JP2011146988A - Radio communication system, base station device, terminal device and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver suppressing expansion of a circuit scale even when the number of correspondent radio frequency bands is increased. <P>SOLUTION: In a radio communication system, a base station device 10 transmits control information which controls transmission of a reception response signal so as to receive the reception response signal, to a signal transmitted to a terminal device, without interference. The terminal device transmits a reception response signal to the signal, which the base station device 10 has transmitted to the terminal device, in accordance with the control information transmitted from the base station device 10 in such a way that the base station device 10 receives the reception response signal without interference. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio communication system, a base station apparatus, a terminal apparatus, and a communication method that perform communication using a plurality of radio bands.

As an example, a wireless communication system in which a base station (see FIG. 19) communicates with a plurality of terminals (see FIG. 20) using a plurality of frequency channels is a wireless LAN (Local Area Network) access point compliant with the IEEE 802.11 standard. And a terminal (see, for example, Non-Patent Document 1). In the IEEE802.11 standard, when a terminal receives a downlink signal in the terminal direction from the base station, the terminal transmits a reception response signal (ACK signal) to the base station using the received frequency channel (see FIG. 21).
In such a wireless communication system, a base station may communicate simultaneously using different frequency channels for communication with a plurality of terminals (see FIG. 22). For example, there are wireless LAN products that use respective frequency channels of 2.4 GHz band and 5 GHz band, which are unlicensed frequency bands (see, for example, Non-Patent Document 2).
When the base station receives an ACK signal transmitted from each terminal, the received power received at the base station varies depending on the influence such as the distance to the terminal.

IEEE Std 802.11TM-2007, July 2007. "Wireless access point" WL-1154 "", [online], East Nippon Telegraph and Telephone Corporation, January 6, 2010 search, Internet <URL: http://www.ntt-east.co.jp/office/ goods / wl1154 / method.html # cstart>

By the way, even when the power spectrum density of each frequency channel satisfies the frequency mask in the frequency spectrum of the received power as prescribed, interference may occur in communication when the frequency channels are adjacent. For example, when ACK signals of adjacent frequency channels are received simultaneously, interference may occur (see FIG. 23). In particular, in adjacent frequency channels, reception failure occurs in a state where reception power balance is poor. For example, the out-of-band power in the spectrum of the frequency channel with high received power may be the same as the power at the center frequency of the spectrum of the frequency channel with low received power. When such a situation occurs, it becomes difficult to receive a frequency channel with low received power.
Therefore, the technique of Non-Patent Document 2 uses a method of securing a bandwidth that does not cause interference using frequency bands that are greatly separated from each other, such as the 2.4 GHz band and the 5 GHz band (see FIG. 22).
However, if the frequency channels are arranged so that interference does not occur between adjacent frequency channels and the guard band bandwidth for avoiding the influence of the respective out-of-band power is secured, an unusable frequency channel is generated. For this reason, there arises a problem that the frequency utilization efficiency is deteriorated and a problem that the analog circuit becomes complicated because it is necessary to generate a plurality of transmission signals having different center frequencies.

  The present invention has been made in view of such circumstances, and provides a radio communication system, a base station apparatus, a terminal apparatus, and a communication method capable of improving the frequency utilization efficiency by suppressing the generation of unusable frequency channels. There is to do.

  In order to solve the above-described problem, the present invention provides a wireless communication system including a plurality of terminal devices and a base station device that communicates with the plurality of terminal devices, wherein the base station device is connected to the terminal device. Control information for controlling the transmission of the reception response signal is transmitted so that the reception response signal with respect to the signal transmitted to the terminal device is received without interference, and the base station device transmits the control information to the terminal device. A reception response signal for the signal transmitted in response to the control information transmitted from the base station apparatus so that the base station apparatus receives the reception response signal without interference. A wireless communication system.

  Further, the present invention provides the base station apparatus according to the above-mentioned invention, wherein the base station apparatus controls transmission start time of the reception response signal so that the reception response signal is not received simultaneously using an adjacent channel, and the terminal The apparatus transmits the reception response signal based on a transmission start time instructed according to control information transmitted from the base station apparatus.

  Also, in the present invention according to the above-described invention, the base station apparatus may be configured such that when the reception response signal is arranged in an adjacent channel, the reception power of the reception response signal becomes a power level that allows reception without interference. The transmission power from the terminal device arranged in a channel adjacent to the base station device is controlled, and the terminal device receives the reception response signal based on the transmission power instructed according to the control information transmitted from the base station device. Is transmitted.

  Further, the present invention provides the directivity characteristics of the transmission wave transmitted by the terminal device so that the reception power of the reception response signal is a power level at which reception is possible without interference. And the terminal apparatus transmits the reception response signal based on a directivity characteristic of the transmission wave instructed according to control information transmitted from the base station apparatus.

  Further, the present invention is characterized in that the control information transmitted from the base station apparatus includes instruction information for instructing a condition for the terminal apparatus to transmit the reception response signal.

  Further, according to the present invention, the control information transmitted from the base station apparatus includes information for determining a condition for the terminal apparatus to transmit the reception response signal, and the terminal apparatus satisfies the condition for transmitting the reception response signal. Instruction information for instructing transmission of the reception response signal is generated based on information to be defined.

  Further, the present invention is a base station device that communicates with a plurality of terminal devices, wherein the base station device receives a reception response signal transmitted from the terminal device according to a reception status of a signal received by the terminal device. The base station apparatus is characterized by transmitting control information for controlling transmission of the reception response signal and receiving a reception response signal from the terminal apparatus.

  Further, the present invention is a terminal apparatus that communicates with the base station apparatus according to any one of the above-described inventions, and receives a signal transmitted from the base station apparatus to the own apparatus, and responds to the reception status. The terminal apparatus transmits the reception response signal according to the control information transmitted from the base station apparatus so that the base station apparatus receives the reception response signal to be transmitted without interference. It is.

  Further, the present invention is a communication method of a radio communication system including a plurality of terminal devices and a base station device communicating with the plurality of terminal devices, the signal transmitted from the base station device to the terminal device A process of transmitting control information for controlling the transmission of the reception response signal so that the reception response signal to be received without interference, and so that the base station apparatus receives the reception response signal without interference And a process in which the terminal apparatus transmits the reception response signal in accordance with the control information transmitted from the base station apparatus.

According to the present invention, in the radio communication system, the base station apparatus transmits control information for controlling the transmission of the reception response signal so that the reception response signal with respect to the signal transmitted to the terminal apparatus is received without interference. To do. The terminal device is a reception response signal for the signal transmitted from the base station device to the terminal device, and the control information transmitted from the base station device so that the base station device receives the reception response signal without interference. In response to this, the reception response signal is transmitted.
Thereby, in a radio | wireless communications system, since generation | occurrence | production of the frequency channel which cannot be used can be suppressed, it becomes possible to improve frequency utilization efficiency.

It is a block diagram which shows the structure of the radio | wireless communications system by 1st Embodiment of this invention. It is a block diagram which shows the structure of the base station apparatus by this embodiment. It is a block diagram which shows the structure of the terminal device by this embodiment. It is a figure which shows the transmission power in the radio | wireless communications system by this embodiment. It is a figure which shows the interference of the received signal in the radio | wireless communications system by this embodiment. It is a figure which shows the interference of the received signal in the radio | wireless communications system by this embodiment. 5 is a timing chart showing the operation of the wireless communication system according to the present embodiment. 6 is a timing chart illustrating an operation of the wireless communication system according to the second embodiment. It is a block diagram which shows the structure of the base station apparatus by 3rd Embodiment. It is a block diagram which shows the structure of the terminal device by this embodiment. It is a figure which shows the interference of the received signal in the radio | wireless communications system by this embodiment. It is a timing chart which shows operation | movement of the radio | wireless communications system by 4th Embodiment. 5 is a timing chart showing the operation of the wireless communication system according to the present embodiment. 5 is a timing chart showing the operation of the wireless communication system according to the present embodiment. It is a block diagram which shows the structure of the terminal device by 5th Embodiment. It is a block diagram which shows the structure of the radio | wireless communications system by 6th Embodiment. It is a block diagram which shows the structure of the base station apparatus by this embodiment. 5 is a timing chart showing the operation of the wireless communication system according to the present embodiment. It is a block diagram which shows the structure of the base station apparatus in background art. It is a block diagram which shows the structure of the terminal device in background art. 6 is a timing chart (part 1) illustrating an operation of the wireless communication system in the background art. 6 is a timing chart (part 2) illustrating the operation of the wireless communication system in the background art. 7 is a timing chart (part 3) illustrating the operation of the wireless communication system in the background art.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a wireless communication system according to an embodiment of the present invention.
A wireless communication system 1 shown in this figure includes a base station apparatus (AP: access point) 10 that performs communication using a wireless communication line, and a terminal apparatus (STA) that communicates with the base station apparatus 10 using a wireless communication line. A plurality of 50 are provided. In this figure, the base station apparatus 10 which communicates with the two terminal devices 50-1 and 50-2 is illustrated as an aspect of this embodiment.
Further, the base station apparatus 10 is connected to other network equipment by a wired line (wired NW) 70. The base station apparatus 10 is supplied with transmission data to be transmitted to the terminal apparatus 50 from the wired NW 70. Further, the base station apparatus 10 supplies the reception data received from the terminal apparatus 50 to the wired NW 70.

