BCH-Turbo编码的设计与仿真实现

本文针对Turbo码在低信噪比下迭代次数多、译码时延长问题,在分析了Turbo码的编译码原理和算法基础上,提出一种可以有效降低平均迭代次数、减少译码时延的基于BCH迭代停止准则的Turbo码迭代译码的设计方案。本方案采用BCH码作为Turbo迭代译码的停止准则。并对每一个分量译码器结果都进行判断。可提前停止迭代。通过Monte Carlo仿真表明在AWGN信道下,误码率有所降低。Turbo码译码的平均迭代次数与交叉熵准则相比有明显下降。本文还分析了BCH码编码效率和分组长度的选择对系统性能的影响。     

BCH-Turbo码的设计与仿真实现

本文针对Turbo码在低信噪比下迭代次数多、译码时延长问题,在分析了Turbo码的编译码原理和算法基础上,提出一种可以有效降低平均迭代次数、减少译码时延的基于BCH迭代停止准则的Turbo码迭代译码的设计方案.本方案采用BCH码作为Turbo迭代译码的停止准则,并对每一个分量译码器结果都进行判断,可提前停止迭代.通过Monte Carlo仿真表明在AWGN信道下,误码率有所降低,Turbo码译码的平均迭代次数与交叉熵准则相比有明显下降.本文还分析了BCH码编码效率和分组长度的选择对系统性能的影响.     

基于非编码信息匹配的自适应Turbo TCM编码调制方案

本文提出了一种通过调整非编码信息量,并与信号映射相结合来改变编码、调制模式的自适应Turbo TCM编码调制方案,称之为基于非编码信息匹配的自适应Turbo TCM编码调制方案.由于将Turbo码和TCM编码调制技术相结合得到的Turbo TCM编码调制方案的带宽效率高,所以,在慢时变无线衰落信道中,自适应Turbo TCM编码调制的平均频谱效率也将很高.给出了该方案的工作原理、设计方法,并通过蒙特卡洛(Monte Carlo)仿真研究了该方案的性能.与现有编码调制方案相比,该方案具有频谱效率高、易于设计和实现的优点.     

基于Turbo乘积码的MIMO-OFDM系统在IMT2000信道下的性能研究

为了提高无线通信系统的可靠性,采用极具纠错性能的Turbo乘积码与空时分组码级联,构成Turbo乘积码编码的MIMO-OFDM系统。测试了采用三种Turbo乘积码的两发两收MIMO-OFDM系统在通过IMT2000信道后的性能。仿真结果表明采用Turbo乘积码后的MIMO-OFDM系统性能有明显改善。     

Turbo码编码FDPIM在弱湍流下的差错性能分析

DPIM调制方式的符号长度变化不固定,分析Turbo码编码DPIM调制下的差错性能存在的困难,针对该问题给出了一种新的调制方式--定长脉冲间隔调制.在给出其调制结构的基础上,在弱湍流信道模型下首先推导分析了未编码FDPIM的误包率,并与DPIM 调制方式的性能进行了比较,然后分别采用三种模型分析了Turbo编码FDPIM调制的误比特率特性.仿真分析结果表明,未编码下的FDPIM的误包率虽然劣于DPIM,但其实现的复杂性简化,相对于DPIM,其符号长度固定,易与Turbo码译码结构相结合实现软判决;在该调制方式下引入Turbo码可使平均发射功率降低约10 dBm,能够有效的改善系统差错性能.     

CCSDS标准的Turbo译码器的硬件设计

Turbo码具有接近Shannon信道理论极限的译码性能,CCSDS在保留原编码方案的前提下已将其加入遥测信道编码建议书。在简要介绍CCSDS标准的编码结构以后,概述了相应的Turbo码译码器的硬件设计方案。详细介绍了具体的设计流程,最后给出了设计结果。     

弱湍流下Turbo码编码数字脉冲间隔调制差错性能分析

数字脉冲间隔调制(DPIM)的符号长度变化不固定,因而分析该调制方式在Turbo码编码下的差错性能存在困难.在建立分析模型和推导差错率的基础上,在弱湍流信道条件下仿真分析了Turbo码编码前后的系统差错性能,同时与高斯信道条件下的系统差错性能进行了比较.仿真分析结果表明,弱湍流信道条件下的系统差错性能不如高斯信道条件下的系统差错性能,但在两种信道条件下,引入Turbo码编码技术均可获得3~6 dB的编码增益,能够有效改善系统的差错性能,具有良好的军事应用价值.     

