JP5213637B2 - Wireless communication system, wireless communication method and program - Google Patents

Description

  The present invention relates to a wireless communication system in which a transmission device and a reception device communicate with each other via a relay device.

  In recent years, research on next-generation mobile communication systems has been actively conducted, and as a method for improving the frequency utilization efficiency of the system, each cell uses the same frequency band, so that each cell is allocated to the system. A one-frequency repetitive cellular system that can be used as a whole has been proposed.

  In particular, in the next generation cellular system, the radio frequency band to be used is higher than the current third generation (3G) cellular system. Even when a new base station for a next-generation cellular system is newly installed, the widest possible coverage area is required, so relaying signals from the base station or mobile station effectively extends the area covered by the base station. Installation of a station is being studied (for example, see Patent Document 1).

  FIG. 11 shows an outline of the relay system. In the figure, a base station 1000 and a relay station 1001 are installed in a cell, and a terminal 1002 and a terminal 1003 exist in the same cell. Here, the terminal 1002 can be connected to both the base station 1000 and the relay station 1001 depending on the position in the cell, and the terminal 1003 is far from the base station 1000 and communicates with the base station via the relay station.

In this case, the terminal 1003 can perform stable communication through the relay station as compared with the case where a conventional relay station is not installed, and can effectively expand the area covered by the base station 1000. . Furthermore, since the terminal 1002 can directly transmit a signal to the base station 1000 and can also pass through the relay station 1001, a route diversity effect by passing through a plurality of routes can also be obtained.
JP 2007-166424 A

  However, in general, a relay station is required to cover a terminal that cannot be directly connected to the base station 1000 (for example, the terminal 1003), and a terminal that can be directly connected to the base station 1000 (for example, the terminal 1002). If the relay station is occupied, communication with a terminal that cannot be directly connected to the base station cannot be performed. Therefore, when a relay station is used for the purpose of acquiring path diversity, there is a problem that the maximum path diversity must be acquired while reducing the amount of information relayed as much as possible in the relay station.

  Furthermore, from the viewpoint of such route diversity, although a higher transmission characteristic can be obtained by jointly relaying using a plurality of relay stations, when a plurality of relay stations are used, a specific terminal has a plurality of relays. Since the station is occupied, that is, other terminals cannot be connected, the same problem as described above occurs.

  In view of the above-described problems, an object of the present invention is to provide a wireless communication system and a relay that efficiently transmit and relay a signal by clipping a part of the relay signal in a wireless communication system in which a relay station is installed. Is to provide a device.

To solve the problems described above, the radio communication system of the present invention is a radio communication system comprising a receiving device and RELAY device, the relay device, a single carrier signal transmitted to the receiving device Receiving means for receiving, and transmitting means for clipping a part of the frequency signal of the single carrier signal received by the receiving means and transmitting as a relay signal to the receiving apparatus, Comprises receiving means for receiving the single carrier signal and a relay signal obtained by clipping a part of the single carrier signal .

  In the radio communication system of the present invention, the transmission means multiplexes other signals in a band to which the clipped frequency signal is allocated and transmits the multiplexed signal as a relay signal.

In the wireless communication system of the present invention, the frequency signal being the clipped is characterized by being clipped in a specific pattern.

In the wireless communication system of the present invention, the frequency signal to be the clipping highly discrete frequency propagation path gain between the relay device and the receiving device is a discrete frequency to be used for relay, allocated to the remaining discrete frequencies The frequency signal is clipped .

In the wireless communication system of the present invention, the receiving device further includes combining means for combining the received single carrier signal and a relay signal obtained by clipping a part of the single carrier signal .

In the wireless communication system of the present invention, the transmission unit of the relay device includes a DFT unit that converts the single carrier signal received by the reception unit into a frequency signal, and a spectrum that clips a part of the frequency signal. A clipping unit; an IDFT unit that converts the frequency signal subjected to the clipping into a time signal; and a unit that transmits the time signal as the relay signal .

Wireless communication system of the present invention, the transmitting device and said receiving device is not line communication via a plurality of the relay device, the plurality of relay devices, clipping the single-carrier signal from the transmission device wherein the relaying to the receiving device.

  In the wireless communication system of the present invention, the clipping is controlled so as to clip frequency signals of different frequencies between the plurality of relay apparatuses.

Wireless communication method of the present invention includes the steps a radio communication method in a radio communication system comprising a receiving device and RELAY device, the relay device, which receives a single carrier signal transmitted to the receiving device, The relay device clipping a part of the frequency signal of the single carrier signal received by the receiving means and transmitting it as a relay signal to the receiving device; and Receiving a signal and a relay signal obtained by clipping a part of the single carrier signal .