FIG. 2 is a block diagram illustrating a configuration of the base station apparatus.
The base station apparatus 10 shown in this figure includes a transmission queue 11, a transmission data selection unit 12, a modulation unit 13, a synthesis unit 14, a TDD (Time Division Duplex) switch 15, a transmission / reception antenna 16, and a frame detection unit 17. A distribution unit 18, a demodulation unit 19, an error detection unit 20, a retransmission control unit 21, a channel access management unit 22, and an ACK timing management unit 23. In this figure, the number of frequency channels (channels) used by the base station apparatus 10 for transmission is k channels.

  The transmission queue 11 is a queue buffer that temporarily holds transmission data supplied from the wired NW 70 for each user of the transmission data. The transmission queue 11 is divided into # 1 to #n, and each is assigned to each user. In the transmission queue 11, the queue buffers provided separately function independently.

The transmission data selection unit 12 extracts transmission information to be transmitted according to instructed control information and the like, and selects a frequency channel (frequency band) to be transmitted.
The transmission data selection unit 12 is supplied with the same number (k) of transmission data as the number of available frequency channels (channels) from the transmission data held in the transmission queue 11. The transmission data selection unit 12 extracts a data frame including the transmission data as transmission information. The transmission data selection unit 12 extracts a control frame including an ACK signal for each channel supplied from the retransmission control unit 21 as transmission information. The transmission data selection unit 12 receives supply from the channel access management unit 22 of channel control information indicating a channel to be transmitted by the terminal device 50. The transmission data selection unit 12 extracts a control frame including the channel control information as transmission information. The transmission data selection unit 12 receives supply of transmission delay control instruction information for delaying the transmission timing of the ACK signal to be transmitted by the terminal device 50 from the ACK timing management unit 23. The transmission data selection unit 12 extracts a control frame including the transmission delay control instruction information as transmission information.
Then, the transmission data selection unit 12 supplies the modulation unit 13 with a data frame including the transmission data and a control frame including at least one of ACK signal, channel control information, and transmission delay control instruction information. The transmission data selection unit 12 notifies the timing management unit 23 of the selected frequency channel (frequency band).

The modulation unit 13 generates a modulated signal obtained by modulating a data frame or control frame including transmission information supplied from the transmission data selection unit 12 at a predetermined frequency. The modulation unit 13 is provided as modulation units 13-1 to 13-k corresponding to the frequency channels (channels) arranged adjacent to each other. The modulators 13-1 to 13-k function independently of each other.
The synthesizer 14 generates a radio frame based on the modulated signal modulated for each channel. Further, the combining unit 14 generates a transmission signal by performing a combining process of multiplexing in at least one of the time domain, the frequency domain, and the spatial domain according to each frequency channel. A general method can be applied to this synthesis process.

The TDD switch 15 supplies the combined transmission signal to the transmission antenna 16 (transmission state). Further, the TDD switch 15 supplies a signal received by the transmission antenna 16 as a reception signal (reception state). The TDD switch 15 switches between a transmission state and a reception state in a time division manner.
The transmission / reception antenna 16 transmits the transmission signal supplied from the combining unit 14 as a radio signal. The transmitting / receiving antenna 16 detects a received radio signal, generates a received signal, and supplies the received signal to the TDD switch. The transmission / reception antenna includes a plurality of antennas, and can transmit and receive independent signals.

The frame detection unit 17 extracts radio frame information and ACK timing information from a radio frame transmitted as a data frame and a control frame from the terminal device 50 based on the received signal. Further, the frame detection unit 17 receives supply of ACK timing information from the ACK timing management unit 23 in which a response signal (ACK signal) from the terminal device 10 is returned. Then, the frame detection unit 17 supplies the extracted radio frame information and ACK timing information to the distribution unit 18 and the demodulation unit 19.
Based on the radio frame information and ACK timing information supplied from the frame detection unit 17, the distribution unit 18 separates the reception signal and ACK signal of each channel for each channel and distributes them to each demodulation unit 19.
The demodulator 19 demodulates the received signal distributed by the distributor 18 based on the radio frame information and ACK timing information supplied from the frame detector 17. The demodulating unit 19 is divided from the demodulating unit 19-1 to the demodulating unit 19-k according to the frequency channel (channel). The demodulator 19-1 to the demodulator 19-k function independently of each other.

The error detection unit 20 performs error detection on the signal demodulated by the demodulation unit 19 and determines whether or not the information transmitted from the terminal device 50 has been received without error.
The retransmission control unit 21 generates an ACK signal for the normally received signal and supplies it to the transmission data selection unit 12 when the demodulated signal is normally received without error as determined by the error detection unit 20.

  The channel access management unit 22 detects the reception state based on the received reception signal, and determines whether the channel is usable based on the reception state for each channel. The channel access management unit 22 generates channel control information that instructs the terminal device 50 on a channel to be transmitted based on the reception state determination result. When it is determined that the channel is usable, the channel access management unit 22 supplies channel control information including channel information that can be used to the transmission data selection unit 12. For example, the channel access management unit 22 determines whether or not the channel can be used based on the level of the received signal strength (RSSI) of the channel and satisfies a predetermined threshold level. Judge as possible channel.

The ACK timing management unit 23 manages the transmission timing of the ACK signal transmitted by the terminal device 50. The ACK timing management unit 23 manages the transmission timing of the ACK signal so that it can be received at a timing that does not interfere with the ACK signal transmitted using an adjacent channel. For example, the ACK timing management unit 23 is realized by the following configuration in order to enable reception at a timing that does not interfere with an ACK signal transmitted using an adjacent channel.
When a signal is transmitted from the base station device 10 to the terminal device 50 using the adjacent channel, the ACK signal from the terminal device 50 arrives at the same timing. When the base station apparatus 10 transmits signals to a plurality of terminal apparatuses 50 at the same timing using adjacent channels, the ACK timing management unit 23 sets different transmission timings of ACK signals from the adjacent terminal apparatuses 50. To. The ACK timing management unit 23 delays the transmission timing from the other terminal device 50 while keeping the transmission timing of the ACK signal from one terminal device 50 of the adjacent terminal devices 50 as the conventional one. Thereby, the base station apparatus 10 can be controlled not to receive at the same timing. The ACK timing management unit 23 generates transmission delay control instruction information that delays the transmission timing of the ACK signal to the terminal device 50 and supplies the transmission delay control instruction information to the transmission data selection unit 12.

  In addition, the ACK timing management unit 23 generates a reception delay instruction that is received by delaying the reception timing of the ACK signal included in the reception signal from the terminal device 50. The reception delay instruction is generated based on a transmission delay control instruction for delaying the transmission timing of the ACK signal to the terminal device 50. The ACK timing management unit 23 supplies the generated reception delay instruction to the frame detection unit 17.

Subsequently, the operation of the base station apparatus 10 shown in FIG. 2 will be described.
First, the operation of the transmission system in the base station apparatus 10 that transmits a signal from the base station apparatus 10 to the terminal apparatus 50 will be described.
The channel access management unit 22 determines whether each channel can be used. For this determination, for example, a carrier sense / random backoff function based on CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) which is channel access control defined in the IEEE 802.11 standard can be used.
When determining that the channel is in an available state, the channel access management unit 22 notifies the transmission data selection unit 12 of a transmission instruction using the channel.
The transmission data selection unit 12 extracts the same number of data frames as the number of available frequency channels (denoted as k) from the transmission queue 11 that holds transmission data for each user, and selects a frequency band for transmitting each data frame To do. The transmission data selection unit 12 supplies information on the selected frequency band to the ACK timing management unit 22.
The ACK timing management unit 22 determines the ACK timing of each data frame and supplies it to the transmission data selection unit 12 so that the ACK timings of adjacent channels do not coincide with each other.
The transmission data selection unit 12 supplies each data frame and timing information of an ACK signal to be responded to each data frame to the modulation units 13-1 to 13-k.
The modulation unit 13 converts the supplied data frame into a radio signal.
The synthesizer 14 synthesizes a plurality of radio signals into a wideband radio signal and transmits it to each terminal device via the transmission / reception antenna 16.

