Communication terminal device and communication relay method

The present invention relates to a communication terminal device and a communication relay method in a multi-hop system adopting an OFDM (Orthogonal Frequency Division Multiplex) method.

Mobile communication systems represented by mobile phones and the like have come to process not only voice data but also large volumes of data such as still images and moving images as information becomes multimedia. Since the amount of data is expected to increase in the future, it is being actively studied to realize a high transmission rate by making the frequency band of wireless signals higher.

However, since the high-frequency radio signal is greatly attenuated by the transmission distance, the radius of the cell covered by the base station becomes small, and it becomes necessary to install more base stations. Installing more base stations may not be as obvious as a problem in densely populated areas, as it is cost-effective, but in less densely populated areas, for example. It is unrealistic to set up base stations every few hundred meters. Therefore, in areas with low population density, it is desired to enable communication between base stations and communication terminals without increasing the number of base stations.

As one measure to solve this problem, there is a technique called a multi-hop system (or a multi-hop network) (see, for example, Patent Document 1). In this multi-hop system, each communication terminal has a communication relay function, and relays communication between another communication terminal and the base station. Therefore, a communication terminal (hereinafter, sometimes referred to as a relay requesting station) that cannot directly communicate with the base station because it is located outside the communication range (outside the cell) can directly communicate with the base station. Request relay from the communication terminal of. Then, the communication terminal requested to relay (hereinafter, may be referred to as a relay station) relays the communication between the communication terminal outside the service area and the base station by establishing a line with the base station. As a result, the communication terminal outside the service area can communicate with the base station.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 11-289349</text></patcit>

<p> However, in a conventional multi-hop system, even if the own station (relay station) is not communicating, the circuit of the own station may be used for communication of another station (relay requesting station) outside the service area. there causes a problem that the power consumption of the mobile station is increased. In particular, a communication terminal located at the cell edge (an area near the boundary with an adjacent cell) has a high probability of relaying a communication terminal outside the service area, so that the increase in power consumption becomes remarkable.</p><p> Therefore, an object of the present invention is a communication terminal device capable of suppressing an increase in power consumption of its own station while realizing relay of communication of another station in a multi-hop system, and communication used in the communication terminal device. It is to provide a relay method.</p>

<p> The communication terminal device of the present invention is a communication terminal device that relays communication between a base station and another communication terminal in an OFDM communication system, and is a communication between the base station and the other communication terminal. A configuration is adopted in which a storage means for storing data and a transmission means for frequency-dividing and multiplexing the stored communication data with the data of the own station and transmitting the data at the transmission timing of the own station are provided.</p><p> The communication system of the present invention is an OFDM type communication system including a base station and a plurality of communication terminals, and the first communication terminal is required to relay communication from the second communication terminal to the base station. In this case, the relay data is temporarily saved, and at the transmission timing of the data of the own station, the data of the own station and the data of the own station are orthogonally multiplexed and transmitted, and the second communication terminal is notified of the relay. The second communication terminal adopts a configuration in which the user of the own station is notified when the first communication terminal notifies that the relay has been performed.</p>

<p> According to the present invention, in a multi-hop system, it is possible to suppress an increase in power consumption of a communication terminal while realizing relay of communication between a communication terminal located outside the service area and a base station.</p>

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. As an example of the communication terminal device, a mobile station device such as a mobile phone will be described as an example.

(Embodiment 1) One of the features of the present invention is that even when a mobile station is requested to be relayed by another mobile station in a multi-hop system, the relay is not always performed, but is relayed. To limit.

Specifically, the mobile station according to the first embodiment of the present invention may directly communicate with the base station in a multi-hop system adopting an OFDM-TDD (Orthogonal Frequency Division Multiplex --Time Division Duplex) system. I'm in a position where I can. Then, when another mobile station located outside the service area requests the relay of communication with the above base station, the mobile station according to the present embodiment performs this relay only in the following cases. To facilitate understanding, the case where the communication between the mobile station outside the service area and the base station is an uplink is particularly called "upstream relay", and the communication between the mobile station outside the service area and the base station is downlink. The case of a line is particularly called "downstream relay", and explanations will be given separately for uplink relay and downlink relay.

FIG. 1 shows the case where the mobile station (relay station) MS1 in the cell relays the uplink communication between the mobile station (relay request station) MS2 located outside the service area of the cell A1 and the base station BS1, that is, It is a figure for demonstrating the case of an upstream relay.

In the uplink, the case where the mobile station MS1 relays is limited as follows. That is, the mobile station MS1 relays the transmission data from the mobile station MS2 to the base station BS1 if it is also the timing to transmit the data to the base station BS1. Specifically, the transmission data S2 transmitted from the mobile station MS2 is transmitted to the base station BS1 together with the transmission data S1 of the own station.

