WO2008069105A1

WO2008069105A1 - Radio transmission device, radio reception device, radio transmission method, and radio reception method

Info

Publication number: WO2008069105A1
Application number: PCT/JP2007/073101
Authority: WO
Inventors: Takaaki Kishigami; Hidenori Kayama
Original assignee: Panasonic Corporation
Priority date: 2006-11-30
Filing date: 2007-11-29
Publication date: 2008-06-12

Abstract

It is possible to provide a radio reception device, a radio transmission device, a radio reception method, and a radio transmission method which can improve the channel estimation accuracy and the reception quality. The radio reception device (200) includes: reception units (203, 204) which receive a data sequence added by a reference signal for channel estimation of a spatial propagation path at a predetermined interval; demodulation units (205, 206) which demodulate the data sequence; a channel estimation unit (208) which estimates a propagation path fluctuation state according to the reference signal in the data sequence and outputs a channel estimation value obtained by interpolating or extrapolating the data sequence; and a decoding processing unit (210) which decodes the data sequence by using the interpolated or extrapolated channel estimation value.

Description

Specification

TECHNICAL FIELD The present invention relates to a wireless transmission device, a wireless reception device, a wireless transmission method, and a wireless reception method.

TECHNICAL FIELD [0001] The present invention relates to a radio transmission apparatus, radio reception apparatus, radio transmission method, and radio reception method that transmit and receive signals during spatial multiplexing transmission using a multicarrier modulation scheme, and in particular, channel estimation technology and channel compensation. The present invention relates to a wireless transmission device, a wireless reception device, a wireless transmission method, and a wireless reception method using technology.

Background art

[0002] In recent years, with the demand for higher capacity and higher speed of wireless communication, research on technology for further improving the utilization efficiency of limited frequency resources has been actively conducted. The method of using the space domain is attracting attention. One such technique is an adaptive array antenna (adaptive antenna).

[0003] When this antenna is used, a signal arriving from a desired direction is strongly received by adjusting the amplitude and phase by a weighting coefficient to be multiplied to the received signal (hereinafter, this weighting coefficient is referred to as "weight"). be able to. Then, interference component signals such as multipath interference and co-channel interference can be suppressed. Such interference suppression effect can improve the communication capacity of the communication system.

[0004] Further, as another technique using the spatial domain, there are two techniques that use spatial orthogonality in the propagation path. One is spatial multiplexing technology that transmits different data sequences to the same terminal device using physical channels of the same time, the same frequency, and the same code. In general, there are the following methods using such a spatial multiplexing technique (for example, Non-Patent Document 1). That is, both the transmitter and the receiver are equipped with multiple antennas. In addition, spatial multiplexing transmission can be realized in a propagation environment where the correlation of received signals between antennas is low.

[0005] Here, at the time of transmission, different data sequences are transmitted from a plurality of antennas in a transmitter using physical channels of the same time, the same frequency, and the same code for each antenna element. Then, each antenna of the receiver receives an estimate of the propagation path characteristics (hereinafter referred to as the The data series are separated and received based on the channel estimation value). This makes it possible to increase the speed of transmission processing without using multilevel modulation by using multiple spatial multiplexing channels.

[0006] In addition, when both the transmitter and the receiver are equipped with the same number of antennas and perform spatial multiplexing transmission, the S / N ratio (signal-to-noise ratio) is sufficiently high and a large number of scatterers between the transceivers. In an environment where there is, the communication capacity can be expanded in proportion to the number of antennas. As such a spatial multiplexing transmission system, a multicarrier modulation system using orthogonal frequency division multiplexing (OFDM) is often used.

Yes

[0007] This is for the following reason. In other words, if the multipath delay of the wireless propagation path is within the guard interval time, the propagation path fluctuation received by each subcarrier can be treated as flat fading. This eliminates the need for multipath equivalent processing and reduces the separation processing of a spatially multiplexed signal.

[0008] On the other hand, at the time of reception, the signal received by the receiver antenna is frequency-converted into a baseband signal. Then, OFDM demodulation processing is performed.

Here, the multicarrier modulation scheme is a transmission scheme using a plurality of subcarriers.

The input data signal to each subcarrier is modulated by M-QQAM modulation or the like to become a subcarrier signal. In OFDM, the frequency of each subcarrier is orthogonal, and subcarrier signals with different frequencies are converted at once using a fast Fourier transform (FFT) circuit.

[0010] Thus, after the subcarrier signal is converted into a time-axis signal, the frequency is converted into the carrier frequency band and transmitted from the antenna. Non-patent document 2 describes OFDM modulation and OFDM demodulation.

Conventionally, under such circumstances, a channel estimation value has been obtained by a two-stage channel estimation process (for example, Patent Document 1). Specifically, first, a received signal corresponding to a reference signal for channel estimation is divided for each subset of transmitting antennas. As the first stage of channel estimation, the first stage of channel estimation is performed based on the reference sequence. Thus, provisional estimation of the channel response in the first dimension (eg, subcarrier direction) is calculated using interpolation processing for each subset of transmitting antennas. [0012] Next, as the second-stage channel estimation, channel estimation in different dimension directions (for example, time direction) is performed for each antenna using a temporary estimation value interpolated in a one-dimensional direction. In this way, the channel estimation value of the data portion existing between the reference signal and the temporary estimation value is obtained using inner interpolation, and the channel estimation values of the other data portions are obtained uniformly using outer interpolation. As a result, for each antenna in the subset of transmit antennas, the power to obtain the channel estimation directly becomes S Kurakura.

Patent Document 1: Japanese Translation of Special Publication 2006—515481

^ Patent 1: G.J.roschini, Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas, "Bell Labs Tech. J., pp.41-59, Autumn 1996

Non-Patent Document 2: Tomohiro Oo, Kenji Ueda "OFDM system technology and MATLAB simulation commentary, ... Trikes, 2002

Disclosure of the invention

Problems to be solved by the invention

[0013] Generally, a channel estimation value obtained by outer interpolation is less accurate than a channel estimation value obtained by inner interpolation. For this reason, in the channel estimation method described in Patent Document 1, since the channel estimation value by the outer interpolation is uniformly applied, the accuracy of channel estimation is reduced and the reception quality is reduced.

An object of the present invention is to provide a wireless transmission device, a wireless reception device, a wireless transmission method, and a wireless reception method that can improve the accuracy of channel estimation and improve reception quality.

Means for solving the problem

[0015] In order to solve the above-described problem, the radio reception apparatus of the present invention receives a data sequence to which a reference signal for channel estimation of a spatial propagation path is added at a predetermined interval, and the reception unit A channel that estimates a channel fluctuation state based on the reference signal in the received data sequence and outputs a channel estimation value obtained by interpolation or outer interpolation for the data sequence based on the fluctuation state Using the estimation unit and the channel estimation value of the inner or outer interpolation or the deviation of the channel estimation, the data series And a demodulation / decoding processing unit for performing the demodulation / decoding process.

[0016] In order to solve the above-described problem, the wireless transmission device of the present invention is a wireless transmission device that uses a transmission format in which a subframe includes a plurality of OFDM symbol powers, and has a spatial propagation path. A generating unit that generates a reference signal for channel estimation, an allocating unit that allocates a data signal to subcarriers of an OFDM symbol, and a transmission power of the reference signal that is greater than a transmission power of the data signal. A power adjustment unit that adjusts transmission power of a reference signal and the reference signal whose transmission power is adjusted by the power adjustment unit are arranged at a predetermined interval in the frequency axis direction of the subcarrier of the OFDM symbol, or Assigned to the reference signal multiplexing unit and OFDM symbol subcarriers arranged at predetermined intervals in the time axis direction. It said data signal and subjected to OFDM modulation to the reference signal, employs a configuration that includes a transmitter for transmitting the OFDM modulation signal obtained, the.

[0017] In addition, in order to solve the above-described problem, the wireless reception method of the present invention includes a step of receiving a data sequence to which reference signals for channel estimation of a spatial propagation path are added at a predetermined interval; Demodulating the data sequence; estimating a fluctuation state of a propagation path based on the reference signal in the demodulated data series; and based on the fluctuation situation, internal interpolation or external interpolation for the data series Outputting a channel estimation value obtained by the above-mentioned method, and performing a demodulation decoding process of the data sequence using the channel estimation value of the inner / outer interpolation or the difference between the inner / outer interpolations. It was.

[0018] In addition, in order to solve the above-described problem, a radio transmission method of the present invention is a radio transmission method using a transmission format in which a subframe includes a plurality of OFDM symbol powers, and includes a spatial propagation path. Generating a reference signal for channel estimation, assigning a data signal to subcarriers of an OFDM symbol, and transmitting the reference signal so that a transmission power of the reference signal is larger than a transmission power of the data signal. The step of adjusting transmission power and the reference signal whose transmission power has been adjusted by the power adjustment unit are arranged at predetermined intervals in the frequency axis direction of subcarriers of OFDM symbols, or predetermined in the time axis direction Steps that are spaced apart And a step of performing OFDM modulation on the data signal and the reference signal assigned to subcarriers of the OFDM symbol and transmitting the obtained OFDM modulated signal.

The invention's effect

[0019] According to the present invention, a data sequence is decoded using a channel estimation value obtained by inner interpolation or outer interpolation based on the propagation state of the propagation path. This improves the accuracy of channel estimation and improves the reception quality.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration example of a radio transmission apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing an example of a frame structure of a multiplexed signal of a reference signal multiplexing unit

FIG. 3 is a diagram illustrating a configuration example of a wireless transmission device in the first embodiment

FIG. 4A is a diagram showing a simulation result in the first embodiment.

FIG. 4B shows another simulation result in the first embodiment.

FIG. 5 is a diagram illustrating another configuration example of the wireless transmission device according to the first embodiment.

FIG. 6 is a diagram showing another frame configuration of the multiplexed signal of the reference signal multiplexing unit.

FIG. 7 is a diagram illustrating another configuration example of the wireless reception device in the first embodiment

FIG. 8 is a diagram showing a configuration example of a channel estimation unit of a wireless reception device in Embodiment 2 of the present invention

FIG. 9 shows a frame structure of a multiplexed signal in Embodiment 3 of the present invention.

FIG. 10 is a diagram illustrating a configuration example of a wireless reception device in a third embodiment

FIG. 11 is a diagram illustrating a configuration example of a wireless transmission device according to a fourth embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration example of a wireless reception device in a fourth embodiment

FIG. 13 is a diagram illustrating an example of transmission power when the reference signal transmission power is increased by method (1) in the fourth embodiment.

FIG. 14 is a diagram showing another example of transmission power when the reference signal transmission power is increased by method (1) in the fourth embodiment.

FIG. 15 is a diagram illustrating an example of transmission power when reference signal transmission power is increased by method (2) in the fourth embodiment. FIG. 16 is a diagram showing another example of transmission power when the reference signal transmission power is increased by method (2) in the fourth embodiment.

FIG. 17 is a diagram showing another frame configuration of the multiplexed signal of the reference signal multiplexing unit

FIG. 18 is a diagram illustrating a configuration example of a wireless transmission device according to method (2) in the fourth embodiment.

