JP4920609B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a radio communication apparatus that transmits channel quality estimated for each subcarrier or each subchannel.

  As a third generation communication method, there is a method called High Speed Down Link Packet Access (HSDPA) formulated by 3GPP. In HSDPA, high-quality and high-speed transmission is realized by using adaptive modulation and coding (AMC) (for example, see Non-Patent Document 1). In HSDPA, an MCS (Modulation and Coding Scheme) modulation scheme and a coding rate are adaptively controlled based on feedback information received from a terminal, that is, a CQI (Channel Quality Indicator). For example, SNR (Signal to Noise power Ratio) or SINR (Signal to Interference Noise Ratio) is used as the channel quality.

  Further, as a promising next-generation communication system, there is an OFDM (Orthogonal Frequency Division Multiplex) system. The OFDM scheme is a scheme for transmitting a large amount of data using a plurality of mutually orthogonal subcarriers. In the OFDM scheme, since there are a large number of subcarriers, it is possible to improve transmission efficiency by adaptively controlling the MCS for each subcarrier having different channel quality. There are many cases where uplink resources are insufficient for all terminals to return information on each subcarrier, and how to compress the information on the channel quality and send it as CQI depends on LTE (Long Term Evolution) and next This is a matter of consideration for the next generation of communication systems.

  Currently, as described in Non-Patent Document 2, 3GPP discusses the contents of CQI in the super 3G communication system. Among communication systems, a Top-M system and a DCT (Discrete Cosine Transform) system are promising.

  FIG. 19 is a conceptual diagram showing a conventional technique (Top-M system). The Top-M system is one of CQI formats. In the Top-M system, the M subchannels (the subcarriers or a plurality of subcarriers combined) having the best quality among the reception quality in all bands are selected, and the frequency and reception quality of the subchannels are selected. In this method, the data to be represented is CQI. FIG. 19 is a graph showing the downlink channel quality of a single terminal, with the horizontal axis representing the subchannel frequency and the vertical axis representing the subchannel channel quality. In FIG. 19, the best 10 channel qualities are represented as black circles. A method of sending data representing the frequency of the black circle and the channel quality as CQI is the Top-M method. Since each terminal has a different reception quality, the subchannels reported as Top-M are also different. When scheduling is performed at the base station, each terminal is assigned a subchannel with good reception quality of the terminal. Therefore, when Top-M is sent as CQI, an effective part with a small amount of CQI is transmitted. Channel quality information can be obtained, and as a result, the transmission efficiency of the entire transmission apparatus can be increased.

FIG. 20 is a conceptual diagram showing a conventional technique (DCT method). The DCT method is also a CQI format. In this method, the relationship between the frequency of the subchannel on the horizontal axis shown in FIG. 20A and the channel quality on the vertical axis is discrete cosine transformed as shown in FIG. 20B. In the graph shown in FIG. 20B, the horizontal axis represents time, and the vertical axis represents channel quality. In the DCT method, as shown in FIG. 20, the inverse discrete cosine transform is performed on the reception quality of the subchannels in the entire band, and the part at a small position on the time axis (for example, the part displayed with a black frame in the figure) ) Send only information. As a result, the amount of information is reduced compared to the amount of information when sending information on all channel qualities, and the rough shape of the overall channel quality excluding components at large positions on the time axis is reproduced at the base station. can do.
T.A. Ue, S .; Sampei, N .; Morinaga and K.M. Hamaguchi, “Symbol Rate and Modulation Level-Controlled Adaptive Modulation / TDMA / TDD System for High-Bit-Rate Wireless Data TransEmission. VT, pp. 1134-1147, vol. 47, no. 4, Nov. 1998 3GPP TSG RAN WG1 # 50 R1-073440 “Selection of CQI reporting scheme”

  As described above, there are a Top-M method and a DCT method as methods for sending feedback information related to channel quality of subcarriers during subcarrier adaptive modulation. However, in the Top-M system, there are few subcarriers that can transmit information among all subcarriers. Also, in the DCT scheme, an error in information regarding subcarriers with good channel quality increases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wireless communication apparatus capable of accurately and efficiently transmitting channel quality for each subcarrier or each subchannel.

  (1) In order to achieve the above object, a radio communication apparatus according to the present invention is a radio communication apparatus that receives data allocated on subcarriers, and each subcarrier or a subgroup in which a plurality of subcarriers are collected. A channel estimation unit that estimates channel quality for each channel, and a CQI unit that approximates a peak portion where the estimated channel quality has a maximum with respect to a frequency by a convex function for each peak portion. The approximation result is transmitted to the transmission source of the data.

  Thus, since the wireless communication apparatus of the present invention approximates the peak portion with an upward convex function, it can efficiently transmit the information on the peak portion as an approximation result. Moreover, since approximation is performed for each peak portion, accurate information for each peak portion can be transmitted. As a result, accurate channel quality information can be transmitted for many subcarriers, and the overall throughput can be improved.

  (2) In the wireless communication apparatus according to the present invention, the CQI unit includes a peak part detection unit that detects a peak part where the estimated channel quality has a maximum, and the estimated peak part in the detected peak part. The peak part approximation unit for calculating the function specific value that uniquely identifies the upward convex function and the function specific value for uniquely specifying the upward convex function And a feedback information generating unit that generates feedback information including.

  As described above, the wireless communication apparatus of the present invention detects a peak portion where the estimated channel quality has a maximum, approximates the peak portion with an upward convex function, and uniquely identifies the upward convex function. Function specific value is calculated. As a result, a peak portion having a maximum can be detected, and information representing a function can be transmitted to the data transmission source. The peak portion is detected by detecting a frequency range corresponding to the peak portion. The peak portion is specified by the detected frequency range.

  (3) In the wireless communication apparatus according to the present invention, the peak portion detection unit detects, as the peak portion, a subchannel whose estimated channel quality is higher than subchannels adjacent on the frequency axis. It is characterized by. As a result, it is possible to easily detect the peak portion where the estimated channel quality is maximum. Adjacent subchannels are subchannels with the closest frequencies.

  (4) Further, in the wireless communication apparatus according to the present invention, the peak portion detection unit is a maximum of the estimated channel quality that monotonously increases over a plurality of subchannels, and monotonously decreases over a plurality of subchannels. The vicinity of the subchannel having the maximum channel quality among the estimated channel qualities is detected as the peak portion. Thus, by detecting the channel quality estimated over a plurality of subchannels, it is possible to accurately detect the peak portion without the influence of the estimation error due to noise or the like. For example, when the channel quality estimated over three subchannels monotonically increases and the channel quality estimated over three subchannels from the largest subchannel monotonically decreases, the maximum is reached in the center subchannel. It can be detected as a peak portion over five subchannels.

  (5) Further, in the wireless communication device according to the present invention, the CQI unit further includes a peak part selection unit that selects a specific condition among the peak parts, and the peak part approximation unit includes the peak part selection unit It is characterized in that the selected peak portion is approximated by a convex function. As described above, since a peak portion satisfying a specific condition is selected and the selected peak portion is approximated to a function, information can be transmitted efficiently.

  (6) Moreover, the radio | wireless communication apparatus which concerns on this invention further has a peak part selection part from which the said CQI part selects the thing which satisfy | fills a specific condition among the said approximate and convex functions, Feedback information generation | occurrence | production The unit is characterized in that it generates feedback information including a function specifying value that uniquely specifies the selected upward convex function. In this way, information can be efficiently transmitted by transmitting a function specifying value that specifies a selected convex function.

  (7) Moreover, the radio | wireless communication apparatus which concerns on this invention is characterized by the said peak part selection part selecting the peak part with the said large estimated channel quality. As a result, a peak portion having a particularly high channel quality is selected, and the effect of scheduling can be enhanced and information can be transmitted efficiently.

  (8) Moreover, the wireless communication apparatus according to the present invention is characterized in that the peak portion selection unit selects a function having a maximum maximum value among the approximate convex functions. As a result, a function having a large maximum value is selected, and information on the function is transmitted to the transmission source. As a result, the effect of scheduling can be improved and information can be transmitted efficiently.

