WO2004059793A1 - Antenne intelligente et dispositif de formation de faisceau adaptatif - Google Patents

Antenne intelligente et dispositif de formation de faisceau adaptatif Download PDF

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Publication number
WO2004059793A1
WO2004059793A1 PCT/CN2002/000947 CN0200947W WO2004059793A1 WO 2004059793 A1 WO2004059793 A1 WO 2004059793A1 CN 0200947 W CN0200947 W CN 0200947W WO 2004059793 A1 WO2004059793 A1 WO 2004059793A1
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WIPO (PCT)
Prior art keywords
weight
signal
iterative
beamforming
error
Prior art date
Application number
PCT/CN2002/000947
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English (en)
French (fr)
Inventor
Lidong Chi
Yanwen Wang
Yunkuan Wang
Original Assignee
Zte Corporation
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Publication date
Application filed by Zte Corporation filed Critical Zte Corporation
Priority to EP02792581A priority Critical patent/EP1580843A4/en
Priority to PCT/CN2002/000947 priority patent/WO2004059793A1/zh
Priority to CNB028300912A priority patent/CN100429826C/zh
Priority to AU2002359956A priority patent/AU2002359956A1/en
Priority to US10/541,316 priority patent/US7362267B2/en
Publication of WO2004059793A1 publication Critical patent/WO2004059793A1/zh

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Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/26Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
    • H01Q3/2605Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842Weighted combining
    • H04B7/086Weighted combining using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/12Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1812Hybrid protocols; Hybrid automatic repeat request [HARQ]
    • H04L1/1819Hybrid protocols; Hybrid automatic repeat request [HARQ] with retransmission of additional or different redundancy
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842Weighted combining
    • H04B7/0848Joint weighting
    • H04B7/0854Joint weighting using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion

Definitions

  • the present invention relates to the field of wireless communications, and in particular to adaptive beamforming techniques for smart antennas.
  • the patent application does not solve the problem of delay accuracy, and the initial weight requirement is high, so that the performance of the smart antenna is guaranteed. Since the accurate determination of the multipath delay is decisive for the adaptive beamforming method, how to accurately search for the delay information fc is a problem that the prior art needs to solve. Summary of the invention
  • a beamforming method for a smart antenna including pre-multibeam processing on an array signal, delay alignment; using a pilot symbol to calculate a suboptimal weight; The weight is used as an initial value, and the optimal weight is iteratively calculated; using the optimal weight, a beam is formed.
  • a beamforming apparatus for a smart antenna including: a spatial domain forming module, configured to perform beamforming on a signal received by an antenna array, where the spatial beamforming module further includes: a beam delay search unit, configured to perform pre-multibeam processing on the array signal, and delay alignment; a time domain processing module, configured to obtain the transmitted data according to the signal formed by the spatial domain forming module beam; and a re-spreading iterative module And generating, by the data information obtained by the time domain matched filtering module, a reference signal, calculating an iteration error, and feeding back to the airspace beamforming module.
  • a beam delay search unit configured to perform pre-multibeam processing on the array signal, and delay alignment
  • a time domain processing module configured to obtain the transmitted data according to the signal formed by the spatial domain forming module beam
  • a re-spreading iterative module And generating, by the data information obtained by the time domain matched filtering module, a reference signal, calculating an iteration error, and feeding back to
  • a smart antenna comprising: an antenna array composed of a plurality of array elements and a beam forming device as described above.
  • FIG. 1 is a perspective view of four narrow beams of coverage sectors generated by pre-multibeam processing in accordance with a preferred embodiment of the present invention
  • FIG. 2A is a flow chart showing a beamforming method according to a preferred embodiment of the present invention; a detailed flow chart illustrating iterative calculation weights in the embodiment shown in FIG. 2;
  • FIG. 3 is a diagram showing a method according to the present invention. a block diagram of the construction of a smart antenna of a preferred embodiment;
  • Figure 5 is a comparison of the output bit error rate of the structure of the present invention with and without pre-multibeam processing. Detailed ways
  • FIG. 2A is a flow chart showing a beamforming method in accordance with a preferred embodiment of the present invention.
  • step 101 accurate delays of the respective multipaths are obtained before adaptive beamforming, thereby ensuring that the beamforming of the smart antenna is more reliable.
  • step 101 accurate delays of the respective multipaths are obtained before adaptive beamforming, thereby ensuring that the beamforming of the smart antenna is more reliable.
  • step 101 accurate delays of the respective multipaths are obtained before adaptive beamforming, thereby ensuring that the beamforming of the smart antenna is more reliable.
  • Multi-beam processing is performed on the received array to provide a time-aligned array received signal to the adaptive weight calculation in real time.
