WO2005053185A1

WO2005053185A1 - Method and device for array antenna omnidirectional overlay

Info

Publication number: WO2005053185A1
Application number: PCT/CN2004/001354
Authority: WO
Inventors: Xuezhi Yang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2003-11-28
Filing date: 2004-11-25
Publication date: 2005-06-09

Abstract

The present invention relates to a method and device for public channel omnidirectional overlay in intelligent antenna communication system. Utilizing all of available antennae in antenna array, instead of selecting from among or additionally increase one antenna, then it is not necessary to employ high power amplifier and high gain antenna. Dividing transmission time of public channel signal into time slots; a public channel beam-forming weighting coefficient generator constructs one weight vector corresponding to each transmission time slot, and each weight vector is composed of M weighting coefficients, the M weighting coefficients are corresponding to M transmit channels; M weighting coefficient adjusters perform weighting with M weighting coefficients to public channel signals in M transmit channels, and the weighted public channel signals of M transmit channels are correspondingly transferred to M transmit antennae to transmit. In implementing, M weighting coefficient sequences in weight vectors can be composed of random sequence in time; N weight vectors can also be generated corresponding to N successive transmission time slots, and each weight vector is utilized cyclically.

Description

04 001354 Method and device for realizing omnidirectional coverage of an array antenna TECHNICAL FIELD

The present invention relates to the field of mobile communication technology, and more particularly, to a method and a device for implementing omnidirectional coverage of a common channel signal based on a smart antenna. Background of the invention

Array signal processing technology first appeared in adaptive antenna combination technology, and array antennas were first used in military communication systems since then. With the development of microcomputers and digital signal processing technologies in recent years, it has also begun to be used in civil cellular mobile communication systems Array antenna.

In an array antenna system, the system adaptively performs beamforming on mobile user signals and tracks the user's movement. Therefore, the array antenna is also called a smart antenna array. In the time division-synchronous code division multiple access (TD-SCDMA) system of the third generation mobile communication system, smart antenna technology is treated as one of its key technologies.

Referring to FIG. 1, a schematic diagram of a steering vector of a smart antenna array. Suppose a smart antenna array with narrowband signals contains M> l antenna elements, m is one of the M antenna elements, and the steering vector of the antenna array is an M-dimensional column vector, which is arranged by the antenna elements The way is unique. If the position of the first antenna array element is used as a reference point, the steering vector of the antenna array can be expressed as: (uppercase boldface represents a matrix, lowercase boldface represents a column vector, ordinary letters represent a scalar, the same applies hereinafter): = [1 e ~ ^{Jr k} … e ~ ^jrLk

In the figure, r „is the distance vector of the mth antenna array element to the reference point (m = ² ,…, M), k is the wave number vector in the direction of the 0 angle, | A | = w / _C = 2; r / A , Is the carrier angular frequency, c is the speed of light, and is the wavelength, where T is the transpose character. Referring to FIG. 2, a typical smart antenna system structure is illustrated. M receiving antennas correspond to M receiving channels, and M transmitting channels correspond to M transmitting antennas.

For a specific user, the direction of arrival estimation module (DOA estimation) 21 estimates the direction of arrival of the specific user based on the received signals on the M antenna elements. The adaptive beam shaping and branching coefficient generator 22 adjusts the weight vector according to the arrival direction information of the specific user. The specific process is: the adaptive beamforming weighting coefficient generator 22 generates a weighting coefficient for each transmission channel, and the weighting coefficients wl, w2 ... wM of the M antenna elements form a weight vector w; the weighting of each channel The coefficient adjuster 23 adjusts (does multiplication) the dedicated channel signal s (t) with the weighting coefficient of its own channel, thereby forming a directional beam for the specific user, and adaptively tracking the user's movement. In the figure, * is a conjugate symbol.

After the smart antenna technology is adopted, the interference of the system can be effectively reduced, the capacity of the system can be increased, and the spectrum efficiency can be improved.

In the smart antenna system shown in Figure 2, the transmission channel of each antenna element is weighted with a weighting coefficient (the weighting coefficient is equivalent to the weight value), and the weight vector is expressed as:

w = [wl w2 ... wMj

The direction coefficient of the antenna array in each direction is:

g (0) = w ^H a (0)

Where H is a conjugate transpose.