  (9) Further, the wireless communication device according to the present invention is characterized in that the peak portion selection unit selects a wide one of the approximate convex functions. As a result, the peak portion is selected based on the width of the upwardly convex function, and the function information is transmitted to the transmission source. As a result, the effect of scheduling can be improved and information can be transmitted efficiently.

  (10) In addition, the wireless communication device according to the present invention is characterized in that the peak portion selection unit selects a convex function that satisfies a condition based on a maximum value and a width. As a result, the peak portion can be selected in consideration of both the maximum value and the width of the upward convex function, and information on the function can be transmitted to the transmission source. As a result, it is possible to select information that is highly effective from various viewpoints and efficiently transmit the information.

  (11) In addition, the wireless communication device according to the present invention is characterized in that the peak portion selection unit determines the number of peak portions to be selected or an upward convex function based on the estimated channel quality. . In this way, by determining the number of peak portions for transmitting information and limiting the number of transmissions, even when a large number of receiving devices return feedback information to one transmitting device at the same time, many subchannels are used. be able to. Also, since the number of peak portions is determined based on the estimated channel quality, transmission information to the transmission source can be determined according to the situation on the receiving side.

  (12) In the wireless communication device according to the present invention, the peak portion selection unit may select a peak portion to be selected or the number of upwardly convex functions based on a feedback information control signal notified from the data transmission source. It is characterized by deciding. In this way, by determining and limiting the number of peak portions for transmitting information, many subchannels can be used even when a large number of receiving devices return feedback information simultaneously to one transmitting device. . In addition, since the number of transmissions of the peak portion is determined based on the feedback information control signal notified from the data transmission source, the reception side can easily determine the number of transmissions of the peak portion, and the transmission side can transmit and receive information. Makes it easier to manage.

  (13) Further, the wireless communication apparatus according to the present invention is characterized in that the peak portion approximation unit approximates the estimated channel quality with respect to a frequency by a quadratic function. Thus, the wireless communication apparatus of the present invention approximates the estimated peak portion of the channel quality with a quadratic function. Thereby, the function approximated by three constants can be specified, and the amount of information transmitted and received can be reduced.

  (14) Further, in the radio communication device according to the present invention, the peak portion approximation unit has a maximum of the estimated channel quality at a frequency at which the estimated channel quality has a maximum value at the peak portion. The peak value is approximated to a quadratic function with a value as a maximum value and a second-order differential with respect to the frequency of the estimated channel quality as a second-order derivative. In this manner, the peak portion is approximated to a quadratic function based on the maximum value of the actually measured value and the value of the second order difference, so that the approximation calculation is simplified.

  (15) Further, in the radio communication apparatus according to the present invention, the peak portion approximation unit has a maximum of the estimated channel quality at a frequency at which the estimated channel quality has a maximum value at the peak portion. The value is set to the maximum value, and the square error from the estimated channel quality is minimized for a predetermined number of subchannels on the frequency axis from the subchannel where the estimated channel quality has a maximum value. The peak portion is approximated to a quadratic function. As described above, since the peak portion is approximated to a quadratic function based on the maximum value and the value of the maximum point, approximation calculation is simplified.

  (16) Further, in the wireless communication device according to the present invention, the peak portion approximating unit sets a maximum value of the estimated channel quality at the peak portion, and the estimated channel quality is the maximum value. Approximating the peak part to a quadratic function as the width of the frequency when taking a value from a value to a small value by a predetermined ratio, and the width of the independent variable when the dependent variable takes a value by a predetermined percentage It is a feature. In this way, the peak value is approximated to a quadratic function based on the estimated maximum value of the channel quality and the frequency width when taking the value from the local maximum value to a value that is smaller by a predetermined percentage, so the approximation calculation is easy. become. As a result, the processing burden on the wireless communication device is reduced. The independent variable of the approximated function represents the frequency of the subchannel, and the dependent variable represents the channel quality.

  (17) In addition, in the wireless communication device according to the present invention, the peak portion approximating unit may be configured so that, in the predetermined number of subchannels from the frequency at which the estimated channel quality has a maximum value at the peak portion, The peak portion is approximated to a quadratic function so that a square error with the estimated channel quality is minimized. Thus, since the peak portion is approximated to a quadratic function so that the square error with the estimated channel quality is minimized in a predetermined number of large and small subchannels, accurate approximation can be performed.

  (18) Further, in the wireless communication device according to the present invention, the feedback information generation unit generates feedback information including a maximum point of the approximated quadratic function and a value of a second-order derivative at the maximum point. It is characterized by. Thus, since the maximum value and the value of the second order differential at the maximum point are transmitted as the function specific value, the amount of information to be transmitted can be reduced and the data transmission efficiency can be improved.

  (19) In the wireless communication device according to the present invention, when the feedback information generation unit takes the maximum point of the approximated quadratic function and the maximum value from the maximum value to a value that the dependent variable is smaller by a predetermined ratio. It is characterized in that feedback information including a value indicating the width of the independent variable is generated. In this way, the maximum value of the approximated quadratic function, the change width of the independent variable when the dependent variable is decreased by a predetermined ratio from the maximum point is transmitted as the function specific value, so the amount of information to be transmitted is reduced, Data transmission efficiency can be improved.

  (20) In addition, the wireless communication apparatus according to the present invention is characterized in that the feedback information generation unit generates feedback information including coefficients of respective orders of the approximated quadratic function. In this way, since the coefficients of the respective orders of the approximated quadratic function are transmitted as function specific values, the amount of information to be transmitted can be reduced and the data transmission efficiency can be improved.

  (21) In the wireless communication device according to the present invention, the feedback information generation unit may replace the approximated second function with at least one of the maximum value of the approximated quadratic function and the second derivative at the maximum point. It is characterized by generating feedback information including an average value of a next function.

  When the number of bits that can be reported as CQI is small, such as when the uplink communication state is poor, it is necessary to reduce the amount of transmission information. By generating the feedback information including the average value of the approximated quadratic function, the time for sending one CQI is shortened, and as a result, the transmission efficiency of the entire transmission apparatus is improved. The present invention is also effective when the number of receiving apparatuses is large and the number of CQI bits that can be allocated to each receiving apparatus is small. The average value of the quadratic function means the average value of the dependent variable with respect to the independent variable.

  (22) In the wireless communication device according to the present invention, the feedback information generation unit may be configured such that the maximum value of the approximated quadratic function and the maximum value of the dependent variable take a value that is smaller by a predetermined ratio. Instead of at least one of the widths of the independent variables, feedback information including an average value of the approximated quadratic function is generated.

  When the number of bits that can be reported as CQI is small, such as when the uplink communication state is poor, it is necessary to reduce the amount of transmission information. By generating the feedback information including the average value of the approximated quadratic function, the time for sending one CQI is shortened, and as a result, the transmission efficiency of the entire transmission apparatus is improved. The present invention is also effective when the number of receiving apparatuses is large and the number of CQI bits that can be allocated to each receiving apparatus is small. The average value of the quadratic function means the average value of the dependent variable with respect to the independent variable.

  (23) In the wireless communication apparatus according to the present invention, the CQI unit further includes a channel estimation value smoothing unit that smoothes the estimated channel quality, and the peak part detection unit and the peak part approximation The unit uses the smoothed channel quality instead of the estimated channel quality.

  As a result, it is possible to reduce the possibility of detecting the peak of channel quality formed by the error of channel estimation. As a result, it is possible to generate a CQI that can restore channel quality closer to a true channel on the transmission device side, and finally, transmission efficiency in the transmission device is improved. An accurate maximum value is detected by eliminating the maximum value of the subchannel different from the original channel.

  (24) In the wireless communication apparatus according to the present invention, the CQI unit further includes a channel quality averaging unit that calculates an average value of the estimated channel quality, and the feedback information generation unit includes the function Feedback information including a specific value and an average value of the channel quality information is generated.

  As a result, accurate channel quality information can be obtained for information about subchannels with good channel quality and information about other subchannels. Since information other than the vicinity of the peak can also be transmitted, more efficient scheduling can be performed for each receiving apparatus. As a result, the transmission efficiency of the entire transmission device can be increased.

