JP2004072624A - Mobile communication system, radio receiver and radio transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the communication quality of a MIMO (multi-input, multi-output) communication system when a mobile station is located near a cell boundary. <P>SOLUTION: In a cell 191, a BS 100 has two antennas 101, an MS 150 has two antennas 151 respectively and transmission using MIMO transmission technology is performed from the BS 100 to the MS 150. Also, in the adjacent cell 192, MIMO transmission using the same frequency as that of the cell 191 is performed from the BS 110 to an MS existing in the cell 192 (not illustrated). Then, when the MS 150 is transferred near the cell boundary, space-time encoding is performed to a stream to be transmitted from the BS 100 and the stream is transmitted to the MS 150. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mobile communication system, a wireless receiving device, and a wireless transmitting device.
[0002]
[Prior art]
Conventionally, as a technique for increasing transmission capacity by transmitting different data streams from a plurality of transmission antennas at the same time and at the same frequency and using the same spreading code, a multi-input multi-output (MIMO) technique has been proposed. Output) transmission technology is known. In the MIMO transmission, if the number of receiving antennas is equal to or larger than the number of transmitting antennas, the transmission capacity may increase linearly in Wireless Personal Communication, Vol. 6, 1998, "On Limits of Wireless Communication in a Fading Environment when Using Multiple Antennas", Foschini G. et al. J. Gans M .; J. In general, the condition regarding the number of antennas is a constraint in the design of a wireless communication system to which the MIMO transmission technology is applied.
[0003]
[Problems to be solved by the invention]
However, when the conventional MIMO transmission technology is applied to a cellular mobile communication system that uses the same frequency in an adjacent cell, a radio wave used in an adjacent cell becomes an interference wave in its own cell. The fact that reception characteristics are greatly affected by interference from other cells is described in IEEE COMMUNICATIONS LETTERS, Vol. 4, No. 11, 2000, "Simulation Results for an Interference-Limited Multiple-Input Multiple-Output Cellular System", Catreux, S.M. Driessen, P .; F. Greenstein, L .; J. It is clarified in.
[0004]
In particular, when the mobile station is located near the boundary between the adjacent cell and the own cell (hereinafter, referred to as a cell edge), the influence of the interference wave from the adjacent cell becomes remarkable. For example, when the mobile station is a user having a communication terminal and is located near a base station, a transmission rate of a certain level or more can be secured, and real-time video can be transmitted to the communication terminal without any problem. However, when the user moves to the cell edge, the data transmission rate is greatly reduced due to the influence of adjacent cell interference. As a result, the video is interrupted, or in extreme cases, the video is not displayed at all. Would.
[0005]
As a means for solving this problem, it is conceivable to use different one of frequency, time slot, and spreading code in adjacent cells. There is a problem that it becomes complicated.
[0006]
In addition, the number of antennas provided by the base station or mobile station that is a source of interference with other cells is also taken into consideration, that is, the number of antennas of the base station that manages its own station is M, When the number of antennas of the station is N and the MIMO transmission wave transmitted from the base station of this adjacent cell is an interference wave, the number of antennas subject to the antenna constraint is (M + N) and the constraint is It is conceivable that the number of receiving antennas of the mobile station should be (M + N) or more for adaptation, but a large number of receiving antennas must be provided, and the number of base stations serving as interference transmission sources is not limited to one. In such a case, a larger number of receiving antennas may be required in such a case, which is difficult to implement.
[0007]
The present invention has been made in view of such a point, and when the reception quality of a wireless reception device is deteriorated, such as when a mobile station is located at a cell edge, the communication quality of a mobile communication system can be improved by a simple configuration. It is an object of the present invention to provide a mobile communication system, a wireless receiving device, and a wireless transmitting device that can maintain the above.
[0008]
[Means for Solving the Problems]
A mobile communication system according to the present invention includes a transmission device that wirelessly transmits mutually independent data streams simultaneously from a plurality of transmission systems using the same frequency, and a signal that is wirelessly transmitted from the transmission device and superimposed on a propagation path. And a receiving device for receiving, wherein the transmitting device is configured such that when a reception quality of the receiving device is equal to or less than a threshold, a transmission data stream is generated from the same data stream from the plurality of independent data streams. A configuration is adopted in which switching to a plurality of substreams is performed and radio transmission is simultaneously performed from a plurality of transmission systems using the same frequency.