In a wireless communication system, in addition to a dedicated channel for a single user communication, a common channel such as a broadcast channel and a paging channel is also required. Common channels and dedicated channels have different requirements for antenna coverage: dedicated channels are required to form as narrow a beam as possible, while common channels are required to cover the entire cell, that is, omnidirectional coverage of common channel signals is required so that all users can receive Public information transmitted by the channel. Therefore, after the mobile communication system uses a smart antenna, the antenna array has directivity, but appropriate technical measures need to be taken to meet the omnidirectional coverage requirements of the public channel. One technique for achieving omnidirectional coverage of the common channel is to use a single antenna array element for transmission. Specific methods include: selecting an antenna array element from an existing array antenna to implement omnidirectional coverage of a common channel; or adding another antenna array element outside the existing antenna array, which is specifically used to implement a common channel Omnidirectional coverage.

In the smart antenna, since multiple antenna array elements are used, the antenna gain can be reduced and the requirements on the power amplifier can be reduced. However, if the above-mentioned single antenna array element is used to achieve omnidirectional coverage, the antenna array element is required to have a ratio The transmission power of other antenna elements is much higher, including the use of high-power power amplifiers and high-gain antenna elements, thus increasing the system cost. Summary of the invention

The purpose of the present invention is to design a method and a device for realizing omnidirectional coverage of an array antenna. The method and device for realizing omnidirectional coverage of a common channel in a smart antenna communication system utilize all antenna elements existing in the antenna array, and Instead of selecting one or adding another antenna array element, a high-power power amplifier and a high-gain antenna array element are not needed, thereby simplifying the system structure and saving system cost.

The object of the present invention can be achieved by the following technical solutions.

A method for realizing omnidirectional coverage of an array antenna. The array antenna includes M transmitting antenna array elements and corresponding M transmitting channels, where M is a positive integer greater than 1, and is characterized by including the following processing steps:

A. Divide the transmission time of the common channel signal into time slots;

B. Create a weight vector corresponding to each transmission slot. Each weight vector is composed of M weighting coefficients, and the M weighting coefficients should be M transmission channels. The M weighting coefficients are used to common the M transmission channels. The channel signal is subjected to corresponding weighting processing, and the common channel signal of each transmission channel after weighting processing is sent to M transmitting antenna array elements for transmission.

The object of the present invention can also be achieved by suppressing the following technical solutions. A device for realizing omnidirectional coverage of an array antenna. The array antenna includes M transmitting antenna array elements and M transmitting channels corresponding to the M transmitting antenna array elements, where M is a positive integer greater than 1, and is characterized by: The common channel beamforming weighting coefficient generator and M weighting coefficient adjusters; the common channel beamforming weighting coefficient generator automatically generates weight vectors according to time slots, and each weight vector is composed of M weighting coefficients and M weighting coefficient adjusters. In each time slot, M weighting coefficients corresponding to the common channel signals of the M transmission channels are used for corresponding weighting processing, and the common channel signals of the weighting processed transmission channels are sent to the M transmitting antenna array elements for transmission.

In the method and device of the present invention, given a weight vector, that is, a set of weighting coefficients, a common channel signal of each transmission channel is weighted, and then sent by an antenna array element for transmission. Corresponding directivity is related to the arrangement of the antenna array and the weighting coefficient. At different times, different weighting coefficient vectors are used, so that the pattern of the antenna array is constantly changed. In a certain direction, the antenna gain shows a change in strength over time, which is equivalent to the fast fading of a channel. This fast fading can be overcome through techniques such as channel coding. From the perspective of the average effect, the gains of the antennas in all directions are basically the same, which is equivalent to an isotropic antenna array, thereby achieving the object of the present invention, that is, using all antenna array elements in the antenna array to achieve the common channel, area Omnidirectional coverage.

