JP2010109914A - Wireless relay system, and wireless relay apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a wireless relay system for preventing information from being lost. <P>SOLUTION: The invention relates to a wireless relay system which includes a relay station 2 for relaying communication between radio units 1-1, 1-2 and adopts network coding, wherein the relay station 2 determines receive power for each radio unit on the basis of reception signals from the radio units 1-1, 1-2, determines an adjustment amount for adjusting power so as to settle a difference in the receive power within a predetermined range and transmits adjustment information indicative of the adjustment amount to the radio units 1-1, 1-2 and the radio units 1-1, 1-2 adjust transmit power on the basis of the adjustment information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio relay system and a radio relay apparatus that perform radio relay transmission.

  In recent high-speed wireless communication systems, large transmission power is required as the transmission speed increases. However, in reality, there is a limit to the transmission power of the transmitter, and there is a need for a technique that can secure a cover area under the limited transmission power. In recent years, relay transmission has attracted attention as a solution to such demands.

  In relay transmission, a relay device amplifies a signal from a transmitter and transmits the amplified signal to a receiver. When relay transmission is performed, the transmission power at the transmitter can be reduced as compared with the case where the transmitter directly transmits a signal to the receiver. Therefore, it is expected as a technique that can solve the coverage problem in an environment where the transmission power of the transmitter is limited.

As one of such relay transmission techniques, for example, there is a network coding technique described in Non-Patent Document 1 below. In the network coding technique, two wireless devices A and B simultaneously transmit signals a (p) and b (p) to a relay station, respectively. Here, p indicates the p-th symbol. At this time, the received signal x _R (p) received by the relay station from the wireless devices A and B is a route from the wireless device A to the relay station R and the square root of the transmission power level of the wireless device A with respect to a (p). A component obtained by multiplying b (p) by the square root of the transmission power level of the radio B and the channel coefficient of the path from the radio A to the relay station R, and a noise component. And a signal obtained by adding together.

The relay station amplifies the received signal and transmits it in the next time slot, and the radios A and B receive the signals transmitted from the relay station, respectively. At this time, the signals received by the radios A and B are multiplied by the square root of the amplification gain and the propagation path coefficient of the path from the radios A and B to the relay station, respectively, with respect to x _R (p). Is a signal obtained by adding That is, the signals received by the radios A and B include a term obtained by multiplying a (p) and b (p) by a propagation coefficient (including an amplification gain) corresponding to each propagation path and a term related to noise.

  The wireless device A recognizes a (p) transmitted by itself. Further, the coefficient (propagation coefficient) of a (p) of the signal received from the relay station can be estimated using the pilot signal included in the signal a (p). Therefore, the wireless device A subtracts the result obtained by multiplying the coefficient estimated from the received signal by a (p) from the relay station, thereby transmitting b (p) transmitted from the wireless device B based on the term b (p). ) Can be obtained.

  Similarly, the wireless device B can obtain a (p) transmitted from the wireless device A. As described above, communication from the wireless device A to the wireless device B is performed using two time slots of signal transmission from the wireless devices A and B to the relay station and signal transmission from the relay station to the wireless devices A and B. Communication from the wireless device B to the wireless device A can be performed simultaneously.

P. Popovski and H. Yomo, “Bi-directional Amplification of Throughput in a Wireless Multi-Hop Network”, IEEE Proc. Of VTC 2006-Spring. Vol. 2, pp.588-593

  However, according to the above conventional technique, when the signals from the wireless devices A and B are received by the relay station, the signal a (p) transmitted from the wireless device A and b (p) transmitted from the wireless device B are received. Are subjected to processing such as A / D (Analog to Digital) conversion as a single received signal. Therefore, when the transmission power is largely different between a (p) and b (p), some signals are quantized when the relay station performs A / D conversion on the received signal and temporarily stores it in the digital domain. There is a problem that information contained in the signals a (p) and b (p) is lost due to errors.

  Further, in the above conventional technique, two-way communication between two wireless devices can be performed. However, in an actual environment, there are many environments in which a transmitting station for forward communication and a receiving station for reverse communication do not match. Therefore, in order to cope with various real environments, it becomes a problem to cope with an environment in which a transmitting station for forward communication and a receiving station for reverse communication do not match.

  Furthermore, the conventional technique assumes one relay station. However, many environments in which a plurality of relay stations exist in the future are assumed, and a configuration capable of performing bidirectional communication by efficiently applying a network code in the presence of a plurality of relay stations is important.

