WO2003081835A1

WO2003081835A1 - A self-adapting weighted space time transmitting diversity receiving method and system thereof

Info

Publication number: WO2003081835A1
Application number: PCT/CN2002/000191
Authority: WO
Inventors: Aijun Cao
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2002-03-22
Filing date: 2002-03-22
Publication date: 2003-10-02
Also published as: AU2002249061A1

Abstract

The present invention discloses a kind of receiving method for self-adapting weighted space time transmitting diversity, which at least comprises following steps: a) after having received the signals from the transmitting terminal, the receiver first utilizes the principle of maximum likelihood to calculate an intermediate value of adjudicate variable of each way signals; b) then, the adjudicate variable intermediate value through linear transformation to calculate final decision variate-value of each way signals, according to assigned matrix of a linear transformation and coefficient thereof, and the value could be acted as an input of later processing modular. The present invention also discloses a kind of system for realizing the such self-adapting weighted space time transmitting diversity reception methods. The methods and architectures can improve the performance of receiver, in which self-adapting weighted space time transmitting diversity system includes, eliminates the interference of signals, enhances the entire performance of the system.

Description

Receiving method and system for adaptive weighted space-time transmit diversity

TECHNICAL FIELD The present invention relates to space-time transmit diversity reception technology, and more particularly, to a receiving method and system based on adaptive weighted space-time transmit diversity. BACKGROUND OF THE INVENTION In a wideband code division multiple access (WCDMA) system of a third generation (3G) mobile communication system, because different users in the same cell and different users in neighboring cells share the same time at the same time A frequency band, so users have interference with each other, and these interferences limit system capacity and information transmission rate. In order to increase the system capacity, multiple diversity methods can be used, such as multipath diversity, space diversity, and antenna diversity. In a system using diversity technology, there are multiple independent copies of the same information content. After receiving these independent copies, the receiver usually makes full use of the redundancy of information according to the principle of Maximum Likelihood (ML) By processing the characteristics, the bit error rate of transmitted information can be greatly reduced, and the energy required for wireless data transmission is reduced, thereby reducing mutual interference between users. It can be seen that the diversity technology can effectively increase the system capacity.

In the downlink of a WCDMA system, to achieve a large number of users and high-speed data transmission, multiple transmission diversity technologies are also required to be used, and the Space Time Transmit Diversity (STTD) method is one of them. The diversity technique is to first perform simple space-time coding on the information to be transmitted, and then divide the space-time-coded signal into two channels and send them to The two independent transmitting channels perform transmission. Correspondingly, the receiving end receives signals from the two independent transmitting channels and processes them according to the maximum likelihood principle. However, because the transmission energy is divided equally in the manner of equal division, the ordinary STTD transmission diversity technology cannot reach the upper performance limit.

In order to improve the performance of space-time transmit diversity, the applicant has proposed a transmit diversity technology based on space-time coding and adaptive weighting. The core idea is that the transmitting end receives the fading amplitude characteristics of the current two wireless channels according to the information received from the feedback channel Information, recalculate the appropriate transmission power weight value, and redistribute the transmission energy. The implementation structure is shown in Figure 1. In FIG. 1, reference numeral 100 represents information to be transmitted, where S ^. S ₂ is two transmission symbols in the same space-time coding block; 101 is a space-time coding module, 102 is a feedback signal processing module, 103 is an optimal weight calculation module, 104 is a feedback channel, and 105 is a transmission power distribution module. 106 is a transmitting antenna array with two antennas, which means that two independent transmitting channels are transmitted through the antennas Antl and Ant2 respectively; Rec is a receiver based on the maximum likelihood (ML) principle at the receiving end, and 107 is a maximum likelihood Receiving module.

Based on the system reception shown in FIG. 1, the diversity method includes at least the following steps: a. The transmitting end uses the two input symbols as a unit block to perform space-time coding according to a certain rule and outputs two signals;

b. The transmitting end adjusts the current transmitting power values of the two transmitting antennas in real time respectively according to the currently given transmitting power weight value, while keeping the total transmitting power unchanged; the transmitting antenna array will pass through the air according to the current transmitting power value. Time-coded output signal is transmitted from two independent antennas;

c The receiver at the receiving end estimates the fading characteristics of the two wireless channels based on the currently received signal, and feeds back the fading amplitude characteristics of the two wireless channels to the transmitting end after encoding;

d. The transmitting end receives and obtains the characteristic information of the fading amplitude of the current two wireless channels from the feedback channel, calculates a new adaptive weight value of the transmission power of the two transmission channels according to formula (1), and adjusts the transmission power according to the weight value.