  According to the present invention, information on peak portions can be efficiently transmitted as an approximation result. Moreover, since approximation is performed for each peak portion, accurate information for each peak portion can be transmitted. As a result, accurate channel quality information can be transmitted for many subcarriers, and the overall throughput can be improved.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

[Embodiment 1]
Hereinafter, as an example, the present invention is described using an OFDM communication scheme using subcarriers orthogonal to each other on the frequency axis. However, the present invention can also be applied to communication systems that transmit data using other plural carriers.

  The transmission device is a communication device that receives CQI and transmits information data. The receiving device (wireless communication device) is a communication device that receives information data and transmits CQI wirelessly. A communication system is configured by the transmission device and the reception device.

  The channel quality information is basically the received signal power-to-interference and noise power ratio (SINR), but may be the received signal power-to-noise power ratio (SNR) in each subchannel. It may be the carrier signal power to interference and noise power ratio (CINR) in the channel. Further, when a subchannel includes a plurality of subcarriers, the average values of the SNR, SINR, and CINR of the subcarriers are used as channel quality information.

  FIG. 1 is a block diagram illustrating a configuration of a receiving device 200 according to the first embodiment. The receiving apparatus 200 includes an antenna 201, a radio reception unit 202, a GI (Guard Interval) removal unit 203, an FFT (Fast Fourier Transform) unit 204, a channel estimation unit 205, a channel compensation unit 206, a demapping unit 207, and a decoding unit 208. A CQI unit 209, an encoding unit 210, a mapping unit 211, a frame configuration unit 212, an IFFT (Inverse Fast Fourier Transform) unit 213, a GI insertion unit 214, and a wireless transmission unit 215.

  In this receiving apparatus, transmission / reception is performed by the OFDM method, but transmission / reception may be performed by a method using a plurality of carriers other than OFDM. As a transmission method, a method using a single carrier may be adopted.

  As illustrated in FIG. 1, the reception device 200 receives a signal transmitted from the transmission device 300 by the antenna 201 and inputs the received signal to the wireless reception unit 202. The wireless reception unit 202 converts the received signal into a baseband digital signal and outputs it. The GI removal unit 203 removes the GI from the baseband digital signal and inputs the signal from which the GI has been removed to the FFT unit 204. FFT section 204 performs FFT on the baseband digital signal from which the GI has been removed to separate the modulation symbols of each subcarrier, and inputs the separated signals to channel estimation section 205 and channel compensation section 206.

  Channel estimation section 205 performs channel estimation for each subcarrier, and inputs the estimated value to CQI section 209 and channel compensation section 206 for each subcarrier. Channel compensation section 206 performs channel compensation based on channel estimation information for each subcarrier input from channel estimation section 205, and inputs data for each subcarrier to demapping section 207.

  Demapping section 207 demodulates data based on the modulation scheme of each subcarrier, and inputs the demodulated data to decoding section 208. The decoding unit 208 decodes data based on the encoding method and outputs it as information data. CQI section 209 generates CQI based on the channel estimation value input from channel estimation section 205 and outputs the CQI to encoding section 210. Details of the CQI unit 209 will be described later.

  Encoding section 210 encodes information data and CQI, and inputs the encoded information to mapping section 211. The mapping unit 211 maps the encoded information data and CQI for each subcarrier, configures transmission data, and inputs the transmission data to the frame configuration unit 212 for each subcarrier. The frame configuration unit 212 configures a frame using transmission data, and inputs the frame to the IFFT unit 213. The IFFT unit 213 performs IFFT on the framed transmission data, creates a baseband digital signal, and inputs the baseband digital signal to the GI insertion unit 214. The GI insertion unit 214 adds a GI to the baseband digital signal and inputs the signal with the GI added to the wireless transmission unit 215. The wireless transmission unit 215 up-converts the baseband digital signal to which the GI is added to the frequency of the carrier wave, and returns transmission data to the transmission device 300 using the antenna 201.

  FIG. 2 is a block diagram illustrating a configuration of the transmission apparatus 300 according to the first embodiment. The transmission apparatus 300 includes an antenna 301, a radio reception unit 302, a GI removal unit 303, an FFT unit 304, an uplink channel estimation unit 305, an uplink channel compensation unit 306, a demapping unit 307, a decoding unit 308, a CQI separation unit 309, a downlink A channel restoration unit 310, a scheduling unit 311, an encoding unit 312, a mapping unit 313, a frame configuration unit 314, an IFFT unit 315, a GI insertion unit 316, and a radio transmission unit 317 are provided.

  In this transmission apparatus, transmission / reception is performed by the OFDM scheme, but transmission / reception may be performed by a scheme using a plurality of carriers other than OFDM. As a receiving method, a method using a single carrier may be adopted.

  As shown in FIG. 2, the antenna 301 receives a feedback signal transmitted from the receiving device. The received signal is input to the wireless reception unit 302. The wireless reception unit 302 converts the received signal into a baseband digital signal, and inputs the converted signal to the GI removal unit 303. The GI removal unit 303 removes the GI from the baseband digital signal and inputs the signal from which the GI is removed to the FFT unit 304. The FFT unit 304 performs FFT on the baseband digital signal from which the GI has been removed, separates the modulated signal of each subcarrier, and inputs it to the channel estimation unit 305 and the channel compensation unit 306 for each subcarrier.

  Uplink channel estimation section 305 performs channel estimation and inputs the estimated value to uplink channel compensation section 306. Based on the channel estimation value input from uplink channel estimation section 305, uplink channel compensation section 306 performs channel compensation on the received signal for each subcarrier input from the FFT section, and demaps the received symbols for each subcarrier. Input to 307. Demapping section 307 demodulates the received symbol based on the modulation scheme of each subcarrier and inputs it to decoding section 308. The decoding unit 308 performs decoding based on the encoding method and inputs the result to the CQI separation unit 309.

  The CQI separation unit 309 separates the CQI control signal from the data input from the decoding unit 308, inputs the CQI control signal to the downlink channel restoration unit 310, and outputs other signals as information data. The downlink channel restoration unit 310 restores channel quality for each downlink subchannel based on the CQI separated from the CQI separation unit 309.

  FIG. 4 is a block diagram illustrating a configuration of the downlink channel restoration unit 310. The downlink channel restoring unit 310 includes a peak part information separating unit 501, a peak part restoring unit 502, and a channel information combining unit 503. The peak part information separation unit 501 separates and outputs information about each peak part included in the input CQI. A function specifying value that uniquely specifies a quadratic function that approximates each separated peak portion is input to the peak portion restoring unit 502. The peak portion information separation unit 501 uses the value to restore the channel quality peak portion to a quadratic function. Then, the peak part restoration unit 502 inputs the channel quality information obtained from each restored peak part to the channel information synthesis unit 503.

  FIG. 5 is a diagram schematically illustrating the function of the channel information combining unit 503. Channel information combining section 503 determines channel quality over all subchannels using channel quality obtained by approximation of all peak portions. As shown in FIG. 5, when determining the channel quality over all subchannels, the channel information combining unit 503 determines the best channel among the peak portions for subchannels in which approximate values related to a plurality of peak portions overlap. An approximate value of a peak portion approximated as having quality is adopted. The approximate value of the channel quality of the subchannel is used.

  Scheduling section 311 uses which sub-channel and which MCS to transmit to each receiving apparatus 200 based on the downlink channel quality information input from each downlink apparatus 200 to each receiving apparatus 200. To decide. At this time, in addition to the above-described downlink channel quality information, which subchannel is used based on the data transmission rate required by each receiving device 200 and the amount of data that needs to be transmitted to the receiving device 200. It may be determined whether to transmit using MCS. Further, the scheduling unit 311 inputs the determined result to the encoding unit 312, the mapping unit 313, and the frame configuration unit 314. At this time, scheduling section 311 inputs control information for CQI returned by the receiving apparatus next, for example, the number of peak parts to report to encoding section 312. At the same time, information indicating an assignment result indicating which MCS is to be transmitted to which subchannel is also input to the encoding unit 312.

  Here, as a method of assigning subchannels to each receiving apparatus 200, a method of assigning the subchannel to the receiving apparatus 200 that shows the best channel quality among the channel qualities of each receiving apparatus 200 in a certain subchannel (MAX) -CIR). In the above example, the scheduling unit 311 uses MAX-CIR, but other allocation methods for each receiving apparatus 200, such as proportional fairness, may be used.