Wireless communication method of the present invention, the transmitting device and said receiving device is not line communication via a plurality of the relay device, the plurality of relay devices, the receiving device by clipping signal from the transmission device It is characterized by relaying to.

The program according to the present invention causes a computer to execute each step performed by the relay device of the above-described wireless communication method .

  According to the present invention, when a relay device relays a signal, a part of the spectrum is dropped and transmitted, and the base station device combines the signals, so that a terminal that requires another relay station while improving the reception situation It becomes possible to provide a wireless communication system that can be relayed and can be relayed efficiently.

  Furthermore, according to the present invention, since the spectrum is lost, the energy can be concentrated on the frequency with good propagation path characteristics, so that the relay can be performed with high energy transfer efficiency.

  Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: It is not the thing of the character which limits the technical scope of this invention.

Embodiment
[First Embodiment]
First, the first embodiment will be described. In this embodiment, a case where a terminal is connected to both a base station and a relay station will be described as an example. FIG. 1 shows an example of a communication system targeted in the present embodiment. Further, in this specification, uplink communication, that is, a terminal as a transmission device, a base station as a reception device, and a relay station as a relay device will be described as an example. Of course, the present invention can be applied even when a terminal is used as the device.

  FIG. 1 is an example of a communication system including a base station 1, a relay station 2, and a terminal 3. In this embodiment, the terminal 3 is connected to the base station 1 and the relay station 2. In the present embodiment, an example is shown in which a single carrier scheme is used assuming an uplink, but the multicarrier scheme may be used in the downlink, and is not limited to the case of using the single carrier scheme in the uplink.

  In the figure, A1 indicates a transmission path from the terminal 3 to the base station 1, A2 indicates a transmission path from the terminal 3 to the relay station 2, and A3 indicates a transmission path from the relay station 2 to the base station 1. Here, in a general relay system, when the terminal 3 transmits, it is simultaneously transmitted to the base station 1 and the relay station 2, and A1 and A2 are transmitted at the same timing. Next, since transmission from the relay station 2 to the base station 1 is performed after the signal from the terminal 3 is once received by the relay station 2, A3 is transmitted at the next transmission opportunity.

  Next, the relay method in the present invention will be described. FIG. 2 shows a frequency signal to be transmitted in each path at each transmission time. First, at the discrete time k−1, the terminal 3 transmits the same waveform to the base station 1 and the relay station 2 using the routes A1 and A2. Here, the signal in the figure is assumed to be a frequency signal. At this point, the base station 1 has received the received signal via the route A1.

  Next, at the discrete time k, the relay station 2 converts the received signal received via the path A2 into a frequency signal, and transmits a part of the frequency signal via the path A3. This signal is the frequency signal indicated at the discrete time k, and indicates that the frequency signal indicated by the dotted line is dropped and relayed.

  Here, the received signal of the path A1 received at the transmission time k−1 is buffered in the base station 1, and a signal combining process such as maximum ratio combining is performed together with the signal received via the path A3. . As a result, for the signal transmitted from the terminal 3, the bandwidth of the signal relayed by the relay station 2 can be narrowed while obtaining the gain of path diversity, and the free band is used for relaying and retransmission of other terminals. As a result, further efficiency improvement using the relay station can be achieved. In this embodiment, half of the continuous band is clipped, but it may be clipped discretely according to the frequency response of the propagation path of A3, and if the level is detectable at the base station, the half band There is no need to be.

  FIG. 3 shows a configuration example of the relay station 2. The relay station 2 includes a receiving antenna 10, a first radio unit 11, a CP (Cyclic Prefix) removing unit 12, a DFT (Discrete Fourier Transform) unit 13, a spectrum clipping unit 14, and an IDFT (Inverse). (DFT) unit 15, clipping information generation unit 16, multiplexing unit 17, CP insertion unit 18, second radio unit 19, and transmission antenna 20. Here, since frequency axis processing is assumed, a signal to which a CP is added is transmitted on the transmission side.

  First, the received signal received by the receiving antenna 10 is down-converted from a radio frequency to a baseband signal by the first radio unit 11, and the CP is removed by the CP removing unit 12. The signal from which the CP has been removed is converted into a frequency signal by the DFT unit 13, and a part of the frequency signal is clipped by the spectrum clipping unit 14.

  The clipped signal is converted into a time signal by the IDFT unit 15 and, in order for the base station to grasp which discrete frequency is clipped, information on the discrete frequency that has not been clipped is generated by the clipping information generation unit 16. And multiplexed in the multiplexing unit 17 together with the output of the IDFT unit 15.