FIG. 19 is a diagram illustrating a configuration example of a wireless reception device according to method (2) in the fourth embodiment.

FIG. 20 is a diagram illustrating a configuration example of a wireless transmission device according to the fifth embodiment of the present invention.

FIG. 21 is a diagram illustrating a configuration example of a wireless reception device in a fifth embodiment

BEST MODE FOR CARRYING OUT THE INVENTION

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

[0022] (Embodiment 1)

[Configuration of wireless transmitter]

First, the configuration of radio transmitting apparatus 100 will be described.

FIG. 1 is a diagram showing a configuration example of a wireless transmission device (wireless communication device) 100 according to Embodiment 1 of the present invention. Here, radio transmission apparatus 100 will be described as adopting, for example, an OFDM multi-carrier transmission scheme.

In FIG. 1, a wireless transmission device 100 includes a reference signal generation unit 101, reference signal multiplexing units 102 and 103, OFDM modulation units 104 and 105, transmission units 106 and 107, and transmission antennas 108 and 109. Have. In the present embodiment, the force transmitting antenna described in the case of two transmitting antennas (the number of transmitting antennas Nt = 2) may be changed to one or three or more.

[0025] Reference signal generation section 101 generates a reference signal composed of a predetermined sequence signal known to the receiving side, and outputs the reference signal to reference signal multiplexing sections 102 and 103. The reference signal is for channel estimation.

[0026] Reference signal multiplexing section 102 receives data signal dl and the reference signal, and multiplexes the reference signal. Each data signal dl, d2 includes a predetermined notification signal, control signal data, and the like.

In the present embodiment, the multiplexing method is not limited to, for example, the power of using FDM (Frequency Division Multiplexing). For example, TDM (Time Divisi on Multiplexing) and CDM (Code Division Multiplexing).

An example of an output signal (data system IJ) of reference signal multiplexing section 102 is shown in FIG. Note that the reference signal multiplexing unit 103 also multiplexes in the same manner as the reference signal multiplexing unit 102.

[0029] The output signal in FIG. 2, that is, the multiplexed signal dlOO is composed of frames including a plurality (Ns) of subframes. One subframe includes Nf OFDM symbols. The subframe is composed of a data signal portion including a reference signal and other control signals.

The reference signal is inserted (intermittently) at predetermined intervals in the subcarrier direction (frequency direction) and the time direction (OFDM symbol direction), respectively. One OF DM symbol includes a plurality (Nc) of subcarriers.

[0031] The insertion position of the reference signal differs depending on each transmission antenna to be transmitted. For example, if a reference signal is inserted in a transmission signal from another transmission antenna, it is set as a null carrier that does not perform transmission using that subcarrier. As a result, during spatial multiplexing, reference signals from different antennas are transmitted using different subcarriers, so that they are frequency division multiplexed (FDM) and can be separately received during reception.

Returning to FIG. 1, each of the OFDM modulation sections 104 and 105 receives the output signal of the reference signal multiplexing section, that is, the multiplexed signal, and performs OFDM modulation. Specifically, each of the OFDM modulation sections 104 and 105 performs IFFT (Inverse Fast Fourier Transform) processing for converting a subcarrier signal into a time domain signal. Then, each OFDM modulation section 104, 105 outputs a time domain signal with a guard interval (GI: Guard Interval) added for multipath countermeasures. The OFDM modulation method is as described in Non-Patent Document 1.

[0033] Each transmission unit 106, 107 performs band limitation processing on the output signal from each corresponding OFDM modulation unit 104, 105 using a band limitation filter (not shown). Then, each transmitting section 106 and 107 frequency-converts the band-limited signal to a predetermined carrier frequency. Further, each of the transmission units 106 and 107 amplifies and outputs the frequency-converted signal using an amplifier (not shown).

[0034] Each transmitting antenna 108, 109 is a data system that is the output of each corresponding transmitting unit 106, 107. Radiate the column into the air. As a result, radio receiving apparatus 200 receives the data series.

[Configuration of Wireless Receiver]

Next, the configuration of radio receiving apparatus 200 will be described.

FIG. 3 is a diagram showing a configuration example of the wireless reception device (wireless communication device) 200 according to Embodiment 1 of the present invention. Here, description will be made assuming that radio receiving apparatus 200 employs, for example, an OFDM multi-carrier transmission scheme.

In FIG. 3, radio receiving apparatus 200 includes receiving antennas 201 and 202, receiving units 203 and 204, and OFDM demodulating units 205 and 206. Radio receiving apparatus 200 further includes a reference signal extraction unit 207, a channel estimation unit 208, a signal separation unit 209, and a decoding processing unit (demodulation decoding processing unit) 210. In the present embodiment, the force S described for the case of two receiving antennas (the number of receiving antennas Nt = 2) may be changed to three or more receiving antennas.

[0038] Each receiving antenna 201, 202 receives a high-frequency signal in a desired carrier frequency band.

Each receiving unit 203, 204 performs amplification processing, band limiting processing, and frequency conversion processing on each high frequency signal received by each receiving antenna 201, 202. Each of the receiving antennas 201 and 202 outputs a complex baseband signal including an in-phase signal and a quadrature phase signal to each of the OFDM demodulating units 205 and 206.

[0039] Each OFDM demodulator 205, 206 performs time and frequency synchronization processing, GI (guided interpolation) removal processing, FFT processing, and serial / parallel conversion processing for each input baseband signal. . Specifically, each OFDM demodulation section 205, 206 performs OFDM demodulation on the baseband signal. Then, each OFDM demodulation section 205, 206 outputs a symbol data sequence for each of Nc subcarriers.

[0040] In the following, when Y (k, fs) is expressed, it means the following symbol data series. That is, the symbol data sequence of the fsth subcarrier at the time of receiving the kth OFDM symbol in the subframe.

[0041] Here, Y (k, fs) represents a column vector including, as elements, signals received by Nr receiving antennas. That is, the signal y (k, fs) output from the OFD M demodulator that receives the signal received by the mth receiving antenna is used as the mth element. Where k = l to N s, fs = 1 to Nc.

[0042] For example, when radio transmitting apparatus 100 performs spatial multiplexing transmission of transmitting Nt spatial multiplexing streams from a plurality of transmission antennas, transmission sequence X (k, fs) of the fs subcarrier is an element. Let X (k, fs) = [x (k, fs),..., X (k, fs)] ^T

Represents 1 Nt. The superscript T represents a vector transposition operator. x _n (k, fs) represents the transmission sequence of the fs subcarrier in the kth OFDM symbol in the subframe transmitted from each transmission antenna.

[0043] If the relative delay time from the multipath preceding wave on the propagation path is within the guard interval (GI) range, even if the radio wave propagation path is in a frequency selective fading environment, the subcarrier unit is flat. It can be treated as a fading propagation environment. In such a case, frequency synchronization can be ideally performed by the wireless receiver.

[0044] Here, there is no sampling clock jitter between transmission and reception! /, In this case! /, And the data sequence (received signal vector) of subcarrier fs that received the kth OFDM symbol.

Y (k, fs) is expressed by equation (1).

[0045] country

Y (k _s ) = H (k, f _s ) X (k _s ) ₊ n (k _s )… (1)

In equation (1), H (k, fs) is a channel response matrix indicating a propagation path variation received by a data sequence (transmission sequence) X (k, fs) transmitted by radio transmitting apparatus 100. H (k, fs) is a matrix (hereinafter referred to as a channel matrix) composed of (number of reception antennas Nr of radio reception apparatus 200) × X (number of transmission antennas Nt of radio transmission apparatus 100) 歹 IJ.

[0047] The matrix element h of i rows and j columns of H (k, fs) represents the propagation path variation when the signal X (k, fs) is received by the i-th receiving antenna of the wireless receiver. . X (k, fs) represents a signal transmitted from the j-th transmission antenna of the wireless transmission device.

[0048] In equation (1), n (k, fs) represents an Nt-order noise component vector. n (k, fs), a vector whose elements are noise components added when received by Nr receive antennas of the wireless receiver.

[0049] Reference signal extraction section 207 extracts an OFDM symbol including a reference signal from a framed signal in a subframe. In addition, reference signal extraction Unit 207 extracts a subcarrier including a reference signal from the extracted OFDM symbol.

[0050] In the following, the reference signal transmitted from the m-th transmission antenna in the j-th OFDM symbol is represented as g (j, G (s)). And g (j, G

The reception result at the n-th receiving antenna for m jm m jm ω) is expressed as y (j, G (s)).

n jm

[0051] G (s) represents the sth subcarrier number of the reference signal transmitted from the mth transmission antenna in the jth OFDM symbol. s is a natural number of Ng (j, m) or less.

[0052] Channel estimation section 208 estimates the propagation state of the propagation path based on the reference signal in the demodulated (received) data sequence, and based on the variation state, internal interpolation or external interpolation for the data sequence is performed. The channel estimation value obtained by interpolation is output.

[0053] Specifically, channel estimation section 208 includes channel fluctuation status detection section 2081, frequency direction interpolation section 2082, inner side interpolation unit 2083, outer side interpolation unit 2084, and output replacement unit (estimated value output unit) 2085. Have

[0054] The frequency direction interpolation unit 2082 uses the reference signal extracted by the reference signal extraction unit 207 to calculate the estimation ^ IH (k, fs) of the channel matrix H (k, fs) shown in Equation (1). Calculate

e

In this embodiment, it is assumed that the reference signal is intermittently inserted in the subcarrier direction (frequency direction) and the time direction (see FIG. 2). For this reason, interpolation processing in the subcarrier direction is used for subcarriers for which no reference signal is inserted.

[0056] For the! /, NA! /, OFDM symbol with the reference signal inserted, the OFDM symbol in which the preceding and following reference signals are inserted is used in the time direction (OFDM symbol direction). ) Is used to calculate channel estimates for all subcarriers and OFDM symbols.

[0057] Further, frequency direction interpolation section 2082 calculates channel estimation value h (j, G (s)) for the subcarrier in which the reference signal is transmitted, in the OFDM symbol including the reference signal. This calculation formula is shown in Formula (2). [0058] [Equation 2]

(2)

In Equation (2), n represents a natural number equal to or less than Nr, m represents a natural number equal to or less than Nt, and j represents a symbol number of an OFDM symbol including a reference signal. G (s) represents the sth subcarrier number of the reference signal transmitted from the mth transmission antenna to the jth OFDM symbol! /. s is a natural number of Ng (j m) or less.

[0060] Then, the frequency direction interpolation unit 2082 calculates the reference signal nm jm based on h (j G (s)) in the equation (2).

Channel estimation values are interpolated in the frequency direction for subcarriers that do not contain a signal. Note that, as described in Patent Document 1, interpolation processing of frequency direction channel estimation values is performed in the frequency domain or the time domain.

[0061] Inner eye interpolation unit 2083 estimates the first channel estimation value by inner eye interpolation. Specifically, the inner interpolation unit 2083 uses the OFDM symbol channel estimation values h (j fs) and h (j fs) for the k th OFDM symbol that does not include the reference signal. nm 2

チャネル Channel estimation value (first channel estimation value) h (kl fs) is calculated by interpolation. Nm

Let J <k <j. For internal interpolation, linear interpolation or Lagrange interpolation can be applied.