At the receiving end, the received signal of the same space-time coding block can be expressed as

Among them, _Γι and r ₂ are the received signals of the same space-time coding block, respectively! ^ And h ₂ represent the fading factors of the wireless channel from the two transmitting antennas to the receiving antenna, 5, and S ₂ are the transmission symbols in the same space-time coding block, and S is the receiving noise, w. w ₂ is the transmit power weight of the two transmit channels at the transmitting end.

According to the traditional method, the receiver mainly performs functions such as maximum likelihood reception and decoding, and the S, S ₂ decision variables calculated by the maximum likelihood reception technology are directly used for decoding. In this case, the decisions of S, S ₂ The variables are:

5, = Λ, + ( ₂ r ₂ )

It can be seen from formula (3) that the two transmitting channels have unequal weights, which will result in a cross term (νν,-^) /!; / ^; In the 5 ₁ decision variable. Similarly, the S ₂ decision variable will also have Similar cross terms appear

(VV ₂ -As the signal energy increases, the interference of this cross term will become larger and larger, which seriously affects the performance of the receiver.

It can be seen that if only the traditional maximum likelihood receiving method is adopted, it is based on space-time coding and adaptive addition. The performance of weighted transmit diversity is severely limited, which affects the emission effect. SUMMARY OF THE INVENTION In view of this, the main object of the present invention is to provide a method for receiving adaptively weighted space-time transmit diversity, which can further improve the reception processing of adaptively weighted space-time diversity, and avoid the result of increasing the adaptive weighting operation. Signal interference to improve system performance.

Another object of the present invention is to provide a system for implementing an adaptive weighted space-time transmit diversity reception method, which can improve the performance of a receiver in an adaptive weighted space-time transmit diversity system, thereby improving the overall performance of the system, and The design is simple and easy to implement.

To achieve the above object, the technical solution of the present invention is implemented as follows:

A method for receiving adaptively weighted space-time transmit diversity includes at least:

a. After receiving the signal from the transmitting end, the receiver first uses the maximum likelihood principle to calculate the intermediate value of the decision variable for each signal;

b. Then the intermediate value of the decision variable is calculated according to the given linear transformation matrix and its coefficients, and the final decision variable value of each signal is calculated by linear transformation, and this value is used as the input of the subsequent processing module.

In the above process, step a further includes: the receiver detects the received input signal in units of space-time coded blocks, and outputs two intermediate values of decision variables each time.

Step b further includes: setting a linear transformation matrix in advance, and calculating a linear transformation matrix coefficient in advance. The linear transformation matrix coefficient is related to the implementation form of adaptive weighted space-time transmit diversity, and can be determined by the adaptive weight value and the fading amplitude characteristic of the wireless channel.

Step b further includes: sending the final decision variable value to a decoding module in the receiver for decoding processing. A system for implementing the above-mentioned adaptive weighted space-time transmit diversity receiving method includes at least a space-time coding module, a transmission antenna array with two antennas, a transmission power distribution module, a feedback channel, a feedback signal processing module, and an optimal weight calculation module. And the maximum likelihood receiving module in the receiving end receiver, the key is: the receiving end receiver further includes a linear transformation module;

The receiver's maximum likelihood receiver module receives and processes the signal from the transmitting end, outputs the intermediate value of the decision variable to the linear transformation module for linear transformation, and the processed decision variable continues to be sent to the subsequent processing module of the receiver. The subsequent processing module at least Including decoding module.

It can be seen from the above scheme that the key of the present invention is: adding line-to-line conversion processing at the receiving end based on adaptive weighted space-time transmit diversity to remove the interference between signals generated during the calculation of the transmission power weight and improve system performance.