  The multiplexed signal is added with a CP by a CP insertion unit 18, up-converted again to a radio frequency by a second radio unit 19, and transmitted from a transmission antenna 20. Here, when the signal of the terminal 3 that is directly connected to the base station 1 is relayed with respect to the spectrum clipping unit 14 that is a point of the present invention, the terminal 3 that can be connected only to the relay station 2 by reducing the amount of information. Since the subject matter of the present invention is to use as a wireless resource, a discrete frequency having a high propagation path gain between the relay station 2 and the base station 1 is used for relay according to the frequency response of the propagation path between the relay station 2 and the base station 1. A clipping pattern may be determined or may be determined randomly. Moreover, you may clip by a specific pattern.

  Here, since the relay station 2 determines the frequency to be clipped, notification to the base station 1 is required, and the function of the clipping information generation unit 16 is provided. However, the base station 1 shown as an example in the second embodiment When the relay station 2 is centrally managed, the clipping information generation unit 16 and the multiplexing unit 17 are not necessarily required because clipping may be performed based on the clipping information notified from the base station 1.

  FIG. 4 shows an example of the base station 1. The base station 1 includes a reception antenna 100, a radio unit 101, a CP removal unit 102, a clipping information detection unit 103, a DFT unit 104, an equalization unit 105, a switching unit 106, a buffer 107, and a signal synthesis. Unit 108, IDFT unit 109, and demodulation unit 110.

  A reception signal received by the reception antenna 100 is down-converted from a radio frequency to a baseband signal by the radio unit 101. Next, the CP removal unit 102 removes the CP from the received signal, and the clipping information detection unit 103 detects whether clipping information exists and the clipping information.

  At this time, if there is no clipping information, it can be understood that the signal has arrived directly from the terminal 3, so the switching unit 106 is connected to the buffer 107. On the other hand, when clipping information is detected, since it can be understood that the signal is from the relay station 2, the switching unit 106 is directly connected to the combining unit 108 and at the same time the clipping information is separated.

  Next, an output signal from the clipping information detection unit 103 is converted into a frequency signal by the DFT unit 104, and distortion due to the propagation path is compensated by the equalization unit 105. Thereafter, a signal is input to the one connected by the switching unit 106.

  Here, as described above, when the switching unit 106 is connected to the buffer 107, the signal directly arrives from the terminal 3, so that the signal that arrives from the relay station 2 is stored in the buffer 107 to be combined.

  On the other hand, when the switching unit 106 is connected to the signal synthesis unit 108, the signal stored in the buffer 107 and the frequency signal subjected to the clipping equalized by the equalization unit 105 are synthesized.

  The synthesized signal is converted into a time signal by the IDFT unit 109 and demodulated by the demodulation unit 110. Thereafter, although not shown, a transmission bit is detected as in the conventional wireless communication system. Although the equalized signal is buffered this time, the received signal on the frequency axis output from the DFT unit 104 is buffered, each received signal in the buffer is weighted, and optimum synthesis is performed. May be applied.

  In this way, the terminal connected to the base station via the relay station can transmit and retransmit signals from other terminals by not relaying more information than necessary, achieving high relay efficiency. can do.

[Second Embodiment]
Next, the second embodiment will be described. FIG. 5 is a diagram illustrating an example of the second embodiment. In this embodiment, the terminal is not directly connected to the base station, but is connected to a plurality of relay stations.

  FIG. 5 shows an example of a cellular system including a base station 200, relay stations 201a and 201b, and a terminal 202. The terminal 202 is assumed to be connected to both the relay stations 201a and 201b. Note that this embodiment is applicable even if the terminal is connected to more than two relay stations.

  A21a and A21b indicate transmission paths from the terminal 202 to the relay stations 201a and 201b, and A22a and A22b indicate transmission paths to the relay stations 201a and 201b. Although the present embodiment assumes an uplink, the present invention is also applicable to the downlink because the relationship between the base station 200 and the terminal 202 is simply switched.

  Next, the relay method will be described. FIG. 6 shows the concept of the frequency signal transmitted by the terminal when relaying. First, at transmission time k-1, the terminal transmits a signal to relay stations 201a and 201b via A21a and A21b. Next, at the transmission time k-1, each relay station cooperates between the relay stations, clips different frequencies, and transmits them via A22a and A22b. Here, regarding cooperation between relay stations, control information may be exchanged between the relay stations, and when the relay station is connected to the base station using a separate line, the base station performs coordination and the like. May be realized.

