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1.
旋转星座下匙孔信道的四元素准正交空时分组码研究   总被引:1,自引:0,他引:1  
提出了一种基于匙孔信道的旋转四元素准正交空时分组码(QQOSTBC-CR,Constellation Rotation Quaternion Quasi-Orthogonal Space Time Block Code),该码可以通过极化天线进行发射和接收,设计出发射天线数为8的QOSTPBC-CR,并对N=8的情况进行成对译码,最后与匙孔信道下传统旋转准正交空时分组码(QOSTBC CR,Constellation Rotation Quasi Orthogonal Space Time Block Code)、准正交空时分组码(QOSTBC,Quasi Orthogonal Space Time Block Code)以及瑞利信道下QQOSTBC-CR进行了仿真比较.结果表明:对4个发射天线的情况,当BER=10(-3)时,BPSK和QPSK调制下本文所提QQOSTBC-CR分别比QOSTBC-CR有4.5dB和7dB的增益,分别比瑞利信道下QQOSTBC-CR有-4dB和-3dB的增益.  相似文献   

2.
Magnetic resonance wireless power transfer is expected to be one of the prevalent schemes because of its high efficiency and long transmission range. However, in this scheme, there is a problem that the characteristics of a transmission channel changes in according with the distance between coil antennas. This paper investigates the performance of data transmission with an array antenna in a wireless power transfer system. In the assumed system, the same antennas for wireless power transfer are used for data transmission. The assumed system uses multiple transmit antennas and beamforming is realized by shifting the phases of signals in a transmitter. Numerical results obtained through computer simulation show that the proposed scheme can mitigate the dependently of a bit error rate (BER) to the distance between the antenna coils. The variation of the performance is suppressed within 1–3 dB at the BER of \(10^{-5}\) in the case of two transmit antennas. In addition, the system with two transmit antennas achieves 2 dB or more improvement in term of the BER performance than that with a single antenna at specific antenna distances.  相似文献   

3.
作为一种软输入软输出的MIMO检测算法,MMSE迭代软干扰抵消算法在MIMO Turbo接收机中得到广泛的关注。为了进一步改善系统性能,采用链路自适应方案是很好的选择。该文给出变发射功率的MMSE迭代软干扰抵消算法,并采用了一种有效的发射功率分配方案,只需要很少的控制信令,就可以获得较大的误码率性能改善。通过没有信道编译码的链路仿真,在4发4收QPSK调制的V-BLAST系统中,如果误码率要求为BER=10^-3,MMSE迭代软干扰抵消检测算法迭代次数为2时,采用推荐的发射功率分配方案比不采用发射功率分配方案的系统性能提高了约2dB,如果调制方式为16QAM,系统性能提高了约6dB。  相似文献   

4.
This paper presents upper bounds on the bit-error rate (BER) of optimum combining in wireless systems with multiple cochannel interferers in a Rayleigh fading environment. We present closed-form expressions for the upper bound on the bit-error rate with optimum combining, for any number of antennas and interferers, with coherent detection of BPSK and QAM signals, and differential detection of DPSK. We also present bounds on the performance gain of optimum combining over maximal ratio combining. These bounds are asymptotically tight with decreasing BER, and results show that the asymptotic gain is within 2 dB of the gain as determined by computer simulation for a variety of cases at a 10-3 BER. The closed-form expressions for the bound permit rapid calculation of the improvement with optimum combining for any number of interferers and antennas, as compared with the CPU hours previously required by Monte Carlo simulation. Thus these bounds allow calculation of the performance of optimum combining under a variety of conditions where it was not possible previously, including analysis of the outage probability with shadow fading and the combined effect of adaptive arrays and dynamic channel assignment in mobile radio systems  相似文献   

5.
Recently, ambient backscatter attracts much attention since it can utilize ambient radio frequency signals to enable battery-free devices to communicate with others. Most existing studies about ambient backscatter assume that the reader is equipped with one receiving antenna. In practice, the reader can utilize multiple antennas to overcome channel fading. In this paper, we investigate the problem of signal detection for ambient backscatter systems with multiple receiving antennas. Specifically, we formulate a new transmission model where the reader is equipped with at least two antennas and propose a ratio detector that exploits the ratio of the signal strength received at each antenna. It is shown that the closed-form expression of the optimal detection threshold for this detector is difficult to derive. Therefore, we derive a reasonable approximate expression for the optimal detection threshold. Moreover, we obtain the closed-form expression for approximate bit error rate (BER). Furthermore, we propose an antenna selection scheme if the reader is equipped with more than two antennas. The selection scheme is investigated through the BER performance. It is found that the largest gain in BER can be achieved when the antenna number increases from two to three, and that much less gain is obtained from enlarging the antenna number when the reader already has four antennas. Finally, simulation results are provided to corroborate our theoretical studies.  相似文献   

