共查询到20条相似文献,搜索用时 15 毫秒
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IDMA技术以其抗多径干扰性好、接收复杂度低等优点成为第四代移动通信的关键技术之一。多层交织分多址复用时空码(ML-IDM-ST)系统是将空时码(STC)思想和IDMA系统相结合的演化而来,它具有接收简单,复杂度低和高吞吐量等优点。本文描述了多层交织分复用空时码系统(ML-IDM-ST)的基本原理和算法流程并对其发展前景进行了预测。 相似文献
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A new design method interleavers, 2-dimension interleavers, are proposed for interleave division multiple access (IDMA) systems. With a same interleaving rule named I', the row indices and column indices of a traditional block interleaving matrix are scrambled to obtain an interleaver, which is marked as the master interleaver. F is produced by a loworder PN sequence generator. Two ways are provided for generating different interleavers. One is that all interleavers are generated by the circular shifting master interleaver. The other is that different inter leavers are generated by different Ts. Besides, we prove that the minimum distance between two adjacent bits resulted from 2-dimension interleaves is much larger than that of other schemes, such as random interleavers, power interleavers, and shiffting interleaves. The simulation results show that 2-dimension interleavers can achieve much better performance with much less resource consumption than random interleavers in IDMA systems. 相似文献
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对一种Turbo码交织器性能分析的方法进行了讨论,用这种方法分析比较了WCDMA和cdma2000中Turbo码交织器的性能,并给出迭代译码的计算机仿真结果,以证实这种方法的正确性.此外,仿真结果还证实文献[3]中的评价交织器的方法不一定适合Turbo码交织器. 相似文献
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为提升海量机器类通信(massive machine-type communication,m MTC)设备的随机接入(random access,RA)性能,提出一种面向大规模多输入多输出(massive multiple-input multiple-output,m MIMO)系统的模式分割随机接入(pattern division random access,PDRA)方案。该方案将导频竞争空间扩展到模式域,通过叠加同一ZC(Zadoff-Chu)根序列的L个不同循环移位序列,设计基于“图样叠加”的模式域导频,在不增加物理资源的前提下扩大导频集合。仿真结果表明,在不影响信道估计和数据检测性能的前提下,与传统RA方案相比,PDRA方案能够显著降低导频碰撞概率,提高接入成功率。 相似文献
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The random access channel (RACH) in UTRA‐TDD systems is an uplink contention‐based transport channel that is mainly used to carry control information from mobile stations to base stations. In this paper, we study the performance of RACH on an additive white Gaussian noise (AWGN) channel whereby successful transmission of a burst requires the spreading code chosen to be collision‐free and the burst is error‐free after convolutional decoding. Based on this model, the code‐collision probability, the data bit error probability and the RACH channel capacity are derived. The random retransmission delay mechanism is not specified in UTRA‐TDD. We therefore choose an access mechanism with binary exponential backoff delay procedure similar to that in IEEE 802.11. Based on that mechanism, the blocking probability and the first two moments of the delay are also derived. Compared with the mean, the standard deviation is found to be very high. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Jun‐Da Chen Fang‐Biau Ueng Ye‐Shun Shen Yuan‐Hung Cheng 《International Journal of Communication Systems》2015,28(13):1931-1954
In this paper, we propose differential phase‐shift keying (DPSK) noncoherent receivers for multicarrier code division multiple access systems in multipath channels. The noncoherent receivers are composed of a linear equalizer and a decision‐feedback differential detector to detect DPSK signals. The performances of the proposed noncoherent receivers can be improved by increasing the number of feedback symbols. For an infinite number of feedback symbols, the optimum weight can be derived analytically, and the performances of the proposed noncoherent receivers approach that of the conventional coherent receiver. For adaptation of the equalizer coefficients, modified least mean square and recursive least squares algorithms are proposed. Furthermore, the reduced‐rank schemes are proposed to simplify the system complexities. Some simulation examples are given to show the system performances of the four proposed receivers. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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为了在跟踪与数据中继卫星系统( TDRSS)中实现码分多址( CDMA)应用,需要完成多用户检测( MUD)及码分多址干扰( MAI)抑制。采用减性多级迭代对消算法,在数字信号处理芯片中完成信号再生、延时校正、时域相减对消,可以完成至少12通道的多用户检测,并能将多址干扰抑制至最小1 dB以内。该算法可作为通用MUD算法的有效补充,并能应用于各类非最优的CDMA系统中,具有迭代级数可选、通道扩展性强、工程实现性好的优点。 相似文献
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Analysis and design of interleavers for iterative multiuser receivers in coded CDMA systems 总被引:1,自引:0,他引:1
Tarable A. Montorsi G. Benedetto S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(5):1650-1666
We deal with the design of interleavers in a coded code-division multiple-access (CDMA) scenario, where at the receiver an iterative turbo-like structure to perform multiuser detection is employed. The choice of the interleavers affects both the maximum-likelihood (ML) performance and the impact of the suboptimality of the iterative receiver. First, heuristic criteria of goodness for a set of interleavers, each assigned to a given active user, are introduced and motivated. One of these criteria is based on the intersection between the equivalent codes seen after the interleavers for each user pair. The design rules are valid for any kind of channel code. In particular, when the channel code used by every user is a terminated convolutional code, a very simple design rule, in the subset of congruential interleavers, is specified. The suitability of an interleaver set to iterative decoding is also treated. The analysis leads to a design rule which is shown to have great importance on the performance of a turbo-like receiver. Numerical results assess the validity of the derived design rules by showing that, for iterative multiuser receivers and reasonable block lengths, the suitability to iterative decoding is more important than the performance optimization. 相似文献
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Shimon Moshavi Emmanuel G. Kanterakis Donald L. Schilling 《International Journal of Wireless Information Networks》1996,3(1):1-17