[0009]
According to this configuration, since the transmission method in the wireless transmission device is changed according to the reception quality in the wireless reception device, even when the reception quality of the wireless reception device is deteriorated such as when the mobile station is located at the cell edge, Communication quality of the mobile communication system can be maintained.
[0010]
The mobile communication system of the present invention, in the above-described configuration, is a cellular mobile communication system in which adjacent cells are operated at the same frequency.
[0011]
In the mobile communication system of the present invention, in the above configuration, the reception quality of the receiving device is a power ratio between a desired signal and adjacent cell interference.
[0012]
In the mobile communication system according to the present invention, the signal used for channel estimation in the adjacent cell is different from the signal used for channel estimation in the own cell, and the mobile communication system is known in the own cell. Take.
[0013]
According to these configurations, since the signal used for propagation path estimation in the adjacent cell is known in the own cell, the replica of the same frequency interference component from the adjacent cell is created using the known signal, so that The interference component from can be removed.
[0014]
In the mobile communication system according to the present invention, in the above configuration, the process of generating a plurality of substreams from the same data stream is space-time coding.
[0015]
According to this configuration, since an existing circuit can be used, the present invention can be implemented immediately.
[0016]
The mobile communication system of the present invention employs a configuration in which, in the above-described configuration, when space-time coding is not performed on a data stream, a circuit related to space-time coding in the transmitting device and the receiving device is stopped.
[0017]
According to this configuration, when space-time coding is not performed, the circuit related thereto is stopped, so that power consumption can be reduced.
[0018]
The wireless receiving apparatus according to the present invention includes: a designation unit that designates whether to use space-time coding for a data stream as a data stream transmission method in a wireless transmission device based on its own reception quality; The wireless communication apparatus adopts a configuration including a notifying unit that notifies the wireless transmission device of a designated transmission method, and an acquisition unit that acquires a data stream from a received signal according to the data stream transmission method used by the wireless transmission device.
[0019]
The wireless receiving device of the present invention is a notifying unit that notifies the wireless transmitting device of its own reception quality, and an obtaining unit that obtains a data stream from a received signal according to a data stream transmitting method used by the wireless transmitting device. Is adopted.
[0020]
The wireless receiving apparatus of the present invention employs a configuration in the above configuration, in which the method of transmitting the data stream used by the wireless transmitting apparatus is specified by analyzing a received signal.
[0021]
According to these configurations, when the reception quality of the wireless reception device deteriorates, the influence of adjacent cell interference can be reduced by space-time coding, and the communication quality of the mobile communication system can be maintained. When adjacent cell interference is not a problem, the transmission rate can be improved by not performing space-time coding.
[0022]
The radio receiving apparatus of the present invention, in the above configuration, wherein the obtaining means performs space-time decoding on an interference component from the adjacent cell based on a space-time code used in the adjacent cell; A configuration is provided that further includes replica creation means for creating a replica of the interference component from the result, and subtraction means for subtracting the replica from the received signal.
[0023]
According to this configuration, by performing space-time decoding also on adjacent cell interference, it is possible to enhance the ability to remove interference components.
[0024]
A wireless transmission apparatus according to the present invention includes: a first transmission unit that simultaneously wirelessly transmits mutually independent data streams from a plurality of transmission systems using the same frequency; and a plurality of sub-streams that perform space-time encoding on the same data stream. And a second transmitting means for simultaneously performing wireless transmission from each of the plurality of transmission systems using the same frequency, respectively, and the first transmission means based on the transmission method notified from the wireless reception apparatus or the reception quality of the wireless reception apparatus. A configuration is adopted in which the data stream is wirelessly transmitted using the transmitting means or the second transmitting means.
[0025]
According to this configuration, since the transmission method of the data stream in the own device is changed according to the transmission method or the reception quality notified from the wireless reception device, the reception of the wireless reception device is performed as when the mobile station is located at the cell edge. Even when the quality deteriorates, the communication quality of the mobile communication system can be maintained.
[0026]
A mobile station device according to the present invention employs a configuration including any one of the above-described wireless receiving devices or wireless transmitting devices.
[0027]
According to this configuration, it is possible to provide a mobile station device having the same functions and effects as described above.