  The present invention has been made in view of the above, prevents information loss, and corresponds to a case where a transmitting station for forward communication and a receiving station for reverse communication do not match and a case where a plurality of relay stations are provided. An object of the present invention is to obtain a wireless relay system and a wireless relay device that can be used.

  In order to solve the above-described problems and achieve the object, the present invention is a wireless relay system that includes a wireless relay device that relays communication between wireless devices and employs network coding, and the wireless relay device includes: The reception power is obtained for each wireless device based on the received signal from the wireless device, the adjustment amount for adjusting the power so that the difference between the reception powers is within a predetermined range, and the adjustment indicating the adjustment amount Information is transmitted to the wireless device, and the wireless device adjusts transmission power based on the adjustment information.

  According to this invention, in the present embodiment, the relay station sets the reception power of the signal received from the first radio device and the signal received from the signal received from the second radio device to the same level. Since the transmission power of the first radio device and the second radio device is controlled, there is an effect that information loss can be prevented.

  Hereinafter, embodiments of a wireless relay system and a wireless relay device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a wireless relay system according to the present invention. As shown in FIG. 1, the wireless relay system according to the present embodiment includes wireless devices 1-1 and 1-2 and a relay station 2. A control signal 3 in the figure indicates a control signal transmitted from the relay station to the radios 1-1 and 1-2.

In the present embodiment, bidirectional relay transmission is performed using a network code. Here, an example of transmission using a network code with the wireless device 1-1 as the wireless device A and the wireless device 1-2 as the wireless device B will be described using equations. When the transmission signals transmitted from the wireless devices A and B are a (p) and b (p) (p indicates a symbol number), the received signals that the relay station 2 receives from the wireless devices A and B are It can be represented by the following formula (1). Note that h _AR is a propagation path coefficient of a path from the wireless device A to the relay station R, h _BR is a propagation path coefficient of a path from the wireless device B to the relay station 2, and P _A and P _B are wireless devices A and B, respectively. , Z _R (p) represents a noise component in the relay station 2.

The relay station 2 amplifies the received signal according to the amplification gain G, and transmits it in the time slot next to the slot that received z _R (p). At this time, signals x _A (p) and x _B (p) received by the radios A and B from the relay station 2 can be expressed by the following equation (2). Note that h _RA is the propagation path system number of the path from the relay station 2 to the wireless device A, h _RB is the propagation path system number of the path from the relay station 2 to the wireless device B, and z _A (p), z _B (p ) Represent noise components in the radios A and B, respectively.

  Here, the wireless device A recognizes its transmission signal a (p). Further, when a pilot signal included in a (p) is used, a propagation coefficient C represented by the following equation (3) can be obtained.

  Therefore, in the wireless device A, x (hat) shown in the following formula (4) can be calculated, and the transmission signal b (p) from the wireless device B can be obtained based on x (hat). Similarly, the wireless device B can obtain the transmission signal a (p) from the wireless device A.

On the other hand, the relay station 2 temporarily stores z _R (p) after receiving it and converts the analog signal z _R (p) into a digital signal for transmission in the next slot. That is, the analog signal received by the relay station 2 is converted into a digital signal by A / D conversion and stored.

At this time, in A / D conversion, the received amplitude is discretized according to the number of quantized bits and stored as bit information. For example, in the case of 8-bit A / D conversion, the analog amplitude is discretized to 2 ⁸ (= 256) levels. Therefore, when the received signal of the analog domain signal received by the relay station 2 differs greatly between the signal transmitted from the wireless device A and the signal transmitted from the wireless device B, it is based on the larger amplitude. Since it is discretized, one received signal power is buried in the quantization error, and the modulation information contained in the signal is lost.

For example, in the 8-bit AD conversion, the amplitude is discretized to 2 ⁸ levels. Therefore, when the amplitude level of the signal a (p) is 1/256 or less of the signal b (p), the maximum amplitude of the signal b (p) is increased. When quantized as a reference, the modulation of the signal a (p) becomes less than the quantization unit and information is lost. In addition, even if the amplitude level of the signal a (p) is 1/256 or more of the signal b (p), if the two signals have greatly different amplitudes, the signal having the smaller amplitude is affected by the quantization error. Receive greatly. As a result, even if the relay station 2 once amplifies the received signal stored in the digital domain and transmits it again, the wireless devices A and B cannot extract the desired signals b (p) and a (p) smoothly and correctly. Arise.