6.
An experimental study of multipath fading effects on an 8-PSK 6 GHz digital radio system was conducted on a 26.4 mi test link near Atlanta, Georgia. Results were obtained for a non-diversity arrangement and a space-diversity arrangement employing a cophasing combiner operating at 70 MHz and fed by two antennas separated by 30 ft. Multipath fading was found to have a significant impact on bit error rate performance, i.e., the digital radio system was fragile by comparison to conventional analog FM radio. Modest in-band linear amplitude dispersion, 0.2 dB/MHz for example, was sufficient to cause aBERgeq10^{-3}. Such dispersion occurred at (average power) fade depths as shallow as 20 dB. However, average fade depth was a poor indicator of BER performance. The measured hop missed short haul outage objectives by an order of magnitude without space-diversity, and was close to acceptable when diversity was activated.  相似文献   

7.
Iteratively decoded bit-interleaved space-time coded modulation (BI-STCM) greatly lowers bit error rate (BER) over fast Rayleigh fading multiple-input multiple-output (MIMO) channels. We develop a general, tight and efficient theoretical error-free feedback bound (EF bound) to analyze the asymptotic BER. The convergence to the EF bound and the accuracy of the prediction are verified by simulation. With the best rate 1/2 4-state convolutional code and the 16-QAM modified set partitioning labeling, the BER of 10/sup -6/ can be achieved at E/sub b//N/sub 0/=1.6 dB with 2 transmit and 2 receive antennas.  相似文献   

8.
唐文岐  辛吉荣  罗来源 《电讯技术》2017,57(11):1289-1294
旋转映射信号将编码比特旋转移位后映射为符号,同时采用了隐性交织、加扰等技术,具有交织复杂度低、信道效率高等特点,是一种典型且使用较为广泛的短波通信信号.针对第三方接收条件下,频率选择性衰落造成该类信号难以有效接收的问题,推导了该类信号的软符号解映射、映射方法,提出了一种针对该类信号的多天线联合Turbo均衡算法,实现了软信息在均衡与译码之间的迭代交换.典型短波信道下的仿真结果表明,迭代4次后的两天线联合Turbo均衡在10-5误码率时相对两天线硬判决译码提供了约4 dB的增益,相对两天线软判决译码提供了约1 dB的增益,在10-4误码率时相对单天线Turbo均衡提供了约5.5 dB的增益.  相似文献   

9.
It is well known that the full rate and full diversity complex space-time block code (STBC) is not existed for four transmit antennas. In this letter, we propose a simple quasi-orthogonal space-time-frequency block code (QO-STFBC) scheme with four transmit antennas and n R receive antennas, where every two transmit antennas constitute one group and each group transmits signals over different subcarriers. The receiver can separate the received signals from each group via odd/even index FFT operation. After recombining the separated received signals with received antennas, an equivalent half rate orthogonal STFBC (O-STFBC) can be used for decoding. Thus, the full rate and full diversity are achieved at the transmitter and receiver, respectively. Simulation result shows that the proposed QO-STFBC scheme has better performance than the other schemes, in rate 2 layered Alamouti scheme is about 4 dB, full rate QO-STBC scheme is about 5 dB and half rate O-STBC scheme is about 7 dB at 10?3 BER for the transmission of 2 bits/s/Hz.  相似文献   

10.
The impulse postfix OFDM (IP‐OFDM) system exploits the IP, which consists of a high power impulse sample and several zero samples at the end of a zero padded‐OFDM symbol block, to estimate channel impulse response (CIR) in time domain. In this paper, the impact of IP length on the BER performance of the IP‐OFDM system is analyzed. According to the analytic results, the BER performance can be significantly degraded with both a shorter length of IP as well as a longer length of IP than that of the CIR. Thus, an adaptive IP scheme, which adjusts the length of IP adaptively depending on the length of CIR, is proposed to enhance the BER performance of IP‐OFDM systems and its effectiveness is demonstrated by computer simulations. The BER performance of the IP‐OFDM systems with the proposed adaptive scheme is compared with that of the conventional IP‐OFDM system over various modulation schemes. Simulation results show that the IP‐OFDM with the proposed scheme can achieve about 2 dB performance enhancement compared with that of conventional systems at BER=10?2. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

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