Wireless communication apparatus and wireless communication method
11637575 · 2023-04-25
Assignee
Inventors
- Atsushi Ota (Musashino, JP)
- Kota Ito (Musashino, JP)
- Kazuto Goto (Musashino, JP)
- Yushi Shirato (Musashino, JP)
- Naoki Kita (Musashino, JP)
Cpc classification
H04B1/10
ELECTRICITY
H04L27/26524
ELECTRICITY
H04W72/0453
ELECTRICITY
H04L5/0048
ELECTRICITY
International classification
Abstract
A first wireless communication apparatus assigns a pilot signal without an effective signal component at least in an adjacent frequency component to a generated transmit signal, and transmits the transmit signal including the pilot signal. A second wireless communication apparatus converts the received signal or a frequency-converted signal obtained by frequency conversion of the signal into a signal in a frequency domain, sets an approximate value of the distance between the second wireless communication apparatus and the first wireless communication apparatus, calculates a coefficient γk, based on the approximate value of the distance, the effective bandwidth, the speed of light, the number of FFT points, and the frequency component number, extracts a signal in the frequency domain, generates a phase noise compensated sampling signal, and reproduces data transmitted by the first wireless communication apparatus.
Claims
1. A wireless communication apparatus in a wireless communication system including a first wireless communication apparatus and a second wireless communication apparatus, the first wireless communication apparatus comprising: a processor; and a storage medium having computer program instructions stored thereon, when executed by the processor, perform to: generate a transmit signal including information to be transmitted in a region or a portion of the region excluding an empty region within an effective bandwidth, the empty region being a predetermined frequency region within the effective bandwidth; generate a pilot signal without an effective signal component at least in an adjacent frequency component to a predetermined frequency component within the effective bandwidth and assign the pilot signal to the transmit signal; and transmit the transmit signal including the pilot signal generated by the pilot signal assigning section at a wireless frequency, and the second wireless communication apparatus comprising: a processor; and a storage medium having computer program instructions stored thereon, when executed by the processor, perform to: receive a signal of the wireless frequency; convert the received signal received by the reception section or a frequency-converted signal obtained by frequency conversion of the received signal from a sampling signal in a time domain to a signal in a frequency domain; set an approximate value L′ of a distance between the second wireless communication apparatus and the first wireless communication apparatus; calculate a coefficient γk given by Equation (1) below for the approximate value L′ of the distance, an effective bandwidth W, a speed of light c, a number of FFT points NFFT, and a frequency component number k; extract, a signal in a frequency domain including a frequency component of the pilot signal and a plurality of peripheral frequency components including at least adjacent frequency components of the pilot signal, and generate a replica of phase noise, based on a coefficient for each frequency component of the extracted signal and the coefficient γk; generate a phase noise compensated sampling signal by using the replica of the phase noise and the sampling signal in the time domain or a sampling signal modified based on the sampling signal in the time domain; and reproduce data transmitted by the first wireless communication apparatus, based on an output signal from the phase noise compensation section
2. The wireless communication apparatus according to claim 1, wherein the computer program instructions further perform to allocate a subcarrier for a pilot signal to frequency components of both ends or to a frequency component of either end of the effective bandwidth, and set a neighboring subcarrier including an adjacent subcarrier as an empty subcarrier.
3. The wireless communication apparatus according to claim 1, wherein the first wireless communication apparatus includes: a memory that stores sampling data of a length of one cycle or an integer multiple times of the cycle of a sine wave signal of a predetermined frequency or a synthesized signal of a plurality of sine wave signals of predetermined frequencies; and wherein the computer program instructions further perform to output continuous time domain signals of the pilot signal by repeatedly reading the sampling data from the memory at predetermined intervals.
4. The wireless communication apparatus according to claim 1, wherein the computer program instructions further perform to generate sampling data at a time t by following Equation (2) or sampling data given by an inverse of Equation (2) as a replica of phase noise, based on a coefficient βk of the pilot signal of a k-th frequency component and a coefficient βk+k′ of a (k+k′)-th frequency component, for a positive integer NPN greater than or equal to 1 and an integer k′ which satisfies −NPN≤k′≤NPN
5. The wireless communication apparatus according to claim 1, wherein the computer program instructions further perform to generate sampling data at a time t by following Equations (3) and (4) or sampling data given by an inverse of Equation (4) as a replica of phase noise, based on a coefficient βk of the pilot signal of a k-th frequency component and a coefficient βk+k′ of a (k+k′)-th frequency component, for a positive integer NPN greater than or equal to 1 and an integer k′ which satisfies −NPN≤k′≤NPN
6. The wireless communication apparatus according to claim 1, wherein the computer program instructions further perform to remove the pilot signal and predetermined frequency components around the pilot signal from a receive signal.
7. A wireless communication method performed by a wireless communication apparatus in a wireless communication system including a first wireless communication apparatus and a second wireless communication apparatus, the wireless communication method comprising: generating, by the first wireless communication apparatus, a transmit signal including information to be transmitted in a region or a portion of the region excluding an empty region within an effective bandwidth, the empty region being a predetermined frequency region within the effective bandwidth; generating, by the first wireless communication apparatus, a pilot signal without an effective signal component at least in an adjacent frequency component to a predetermined frequency component within the effective bandwidth and assigning the pilot signal to the transmit signal generated by the generating of the transmit signal; transmitting, by the first wireless communication apparatus, the transmit signal including the pilot signal generated by the assigning of the pilot signal at a wireless frequency; receiving, by the second wireless communication apparatus, a signal of the wireless frequency; converting, by the second wireless communication apparatus, the received signal received by the receiving or a frequency-converted signal obtained by frequency conversion of the received signal from a sampling signal in a time domain to a signal in a frequency domain; setting, by the second wireless communication apparatus, an approximate value L′ of a distance between the second wireless communication apparatus and the first wireless communication apparatus; calculating, by the second wireless communication apparatus, a coefficient γk given by Equation (5) below for the approximate value L′ of the distance, an effective bandwidth W, a speed of light c, a number of FFT points NFFT of the time/frequency conversion section, and a frequency component number k; extracting, by the second wireless communication apparatus, from an output in the converting of the signal, a signal in a frequency domain including a frequency component of the pilot signal and a plurality of peripheral frequency components including at least adjacent frequency components of the pilot signal, and generating a replica of phase noise, based on a coefficient for each frequency component of the extracted signal and the coefficient γk; generating, by the second wireless communication apparatus, a phase noise compensated sampling signal by using the replica of the phase noise and the sampling signal in the time domain or a sampling signal modified based on the sampling signal in the time domain; and reproducing, by the second wireless communication apparatus, data transmitted by the first wireless communication apparatus, based on an output signal in the compensating of the phase noise
Description
BRIEF DESCRIPTION OF DRAWINGS
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DESCRIPTION OF EMBODIMENTS
(28) In the following description, the processing of the related inventions which are the background of the present invention will be cited for description.
Basic Principles of Present Invention
(29) The fundamental cause of the above problem is because the channel information used to estimate the phase noise includes a term of phase rotation proportional to the distance. For example, assuming that the approximate value of the distance of the two wireless station apparatuses is L, the cancellation of the phase rotation amount proportional to the distance can be performed by the coefficient γ.sub.k for the subcarrier number k indicated by the following Equation (10).
(30)
(31) Here, for the subcarrier number of k, the center frequency may be considered as zero, or the subcarrier having the lowest frequency may have k=1. In any case, all the subcarriers are only multiplied by a predetermined coefficient, and thus, for the subcarrier number of k, the subcarrier number may be assigned in a manner that is added one at a time from the lower to the higher of the frequency. With such a configuration, for the influence of the phase rotation proportional to the distance per subcarrier, the error can be suppressed to the value of the error of the estimated distance L instead of the actual distance L, that is, the degree of δL=(L−L). As an example, assuming that L=100 [m], δL=3 [m], and W=1 [GHz], the original phase rotation N.sub.p (=L*W/c) is approximately 333, and the time lag of 333 samples cannot be ignored. On the other hand, in a case that the above-described compensation is performed, the phase rotation amount remaining in the bandwidth is 2π*(L−L)*W/c, and in a case where this is let to be N.sub.p, N.sub.p is approximately 10. In a case where the error is approximately 10 samples, the amount of phase shift due to phase noise is expected to be within error margin, so the problem described above can be generally solved.
(32) Note that the measurement of this distance may be measured directly by using a laser pointer type distance measurement apparatus, or may be calculated based on the information of the installation location. In any case, in a case where the distance can be determined with an error of a few percent, the time lag of the replica of the phase noise will be significantly modified.
(33) The coefficient determined in this manner can be used, for example, by replacing Equation (5) with the following Equation (11).
(34)
(35) Alternatively, the coefficient determined in this manner can be used by replacing Equation (7) with the following Equation (12).
(36)
(37) In the present invention, the coefficient γ.sub.k is calculated in the wireless station apparatus of the receiving side so as to cancel the phase rotation amount proportional to the distance as described above. The wireless station apparatus of the receiving side generates a replica signal of the phase noise by using the calculated coefficient γ.sub.k and the coefficient for each frequency component of the signal, and cancels the phase rotation amount by using the generated replica signal of the phase noise. The problem described above is solved by performing such a process.
(38) Features of the circuit configurations in each embodiment will be described below with reference to the drawings. For a representative example, an OFDM modulation scheme is described as an example herein, but extension is possible even in a case of other single carrier transmission, which will be described later. Although the transmission weight and the reception weight in the time domain are also referred to herein as the time axis transmission weight and the time axis reception weight, these “time axis” and “time domain” are synonymous.
First Embodiment
(39) Hereinafter, the first embodiment of the present invention will be described with mainly reference to diagrams related to circuit configurations.
(40) Circuit Configuration According to First Embodiment
(41)
The wireless station apparatus 70 inputs/outputs data from/to an external device or a network via the interface circuit 67. The interface circuit 67 detects data to be transferred on the wireless circuit from the data input, and outputs the detected data to the MAC layer processing circuit 68. The MAC layer processing circuit 68 performs processing related to the MAC layer in accordance with an instruction from the communication control circuit 51 configured to perform management control of the operation of the entire wireless station apparatus 70. In MIMO transmission, for spatially multiplexing and transmitting signals to one wireless station apparatus 70, signal sequences of a plurality of systems are output from the MAC layer processing circuit 68 to the transmitter 71.
(42)
(43) The transmission weight processing unit 840 includes a channel information acquisition circuit 841, a channel information storage circuit 842, and a transmission weight calculation circuit 843. Here, the subscript N.sub.SDM of the transmit signal processing circuits 311-1 to 311-N.sub.SDM in
(44) Here, the transmit signal processing circuits 311-1 to 311-N.sub.SDM differ from the transmit signal processing circuits configured to generate the OFDM signal having the effective bandwidth W illustrated in
(45) In the background art, because a single wireless station apparatus 70 spatially multiplexes and transmits signals to other wireless station apparatuses 70, signal sequences of a plurality of systems are input from the MAC layer processing circuit 68 to the transmitter 71, and the input signal sequences of a plurality of systems are input to the transmit signal processing circuits 311-1 to 311-N.sub.SDM. The transmit signal processing circuits 311-1 to 311-N.sub.SDM perform modulation processing on the data (data input #1 to #N.sub.SDM) to be transmitted to a destination wireless station apparatus 70 when the data to be transmitted (wireless packets) is input from the MAC layer processing circuit 68 on a wireless circuit. Here, modulation processing is performed on signals of each signal sequence for each subcarrier in the reduced effective bandwidth W″ illustrated in
(46) The signal multiplied by the transmission weight corresponding to each of the antenna elements 819-1 to 819-N.sub.Ant is subjected to a remaining signal processing as necessary, and the signal is input from each of the transmit signal processing circuits 311-1 to 311-N.sub.SDM to the addition synthesis circuits 812-1 to 812-N.sub.Ant as a signal in the frequency domain of the transmit signal in the baseband. The signal input to the addition synthesis circuits 812-1 to 812-N.sub.Ant is synthesized for each subcarrier. The synthesized signal is converted from a signal on the frequency axis to a signal on the time axis in the IFFT & GI assigning circuits 813-1 to 813-N.sub.Ant, and is further subjected to processing such as insertion of a guard interval or waveform shaping in between OFDM symbols (between blocks of block transmission in a case of SC-FDE). Sampling data of the pilot signal is output from the pilot signal storage circuit 321 and is added to the output signal from the IFFT & GI assigning circuits 813-1 to 813-N.sub.Ant by the adders 320-1 to 320-N.sub.Ant. From the pilot signal storage circuit 321, the sampling data is repeatedly output in a form that each sine wave waveform of the pilot signal is continuous. The signal added by the adders is converted for each system of the antenna elements 819-1 to 819-N.sub.Ant from digital sampling data to analog signals in the baseband at the D/A converters 814-1 to 814-N.sub.Ant. Further, each analog signal is multiplied by a local oscillating signal input from the local oscillator 815 by the mixers 816-1 to 816-N.sub.Ant and up-converted to a wireless frequency signal. Here, the up-converted signal includes a signal in a region outside of the band of the channel to be transmitted, so that a signal outside of the band is removed at the filters 817-1 to 817-N.sub.Ant to generate a signal to be transmitted. The generated signal is amplified by the high power amplifiers 818-1 to 818-N.sub.Ant and transmitted from the antenna elements 819-1 to 819-N.sub.Ant.
(47) Note that, in
(48) The transmission weight multiplied by the transmit signal processing circuits 311-1 to 311-N.sub.SDM is acquired from the transmission weight calculation circuit 843 included in the transmission weight processing unit 840 during the signal transmission processing. The transmission weight processing unit 840 separately acquires the channel information acquired at the receiver 75 via the communication control circuit 51 in the channel information acquisition circuit 841, and stores the channel information in the channel information storage circuit 842 while sequentially updating the channel information. Upon transmission of the signal, in accordance with an instruction from the communication control circuit 51, the transmission weight calculation circuit 843 reads the channel information corresponding to the destination station from the channel information storage circuit 842, and calculates the transmission weight on the basis of the read channel information. The transmission weight calculation circuit 843 outputs the calculated transmission weight to the transmit signal processing circuits 311-1 to 311-N.sub.SDM. In a case that the wireless station apparatus is a base station, the communication control circuit 51 manages which terminal station apparatus the destination station is to communicate with a plurality of terminal station apparatuses.
(49) Note that the signals of the N.sub.SDM systems output from the transmit signal processing circuits 311-1 to 311-N.sub.SDM are synthesized in the addition synthesis circuits 812-1 to 812-N.sub.Ant, and the following D/A converters 814-1 to 814-N.sub.Ant to the antenna elements 819-1 to 819-N.sub.Ant are used together, but the signals may be implemented individually from the following D/A converters 814-1 to 814-N.sub.Ant to the antenna elements 819-1 to 819-N.sub.Ant without being synthesized at the addition synthesis circuits 812-1 to 812-N.sub.Ant, and a subarray may be configured by the antenna elements 819-1 to 819-N.sub.Ant in each of the antennas. Furthermore, in this case, the transmission weight calculation circuit 843 can use a virtual transmission line corresponding to the first singular value between the array antennas or the subarrays in the transmitter 71 of a wireless station apparatus 70 and in the receiver 75 of a wireless station apparatus 70 in the calculation of the transmission weight. There are several variations in the method of channel estimation and the method of calculating the transmission and/or reception weight in a case of utilizing the virtual transmission line corresponding to the first singular value. For example, a first right singular vector upon singular value decomposition may be used for the transmission weight vector for each channel matrix from the wireless station apparatus 70 towards the antenna elements 819-1 to 819-N.sub.Ant of another wireless station apparatus 70. In this case, the transmission weight calculation circuit 843 has the function of calculating this first right singular vector. Otherwise, various approaches to acquiring an approximate solution of such a singular vector may be used.
(50) For example, a first right singular vector upon singular value decomposition may be used for the transmission weight vector for each channel matrix from the wireless station apparatus 70 towards the antenna elements 819-1 to 819-N.sub.Ant of another wireless station apparatus 70. In this case, the transmission weight calculation circuit 843 has the function of calculating this first right singular vector. Otherwise, various approaches to acquiring an approximate solution of such a singular vector may be used.
(51) In the above description, the assignment of the pilot signal at both ends of the effective bandwidth is performed at the adders 320-1 to 320-N.sub.Ant between the IFFT & GI assigning circuits 813-1 to 813-N.sub.Ant and the D/A converters 814-1 to 814-N.sub.Ant. In contrast, a configuration may be adopted in which a signal allocated a pilot signal to the subcarriers on both ends of the effective bandwidth is generated in the transmit signal processing circuits 311-1 to 311-N.sub.SDM, and a predetermined signal processing such as multiplication of the transmission weight is performed on the signal. In this case, the adders 320-1 to 320-N.sub.Ant and the pilot signal storage circuit 321 are unnecessary, and equivalent processing is performed in the transmit signal processing circuits 311-1 to 311-N.sub.SDM.
(52) Next,
(53) First, a signal received at the antenna elements 851-1 to 851-N.sub.Ant is amplified by the low noise amplifiers 852-1 to 852-N.sub.Ant. The amplified signal and a local oscillating signal output from the local oscillator 853 are multiplied by the mixers 854-1 to 854-N.sub.Ant, and the amplified signal is down-converted from the wireless frequency signal to the baseband signal. The down-converted signal also includes signals outside of the frequency band to be received, so that the filters 855-1 to 855-N.sub.Ant remove out-of-band components. The signal from which the out-of-band components have been removed is converted to a digital baseband signal by the A/D converters 856-1 to 856-N.sub.Ant. For example, in a case that OFDM is used, the digital baseband signal is input to the extended FFT circuits 357-1 to 357-N.sub.Ant, the extended FFT circuits 357-1 to 357-N.sub.Ant perform the phase noise compensation processing described below, and a signal on the time axis is converted (separated into a signal of each subcarrier) to a signal on the frequency axis at a predetermined symbol timing determined by a circuit for timing detection of which description is omitted herein. The signal separated into each subcarrier is input to the receive signal processing circuits 345-1 to 345-N.sub.SDM, and is also input to the channel information estimation circuit 846.
(54) In the channel information estimation circuit 846, a channel vector of channel information between the antenna elements 819-1 to 819-N.sub.Ant on the transmitting station side and the antenna elements 851-1 to 851-N.sub.Ant on the receiving station side are estimated for each subcarrier, based on a known signal for channel estimation separated into each subcarrier (such as a preamble signal assigned to the head of the wireless packet), and the estimation result is output to the reception weight calculation circuit 847. In the reception weight calculation circuit 847, the reception weight to be multiplied is calculated for each subcarrier, based on the input channel information.
(55) For this reception weight, for example, a ZF type pseudo-inverse is utilized as described above, or an MMSE type reception weight matrix is utilized. At this time, the reception weight vectors for synthesizing the signals received at each of the antenna elements 851-1 to 851-N.sub.Ant are different from each other for each signal sequence, correspond to a row vector, such as the ZF type pseudo-inverse matrix or the MMSE type reception weight matrix described above, and are input to the receive signal processing circuits 345-1 to 345-N.sub.SDM corresponding to the signal sequence to be extracted.
(56) In the receive signal processing circuits 345-1 to 345-N.sub.SDM, the reception weight input from the reception weight calculation circuit 847 is multiplied by the signal input from the extended FFT circuits 357-1 to 357-N.sub.Ant for each subcarrier, and the signals received at each of the antenna elements 851-1 to 851-N.sub.Ant are added and synthesized for each subcarrier. The receive signal processing circuits 345-1 to 345-N.sub.SDM perform demodulation processing on the added and synthesized signals, and output the reproduced data to the MAC layer processing circuit 68.
(57) Here, different signal processing of signal sequences are performed in different receive signal processing circuits 345-1 to 345-N.sub.SDM. MLD or simple MLD using QR decomposition or the like may be used as the receive signal processing across the plurality of receive signal processing circuits 345-1 to 345-N.sub.SDM. The MAC layer processing circuit 68 performs processing related to the MAC layer (e.g., conversion of data input and output to and from the interface circuit 67, and data transmitted and/or received on the wireless circuit, i.e., wireless packets, termination of header information of the MAC layer, or the like). The receive data processed by the MAC layer processing circuit 68 is output to an external device or a network via the interface circuit 67. The communication control circuit 51 manages control related to the overall communication, such as overall timing control.
(58) Similarly to the transmitter 71, the receiver 75 uses the antenna elements 851-1 to 851-N.sub.Ant to the extended FFT circuits 357-1 to 357-N.sub.Ant together, and copies the output from the extended FFT circuits 357-1 to 357-N.sub.Ant into N.sub.SDM systems to input to the individual receive signal processing circuits 345-1 to 345-N.sub.SDM. In contrast, the antenna elements 851-1 to 851-N.sub.Ant to the extended FFT circuits 357-1 to 357-N.sub.Ant may be implemented individually, and each of the antenna elements 851-1 to 851-N.sub.Ant may be implemented to have a subarray configuration.
(59) Furthermore, in this case, a virtual transmission line corresponding to the first singular value may be used between the array antennas or the subarrays in the transmitter 71 of a wireless station apparatus 70 and in the receiver 75 of a wireless station apparatus 70 in the calculation of the reception weight. There are several variations in the method of channel estimation and the method of calculating the transmission and/or reception weight in a case of utilizing the virtual transmission line corresponding to the first singular value. For example, a first left singular vector upon singular value decomposition may be used for the reception weight vector for each channel matrix from another wireless station apparatus 70 towards the antenna elements 819-1 to 819-N.sub.Ant of the self-station. In this case, the reception weight calculation circuit 847 has the function of calculating this first left singular vector. Otherwise, various approaches to acquiring an approximate solution of such a singular vector may be used.
(60) The phase noise compensation processing performed by the extended FFT circuits 357-1 to 357-N.sub.Ant will be described below.
(61) First, when the wireless station apparatus is placed before the operation is started, the installer calculates an approximate value L of the distance between two wireless station apparatuses in any approach, and sets this by the distance L setting circuit 194. For this setting, there may be a section for numerical input on the apparatus, or a configuration may be used in which another apparatus for control (such as a PC) is connected and setting is performed from outside. The distance L′ set in this way is input to the γ.sub.k setting circuit 193, γ.sub.k is calculated by Equation (10) by using the L′ in the γ.sub.k setting circuit 193, and this is input to the function Φ (t) acquisition circuit 183 for preliminary preparation.
(62) Next, digital sampling data is input from the A/D converter 856 to the extended FFT circuits 357 (block 190), the sampling data is replicated in the replication circuit 181, and one of the replicated sampling data is input to the FFT circuit 182 and the other is input to the phase noise compensation circuit 185. The FFT circuit 182 performs FFT on the sampling data cut at a predetermined symbol timing determined by the timing detection unit not illustrated in the drawing, extracts components related to the pilot signal and the subcarrier regions 917 and 918 in the vicinity of this in
(63) Furthermore, based on this information, the IFFT circuit 184 converts the signal in the frequency domain into a signal in the time domain, and inputs the signal in the time domain into the phase noise compensation circuit 185. The phase noise compensation circuit 185 multiplies the values of the inverse of the time domain signal input from the IFFT circuit 184 (i.e., function ϕ (t)) and the time domain signal to be input from the replication circuit 181 (precisely, the time axis signal corresponding to the region from which the guard interval has been removed with FFT performed in the FFT circuit 182) for each sampling data as illustrated in Equation (6), and reproduces the signal in the time domain on which phase noise compensation has been performed. This reproduced signal in the time domain (sampling data) is input to the FFT circuit 857, and is again converted from the signal in the time domain to the signal in the frequency domain. However, the signal in the frequency domain is a signal compensated for phase noise, and the leakage of power between subcarriers is suppressed. The signal in the frequency domain is input to the receive signal processing circuit 345, and the receive signal processing circuit 345 performs predetermined receive signal processing.
(64) Although the signal processing performed by the receive signal processing circuit 345 is basically equivalent to the conventional receive signal processing circuit, the receive signal processing circuit of related art processes the OFDM signal of the effective bandwidth W illustrated in s changed to the reduced effective bandwidth W″ in this manner, including the output of the information to the reception weight processing unit 844.
(65) For another configuration to achieve a similar effect, the configuration of
(66) In
(67) As a difference of processing other than this, the FFT circuit 182 performs FFT on the sampling data cut at a predetermined symbol timing determined by the timing detection unit not illustrated in the drawing, extracts components related to the pilot signal and the subcarrier regions 917 and 918 in the vicinity of this in
(68) Furthermore, based on this information, the IFFT circuit 184 converts the signal in the frequency domain into a signal in the time domain, and inputs the signal to the function ϕ (t) acquisition circuit 196. The function ϕ (t) acquisition circuit 196 calculates the function ϕ (t) by using Equation (8) and inputs the signal in the time domain into the phase noise compensation circuit 185. Processing other than this is similar to
(69) According to the wireless station apparatus 70 configured as described above, the phase rotation amount is canceled by using an approximate value of the distance between the two wireless station apparatuses 70 obtained by using some approach (for example, it may be measured directly by using a laser pointer type distance measurement apparatus, or calculated based on the information of the installation location). In this way, the time lag of the replica of the phase noise can be significantly modified.
(70) As a result, a decrease in throughput can be suppressed.
Second Embodiment
(71) In the first embodiment, a description has been given of a case that phase noise compensation is performed for a circuit configuration in which an FFT circuit is implemented for each antenna element. However, in the background art, there is a signal processing technique that aggregates signals of antennas of a plurality of elements for each signal sequence to be transmitted, and limits the signal processing of FFT or IFFT to the number of signal sequences to be spatially multiplexed. Thus, in the second embodiment, an embodiment in a case that the present invention is applied to the technique described in NPL 1 will be described.
(72) Circuit Configuration According to Second Embodiment
(73) In the second embodiment of the present invention, the configuration of the wireless station apparatus 70 takes an equivalent configuration as the wireless station apparatus 70 illustrated in
(74)
(75) The difference between the configurations of the transmitters described in
(76) This is similar to the first embodiment in that the difference between the configuration of related art and
(77) In other words, while performing the equivalent operation as the transmitter according to NPL 1, the transmitter 72a of
(78) In the above description, the assignment of the pilot signal at both ends of the effective bandwidth is performed at the adders 420-1 to 420-N.sub.SDM between the IFFT & GI assigning circuits 313-1 to 313-N.sub.SDM and the time axis transmission weight multiplication circuits 761-1 to 761-N.sub.SDM. In contrast, in the same manner as in the first embodiment, a configuration may be adopted in which a signal allocated a pilot signal to the subcarriers on both ends of the effective bandwidth is generated in the transmit signal processing circuits 411-1 to 411-N.sub.SDM. In this case, the adders 420-1 to 420-N.sub.SDM and the pilot signal storage circuit 321 are unnecessary, and equivalent processing is performed in the transmit signal processing circuits 411-1 to 411-N.sub.SDM.
(79) Note that, in the second embodiment, a configuration is taken in which the signals of the N.sub.SDM systems output from the time axis transmission weight multiplication circuits 761-1 to 761-N.sub.SDM are synthesized in the addition synthesis circuits 812-1 to 812-N.sub.Ant, and the following D/A converters 814-1 to 814-N.sub.Ant to the antenna elements 819-1 to 819-N.sub.Ant are used together. In contrast, the signals may be implemented individually from the following D/A converters 814-1 to 814-N.sub.Ant to the antenna elements 819-1 to 819-N.sub.Ant without being synthesized at the addition synthesis circuits 812-1 to 812-N.sub.Ant, and a subarray may be configured by the antenna elements 819-1 to 819-N.sub.Ant in each of the antennas.
(80)
(81) The difference between the configurations of the receivers described in
(82) This is similar to the first embodiment in that the FFT circuits 257-1 to 257-N.sub.SDM are changed to the extended FFT circuits 157-1 to 157-N.sub.SDM, and the receive signal processing circuits 845-1 to 845-N.sub.SDM are further changed to the receive signal processing circuits 345-1 to 345-N.sub.SDM.
(83) In other words, the difference corresponds to the change that the receiver 76a in
(84) According to the wireless station apparatus 70 according to the second embodiment configured as described above, the same effects as those of the first embodiment can be obtained in other configurations.
Third Embodiment
(85) In the background art described in NPL 1, the time axis transmission weight multiplication circuits 761-1 to 761-N.sub.SDM digitally multiply the time axis transmission weight, and the time axis reception weight multiplication circuits 755-1 to 755-N.sub.SDM digitally multiply the time axis reception weight. However, the multiplication of the transmission and/or reception weight in the time domain corresponds to multiplying the entire frequency band by a common coefficient, and is equivalent to the process of rotating the phase by using a phase shifter directly to analog transmit signals or analog receive signals. Using this feature, in NPL 2, a method is adopted in which the calculation of the transmission and/or reception weight to be digitally multiplied is performed by the approach described in NPL 1, while processing corresponding to the multiplication of the actual time axis transmission and/or reception weight is performed in a phase shifter. In the following description, first, a description will be given of another circuit configuration in a case that the technique described in NPL 2 is applied as a background art of the present invention, and then the third embodiment will be described as a difference with it.
(86) An embodiment in a case that the present invention is applied to the technique described in NPL 2 will be described below.
(87) Circuit Configuration According to Third Embodiment
(88) In the third embodiment of the present invention, the configuration of the wireless station apparatus takes an equivalent configuration as the wireless station apparatus 70 illustrated in
(89)
(90) The difference from
(91) This is similar to the first embodiment in that the difference between
(92) In other words, while performing the equivalent operation as the transmitter 62b in
(93) In the above description, the assignment of the pilot signal at both ends of the effective bandwidth is performed at the D/A converters 414-1 to 414-N.sub.SDM. In contrast, in the same manner as the supplemental description of the second embodiment, a configuration may be adopted in which a signal allocated a pilot signal to the subcarriers on both ends of the effective bandwidth is generated in the transmit signal processing circuits 411-1 to 411-N.sub.SDM. In this case, while the pilot signal storage circuit 321 is omitted, the D/A converters 414-1 to 414-N.sub.SDM are replaced with the D/A converters 314-1 to 314-N.sub.SDM that do not have an addition function with the pilot signal, and equivalent processing is performed in the transmit signal processing circuits 411-1 to 411-N.sub.SDM.
(94) Note that, in the third embodiment, in the same manner as the background art illustrated in
(95)
(96) The difference from
(97) In other words, the difference corresponds to the change that the receiver 76b in
(98) According to the wireless station apparatus 70 according to the third embodiment configured as described above, the same effects as those of the first embodiment can be obtained in other configurations.
Fourth Embodiment
(99) In the first to third embodiments of the present invention, the configurations of the extended FFT circuits 357 and 157 in the receiver uses the configuration illustrated in
However, because the FFT circuit 857 and the receive signal processing circuits 345-1 to 345-N.sub.SDM or the receive signal processing circuits 445-1 to 445-N.sub.SDM do not require the pilot signal at both ends of the effective bandwidth W, it is possible to exclude the pilot signal on both ends of the effective bandwidth W before inputting into the FFT circuit 857. The configuration of the extended FFT circuit according to the fourth embodiment with this function is illustrated in
(100) As illustrated in
(101) The difference from
(102) Similarly, corresponding to
(103) According to the wireless station apparatus 70 according to the fourth embodiment configured as described above, the same effects as those of the first embodiment can be obtained in other configurations.
Fifth Embodiment
(104) In the description of the first to fourth embodiments, the case that the OFDM modulation scheme is applied is illustrated as a representative example, but the same process can be applied to a system of single carrier transmission. Systems of single carrier transmission include a SC-FDE scheme that performs equalization processing in the frequency domain, and the like, in addition to a common single carrier transmission. In the SC-FDE scheme among them, a common SC-FDE processing may be performed instead of signal processing of the OFDM modulation scheme in the receive signal processing circuits 345-1 to 345-N.sub.SDM or the receive signal processing circuits 445-1 to 445-N.sub.SDM, for involving signal processing of the frequency domain. These are common techniques, and thus detailed description thereof is omitted. Similarly, the signal processing of the OFDM modulation scheme may be changed to a common SC-FDE processing on the transmitter side. For example, by generating a normal signal of a single carrier in the time domain in the transmit signal processing circuits 311-1 to 311-N.sub.SDM or the transmit signal processing circuits 411-1 to 411-N.sub.SDM, and by implementing a circuit configured to assign GI without performing IFFT in the part of the IFFT & GI assigning circuits 313-1 to 313-N.sub.SDM, the processing can correspond to single carrier transmission.
(105) However, in a case of a pure single carrier transmission rather than the SC-FDE scheme, it is not necessary to convert the signal in the time domain into the signal in the frequency domain by using the FFT circuit. Thus, the FFT circuit 857 implemented in the extended FFT circuit 357 is not needed, so that the extended FFT circuit will be replaced by a single carrier compensation circuit, and the assignment of GI in the part of the IFFT & GI assigning circuits 313-1 to 313-N.sub.SDM is also not needed.
(106) As illustrated in
(107) Similarly, corresponding to
(108) A configuration example of a transmitter and a receiver in single carrier transmission according to the fifth embodiment is illustrated in
(109) As illustrated in
(110) The difference from
(111) Thus, it is changed from generating a transmit signal in the time domain of the digital baseband using an OFDM modulation scheme in combination of the transmit signal processing circuits 411-1 to 411-N.sub.SDM and IFFT & GI assigning circuits 313-1 to 313-N.sub.SDM, to generating a transmit signal in the time domain of the digital baseband for single carrier transmission by the transmit signal processing circuits 511-1 to 511-N.sub.SDM. Signal processing of single carrier transmission performed by the transmit signal processing circuits 511-1 to 511-N.sub.SDM is a common signal processing, and the signal such as a unique word is assigned as an overhead in advance of a signal that is subjected to modulation processing on the user data, although the details are omitted herein. The signal in the time domain including these will be output.
(112) Note that, in the fifth embodiment as well, similar to the third embodiment, the high power amplifiers 818-1 to 818-N.sub.Ant, the antenna elements 819-1 to 819-N.sub.Ant, or the like may be implemented individually for each signal sequence spatially multiplexed, and a subarray may be configured for each of the signal sequences. Furthermore, other features are the same as those described with respect to the third embodiment.
(113) As illustrated in
(114) The difference from
(115) Thus, it is changed from performing the signal detection processing of the time domain of the digital baseband using the OFDM modulation scheme by the receive signal processing circuits 445-1 to 445-N.sub.SDM, to performing the signal detection processing of the time domain of the digital baseband in single carrier transmission by the receive signal processing circuits 545-1 to 545-N.sub.SDM. Signal processing of single carrier transmission performed by the receive signal processing circuits 545-1 to 545-N.sub.SDM is a common signal processing, and the signal such as a unique word assigned in advance of a signal that is subjected to modulation processing on the user data is detected, the signal detection processing is started at an appropriate timing, and the signal on the transmitting side is reproduced and output to the MAC layer processing circuit 68 side, although the details are omitted herein.
(116) The signal processing performed by the single carrier compensation circuits 557-1 to 557-N.sub.SDM is as described above, which performs the compensation processing of the phase noise, and outputs a single carrier signal within the reduced effective bandwidth W″ from which the pilot signal has been removed to the receive signal processing circuits 545-1 to 545-N.sub.SDM.
(117) Note that, in the fifth embodiment as well, similar to the third embodiment, low noise amplifiers 852-1 to 852-N.sub.Ant, antenna elements 851-1 to 851-N.sub.Ant, or the like may be implemented individually for each signal sequence spatially multiplexed, and a subarray may be configured for each of the signal sequences. Furthermore, other features are the same as those described with respect to the third embodiment.
(118) According to the wireless station apparatus 70 according to the fifth embodiment configured as described above, the same effects as those of the first embodiment can be obtained even in a configuration in which single carrier transmission is performed.
Sixth Embodiment
(119) In the first to fifth embodiments, in the transmitters 71, 72a, 72b, and 74 of each of the wireless station apparatuses 70, the antenna elements 819-1 to 819-N.sub.Ant, the high power amplifiers 818-1 to 818-N.sub.Ant, and the like may be implemented individually for each signal sequence spatially multiplexed, and a subarray may be configured for each of the signal sequences. Similarly, in the receivers 75, 76a, 76b, and 78, the antenna elements 851-1 to 851-N.sub.Ant, the low noise amplifiers 852-1 to 852-N.sub.Ant, and the like may be implemented individually for each signal sequence spatially multiplexed, and a subarray may be configured for each of the signal sequences. In a case that the subarray antennas of the transmitters 71, 72a, 72b, and 74 and the receivers 75, 76a, 76b, and 78 are physically installed, for example, at positions separated by several m, each of the local oscillator 815 and the local oscillator 853 may be individually implemented, and different phase noises may be added between each of the subarrays.
(120)
(121) For example, as described with reference to the third embodiment, processing is performed in which transmit directivity beams 93-1 to 93-N.sub.SDM are formed in the synthesizers 671-1 to 671-N.sub.Ant, the phase shifter groups 681-1 to 681-N.sub.SDM, and the distributors 673-1 to 673-N.sub.SDM in the transmitter 72b of
(122) At this time, because the receiver 75a and 75b are applied with the local oscillator 815 and/or the local oscillator 853 different for each signal sequence to be spatially multiplexed, individual independent phase noises are added. At this time, for example, with the third embodiment as an example, the interference components are expected to be suppressed to some extent in the input signal to each of the extended FFT circuits 157-1 to 157-N.sub.SDM because the mutual signal separation is generally made by the above-described directivity formation. In this case, in a case where the above-described processing is performed individually on each of the extended FFT circuits 157-1 to 157-N.sub.SDM, appropriate phase noise compensation can be performed in each signal sequence.
(123) Similarly, even in a multi-user MIMO environment in which one base station apparatus performs spatial multiplex transmission with a plurality of terminal station apparatuses, the same phase noise compensation may be performed by each of the individual extended FFT circuits 157-1 to 157-N.sub.SDM because the mutual signal separation is generally made by the above-described directivity formation. Here, in a case that the number of users of the multi-user MIMO is two, it is possible to operate to further reduce the mutual interference by allocating one of the pilot signals at both ends of the effective bandwidth W to the user #1, and the other to the user #2. Otherwise, while taking a subarray configuration, in a case that the local oscillator 815 and/or the local oscillator 853 are used together between subarrays, it is expected that the phase noise added to each signal sequence will be completely equivalent phase noise. In
(124) In this way, the embodiments of the present invention can be applied even in a case of taking a subarray configuration or a case of performing multi-user MIMO transmission in addition to single user MIMO.
(125) Although the embodiments of the present invention have been described above with reference to the drawings, it is clear that the above embodiments are merely examples of the present invention, and the present invention is not limited to the embodiments described above. For example, in the descriptions of the embodiments of the present invention, the apparatus configurations and signal processing are mainly described assuming the OFDM modulation scheme, the single carrier transmission scheme, the SC-FDE scheme, and the like, but in order to apply other schemes, an apparatus configuration of the scheme according to related art may be reflected in the embodiments of the present invention. Although the present invention has been described in the context of a general Point-to-Point type of spatial multiplex transmission without clearly expressing in the present invention, the same discussion holds true even in a case of a Point-to-Multipoint type of communication configuration equipped with a plurality of wireless station apparatuses. Furthermore, at this time, the configuration can also be extended to a configuration in which communication is performed concurrently in parallel with a plurality of wireless station apparatuses by the multi-user MIMO transmission.
(126) The processing of the assignment on the transmitting side of the pilot signal used in the embodiment of the present invention may be achieved by separately adding the information (sampling data) in the time domain of the pilot signal stored in the memory to the transmit signal generated by any section. In a case that signal processing in the frequency domain is involved on the transmitting side, such as an OFDM modulation scheme, an SC-FDE scheme, or the like, it can be managed by allocating the components of the pilot signals in the frequency domain, and collectively generating the pilot signals. In this sense, the pilot signal is essentially assigned to the transmit signal, and the manner in which the pilot signal is assigned can be achieved by various variations.
(127) While terms such as frequency domain, time domain, time axis, and the like are used herein. the digital sampling data can be converted into signals of a plurality of frequency components or subcarriers by FFT processing performed when applying an OFDM modulation scheme or a SC-FDE scheme, for example, and the signal of each frequency component or each subcarrier is referred to herein as the signal in the frequency domain (or frequency axis). In contrast to this, the digital sampling data is a signal of time sequence, which is referred to as a signal in the time domain (or time axis), and in this sense, because the analog signal is a temporally continuous signal, and the rotation processing of the complex phase performed by the phase shifter, for example, in the third embodiment or the like, corresponds to signal processing in the time domain. Basically, signal processing in the time domain does not require FFT processing unlike the signal processing in the frequency domain, and thus basically has a feature of being easy to avoid the problem of signal leakage to adjacent frequency components. Thus, even in a case where other signal processing of the time domain not described herein may be added additionally, the present invention can be operated without any influence.
(128) Here, the descriptions have been made mainly of the embodiments provided with a plurality of antenna elements, assuming a case that phase noise compensation is performed for spatial multiplex transmissions that cannot be managed by the known background arts. However, the essence of the present invention is a feature that a pilot signal in the band (the feature is not to allocate signal in the frequency domain around the pilot signal) is assigned on the transmitting side, a replica of phase noise is generated on the receiving side by using the pilot signal and the frequency components around the pilot signal, and the phase noise is removed from the receive signal by using these, as illustrated in
(129) Thus, addition, omission, substitution, and other modifications of the constituent components may be made without departing from the spirit and scope of the present invention.
REFERENCE SIGNS LIST
(130) 51, 51a, 51b, 52, 53 Communication control circuit 60 Wireless station apparatus 61, 62 Transmitter 65, 66 Receiver 67, 67a, 67b Interface circuit 68, 68a, 68b MAC layer processing circuit 70 Wireless station apparatus 71, 71a, 71b, 72a, 72b, 74 Transmitter 75, 75a, 75b, 76a, 76b, 78 Receiver 157-1 to 157-N.sub.SDM Extended FFT circuit 181 Replication circuit 182 FFT circuit 183 Function Φ (t) acquisition circuit 184 IFFT circuit 185 Phase noise compensation circuit 186 Pilot signal removal circuit 187 IFFT circuit 189 Phase noise compensation circuit 191 Extended FFT circuit 193 γ.sub.k setting circuit 194 Distance L setting circuit 195 Function ψ (t) acquisition circuit 196 Function Φ (t) acquisition circuit 192 Single carrier compensation circuit 254-1 to 254-N.sub.SDM Mixer 255-1 to 255-N.sub.SDM Filter 256-1 to 256-N.sub.SDM A/D (analog to digital) converter 257-1 to 257-N.sub.SDM FFT circuit 311-1 to 311-N.sub.SDM Transmit signal processing circuit 313-1 to 313-N.sub.SDM IFFT & GI assigning circuit 314-1 to 314-N.sub.SDM D/A converter 316-1 to 316-N.sub.SDM Mixer 317-1 to 317-N.sub.SDM Filter 320-1 to 320-N.sub.Ant Adder 321 Pilot signal storage circuit 345-1 to 345-N.sub.SDM Receive signal processing circuit 357-1 to 357-N.sub.Ant Extended FFT circuit 411-1 to 411-N.sub.SDM Transmit signal processing circuit 414-1 to 414-N.sub.SDM D/A converter 420-1 to 420-N.sub.SDM Adder 445-1 to 445-N.sub.SDM Receive signal processing circuit 511-1 to 511-N.sub.SDM Transmit signal processing circuit 642 Time axis transmission weight calculation circuit 657 Time axis reception weight calculation circuit 671-1 to 671-N.sub.Ant Synthesizer 672-1 to 672-N.sub.Ant Distributor 673-1 to 673-N.sub.SDM Distributor 674-1 to 674-N.sub.SDM Synthesizer 678 Phase control circuit 681-1 to 681-N.sub.SDM Phase shifter group 682-1 to 682-N.sub.SDM Phase shifter group 688 Phase control circuit 740 Transmission weight processing unit 741 Channel information acquisition circuit 742 Channel information storage circuit 743 Transmission weight calculation circuit 744 Reception weight processing unit 746 Channel information estimation circuit 747 Reception weight calculation circuit 755-1 to 755-N.sub.SDM Time axis reception weight multiplication circuit 757 Time axis transmission weight calculation circuit 761-1 to 761-N.sub.SDM Time axis transmission weight multiplication circuit 812-1 to 812-N.sub.Ant Addition synthesis circuit 813-1 to 813-N.sub.Ant IFFT & GI assigning circuit 814-1 to 814-N.sub.Ant D/A converter 815 Local oscillator 816-1 to 816-N.sub.Ant Mixer 817-1 to 817-N.sub.Ant Filter 818-1 to 818-N.sub.Ant High power amplifier (HPA) 819-1 to 819-N.sub.Ant Antenna element 840 Transmission weight processing unit 841 Channel information acquisition circuit 842 Channel information storage circuit 843 Transmission weight calculation circuit 844 Reception weight processing unit 846 Channel information estimation circuit 847 Reception weight calculation circuit 851-1 to 851-N.sub.Ant Antenna element 852-1 to 852-N.sub.Ant Low noise amplifier (LNA) 853 Local oscillator 854-1 to 854-N.sub.Ant Mixer 855-1 to 855-N.sub.Ant Filter 856-1 to 856-N.sub.Ant A/D (analog to digital) converter 857-1 to 857-N.sub.Ant FFT circuit 887 Local oscillator