混合DS—SFH扩频多址通信系统采用RS码的性能界限的分析

本文推导了混合直接序列和慢跳频扩频多址通信系统，在Ｒｉｃｉａｎ和Ｒａｙｌｅｉｇｈ多径衰落信中，采用ＲＳ编码和非相干ＤＰＳＫ、ＦＳＫ调制的系统性能界限，提出了利用探测多径干扰和多址干扰是否存在的信道信息的ＲＳ译码新算法。     

混合DS－SFH扩频多址通信系统采用RS码的性能界限的分析

本文推导了混合直接序列和慢跳频扩频多址通信系统，在Ｒｉｃｉａｎ和Ｒａｙｌｅｉｇｈ多径衰落信道中，采用ＲＳ编码和非相干ＤＰＳＫ、ＦＳＫ调制的系统性能界限，提出了利用探测多径干扰和多址干扰是否存在的信道信息的ＲＳ译码新算法。     

DS－SFH扩频多址系统在瑞利衰落信道中多径分集的性能研究

本文讨论了混合ＤＳ－ＳＦＨ扩频多址ＳＳＭＡ通信系统在瑞利衰落信道中多径分集接收的性能。基于多径干扰、多址干扰和信道噪声之和为一个高斯随机变量的分析，推导了在等增益组合（ＥＧＣ）和选择最大（ＳＭ）多径分集接收算法下，扩频系统的平均差错概率。理论分析和数值模拟指出：扩频多径分集接收可以明显地改善ＤＳ－ＳＦＨＳＳＭＡ系统的性能，在提高系统性能方面，等增益组合算法优于选择最大分集算法。     

DS—SFH扩频多址系统在瑞利衰落信道中多径分集的性能研究

本文讨论了混合ＤＳ－ＳＦＨ扩频多址ＳＳＭＡ通信系统在瑞利衰落信道中多径分集接收的性能，基于多径干扰、多址干扰和信道噪声之和为一个高斯随机变量的分析，推导了在等增益组合和选择最大多径分集接收算法下，扩频系统的平均差错概率，理论分析和数值模拟指出：扩频多径分集接收可以明显地改善ＤＳ－ＳＦＨ ＳＳＭＡ系统的性能，在提高系统性能方面，等增益组合算法优于选择最大分集算法。     

可变速率编码技术在跳频多址系统中的应用

本文从实际出发,研究了可变速率编码（ＶＲＣ）技术在跳频多址（ＦＨＭＡ）通信系统中的应用,讨论了在系统采用使接收误码率低于某规定值（以１０＾－２为例）的最大码速率时,该结构相对于固定速率编码（ＦＲＣ）结构的系统平均标准吞吐量增益,通过对解调器有、无ＰＳ信息（即有关被传输的符号中哪些受到多址干扰的信息）及信道有、无衰落情况下的分析,验证此技术在实际系统中的实用性。     

DS／FH混合扩频系统抗干扰性能分析

在建立DS／FH混合扩频系统数学模型的基础上,本文对三种组合条件下（高斯白噪声和多址干扰;高斯白噪声、多址干扰和部分带宽干扰;高斯白噪声、多址干扰和信道衰落）DS／FH混合扩频系统进行了系统性能仿真分析。     

随机M进制正交码混合DS—SFH CDMA扩频通信系统性能分析

本文研究了随机ＭＦ是制正交码混合ＤＳ－ＳＦＨ扩频码分多址信号经过多径瑞利频率非选择性衰落信道，在非相干ＲＡＫＥ接收机中采用最大输出信噪比选择或最大输出选择接收时系统的性能；给出了两种分集接收情况下差错概率表示式。数值计算研究了分集数，Ｍ值，多用户干扰对系统性能的影响，并且对这两种分集接收情况下系统性能进行了比较。     

相干接收随机多码CDMA在多径衰落信道中的容量性能研究

本文研究采用ＢＰＳＫ调制、相干ＰＡＫＥ接收的随机访问多码ＣＤＭＡ）ＲＡＭＣ＿ＣＤＭＡ）在频率选择性Ｎａｋａｇａｍｉ多径衰落、噪声信道（ＭＦＮＣ）中的容量性能,建立系统模型后,推导出了多用户条件下接收机输出的条件概率分布及判决平均比特误码率,并以Ｒａｙｌｉｇｈ多径衰落、噪声信道为例,计算了系统容量的数值解,分析表明：ＲＡＭＣ－ＣＤＭＡ解决了普通ＤＳ－ＣＤＭＡ系统存在的用户可传信息速率受限的问题,能在     

P－TCM在卫星移动通信信道上的性能

实用化网格编码调制（Ｐ－ＴＣＭ）方案能够利用同一芯片实现不同码率的网格码之编译码过程，其性能在加性高斯白噪声信道上与ＵｎｇｅｒｂｏｅｃｋＴＣＭ码相比差别不大。本文针对编码率为２／３的６４状态Ｐ－ＴＣＭ码，从理论上计算了在相干检测和差分检测两种情况下，该码在Ｒｉｃｉａｎ信道上和轻微遮挡的Ｒｉｃｉａｎ信道上的误比特率上、下限或渐进曲线，并且给出了相应的计算机仿真结果。结果表明，当误比特率为１０－３时，该码在上述信道上约有３．４ｄＢ～５．２ｄＢ的编码增益。     

