Efficient adaptive forward error control schemes for Ka-band satellite systems

Adaptive fade margin is required to counter the severe but varying rain attenuation in K_a-band satellite communications. In a search for a suitable rain countermeasure, the effectiveness of adaptive forward error control (AFEC) schemes is studied. Two AFEC schemes using convolution codes and concatenated codes are proposed and their performances analysed. The schemes can provide progressively adaptive fade margins of 10-1 and 10-4 dB, respectively, in excess of the system's fixed fade margin. To improve the efficient use of shared resources of the system, an AFEC scheme using double coding is introduced and its performance analysed. In this scheme a single codec is used repeatedly, resulting in reduced hardware cost and increased use. By using convolutional code and Golay code the above scheme can provide adaptive fade margins of 10°8 dB and 8°1 dB, respectively. Although concatenated codes have slightly better performance than double codes, the hardware implementation and decoding complexity of the latter are significantly less. Implementation complexity of AFEC resource sharing in the light of code complexity, time frame expansion, link condition monitoring and signalling is discussed in detail.     

Hybrid ARQ schemes for DS spread spectrum systems in the presence of narrow‐band interference

This paper is concerned with a direct sequence spread spectrum system making use of automatic repeat request (ARQ) schemes and operating in the presence of narrow‐band (NB) interference and additive white Gaussian noise. In this study, we evaluate the system's throughput efficiency when a suppression filter is employed at the receiver to mitigate the effect of NB interference. Specifically, we investigate how the performance is influenced by various parameters such as the number of filter taps, processing gain, type of interference, and the signal power‐to‐interference power ratio. The simulation results show that using the suppression filter significantly improves the throughput performance of the hybrid ARQ schemes in the presence of NB interference. Copyright © 2002 John Wiley & Sons, Ltd.     

ARQ error control for fading mobile radio channels

In this paper, we study the correlation properties of the fading mobile radio channel. Based on these studies, we model the channel as a one-step Markov process whose transition probabilities are a function of the channel characteristics. Then we present the throughput performance of the Go-Back-N and selective-repeat automatic repeat request (ARQ) protocols with timer control, using the Markov model for both forward and feedback channels. This approximation is found to be very good, as confirmed by simulation results     

Some new hybrid ARQ techniques for high error rate conditions

Some new hybrid ARQ schemes for error control in communication systems are presented in which redundancy, achieved by retransmission of a code word, is exploited to facilitate correct code-word recovery. In the first two techniques, applicable to cases in which a code word detected in error is retransmitted several times consecutively, an error-correcting code is used in conjunction with a normal ARQ code to enhance performance even at high error rates. These two techniques have been modified to allow application to protocols in which only one copy is sent each time a code word must be transmitted. Theoretical analysis of the protocols shows that these techniques outperform similar ARQ schemes, particularly for high error rates.     

Cooperative ARQ protocol for correlated wireless channels

A novel Automatic repeat ReQuest （ARQ） protocol called cooperative ARQ is presented in this letter, where a relay terminal is requested to retransmit an erroneously received packet, instead of the source terminal. The data link layer Packet Error Rate （PER） performance of cooperative ARQ is derived in correlated wireless channel. The results show that even though the relay-destination channel is worse than the sourcedestination channel, the new protocol outperforms the traditional one as long as the average SNR of the relaydestination channel is better than a certain threshold. It is also demonstrated that a second order diversity gain can be achieved with the cooperative ARQ protocol.     

Efficient Integration of IP-Based Terrestrial and Satellite Systems: ARQ Techniques and Inter-Segment Handover

A satellite communication system is an excellent candidate toprovide broadband integrated Internet services to globallyscattered users. The inter-operation between a satellite systemand the existing terrestrial Internet infrastructure introducesnew challenges at different layers. Automatic Repeat reQuest (ARQ)techniques have been introduced at radio link layer to improve theperformance of Transport Control Protocol (TCP)/IP over wirelessterrestrial links, but these techniques are usually dismissed inpresence of high latency links such as satellite links. In thispaper, we will show that a truncated power control can effectivelyimprove the trade-off delay-residual error after retransmissionsand makes ARQ techniques a feasible solution for error control insatellite links. Furthermore, mobility management issues inpresence of satellite diversity are addressed. Performance of anInter-Segment Hand-Over (ISHO) procedure, in terms of propagationdelay, will be carried out through simulation for different spacesegment configurations.     

