JP3004638B1 - CDMA rake receiver and receiving method based on FFT - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a CDMA RAKE with FFT matched filter detection.
Provide a receiver. A received signal is processed in a frequency domain by a RAKE receiver. The RAKE receiver includes a pilot signal spreading code matched filter that removes the spreading code of the pilot signal, a data signal spreading code matched filter that removes the multiple access spreading code of the data signal, and a channel frequency response which is estimated before the decision is made. And a channel matched filter for combining data signals received from different paths. To increase the CDMA system capacity, the receiver uses interference cancellation. The mobile station downlink receiver estimates the interference of the pilot signal and subtracts the pilot interference from the received signal prior to data decision. The uplink receiver of the base station uses a multi-stage parallel interference cancellation process to cancel the multiple access interference of other users.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to code division multiple access (CDMA) communications, and more particularly to a RAKE receiver for CDMA signal interference cancellation.

[0002]

BACKGROUND OF THE INVENTION Wireless cellular communications around the world are moving toward CDMA systems in a third generation fashion. CDM
The A system is the most efficient use of limited radio spectrum. A CDMA system uses frequency division multiple access (FDMA) and time division multiple access (TDM).
It has been shown to ideally provide greater channel capacity gains than other access methods such as A).
In general, CDMA systems must use a RAKE receiver to combine paths of different received signal energy types to combat the effects of multipath attenuation.

A RAKE receiver implements a form of path diversity by collecting signal energy from different paths and optimally combining all multipath signals together. The path diversity feature provides a robust communication channel such that if one path is attenuated, communication is still possible over a path that is not attenuated. A CDMA RAKE receiver detects a multipath signal using either an adaptive filter method or a correlation method.

Conventionally, a RAKE receiver in a CDMA system despreads a multiple access code.
d) traverse to the spreading code adaptive filter and channel impulse response matching to
al) A filter was used. The spreading code matched filter is implemented in IF band using SAW filter or baseband using digital matched filter. The transverse filter used at baseband after code despreading is used to combine the different paths of the received signal energy type. A disadvantage of the SAW filter scheme is that the SAW filter cannot be easily integrated with the cross-baseband filter in the IC. As IC technology has advanced rapidly, digital spreading code matched filters have become the preferred choice. Although current IC technology offers significant computational power, it is still difficult to implement a rake receiver-based traversal filter in the IC as the length of the multiple access code increases.

[0005] An alternative to providing a RAKE receiver is to use a bank of correlators. Each correlator detects the received signal path separately. The number of correlators in a correlator bank is typically three or four. Therefore, this RAKE receiver structure needs to look for three or four stronger paths of the received signal. The above two RAKE receiver installations both require a sounding receiver to estimate the multipath channel impulse response. R
The AKE receiver needs to know the delay time, carrier phase shift, and main path strength. Furthermore, the installation of correlator banks requires extra computation to select the main path.

[0006] One way to increase the capacity of a CDMA system is to use, for example, Darius Divsalar, Mar.
vin K. IEEE MILCO by Simon
M, pp. 911-917, Im of October 1994
proved CDMA performance u
sing parallel Interferenc
e-cancellation ", the use of parallel interference cancellation (PIC). Even if the CDMA system capacity can be increased as described in this article, these receivers will have additional white Gaussian. Applicable only to the noise (AWGN) channel and not appropriate for the multipath attenuation channel.
atti Latva-aho, Markku Jun
tti, IEEE by Marku Heikkila
PIMRC, pp. 559-564, September 1997, "Parallel Interference C
anceleration Receiver for
DS-CDMA Systems in Fading
Channels ". However, these methods are compatible with time-domain signal processing methods for canceling multiple access interference, but are therefore complicated.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above limitations by providing a CDMA RAKE receiver that detects in the frequency domain by using a fast Fourier transform (FFT) matched filter. .

[0008]

SUMMARY OF THE INVENTION A receiver according to the present invention is implemented on both the downlink and the uplink when the received signal includes both data and pilot signals. The signal detection process is performed in the frequency domain for both the downlink and the uplink. The received signal is conveniently processed in the frequency domain by a spreading code matched filter and a channel matched filter before making a decision.

[0009] Spreading code matching filters are used to despread the spreading codes of the pilot and data signals. Channel matched filters are used to combine received signals from different paths before a decision is made. The channel matched filter includes a channel frequency response estimation unit used to calculate the coefficients of the channel matched filter.

After code despreading, the pilot signal is used to calculate a channel frequency response estimate. There are two types of methods for channel frequency response estimation. One uses the pilot signal after code despread to directly estimate the channel frequency response. The other converts the pilot signal into a channel impulse response estimate in the time domain after code despreading, and then provides the main path for channel impulse response estimation. After the main path has been provided, the channel impulse response estimate is converted to a channel frequency response estimate.

