suppressing a period during which data communication between the connecting base station 110 and the terminal 130 is possible from being shortened.

As described above, according to the radio base station, the radio terminal, the radio communication system, and the radio communication method, it is possible to efficiently detect the synchronization signal transmitted by beam sweeping.

For example, the fifth generation mobile communication system is expected to start commercial service from around 2020. In the fifth generation mobile communication system, an ITU that a peak data rate of 20 [Gbps] at the maximum in the downlink (DL) and 10 [Gbps] at the maximum in the uplink (UL) should be obtained. There is a request from. As a method for realizing this, there is a utilization of a millimeter wave band capable of securing a wide band. ITU is an abbreviation for International Telecommunication Union.

In the millimeter wave band, radio wave propagation loss increases and the radio cell becomes smaller, but it is considered effective to expand the range of the radio cell by performing beamforming transmission using a multi-element antenna. In addition, by performing spatial stream multiplex transmission using a multi-element antenna, the data rate can be increased. Therefore, the use of multi-element antennas in the millimeter wave band is considered an effective method. For example, the maximum number of antenna elements included in one transmission antenna is assumed to be 256.

One of the important things in wireless cellular communication is that the process of connecting a terminal to a wireless cell base station and the signal for maintaining the connection and the system control signal can be received by the terminal throughout the wireless cell. That is.

For a radio signal transmitted individually for each terminal, beamforming transmission (beam generation based on an arrival angle obtained from measurement of a signal transmitted by the terminal) in which a beam is directed to the terminal is effective. In beamforming transmission, a beam that is transmitted multiple times so that a beam with a narrow width with a changed beam angle reaches the entire area of the cell is used for transmission of a common radio signal that is received by all terminals in the cell. It is preferable to apply sweeping transmission. Beam sweeping is realized by changing with the time of a weight matrix composed of amplitude and phase every time transmission is performed.

Also, 3GPP has started basic study work for the specification of the fifth generation mobile communication system. For example, in the millimeter wave band, it is considered to perform beam sweep transmission of a radio downlink synchronization signal (equivalent to PSS or SSS in LTE) which is one of common radio signals.

Digital beam forming transmission, hybrid beam forming transmission or analog beam forming transmission is used when beam forming transmission is performed using a multi-element transmission antenna. Hybrid beamforming transmission is a combination of digital beamforming transmission and analog beamforming transmission.

It is required that the radio signal introduced into the radio section of the fifth generation mobile communication system does not depend on these beamforming transmission methods. That is, it is required that the terminal can receive the radio signal transmitted by beamforming without knowing the type of beamforming transmission method used on the base station side.

Also, when the signal is transmitted by beam forming, the number of beams transmitted at the same time can be varied by making the setting contents of the phase matrix given between the antenna elements appropriate. As the number of beams increases, the power allocated to one beam decreases and the beam reaching distance decreases. When the power allocated to one beam is the same, the beam reaching distance decreases as the beam width increases. .

Therefore, when beam sweeping a radio signal, the beam width and the number of sweeps are set for each radio base station in consideration of the cell size, the configuration of the transmission antenna, the radio carrier frequency, and the like. For this reason, the terminal needs to be able to receive a signal to be transmitted by beam sweeping without knowing the beam width or the number of sweeps of beam sweeping.

Wireless communication in the millimeter wave band (for example, 24 to 40 [GHz] or 66 to 86 [GHz] band) is more effective than the wireless communication in the low frequency band such as 2 to 3 [GHz]. It is strongly influenced by the environment between the transmission / reception point (wireless base station) and the wireless terminal. This is due to the fact that the higher the frequency, the stronger the straightness of radio waves and the greater the spatial propagation loss of radio signals.

The fluctuation of the quality of the radio link between the radio terminal and the radio base station in the millimeter wave band becomes larger, and it is thought that the state where the quality deteriorates rapidly until the situation where communication becomes impossible frequently occurs. Yes. For this reason, it is necessary to increase the frequency of radio measurement for adjacent base stations so that the connected base station can be quickly changed.

As described above, for example, in a radio base station radio cell operated in the millimeter wave band, when beam sweep transmission of a radio signal such as a synchronization signal is performed, the number of beam sweeps and beam sweep patterns of the same signal are different for each radio cell. It will be possible to set.

When a wireless terminal performs wireless measurement on a plurality of nearby wireless base stations, a measurement gap (wireless measurement gap) needs to be set particularly when performing different frequency measurement. The measurement gap is a time interval in which the wireless network interrupts transmission of a data signal to the wireless terminal and the wireless terminal performs wireless measurement.

The current LTE specification does not assume beam sweep transmission of synchronization signals. For this reason, beam sweep transmission of the synchronization signal is performed in the peripheral base station, and when different beam sweep numbers and beam sweep patterns are set for each radio base station, the measurement gap pattern set for the radio terminal is It becomes complicated. The number of measurement gaps and the length of time are expected to increase, but the measurement gaps to be set will be excessive, and there will be no need to interrupt data transmission from the wireless base station to which the wireless terminal is connected. It will be longer.

According to the above-described embodiment, for example, the length of the measurement gap can be set for each measurement gap, so that efficient measurement can be performed even when different beam sweep numbers and beam sweep patterns are set in the radio base station. It becomes possible to set a gap.