慢瑞利衰落信道下一种变分组长度的自适应ARQ协议

信道的慢瑞利衰落特性导致通信系统的性能——吞吐量的下降。本文基于选择重传(SRARQ)与返回-n(GBN ARQ)相结合的混合ARQ协议(SR GBN ARQ),依据发送方连续收到的确认(ACK)/非确认(NACK)消息的次数,正确评估慢瑞利衰落信道的状况以改变分组长度的一种自适应ARQ协议。仿真结果表明对于慢瑞利衰落、长往返旅程延迟(T)信道,该协议能取得较优的吞吐性能。     

一种有效的水声通信网络中用于半双工信道的ARQ协议

自动重传请求(ARQ)在保证通信网络可靠传输中起着关键的作用。但是，在水声通信网络中，由于水声信道的半双工以及信道的长传播时延特性，使得水声通信网络的吞叶性能受到极大的制约。本文针对水声信道长传播时延这一特点，利用扩频通信技术，将单个信道分成两个子信道；一个用于前向信道(从发送方到接收方)，另一个用于反向信道(从接收方到发送方)，从而使得对每个分组数据的响应时间大大缩短，提出了一种有效的适合于半双工特性的ARQ协议。理论分析和仿真结果表明，相对于传统的SW ARQ协议而言，该协议在水声信道下具有更优的吞吐性能。     

基于截短ARQ协议的协作分集系统吞吐量研究

研究协作分集通信系统的跨层设计使系统吞吐量最大化.首先推导基于截短ARQ协议的协作分集和两跳系统的吞吐量理论表达式,揭示数据包长度和调制方式对系统吞吐量的影响,在此基础上用自适应技术优化系统性能,采用连续二维优化求出了吞吐量的最大值,进而提出了实用的二维离散吞吐量优化算法,该算法的优化结果与吞吐量最大值相差很小,最后提出了计算量更小的一维离散优化算法,且其吞吐量性能损失也很小.     

HARQ–ARQ interaction method for LTE‐based mobile satellite communication system

Hybrid automatic repeat request (HARQ) and automatic repeat request (ARQ) of the terrestrial long‐term evolution (LTE) system are designed considering the very short propagation delay of terrestrial environment. Therefore, when HARQ and ARQ are applied to the LTE‐based mobile satellite communication system, the inefficiency is caused by the long propagation delay of satellite environment. This paper proposes the interaction method between HARQ and ARQ for the decrease of inefficiency in the LTE‐based mobile satellite communication system. The existing concept of layered architecture about HARQ and ARQ is also maintained in our interaction method. Simulation results reveal that our proposed scheme can provide the larger spectrum efficiency than that of the non‐interaction scheme in all environments. The performance improvement can be up to 2.04 times through the interaction method. Copyright © 2014 John Wiley & Sons, Ltd.     

Practical packet combining for use with cooperative and non-cooperative ARQ schemes in resource-constrained wireless sensor networks

An improved implementation of a post-detection packet combining scheme, which is especially applicable to low power, resource-constrained sensor networks, is developed and practically implemented on popular off-the-shelf wireless motes. The algorithm can be used as part of protocols such as cooperative communications and hybrid-ARQ schemes which have been shown to be of major benefit for wireless communications. Using the packet combining implementation developed in this paper more than an 85% reduction in energy costs are possible over previous, similar approaches. Both simulated and practical experiments are developed in which packet combining is shown to offer up to approximately 2.5 dB reduction in the required Signal-to-Noise Ratio (SNR) for a desired Packet Error Rate (PER). This is a welcome result as complex schemes, such as maximal-ratio combining, are not implementable on many of the resource constrained devices under consideration.     

无线传感器网络中协作ARQ协议能量效率分析及优化

文章研究了无线传感器网络中协作自动请求重传（Cooperative Automatic Repeat Request, CARQ）协议的能量效率及其优化问题。定义协议的能量效率为单位能耗所支持的分组成功传输的个数,导出了CARQ协议和传统ARQ协议的能量效率表达式以及CARQ协议相对ARQ协议的能效增益表达式,依此对两协议的能量效率进行了仿真研究,发现协作节点的位置对协议的能量效率有重要影响,当通信距离大于“门限距离”时,CARQ协议的能量效率才高于传统ARQ协议能效;进而提出了一种离散优化算法,通过优化调制水平,大大提高了CARQ协议的能效及能效增益。      