  FIG. 7 shows an example of the configuration of the relay station of this embodiment. Here, an example of the relay station apparatus when the base station centrally manages the relay stations is shown. The relay station includes a reception antenna 301, a first radio unit 302, a CP removal unit 303, a DFT unit 304, a spectrum clipping unit 305, an IDFT unit 306, a CP insertion unit 307, and a second radio unit 308. It is configured with.

  The basic operation of all the blocks is the same as that of the first embodiment, but the spectrum clipping unit 305 performs clipping using the information on the frequency to be clipped transmitted from the centrally managed base station. The At this time, when setting the frequency to be clipped by exchanging control information only between the relay stations, a function of communicating the clipping information to the base station is added like the clipping information generating unit 16 of the first embodiment.

  By performing such processing, cooperative relay using a plurality of relay stations can be performed efficiently. Here, in this embodiment, control is performed so that half of the signal band is clipped, but the clipping ratio may be changed between the relay stations according to the propagation path between the base station and the relay station. Further, in the present embodiment, a diagram is shown in which the continuous band is clipped so that the clipping information is reduced. However, if it is determined whether to perform clipping in discrete spectrum units in consideration of the frequency selectivity of the radio propagation path, a higher frequency is obtained. Since the selection diversity effect is obtained, the transmission characteristics are also improved. Therefore, the optimization may be performed in consideration of the overhead due to the notification information for notifying the clipping pattern.

  Further, this embodiment can also be used for the purpose of relaying a retransmission signal of another terminal signal or a data signal in a frequency band clipped by each relay station.

[Third Embodiment]
Subsequently, the third embodiment will be described. The third embodiment shows a case where the terminal cannot be directly connected to the base station and performs clipping according to the propagation path characteristic between the relay station and the base station when communicating with the base station via the relay station.

  FIG. 8 shows an example of a target system in the present embodiment, and FIG. 9 shows frequency signals transmitted by the route A41 and the route A42 at each transmission time. When the terminal 412 communicates with the base station 410, since the terminal 412 cannot connect to the base station 410, it is assumed that communication is performed via the relay station 411.

  First, at the transmission time k, the terminal 412 transmits toward the relay station 411. The relay station 411 clips and transfers some frequencies to the base station 410 at the transmission time k + 1. At this time, as a clipping method, clipping may be performed randomly, or if the frequency characteristics of the propagation path between the relay station and the base station are known, only the frequency with a high propagation path gain is used for transmission. Clipping may be performed, or power may be redistributed and transmitted according to the gain of each discrete frequency as in the water injection theorem.

  In the base station 410, it is known that even if a clipped discrete frequency exists, the clipped discrete frequency is regarded as a propagation path with a gain of 0 and can be reproduced by using a turbo equalization technique that is a nonlinear iterative process. Therefore, the signal is reproduced by turbo equalization technology.

  FIG. 10 shows an example of the configuration of the base station 410. The base station 410 includes a reception antenna 501, a radio unit 502, a CP removal unit 503, a clipping information detection unit 504, a first DFT unit 505, a spectrum extraction unit 506, a cancellation unit 507, and an equalization unit 508. , Demodulation section 509, IDFT section 510, deinterleaver 511, decoding section 512, interleaver 513, soft replica generation section 514, second DFT section 515, equivalent channel multiplication section 516, and determination section 517.

  As can be confirmed from the configuration of the base station 410, since turbo equalization repeats equalization and decoding, the signal transmitted from the relay station 411 is subjected to error correction coding, and then the encoded bits are set by the interleaver. It is assumed that the rearranged signal is modulated.

  A reception signal received by the reception antenna 501 is down-converted from a radio frequency to a baseband signal by the radio unit 502. Next, when the CP is removed by the CP removal unit 503 and the clipping information is transmitted as in the first embodiment, the clipping information detection unit 504 detects the clipping information.

  Next, the received signal from which the clipping information has been extracted is converted into a frequency signal by the first DFT unit 505, the signal not clipped by the spectrum extracting unit 506 is extracted, and the received signal of the remaining clipped frequency signal is set to 0. Replace with Thereafter, the signal is input to the cancel unit 507 to cancel the signal.

  At this time, nothing is canceled by the cancel unit 507 for the first time. Next, the distortion of the received signal input to the equalization unit 508 and canceled is compensated. The equalized signal is decomposed by a demodulator 509 into a log likelihood ratio (LLR) that quantifies the reliability of whether the code bit is 1 and is modulated by a deinterleaver 510. Restore the alignment for the signal. The LLRs of the code bits whose arrangement is changed by the deinterleaver 510 are subjected to error correction processing by the decoding unit 511, and the LLRs of the code bits with higher reliability are output.