In order to solve such a problem, in the present embodiment, the received power of the transmission signal from the wireless device A and the transmission signal B from the wireless device B received by the relay station 2 is the same or within a certain ratio. The transmission powers P _A and P _B of the radios A and _B are controlled. By performing such transmission power control, the relay station 2 does not lose the modulation information included in the signals a (p) and b (p) even after A / D conversion is performed on the received signal. Therefore, relay transmission can be performed while maintaining the modulation information.

  Such a transmission power control method, that is, transmission of the radios A and B so that the reception power when the relay station 2 receives the transmission signals a (p) and b (p) is the same or within a certain ratio. There are various methods for controlling power.

As an example, there is a method in which the relay station 2 transmits a control signal 3 instructing the radio devices A and B to increase or decrease the transmission power so that the received power at the relay station 2 becomes the required power P _req . In this case, the relay station 2 measures the received power from the radio A, and if the received power is smaller than the P _req by a predetermined value α or more, the relay station 2 instructs the radio A to increase the transmission power, and the received power exceeds the P _req . If it is larger than the predetermined value β, the wireless device A is instructed to lower the transmission power. The relay station 2 performs this operation individually for the radios A and B, so that the reception power levels of the two signals at the relay station 2 are approximately the same (P _req −α or more and P _req −β or less). can do.

  Note that the received power measurement of the signal from the wireless device A (or B) performed by the relay station 2 can be easily performed using a pilot signal (known signal). For example, if the radios A and B simultaneously transmit known signals having different orthogonal patterns, the relay station 2 receives interference from other orthogonal known signals by correlating each known pattern with the received signal. It is possible to measure only the propagation path of one radio. If this measurement method is used, it is possible to simultaneously measure the received power of the signals from the wireless device A and the wireless device B.

  Further, as an example different from the above transmission power control method, the relay station 2 transmits a pilot signal, the wireless devices A and B receive the pilot signal, measure the amount of propagation loss, and the wireless devices A and B There is a method of transmitting a signal by setting transmission power capable of compensating for propagation loss.

  Further, a specific transmission power control method will be described with reference to FIGS. FIG. 2 is a diagram illustrating an example of a reception power control method in the relay station 2. As shown in FIG. 2, it is assumed that the reception power difference between the signal received by the relay station 2 from the wireless device A and the signal received from the signal received from the wireless device B is ΔdB before the transmission power control is performed. At this time, in order to reduce the reception power difference between them, the relay station 2 performs transmission power control so as to decrease the transmission power of the wireless device A by Δ / 2 dB and increase the transmission power of the wireless device B by Δ / 2 dB. .

Specifically, the relay station 2 first measures the received power of the signal received from the radio A and the signal received from the radio B. The received power is measured using pilot signals included in signals received from the radio A and signals received from the radio B. Next, the relay station 2 transmits the control signal 3 toward the radio devices A and B. FIG. 3 is a diagram illustrating a configuration example of the control signal 3 transmitted from the relay station 2 to the radios A and B. The control signal 3 includes a power increase bit for identifying an instruction to increase or decrease the power, and a power change amount indicating the power amount to be changed. Here, when the amount of power change is D, the power increase bit indicates the following instruction.
Power increase bit = 0: Radio A increases transmission power DdB, Radio B increases transmission power DdB lower power increase bit = 1: Radio A decreases transmission power DdB, Radio B increases transmission power DdB

  When receiving the control signal 3, the radios A and B change the transmission power based on the value of the power increase bit and the power change amount D. At this time, if the received power difference based on the measurement result is ΔdB as shown in FIG. 2, if D = Δ / 2 dB is set, the radios A and B simultaneously change the transmission power with one control signal. The reception power of the signal received from the radio device A and the signal received from the signal received from the radio device B at the relay station 2 can be set to the same level.

  Thus, by performing transmission power control of two wireless devices simultaneously with one control signal, highly efficient transmission power control becomes possible. In conventional transmission power control, a separate control signal is required for each radio.In this method, multiple radios change the transmission power using a common control signal. Can be reduced as compared with the prior art.

  Thus, in the present embodiment, the radio A and the radio are set so that the reception power of the signal received from the radio A received by the relay station 2 and the signal received from the signal received from the radio B are the same level. The transmission power of the machine B was controlled. For this reason, even if the relay station 2 performs AD conversion on the received signal, the modulation information is not lost. In this way, by introducing transmission power control centered on the relay station 2, a new effect capable of avoiding signal information loss can be obtained.

Embodiment 2. FIG.
FIG. 4 is a diagram illustrating a configuration example of the second embodiment of the wireless relay system according to the present invention. As shown in FIG. 4, the wireless relay system according to the present embodiment includes wireless devices 1-1 to 1-3 and a relay station 2.