[0028]
A base station apparatus according to the present invention employs a configuration including any one of the above-described radio reception apparatuses or radio transmission apparatuses.
[0029]
According to this configuration, it is possible to provide a base station apparatus having the same functions and effects as described above.
[0030]
A mobile communication method according to the present invention includes a first transmission step of simultaneously transmitting data streams independent of each other from a plurality of transmission systems by using the same frequency simultaneously, and wirelessly transmitting the data streams from the plurality of transmission systems and superimposing the data streams on a propagation path. Receiving the received signal, if the reception quality of the receiving step is equal to or less than a threshold, the transmission data stream into a plurality of sub-streams generated from the same data stream from the plurality of independent data streams Switching, and a second transmission step of simultaneously performing radio transmission simultaneously from the plurality of transmission systems using the same frequency.
[0031]
According to this method, since the transmission method is changed according to the reception quality, the communication quality of the mobile communication system can be reduced even when the reception quality of the wireless reception device is deteriorated such as when the mobile station is located at the cell edge. Can be maintained.
[0032]
The wireless receiving method according to the present invention includes: a specifying step of specifying whether to perform space-time encoding on a data stream as a method of transmitting a data stream in a wireless transmitting apparatus based on its own reception quality; And a notifying step of notifying the wireless transmission device of the transmission method specified by the wireless transmission device, and an acquisition step of acquiring a data stream from a received signal according to the data stream transmission method used by the wireless transmission device. .
[0033]
The wireless receiving method of the present invention is a notifying step of notifying the receiving apparatus of its own reception quality to a wireless transmitting apparatus, and an obtaining step of obtaining a data stream from a received signal according to a data stream transmitting method used by the wireless transmitting apparatus. , Was provided.
[0034]
According to these methods, when the reception quality of the wireless reception device deteriorates, the influence of adjacent cell interference can be reduced by space-time coding, and the communication quality of the mobile communication system can be maintained. When adjacent cell interference is not a problem, the transmission rate can be improved by not performing space-time coding.
[0035]
A wireless transmission method according to the present invention includes a first transmission step of simultaneously transmitting data streams independent of each other from a plurality of transmission systems using the same frequency at the same time, and performing space-time encoding on the same data stream to generate a plurality of sub-streams. And simultaneously performing wireless transmission from the plurality of transmission systems using the same frequency, respectively, at the same time. The first transmission step is performed based on the transmission method notified from the wireless reception device or the reception quality of the wireless reception device. The data stream is wirelessly transmitted using the transmission step or the second transmission step.
[0036]
According to this method, the transmission method of the data stream in the own device is changed in accordance with the transmission method or the reception quality notified from the wireless reception device, so that the reception of the wireless reception device is performed as when the mobile station is located at the cell edge. Even when the quality deteriorates, the communication quality of the mobile communication system can be maintained.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
The gist of the present invention is to enable efficient transmission by performing communication by switching the presence / absence of space-time coding processing of a mobile communication system in accordance with the reception quality of a wireless reception device.
[0038]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a case will be described as an example where mobile communication is performed between a base station and a mobile station adopting the cellular system.
[0039]
(Embodiment 1)
FIG. 1 is a diagram showing an outline of a downlink through which communication is performed by the mobile communication system according to Embodiment 1 of the present invention.
[0040]
In FIG. 1, a base station (BS) 100 manages a cell 191, and a BS 110 manages a cell 192. The mobile station (MS) 150 exists in the cell 191.
[0041]
In the cell 191, the BS 100 has two antennas 101 and the MS 150 has two antennas 151, and performs transmission using the MIMO transmission technology from the BS 100 to the MS 150 (hereinafter, referred to as MIMO transmission). Also in the adjacent cell 192, MIMO transmission using the same frequency as that of the cell 191 is performed from the BS 110 to an MS (not shown) in the cell 192.
[0042]
Generally, when MS 150 is located near BS 100, the amount of power of desired signal S1 transmitted from BS 100 is larger than the amount of co-channel downlink interference from other cell base station BS 110, and in a good reception state. It is expected that there is.