Turbo编译码在3G中的应用及前景

Turbo码是一种接近Shannon编码理论极限性能的并行级联码。介绍了Turbo码的编、译码原理,并对它的性能进行分析。然后,详述了Turbo码在第三代移动通信中的应用。     

基于Turbo协同分集的通信方案的性能仿真

本文基于Turbo码和协同通信的相关理论,提出一种新的基于Turbo协同分集的协同通信方案。在加性高斯白噪声和瑞利快衰落的两种信道条件下的仿真结果表明,基于Turbo协同分集的协同通信方案比现有的基于Turbo编码的协同通信方案具有更优的误比特率性能。     

Turbo码的迫零方案研究

介绍了Turbo码的编码和译码原理,分析了迫零比特对于Turbo 码的性能的影响,介绍了目前常用的几种迫零方式,并且通过仿真对迫零比特对于Turbo码的性能影响进行了研究。仿真结果表明,Turbo码编码器迫零处理有助于改善Turbo码的性能。     

Antenna subset selection at multi‐antenna relay with adaptive modulation

In this paper, we proposed several antenna selection schemes for cooperative diversity systems with adaptive transmission. The proposed schemes were based on dual‐hop relaying where a relay with multiple‐antenna capabilities at reception and transmission is deployed between the source and the destination nodes. We analyzed the performance of the proposed schemes by quantifying the average spectral efficiency and the outage probability. We also investigated the trade‐off of performance and complexity by comparing the average number of active antennas, path estimations, and signal‐to‐noise ratio comparisons of the different proposed schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

On the feedback error compensation for adaptive modulation and coding scheme

In this paper, we consider the effect of feedback error on the performance of the joint adaptive modulation and diversity combining (AMDC) scheme which was previously studied with an assumption of perfect feedback channels. We quantify the performance of two joint AMDC schemes in the presence of feedback error, in terms of the average spectral efficiency, the average number of combined paths, and the average bit error rate. The benefit of feedback error compensation with adaptive combining is also quantified. Selected numerical examples are presented and discussed to illustrate the effectiveness of the proposed feedback error compensation strategy with adaptive combining. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance of DSWC diversity system using suboptimum adaptive switching threshold in independent and correlated nakagami‐m fading channels

The use of dual switched combining (DSWC) diversity reception scheme, for combating the detrimental effects of fading on digital transmissions, is popular due to its simpler implementation. The performance of switched diversity strategy is dependent on the selection of the switching threshold. But, for the analysis and design of the DSWC diversity system, the closed form analytical solution for optimum adaptive switching threshold is not possible for most of the modulation schemes in correlated fading environment. This letter presents an approximate, but simple and closed form, generic expression for adaptive switching threshold, called in this case as suboptimum adaptive switching threshold, in independent and correlated Nakagami‐m fading channels for a wide range of binary and M‐ary modulation schemes. It is shown that the average symbol error rate (ASER) performance obtained using this suboptimum adaptive switching threshold is almost same as obtained using optimum adaptive switching threshold. Copyright © 2005 John Wiley & Sons, Ltd.     

Dynamic channel allocation techniques using adaptive modulation andadaptive antennas

This article studies the impact of adaptive quadrature amplitude modulation (AQAM) on network performance when applied to a cellular network, using adaptive antennas in conjunction with both fixed channel allocation (FCA) and locally distributed dynamic channel allocation (DCA) schemes. The performance advantages of using adaptive modulation are investigated in terms of the overall network performance, mean transmitted power, and the average network throughput. Adaptive modulation allowed an extra 51% of users to be supported by an FCA 4-QAM network, while in conjunction with DCA, an additional 54% user capacity was attained     

一种基于遗传计算的新型白适应路由算法

自适应路由算法能够根据网络状态选择路径,减少平均传输延时,最大限度地提高网络的性能。丈中构造了一种新型的路由表,设计了基于遗传算法的自适应网络路由算法（GAR）,并在Pc机上实现了简化的GAR。在局域网环境下,对GAR和基于跳计数准则的RIP的模拟试验表明,在相同的网络负载下GAR的平均通信延时是RIP的20％。丈中提出的自适应的路由算法能够降低网络延时,平衡网络负载,提高网络性能。     

Performance of truncated type-II hybrid ARQ schemes with noisyfeedback over block fading channels