Compared with the single antenna array element transmission of the common channel, the technical scheme of the present invention does not need to use a high-power power amplifier and a high-gain antenna array element, thereby reducing the system cost and simplifying the system structure. Brief description of the drawings

FIG. 1 is a schematic diagram of a steering vector of a smart antenna array;

Figure 2 is a schematic diagram of a typical smart antenna system structure;

FIG. 3 is a structural diagram and an apparatus of an array antenna according to the present invention for implementing omnidirectional coverage of a common channel; Method flowchart, which can be implemented in two ways;

4 is a schematic diagram of a linear antenna array;

Fig. 5 is an effect diagram of an antenna array pattern using the method and device of the present invention and adopting the first method flow.

FIG. 6 is an effect diagram of an antenna array pattern after using the method and device of the present invention and adopting two methods. Mode of Carrying Out the Invention

The present invention is described in detail below with reference to the drawings.

Referring to FIG. 3, the structure and method flow of the device for realizing omnidirectional coverage of a common channel by an array antenna. The device includes a common channel beamforming weighting coefficient generator 31 and M weighting coefficient adjusters 32, and 1 to M transmission antennas correspond to 1 to M transmission channels. The common channel beamforming weighting coefficient generator 31 autonomously generates a weight vector, and each weight vector is composed of M weighting coefficients w _M , w ₂ , _t ... ¾ _t , where the subscript _t represents time, and the weight vector is written as Wt is the weight vector used at time t.

The time for transmitting the common channel signal s (t) is divided into time slots. The common channel beamforming weighting coefficient generator 31 uses a specific weight vector construction method to construct a weight vector Wt for each transmission slot, and uses the weight vector Wt M weighting coefficients Wi, _t , w ₂ , t... W _M , _t correspond to M transmission channels, and the M weighting coefficient adjusters 32 respectively use the corresponding weighting coefficients to the common channel signal s of the transmission channel of itself ( t) Perform weighting processing, and send the processed results to the corresponding M transmitting antenna array elements for transmission.

Two methods for constructing a specific weight vector by the common channel beamforming weighting coefficient generator 31 are given below, which are the first embodiment and the second embodiment, respectively.

In Embodiment 1, the common channel wave ^ shaping weighting coefficient generator 31 generates a weight vector Wt corresponding to one transmission slot, and each of the M weighting coefficients w ^ w ^ .. ^^ of the weight vector Wt. Each appears in time as a random sequence, forming a total of M random sequences. The M random sequences are mutually unrelated or related, and f generates very weak random sequences, such as M sequences with different phases (M is A positive integer greater than 1).

In the first embodiment, the common channel beamforming weighting coefficient generator 31 generates a weight vector corresponding to each common channel transmission slot. Each weight vector is a vector composed of M weighting coefficients. The weighting coefficients appear as a random sequence in time. By using a random sequence of uncorrelated or weakly correlated weighting coefficients in each transmission channel, the weighting processing is performed on the common channel signals by the weighting coefficient adjuster 32 during continuous common channel signal transmission time, and the weighted processing result is sent to M accordingly. Transmitting antenna array elements. By using all antenna elements of the array antenna, omnidirectional coverage of the common channel signal is achieved.

This embodiment 1 uses a common channel beamforming weighting coefficient generator to generate M random sequences; these M random sequences are used as M weighting coefficient sequences and correspond to M transmission channels, and are used in M weighting coefficient adjusters M weighting coefficient sequences—corresponding to the common channel signals of the M transmitting channels, and the weighted common channel signals in the M transmitting channels are sent to the corresponding M transmitting antennas for transmission.

In Embodiment 1, since each antenna element is weighted with an uncorrelated random sequence, for example, m-sequences with different phases are used on different antenna elements, there is no need to know the correction information of each transmission channel, even if a certain The failure of the antenna array element will not affect the omnidirectional coverage characteristics of the common channel of the antenna array, so it has better robustness.

In Embodiment 2, the common channel beamforming weighting coefficient generator 31 generates N weight vectors Wt corresponding to N consecutive transmission time slots, and each weight vector Wt is composed of M weighting coefficients vh, _t , w ₂ , t... w _M , _t , subscript _t represents time, and Wt is the weight vector used at time t.

Common channel beamforming weighting coefficient generator 31 autonomously generates N weight vectors (N is greater than

1 is a positive integer), denoted by w, wt ₂ wt _N , each weight vector includes M weighting coefficients, denoted by ^^^^ ... "The M weighting coefficients correspond to M transmission channels, and are weighted by M Coefficient adjustment The node 32 weights its own transmission channel with a corresponding weighting coefficient.