Next, an operation of the reception system in the base station apparatus 10 that receives information transmitted from the terminal apparatus 50 will be described.
When receiving an ACK frame from each terminal device 50, the frame detector 17 detects the frequency band and timing at which the radio frame arrives. The distribution unit 58 distributes the received signal to the respective demodulation units 19-1 to 19-k for each frequency band based on the detected radio frame.
Alternatively, the reception timing may be determined using the ACK timing information of each channel supplied from the ACK timing management unit 23.
Each demodulator 19-1 to 19-k demodulates the supplied signal and converts it into a baseband signal.
The information of the ACK frame demodulated by the demodulation units 19-1 to 19-k is determined by the error detection unit 20 to determine whether there is an error, and the determination result is supplied to the retransmission control unit 21. A data frame corresponding to the received ACK frame is considered to have been successfully communicated, and is deleted from the transmission queue 11. For a data frame for which an ACK frame is not received, the retransmission control unit 21 notifies the transmission data selection unit 22 to perform retransmission, and performs retransmission processing.

FIG. 3 is a block diagram illustrating a configuration of the terminal device.
The terminal apparatus shown in this figure includes a transmission queue 51, a transmission data selection unit 52, a modulation unit 53, a TDD switch 55, a transmission / reception antenna 56, a frame detection unit 57, a demodulation unit 59, an error detection unit 60, a retransmission control unit 61, A channel access management unit 62 and an ACK timing control unit 63 are provided.

  The transmission queue 51 is a queue buffer that temporarily holds transmission data supplied from application software that functions as an upper layer of the communication protocol of the terminal device.

The transmission data selection unit 52 selects a frequency channel (frequency band) for transmitting transmission information in accordance with instructed control information and the like. The frequency channel (frequency band) used for transmission is a frequency channel instructed from the base station apparatus 10.
The transmission data selection unit 52 receives the transmission data from the transmission data held in the transmission queue 51 according to the transmission order, and extracts a data frame including the transmission data as transmission information. The transmission data selection unit 52 is supplied with an ACK signal for each channel supplied from the retransmission control unit 61. The transmission data selection unit 52 extracts the ACK signal as transmission information. The transmission data selection unit 52 receives supply from the channel access management unit 62 of channel control information indicating a channel to be transmitted by the terminal device 50. The transmission data selection unit 52 extracts a control frame including the channel control information as transmission information. Then, the transmission data selection unit 52 supplies the modulation unit 53 with a data frame including the transmission data and a control frame including an ACK signal or channel control information.

The modulation unit 53 generates a modulated signal obtained by modulating a data frame or control frame included as transmission information supplied from the transmission data selection unit 52 at a predetermined frequency.
The TDD switch 55 supplies the combined transmission signal to the transmission antenna 56 (transmission state). The TDD switch 55 supplies a signal received by the transmission antenna 56 as a reception signal (reception state). The TDD switch 55 switches between a transmission state and a reception state in a time division manner.
The transmission / reception antenna 56 transmits the transmission signal supplied from the modulation unit 53 as a radio signal. The transmitting / receiving antenna 56 detects a received radio signal, generates a received signal, and supplies the received signal to the TDD switch. The transmission / reception antenna 56 includes a plurality of antennas and can transmit and receive independent signals.

Based on the received signal, the frame detection unit 57 extracts radio frame information and ACK timing information from the radio frame transmitted from the base station apparatus 10 as the data frame and the control frame. Then, the frame detection unit 57 supplies the extracted radio frame information and ACK timing information to the demodulation unit 59.
The demodulator 59 demodulates the received signal based on the radio frame information and channel information supplied from the frame detector 57.

The error detection unit 60 detects an error of the signal demodulated by the demodulation unit 59 and determines whether or not the information transmitted from the base station apparatus 10 is received without error.
If the error detection unit 60 determines that the demodulated signal can be received without error, the retransmission control unit 61 generates an ACK signal for the normally received signal and supplies the ACK signal to the transmission data selection unit 52.
The channel access management unit 62 detects the reception state based on the received reception signal, and determines whether the channel is usable based on the reception state of the channel.
The channel access management unit 62 generates channel control information indicating a channel to be transmitted by the terminal device 50 based on the reception state determination result. When it is determined that the channel is usable, the channel access management unit 62 supplies channel control information including channel information that can be used to the transmission data selection unit 52. For example, in the channel access management unit 62, whether or not the channel is usable is determined based on the received signal strength (RSSI) level of the channel, and a case where a predetermined threshold level is satisfied is used. Judge as possible channel.

The ACK timing control unit 63 controls the transmission timing of the ACK signal to be transmitted. The ACK timing control unit 63 controls the transmission timing of the ACK signal so that it is transmitted using a timing that does not interfere with the ACK signal transmitted using the adjacent channel. For example, the ACK timing control unit 63 performs control so that transmission is performed at a timing that does not interfere with an ACK signal transmitted using an adjacent channel, by the following configuration.
When there is header information of the data frame extracted by the frame detection unit 57, the ACK timing control unit 63 acquires this. Moreover, the ACK timing control part 63 acquires this when the ACK timing information contained in the management frame obtained as an output of the demodulation part 59 exists. When acquiring at least one of the header information of the extracted data frame and the ACK timing information included in the management frame, the ACK timing control unit 63 should transmit the ACK frame based on the acquired information Timing information is generated and supplied to the transmission data selection unit 52.

The operation of the terminal device 50 shown in FIG. 3 will be described.
First, an operation of a reception system that receives a signal transmitted from the base station apparatus 10 will be described.
The terminal device 50 receives the control frame and the data frame transmitted from the base station device 10 by the transmission / reception antenna 56.
The frame detection unit 57 detects an incoming frequency band. The demodulator 59 generates reception data from the detected modulated signal in the frequency band, and restores the transmission data transmitted from the base station apparatus 10.

The error detection unit 60 performs data correctness determination on the received data and supplies the result to the retransmission control unit 61.
The retransmission control unit 61 generates ACK frame information and inputs it to the transmission data selection function when the data frame is correctly received.
The ACK timing control unit 63 acquires the ACK timing information included in the header information of the data frame extracted by the frame detection function or the ACK timing information included in the management frame obtained as the output of the demodulation unit 59, and receives the ACK frame. Is notified to the transmission data selection unit 52.
The transmission data selection unit 52 outputs the ACK frame output from the retransmission control unit 61 to the modulation unit 59 so that the ACK frame is transmitted at the timing specified by the ACK timing control unit 63.
The modulation unit 59 converts the ACK frame into a radio signal, and transmits the radio signal to the base station apparatus 10 using the transmission / reception antenna 56.
The TDD switch 55 has a function of transmitting a transmission signal to the transmission / reception antenna 56 at the time of transmission and transmitting a received radio signal to each function at the time of reception.

With reference to the figure, it shows about the transmission power in the radio | wireless communications system of this embodiment.
FIG. 4 is a diagram illustrating transmission power in the wireless communication system of the present embodiment.
The waveform shown in the figure indicates the transmission signal spectrum of the transmission signal, the vertical axis indicates the power spectrum density (dB: decibel), and the horizontal axis indicates the frequency (MHz: megahertz). This transmission signal conforms to the IEEE802.11a standard, and shows a transmission power spectrum mask of the IEEE802.11a standard together with actual measurement values.
A flat frequency characteristic (0 dBr) is allowed in the band range up to 9 MHz symmetrically with respect to the center frequency in this figure, and a main lobe including a data signal exists in this portion. From 9 MHz to 11 MHz, where the frequency exceeds its bandwidth, the tolerance indicated by the transmit power spectrum mask decays steeply to -20 dBr. In a range where the frequency exceeds 11 MHz, an allowable value limited as out-of-band radiation power is shown. In the frequency range from 11 MHz to 30 MHz, the allowable value gradually decreases, but the attenuation factor corresponding to the frequency decreases.

  In the case where the channels are arranged with the center frequency at 20 MHz intervals and the frequency bandwidth is 20 MHz, the range from about 10 MHz to 30 MHz shown in this figure becomes the frequency region of the adjacent channel. When adjacent channels are used simultaneously, if the signal level in the range from about 10 MHz to 30 MHz exceeding the frequency bandwidth is low, the influence on the adjacent channel is reduced.