  In addition to this method, the allocation method may be changed using information included in another transmitting apparatus 300 in addition to the channel quality information. For example, the scheduling unit 311 may control the subchannel to be allocated according to the transmission rate of data necessary for each receiving apparatus 200 in addition to the channel quality information. With respect to the receiving apparatus 200 that can satisfy the required transmission rate even if the allocated subchannel rate is limited, a method of limiting the allocated subchannel may be used. Furthermore, a subchannel may be preferentially assigned to a receiving apparatus having a large amount of data that needs to be transmitted over other receiving apparatuses.

  Next, an example of an MCS determination method for the assigned subchannel will be described. FIG. 6 is a diagram illustrating an example of MCS determined based on channel quality information by adaptive modulation. The MCS is changed in the order shown in FIG. 6 from the worst channel quality to the best channel quality. At this time, the threshold value for changing the two MCSs is determined as follows, for example.

  When the noise power of white Gaussian noise is increased in an environment where only white Gaussian noise is added to the propagation path and fading does not occur, the throughput changes in each MCS. The region with low channel quality shown in FIG. 6 is more resistant to high power noise. On the other hand, when the noise power is small, the higher channel quality region shown in FIG. 6 has a higher throughput because the bit rate being sent is higher. Therefore, when the white Gaussian noise reaches a certain power, the throughput between the MCS on the higher channel quality side and the MCS on the lower side is reversed. The channel quality corresponding to the noise power at that time is set as the MCS threshold. In addition to the throughput, an MCS that controls the packet error rate below a certain value may be used, or a method of adaptively controlling the MCS may be used.

  As described above, based on the MCS assigned to each subcarrier of each receiving apparatus 200, encoding section 312 encodes information data and allocation information, and inputs information bits to mapping section 313. The mapping unit 313 maps the encoded information bits for each subcarrier based on the MCS assigned to each subcarrier of each receiving device 200. Then, mapping section 313 configures transmission data and inputs it to frame configuration section 314 for each subcarrier.

  The frame configuration unit 314 configures a frame using the MCS information input from the scheduling unit 311 and the transmission data, and inputs the configured frame to the IFFT unit 315. IFFT section 315 performs IFFT on the transmission data to create a baseband digital signal, and inputs the baseband digital signal to GI insertion section 316. The GI insertion unit 316 adds a GI to the baseband digital signal and inputs the signal with the GI added to the wireless transmission unit 317. The wireless transmission unit 317 up-converts the baseband digital signal to which the GI is added to the carrier frequency, and transmits the transmission data to the reception device 200 using the antenna 701.

  Here, the CQI unit 209 shown in FIG. 1 will be described in detail. FIG. 3 is a block diagram showing the configuration within the CQI unit 209. The CQI unit 209 includes a peak part detection unit 401, a peak part selection unit 402, a peak part approximation unit 403, and a CQI generation unit (feedback information generation unit) 404.

  The peak portion detection unit 401 detects a peak portion that is maximum when the input channel estimation values are arranged in the frequency direction for each subchannel. This method for detecting the peak portion is performed by detecting a subchannel having a channel quality higher than both the subchannel having a low frequency and the subchannel having a high frequency as a maximum. By this method, the peak portion can be detected with a simple process. The detection of the peak portion is performed by detecting a frequency range corresponding to the peak portion.

  In addition, when the value indicating the reception quality monotonously increases over a plurality of subchannels up to a certain subchannel, and when the value indicating the reception quality monotonously decreases from that subchannel to a plurality of subchannels, the increase and decrease Alternatively, a method may be used in which the subchannel at the boundary is set to the maximum value. By this method, it is possible to prevent detection of a peak portion caused by an error other than the true channel quality, such as an estimation error due to noise in the channel estimation value. In addition, other local maximum value detection methods may be used. The peak portion detection unit 401 inputs data representing the detected subchannel that takes the maximum value to the peak portion selection unit 402.

  The peak portion selection unit 402 calculates a value indicating one or a plurality of peak portions from a peak portion having a maximum maximum value, from the value indicating the subchannel taking the maximum value input from the peak portion detection unit 401 and the channel estimation value. select. Then, a value indicating the peak portion is input to the peak portion approximating unit 403.

  As the number of peak portions to be selected at this time, the number determined in advance between the transmitting and receiving apparatuses is used. However, the number of peak portions to be selected may be determined based on a value obtained from the channel estimation value input from the channel estimation unit 205. In this case, the number is determined so that the number of peak portions to be reported increases as the delay spread increases. This is because when the delay spread is increased, the channel quality varies greatly between frequencies, and it is considered that many peaks having a narrow peak portion are formed.

  For example, the peak portion approximating unit 403 matches the subchannel taking the maximum value and the maximum value input from the peak portion selecting unit 402 with the subchannel taking the maximum value of the approximated quadratic function and the maximum value. Then, an index representing the width of the quadratic function is obtained. In this way, the peak portion approximating unit 403 approximates the peak portion with a quadratic function. The function to be approximated is not limited to a quadratic function, but may be a function convex upward. For example, instead of a quadratic function, a semicircle may be approximated. In that case, the function can be specified by three parameters, the coordinate of each axis at the center of the semicircle and the radius of the semicircle. Furthermore, approximation accuracy may be increased by approximating an ellipse. In this case, four parameters are required. However, the approximate function is preferably a quadratic function. A quadratic function can be specified with only three parameters. Furthermore, the quadratic function can approximate the peak portion in the receiving device and restore it in the transmitting device only by calculating a quadratic simple polynomial, and can reduce the calculation amount of the receiving device and the transmitting device. .

  FIG. 7 is a diagram illustrating an example of the approximation method. The portion represented by the black circle is the maximum value of the channel quality, which coincides with the maximum value of the quadratic function to be approximated. Further, the width of the quadratic function is determined as indicated by the arrow in FIG. 7, and the peak portion is approximated by the quadratic function.

In order to obtain an index representing this width, the following equation (1) is used.

  The estimated channel quality maximum value is substituted for H (f), and the estimated channel of the subchannel adjacent to the subchannel that takes the maximum value on the frequency axis for H (f−Δ) and H (f + Δ). By substituting the quality, an approximate value of the second derivative of the function H is obtained. When the above value is substituted, the right side of the expression (1) is the value of the second-order difference of the estimated channel quality at the frequency having the maximum value.

When an approximation function of the channel quality estimated in the vicinity of the frequency f at which the peak portion has a maximum is represented by H, H (f ± Δ) representing the channel quality at a frequency that is separated by ± Δ from the frequency f at which the peak portion has a maximum. If Taylor expansion is performed up to the third order term around f, the following two equations are obtained.

Δ is the difference between the frequency representing the maximum subchannel and the frequency representing the adjacent subchannel. H ⁽³⁾ (f) is the value of the third order derivative of H (f). Where (2) subtract (3) from the equation, the equation (1) is derived Neglecting delta ⁴ or more order terms.

That is, Equation (1) will be is suppressed to the order of the error delta ⁴ by approximation in frequency away delta from the frequency of the peak portion takes a maximum value, when reconstituted in the base station, the true channel quality And the error is kept low. Further, Δ may not be the interval on the frequency axis between the maximum value and the adjacent subchannel, but may be the interval on the frequency axis with a plurality of subchannels that are separated from the maximum value by a plurality of magnitudes on the frequency axis.

  In addition, as a method of obtaining an index representing this width, the width is set so that the square error when the channel quality of the subchannels of the number of subchannels from the maximum value to one or more is approximated by a quadratic function is minimized. You may decide.

When the square error is calculated for the subchannel having the maximum and one or more subchannels whose frequencies are close to the subchannel, the evaluation function of the square error is expressed as the following equation (4).

  Σ is the sum over all subchannels evaluating the square error. a is a value representing the width of the approximated quadratic function. This equation is the square error between the measured value and the quadratic function of the channel quality in one or more subchannels whose frequencies are close to the subchannel having the maximum and the estimated channel quality having the maximum. A is determined so that J (a) is minimized. a is an index representing the width of the quadratic function.

  In the above example, the value indicating the width of the quadratic function is determined from the channel quality of one or more subchannels whose frequencies are close to the subchannel having the maximum value, and therefore adjacent to the subchannel having the maximum value. It is possible to approximate not only the subchannel but also the range including the subchannel that is a specified number away from the subchannel that takes the maximum, and the channel quality can be accurately approximated.