This paper considers truncated type-II hybrid automatic repeat-request (ARQ) schemes with noisy feedback over block fading channels. With these ARQ techniques, the number of retransmissions is limited, and, similar to forward error correction (FEC), error-free delivery of data packets cannot be guaranteed. Bounds on the average number of transmissions, the average coding rate as well as the reliability of the schemes are derived using random coding techniques, and the performance is compared with FEC. The random coding bounds reveal the achievable performance with block codes and maximum-likelihood soft-decision decoding. Union upper bounds and simulation results show that over block fading channels, these bounds can be closely approached with simple terminated convolutional codes and soft-decision Viterbi decoding. Truncated type-II hybrid ARQ and the corresponding FEC schemes have the same probability of packet erasure; however, the truncated ARQ schemes offer a trade-off between the average coding rate and the probability of undetected error. Truncated ARQ schemes have significantly higher average coding rates than FEC at high and medium signal-to-noise ratio even with noisy feedback. Truncated ARQ can be viewed as adaptive FEC that adapts to the instantaneous channel conditions     

Adaptive energy conserving algorithms for neighbor discovery in opportunistic Bluetooth networks

In this paper, we introduce and evaluate novel adaptive schemes for neighbor discovery in Bluetooth-enabled ad-hoc networks. In an ad-hoc peer-to-peer setting, neighbor search is a continuous, hence battery draining process. In order to save energy when the device is unlikely to encounter a neighbor, we adaptively choose parameter settings depending on a mobility context to decrease the expected power consumption of Bluetooth-enabled devices. For this purpose, we first determine the mean discovery time and power consumption values for In different Bluetooth parameter settings through a comprehensive exploration of the parameter space by means of simulation validated by experiments on real devices. The fastest average discovery time obtained is 0.2 s, while at an average discovery time of I s the power consumption is just 1.5 times that of the idle mode on our devices. We then introduce two adaptive algorithms for dynamically adjusting the Bluetooth parameters based on past perceived activity in the ad-hoc network. Both adaptive schemes for selecting the discovery mode are based only on locally-available information. We evaluate these algorithms in a node mobility simulation. Our adaptive algorithms reduce energy consumption by 50% and have up to 8% better performance over a static power-con serving scheme     

New Relay Protocols with AMC Scheme for Throughput Enhancement in LTE-Advanced System

We propose an adaptive modulation and coding (AMC) scheme using relay protocols AF, DF and DMF. The AMC scheme is used for improving the throughput and reliability of a communication system, using different modulation and coding schemes. We analyze the performance of relay protocols with the AMC scheme and observe that relay protocols with the AMC scheme are capable of providing better average throughput at a lower signal to noise ratio (SNR) level as compared to the conventional scheme with no AMC. We perform Monte Carlo simulations based on 3GPP long term evolution-advanced parameters to prove the performance comparison of adaptive modulation and coding scheme (MCS) relay protocols with non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the amplify-and-forward (AF), decode-and-forward (DF) and de-modulate-and-forward (DMF), the DMF protocol performs best, at a lower SNR value and higher average throughput.     

Variable‐rate adaptive modulation with optimum switching thresholds for cooperative systems with relay selection

In this paper, the performance of variable‐rate adaptive modulation schemes in the amplify‐and‐forward cooperative systems with relay selection is analyzed over Rayleigh fading channels. We consider constant power and discrete‐rate adaptive multi‐level modulation techniques. The switching levels required for discrete‐rate adaptive modulation have been determined for two schemes, namely fixed switching levels and optimum switching levels, both respecting a target bit error rate requirements, where in the later scheme, the switching levels are optimally determined in a way that the average spectral efficiency of the system is maximized. Two M‐ary modulation schemes, namely quadrature amplitude modulation and phase shift keying, are considered. Closed‐form expressions are derived for three performance metrics, namely average spectral efficiency, outage probability, and average bit error rate, for two cases: independent and identically distributed fading relay links and independent and non‐identically distributed links. It is shown that, compared with using fixed switching levels, employing optimum switching levels provides a slight improvement in the spectral efficiency and moderate improvements in the signal‐to‐noise ratio gain and in the outage probability of the system. It is also shown that compared with the independent and identically distributed links, independent and non‐identically distributed relay links yield a slight increase in the signal‐to‐noise ratio gain and a slight decrease in the diversity order of the system. Copyright © 2011 John Wiley & Sons, Ltd.     

Minimum estimation and combining generalized selection combining (MEC-GSC)

This paper introduces and analyzes a new adaptive minimum-estimation minimum-combining switched-combining based scheme that reduces considerably the average receiver channel estimation complexity and the power drain from the battery while satisfying a certain desired performance requirement. The mathematical formalism is supported by some selected numerical examples that show that the newly proposed combining scheme can essentially achieve the same performance as competing schemes such as generalized selection combining (GSC) while offering 50 % channel estimation and 75 % processing power savings for some system parameters of interest