In addition, interference of received signals in the wireless communication system of this embodiment will be described.
FIG. 5 is a diagram illustrating interference of received signals in the wireless communication system of the present embodiment.
The waveform shown in this figure shows an example of a reception spectrum of reception signals from two terminal devices that transmit using channels adjacent to each other.
The waveform shown in this figure shows a waveform PS51 indicating the power spectrum density of the terminal device 50-1 (STA1) and a waveform PS52 indicating the power spectrum density of the terminal device 50-2 (STA2) using an adjacent channel. . The vertical axis of the graph showing this waveform indicates the power spectrum density (dB: decibel), and the horizontal axis indicates the frequency (MHz: megahertz).

As an operation of the reception system of the base station apparatus 10, a baseband signal is obtained by performing band-limiting filter processing on both channels of the frequency bands f1 and f2 and performing frequency conversion (down-conversion) processing. .
The out-of-band radiated power (waveform PS51) of the terminal device STA1 becomes interference power with respect to the received signal (waveform PS52) from the terminal device STA2. In the example shown in this figure, since the SIR (Signal-to-Interference Ratio) exceeds 20 dB (SIR> 20 dB), the influence of out-of-band radiated power is small. Therefore, the base station apparatus 10 can correctly receive the ACK frame of the terminal apparatus STA2. The same applies to the reception signal of the terminal device STA1 with respect to the out-of-band radiated power of the terminal device STA2.

FIG. 6 is a diagram illustrating interference of received signals in the wireless communication system according to the present embodiment.
The waveform shown in this figure shows an example of a reception spectrum of reception signals from two terminal devices that transmit using channels adjacent to each other. In this figure, unlike FIG. 5, the case where the balance of received power of adjacent channels is different is shown.

The waveform shown in this figure shows a waveform PS61 indicating the power spectrum density of the terminal device 50-1 (STA1) and a waveform PS62 indicating the power spectrum density of the terminal device 50-2 (STA2) using an adjacent channel. . The vertical axis of the graph showing this waveform indicates the power spectrum density (dB: decibel), and the horizontal axis indicates the frequency (MHz: megahertz).
Since the out-of-band radiation (waveform PS62) of the terminal device STA2 with respect to the received signal power of the terminal device STA1 is greatly reduced, the received signal quality of the terminal device STA1 is high. However, the out-of-band radiated power of the terminal device STA1 is relatively greater than the received signal power of the terminal device STA2, and if this adjacent channel is received at the same time, the received signal of the terminal device STA2 cannot be received. become. Therefore, even when each terminal device 50 can receive the transmission signal transmitted from the base station device 10 at the same timing, the processing when receiving the ACK signal (ACK frame) transmitted simultaneously from the terminal device 50 is as follows: Will interfere with each other. As a result, the base station apparatus 10 may not be able to correctly receive the ACK frame of the terminal apparatus STA2.

  In order to avoid adjacent channel interference, the method of providing a guard band between the frequency band used by the terminal apparatus STA1 and the frequency band used by the terminal apparatus STA2 (see FIG. 21) decreases the frequency utilization efficiency. In the case of FIG. 21, the guard band corresponds to the frequency band f2, and the frequency band cannot be used. The bandwidth of a signal generated when a guard band is provided is wider than in the case of parallel transmission using adjacent channels. Therefore, the method of providing the guard band is not desirable because the complexity and cost of the digital circuit / analog circuit are improved.

With reference to the drawings, an embodiment that solves a problem that may occur when adjacent channels that may occur in the base station apparatus 10 are used at the same time will be described below.
FIG. 7 is a timing chart showing the operation of the wireless communication system of this embodiment.
The vertical axis shown in this figure shows frequency channels f1 and f2 arranged adjacent to each other, and the horizontal axis shows the passage of time. The rectangle shown in the figure indicates that there is a radio frame transmitted using the frequency channel at the time.
The terminal devices STA1 and STA2 are assumed to allocate frequency channels used for communication to the frequency channels f1 and f2, respectively. The terminal apparatuses STA1 and STA2 receive radio frames (FR11 and FR21) transmitted from the base station apparatus 10 at the same timing.
Here, the base station apparatus 10 performs control so that the ACK frames responding to the radio frames FR21 and FR22 received by the terminal apparatuses STA1 and STA2 are not received simultaneously.

For example, the terminal devices STA1 and STA2 that can delay the time to start transmission of the ACK frame according to the control of the base station device 10 are referred to as the terminal device 50 of the present embodiment.
Then, the base station apparatus 10 performs control so that the period in which the terminal apparatus STA1 transmits the ACK frame and the period in which the terminal apparatus STA2 transmits the ACK frame do not overlap.
Furthermore, when the terminal device STA2 that responds first acquires a channel access right based on DCF (Distributed Coordination Function), a transmission data frame from the terminal device STA2 and an ACK frame transmitted by the terminal device STA1 Do not overlap. In other words, the time length of SIFS (Short Inter Frame Spacing) and the minimum time length of random backoff have elapsed since the time at which the terminal device STA1 transmits the ACK frame is calculated from the timing at which the terminal device STA2 has transmitted the ACK frame. Set to be earlier than the set time.

  Note that the terminal apparatuses STA1 and STA2 can delay the time to start transmitting the ACK frame according to the control of the base station apparatus 10, but in the case shown in the figure, at least the terminal apparatus STA1 Needs to be able to delay the time to start transmission of the ACK frame in accordance with the control of the base station apparatus 10. That is, terminal device STA2 may be a conventional terminal device that cannot control the timing for transmitting an ACK frame.

  Therefore, backward compatibility can be maintained even in a wireless communication system in which terminal devices (referred to as conventional terminal devices) that do not have the functions shown in the present embodiment are mixed. The wireless communication system shown in the present embodiment avoids the occurrence of adjacent channel interference due to temporal overlap of ACK frames and maintains the transmission quality of ACK frames even when conventional terminal devices coexist. It is possible to produce an effect.

In the present embodiment, the transmission start time of the ACK frame is controlled in order to reduce the influence of out-of-band radiation in transmission using a plurality of bands (frequency channels). When controlling the transmission start time of the ACK frame, the transmission start time at which the transmission of the channel is started is set not only to match the actual transmission time but also to prevent interference between the channel and the adjacent channel. Control.
Thereby, since the transmission timing of the terminal device STA1 can be shifted backward, it is possible to prevent out-of-band emission from the frequency channel f1 during the period in which the terminal device STA2 returns an ACK frame to the AP.

As an existing technology, there is a concept of “scheduled ACK”. The control by “scheduled ACK” shown as an existing technique is timing control on a single frequency channel, and is not a control method for transmission using a plurality of bands simultaneously as shown in the present embodiment. Even if control by “scheduled ACK” is individually applied to each band (channel), interference caused by communication using adjacent frequency channels cannot be removed. Will occur.
In the wireless communication system shown in the present embodiment, it is possible to reduce the influence of such interference.
In addition, by applying control by “scheduled ACK” individually to each band (channel) and controlling the control performed for each band in cooperation between the bands, an operation equivalent to this embodiment is realized. It is also possible.

  In the present embodiment, in the control of the transmission timing of the ACK frame transmitted in response by the terminal device 50, the base station device 10 transmits control information to the terminal device 50 in advance before the terminal device 50 sends an ACK signal. To be notified.

(Second Embodiment)
With reference to the drawings, different embodiments for solving problems that may occur when adjacent channels that may occur in the base station apparatus 10 are simultaneously used will be described below. In the present embodiment, a case of a wireless communication system in which four terminal apparatuses communicate with a base station apparatus will be described.
FIG. 8 is a timing chart showing the operation of the wireless communication system of the present embodiment.
The vertical axis shown in this figure indicates frequency channels f1, f2, f3, and f4 arranged adjacent to each other, and the horizontal axis indicates the passage of time. The rectangle shown in the figure indicates that there is a radio frame transmitted using the frequency channel at the time.

The base station apparatus 10 and the terminal apparatus 50 applied to the radio communication system shown in the present embodiment can apply the same configurations as those shown in FIGS. 1, 2, and 3, and are different in the number of channels used simultaneously.
The four terminal devices 50 are shown as terminal devices STA1, STA2, STA3, and STA4.
The terminal devices STA1, STA2, STA3, and STA4 are assigned frequency channels f1, f2, f3, and f4 for use in communication. The terminal devices STA1, STA2, STA3, and STA4 receive the radio frames (FR11, FR21, FR31, and FR41) transmitted from the base station device 10 at the same timing.
Here, control is performed so that the base station apparatus 10 does not simultaneously receive ACK frames responding to the radio frames FR11, FR21, FR31, and FR41 received by the terminal apparatuses STA1, STA2, STA3, and STA4.
For example, the base station apparatus 10 delays the time for starting transmission of the ACK frame with respect to the terminal apparatuses STA2 and STA4. The terminal devices STA1 and STA3 do not perform the delay control shown in this embodiment. That is, in the channel arrangement shown in this figure, non-adjacent channels can transmit simultaneously.