[0011] Interference cancellation techniques are used to increase CDMA system capacity. The downlink receiver estimates the pilot interference. The estimated pilot interference is then subtracted from the signal received in the frequency domain for pilot interference cancellation. In an uplink receiver, the method of the present invention is used in multi-stage parallel interference cancellation. Such multi-stage parallel interference cancellation is used in fast decay channels. This is because at each stage the interference signal estimate is obtained from both the channel frequency response estimate and the previous user's tentative decision at the previous stage.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS The above features and many advantages of the present invention will be readily understood and apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which: FIG. CDMA RAKE based on FFT
The receiver is a direct sequence spread spectrum system (DS)
SS). The transmitted signal of the DSSS includes a data signal and a pilot signal. The data signal is modulated by using binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) and multiplexed with a multiple access spreading code (code) (data signal spreading code). The pilot signal is multiplexed without being modulated by the pilot signal spreading code. The data signal and the pilot signal are combined into a transmission signal. This DSSS multiple access code and this DSS
The S pilot signal spreading code is a short code of equal length. That is, the cycle of the multiple access code or the cycle of the pilot signal spreading code is the same as the cycle of the transmission symbol.

FIGS. 1 and 2 show a downlink and uplink RAKE receiver system 20 provided in accordance with the present invention.
It is a schematic block diagram of 40. The downlink RAKE system 20 includes an antenna 22, an RF front end 24,
Analog / Digital (AD) converter 26, Fast Fourier Transform unit (FFT) 28, CDMA based on FFT
A rake receiver 30 is included. Uplink RAKE system 40 includes the same components as downlink RAKE system 20, plus an FFT-based CDMA RAKE receiver 50 for each user. The RF signal from the antenna enters the RF front ends 24, 44 and converts the RF signal to an equivalent baseband complex signal (complex envelope) having a real part I (t) and an imaginary part Q (t). Convert to Analog / digital (AD) converter 2
Reference numerals 6 and 46 denote I [n] and Q [n] at a sampling rate of 1 / Tc to generate I [n] and Q [n], respectively.
The (t) and Q (t) components are sampled, where Tc represents the chip period for the spreading code. Discrete time signal I
[N] and Q [n] consist of an equivalent baseband discrete-time complex signal r [n], where r [n] = I [n] + jQ
[N]. The signal r [n] is output from the FFT conversion unit 2
8, 48, which consists of N FFTs of r [n], denoted by the symbol R [k], where N is the length of the pilot and data signal spreading code (or its integral multiplex). . The N-point FFT calculation is synchronized with the received code time. Signal processing is performed in the frequency domain. The signal R [k] is a CDMA rake receiver 3 based on FFT.
0, 50.

FIG. 3 is a block diagram of a downlink rake receiver 30 having a selectively designated main path and data signal reconstruction. The downlink rake receiver 30 includes a pilot signal spreading code matched filter 62, a pilot interference canceling unit 64, a data signal spreading code matched filter 66, a channel matched filter 68, and a decision unit 70.

Signal R [k] is transferred from FFT unit 28 to pilot signal spreading code matched filter 62. The pilot signal spreading code matching filter 62 removes (despreads) the pilot signal spreading code, and includes a multiplier 72, a complex conjugate unit 74, and a unit 76 for storing the FFT of the pilot signal spreading code c _p [n]. The FFT of c _p [n] is C _p [k], which is stored in ROM in unit. Complex conjugate unit 74 computes the complex conjugate of C _p [k] to generate the C _p ^* [k]. R [k] generated by multiplier 72
And _Cp ^* [k] remove the pilot signal spreading code to generate R [k] _Cp ^* [k].

R [k] is also forwarded to pilot interference cancellation unit 64. The pilot interference cancellation unit 64 includes a pilot signal estimation unit 80 and an adder 8.
2 is included. The pilot signal estimating unit 80 is a pilot interference signal.

[0017]

[Outside 1]

The details are shown in FIGS. Summer 82 subtracts from the R [k] signal to cancel the pilot interference to generate R1 [k].

[0019]

[Outside 2]

Is subtracted. The data signal reconstruction portion 84 is coupled to a pilot estimation unit 80 to remove the effects of the data signal, which is shown in more detail in FIG. Data signal spreading code matched filter 66 operates similarly to pilot signal spreading code matched filter 62, except that it removes (despreads) the data signal spreading code from R1 [k] received from pilot interference cancellation unit 64. Data signal spreading code matching filter 6
6 includes a multiplier 88, a complex conjugate unit 90, and a storage unit 92. The storage unit 92 stores the FFT of the data signal spreading code c _p [n], which is stored in the unit RO
M. The complex conjugate unit 90 is C _d ^* [k]
Compute the complex conjugate of C _d [k] to produce Multiplier 88 generates R [k] to generate R [k] _Cp ^* [k].
And C _p ^* [k].

