KR20060005826A - Transmission diversity method and antenna system therefor - Google Patents

Abstract

The present invention relates to a transmit diversity method and an antenna system therefor. In the transmit diversity method according to the present invention, a plurality of transmit antennas are transmitted by combining a plurality of transmit antennas into two antenna groups and transmitting different data streams through each antenna group. Receiving information for combining the antennas into two antenna groups; Recombining the plurality of transmit antennas into two antenna groups according to the received information; And transmitting a different data stream through each of the recombined antenna groups.

Antenna, Transmit, Diversity, D-STTD, D-TxAA, Throughput

Description

Transmission diversity method and antenna system therefor {transmission diversity method and antenna system therefor}

1 is a configuration diagram of a transmitting and receiving end of a conventional D-STTD system.

2 and 3 is a configuration diagram of a transmitting and receiving end of a conventional TxAA, D-TxAA system.

Figure 4 is a block diagram of a preferred embodiment of the present invention.

5 is a block diagram of another preferred embodiment of the present invention.

6 is a procedure flow diagram illustrating a process for determining antenna combination selection information in preferred embodiments of the present invention.

<Description of Major Reference Drawings>

41, 51 antenna combination selector 43, 53 antenna combination selector

The present invention relates to a transmit diversity method and an antenna system therefor. More specifically, in an antenna system in which a plurality of transmit antennas are combined into two antenna groups to transmit different data streams to a receiver through each antenna group, the throughput of the system is minimized by minimizing interference between different data streams transmitted. The present invention relates to a transmission diversity method capable of maximizing throughput and an antenna system therefor.

DSTTD and DTxAA have been proposed as one of MIMO (Multi Input Multi Output) transmission methods in 3GPP (3rd Generation Partnership Project), an IMT-2000 asynchronous standardization group. These two technologies extend the existing transmit diversity scheme to MIMO transmission. When four transmit antennas are used, two different data streams are combined by combining the transmit antennas into two antenna groups. It is a technology for transmitting with STTD or TxAA, which is a transmit diversity transmission method.

Brief description of the STTD is as follows. STTD is a method of obtaining diversity effect through space-time coding in which an extended channel coding technique mainly applied on a time axis is extended in space. This method is applicable to all downlink physical channels except SCH (Synchronization CHannel) of WCDMA. Since the STTD method does not require a feedback signal, there is an advantage in that there is no performance degradation due to a feedback signal delay depending on speed. The operation principle of the STTD can be shown in Table 1.

t t + T Antenna 1 s ₁ s ₂ Antenna 2 -s ^* ₂ s ^* ₁

As shown in Table 1, the symbol to be transmitted is STTD encoded and transmitted to antenna 1 and antenna 2 according to a time sequence, respectively. The signals transmitted to each antenna pass through different independent channels, and if the channel at time t and the channel at (t + T) are the same, the receiving antenna stages in Equations 1 and 2 Are received together.

,

는 각각 송신 안테나 1 및 송신 안테나 2와 수신 안테나 간의 채널을 의미하며, n ₁ , n ₂ 은 수신단에서의 복소 잡음을 의미한다. 각각의 채널은 파일럿 신호로 추정이 가능하며, 수신신호를 다음의 수학식3과 수학식4와 같이 결합을 하게 되면 수신 다이버시티의 MRC(Maximum Ratio Combining) 방식과 같은 값을 얻을 수 있고 이를 바탕으로 송신된 심볼을 추정할 수 있게 된다. here ,

,

Denotes a channel between a transmitting antenna 1, a transmitting antenna 2, and a receiving antenna, and n ₁ and n ₂ denote complex noises at a receiving end, respectively. Each channel can be estimated as a pilot signal, and when the received signals are combined as in Equation 3 and Equation 4 below, the same values as the MRC (Maximum Ratio Combining) method of the reception diversity can be obtained. It is possible to estimate the symbol transmitted by.