The transmission time of the common channel signal s (t) is divided into time slots, and in each transmission time slot, a weight vector is selected from N weight vectors. In successive transmission time slots, the N weight vectors are used in turn, that is, in each transmission time slot, each transmission channel is weighted by a weighting coefficient in a weight vector. The design of each of the M weights (weighting coefficients) in the N weight vectors makes the power average gain of the antenna array pattern weighted by the N sets of weights isotropic. Generally speaking, two weight vectors (N = 2), that is, two sets of weights (weighting coefficients) can be used to achieve the above purpose.

This embodiment 2 implements omnidirectional coverage of a common channel by designing each weight vector and a set of weighting coefficients in each weight vector and using all antenna elements in the array antenna.

In each transmission slot of the continuous common channel signal transmission time, the common channel beamforming weighting coefficient generator 31 cyclically uses one weight vector among N weight vectors, and uses the M weighting coefficients in the weight vector to correspond to M For the transmission channels, the common channel signals in the M transmission channels are weighted by the M weighting coefficient adjusters 32. The cyclic use of the N weight vectors can be used according to the sequence number of the N weight vectors, that is, each weight vector is sequentially and cyclically selected from the N weight vectors in consecutive transmission time slots.

The linear antenna array is taken as an example to further explain the technical solution of the present invention.

Referring to FIG. 4, for a linear array, the pattern is expressed as: g (0) where d is the distance between antenna array elements. Set the antenna array to 8

The antenna elements M = 8, and the distance d between the antenna elements is a half wavelength λ / 2.

If the solution of Embodiment 1 is adopted, each antenna array element is excited with m-sequences of different phases, and averaged with 1000 points (1000 patterns) to obtain the normalized pattern shown in FIG. 5 (the figure only Draw a gain of 0 °-180 °), which is approximately a semicircle. The average result is the same as the coverage of a single antenna, except that a fast fading is superimposed on time.

If the solution of Embodiment 2 is adopted, two weight vectors (N = 2) are selected, that is, two sets of weight coefficients, for:

wt ₂ = [li -1 i 1 —i -1-] These two weight vectors are automatically generated by the common channel beamforming weighting coefficient generator, and each weight vector includes 8 weighting coefficients. It is required that the patterns of the two weight vectors are complementary, that is, the average gain of the patterns of the two weight vectors is approximately isotropic. As long as the generation principle is available, the common channel beamforming weighting coefficient generator can generate weight vectors according to the principle. There can be multiple implementation techniques, which are not listed here.

The transmission time of the common channel signal is divided into time slots. In the first transmission slot, a weight vector is selected from the two weight vectors, ^ port wt '^ l 1 1 -1 1 -1 1 1], and the corresponding weighting coefficients are used in 8 weighting coefficient adjusters. The common channel signal s (t) is weighted, that is, the common channel signal s (t) in the transmission channel 1 is weighted by a weighting coefficient "Γ, and the common channel signal S ( t) weighting, · .. weighting the common channel signal s (t) in the transmission channel 4 with a weighting factor "-1", ..., weighting the common channel signal s in the transmission channel 8 with a weighting factor "1" (t) weighting. In the second transmission slot, another weight vector is selected from these two weight vectors: wt ₂ = [li -1 i 1-/ -1-/], at 8 weighting coefficients The regulator uses the corresponding weighting coefficient to weight the common channel signal s (t), that is, the weighting coefficient "1" is used to weight the common channel signal s (t) in the transmission channel 1, and the weighting coefficient "i" is used to weight the transmission. The common channel signal s (t) in channel 2 is weighted, and the common channel signal s (t) in transmission channel 3 is weighted with a weighting coefficient "-1" Port rights, ... by the weighting coefficient "- i" of the transmitting channel 8 common channel signal s (t) is weighted (i is an imaginary unit) In a third transmit timeslot, and by wt _{I =} [l 1. 1 -1 1 -1 1 1] weight the common channel signal s (t) ...

These two weight vectors, that is, the patterns of the two sets of weighting coefficients are complementary. In either direction, the pattern gain of the one set of weighting coefficients is weak, and the pattern gain of the other set of weighting coefficients is strong. Complementary, as shown in Figure 6, the superposition of the two patterns.