DESCRIPTION OF SYMBOLS 100 Wireless communication system 110 Connection base station 120 Peripheral base station 121,122,510 Beam 130 Terminal 200 Cell 300 Radio frame 311 321 PSS
312,322 SSS
330 Sync signal period 410, 521 to 544, 610, 620, 630, 711 to 726 Gap period 411, 611, 621, 631 Measurement gap 412, 612, 622, 632, 633 Communication period 413 Gap shift period 550 Division search 810 UE
820 EUTRAN
911 to 913, 920 Maximum detection time vs. loss ratio 1001 Inter-base station communication unit 1002 Beam sweep control unit 1003 Synchronization signal weight coefficient calculation unit 1004 Synchronization signal generation unit 1005 Synchronization signal modulation unit 1006, 1206 Measurement gap control unit 1007, 1207 Transmission Data generation unit 1008, 1208 Encoding / modulation unit 1009 Beamforming / radio transmission unit 1010 Antenna group 1011, 1202 Radio reception unit 1012, 1203 Demodulation / decoding unit 1013, 1204 Reception data processing unit 1014 Transmission signal weight coefficient calculation unit 1100, 1300 Digital circuit 1201 Antenna 1205 Synchronization signal detection / measurement unit 1209 Wireless transmission unit

Claims (11)

A setting unit capable of setting, for each time interval, a length of an intermittent time interval in which a wireless terminal does not need to receive a signal from the own station;
A generation unit that generates a signal including information on the length of the time interval set by the setting unit;
A transmitter that transmits the signal generated by the generator to the wireless terminal;
A radio base station comprising: The setting unit includes a period for setting the time interval having a first length, a period for setting the time interval having a second length shorter than the first length, and a period shorter than the first length. Determining the length of the time interval such that the time interval of 3 and the period of setting the time interval different in timing from the time interval of the second length are mixed. The radio base station according to claim 1. The setting unit changes at least one of a phase difference between the plurality of transmission antennas and a phase difference between transmission streams of the same signal each time the same signal is transmitted using the plurality of transmission antennas. Based on information about changing at least one of a phase difference between the plurality of transmit antennas and a phase difference between transmission streams of the same signal received from another radio base station capable of The radio base station according to claim 1 or 2, wherein a length is determined. The setting unit sets the length of the period for setting the time interval for each period,
The generation unit generates a signal including information on the length of the period set by the setting unit;
The radio base station according to any one of claims 1 to 3, wherein: The setting unit changes at least one of a phase difference between the plurality of transmission antennas and a phase difference between transmission streams of the same signal each time the same signal is transmitted using the plurality of transmission antennas. The length of the period based on information about changing at least one of a phase difference between the plurality of transmission antennas and a phase difference between transmission streams of the same signal received from another radio base station capable of The radio base station according to claim 4, wherein the radio base station is determined. The setting unit includes a length of a period in which the other radio base station transmits the same signal, a phase difference between the plurality of transmission antennas by the other radio base station, and a transmission stream of the same signal. 6. The radio according to claim 5, wherein a period length for setting the time interval is set for each period in accordance with a comparison result with a period length for switching at least one of the phase differences. base station. The radio base station according to any one of claims 3, 5, and 6, wherein the same signal is a synchronization signal. Includes information on the length of the time interval from the first radio base station capable of setting, for each time interval, the length of an intermittent time interval in which the wireless terminal may not receive a signal from the own station A first receiver for receiving a signal;
Based on the signal received by the first receiver, a signal from the first radio base station is received in a period different from the time period, and a second different from the first radio base station in the time period. Each time a wireless base station transmits the same signal from its own station using a plurality of transmission antennas, at least a phase difference between the plurality of transmission antennas and a phase difference between transmission streams of the same signal A second receiving unit for receiving a signal from the second radio base station capable of changing either of them;
A wireless terminal comprising: A first radio base station capable of setting, for each time interval, a length of an intermittent time interval in which a radio terminal does not need to receive a signal from the own station;
A signal from the first radio base station is received in a section different from the time section, and the second radio base station is different from the first radio base station in the time section, and a plurality of transmission antennas are transmitted from the own station. From the second radio base station that can change at least one of the phase difference between the plurality of transmission antennas and the phase difference between the transmission streams of the same signal each time the same signal is transmitted using A wireless terminal that receives the signal;
A wireless communication system comprising: A radio base station capable of setting, for each time interval, a length of an intermittent time interval in which a radio terminal does not need to receive a signal from the own station,
Generating a signal including information on the length of the set time interval;
Transmitting the generated signal to the wireless terminal;
A wireless communication method. Wireless terminal
Includes information on the length of the time interval from the first radio base station capable of setting, for each time interval, the length of an intermittent time interval in which the wireless terminal may not receive a signal from the own station Receive the signal,
Based on the received signal, a signal from the first radio base station is received in a section different from the time section, and the second radio base station is different from the first radio base station in the time section, Each time the same signal is transmitted from a local station using a plurality of transmission antennas, it is possible to change at least one of the phase difference between the plurality of transmission antennas and the phase difference between transmission streams of the same signal. Receiving a signal from the second radio base station,
A wireless communication method.

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