A new family of multistage low-complexity linear receivers for direct sequence code division multiple access (DS-CDMA) communications is introduced. The objective of the proposed design is to mitigate the effect of multiple access interference (MAI), the most significant limiting factor of user capacity in the conventional DS-CDMA channel. The receivers presented here employ joint detection of multiple users and therefore require knowledge of all the signature codes and their timing. In addition, for a multipath environment, reliable estimates of the received powers and phases are assumed available for maximal ratio RAKE combining. Each stage of the underlying design recreates the overall modulation, noiseless channel, and demodulation process. The outputs of these stages are then linearly combined. The combining weights can be chosen to implement different linear detectors, including the decorrelating and minimum mean square error (MMSE) detectors. In this paper, we focus on implementing the MMSE detector. Simulation results illustrate that significant performance gains can be achieved in both synchronous and asynchronous systems.This work was presented in part at IEEE Communication Theory Workshop, April 23–26, 1995, and at IEEE MILCOM '95, November 5–8, 1995.This work was submitted in partial fulfillment of Ph.D. requirements at The City University of New York. 相似文献
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Jui‐Chi Chang Fang‐Biau Ueng Hsuan‐Fu Wang Ming‐Hsiao Hsu 《International Journal of Communication Systems》2015,28(10):1675-1691
Single carrier‐frequency division multiple access (SC‐FDMA) has been adopted as the uplink transmission standard in fourth generation cellular network to enable the power efficiency transmission in mobile station. Because multiuser MIMO (MU‐MIMO) is a promising technology to fully exploit the channel capacity in mobile radio network, this paper investigates the uplink transmission of SC‐FDMA systems with orthogonal space frequency block codes (SFBC). Two linear MU‐MIMO receivers, orthogonal SFBC (OSFBC) and minimum mean square error (MMSE), are derived for the scenarios with limited number of users or adequate receive antennas at base station. In order to effectively eliminate the multiple access interference (MAI) and fully exploit the capacity of MU‐MIMO channel, we propose a turbo MU‐MIMO receiver, which iteratively utilizes the soft information from maximum a posteriori decoder to cancel the MAI. By the simulation results in several typical MIMO channels, we find that the proposed MMSE MU‐MIMO receiver outperforms the OSFBC receiver over 1 dB at the cost of higher complexity. However, the proposed turbo MU‐MIMO receivers can effectively cancel the MAI under overloaded channel conditions and really achieve the capacity of MU‐MIMO channel. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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研究发送功率以及干扰温度约束下的认知多入多出多址接入信道(MIMO MAC)的速率和最大化问题。通过部分对偶分解技术松弛干扰温度约束,原始问题被分解为较易处理的子问题,并提出一种迭代算法,通过交替进行对偶变量更新与迭代注水运算求解使得速率和最大的最优发送协方差矩阵。最后通过仿真表明算法的有效性。 相似文献
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For the Gaussian multiple access channel, we studied a joint channel decoderand multiple access interference canceller. For each user, the decoderoutput was used to generate a soft estimate of the user signal. Theestimate was improved by iterating decoding and cancellation untilconvergence was reached. A final, hard decoding was then performed.Simulation results are presented. 相似文献
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Kai Yu Pingzhi Fan Li Hao Xianfu Lei 《Wireless Communications and Mobile Computing》2012,12(6):503-515
In this paper, large code division multiple access (CDMA) random access systems employing the decorrelator and minimum mean square error (MMSE) detectors are investigated over Rayleigh fading channels under the assumption that both the number of users and the spreading gain tend to infinity, but their ratio converges to a constant. The signal to interference ratio (SIR) is shown to converge almost surely to a constant and the bit‐error rate (BER) is expressed as a function of the traffic load, transmission probability, channel coefficient, and distribution of transmission power. Furthermore, the throughput, the spectrum efficiency, and the stability region are analyzed and simulated. For dominating systems, it is shown that the MMSE detector achieves much higher throughput and spectral efficiency than decorrelator detector. Besides, it is also disclosed that, when the signal to noise ratio (SNR) is larger than an optimum value, the spectrum efficiency increases as the ratio of bit energy to noise power spectrum density (Eb/N0) increases; however, when SNR is smaller than the optimum value, the spectrum efficiency decreases as Eb/N0 increases. For ordinary stable systems, it is demonstrated that their stability region gets narrower as the traffic load increases. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Nargis Bibi Nazeer Muhammad Barry Cheetham 《International Journal of Communication Systems》2019,32(9)
Orthogonal frequency‐division multiplexing (OFDM) is considered an efficient modulation approach in the field of wireless systems. However, the significant high peak to average power ratios (PAPR) are one of the prominant shortcomings of the OFDM systems leading to severe signal distortions and acute power inefficiency. Iterative receivers, which use Bussgang algorithm approach along with clipping at the transmitter, have been presented in the literature. This methodology is majorly receiver based in order to compensate the effects of the clipping noise that was added at the transmitter. These receivers are used to analyse the distortions of clipping noise directly subtracting from the signals that are received in order to get the original signal. We demonstrate in this study a detailed and technical investigation of the Bussgang noise cancellation (BNC) receiver along with some significant results. Simulation results are presented to show that the BNC iterative receiver does not estimate the accurate clipping noise, and the performance may be improved if at the receiver end, it is somehow capable to analyze the precise clipping noise for each OFDM signal. 相似文献