Thus, interference between adjacent frequency channels can be avoided by assigning frequency channels and selecting a terminal device to be controlled.
Also, it becomes possible for a plurality of terminal devices to transmit ACK frames at the same time, assigning different delay times for each terminal device, and in comparison with the case where the terminal devices transmit ACK frames individually one by one in that order, Response time can be shortened.
In this figure, four terminal devices are illustrated, but the number can be set as necessary.

In addition, the interval between the data frame and the ACK frame, and the interval between the ACK frames, for example, by providing an interval that secures a period defined as SIFS (Short Inter Frame Spacing: 16 μs in the IEEE 802.11n standard) Interference can be avoided.
Further, by shifting the transmission timings of the terminal devices STA2 and STA4 backward, in the period in which the terminal device STA1, which is an existing terminal, returns an ACK frame to the base station device 10, no out-of-band radiation is generated from the frequency channel f2. Can be.

(Third embodiment)
With reference to the drawings, different aspects in the present embodiment are shown.
The wireless communication system shown in the present embodiment includes a base station device 10a and a terminal device 50a instead of the base station device 10 and the terminal device 50 shown in FIG.

FIG. 9 is a block diagram illustrating a configuration of the base station apparatus.
The base station apparatus 10a shown in this figure includes a transmission queue 11, a transmission data selection unit 12a, a modulation unit 13, a synthesis unit 14, a TDD switch 15, a transmission / reception antenna 16, a frame detection unit 17a, a distribution unit 18, a demodulation unit 19, An error detection unit 20, a retransmission control unit 21, a channel access management unit 22, and a channel gain estimation unit 24 are provided. The same components as those in FIG.

The transmission data selection unit 12a extracts transmission information to be transmitted according to instructed control information and the like, and selects a frequency channel (frequency band) to be transmitted.
The transmission data selection unit 12 a is supplied with the same number (k) of transmission data as the number of available frequency channels (channels) from the transmission data held in the transmission queue 11. The transmission data selection unit 12a extracts a data frame including the transmission data as transmission information. The transmission data selection unit 12a extracts a control frame including an ACK signal for each channel supplied from the retransmission control unit 21 as transmission information. The transmission data selection unit 12 a receives supply from the channel access management unit 22 of channel control information indicating a channel to be transmitted by the terminal device 50. The transmission data selection unit 12a extracts a control frame including the channel control information as transmission information.

The transmission data selection unit 12 a receives the channel gain information of the frequency channel selected by the channel gain estimation unit 24 from the channel gain estimation unit 24. The transmission data selection unit 12a extracts a control frame including an ACK signal for each channel supplied from the retransmission control unit 21 as transmission information. The transmission data selection unit 12a extracts a control frame including the channel gain information supplied from the channel gain estimation unit 24 as transmission information.
Further, the transmission data selection unit 12a selects the frequency channel selected by the channel gain estimation unit 24, and receives at least one of the data frame including the transmission data and the ACK signal, channel control information, and channel gain information. The control frame including the signal is supplied to the modulation unit 13.
The frame detection unit 17a extracts radio frame information and ACK timing information from the data frame and control frame transmitted from the terminal device 50a included in the received signal. Then, the frame detection unit 17 supplies both the extracted radio frame information and ACK timing information to the distribution unit 18 and the demodulation unit 19.

  The channel gain estimation unit 24 detects the reception power of the radio frame transmitted from the terminal device 50a. The channel gain estimator 24 has a storage area inside and stores the value of the received power of the detected radio frame according to the detected time. The received power to be stored is stored for each frequency channel. The channel gain estimator 24 can refer to the stored received power value as history information. The channel gain estimator 24 detects temporal variations in received power and estimates changes in the reception environment that vary with time. The channel gain estimator 24 selects a frequency channel to be used according to the estimation result. The channel gain estimation unit 24 supplies channel gain information of the selected frequency channel to the data selection unit 12a.

The operation of the base station apparatus 10 shown in FIG. 9 will be described.
The channel gain estimator 24 detects the received power of the radio frame transmitted from the terminal device 50 (STA), and stores the detected received power value in time series in a storage area provided therein. The channel gain estimator 24 generates history information from the stored received power.
The channel access management unit 22 determines whether the channel is available. For the determination, for example, a carrier sense / random backoff function by CSMA / CA can be applied.

When it is determined that the channel is usable, the channel access management unit 22 notifies the transmission data selection unit 12a.
The transmission data selection unit 12a extracts the same number of data frames as the number of available frequency channels (denoted k) from the transmission queue 11 for each user, selects a frequency band in which each data frame is transmitted, and selects a modulation unit. 13-1 to 13-k.
At this time, the channel gain estimator 24 stores the received signal gain detected from the received signal received from the terminal device 50a that is the transmission destination of each data frame in the internal storage area. Refers to the value.

The channel gain estimation unit 24 determines the transmission power of each STA from the referenced information so that the reception power of the ACK frame transmitted by the terminal device 50a (STA) in the base station device 10a (AP) is uniform in all channels. decide. This information is supplied to the modulators 13-1 to 13-k.
Modulators 13-1 to 13-k convert the data frame into a radio signal.
A transmission signal in each frequency band is converted from a plurality of radio signals into a wideband radio signal by the synthesizer 14 and transmitted to each terminal device 50 a (STA) by the transmission / reception antenna 16.
The operation when the ACK frame is simultaneously received from each terminal device 50a may be the same as a general operation shown as a conventional example. Further, as shown in the first embodiment, control for delaying the response time of the ACK frame may be performed.

FIG. 10 is a block diagram illustrating a configuration of the terminal device.
The terminal device 50a shown in this figure includes a transmission queue 51, a transmission data selection unit 52, a modulation unit 53, a transmission power control unit 54, a TDD switch 55, a transmission / reception antenna 56, a frame detection unit 57a, a demodulation unit 59, and an error detection unit. 60, a retransmission control unit 61, a channel access management unit 62, and an ACK transmission power holding unit 64. The same components as those in FIG.

The transmission power control unit 54 controls the transmission power of a signal to be transmitted according to the power instructed from the base station apparatus 10a.
In addition to the configuration of the frame detection unit 57 illustrated in FIG. 3, the frame detection unit 57 a supplies both the extracted radio frame information and ACK timing information to the ACK transmission power holding unit 64.
The ACK transmission power holding unit 64 acquires the transmission power information of the ACK frame based on the header part of the data frame extracted by the frame detection unit 57a or the control frame part received prior to the reception of the data frame. The ACK transmission power holding unit 64 stores the acquired transmission power information in a storage area provided therein. The stored transmission power information is updated when new information is notified from the base station apparatus 10a. The ACK transmission power holding unit 64 supplies the stored transmission power information to the transmission power control unit 54.

The operation of the terminal device 50a shown in FIG. 10 will be described.
The control frame and the data frame transmitted from the base station apparatus 10a (AP) are received by the transmission / reception antenna 56, the frequency band coming from the frame detection unit 57a is detected, and then the demodulation unit 59 restores the data.
The error detection unit 60 performs correct / incorrect determination on the received data. The determination result is supplied to the retransmission control unit 61 and the channel access unit 62.

The retransmission control unit 61 generates ACK frame information and inputs it to the transmission data selection function when the data frame is correctly received.
The channel access management unit 62 controls the transmission data selection unit 52 to transmit the ACK frame at a timing when a predetermined time has elapsed after receiving the data frame.
The channel access management unit 62 transmits an ACK frame with a time interval of SIFS (Short Inter Frame Spacing) after receiving a data frame, for example, as in a wireless LAN system of the IEEE 802.11n standard.
The ACK transmission power holding unit 64 acquires and holds transmission power information of the ACK frame from the header portion of the data frame extracted by the frame detection unit 57a or the control frame received prior to the reception of the data frame.

The modulation unit 59 converts the ACK frame into a radio signal. The transmission power control unit 54 detects the transmission power of the ACK frame from the ACK transmission power holding unit 64. Modulator 59 sets the transmission power of the radio signal to that value. The transmission / reception antenna 56 is used to transmit an ACK frame to the base station apparatus 10a.
The TDD switch 55 transmits a transmission signal to the transmission / reception antenna 56 at the time of transmission, and transmits a received radio signal to each function at the time of reception.

The operation of the wireless communication system shown in the present embodiment will be described with reference to the drawings.
FIG. 11 is a diagram illustrating interference of received signals in the wireless communication system according to the present embodiment.
The waveform shown in this figure shows an example of a reception spectrum of reception signals from two terminal devices that transmit using channels adjacent to each other. In this figure, unlike FIG. 5 and FIG. 6, when the balance of the reception power of adjacent channels is different, the balance of the reception power in the base station apparatus 10 a is ensured by changing the transmission power transmitted from the terminal apparatus 50 a. One mode to be made is shown.

  The waveform shown in this figure shows a waveform PS111 indicating the power spectrum density of the terminal device 50a-1 (STA1) and a waveform PS112 indicating the power spectrum density of the terminal device 50a-2 (STA2) using an adjacent channel. . The vertical axis of the graph showing this waveform indicates the power spectrum density (dB: decibel), and the horizontal axis indicates the frequency (MHz: megahertz).

Assume that the transmission timings of the ACK frames transmitted by the two terminal devices 50a are the same.
After controlling the transmission power of the terminal device STA2 so that the reception power at the AP of the ACK frame transmitted by the terminal device STA1 and the reception power at the AP of the ACK frame transmitted by the terminal device STA2 are equal, at the same timing ACK frame is transmitted.
By making the received signal power of each ACK frame equal, the influence of adjacent channel interference is reduced.
For example, if the transmission power of the terminal device STA2 is P, the propagation loss from the terminal device STA2 to the base station device 10a (AP) is L2, and the propagation loss from the terminal device STA1 to the base station device 10a (AP) is L1, The transmission power of the device STA1 is set to (P × L2 / L1).
The figure shows an example in which the power difference between the ACK frames transmitted by the terminal apparatuses STA1 and STA2 is 20 dB. In this case, by reducing the transmission power of the terminal device STA1 by 20 dB, it is possible to eliminate the reception power difference between the terminal devices STA1 and STA2, and to correctly receive the ACK frame from the terminal device STA2.

  As a result, it is possible to reduce the amount of adjacent channel interference caused by temporal overlap of ACK frames while maintaining backward compatibility with the terminal device STA2, so that the effect of maintaining the transmission quality of the ACK frame can be produced. it can.

  In the present embodiment, in the control of the transmission power of the ACK frame transmitted by the terminal device 50a-2, the control information notified by the base station device 10a is stored in advance before the terminal device 50a-2 sends the ACK signal. It has been notified to the terminal device 50a-2.

(Fourth embodiment)
With reference to the figure, the transmission timing of the control frame from the base station apparatus to the terminal apparatus is shown.
FIG. 12 is a timing chart showing the operation of the wireless communication system of this embodiment.
The vertical axis shown in this figure shows frequency channels f1 and f2 arranged adjacent to each other, and the horizontal axis shows the passage of time. The rectangle shown in the figure indicates that there is a radio frame transmitted using the frequency channel at the time.
The terminal devices STA1 and STA2 are assumed to allocate frequency channels used for communication to the frequency channels f1 and f2, respectively. The terminal apparatuses STA1 and STA2 respectively receive the control frame (FC11 and FC21) and the radio frame (FR11 and FR21) transmitted from the base station apparatus 10 at the same timing.
Here, the operation according to the control information contained in the control frames FC11 and FC21 received by the terminal devices STA1 and STA2 is performed. ACK frames (FA11 and FA21) responding to the radio frames FR21 and FR22 received by the terminal devices STA1 and STA2 are controlled and transmitted so as not to interfere in the base station device 10.

For example, the terminal devices STA1 and STA2 that can control the transmission power of ACK frames (FA11 and FA21) in accordance with the control of the base station device 10a are assumed to be the terminal devices 50a shown in the present embodiment.
Then, the base station apparatus 10 performs control so that the transmission power at which the terminal apparatus STA1 transmits the ACK frame (FA11) and the transmission power at which the terminal apparatus STA2 transmits the ACK frame (FA21) do not interfere with each other. For details of transmission power control, refer to the third embodiment.

The base station apparatus 10a transmits the same control frames FC11 and FC21 using the frequency channels f1 and f2.
The terminal device 50a receives a signal of any one of the frequency channels f1 and f2, and detects the control frame FC11 or FC21.
As a result, the terminal device 50a has the frequency channel f1 followed by the signal of the data frame FR11 (AP → STA1) from the base station device 10a to the terminal device 50a-1 (STA1) after the control frame FC11. Detects being sent. Further, the terminal device 50a transmits the signal of the data frame FR21 (AP → STA2) from the base station device 10a to the terminal device 50a-2 (STA2) after the control frame FC21 in the frequency channel f1. It is detected that
Each of the terminal devices 50a-1 and 50a-2 can control transmission power according to control information included in the received control frame.

The transmission of the control frame may be performed by specifying a specific frequency channel.
FIG. 13 is a timing chart showing the operation of the wireless communication system of this embodiment.
The sequence shown in this figure is different in that the control frame FC21 in the frequency channel f2 included in the sequence shown in FIG. 12 is deleted.

In this embodiment, a configuration in which the control frame is transmitted using the frequency channel f1 is shown as an example.
Each terminal device 50a first receives the control frame FC11 transmitted using the frequency channel f1 in the reception standby state. Each terminal device 50a refers to the frequency channel allocation information notified by the received control frame FC11, and determines the allocated frequency channel. As a result of the determination, the terminal device 50a can determine in advance which frequency channel f1, f2 is used by the data frames FR11, FR21 transmitted using the allocated frequency channel. By using such a procedure, even if the data frames FR11 and FR21 transmitted from the base station apparatus 10a are assigned to an arbitrary frequency channel, the data frame can be received.
Such a control method is suitable for a system having a concept of primary channel / secondary channel, such as the IEEE802.11n standard.

Moreover, it is good also as transmitting using the header information part of a data frame, without using a control frame for transmission of control information.
FIG. 14 is a timing chart showing the operation of the wireless communication system of the present embodiment.
Since the data frame and the control information can be transmitted as one frame (FCR 11 and FCR 21), it is possible to improve the frequency utilization efficiency.

In the above description, the base station apparatus 10a and the terminal apparatus 50a capable of controlling the transmission power have been illustrated and described in the present embodiment. However, as in the first and second embodiments, the ACK frame (FA11 and FA21) The present invention can also be applied to a terminal device that performs transmission time control.
Note that the control information for controlling the transmission power may be transmitted using any frequency channel.
Further, the transmission power is not limited to the aspect of controlling the transmission power of the terminal apparatus allocated to the frequency channel f1, and may be the aspect of controlling the transmission power of the terminal apparatus allocated to the frequency channel f2.
Furthermore, the transmission power of both terminal apparatuses allocated to adjacent frequency channels may be controlled so that the reception power at the base station apparatus (access point) becomes a certain target value. That is, the base station apparatus transmits control information for the terminal apparatus based on the result of comparing the detected received power with the reference target value. Each terminal can control transmission power according to the control information.

(Fifth embodiment)
FIG. 15 is a block diagram illustrating a configuration of the terminal device.
The terminal device 50b shown in this figure includes a transmission queue 51, a transmission data selection unit 52, a modulation unit 53, a transmission power control unit 54, a TDD switch 55, a transmission / reception antenna 56, a frame detection unit 57, a demodulation unit 59, and an error detection unit. 60, a retransmission control unit 61, a channel access management unit 62, and an ACK transmission power setting unit 65. The same components as those in FIGS. 3 and 10 are denoted by the same reference numerals.

  The ACK transmission power setting unit 65 detects the reception power of the data frame. The ACK transmission power setting unit 65 determines the transmission power of the ACK frame based on the detected reception power of the data frame. The ACK transmission power setting unit 65 supplies the determined transmission power information to the transmission power control unit 54.

The operation of the terminal device 50b shown in FIG. 15 will be described.
The control frame and the data frame transmitted from the base station apparatus 10a (AP) are received by the transmission / reception antenna 56, and the data is restored by the demodulation unit 59 after detecting the incoming frequency band by the frame detection unit 57.
For the received data, the error detection unit 60 determines whether the received data is correct. The determination result is supplied to the retransmission control unit 61 and the channel access unit 62.

The retransmission control unit 61 generates ACK frame information and inputs it to the transmission data selection function when the data frame is correctly received.
The channel access management unit 62 controls the transmission data selection unit 52 to transmit the ACK frame at a timing when a predetermined time has elapsed after receiving the data frame.
The channel access management unit 62 transmits an ACK frame with a time interval of SIFS (Short Inter Frame Spacing) after receiving a data frame, for example, as in a wireless LAN system of the IEEE 802.11 standard.

The ACK transmission power setting unit 65 determines the reception power of the ACK frame after referring to the reception power of the data frame. The ACK transmission power setting unit 65 makes the reception power of the ACK frame inversely proportional to the reception power of the data frame, for example, and sets a predetermined value for the proportionality coefficient.
The modulation unit 59 converts the ACK frame into a radio signal, the transmission power control unit 54 refers to the value of the transmission power of the ACK frame held in the ACK transmission power setting unit 65, and determines the transmission power of the radio signal. Set to value. The transmission power control unit 54 transmits an ACK frame to the base station apparatus (AP) using the transmission / reception antenna 56.

The TDD switch 55 has a function of transmitting a transmission signal to the transmission / reception antenna 56 at the time of transmission and transmitting a received radio signal to each function at the time of reception.
Note that a base station apparatus using the same method as the conventional one may be applied to the base station apparatus in the present embodiment.

(Sixth embodiment)
FIG. 16 is a block diagram showing a configuration of a wireless communication system according to an embodiment of the present invention.
The wireless communication system 1 shown in this figure uses a base station apparatus (AP: access point) 10b that performs communication using wireless communication lines 30-1 and 30-2, and a base station apparatus 10b and a wireless communication line. A plurality of terminal devices (STA) 50b for communication are provided. In this figure, as an aspect of the present embodiment, a base station apparatus 10b that communicates with two terminal apparatuses 50b-1 and 50b-2 is illustrated.
The base station apparatus 10b is connected to other network facilities by a wired line (wired NW) 70. The base station apparatus 10b is supplied with transmission data transmitted from the wired NW 70 to the terminal apparatuses 50b-1 and 50b-2. Further, the base station apparatus 10b supplies the reception data received from the terminal apparatuses 50b-1 and 50b-2 to the wired NW 70.

The radio communication line 30-1 shown in this figure forms an antenna directivity in which a null is directed toward the terminal device (STA2) with respect to a data frame transmitted from the base station device 10b to the terminal device (STA1). Composed. The radio communication line 30-2 is configured by forming an antenna directivity in which a null is directed toward the terminal device (STA1) with respect to a data frame transmitted from the base station device 10b to the terminal device (STA2). .
In the wireless communication system 1b shown in this figure, the spatial degree of freedom of the base station apparatus 10b is used for the purpose of reducing adjacent channel interference. As a result, it is possible to reduce the amount of adjacent channel interference included in the signals received by the terminal apparatuses STA1 and STA2, thereby improving downlink transmission quality.

With reference to the drawings, different aspects in the present embodiment are shown.
The wireless communication system shown in the present embodiment includes a base station device 10b and a terminal device 50a instead of the base station device 10 and the terminal device 50 shown in FIG.

FIG. 17 is a block diagram illustrating a configuration of the base station apparatus.
The base station apparatus 10b shown in this figure includes a transmission queue 11, a transmission data selection unit 12a, a modulation unit 13, a synthesis unit 14, a TDD switch 15, a transmission / reception antenna 16, a frame detection unit 17a, a distribution unit 18, a demodulation unit 19, An error detection unit 20, a retransmission control unit 21, a channel access management unit 22, a transmission directivity control unit 25, a channel estimation unit 26, and a transmission directivity calculation unit 27 are provided. The same components as those in FIGS. 2 and 9 are denoted by the same reference numerals.

  The transmission directivity control unit 25 controls gain and phase that differ for each frequency with respect to the modulation signal supplied from the modulation unit 13 in accordance with the control signal from the transmission directivity calculation unit 27. When the signal modulated by the transmission directivity control is transmitted via the transmission / reception antenna 16, the beam can be directed to a desired terminal device.

  The channel estimation unit 26 detects the reception power of the radio frame transmitted from the terminal device 50a. The channel estimation unit 26 has a storage area inside and stores the value of the received power of the detected radio frame according to the detected time. The received power to be stored is stored for each frequency channel. The channel estimation unit 26 can refer to the stored received power value as history information.

The transmission directivity calculation unit 27 detects temporal variations in received power for each frequency channel, and detects the direction in which the terminal device exists. The detection of the direction in which the terminal device exists is realized using a general method. The transmission directivity calculation unit 27 controls the transmission directivity control unit 25 so that the directivity of the radio wave transmitted in the direction of the detected terminal device is suitable.
Since directivity can be set for the propagation characteristics of the radio wave used for the radio communication line with the terminal device, interference other than the desired signal can be reduced, and the gain for detecting the desired signal can be increased.

The operation of the base station apparatus 10b shown in FIG. 17 will be described.
The channel estimation unit 26 detects the reception power of the radio frame transmitted from the terminal device 50a. The channel estimation unit 26 has a storage area inside and stores the value of the received power of the detected radio frame according to the detected time.
The channel access management unit 22 determines whether each channel can be used. For this determination, for example, a carrier sense / random backoff function by CSMA / CA can be used.
When determining that the channel is in an available state, the channel access management unit 22 notifies the transmission data selection unit 12 of a transmission instruction using the channel.
The transmission data selection unit 12 extracts the same number of data frames as the number of available frequency channels (denoted as k) from the transmission queue 11 that holds transmission data for each user, and selects a frequency band for transmitting each data frame To do. The transmission data selection unit 12 supplies information on the selected frequency band to the ACK timing management unit 22.

  At this time, the channel estimation unit 26 detects and stores the received signal gain of the terminal device to which each data frame is transmitted from the received power of the radio frame transmitted from the terminal device 50a. The channel estimation unit 26 refers to the stored received power value, and determines the transmission power transmitted by each terminal device 50a from this information. The channel estimation unit 26 controls the value of the transmission power so that the reception power at the base station apparatus (AP) is uniform for all channels in the ACK frame.

The transmission directivity calculation unit 27 determines the transmission power transmitted by each terminal device and supplies this information to the modulation units 13-1 to 13-k.
Modulators 13-1 to 13-k convert the data frame into a radio signal.
A transmission signal in each frequency band is converted into a wideband wireless signal by the synthesizer 14 and transmitted to each STA by the transmission / reception antenna 16.
The operation when receiving the ACK frame simultaneously from each terminal device is the same as in the conventional example.

With reference to the figure, the transmission timing of the control frame from the base station apparatus to the terminal apparatus is shown.
FIG. 18 is a timing chart showing the operation of the wireless communication system of this embodiment.
The vertical axis shown in this figure shows frequency channels f1 and f2 arranged adjacent to each other, and the horizontal axis shows the passage of time. The rectangle shown in the figure indicates that there is a radio frame transmitted using the frequency channel at the time.
The terminal devices STA1 and STA2 are assumed to allocate frequency channels used for communication to the frequency channels f1 and f2, respectively. The terminal apparatuses STA1 and STA2 receive the control frames (FC11, FC21) and radio frames (FR11 and FR21) transmitted from the base station apparatus 10 at the same timing, respectively.
Further, the base station apparatus 10b receives control frames (FC12 to FC13, FC22 to FC23) transmitted from the terminal apparatus at different timings, respectively.

Here, the terminal apparatuses STA1 and STA2 perform an operation according to the control information included in the received control frames FC11 and FC21. The terminal apparatuses STA1 and STA2 sequentially transmit control frames to the base station apparatus 10b.
First, the terminal apparatus STA1 transmits the control frame FC22 using the frequency channel f2. Receiving this control frame, the base station apparatus 10b estimates the transmission path characteristics from the terminal apparatus STA1 in the frequency channel f2. The terminal device STA2 transmits the control frame FC12 using the frequency channel f1. Receiving this control frame, the base station apparatus 10b estimates the transmission path characteristics from the terminal apparatus STA2 in the frequency channel f1. The terminal device STA1 transmits the control frame FC13 using the frequency channel f1. Receiving this control frame, the base station apparatus 10b estimates transmission path characteristics from the terminal apparatus STA1 in the frequency channel f1. The terminal device STA2 transmits the control frame FC23 using the frequency channel f2. Receiving this control frame, the base station apparatus 10b estimates the transmission path characteristics from the terminal apparatus STA2 in the frequency channel f2.