A channel matched filter 68 combines the data signal power received from the different paths before a decision is made. The channel matched filter 68 includes a channel frequency response estimation unit 94, a multiplier 96, and a block addition unit 98. The channel frequency response estimation unit 94 includes a complex conjugate unit 100, a delay unit 102, a block-by-block averaging unit 104, and an optional main path assignment unit 106. Signal R [k] C _p from pilot signal spreading code matched filter 62
^* [K] is forwarded to the channel frequency response estimation unit 94. R [k] C _p ^* [k] is the delay unit 102
Is delayed by one cycle of the spreading code. The averaging unit 104 then estimates the channel frequency

[0022]

[Outside 3]

Calculate a weighted block-by-block average of a delayed version of R [k] C _p ^* [k] to generate the block period, where the block period is one period of the spreading code. The complex conjugate unit 100

[0024]

[Outside 4]

To generate

[0026]

[Outside 5]

Calculate the complex conjugate of The multiplier 96

[0028]

[Outside 6]

R1 [k] C _d * [k] from the data signal spreading code matched filter 66 to generate

[0030]

[Outside 7]

Is multiplied by Block addition unit 98
Is

[0032]

[Outside 8]

In one cycle of the spreading code indicated by

[0034]

[Outside 9]

Calculate the sum of The decision unit 70 outputs from the channel matched filter 68

[0036]

[Outside 10]

Then, data is determined. If the data modulation of the data signal is BPSK, the decision unit is

[0038]

[Outside 11]

It is determined whether the real part is 0 or more or less. If the data modulation of the data signal is QPSK, the decision unit is

[0040]

[Outside 12]

The real part of

[0042]

[Outside 13]

It is determined whether or not the imaginary part is greater than or equal to zero. FIG.
Is an alternative downlink R with optional primary path designation
FIG. 2 shows a block diagram of an AKE receiver 110. In this embodiment, pilot signal estimation unit 80 is also coupled to multiplier 72. When the pilot signal estimation unit 80 is combined in this way, the delay unit 102 and the averaging unit 104
No longer needed. This is because the pilot signal estimation unit 80 already includes these parts, as described below.

FIG. 5 is a block diagram of an uplink rake receiver with selective main path designation. An uplink RAKE receiver as shown in FIG. 2 can simultaneously detect L users. Each user has an uplink CDMA rake receiver 50 of the same type. That is, the L users receive the FFT unit 48 from the antenna 42.
Up to L [k] to detect L users, and use L uplink CDMA receivers 5 to detect L users.
0 is transferred. Uplink receiver 50 is implemented using a multi-stage parallel interference cancellation method to increase system capacity. The multi-stage interference cancellation method performs an iterative process.
At each stage, the reconstructed interference signal generated by the other user's uplink receiver 50 at a stage prior to operation is subtracted from R [k] for each user. Thus, the signal after the interference cancellation is used for data detection. After data detection, the reconstructed interference signal is generated at each user's uplink receiver and provided to the other user's uplink receiver for the next stage detection process.

As shown in FIG. 5, the uplink receiver 50 includes a multi-user interference canceling unit 110, a data signal spreading code matched filter 112, a channel matched filter 114, a determining unit 116, an interference signal estimating unit 118, a pilot signal spreading code. A matched filter 120 is included. Without loss of generality, the operation of the uplink receiver for the first user, user 1, or n = 1 is described below.

Multi-user interference cancellation unit 110
From the signal R [k] by using a first adder 122 and a second adder 124 to generate the remaining signal after multi-user interference cancellation indicated by the code R1 _i [k]. Remove the reconstructed interfering signals from the users. The code i in R1 _i [k] indicates the ith stage of data detection for the currently received symbol. The first adder 122

[0047]

[Outside 14]

Combining the reconstructed interference signals from other users to generate the entire reconstructed interference signal represented by

[0049]

[Outside 15]

Is the reconstructed interference signal generated by the j-th user's uplink receiver at the i-1 stage of data detection. Furthermore, all of the reconstructed interference signals (In _{j, 0} [k] = 0, j = 1 ... L) are set to 0 in the first stage of data determination (i = 1). After collecting the reconstructed interference signal generated from the other user's uplink receiver, the second adder 124 generates the signal R1
_the signal from signal R [k] to generate _i [k]

[0051]

[Outside 16]

Is subtracted. The signal R1 _i [k] is represented by the following equation:

[0053]

[Outside 17]

Data detection i of currently received symbol
In the third stage, R1 _i [k] is transferred through data signal spreading code matched filter 112 and channel matched filter 114. Data signal spreading code matching filter 1
12 removes (despreads) the data signal spreading code to generate R1 _i [k] C _d ^* [k]. The data signal spreading code matched filter 112 is described in the detailed description above with respect to FIG.