  • the process includes generating a fixed narrow beam of a plurality of coverage sectors.
  • the sector is 120 degrees and four fixed narrow beams are generated (as shown in Figure 1).
  • the data received by the array is beamformed by using the fixed narrow beam, and the generated beam domain signal is subjected to a delay search to find a beam with the largest energy value, and the delay value in the beam is the delay value of the received signal of the array.
  • the data received by the array is time-delay-aligned according to the delay value, where the array received vector of the information bits after the delay is recorded as X.
  • the size of the sector and the coverage of the beam can be adjusted as required to ensure that all mobile station arrival directions within the sector are included in the pre-multibeam.
  • the number of beams and beam width can also be adjusted as required. If the direction of arrival of the mobile station is exactly between the two beams, the two beams can be combined into one wide beam to ensure effective beam coverage.
  • the pre-multibeam processing of the present invention can provide accurate delay information for the adaptive calculation method of the smart antenna, and can further ensure the accuracy and reliability of the adaptive algorithm.
  • the processing result of the pure adaptive algorithm is compared , greatly improve the signal-to-noise ratio of the smart antenna receiving signal, and give full play to the superior performance of the smart antenna.
  • a suboptimal weight is calculated.
  • the known pilot symbol is used as a reference signal, and the correlation matrix is obtained by spreading, scrambling, and delay-aligning the array receiving vector. Excellent value.
  • the array received vector after the spread spectrum scrambling and delay is used to obtain the optimal weight as the initial value of the subsequent minimum mean square error iteration, the initial value
  • the selection is closer to the ideal weight, which greatly improves the convergence speed (often 3-4 symbol bits can converge), which satisfies the real-time processing of the communication system. Requirements.
  • step 103 the weight is calculated iteratively with the suboptimal weight as the initial value. This step will be described below in conjunction with Fig. 2B.
  • FIG. 2B A detailed flow chart of the iterative calculation weights in the embodiment of Fig. 1 is illustrated.
  • the initial weight is used to form a beam.
  • the signal after beam formation is ⁇
  • Y W X, where is the weight.
  • represents the J'th information symbol
  • K represents the spreading factor, and represents the imaginary part.
  • step 117 the newly calculated weight is used as the initial weight, and the process returns to step 110.
  • the iterative calculation described above is performed for each time slot in a frame.
  • the optimal weight of the first time slot in the frame obtained according to the foregoing method may be flexibly used as the optimal weight of all time slots in the frame under the condition that the accuracy meets the requirement.
  • using the optimal weight of any time slot in the frame as the optimal weight of the subsequent time slot processing the signal data of the corresponding time slot, so that the calculation amount of the weight iteration can be further reduced.
  • step 104 Determine whether the iteration error satisfies the requirement. According to an embodiment of the invention, this can be done by determining if the mean squared value of the error is within a predetermined threshold. If the requirements are not met, then steps 102, 103 are repeated until the mean square error is within a predetermined threshold. If the requirement is met, proceeding to step 105, the new weight is saved as the optimal weight of the time slot, and the received signal is beamformed, the I channel data of the uplink channel is descrambled, and the information is received. , statistical output signal to noise ratio.
  • the smart antenna beamforming method according to the embodiment of the present invention avoids large matrix multiplication and matrix inversion by using the minimum mean square error iteration, and instead replaces with the addition and multiplication of the single tube, which is reduced.
  • the difficulty of hardware implementation is easier to implement.
  • the smart antenna includes: an antenna array composed of a plurality of array elements (1-M), a spatial domain forming module 21, a time domain processing module 22, and a respreading iteration module 23.
  • the spatial domain forming module 21, the time domain processing module 22 and the re-spreading iterative module 23 simultaneously constitute a beam forming apparatus for a smart antenna according to an embodiment of the present invention.
  • the smart antenna and its beam forming apparatus according to the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
  • the spatial domain forming module 21 is connected to each of the array elements of the antenna array (1-M) for performing spatial processing, beamforming on the received signals of the antenna array ⁇ ' ⁇ , ⁇ , ...;
  • the airspace forming module 21 includes: pre-multibeam delay search units 215.1-215. ⁇ , a weight update unit 213, multipliers 211.1-211.M, and an adder 212 respectively connected to respective antenna elements.
  • the pre-multi-beam delay search unit 215 generates several fixed narrow beams (as shown in FIG. 1) during operation, and uses these beams to separately receive signals from the beamforming array to obtain a beam signal. Then, the searcher performs delay search on the beam signal, selects the beam with the largest energy value, remembers the delay value of the beam, and uses the path delay of the received signal of the array, and delays the alignment of the received signals of the array.