  FIG. 8 is a diagram schematically showing a modification of the method for determining the width of the quadratic function. As shown in FIG. 8, a method of matching the half-value width of the peak portion (width between the arrows) with the half-value width of the quadratic function may be used, or it may be smaller than the half value by a predetermined ratio from the maximum channel quality. A method of matching the width of the frequency when taking up to the value with the corresponding value of the quadratic function may be used.

  For example, the channel quality is first reduced by half or a predetermined percentage from the maximum channel quality, and the channel quality of the subchannel shifted by one in the direction of decreasing frequency and increasing direction from the subchannel where the channel quality is maximized. Compare If the channel quality value when the channel quality is reduced by a predetermined percentage from the subchannel that has the maximum due to the channel quality of the subchannel in either direction is smaller, then the channel quality of the subchannel shifted by two in the same direction Compared with the channel quality when the sub-channel having the maximum value is decreased by a predetermined ratio. Similarly, the target subchannels are shifted and compared one by one in the direction of low frequency and in the direction of high frequency, respectively, in the direction of small frequency and large direction. The comparison is performed until the value obtained by subtracting a predetermined ratio from the channel quality of the subchannel having the maximum becomes larger than the channel quality of the target subchannel.

  When the comparison target is shifted in the direction with higher frequency and when the target is shifted in the lower direction, if the value obtained by reducing the maximum value from the maximum value by a certain percentage is larger, the same comparison is performed only in the other direction. repeat. The comparison is repeated until the value obtained by reducing the maximum channel quality by a predetermined ratio becomes smaller than the channel quality of the subchannel that is shifted. In both cases, the comparison is repeated until the channel quality of the shifted subchannel becomes smaller. The sum of the number of subchannels that are larger than the maximum channel quality reduced by a predetermined percentage in both directions is independent when the dependent variable takes the same percentage of the dependent variable from the maximum value to a predetermined percentage smaller value in the quadratic function. A value indicating the width of the variable. The independent variable of the quadratic function represents the frequency of the subchannel, and the dependent variable represents the channel quality.

  In this method, the channel width information in each subcarrier may be compared with the half width or the value at which the peak portion has decreased by a predetermined ratio. Therefore, the width of the peak portion can be approximated by a simple process. In addition, the width of the quadratic function may be determined so that the error from the peak portion becomes small.

  Further, when determining the quadratic function, the channel quality at which the peak portion is maximized does not necessarily need to match the maximum value of the quadratic function. What is necessary is just to determine the quadratic function which decreases. FIG. 9 is a diagram illustrating an approximation example of the peak portion. As shown in FIG. 9, the maximum point of the quadratic function does not necessarily match the channel quality at which the peak portion is maximized and the frequency at that time. The maximum point is a point determined by the maximum value of the dependent variable of the function and the value of the independent variable at that time.

  The peak portion approximation unit 403 includes a subchannel that takes a vertex of the quadratic function so that a square error between the quadratic function and the measurement value for one or more subchannels closest to the subchannel that takes the maximum is minimized, The value of the vertex and the second derivative at the vertex may be obtained. When approximated to a quadratic function by this method, as shown in FIG. 9, the channel quality at which the peak is maximized and the frequency at which the maximum is taken may not match the maximum value and the maximum point of the quadratic function. The approximation criterion is that the square error is minimized in one or more subchannels closest to the subchannel having the maximum peak portion.

In this method, the following equation (5) is used as an evaluation function of the square error.

  Σ is a sum over all subchannels for evaluating the square error, and a, b, and c are variables of the evaluation function K (a, b, c). A combination of a, b, and c that minimizes K (a, b, c) is determined as each order coefficient of the approximated quadratic function.

  The maximum value of the quadratic function approximated in this way does not necessarily match the channel quality that takes the maximum. However, by approximating the peak part with a quadratic function so that the square error is the smallest in the range of one or more subchannels that are closest to the channel quality that takes the maximum, the transmitter side can accurately determine the peak part. Channel quality peak portion information can be obtained.

  The peak portion approximating unit 403 inputs, to the CQI generating unit 404, a function specifying value that uniquely specifies, for example, a quadratic function determined by any one of the methods described above. The function specific value that uniquely specifies the quadratic function at this time generates and outputs a CQI from the maximum point of the quadratic function and the value of the second derivative at the maximum point. In addition, it may be a value corresponding to the maximum point of the quadratic function and the width of the independent variable when the dependent variable takes a value that is smaller by a predetermined percentage from the maximum value. It may be a coefficient. The CQI generating unit 404 quantizes a function specifying value that uniquely specifies a quadratic function so that it falls within the number of bits allocated for CQI, and generates a CQI.

  FIG. 10A shows an approximation method of the present invention, and FIGS. 10B and 10C show a conventional approximation method. As shown in FIG. 10, the system of the present invention can send more detailed channel quality information to the base station with the same amount of information as the Top-M system or the DCT system. In the Top-M method, even though a plurality of M subchannels with good channel quality may be adjacent to each other, subchannels with good channel quality are designated independently, and the channel quality between neighbors is specified. It is not fully used that there is a correlation. On the other hand, in the DCT system, it is impossible to transmit accurate information about the peak part of the channel quality for which accurate channel quality information is required because data is likely to be assigned by scheduling on the transmitting device side. In the method of the present invention, by approximating the peak portion of the channel with a quadratic function, the channel quality of the peak portion that is likely to be allocated can be accurately fed back to the base station with a small number of bits. As a result, the overall throughput can be improved.

  In addition, it is preferable to change the number of peak portions to be information transmission according to the situation. When data must be transmitted from the transmission device 300 to the specific reception device 200 at a high speed, there is a possibility that the transmission device 300 allocates many subchannels to the specific reception device 200 in order to satisfy the transmission rate. high. For this reason, it is necessary for the specific receiving apparatus 200 to return a large number of peak portions as approximate values so that the transmitting apparatus 300 can perform more efficient scheduling. In addition, when many receiving devices 200 try to return feedback information to one transmitting device 300 at the same time, the amount of feedback information that can be returned per one receiving device 200 decreases, resulting in a small peak portion. Only information about can be returned. In such a case, it is possible to cope with the problem by changing the number of peak portions.

[Embodiment 2]
FIG. 11 is a block diagram illustrating a configuration of a receiving device 600 according to the second embodiment. The receiving apparatus 600 includes an antenna 601, a radio reception unit 602, a GI removal unit 603, an FFT unit 604, a channel estimation unit 605, a channel compensation unit 606, a demapping unit 607, a decoding unit 608, a CQI control signal separation unit 609, and a CQI. A unit 610, an encoding unit 611, a mapping unit 612, a frame configuration unit 613, an IFFT unit 614, a GI insertion unit 615, and a wireless transmission unit 616. Note that the receiving apparatus 600 performs transmission / reception by the OFDM scheme, but may perform transmission / reception by a scheme using a plurality of carriers. In the transmission scheme, a scheme using a single carrier or a scheme using a plurality of carriers other than the OFDM scheme may be adopted.

  As illustrated in FIG. 11, the antenna 601 receives a signal transmitted from the transmission device, and inputs the received signal to the wireless reception unit 602. The wireless reception unit 602 converts the received signal into a baseband digital signal and outputs the converted signal. The GI removal unit removes the GI from the baseband digital signal and inputs the signal from which the GI has been removed to the FFT unit 604. The FFT unit 604 performs FFT on the baseband digital signal from which the GI has been removed to separate the modulation symbols of each subcarrier, and inputs the signal from which the modulation symbols have been separated to the channel estimation unit 605 and the channel compensation unit 606. .

  Channel estimation section 605 performs channel estimation for each subcarrier using pilot symbols, and inputs the estimated value to CQI section 610 and channel compensation section 606 for each subcarrier. The channel compensation unit 606 performs channel compensation based on the input channel estimation information for each subcarrier, and inputs data for each subcarrier to the demapping unit 607.