2A to 2C are diagrams for explaining the timing at which the mobile station MS1 relays the data of the mobile station MS2.

FIG. 2A is a diagram showing the timing of uplink / downlink communication between the base station BS1 and the mobile station MS1, that is, the timing of uplink / downlink communication of the TDD system. In this figure, the downward arrow indicates the downlink communication, and the upward arrow indicates the uplink communication. Further, FIG. 2B is a diagram showing a transmission signal of the mobile station MS2 outside the service area (reception signal of the relay station MS1), and FIG. 2C is a diagram showing a transmission signal of the relay station MS1.

As shown in FIG. 2B, the mobile station MS2 transmits the data S2 to the base station BS1 to the mobile station MS1 at the downlink communication timing t1 of the cellular system (TDD system) of the base station BS1. Here, the case where the mobile station MS2 is synchronized with the TDD system is described as an example, but it is not always necessary that the mobile station MS2 is synchronized.

The mobile station MS1 receives this data S2 and temporarily stores it in a buffer. Then, as shown in FIG. 2C, wait until the timing t4 for transmitting the data S1 of the own station is reached, and at this timing, the data S2 stored in the buffer is multiplexed with the data S1 of the own station. Send to base station BS1. If the waiting time for data relay exceeds a predetermined time, the mobile station MS1 discards the relay data and does not relay the data.

Further, at this time, the mobile station MS1 is a subcarrier that is not used in the OFDM frequency, that is, a transmission data or a control channel destined for the base station BS1 of the own station among the subcarriers that the own station can use at the time of transmission. Check if there is a subcarrier (free subcarrier) to which the signal is not mapped. Then, if there is a free subcarrier, it is determined whether the capacity of the free subcarrier is sufficient for data relay (whether the capacity of the free subcarrier is equal to or larger than the relay data size). If there is not enough capacity for data relay, mobile station MS1 does not relay.

FIG. 3 is a diagram showing an example of the usage status of the transmission subcarrier of the relay station MS1.

In this example, the subcarriers with center frequencies f1 to f12 are the subcarriers to which the transmission data of the mobile station MS1 is mapped (subcarriers for MS1), and the subcarriers with center frequency f17 are mapped to the control channel. Is a sub-carrier. Therefore, the subcarriers having center frequencies f13 to f16 become the above-mentioned empty subcarriers.

Therefore, since the mobile station MS1 has a free subcarrier, after confirming the capacity of the free subcarrier, the communication with the base station BS1 of the mobile station MS2 is relayed. Specifically, the mobile station MS1 maps the data desired to be transmitted from the mobile station MS2 to the base station BS1 to the above-mentioned free subcarrier. Here, when the frequency of the transmission subcarrier of the mobile station MS2 is covered (included) by the frequency of the free subcarrier of the mobile station MS1, the mobile station MS1 is transferred to the subcarrier of the same frequency as the mobile station MS2. Map the data of.

Then, the mobile station MS1 multiplexes the subcarrier to which the data of the mobile station MS2 is mapped and the subcarrier to which the data of its own station is mapped to multi-carrier, and then transmits this multi-carrier signal to the base station BS1. To do.

If the frequency of the transmission subcarrier of the mobile station MS2 is not covered by the frequency of the free subcarrier of the mobile station MS1, the mobile station MS1 changes the frequency as shown below. FIG. 4 is a diagram showing an example of the relationship between the transmission subcarrier of the mobile station (relay request station) MS2 outside the service area and the free subcarrier of the relay station MS1, that is, the case where both subcarriers have the above relationship. Here, FIG. 4A is a transmission subcarrier of the mobile station (relay request station) MS2, and FIG. 4B is a free subcarrier of the relay station MS1.

In the example of this figure, the center frequency range of the transmission subcarrier of the mobile station MS2 outside the service area is f13 to f16, while the center frequency range of the free subcarrier of the relay station MS1 is f1 to f6. As described above, the frequency of the transmission subcarrier of the mobile station desired to be relayed is not always covered (included) by the frequency of the free subcarrier of the relay station. Therefore, in such a case, the relay station MS1 maintains (fixes) the frequency of the transmission subcarrier of its own station, and the frequency of the transmission subcarrier of the relay data is included in the frequency range of the free subcarrier. Frequency shift the frequency of the transmission subcarrier. In the example of FIG. 4, the range of the center frequency of the subcarrier of the relay data is changed from f13 to f16 to f1 to f6. As a result, the mobile station MS1 can relay data without delay. Further, since the relay station MS1 does not change the frequency of the transmission subcarrier of its own station, frequency scheduling is effective even in a communication system such as frequency scheduling in which the subcarrier to be used is assigned to each mobile station in advance. Work on.