1 is a diagram for explaining an open loop D-STTD. The open-loop D-STTD is a system in which two independent data streams are space-time coded through an STTD encoder and transmitted in diversity in a system using a plurality of transmit / receive antennas using a space-time channel. Each stream to be transmitted can be transmitted by changing the data rate independently according to its state through channel quality information (CQI) sent from the receiving end. In FIG. 1, the MCS controller is a component that controls a modulation scheme and a code rate according to the CQI fed back from the receiving end.

FIG. 2 is a diagram for explaining TxAA mode 1 and mode 2, and TxAA mode 1 and mode 2 are diversity systems for multiplying data transmitted by a weight transmitted from a receiver. In TxAA mode 1 and mode 2, the receiver obtains a weight to maximize the SNR at the receiver and transmits the weight to the transmitter. The transmitter multiplies and transmits the weight value to the transmission signal. Assuming two reception antennas, the reception signal at each antenna of the reception end can be expressed as follows.

In Equations 5 and 6, s is a data symbol, and n ₁ and n ₂ are AWGN.

Data symbol recovery in TxAA mode 1 and mode 2 is performed by the following equation.

One example of obtaining the weight may be defined as the eigenvector for the maximum eigenvalue of the covariance matrix of the channel. This can be obtained by the following equation (8).

은 채널의 공분산 행렬(covariance matrix)이다. here

Is the covariance matrix of the channel.

Mode 1 and mode 2 are distinguished according to the difference in how the weight vector is actually implemented. That is, mode 1 expresses feedback by expressing the weight vector in 1 bit, while mode 2 expresses feedback in 4 bits. Specifically, in the case of mode 1, one bit of phase information is fed back to each slot without power information, and the mode 2 is fed back one bit of power information and three bits of phase information by one bit per slot.

Referring to the pilot symbols of the Dedicated Physical Control CHannel (DPCCH), pilot symbols having orthogonality to each other are transmitted in two antennas in mode 1, and the same pilot symbols are transmitted in two antennas in mode 2. The terminal estimates a channel of each transmit antenna on a slot basis by using a common pilot channel (CPICH) of each antenna, and calculates weights w ₁ and w ₂ of a transmitting end maximizing the received signal power from the channel estimation information. Phase and power adjustment information of the antenna is transmitted to the base station.

의 고정값을 사용하고 두 번째 안테나의 가중치는 각 슬롯에 피드백되는 위상 정보에 대응하는 표 3의 φ _i 값에 따라 다음의 수학식9와 같이 구해진다. The feedback signal message in mode 1 of closed loop transmit diversity has phase information and power information. The UTRAN interprets the received information according to Table 2. This method uses a constellation rotation to vary the weight of four phases using one bit of information. The weight of the first antenna

Use a fixed value of, and the weight of the second antenna is φ _{i in} Table 3, which corresponds to the phase information fed back to each slot. According to the value, it is calculated as in the following equation (9).

Slot No. 0 One 2 3 4 5 6 7 8 9 10 11 12 13 14 FSM 0 1 0 π π / 2 -π / 2 0 π π / 2 -π / 2 0 π π / 2 -π / 2 0 π π / 2 -π / 2 0 π π / 2 -π / 2 0 π π / 2 -π / 2 0 π π / 2 -π / 2 0 π

Some deformation is applied at the boundary of the frame. For phase adjustment of slot 0, the information of slot 13 is used instead of the information of slot 14 of the previous frame. This is always to take an average based on (0, π) and (π / 2, -π / 2), and is obtained as in Equation 10 below.

은 현재 프레임의 슬롯 0으로 피드백된 위상 조절 명령이고,

는 바로 이전 프레임의 슬롯 13으로 피드백된 위상 조절 명령이다.here

Is a phase adjustment command fed back to slot 0 of the current frame,

Is the phase adjustment command fed back to slot 13 of the previous frame.

Since there is no feedback information in the initialization stage, the initial value uses w ₂ = (1 + j) / 2 and after receiving feedback, the following equation (11) is used.