1 1 2

Is possible.

[0062] In Fig. 2, the inner interpolation interval means, for example, the 2nd power and the j-1st OFDM symbol interval.

[0063] Outer interpolation unit 2084 estimates the second channel estimation value by outer interpolation. Specifically, the outer interpolation unit 2084 is not sandwiched between OFDM symbols including a reference signal and does not include a reference signal in a subframe.

2

On the other hand, the channel estimation value (second channel estimation nm 3) is calculated by external interpolation using the channel estimation value h (j fs) of the OFDM symbol including the reference signal before it in the time axis direction.

Fixed value) h (k fs) is calculated. Note that j <k. Outer interpolation is linear interpolation or lagra nm 2 3 2

It is possible to apply non-linear interpolation.

[0064] In Fig. 2, the outer interpolation interval means, for example, the j + 1st and subsequent OFDM symbol intervals. [0065] The line fluctuation state detection unit 2081 detects the fluctuation state D (j, j,) of the propagation path. This nm 2 1

When the line fluctuation status detection unit 2081 includes the reference signal, the jth and jth

1 Calculate the inner product of the channel estimate h (j,) and h (j,) between the OFDM symbols of 2 nm nm 1 nm 2

Yeah. This arithmetic expression is expressed by Expression (3) or Expression (4). Note that j <j.

1 2

[0066] [Equation 3]

[0067] [Equation 4]

D _nm (h _s ) = R ^ "'( ^Λ) ]… (4)

[0068] In Equation (3) and Equation (4), the asterisk (*) represents the complex conjugate operator, and Re [X] represents the real part of X, respectively. Also, j ≠].

1 2

[0069] From equation (3) and equation (4), if the propagation path fluctuation state D (j, j, fs) is smaller than 1, nm 2 1

The more the fading fluctuation of the propagation path increases. And D (j, j, fs) approximates 1 nm 2 1

The more you do, the more you can assume that the fluctuation of the propagation path is small.

[0070] It should be noted that the fluctuation state D (j, j, fs) may be detected for each subcarrier, or a plurality of nm 2 1

You may carry out as a value which averaged the fluctuation condition of the subcarrier of. Alternatively, this detection may be performed using a part of subcarriers other than all subcarriers, or subcarriers may be grouped and an average value for each group may be performed as a representative value. Furthermore, subcarriers can be grouped, and the grouped subcarriers near the center can be detected as representative values of the group.

[0071] The output replacement unit 2085 performs nm 2 1 for internal interpolation based on the fluctuation state D (j, j, fs) of the propagation path.

Select the channel estimation value or channel estimation value by external interpolation and output the final channel estimation value.

[0072] Specifically, output substitution section 2085 outputs the calculation result (channel estimation value) in frequency direction interpolation section 2082 in the case of an OFDM symbol including a reference signal.

[0073] On the other hand, in the case of the kth OFDM symbol not including the reference signal (in the case of the OFDM symbol including the reference signal before and after in the time axis direction), the output replacement unit 2085 Regardless of the fluctuation state in the line fluctuation state detection unit 2081, the calculation result channel estimation value in the inner frame interpolation unit 2083 is output as it is.

[0074] Alternatively, in the time axis direction in the subframe, when there is no OFDM symbol including the reference signal following the k-th OFDM symbol not including the reference signal, between the OFDM symbols including the reference signal Output substitution unit 2085 is based on the detection result of line fluctuation status detection unit 2081, that is, fluctuation status D (j, j, fs). Perform the following channel estimation value replacement process:

That is, in the output replacement unit 2085, the fluctuation state D (j, j, fs) has a predetermined value Ld (predetermined 1 nm 2 1

Is greater than), it is determined that the propagation path fluctuation is relatively small, and the channel estimation value h (k, fs) obtained by the inner interpolation unit 2083 is output. h (k, fs) is the maximum nm nm 2 where j is k

A natural number of ヽ uses a value in the vicinity thereof.

On the other hand, when the fluctuation state D (j, j, fs) is equal to or less than the predetermined value Ld, the output replacement unit 2085 transmits the nm 2 1

It is determined that the change in the transport path is relatively large, and the channel estimation value h (k,) obtained by the outer interpolation unit 2084 is output.

nm

[0077] Signal demultiplexing section 209 performs demultiplexing and reception processing of the spatially multiplexed signal using the channel estimation value that is the output of channel estimation section 208 (inner interpolation section or outer interpolation section). This separation reception process adopts the method described in Non-Patent Document 1.

[0078] For example, in the case of separate reception using the ZF (Zero Forcing) method, the signal separation unit 209 uses the channel estimation value H (for each subcarrier obtained by the channel estimation unit 208 (

For e k, fs), an inverse matrix is calculated, and the transmission symbol sequence X (k, fs) is received separately. The formula for calculating the inverse matrix is shown in Equation (5). In this embodiment, for example, the signal separation method based on the ZF method has been described, but the present invention is not limited to the ZF method, and a method such as MMSE (mean square error minimization) or MLD (Maximum likelihood Detection) is applied. May be.

[0079] [Number 5

x (k _s ) = HA sy ^l Y (k, f _s )… (5)

[0080] Decoding processing section 210 performs decoding processing of a data sequence using the channel estimation value of V or shift of inner interpolation or outer interpolation output from output replacement section 2085. [0081] Specifically, decoding processing section 210 performs a transmission bit sequence on the output signal of signal separation section 209 based on the encoded modulation information of the transmission signal included in the transmitted subframe (control signal). Receive processing to restore. In this reception process, the decoding processing unit 210 performs a de-mapping process, a dingter bar process, a correction decoding process, and the like. The demapping process is a process of converting a symbol data string by a predetermined modulation method into a bit data string.

The dingter processing is processing for restoring the bit order by performing an operation reverse to the interleaving performed in the wireless transmission device 100, for example. The correction decoding process is a process for performing error correction decoding on an input bit data string.

As described above, according to the present embodiment, a data sequence (multiplexed signal) to which a reference signal is added at a predetermined interval is received by a plurality of receiving antennas 201 and 202, and the data sequence is received. Are demodulated by the OFDM demodulation sections 205 and 206. Based on the reference signal in the data sequence demodulated (received) by the channel estimator 208, the channel fluctuation state D (j, j, fs) is estimated based on the reference signal in the demodulated (received) data sequence. Based on situation D (j, j, fs), the data nm 2 1 nm 2 1

A channel estimation value obtained by inner interpolation or outer interpolation for the sequence is output. Further, decoding processing section 210 performs iterative decoding processing of the data sequence using either channel estimation values of inner-side interpolation or outer-side interpolation.

In this case, the channel fluctuation status detection unit 2081 detects the fluctuation status of the propagation path (see formulas (3) and (4)). When the propagation path variation due to fading or the like is smaller than a predetermined level (predetermined value), the output replacement unit 2085 outputs an OFDM symbol (for example, j + 1 in FIG. 2) obtained by outer interpolation. The channel estimation value of the subsequent symbols is replaced with the channel estimation value obtained by the interpolation of the OFDM symbol preceding the OFDM symbol (for example, the i 1st symbol in Fig. 2) and output.

[0085] On the other hand, when the fluctuation of the propagation path due to fading or the like is larger than a predetermined level, the output replacement unit 2085 outputs the channel estimation by the outer interpolation without performing the channel estimation value replacement.

[0086] According to the above description, the channel estimation value obtained by outer interpolation, in which the accuracy of channel estimation is deteriorated compared to inner interpolation, is not used as much as possible depending on the propagation state of the propagation path. The channel estimation error is reduced, and as a result, the reception quality is improved. [Simulation condition · Result]

Here, CNR (Carrier to Noise Ratio) and PER (Packet Error Rate) (CNR) when the channel estimation value obtained by the present invention is used. , PER is called reception quality). Simulation conditions include 2 X 2 MIMO (Multiple Input Multiple Output), use of MLD separation algorithm, 64QAM modulation method, turbo code (coding rate R = 3 /

The simulation results are shown in FIG. Here, three types of patterns under the same simulation conditions are shown. That is, in the case of the ideal channel estimation method, in the case of the channel estimation method of the present invention, the case of the conventional channel estimation method (a method that uniformly uses channel estimation values by external interpolation) as a comparative example.

[0089] FIG. 4A shows the simulation result when the Doppler fading frequency is fd = 5.6 Hz, and FIG. 4B shows the simulation result when fd = 55.6 Hz.

4A and 4B, the channel estimation method of the present invention shows that the PER characteristic is improved and the reception characteristic is improved as compared with the case of the conventional channel estimation method. For example, in the case of the channel estimation method of the present invention, the CNR is improved by about 2 dB at PER = 10% (PER = 0. 1) compared to the conventional case. Therefore, it can be seen that the effect of improving the reception characteristics can be obtained.

[0091] [Modification of Radio Transmission Device and Radio Reception Device]

In the present embodiment, force spatial multiplexing transmission described in the case where radio transmitting apparatus 100 and radio receiving apparatus 200 perform spatial multiplexing transmission need not be performed. Hereinafter, configuration examples of radio transmitting apparatus 100A and radio receiving apparatus 200A at this time will be described.

FIG. 5 is a diagram illustrating a configuration example of the wireless transmission device 100A.

[0093] Unlike the case of the wireless transmission device 100 in FIG. 1, the wireless transmission device 100A in FIG. 5 has a reference signal generation unit 101, a reference signal multiplexing unit 102, an OFDM modulation unit 104, a transmission unit 106, and one transmission. Only antenna 108 is provided.

[0094] Reference signal generation section 101 generates a reference signal composed of a predetermined sequence signal and outputs the reference signal to reference signal multiplexing section 102. Then, the reference signal multiplexing unit 102 As in the first embodiment, the data signal dl and the reference signal are input, and the reference signal is multiplexed and output.

An example of the multiplexed signal at this time is shown in FIG. Unlike the case of FIG. 2, the multiplexed signal dlOl in FIG. 6 has only the first reference signal inserted. The first reference signal is

They are inserted at a predetermined interval in the frequency direction and the time direction.

The configuration of other radio transmitting apparatus 100A is the same as that of radio transmitting apparatus 100 in FIG.

FIG. 7 is a diagram illustrating a configuration example of the wireless reception device 200A. The radio receiving device 200A shown in Fig. 7 has two receiving antennas (the number of receiving antennas Nt = 2). The force is S, and the receiving antenna may be changed to one or more than three! /.

In FIG. 7, radio receiving apparatus 200A has line compensation section 211 instead of signal demultiplexing section 209 of radio receiving apparatus 200 in FIG. Note that the channel estimation unit 208 in FIG. 7 applies the above Nt and Nr as Nt = 1 and Nr = 1, respectively.

[0099] Channel compensation section 211 uses the channel estimation value that is the output of channel estimation section 208 (output replacement section 2085) to compensate for channel fluctuations in the signal received by reception antenna 201.

[0100] For example, in the case of separate reception by ZF, the channel compensation unit 211 calculates the calculation formula shown in Equation (6) for the channel estimation value H (k, fs) for each subcarrier obtained by the channel estimation unit 208. e

To compensate for line fluctuations.