[0043]
However, when the MS 150 moves from the area (193) near the BS 100 to the vicinity of the boundary of the cell 191 (hereinafter, referred to as a cell edge), the situation changes completely. That is, when the MS 150 is located at the cell edge of the cell 191 as shown by the dashed line in FIG. 1, the level difference between the co-channel downlink interference amount from the base station BS 110 of another cell and the power amount of the desired signal from the BS 100 is Because of the small size, the influence of the interference wave I1 arriving from the BS 110 cannot be ignored. For this reason, the reception characteristics of the MIMO communication of the MS 150 are significantly deteriorated. At this time, the MS 150 cannot separate the data stream using a simple separation algorithm such as V-BLAST (stream separation based on the inverse matrix operation for the channel matrix). Although it is conceivable to separate the data stream based on a more complicated MMSE (least square error) criterion or the like, the data stream separation ability is reduced due to the influence of the interference wave.
[0044]
Therefore, in the present embodiment, when MS 150 is located at the cell edge, space-time coding (STC; Space-Time Coding) is performed on the stream transmitted from BS 100, and the stream is transmitted to MS 150 as STC transmission wave S2. Here, STC is a transmission technique disclosed in U.S. Pat. No. 6,115,427 as a method for simultaneously transmitting encoded substreams from a plurality of antennas.
[0045]
STC is a technology that combines encoding and transmission diversity. Although the original data stream is one, by performing space-time encoding on this data stream, a plurality of different data streams are generated, These data streams are simultaneously wirelessly transmitted from a plurality of transmitting antennas using the same frequency. A radio receiving apparatus that receives a signal transmitted using the STC performs channel estimation of a propagation path corresponding to each pair of a transmission antenna and a reception antenna using pilot symbols included in the reception signal, and adjusts the estimated channel characteristics. Based on the information bit, the received signal on which the information bit and the parity bit are superimposed is decoded to extract the information bit.
[0046]
In the STC, there are no restrictions on the number of antennas as in the MIMO wireless communication system. Therefore, it is possible to design a multiple-input one-output (MISO) wireless communication system or a wireless communication system in which the number of receiving antennas is equal to or less than the number of transmitting antennas.
[0047]
Whereas MIMO transmission transmits different data streams from multiple transmission systems, space-time coded transmission transmits multiple coded sub-streams generated from one data stream, so that The transmission capacity of the device is reduced. However, in space-time coded transmission, since a coding gain is expected, it is expected that the stream separation capability is improved by that much. This makes it less susceptible to interference components. In addition, since each bit has a transmission antenna diversity gain, the received power of each bit can be increased. Therefore, under the situation where co-channel interference is large as described above, space-time coded transmission can be expected to achieve better throughput characteristics than MIMO transmission.
[0048]
Note that whether or not the MS 150 is located at the cell edge is actually determined by comparing its own reception quality (SIR or the like) with a threshold. That is, when the reception quality is equal to or less than the threshold, it is determined that the mobile station is located at the cell edge. The reason why such a configuration is adopted is that even when the mobile station is located at the cell edge, it is not necessary to switch the communication method as long as the reception quality does not deteriorate.
[0049]
For example, in FIG. 1, the desired radio wave received when MS 150 is located at the cell edge is STC transmission wave S2 transmitted from BS 101. Here, when no mobile station exists at the cell edge of the adjacent cell 192, the transmission wave transmitted from the BS 110 is only a downlink MIMO transmission signal to a mobile station (not shown) located around the BS 110. When proper downlink transmission power control is performed, the MIMO transmission signal has little effect on the MS 150 as other-cell interference I1 due to distance attenuation.
[0050]
On the other hand, as shown in FIG. 2, when MS 150 is located at the cell edge and MS 160 is also located at the cell edge in adjacent cell 192, the influence of other-cell interference increases. In the present embodiment, it is assumed that BS 110 performs STC transmission (S3) to MS 160 similarly to BS 100. In this case, STC transmission wave I2 transmitted from BS 110 is also transmitted at the cell edge of cell 191. Reach while maintaining some strength.
[0051]
Therefore, in the present embodiment, space-time decoding is also performed on downlink co-channel interference from other cells, and interference components are removed by using the decoding result. As a result, it is possible to maintain the communication quality of the downlink of the mobile station existing near the cell boundary. Note that the radio receiving apparatus according to the present embodiment needs to know the space-time code used in the other cell, and desirably has synchronization between the desired signal and the interference signal. .
[0052]
With the above configuration, the user who was near the base station and displayed the real-time video on the communication terminal without any problem moves to the cell edge. It can be avoided that the video is not displayed at all.