  In the first embodiment, an example in which complete bidirectional communication is performed when a relay transmission method using a network code is employed has been described. In this embodiment, a relay transmission to which a network code is applied is performed as in the first embodiment, but a case where communication that is not completely bidirectional is performed will be described.

Hereinafter, the wireless device 1-1 will be described as wireless device A, the wireless device 1-2 will be described as wireless device B, and the wireless device 1-3 will be described as wireless device C. In a real environment, as shown in FIG. 4, a state occurs in which the wireless device A transmits a signal to the wireless device B, and the wireless device B transmits a signal to a wireless device C different from the wireless device A. References “S. Katti, D. Katabi, W. Hu, H. Rahul, and Ml Medard.“ The importance of being opportunistic: Practical network coding for wireless environments, ”In Proc. Of 43 ^rd Allerton Conference on Communication, "Control, and Computing, 2005." shows a configuration using a network code using a logical OR to support such an environment. The network code used in this reference is different in type from the network code employed in this embodiment (a method for amplifying a received signal as it is), but its configuration can be extended to the network code handled in this embodiment.

FIG. 4 shows a configuration example when the configuration of the above-mentioned reference is extended to the network code system of the present embodiment. In this configuration, the wireless devices A and B transmit signals a (p) and b (p) simultaneously to the relay station 2 as in the conventional case. At this time, the wireless device C located in the vicinity of the wireless device A receives and detects the signal a (p) from the wireless device A. Next, when the relay station 2 receives signals from the radios A and B, it amplifies and transmits the received signal x _R (p) shown in the expression (1) of the first embodiment as in the prior art.

The wireless device C receives the signal transmitted by the relay station 2 after amplifying x _R (p). At this time, if the wireless device C knows the signal a (p), it can measure the propagation coefficient of the signal a (p) using the pilot signal a (p) included in the received signal. Therefore, similarly to the wireless device A of the first embodiment, the wireless device C can detect the signal b (p) instead of the wireless device A by subtracting the term of the signal a (p) from the received signal. On the other hand, the wireless device B can obtain the signal a (p) transmitted from the wireless device A, as in the first embodiment. In this way, transmission of the signal a (p) from the wireless device A to the wireless device B and transmission of the signal b (p) from the wireless device B to the wireless device C can be performed simultaneously.

  In order to enable the transmission as described above, it is an important condition that the wireless device C is close to the wireless device A to the extent that the signal transmitted from the wireless device A can be detected. In an actual wireless communication system found in mobile communication or the like, there are many cases where there are many terminals around a base station. In such a wireless communication system, when wireless device B is a base station and two terminals are appropriately selected as wireless devices A and C (which are in a close positional relationship), uplink / downlink communication is performed using the network code described above. It can be carried out.

  FIG. 5 is a diagram illustrating a configuration example of a wireless communication system to which the wireless relay method according to the present embodiment is applied. As shown in FIG. 5, this wireless communication system includes a base station 4 and terminals 5-1 to 5-12. In a real environment, many terminals are distributed in a wide area. Therefore, in the present embodiment, as shown in FIG. 5, many terminals are classified (grouped) into a plurality of groups having a close positional relationship. Groups 6-1 to 6-3 represent groups to which the terminals 5-1 to 5-12 belong. In FIG. 5, the terminals 5-1 to 5-4 belong to the group 6-1 and the terminals 5-5 ˜5-8 belong to group 6-2, and terminals 5-9 to 5-12 belong to group 6-3. In addition, group IDs that are group identifiers of the groups 6-1 to 6-3 are # 1, # 2, and # 3, respectively. The control signal 7 is a control signal for the base station 4 to control radio resources.

  This grouping is performed by the following processing, for example. First, a channel measurement using a pilot signal is performed between terminals, and each terminal grasps a nearby terminal in a position based on a transmission channel measurement result. For example, each terminal transmits its own terminal ID (identifier) number and a pilot signal at different times, and the peripheral terminal performs propagation measurement using the pilot signal and corresponds to the measurement result. The operation of recognizing the transmission terminal ID is repeated. Each terminal recognizes a peripheral terminal with a good propagation state as a peripheral terminal close in position, and holds the terminal ID number of the terminal ascertained as peripheral terminal information.

