一种抗误码能力强的无线信道图像传输方案

本文提出一种新的综合源编码和信道编码的无线信道图像传输方案，对子波变换后各个子带采用基于统计特性的变系数定长（VCFL）编码，数据经过Reed-Solomon编码后选择不同码率的码率兼容删除卷积码（RCPC）编码以提供不同程度的差错保护（UEP），最后数据经交织后传输。在给定传输的总比特数的情况下，通过优化算法使总体失真最小。模拟结果表明新方案在无线衰落信道上表现出良好的性能。     

Joint source/channel coding for image transmission with JPEG2000 over memoryless channels.

The high compression efficiency and various features provided by JPEG2000 make it attractive for image transmission purposes. A novel joint source/channel coding scheme tailored for JPEG2000 is proposed in this paper to minimize the end-to-end image distortion within a given total transmission rate through memoryless channels. It provides unequal error protection by combining the forward error correction capability from channel codes and the error detection/localization functionality from JPEG2000 in an effective way. The proposed scheme generates quality scalable and error-resilient codestreams. It gives competitive performance with other existing schemes for JPEG2000 in the matched channel condition case and provides more graceful quality degradation for mismatched cases. Furthermore, both fixed-length source packets and fixed-length channel packets can be efficiently formed with the same algorithm.     

Performances of 16QAM with fading compensation and postdetection diversity reception in satellite mobile channels

This paper studies the effects of N-branch postdetection selection diversity reception, where N = 1, 2, 3 or 4, incorporated with fading compensation on a digital satellite mobile system. The digital satellite mobile system transmits a pilot-symbol-aided 16-ary quadrature-amplitude modulated (PSA-16QAM) signal over the Rician channels. A selection method that makes use of the pilot symbols to select one of the N branches in the diversity reception system for signal detection, and a novel PSA technique that makes use of both the pilot symbols and data symbols for fading compensation, are proposed. Computer simulation tests are used to assess the effects of the proposed techniques on bit-error rate performances (BER) of the PSA-16QAM system in the presence of additive white Gaussian noise (AWGN) or co-channel interference (CCI) in the Rician faded channels. When frequency diversity is used, PSA-16QAM with 2-branch and 4-branch diversity reception occupies about the same bandwidths as quaternary phase-shift-keying (QPSK) without using diversity and with 2-branch diversity, respectively, yet achieving the same capacity. Thus, simulation tests on the BER performances of a QPSK system without diversity and with 2-branch diversity are also carried out and the results are used to determine the preferred system arrangements. © 1997 John Wiley & Sons, Ltd.     

Outage probability of cellular mobile radio systems with selective co‐channel interference cancellation receiver in overloaded array environments

This article outlines a general numerical procedure for computing the probability of outage of a cellular mobile radio system that is equipped with a smart antenna to suppress a few strongest co‐channel interferers (CCI) out of a total of N_I active interferers by adaptive null‐steering. Aside from the interference‐limited case, refined outage criterion that either treat receiver noise as CCI or consider a minimum detectable receiver signal threshold are studied. Exact closed‐form expressions for both the basic and refined outage criterion are also derived by assuming that all the CCI signals are subject to Nakagami‐m fading with a positive integer fading severity index. Selected numerical examples are provided to illustrate the application of the theory which includes the investigation into the effects of fade distribution of the CCI signals and traffic loading on the outage probability, and also the study of spectrum utilization efficiency improvement using a selective co‐channel interference nulling (cancellation) technique. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance study of mobile WiMAX network with changing scenarios under different modulation and coding

WiMAX—the Worldwide Interoperability for Microwave Access is a promising technology for offering high‐speed data, video and multimedia services over mobile platform evolving toward all IP networks. The increasing demand of WiMAX for VoIP and high‐speed multimedia is due to the simplicity of installation and cost reduction compared with the traditional wired DSL cable. The challenges to service providers lie with the Quality of Service (QoS) under varying fading environment while at the same time maximizing for resource utilization. In this paper, a rigorous and comprehensive performance study of mobile WiMAX has been made with respect to adaptive modulation and coding techniques considering the variation in the speed of the mobile, path‐loss, scheduling services and application type for comparing with the fixed type of modulations. The OPNET 14.5.A modeler for WiMAX platform has been used as simulator for adaptation at the physical layer of the transmission in WiMAX OFDMA structure. Observation reveals that dynamic adaptation of modulation and coding schemes based on channel condition enables better QoS while consuming low overall bandwidth of the system. Copyright © 2011 John Wiley & Sons, Ltd.     

Trellis-coded dpsk with multiple-symbol viterbi decoding over mobile satellite channel at K and L bands

Mobile satellite communication systems at K_a/K band (30/20 GHz) are attractive because of their large bandwidth availability and potentiality to support smaller earth-stations and satellite antennas compared with L-band (1·6/1·5 GHz) systems. In this paper, multiple-symbol Viterbi decoding and dual-space equal-gain diversity reception for trellis-coded differential M-ary phase-shift-keying (DPSK) modulation are investigated as two mitigation techniques for severe channel impairments expected from a land mobile satellite communication channel at K band and, for comparison purposes, at L band. The multiple-symbol Viterbi decoder (MSVD) is a modified Viterbi decoder with inputs from multiple differential detectors. The channel is modelled as Rayleigh distributed multipath fading with a lognormally distributed line-of-sight (LOS) component due to shadowing. Four trellis-coded modulation (TCM) schemes are studied. The dependency of the system performance improvement on the decoder structure, the TCM scheme, and the system RF frequency band is presented.     

Spatial modulation and physical layer network coding based bidirectional relay network with transmit antenna selection over Nakagami‐m fading channels

In this paper, a high data rate bidirectional relay network is proposed by combining the merits of spatial modulation (SM) and physical layer network coding. All nodes in the network are equipped with multiple antennas. Spatial modulation technique is used to reduce hardware complexity and interchannel interference by activating only one antenna at any time during transmission. In the proposed bidirectional relay network, transmit antennas are selected at the source nodes and relay node on the basis of the order statistics of channel power. It increases received signal power and provides a significant improvement in the outage performance. Also, the data rate of the proposed network is improved by physical layer network coding at the relay node. A closed form analytical expression for the outage probability of the network over Nakagami‐m fading channel is derived and validated by Monte Carlo simulations. In addition, asymptotic analysis is investigated at high signal‐to‐noise ratio region.The outage performance of the proposed network is compared with SM and physical layer network coding bidirectional relay network without transmit antenna selection and point‐to‐point SM. With approximate SNR≈1 dB difference between the two networks, the same data rate is achieved.