  • the array-aligned signals after the delay alignment are respectively transferred to the corresponding multipliers (211.1-211.MX, these multipliers are respectively according to the corresponding values provided by the weight updating unit 213
  • the weights are multiplied separately.
  • the result of the multiplication operation is summed in adder 212 and output to time domain processing module 22 as a result of beamforming.
  • the weight update unit 213 uses the minimum mean square according to the error information sent by the respreading iteration module 23 or the first slot pilot bit spread scrambled signal used as the reference signal for calculating the suboptimal weight. The error criterion, iteratively calculates the weight, and assigns the calculated weights to the corresponding multipliers (211.1-211 ⁇ ).
  • the time domain processing module 22 includes a descrambler 221, a despreader 222, a channel estimation and compensation Rake unit (223, 224), and a decider 225.
  • the descrambler 221 and the despreader 222 are configured to perform descrambling and despreading on the signal formed by the beam.
  • Channel estimation and compensation Rake unit 223 is used to process the despread data, reduce the influence of the channel, and combine the signals of multiple paths by Rake.
  • a determiner 225 is configured to output a transmitted data bit to the Rake combined signal.
  • the re-spreading iteration module 23 mainly includes: a re-expander 231, a scrambler 232, and an iterative error calculation unit 233.
  • the respreader 231 and the scrambler 232 perform spreading and scrambling on the data obtained from the decision output from the time domain processing module 22 to generate an iterative reference signal, '.
  • the iterative error calculation unit 233 calculates the iteration error E based on the calculated iterative reference signal and the received signal 7 of the beamforming module of the spatial domain forming module 21.
  • the iterative error calculation unit 233 transmits the iteration error to the weight update unit 213 of the airspace formation module 21.
  • the respreading iteration module 23 further includes a unit 234 for spreading and scrambling pilot bits of the first slot, and a unit 235 for spreading and scrambling pilot bits of other slots as reference signals. .
  • the pre-multi-beam delay search unit 215 searches for the delay information, and delays the array received signals into a delay-aligned baseband received signal [ ⁇ ⁇ ]. Next, the baseband signal will be processed.
  • the known pilot bit re-spread scrambled signal provided by unit 234 is used as a reference signal, and the time-delayed baseband signal [X R X M ] is found to be cross-correlated.
  • the matrix calculates the suboptimal weight until the pilot bit of one time slot ends.
  • the suboptimal weight at the end of the pilot bit of the first time slot is input to the multiplier 211, and the beamforming signal of each element is synthesized by the adder 212.
  • This signal is further decomposed into two signals, one input to the iterative error calculation module 233 of the re-spreading iteration module 23 as the subtracted vector at the time of calculating the error, and the other input to the descrambler 221 of the time domain processing module 22.
  • the descrambled data of the descrambled data is 222.
  • the despread data unit is a bit, and the despread data can be processed by the channel estimation and compensation RAKE units 223, 224 to reduce the influence of the channel.
  • the data after passing through the decider 225 is a sign bit of 1, - 1, ..., which is input to the re-spreading iteration module 23.
  • the symbol bit input by the time domain processing module 22 is input to the iterative error calculation module 233 via the re-expander 231 and the scrambler 232, and subtracted from the previously input adder 212 signal to obtain an error.
  • the signal is input to the weight update module 213 of the airspace beamforming module 21.
  • the respread scrambled signal of the known pilot bit provided by unit 235 is used as an input to the iterative error calculation module 233, and subtracted from the previously input adder 212 signal, An error signal is obtained and input to the weight new module 213 of the airspace beamforming module 21.
  • the error calculated by the error calculation unit 233, ⁇ is its conjugate transpose.
  • the iterative error (calculated by the iterative error calculating unit 233) for beamforming with this weight satisfies the requirements, the data descrambling, despreading, channel estimation compensation, and RAKE combining of the beamforming are performed.
  • the components of the beam forming apparatus constituting the smart antenna of the embodiment of the present invention may be hardware modules or software modules.
  • the modules may be implemented in a dedicated chip or an FPGA, or some modules may be DSP is implemented in software.
  • FIG. 4 is a simulation comparison curve of the output noise ratio before and after the pre-multibeam processing of the adaptive beam algorithm of the present invention.
  • the abscissa of Fig. 4 represents the input signal-to-noise ratio, Eb/N0, and the variation range is 4-12 dB.
  • the ordinate represents the output signal to noise ratio.
  • the horizontal and vertical coordinates are in 2dB intervals.
  • the simulation condition is a macro cell of 20 users, the data length is 20 frames, and the symbol rate is 60 kbps.