In Figure 6,

1 1 -1 1 -1 1 1] at 0 °, 90 °, 180 °, 270. The directional gain is the strongest at 60 °, 120 °, 240. The direction gain at 300 ° is the weakest; the dashed line is a directional pattern with weight vector wt ₂ = [li -1 i 1 —i -1-], at 60. , 120 °, 240 °, 300 ° The directional gain is the strongest, at 0 °, 90 °. The directional gains of 180 ° and 270 ° are the weakest. Therefore, the two weight vectors and two sets of weighting coefficients are used alternately to achieve omnidirectional coverage.

By adopting the scheme of the present invention, the power of all antennas is fully utilized, and high-power power amplifiers and high-gain antennas are avoided in an intelligent antenna system to achieve omnidirectional coverage, which simplifies the system and saves costs.

Claims

Claim

A method for realizing omnidirectional coverage of an array antenna, the array antenna comprising M transmitting antenna array elements and corresponding M transmitting channels, where M is a positive integer greater than 1, and is characterized by including the following processing steps:

A. Divide the transmission time of the common channel signal into time slots;

B. Construct a weight vector corresponding to each transmission slot. Each weight vector is composed of M weighting coefficients. The M weighting coefficients correspond to M transmission channels. The M channel weighting coefficients are used for common channel signals in the M transmission channels. The weighting processing is performed, and the common channel signals of the transmission channels after the weighting processing are sent to M transmitting antenna array elements for transmission.

2. The method according to claim 1, wherein in the step B, the M weighting coefficients constituting the weight vector form M weighting sequences in time, and the M weighting sequences use M random sequences.

3. The method according to claim 2, wherein: the M random sequences are irrelevant or weakly correlated.

The method according to claim 2, characterized in that: the M random sequences are M m sequences with different phases.

5. The method according to claim 1, characterized in that: in said step B, N weight vectors are constructed corresponding to N consecutive transmission slots, and the N weight vectors are cyclically used, and N is a positive integer greater than 1. .

6. The method according to claim 5, characterized in that: the N weight vectors are represented by an average gain of the N weight vector pattern as an approximately isotropic structure.

7. The method according to claim 5, characterized in that: the cyclic use of the N weight vectors is selected according to the sequence number of the weight vector and in the sequence of the sequence number of the weight vector Every weight vector.

8. A device for realizing omnidirectional coverage of an array antenna. The array antenna includes M transmit antenna array elements and M transmit channels corresponding to the M transmit antenna array elements, where M is a positive integer greater than 1, and is characterized by: It includes a common channel beamforming weighting coefficient generator and M weighting coefficient adjusters; the common channel beamforming weighting coefficient generator automatically generates weight vectors according to time slots, and each weight vector is composed of M weighting coefficients and M weighting coefficients. In each time slot, the regulator performs weighting processing using M weighting coefficients corresponding to the common channel signals of the M transmission channels, and the weighted processed common channel signals of each transmission channel are sent to the M transmitting antenna array elements for transmission.

9. The apparatus according to claim 8, wherein the common channel beamforming weighting coefficient generator autonomously generates weight vectors according to time slots, and the M weighting coefficients constituting the weight vector form M weighting sequences in time, The weighting coefficient generator generates M random sequences as the M weighting sequences.

10. The apparatus according to claim 9, wherein: the M random sequences are irrelevant or weakly correlated.

11. The apparatus according to claim 9, wherein: the M random sequences are M m sequences with different phases.

12. The device according to claim 8, characterized in that: the autonomously generated weight vectors are N weight vectors cyclically constructed by a common channel beamforming weighting coefficient generator, and when N consecutive common channels are transmitted. Gap corresponds, N is a positive integer greater than 1.

13. The apparatus according to claim 12, wherein: the N weight vectors are represented by an average gain of the N weight vector pattern as an approximately isotropic structure.

14. The device according to claim 12, characterized in that: the N weight vectors are weighted by a common channel beamforming coefficient generator, and in the continuous transmission time slot, according to the sequence number of the weight vector Sequentially and cyclically select each weight vector.