In mode 2, 16 phases and power can be combined with 4 bits of feedback information. Unlike mode 1, the phase resolution is large, eliminating the need for constellation rotation and weight filtering. As shown in Tables 3 and 4, the weighted phase is determined based on one power feedback information and three phase feedback information, and a gradual update method is used to obtain maximum performance.

를 구할 수 있다.Since all combinations are possible for the first bit, the terminal selects the optimal value among the 16 weights and proceeds to the next bit to find the optimal weight in the order of 8>4> 2 combinations under the constraint that the already determined bit is fixed. That's the way. With the phase and power information obtained as above, the weight vector,

Can be obtained.

FSMpo Antenna 1 power Antenna 2 power 0 1 0.2 0.8 0.8 0.2

FSMph Phase difference between antennas φ _i (radians) 000 001 011 010 110 111 101 100 π -3π / 4 -π / 2 -π / 4 0 π / 4 π / 2 3π / 4

Since feedback information of 4 bits is transmitted over 4 slots in 15 slots, power feedback information is not transmitted in the last 3 slots. In this case, information of previous power is used.

Since there is no feedback information in the initialization stage, the phase shown in Table 5 is used, and the power of the two antennas is distributed by 50% of the total transmit power.

FSMph Phase difference between antennas φ _i (radians) ---                                                                                                            0-- 1-- 00-01 01-11 10- 000 001 011 010 110 111 101 100 π (nominal initialisation) or held from pervious setting (compressed mode recovery) π 0 π -π / 2 0 π / 2 π -3π / 4 -π / 2 -π / 4 0 π / 4 π / 2 3π / 4

Fig. 3 shows an example of a transmitter signal processing configuration and a receiver signal processing configuration of D-TxAA. Here, the number of transmitting antennas was four. As shown in FIG. 3, four TxAAs are bundled in two to perform TxAA operation. Two separate groups allow different data streams to be transmitted. Each data stream makes it possible to vary the transmission data rate depending on the channel conditions. The receiving end obtains a weight suitable for the channel and transmits the weight to the transmitting end. The transmitting end multiplies this weight by the transmission signal and then transmits the weight. Since two transmit antennas are bundled and multiplied by the weight, the received signal of the receiver can be expressed as Equation 13 and Equation 14 below. It is assumed here that the number of receiving antennas is two.

Since both s ₁ and s ₂ are transmitted to the receiving antenna, the data can be recovered by removing the channel component and the weight component after combining. And, as long as it is reliable, interference cancellation technique can be used. That is, when s ₁ is recovered and the interference component generated by it is removed, the stability of s ₂ is increased.

At this time, the weight to be fed back to the base station is selected as the eigenvector corresponding to the maximum eigenvalue of the channel matrix defined as follows. The eigenvectors corresponding to the maximum eigenvalues of the channel matrix may be obtained as in Equations 17 to 20 below.

,

이고 R ₁₂ , R ₃₄ ,은 각각 h ₁₂ , h ₃₄ 의 자기 상관 행렬, λ₁₂, λ₃₄와

는 각각 자기 상관 행렬의 최대 고유치 및 각 최대 고유치에 해당하는 고유 벡터를 나타낸다. 상기 방법은 가중치(weight)를 구하는 일례로서 이외에도 여러 다양한 방법들이 가능하다.At this time ,

,

And R ₁₂ , R ₃₄ , are autocorrelation matrices of h ₁₂ , h ₃₄ , λ ₁₂ , λ ₃₄ and

Denote the maximum eigenvalue of each autocorrelation matrix and the eigenvector corresponding to each maximum eigenvalue. The above method is an example of obtaining a weight, and various other methods are possible.

In Equation 17 to Equation 20, two reception antennas are used as an example. Even in the case of multiple reception antennas, the transmission symbols may be recovered by the same method after combining.