  • NO Beam represents an adaptive beamforming method that does not use pre-multibeam processing in the prior art.
  • the Beam+ method represents a combination of the pre-multibeam of the present invention and a pilot-bit assisted despreading and re-spreading multi-target array based on a minimum mean square error criterion.
  • V represents the speed of movement in kmph.
  • Fig. 5 represent the bit error rate curves of the received signals using the prior art and the method and structure of the present invention, respectively. Similarly, as can be seen from Figure 5, the method and structure of the present invention allows the received output error rate to be greatly reduced as compared to the prior art.

Description

智能天线及其自适应波束形成方法和装置 技术领域
本发明涉及无线通信领域, 具体地, 涉及智能天线的自适应波束形成 技术。 技术背景
近年来, 现代数字信号处理技术的¾4 , DSP芯片处理能力的不 断提高和芯片价格的不断下降, 使得利用数字技术在基带形成天线波束成 为可行, 从而促使以自适应波束形成算法为技术核心的智能天线技术在码 分多址无线通信中获得广泛应用。
在码分多址无线通信系统中, 在进行智能天线自适应波束形成之前, 要求具有精确的时延信息, 否则由于码的相关性, 将严重影响自适应的处 理结果。 目前, 智能天线的波束形成算法很多, 但其共同存在的问题是没 有解决多径时延问题。 在现有的智能天线自适应波束形成算法中, 或者是 假设时延信息精确已知, 或者是假定时延已知, 而且具体的实现方式或结 构涉 5 艮少。 ^公告号为 1235391的名称为 "用于码分多址系统的预先优 化成形波束的自适应阵列天线" 的中国申请中, 在进行自适应处理时, 起 复数权值的计算被分解为两个部分, 即初始权设计和运行权处理, 该专利 申请未解决时延精度问题, 对初始权的要求较高, 这样智能天线的性能就 保证。 鉴于多径时延的精确确定对自适应波束形成方法具有决定性的 意义, 因此,如何精确搜索出时延信息 fc 现有技术亟需解决的一个问题。 发明内容
根据本发明的一个方面, 提 了一种智能天线的波束形成方法, 包括 对阵列信号进行预多波束处理, 时延对齐; 利用导频符号, 计算次最优权 值; 以所述次最优权值作为初始值, 迭代计算最优权值; 利用所述最优权 值, 形成波束。 才艮据本发明的另一个方面, 提供了一种智能天线的波束形成装置, 包 括: 空域形成模块, 用于对天线阵列接收的信号进行波束形成, 所述空域 波束形成模块还包括: 预多波束时延搜索单元, 用于对阵列信号进行预多 波束处理, 时延对齐; 时域处理模块, 用于根据由所述空域形成模块波束 形成的信号, 获得传送的数据; 以及重扩迭代模块, 用于根据由所述时域 匹配滤波模块获得的数据信息, 生成参考信号, 计算迭代误差, 并反馈给 所述空域波束形成模块。
根据本发明的另一个方面, 提供了一种智能天线, 包括: 由多个阵元 組成的天线阵列和前面所述的波束形成装置。 附图说明
相信通过下面结合附图对本发明优选实施例的描述, 可以使本发明的 以上和其他优点、 目的和特征变得明了。
图 1是根据本发明一个优选实施例的预多波束处理生成的覆盖扇区的 四个窄波束的指向图;
图 2 A是展示了根据本发明一个优选实施例的波束形成方法的流程图; 图 示了图 2所示实施例中的迭代计算权值的详细流程图; 图 3 是展示了根据本发明一个优选实施例的智能天线的构成的方块 图;
图 4为本发明的结构采用和不采用预多波束处理的输出信噪比的对比 曲线;