  Demapping section 607 demodulates data based on the modulation scheme of each subcarrier, and inputs the demodulated data to decoding section 608. Decoding section 608 decodes data based on the encoding method, and inputs the combined data to CQI control signal separation section 609. The CQI control signal separation unit 609 separates the CQI control signal from the data input from the decoding unit 608, inputs it to the CQI unit 610, and outputs other signals as information data.

  CQI section 610 generates CQI based on the channel estimation value input from channel estimation section 605 and the CQI control signal separated from CQI control signal separation section 609, and outputs the CQI to encoding section 611. The encoding unit 611 encodes the information data and the CQI and inputs them to the mapping unit 612. The mapping unit 612 maps the encoded information data and CQI for each subcarrier, configures transmission data, and inputs the transmission data to the frame configuration unit 613 for each subcarrier. The frame configuration unit 613 configures a frame using the transmission data and inputs the frame to the IFFT unit 614. IFFT unit 614 performs IFFT on the transmission data, and inputs the data subjected to IFFT to GI insertion unit 615. The GI insertion unit 615 adds a GI to the transmission data, and inputs the data with the GI added to the wireless transmission unit 616. The wireless transmission unit 616 returns transmission data to the transmission device 700 using the antenna 601.

  FIG. 12 is a block diagram illustrating a configuration of a transmission apparatus 700 according to the second embodiment. The transmission apparatus 700 includes an antenna 701, a radio reception unit 702, a GI removal unit 703, an FFT unit 704, an uplink channel estimation unit 705, an uplink channel compensation unit 706, a demapping unit 707, a decoding unit 708, a CQI separation unit 709, a downlink A channel restoration unit 710, a scheduling unit 711, an encoding unit 712, a mapping unit 713, a frame configuration unit 714, an IFFT unit 715, a GI insertion unit 716, and a radio transmission unit 717 are included.

  In addition, although transmission apparatus 700 performs transmission / reception by the OFDM scheme, transmission / reception may be performed by a scheme using a plurality of carriers. In the reception scheme, a scheme using a single carrier or a scheme using a plurality of carriers other than the OFDM scheme may be adopted.

  As illustrated in FIG. 12, the antenna 701 receives a feedback signal transmitted from the receiving device 600. The received signal is input to the wireless reception unit 702, and the wireless reception unit 702 converts the received signal into a baseband digital signal, and inputs the baseband digital signal to the GI removal unit 703. The GI removal unit 703 removes the GI from the baseband digital signal, and inputs the signal from which the GI is removed to the FFT unit 704. The FFT unit 704 performs FFT on the baseband digital signal from which the GI has been removed, separates the modulation signal of each subcarrier, and sends the signal from which the modulation signal has been separated to the channel estimation unit 705 and the channel compensation unit 706. Enter for each subcarrier.

  Uplink channel estimation section 705 performs channel estimation for each subcarrier using pilot symbols, and inputs the estimated value to uplink channel compensation section 706. Uplink channel compensation section 706 performs channel compensation for each subcarrier input from uplink channel estimation section 705, and inputs data for each subcarrier to demapping section 707.

  Demapping section 707 demodulates data based on the modulation scheme of each subcarrier, and inputs the demodulated data to decoding section 708. Decoding section 708 decodes data based on the encoding method, and inputs the decoded data to CQI separation section 709. The CQI separation unit 709 separates the CQI control signal from the data input from the decoding unit 708. Then, the separated CQI control signal is input to downlink channel restoration section 710, and other signals are output as information data.

  The downlink channel restoration unit 710 restores channel quality for each downlink subchannel based on the CQI separated from the CQI separation unit 709. The scheduling unit 711 determines which sub-channel is used for each receiving device 600 and which MCS is used for transmission. The determination is based on, for example, the priority assigned to each receiving device 600 and the amount of data that needs to be sent to each receiving device 600 in addition to the downlink channel quality information input from each receiving device 600 from the downlink channel restoring unit 710. Etc. The scheduling unit 711 inputs the determined result to the encoding unit 712, the mapping unit 713, and the frame configuration unit 714. At this time, information for controlling the number of peak parts reported in the CQI returned by receiving apparatus 600 is input to encoding section 712.

  By controlling the number of peak parts reported by the CQI returned by the receiving apparatus 600, the following effects can be obtained. If a large number of receiving devices 600 perform CQI returning operations on one transmitting device 700 at the same time, the amount of communication exceeds the communication capacity to the transmitting device 700 that can be used for CQI. As a result, all receiving apparatuses 600 may not be able to return CQI. Therefore, by reducing the number of peak portions to be reported and reducing the number of CQI bits per receiving apparatus 600, all receiving apparatuses 600 can return CQI simultaneously. Further, when information data needs to be transmitted at high speed to a certain receiving device 600, it is necessary to allocate many subchannels to the receiving device 600. Therefore, by increasing the number of peak portions to be reported for the receiving device 600, channel quality related to more subchannels can be transmitted to the transmitting device 700, and thus data that must be transmitted at high speed is efficiently transmitted. be able to.

  Next, scheduling section 711 inputs information indicating an assignment result indicating which MCS is transmitted to which subchannel to encoding section 712, mapping section 713, and frame configuration section 714. The MCS selection method is the same as the selection method in the first embodiment.

  Encoding section 712 encodes information data and CQI control information and allocation information input from scheduling section 711 based on MCS determined for each subcarrier of each receiving apparatus 600 by scheduling section 711, and mapping section An information bit is input to 713. The mapping unit 713 maps the encoded information bits for each subcarrier based on the MCS determined for each subcarrier of each receiving device 600 by the scheduling unit 711. Then, transmission data is configured and input to the frame configuration unit 714 for each subcarrier.

  The frame configuration unit 714 configures a frame using the MCS information input from the scheduling unit 711 and the transmission data, and inputs the frame to the IFFT unit 715. The IFFT unit 715 performs IFFT on the framed transmission data to create a baseband digital signal and inputs the baseband digital signal to the GI insertion unit 716. The GI insertion unit 716 adds a GI to the baseband digital signal and inputs it to the wireless transmission unit 717. Radio transmission section 717 up-converts the baseband digital signal to which GI is added to the frequency of the carrier wave, and transmits transmission data to receiving apparatus 600 using antenna 701.

  FIG. 13 is a block diagram showing a configuration of CQI section 610. The CQI unit 610 includes a peak part detection unit 801, a peak part selection unit 802, a peak part approximation unit 803, and a CQI information generation unit (feedback information generation unit) 804.

  The peak part detection unit 801, the peak part approximation unit 803, and the CQI generation unit 804 have the same functions as the peak part detection unit 401, the peak part selection unit 402, and the CQI generation unit 404 in the first embodiment, respectively. The peak portion selection unit 802 selects a peak portion based on the channel quality information input from the channel estimation unit 605 and the CQI control information input from the CQI control signal separation unit 609, and a value indicating the selected peak portion Is input to the peak portion approximation unit 803. At this time, the CQI control information includes the number of peak portions to be reported.

  In the present embodiment, when a large number of receiving apparatuses 600 return CQIs simultaneously to one transmitting apparatus 700, the CQI information that each receiving apparatus 600 can send decreases. For this reason, in this embodiment, when it is necessary to reduce the number of peak portions to be reported, the base station controls the number of peak portions to be reported. In addition, when information data must be transmitted to a receiving device 600 at a high speed, there is a need to allocate many subchannels to the receiving device 600. In such a case, increasing the number of peak portions to be reported enables more efficient subchannel allocation and adaptive modulation coding.

[Embodiment 3]
In the above embodiment, the peak portion is selected on the basis of the channel quality that takes the maximum. However, information on the quadratic function selected after approximating all the peak portions with a quadratic function can also be fed back as CQI. As a result, efficient scheduling is possible, and a larger throughput can be obtained. FIG. 14 is a block diagram showing a configuration of the CQI unit 209. The CQI unit 209 includes a peak part detecting unit 901, a peak part approximating unit 902, a peak part selecting unit 903, and a CQI generating unit 904.

  The peak part detector 901 has the same function as the peak part detector 401 in the first embodiment. However, the peak part detection unit 901 inputs a value indicating the detected peak part to the peak part approximation unit 902. The peak part approximation unit 902 approximates the input peak part with a quadratic function. Then, a value indicating the approximated quadratic function is input to the peak portion selection unit 903. The peak portion selection unit 903 selects a peak portion to be fed back as CQI using a function specific value that specifies an approximated quadratic function. The selection of the peak portion is performed by, for example, selecting a predetermined number from the larger maximum value of the approximated quadratic function.