Next, the effect of adopting the above communication relay method will be described. FIG. 5 is a diagram showing the relationship between the number of transmission subcarriers of the mobile station and the power consumption.

As shown in this figure, when there is at least one transmitting subcarrier (subcarrier that actually transmits), the power consumption of the mobile station increases sharply as compared with the case where there is no transmitting subcarrier. However, when the number of transmitting subcarriers further increases, the tendency of increasing power consumption slows down, and even if the number of transmitting subcarriers increases, the power consumption does not change much as compared with the case where the number of transmitting subcarriers is 1. Become.

Therefore, the mobile station (relay station) MS1 according to the present embodiment has another station (mobile station MS2, etc.) as an empty subcarrier when its own station transmits, that is, when the number of transmission subcarriers is 1 or more. ) Data is mapped and sent. It can be seen from FIG. 5 that the power consumption of the own station MS1 hardly increases even if such transmission is performed. Further, as described above, the relay station MS1 maps the relay data to the free subcarriers, and does not change the frequency of the transmission subcarrier of its own station. That is, even if the relay station MS1 has a function of relaying data, the data transmission of its own station is given first priority for transmission. Therefore, it can be seen that the relay station MS1 is hardly affected by the data relay.

Figure 6 shows the case where the mobile station (relay station) MS1 in the cell relays the downlink communication between the mobile station (relay request station) MS2 outside the service area and the base station BS1, that is, the case of downlink relay. It is a figure for demonstrating.

In the downlink, the case where the mobile station MS1 relays is limited as follows. That is, the mobile station MS1 relays the transmission data from the base station BS1 to the mobile station MS2 if it is also the timing to transmit the data to the base station BS1. Specifically, the transmission data S6 transmitted from the base station BS1 is transmitted to the mobile station MS2 at the same timing as the transmission data S5 of the own station.

7A to 7C are diagrams for explaining the timing at which the mobile station MS1 relays the data of the base station BS1.

FIG. 7A is a diagram showing the timing of uplink / downlink communication of the TDD system. Further, FIG. 7B is a diagram showing a transmission signal of the base station BS1 (reception signal of the relay station MS1), and FIG. 7C is a diagram showing a transmission signal of the relay station MS1.

As shown in FIG. 7B, at the timing t11, the base station BS1 transmits the data S6 to the mobile station MS2 to the mobile station MS1. The mobile station MS1 receives this data S6 and temporarily stores it in a buffer. Then, as shown in FIG. 7C, wait until the timing of transmitting the data S5 of the own station to the base station BS1, that is, the timing of uplink communication t14, and when this timing is reached, the relay stored in the buffer is relayed. The data S6 is multiplexed with the data S5 of the own station and transmitted.

The relay data S6 is transmitted at the timing t14 of the uplink communication, but is the data of the downlink relay. Therefore, the mobile station MS2 that receives this needs to perform reception processing at the timing of uplink communication.

At this time, the mobile station MS1 determines whether or not there is a free subcarrier in the OFDM frequency as described in the uplink.

FIG. 8 is a diagram showing an example of the usage status of the transmission subcarrier of the relay station MS1.

In this example, the subcarriers with center frequencies f13 to f16 are free subcarriers (subcarriers for base station BS1). Therefore, the mobile station MS1 maps the data from the base station BS1 to the mobile station MS2 to this free subcarrier, and multiplexes and transmits the data from its own station to the base station BS1.

FIG. 9 is a block diagram showing a main configuration of the mobile station MS1 (mobile station apparatus 100) according to the present embodiment that realizes the above operation.

Each part of the mobile station apparatus 100 performs the following operations.

The antenna 101 receives a radio signal from another station (another mobile station such as base station BS1 or mobile station MS2), and also transmits a radio signal from its own station. The TDD switch 102 switches between transmission and reception of wireless signals in synchronization with the uplink / downlink timing of the TDD system. The reception RF unit 103 performs a predetermined radio reception process such as down-conversion on the radio signal received via the antenna 101 to obtain a baseband signal. The OFDM receiver 104 performs a predetermined OFDM reception process such as an inverse fast Fourier transform (IFFT) on the baseband signal to obtain each subcarrier signal from the multicarrier baseband signal.

