WO2015001981A1 - Terminal device, base station device, and receiving method - Google Patents

Abstract

An objective of the present invention is, even when receiving a plurality of interference streams, to reduce receiving performance degradation from inter-cell interference and inter-user interference. Provided is a terminal device which receives a first interference signal and a second interference signal which are same-channel interference directed at another terminal device, said terminal device receiving terminal information from a base station device which is demodulation assistance information for the first interference signal. The first interference signal is demodulated using the terminal information, and the second interference signal is canceled using a reception weight. The first interference signal and the second interference signal are signals which are transmitted from different base station devices.

Description

Terminal apparatus, base station apparatus, and reception method

The present invention relates to a terminal device, a base station device, and a receiving method.

In recent years, with the spread of smartphones and tablet terminals, traffic in mobile transmission continues to increase exponentially and is expected to increase further in the future. As one countermeasure against such an increase in wireless traffic, high-density arrangement of base stations using a heterogeneous network has been studied. The high-density arrangement of base stations reduces the load on the macro base station by placing a low power base station (LPN) in the macro cell and connecting the terminal device to the low power base station. is there. At this time, inter-cell interference is a problem.

In addition, in order to improve cell throughput, MU-MIMO (Multi-User Multiple Input Multiple Output) in which a plurality of terminal devices are spatially multiplexed is also being studied. In MU-MIMO, interference between terminal devices (inter-user interference) becomes a problem.

For such inter-cell interference and inter-user interference, 3GPP (3rd Generation Partnership Project) is examining NAICS (Network Assisted Interference and Suppression) in which terminal devices suppress or remove interference signals. In NAICS, a terminal device receives information related to another terminal device causing interference, detects a signal addressed to the other terminal device causing interference, and performs interference removal. The NAICS is described in Non-Patent Document 1.

RP-130404, “Study on Network-Assisted Interference Cancellation and Suppression for LTE,” 3GPP TSG RAN Meeting # 59, March 2013.

However, in NAICS, since interference signals are detected and removed, in order to detect interference signals with high accuracy, it is necessary to increase the number of reception antennas provided in the terminal device more than the number of interference signal streams. Therefore, when receiving a larger number of interference streams than the number of reception antennas or in a small terminal device that cannot be equipped with a large number of reception antennas, there is a problem that interference cannot be removed with high accuracy and reception performance deteriorates.

The present invention has been made in view of such circumstances, and an object of the present invention is to reduce deterioration in reception performance due to inter-cell interference and inter-user interference even when many interference streams are received. It is an object to provide a terminal device, a base station device, and a receiving method that can be used.

In order to solve the above-described problems, the configurations of the terminal device, the base station device, and the reception method according to the present invention are as follows.

A terminal apparatus according to the present invention is a terminal apparatus that receives a first interference signal and a second interference signal, and receives terminal information that is demodulation support information from a base station apparatus for the first interference signal. It is characterized by doing.

In the terminal apparatus of the present invention, the first interference signal and the second interference signal are received, the first interference signal is demodulated using terminal information notified from the base station apparatus, and the second interference signal is received. The signal is suppressed using the reception weight.

In the terminal device of the present invention, the first interference signal and the second interference signal are signals transmitted from different base station devices.

Further, in the terminal device of the present invention, the first interference signal is demodulated after pre-filtering with respect to the second interference signal.

The base station apparatus of the present invention is a base station apparatus that transmits data to a terminal apparatus in cooperation with a plurality of base station apparatuses, and is an interference signal generated by a part of the plurality of base station apparatuses. Terminal information which is support information for demodulating the signal is notified to the terminal device.

Further, in the base station apparatus of the present invention, information indicating the part of base station apparatuses is notified to another base station apparatus that cooperates.

Further, in the base station apparatus of the present invention, precoding is performed on the terminal apparatus.

The reception method of the present invention receives a first interference signal and a second interference signal, the first interference signal is demodulated using terminal information notified from the base station apparatus, and the second interference signal is received. These interference signals are suppressed using reception weights.

According to the present invention, the first interference signal and the second interference signal are received, the first interference signal is demodulated using terminal information notified from the base station apparatus, and the second interference signal is received. Was suppressed using the reception weight. Therefore, even when a large number of interference streams are received, it is possible to reduce the degradation of reception performance due to inter-cell interference and inter-user interference, so that throughput can be improved.

1 is a schematic diagram of a communication system according to a first embodiment. It is a sequence diagram of the communication system which concerns on 1st Embodiment. It is a schematic block diagram of the base station apparatus which concerns on 1st Embodiment. It is a schematic block diagram of the terminal device which concerns on 1st Embodiment. It is a schematic block diagram of the signal detection part which concerns on 1st Embodiment. It is a schematic block diagram of the signal detection part which concerns on 2nd Embodiment. It is a sequence diagram of the communication system which concerns on 3rd Embodiment. It is a schematic block diagram of the base station apparatus which concerns on 3rd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described. The communication system in this embodiment includes a base station (transmitting device, cell, transmission point, transmitting antenna group, transmitting antenna port group, component carrier, eNodeB) and terminal (terminal device, mobile terminal, receiving point, receiving terminal, receiving device). , Receiving antenna group, receiving antenna port group, UE).