[0101] [Equation 6] / J)-(6)

In this way, after channel compensation section 211 compensates for line fluctuations, decoding processing section 210 performs reception processing for restoring the transmission bit sequence on the output signal of circuit compensation section 211. The reception characteristics are further improved by the reception process.

[0103] In Embodiment 1 (including the modified example), channel estimation section 208 calculates the channel estimation value using the reception result of the OFDM symbol including the reference signal in the subframe. It is not limited to the method. For example, the channel estimation unit 208 indicates the reception result of the OFDM symbol including the reference signal that appears at the beginning of the next subframe. In addition, the channel estimation value may be calculated.

[0104] In this case, the channel estimation value calculated based on the reception result of the OFDM symbol including the reference signal that appears last in the subframe, and the OFDM symbol including the reference signal that appears first in the next subframe. The channel estimation of the OFDM symbol existing between the channel estimation value calculated based on the reception result is calculated by interpolation. For this reason, channel estimation accuracy can be improved and reception quality can be improved.

[0105] Also, in Embodiment 1 (including the modification), first, line fluctuation state detection section 2081 detects the fluctuation state of the channel estimation value in the time axis direction. When the fluctuation state is small, the output replacement unit 2085 replaces the channel estimation value of the OFD M symbol calculated by the channel estimation value obtained by the outer interpolation with the channel estimation value obtained by the inner interpolation. . However, the channel estimation value used for detecting the fluctuation state may be applied to the frequency direction not in the time axis direction.

[0106] In this case, first, the line fluctuation state detection unit 2081 detects the fluctuation state of the channel estimation value in the frequency direction. When the fluctuation state is small, the output replacement unit 2085 obtains the OFDM symbol channel estimation value calculated by the channel estimation value obtained by frequency direction outer interpolation by frequency direction inner interpolation. Replace with channel estimate. With the above replacement method, it is possible to improve the accuracy of channel estimation in the frequency direction and improve the reception quality.

[Embodiment 2]

In the second embodiment, the channel estimation is calculated by separating it into a phase component and an amplitude component, thereby improving the accuracy of channel estimation. Therefore, the configuration of the channel estimation unit will be mainly described below.

[0108] FIG. 8 is a diagram illustrating a configuration example of the channel estimation unit 208A of the radio reception device according to Embodiment 2 of the present invention.

[0109] The channel estimation unit 208A in Fig. 8 uses the reference signal extracted by the reference signal extraction unit 207 to estimate the channel matrix H (k, fs) shown in Equation (1) ^ IH (k, fs) e

Put out.

[0110] The reference signal in the present embodiment is intermittent in the frequency direction and the time direction. It is assumed that Therefore, first, channel estimation section 208A performs interpolation processing in the frequency direction for subcarriers into which no reference signal is inserted.

[0111] Then, channel estimation section 208A performs an interpolation process in the time direction on the OFDM symbol in which the reference signal is not inserted, using the OFDM symbol in which the preceding and following reference signals are inserted. Then, channel estimation section 208A calculates OFDM symbol channel estimation values for all subcarriers.

[0112] Specifically, the channel estimation unit 208A includes a frequency direction interpolation unit 2082, a phase component separation unit 2086, an amplitude component separation unit 2087, and a first inner interpolation unit (phase component time direction inner interpolation unit) 2088. And a first outer interpolation unit (phase component time direction outer interpolation unit) 2089. In addition, the channel estimation unit 208A includes a second inner interpolation unit (amplitude component time direction inner interpolation unit) 2090, a second outer interpolation unit (amplitude component time direction outer interpolation unit) 2091, and an interpolation interpolation unit. A generation unit 2092, an outer interpolation synthesis unit 2093, and an output replacement unit 2085.

[0113] Frequency direction interpolation section 2082 uses channel estimation values h (j, G (s)) for the subcarriers to which the reference signal is transmitted for OFDM symbols including the reference signal.

Calculate nm jm. This calculation formula is as shown in Formula (2). Then, the frequency direction interpolation unit 2082 circulates the subcarriers that do not include the reference signal based on h (j, G (s)) in Equation (2).

nm jm

Interpolation processing of channel estimation values in the wavenumber direction is performed (refer to the method described in Patent Document 1 for this interpolation processing).

[0114] Note that n represents a natural number equal to or less than Nr, m represents a natural number equal to or less than Nt, and j represents an OF DM symbol number including a reference signal. G (s) represents the sth subcarrier number of the reference signal transmitted from the mth transmission antenna in the jth OFDM symbol. s is a natural number of Ng (j, m) or less.

[0115] Phase component separation section 2086 separates the phase component of channel estimation obtained from the reference signal. Specifically, the phase component separation unit 2086 outputs the phase components Θ (j, fs), θ (j of the channel estimation values h (j, fs), h (j, fs) of the OFDM symbol including the reference signal.

nm 1 nm 2 nm 1 nm 2

,) Are separated and output.

[0116] The amplitude component separation unit 2087 separates the amplitude component of the channel estimation obtained from the reference signal. Specifically, the amplitude component separation unit 2087 includes an OFDM including a reference signal. Symbol channel estimates h (j, fs), amplitude components of h (j, fs) I h (j, fs) I, I

nm 1 nm 2 nm 1

(j, fs) I is separated and output.

nm 2

[0117] The first internal interpolation unit 2088 calculates the phase components of the two channel estimation values h (j, fs) and h (j, fs) for the kth OFDM symbol not including the reference signal. Θ (j, fs)

nm 1 nm 2 nm 1

, Θ (j, fs), and phase component of channel estimate h (k, fs) by internal interpolation Θ nm 2 nm nm

Calculate (k, fs).

[0118] Each channel estimation value h (j, fs), h (j, fs)

nm 1 nm 2

Represents the channel estimation value of the OFDM symbol including the reference signal. At this time, j <k <j.

1 1 2

[0119] Note that linear interpolation, Lagrange interpolation, or the like can be applied to the inner interpolation.

[0120] The first outer interpolation unit 2089 includes the k-th OFDM symbol in the subframe.

2

The outer phase interpolation using the phase component Θ (j, fs) of the channel estimate h (j, fs)

nm 3 nm 3

To calculate the phase component Θ (k, fs) of the channel estimation value h (k, fs). At this time, j <

nm 2 nm 3 k.

2

[0121] The kth ○ FDM symbol is sandwiched between ○ FDM symbols including the reference signal

2

And a symbol that does not include a reference signal. The channel estimation straight h (j, fs) is

nm 3

OFD including the reference signal before the kth OFDM symbol in the time axis direction

2

This is a channel estimation value of M symbols.

[0122] Note that linear interpolation, Lagrange interpolation, or the like can be applied to the outer interpolation.

[0123] The second inner interpolation unit 2090 calculates each amplitude component of two channel estimation values h (j, fs) and h (j, fs) for the kth OFDM symbol not including the reference signal. I h (j, fs

nm 1 nm 2 nm 1

) I, I h (j, fs) I is used to calculate the amplitude of the channel estimate h (k,) by internal interpolation.

nm 2 nm min I h (k, fs) I is calculated.

nm 1

[0124] Each channel estimation value h (j, fs), h (j, fs)

nm 1 nm 2

Represents the channel estimation value of the OFDM symbol including the reference signal. At this time, j <k <j. For internal interpolation, linear interpolation or Lagrange interpolation can be applied.

1 1 2

Noh.

[0125] The second outer interpolation unit 2091 includes the kth OFDM symbol in the subframe. For the channel estimation value h (j, fs) using the amplitude component I h (j, fs) I

nm nm

The amplitude component I h (k,) I of the channel estimation value h (k, fs) is calculated according to the interval.

nm 2 nm 2

[0126] The kth OFDM symbol is sandwiched between OFDM symbols including a reference signal.

2

And a symbol that does not include a reference signal. The channel estimate h (j, fs) is

nm 3

2

Estimated value. At this time, j <k. Outer interpolation is linear interpolation

3 2

Ne interpolation or the like can be applied.

The inner interpolation interpolation unit 2092 synthesizes a channel estimation value by inner interpolation based on the phase component and the amplitude component.

Specifically, the inner interpolation interpolation unit 2092 outputs the phase component Θ (k, fs) of the channel estimation value h (k, fs), which is the output of the first inner interpolation unit 2088, and the first 2 internal interpolation unit 2090 output

nm nm

Channel estimation based on the amplitude component I h (k, fs) I of a certain channel estimation value h (k, fs)

nm nm

The value h (k, fs) = I h (k, fs) I exp (j Θ (k, fs)) is synthesized into the output substitution unit 2085 nm nm nm

Output.

Outer interpolation synthesis section 2093 synthesizes a channel estimation value by outer interpolation based on the phase component and the amplitude component.

[0130] Specifically, the outer interpolation interpolation unit 2093 outputs the phase component Θ (k, fs) of the channel estimation value h (k, fs) that is the output of the first outer interpolation unit 2089, and the first 2 Outer interpolation unit 2091 output

nm nm

Output.

[0131] By synthesizing the channel estimation values, the output replacement unit 2085 outputs the channel estimation value based on the inner interpolation or the channel estimation value based on the outer interpolation based on the propagation state of the propagation path.

[0132] Specifically, the output replacement unit 2085 outputs the channel estimation value h (k,) that is the output of the inner interpolation interpolation synthesis unit 2092 and the channel estimation value h (nm that is the output of the outer interpolation interpolation synthesis unit 2093. nm k, fs). Then, output substitution section 2085 outputs the final channel estimation value by the same method as in the first embodiment. [0133] For example, in the case of an OFDM symbol including a reference signal, the output replacement unit 2085 outputs the calculation result channel estimation value) in the frequency direction interpolation unit 2082.

On the other hand, in the case of the kth OFDM symbol that does not include the reference signal (in the case of the OFDM symbol that includes the reference signal before and after in the time axis direction), the output replacement unit 2085 Regardless of the situation, the inner channel interpolation unit 2083 outputs the calculation result channel estimation value) as it is.

[0135] The configuration of the channel estimation unit including the other channel fluctuation state detection unit 2081 is the same as that of the first embodiment in FIG.

[0136] As described above, in the present embodiment, since channel estimation is calculated separately for phase components and amplitude components, the accuracy of channel estimation is further improved.

[0137] (Embodiment 3)

Embodiment 3 is a case where a frame different from the multiplexed signal of Embodiment 1 in FIG. 2 is used.

[0138] FIG. 9 is a diagram showing a frame structure of a multiplexed signal in the third embodiment.

[0139] The multiplexed signal dl02 (l frame) shown in Fig. 9 includes a plurality (Ns) of subframes. One subframe includes Nf OFDM symbols. The subframe is composed of a data signal portion including a reference signal and other control signals.

[0140] The reference signals are all inserted in the frequency direction of one OFDM symbol and inserted intermittently in the time direction. One OFDM symbol includes a plurality of Nc subcarriers.

[0141] In the case of spatial multiplexing transmission, the subcarrier insertion positions of reference signals of transmission signals transmitted from different transmission antennas are shifted for each transmission antenna.