  Further, each terminal notifies the peripheral terminal information to the base station 4. The base station 4 classifies the terminals 5-1 to 5-12 into a plurality of groups using the peripheral terminal information notified from each terminal. By dividing the terminals into a plurality of groups in this way, the base station 4 can easily grasp the combination of terminals that transmit and receive signals using the network code, and can smoothly perform radio resource control. For example, when the base station 4 grants uplink signal transmission permission to any of the terminals 5-1 to 5-4 belonging to the group 6-1, the downlink is transmitted to other terminals belonging to the same group 6-1. Transmit the signal at. As described above, by classifying the terminals 5-1 to 5-12 into a plurality of groups and granting permission for uplink transmission and downlink transmission to terminals belonging to the same group, smooth radio resource control becomes possible.

  In addition, the base station 4 selects a transmitting terminal that performs signal transmission and a receiving terminal that performs signal reception as described above, and notifies the terminals 5-1 to 5-12 of the selection result using the control signal 7. This notification may be performed for all terminals or only for selected terminals. The terminals 5-1 to 5-12 receive this control signal 7, and the terminal designated by the control signal 7 transmits or receives a signal based on the instruction of the control signal 7.

  FIG. 6 is a diagram illustrating an example of a control signal format according to the present embodiment. As shown in FIG. 6, the control signal of the present embodiment includes a group ID indicating the ID of a terminal group that performs relay transmission using radio resources, and an intra-group for identifying a terminal that performs signal transmission in the uplink. And a sub ID for identifying a terminal that performs signal reception on the downlink. The sub-ID is an ID for identifying a terminal in the group. In the same group, it is assumed that an ID is assigned so that the sub-ID corresponds to the terminal on a one-to-one basis.

  If the uplink transmitting terminal and the downlink transmitting terminal are individually specified without using the group ID, one terminal is selected for each uplink and downlink from all terminals including other groups. Must be specified. As a result, the number of bits for specifying the terminal increases as compared with the case where the group ID is used. On the other hand, in the present embodiment, the terminal group ID is specified in the control signal by using the fact that the terminal that transmits signals in the uplink and the terminal that receives signals in the downlink belong to the same terminal group. The number of information bits required to identify the terminal is reduced.

  In the wireless relay system described in the first embodiment, the grouping process according to the present embodiment may be performed. In this case, for example, in complete bidirectional communication, communication is performed using the method described in the first embodiment. When the communication is not bidirectional communication, the wireless device that simultaneously transmits data when performing the operation of the present embodiment. What is necessary is just to control similarly to Embodiment 1 so that the received power from A and B becomes comparable.

  As described above, in this embodiment, the base station 4 groups terminals into terminals that are in a close positional relationship, and selects terminals that perform transmission and reception from the same group. Therefore, smooth radio resource control is possible. Furthermore, the base station 4 designates the terminal selected using the control signal 7 by the sub ID which is the terminal ID in the group. For this reason, a radio | wireless resource control load can be reduced.

Embodiment 3 FIG.
FIG. 7 is a diagram showing a configuration example of a third embodiment of the wireless relay system according to the present invention. As shown in FIG. 7, the radio relay system according to the present embodiment includes radio units 1-1 and 1-2 and relay stations 2a-1 and 2a-2. A signal transmission path 8 indicates a transmission path for signals transmitted and received in the present system. The control signal 9 indicates a control signal that the wireless device 1-1 transmits to the relay stations 2a-1 and 2a-2 in the present embodiment. Radio devices 1-1 and 1-2 of the present embodiment are the same as radio devices 1-1 and 1-2 of the first embodiment, respectively. In this embodiment, a case where there are a plurality of relay stations will be described.

  FIG. 8 is a diagram illustrating an example of signal transmission according to the present embodiment. In the present embodiment, a network code is applied as in the first embodiment. Similarly to the first embodiment, in the following description, the wireless device 1-1 is described as the wireless device A, and the wireless device 1-2 is described as the wireless device B.

Radio units A and B transmit signals a (p) and b (p) at the same time as in the first embodiment. The reception signals x _R1 (p) and x _R2 (p) received by the relay stations 2a-1 and 2a-2 use the same variables as in the first embodiment, and h _ARi (i = 1, 2) _Is the propagation path coefficient of the path from the wireless device A to the relay station 2a-i, h _BRi is the propagation path coefficient of the path from the wireless device B to the relay station 2a-i, and z _Ri (p) is the relay station 2a-. If it is a noise component in i, it can represent with the following formula | equation (5).