The base station apparatus 10b can detect transmission path characteristics for each frequency channel according to the terminal apparatus by exchanging control frames according to the procedure shown in the figure. Until this detection process is completed, other control frames and data frames are not transmitted. Therefore, since the base station apparatus 10b can detect without being affected by interference, it can perform transmission path estimation with improved detection accuracy.
The base station apparatus 10b can determine the directivity characteristics of the radio communication lines 30-1 and 30-2 based on this transmission path estimation process.

  Note that the terminal apparatuses STA1 and STA2 can delay the time to start transmitting the ACK frame according to the control of the base station apparatus 10b. For that purpose, in the case shown in the figure, at least the terminal apparatus STA1 needs to delay the time to start transmitting the ACK frame in accordance with the control of the base station apparatus 10b. That is, terminal device STA2 may be a conventional terminal device that cannot control the timing for transmitting an ACK frame.

In the present embodiment, the transmission start time of the ACK frame is controlled in order to reduce the influence of out-of-band radiation in transmission using a plurality of bands (frequency channels). When controlling the transmission start time of the ACK frame, not only does the actual transmission time not coincide, but also the transmission start time at which transmission of the channel starts to prevent interference with the frequency channel adjacent to the frequency channel. To control.
Thereby, since the transmission timing of the terminal device STA1 can be shifted backward, it is possible to prevent out-of-band emission from the frequency channel f1 during the period in which the terminal device STA2 returns an ACK frame to the base station device 10b.

The configuration shown in the above embodiment is shown as an embodiment, and the quantity, combination, and the like can be changed without changing the characteristics of the present invention.
Regarding the timing of transmitting a control frame for controlling the reception response signal (ACK frame), control for controlling the channel information used by each user and the reception response signal (ACK frame) in each control method shown in the embodiment. A control frame combined with information may be transmitted to the terminal device.

  Further, the control information transmitted by the base station device 10 may include instruction information that directly instructs the condition for the terminal device 50 to transmit the reception response signal. Alternatively, the control information transmitted by the base station apparatus 10 includes information that indirectly defines a condition for the terminal apparatus 50 to transmit a reception response signal, and the terminal apparatus 50 is based on information that defines a condition for transmitting the reception response signal. Instruction information for instructing transmission of the reception response signal is generated. For example, the information that indirectly determines the condition for the terminal device 50 to transmit the reception response signal may be information indicating the reception level of each received signal from each terminal device 50 received by the base station device 10 or information indicating the reception level. Good.

In addition, the base station apparatus 10 of this embodiment controls the transmission of the reception response signal (ACK frame) so that the reception response signal for the signal transmitted to the terminal apparatus 50 is received without interference ( Control information). The terminal device 50 is a reception response signal for the signal transmitted from the base station device 10 to the terminal device 50, and the base station device 10 receives the reception response signal without interference from the base station device 10. A reception response signal is transmitted according to the transmitted control information.
As a result, in the wireless communication system, it is not necessary to make a large guard band, and the generation of frequency channels that cannot be used can be suppressed, so that it is possible to improve frequency utilization efficiency.

In addition, the base station apparatus 10 of the present embodiment controls the transmission start time of the reception response signal and arranges the reception response signal so as not to be received simultaneously using adjacent channels. The terminal device 50 transmits a reception response signal based on the transmission start time instructed according to the control information transmitted from the base station device 10.
As a result, in the wireless communication system, it is possible to avoid the period in which interference occurs by controlling the transmission start time of the ACK frame.

In addition, when the reception response signal is arranged in an adjacent channel, the base station apparatus 10 according to the present embodiment is arranged in an adjacent channel so that the reception power of the reception response signal becomes a power level that can be received without interference. The transmission power from the terminal device 50 is controlled. The terminal device 50 transmits a reception response signal based on the transmission power instructed according to the control information transmitted from the base station device 10.
Thereby, in the wireless communication system, by controlling the transmission power for transmitting the ACK frame, a level difference that causes interference does not occur, and signals of adjacent frequency channels can be received.

In addition, the base station apparatus 10 according to the present embodiment controls the directivity characteristics of the transmission wave transmitted by the terminal apparatus 50 so that the reception power of the reception response signal becomes a power level that can be received without interference. The terminal device 50 transmits a reception response signal based on the directivity characteristic of the transmission wave instructed according to the control information transmitted from the base station device 10.
As a result, in the wireless communication system, by controlling the directivity characteristics of the wireless communication line with the desired terminal device that transmits the ACK frame, it is possible to avoid unnecessary interference and secure a line with an increased gain. It becomes.

Further, the control information transmitted from the base station apparatus 10 according to the present embodiment includes instruction information for instructing conditions for the terminal apparatus 50 to transmit the reception response signal.
Thereby, further, in the radio communication system, the terminal device 50 can transmit an ACK frame in accordance with an instruction based on the instruction information included in the control information transmitted from the base station apparatus 10.

Moreover, the control information transmitted from the base station apparatus 10 of the present embodiment includes information that defines conditions for the terminal apparatus 50 to transmit the reception response signal, and the terminal apparatus 50 includes information that defines the conditions for transmitting the reception response signal. The instruction information for instructing transmission of the reception response signal is generated based on the above.
Thereby, further, in the radio communication system, the terminal device 50 can transmit an ACK frame according to the instruction based on the instruction information generated by the terminal device 50 based on the control information transmitted from the base station device 10. It becomes possible.

DESCRIPTION OF SYMBOLS 10 Base station apparatus 11 Transmission queue 12 Transmission data selection part 13 Modulation part 14 Combining part 15 TDD switch 16 Transmission / reception antenna 17 Frame detection part 18 Distribution part 19 Demodulation part 20 Error detection part 21 Retransmission control part 22 Channel access management part 23 ACK timing Management Department

Claims (9)

A wireless communication system including a plurality of terminal devices and a base station device communicating with the plurality of terminal devices,
The base station device
Transmitting control information for controlling the transmission of the reception response signal so that the reception response signal for the signal transmitted to the terminal device is received without interference;
The terminal device
A control signal transmitted from the base station apparatus so that the base station apparatus receives a reception response signal for the signal transmitted from the base station apparatus to the terminal apparatus, and the base station apparatus receives the reception response signal without interference. A wireless communication system, wherein the reception response signal is transmitted according to information. The base station device
The transmission start time of the reception response signal is controlled, and the reception response signal is arranged not to be received simultaneously using an adjacent channel,
The terminal device
The radio communication system according to claim 1, wherein the reception response signal is transmitted based on a transmission start time instructed according to control information transmitted from the base station apparatus. The base station device
When the reception response signal is arranged in an adjacent channel, the transmission power from the terminal device arranged in the adjacent channel is set so that the reception power of the reception response signal becomes a power level that can be received without interference. Control
The terminal device
The radio communication system according to claim 1 or 2, wherein the reception response signal is transmitted based on the transmission power instructed according to control information transmitted from the base station apparatus. The base station device
Control the directivity characteristics of the transmission wave transmitted by the terminal device so that the reception power of the reception response signal is a power level that can be received without interference,
The terminal device
4. The reception response signal is transmitted based on a directivity characteristic of the transmission wave instructed according to control information transmitted from the base station apparatus. 5. Wireless communication system. The radio according to any one of claims 1 to 4, wherein the control information transmitted from the base station apparatus includes instruction information for instructing a condition for the terminal apparatus to transmit the reception response signal. Communications system. The control information transmitted from the base station device includes information that defines a condition for the terminal device to transmit the reception response signal,
5. The terminal device generates instruction information for instructing transmission of the reception response signal based on information defining conditions for transmitting the reception response signal. 6. Wireless communication system. A base station device that communicates with a plurality of terminal devices,
The base station device
According to the reception status of the signal received by the terminal device, transmit control information for controlling the transmission of the reception response signal so as to receive without receiving the reception response signal transmitted from the terminal device, A base station apparatus that receives a reception response signal from the terminal apparatus. A terminal apparatus that communicates with the base station apparatus according to claim 1,
The base station apparatus receives a signal transmitted from the base station apparatus to the own apparatus and receives a reception response signal transmitted according to the reception state without interference by the base station apparatus. The terminal apparatus transmits the reception response signal according to the transmitted control information. A communication method of a wireless communication system including a plurality of terminal devices and a base station device communicating with the plurality of terminal devices,
Transmitting control information for controlling transmission of the reception response signal so that a reception response signal for a signal transmitted from the base station apparatus to the terminal apparatus is received without interference;
A process in which the terminal apparatus transmits the reception response signal according to the control information transmitted from the base station apparatus so that the base station apparatus receives the reception response signal without interference;
A communication method comprising:

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