混合ARQ无线传输系统在多机牵引中的应用

为了保障多机牵引无线同步控制系统数据传输的可靠性,提出一种多机牵引无线同步控制系统的混合ARQ数据传输子系统设计方案,并讨论了其在机车信号传输中存在的问题。     

Transmission of group 3 facsimile over inmarsat maritime digital satellite mobile channels

The importance of facsimile communication over public telephone networks is evidenced by the rapid growth in the number of Group 3 facsimile end-user terminals. In this paper the main characteristics of a real-time bit-rate reducing approach are described whereby facsimile signals are demodulated and their associated protocols converted by a facsimile interface unit (FIU) to a format suitable for transmission over Inmarsat-B maritime digital satellite channels. The FIU concept was developed to allow ‘off-the-shelf’ facsimile terminals to be interconnected via the PSTN through Inmarsat's satellite networks and to permit the provision of enhanced user services by converting Group 3 facsimile protocols to broadcast operation. In addition, the FIU concept is designed to compensate for the longer access and transport link delays encountered in mobile satellite systems, and to permit facsimile call recovery procedures to be successfully concatenated with satellite channel error detection mechanisms.     

Hybrid Turbo FEC/ARQ Systems and Distributed Space-Time Coding for Cooperative Transmission

Cooperative transmission can be seen as a “virtual” MIMO system, where the multiple transmit antennas are in fact implemented distributed by the antennas both at the source and the relay terminal. Depending on the system design, diversity/multiplexing gains are achievable. This design involves the definition of the type of retransmission (incremental redundancy, repetition coding), the design of the distributed space-time codes, the error correcting scheme, the operation of the relay (decode & forward or amplify & forward) and the number of antennas at each terminal. Proposed schemes are evaluated in different conditions in combination with forward error correcting codes (FEC), both for linear and near-optimum (sphere decoder) receivers, for its possible implementation in downlink high speed packet services of cellular networks. Results show the benefits of coded cooperation over direct transmission in terms of increased throughput. It is shown that multiplexing gains are observed even if the mobile station features a single antenna, provided that cell wide reuse of the relay radio resource is possible.     

Performance of Hybrid ARQ Schemes for OFDM Systems

In this paper,four schemes of Hybrid Automatic-Repeat-Request(HARQ)for Orthogonal Frequency DivisionMultiplexing(OFDM)systems are evaluated when they are used in different channel environments.The AccumulativeCorrect Packet Reception Rate(ACPRR)performance of four HARQ schemes is compared in order to verify which ARQschemes are more suitable for different mobility OFDM systems.Computer simulation results show that the maximal ratiocombining frequency diversity ARQ scheme and type Ⅲ HARQ with frequency diversity is more suitable for low mobilityOFDM system.However the type Ⅲ HARQ without frequency diversity is more suitable for high mobility OFDM systembecause of the remarkable time diversity which reduces the required retransmission number to about 2 at the ACPRR of0.96.     

卷积码混合ARQ系统的自适应最优子包传输

针对有突发性错误的卷积码混合ARQ系统,提出了一种估计最优子包数的有效方法以及自适应子包传输方案.在理论分析最优子包数的基础上,对卷积码系统采用自适应子包传输后的性能进行了仿真验证.仿真结果表明,在动态信道中,自适应子包传输方案可使系统根据不同信道条件,采用不同的最优子包数可达到最大的吞吐量.     

Cross-layer combining of power control and adaptive modulation with truncated ARQ for cognitive radios

To maximize throughput and to satisfy users＇ requirements in cognitive radios, a cross-layer optimization problem combining adaptive modulation and power control at the physical layer and truncated automatic repeat request at the medium access control layer is proposed. Simulation results show the combination of power control, adaptive modulation, and truncated automatic repeat request can regulate transmitter powers and increase the total throughput effectively.     

基于cdma2000系统的数据传输控制方案的研究

数据传输控制方案对分组传输时延和系统容量有显著的影响。该文提出了三种不同的数据传输控制方案,通过计算机仿真,比较了它们对系统性能的影响,得出了相应的结论。     

Performance of regenerative/conventional satellite systems

A great many papers have been devoted in the last few years to the advantages of regenerative communications satellite systems when compared to conventional ones. This paper attempts to summarize the most significant results which are scattered in the literature, and to provide a tutorial overview of this comparison. Linear and non-linear satellite channel performances, with and without interference, are discussed. The major impacts on system design provided by on-board regeneration are also presented.