JPH1155208A - Wireless burst signal receiver - Google Patents

Abstract

(57) [Problem] To reduce erroneous detection of a unique word when maintaining frame synchronization by receiving a TDMA-type burst and detecting the unique word thereof. SOLUTION: The timing and width of an aperture gate at the time of unique word detection are controlled, the aperture gate for unique word detection is set wide for the first synchronization establishment, and thereafter the aperture gate is set narrow. Prevent erroneous detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to communication between a radio base station and a radio terminal. In particular, wireless LAN (Local
The present invention relates to detection of a radio burst signal in an area network (PW) system, a public wireless communication system, or a WLL (Wireless Local Loop) system.

[0002]

2. Description of the Related Art Time Division Multiple Access
In communication using ltiple access (hereinafter referred to as "TDMA"), a signal is divided into bursts, and a signal is received by detecting a unique word preceding data in each burst. Aperture gate (narrow aperture) to suppress erroneous detection when detecting unique words
Is generally used.

FIG. 14 is a diagram for explaining unique word detection by an aperture gate, and shows a signal structure of a TDMA frame and its constituent slots, an aperture gate corresponding thereto, and a unique word detection signal for the k-th slot. The narrow aperture is a method for suppressing erroneous detection of a unique word.
In the case of performing the unique word detection of the MA slot, this is a method of validating the unique word only during the time when it is estimated that the unique word is detected. In other slots or in a pattern portion different from the unique word, it is meaningless to detect the unique word, and it only causes a false detection of the unique word. Therefore, it is necessary to detect only the vicinity of the unique word of the corresponding slot in the TDMA frame. An aperture gate is used as a gate signal for making it valid.

[0004] The time of the aperture gate in the radio base station needs to be longer than the maximum propagation delay time so that communication with a radio terminal located at the maximum distance in the zone is possible. That is, since the timing of unique word detection differs depending on the propagation distance, it is necessary to turn on the aperture gate so as to cover all propagation delays in the service zone.

[0005]

Recently, a high-speed wireless access system using the TDMA system has been studied. As the transmission speed increases, the symbol length decreases. Assuming that the propagation distance is constant, the propagation delay time requires a relatively large number of symbol lengths as an aperture gate as the transmission speed becomes higher, when the symbol length is considered as a unit. This is equivalent to a longer aperture gate time from the viewpoint of unique word detection. If the aperture gate time becomes longer, unique word detection is enabled even when an uncertain signal is input to the unique word detector, and thus erroneous detection of unique words increases. In order to suppress erroneous detection of a unique word, it is generally necessary to lengthen the pattern length of the unique word, which causes problems such as a decrease in transmission efficiency and an increase in the circuit size of the unique word detection circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radio burst signal receiving apparatus which solves such a problem and can reduce erroneous detection of a unique word without having to lengthen the pattern length of the unique word.

[0007]

According to a first aspect of the present invention, there is provided a receiving means for receiving a burst signal of a time division multiple access system, and detecting a unique word included in the received burst signal to perform frame synchronization. In a wireless burst signal receiving apparatus, comprising: a frame synchronizing means for holding and a unique word detection control means for enabling the unique word detection by the frame synchronizing means at a time when it is presumed that a unique word is detected. The means sets the time at which unique word detection is enabled upon reception of the first burst signal to a first time length equal to or greater than the maximum length of the estimated time, and sets the time following the frame in which the unique word is detected. Means to set the time for which unique word detection is valid from the frame to the second time length shorter than the first time length Radio burst signal receiving apparatus according to claim Mukoto is provided.

According to a second aspect of the present invention, a receiving means for receiving a burst signal of the time division multiple access system, a frame synchronizing means for detecting a unique word contained in the received burst signal and maintaining frame synchronization. And a unique burst detection control means for enabling unique word detection by frame synchronization means at a time at which a unique word is estimated to be detected. And a dedicated channel allocated exclusively to each wireless terminal. The unique word detection control means enables unique word detection for the shared channel. Set the time to the first time length that is equal to or greater than the maximum Radio burst signal receiving apparatus characterized by comprising means for setting the first time the second time length shorter than the length of time to enable the unique word detection is provided to channel.

[0009] The wireless burst signal receiving apparatus according to the first or second aspect may be provided in a wireless base station that receives burst signals from a plurality of wireless terminals, or may be provided in each wireless terminal. Good.

[0010] When provided in the radio base station, the frame synchronization means and the unique word detection control means are provided for each of the plurality of radio terminals, and the first time length is set to be equal to or longer than the maximum propagation delay time in the service zone. It is preferable to set the time length and set the second time length to a time length shorter than the propagation delay time.

[0011] In both cases where the unique word detection control means is provided in the radio base station and the radio terminal, the unique word detection control means includes means for storing the timing of the detected unique word, and the timing stored in the means. Means for updating the unique word detection timing in the next frame based on the In this case, the unique word detection control means further includes a means for setting a time period during which the unique word detection is valid in accordance with the number of times the unique word is not detected in the frame synchronization means. It is good to include.

[0012]

FIG. 1 shows a TDMA embodying the present invention.
2 shows a configuration example of a communication device. This TDMA communication device includes a radio base station 1 and a radio terminal 2- in its service zone.
1, 2-2 can be communicated. The wireless terminal 2-3 outside the service zone cannot communicate with the wireless base station 1.

FIG. 2 shows an example of the format of a TDMA frame used in this device, and FIG. 3 shows an example of the format of each channel in the TDMA frame. TDMA
The frame is divided into a plurality of channels, and a burst is transmitted on each channel. The burst of each channel is composed of a guard time, a clock recovery code, a unique word, and a message.

FIG. 4 shows a configuration example of the radio base station 1. The wireless base station 1 includes a transmission signal processing unit 11, a wireless transmission unit 12,
It includes a wireless reception unit 13, a reception signal processing unit 14, a unique word detection unit 15, a frame synchronization unit 16, a unique word detection control unit 17, and a memory 18. The transmission signal processing unit 11 processes a signal to be transmitted to each wireless terminal,
Insert into each slot of the frame. The wireless transmission unit 12 transmits the TDMA frame to a wireless section. The wireless receiving unit 13 receives a burst signal from each wireless terminal, and the received signal processing unit 14 processes the burst signal according to the synchronization signal from the frame synchronization unit 16. The unique word detection unit 15 detects a unique word included in the received burst signal. The frame synchronization unit 16 maintains frame synchronization according to the unique word detection result by the unique word detection unit 15. The unique word detection control unit 17 performs control to enable unique word detection by the unique word detection unit 15 at a time when it is estimated that a unique word is detected. The memory 18 stores the timing of the unique word detected by the unique word detection unit 15. Since the detection of the unique word and the control of the frame synchronization are performed for each wireless terminal, the drawing shows the unique word detection unit 15 and the frame synchronization unit 1.
6, a plurality of unique word detection control units 17 and memories 18 are shown. Practically, the same one can be used in a time-sharing manner.

FIG. 5 shows a flowchart of the receiving operation of the radio base station. The wireless base station waits for the first uplink burst from the wireless terminal at the timing (slot) of the uplink burst in the TDMA frame. At this time, unique word detection is performed by setting the aperture gate time to a time Tw equal to or longer than the maximum delay time. When an uplink burst from the wireless terminal is detected, its timing is stored, and in the next frame, unique word detection is performed only in the vicinity of the timing using an aperture gate having a time Tn shorter than the maximum propagation delay time. Since the reception timing of the uplink burst differs for each wireless terminal, the above processing is managed for each wireless terminal.

FIG. 6 shows the relationship between the aperture gate of the radio base station for the first uplink burst from the radio terminal and the timing of actual unique word detection from each radio terminal. For the first slot, the time of the aperture gate in the radio base station should be longer than the maximum propagation delay time so that communication with the radio terminal located at the maximum distance in the service zone is possible. is necessary.

FIG. 7 shows switching of the aperture gate for one wireless terminal. Here, it is assumed that the wireless terminal #i transmits a TDMA burst to the wireless base station using the channel #i. The radio base station is ready to receive a TDMA burst from the radio terminal on the uplink channel (channel # 1). At this time, the aperture gate time is T
w. When the burst is received on channel #i, the radio base station stores the delay time Di of the unique word detection timing of the received burst, and in the next (next frame) unique word detection of channel #i, the timing is determined. Detection is performed by an aperture gate of Tn (Tn <Tw) as a center.

Thus, for the first slot,
By setting the time of the aperture gate in the wireless base station to be equal to or longer than the maximum propagation delay time, it is possible to communicate with the wireless terminal located at the maximum distance in the service zone.
On the other hand, for subsequent slots, unique words can be detected with a short aperture gate time at a highly reliable timing, and erroneous detection of unique words can be suppressed, so that good quality can be obtained with a shorter unique word length. .

In a system in which a wireless terminal such as a WWL does not move during communication, the opening timing of the aperture gate does not deviate from the first reception timing, and only the first reception timing needs to be stored. In contrast,
In a system that allows the movement of the wireless terminal during communication, the movement may change the distance from the wireless base station and may deviate from the initial reception timing. Therefore, it is desirable to update the reception timing as needed even during communication to prevent the unique word from being undetectable outside the width of Tn. Therefore, the unique word detection timing is stored in the memory 18 and updated as needed, so that the unique word detection timing is controlled so as not to be outside the aperture gate. The timing is updated, for example, k times in N frames or when M symbols are shifted.

FIG. 8 shows an example of changing the aperture gate time when a unique word is not detected.

When the transmission channel quality is normal, erroneous detection can be suppressed, so that the aperture gate time should be short. However, if the unique word non-detection time due to the deterioration of the transmission channel continues for a long time, the clock error between the radio base station and the radio terminal will increase. In some cases, the TDMA frame timing on the transmitting side and the receiving side is shifted due to the movement of the wireless terminal and the unique word detection timing does not fall within the range of the aperture gate even after the transmission path quality is restored, and communication cannot be restored. is there. Therefore,
If a unique word is not detected, the aperture gate time is increased in the range from Tn to Tw in accordance with the duration (number of times). Thereby, it is possible to prevent the aperture gate from coming off the aperture gate for a certain period of time.

FIGS. 8A and 8B show an aperture gate and a unique word detection signal in a normal radio base station. If a unique word non-detection occurs and continues N1 times, the aperture gate is set to Tn + Δ as shown in FIG.
Change to T1. If non-detection continues N2 times,
As shown in (d), Tn + ΔT1 + ΔT2. As described above, the aperture gate time is increased with Tw as the upper limit of the delay covering the time from zero to the maximum depending on the duration (number of times) of the non-detection of the unique word. By gradually increasing the length, erroneous detection of unique words can be minimized. When the quality of the transmission path is restored and a unique word is detected in the aperture gate as shown in (e),
At the detection timing, it returns to the aperture gate of Tn as shown in (f).

FIG. 9 shows another example of the signal configuration of the TDMA frame, FIG. 10 is a flowchart example of the reception operation of the radio base station corresponding to this signal configuration, and FIG. 11 shows an example of switching the aperture gate for the radio terminal.

In the signal configuration shown in FIG. 9, in the TDMA frame, an access channel (Ac) shared by all wireless terminals in the service zone and used for initial access is used.
h), a control channel (Cch) for exclusively assigning control information to each wireless terminal and communicating control information, and a user channel (Uch) for constantly exchanging user data. The channel format is equivalent to that of FIG. Each wireless terminal performs initial access using Ach, and assignment of Cch is specified by an Ach message. Uch controls allocation using Ach or Cch. For a system using such a TDMA frame format, see “A Study of Antenna / Radio Channel Control in High-Speed Wireless Access System”,
It is shown in 997 of the IEICE General Conference B-5-269.

For a TDMA frame having such a signal configuration, the aperture gate in the unique word detection of Ach is Tw, the aperture gate in the unique word detection of Cch and Uch is Tn, and the reception of the upstream Ach is performed for each wireless terminal. Up Cch based on timing
And the reception timing of the uplink Uch. As a result, the unique words of Cch and Uch can be shorter than the unique words of Ach. Also in this case, when the wireless terminal moves, Cch during communication is performed.
And Uch reception timing is updated as needed.

Here, the operation of the radio base station will be described in more detail assuming that TDMA radio terminal #i transmits a TDMA burst to the radio base station using channel #i. First, the radio base station is ready to receive a TDMA burst from a radio terminal in the uplink Ach. At this time, the aperture gate time is set to Tw. Upon receiving the burst, the radio base station stores the delay time Di of the unique word detection timing of the received burst. At this time, the wireless base station associates the detected unique word detection timing with which wireless terminal by reading the identification code of the Ach message or the like. If Cch # i is assigned to wireless terminal # 1, Cch #
In the detection of the unique word of i, the timing without delay is centered on the timing delayed by Di.
Detection is performed by an aperture gate of n (Tn <Tw). The same applies to Uch.

FIG. 12 shows an example of the configuration of a wireless terminal.
Shows a flowchart of the receiving operation.

The radio terminal includes a transmission / reception sharing unit 21, a radio reception unit 22, a reception signal processing unit 23, a transmission signal processing unit 24,
It includes a wireless transmission unit 25, a unique word detection unit 26, a frame synchronization unit 27, a unique word detection control unit 28, and a memory 29. The transmission / reception sharing unit 21 is for sharing an antenna for transmission / reception, and transmits a reception signal to the radio reception unit 2
2 and outputs a signal from the wireless transmission unit 25 to the antenna. The wireless receiving unit 22 receives a burst signal from the wireless base station, and the received signal processing unit 23 processes the burst signal according to the synchronization signal from the frame synchronization unit 27. The transmission signal processing unit 24 processes a signal to be transmitted to the wireless base station, processes a signal to be transmitted to each wireless terminal, and outputs the signal according to a synchronization signal from the frame synchronization unit 27. Radio transmitting section 25 outputs the signal as a burst signal. The unique word detector 26 detects a unique word included in the received burst signal. The frame synchronization unit 27 holds the frame synchronization according to the unique word detection result by the unique word detection unit 26. The unique word detection control unit 28 performs control to enable unique word detection by the unique word detection unit 26 at a time when it is estimated that a unique word is detected. The memory 29 stores the timing of the unique word detected by the unique word detection unit 26.

The reception operation of this wireless terminal is performed by the fact that there is only one communication partner, the time Tw of the aperture gate,
The operation is the same as that of the radio base station except that Tn is different from that of the radio base station.

[0030]

As described above, according to the present invention, the start timing and time of the aperture gate are controlled for each wireless terminal using the previously obtained unique word detection timing. As a result, the aperture gate time can be reduced, and erroneous detection of a unique word during communication can be suppressed to a minimum.

According to the present invention, erroneous detection of a unique word is suppressed, so that the pattern length of the unique word can be reduced for a desired error rate. Therefore, transmission efficiency (TDMA frame use efficiency) is improved,
The hardware scale of the unique word detector can be reduced.

When the aperture gate time is controlled in accordance with the duration (number of times) of non-unique word non-detection, erroneous detection of a unique word when transmission quality is degraded can be suppressed to a minimum.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a TDMA communication apparatus embodying the present invention.

FIG. 2 is a diagram showing an example of a TDMA frame format.

FIG. 3 is a diagram illustrating an example of a format of an individual channel in a TDMA frame.

FIG. 4 is a block diagram showing an example of a radio base station.

FIG. 5 is a flowchart of a receiving operation of the wireless base station.

FIG. 6 is a diagram showing the relationship between the aperture gate of the wireless base station for the first uplink burst from the wireless terminal and the actual unique word detection timing from each wireless terminal.

FIG. 7 is a diagram illustrating switching of an aperture gate for one wireless terminal.

FIG. 8 is a diagram showing an example of changing the aperture gate time when a unique word is not detected.

FIG. 9 is a diagram showing another signal configuration example of a TDMA frame.

FIG. 10 is a flowchart of a reception operation of a radio base station corresponding to this signal configuration.

FIG. 11 is a diagram illustrating switching of an aperture gate for one wireless terminal.

FIG. 12 is a block diagram illustrating an example of a wireless terminal.

FIG. 13 is a flowchart of a receiving operation.

FIG. 14 is a view for explaining unique word detection by an aperture gate.

[Explanation of symbols]

 Reference Signs List 1 radio base station 2-1 to 2-3 radio terminal 11, 24 transmission signal processing unit 12, 25 radio transmission unit 13, 22 radio reception unit 14, 23 reception signal processing unit 15, 26 unique word detection unit 16, 27 frame Synchronization unit 17, 28 Unique word detection control unit 18, 29 Memory 21 Transmission / reception shared unit

Claims (5)

[Claims] 1. A receiving means for receiving a burst signal of the time division multiple access system, a frame synchronizing means for detecting a unique word included in the received burst signal to maintain frame synchronization, and when a unique word is detected. A unique word detection control means for enabling a unique word detection by the frame synchronization means at an estimated time, wherein the unique word detection control means comprises: The time to enable detection is set to a first time length equal to or longer than the maximum length of the estimated time, and the time to enable unique word detection from the frame next to the frame where the unique word is detected Means for setting a second time length shorter than the first time length. Blast signal receiving device. 2. A receiving means for receiving a burst signal of the time division multiple access system, a frame synchronizing means for detecting a unique word included in the received burst signal to maintain frame synchronization, and when a unique word is detected. A wireless burst signal receiving device comprising: a unique word detection control unit that enables unique word detection by the frame synchronization unit at an estimated time; wherein a burst signal is shared by all wireless terminals in a service zone. A shared channel for initial access and a dedicated channel assigned exclusively to each wireless terminal are provided, and the unique word detection control means estimates the time to enable unique word detection for the shared channel. To the first time length that is longer than the maximum length of Radio burst signal receiving apparatus characterized by a time to enable the unique word detecting comprises means for setting the first time the second time length shorter than the length respect. 3. A wireless base station which receives burst signals from a plurality of wireless terminals, wherein the frame synchronization means and the unique word detection control means are provided for each of the plurality of wireless terminals, 3. The wireless burst signal reception according to claim 1, wherein one time length is set to a time length equal to or longer than the maximum propagation delay time in the service zone, and the second time length is set to a time length less than the propagation delay time. apparatus. 4. The unique word detection control means includes means for storing the timing of the detected unique word, and means for updating the timing of detecting the unique word in the next frame based on the timing stored in the means. The wireless burst signal receiving device according to claim 1, further comprising: 5. The unique word detection control means sets a time period during which the unique word detection is valid according to the number of times that the non-detection of the unique word occurs in the frame synchronization means. 5. The radio burst signal receiving apparatus according to claim 4, further comprising: means.