  The LLR of the obtained code bit is a sequence of code bits to be modulated again by the interleaver 513, a soft replica having an amplitude proportional to the reliability is generated by the soft replica generation unit 514, and the frequency signal of the frequency signal is generated by the second DFT unit 515. A replica is generated and input to the equivalent channel multiplication unit 516, and a replica of the received signal is generated.

  At this time, since the clipped discrete frequency is handled with the propagation path gain set to zero, information on the frequency subjected to clipping is input from the clipping information detection unit 504. The received signal replica obtained in this way is input to the cancel unit 507 to cancel the received signal. Then, it is input again to the equalization unit 508 and the above-described processing is repeated. This is repeated an arbitrary number of times (for example, a predetermined number of times or until there is no detection error), and finally the determination unit 517 determines the information bit.

  As described above, when the relay station performs clipping and relays, the relay station can also relay signals of other terminals at the same time, and can perform efficient relay.

It is a figure which shows the outline | summary of the radio | wireless communications system in 1st Embodiment. It is a figure for demonstrating an example of the frequency signal in 1st Embodiment. It is a figure for demonstrating the structure of the relay station in 1st Embodiment. It is a figure for demonstrating the structure of the base station in 1st Embodiment. It is a figure which shows the outline | summary of the radio | wireless communications system in 2nd Embodiment. It is a figure for demonstrating an example of the frequency signal in 2nd Embodiment. It is a figure for demonstrating the structure of the relay station in 2nd Embodiment. It is a figure which shows the outline | summary of the radio | wireless communications system in 3rd Embodiment. It is a figure which shows an example of the frequency signal in 3rd Embodiment. It is a figure for demonstrating the structure of the base station in 3rd Embodiment. It is a figure which shows the outline | summary of the conventional radio | wireless communications system.

Explanation of symbols

1, 200, 410 Base station 2, 201a, 201b, 411 Relay station 3, 202, 412 Terminal

Claims (11)

A wireless communication system comprising a receiving device and RELAY device,
The relay device is
Receiving means for receiving a single carrier signal transmitted to the receiving device,
Transmitting means for clipping a part of the frequency signal of the single carrier signal received by the receiving means and transmitting it as a relay signal to the receiving device;
With
The receiving device is:
A wireless communication system, comprising: a receiving unit configured to receive the single carrier signal and a relay signal obtained by clipping a part of the single carrier signal .   2. The wireless communication system according to claim 1, wherein the transmission unit multiplexes another signal in a band to which the clipped frequency signal is allocated and transmits the multiplexed signal as a relay signal. The radio communication system according to claim 1, wherein the clipped frequency signal is clipped with a specific pattern . Frequency signal the clipping highly discrete frequency propagation path gain between the relay device and the receiving device is a discrete frequency to be used for relay, characterized in that the frequency signal assigned to the remaining discrete frequencies is clipped The wireless communication system according to claim 1. The receiving device is:
Combining means for combining the received single carrier signal and a relay signal obtained by clipping a part of the single carrier signal
The wireless communication system according to claim 1 , further comprising: The transmission means of the relay device is
A DFT unit for converting the single carrier signal received by the receiving means into a frequency signal;
A spectral clipping unit for clipping a part of the frequency signal;
An IDFT unit for converting the clipped frequency signal into a time signal;
Means for transmitting the time signal as the relay signal;
The wireless communication system according to any one of claims 1 to 5, further comprising: The transmitting device and said receiving device is not line communication via a plurality of relay devices,
Wherein the plurality of relay devices, a wireless communication system according to one of claims 1 to 6, characterized in that to relay to the receiving device said clipping a single carrier signal from the transmission device. 8. The wireless communication system according to claim 7, wherein the clipping is controlled so as to clip frequency signals having different frequencies between the plurality of relay apparatuses. A radio communication method in a radio communication system comprising a receiving device and RELAY device,
A step wherein the relay device, which receives a single carrier signal transmitted to the receiving device,
The relay device clips a part of the frequency signal of the single carrier signal received by the receiving means, and transmits it as a relay signal to the receiving device;
Receiving the single carrier signal and a relay signal obtained by clipping a part of the single carrier signal;
A wireless communication method comprising: The transmitting device and said receiving device is not line communication via a plurality of the relay device, the plurality of relay devices, characterized in that to relay to the receiving device by clipping signal from the transmission device The wireless communication method according to claim 9 . The program for making a computer perform each step which the relay apparatus of the wireless communication method of Claim 9 or Claim 10 performs .

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