[0142] The insertion position of the reference signal differs depending on each transmission antenna to be transmitted. For example, if a reference signal is inserted in a transmission signal from another transmission antenna, it is set as a null carrier that does not perform transmission using that subcarrier. When spatial multiplexing is performed using the above insertion position method, reference signals from different antennas are transmitted using different subcarriers, so that they are frequency division multiplexed (FDM) and received separately when received. That power s. The configuration of the wireless transmission device including other reference signals is the same as that of the first embodiment shown in FIGS.

[0143] FIG. 10 is a diagram illustrating a configuration example of radio receiving apparatus 200B in the third embodiment.

Radio reception apparatus 200B in FIG. 10 has provisional estimated value calculation section (temporary estimated value calculation section) 2094 instead of frequency direction interpolation section 2082 in FIG. Other configurations are the same as those in the first embodiment.

[0145] Temporary estimation value calculation section 2094 calculates channel estimation value h (j G (s)) for the subcarrier on which the reference signal is transmitted, for the OFDM symbol including the reference signal.

Calculate nm jm. This calculation formula is as shown in Formula (2). Then, the temporary estimated value calculation unit 2094 calculates the frequency direction nm jm for subcarriers not including the reference signal based on h (j G (s)).

The channel estimation value is interpolated (see the method described in Patent Document 1 for this interpolation processing)

Furthermore, temporary estimated value calculation section 2094 outputs the result of the interpolation processing to inner eye interpolation section 2083 and outer eye interpolation section 2084. Inner side interpolation unit 2083 and outer side interpolation unit 2084 each perform the same processing as in Embodiment 1 using the result of the interpolation processing in temporary estimated value calculation unit 2094.

[0147] With the configuration as described above, the ratio of the reference signal in the subframe is increased, so that the data transmission efficiency is reduced, but the following effects are obtained. In other words, the channel estimation value is calculated without performing interpolation processing in the frequency direction for the OFDM symbol including the reference signal. For this reason, the accuracy of channel estimation is improved.

[Embodiment 4]

Embodiment 4 is for a case where a reference signal having a transmission power larger than that of a data signal section is transmitted in a radio transmission apparatus.

[0149] FIG. 11 is a diagram illustrating a configuration example of a wireless transmission device 100B in the fourth embodiment.

Radio transmitting apparatus 100B in FIG. 11 further includes power control section 112 and two multiplying sections 110 111 in radio transmitting apparatus 100 in Embodiment 1 in FIG. The configuration of other radio transmission apparatuses is the same as that of the radio transmission apparatus in the first embodiment. Therefore, the following description will focus on the differences from the first embodiment. [0151] The power control section 112 outputs a weighting factor for changing the transmission power of the reference signal included in the OFDM symbol to each of the multiplication sections 110, 111.

[0152] Each multiplier 1 10, 1 1 1 multiplies the weighting factor that is the output of the power controller 1 12 by the reference signal that is the output of the reference signal generator 101, and each corresponding reference signal. It outputs to the number multiplexing part 102,103. Thereafter, each reference signal multiplexing section 102, 103 multiplexes the reference signal based on the output of each multiplication section 1 10, 1 1 1 1, as in the case of Embodiment 1, and each OFDM modulation section 104, Output to 105. In the present embodiment, each reference signal multiplexing section 102, 103, when multiplexing a reference signal, includes power information including a weighting factor (eg, / 3) and the position of the reference signal (OFDM symbol position). Is inserted into the control information.

[0153] With this configuration, a reference signal having a transmission power larger than that of the data signal unit is radiated from the transmission antennas 108 and 109 into the air.

[0154] Here, the weighting factor is a factor (for example, / 3 times, 1) such that the transmission power of the reference signal is larger than that of the data signal part (the last OFDM symbol including the reference signal in a certain subframe). <β). This increases the possibility of receiving the reference signal in the wireless reception device.

[0155] FIG. 12 is a diagram illustrating a configuration example of radio receiving apparatus 200C in the fourth embodiment.

Radio reception apparatus 200C in FIG. 12 further includes power information extraction section 212 in radio reception apparatus 200 in Embodiment 1 in FIG. Other configurations of the radio receiving apparatus are the same as those of the radio receiving apparatus in the first embodiment. Therefore, the following description will focus on the parts different from the first embodiment.

[0157] The power information extraction unit 212 extracts the power information from the control information added to the data sequence transmitted from the wireless transmission device 100B (respective transmission antennas 108 and 109) in FIG. Note that the power information includes a weighting coefficient (for example, / 3) and the position of the reference signal.

[0158] Frequency direction interpolation section 2082 uses the reference information for the OFDM symbol including the reference signal based on the power information (weight coefficient (/ 3), position of reference signal) obtained from power information extraction section 212. Channel estimation for the subcarrier on which is transmitted Calculate the value h (j, G (s)). This calculation formula is shown in Formula (7).

nm jm

[0159] [Equation 7]

, A ₍ J, rG »,, y", ^G j ^s y)… ((?)

[0160] In equation (7), n represents a natural number of Nr or less, m represents a natural number of Nt or less, and j represents an OFDM symbol number including a reference signal. G (s) represents the sth subcarrier number of the reference signal transmitted from the mth transmission antenna for the jth OFDM symbol. s is a natural number of Ng (j, m) or less.

[0161] Then, the frequency direction interpolation unit 2082 uses the reference signal h (j, G (s)) in Equation (7).

nm jm

Channel estimation values are interpolated in the frequency direction for subcarriers that do not contain a signal (refer to the method described in Patent Document 1 for this interpolation processing).

[0162] With the configuration as described above, the effects of Embodiment 1 can be obtained, and the transmission power of the reference signal can be increased, and the accuracy of channel estimation can be improved. Therefore, the reception quality can be improved.

[0163] Specifically, power control section 112 of radio transmitting apparatus 100B outputs a weighting factor (/ 3 times) so that the transmission power of the reference signal is larger than that of the data signal section. This increases the transmission power of the reference signal and increases the accuracy of channel estimation.

[0164] [Other transmission power control methods]

The power control unit 112 uses the following first to fourth control methods,

The transmission power of the signal may be controlled.

[0165] In the case of the first control method, the power control unit 112

The transmission power of the last OFDM symbol including the signal may be controlled so as to be larger than other OFDM symbols (the weight coefficient of the last OFDM symbol is set to / 3). in this case

In radio receiving apparatus 200C, it is possible to improve the accuracy of channel estimation of OFDM symbols obtained by outer interpolation.

[0166] In the case of the second control method, the power control section 112 has the transmission power of the last OFDM symbol including the reference signal larger than that of other OFDM symbols in the last subframe of the user's personal data. (The last OFDM symbol) The weighting factor of the router is / 3). Also in this case, it is possible to improve the accuracy of channel estimation of OFDM symbols obtained by outer interpolation.

[0167] Further, unlike the first control method, the second control method increases the transmission power of the reference signal with respect to the minimum OFDM symbol. For this reason, it is possible to prevent the transmission power distribution of the data signal part in the data series from being lowered. Therefore, a decrease in data transmission efficiency can be suppressed.

[0168] In the case of the third control method, the power control unit 112 of the wireless transmission device 100B is the wireless reception device.

Controls the transmission power of the reference signal according to the line fluctuation situation at 200C (see Equations (3) and (4)). In this case, the wireless reception device 200C further includes a feedback unit (detection result transmission unit: not shown) that transmits the detection result of the line fluctuation state detection unit 2081 to the wireless transmission device 100B (power control unit 112).

[0169] Radio transmission apparatus 100B (power control unit 112) controls the transmission power according to the detection result. For example, only when the line fluctuation indicated in the detection result is larger than a predetermined value, the wireless transmission device 100B (power control unit 112) causes the weighting factor (// so that the transmission power of the reference signal is larger than that of the data signal unit. 3 times).

[0170] Thereby, when the line fluctuation is larger than a predetermined value, the transmission power of the reference signal is increased. For this reason, in particular, the accuracy of channel estimation of OFDM symbols obtained by outer interpolation can be improved.

On the other hand, when the line fluctuation is smaller than the predetermined value, the transmission power of the reference signal does not increase, so that the same effect (characteristic improvement effect) as in Embodiment 1 can be obtained.

[0172] In the case of the fourth control method (TDD (Time Division Duplex) transmission), the wireless transmission device 100B is different from the third control method in that the reverse link (wireless reception from the wireless transmission device 100B) is performed. It further has a fading fluctuation status detection unit (not shown) that detects a fading fluctuation status based on a received signal from the transmission link to the device 200C and the radio link in the reverse direction.

[0173] Even with this configuration, the fading fluctuation status in the radio reception device 200C (reception side) is detected in the fading fluctuation status detection unit (not shown) of the radio transmission device 100B by using the relativity of the propagation paths. (Line fluctuation) can be detected. For this reason, Radio transmitting apparatus 100B (power control unit 112) controls the transmission power of the reference signal according to the fading fluctuation state. Even in this case, the same effect as in the third control method can be obtained.

[0174] [Another Transmission Power Control Method]

In the present embodiment described above, when transmitting a reference signal having higher transmission power than the data signal unit in radio transmission apparatus 100B, the transmission power of the data signal unit is not changed as shown in FIG. The method for increasing the reference signal transmission power for transmission (hereinafter referred to as “method (1)”) has been described. In method (1), the bandwidth for increasing the transmission power of the reference signal is the entire bandwidth in the communication operation bandwidth (all subcarriers used for data transmission in OFDM). In this case, the transmission power of the OFDM symbol including the reference signal is increased as compared to the OFDM symbol not including the reference signal.

[0175] In method (1), the transmission power distribution of the data signal section and the reference signal is made variable so that the sum of the transmission powers of the subcarrier signals included in the OFDM symbol is substantially constant. Also good. That is, the transmission power obtained by adding “the total transmission power of all subcarrier signals allocated except for the reference signal” to the “total transmission power of all subcarrier signals allocated as reference signals” within the subframe. Send it so that it is almost constant.

[0176] Fig. 14 shows the reference signal and the data signal section when the transmission power distribution of the data signal section and the reference signal is varied so that the sum of the transmission power of the subcarrier signals included in the OFDM symbol is substantially constant. 2 shows an example of the relationship between the transmission powers. As can be seen from FIG. 14, since the total transmission power is made constant in the subframe, the transmission power of the data signal section decreases, but the data signal whose transmission power decreases as described later. The effect can be reduced by inserting a signal with a small deterioration in reception quality into the part.

[0177] As a method different from method (1), as shown in Fig. 15, a partial band (hereinafter referred to as "subband"), which is selected from all bands, is used for data transmission in OFDM. It is also possible to apply a method of increasing the reference signal transmission power for transmission (hereinafter referred to as “method (2)”).ぅ). [0178] Note that, when the transmission power of the reference signal is increased only in the subband (method (2)), the transmission power of the subcarrier signal included in the OFDM symbol as shown in FIG. The transmission power distribution of the data signal section and the reference signal may be varied so that the sum of the two becomes substantially constant. As can be seen from FIG. 16, in this case, when the transmission power of the reference signal is increased, the transmission power of the data signal portion is reduced, but the data signal portion where the transmission power is reduced is less deteriorated in reception quality. The effect can be reduced by inserting a signal.