Data signal spreading code matching filter 112
The signal R1 _i [k] C _d ^* [k] is transferred to the channel matching filter 114. When i = M, M is the total number of stages, switch 126 is closed, thereby causing pilot signal spreading code matched filter 120 to switch to R1.
Generate _M [k] _Cp ^* [k] and allow it to be sent to the channel matched filter 113. The channel matched filter 114 includes a channel frequency response estimation unit 128, a multiplier 130, and a block addition unit 132. The channel frequency response estimation unit 128 includes a delay unit 136, an averaging unit 138, a selective main path assignment unit 140, and a complex conjugate unit 142. Generated by the averaging unit 138 from the output of the delay unit 136

[0056]

[Outside 18]

Is sent to the complex conjugate unit 142. i
= M, pilot signal spreading code matched filter 1
The output of 20 is sent to delay unit 136. Delay unit 136 delays the received signal until the start of the next symbol processing. The complex conjugate unit 142

[0058]

[Outside 19]

To generate

[0060]

[Outside 20]

The complex conjugate of is calculated. The multiplier 130

[0062]

[Outside 21]

To form R1 _i [k] C
_d ^* [k] from the complex conjugate unit 142

[0064]

[Outside 22]

Is multiplied. Block addition unit 1 again
32 is the code

[0066]

[Outside 23]

In one cycle of the spreading code indicated by

[0068]

[Outside 24]

Is calculated. The decision unit 116 receives the block sum from the channel matched filter 114 and makes a data decision. Data modulation of data signal is BP
In the case of SK, the decision unit is

[0070]

[Outside 25]

Determine whether the real part is greater than or less than 0 to generate a tentative decision d _{1, i} for the currently received symbol. If the data modulation of the data signal is QPSK, the decision unit is

[0072]

[Outside 26]

The real part of

[0074]

[Outside 27]

Determine if the imaginary part of the symbol is greater than or less than 0 to generate a tentative decision d _{1, i} of the currently received symbol. In the example of QPSK, the provisional decision d _{1, i} generated is a complex signal. In the ith step of determining data for the currently received symbol, the signal from channel frequency response estimation unit 128

[0076]

[Outside 28]

The tentative decision d _{1, i} of the current symbol from the decision unit 116 is transferred to an interference signal estimation unit 118 which generates a reconstructed interference signal. Interference signal estimation unit 118 is used to reconstruct the user's transmitted symbols, which is User 1's multiple access interference used by other users' uplink receivers. User 1's reconstructed interference signal is forwarded to another user's uplink receiver for multi-user interference cancellation. Interference signal estimation unit 11
8 includes a first multiplier 150, an adder 152, a second multiplier 154, and a normalization unit 155. First multiplier 1
50 is a data modulated data signal spreading code C
The FFT of the data signal spreading code C _d [k] is multiplied by the signal d _{1, i} from the decision unit 116 to generate _d [k] d _{1, i} . The adder 152 calculates C _p [k] + C
The FFT of the pilot signal spreading code is combined with the signal C _d [k] d _{1, i} to generate _d [k] · d _{1, i} . The second multiplier 154

[0078]

[Outside 29]

To generate C _p from adder 152
[K] + C _d [k] · d _{1, i}

[0080]

[Outside 30]

To Channel frequency response estimation

[0082]

[Outside 31]

Since is weighted by | C _p [k] | ² by the pilot signal spreading code matching filter 120, the normalization unit 155 is used to remove the weighting coefficient | C _p [k] | ² . Normalization unit 155 is |
Normalize the output of the second multiplier 154 to generate a reconstructed interference signal indicated by the code In _{1, i} [k] by C _p [k] | ² . The signal In _{1, i} [k] is represented by the following equation:

[0084]

[Outside 32]

The uplink RAKE receiver 50 performs M stages of data detection for each received symbol, ie, after M data detections, the uplink receiver repeats the next symbol for data detection. Process. At the M-th stage of the data detection of the received symbol of the present invention (at the end of the data detection of the received symbol of the present invention), the switch 126 is closed and the signal R1, _M [k] is output from the multi-user interference canceling unit 110 by the The signal is transmitted to the code spreading code matching filter 120. The pilot signal spreading code matching filter 120 removes (despreads) the pilot signal spreading code, and outputs R _M [k] C _p ^* [k].
Generate a signal. The R _M [k] C _p ^* [k] signal is converted to a channel matched filter 1 for channel frequency response estimation.
14 to the channel frequency response estimation unit 128.

FIG. 6 is a flow chart of data detection not specified by the user of the uplink receiver shown in FIG. 5 (for example, n users). In step 160, the uplink receiver 50 is initialized to i = 0 for each received symbol, and sets all of the interference signals reconstructed from other users to 0 (In _{j, 0} [k]). = 0, j
= 1. . . L). In step 162, the index i of the data detection step is incremented by one, as shown by the equation i = i + 1. In step 164, the receiver 50 receives the reconstructed interference signal In _{j, i-1} [k] generated from another user. In the first stage of data detection, uplink receivers of n users do not receive reconstructed interference signals (In _{j, 0} [k]) from other users. The n users' uplink receivers reconstruct the interfering signal (In _{j, 0) in} the first stage of data detection of the current received symbol.
[K]) is set to 0. After the first stage of data detection of the currently received symbol, the n users' uplink receivers receive reconstructed interference signals from other users generated in the previous stage of data detection. . In step 166, the reconstructed interference signals from other users are subtracted from R [k] as shown in the following equation:

[0087]

[Outside 33]

At step 168, R1 _i [k] is set to R1
Multiplied by the complex conjugate of the FFT of the data signal spreading code to generate _i [k] C _d ^* [k]. In step 170, the output of step 168 is

[0089]