图 5为本发明的结构采用和不采用预多波束处理的输出误码率的对比 曲线。 具体实施方式
下面就结合附图对本发明的具体实施方式进行详细的说明。
图 1为波束指向图,可以看到四个波束能艮好地覆盖 -60G-60Q范围内的 120Q扇区, 旁瓣较低。 图 2A是展示了根据本发明一个优选实施例的波束形成方法的流程图。 如图 2A所示,首先在步驟 101 ,为在自适应波束形成之前获得各个多径的 精确时延, 从而保证智能天线的波束形成更可靠, 在计算自适应权值的过 程中, 同时并行地对接收的阵列进^多波束处理, 以实时地向自适应权 值计算提供经时延对齐的阵列接收信号。
具体地, 该处理包括生成若干覆盖扇区的固定窄波束, 例如, 在一实 施例中, 所述扇区为 120度, 生成四个固定窄波束(如图 1所示)。 使用所 述固定窄波束对阵列接收的数据进行波束形成, 对该生成波束域信号进行 时延搜索, 找到能量值最大的波束, 该波束内的时延值即为阵列接收信号 的时延值。 根据该时延值对阵列接收的数据进行时延对齐, 这里将时延对 齐后的信息位的阵列接收矢量记为 X。
在本发明的不同实施例中, 可根据要求调节扇区的大小以及波束的覆 盖范围, 保证扇区内所有移动台波达方向均包含在预多波束内。 也可根据 要求调整波束的数目和波束宽窄。 如果移动台的波达方向正好位于两个波 束之间, 可以把两个波束合成一个宽波束, 保证有效的波束覆盖。
本发明的预多波束处理能够为智能天线的自适应计算方法提供精确 的时延信息,能够更进一步保证自适应算法的精度和可靠性,经实验表明, 纯的自适应算法的处理结果相比, 大大提高了智能天线接收信号的信噪 比, 充分发挥了智能天线的优越性能。
接着在步驟 102, 计算次最优权值。 在当前帧的第一时隙的所有导频 位期间, 以已知导频符号为参考信号, 对其进行扩频、 加扰后与时延对齐 后的阵列接收矢量求相关矩阵, 作为次最优权值。 其中, 导频位重扩加扰 的信号为^ ,。, .^ , 次最优权值为 = E[ r'], 其中, bp;,。,为已知的导频符 号, 为扩频码和扰码相乘的结果序列。 在该步骤中, 利用已知导频位作 为参考信号, 经扩频加扰后与时延对齐的阵列接收矢量求最优权值, 作为 后续最小均方误差迭代的初值, 该初值的选取更加贴近理想权值, 大大提 高了收敛速度 (往往 3-4个符号比特即可收敛), 满足了通讯系统实时处理 的要求。
然后在步骤 103, 以次最优权值为初值, 迭代计算权值。 下面结合图 2B对这一步驟进行说明。
图 示了图 1所示实施例中的迭代计算权值的详细流程图。 如 图 2B所示, 首先在步骤 110, 用初始权值形成波束, 假设形成波束后的信 号为 Τ, 则: Y = W X, 其中 为权值。
接着在步驟 111, 对形成波束的信号解扰解扩: v/) = lmag((HV(t)C(t)),
人 -=1+ jK
其中 ·代表第 J'个信息符号, K表示扩频因子, 表示取虚部。
在步骤 112, 用导频部分解扰解扩的结果估计 RAKE合并的第 条多 径的复增益: (/) =丄 m. 其中 为导频位位数, ,为已知导频位。 在步骤 113, 对传送的控制信息进行判决: b = sig7i(m ag(v)Gc* (/)) 在步驟 114, 将判决出的控制信息扩频
Figure imgf000006_0001
, 将控制信息加扰 r = dxS , 如果位于导频位期间则直接使用已知导频位 b = to。 从而得到参 考信号 r。
在步骤 115, 计算迭代误差: E = r-Y, r为前面计算出的参考信号, ; r 为最新波束形成的信号。 _
在步驟 116, 利用迭代公式计算新权值: wM=wi + -XxEH , 其中, Wi 为上一步计算或迭代出的权值; 〃为迭代步长, 可取 0.1或 0.01; 为前 面计算的误差矩阵, 为其共轭转置。
然后在步骤 117, 将新计算出的权值作为初始权值, 返回步驟 110。 在本发明一个实施例中, 针对一个帧中的每个时隙进行上述的迭代计 算。 在其他较佳实施例中, 在精确度满足要求的条件下, 可灵活地将根据 上述方法获得的该帧内第一时隙的最优权值作为该帧内所有时隙的最优 权值, 或以该帧内任何一时隙的最优权值作为后续时隙的最优权值, 对相 应时隙的信号数据进行处理, 如此可进一步减小权值迭代的计算量。