Data streams s ₁ and s ₂ input to two TxAA blocks can change data rates according to channel conditions, respectively. That is, when the channel condition is good, it can be transmitted by using high order modulation such as QAM or by increasing the code rate, and when the channel condition is bad, low order modulation such as QPSK. However, it is possible to transmit at a lower code rate. By doing so, the data rate suitable for the channel is determined and transmitted, thereby maximizing throughput. On the other hand, the information on the channel state should be informed from the receiver to the transmitter by the feedback.

As described above, in the prior arts such as D-STTD and D-TxAA, antennas are selected to transmit in pairs without considering correlation or throughput between antennas, and thus performance degradation and throughput due to interference between streams according to the correlation between antennas. There is a possibility of degradation.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to group the antennas in a combination that can maximize the throughput in consideration of the correlation between the channels (the entire system) It is to provide a transmission diversity method capable of improving throughput and an antenna system for the same.

Summary of the Invention

In one aspect of the present invention, a transmit diversity method according to the present invention is a transmit diversity method for transmitting a different data stream through each antenna group by combining a plurality of transmit antennas into two antenna groups, Receiving information from the side for combining the plurality of transmit antennas into two antenna groups; Recombining the plurality of transmit antennas into two antenna groups according to the received information; And transmitting a different data stream through each of the recombined antenna groups.

According to another aspect of the present invention, an antenna system according to the present invention comprises: combining a plurality of transmitting antennas into two antenna groups and transmitting a different data stream to a receiving side through each antenna group, wherein the receiving side A receiving unit for receiving information for combining the plurality of transmitting antennas into two antenna groups from a network; And an antenna combination selection unit for recombining a plurality of transmit antennas into two antenna groups according to the received information.

Example

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. 4 and 5 are schematic diagrams of preferred embodiments of the present invention.

4 is a block diagram of a transmitter 40 and a receiver 45 when the technical features of the present invention are applied to a D-STTD system. Compared with the conventional D-STTD system shown in FIG. 3, as shown in FIG. 4, an antenna combination selector 40 is added to the transmitter 40 and an antenna combination determiner 43 is added to the receiver 45. Have different differences.

More specifically, the conventional D-STTD system shown in FIG. 1 combines a total of four transmit antennas into two antenna groups and transmits an STTD encoded data stream through each antenna group. In this case, once the combination of antenna groups is determined, the combination has a feature that is fixed regardless of the channel situation. In the D-STTD system according to the preferred embodiment of the present invention shown in FIG. 4, the combination of the antenna groups determined initially may be variable according to the information fed back from the receiver, that is, the antenna combination selection information, rather than being fixed. It features. The antenna combination selection information is determined by the antenna combination determination unit 43 of the receiver 45 and fed back to the transmitter 40, and the antenna combination selection unit 41 of the transmitter 40 according to the antenna combination selection information. Recombine the antenna groups. The determination procedure of the antenna combination selection information by the antenna combination determination unit 43 of the receiving end 45 will be described in detail later.

5 is a configuration diagram of an embodiment applied to the D-TxAA system as a technical feature of the present invention. In the embodiment shown in Fig. 5, when compared with the conventional D-TxAA system shown in Fig. 3, the antenna combination selecting unit 51 of the transmitting end 50 and the antenna combination determining unit 53 of the receiving end 55 It has a newly added difference. When there are four transmit antennas and the antenna numbers are 1, 2, 3, and 4, in the conventional D-TxAA system of FIG. 3, the combination of antenna groups is fixed to (1, 2) (3, 4). In the embodiment of the present invention of 5, the combination of antenna groups according to the antenna combination selection information fed back from the receiving end 53 is (1, 2) (3, 4), (1, 3) (2, 4) and (1). , 4) (2, 3) can be varied.

FIG. 6 is a flowchart illustrating a process of determining antenna combination selection information at the receiving ends 45 and 55 of the embodiments illustrated in FIGS. 4 and 5. The antenna combination selection information is basically information about a combination of antenna groups having the best performance according to channel conditions.