[0179] As described above, the band for increasing the transmission power of the reference signal is the entire band (method (1)) in the communication operation band, or a partial band (subband) selected from all bands. There is a method of transmitting by limiting (method (2)).

[0180] In the following, the band for increasing the transmission power of the reference signal is limited to subbands (method

(2)) In addition, a supplementary explanation will be given using FIG. 16 for the case where the total transmission power is constant in the subframe.

[0181] FIG. 16 shows the reference signals arranged intermittently and the transmission signal level of the data signal when transmission is limited to the subband. In the example shown in FIG. 16, a plurality of reference signals with higher transmission power are assigned only to a specific subband. In addition, data signals that are sandwiched between subcarriers of the reference signal with increased transmission power are allocated! /, And only a plurality of subcarriers (reference signal transmission power increased partial band) are compared to other data signals. Reduce transmission power at a constant rate. As a result, the transmission power obtained by adding “the total transmission power of all subcarrier signals allocated to other than the reference signal” to “the total transmission power of all subcarrier signals allocated as the reference signal”. Transmission can be performed so as to satisfy a constant relationship within a subframe.

[0182] With such a transmission method, the channel estimation value for the data signal part whose transmission power was reduced at a constant rate was extracted, and only the subbands to which a plurality of reference signals with increased transmission power were assigned were extracted. In the above calculation, interpolation is performed, and further, the reference signal transmission power offset amount is used and multiplied by a coefficient considering the offset amount. Details of the channel estimation value calculation method will be described later. As a result, the channel estimation accuracy can be improved and the sub-carrier sandwiched between the reference signal sub-carriers. Since the carrier transmission power is reduced or increased at a certain rate, the configuration of the channel estimation unit can be simplified. In addition, the reception characteristics can be improved by improving the channel estimation accuracy.

[0183] It should be noted that transmission is performed by limiting the transmission power of the reference signal to the subband (method (2)), and the following two subband limiting methods (a) and subband limiting method (b) Apply power S with power S.

[0184] [Subband limitation method (a)]

The subband that increases the reference signal transmission power is fixedly assigned to a specific subband in the communication operation band. As a result, the subband for increasing the transmission power of the reference signal is fixed, so that only the information related to the transmission power of the reference signal is notified from the wireless transmission device to the wireless reception device. It is not necessary to notify the information on the position of the subcarrier that increases the power. When the transmission power of the reference signal is adaptively changed, information on the transmission power is notified whenever the transmission power of the reference signal fluctuates or periodically (for each subframe or frame period). .

[0185] Further, frequency resource allocation may be performed in which a radio reception device at a cell edge is preferentially allocated to a subband in which reference signal transmission power is increased. As a result, it is possible to improve the channel estimation value in the radio reception apparatus at the cell edge that causes a particular problem in channel estimation accuracy, and to improve the reception quality.

[0186] [Subband limitation method (b)]

The subband that increases the transmission power of the reference signal is dynamically allocated to the subband in the communication operation band. In this case, transmission power control for increasing transmission power may be performed on a reference signal included in a subband to which a wireless reception device satisfying a specific condition is assigned. Here, as the specific condition, for example, a radio receiving apparatus that reduces reception power (reception quality) such as a cell edge is selected. This improves the estimation accuracy of the channel estimation value in the wireless receiver that satisfies the specific condition, and improves the reception quality with the power S.

[0187] It should be noted that every time the subband for increasing the transmission power of the reference signal fluctuates, or Information on the transmission power of the reference signal is notified from the wireless transmission device to the wireless reception device periodically (subframe or every frame period). In subband limiting method (b), the amount of information to be reported is increased compared to subband limiting method (a), but the reference is based on the number of wireless receivers that satisfy specific conditions in the communication area. The effect is that the setting of the subband for increasing the transmission power of the signal can be made flexible.

[0188] In this case, by increasing the transmission power of the reference signal intermittently inserted in the frequency direction, the transmission power of the subcarrier signal other than the reference signal in the same OFDM symbol is reduced. . However, for signals other than the reference signal, it is possible to reduce the effect by inserting a signal with little degradation in reception quality even if the transmission power is reduced. This will be described below with reference to FIG.

FIG. 17 shows an example of the frame structure of the multiplexed signal in the present embodiment. In the data signal part B in the figure, a signal modulated with a low MCS that can ensure reception quality even with a low SNR (a signal modulated with a low modulation index and low coding rate) is used. Signals modulated with a low MCS include individual control signals, shared control signals, and broadcast signals. Alternatively, the data signal to the radio receiver at the cell edge modulated by MCS may be used. In FIG. 17, data signal section A sets the MCS and transmits a data signal by the conventional method. In this way, in the same OFDM symbol, the subcarrier signal other than the reference signal is a signal modulated using MCS that is low and / or MCS that can ensure reception quality even with low signal and SNR. It is possible to reduce the influence of degradation of reception quality due to a decrease in transmission power of subcarrier signals other than.

[0190] The above-mentioned subband limiting methods (a) and (b) are effective when a cell edge radio receiver is allocated to a subband that increases the transmission power of the reference signal and a low MCS data signal is transmitted. With these methods, it is possible to reduce the deterioration of the reception quality of the data signal.

[0191] Also, when the above method is used, by making the average transmission power of each OFDM symbol constant, the power that can be applied even when the wireless transmission device is transmitting at the maximum transmission power S it can.

[0192] The configuration of the wireless transmission device to which the method (2) is applied and the configuration of the wireless reception device are described below. And explain.

[Configuration of wireless transmission device]

FIG. 18 is a diagram illustrating a configuration of a wireless transmission device 100C that transmits a reference signal transmission power increase limited to a subband (method (2)). Radio transmission apparatus 100C in FIG. 18 further includes frequency resource allocation control section 120, frequency resource allocation section 121, and multiplication sections 123 and 124 for data signals, in addition to radio transmission apparatus 100B shown in FIG. The configuration of the other wireless transmission device 100C is the same as that of the wireless transmission device 100B. Therefore, the following description will focus on the parts that are different from radio transmitting apparatus 100B.

[0194] Frequency resource allocation control section 120 uses the reception quality information (information such as SIR and SINR) notified from the radio reception apparatus so that it is at the cell edge in the subband that increases the transmission power of the reference signal. Radio frequency resources are allocated to preferentially assign radio receivers with low reception quality (low SIR). Here, the subband for increasing the transmission power of the reference signal may be fixedly set in advance (subband limiting method (a)), or according to the frequency resource allocation status for the radio receiving apparatus. Depending on the situation, you may change the setting dynamically! /, (Subband limiting method (b)).

[0195] Frequency resource allocating section 121 receives data signals including data to be transmitted to different radio receiving apparatuses based on the frequency resource allocation information output from frequency resource allocation control section 120. The data signal is assigned to the subcarrier included in the specified frequency resource.

[0196] Power control section 112a outputs a weighting coefficient (for example, / 3) for changing the transmission power of the reference signal included in the OFDM symbol to each of multiplication sections 110 and 111. Further, a weighting coefficient (for example, α) for changing the transmission power of a signal (data signal or control signal) other than the reference signal included in the OFDM symbol is output to each of the multipliers 123 and 124. In the present embodiment, the reference signal included in the subband that increases the transmission power of the reference signal is multiplied by a weight coefficient of 1 or more (/ 3≥1). Also, a signal other than the reference signal included in the subband that increases the transmission power of the reference signal is multiplied by a weighting factor (α≤1) of 1 or less. Note that Lp in FIG. 13 to FIG. 16 indicates the reference signal transmission power offset amount, and is the power information (α, / 3). , Lp = / 3. The power control unit 112a outputs the power control information to the control information generation unit 122.

[0197] The control information generating unit 122 generates a control signal based on the control information including the power control information. For example, when each of the reference signal multiplexing units 102 and 103 multiplexes the reference signal, the control information generating unit 122 uses the power information (α, / 3) regarding the reference signal transmission power offset amount Lp and the position of the reference signal. The control signal is generated using the reference signal power information including (OFDM symbol position) as control information. The transmission power information included in the reference signal power information uses an offset amount based on the transmission power of the data signal section. For example, when the transmission power of the data signal part is reduced, an offset value of the transmission power based on the data signal part of the transmission power is used for the transmission power information. As a result, the receiving side can estimate the transmission power offset amount of the data signal section based on the reception result of the reference signal, and even if the transmission power between the reference signal and the data signal section is variable, Demodulation can be performed without degrading the data signal using the transmission power information included in the signal power information.

[0198] Each multiplying section 110, 111 multiplies the weighting factor / 3 that is the output of power control section 112a by the reference signal that is the output of reference signal generating section 101, and each corresponding reference signal multiplexing section 102. , Output to 103. Similarly, each of the multiplying units 123 and 124 multiplies the weighting factor α that is the output of the power control unit 112a and the output signal of the frequency resource allocating unit 121, to the corresponding reference signal multiplexing units 102 and 103. Output.

[0199] Thereafter, each reference signal multiplexing section 102, 103 is replaced with each multiplication section 110, 111 and each multiplication section.

Based on the outputs of 123 and 124, the reference signal and signals other than the reference signal (data signal dl, control signal d3) are multiplexed and output to OFDM modulation sections 104 and 105, respectively.

[0200] In this way, each of the reference signal multiplexing units 102 and 103 receives the control information including the control information and the data signal for the reference signal transmission power offset amount Lp. A reference signal is further multiplexed on the included signal.

[0201] When transmitting a reference signal with increased transmission power using the subband limiting method (a), the amount of information notified as power control information is reduced by using the following method. The power to do S. Specifically, the reference signal Only a plurality of subcarriers (reference signal transmission power increasing partial band) to which data signals are allocated, which are sandwiched between carriers, reduce the transmission power at a certain rate, thereby increasing the transmission power of the reference signal. The ability to uniquely relate the number of subcarriers of signals (data signals and control signals) with reduced transmission power other than the reference signal to the number of carriers. In other words, as shown in Equation (8), when / 3 is determined, α is determined, so that the amount of information notified as power control information can be reduced.

[0202] [Equation 8]

_{ad - N DS -) = pN} PRS ... (8)

[0203] In Equation (8), N is the reference signal transmission power increasing partial band.

PRS

Indicates the number of subcarriers to which the reference signal is assigned.N is the reference signal.

DS

Is the insertion interval in the subcarrier direction. Reference signal transmission power increasing portion When the bandwidth is fixed, N is a known constant value, and N is a known constant value.

PRS DS

[0204] Also, when the subband limiting method ω is used, notification of information on the position of a signal whose transmission power other than the reference signal has been reduced is not required, so that it is possible to suppress a reduction in efficiency during data transmission. it can.

[0205] If transmission is performed using a known weighting factor in advance without changing the weighting factor, notification of power control information (α, β) can be further eliminated.

[0206] When using the subband limiting method (b) and dynamically changing the setting of the subband to which the reference signal with increased transmission power is added according to the frequency resource allocation situation for the radio receiver, Resource allocation control section 120 outputs subband information including a reference signal with increased transmission power to control information generation section 122.