Next, the relay station 2a-i multiplies the received signal x _Ri (p) by a predetermined weight w _i and transmits it in the time slot next to the slot that received x _Ri (p). At this time, the signals x _A (p) and x _B (p) received by the wireless devices A and B from the relay station 2a-1 and the relay station 2a-2, respectively, can be expressed by the following equation (6). _Here , h _RiA is a propagation path coefficient of the path from the relay station 2a-i to the radio A, h _RiB is a propagation path coefficient of the path from the relay station 2a-i to the radio B, z _A (p), z _B (P) represents noise components in the radios A and B, respectively. The weight is a parameter including the amplification factor in the amplifier.

  FIG. 9 is a diagram illustrating a functional configuration example of the relay station 2a-1 according to the present embodiment. As shown in FIG. 9, the relay station 2a-1 of this embodiment includes an antenna 11, an LNA (Low Noise Amplifier) 12, a first DC (Down Converter) 13, and an A / D (Analog to Digital). Converter) 14, second DC 15, signal receiver 16, signal converter 17, signal transmitter 18, second UC (Up Converter) 19, and D / A (Digital to Analog converter) ) 20, a first UC 21, an HPA (High Power Amplifier) 22, a local oscillator 23, and a frequency estimation unit 24. An analog area 31 indicates an area where the received signal is processed as an analog signal, and a digital area 32 indicates an area where the received signal is processed as a digital signal. The relay station 2a-2 has the same configuration as the relay station 2a-1.

  In the relay station 2a-i, the first DC 13 once down-converts the received signal simultaneously received from the radios A and B via the antenna 11 and the LNA 12, and the A / D 14 converts the analog signal of the intermediate frequency. After converting into a digital signal and the second DC 15 converting into a baseband signal, the signal receiving unit 16 stores the baseband signal which is a digital signal. Next, the signal conversion unit 17 performs weight multiplication processing on the baseband signal, and the signal transmission unit 18 transmits the signal after the weight multiplication processing in the next time slot. This signal is transmitted from the antenna 11 after being up-converted and amplified to a radio frequency via a first UC 21 and a high power amplifier (HPA) 22. With such a configuration, the relay stations 2a-1 and 2a-2 perform weight multiplication.

  Here, the wireless device A recognizes its own transmission signal a (p), and estimates a propagation coefficient which is a coefficient of a (p) by propagation path measurement using a pilot signal included in the reception signal. . When the term of the signal a (p) is subtracted from the received signal based on these pieces of information, the wireless device A obtains a signal represented by the following equation (7).

  Similarly, the wireless device B obtains a signal represented by the following equation (8).

Here, it is desirable that the weight w _{i on} which the relay station 2a-i performs multiplication processing is set so that the reception power of the desired signal at the radios A and B is increased. Therefore, in the present embodiment, the wireless device A individually measures the propagation coefficient h _BR1 h _{R1A of the} path passing through the relay station 2a-1 and the propagation coefficient h _BR2 h _R2A of the path passing through the relay station 2a-1. In this measurement, for example, only one of the relay stations 2a-1 and 2a-2 amplifies and transmits the pilot signal from the wireless device B, and the pilot signal is amplified by measuring the pilot signal with the wireless device A. It is possible to measure the propagation coefficient of the route passing through the relay station. And after measuring one path | route, the propagation coefficient of the path | route which passes each relay station can be measured separately by measuring similarly about the path | route of the other relay station.

Radio A uses the propagation coefficients h _BR1 h _R1A and h _BR2 h _R2A measured individually, and weights w ₁ , w so that the value of | h _BR1 w ₁ h _R1A + h _BR2 w ₂ h _R2A | Determine ₂ . For example, if the weight is determined so as to satisfy the following expression (9), the value of | h _BR1 w ₁ h _R1A + h _BR2 w ₂ h _R2A | can be maximized. Note that * represents a complex conjugate.
_{w 2 / w 1 = (h} BR2 h R2A) * / (h BR1 h R1A) * ... (9)

In this way, the wireless device A determines appropriate weights w ₁ and w ₂ based on the measurement values. The weights w ₁ and w ₂ determined by the wireless device A are notified to the relay stations 2a-1 and 2a-2 by the control signal 9, and the relay stations 2a-1 and 2a-2 receive the weights notified by the control signal 9. Of these, relay transmission is performed using the weight corresponding to the own station. Thus, by appropriately determining the weights multiplied by the relay stations 2a-1 and 2a-2 based on the propagation measurement result, it is possible to receive the desired signal b (p) received by the wireless device A with high power. it can.