In FIG. 6, the antenna combination determination units 43 and 53 of the receivers 45 and 55 estimate the channel through the pilot of the transmitting antenna [S41]. Then three antenna combinations selectable for the four transmit antennas according to the estimated channel [(1, 2) (3, 4), (1, 3) (2, 4) and (1, 4) (2, 3)] to calculate the received Signal to Noise-plus-Interference Ratio (SINR) [S42], and calculates the transmittable throughput for each received SINR [S43]. Once the received SINR is calculated, the transmittable throughput can be easily determined. Here, the throughput means, for example, a data rate that can be transmitted at the transmitting end. The combination of antenna groups having the largest throughput among the calculated throughputs is determined as the antenna combination selection information [S44]. The antenna combination having the largest throughput is compared with the existing combination [S45]. In other cases, the antenna combination selection information is fed back to the transmitting end [S46]. If the received SINR is calculated in the above process, it is possible to omit the rest of the process and determine the antenna combination selection information for the antenna combination having the largest received SINR according to the calculated received SINR.

If there is little change in the channel, it is preferable that the transmitter transmits data in the previously set combination without feeding back the antenna combination selection information. In addition, in order to reduce the increase in the uplink and downlink signaling of the system due to the periodic or every change of feedback and downlink control signals of the antenna combination, only when the combination is fed back at the initial setting of the system or there is a significant change in the channel. It may also be possible to update the antenna combination settings.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes that come within the equivalent scope of the invention are included in the scope of the invention.

According to the transmission diversity method and the antenna system therefor according to the present invention, it is possible to improve the overall throughput of the system by transmitting data by selecting an antenna combination having the maximum throughput.

Claims (12)

In the transmit diversity method of combining a plurality of transmit antennas into two antenna groups to transmit different data streams through each antenna group, Receiving information for combining the plurality of transmit antennas into two antenna groups from a receiving side; Recombining the plurality of transmit antennas into two antenna groups according to the received information; And And transmitting a different data stream through each of the recombined antenna groups. The method of claim 1, And wherein the information is determined according to a channel state at the receiving side. The method of claim 1, The information is obtained by measuring received signal to noise-plus-interference ratio (SINR) for all cases in which the plurality of transmit antennas can be combined into two antenna groups. The transmission diversity method characterized by the above-mentioned. The method of claim 1, wherein the information on the receiving side, Estimating a channel through a pilot signal; Measuring received SINR for all cases in which the plurality of transmit antennas can be combined into two antenna groups; Calculating a transmittable throughput for each received SINR, And selecting an antenna combination having the largest throughput among the calculated throughputs. The method of claim 1, And the plurality of transmit antennas is included in a D-STTD system. The method of claim 1, Wherein the plurality of transmit antennas is included in a D-TxAA system. An antenna system for combining a plurality of transmit antennas into two antenna groups to transmit different data streams to a receiver through each antenna group, A receiving unit for receiving information for combining the plurality of transmitting antennas into two antenna groups from the receiving side; And And an antenna combination selector configured to recombine the plurality of transmit antennas into two antenna groups according to the received information. The method of claim 7, wherein Wherein the information is determined according to a channel condition at the receiving side. The method of claim 7, wherein The information is an antenna system, characterized in that the data on the antenna combination having the best received SINR as a result of measuring the received SINR for all cases where the plurality of transmit antennas can be combined into two antenna groups. The method of claim 7, wherein the information is received at the receiving end, Estimating a channel through a pilot signal; Measuring received SINR for all cases in which the plurality of transmit antennas can be combined into two antenna groups; Calculating transmittable throughput for each received SINR, And selecting an antenna combination having the largest throughput among the calculated throughputs. The method of claim 7, wherein And the plurality of transmit antennas are included in a D-STTD system. The method of claim 7, wherein And the plurality of transmit antennas are included in a D-TxAA system.

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