回到图 2A, 在迭代计算权值(步骤 103)之后, 所述过程进行到步骤 104, 判断迭代误差是否满足要求。根据本发明的一个实施例, 可以通过判 断该误差的均方值是否在一预定门限内来完成。 如果不满足要求, 则重新 步骤 102, 103, 直到均方差在预定门限内。如果满足要求, 则进行到步骤 105,保存该新的权值作为该时隙的最优权值,并用其对接收信号进行波束 形成, 解扰解扩上行信道的 I路数据, 完成信息的接收, 统计输出信噪比。
通过以上描述可以看出, 据本发明实施例的智能天线波束形成方法 通过采用最小均方误差迭代, 避免了大型矩阵相乘和矩阵求逆, 转而以筒 单的加法和乘法代替, 降低了硬件实现的难度, 更易于工程实现。
图 3 是展示了根据本发明一个优选实施例的智能天线的构成的方块 图。 如图 3所示, 根据该实施例的智能天线包括: 由多个阵元(1-M )组 成的天线阵列、 空域形成模块 21、 时域处理模块 22和重扩迭代模块 23。 所述天线阵元( 1-M )还分别包括各自的天线前端(图中未示出), 用于接 收无线射频信号并且转换为接收信号 = [ c,,x2,… , 这对于本领域技术人 员是熟知的。
空域形成模块 21, 时域处理模块 22和重扩迭代模块 23同时又组成了 才艮据本发明实施例的用于智能天线的波束形成装置。 下面就结合附图对才艮 据本发明实施例的智能天线及其波束形成装置进行详细描述。
空域形成模块 21与天线阵列(1-M )的每个阵元相连, 用于对天线阵 列的接收信号 Α' ^Χ, Α,...;^]进行空域处理, 波束形成。 空域形成模块 21 包括: 分别与各个天线阵元相连的预多波束时延搜索单元 215.1-215.Μ、 权值更新单元 213、 乘法器 211.1-211.M和加法器 212。
预多波束时延搜索单元 215,在工作时, 生成几个固定窄波束(如图 1 所示), 用这几个波束分别波束形成阵列接收信号, 得到波束信号。 然后 利用搜索器对波束信号进行时延搜索, 选择能量值最大的波束, 记住该波 束的时延值, 作为阵列接收信号的路径时延, 并对阵列接收信号进行时延 对齐。
时延对齐后的阵列接收信号被分别传递给对应的乘法器 ( 211.1-211.M X 这些乘法器则分别根据由权值更新单元 213提供的相应 的权值 进行各自的乘法运算。乘法运算的结果在加法器 212中 被求和, 并作为波束形成的结果输出给时域处理模块 22。
权值更新单元 213,则根据重扩迭代模块 23发送过来的误差信息或者 作为用于计算次最优权值的参考信号的第一时隙导频位扩频加扰的信号, 利用最小均方误差准则, 迭代计算权值, 并将计算出的权值分别赋给相应 的乘法器(211.1-211·Μ )。
时域处理模块 22包括:解扰器 221、解扩器 222、信道估计与补偿 Rake 单元(223、 224 )和判决器 225。 解扰器 221和解扩器 222, 用于对波束形 成后的信号, 进行解扰和解扩。信道估计与补偿 Rake单元 223 , 用于对解 扩数据进行处理, 减少信道的影响, 将多个路径的信号进行 Rake合并。 判决器 225, 用于将对 Rake合并后的信号判决输出所传送的数据比特。
重扩迭代模块 23主要包括: 重扩器 231、加扰器 232和迭代误差计算 单元 233。重扩器 231和加扰器 232对从时域处理模块 22输出的判决得到 的数据, 进行扩频和加扰, 从而生成迭代参考信号 ,'。 迭代误差计算单元 233则根据计算出的迭代参考信号和空域形成模块 21波束形成的接收信号 7, 计算出迭代误差 E。 迭代误差计算单元 233并且将迭代误差 传送给 空域形成模块 21的权值更新单元 213。 另外, 在重扩迭代模块 23中还包 括了一个用于扩频加扰第一时隙的导频位的单元 234以及用于扩频加扰其 它时隙的导频位作为参考信号的单元 235。
下面说明本发明该实施例的波束形成装置的工作过程。
首先通过预多波束时延搜索单元 215搜索出时延信息, 对阵列接收信 号进行时延对齐, 成为时延对齐的基带接收信号 [ΧΓ·Χμ】。 接下来, 将针对 基带信号进行处理。
在第一个时隙的所有导频位期间, 由单元 234提供的已知导频位重扩 加扰的信号作为参考信号,和时延对齐的基带信号〖XRXM】一起求互相关矩 阵, 计算出次最优权值, 直到笫一个时隙的导频位结束。 把第一个时隙的 导频位结束时的次最优权值输入到乘法器 211 , 把每个阵元的波束形成信 号通过加法器 212合成一路信号。 再把这个信号分解成两路信号,一路输入到重扩迭代模块 23的迭代误 差计算模块 233作为计算误差时的被减向量, 另一路输入到时域处理模块 22的解扰器 221。 解扰后的数据的 据 解扩器 222, 解扩出来的 数据单位是比特, 可利用信道估计和补偿 RAKE单元 223, 224对解扩数 据进行处理, 减少信道的影响。