[Outside 34]

Is matched to the channel frequency response estimate to generate In step 172, a tentative decision d _{n, i} is formed for the current received symbol. Step 174
If the i-th data detection stage is equal to the final stage of the data decision M, the tentative decision is dn _{, M.} Otherwise, at step 176, the reconstructed interference signals of the n users at the i-th stage of data detection are calculated and then sent to the other user's uplink receiver. Where the reconstructed interference signals of n users are

[0091]

[Outside 35]

Is represented by The data detection process then loops back to step 162, where the code i is incremented by one for the next step of data detection of the currently received symbol. FIG. 7 shows a pilot signal estimation unit 180 for low speed users. The received R [k] signal is delayed by a one-cycle delay unit 182 of the spreading code.
A simple block-by-block average of R [k] estimates pilot interference since the pilot signal is fixed because it is unmodulated. Averaging unit 184 is pilot interference

[0093]

[Outside 36]

In order to generate the above, the average of each weighted block of the R [k] signal is calculated. Here, the block cycle is one cycle of the spreading code. This setting is effective for low speed systems. This is because the averaging is performed over a long period of time. FIG. 8 shows a pilot signal estimation unit 186 for a high speed user. Adder 188 is included between the delay unit and the averaging unit. The adder 188 calculates the data signal component from the delayed signal.

[0095]

[Outside 37]

Is removed. The data signal components are reconstructed by the data signal reconstruction unit 84 described in FIG. Because the average length of the signal is not large enough for high speed users, the reconstructed data signal components must be removed for pilot signal estimation to avoid "data signal cancellation". As shown in FIG. 9, the data signal reconstruction unit 84 includes first and second multipliers 190 and 192 and a normalization unit 194 for reconstructing a data signal using a decision feedback method. The first multiplier 190 is a data signal spreading code d · C _d [k].
Is multiplied by the FFT of the data signal spreading code C _d [k] with the data detection output of the previous received symbol d to generate The second multiplier 192 provides a reconstructed data signal component of a previously received symbol.

[0097]

[Outside 38]

The channel frequency response estimate normalized by d · C _d [k] by the normalization unit 194 to generate

[0099]

[Outside 39]

Is multiplied by As shown in FIG. 10, the main path designation unit 106 performs an inverse fast Fourier transform (IFF).
T) unit 200, peak search unit 202, selection unit 204, and FFT unit 206. IFF
T unit 200 includes pilot signal spreading code matched filter 62 or averaging unit 104 or averaging unit 13
8 (see FIGS. 4, 3 and 5, respectively) and calculate the IFFT, thereby obtaining the code

[0101]

[Outside 40]

A channel impulse response estimation is generated as shown in FIG. The peak search unit 202 is from the IFFT unit 200

[0103]

[Outside 41]

[0104]

[0105]

[Outside 42]

The peak amplitude is searched or determined. Next, the selected path unit 204

[0107]

[Outside 43]

Select the signal with the higher amplitude from and discard the remaining signals with the lower amplitude by setting the low amplitude signal to zero. For example, high amplitude signals are typically

[0109]

[Outside 44]

A low amplitude signal is a signal having a relatively small amplitude, while a signal having an amplitude 10 dB greater than the peak value of the signal. High amplitude signal selection is a modulated channel impulse response estimation signal containing only the signal on the main path

[0111]

[Outside 45]

Is generated. FFT unit 206 performs channel frequency response estimation

[0113]

[Outside 46]

From the selection unit 204 to generate

[0115]

[Outside 47]

Calculate the FFT transform of

[0117]

[Outside 48]

Provides the coefficients of the channel matched filters 68,114. The primary path assignment unit 106 is not required, but provides more reliable channel estimation. While specific embodiments have been described and described, it will be obvious to those skilled in the art that various changes can be made without departing from the spirit of the invention, which is limited only by the claims.
For example, FIGS. 5 and 6 show user 1's uplink receiver, but a similar process can be repeated for other users' data detection. Thus, while preferred embodiments of the invention have been shown and described, various modifications can be made without departing from the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a CDMA rake system for a downlink receiver.

FIG. 2 is a schematic block diagram of a CDMA rake system for an uplink receiver.

FIG. 3 is a schematic block diagram of a CDMA rake system for a downlink receiver having a selectively designated main path and data signal reconstruction.

FIG. 4 is a schematic block diagram of an alternative downlink rake receiver.

FIG. 5 is a schematic block diagram of a CDMA RAKE system for an uplink receiver having a selectively designated main path.

6 is an uplink RAK for the receiver shown in FIG.
It is a data detection flowchart of E receiver.

FIG. 7 illustrates different pilot signal estimations made at the downlink rake receiver shown in FIG. 3;

FIG. 8 illustrates different pilot signal estimations made at the downlink rake receiver shown in FIG.

FIG. 9 is a diagram illustrating data signal reconstruction selectively performed by the downlink rake receiver illustrated in FIGS.