Next, the received power of the signal received by the wireless device B will be described. In the relay transmission of the present embodiment, the radios A and B perform signal transmission using the same frequency. Usually, at the same frequency, the propagation coefficient is the same even if the signal traveling direction is reversed. This principle is widely known as propagation path reversibility, and the following equation (10) is generally established.
h _BRi = h _RiB , h _{ARi =} h _RiA (i = 1, 2) (10)

h _BR1 w ₁ h _R1A + h _BR2 w ₂ h _R2A = h _AR1 w ₁ h _R1B + h _AR2 w ₂ h _R2B (11)

  From the above formulas (9), (10), and (11), the weight for maximizing the reception power of the signal b (p) by the wireless device A maximizes the reception power of the signal a (p) by the wireless device B. Matches the weight to be From this result, if the weight control is performed so that the reception power of the wireless device A is maximized, the reception power of the desired signal of the wireless device B is maximized without performing any special weight control for the wireless device B. Is done. Thus, in relay transmission using a network code, if the transmission weight of one-way communication is optimized, it becomes the optimum weight for two-way communication. Using this result, it is not necessary to set transmission weights separately for both directions, and optimal weight setting for bidirectional communication can be performed with only one weight control.

In this embodiment, the case where the number of relay stations is two has been described. However, i = 1 to N (N> 2), the same processing is performed for N relay stations, and w _i is obtained. Each relay station may perform weight multiplication using a corresponding weight.

As described above, in the present embodiment, when there are a plurality of relay stations, the wireless device A individually transmits the propagation coefficients h _BR1 h _R1A and h _BR2 h _R2A from the wireless device B via the relay stations. Based on the measurement results, the weights w ₁ and w ₂ are determined so as to maximize the value of | h _BR1 w ₁ h _R1A + h _BR2 w ₂ h _R2A |, and the relay stations 2a-1, 2a- 2, the relay station 2 a-i performs weight multiplication using the weight w _i . For this reason, when there are a plurality of relay stations, a desired signal can be obtained efficiently.

  In the wireless relay system described in the first or second embodiment, a configuration in which a plurality of relay stations exist may be used, and the weight control according to the present embodiment may be performed. Further, in the radio relay system that performs the operations of both the first embodiment and the second embodiment, a configuration in which there are a plurality of relay stations may be performed, and the weight control of the present embodiment may be performed.

  In the present embodiment, since the weight is determined as described above, if the above-described weight control is performed on one transmission line, the transmission path in the reverse direction is also optimized, so the weight control load Can be greatly reduced.

  As described above, the wireless relay system and the wireless relay device according to the present invention are useful for a wireless communication system that performs relay transmission, and are particularly suitable for a wireless communication system to which a network code is applied.

It is a figure which shows the structural example of Embodiment 1 of the radio relay system concerning this invention. It is a figure which shows an example of the received power control method in a relay station. It is a figure which shows the structural example of the control signal which a relay station transmits to a radio | wireless machine. 6 is a diagram illustrating a configuration example of a wireless relay system according to a second embodiment. FIG. 6 is a diagram illustrating a configuration example of a radio communication system to which a radio relay method according to a second embodiment is applied. FIG. 6 is a diagram illustrating an example of a control signal format according to Embodiment 2. FIG. FIG. 10 is a diagram illustrating a configuration example of a wireless relay system according to a third embodiment. 10 is a diagram illustrating an example of signal transmission in Embodiment 3. FIG. 6 is a diagram illustrating a functional configuration example of a relay station according to Embodiment 3. FIG.

Explanation of symbols

1-1, 1-2, 1-3 Radio equipment 2, 2a-1, 2a-2 Relay station 3, 7, 9 Control signal 4 Base station 5-1 to 5-12 Terminal 6-1 to 6-3 Group 8 Signal transmission path 11 Antenna 12 LNA
13 First DC
14 A / D
15 Second DC
16 Signal receiver 17 Signal converter 18 Signal transmitter 19 Second UC
20 D / A
21 First UC
22 HPA
23 Local Oscillator 24 Frequency Estimator 31 Analog Domain 32 Digital Domain

Claims (17)