经过判决器 225后的数据为 1, - 1, …的符号比特, 输入到重扩迭代 模块 23。 当当前时刻为信息位期间, 由时域处理模块 22输入的符号比特 经过重扩器 231、加扰器 232后输入到迭代误差计算模块 233,和先前输入 的加法器 212信号相减, 得到误差信号, 并将该误差信号输入到空域波束 形成模块 21的权值更新模块 213中。当当前时刻为其它时隙的导频位期间, 由单元 235提供的已知导频位的重扩加扰信号作为迭代误差计算模块 233 的一个输入, 和先前输入的加法器 212信号相减, 得到误差信号, 并输入 到空域波束形成模块 21的权值 新模块 213中。
输入到权值更新单元 213的参考信号和时延对齐的接收信号 [ -ΧΜΙ , 基于最小均方误差准则, 迭代, 求出最优权。 具体做法是: 利用迭代公式: WM = Wi + Ju - X x EH , 其中, ^为上一步计算或迭代出的权值; 为迭代步 长, 可取 0.1或 0.01; £:为迭代误差计算单元 233计算出的误差, ^为其 共轭转置。
如果用这个权值进行波束形成的迭代误差 (由迭代误差计算单元 233 计算) 满足要求, 则对此波束形成的数据解扰、 解扩、 信道估计补偿和 RAKE合并, 进行输出。
以上所迷的构成本发明实施例的智能天线的波束形成装置的各个组 成部分, 可以是硬件模块, 也可以是软件模块, 可以把这些模块做在专用 芯片或 FPGA中, 也可以把一部分模块在 DSP中用软件实现。
图 4为本发明的自适应波束算法采用预多波束处理前后输出噪声比的 仿真对比曲线。图 4的横坐标表示输入信噪比, Eb/N0,变化范围是 4-12dB。 纵坐标表示输出信噪比。 横纵坐标的间隔单位均为 2dB。 仿真条件是 20 个用户的宏小区, 数据长度是 20 帧, 符号速率是 60 kbps, 图上标注的 NO Beam表示现有技术中未采用预多波束处理的自适应波束形成方法, Beam+方法代表本发明的预多波束和基于最小均方误差准则的导频位辅 助解扩重扩多目标阵列相结合的自适应波束形成方法。 V代表移动的速度, 单位为 kmph。 从图中可以看出, 当输入信噪比为 4dB, 移动台速度为 30kmph时, 本专利获得的输出信噪比为接近 13dB, 而未采用预多波束处 理的方法的输出信噪比大约为 5.8dB,相差为大约 7.2dB, 同样,在输入信 噪比为 6、 8、 10和 12dB时, 结果类似, 所以与现有技术的未经预多波束 处理的自适应算法相比, 本发明的方法使输出信噪比大大提高。
图 5中的虚线和实线分别表示采用现有技术和本发明的方法和结构来 接收信号的误码率曲线。 同样, 由图 5可以看出, 与现有技术相比, 采用 本发明的方法和结构使接收输出误码率大大降低。
以上虽然通过本发明的一些示例性的实施例对本发明进行了详细的 描述, 但是以上这些实施例并不是穷举的, 本领域技术人员可以在本发明 的精神和范围内实现各种变化和修改。 例如, 以上所描述的实施例虽然是 针对 WCDMA 系统, 但是本领技术人员应当可以理解, 对于其它基于码 分多址的系统, 也是适用的。 因此, 本发明并不限于这些实施例, 本发明 的范围仅由所附权利要求为准。

Claims

权利要求
1. 一种智能天线的波束形成方法, 包括
对阵列信号进行预多波束处理, 时延对齐;
利用导频符号, 计算次最优权值;
以所述次最优权值作为初始值, 迭代计算最优权值;
利用所述最优权值, 形成波束。
2. 根据权利要求 1所述的智能天线的波束形成方法, 其中, 所述对阵 列信号进行的预多波束处理的步骤包括:
生成若干覆盖扇区的固定波束, 使用所述固定波束对阵列接收的数据 进行波束形成;
对生成的波束域信号进行波束时延搜索, 选出每个多径中最大的波 束, 并利用该波束的时延值对齐阵列数据。
3. 根据权利要求 2所述的智能天线的波束形成方法, 其中, 可随着扇 区的大小调节波束的覆盖范围、 波束的数目和宽窄, 保证扇区内的所有移 动台的波达方向均包含在所述预多波束内。
4. ^艮据权利要求 1所述的智能天线的波束形成方法, 其特征在于所 述计算次最优权值的步骤包括:
将当前帧的第一时隙的已知导频位扩频加扰, 作为参考信号; 根据最小均方误差准则, 计算所述参考信号和时延对齐后的阵列接收 信号的相关矩阵的近似解, 作为次最优权值。