FIG. 10 is a block diagram of designation of a main path selectively performed by the RAKE receiver shown in FIGS. 3, 4, and 5;

[Explanation of symbols]

20, 40 RAKE receiver system 22 Antenna 24 RF front end 26 AD converter 28 FFT unit 30, 50 CDMA RAKE receiver 24, 44 RF front end 26, 46 AD converter 28.48 FFT conversion unit 62 Pilot signal spreading code Matched filter 64 pilot interference canceling unit 66 data signal spreading code matched filter 68 channel matched filter 70 decision unit 72 multiplier 74 complex conjugate unit 76 storage unit 80 pilot signal estimation unit 82 adder 84 data signal reconstruction part 88 multiplier 90 complex Conjugate unit 92 Storage unit 94 Channel frequency response estimation unit 96 Multiplier 98 Block addition unit 100 Complex conjugate unit 102 Delay unit 10 Averaging unit 106 Main path designation unit 110 Multiple user interference cancellation unit 112, Data signal spreading code matched filter 114 Channel matched filter 116 Decision unit 118 Interference signal estimation unit 120 Pilot signal spreading code matched filter 122 First adder 124 Second Adder 128 channel frequency response estimation unit 130 multiplier 132 block addition unit 136 delay unit 138 averaging unit 140 selective main path designation unit 142 complex conjugate unit 150 first multiplier 152 adder 154 second multiplier 155 normalization Unit 180 Pilot signal estimation unit 182 One-cycle delay unit 184 Average unit 186 Pilot signal estimation unit 188 Adder 190, 192 When the second multiplier 194 normalization unit 200 IFFT unit 200 202 peak search unit 204 selection unit 206 FFT unit I (t) the real part Q (t) imaginary part c _p [n] pilot signal spreading code I [n], Q [n] discrete time signal R [k] received signal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 5-122194 (JP, A) JP 5-75573 (JP, A) JP 9-130300 (JP, A) JP 10-A 41856 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04J 13/02

Claims (32)

