JP2003101441A - Rake receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a RAKE receiver of small circuit scale. SOLUTION: In a communication system adopting code division multiple access (CDMA) to use pilot signals for synchronism capture/hold and propagation path estimation, the RAKE receiver is composed of a plurality of inversion diffusion means equipped witan inverse diffusion means for information and an inverse diffusion means for pilot, a propagation path estimating means for estimating the state of a propagation path from the output of the inverse diffusion means for pilot, a detection means for detecting an information signal by using the output of the inverse diffusion means for information and the output of the propagation path estimating means and a compositing means for compositing the outputs of the detection means, and each of a mobile station device and a base station device is provided with this RAKE receiver.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rake receiver applied to a CDMA communication system.

[0002]

2. Description of the Related Art Transmitted radio waves are blocked by obstacles (for example, mountains, buildings,
When a multipath propagation path is formed by being reflected by a vehicle, etc., the demodulation result of each propagation path is combined and combined at the receiver side to improve the signal power to noise power ratio and improve communication quality. Be improved. Such a receiver is called a rake receiver.

FIG. 2 shows the configuration of a conventional rake receiver. In FIG. 2, 201 is a first demodulation means, which is an information despreading means 20 for inputting a baseband signal and despreading an information signal.
2, a pilot despreading means 203 for despreading a pilot signal, a propagation path estimating means 204 for estimating a propagation path state from a pilot despreading signal, and a detecting means 205 for detecting an information signal from propagation path estimation information. including. Reference numeral 206 denotes a k-th demodulation means, which is an information despreading means 207 for despreading an information signal by inputting a baseband signal, a pilot despreading means 208 for despreading a pilot signal, and a propagation from a pilot despread signal. Propagation path estimation means 20 for estimating the state of the path
9 and detection means 2 for detecting the information signal from the propagation path estimation information
Including 10. Reference numeral 211 is a combining means for combining the phases of the detection results of the information output from the demodulation means 201 to the demodulation means 206.

Next, the operating principle of the rake receiver will be described.

As shown in FIG. 3, in a mobile communication environment, a radio wave transmitted from a transmitter is reflected by a natural environment or an artificial object and reaches a receiver via a plurality of different propagation paths.
That is, a plurality of radio waves having different propagation delay times arrive at the receiver. If there are k propagation paths,
The transmission signal of the transmitter is S (t) and the reception signal of the receiver is r (t)
Then, r (t) = S (t-τ1) + S (t-τ2) + ... + S (t-τk) + n. Here, τ1 is the propagation delay time of the propagation path 1, τ2 is the propagation delay time of the propagation path 2, τk is the propagation delay time of the propagation path k, and n is the transmission path noise.

In the information despreading means 202 and the pilot despreading means 203, S (t-τ1) reached via the propagation path 1 is reached.
Are despread, and the information despreading means 207 and the pilot despreading means 208 despread S (t-τk) that has arrived via the propagation path k.

Therefore, each despreading means in the receiver executes the despreading process by generating the same pseudo-random code as the base station at individual timings synchronized with each propagation path. That is, in the demodulation means 201, PNI (t-τ1) is generated as the I-phase pseudo random code and PNQ (t-τ1) is generated as the Q-phase pseudo random code. Similarly, in the demodulation means 206, as the I-phase pseudo random code, PNI
PNQ as (t-τk) as a Q-phase pseudo-random code
Generate (t-τk).

The pseudo-random code used is shown in FIG.
A code having a sharp autocorrelation characteristic as shown in (1) is used (as an example, an M-sequence PN code). Therefore, due to the autocorrelation characteristic of this pseudo-random code, the information despreading means 20
2 and the pilot despreading means 203 can obtain only the demodulated signal of the data that has arrived through the propagation path 1, and the information despreading means 207 and the pilot despreading means 208 can arrive through the propagation path k. Only a demodulated signal of data will be obtained.

The transmission information transmitted by the transmitter is d. Here, the coefficient indicating the propagation path state of the propagation path 1 is m1,
The data demodulated signal of the information despreading means 202 is set to m1d + n1 (n
(1 is a noise signal of the propagation path 1) and the output of the propagation path estimation means 204 is 1 / m1, the detection means 205 multiplies both, and d
+ N1 'is obtained. Similarly, when the coefficient indicating the propagation path state of the propagation path k is mk, the data demodulation signal of the information despreading means 207 is mkd + nk (nk is a noise signal of the propagation path k), and the output of the propagation path estimating means 209 is 1 / If mk, the detection means 210 multiplies both to obtain d + nk '. Since these detection results are added in phase by the synthesizing means 211, as a result, the output signal of the synthesizing means 211 is kd + (n1 ′ + ... + n
k ′), and usually, a demodulation result with a large signal-to-noise ratio can be obtained, and a communication error is unlikely to occur. In addition,
n1 ', ..., Nk' are noise signals independent of each other.

