WO2020114309A1 - 一种盲自适应波束成形算法 - Google Patents
一种盲自适应波束成形算法 Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/14—Two-way operation using the same type of signal, i.e. duplex
- H04L5/16—Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission
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- the invention relates to a blind adaptive beamforming algorithm applied to a half-duplex passive UHF radio frequency identification system.
- UHF radio frequency identification technology has received widespread attention.
- the technology uses 860 ⁇ 960 MHz frequency and can be applied in many fields, such as: supply chain management, logistics support system, automatic toll collection system, intelligent transportation system, etc. Wait, its recognition efficiency is higher than the traditional bar code system.
- Passive UHF RFID systems usually contain several modules: readers, tags and data processing centers. Among them, there are usually multiple antennas in the reader, and there is usually only one antenna in the tag. In this system, the tag is not powered by a battery, but works by absorbing the energy carried by the electromagnetic field emitted by the transmitting antenna on the reader. In this system, the tag will be as low-cost and small as possible, but the reading range and read-write stability in this system will be limited accordingly.
- the present invention proposes a blind adaptive beamforming algorithm applied to a half-duplex passive UHF radio frequency identification system.
- the algorithm does not require exact channel estimation, which greatly reduces radio frequency identification The complexity of the system.
- a blind adaptive beamforming algorithm which is applied to a half-duplex passive UHF radio frequency identification system, and its special feature is that it includes the following steps:
- W represents the weight of the antenna
- M represents the number of transmitting antennas
- N represents the number of receiving antennas
- ⁇ is the threshold (Threshold), It is the backscattered energy received in the reader in the reverse link;
- ⁇ is the weight adjustment size
- G r represents the gain of the reader antenna
- G t represents the gain of the tag antenna
- P TX represents the transmission energy of the reader
- PL represents the channel loss
- h is the channel vector
- the corresponding backscatter energy will be measured in the reader, and finally the reader will adjust the new weight value according to the maximum backscatter energy received;
- the required weight can be obtained, and the performance of the weight value is close to the performance of the optimal beamforming weight.
- the blind adaptive beamforming algorithm applied to the half-duplex passive UHF radio frequency identification system of the present invention can significantly increase the reading range of the system, and its performance is close to the performance of optimized beamforming, and enhances the transmission of identity information stability. Therefore, it is proved that the blind adaptive beamforming algorithm can effectively increase the reading range of the UHF radio frequency identification system; the algorithm innovatively proposes an iterative concept, thereby reducing the necessity of channel estimation compared with the original method And complexity, the operation process is simple, greatly reducing the cost of system operation, while improving efficiency.
- Figure 1 is a structural diagram of a half-duplex UHF RFID system
- FIG. 2 is a flowchart of a blind adaptive beamforming algorithm applied to a half-duplex passive UHF radio frequency identification system according to the present invention.
- Half-duplex UHF radio frequency identification system (HalfDuplex), assuming that each tag is stationary.
- the system block diagram of the half-duplex passive UHF radio frequency identification system is shown in FIG. 1.
- the forward link and the reverse link have different channel coefficients.
- the maximum read range can be expressed as:
- the energy received at the label can be expressed as:
- P TS represents the sensitivity of the receiving tag
- ⁇ represents the wavelength of the carrier
- P TX represents the transmission energy of the reader
- G r represents the gain of the reader antenna
- G t represents the gain of the tag antenna
- h is the channel vector
- the maximum read range can be expressed as:
- W 1 and W 2 are the weights of the antennas at the transmitting end and the receiving end, respectively.
- EqualWeightBeamforming equal weight beamforming algorithm
- RandomBeamforming random beamforming algorithm
- OBF optimal beamforming algorithm
- each weight value is a normalized vector, for example:
- M is the total number of antennas.
- the weights are randomly generated and normalized according to a specific distribution, for example:
- the blind adaptive beamforming algorithm proposed by the present invention can find suitable weights to increase the reading range of the system.
- the steps of the blind adaptive beamforming algorithm are shown in FIG. 2.
- the blind adaptive beamforming algorithm updates the channel weights W 1 and W 2 simultaneously.
- M transmit antennas and N receive antennas in a half-duplex system, we will generate M+N-dimensional weight vectors and divide them into M transmit beamforming weights and N receive beamforming weights.
- Kp new weight vector quantities will be generated, the specific algorithm execution process can be expressed as:
- W represents the weight of the antenna
- M represents the number of transmitting antennas
- N represents the number of receiving antennas
- ⁇ is the threshold (Threshold), It is the backscattered energy received in the reader in the reverse link;
- ⁇ is the weight adjustment size
- G r represents the gain of the reader antenna
- G t represents the gain of the tag antenna
- P TX represents the transmission energy of the reader
- PL represents the channel loss
- h is the channel vector
- the corresponding backscatter energy will be measured in the reader, and finally the reader will adjust the new weight value according to the maximum backscatter energy received;
- the required weight can be obtained, and the performance of the weight value is close to the performance of the optimal beamforming weight.