  In this case, since the peak portion having a good channel quality with the maximum value of the quadratic function is reported to the transmission apparatus, it is possible to preferentially report subchannels that can be transmitted at a higher transmission rate. As a result, efficient scheduling is possible. In addition to the above, a method may be used in which one or more predetermined numbers of quadratic functions are selected from the larger value indicating the width. In this method, when the quadratic function is wide, information about many subchannels can be represented by one quadratic function. As a result, the limited number of bits for CQI can be used effectively.

  Alternatively, a method may be used in which the peak portion is selected using both the maximum value and the width of the quadratic function. For example, a value obtained by multiplying the maximum value by a value indicating the width can be obtained for all quadratic functions, and a predetermined number of peak portions can be selected from the larger value. Thereby, each advantage of said two quadratic function selection methods can be utilized. In addition, the peak portion to be reported may be selected from the approximated quadratic function value.

[Embodiment 4]
In the above embodiment, the estimated channel quality for each subchannel is used for detection of the peak portion, but a value obtained by smoothing the estimated value of channel quality may be used. In the first embodiment, due to the influence of noise included in a pilot symbol at the time of channel quality estimation, estimated values having a maximum and a minimum that are greater than the true channel quality may be obtained, and an accurate maximum value may not be detected. If the peak portion is detected as it is, a sub-channel different from the channel that should be detected is detected. In such a case, it is effective to smooth the estimated channel quality value.

  FIG. 15 is a block diagram showing the configuration of the CQI unit 209. The CQI unit 209 includes a channel estimation value smoothing unit 1001, a peak part detecting unit 1002, a peak part selecting unit 1003, a peak part approximating unit 1004, and a CQI generating unit 1005. Channel estimation value smoothing section 1001 smoothes the input channel estimation value (estimated channel quality). Channel estimation value smoothing section 1001 sets, for example, an average value of channel quality including one or more sub-channels having close frequencies for each sub-channel as the channel quality of that sub-channel. The estimated channel quality is once subjected to inverse discrete cosine transform, the time component on the time axis is set to 0, discrete cosine transform is performed, and the channel quality is restored to the original channel quality on the frequency axis. May be smoothed or an average of the estimated channel quality may be taken over a plurality of pilot signals. Further, an average may be obtained by applying appropriate weights over a plurality of pilot signals, or other methods for smoothing the estimated channel quality may be used.

  The peak part detection unit 1002, the peak part selection unit 1003, the peak part approximation unit 1004, and the CQI generation unit 1005 are respectively the peak part detection unit 401, peak part selection unit 402, peak part approximation unit 403, and CQI generation unit in the first embodiment. It has the same function as 404. By introducing the channel estimation value smoothing unit 1001, it is possible to reduce the possibility that the peak portion of the channel quality caused by the channel estimation error is erroneously detected as the peak portion related to the true channel quality. As a result, channel quality close to a true channel can be restored on the transmission device side, and transmission efficiency in the transmission device can be improved.

[Embodiment 5]
In the above embodiment, only high channel quality information is transmitted, but in addition to that, an average value of channel quality of all subchannels may be transmitted. As a result, it is possible to prevent an approximation error for information other than the sub-channel with good channel quality from increasing, and accurate channel quality information from being obtained.

  FIG. 16 is a block diagram showing a configuration of the CQI unit 209. The CQI unit 209 includes a peak part detection unit 1101, a peak part selection unit 1102, a peak part approximation unit 1103, a channel quality averaging unit 1104, and a CQI generation unit 1105. Channel quality averaging section 1104 averages the input channel quality estimation values over all subcarriers and outputs the average value to CQI generating section 1105.

  The peak part detection unit 1101, the peak part selection unit 1102, and the peak part approximation unit 1103 have the same functions as the peak part detection unit 401, the peak part selection unit 402, and the peak part approximation unit 403 in the first embodiment, respectively. The CQI generation unit 1105 generates and outputs a CQI from the information regarding the quadratic function that approximates the input peak portion and the average value of the channel quality input from the channel quality averaging unit 1104.

  FIG. 17 is a block diagram illustrating a configuration of the downlink channel restoration unit 310. The downlink channel restoring unit 310 includes a peak part information average value information separating unit 1201, a peak part restoring unit 1202, and a channel information combining unit 1203.

  Peak part information average value information separation section 1201 separates CQI fed back from the receiving apparatus, inputs information about each peak part to peak part restoration section 1202, and inputs an average value of channel quality to channel information combining section 1203 To do. The peak part restoration unit 1202 has the same function as the peak part restoration unit 502 in the first embodiment. Channel information combining section 1203 determines channel quality for all subchannels based on the approximate value for each restored peak portion and the average value of channel quality input by peak portion information average value information separating section 1201.

  The channel information combining unit 1203 selects, for each subchannel, the highest channel quality among the quality of the subchannel approximated by the average value of the channel quality and each peak portion, and finally the restored channel You may output as quality. In addition to this method, the restored channel quality may be determined based on the approximate value of the restored peak portion and the average value of the channel quality.

  As described above, information other than the vicinity of the peak portion that could not be transmitted in the first embodiment can also be transmitted, and more efficient scheduling can be performed for each receiving device 600. As a result, the transmission efficiency of the entire transmission device can be increased.

[Embodiment 6]
In the above embodiment, the receiving apparatus transmits the function specific value, and averages over the peak portion to be reported for at least one of the maximum value of the quadratic function and the value indicating the width of the quadratic function, and the average Only the value may be sent. When the number of bits that can be reported as CQI is small, such as when the uplink communication state is poor, it is necessary to reduce the CQI. In order to uniquely identify the quadratic function, at least three values are required, and it is necessary to return a value obtained by multiplying the number of peak portions reported as CQI by 3. These three values are the maximum point of the approximated quadratic function, the maximum value, and the value representing the width of the quadratic function (that is, the second derivative or quadratic function at the maximum value of the quadratic function is determined from the maximum value by a predetermined value). The width of the independent variable when taking a value that is smaller by a percentage), and taking the average over all the peak parts to be reported for at least one of the maximum value of the quadratic function and the value indicating the width of the quadratic function. It is effective to send only the value.

  FIG. 18 is a diagram illustrating a configuration of the CQI unit 209. The CQI unit 209 includes a peak part detection unit 1301, a peak part approximation unit 1302, a peak part information averaging unit 1303, and a CQI generation unit 1304. The peak part detection unit 1301 and the peak part approximation unit 1302 have the same functions as the peak part detection unit 401 and the peak part approximation unit 403 in the first embodiment, respectively.

  For example, the peak portion information averaging unit 1303 averages the height of each peak portion, that is, the maximum value of the quadratic function, but the width of the peak portion, that is, the second order derivative or dependent variable at the maximum point is smaller by the maximum value. The width of the independent variable when taking up to the value may be averaged. Further, both the maximum value and the width may be averaged. The peak part information averaging unit 1303 compresses information on the peak part in this way and inputs the compressed information to the CQI generating unit 1304.

  The CQI generation unit 1304 configures and outputs a CQI based on a predetermined CQI format from information on a quadratic function that approximates the input peak portion. At this time, although the accuracy of the channel that can be restored on the transmission device side is reduced, only the CQI composed of a small number of bits may be sent to the transmission device. As a result, even a receiving terminal having a low uplink transmission rate can reduce the time for sending one CQI, and as a result, the transmission efficiency of the entire transmitting apparatus can be improved and the channel quality can be restored with sufficient accuracy. The present embodiment is also effective when the number of receiving apparatuses is large and the number of CQI bits that can be allocated to each receiving apparatus is small.