[0010]

The rake receiver of the prior art has a problem that the circuit scale becomes large because each demodulation means requires one channel estimation means and one detection means.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a communication system employing code division multiple access (CDMA) using a pilot signal for synchronization acquisition / holding and channel estimation. Despreading means including a despreading means for pilot and a despreading means for pilot, a propagation path estimating means for estimating a state of a propagation path from an output of the despreading means for pilot, and a despreading means for the information. A rake receiver comprising a detecting means for detecting an information signal using the output of the despreading means and the output of the propagation path estimating means, and a rake receiver comprising a combining means for combining the outputs of the detecting means, wherein the propagation path estimating means and the A rake receiver characterized in that the detection means processes the outputs of the plurality of despreading means in a time division manner;
A mobile station apparatus and a base station apparatus equipped with this rake receiver.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Here, a mobile communication system (for example, a mobile communication system in which code division multiple access (CDMA) is adopted as a radio access system and a transmitter sends out a pilot signal with no data modulation is used.
The description will be made assuming the US standard IS-95 standard).

FIG. 1 is a block diagram of the rake receiver of the present invention.

In FIG. 1, 101 is a first despreading means,
Information despreading means 102 for inputting an I-phase QPSK demodulated signal and a Q-phase QPSK demodulated signal and outputting an information despreading result.
Similarly, it is composed of pilot despreading means 103 which inputs the I-phase QPSK demodulated signal and the Q-phase QPSK demodulated signal and outputs the despread result of the pilot. The rake receiver of the present invention comprises a plurality of despreading means similar to the first despreading means 101. 107 is a propagation path estimation means for inputting the despreading results of the pilots output from the plurality of despreading means 101, 104 in a time division manner and outputting the propagation path estimation results corresponding to the individual propagation paths from these. Is a plurality of despreading means 1
The detection means for inputting the despreading result of the information output from 01, 104 and the propagation path estimation result corresponding to the signal despreading by the despreading means 101, 104 in time division and outputting the detection result of each information , 109 is a synthesizing means for inputting the detection results of individual information corresponding to the signals despread by the despreading means 101, 104 and adding them in phase to obtain a demodulation result.

The rake receiver of the present invention can be used in mobile stations and base stations of CDMA systems.

Next, the operation principle of the rake receiver of the present invention will be described.

As shown in FIG. 3, in a mobile communication environment, a radio wave transmitted from a transmitter is reflected by a natural environment or an artificial object and reaches the receiver via a plurality of different propagation paths.
That is, a plurality of radio waves having different propagation delay times arrive at the receiver. If there are k propagation paths,
The transmission signal of the transmitter is S (t) and the reception signal of the receiver is r (t)
Then, r (t) = S (t-τ1) + S (t-τ2) + ... + S (t-τk) + n. Here, τ1 is the propagation delay time of the propagation path 1, τ2 is the propagation delay time of the propagation path 2, τk is the propagation delay time of the propagation path k, and n is the transmission path noise.

In the information despreading means 102 and the pilot despreading means 103, S (t-τ1) reached via the propagation path 1 is reached.
Are despread, and the information despreading means 105 and the pilot despreading means 106 despread S (t-τk) that has arrived via the propagation path k.

Therefore, each despreading means in the receiver executes the despreading process by generating the same pseudo-random code as the base station at individual timings synchronized with each propagation path. That is, in the despreading means 101, PNI (t-τ1) is generated as the I-phase pseudo random code and PNQ (t-τ1) is generated as the Q-phase pseudo random code. Similarly,
In the despreading means 104, P as an I-phase pseudo-random code is used.
NI (t-τk) is PN as Q-phase pseudorandom code
Generate Q (t-τk).

The pseudo random code used is shown in FIG.
A code having a sharp autocorrelation characteristic as shown in (1) is used (as an example, an M-sequence PN code). Therefore, due to the autocorrelation characteristic of this pseudo-random code, the information despreading means 10
2 and the pilot despreading means 103 obtains only the despreading result of the data arriving through the propagation path 1, and the information despreading means 105 and the pilot despreading means 106 arrive through the propagation path k. Only the result of despreading the data obtained will be obtained.