- the experiment covers different numbers of transmitting antennas and receiving antennas, and makes comparisons among several beamforming algorithms.
- the experimental results show that blind adaptation is applied in UHF radio frequency identification systems.
- the beamforming algorithm can significantly increase the reading range of the system, and its performance is close to the performance of optimal beamforming. Therefore, it is proved that the blind adaptive beamforming algorithm can effectively increase the reading range of the UHF radio frequency identification system.
- the technical solution can be applied to radio frequency wireless charging occasions and Internet of Things application scenarios.
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Abstract
本发明涉及一种盲自适应波束成形算法,特别涉及一种应用在半双工被动特高频射频识别系统上的盲自适应波束成形算法,该算法创新地提出一个迭代的理念,从而较原来的方法上,减去了信道估计的必要性以及复杂性,操作过程简单,大大减少了系统运行的成本,同时提高了效率。
Description
本发明涉及一种应用在半双工被动特高频射频识别系统上的盲自适应波束成形算法。
目前,特高频射频识别技术受到广泛关注,该技术采用860~960兆赫兹的频率,能够被应用在多个领域中,例如:供应链管理、后勤保障系统、自动收费系统、智能交通系统等等,它的识别效率比传统的条形码系统更高。
被动特高频射频识别系统(PassiveUHFRFIDsystems)通常包含几个模块:读写器、标签以及数据处理中心。其中,读取器中通常有多个天线,标签中通常只有一个天线。在这种系统中,标签并不是通过电池供电,而是通过吸收读写器上的发射天线所发射出来的电磁场所携带的能量来进行工作。在这种系统中,标签会尽可能做到低成本和小尺寸,但是这种系统中的读取范围和读写稳定性会相应受到限制。
很多学者相继提出不同类型的算法方案来提高被动特高频射频识别系统的读取范围,其中,最佳波束成形是信道匹配的(Channelmatched),它的性能往往是最好。要实现最佳波束成形必须要掌握所有的信道信息。虽然这能是波束成形算法的效果达到最佳,但同时这方法引入了复杂的信道估计,所以会大大增加射频识别系统的复杂性。
发明内容
为解决上述背景技术中存在的问题,本发明提出一种应用在半双工被动特高频射频识别系统上的盲自适应波束成形算法,该算法不要求确切的信道估计,大大减少了射频识别系统的复杂性。
本发明解决上述问题的技术方案是:一种盲自适应波束成形算法,应用在半双工被动特高频射频识别系统上,其特殊之处在于,包括以下步骤:
1)系统初始值的设定,使:
n=0和n=0,w
(0)~N
c(0,I
M+N);
其中,W表示天线的权重,M表示发射天线的数量,N表示接收天线的数量;
2)判断下列条件是否成立:
若成立,即表明接收到的反向散射能量波动范围小于阈值,重复过程终止;
若不成立,则执行下一步;
3)n=n+1;
4)产生Kp个扰动向量:
p
i~N
c(0,I
M+N),i=1,...,K
p;
5)产生Kp个新的权重矢量:
其中,β是权重调整尺寸;
6)将产生的向量分区并归一:
7)计算接收到的能量:
其中,G
r表示读写器天线的增益,G
t表示标签天线的增益,P
TX表示读写器的发射能量,P
L表示信道损失,h是信道矢量;
对于Kp个产生的权重,对应接收到的反向散射能量会在读写器中测量,最后读写器会根据接收到的最大反向散射能量来调整新的权重值;
8)更新下式:
9)执行步骤2)。
当循环上述的过程后,便能得出所需要的权重,将该权重值的性能接近于最佳波束成形权重的性能。
本发明的优点:
本发明一种应用在半双工被动特高频射频识别系统上的盲自适应波束成形算法,能够显著增加系统的读取范围,而且其性能接近最优化波束成形的性能,增强身份信息的传输稳定性。所以证明该盲自适应波束成形算法能够有效地增大特高频射频识别系统的读取范围;该算法创新地提出一个迭代的理念,从而较原来的方法上,减去了信道估计的必要性以及复杂性,操作过程简单,大大减少了系统运行的成本,同时提高了效率。
图1是半双工型特高频射频识别系统结构图;