(57) [Claims] 1. A pilot interference cancellation unit for subtracting pilot signal interference from an FFT of a received baseband signal; a data signal spreading code matched filter for removing a data signal spreading code from an output of the pilot interference cancellation unit; Baseband signal FF
A pilot signal spreading code matching filter for removing a pilot signal spreading code from T; a channel frequency response estimation based on an output of the pilot signal spreading code matching filter, and a complex of an output of the data signal spreading code matching filter and the channel frequency response estimation A channel matched filter for generating a product with the conjugate and finally calculating a block sum of the product within one period of the spreading code; determining a data value from the block sum generated based on the previously selected modulation type A downlink receiver comprising a decision unit to perform. 2. A pilot interference cancellation unit comprising: a pilot signal estimation unit for estimating a pilot signal component from an FFT of a received baseband signal; and a pilot signal component for subtracting the estimated pilot signal component from the FFT of the received baseband signal. The downlink receiver according to claim 1, comprising a combiner. 3. The pilot signal estimating unit comprises: an FFT of a baseband signal received for one period of a spreading code;
The downlink receiver according to claim 2, comprising: a delay unit for delaying the received baseband signal; and an averaging unit for averaging the weighted blocks of the delayed FFT of the received baseband signal. 4. A pilot signal estimating unit comprising: an FFT of a baseband signal received for one period of a spreading code;
A data unit reconstructing a data signal component based on the concept of data decision feedback; and subtracting the reconstructed data signal component from the delayed FFT of the received baseband signal. 3. The downlink receiver according to claim 2, comprising: a pilot signal estimation combiner; and an averaging unit for averaging the weighted block-by-block average of the result of the pilot signal estimation combiner. 5. The data signal spreading code matched filter comprises:
A storage unit for storing an FFT of the data signal spreading code; a complex conjugate unit for calculating a complex conjugate of the FFT of the data signal spreading code; and a multiplier for multiplying an output of the pilot interference canceling unit by an output of the complex conjugate unit. The downlink receiver according to claim 1. 6. The data signal spreading code matched filter comprises:
A storage unit for storing an FFT of the data signal spreading code; a complex conjugate unit for calculating a complex conjugate of the FFT of the data signal spreading code; a multiplier for multiplying the FFT of the received baseband signal by an output of the complex conjugate unit; The downlink receiver according to claim 1, comprising: 7. The channel matched filter comprises a channel frequency response estimation unit for generating a channel frequency response estimate based on the output of the pilot signal spreading code matched filter, the channel frequency response estimating unit comprising: an output of the pilot signal spreading code matched filter. A delay unit that delays by one period of the spreading code; an averaging unit that averages the delayed output of the pilot signal spreading code matched filter on a weighted block basis; and a delayed output of the pilot signal spreading code matched filter. And a complex conjugate unit for calculating an average complex conjugate of each weighted block. 8. The channel frequency response estimating unit comprises a main path specifying unit for specifying a main path, the unit for specifying a main path being: a pilot signal spreading code matched filter delayed to generate a channel impulse response estimate. IFFT calculating the inverse fast Fourier transform (IFFT) of the weighted block-wise average of the output
A search unit for searching for an amplitude peak from the IFFT; a selection unit for generating a channel impulse response estimate for a specified main path based on the found peak amplitude; a channel impulse response for the specified main path generated The downlink receiver according to claim 7, comprising an FFT unit that calculates an estimated FFT. 9. The channel matched filter further comprises: a multiplier for multiplying the output of the data signal spreading code matched filter by the channel frequency response estimate; and an adder for calculating a block sum of the multiplier output within one period of the spreading code. The downlink receiver according to claim 7, comprising: 10. Subtracting pilot signal interference from an FFT of a received baseband signal; removing a data signal spreading code from an FFT of a received baseband signal after subtraction of the pilot signal interference; Generating a channel frequency response estimate from the FFT of the received baseband signal after the pilot signal spreading code removal; and a channel frequency response estimation after the pilot signal interference subtraction and data signal spreading code removal. Generating the product of the complex conjugate of FFT and the received base signal; calculating the block sum of the product within the period of the spreading code; determining the data value from the sum value based on the previously selected modulation type Downlink reception method consisting of each step. 11. FFT of a received baseband signal
Subtracting the pilot signal interference from: estimating the pilot signal component from the FFT of the received baseband signal;
2. The method of claim 1, further comprising subtracting the estimated pilot signal component from the FFT of the received baseband signal.
0. The method of claim 0. 12. A pilot signal component is estimated by: FFT of a baseband signal received for one period of a spreading code.
And delay F of the received baseband signal.
The method of claim 11, further comprising the steps of averaging the FT weighted block-by-block. 13. Estimating a pilot signal component: reconstructing a data signal component from a previously received symbol; FF of a baseband signal received for one period of the spreading code.
Delaying T; subtracting the reconstructed data signal component from the delayed FFT of the received baseband signal; delayed FFT of the received baseband signal after subtraction of the reconstructed data signal component 12. The method of claim 11, further comprising the step of taking a weighted block-by-block average of: 14. Removing a data signal spreading code from an FFT of a received baseband signal after subtraction of pilot signal interference: generating an FFT of the data signal spreading code;
The method of claim 10, further comprising calculating a complex conjugate of an FFT of the data signal spreading code; and multiplying the calculated complex conjugate of the FFT of the received baseband signal after pilot signal interference subtraction. 15. An FFT of a received baseband signal.
Removal of the pilot signal spreading code from: generating the FFT of the pilot signal spreading code; calculating the complex conjugate of the FFT of the pilot signal spreading code; multiplying the FFT of the received baseband signal by the calculated complex conjugate The method of claim 10, further comprising a step. 16. Estimating the channel frequency response: delaying the FFT of the baseband signal received after removing the pilot signal spreading code by one period of the spreading code; the base received after removing the pilot signal spreading code. 11. The method of claim 10, further comprising: taking a weighted block-by-block average of the delayed FFT of the band signal; and calculating a complex conjugate of the weighted block. 17. The channel frequency response estimate comprises a dominant path designation, the dominant path designation of which is: delay of the baseband signal received after removing the pilot signal spreading code to generate the channel impulse response estimate. Calculate the weighted block-wise average inverse Fourier transform (IFFT) of the weighted FFT; search for the amplitude peak from the calculated IFFT; estimate the specified main path channel impulse response based on the found peak amplitude 17. The method of claim 16, further comprising: calculating an FFT of the generated channel impulse response estimate of the designated main path. 18. The sum of the product of the complex conjugate of the estimate of the channel frequency response and the FFT of the received baseband signal within one period of the spreading code after subtracting the pilot signal interference and removing the data signal spreading code is: Multiplying the complex conjugate of the channel frequency response estimate by the FFT of the received baseband signal after subtracting the pilot signal and removing the data signal spreading code; calculating the block sum of the product within one period of the spreading code 17. The method of claim 16, further comprising: 19. A pilot interference cancellation unit for subtracting pilot signal interference from an FFT of a received baseband signal; a data signal spreading code matched filter for removing a data signal spreading code from an output of the pilot interference cancellation unit; A pilot signal spreading code matched filter for removing a pilot signal spreading code of a pilot signal component estimated directly from the cancellation unit; a product of an output of the data signal spreading code matched filter and a complex conjugate of the channel frequency response estimation; A downlink filter comprising: a channel matched filter for calculating a block sum of the product within one period of the spreading code; and a decision unit for determining a data value from the block sum generated based on the previously selected modulation type. Machine. 20. The pilot interference cancellation unit:
