JP2007221357A - Wireless relay device and wireless relay method - Google Patents

Abstract

[PROBLEMS] To realize a wireless relay device capable of extending the distance of a line while ensuring sufficient line quality even in rain.
In a radio relay system including radio relay apparatuses 1 and 2, a rain attenuation amount is calculated by a rain attenuation amount calculation 34. This adaptive modulation that takes into account the amount of rainfall attenuation performs adaptive modulation that employs the optimum modulation method according to the propagation situation, compares the required reception level in that modulation method with the actual reception level, and levels between both levels According to the difference, transmission level information is generated and transmission power control is performed.
[Selection] Figure 5

Description

  The present invention relates to a wireless relay device and a wireless relay method, and more particularly to a wireless relay device and a wireless relay method that constitute a wireless relay system used as a wireless transmission path in a mobile communication network or the like.

  Wireless relay systems are used in various applications such as subscriber transmission lines, relay systems, and backbone systems. Among them, the current maximum transmission capacity is 155.52 Mbps in a radio entrance system used as a base station transmission path (between a radio base station controller and a radio base station) in a mobile communication network (for example, Non-patent document 1, Non-patent document 2).

In mobile communication networks, wireless access speeds are expected to increase further with the development of wireless broadband communication. Along with this, it is indispensable to increase the capacity and efficiency of frequency utilization by increasing the number of values in the wireless entrance system. Is the situation.
FIG. 9 is a block diagram illustrating a configuration example of a conventional wireless relay system. In the figure, the conventional radio relay system includes a radio relay device 100 connected to the base station control device and a radio relay device 200 connected to the base station device. The interval between the wireless relay device 100 and the wireless relay device 200 is fixed, and the radio wave propagation distance is constant.

  The radio relay device 100 includes an encoding unit 11 that performs encoding processing, a modulation unit 120 that performs multi-level modulation with a predetermined modulation multi-level number, a radio unit 13 that is connected to the antenna ANT1, and multi-level conversion. The demodulator 14 includes a demodulator 14 that performs demodulation on the modulated signal, and a decoder 15 that performs a decoding process. The radio unit 13 includes a transmission unit 13a that performs conversion into a high-frequency signal, a transmission / reception sharing unit 13b that performs input and output of signals to the antenna ANT1, and a reception unit 13c that performs conversion into an intermediate frequency band signal. .

  The radio relay apparatus 200 includes an encoding unit 21 that performs encoding processing, a modulation unit 220 that performs multilevel modulation with a predetermined modulation multilevel number, a radio unit 23 connected to the antenna ANT2, and multilevel conversion The demodulator 24 includes a demodulator 24 that performs a demodulation process on the modulated signal, and a decoder 25 that performs a decoding process. The radio unit 23 includes a transmission unit 23a that performs conversion into a high-frequency signal, a transmission / reception common unit 23b that performs input / output of a signal to / from the antenna ANT2, and a reception unit 23c that performs conversion into an intermediate frequency band signal. . In the radio entrance system employed in the radio relay system having such a configuration, the transmission power and the modulation system are fixed.

  In the figure, the signal transmitted from the antenna ANT1 of the wireless relay device 100 is received by the antenna ANT2 of the wireless relay device 200. After passing through the transmission / reception sharing unit 23b of the radio unit 23, the reception unit 23c down-converts it to the intermediate frequency band. Then, the signal is demodulated by the demodulator 24 and then decoded by the decoder 25. Further, the signal input from the encoding unit 21 of the radio relay apparatus 200 to the modulation unit 220 is multi-valued with the corresponding modulation multi-value number. This signal is converted into a high frequency signal by the transmission unit 23a, then input to the transmission / reception common unit 23b, and transmitted from the antenna ANT2 toward the radio relay apparatus 100.

Here, in the current radio entrance line design of 11 GHz band or more, a required carrier-to-noise ratio (hereinafter abbreviated as C / N) determined for each modulation method is an annual line unavailability. It is designed to allow a required rainfall margin Zp corresponding to p. In other words, route parameters such as maximum propagation distance and antenna aperture are designed assuming that it is raining. Similarly, the transmission power is always constant at a value set assuming raining.
By the way, a technique (for example, Patent Document 1) that adaptively changes the modulation method according to the state of the transmission path, and a technique for measuring the attenuation amount during precipitation and controlling the power level (for example, Patent Document 2) are also available. Are known.