[0053]
FIG. 3 is a diagram illustrating an outline of an uplink in which communication is performed by the mobile communication system according to the present embodiment.
[0054]
In cell 191, MIMO transmission is performed from MS 150 to BS 100. In the neighboring cell 192, MIMO transmission using the same frequency is performed from the MS 160 to the BS 110.
[0055]
Here, if MS 150 and MS 160 are both located near the base station and appropriate uplink transmission power control is performed, the reception power of the desired signal in BS 100 and BS 110 is compared with the uplink interference power from the adjacent cell. Therefore, good uplink MIMO transmission is possible.
[0056]
However, when the MS 150 is located at the cell edge of the cell 191 and the MS 160 is located at the cell edge of the cell 192, as shown by the dashed line in FIG. Since the level difference of the power amount of the signal becomes small, the influence of the MIMO transmission wave (interference wave) I3 arriving from the MS 160 cannot be ignored.
[0057]
Therefore, in the present embodiment, when MS 150 is located at a cell edge, space-time encoding is performed on a stream transmitted from MS 150. Similarly, space-time encoding is performed on the stream transmitted from MS 160. At this time, the radio waves received by BS 100 are STC transmission wave S5 transmitted from MS 150 and STC transmission wave (interference wave) I3 transmitted from MS 160. The BS 100 also performs space-time decoding processing on uplink co-channel interference from other cells 192, and removes interference components by using the decoding result. Thereby, the communication quality of the uplink of the base station can be maintained.
[0058]
That is, when the mobile station is located at the cell edge of the adjacent cell also in the uplink, the transmission wave transmitted from the mobile station becomes an interference wave for BS 100, so that the transmission is changed to STC transmission.
[0059]
As described above, according to the present embodiment, when the mobile station is located at the cell edge and the communication quality is degraded, the communication method is switched, and the effect of adjacent cell interference is reduced by space-time coding. Quality can be maintained.
[0060]
Here, a case has been described as an example where the influence of the amount of other cell interference received by the radio receiving apparatus (mobile station or base station) is reduced. However, as described above, space-time coded transmission is more effective than MIMO transmission. This has the advantage that the stream separation capability is improved, the effect of interference components is reduced, and the received power of each bit can be increased. Therefore, when the reception quality of the radio receiving apparatus is deteriorated, not limited to the interference of other cells, the improvement of the communication quality can be expected by using the mobile communication system according to the present embodiment.
[0061]
(Embodiment 2)
FIG. 4 is a block diagram showing an example of a configuration of the wireless reception device according to Embodiment 2 of the present invention.
[0062]
The radio reception apparatus shown in FIG. 4 includes reception antennas 201-1 and 201-2, a reception radio process (R _X RF) units 202-1 and 202-2, A / D conversion units 203-1 and 203-2, a reception SIR measuring unit 204, a switching control unit 205, an STC reception processing unit 210, and a MIMO reception processing unit 220.
[0063]
Then, STC reception processing section 210 has STC canceller 211 having space-time decoder 213, replica generation section 214, and subtractors 215-1 and 215-2, and space-time decoder 212. On the other hand, the MIMO reception processing section 220 has a MIMO detection section 221 and a multiplexer (MUX) 222.
[0064]
The signals received by the reception antennas 201-1 and 201-2 are subjected to predetermined processing via the reception radio processing units 202-1 and 202-2 and the A / D conversion units 203-1 and 203-2. After that, it is output to the reception SIR measuring device 204 and the switching control unit 205.
[0065]
The reception SIR measuring device 204 measures a desired signal power to interference signal power ratio of the reception signal, and notifies the switching control unit 205 of SIR (Signal-to-Interference Ratio) information.
[0066]
The switching control unit 205 analyzes the frame of the received signal and extracts the transmission method used in the wireless transmission device. Then, based on the extracted information, the received signal is output to either STC reception processing section 210 or MIMO reception processing section 220. Further, based on the SIR information notified from the reception SIR measuring device 204, a transmission method designation command for designating a transmission method in the wireless transmission device is generated, and the transmission wireless processing unit and the transmission antenna (both not shown) are set. To the wireless transmission device via
[0067]
The signal output to STC reception processing section 210 is subjected to STC canceller 211, from which STC interference waves are removed, and is then space-time decoded by space-time decoder 212 to become reception data.
[0068]
In STC canceller 211, space-time decoder 213 performs space-time decoding of the interference signal and outputs the result to replica generation section 214.
[0069]
The replica generation unit 214 generates an interference replica from the decoding result of the interference signal output from the space-time decoder 213, and outputs the generated replica to the subtractors 215-1 and 215-2.
[0070]
In the subtracters 215-1 and 215-2, the interference component is removed by subtracting the output of the replica generation unit 214 from the signal output from the switching control unit 205. Thereby, the space-time decoding performance for the desired signal is enhanced.
[0071]
In MIMO reception processing section 220, MIMO detection section 221 performs MIMO separation processing for separating information streams transmitted by a plurality of transmission systems based on the MMSE standard or the like, and outputs the result to MUX 222. The MUX 222 performs parallel / serial conversion on the plurality of streams after the separation processing to obtain received data.
[0072]
Note that when transmission is performed without performing space-time encoding, the switching control unit 205 stops the STC reception processing unit 210 by the control signal C1 to reduce power consumption.
[0073]
Next, a procedure of a wireless frame receiving process of the wireless receiving apparatus having the above configuration will be described with reference to a flowchart shown in FIG.
[0074]
In step (hereinafter referred to as ST) 2010, switching control section 205 analyzes control information included in the radio frame, and extracts a transmission method by using the radio transmission apparatus to transmit the radio frame. .
[0075]
It is determined whether or not space-time coding has been performed in the wireless transmission device based on the extracted information (ST2020). If space-time coding has been performed, STC reception processing (ST2030) is performed, and space-time coding is performed. If not, a MIMO reception process (ST2040) is performed.
[0076]
After the reception processing, reception SIR measurement is performed (ST2050). It is determined whether or not the reception SIR is equal to or smaller than the threshold (ST2060). If the reception SIR is equal to or smaller than the threshold, a command for designating the transmission method to STC is generated (ST2070). On the other hand, if the amount of interference is small and the reception SIR is larger than the threshold, a command specifying the transmission method to MIMO is generated (ST2080). The transmission method designation command generated in the above step is notified from the wireless reception device to the wireless transmission device via the reverse link (ST2090).
[0077]
FIG. 6 is a block diagram showing an example of a configuration of the radio transmission apparatus according to Embodiment 2 of the present invention.
[0078]
6 includes a demultiplexer (DEMUX) 251, a space-time encoder 252, a switch 253, D / A conversion units 254-1 and 254-2, a transmission radio process (T _X RF) units 255-1 and 255-2, and transmission antennas 256-1 and 256-2.
[0079]
The transmission data sequence is input to a demultiplexer (DEMUX) 251 and a space-time encoder 252. The demultiplexer (DEMUX) 251 splits the input transmission data sequence into a plurality of data streams, and outputs the plurality of data streams to the switch 253.
[0080]
The space-time encoder 252 generates a plurality of encoded substreams by performing space-time encoding on the input transmission data sequence, and outputs the plurality of encoded substreams to the switch 253.
[0081]
The switch 253 is based on a transmission method designation command fed back from the above-described wireless receiving device and received via a receiving antenna and a receiving wireless processing unit (both not shown), or an output stream from the demultiplexer 251 or a space-time. One of the streams space-time encoded by the encoder 252 is selected, switched, and output to the D / A conversion units 254-1 and 254-2. When space-time encoding is not specified as the transmission method, the space-time encoder 252 is stopped by the control signal C2 to reduce power consumption.
[0082]
The plurality of streams output from the switch 253 are subjected to predetermined processing in the D / A conversion units 254-1 and 254-2 and the transmission radio processing units 255-1 and 255-2, respectively. 1, 256-2.
[0083]
The transmission streams transmitted from the transmission antennas 256-1 and 256-2 pass through different propagation paths, are spatially superimposed after transmission, and are received by the wireless reception device.
[0084]
Note that the radio receiving apparatus and the radio transmitting apparatus according to the present embodiment can be mounted on a mobile station apparatus and a base station apparatus using a cellular system, whereby the mobile station apparatus having the same operation as above can be provided. And a base station device.
[0085]
As described above, according to the present embodiment, when the reception SIR is low, the communication method is switched, and the influence of adjacent cell interference is reduced by space-time coding, so that communication quality can be maintained. Further, since there are many parts having a common configuration between the circuit related to the MIMO transmission and the circuit related to the space-time coding, the circuit scale can be reduced.
[0086]
Note that, in the present embodiment, the case where SIR is used as the reception quality of the wireless reception device has been described as an example, but the reception quality is not limited to SIR, and may be Eb / No, RSSI (Received Signal Strength Indicator), or the like. good.
[0087]
(Embodiment 3)
FIG. 7 is a block diagram showing an example of a configuration of the wireless reception device according to Embodiment 3 of the present invention. Note that this radio receiving apparatus has the same basic configuration as the radio receiving apparatus shown in FIG. 4, and the same components are denoted by the same reference numerals and description thereof will be omitted.
[0088]
The feature of the present embodiment is that when performing MIMO transmission / reception between a base station and a mobile station located near the base station, other cell interference occurs rapidly, and the influence of this interference amount cannot be ignored. This is to remove other-cell interference using the STC canceller 211. Here, it is assumed that the data stream of the other-cell interference is space-time coded.
[0089]
The signals received by the receiving antennas 201-1 and 201-2 are subjected to predetermined processing through the reception radio processing units 202-1 and 202-2 and the A / D conversion units 203-1 and 203-2. Thereafter, the signal is output after being divided into two signal systems. The first signal system is a system that is directly output to the switching control unit 301, and the second signal system is a system that is output to the switching control unit 301 via the STC canceller 211.
[0090]
In the first signal system, the signal is also output to the reception SIR measuring device 204. The reception SIR measuring device 204 measures the ratio of the desired signal power to the interference signal power of the received signal, and notifies the switching control unit 301 of the SIR information.
[0091]
Switching control section 301 outputs to MIMO reception processing section 220 either the received signal or a signal obtained by subtracting the interference replica from the received signal based on the SIR information. The subsequent signal processing is the same as in the second embodiment.
[0092]
As described above, according to the present embodiment, even if a mobile station is near the base station, or if the influence of the amount of interference of other cells cannot be ignored in the base station, other cell interference is removed and MIMO transmission is performed. Communication quality can be maintained.
[0093]
Note that this embodiment can be implemented in combination with Embodiment 2.
[0094]
【The invention's effect】
As described above, according to the present invention, the communication quality of the mobile communication system can be maintained even when the reception quality of the wireless reception device is deteriorated such as when the mobile station is located at the cell edge.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a downlink on which communication is performed by a mobile communication system according to Embodiment 1 of the present invention.
FIG. 2 is a diagram for explaining a case where a mobile station is located at a cell edge in the mobile communication system according to Embodiment 1 of the present invention.
FIG. 3 is a diagram showing an outline of an uplink in which communication is performed by the mobile communication system according to the first embodiment of the present invention.
FIG. 4 is a block diagram showing an example of a configuration of a wireless reception device according to Embodiment 2 of the present invention.
FIG. 5 is a flowchart showing a procedure of a wireless frame receiving process of the wireless receiving apparatus according to Embodiment 2 of the present invention
FIG. 6 is a block diagram showing an example of a configuration of a radio transmission apparatus according to Embodiment 2 of the present invention.
FIG. 7 is a block diagram showing an example of a configuration of a wireless receiving apparatus according to Embodiment 3 of the present invention.