P—TCM在卫星移动通信信道上的性能

实用化网格编码调制方案能够利用同一芯片实现不同码率的网格码之编译码过程，其性能在加性斯白噪声信道上与Ｕｎｇｅｒｂｏｅｃｋ ＴＣＭ码玎比差别不大。本文针对编码率为２／３的６４状态－ＰＴＣＭ码，从理论上计算了在相干检测和差分检测两种情况下，该码在Ｒｉｃｉａｎ信道上和轻微遮挡的Ｒｉｃｉａｎ信道上的误比特率上，下限或渐进曲线，并且给出了相应的计算机仿真结果。     

Error probabilities of fast frequency-hopped MFSK withnoise-normalization combining in a fading channel with partial-bandinterference

An error probability analysis performed for an M-ary orthogonal frequency-shift keying (MFSK) communication system employing fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a frequency-nonselective, slowly Rician fading channel with partial band interference is discussed. Diversity is obtained using multiple hops per data bit. Noise-normalization combining is employed by the system receiver to minimize partial-band interference effects. The partial-band interference is modeled as a Gaussian process. Thermal noise is also included in the analysis. Forward error correction coding is applied using convolutional codes and Reed-Solomon codes. Diversity is found to dramatically reduce the degradation of the noise-normalization receiver caused by partial-band interference regardless of the strength of the direct signal component. Diversity offers significant performance improvement when channel fading is strong, and performance improvement is obtained for high modulation orders (M>2). Receiver performance is improved when diversity, higher modulation orders, and coding are combined     

Coded FH/SS Communications in the Presence of Combined Partial-Band Noise Jamming, Rician Nonselective Fading, and Multiuser Interference

In this paper we address the problem of combatting combined interference in spread-spectrum communication links. We consider frequency-hopped spread-spectrum systems withM-ary FSK modulation and noncoherent demodulation which employ forward-error-control coding. The interference consists of partial-band noise jamming, nonselective Rician fading, other-user interference, and thermal noise. The coding schemes which we analyze include: ReedSolomon codes (with or without diversity and error-only, erasure-only, or parallel erasure/error decoding), binary, nonbinary, and dual-kconvolutional codes with and without side information (information about the state of the channel), and concatenated schemes (Reed-Solomon outer codes with either inner detection-only block codes or inner convolutional codes). In all cases we derive 1) the minimum signal-to-jammer energy ratio required to guarantee a desirable bit error rate as a function of ρ, the fraction of the band which is jammed, when the number of interfering users is fixed; and 2) the maximum number of users that can be supported by the system as a function of ρ, when the signal-to-jammer energy ratio is fixed.     

Concatenated Reed-Solomon/convolutional coding for datatransmission in CDMA-based cellular systems

A robust error control scheme for data transmission in CDMA-based cellular systems is proposed which employs outer Reed-Solomon codes concatenated with inner convolutional codes. The performance of this scheme is analyzed assuming nonperiodic random spreading sequences and a Rake receiver with perfect knowledge of the channel. In particular, a simple model for the memoryless inner coding channel that encompasses the effects of multiple access interference, self-noise and thermal noise is first derived. Using new tight upper bounds on bit- and symbol-error probabilities of convolutional codes over Nakagami, Rayleigh, and Rician fading multipath channels, the performance of the concatenated coding scheme is then evaluated. The Reed-Solomon/convolutional coding scheme has been adopted by the European RACE Project Code Division Testbed (CODIT) and implemented in an experimental testbed. The code design methodology, which has been used to specify the 9.6-, 64-, and 128-kbit/s data traffic channels of the CODIT testbed, is presented and the single-cell CDMA capacity is computed     

Path diversity for DS-SSMA communications in Nakagami fading channels

Average error probability and outage probability for an asynchronous direct sequence spread spectrum multiple access communications through slow nonselective Nakagami fading channels are evaluated for nondiversity and diversity receptions. Using the Gauss quadrature rule, the moments of the self-interference and the multiple access interferences are used to evaluate average error probability and outage probability. Combining the diversity technique and error correcting codes, comparisons between the uncoded nondiversity DS-SSMA system and that of the coded diversity system are shown for the Gold Code of codelength 127. Using fourth-order diversity and the Reed-Solomon code, the maximum achievable number of users is 12 percent of the codelength for Rayleigh fading, when the average probability is 10^–3. The corresponding outage probability is less than 5 percent. Performance comparisons between Rician and Nakagami fading channels are made. Since the system is interference limited, the performance seems to show no significant difference for the two fading channel models when the number of users is large.     