FIG. 1 is a diagram illustrating an example of a communication system according to the first embodiment. FIG. 1 shows a base station apparatus (also referred to as a macro base station or a first base station) 100-1, a base station apparatus (LPN: Low Power Node, a low power base station, a base station apparatus whose transmission power is lower than that of the macro base station, 2) (100-2, 100-3) and terminal devices 101 and 102. 100-1a is the coverage (macro cell) of the macro base station 100-1, and 100-2a and 100-3a are the coverages (pico cell, small cell, etc.) of the low power base stations 100-2 and 100-3, respectively. Coverage refers to a range (communication area) in which a base station device can be connected to a terminal device. In the following, an example is described in which a multi-cell is configured with a macro base station and a low-power base station. However, the present invention is not limited to this, and a multi-cell may be configured with only a macro base station. You may comprise a multicell only with a base station. Further, FIG. 1 illustrates only when one terminal apparatus is connected to the low power base station, but the present invention includes a case where a low power base station and a plurality of terminal apparatuses are connected. Moreover, although the case where a macro base station and a terminal device are connected is not illustrated, the case where a macro base station and a terminal device are connected is also included in the present invention. In addition, the base station apparatuses may be wirelessly connected or may be wired.

In addition, when there are a plurality of low-power base stations, the transmission power may be different for each low-power base station. In addition, the macro base station and the low power base station are not only distinguished from each other in transmission power, but also a backward compatible base station that supports a service-in method and a newly defined base station that is not backward compatible. And may be distinguished.

Also, the service method (communication system version, options, etc.) may differ between low-power base stations.

In the present invention, the number of cells, the number of base stations, the number of terminal devices, the type of cell (for example, macro cell, pico cell, femto cell, small cell, etc.) and the type of base station are not limited to the following embodiments. Moreover, in FIG. 1, although the small cell has overlapped with the macro cell completely, it may overlap partially and does not need to overlap.

FIG. 2 is a sequence diagram between the base station apparatus and the terminal apparatus according to the present embodiment. As an example, a case where the terminal apparatus 102 connects to the base station apparatus 100-3 will be described. Terminal apparatus 102 receives interference signals from base station apparatuses 100-1 and 100-2. The terminal apparatus 102 detects a cell (cell ID) that can be used for communication using the synchronization signal, performs a cell search, and performs initial connection to the base station apparatus 100-3 (step s201). The base station device 100-3 grasps the neighboring cell (step s202). The base station device 100-3 requests the terminal device 102 to perform channel measurement of neighboring cells (step s203). Terminal apparatus 102 measures the channel of the neighboring cell instructed from base station apparatus 100-3, and feeds back CSI (Channel State Information) to base station apparatus 100-3 (step s204). The CSI may include statistics such as a channel matrix and a channel covariance matrix. At this time, terminal apparatus 102 also feeds back the channel between base station apparatus 100-3 and terminal apparatus 102. The base station apparatus 100-3 determines a base station apparatus that detects (demodulates and decodes) and removes the interference signal in the terminal apparatus 102 (step s205). Here, it is assumed that terminal apparatus 102 detects and removes a signal from base station apparatus 100-1. In step s205, it is not necessary to determine the base station apparatus, and it may be determined for each interference signal. For example, it may be determined that a part of the interference signals from the base station apparatus 100-1 and a part of the interference signals from the base station apparatus 100-2 are detected and removed. . Therefore, even if there is one base station apparatus that causes interference, a part of the incoming interference signal can be determined as an interference signal to be detected and removed. Further, an interference signal demodulated by the terminal device is also referred to as a first interference signal. The base station apparatus 100-3 notifies the information determined in step s205 to the base station apparatus 100-1, and requests information on a terminal apparatus that interferes with the terminal apparatus 102 (step s206). The base station apparatus 100-1 notifies the base station apparatus 100-3 of terminal information that interferes with the terminal apparatus 102 (step s207). Here, the terminal information is support information used when the terminal apparatus 102 suppresses or eliminates interference. The base station device 100-3 notifies the terminal device 102 of the terminal information obtained in step s207. The base station device 100-3 transmits data to the terminal device 102 (step s209). The terminal apparatus 102 detects and removes the interference signal from the base station apparatus 100-1, and suppresses the interference signal from the base station apparatus 100-2 (step s210). An interference signal that is suppressed without being demodulated by the terminal device is also referred to as a second interference signal. In the present embodiment, each of the first interference signal and the second interference signal is an interference signal from one base station apparatus, but the first interference signal and the second interference signal are a plurality of base stations. The case of transmission from the apparatus is also included in the present invention.

FIG. 3 is a schematic block diagram showing the configuration of the base station device 100-3 in the present embodiment. Base station apparatus 100-3 includes upper layer 301, encoding sections 302-1 to 302-S, scramble sections 303-1 to 303-S, modulation sections 304-1 to 304-S, layer mapping section 305, reference signal Generation unit 306, precoding unit 307, terminal information generation unit 308, resource mapping 309-1 to 309-T, OFDM signal generation units 310-1 to 310-T, transmission units 311-1 to 311-T, transmission antenna 312 -1 to 312-T, receiving antennas 313-1 to 313-R, receiving units 314-1 to 314-R, and report information detecting unit 315. Note that S, T, and R in the figure represent the number of streams, the number of transmission antennas, and the number of reception antennas, respectively. In the case where a part or all of the base station device 100-3 is formed as a chip to form an integrated circuit, a chip control circuit that controls each functional block is provided.