The method and system for receiving adaptively weighted space-time transmit diversity provided by the present invention have the following advantages and characteristics:

1) The present invention adds a level of simplicity based on the information about the fading amplitude of the wireless channel obtained by the receiver itself and the optimal weight calculation method based on the space-time coding adaptive weighted closed-loop transmit diversity technology. The linear transform (LT, Linear Transform) removes the cross terms in the adaptive weight calculation through the linear transform process, thereby avoiding the signal interference generated by the cross terms, and greatly improving the reception performance of the transmit diversity; and the linear transform and The use of adaptive weighted transmit diversity technology based on space-time coding can greatly improve the overall performance of the system.

2) The present invention only needs to add a linear conversion module to the receiver at the receiving end, and the system of the existing technology is slightly changed, the system performance is further improved on the original basis, and the structure design is simple and easy to implement.

3) After simulation tests and theoretical analysis, it is proved that the method and system of the present invention are simple to implement and superior in performance. When the signal-to-noise ratio is equal, the bit error rate is much lower than the existing STTD transmit diversity; and Moreover, under the condition that the bit error rate is the same, the signal transmission power required by the present invention is lower. Therefore, as the signal-to-noise ratio increases, the performance gain obtained by the system is greater. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural diagram of a conventional adaptive weighted space-time transmit diversity system;

FIG. 2 is a schematic diagram of a system composition structure of adaptive weighted space-time transmit diversity according to the present invention; FIG. 3 is a schematic diagram of performance comparison of the present invention with existing space-time transmit diversity and existing adaptive weighted space-time transmit diversity. Mode for Carrying Out the Invention The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

FIG. 2 is a schematic structural diagram of a system of space-time transmit diversity according to the present invention. As shown in FIG. 2, the system includes a space-time coding module 101, a feedback signal processing module 102, an optimal weight calculation module 103, a feedback channel 104, and a transmission power allocation. The module 105, the transmitting antenna array 106 with two antennas, and the maximum likelihood receiving module 107 in the receiving end receiver, especially after the maximum likelihood receiving module 107 in the receiving end receiver further include: a linear transformation module 108 . The feedback channel 104 is used to output information about the current wireless channel characteristics from the receiver; the feedback signal processing module 102 is used to receive information about the current wireless channel characteristics from the feedback channel and perform mapping processing; an optimal weight calculation module 103. Calculate the transmit power weights of the two transmit channels based on the relevant wireless channel characteristic information from the feedback receiving module 102. The transmit power allocation module 105 is used to adjust the transmit power values of different antennas based on the received transmit power weights. The antenna array 106 uses two independent antennas to output the coded output of the space-time coding module 101 according to the current transmission power value. Submit. The linear transformation module 108 is configured to receive the output of the maximum likelihood receiving module 107, calculate a linear transformation matrix coefficient based on the adaptive weight calculation method, and use the matrix to linearly transform the input.

Referring to FIG. 2, in the present invention, a maximum likelihood receiving module 107 first detects a received input signal from a transmitting end by using a space-time coding block as a unit, following a normal maximum likelihood principle. Here, each signal after space-time coding contains a copy of the information, but the form and sequence are different. The space-time coding block actually refers to two copies of the information of the two signals. Therefore, the receiver Receive two signals at the same time, use the two copies of the information to perform joint processing according to formula (4), and output the intermediate value of the two decision variables each time to the linear transformation module 108. The intermediate value of the decision variable can be expressed as:

= (w, I Λ, | ² + ιν ₂ I h ₂ | ² ) 5, + (w,-w ₂ ) h [h ₂ S ₂ '+ (h (n + h ₂ n ₂ )

"(4)

r ₂ = i, r _2- (h ₂ r,)

= (w, I h + w ₂

set up:

2 + w ₂ \ h ₂ I ² ) ( ₅ )

In fact, the coefficients A and B can also be expressed in other forms or determined by other factors, which mainly depend on the different implementation forms of adaptive weighted space-time transmit diversity.

According to the formula (1) described above and the radio channel fading characteristics obtained by the receiver itself, the linear transformation module 108 can calculate the linear transformation matrix coefficients A and B represented by the formula (5), and then according to the formula (6) ' The linear transformation matrix shown performs linear transformation on the intermediate values (;,; ₂ ) of the decision variables output by the maximum likelihood receiving module 107: 5, = Α 'r _x -B r ₂ ^ (6)

S ₂ = Α ′ r ₂ + B r The result of the linear transformation is output by the linear transformation module 108 and sent as a final decision variable to a subsequent processing module in the receiver, such as a decoding module, which performs subsequent processing such as decoding in a conventional manner.