[0207] Control information generation section 122 generates a control signal based on control information including power control information and subband information including a reference signal with increased transmission power. In addition, the information regarding the position of the reference signal for changing the transmission power may be assigned with a variable band, or the band may be divided into N in advance and the number of the divided band may be transmitted. In the latter case, although the band division is fixed, the amount of control information related to the reference position included in the reference signal power information can be reduced. In addition, the division band number can be sent by fixedly setting the division band to increase the transmission power in advance. The ability to make it unnecessary S Alternatively, transmission can be performed using 1-bit information indicating whether transmission to increase transmission power is performed or transmission to increase transmission power is not performed.

[0208] With this configuration, a reference signal having a transmission power larger than that of the data signal unit is radiated from the transmission antennas 108 and 109 into the air.

[0209] [Wireless receiver]

Next, the configuration of the wireless reception device is shown. FIG. 19 is a diagram illustrating a configuration example of a wireless reception device 200D with respect to the wireless transmission device 100C of FIG.

[0210] Radio receiving apparatus 200D in Fig. 19 further includes power information extracting section 212 and transmission power offset compensating section 213 in radio receiving apparatus 200B in Fig. 10. The configuration of other radio reception apparatuses is the same as that of the radio reception apparatus in the first embodiment. Therefore, the following description will focus on the differences from the first embodiment.

[0211] The power information extraction unit 212 uses the control information added to the data sequence transmitted from the wireless transmission device 100C in Fig. 18 to obtain the transmission power information and subband information including the reference signal with increased transmission power. Extract. The transmission power information includes (<<, / 3) or information on the reference signal transmission power offset amount Lp.

[0212] Based on the transmission power information (α, / 3) obtained from the power information extraction unit 212, the frequency direction interpolation unit 2082 transmits a reference signal with increased transmission power for the OFDM symbol including the reference signal. For the subcarriers that are present, the channel estimation value h (j, G (s)) is calculated using equation (9) in consideration of the increase in transmission power.

nm jm

[0213] [Numerical 9

,, ヽ „U, G _jm ^)), _Ω ,

AJ, G _jn i) =… (9)

[0214] In equation (9), n represents a natural number equal to or less than Nr, m represents a natural number equal to or less than Nt, and j represents an OFDM symbol number including a reference signal. G (s) represents the sth subcarrier number of the reference signal with increased transmission power transmitted from the mth transmission antenna for the jth OFDM symbol. s is a natural number equal to or less than Np (j, m) subcarriers of the reference signal with increased transmission power.

[0215] As in the subband limiting method (b), the frequency resource allocation for the radio receiving device When the subcarrier allocation that increases the transmission power of the reference signal is dynamically changed according to this situation, the reference signal that increases the transmission power is transmitted and the subcarrier varies. Therefore, transmission power information (s), 13 (s)) obtained from the power information extraction unit 212 changes depending on the subcarrier number s. Therefore, frequency direction interpolation section 2082 uses equation (10) to calculate the channel estimation value h nm for the subcarrier including the reference signal.

(j, G ω) is calculated, and channel estimation value interpolation processing is performed in the frequency direction for subcarriers that do not include a reference signal. Thereafter, channel estimation section 208 performs the same operation as in Embodiment 1, and calculates and outputs a channel estimation value.

[0216] [Equation 10]

(G (s))

KM, G _jm (s))- ^{1 0} )

Λ] β (, (

g _m ； _{r (}

(j, G _Jm (s))

[0217] Transmission power offset compensation section 213 is a signal (data signal, control signal) in which transmission power other than the reference signal included in the reference signal transmission power increased partial band is changed with respect to the output of signal separation section 209 To compensate for the offset. This offset is caused by the fact that the transmission power change in the data signal and control signal is not considered in the channel estimation value that is the output of the channel estimation unit 208. That is, the transmission power offset compensation unit 213 uses the offset amount (with respect to the subcarrier signal included in the reference signal transmission power increase partial band of the signals output from the signal separation unit 209 based on the power control information α. a) Multiply by ^1/2 .

[0218] Note that, when the subband limiting method (b) is used, the subband of the reference signal whose transmission power is increased dynamically changes according to the frequency resource allocation status for the radio reception apparatus, and the transmission power is reduced. Since the increased reference signal is transmitted and the subcarrier fluctuates, the power information extraction unit 212 uses the subband information that is extracted from the control signal and includes the reference signal with increased transmission power to transmit. The above operation of the power offset compensation unit 213 is performed.

[0219] With this configuration, a reference signal having a transmission power larger than that of the data signal unit is radiated in the air from each of the transmission antennas 108 and 109 of the wireless transmission device 100C. Here, the weighting factor is such that the transmission power of the reference signal is the data signal part (a certain subframe). The coefficient is such that the power is larger than the last OFDM symbol including the reference signal) (eg, / 3 times, 1/3). Thereby, in radio receiving apparatus 200D, the reception quality (SNR, SINR) of the reference signal can be improved.

[0220] Also, when the transmission power of the reference signal is increased for some subbands in all communication operation bands, as shown in Fig. 16, transmission is performed to both sides of the data signal with variable transmission power. A reference signal with increased power is transmitted so as to be arranged. With this arrangement, the channel estimation value of the reference signal whose transmission power is increased is used to internally interpolate the estimation result, so that the channel estimation value of the portion where the transmission power is reduced Estimate more quickly.

[0221] On the other hand, when a reference signal with increased transmission power is not arranged on both sides of a data signal with variable transmission power, for example, one side is a reference signal with increased transmission power and the other side is with transmission power. For a data signal sandwiched between reference signals that do not increase the signal, 1) calculate the channel estimation value by external interpolation based on the reference signal with increased transmission power, or 2) with the reference signal with increased transmission power Since the channel estimation value is calculated by internal interpolation between reference signals whose transmission power is not increased, the channel estimation accuracy by interpolation becomes insufficient. Specifically, in the case of 1), the estimation accuracy deteriorates due to external interpolation, and in the case of 2), the estimation accuracy deteriorates due to the influence of the noise component added to the reference signal whose transmission power is not increased. End up. In this case, the frequency direction interpolation unit 2082 in the channel estimation unit 208 may use the following method as the frequency direction interpolation processing. That is, a method may be used in which interpolation processing in the frequency direction is interpolated in band units in subband units including a reference signal with increased transmission power. As a result, the channel estimation value of the reference signal with increased transmission power can be used to interpolate the estimation result in subband units, so that the channel estimation accuracy can be improved.

[0222] When this embodiment is applied to a cellular system that configures a plurality of cells, it is necessary to consider inter-cell interference. In this case, by applying the following method, the effect of inter-cell interference can be reduced and the system throughput can be improved.

[0223] Specifically, a subband that increases the transmission power of the reference signal is shared between cells. Then, by changing the frequency subcarrier position where the reference signal is inserted in the subband or the temporal OFDM symbol position for each cell, the subcarrier position where the reference signal is transmitted between different cells or Make sure the times do not match. Alternatively, shift the frequency signal subcarrier insertion position of the reference signal and temporal OFDM symbol position for each cell, including the inside and outside of the subband, and then move the subband that increases the reference signal transmission power between cells. Make common.

[0224] Further, the data signal in the subband that increases the transmission power of the reference signal may be a low MCS modulation signal. By doing this, the frequency signal subcarrier insertion positions and temporal OFDM symbol positions of the reference signals differ between adjacent cells, reducing interference between reference signals with increased transmission power. I can do it. On the other hand, in the subband where the transmission power of the reference signal is increased even if SINR deteriorates due to an increase in the interference signal from other cells S, the interference S between the reference signal with increased transmission power and the data signal becomes a problem. By using a low MCS modulation signal as the data signal and transmitting a low MCS modulation signal that has a relatively small influence on the reception characteristics, tolerance against interference signals can be improved.

[0225] As another method, the following method can be considered. For example, subbands that increase the transmission power of the reference signal are arranged differently between cells. Alternatively, by making the subband that increases the transmission power of the reference signal common between cells and changing the frequency position (subcarrier) for inserting the reference signal within the subband for each cell, the reference signal can be changed. Make sure that the frequency positions transmitted do not match. Alternatively, the subband for increasing the transmission power of the reference signal is made common between cells after shifting the insertion position of the frequency signal subcarrier of the reference signal for each cell including inside and outside the subband. In the subband of the own cell that overlaps the subband that increases the transmission power of the reference signal in the adjacent cell, the data signal is a low MCS modulation signal.

[0226] By doing so, the insertion positions of the frequency subcarriers of the reference signal are different between adjacent cells, so that it is possible to reduce interference between reference signals with increased transmission power. it can. On the other hand, interference between the reference signal with higher transmission power and the data signal is a problem, but the subband increases the transmission power of the reference signal in the neighboring cell. In this case, by transmitting a low MCS modulated signal that has a relatively small influence on the reception characteristics, even if SINR deteriorates due to an increase in the interference signal from other cells, the tolerance to the interference signal can be improved. .

[0227] (Embodiment 5)

Embodiment 5 is for changing the position of a reference signal in an OFDM symbol.

[0228] FIG. 20 is a diagram illustrating a configuration example of a wireless transmission device 100D in the fifth embodiment.

Radio transmitting apparatus 100D in FIG. 20 is different from radio transmitting apparatus 100 in Embodiment 1 in FIG.

The transmission position control unit 130 is further included. The configuration of the other radio transmission apparatus is the same as that of the radio transmission apparatus in the first embodiment. Therefore, the following description will focus on the parts different from the first embodiment.

[0230] Transmission position control section 130 transmits position information (control signal) indicating the transmission position of the transmission reference signal to each reference signal multiplexing section for the OFDM symbol including the reference signal.

Output to 102 and 103.

[0231] The position information is associated in advance with the state of line fluctuation (see equations (3) and (4)) in radio receiving apparatus 200C (line fluctuation state detection unit 2081: see FIG. 21). Specifically, a predetermined value (which is set in advance) indicating the state of line fluctuation (see equations (3) and (4)) and the transmission position in the data sequence (for example, the Nf-th item in FIG. 2). Etc.)

Note that such association is performed using, for example, a table (memory) in the transmission position control unit 130. As a result, for example, the transmission position control unit 130 changes the channel fluctuation status (formula (Equation ( 3) and Equation (4)) are input, and when the state of the line fluctuation indicates a low speed (predetermined value set in advance), the transmission position control unit 130 Nf-th (Fig. 2) is output.

[0233] Alternatively, when the state of line fluctuation indicates medium-speed / high-speed (predetermined preset value), the transmission position control unit 130, for example, the i-th to Nf-th associated with medium-speed / high-speed (See Figure 2) Output position information indicating one of the following. [0234] Each reference signal multiplexing section 102, 103 receives position information from transmission position control section 130. Then, each of the reference signal multiplexing units 102 and 103 arranges and multiplexes the reference signal at the transmission position (change in time) indicated by the position information, and outputs the multiplexed signal to each of the OFDM modulation units 104 and 105. At this time, the position information is included in the control information in the data series.

[0235] For example, when a plurality of subframes are transmitted to a specific user terminal, each reference signal multiplexing unit transmits the reference signal included in the last subframe to be transmitted as the subframe. Set to the position of the OFDM symbol located at the end of the frame. The other multiplexed signal configurations are as shown in Fig. 2.