The upper layer 301 is a layer of functions higher than the physical layer (Physical Layer) among the layers of communication functions defined by the OSI reference model, for example, MAC (Media Access Control), data link layer, network Layer etc. The upper layer 301 also notifies other parameters necessary for each part constituting the base station device 100-3 to perform its function.

The encoding units 302-1 to 302-S perform error correction encoding on the information data input from the upper layer 301, and generate encoded bits (also referred to as code words). The information data is, for example, an audio signal accompanying a call, a still image or moving image signal representing a captured image, a character message, or the like. The encoding schemes used when the encoding units 302-1 to 302-S perform error correction encoding include, for example, turbo encoding, convolutional encoding, and low density parity check encoding ( For example, Low Density Parity Check Coding (LDPC).

Note that the encoding units 302-1 to 302-S perform encoding on the encoded bit sequence in order to match the coding rate of the error correction-encoded data sequence with the encoding rate corresponding to the data transmission rate. Rate matching processing may be performed. The encoding units 302-1 to 302-S may have a function of rearranging and interleaving the error correction encoded data series.

The scramblers 303-1 to 303-S scramble the code words input from the encoders 302-1 to 302-S based on the cell IDs.

The scrambled codeword is mapped to the modulation symbol in the modulators 304-1 to 304-S. The modulation processes performed by the modulation units 304-1 to 304-S are, for example, BPSK (Binary Phase Shift Keying; two-phase phase modulation), QPSK (Quadrature Phase Shift Keying; four-phase phase modulation), M-QAM (M-Quadrature). Amplitude Modulation; M-value quadrature amplitude modulation (for example, M = 16, 64, 256, 1024, 4096). Modulating sections 304-1 to 304-S may have a function of rearranging generated modulation symbols and interleaving them.

The modulation symbol is layer-mapped for spatial multiplexing in the layer mapping unit 305. For example, LTE-A (LTE-Advanced) supports up to 8 layers, and one codeword is mapped to 4 layers at the maximum.

The reference signal generation unit 306 generates a reference signal, and outputs a reference signal that requires precoding to the precoding unit 307 and a reference signal that does not precode to the resource mapping units 309-1 to 309-T.

The precoding unit 307 performs precoding on the output of the layer mapping unit 305. Some reference signals, for example, DMRS (demodulation reference symbol) may be precoded in the same way as the data signal to be demodulated.

The terminal information generation unit 308 generates terminal information for the terminal device 102 to detect and remove interference signals. The terminal information is information necessary for demodulating and decoding a signal addressed to another terminal, such as a cell ID, a modulation scheme, a coding rate, a reference signal, an antenna port number, and resource allocation information. The terminal information can be a control signal.

Resource mapping units 309-1 to 309-T map the output of the precoding unit 307, reference signals, and terminal information to resources.

Outputs of the resource mapping units 309-1 to 309-T are OFDM (Orthogonal Frequency Division Multiplexing) signal generation units 310-1 to 310-T, and IFFT (Inverse Fast Fourier Transform: Inverse Fast Fourier Transform) , A cyclic prefix (CP) is inserted, and digital / analog conversion, filtering, frequency conversion, and the like are performed in the transmission units 311-1 to 311-T, and the transmission antennas 312-1 to 312-T are transmitted. Sent.

The base station device 100-3 also has a receiving function. The receiving antennas 313-1 to 313-R receive signals from the terminal apparatus 102, and the receiving units 313-1 to 313-R perform frequency conversion, filtering, analog / digital conversion, and the like. The report information detection unit 315 includes the number of ranks such as CSI (Channel State Information) fed back from the terminal apparatus 102, information necessary for determining MCS (Modulation Coding Scheme: Modulation and Coding Scheme), channel information of interference signals, and the like. Ask for. The channel information includes information necessary for precoding such as a channel matrix, a channel covariance matrix, and information indicating the channel matrix and the channel covariance matrix.

FIG. 4 is a schematic block diagram showing the configuration of the terminal device 102 in the present embodiment. The terminal device 102 includes receiving antennas 401-1 to 401-R, receiving units 402-1 to 402-R, CP removing units 403-1 to 403-R, FFT units 404-1 to 404-R, and a channel estimating unit 405. , A signal detection unit 406, an upper layer 407, a reference signal generation unit 408, an uplink signal generation unit 409, transmission units 410-1 to 410-T, and transmission antennas 411-1 to 411-T. Further, in the case where a part or all of the terminal device 102 is formed into a chip to form an integrated circuit, a chip control circuit (not shown) that controls each functional block is provided. Note that the number of transmitting antennas T and the number of receiving antennas R are the same as those of the base station apparatus 100-3, but the number of antennas of the terminal apparatus and the base station apparatus may be the same or different.

The terminal device 102 receives signals with the receiving antennas 401-1 to 401-R, and performs frequency conversion, filtering, analog / digital conversion, etc. with the receiving units 402-1 to 402-R. The output of the reception units 402-1 to 402-R is subjected to cyclic prefix removal by the CP removal units 403-1 to 403-R, and time-frequency conversion is performed by the FFT units 404-1 to 404-R. The channel estimation unit 405 obtains a channel estimation value using DMRS. If the DMRS is precoded, a channel estimate including precoding is obtained. The signal detection unit 406 removes the interference signal notified of the terminal information from the base station device 100-3, suppresses other interference signals with linear weights, obtains information data transmitted to itself, and obtains the upper layer 407. Output to.

The terminal device 102 also has a transmission function. The reference signal generation unit 408 generates an uplink reference signal. The uplink signal generation unit 409, information data obtained from higher layers, parameters for generating an uplink signal, reference signals obtained from the reference signal generation unit 408, information to be reported to the base station apparatus 100-3, etc. To generate an uplink signal. The uplink signal is a signal composed of an SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbol or an OFDMA symbol. The output of the uplink signal generation unit 409 undergoes digital / analog conversion, filtering, frequency conversion, and the like in the transmission units 410-1 to 410-T, and is transmitted from the transmission antennas 411-1 to 411-T.

FIG. 5 is a schematic block diagram showing the configuration of the signal detection unit 406. The signal detection unit 406 includes propagation path compensation units 501 and 506, a demodulation unit 502, a descrambling unit 503, a decoding unit 504, and an interference removal unit 505. The propagation path compensation unit 501 performs propagation path compensation using the reception weight and suppresses the second interference signal (and noise). The demodulator 502 performs a demodulation process to obtain a bit log likelihood ratio (LLR: Log Likelihood Ratio). When demodulating a signal addressed to another terminal apparatus, the demodulator 502 demodulates using the terminal information. The descrambling unit 503 unscrambles the base station apparatus and obtains the bit log likelihood ratio of the codeword. The decoding unit 504 performs error correction decoding on the bit log likelihood ratio of the codeword. In the case of a signal transmitted to another terminal apparatus, the decoding unit 504 performs decoding using the terminal information and obtains the encoded bit obtained The log likelihood ratio is output to the interference removal unit 505. When it is a signal addressed to its own terminal device, information bits are obtained by decoding, and when decoding of all the streams has not been completed, the coded bit log likelihood ratio after decoding is output to the interference removal unit 505. The propagation path compensation unit 506 performs propagation path compensation on the signal after interference removal.

The processing of the signal detection unit 406 will be described using mathematical expressions. A received signal r (k, t) in the resource element (k, t) is shown in (1). Note that k and t are a subcarrier index and an OFDM symbol index, respectively.

H ₁₁ is a channel matrix between base station apparatus 100-3 and terminal apparatus 102, s ₁ is a signal transmitted from base station apparatus 100-3 to terminal apparatus 102, and H ₁₂ is base station apparatus 100- 1 is a channel matrix between 1 and the terminal apparatus 102, s ₂ is a signal transmitted from the base station apparatus 100-1 to another terminal apparatus, and H ₁₃ is a channel between the base station apparatus 100-2 and the terminal apparatus 102. The matrix s ₃ represents a signal transmitted from the base station apparatus 100-2 to the other terminal apparatus. N represents noise.

The propagation path compensation unit 501 performs propagation path compensation so as to suppress H ₁₃ and n (that is, the second interference signal and noise). For this, for example, a weight as shown in Equation (2) can be used. The channel compensation can be performed by multiplying the weight obtained by the equation (2) by the equation (1) from the left.

However, H ^ represents a channel estimation value, and the channel estimation value estimated by the channel estimation unit 405 is used. Superscript H represents a complex conjugate transpose matrix. Note that R is an autocorrelation matrix of a received signal, and can be obtained using a resource element in which a reference signal (RS: Reference Signal) is arranged or a data channel (downlink shared channel: Physical Downlink Shared Channel).

In the case of obtaining using a reference signal, R can be obtained as in the following equation (3).

However, Q is a covariance matrix of interference noise, and when Equation (4) is obtained using CRS (Cell Specific Reference Signal: Cell-Specific RS), Equation (5) is obtained using DMRS. This is the case.

N _CRS is the number of CRS resource elements used for calculating Q, and N _DMRS is the number of DMRS resource elements used for calculating Q.

Moreover, following Formula (7) is a method of calculating | requiring R using a data channel or a DMRS resource element.

N _{PDSCH, DMRS} is the sum of the number of data channels and DMRS resource elements used to calculate R.

Although all the streams can be demodulated and decoded after propagation path compensation, a case where a successive interference canceller (SIC) is applied will be described below.

After propagation path compensation using Equation (2), the first interference signal is demodulated and decoded, and then interference cancellation is performed. Although it is possible to remove all the interference streams at once, here, a case where the interference streams are sequentially removed one by one will be described. In the following description, interference removal is performed in order from the stream index 1, but the present invention is not limited to this, and an arbitrary interference removal order can be applied.

When removing the first interference stream from the base station apparatus 100-1, the interference removal unit 505 removes the interference as shown in Equation (8). Expression (8) is an expression representing processing in a certain resource element, but (k, t) will be omitted in the following unless it is necessary.

Note that (·) ₁ represents the first column in the case of a matrix and the first element in the case of a vector. Further, s ^ is a vector having as an element a symbol replica that is an expected value of a modulation symbol. The symbol replica can be obtained as shown in Equation (9) when QPSK modulation is taken as an example.

Here, λ ₁ and λ ₂ represent the log likelihood ratio of the first bit and the log likelihood ratio of the second bit, respectively, constituting the QPSK symbol. Tanh represents a hyperbolic tangent function, and j represents an imaginary unit.

At this time, the propagation path compensation unit 506 performs propagation path compensation using the following weights.

However, E [] represents an expected value. Further, diag [] is a diagonal matrix having the parenthesized elements as diagonal elements. Q can be obtained using a reference signal in the same manner as in equations (4) and (5). Further, when obtaining using data, it can be obtained from the signal after interference removal as shown in the following equation (13).

After propagation path compensation, the second interference stream is decoded and, if necessary, the second interference stream is removed. Interference removal up to the xth (> 1) interference stream can be performed as in the following equation (14).

At this time, the propagation path compensation unit 506 performs propagation path compensation using a weight such as the following equation (15).

In addition, when calculating _| requiring _{R0, x} using data, it can carry out like following Formula (18).

Thereafter, all interference streams from the base station apparatus 100-2 can be removed. Even if the signal is destined for the terminal device itself, inter-stream interference occurs when the signals are spatially multiplexed, and thus the interference can be similarly removed by SIC. The interference removal up to the x-th (> 0) stream addressed to the own terminal apparatus can be performed by the following equation (19). However, S represents the number of interference streams from the base station apparatus 100-1.

At this time, the propagation path compensation unit 506 can use a weight like the following equation (20).

Moreover, when using data, _{Rx, S} can be calculated | required like following Formula (23).

In this way, the SIC is performed until all signals destined for its own terminal device are decoded.

Thus, in this embodiment, some interference streams (first interference signals) are detected and removed from the interference streams received by the terminal device, and other streams (second interference signals) are received. Interference suppression was performed using weights. Therefore, the terminal device can suppress interference even when all the interference streams cannot be detected, and can improve the throughput. Also, in this embodiment, the number of interference streams for detecting and removing interference is reduced, so that the amount of computation of the terminal device can be reduced.

As described above, in the present embodiment, interference streams are detected and removed one by one, but the present invention is not limited to this, and a plurality of interference streams can be detected and removed. In this embodiment, detection and removal are performed from the interference stream. However, the present invention is not limited to this, and detection and removal may be performed from the desired stream. In this case, after removing the desired stream, the interference stream is detected and removed, and the desired stream is obtained again. Further, detection and removal of a desired stream and an interference stream may be repeated. When the detection and removal of the desired stream and the interference stream are repeatedly performed, the terminal device can set the interference stream to be detected and removed according to the number of repetitions. For example, when a part of the first interference signals can be detected with high accuracy by repeating the previous one, there is no need to detect again. In this way, it is possible to reduce the amount of calculation compared to the case where all the first interference signals are detected and removed by every repetition.
(Second Embodiment)

Since the present embodiment and the first embodiment are different only in the signal detection unit 406, only the signal detection unit 406 will be described.

FIG. 6 is a schematic block diagram showing the configuration of the signal detection unit 406 in the present embodiment. The signal detection unit 406 includes a prefilter unit 601, a maximum likelihood detection unit 602, descrambling units 603-1 to 603-N, and decoding units 604-1 to 604-N. N represents the sum of the number of streams of the desired signal and the interference signal demodulated by the terminal device. That is, in the present embodiment, N is the sum of the number of streams from the base station apparatus 100-3 and the number of streams from the base station apparatus 100-1.

The prefilter unit 601 multiplies the received signal by a weight for whitening the interference noise. The maximum likelihood detection unit 602 performs maximum likelihood detection (MLD: Maximum Likelihood Detection) on the output of the prefilter unit 601, and obtains an encoded bit log likelihood ratio of the desired signal. The coded bit log likelihood ratio is descrambled by descrambling units 603-1 to 603-N, and error correction decoded by decoding units 604-1 to 604-N.

The processing of the signal detection unit 406 in the present embodiment will be described using mathematical expressions. The prefilter unit 601 multiplies the received signal r by a weight for whitening the interference noise as shown in Expression (24). The whitening weight can be obtained as, for example, the interference noise covariance matrix Q to Q ^−1/2 . Q ^−1/2 can be obtained by Cholesky decomposition or eigenvalue decomposition of the covariance matrix Q.

Expression (25) is obtained by rewriting Expression (24) with r ′, H ₁₁ ′, H ₁₂ ′, H ₁₃ ′, and n ′ being the received signal, channel matrix, and noise after multiplication by the whitening weight, respectively. is there.

Note that when the MMSE weight is obtained for Equation (25), it is the same as Equation (2). Since the whitening weight is multiplied, the covariance matrix of the interference noise is not obtained again and may be a unit matrix. The maximum likelihood detection unit 602 performs maximum likelihood detection on r ′ as shown in Expression (26).

λ _{q, n} represents the log likelihood ratio of the nth bit of the modulation symbol of the qth stream in the desired signal. s _{1, b} represents a transmission signal candidate of s ₁ defined by the bit string b = [b _1,1 ,..., b _{N1, M1} ]. N1 is the number of streams of the desired signal, M1 is the number of constellations of the modulated signal in the desired signal, M1 = 4 for QPSK, M1 = 16 for 16QAM, and M1 = 64 for 64QAM. Further, s _{2, c} represents a transmission signal candidate of s ₂ defined by the bit string c = [c _1,1 ,... C _{N2, M2} ]. N2 is the sum of the number of streams of the interference signal demodulated by the terminal device, and M2 is the sum of the number of constellations of the modulation signal in the interference signal. B ⁺ represents a set of b in which b _{q, n} = 1, and b ⁺ = [b _1,1 ,..., B _{q, n} = 1,..., B _{N1, M1} ]. b ⁻ represents a set of b _{q, n} = 0 in b, and b ⁻ = [b _1,1 ,..., b _{q, n} = 0,..., b _{N1, M1} ]. Therefore, λ _{q, n} is obtained by the difference between the minimum metric generated using b ⁺ and the minimum metric generated using b ⁻ .

Note that the maximum likelihood detection unit 602 does not have to calculate all transmission signal candidates, and can also obtain a bit log likelihood ratio from a part of the transmission signal candidates. As a method of reducing transmission signal candidates, for example, a method such as Sphere Decoding, M algorithm, QRM (QR decomposition and M algorithm) -MLD can be used.

As described above, in the second embodiment, the maximum likelihood detection is performed after multiplying the interference filter received by the terminal device by the prefilter that whitens the interference noise excluding the partial interference stream. Therefore, maximum likelihood detection can be performed for some interference streams while suppressing interference with the reception weight.
(Third embodiment)

FIG. 7 is a sequence diagram between the base station apparatus and the terminal apparatus according to the present embodiment. As an example, a case where the terminal apparatus 102 in FIG. 1 is connected to the base station apparatus 100-3 will be described. The terminal apparatus 102 detects a cell (cell ID) that can be used for communication using the synchronization signal, performs cell search, and performs initial connection to the base station apparatus 100-3 (step s701). The base station device 100-3 grasps the neighboring cell (step s702). The base station device 100-3 requests the terminal device 102 to perform channel measurement of neighboring cells (step s703). The terminal apparatus 102 measures the channel of the neighboring cell instructed from the base station apparatus 100-3, and feeds back CSI to the base station apparatus 100-3 (step s704). At this time, terminal apparatus 102 also feeds back the channel between base station apparatus 100-3 and terminal apparatus 102. The base station apparatus 100-3 selects a base station apparatus that detects and removes interference in the terminal apparatus 102 and a base station apparatus that suppresses inter-cell interference using transmission / reception weights (step s705). Here, the interference signal from base station apparatus 100-1 is detected and removed by terminal apparatus 102, and the interference signal from base station apparatus 100-2 is subjected to interference suppression using transmission / reception weights. That is, in this embodiment, the interference signal from base station apparatus 100-1 is the first interference signal, and the interference signal from base station apparatus 100-2 is the second interference signal. Also, the interference signal from base station apparatuses 100-1 to 100-2 is an interference signal (first interference signal) for detecting and removing the interference signal in terminal apparatus 102, or using transmission / reception weights Information indicating whether an interference signal (second interference signal) for interference suppression is used as base station information. Note that the transmission source of the first interference signal and the second interference signal may be the same base station apparatus. The base station apparatus 100-3 notifies the base station information determined in step s705 to the base station apparatuses 100-1 and 100-2 (step s706). Base station apparatuses 100-1 to 100-3 share a channel matrix between each base station apparatus and terminal apparatus 102 so that transmission / reception weights can be generated in each base station apparatus (step 707). For information sharing between base station apparatuses, an X2 interface can be used, and other methods can also be used. Base station apparatuses 100-1 to 100-3 calculate transmission / reception weights such that interference signals from base station apparatus 100-2 are suppressed (steps s708-1 to s708-3). The base station apparatus 100-1 notifies the terminal apparatus 102 of terminal information that causes interference with the terminal apparatus 102 (step s709). The base station device 100-3 notifies the terminal device 102 of the terminal information obtained in step s709 (step s710). The base station apparatus 100-3 notifies the terminal apparatus 102 of the necessary transmission weight of each base station apparatus and the reception weight of the terminal apparatus 102. The notification of the weight may be changed depending on the version of the standard and the transmission mode. For example, when CRS is used for demodulation, the transmission weight is notified, but when RS and data are multiplied by the same precoding weight (for example, DMRS), the weight is not notified. The notification of the reception weight can be changed depending on whether the terminal device obtains the reception weight. Base station apparatus 100-3 transmits the precoded data to terminal apparatus 102 (step s712). The terminal apparatus 102 suppresses the interference signal from the base station apparatus 100-2 by multiplying the reception weight, and detects and removes the interference signal from the base station apparatus 100-1.

FIG. 8 is a schematic block diagram showing the configuration of the base station apparatus 100-1 according to this embodiment. The base station apparatus 100-1 includes an upper layer 801, encoding units 802-1 to 802-S, scrambling units 803-1 to 803-S, modulation units 804-1 to 804-S, a layer mapping unit 805, weight generation Unit 806, reference signal generation unit 807, precoding unit 808, terminal information generation unit 809, resource mapping units 810-1 to 810-T, OFDM signal generation units 811-1 to 811-T, transmission units 812-1 to 812 -T, transmission antennas 813-1 to 813-T, reception antennas 814-1 to 814-R, reception units 815-1 to 815-R, and report information detection unit 816. Note that, when a part or all of the base station device 100-2 is formed into a chip to form an integrated circuit, a chip control circuit that controls each functional block is provided.