Capacity of synchronous coded DS SFH and FFH spread-spectrummultiple-access for wireless local communications

The performance of synchronous spread-spectrum multiple-access (SSMA) communications based on direct-sequence (DS), slow frequency-hopped (SFH), and fast frequency-hopped (FFH) systems for wireless local communications of micro-cellular personal communications is analyzed. Using an indoor multipath fading channel model with clusters of arriving rays, we investigate multiuser DS systems with RAKE and diversity reception by selection combining (SC), multiuser SFH systems with equal-gain (EG) diversity reception, and multiuser FFH systems with correlated EG and self-normalization (SN) combining techniques. Reed-Solomon codes are considered to further improve the system performance. Given a fixed available bandwidth with narrow band interference (NBI), capacities and packet error rates are determined under various system configurations. Total capacities of hybrid frequency-division multiple-access (FDMA)/SSMA (DS and SFH) systems are compared with those of wide-band SSMA systems. For high data rate communications, wide-band DS-SSMA systems have larger capacities than hybrid FDMA/DS-SSMA systems. For low data rate communications, a capacity comparison between wide-band DS-SSMA and hybrid FDMA/DS-SSMA systems depends on fading statistics. Hybrid FDMA/SFH-SSMA systems have larger capacities than wide-band DS-SSMA systems, FFH-SSMA systems could not provide satisfactory performance due to correlation among hopping bands     

Reed-Solomon codes for land mobile satellite channels

The performance of Reed-Solomon codes is determined for land mobile satellite communications where a shadowed Rician channel model is used. An effective coding/interleaving scheme is proposed which uses the multipath fading and shadowing statistics of the channel.<>     

Bandwidth efficient concatenated coding schemes for fading channels

Concatenated codes consisting of trellis inner codes and Reed-Solomon outer codes are considered to achieve large coding gains with small bandwidth expansion in the presence of frequency-nonselective slow Rician fading. Both errors-only and errors-erasures decoding algorithms for outer codes are applied. New upper bounds on bit error probability performance in the presence of fading are obtained and compared with simulation results for zero channel memory. The effect of interleaving in eliminating channel memory is investigated. The performance gains that are achieved by the coding scheme relative to the reference uncoded systems are illustrated via some examples     

Performance of a fast frequency-hopped noncoherent MFSK receiverwith nonideal adaptive gain control

An error probability analysis is performed for an orthogonal noncoherent M-ary frequency-shift keying (MFSK) communication system employing fast frequency-hopped (FFH) spread spectrum with diversity. The signal is assumed to be transmitted through a frequency-nonselective slowly fading channel with partial-band noise interference. The partial-band interference is modeled as a Gaussian process. Both the information signal and the partial-band noise interference signal are assumed to be affected by channel fading; it is assumed that the two fading processes are independent and that channel fading need not necessarily affect the information signal and the interference signal in the same way. Each diversity reception is assumed to fade independently according to a Rician process. Adaptive gain control is employed to minimize partial-band interference effects, and the effect of inaccurate noise measurement on the ability of the adaptive gain control receiver to reject partial-band interference is examined. The effect of thermal noise is included in the analysis     

Error probabilities of an FFH/BFSK self-normalizing receiver in aRician fading channel with multitone jamming

We derive the analytical bit-error rate (BER) expressions for a fast frequency-hopped binary frequency-shift keying self-normalizing receiver over a fading channel with the worst-case band multitone jamming (MTJ) and additive white Gaussian noise (AWGN). The desired signal and MTJ are assumed to undergo independent Rician fading and our analyses, validated with simulation results, show that the system performance is not sensitive to different types of MTJ fading conditions. The self-normalizing receiver is found to be superior to the linear-combining receiver when the signal amplitude does not experience severe fading, while the converse is true under Rayleigh fading signal conditions. Under a Rician fading channel and AWGN conditions, the worst-case MTJ and the worst-case partial-band noise jamming are shown to have similar effects on the BER performance of the self-normalizing receiver with diversity     

Bit-error-probability for noncoherent orthogonal signals in fadingwith optimum combining for correlated branch diversity

Due to the interest in wireless personal communications, there has been a lot of research on the performance of receivers with diversity. Most analyses assume the diversity branches are independent. This paper presents an analysis of the bit-error probability for receivers in which the diversity branches are correlated. Noncoherent orthogonal digital modulation (NCODM) with Rician and Rayleigh slow, nonselective fading models are assumed. Through the use of the diagonalization of quadratic forms, most of the calculations of the bit-error probability can be reduced to a two-dimensional numerical integration. For some cases for dual diversity, a closed-form expression for the error probability is given. A number of diversity combining laws, including square law and maximum likelihood, are considered. We find that Rician fading can be worse than Rayleigh fading in correlated diversity environments, a situation quite different from the independent diversity case. Also, for the Rayleigh fading model with correlated branch diversity, we find that an equal-weight, square-law combiner usually has the same error performance as the more complex maximum-likelihood combiner. However, this is not the case for a Rician fading model with the same correlation environment. Simple diagonalization methods that compensate for the lossy effect of correlation are specified and found to be effective when the dominant noise and interference have almost the same correlation distribution as the fading signals