图2是本发明应用在半双工被动特高频射频识别系统上的盲自适应波束成形算法流程图。
为使本发明实施方式的目的、技术方案和优点更加清楚,下面将结合本发明实施方式中的附图,对本发明实施方式中的技术方案进行清楚、完整地描述,显然,所描述的实施方式是本发明一部分实施方式,而不是全部的实施方式。基于本发明中的实施方式,本领域普通技术人员在没有作出创造性劳动前提下 所获得的所有其他实施方式,都属于本发明保护的范围。因此,以下对在附图中提供的本发明的实施方式的详细描述并非旨在限制要求保护的本发明的范围,而是仅仅表示本发明的选定实施方式。基于本发明中的实施方式,本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施方式,都属于本发明保护的范围。
半双工特高频射频识别系统(HalfDuplex),假设每个标签都是静止的。半双工被动特高频射频识别系统的系统框图如附图1所示。对于此系统,前向链接和反向链接具有不同的信道系数。当系统是前向链接限制的时候,最大的读取范围可以被表示为:
在前向链接中,在标签处接收到的能量可以表示为:
其中,P
TS表示接收标签的灵敏度,λ表示载波的波长,P
TX表示读写器的发射能量,G
r表示读写器天线的增益,G
t表示标签天线的增益,h是信道矢量,W表示天线的权重,即波束成形权重。
当系统是反向链接限制的时候,最大的读取范围可以被表示为:
其中W
1和W
2分别为发射端和接收端天线的权重。
目前,有几种波束成形的算法比比较常用,等权重波束成形算法(EqualWeightBeamforming);随机波束成形算法(RandomBeamforming)以及最佳波束成形算法(OBF)。
对于EBF,每个权重值都是一个归一化矢量,例如:
其中,M是天线的总数量。
对于RBF,权重是根据特定的分布随机产生并正态化的,例如:
而本发明提出的一种盲自适应波束成形算法,该算法能找到合适的权重从而使系统的读取范围增大。
对于半双工被动特高频射频识别系统,盲自适应波束成形算法的步骤如附图2所示。半双工特高频射频识别系统,盲自适应波束成形算法会同时更新信道权重W
1和W
2。假设半双工系统中,存在M个发射天线和N个接收天线,我们会根据产生M+N维的权重向量,并把其分成M个发射端波束成形权重和N个接收端波束成形权重。在第N次循环中,会生生成Kp个新的权重向量量,具体的算法执行过程可以表示为:
1)系统初始值的设定,使:
n=0和n=0,w
(0)~N
c(0,I
M+N);
其中,W表示天线的权重,M表示发射天线的数量,N表示接收天线的数量;
2)判断下列条件是否成立:
若成立,即表明接收到的反向散射能量波动范围小于阈值,重复过程终止;
若不成立,则执行下一步;
3)n=n+1;
4)产生Kp个扰动向量:
p
i~N
c(0,I
M+N),i=1,...,K
p;
5)产生Kp个新的权重矢量:
其中,β是权重调整尺寸;
6)将产生的向量分区并归一:
7)计算接收到的能量:
其中,G
r表示读写器天线的增益,G
t表示标签天线的增益,P
TX表示读写器的发射能量,P
L表示信道损失,h是信道矢量;
对于Kp个产生的权重,对应接收到的反向散射能量会在读写器中测量,最后读写器会根据接收到的最大反向散射能量来调整新的权重值;
8)更新下式:
9)执行步骤2)。
当循环上述的过程后,便能得出所需要的权重,将该权重值的性能接近于最佳波束成形权重的性能。
本技术方案经过了具体实验的验证,实验覆盖了不同数量的发射天线与接收天线,并且在几种波束成形算法中作出对比,实验结果显示出,在特高频射频识别系统中应用盲自适应波束成形算法,能够显著增加系统的读取范围,而且其性能接近最优化波束成形的性能。所以证明该盲自适应波束成形算法能够有效地增大特高频射频识别系统的读取范围。
本技术方案能够应用在射频无线充电场合和物联网应用场景上。
以上所述仅为本发明的实施例,并非因此限制本发明的专利范围,凡是利 用本发明说明书及附图内容所作的等效结构或等效流程变换,或直接或间接运用在其他相关的系统领域,均同理包括在本发明的专利保护范围内。
Claims (1)
- 一种盲自适应波束成形算法,应用于半双工被动特高频射频识别系统,其特征在于:1)系统初始值的设定,使:n=0和n=0,w (0)~N c(0,I M+N);其中,W表示天线的权重,M表示发射天线的数量,N表示接收天线的数量;2)判断下列条件是否成立:若成立,即表明接收到的反向散射能量波动范围小于阈值,重复过程终止;若不成立,则执行下一步;3)n=n+1;4)产生Kp个扰动向量:p i~N c(0,I M+N),i=1,…,K p;5)产生Kp个新的权重矢量:其中,β是权重调整尺寸;6)将产生的向量分区并归一:7)计算接收到的能量:其中,G r表示读写器天线的增益,G t表示标签天线的增益,P TX表示读写器的发射能量,P L表示信道损失,h是信道矢量;对于Kp个产生的权重,对应接收到的反向散射能量会在读写器中测量,最后读写器会根据接收到的最大反向散射能量来调整新的权重值;8)更新下式:9)执行步骤2)。
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