JP 2003-319457 A JP-A-5-218924 Koizumi et al., “Development of 11/15/18 GHz band high-capacity digital radio equipment”, 2005 Shinbun University B-5-246. Tanizawa et al., “11/15/18 GHz band high-capacity wireless device”, 2005 Shinbun University B-5-247

When the modulation multi-level number is fixed, the current circuit design is premised on satisfying a certain line disconnection rate during rainfall as described above. For this reason, as the number of values increases, the allowable rain margin becomes smaller, and the maximum propagation distance becomes smaller when considering the same interruption rate.
This will be described with reference to FIG. This figure is a diagram showing the total C / N characteristics according to the propagation distance in fine weather and rainy weather. In the figure, the horizontal axis represents the propagation distance, and the vertical axis represents the C / N value. Further, in the figure, the solid line indicates the total C / N during rainy weather, and the broken line indicates the total C / N during fine weather.

  Referring to the figure, it can be seen that the resistance to rain deterioration is lost as the modulation scheme becomes multi-valued (multi-value number; modulation β> modulation α). That is, paying attention to the total C / N during rainy weather, the maximum propagation distance of the modulation β having a large multi-value number is smaller than the modulation α having a small multi-value number indicated by a one-dot chain line. In the trial calculation, in the route having a maximum propagation distance of 2.2 km by 64 QAM (Quadrature Amplitude Modulation), the distance is halved to 1.0 km by 1024 QAM.

  In addition, in the current line design of the 11 GHz band or higher, as described above, the line design is based on heavy rain with low annual frequency. For this reason, even in a route that can be designed with multiple margins in fine weather, the circuit may not be constructed because the required rain margin is not satisfied. Furthermore, the extra power used as a margin in fine weather is a factor of interference with other routes.

As described above, line design is performed on the wireless transmission path based on a certain error rate criterion. At that time, the required C / N is determined for each modulation method, and the more the modulation method is multi-valued, the larger the required C / N is and the less margin for rainfall is. There is a problem of coming.
The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to use adaptive modulation that employs an optimal modulation scheme according to the propagation situation, and to obtain the required reception level in the modulation scheme. Compared to the actual reception level, generates transmission level information according to the level difference between the two levels, and performs transmission power control, so that the line distance can be increased while ensuring sufficient line quality even during rain To provide a wireless relay device and a wireless relay method that can be extended.

  A radio relay apparatus according to claim 1 of the present invention is a radio relay apparatus that constitutes a radio relay system together with other devices facing each other, and is a reception level measuring unit that measures a reception level of a signal transmitted from the other apparatus. And adaptive modulation means for setting a modulation multi-level number of a transmission signal to the other device based on a difference between a current reception level measured by the reception level measurement means and a predetermined required reception level; And transmission power control means for setting a transmission level of a transmission signal to the other device based on a difference between the current reception level and the required reception level. Use adaptive modulation that adopts the optimal modulation method according to the propagation situation, compare the required reception level in that modulation method with the actual reception level, and send the transmission level information according to the level difference between both levels. By generating and performing transmission power control, it is possible to extend the distance of the line while ensuring sufficient line quality.

The wireless relay device according to claim 2 of the present invention further includes storage means for storing a table in which a required reception level corresponding to each modulation multi-level number is defined in claim 1, with reference to the contents of the table. The required transmission level is determined. By determining the required transmission level based on a preset table, transmission power control can be performed appropriately.
According to a third aspect of the present invention, the wireless relay device according to the first aspect further includes a rain attenuation amount calculating means for calculating a rain attenuation amount based on a signal transmitted from the other device, and the adaptive modulation means includes: The modulation multi-value number of the transmission signal to the other device is set with reference to the rain attenuation amount calculated by the rain attenuation amount calculating means. With this configuration, it is possible to extend the distance of the line while ensuring sufficient line quality even during rain.

  According to a fourth aspect of the present invention, the wireless relay device according to the third aspect stores a table in which the required reception level corresponding to each modulation multi-level number and the rain attenuation amount corresponding to each modulation multi-level number are defined. It further comprises storage means, and the required transmission level is determined with reference to the contents of the table. By determining the required transmission level based on a preset table, transmission power control can be performed appropriately.

The radio relay apparatus according to claim 5 of the present invention is the radio relay apparatus according to claim 3 or 4, wherein the rain attenuation amount calculating means includes data relating to a transmission level of the signal inserted in a signal transmitted from the other apparatus, and The rain attenuation amount is calculated based on a difference from the current reception level measured by the reception level measuring means. By using the data extracted from the received signal, the rain attenuation can be easily calculated.
The wireless relay device according to a sixth aspect of the present invention is the wireless relay device according to any one of the first to fifth aspects, wherein the adaptive modulation means includes a threshold value for increasing the multi-value number and a threshold value for reducing the multi-value number. Is characterized by having a difference. With this configuration, it is possible to prevent the modulation multi-level number switching from flapping.