2 is a block diagram illustrating a configuration of a receiving apparatus according to Embodiment 1. FIG. 1 is a block diagram illustrating a configuration of a transmission device according to Embodiment 1. FIG. It is a block diagram which shows the structure in a CQI part. It is a figure which shows the block in a downlink channel decompression | restoration part. It is a figure which shows the function of a channel information synthetic | combination part typically. It is a figure which shows an example of MCS determined based on channel quality information. It is a figure which shows an example of the approximation method. It is a figure which shows typically the modification of the method of determining the width | variety of a quadratic function. It is a figure which shows the example of an approximation of a peak part. (A) It is a figure which shows the approximation system of this invention. (B), (c) It is a figure which shows the conventional approximation system. 6 is a block diagram illustrating a configuration of a receiving device according to Embodiment 2. FIG. 6 is a block diagram illustrating a configuration of a transmission device according to Embodiment 2. FIG. It is a block diagram which shows the structure of a CQI part. It is a block diagram which shows the structure of a CQI part. It is a block diagram which shows the structure of a CQI part. It is a block diagram which shows the structure of a CQI part. It is a block diagram which shows the structure of a downlink channel decompression | restoration part. It is a figure which shows the structure of a CQI part. It is a conceptual diagram which shows a prior art (Top-M system). It is a conceptual diagram which shows a prior art (DCT system).

Explanation of symbols

200, 600 Receivers 201, 301, 601, 701 Antennas 202, 302, 602, 702 Radio receivers 203, 303, 603, 703 GI removal units 204, 304, 604, 704 FFT units 205, 605 Channel estimation unit 206, 606 Channel compensation unit 207, 307, 607, 707 Demapping unit 208, 308, 608, 708 Decoding unit 209, 610 CQI unit 210, 312, 611, 712 Encoding unit 211, 313, 612, 713 Mapping unit 212, 314, 613, 714 Frame configuration unit 213, 315, 614, 715 IFFT unit 214, 316, 615, 716 GI insertion unit 215, 616, 717 Radio transmission unit 300, 700 Transmission device 305, 705 Upstream channel estimation unit 306, 706 Up channel Compensation unit 309, 709 CQI separation unit 310, 710 Downlink channel restoration unit 311, 711 Scheduling unit 317 Radio transmission unit 401, 801, 901, 1002, 1101, 1301 Peak portion detection unit 402, 802, 903, 1003, 1102 Peak portion Selection unit 403, 803, 902, 1004, 1103, 1302 Peak part approximation unit 404, 804, 904, 1005, 1105, 1304 CQI generation unit 501 Peak part information separation unit 502, 1202 Peak part restoration unit 503, 1203 Channel information synthesis Unit 609 CQI control signal separation unit 1001 channel estimation value smoothing unit 1104 channel quality averaging unit 1201 peak partial information average value information separation unit 1303 peak partial information averaging unit

Claims (24)

A wireless communication apparatus that receives data that has been adaptively modulated and encoded and assigned to each subcarrier for each subcarrier or for each subchannel in which a plurality of subcarriers are combined ,
A channel estimator for estimating a channel quality of said each subcarrier or each of the sub-channel,
A CQI portion that approximates a peak portion where the estimated channel quality has a maximum with respect to a frequency by a convex function for each peak portion;
A wireless communication apparatus, wherein the approximation result is transmitted to a transmission source of the data. The CQI part is
A peak portion detector for detecting a peak portion where the estimated channel quality takes a maximum;
Approximating the estimated channel quality in the detected peak portion with an upward convex function and calculating a function specific value that uniquely specifies the upward convex function;
A feedback information generating unit that generates feedback information including a function specifying value that uniquely specifies the upward convex function;
The wireless communication apparatus according to claim 1, further comprising: The peak part detector is
The radio communication apparatus according to claim 2, wherein a subchannel whose estimated channel quality is higher than a subchannel adjacent on the frequency axis is detected as the peak portion. The peak part detector is
The vicinity of the subchannel having the maximum channel quality among the estimated channel qualities monotonously increasing over a plurality of subchannels and the maximum channel quality among the estimated channel qualities monotonously decreasing over a plurality of subchannels is The wireless communication device according to claim 2 or 3, wherein the wireless communication device is detected as a peak portion. The CQI part is
Further comprising a peak portion selection unit for selecting a specific condition among the peak portions;
The wireless communication apparatus according to claim 2, wherein the peak portion approximating unit approximates the selected peak portion with a convex function. The CQI part is
A peak portion selection unit that selects a function satisfying a specific condition among the approximate convex functions;
The wireless communication according to any one of claims 2 to 4, wherein the feedback information generation unit generates feedback information including a function specifying value that uniquely specifies the selected upward convex function. apparatus. The peak portion selector is
6. The wireless communication apparatus according to claim 5, wherein a peak portion having a large estimated channel quality is selected. The peak portion selector is
The wireless communication apparatus according to claim 6, wherein a function having a large maximum value is selected from the approximate upward convex functions. The peak portion selector is
7. The wireless communication apparatus according to claim 6, wherein a wide one of the approximate convex functions is selected. The peak portion selector is
7. The wireless communication apparatus according to claim 6, wherein a convex function that satisfies a condition based on a maximum value and a width is selected. The peak portion selector is
The radio communication apparatus according to claim 5, wherein the number of peak portions to be selected or an upward convex function is determined based on the estimated channel quality. The peak portion selector is
11. The radio according to claim 5, wherein the number of peak portions to be selected or the number of convex functions is determined based on a feedback information control signal notified from the data transmission source. Communication device. The peak portion approximation portion is
13. The wireless communication apparatus according to claim 2, wherein the estimated channel quality with respect to frequency is approximated by a quadratic function. The peak portion approximation portion is
In the peak portion, at the frequency at which the estimated channel quality takes a maximum value, the maximum value of the estimated channel quality is set as the maximum value, and the second order difference with respect to the frequency of the estimated channel quality is set as the second order differential. The wireless communication apparatus according to claim 13, wherein the peak portion is approximated to a quadratic function. The peak portion approximation portion is
In the peak portion, at the frequency at which the estimated channel quality takes a maximum value, the maximum value of the estimated channel quality is set to the maximum value, and the frequency from the sub-channel at which the estimated channel quality takes the maximum value. The wireless communication according to claim 13, wherein the peak portion is approximated to a quadratic function so that a square error with the estimated channel quality is minimized for a predetermined number of upper and lower subchannels on the axis. apparatus. The peak portion approximation portion is
In the peak portion, the maximum value of the estimated channel quality is set as a maximum value,
The peak width is defined as the width of the frequency when the estimated channel quality takes a value from the maximum value to a value smaller by a predetermined percentage, and the width of the independent variable when the dependent variable takes a value smaller by a predetermined percentage. The wireless communication apparatus according to claim 13, wherein the portion approximates a quadratic function. The peak portion approximation portion is
In the peak portion, the peak portion is divided into two so that a square error with the estimated channel quality is minimized in a predetermined number of subchannels from the frequency at which the estimated channel quality takes a maximum value. The wireless communication apparatus according to claim 13, wherein the wireless communication apparatus approximates a quadratic function. The feedback information generation unit
18. The wireless communication apparatus according to claim 13, wherein feedback information including a maximum point of the approximated quadratic function and a second-order differential value at the maximum point is generated. The feedback information generation unit
The feedback information including a maximum point of the approximated quadratic function and a value indicating a width of the independent variable when the dependent variable takes a value that is smaller by a predetermined ratio from the maximum value, is generated. The wireless communication apparatus according to any one of claims 13 to 17. The feedback information generation unit
The radio communication apparatus according to any one of claims 13 to 17, wherein feedback information including coefficients of respective orders of the approximated quadratic function is generated. The feedback information generation unit
The feedback information including the average value of the approximated quadratic function is generated instead of at least one of the maximum value of the approximated quadratic function and the second order differential at the maximum point. The wireless communication device described. The feedback information generation unit
In place of at least one of the maximum value of the approximated quadratic function and the width of the independent variable when the dependent variable takes a value that is smaller by a predetermined percentage from the maximum value, the average value of the approximated quadratic function The wireless communication apparatus according to claim 19, wherein feedback information including: is generated. The CQI part is
A channel estimation value smoothing unit for smoothing the estimated channel quality;
The radio according to any one of claims 2 to 22, wherein the peak portion detection unit and the peak portion approximation unit use the smoothed channel quality instead of the estimated channel quality. Communication device. The CQI part is
A channel quality averaging unit for calculating an average value of the estimated channel quality;
23. The radio communication apparatus according to claim 2, wherein the feedback information generation unit generates feedback information including the function specific value and an average value of the channel quality information.

Images