The frequency separation unit 105 separates each subcarrier signal by frequency (see FIGS. 3 and 8), and separates the data addressed to its own station and the data addressed to another station. The data channel demodulation unit 106 addressed to the own station demodulates the data addressed to the own station and obtains the received data addressed to the own station. The data channel demodulation unit 107 addressed to another station demodulates the data addressed to another station, and temporarily stores the demodulated data in the buffer 108.

On the other hand, the buffer 111 temporarily stores the transmission data when the transmission data is generated.

The transmission timing determination unit 112 determines the transmission timing of the data of the own station according to the uplink / downlink timing of the TDD system, reads the transmission data stored from the buffer 111 according to this timing, and causes the transmission frequency determination unit 113. Output. Further, the transmission timing determination unit 112 notifies the buffer 108 of the transmission timing of its own station.

The transmission frequency determination unit 113 determines the frequency (subcarrier) required for transmission of this data based on the size and the like of the transmission data output from the transmission timing determination unit 112, and also determines the subs required for transmission of the control channel. The carrier is also decided. Further, when the free subcarriers already exist as described with reference to FIGS. 3 and 8, the transmission frequency determination unit 113 informs the other stations that there are free subcarriers and information on these free subcarriers. Notify the destination data channel modulation unit 114. Further, the transmission frequency determination unit 113 notifies the control channel generation unit 115 of information about the used subcarrier and the free subcarrier of the own station.

The buffer 108 outputs the stored data addressed to another station to the data channel modulation unit 114 addressed to another station based on the transmission timing of the own station notified from the transmission timing determination unit 112.

When the transmission frequency determination unit 113 notifies the existence of a free subcarrier, the data channel modulation unit 114 addressed to another station performs a predetermined modulation process such as QPSK on the data addressed to the other station output from the buffer 108. , Output to frequency multiplexing section 118.

The control channel generation unit 115 generates a control channel signal for notifying information about the used subcarrier and an empty subcarrier of the own station notified from the transmission frequency determination unit 113, and outputs the control channel signal to the control channel modulation unit 116.

The control channel modulation unit 116 performs a predetermined modulation process such as QPSK on the control channel signal and outputs the control channel signal to the frequency multiplexing unit 118. The data channel modulation unit 117 addressed to BS performs a predetermined modulation process such as QPSK on the data addressed to the base station BS1 from its own station, and outputs the data to the frequency multiplexing unit 118.

The frequency multiplexing unit 118 maps the modulation signals output from the data channel modulation unit 114 addressed to other stations, the control channel modulation unit 116, and the data channel modulation unit 117 addressed to BS to the subcarriers determined by the frequency determination unit 113, respectively. By doing so, the transmitted signal multiplexed on the frequency axis is obtained and output to the OFDM transmission unit 119.

The OFDM transmission unit 119 performs a predetermined OFDM transmission process such as a fast Fourier transform (FFT) on the transmission signal to obtain a multicarrier baseband signal. The transmission RF unit 120 performs a predetermined radio transmission process such as up-conversion on the baseband signal, and transmits the obtained radio signal via the TDD switch 102 and the antenna 101.

The mobile station MS1 includes the identifier of its own station in the relay data so that the base station BS1 can recognize the fact that the data has been relayed from another mobile station.

FIG. 10 is a block diagram showing a main configuration of the base station BS1 (base station apparatus 150) according to the present embodiment.

Each part of the base station apparatus 150 performs the following operations.

The modulation unit 151 performs a predetermined modulation process such as QPSK on the transmitted data. The transmission timing determination unit 152 determines the transmission timing of its own station according to the uplink / downlink timing of the TDD system, and notifies the buffer 153 of this timing. The buffer 153 temporarily stores the modulation signal output from the modulation unit 151, and outputs the stored modulation signal to the OFDM transmission unit 154 based on the transmission timing of the own station notified from the transmission timing determination unit 152. .. The OFDM transmission unit 154 performs a predetermined OFDM transmission process such as a fast Fourier transform on the modulated signal to obtain a multicarrier baseband signal. The transmission RF unit 155 performs a predetermined radio transmission process such as up-conversion on the baseband signal, and transmits the obtained radio signal via the TDD switch 156 and the antenna 157.