20. The down converter according to claim 19, comprising: a pilot signal estimation unit for estimating a pilot signal component from the FFT of the received baseband signal; and a combiner for subtracting the estimated pilot signal component from the FFT of the received baseband signal. Link receiver. 21. A pilot signal estimating unit comprising: an FF of a baseband signal received for one period of a spreading code;
21. The downlink receiver according to claim 20, comprising: a delay unit for delaying T; and an averaging unit for averaging a weighted block-by-block of the delayed FFT of the received baseband signal. 22. A pilot signal estimating unit comprising: an FF of a baseband signal received for one period of a spreading code;
A delay unit for delaying T; a data signal reconstruction unit for reconstructing the data signal component based on the decision feedback; a delayed FF of the received baseband signal
21. The downlink reception according to claim 20, comprising: a pilot signal estimation combiner for subtracting the reconstructed data signal component from T; and an averaging unit for averaging the weighted block-by-block average of the result of the pilot signal estimation combiner. Machine. 23. A channel matched filter comprising: a complex conjugate unit for calculating a complex conjugate of a channel frequency response estimate; a multiplier for multiplying an output of the data signal spreading code matched filter by an output of the complex conjugate unit; 20. The downlink receiver according to claim 19, further comprising: an adder for performing a block sum of a product of the multipliers within a period. 24. The channel matched filter further includes a principal path designating unit that designates a dominant path, the unit that designates a dominant path comprising: an inverse fast Fourier transform of the channel frequency response estimate to generate a channel impulse response estimate. IFFT unit for calculating IFFT); IF
A search unit for searching for an amplitude peak from the FT; a selection unit for generating a channel impulse response estimate of a specified main path based on the found peak amplitude; and an FFT of the generated channel impulse response estimate of a specified main path. 3. An FFT unit for calculating
3. The downlink receiver according to 3. 25. The FF of the received baseband signal
A multi-user interference cancellation unit for subtracting the estimated interference signal from T; a data signal spreading code matched filter for removing the data signal spreading code from the FFT of the baseband signal received after the estimated interference signal subtraction; A pilot signal spreading code matched filter for removing the pilot signal spreading code from the FFT of the received baseband signal after the received interference subtraction; and closing when reaching the last stage data detection of the currently received symbol; A switch connected between the user interference canceling unit and the pilot signal spreading code matched filter; generating a channel frequency response estimate based on the output of the pilot signal spreading code matched filter; Complex conjugate of response estimate And a channel matched filter for generating a block sum of the product within one period of the spreading code; and a provisional data value and a final data value from the block sum generated based on the previously selected modulation type. A determination unit for determining a data value; a channel frequency response estimation;
An uplink receiver comprising: an FFT of pilot and data signal spreading codes; and an interference signal estimation unit that generates an estimated interference signal for interference cancellation by other users based on the determined provisional data values. 26. A multi-user interference cancellation unit comprising: a first adder for adding an estimated interference signal from another receiver; and an estimated interference added from an FFT of the received baseband signal. The uplink receiver according to claim 25, further comprising a second adder for subtracting a signal. 27. A data signal spreading code matched filter comprising: a storage unit for storing an FFT of the data signal spreading code; a complex conjugate unit for calculating a complex conjugate of the FFT of the data signal spreading code; and an output of the multi-user interference cancellation unit. 26. The uplink receiver according to claim 25, further comprising: a multiplier for multiplying the output of the complex conjugate unit by a multiplier. 28. A data signal spreading code matching filter, comprising: a storage unit for storing an FFT of the data signal spreading code; a complex conjugate unit for calculating a complex conjugate of the FFT of the data signal spreading code; 26. The uplink receiver according to claim 25, further comprising a multiplier for multiplying an output of the user interference cancellation by an output of a complex conjugate of an FFT of the pilot signal spreading code. 29. The channel matched filter comprises a channel frequency response estimation unit for generating a channel frequency response estimate based on the output of the pilot signal spreading code matched filter, the channel frequency response estimating unit comprising: an output of the pilot signal spreading code matched filter. A delay unit that delays by one period of the spreading code; an averaging unit that averages the delayed output of the pilot signal spreading code matched filter on a weighted block basis; and a delayed output of the pilot signal spreading code matched filter. 26. The uplink receiver according to claim 25, further comprising: a complex conjugate unit that calculates an average complex conjugate of each weighted block. 30. The channel frequency response estimating unit comprises a main path specifying unit for specifying a main path, the unit for specifying a main path being: a pilot signal spreading code matched filter delayed to generate a channel impulse response estimate. Calculates the inverse fast Fourier transform (IFFT) of the weighted per-block average of the output
A T unit; a search unit for searching for an IFFT amplitude peak; a selection unit for generating a channel impulse response estimate of a specified main path based on the found peak amplitude; and a generated channel impulse of a specified main path. The uplink receiver according to claim 29, further comprising: an FFT unit that calculates an FFT of the response estimation. 31. The channel matched filter further comprises: a multiplier for multiplying the output of the data signal spreading code matched filter by a complex conjugate of the channel frequency response estimate; and calculating a block sum of the output of the multiplier within one period of the spreading code. 30. The uplink receiver according to claim 29, comprising an adder that performs the operation. 32. The interference signal estimation unit: a first multiplier for multiplying the FFT of the data signal spreading code signal by a provisional data decision; and adding the FFT of the pilot signal spreading code to the output of the first multiplier. An adder; a second multiplier that multiplies the output of the adder by the channel frequency response estimate; and a normalization unit that normalizes the output of the second multiplier by the square norm of the FFT of the pilot signal spreading code. 26. The uplink receiver according to claim 25.