According to a seventh aspect of the present invention, in the radio relay apparatus according to any one of the first to sixth aspects, information indicating a transmission level and a modulation multi-level number is inserted into a signal transmitted to the other apparatus. And an information insertion means. By using the inserted information in the opposing device, transmission power control can be performed appropriately.
A radio relay apparatus according to an eighth aspect of the present invention is the wireless relay apparatus according to any one of the first to sixth aspects, wherein the transmission level and the modulation level are inserted in a signal transmitted from the other apparatus. And an information extraction means for extracting information indicating the transmission level and the switching timing of the transmission level and the modulation multilevel number are made to coincide with those of the other devices.

  A radio relay method according to claim 9 of the present invention is a radio relay method using opposing devices, the reception level measuring step for measuring the reception level of a signal transmitted from another device, and the reception level measuring step. An adaptive modulation step for setting a modulation multi-level number of a transmission signal to the other device based on a difference between the current reception level measured in step 1 and a predetermined required reception level; and the current reception level; And a transmission power control step of setting a transmission level of a transmission signal to the other device based on a difference from the required reception level. Use adaptive modulation that adopts the optimal modulation method according to the propagation situation, compare the required reception level in that modulation method with the actual reception level, and send the transmission level information according to the level difference between both levels. By generating and performing transmission power control, it is possible to extend the distance of the line while ensuring sufficient line quality.

  A radio relay method according to claim 10 of the present invention further includes a storage step of storing a table in which a required reception level corresponding to each modulation multi-level number is defined in claim 9, with reference to the contents of the table The required transmission level is determined. By determining the required transmission level based on a preset table, transmission power control can be performed appropriately.

  According to Claim 11 of the present invention, the wireless relay method according to Claim 9 or 10 further includes a rain attenuation amount calculating step of calculating a rain attenuation amount based on a signal transmitted from the other device, and the adaptive modulation step. Is characterized in that the modulation multi-value number of the transmission signal to the other device is set with reference to the rain attenuation amount calculated in the rain attenuation amount calculating step. In this way, it is possible to extend the distance of the line while ensuring sufficient line quality even during rainfall.

  According to a twelfth aspect of the present invention, a radio relay method according to the twelfth aspect stores a table in which a required reception level corresponding to each modulation multi-level number and a rain attenuation amount corresponding to each modulation multi-level number are defined. A storage step is further included, and the required transmission level is determined with reference to the contents of the table. By determining the required transmission level based on a preset table, transmission power control can be performed appropriately.

  According to Claim 13 of the present invention, in the wireless relay method according to Claim 11 or 12, the rain attenuation amount calculating step includes data relating to a transmission level of the signal inserted in a signal transmitted from the other device, and The rain attenuation amount is calculated from a difference from the current reception level measured in the reception level measurement step. By using the data extracted from the received signal, the rain attenuation can be easily calculated.

A wireless relay method according to a fourteenth aspect of the present invention is the wireless relay method according to any one of the ninth to thirteenth aspects, wherein in the adaptive modulation step, a threshold value for increasing the multi-value number and a threshold value for decreasing the multi-value number. Is characterized by having a difference. With this configuration, it is possible to prevent the modulation multi-level number switching from flapping.
According to claim 15 of the present invention, in the radio relay method according to any one of claims 9 to 14, information indicating a transmission level and a modulation multi-level number is inserted in a signal transmitted to the other device. The method further includes an information insertion step. By using the inserted information in the opposing device, transmission power control can be performed appropriately.

  According to a sixteenth aspect of the present invention, there is provided a radio relay method according to any one of the ninth to fourteenth aspects, wherein a transmission level and a modulation multilevel number inserted in a signal transmitted from the other device. And an information extraction step for extracting information indicating the transmission level, and the switching timing of the transmission level and the modulation multilevel number is made to coincide with that of the other device. By using the information inserted in the opposite device, the control timing can be matched.

  In short, in the present invention, as a means for realizing multi-value modulation schemes without reducing the maximum propagation distance, adaptive modulation employing an optimum modulation scheme according to the propagation situation is used. Further, the required reception level in the selected modulation scheme and the actual reception level are compared in the radio relay apparatus, transmission level information is generated according to the level difference between the two levels, and transmission power control is performed. With this configuration, it is possible to prevent the modulation multi-level number switching from flapping.

  According to the present invention, it is possible to extend the distance of a line while ensuring sufficient line quality even when it rains. Therefore, it is possible to reduce the number of wireless entrance lines and to construct a communication network at a low cost. Similarly, when compared at the same transmission distance, the annual unavailability decreases, so that the reliability of the network is improved. In addition, in order to suppress transmission power in fine weather, it is possible to reduce power consumption, and to effectively reduce the interference of other lines, thus enabling effective use of frequencies.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.
(System configuration example)
FIG. 1 is a block diagram showing a configuration of a wireless relay system using a wireless relay device according to a first embodiment of the present invention. The distance between the wireless relay device 1 and the wireless relay device 2 constituting this wireless relay system is fixed, and the radio wave propagation distance is constant.

  In the figure, the radio relay apparatus 1 connected to the base station control apparatus has a modulation multilevel number extraction unit that extracts the modulation multilevel number from the output of the demodulation unit 14 in the configuration of the radio relay apparatus 100 in FIG. 16, a modulation / demodulation multilevel number control unit 17 that controls the modulation / demodulation multilevel number according to the modulation multilevel number extracted by the modulation multilevel number extraction unit 16, and a transmission level control unit that controls the transmission level of the transmission unit 13a 18 and a transmission power control information extraction unit 19 that extracts transmission power control information from the output of the demodulation unit 14 are added. Note that the adaptive modulation unit 12 is used instead of the modulation unit 120.

  The radio relay apparatus 2 connected to the base station apparatus stores a reception level extraction unit 26 that extracts a reception level from the reception unit 23c and initial setting information in the configuration of the radio relay apparatus 200 in FIG. A memory 27, a transmission level determination unit 28 that determines a transmission level based on the reception level extracted by the reception level extraction unit 26, a modulation multilevel number determination unit 29 that determines the modulation multilevel number, and a modulation level A modulation / demodulation multi-value control unit 30 that controls the modulation / demodulation multi-value number according to the modulation multi-value number determined by the value number determination unit 29, a transmission power control unit 31 that controls the transmission power of the transmission unit 23a, and a wireless relay In this configuration, an information addition unit 32 that adds information on the transmission power value and the modulation multi-level number is added to the transmission frame to the apparatus 1. Note that an adaptive modulation unit 22 is used instead of the modulation unit 220.

  An outline of the operation of the wireless relay system having the above configuration will be described. In the wireless relay device 2, the reception level Pr extracted by the reception level extraction unit 26 is sent to the transmission level determination unit 28. Here, the transmission level determination unit 28 and the modulation multilevel number determination unit 29 determine the transmission level and the modulation multilevel number based on the reception level Pr and the initial setting information stored in the memory 27.

Next, the transmission power control unit 31 controls the output of the amplifier in the transmission unit 23a based on the determined transmission level information, thereby setting the transmission level of the wireless relay device 2 to a desired value. Further, based on the determined modulation multilevel number information, the modulation / demodulation multilevel number control unit 30 changes the modulation multilevel number of the adaptive modulation unit 22 to set the modulation multilevel number to a desired value.
Further, the information adding unit 32 adds information on the transmission power value and the modulation multi-level number to the header part of the transmission frame to the radio relay device 1 and sends the information to the radio relay device 1. For example, as shown in FIG. 2, the transmission frame 300 includes a header part 301 and a payload part 302, and the information adding part 32 includes information on the transmission power value and the modulation multilevel number in the header part 301. Is added.

  Returning to FIG. 1, the wireless relay device 1 extracts information of the header part added by the wireless relay device 2. That is, the modulation multilevel number extraction unit 16 extracts the modulation multilevel number, and the transmission power control information extraction unit 19 extracts the transmission power value. Then, the modulation / demodulation multi-level number control unit 17 controls the adaptive modulation unit 12 and the demodulation unit 14 in accordance with the extracted modulation multi-level number. Further, according to the extracted transmission power value, the transmission level control unit 18 controls the output of the amplifier in the transmission unit 13a.

Note that the information on the modulation multi-level number added in the information adding unit 32 is also added with information on the switching timing so that the demodulating unit 14 can synchronize the switching timing. For example, in the demodulation units 14 and 24 of the wireless relay device 1 and the wireless relay device 2, the demodulation method is switched in accordance with the timing at which the modulation multi-level number transmitted from the opposite device is changed.
The feature of the operation of the present embodiment is that the maximum transmission power information (Pt_max) and the required reception level table information for each modulation multi-level number are stored in advance in the memory 27 in the radio relay apparatus 2, and the required reception level table Is used to determine the modulation level (modulation α) by comparing the transmission level information (Pt ′) calculated with reference to the maximum transmission power information (Pt_max).

(System operation)
The operation of this system will be described with reference to the flowchart of FIG.
In the figure, the wireless relay device 2 measures the reception level (Pr) (step S101). Then, the difference between the required reception level (Prα) and the current reception level (Pr) in the current modulation multilevel number (modulation α) is extracted (step S102). Thereby, the optimum transmission level (Pt ′) is determined (step S103).

  Next, by determining the difference between the determined transmission level information (Pt ′) and maximum transmission power information (Pt_max), it is determined whether or not the modulation multi-level number is switched (step S104). Here, the wireless relay device 2 is controlled based on the generated transmission level information (Pt ′) and modulation multilevel number information (modulation α) (steps S105a and S105b). At the same time, a signal added with the transmission power control information and the like is transmitted to the wireless relay device 1 (step S106), and the wireless relay device 1 is controlled.

The wireless relay device 1 extracts transmission power control information and modulation multilevel number control information from the received signal (steps S107a and S107b). Transmission power is controlled based on the extracted transmission power control information (step S108a). Further, the modulation multi-level number is controlled by the extracted modulation multi-level number control information (step S108b).
Here, with reference to FIG. 4, the determination flow of the transmission level (Pt ′) and the determination of whether or not the modulation multi-level number is changed (the process of the broken line portion in FIG. 3) will be described in detail.

The memory 27 in the wireless relay device 2 stores the following information as initial setting information.
Memory information (1): Maximum transmission power information (Pt_max)
Memory information (2): Required reception level table for each modulation multi-level number The memory information (1) is, for example, Pt_max = + 30 dBm.

  The required Pr of the memory information (2) is a numerical value obtained by adding thermal noise (kTBF) and a margin to the theoretical C / N in each modulation method, and indicates the limit point of the reception level. Here, k is the Boltzmann constant, T is the absolute temperature, B is the passband width of the receiver, and F is the noise figure of the receiver. Here, when the required Pr value when the absolute temperature is 300 K, the equivalent noise bandwidth is 40 MHz, the noise figure is 5 dB, and the margin is not expected, the required Pr of “1024QAM” is −55 dBm, and the required Pr of “256QAM” is − The required Pr for 62 dBm, “64QAM” is −68 dBm, the required Pr for “Modulation α” is Prα, and the required Pr for “Modulation α + 1” is Prα + 1.

First, the required reception level (Prα) is calculated from the current modulation multilevel number (modulation α) with reference to the memory information (2) (step S201). Next, the calculated required reception level (Prα) is compared with the current reception level (Pr) (step S202). Based on the comparison result, transmission level information (Pt ′) optimum for the current propagation path condition is determined.
The subsequent processing will be described separately for the operation of increasing the current transmission level (Pt) and the operation of decreasing it.

  In the case of an operation of increasing the current transmission level (Pt), the determined transmission level information (Pt ′) is determined to be the maximum transmission power by referring to the memory information (1) for the determined transmission level information (Pt ′). If it is less than (Pt_max), the transmission level is determined as Pt ′ (steps S202 → S203 → S204 → S205). On the contrary, when the determined transmission level information (Pt ′) exceeds the maximum transmission power (Pt_max), the modulation multi-level number is multi-valued (modulation α−1) (steps S202 → S203 → S204). → S206), the transmission level (Pt) and the reception level (Pr (α-1)) are compared again, and the generation flow of the transmission level information (Pt ′) is performed again.

  On the other hand, in the operation of decreasing the current transmission level (Pt), if the value of (Pt_max−Pt) is less than the value of (Prα−Pr (α + 1) + Δ), the transmission level is set to the transmission level information (Pt ′ (Step S202 → S207 → S208 → S209). Conversely, if the value of (Pt_max−Pt) is equal to or greater than (Prα−Pr (α + 1) + Δ), the modulation multi-value number is changed to modulation (α + 1) (steps S202 → S207 → S208 → S210), and again. Pr and Pr (α + 1) are compared, and the transmission level information (Pt ′) generation flow is performed again.

  Note that “Δ” applied to Prα−Pr (α + 1) + Δ is set when switching back from modulation (α + 1) to modulation α in order to prevent variation in modulation system switching between modulation α and modulation (α + 1). Margin. Since this margin is set, there is a difference between a threshold for changing from modulation α to modulation (α + 1) and a threshold for changing from modulation (α + 1) to modulation α. In short, there is a difference between a threshold value for increasing the multi-value number and a threshold value for reducing the multi-value number. An arbitrary value can be set for this margin. In other words, by appropriately setting this margin, when the modulation multi-value number is switched, the original modulation multi-value number does not return immediately, so the timing for increasing the multi-value number and the multi-value number are reduced. There will be a difference in timing.

(Other system configuration examples)
FIG. 5 is a block diagram showing a configuration of a wireless relay system using the wireless relay device according to the second embodiment of the present invention.
In the figure, the radio relay apparatus 1 connected to the base station control apparatus has a configuration in which a transmission level information adding unit 20 for adding transmission level information is added to the configuration of the radio relay apparatus 1 in FIG. The radio relay apparatus 2 connected to the base station apparatus has a transmission level information extraction unit 33 that extracts transmission level information and a rain attenuation that calculates a rain attenuation amount in the configuration of the radio relay apparatus 2 in FIG. In this configuration, an amount calculation unit 34 is added. A transmission power control information generation unit 35 that generates transmission power control information is used instead of the transmission level determination unit 28 in the wireless relay device 2 in FIG.

  In this embodiment, unlike the case of the first embodiment described above, the section parameter information (A), the rainfall attenuation amount table information for each modulation multi-value number, the modulation multi-value number are stored in the memory 27 in the wireless relay device 2. The required reception level table information for each is stored in advance, and the modulation multi-level number and transmission power control information are determined based on the rain attenuation amount (Z) calculated from the section parameter information (A).

(System operation)
The operation of this embodiment will be described with reference to the flowchart of FIG.
In the figure,
The wireless relay device 2 measures the reception level (Pr) and extracts the transmission level (Pt) of the wireless relay device 1 from the received signal (step S301). Then, the rain attenuation amount Z is calculated by referring to the section parameter (A) (step S302). The calculated rainfall attenuation amount Z and the required rainfall margin Zp in the current modulation method are compared, and it is determined whether or not the modulation method is switched, that is, the optimum modulation multi-value number is determined (step S303).

Further, by comparing the current reception level (Pr) with the required reception level (Prα) and extracting the difference with the corresponding modulation method (step S304), transmission power control information (ΔPt) is generated. (Step S305).
Here, the wireless relay device 2 is controlled based on the generated modulation multilevel number information (modulation α) and transmission power control information (ΔPt) (steps S306 and S307). At the same time, the information is added to the transmission signal from the wireless relay device 2 to the wireless relay device 1 and transmitted to control the wireless relay device 1.

  The wireless relay device 1 extracts transmission power control information and modulation multilevel number information from the received signal (steps S309 and S310). Based on the extracted information, the transmission power and the modulation multi-level number are controlled (steps S311 and S312). Finally, the wireless relay device 1 adds transmission level information (Pt) to the wireless relay device 2 and sends a signal (step S313).

Here, with reference to FIG. 7, the flow of modulation multilevel number determination and transmission power control information generation will be described in detail.
The memory 27 in the wireless relay device 2 stores the following information as initial setting information.
Memory information (1): Section parameter information A
Memory information (2): Rain attenuation amount table memory information for each modulation multi-level number Memory information (3): Required reception level table for each modulation multi-level number The section parameter information A is
A = (gain of antennas ANT1 and ANT2) − (free space loss) − (feed loss of radio relay apparatuses 1 and 2)
It is.

  First, the rain attenuation amount Z is calculated with reference to the memory information (1) (step S401). By referring to the table of the memory information (2) for the calculated Z, the optimum modulation multilevel number (modulation α) for the current propagation path condition is determined (step S402). Here, by referring to the table of the memory information (3) for the determined modulation multilevel number information (modulation α), the optimum required reception level (Prα) for the current channel condition is determined (step S403). .

  Next, regarding the determined required reception level (Prα), if the reception level (Pr) observed by the current device is lower than the required reception level (Prα), the transmission level is increased by a shortage. Control information (ΔPt) is generated (step S404 → S405). On the contrary, if the reception level (Pr) observed by the current device is equal to or higher than the required reception level (Prα), control information (ΔPt) to be decreased by that amount is generated (steps S404 → S406).

(Example of transmission power control)
FIG. 8 is a diagram illustrating the relationship between the transmission level and the reception level for each modulation multi-level number in the first and second embodiments described above. In the figure, the horizontal axis is the rain attenuation.
Referring to the figure, as the rain attenuation increases on the horizontal axis, as in the above example, 1024QAM (reception level Pr0 = −55 dBm), 256QAM (reception level Pr1 = −62 dBm), 64QAM (reception level Pr2 = −68 dBm). ), 16QAM (reception level Pr3 = −74 dBm), QPSK (reception level Pr4 = −81 dBm), and the multi-value number of the modulation scheme are sequentially decreased. In other words, as the rain attenuation amount on the horizontal axis increases, the number of modulation schemes is reduced, and the margin of the reception level associated therewith is assigned to rain attenuation.
Further, since the transmission power is controlled within a range not exceeding the maximum transmission power Pt_max (in this example, +30 dBm), the same reception level is always maintained in the same modulation scheme. Furthermore, the transmission level at the modulation system switching point is the maximum transmission power Pt_max.

(Wireless relay method)
In the wireless relay system configured using the wireless relay device described above, the following wireless relay method is realized. In other words, it is a wireless relay method using an opposite device, and a reception level measurement step for measuring the reception level of a signal transmitted from another device (for example, step S101 in FIG. 3, step S301 in FIG. 6). Adaptive modulation for setting the modulation multi-level number of the transmission signal to the other device based on the difference between the current reception level measured in the reception level measurement step and the predetermined required reception level. Based on the step (for example, corresponding to step S105a in FIG. 3 and step S306 in FIG. 6) and the difference between the current reception level and the required reception level, the transmission level of the transmission signal to the other device And a transmission power control step (for example, corresponding to step S105b in FIG. 3 and step S307 in FIG. 6) is implemented. . Use adaptive modulation that adopts the optimal modulation method according to the propagation situation, compare the required reception level in that modulation method with the actual reception level, and send the transmission level information according to the level difference between both levels. By generating and performing transmission power control, it is possible to extend the distance of the line while ensuring sufficient line quality.

The method further includes a storage step of storing a table in which a required reception level corresponding to each modulation multi-level number is determined, and appropriately determines transmission power control by determining the required transmission level with reference to the contents of the table. It can be carried out.
Further, in the wireless relay system according to the second embodiment described above, a rain attenuation amount calculating step (for example, corresponding to step S302 in FIG. 6) for calculating the rain attenuation amount based on the signal transmitted from the other device. ), And in the adaptive modulation step, the radio multi-level value of the transmission signal to the other device is set with reference to the rain attenuation amount calculated in the rain attenuation amount calculating step. The relay method is realized. In this way, it is possible to extend the distance of the line while ensuring sufficient line quality even during rainfall.

The method further includes a storage step of storing a table in which a required reception level corresponding to each modulation multi-value number and a rain attenuation amount corresponding to each modulation multi-value number are defined, and the required contents are referred to with reference to the contents of the table. By determining the transmission level, transmission power control can be appropriately performed.
Here, the rain attenuation calculation step is based on the difference between the data related to the transmission level of the signal inserted in the signal transmitted from the other device and the current reception level measured in the reception level measurement step. The rain attenuation amount is calculated. By using the data extracted from the received signal, the rain attenuation can be easily calculated.
In the adaptive modulation step, there is a difference between a threshold value for increasing the multi-value number and a threshold value for reducing the multi-value number. With this configuration, it is possible to prevent the modulation multi-level number switching from flapping.

  In addition, the method further includes an information insertion step of inserting information indicating the transmission level and the modulation multi-level number into a signal transmitted to the other device, and the transmission power is obtained by using the inserted information in the opposite device. Control can be performed appropriately. And it further includes an information extraction step for extracting information indicating the transmission level and the modulation multi-level number inserted in the signal transmitted from the other device, and the switching timing of the transmission level and the modulation multi-level number, Match with the other devices. In this way, the control timing can be matched by using the information inserted in the opposing device.

(Summary)
As described above, in the present invention, as means for realizing multi-level modulation without reducing the maximum propagation distance, adaptive modulation that employs an optimal modulation method according to the propagation situation is used. Furthermore, transmission level information is generated according to the difference between the required reception level and the actual reception level in the selected modulation method, and transmission power control is performed. By such control, the distance of the line can be extended while ensuring sufficient line quality even when it rains, so that the number of radio entrance lines can be reduced and a communication network can be constructed at a low cost. Similarly, when compared at the same transmission distance, the annual unavailability decreases, so that the reliability of the network is improved. In addition, in order to suppress transmission power in fine weather, it is possible to reduce power consumption, and to effectively reduce the interference of other lines, thus enabling effective use of frequencies.

  The present invention can be used when performing adaptive modulation and transmission power control in a radio entrance system.

It is a block diagram which shows the radio relay system comprised using the radio relay apparatus by 1st Example based on this invention. It is a figure which shows the structural example of a transmission frame. It is a flowchart which shows operation | movement of each part in FIG. FIG. 4 is a diagram illustrating in detail a generation flow of modulation multilevel number information and transmission power control information in FIG. 3. It is a block diagram which shows the radio relay system comprised using the radio relay apparatus by 2nd Example which concerns on this invention. It is a flowchart which shows operation | movement of each part in FIG. It is the figure which showed in detail the production | generation flow of the modulation | alteration multi-value number information in FIG. 6, and transmission power control information. FIG. 6 is a diagram illustrating a transmission power level and a reception power level when transmission power control is performed in the wireless relay system of FIG. 1 or FIG. 5. It is a block diagram which shows the structural example of the conventional radio relay apparatus. It is a figure which shows the maximum propagation distance for every modulation | alteration multi-value number from total C / N for every fine weather and rainy weather.

Explanation of symbols

1, 2, 100, 200 Wireless relay device 11, 21 Encoding unit 12, 22 Adaptive modulation unit 13, 23 Wireless unit 13a, 23a Transmitting unit 13b, 23b Transmission / reception sharing unit 13c, 23c Receiving unit 14, 24 Demodulation unit 15, 25 Decoding unit 16 Modulation multi-level number extraction unit 17 Modulation / demodulation multi-level number control unit 18 Transmission level control unit 19 Transmission power control information extraction unit 20 Transmission level information addition unit 26 Reception level extraction unit 27 Memory 28 Transmission level determination unit 29 Modulation Multi-level number determination unit 30 Modulation / demodulation multi-level number control unit 31 Transmission power control unit 32 Information addition unit 33 Transmission level information extraction unit 34 Rain attenuation amount calculation unit 35 Transmission power control information generation unit 120, 220 Modulation unit 300 Transmission frame 301 Header Part 302 Payload part ANT1, ANT2 Antenna

Claims (16)

  A wireless relay device that constitutes a wireless relay system together with other devices facing each other, the reception level measuring means for measuring the reception level of a signal transmitted from the other device, and the current measured by the reception level measuring means Adaptive modulation means for setting the modulation level of a transmission signal to the other device based on the difference between the reception level of the received signal and a predetermined required reception level, the current reception level and the required reception level, And a transmission power control means for setting a transmission level of a transmission signal to the other device based on the difference between them.   2. The radio according to claim 1, further comprising storage means for storing a table in which a required reception level corresponding to each modulation multi-level number is determined, and determining a required transmission level with reference to the contents of the table. Relay device.   Further comprising rain attenuation amount calculating means for calculating a rain attenuation amount based on a signal transmitted from the other device, wherein the adaptive modulation means also refers to the rain attenuation amount calculated by the rain attenuation amount calculating means. The radio relay apparatus according to claim 1, wherein a modulation multi-level number of a transmission signal to the other apparatus is set.   It further includes storage means for storing a table in which a required reception level corresponding to each modulation multi-level number and a rain attenuation amount corresponding to each modulation multi-level number are defined, and a required transmission level with reference to the contents of the table The wireless relay device according to claim 3, wherein the wireless relay device is determined.   The rain attenuation amount calculating means is configured to reduce the rain attenuation based on a difference between data relating to a transmission level of the signal inserted in a signal transmitted from the other device and a current reception level measured by the reception level measuring means. The wireless relay device according to claim 3 or 4, wherein the amount is calculated.   6. The adaptive modulation means according to any one of claims 1 to 5, wherein a difference is provided between a threshold value for increasing the multi-value number and a threshold value for decreasing the multi-value number. The wireless relay device described.   7. The information insertion unit according to claim 1, further comprising information insertion means for inserting information indicating a transmission level and a modulation multi-level number into a signal transmitted to the other device. Wireless relay device.   And further comprising information extracting means for extracting information indicating the transmission level and the modulation multi-level number inserted in the signal transmitted from the other device, wherein the switching timing of the transmission level and the modulation multi-level number is set to the other level. The wireless relay device according to any one of claims 1 to 6, wherein the wireless relay device is made to coincide with the device.   A wireless relay method using opposite devices, wherein a reception level measurement step for measuring a reception level of a signal transmitted from another device, and a current reception level measured in the reception level measurement step are predetermined. Based on the difference between the required reception level and an adaptive modulation step for setting the modulation level of the transmission signal to the other device, and on the basis of the difference between the current reception level and the required reception level, And a transmission power control step of setting a transmission level of a transmission signal to another device.   10. The radio according to claim 9, further comprising a storage step of storing a table in which a required reception level corresponding to each modulation multi-level number is determined, and determining a required transmission level with reference to the contents of the table. Relay method.   It further includes a rain attenuation amount calculating step for calculating a rain attenuation amount based on a signal transmitted from the other device, and the adaptive modulation step also refers to the rain attenuation amount calculated in the rain attenuation amount calculating step. The wireless relay method according to claim 9 or 10, wherein a modulation multi-level number of a transmission signal to the other device is set.   The method further includes a storage step of storing a table in which a required reception level corresponding to each modulation multi-level number and a rain attenuation amount corresponding to each modulation multi-level number are defined, and a required transmission level with reference to the contents of the table The wireless relay method according to claim 11, wherein:   In the rain attenuation amount calculating step, the rain attenuation is calculated based on a difference between data relating to a transmission level of the signal inserted in a signal transmitted from the other device and a current reception level measured in the reception level measuring step. The wireless relay method according to claim 11 or 12, wherein the amount is calculated.   The adaptive modulation step has a difference between a threshold value for increasing the multi-value number and a threshold value for decreasing the multi-value number, according to any one of claims 9 to 13. The wireless relay method described.   The information insertion step of inserting information indicating a transmission level and a modulation multi-level number into a signal transmitted to the other apparatus, further comprising: Wireless relay method.   An information extraction step of extracting information indicating a transmission level and a modulation multi-level number inserted in a signal transmitted from the other device, wherein the switching timing of the transmission level and the modulation multi-level number is The wireless relay method according to any one of claims 9 to 14, wherein the wireless relay method is made to coincide with the apparatus.

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