On the other hand, the reception RF unit 158 performs a predetermined radio reception process such as down-conversion on the radio signal received via the antenna 157 and the TDD switch 156 to obtain a baseband signal. The OFDM receiver 159 performs a predetermined OFDM reception process such as an inverse fast Fourier transform on the baseband signal, and obtains each subcarrier signal from the multicarrier baseband signal. The control channel demodulation unit 160 performs demodulation processing on the control channel transmitted from the mobile station MS1, extracts information on the subcarriers used (subcarriers for mobile station MS1) and free subcarriers of the mobile station MS1, and extracts frequencies. Output to the separation unit 161. The frequency separator 161 separates each subcarrier signal by frequency based on the information about the subcarriers used and the free subcarriers of the mobile station MS1, and separates the signal from the mobile station MS1 and the signal from the mobile station MS2. .. The data channel demodulation units 162-1 and 162-2 perform demodulation processing on the signal from the mobile station MS1 and the signal from the mobile station MS2, respectively, and obtain the data from the mobile station MS1 and the data from the mobile station MS2. ..

As described above, according to the present embodiment, in the multi-hop system, the relay station MS1 receives the data desired to be relayed by another station (mobile station MS2 or base station BS1 outside the service area) and temporarily stores the data in the buffer. .. Then, wait until the transmission timing of the data of the own station is reached, and when this timing is reached, the relay data saved is frequency-division-multiplexed with the data of the own station, and the data after the multiplexing is relayed to the relay destination station (base station BS1 or Send to mobile station MS2). As a result, it is possible to suppress an increase in power consumption of the own station while realizing relay of communication of another station.

Further, in the above configuration, the relay station MS1 determines whether or not there is a subcarrier (free subcarrier) that is not used by the relay station in the OFDM frequency, and maps the relay data to this free subcarrier. As a result, it is possible to relay the data of another station without sacrificing the transmission of the data of the own station.

When the relay station MS1 executes data relay, the relay station MS1 may notify the mobile station MS2 outside the service area to that effect. As a result, the following effects are recognized.

Normally, the mobile station constantly monitors the reception level of the pilot signal transmitted from the base station, so that the user of the mobile station can determine whether or not he / she is located in the cell. Therefore, the user of the mobile station MS2 according to the present embodiment is trying to transmit data to the base station BS1 while recognizing that he / she is located outside the cell. Under these circumstances, users of mobile station MS2 should be driven by the desire to check whether data can be transmitted (or was possible). As a method of instructing this user whether or not to transmit data, it is conceivable that the mobile station MS2 searches for a relay station before transmitting data, secures a relay station, and then transmits data to this relay station. In such a case, since the mobile station MS2 performs communication after securing a relay station, it can be naturally determined that data transmission is possible. However, in this method, signaling (exchange of control signals) with this relay station is required to search for the relay station and secure the relay station, and this signaling is a normal communication process when the mobile station is in the cell. Therefore, a new signaling circuit is required. On the other hand, as described above, if the relay station MS1 notifies the mobile station MS2 to that effect when the data is relayed, the mobile station MS2 does not need to perform signaling in advance and has a simple configuration. It can be determined that the data transmission was possible. Then, by displaying on a display or the like that the data transmission has been successful, this fact can be notified to the user of the own station. Further, the relay station MS1 can also notify the mobile station MS2 outside the service area at the same time when the data is transmitted to the base station BS1, so that the transmission power does not increase significantly. Further, the signal transmitted by the relay station MS1 to the base station BS1 can also be received by the mobile station MS2 except when the directivity is added and transmitted. Therefore, if this signal is used as the above notification signal, it can be received. , It is no longer necessary for the relay station MS1 to separately transmit the notification signal to the mobile station MS2.

Further, in the present embodiment, the case where the relay station MS1 directly communicates with the base station BS1 has been described as an example, but the present invention is not limited to this, and there is yet another case between the mobile station MS1 and the base station BS1. It may be via a relay station.

Further, in the present embodiment, the case where the relay station is one of the mobile stations MS1, that is, the case where the relay data has one communication route (relay route) has been described as an example, but there are a plurality of relay routes. You may be doing it. For example, the data of the mobile station MS2 outside the service area may be relayed by two mobile stations, the mobile station MS1 and the mobile station MS1'. At this time, if the transmission timing of the relay data of the two relay stations (the timing of the uplink in the TDD system) is the same, the data of the mobile station MS2 outside the service area arrives through the two communication paths for the base station BS1. It's just a story, and the situation is almost the same as communication in a multipath environment. Further, if the transmission timings of the two relay stations are different, the situation for the base station BS1 is almost the same as that of the mobile station MS2 retransmitting data.

Further, here, the case of relaying data from the mobile station MS2 located outside the range of the cellular system has been described as an example, but the mobile station located in the cell but unable to receive the signal from the base station BS1 ( Data from a mobile station located in a non-sensing area) may be relayed. That is, the present invention is also useful as a countermeasure against non-sensitivity.

Further, in the examples of FIGS. 3 and 8, the case where the free subcarriers of the relay station are continuous on the frequency axis has been described as an example, but the free subcarriers may be discontinuously and discretely distributed. ..

