采用相位判决的低复杂度广义空间调制检测算法

针对广义空间调制(GSM)系统中信号检测复杂度过高的问题,提出了一种基于相位判决的低复杂度检测算法.首先根据一种排序准则对天线组合进行排序,然后将排序后的天线组合中的符号向量依次通过基于相位判决的迫零(ZF)均衡器进行检测,最终得到星座调制符号和激活天线组合.分析和仿真结果表明,该检测算法可以有效缩小接收端的搜索范围,在提供与最大似然(ML)检测算法相近的误比特率(BER)性能的同时,计算复杂度降低了98％.     

基于次最优排序的混合DFE分层检测算法

本文提出了一种针对V-BLAST系统的检测算法。它基于对次最优排序的信道矩阵的QR分解，对发送符号进行分层检测，下层采用MMSE—BLAST，上层采用DFE。此外，提出了一种复杂度较低的排序度量来对待检测的下层符号进行排序。经仿真与复杂度分析，该算法以更低的复杂度获得比MMSE线性检测更好的性能，且其复杂度远低于MMSE-BLAST和ML检测，是一种高性能低复杂度的检测方法。     

一种用于低功耗低成本的IEEE802.15.4接收器的新颖解调算法

提出了一种基于低中频、适用于ISM2.4 GHz频段ZigBee接收机的新型解调算法,满足IEEE802.15.4标准.作为数字相位解调,本算法采用相位差分、频率补偿和符号恢复,不用分别恢复出I路和Q路的码序列,而直接提取出相位斜率码,恢复出符号,从而简化了解调结构、降低了功耗和成本.通过与零中频过零检测算法的比较,本算法具有更低复杂度,更好的误符号率和误包率,完全满足IEEE802.15.4/ZigBeeTM标准的要求.     

4×4 V-BLAST系统分组最大似然检测算法

对于V-BLAST系统的检测,最大似然(ML)算法有着最优的性能却也有最大的计算复杂度;经典的排序连续干扰抵消(OSIC)算法复杂度较低,但数值稳定性差,且性能与ML差距较大.因此,本文基于检测性能和计算复杂度折中的思想,针对4×4 V-BLAST系统提出了一种分组最大似然(Group ML,GML)检测算法,在保证较好检测性能的基础上,通过将四维ML检测器分成两组二维ML检测器来降低计算复杂度.此外,本文还提出了一种简化的最大似然(Simpli-fled ML,SML)检测算法,通过将每组中的二维ML检测器的搜索空间从二维降至一维,进一步降低了计算复杂度,并证明其与ML算法具有一致的性能.仿真表明,在误符号率为10~(-3)时GML算法相比OSIC算法有约7dB的性能提升.经分析知.GML算法复杂度与ML-OSIC算法相比在高阶调制方式下有着显著的降低,易于硬件实现.     

PSK调制下空频块码的低复杂度复数球形译码

对于PSK调制下的空频块码,复数球形译码相对实数球形译码有较低的复杂度.当复数球形译码的初始半径趋向无穷大时,排序的复杂度高.本文针对PSK符号提出每层符号以排序中心点为中心,在极坐标角度维按照之字(Zigzag)排序的方法.通过查表可以快速获得排序后的符号序列,查表排序球形译码算法相对于通用复数球形译码算法在16-PSK调制14dB平均比特信噪比下节省约61%的复杂度.     

自适应减少复杂度的盲最大似然序列估计

 基于逐幸存路径处理原理和自适应选择幸存路径的思想,本文提出了一种自适应减少计算复杂度的盲最大似然序列估计新算法.通过分析和推导,给出了一种近似估计网格图最小欧式距离的方法,并利用该估计值对幸存路径进行取舍,在网格搜索中仅保留少数幸存路径来进行信道参数和发送符号序列的联合盲估计.理论分析和计算机仿真结果表明,对严重符号干扰信道,在较高信噪比条件下,本文提出的新算法具有较理想的误符号率性能和较低的计算复杂度.     

广义空间调制MIMO系统的优化检测算法

针对大规模多输入输出（multiple-input multiple-output,MIMO）系统中采用广义空间调制（generalized spatial modulation,GSM）时信号检测复杂度过高的问题,提出一种新型天线分组激活方案.该方案首先需将发送天线分组激活,得到天线索引备选集,然后把天线组合符号按质量因子大小进行排序,最后遵循可信度判断准则进行量化判决检测,以此得到最佳的检测结果.相较于传统算法,所提出的检测算法避免了对信号空间的遍历搜索,在大规模天线系统下的性能更加优异.计算和仿真结果表明,本文提出的算法具有复杂度低、误码率低的特点,在采用广义空间调制的通信系统中具有较高的工程应用价值.     

基于接收信噪比和网络寿命的最优中继选择

为了增大网络寿命,降低误符号率,优化无直传链路协作通信系统的性能,本文提出基于接收信噪比和网络寿命的最优中继选择算法。由于网络寿命的问题无法直接求解,将其转化为中继节点剩余能量与目的节点达到接收信噪比门限时发射功率的比值。首先计算各个中继在目的节点的接收信噪比,将大于信噪比门限加入候选中继,然后依次计算候选中继的联合优化函数值并排序,值最大者即为最优中继。理论推导了系统误符号率的上下界,仿真表明理论值与仿真值较为吻合,验证了系统在保证较低误符号率的基础上延长了网络寿命。     

一种8×8 MIMO系统的近最优检测算法

为了进一步提升MIMO检测算法的性能、降低其复杂度,提出了一种基于格基规约和K-Best的近最优低复杂度检测算法。通过应用格基规约提升信道矩阵的正交性,减少了检测所需保留的路径数;同时考虑到该算法对信道矩阵各列的比较、交换,将预处理阶段传统的排序QR分解改为QR分解,在较小的性能损失下提高了系统吞吐率。并且提出一种新的节点展开策略,大幅减少了展开节点数和节点间的比较次数。仿真结果表明该算法在8×8规模MIMO系统,误比特率为10-5时,和最优性能仅差0. 5dB。     

基于GFDM的空口波形实现及干扰抑制

广义频分复用(GFDM)具有比正交频分复用(OFDM)更低的峰均功率比(PAPR)和带外频谱泄露。因为本身固有的子载波间干扰(ICI),传统GFDM解调具有较高复杂度。本文基于导频子载波,提出一种适用于卫星通信的数据辅助干扰消除GFDM接收算法,消除了匹配滤波(MF)接收中的子载波干扰,降低了误符号率(SER)。仿真结果与复杂度分析表明,本文所提算法优于传统串行干扰消除匹配滤波算法,有助于促进GFDM在天地一体化通信系统中的应用。     

Relay ordering in a multi-hop cooperative diversity network

In this paper, we first propose an optimum relay ordering algorithm for the multi-branch multi-hop cooperative diversity networks. This optimum algorithm has a high complexity that makes it hard to implement. Therefore, a suboptimum relay ordering algorithm, which considerably reduces the complexity, is then developed. Furthermore, for a cooperative network with two relays, we analytically evaluate the performance of the suboptimum algorithm by using an approximate end-to-end signal-to-noise ratio expression. Specifically, an approximate probability of wrong selection and an approximate expression of the symbol error rate are derived. The analysis and the numerical results demonstrate that the suboptimum algorithm performs very well as the optimum one at a much lower complexity.     

Improved layered MIMO detection algorithm with near-optimal performance

A new layered symbol detection algorithm for multiple-input multiple-output systems is presented. In this scheme, the layers are divided into two groups and detected differently. For the layer with the smallest post-detection signal-to-noise ratio, an exhaustive search is performed over the signal constellation; for the remaining layers the conventional iterative vertical Bell laboratories layered space-time (V-BLAST) technique is utilised. The proposed algorithm also uses a different symbol detection ordering from that recommended in the original V-BLAST algorithm. Simulation results show that the error rate performance of the proposed detection algorithm approaches closely that of an optimal maximum likelihood detector with no reduction in the symbol detection throughput, while the computational complexity is less than |Q| times that of V-BLAST, where |Q| is the cardinality of signal constellation Q.     

高速移动环境下基于动态CSI的MIMO系统改进模代数预编码

针对高速移动场景下信道快时变特性给多输入多输出（Multiple Input Multiple Output,MIMO）系统预编码带来的技术挑战,提出基于动态信道状态信息（Channel State Information,CSI）的MIMO系统改进模代数预编码（Tomlinson-Harashima Precoding,THP）算法.该算法利用信道统计量信息以及相关性构建动态CSI模型,更准确实时地体现当前信道状况;进一步地,提出一种基于循环遍历搜索的多用户调度算法,以最大化信干噪比为目标进行用户调度,且将多用户调度算法应用到THP中,提高了预编码精度.仿真结果表明,所提算法相比传统预编码算法具有更优的误码率性能和信道容量,验证了所提算法能有效地适应高速移动场景.     

Reliability feedback–aided low‐complexity detection in uplink massive MIMO systems

Massive multiple‐input multiple‐output (MIMO) plays a crucial role in realizing the demand for higher data rates and improved quality of service for 5G and beyond communication systems. Reliable detection of transmitted information bits from all the users is one of the challenging tasks for practical implementation of massive‐MIMO systems. The conventional linear detectors such as zero forcing (ZF) and minimum mean square error (MMSE) achieve near‐optimal bit error rate (BER) performance. However, ZF and MMSE require large dimensional matrix inversion which induces high computational complexity for symbol detection in such systems. This motivates for devising alternate low‐complexity near‐optimal detection algorithms for uplink massive‐MIMO systems. In this work, we propose an ordered sequential detection algorithm that exploits the concept of reliability feedback for achieving near‐optimal performance in uplink massive‐MIMO systems. In the proposed algorithm, symbol corresponding to each user is detected in an ordered sequence by canceling the interference from all the other users, followed by reliability feedback‐based decision. Incorporation of the sequence ordering and the reliability feedback‐based decision enhances the interference cancellation, which reduces the error propagation in sequential detection, and thus, improves the BER performance. Simulation results show that the proposed algorithm significantly outperforms recently reported massive‐MIMO detection techniques in terms of BER performance. In addition, the computational complexity of the proposed algorithm is substantially lower than that of the existing algorithms for the same BER. This indicates that the proposed algorithm exhibits a desirable trade‐off between the complexity and the performance for massive‐MIMO systems.     

Tomlinson-Harashima Precoded MIMO in wireless networks: to THP or not to THP?

We investigate a wireless network architecture that utilizes Tomlinson Harashima Precoded Multiple Input Multiple Output (THP MIMO) technique for improved system capacity. We consider THP MIMO in a multi user scenario, together with a proposed smart scheduling technique and we explore the capacity performance through extensive capacity analysis considering varying SNR levels, varying number of users and number of transmit/receive antennas, under fading and shadowing, also considering errors in channel state information (CSI). We also evaluate the complexity of THP MIMO and present a low-complexity scheduling algorithm that employs Gram-Schmidt algorithm for incremental implementation of THP’s QR factorization. In the end, we identify the network and channel conditions under which THP MIMO can be preferred over classical conventional MIMO, and we conclude that for practical transceivers with up to four antennas, THP MIMO can provide significant capacity enhancement over conventional MIMO at lower complexity, performing slightly below the sum rate capacity bound. Another important advantage that is observed in this study is better immunity of THP MIMO to CSI errors, as compared to conventional MIMO.     

A Novel Nonlinear Joint Transmitter-Receiver Processing Algorithm for the Downlink of Multiuser MIMO Systems

This paper focuses on signal processing algorithms for the downlink of multiuser multiple-input multiple-output (MIMO) systems with multiple-antenna mobiles. A novel nonlinear joint transmitter-receiver processing algorithm is proposed based on the zero-forcing (ZF) criterion. In this algorithm, nonlinear Tomlinson-Harashima precoding (THP) is applied at the base station, whereas linear receiver processing and modulo operation are applied at each mobile. It is first shown that the proposed algorithm effectively decomposes the multiuser MIMO channel into parallel independent single-user MIMO channels, and then, the performance of each mobile can be separately optimized. Subsequently, closed-form expressions for the transmitter and receiver processing matrices are derived to optimize the asymptotic bit error rate (BER) of each mobile. When used on the downlink of multiuser MIMO systems with multiple-antenna mobiles, this algorithm achieves significantly better performance than the ZFcriterion-based nonlinear preprocessing algorithm designed for the multiuser MIMO systems with single-antenna mobiles, because it effectively utilizes the processing capabilities of the mobiles. Moreover, the proposed algorithm achieves a much higher sum capacity at a high signal-to-noise ratio (SNR) than the known block diagonalization technique due to the effective application of the nonlinear preprocessing at the transmitter. When the proposed algorithm is applied, it is found that better system performance can be achieved by suitably ordering the channel matrices of different mobiles, and a combined optimal diversity and best-first (CODBF) ordering method is proposed to perform the ordering. Simulation is used to show the advantages of the proposed algorithm and the CODBF ordering method.     

一种公平的多天线多小区联合调度算法

为了能够以较小的实现复杂度有效减少多天线蜂窝系统中的小区间干扰,同时保证系统中的用户公平性,提出一种新的多小区联合调度算法,提出的算法的复杂度远远低于最优多小区联合调度算法。该算法将系统分簇并在每个簇内按一定比例选择部分平均速率较低的用户,之后在簇内按照给定的优化目标进行联合调度。仿真结果表明：与单小区调度算法相比,提出的多小区联合调度算法可以显著增加系统平均速率,而且可以取得与单小区调度算法类似的用户公平性。     

An Efficient Soft‐Output MIMO Detection Method Based on a Multiple‐Channel‐Ordering Technique

In this paper, we propose an efficient soft‐output signal detection method for spatially multiplexed multiple‐input multiple‐output (MIMO) systems. The proposed method is based on the ordered successive interference cancellation (OSIC) algorithm, but it significantly improves the performance of the original OSIC algorithm by solving the error propagation problem. The proposed method combines this enhanced OSIC algorithm with a multiple‐channel‐ordering technique in a very efficient way. As a result, the log likelihood ratio values can be computed by using a very small set of candidate symbol vectors. The proposed method has been synthesized with a 0.13‐μm CMOS technology for a 4×4 16‐QAM MIMO system. The simulation and implementation results show that the proposed detector provides a very good solution in terms of performance and hardware complexity.     

时频双选信道OFDM系统的ICI消除与均衡

在正交频分复用（OFDM）系统中,因高速移动造成的多普勒效应导致子载波间正交性的破坏并产生载波间干扰（ICI）。为了消除ICI,本文通过分析ICI分布特性及带状矩阵特性,提出了低复杂度的迭代干扰抵消算法和基于最小均方误差准则的排序串行干扰抵消(MMSE-OSIC)算法。仿真结果表明,与传统子载波间干扰频域均衡算法相比,新算法在计算复杂度和性能之间取得了良好的平衡,且MMSE-OSIC算法可以利用时变信道的时间分集特性在高信噪比情况下有效地消除“地板效应”。      

Minimum Mean-Squared Error Iterative Successive Parallel Arbitrated Decision Feedback Detectors for DS-CDMA Systems

In this paper we propose minimum mean squared error (MMSE) iterative successive parallel arbitrated decision feedback (DF) receivers for direct sequence code division multiple access (DS-CDMA) systems. We describe the MMSE design criterion for DF multiuser detectors along with successive, parallel and iterative interference cancellation structures. A novel efficient DF structure that employs successive cancellation with parallel arbitrated branches and a near-optimal low complexity user ordering algorithm are presented. The proposed DF receiver structure and the ordering algorithm are then combined with iterative cascaded DF stages for mitigating the deleterious effects of error propagation for convolutionally encoded systems with both Viterbi and turbo decoding as well as for uncoded schemes. We mathematically study the relations between the MMSE achieved by the analyzed DF structures, including the novel scheme, with imperfect and perfect feedback. Simulation results for an uplink scenario assess the new iterative DF detectors against linear receivers and evaluate the effects of error propagation of the new cancellation methods against existing ones.