5. 艮据权利要求 1所述的智能天线的波束形成方法, 其特征在于所 述迭代计算最优权值的步驟包括:
用初始权值, 对时延对齐后的阵列接收信号形成波束;
对形成波束的接收信号解扰、 解扩, 并判决出控制信息;
将判决出的控制信息重扩加扰, 作为迭代参考信号;
用迭代参考信号和形成波束的接收信号, 计算迭代误差;
计算新权值; 以新权值作为初始权值进行迭代。
6. 艮据权利要求 5所述的智能天线的波束形成方法, 其特征在于所 述计算新权值使用迭代公式: ,+1 = ^. + ^ X E", 其中, ^为前一次迭代 计算出的权值, 为迭代步长, 为迭代误差, ^为其共轭转置, r为迭 代参考信号, ; T为波束形成的接收信号。
7. 根根据权利要求 5所述的智能天线的波束形成方法, 其特征在于, 所述判决步骤, 在导频位期间, 用已知的导频位信息作为判决输出。
8. 根根据权利要求 5所述的智能天线的波束形成方法, 其特征在于, 所述方法在利用所述最优权值形成波束的步骤之前还包括:
判断迭代误差是否满足要求;
如果迭代误差不满足要求, 则重复所述计算次最优权值的步驟和迭代 计算最优权值的步骤。
9. 艮据权利要求 8所述的智能天线的波束形成方法, 其特征在于, 所述判断步骤包括:
计算迭代误差的均方值;
如果计算出的迭代误差的均方值大与一个预定门限, 则判断迭代误差 不满足要求, 否则判断判断迭代误差满足要求。
10. 艮据权利要求 8所述的智能天线的波束形成方法, 其特征在于, 将每帧第一时隙中获得的最优权值作为该整个帧的最优权值, 用于对该帧 中所有时隙的信号数据进行处理。
11. 一种智能天线的波束形成装置, 包括:
空域形成模块, 用于对天线阵列接收的信号进行波束形成, 所述空域 波束形成模块还包括: 预多波束时延搜索单元, 用于对阵列信号进行预多 波束处理, 时延对齐;
时域处理模块, 用于根据由所述空域形成模块波束形成的信号, 获得 传送的数据; 以及
重扩迭代模块, 用于根据由所述时域匹配滤波模块获得的数据信息, 生成参考信号, 计算迭代误差, 并反馈给所述空域波束形成模块。
12. 根据权利要求 11所述的波束形成装置,其特征在于,所述空域形成 模块进一步包括:
权值更新单元, 用于根据重扩迭代模块反馈的迭代误差, 计算用于波 束形成的多个权值;
多个乘法器, 分别用于将权值更新单元计算出来的相应权值与相应天 线阵列的阵元的接收信号相乘; 以及
加法器, 用于将多个乘法器的输出相加。
13. 根据权利要求 11所述的波束形成装置,其特征在于,所述时域处理 模块包括:
解扰解扩单元, 用于对由所述空域形成模块波束形成的信号, 解扰解 扩;
Rake合并单元, 用于将多个路径的信号进行 Rake合并; 以及 判决器, 用于将对 Rake合并后的信号判决输出所传送的数据。
14. 根据权利要求 11所述的波束形成装置,其特征在于,所述重扩迭代 模块包括:
重扩加扰单元, 用于对由所述时域处理模块获得的传送数据, 重扩加 扰, 作为迭代参考信号;
迭代误差计算单元, 用于根据来自所述重扩加扰单元的迭代参考信号 和来自所述空域形成模块的波束形成的接收信号, 计算迭代误差。
15. 根据权利要求 14所述的波束形成装置,其特征在于,所述空域形成 模块的权值更新单元, 利用由所述迭代误差计算单元计算的迭代误差, 迭 代计算最优杈值。
16. 根据权利要求 15所述的波束形成装置,其特征在于,所述空域形成 模块的权值更新单元, 根据最小均方误差准则, 计算已知导频位扩频加扰 信号和接收的导频段信号的互相关矩阵, 得到次最优权值, 作为迭代计算 的初始权值。
17. 据权利要求 16所述的波束形成装置,其特征在于,所述权值更新 单元, 当判断所述迭代误差不满足要求时, 重新计算次最优权值。
18. 根据权利要求 14所述的波束形成装置,其特征在于,所述迭代误差 计算单元, 在导频位期间, 利用已知导频位扩频加扰后的信号作为迭代参 考信号。
19. 一种智能天线, 包括: 由多个阵元组成的天线阵列和权利要求 11 至 18所述的波束形成装置。
PCT/CN2002/000947 2002-12-31 2002-12-31 Antenne intelligente et dispositif de formation de faisceau adaptatif WO2004059793A1 (fr)

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