Further, in the present embodiment, when the capacity of the free subcarrier is not sufficient for data relay, the mobile station MS1 does not relay as an example, but the mobile station MS1 relays only a part of the data. You may try to do it. Specifically, the mobile station MS2 located outside the service area prioritizes each data transmitted to the base station BS1 in advance based on the accuracy of the data and the like. Then, each of the prioritized data is transmitted to the relay station MS1. The relay station MS1 maps the received data from the data with the highest priority to the free subcarriers of its own station, and the mapping of all the relay data is completed or the free subcarriers are all filled. Then, it is multiplexed with the data of its own station and transmitted to the base station BS1. As a result, even if the size of the relay data is larger than the capacity of the free subcarrier, the data having the highest priority is selected and relayed to the base station BS1. Therefore, in the base station BS1, although the accuracy of the data is poor, it is possible to secure a state that is meaningful for communication (communication is substantially established).

(Embodiment 2) In the first embodiment, the case where the present invention is applied to an OFDM-TDD system has been described as an example, but in the second embodiment, the present invention is applied to an OFDM-FDD (Orthogonal Frequency Division Multiplex-Frequency Division). Duplex) The case of applying to the system will be described. In the TDD system shown in the first embodiment, since the same frequency band is used for the uplink and the downlink, the relay station does not need to switch the frequency used depending on whether it is an uplink or a downlink. However, in the FDD system described in the present embodiment, since the frequency bands used are different between the uplink and the downlink, the configuration of the relay station is significantly different from that of the first embodiment. The configuration of the relay station will be described in detail later.

11A and 11B are diagrams for explaining the flow when the relay station MS1 relays the data of the relay requesting station MS2. The assumed situation is the same as in FIG. 1, and the mobile station MS1 in the cell relays the uplink communication between the mobile station MS2 located outside the service area of the cell A1 and the base station BS1. Each signal has the same reference numeral as in FIG.

The relay station MS1 receives the transmission signal S2 at the uplink frequency from the relay request station MS2 at an arbitrary timing. Then, the relay station MS1 temporarily stores the received signal in a buffer, and at the timing of data transmission to the base station BS1 of its own station, the data from the relay request station MS2 is sent to the subcarrier which is a free subcarrier. By mapping S2, the data S1 of the own station and the relay data S2 are multiplexed and transmitted. Since the timing at which the relay station MS1 transmits the relay data S2 to the base station BS1 is irregular, the time interval between the time when the relay station MS1 receives the relay data S2 and the time when this data is transmitted to the base station BS1 is constant. Absent. Therefore, when the predetermined time elapses while waiting for the transmission of the relay data S2, the relay station MS1 cancels the relay and discards the relay data S2.

FIG. 12 is a diagram showing an example of the usage status of the transmission subcarrier of the relay station MS1.

Subcarriers with center frequencies f13 to f16 are subcarriers used for transmission from relay station MS1 to base station BS1, that is, transmission of own station data, and subcarriers with center frequencies f1 to f12 are empty subcarriers. Is. Therefore, the relay station MS1 maps the signal S2 received from the relay request station MS2 to the free subcarriers (center frequencies f1 to f12), and relays and transmits the signal S2 to the base station BS1.

The subcarrier to which the relay data is mapped may be any subcarrier as long as it is a free subcarrier. For example, when a plurality of continuous subcarriers can be secured as free subcarriers, the subcarriers are relayed to those subcarriers. Map the data. Also, when the free subcarriers are separated from each other, that is, they are located discretely, the relay data is also discretely mapped.

In FIGS. 11 and 12, the case of upstream relay has been described as an example, but the same relay method can be used for downstream relay. Since this has already been described in the first embodiment, the description thereof will be omitted here.

FIG. 13 is a block diagram showing a main configuration of the mobile station apparatus 200 according to the present embodiment that realizes the above operation. Since the mobile station device 200 has the same configuration as the mobile station device 100 (see FIG. 9) shown in the first embodiment, the components that basically perform the same operation are the same. Reference numerals are given, and the description thereof will be omitted. Further, for those having the same configuration but having a plurality of existing ones, a branch number is added after the reference numeral.

One of the features of this mobile station device 200 is a function of receiving relay data which is data addressed to other stations (for example, frequency reception RF unit 202 for uplink, OFDM reception unit 104-2, in addition to the normal reception function. It is equipped with a frequency separator 105-2).

Hereinafter, the functions of each part of the mobile station apparatus 200 will be described.

The downlink frequency reception RF unit 201 receives a predetermined wireless reception process such as down-conversion for the downlink radio signal from the base station BS1 received via the antenna 101, that is, the downlink frequency radio signal. To obtain a baseband signal. Here, the data included in the wireless signal of the downlink frequency may be the data of normal communication addressed to the own station or the relay data addressed to another station.

The uplink frequency reception RF unit 202 performs down-conversion or the like for a signal such as relay data received from another station (for example, MS2 or the like) received via the antenna 101, that is, a radio signal having an uplink frequency. A baseband signal is obtained by performing a predetermined radio reception process. Here, as shown in FIGS. 11 and 12, the data included in the wireless signal of the uplink frequency may be the relay data of the uplink relay from another station to the base station BS1, or as described later, the self. In some cases, the station is a relay requesting station outside the cell area, and is the relay data of the downlink relay transmitted from the relay station to its own station. The downlink relay will be described in more detail later.

There are two OFDM receivers 104, one for the downlink frequency and one for the uplink frequency (104-1, 104-2). In addition, there are two frequency separation units 105, one for the downlink frequency and the other for the uplink frequency (105-1, 105-2).

The data channel demodulation unit 106 addressed to the own station demodulates the data addressed to the own station output from the OFDM receiving unit 104-1 or the OFDM receiving unit 104-2, and obtains the data addressed to the own station. The data channel demodulation unit 107 addressed to another station demodulates the data destined for another station output from the OFDM receiving unit 104-1 or the OFDM receiving unit 104-2, and temporarily stores the demodulated data in the buffer 108.

On the other hand, the uplink frequency transmission RF unit 211 performs a predetermined radio transmission process such as up-conversion on the baseband signal output from the OFDM transmission unit 119, and transmits the obtained uplink frequency radio signal via the antenna 101. And send. Here, the data included in the wireless signal of the uplink frequency may be the data of normal communication to the base station BS1 of the own station, or may be the relay data of the uplink relay and the downlink relay as described later. ..

FIG. 14 is a diagram summarizing how to use each frequency band in the communication system according to the present embodiment.

First, the case of upstream relay, which has already been described in FIGS. 11 and 12, will be described.

In the case of uplink relay, transmission (signal S2) from relay request station MS2 to relay station MS1 is performed using an uplink as in normal communication. Further, the transmission (signal S2) from the relay station MS1 to the base station BS1 is also performed by using the uplink as in the normal communication. Therefore, the frequency used is the uplink frequency for any route.

Next, the case of downlink relay will be described.

In the case of downlink relay, transmission (signal S6) from the base station BS1 to the relay station MS1 is performed using the downlink (downlink frequency) as in normal communication. However, the transmission (signal S6) from the relay station MS1 to the relay request station MS2 is performed using the uplink frequency unlike the normal communication.

As described above, in the FDD system, since the frequency bands used are different between the uplink and the downlink, the normal (conventional) mobile station device cannot receive the transmission data of the other mobile station device. However, as shown in FIG. 13, the mobile station apparatus 200 according to the present embodiment includes a receiving system (uplink frequency receiving RF section 202 to frequency separating section 105-2) for the uplink frequency. Therefore, transmission data from other mobile station devices can be received. That is, assuming that both the relay station MS1 and the relay request station MS2 have the configuration of the mobile station device 200, the relay request station MS2 transmits the relay data transmitted from the relay station MS1 using the uplink frequency. , It can be received by the receiving system for the uplink frequency. Therefore, as shown in FIG. 14, the downlink relay between the mobile station devices is performed using the uplink frequency.

The relay station embeds an identifier in the transmission signal so that it can identify whether the transmission data is addressed to the base station BS1 or the relay requesting station.

As described above, according to the present embodiment, in the multi-hop system, the relay station MS1 receives the data desired to be relayed by another station (mobile station MS2 or base station BS1 outside the service area) and temporarily stores the data in the buffer. .. Then, wait until the transmission timing of the data of the own station is reached, and when this timing is reached, the relay data saved is frequency-division-multiplexed with the data of the own station, and the data after the multiplexing is relayed to the relay destination station (base station BS1 or Send to mobile station MS2). As a result, it is possible to suppress an increase in power consumption of the own station while realizing relay of communication of another station. That is, since the relay station relays the signal of the relay requesting station only when the transmission signal of its own station exists, the power consumption can be suppressed to a low level.