[Explanation of symbols]
100, 110 base stations
101, 111, 151, 161 antenna
150, 160 mobile station
191, 192 cells
201-1 and 201-2 receiving antenna
204 Received SIR measuring instrument
205 Switching control unit
210 STC reception processing unit
211 STC canceller
212, 213 space-time decoder
214 Replica generation unit
220 MIMO reception processing unit
252 space-time encoder
253 switch
256-1, 256-2 transmitting antenna
301 Switching control unit
S1 to S6 wireless transmission wave
I1-I3 interference wave

Claims (19)

A transmission device that simultaneously wirelessly transmits mutually independent data streams from a plurality of transmission systems using the same frequency,
And a receiving device that receives a signal wirelessly transmitted from the transmitting device and superimposed on a propagation path,
The transmitting device,
When the reception quality of the receiving device is equal to or less than a threshold, the transmission data stream is switched from the plurality of independent data streams to a plurality of sub-streams generated from the same data stream, and the same frequency is respectively transmitted from the plurality of transmission systems. Wireless transmission at the same time using
A mobile communication system characterized by the above-mentioned. 3. The mobile communication system according to claim 1, wherein adjacent cells are operated at the same frequency. The mobile communication system according to claim 2, wherein the reception quality of the receiving device is a power ratio between a desired signal and adjacent cell interference. 4. The mobile station according to claim 2, wherein a signal used for propagation path estimation in an adjacent cell is different from a signal used for propagation path estimation in the own cell, and is known in the own cell. Body communication system. The mobile communication system according to claim 1, wherein the processing of generating a plurality of substreams from the same data stream is space-time coding. The mobile communication system according to any one of claims 1 to 5, wherein, when space-time coding is not performed on the data stream, a circuit related to space-time coding is stopped in the transmitting device and the receiving device. Designation means for designating whether to use space-time coding for a data stream as a method for transmitting a data stream in a wireless transmission device based on its own reception quality,
Notifying means for notifying the wireless transmission device of the transmission method specified by the specifying means,
Acquisition means for acquiring a data stream from a received signal according to the data stream transmission method used by the wireless transmission device,
A wireless receiving device comprising: Notification means for notifying the wireless transmission device of the reception quality of the own device,
Acquisition means for acquiring a data stream from a received signal according to the data stream transmission method used by the wireless transmission device,
A wireless receiving device comprising: 9. The wireless receiving device according to claim 7, wherein a method of transmitting the data stream used by the wireless transmitting device is specified by analyzing a received signal. The acquisition means,
Space-time decoding means for performing space-time decoding on the interference component from the adjacent cell based on the space-time code used in the adjacent cell,
Replica creation means for creating a replica of the interference component from the space-time decoding result,
Subtraction means for subtracting the replica from a received signal;
The wireless receiving device according to claim 7, further comprising: First transmitting means for simultaneously wirelessly transmitting mutually independent data streams from a plurality of transmission systems using the same frequency,
A second transmitting unit that performs space-time encoding on the same data stream to generate a plurality of substreams, and simultaneously performs wireless transmission from the plurality of transmission systems using the same frequency, respectively,
Wirelessly transmitting the data stream using the first transmitting means or the second transmitting means based on the transmission method notified from the wireless receiving apparatus or the reception quality of the wireless receiving apparatus;
A wireless transmission device characterized by the above-mentioned. A mobile station device comprising the wireless receiving device according to claim 7. A mobile station device comprising the wireless transmission device according to claim 11. A base station apparatus comprising the wireless receiving apparatus according to claim 7. A base station device comprising the wireless transmission device according to claim 11. A first transmission step of simultaneously wirelessly transmitting mutually independent data streams from a plurality of transmission systems using the same frequency,
A receiving step of receiving a signal wirelessly transmitted from the plurality of transmission systems and superimposed on a propagation path,
If the reception quality of the receiving step is equal to or less than a threshold, the transmission data stream is switched from the plurality of independent data streams to a plurality of sub-streams generated from the same data stream, and the same frequency is respectively transmitted from the plurality of transmission systems. A second transmission step of simultaneously performing wireless transmission using
A mobile communication method comprising: A designation step of designating whether to perform space-time encoding on a data stream as a transmission method of the data stream in the wireless transmission device based on its own reception quality,
A notification step of notifying the wireless transmission device of the transmission method designated by the designation step,
An obtaining step of obtaining a data stream from a received signal according to a data stream transmitting method used by the wireless transmitting apparatus,
A wireless receiving method comprising: A notification step of notifying the wireless transmission device of the reception quality of the own device,
An obtaining step of obtaining a data stream from a received signal according to a data stream transmitting method used by the wireless transmitting apparatus,
A wireless receiving method comprising: A first transmission step of simultaneously wirelessly transmitting mutually independent data streams from a plurality of transmission systems using the same frequency,
A second transmission step of performing a space-time encoding on the same data stream to generate a plurality of substreams, and simultaneously performing wireless transmission from the plurality of transmission systems using the same frequency, respectively,
Wirelessly transmitting the data stream using the first transmission step or the second transmission step based on the transmission method notified from the wireless reception device or the reception quality of the wireless reception device;
A wireless transmission method characterized by the above-mentioned.

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