The upper layer 801 is a layer higher than the physical layer, for example, a MAC layer, a data link layer, a network layer, or the like. The upper layer 801 also notifies other parameters necessary for each part of the base station device 100-2 to perform its function.

The encoding units 802-1 to 802-S perform error correction encoding on the information data input from the upper layer 801 to generate encoded bits (codewords). Encoding sections 802-1 to 802-S perform rate correction on the encoded bit sequence in order to match the coding rate of the data sequence subjected to error correction encoding to the encoding rate corresponding to the data transmission rate. A matching process may be performed. In addition, the encoding units 802-1 to 802-S may have a function of rearranging and interleaving the error correction encoded data series.

The scramblers 803-1 to 803-S scramble the code words input from the encoders 802-1 to 802-S based on the cell IDs. The scrambled codeword is mapped to modulation symbols by modulation sections 804-1 to 804-S. Modulating sections 804-1 to 804-S may have a function of rearranging modulation symbols and interleaving. Modulation symbols are layer-mapped for spatial multiplexing by a layer mapping unit 805.

The weight generation unit 806 generates transmission / reception weights for interference suppression using channel information from neighboring cells. The reference signal generation unit 807 generates a reference signal, and outputs a reference signal that requires precoding to the precoding 808 and a reference signal that does not perform precoding to the resource mapping units 810-1 to 810-T.

The precoding unit 808 performs precoding on the output of the layer mapping unit 805 and the input reference signal using the transmission weight generated by the weight generation unit 806.

The terminal information generation unit 809 generates information on other terminal devices for the terminal device 102 to detect and remove interference signals.

Resource mapping units 810-1 to 810-T map information indicating the output of precoding unit 808, reference signals, and terminal information to resources. When the terminal device 102 needs to notify the transmission / reception weight, information indicating the transmission / reception weight is mapped to the resource.

Outputs of the resource mapping units 810-1 to 810-T are IFFT and cyclic prefix insertion performed by the OFDM signal generation units 811-1 to 811-T, and digital signals are transmitted from the transmission units 812-1 to 812-T. Analog conversion, filtering, frequency conversion, and the like are performed and transmitted from the transmission antennas 813-1 to 813-T.

The base station device 100-3 also has a receiving function. The receiving antennas 814-1 to 814-R receive signals from the terminal device 102, and the receiving units 815-1 to 815-R perform frequency conversion, filtering, analog / digital conversion, and the like. Report information detection section 816 obtains a channel matrix between base station apparatuses 100-1 to 100-3 and terminal apparatus 102 and information necessary for scheduling based on CSI fed back from terminal apparatus 102.

Since the schematic block configuration of the terminal device 102 is the same as that of FIG. 4 of the first embodiment, description thereof is omitted. However, since the details of the processing in the signal detection unit 406 are different, a description will be given using equations together with the processing of the weight generation unit 806 in FIG.

In the present embodiment, since the transmission weight is multiplied in the base station apparatus, the received signal in the terminal apparatus 102 is expressed by the following equation (27). Note that Expression (27) is a received signal in the resource element (k, t) as in Expression (1), but (k, t) is omitted unless necessary.

V ₁ , V ₂ , and V ₃ represent the transmission weight in base station apparatus 100-3, the transmission weight in base station apparatus 100-1, and the transmission weight in base station apparatus 100-2, respectively. Each transmission weight and reception weight may be different for each subcarrier, or may be the same for a plurality of subcarriers such as resource blocks. An equivalent channel obtained by combining the channel matrix and the transmission weight is represented by Expression (28), and an equivalent channel obtained by combining the channel matrix and the reception weight is represented by Expression (29). Note that _Up is a reception weight.

At this time, the transmission weight in each base station apparatus can be obtained as an eigenvector of several eigenvalues of signals detected by the terminal apparatus connected from the larger one of the equations (30) to (32). That is, the eigenvector of equation (30) is V ₁ , the eigenvector of equation (31) is V ₂ , and the eigenvector of equation (32) is V ₃ .

However, V ₁ to V ₃ obtained here are obtained so as to maximize SLNR (Signal to Leakage and Noise power Ratio), but the present invention is not limited to this. Alternatively, it may be obtained by a ZF (Zero Forcing) standard or an MMSE (Minimum Mean Square Error) standard. Further, in Expressions (30) to (32), the transmission weight is obtained assuming the reception weight, but the transmission weight may be obtained without assuming the reception weight. When no reception weight is assumed, the reception weight may be a unit matrix.

The reception weight in each terminal device can be obtained as an eigenvector of eigenvalues of several streams from the larger one in each of equations (33) to (35).

It should be noted that the reception weight in the terminal device 102 can be obtained from Equation (33). In Expression (34), it is possible to obtain a reception weight in a terminal device (not shown) connected to the base station device 100-1. In Expression (35), the reception weight in the terminal device 101 can be obtained.

When determining the transmission weight assuming the reception weight, the base station apparatus determines both the transmission weight and the reception weight. Further, by repeatedly obtaining the transmission weight and the reception weight repeatedly, the interference suppression performance can be improved. Note that the initial values of the transmission weight and the reception weight may be arbitrarily set, and the weights when the mutual weights are not taken into consideration can be used. Also, the transmission weight and the reception weight can be obtained using a channel covariance matrix.