In this embodiment, a case where downlink relay between each mobile station (relay station-relay request station) is performed using an uplink frequency has been described as an example. However, the downlink frequency may be used in the same manner as in normal downlink communication. The configuration of the mobile station device 200a in such a case is as shown in FIG. The OFDM transmission unit 119-2 and the downlink frequency transmission RF unit 212 are transmission systems that perform downlink relay from the relay station to the relay request station. In such a case, since there is no data addressed to the own station in the wireless signal of the uplink frequency, the frequency separation unit 105-2 separates (extracts) only the relay data addressed to the other station, and the data addressed to the other station. Output to channel demodulation unit 107.

Further, when the relay station MS1 executes data relay, the relay station MS1 may notify the mobile station MS2 outside the service area to that effect.

Further, in the present embodiment, the case where the relay station MS1 directly communicates with the base station BS1 has been described as an example, but the present invention is not limited to this, and there is yet another case between the mobile station MS1 and the base station BS1. It may be via a relay station.

Further, in the present embodiment, the case where there is one relay route has been described as an example, but a plurality of relay routes may exist.

Further, in the present embodiment, the case of relaying the data from the mobile station MS2 located outside the service area of the cellular system has been described as an example, but the data from the mobile station located in the non-sensing area may be relayed.

Each embodiment of the present invention has been described above.

The mobile station apparatus and the communication relay method according to the present invention are not limited to the above-described embodiments, and can be modified in various ways. For example, each embodiment can be implemented in an appropriate combination.

In each of the above embodiments, a mobile station device such as a mobile phone has been described as a relay station or a relay request station as an example, but other communication terminal devices may be used, for example, a PDA (Personal Digital Assistant), a notebook PC, or the like. But it's okay.

Further, although the case where the present invention is configured by hardware has been described here as an example, the present invention can also be realized by software. For example, by describing the algorithm of the communication relay method according to the present invention in a programming language, storing this program in a memory, and executing it by an information processing means, the same as the mobile station device and the communication terminal device of the present invention. The function can be realized.

Further, each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them.

In addition, although LSI is used here, it may be called IC, system LSI, super LSI, ultra LSI, etc. depending on the degree of integration.

Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection or setting of circuit cells inside the LSI may be used.

Furthermore, if an integrated circuit technology that replaces the LSI appears due to advances in semiconductor technology or another technology derived from it, it is naturally possible to integrate functional blocks using that technology. There is a possibility of adaptation of biotechnology.

The communication terminal device and the communication relay method according to the present invention have an effect of suppressing an increase in power consumption of the own station while realizing relay of communication of another station, and can be applied to applications such as a multi-hop system.

<figref num="1">The figure for demonstrating the case where the mobile station in a cell relays the uplink communication between a mobile station located outside the cell area and a base station.</figref><figref num="2">FIG. 2A is a diagram showing the timing of uplink / downlink communication of the TDD system, FIG. 2B is a diagram showing a transmission signal of a mobile station outside the service area, and FIG. 2C is a diagram showing a transmission signal of a relay station.</figref><figref num="3">Diagram showing an example of the usage status of the transmission subcarrier of the relay station</figref><figref num="4">A diagram showing an example of the relationship between a transmission subcarrier of a mobile station outside the service area and an empty subcarrier of a relay station.</figref><figref num="5">Diagram showing the relationship between the number of transmission subcarriers and power consumption</figref><figref num="6">A diagram for explaining a case where a mobile station in a cell relays downlink communication between a mobile station outside the service area and a base station.</figref><figref num="7">FIG. 7A is a diagram showing the timing of uplink / downlink communication of the TDD system, FIG. 7B is a diagram showing a transmission signal of a base station, and FIG. 7C is a diagram showing a transmission signal of a relay station.</figref><figref num="8">Diagram showing an example of the usage status of the transmission subcarrier of the relay station</figref><figref num="9">A block diagram showing a main configuration of the mobile station apparatus according to the first embodiment.</figref><figref num="10">Block diagram showing the main configuration of the base station apparatus according to the first embodiment</figref><figref num="11">Diagram for explaining the flow when the relay station relays the data of the relay requesting station</figref><figref num="12">Diagram showing an example of the usage status of the transmission subcarrier of the relay station</figref><figref num="13">A block diagram showing a main configuration of the mobile station apparatus according to the second embodiment.</figref><figref num="14">The figure which summarized the usage of each frequency band in the communication system which concerns on Embodiment 2.</figref><figref num="15">A block diagram showing variations of the mobile station apparatus according to the second embodiment.</figref>

Code description

100 Mobile station equipment 104 OFDM receiver 108 buffer 112 Transmission timing determination unit 113 Transmission frequency determination unit 118 Frequency multiplexing unit 119 OFDM transmitter 150 Base station equipment 152 Transmission timing determination unit 153 Buffer 159 OFDM receiver 160 Control channel demodulation unit 161 Frequency Separation part