[0236] Each OFDM modulation section 104, 105 performs the same processing as in Embodiment 1 based on the output signal (multiplexed signal) of each corresponding reference signal multiplexing section 102, 103. After that, each OF DM modulation section 104, 105, each transmission section 106, 107, and each transmission antenna 108, 109 perform the same processing as in Embodiment 1, and the data series including the position information is transmitted to each transmission antenna 10. 8 and 109 are emitted into the air. As a result, radio receiving apparatus 200E receives a data sequence including position information.

[0237] FIG. 21 is a diagram illustrating a configuration example of a wireless reception device 200E in the fifth embodiment.

Radio reception apparatus 200E in FIG. 21 further includes position information extraction section 215 and feedback section 214 in radio reception apparatus 200 in Embodiment 1 in FIG. The configuration of the other radio reception apparatuses is the same as that of the radio transmission apparatus in the first embodiment. Therefore, the following description will focus on the differences from the first embodiment.

[0239] Position information extraction section 215 inputs a data sequence including position information from each of OFDM demodulation sections 205 and 206. Then, the position information extraction unit 215 extracts position information from the data series and outputs it to the frequency direction interpolation unit 2082.

[0240] Frequency direction interpolation section 2082 performs channel estimation for the subcarrier on which the reference signal is transmitted for the OFDM symbol including the reference signal indicated by the position information obtained from position information extraction section 215! Calculate the value h (j, G (s)). This formula is

nm jm

It is as Formula (2). Then, the frequency direction interpolation unit 2082 performs the redirection based on h (j, G (s)).

nm jm

Interpolation processing of the channel estimation value is performed in the frequency direction for the subcarriers not including the reference signal (see the processing described in Patent Document 1 for this interpolation processing). [0241] The feedback unit 214 acquires the detection result of the line fluctuation state detection unit 2081, and radiates the line fluctuation state (see equations (3) and (4)) indicated in the detection result into the air. . As a result, radio transmitting apparatus 100D (transmission position control unit 130: see FIG. 20) acquires the state of line fluctuation and controls the transmission position of the reference signal according to the state.

[0242] For example, radio transmission apparatus 100D (transmission position control section 130) includes a reference signal located at the end of a subframe as the channel fluctuation (see equations (3) and (4)) is smaller. The position information of the reference signal is set so that the OFDM symbol position is multiplexed in the time direction.

[0243] As described above, according to Embodiment 5, the transmission position control unit 130 of the wireless transmission device 100D performs line fluctuations from the wireless reception device 200E (feedback unit 214) (see Equations (3) and (4)). The position information of the reference signal is controlled according to For this reason, in addition to the effects of the first embodiment, the following effects are also obtained.

[0244] For example, when a plurality of subframes are transmitted to a specific user terminal, the position of the reference signal included in the subframe positioned at the end of the subframe to be transmitted is The last symbol is set to the OFDM symbol located in the direction of delay in the time direction (the other frames are as shown in Fig. 2).

[0245] Thus, as in Embodiment 1, the channel estimation value calculated based on the reception result of the OFDM symbol including the reference signal located at the end in the subframe, and the next sub Channel estimation of the OFDM symbol existing between the channel estimation value calculated based on the reception result of the OFDM symbol including the reference signal located at the beginning of the frame is obtained by internal interpolation.

[0246] In addition, for the OFDM symbol located at the end of a plurality of subframes for a specific user, the position of the reference signal is located at the end of the subframe (the position in the direction delayed in the time direction) OFDM symbol. Set to For this reason, the channel estimation characteristics can be prevented from degrading without obtaining the channel estimation value by outer interpolation, or by reducing the OFDM symbol period subject to outer interpolation). As a result, the power S can be improved to improve the reception quality.

[0247] Also, for example, the wireless transmission device 100D (transmission position control unit 130) is connected to the wireless reception device 200. E Obtain the line fluctuation (see Equations (3) and (4)) from the feedback unit 214, and the smaller the line fluctuation force S, the more the position of the OFDM symbol including the reference signal located at the end of the subframe. The position information is output so as to be delayed in the time direction.

[0248] As a result, when the fluctuation of the propagation path is relatively small, the OFDM symbol interval of the channel estimation value obtained by the inner interpolation is lengthened. That is, the symbol interval of the channel estimation value obtained by the outer interpolation is shortened. Therefore, it is possible to suppress the degradation of channel estimation accuracy. Therefore, the reception quality can be improved.

[0249] Japanese Patent Application No. 2006-324522 for Nov. 30 2006 and Japanese Patent Application No. 2007- No. 307757 for Nov. 2007 2007—All the disclosures in the description, drawings and abstract contained in 307757 are incorporated herein by reference. The

Industrial applicability

[0250] The radio reception apparatus, radio transmission apparatus, radio reception method, and radio transmission method of the present invention include, in particular, a radio reception apparatus, radio transmission apparatus, and radio reception in spatial multiplexing transmission in which channel estimation is performed using a reference signal. This method is useful for a method and a wireless transmission method.

Claims

The scope of the claims

[1] A receiving unit that receives a data sequence to which a reference signal for channel estimation of a spatial propagation path is added at a predetermined interval;

Based on the reference signal in the received data series, the fluctuation state of the propagation path is estimated, and based on the fluctuation state, a channel estimation value obtained by internal interpolation or external interpolation for the data series is output. A channel estimator to perform,

A demodulation / decoding processing unit that performs demodulation / decoding processing of the data series using the channel estimation value of either the inner interpolation or outer interpolation,

Including a wireless receiver.

[2] The channel estimation unit includes:

An interpolation unit that estimates a first channel estimation value by the interpolation, and

An outer interpolation unit that estimates a second channel estimation value by the outer interpolation,

An estimated value output unit that selects and outputs the first channel estimated value or the second channel estimated value based on the fluctuation state;

The wireless receiver according to claim 1.

[3] When the fluctuation state is smaller than a predetermined level! /, The estimated value output unit replaces the second channel estimated value with the first channel estimated value and outputs the result.

The wireless receiver according to claim 2.

4. The radio reception apparatus according to claim 1, wherein the channel estimation unit obtains the channel estimation value by performing interpolation processing independently for each phase and amplitude component of channel estimation obtained from the reference signal.

[5] The channel estimation unit includes:

A phase component separating unit for separating a phase component of channel estimation obtained from the reference signal;

An amplitude component separation unit for separating the amplitude component of channel estimation obtained from the reference signal;

An interpolation interpolating and synthesizing unit that synthesizes a first channel estimated value by the inner interpolation based on the phase component and the amplitude component; Based on the phase component and the amplitude component! /, A gutter interpolation synthesizer that synthesizes a second channel estimated value by the gutter interpolation;

An estimated value output unit that outputs the first channel estimated value or the second channel estimated value based on the fluctuation state;

The wireless receiver according to claim 4.

[6] The data sequence includes the reference signal and a data signal having transmission power lower than that of the reference signal! /

The wireless receiver according to claim 1.

[7] The predetermined interval is set to be variable according to the fluctuation state.

The wireless receiver according to claim 1.

[8] The data sequence is an OFDM signal, and the reference signal is inserted into the OFDM signal at a predetermined interval in the frequency axis direction and the time axis direction of the data sequence.

The wireless receiver according to claim 1.

[9] The transmission format of the OFDM signal includes a predetermined number of subcarriers and a predetermined number of OFs.

9. The radio reception apparatus according to claim 8, wherein the radio reception apparatus is a transmission format for transmitting individual data for a plurality of users by using subframes composed of DM symbols and transmitted continuously in time as a minimum unit.

[10] The interpolation interpolation synthesis unit

10. The radio reception apparatus according to claim 9, wherein channel estimation values of OFDM symbols existing between the reference signals are calculated by interpolation using the reference signals existing in different subframes.

[11] The predetermined interval is inserted by delaying the insertion position of the last OF DM symbol including the reference signal in the subframe in the time direction when the propagation path variation is small.

The wireless receiver according to claim 9.

[12] A radio transmission apparatus using a transmission format in which a subframe is composed of a plurality of OFDM symbols, A generating unit that generates a reference signal for channel estimation of a spatial propagation path, an allocating unit that allocates a data signal to subcarriers of an OFDM symbol, and a transmission power of the reference signal is larger than a transmission power of the data signal. A power adjusting unit for adjusting the transmission power of the reference signal;

The reference signals, the transmission power of which has been adjusted by the power adjustment unit, are arranged at a predetermined interval in the frequency axis direction of subcarriers of the OFDM symbol, or are arranged at a predetermined interval in the time axis direction A reference signal multiplexing unit;

A radio transmission apparatus comprising: a transmission unit that performs OFDM modulation on the data signal and the reference signal allocated to subcarriers of an OFDM symbol and transmits the obtained OFDM modulation signal.

13. The radio transmission apparatus according to claim 12, wherein the predetermined interval is set so as to vary according to propagation path fluctuation conditions.

[14] The reference signal multiplexing unit arranges the reference signal in a specific region in the frequency axis direction.

The wireless transmission device according to claim 12.

[15] The specific region in the frequency axis direction is a region assigned to each cell, and is different for each adjacent cell.

The wireless transmission device according to claim 14.

[16] The specific region in the frequency axis direction is a region assigned to each cell, and is common to adjacent cells.

The wireless transmission device according to claim 14.

17. The data signal having lower transmission power than the reference signal in a specific region in the frequency axis direction is configured to include a modulation signal having a binary or quaternary modulation number. Wireless transmitter.

[18] The transmission power of the data signal in the specific region in the frequency axis direction is lower than the transmission power of the data signal outside the specific region in the frequency axis direction.

The wireless transmission device according to claim 14.

[19] The transmission format is a format in which individual data is assigned to a plurality of users, with subframes transmitted continuously in time as a minimum unit.

The wireless transmission device according to claim 12.

[20] In the subframe, as the propagation path variation is smaller, the last reference signal arranged in the subframe is arranged in the OFDM symbol further away in the time axis direction.

The wireless transmission device according to claim 12.

[21] receiving a data sequence in which a reference signal for channel estimation of a spatial propagation path is added at a predetermined interval;

Demodulating the data sequence;

Based on the reference signal in the demodulated data sequence, the fluctuation state of the propagation path is estimated, and based on the fluctuation state, a channel estimation value obtained by internal interpolation or external interpolation for the data sequence is output. And steps to

Performing demodulation decoding processing of the data sequence using the channel estimation value of either the inner interpolation or outer interpolation,

A wireless reception method including:

[22] A radio transmission method using a transmission format in which a subframe is composed of a plurality of OFDM symbols,

Generating a reference signal for channel estimation of a spatial propagation path, assigning a data signal to subcarriers of an OFDM symbol,

Adjusting the transmission power of the reference signal such that the transmission power of the reference signal is larger than the transmission power of the data signal;

The reference signals, the transmission power of which has been adjusted by the power adjustment unit, are arranged at a predetermined interval in the frequency axis direction of subcarriers of the OFDM symbol, or are arranged at a predetermined interval in the time axis direction Steps,

Performing OFDM modulation on the data signal and the reference signal allocated to subcarriers of the OFDM symbol, and transmitting the obtained OFDM modulated signal; A wireless transmission method including: