A Soft Combining Hybrid-ARQ Technique Applied to Throughput Maximization Within 3G Satellite IP Networks

This paper deals with the application of Hybrid-Automatic-Repeat-reQuest (H-ARQ) techniques to reliable end-to-end data communications in satellite networks, whose applications have to cope with accurate Quality-of-Service (QoS) requirements. Particularly, we face this problem by introducing a modified H-ARQ scheme based on the use of the turbo codes' error-correction capabilities. According to our scheme, each packet is turbo coded, and packet retransmissions are lowered by keeping track of previous erroneous packet-decoding results. Moreover, two kinds of these techniques are proposed and applied, respectively, to consecutive received packet replicas or to decoding algorithm outputs. The benefits achieved through this approach have a positive effect both on the error-recovery strategies and, above all, on the congestion-control protocols, since they rely on a retransmission scheme. By means of analytical derivations carried out under the assumption of a wideband-code-division multiple-access communications, it has been possible to highlight noticeable performance improvements in terms of bit- and frame-error rates and link throughput. Computer simulations performed focusing on a typical satellite-universal-mobile-telecommunication-system environment validate analytical predictions and point out a remarkable gain without requiring a significant hardware-complexity increase. As a result, it has been possible to allow active users a better QoS, in terms of error rate, throughput, and delivery delay, or to increase access-network capacity, besides avoiding transmitted-power wasting     

Trickle-based interference cancellation schemes for CDMA systems

In this paper, we introduce a novel approach to interference cancellation (IC) for code division multiple access (CDMA) uplink transmission. Several models combining principles of serial (SIC) and parallel (PIC) interference cancellation are discussed. The proposed scheme is derived from the analysis of these hybrid models and applies a user configuration algorithm (termed “trickle”) in order to provide improved bit-error-rate (BER) performance. The algorithm utilizes an adaptive matrix to compute the required configuration to be used for the subsequent interference cancellation stage. We demonstrate that significant performance improvements can be achieved over various hybrid schemes. A reduced-complexity version of the trickle algorithm is also introduced where the processing delay is greatly reduced while maintaining similar performance. We present several numerical examples through which we demonstrate the efficacy of the proposed algorithms relative to existing interference cancellation algorithms.     

时变信道下OFDM系统中基于载频间干扰抑制的迭代检测算法

为了有效地抑制OFDM系统载频间干扰（ICI），提出一种并行干扰消除的迭代检测算法。基于检测信号的信干噪比最大化的准则，通过对接收信号进行判决、重构、干扰抵消处理，建立了ICI抑制的迭代检测算法，给出了信号检测流程。通过对时变信道的分析，研究了时变信道中归一化频偏对系统陛能的影响，给出了性能仿真结果。仿真结果表明所建议的算法可有效地利用时变信道的时间分集特性来提高系统性能，计算复杂度从O（N^3）降低到O（N）。     

OFDM雷达通信一体化的同频干扰抑制技术

雷达通信一体化系统（Integrated Radar and Communication System,IRCS）可提升设备的可用性、可靠性和电磁兼容性,已成为雷达和通信交叉领域的研究热点。正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）具有高信息传输性能,且其模糊函数具有低旁瓣特性,在IRCS中得到广泛关注。在OFDM-IRCS中,组网时同频干扰严重影响雷达探测性能。针对这一问题,从信干比（Signal to Interference Ratio,SIR）分析了IRCS同频干扰特性,推导了回波信号SIR的表达式。然后,结合OFDM中交织多址（Interleave Division Multiple Access,IDMA）和干扰重构的思想,提出了基于OFDM-IDMA的IRCS同频干扰抑制算法。所提算法通过不同的交织方式区分不同IRCS节点的信号,同时利用基于干扰重构的干扰消除算法实现干扰抑制。仿真结果表明,所提算法有效地抑制了IRCS同频干扰,实现了同频干扰环境下雷达目标探测性能提升。     

Power controlled H-ARQ in cdma2000 1/spl times/EV-DV

The newly applied H-ARQ technique in the reverse link of a cdma2000/spl reg/ 1/spl times/EV-DV system is shown to be similar in nature to the fast power control technique such that the two techniques both reduce interference to other users. In order to balance the H-ARQ gain and packet delay time, four modes of operation are defined: normal, reduction, boost, and boost reduction. The four modes are defined according to the way the channel gain is set for the H-ARQ operation. Simulation results show that the reduction modes have better performance in terms of both PER and packet delay time. It is also shown that the boost modes have lower PER and packet delay time than the non-boost modes, but at the expense of more energy.     

A single antenna interference cancellation algorithm for increased gsm capacity

In mobile communications networks, system capacity is often limited by cochannel interference. Therefore, receiver algorithms for cancellation of cochannel interference have recently attracted much interest. At the mobile terminal, algorithms can usually rely only on one received signal delivered by a single receive antenna. In this letter, a low-complexity single antenna interference cancellation (SAIC) algorithm for real-valued modulation formats referred to as mono interference cancellation (MIC) is introduced which is well suited for practical applications. Field trials in commercial GSM networks using prototype terminals with the proposed MIC algorithm have demonstrated that the novel concept may yield capacity improvements of up to 80%. The underlying principle is also beneficial for adjacent channel interference and receivers with multiple antennas. Furthermore, in coverage-limited scenarios, there is no performance degradation compared with conventional receivers     

V-BLAST系统中选择性最大比合并算法

通过选择性最大比合并(SC/MRC)算法,在并行干扰抵消(PIC)技术的基础上,对V-BLAST系统各接收天线的干扰抵消结果按照SC/MRC合并,实现了分集接收.该算法最多可以实现与接收天线数等同的分集增益,而通过选择信道条件较好的几个接收天线进行合并,可以在性能与复杂度之间取得折衷.MRC合并只需与选择合并的天线数线...     

Adaptive multistage parallel interference cancellation for CDMA

Although the multistage interference cancellation detector is simple in structure, its performance degrades when the number of active users becomes large. In some cases, the performance is even worse than that without cancellation, due to the lack of the exact knowledge of the interfering signal in cancellation. Partial interference cancellation suggested by Divsalar and Simon (see IEEE Trans. Commun., vol.46, p.258-68, 1998) tries to remedy this weakness by reducing the cost of a wrong interference estimation through a weight in each stage. This paper presents an adaptive multistage structure based on the partial interference cancellation approach. In this structure, the weights are obtained by minimizing the mean-square error between the received signal and its estimate through a least mean square (LMS) algorithm. The resulting weights contain reliability information for the hard decisions made in the previous stage. Neither a training sequence nor a pilot signal is needed in the proposed scheme, and its complexity is much lower than that of linear multiuser detectors. Simulation results show that the proposed scheme can outperform some of the existing interference cancellation methods in both the additive white Gaussian noise (AWGN) and the multipath fading channels     

高速移动信道中的ICI消除算法

针对当前研究中的子载波干扰(ICI)消除算法不支持高速移动环境的缺点,提出一种基于线性时变模型的ICI迭代消除算法。使用相邻3个正交频分复用(OFDM)信号帧对信道进行近似处理,将时变的无线信道建模为基于每条信号径的线性时变信道,信道线性时变斜率可通过相邻的导频符号获得,这样就可以预先构造频域干扰矩阵,然后通过循环迭代的方法将接收符号中的干扰消除。仿真结果表明,本文提出的ICI迭代消除算法可有效消除高速移动信道中的ICI。在多普勒偏移小的条件下,此算法带来的性能提升更大。     

HSDPA中的H-ARQ技术分析

HSDPA（High Speed Downlink Packet Access）即高速下行分组接入技术是3G中的一项重要技术。它作为一种无线增强技术极大的提高了系统的下行数率，而且同时适用于WCDMA和TD—SCDMA系统。HSDPA中引入了自适应调制和编码技术（AMC）、混合自动请求重发（H—ARQ）、快速小区选择（FCSS）、MIMO技术等关键技术。主要研究其中的H—ARQ（Hybrid Automatic Repeat reQuest）技术。首先介绍H—ARQ的起源及三种不同类型H—ARQ的特点，其次研究了H—ARQ在HSDPA中的应用，最后对不同H—ARQ方案的性能进行了分析。     

Packet scheduling with playout adaptation for scalable video delivery over wireless networks

In this paper, we propose a playout deadline-aware packet scheduling for scalable video delivery over wireless networks. We develop a novel playout adaptation algorithm to reduce playback interruptions by jointly considering the active playout buffer status and adaptive playout rate. We also propose a packet priority analysis method based on the layer information of Scalable Video Coding (SVC). Based on the priority of the video packet and the adaptive playout-deadline, an optimal packet scheduling algorithm is proposed. Packets are selected for transmission to minimize the quality degradation caused as well as to reduce the playout latency. We also adopt a benchmark for the packet priority analysis by calculating the distortion impact of each packet with the consideration of the packet dependency in SVC. When compared with the state-of-the-art algorithms as well as the benchmark, our proposed scheduling algorithm shows a good trade-off between the video quality and the playout latency.     

Advanced Receiver for Interference Suppression and Cancellation in Sidelink System of LTE-Advanced

Recently, the 3rd Generation Partnership Project (3GPP) has developed a sidelink system to compensate for the explosive increase in mobile data traffic. However, there are numerous challenging technical problems that must be overcome. One major problem is inter-cell interference management. 3GPP has considered network-assisted interference cancellation and suppression to improve both the signal-to-noise-plus-interference ratio (SINR) and receiver performance by suppression or cancellation of inter-cell interference signals. In this paper, we propose a novel advanced receiver to reduce the interference from neighbor cell in sidelink systems. The proposed receiver can suppress and cancel the interference by combining interference rejection combining with successive interference cancellation. We perform a system-level simulation based on 20 MHz bandwidth of 3GPP LTE-Advanced system. Simulation results show that the proposed receiver can improve the SINR, throughput, and spectral efficiency, relative to a conventional system.

     

MIMO SC-FDMA定时同步的并行干扰消除算法

针对LTE-Advanced上行链路MIMO SC-FDMA系统中定时同步问题,提出一种基于QR分解与并行干扰消除PIC相结合的定时同步算法。该算法通过QR分解检测获得初步的信息估计值,应用并行干扰消除方法,将定时偏移所产生的干扰从接收信号中消除。理论分析与仿真结果表明,该算法可显著提高系统性能。     

MAP multiuser detection with soft interference cancellation for UTRA-TDD receivers

A new multiuser detector (MUD) exploiting the MAP algorithm is proposed for channels affected by severe multipath and is then suitable for time-division duplexing (TDD)-CDMA receivers. After coherent combining the received multipaths, a multidimensional MAP non-linearity is employed to compute step-by-step the a posteriori probabilities (APPS) of the transmitted data for each user separately and then their expected values conditional to the available observations. These are then employed for soft ISI and MAI removal from the received sequences so that the APPS can be more reliably re-computed. The procedure is iterated in a multistage structure until final decisions are taken. From the comparison with other existing techniques (interference cancellation, zero-forcing) the proposed reduced MAP-MUD receiver exhibits better performance and equal or minor complexity.     

基于网络编码的分级视频权限控制方法

提出一种基于随机线性网络编码的可分级视频流的权限控制算法,该算法充分考虑了网络编码技术和可分级技术的有机结合,从数据包加密和分配2个方面详细阐述了其实现机制,给出了基于全局编码向量的加密和分层的视频证书认证算法。提出的方法具有运算复杂度低和易于实现的优点。仿真结果证明提出的方法可以有效且简便地控制视频的使用权限。     

Joint resource optimization for nonorthogonal multiple access-enhanced scalable video coding multicast in unmanned aerial vehicle-assisted radio-access networks

A joint resource-optimization scheme is investigated for nonorthogonal multiple access (NOMA)-enhanced scalable video coding (SVC) multicast in unmanned aerial vehicle (UAV)-assisted radio-access networks (RANs). This scheme allows a ground base station and UAVs to simultaneously multicast successive video layers in SVC with successive interference cancellation in NOMA. A video quality-maximization problem is formulated as a mixed-integer nonlinear programming problem to determine the UAV deployment and association, RAN spectrum allocation for multicast groups, and UAV transmit power. The optimization problem is decoupled into the UAV deployment–association, spectrum-partition, and UAV transmit-power–control subproblems. A heuristic strategy is designed to determine the UAV deployment and association patterns. An upgraded knapsack algorithm is developed to solve spectrum partition, followed by fast UAV power fine-tuning to further boost the performance. The simulation results confirm that the proposed scheme improves the average peak signal-to-noise ratio, aggregate video-reception rate, and spectrum utilization over various baselines.     

基于投影对消处理技术的稳健自适应波束形成

针对传统自适应波束形成算法中目标波达方向(Direction of Arrival,DOA)估计不准确引起的波束形成性能下降问题,提出了一种采用投影对消矩阵的稳健自适应波束形成算法.首先,寻找与估计波达方向有最大相关性的特征矢量作为目标信号特征矢量,然后构建对消矩阵消除协方差矩阵中的信号分量,最后通过增加零点约束实现干扰抑制.与传统对角加载类稳健波束形成算法相比,所提算法不受对角加载因子的影响,且在信干噪比较大时仍然具有良好的抗干扰性能.仿真对比实验验证了所提算法的有效性.     

H-ARQ信道上高性能全分集LDPC码的构造与性能分析

为了提高混合自动重传请求(H-ARQ)系统的通信性能,研究了H-ARQ块衰落信道上全分集低密度奇偶校验(LDPC)码的构造与性能.首先分析了H-ARQ块衰落信道的中断概率及其固有分集,然后构造了在H-ARQ块衰落信道上能取得全分集的LDPC码,新构造的码字采用根校验节点把每次传输联系起来,从而获得全分集.在此基础上,分析了全分集LDPC码的结构,提出了通过提高全分集校验比特的比例,改善全分集LDPC码在H-ARQ信道上编码增益的方法.仿真结果表明,所提算法在H-ARQ信道上不仅能取得全分集,而且具有较高的编码增益     

Interference management using basestation coordination in broadband wireless access networks

This paper proposes a transmission‐scheduling algorithm for interference management in broadband wireless access networks. The algorithm aims to minimize the cochannel interference using basestation coordination while still maintaining the other quality of service (QoS) requirements such as packet delay, throughput and packet loss. The interference reduction is achieved by avoiding (or minimizing) concurrent transmission of potential dominant interferers. Dynamic slot allocation based on traffic information in other cells/sectors is employed. In order to implement the algorithm in a distributed manner, basestations (BSs) have to exchange traffic information. Both real‐time and non‐real‐time services are considered in this work. Results show that significant reduction in the packet error rate can be achieved without increasing the packet delay at low to medium loading values and with a higher but acceptable packet delay at high loading values. Since ARQ schemes can also be used for packet error rate reduction, we compare the performance of the proposed scheme with that of ARQ. Results indicate that although ARQ is more effective in reducing packet error rate, the proposed algorithm incurs much less packet delay particularly at medium to high loading. Copyright © 2006 John Wiley & Sons, Ltd.     

一种比较决策多用户检测器的研究

以多速率码分多址(CDMA)传输为出发点，以满足不同用户信号的信干比(SIR)检测要求为目标，给出了在具有决策反馈的并行干扰抵消(PIC)检测框架下，通过实施基于概率数据关联(PDA)预估计软判决和并行干扰抵消硬判决的两种决策比较，进而选择最佳判决的方法，有效地抑制了由于信号估计不准确而造成的错误干扰抵消及相应的判决错误。文中给出了仿真结果，并分别就单一的软、硬判决及比较决策的检测性能进行了分析和比较。