A wireless relay system that includes a wireless relay device that relays communication between wireless devices and employs network coding,
The wireless relay device obtains received power for each wireless device based on a received signal from the wireless device, obtains an adjustment amount for adjusting the power so that the difference in the received power is within a predetermined range, Send adjustment information indicating the adjustment amount to the radio,
The wireless relay system, wherein the wireless device adjusts transmission power based on the adjustment information.   The wireless relay system according to claim 1, wherein the wireless relay device determines the adjustment amount based on a difference between a predetermined reference value and received power for each wireless device. The wireless relay device has a first adjustment power amount that is an amount of power that is increased by one of the wireless devices to be relayed and a second amount of power that is decreased by the other wireless device based on the difference in the received power. The first adjustment power amount and the second adjustment power amount are obtained so that the adjustment power amount is equal, and the adjustment amount is set as the first adjustment power amount or the second adjustment power amount. , Including the radio designation information for determining the one radio that increases the transmission power in the adjustment information,
When the wireless device is designated as a wireless device for increasing transmission power in the designation information, the wireless device increases the transmission power by the amount of adjustment, and also increases the transmission power. 2. The wireless relay system according to claim 1, wherein when the own device is not designated as the transmission power, the transmission power is decreased by the amount of adjustment.   The wireless relay system according to claim 1, 2, or 3, wherein the received power is obtained using a pilot signal transmitted from the wireless device. The wireless device obtains the wireless device side received power that is the received power of the received signal from the wireless relay device, and notifies the wireless device of the wireless device side received power,
4. The wireless relay system according to claim 1, wherein the wireless relay device obtains reception power for each of the wireless devices based on the wireless device-side reception power. 5.   6. The radio relay system according to claim 5, wherein the radio side reception power is obtained using a pilot signal transmitted from the radio relay apparatus. When the radio device that is the transmission source of the received signal in uplink communication is an uplink transmission station, and when the radio is received and the radio device is an uplink reception station,
The wireless relay system according to any one of claims 1 to 6, wherein, in downlink communication, the wireless relay device transmits a signal received from the upstream receiving station to the upstream transmitting station. . When an uplink transmitting station is a radio that is a transmission source of the received signal in uplink communication, and a radio that has received the signal is an uplink receiving station,
In downlink communication, the radio relay apparatus transmits a signal received from the uplink receiving station to a radio device other than the uplink transmitting station. Wireless relay system.   The wireless devices are classified into a plurality of groups so that the distance between the wireless devices in the same group falls within a predetermined range, and the wireless devices to be relayed by the wireless relay device are wireless devices belonging to the same group. The wireless relay system according to claim 8. A plurality of the wireless relay devices are provided,
The wireless device determines a weighting factor used for weight multiplication of the wireless relay device for each wireless relay device based on a propagation path state of a route passing through the wireless relay device, and transmits the weighting factor,
The wireless relay system according to claim 1, wherein the wireless relay device multiplies the received signal by the weighting factor corresponding to the wireless relay device, and transmits the multiplied signal. . A wireless relay system configured with a base station, a plurality of terminals, and a wireless relay device that relays communication between the base station and the terminal, adopting network coding,
The base station classifies the terminals into a plurality of groups so that a distance between terminals in the same group falls within a predetermined range, and selects a terminal to be relayed by the wireless relay device from terminals belonging to the same group And transmitting selected terminal information that is information for identifying the selected terminal,
A radio relay system characterized in that a terminal that recognizes its own terminal as a terminal selected by the base station based on the selection information performs communication via the radio relay apparatus.   The radio relay system according to claim 11, wherein the selected terminal information includes an identifier of a group to which the selected terminal belongs and an identifier in the group of the selected terminal. A plurality of the wireless relay devices are provided,
The base station or the terminal determines a weighting factor used for weight multiplication of the wireless relay device for each wireless relay device based on a propagation path state of a route passing through the wireless relay device, and transmits the weighting factor,
The wireless relay system according to claim 11 or 12, wherein the wireless relay device multiplies a reception signal by the weighting factor corresponding to the device itself and transmits the multiplied signal. A wireless relay system that includes a plurality of wireless relay devices that relay communication between wireless devices and employs network coding,
The wireless relay device multiplies the received signal by a predetermined weighting factor and transmits it,
The wireless relay system, wherein the wireless device determines the weighting factor for each wireless relay device based on a propagation path state of the relay route, and notifies the wireless relay device of the weighting factor.   The wireless relay system according to claim 10, 13 or 14, wherein the weighting factor is determined based on the propagation path state of unidirectional communication. A wireless relay system including a wireless relay device that relays communication between wireless devices and adopting network encoding,
Based on the received signal from the wireless device, the reception power for each wireless device is obtained, the adjustment amount for adjusting the power so that the difference in the received power is within a predetermined range, and the adjustment information indicating the adjustment amount Is transmitted to the wireless device. A wireless relay system including a plurality of wireless relay devices that relay communication between wireless devices and adopting network coding,
A wireless relay characterized by multiplying a received signal by a weighting factor determined based on a propagation path state of a path passing through each wireless relay device measured by the wireless device, and transmitting the multiplied signal apparatus.

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