The despreading results of the pilots output from the pilot despreading means 103 to the pilot despreading means 106 are input to the propagation path estimating means 107 in time division, and the propagation path estimation corresponding to each propagation path is performed. The result is obtained.
Further, the despreading result of the information output from the information despreading means 102 from the information despreading means 102, and the propagation path estimation result corresponding to each propagation path output from the propagation path estimating means 107 are respectively, The data is divided and input to the detection means 108, and the detection result of the information corresponding to each propagation path is obtained.

The transmission information transmitted by the transmitter is d. Here, the coefficient indicating the propagation path state of the propagation path 1 is m1,
M1 is the despreading result of the information output by the information despreading means 102.
If d + n1 (n1 is a noise signal of the propagation path 1) and the propagation path estimation result of the propagation path 1 output from the propagation path estimation means 107 is 1 / m1, the detection means 108 multiplies the two to obtain the propagation path 1 As the detection result of the information that has passed through, d + n1 'is obtained.
Similarly, when the coefficient indicating the propagation path state of the propagation path k is mk, the despreading result of the information output by the information despreading means 105 is mkd + nk (nk is a noise signal of the propagation path k), and the propagation path estimating means 107 If the propagation path estimation result of the propagation path k to be output is 1 / mk, the both are multiplied by the detection means 108, and d + nk 'is obtained as the detection result of the information that has passed through the propagation path k. Since these detection results are added in-phase by the synthesizing means 109, the output signal of the synthesizing means 109 is kd +
(N1 '+ ... + nk'), and usually a demodulation result with a large signal-to-noise ratio can be obtained. Note that n1 ',
..., nk 'are independent noise signals.

[0024]

As described above, the rake receiver of the present invention is characterized in that one propagation path estimating means and one detecting means process the outputs of a plurality of despreading means in a time division manner. Therefore, the circuit scale becomes smaller.

[Brief description of drawings]

FIG. 1 is a block diagram of a rake receiver of the present invention.

FIG. 2 is a block diagram of a conventional rake receiver.

FIG. 3 is a diagram illustrating a mobile communication channel.

FIG. 4 is a diagram illustrating autocorrelation characteristics of a pseudo-random code.

[Explanation of symbols]

101 despreading means 102 information despreading means 103 Despreading means for pilot 104 despreading means 105 Information despreading means 106 Despreading means for pilot 107 Channel estimation means 108 Detection means 109 Synthetic means 201 demodulation means 202 Information despreading means 203 Despreading means for pilot 204 Channel estimation means 205 Detection means 206 Demodulation means 207 Information despreading means 208 Despreading means for pilot 209 Propagation path estimation means 210 Detection means 211 Synthetic means.

Claims (3)

[Claims] 1. A rake receiver in a communication system to which a code division multiple access (CDMA) system is applied, the rake receiver including information despreading means and pilot despreading means, and receiving at different timings. A plurality of despreading means for despreading a plurality of received signals, a propagation path estimation means for estimating a propagation path state from an output of the pilot despreading means, an output of the information despreading means and the propagation A detection means for detecting an information signal using the output of the path estimation means, and a combining means for combining the outputs of the detection means,
A rake receiver characterized in that the propagation path estimation means and the detection means process the outputs from the plurality of despreading means in a time division manner, and the combining means combines the plurality of outputs from the detection means. . 2. A mobile station apparatus in a communication system applying a code division multiple access (CDMA) system, comprising a rake receiver, wherein the rake receiver is a despreading means for information and a despreading means for pilot. A plurality of despreading means each including a spreading means for despreading a plurality of reception signals received at different timings; and a propagation path estimation means for estimating a propagation path state from an output of the pilot despreading means. When,
The propagation path estimating means includes a detecting means for detecting an information signal using the output of the information despreading means and the output of the propagation path estimating means, and a combining means for combining the outputs of the detecting means. The mobile station device, wherein the detection means processes the outputs from the plurality of despreading means in a time division manner, and the combining means combines the plurality of outputs from the detection means. 3. A base station apparatus in a communication system applying a code division multiple access (CDMA) system, comprising a rake receiver, wherein the rake receiver is a despreading means for information and an inverse spread means for pilot. A plurality of despreading means each including a spreading means for despreading a plurality of reception signals received at different timings; and a propagation path estimation means for estimating a propagation path state from an output of the pilot despreading means. When,
The propagation path estimating means includes a detecting means for detecting an information signal using the output of the information despreading means and the output of the propagation path estimating means, and a combining means for combining the outputs of the detecting means. The base station device, wherein the detection means processes the outputs from the plurality of despreading means in a time division manner, and the combining means combines the plurality of outputs from the detection means.