In this embodiment, a case has been described in which each base station apparatus obtains all transmission weights and reception weights. However, the present invention is not limited to this, and one base station apparatus obtains all transmission weights and reception weights. It is also possible to notify each base station apparatus of the necessary weight. Further, the base station apparatus may notify the terminal apparatus of the calculated reception weight, or the base station apparatus may determine the terminal apparatus without notifying the terminal apparatus.

The transmission / reception weight suppresses the interference signal from the base station apparatus 100-2. The interference signal from the base station apparatus 100-1 can be eliminated in the same manner as in the first embodiment, and a prefilter is generated using an equivalent channel including precoding as in the second embodiment. In addition, maximum likelihood detection can be performed.

As described above, in the third embodiment, the terminal apparatus detects and removes some of the interference streams, and suppresses other streams using transmission weights or transmission weights and reception weights. Explained. Therefore, even when all the interference streams cannot be detected, the interference can be suppressed and the throughput can be improved.

In the above embodiment, the case where the interference signal from one base station apparatus is detected and removed has been described. However, the present invention is not limited to this, and the case where interference signals arrive from a plurality of base station apparatuses. The present invention can also be applied.

In the above embodiment, interference signals from one base station apparatus are suppressed using weights. However, the present invention is not limited to this, and is a case where interference signals from a plurality of base station apparatuses are suppressed. However, the present invention can be applied.

In the above embodiment, inter-cell interference has been described. However, the present invention is not limited to this, and a desired signal and an interference signal are transmitted from one base station apparatus, such as MU-MIMO (Multi User-Multiple Input Multiple Output). The present invention can also be applied when transmitted.

Note that the program that operates in the base station apparatus and mobile station apparatus according to the present invention is a program (a program that causes a computer to function) that controls the CPU and the like so as to realize the functions of the above-described embodiments according to the present invention. Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU as necessary, and corrected and written. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

Also, when distributing to the market, the program can be stored and distributed on a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Further, part or all of the mobile station apparatus and the base station apparatus in the above-described embodiment may be realized as an LSI that is typically an integrated circuit. Each functional block of the receiving apparatus may be individually chipped, or a part or all of them may be integrated into a chip. When each functional block is integrated, an integrated circuit controller for controlling them is added.

Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

Note that the present invention is not limited to the above-described embodiment. The terminal device of the present invention is not limited to application to a mobile station device, but is a stationary or non-movable electronic device installed indoors or outdoors, such as AV equipment, kitchen equipment, cleaning / washing equipment Needless to say, it can be applied to air conditioning equipment, office equipment, vending machines, and other daily life equipment.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope not departing from the gist of the present invention are also claimed. Included in the range.

The present invention is suitable for use in a terminal device, a base station device, and a receiving method.

100-1, 100-2, 100-3 Base station apparatus 101, 102 Terminal apparatuses 301, 407, 801 Upper layers 302-1 to 302-S, 802-1 to 802-S Encoding sections 303-1 to 303- S, 803-1 to 803-S Scrambler 304-1 to 304-S, 804-1 to 804-S Modulator 305, 805 Layer mapping unit 306, 807 Reference signal generator 307, 808 Precoding unit 308, 809 Terminal information generation units 309-1 to 309-T, 810-1 to 810-T Resource mapping units 310-1 to 310-T, 811-1 to 811-T OFDM signal generation units 311-1 to 311-T, 812 -1 to 812-T transmitting units 312-1 to 312-T, 813-1 to 813-T transmitting antennas 313-1 to 313-R, 814- 814-R receiving antennas 314-1 to 314-R, 815-1 to 815-R receiving units 315 and 816 Report information detecting units 401-1 to 401-R receiving antennas 402-1 to 402-R receiving unit 403- 1 to 403-R CP removing section 404-1 to 404-R FFT section 405 channel estimating section 406 signal detecting section 408 reference signal generating section 409 uplink signal generating sections 410-1 to 410-T transmitting sections 411-1 to 411 -T transmission antennas 501, 506 propagation path compensation unit 502 demodulation unit 503 descrambling unit 504 decoding unit 505 interference removal unit 601 prefilter unit 602 maximum likelihood detection units 603-1 to 603-N descrambling units 604-1 to 604 N decoding unit 806 weight generation unit

Claims (6)

A terminal device that receives a first interference signal and a second interference signal that are co-channel interference addressed to another terminal device,
For the first interference signal, a terminal apparatus that receives terminal information that is demodulation support information from the base station apparatus. The terminal apparatus according to claim 1, wherein the first interference signal is demodulated using the terminal information, and the second interference signal is suppressed using a reception weight. The terminal device according to claim 1, wherein the first interference signal and the second interference signal are signals transmitted from different base station devices. The terminal device according to claim 2, wherein the first interference signal is demodulated after pre-filtering with respect to the second interference signal. A base station device that transmits support information for demodulating an interference signal to a terminal device,
A base station apparatus that transmits terminal information, which is support information for demodulating a part of interference signals received by the terminal apparatus, to the terminal apparatus. A terminal apparatus that receives a first interference signal and a second interference signal, and for the first interference signal, a reception method for receiving terminal information that is demodulation support information from a base station apparatus.

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