According to the above scheme, the average signal-to-noise ratio SNR corresponding to the decision variable can be obtained as:

SNR _w _, _nv = ίε ₅ (7)

σ can be calculated according to formula (7), and the present invention has an average increase of 1.55dB compared with the performance of ordinary STTD transmit diversity, and an average increase of 0.7 ~ 0.8dB compared with the increase of adaptive weighted ST D transmit diversity performance.

FIG. 3 is a schematic diagram showing the performance comparison between the present invention and the existing space-time transmit diversity and the existing adaptive weighted space-time transmit diversity, where the abscissa represents the number of decibels (dB) of the signal-to-noise ratio (Eb / No), and the ordinate Represents the original bit error rate, curve 31 is the performance curve of ordinary STTD transmit diversity, curve 32 is the performance curve of STTD transmit diversity after increasing adaptive weighted adjustment of transmit power, curve 33 is the performance of STTD transmit diversity after linear transformation processing is added according to the present invention curve. From the comparison of the three curves, it can be seen that when the bit error rate is the same, the signal-to-noise ratio of the adaptively weighted transmit diversity with linear transformation processing at the receiving end is lower than that of the other two cases, that is, When the bit error rate is the same, the transmission power required by the signal of the present invention is the lowest. From another perspective, when the signal-to-noise ratios of the three curves are the same, the receiving end increases the bit error rate of the adaptive weighted transmit diversity of linear transformation processing. Compared with the other two cases, it is obviously the lowest, and it is obvious that the overall performance of the system of the transmit diversity of the present invention is higher.

The present invention is not only applicable to the aforementioned adaptive weighted space-time transmit diversity method and structure proposed by the applicant, but also applicable to various other adaptive weighted space-time transmit diversity techniques implemented through different approaches. The concepts of the present invention are applicable, except that for different implementations of various adaptive weighted space-time transmit diversity technologies, the corresponding linear transformation coefficients will be different.

The above description is only the preferred embodiments of the present invention, and is not intended to limit the protection scope of the present invention.

Claims

Claim

1. A method for receiving adaptive weighted space-time transmit diversity, characterized in that the method includes at least:

a. After receiving the signal from the transmitting end, the receiver first uses the maximum likelihood principle to calculate the intermediate value of the decision variable of each signal;

b. The intermediate value of the decision variable is then used to calculate the final decision variable value of each signal according to the given linear transformation matrix and its coefficients, and this value is used as the input of the subsequent processing module.

2. The method according to claim 1, characterized in that step a further comprises: the receiver detects the received input signal in units of space-time coded blocks, and outputs two intermediate values of decision variables each time.

3. The method according to claim 1, wherein step b further comprises: setting a linear transformation matrix in advance.

4. The method according to claim 1, wherein step b further comprises: calculating a linear transformation matrix coefficient in advance.

5. The method according to claim 1, wherein step b further comprises: sending the final decision variable value to a decoding module in the receiver for decoding processing.

6. The method according to claim 1 or 4, characterized in that: said linear transformation matrix coefficient is related to an implementation form of adaptive weighted space-time transmit diversity.

7. The method according to claim 6, wherein: the linear transformation matrix coefficient is determined by an adaptive weight value and a fading amplitude characteristic of a wireless channel.

8. A system for implementing the above-mentioned adaptive weighted space-time transmit diversity receiving method, including at least The space-time coding module, the transmitting antenna array with two antennas, the transmitting power distribution module, the feedback channel, the feedback signal processing module and the optimal weight calculation module, and the maximum likelihood receiving module in the receiving end receiver are characterized by: The receiver at the receiving end further includes a linear transformation module; the receiver's maximum likelihood receiving module receives and processes the signal from the transmitting end, and outputs the intermediate value of the decision variable to the linear transformation module for linear transformation. Receiver's subsequent processing module.

9. The system according to claim 8, wherein the subsequent processing module includes at least a decoding module.