Coded Error Probability for DS Spread-Spectrum Systems with Periodic Pulsed Multiple-Tone Interference

The coded error probability for direct sequence (DS) BPSK or QPSK spread-spectrum systems, used with or without interleaving, and operating in the presence of pulsed multiple-tone interference, is investigated. We consider the worst-case channel error probability under conditions of pulsed multiple-tone jamming for the various systems, and present coded error probability as a function of interleaving delay for(n, k)block codes with hard-decision decoding. It is shown that when the maximum level of continuous multiple-tone interference does not exceed the level of the desired signal, the duty cycle of the corresponding pulsed interference which yields the worst-case error probability is usually small, and that the smaller the duty factor of the jamming, the more considerable is the performance improvement due to the use of interleaving in conjunction with the coding.     

Low Probability of Intercept Performance Bounds for Spread-Spectrum Systems

An important application of spread-spectrum (SS) in military communication systems is that of making the signal difficult to intercept by unauthorized receivers. Error-correction coding techniques may be employed to reduce the required input signal-to-noise ratio at the receiver, allowing the system to operate at a lower power level, hence resulting in a lower probability of interception. In the absence of error-correction coding, a specified message bit rate, transmitted signal bandwidth, and required bit-error probability at the receiver will yield a required signal-to-noise ratio for each type of spread-spectrum system. When coding is employed, a specified decoder delay time implies a specified code complexity, and can be used to determine bounds on the required receiver signal-to-noise ratio. These performance bounds are evaluated as functions of the specified parameters. In addition, one may specify a burst interference environment in that the system must operate. Presented is the evaluation of the increase in the upper bound on signal-to-noise ratio as a result of the specification of a correctable single-burst time. This increase indicates an antiintercept /antijam tradeoff.     

A Two-Power-Level Method for Multiple Access Frequency-Hopped Spread-Spectrum Communication

This paper suggests a technique applicable to chip-synchronous frequency-hopping MFSK multiaccess communication whereby each user has some high-power-level slots and some low-power-level slots. The optimum proportion of high-power slots is slightly less than1/ewhereeis the natural logarithm base. For this optimum proportion, the data rate efficiency is improved by about 50 percent for fixed bit error rate in the interference-only case.     

A Spectral Analysis of M-ary Direct Sequence Spread-Spectrum Multiple Access Communication Systems

This paper presents the power spectrum of the transmitted signal in a synchronous spread-spectrum communication system in which the users' information symbol sequences are encoded intoM-ary channel symbol sequences. Furthermore, when maximal-length shift register sequences are used as the spreading code sequences of the system, the average power spectrum over all possible sets of the allowable simultaneous users is presented. It is shown that distribution of the spectrum is influenced considerably by the spreading code and the channel symbol sequences.     

Error Performance of FH Wireless LANs in DS and Tone Interference

In this paper the bit error probability of the SFH/MFSK system in presence ofwideband and tone interference in a fading environment is evaluated.Simultaneous license-free operation of tone-like applications, FrequencyHopping (FH), and Direct Sequence (DS) based LAN clusters is assumed to be theprime interference facing the subject FH wireless LAN (of the IEEE 802.11standard). The wideband DS interference is considered to have asinc²() shape Power Spectral Density (PSD) centered at the middleof FH signal band and tone interferers are assumed to be spread over the wholeFH band of the intended signal. Assumptions of slow non-selective fading alongwith slow hopping justify a quasi-static treatment. Results shows that the FHsystem is more sensitive to tone interference and fading and less sensitiveto wideband interference variations. The paper sheds light on the performanceof wireless LAN operation in the unlicensed free band where many other LANsmay exist.     

Error Rate Lower Bounds for Digital Communication with Multiple Interferences

This paper presents simple and general lower bounds for error rates in digital communication systems. The information bearing signal is taken to be impaired by additive interference and carrier phase jitter. The former is taken to be composed of two components; one component is peak-limited while the other is not. Intersymbol and cochannel interference are examples of peak-limited interference while additive thermal noise is an example of a nonpeak-limited interference. The novelty of the paper is in the generality of the results and in obtaining a simple error bound for transmission in the presence of cochannel interference and carrier phase jitter.     

Blind Multiple Access Interference Suppression Algorithm Based on Relaxed Subgradient Projection for DS/CDMA Systems

A novel blind multiple access interference suppression algorithm based on relaxed parallel subgradient projection is proposed for DS/CDMA systems. The qualification “relaxed” is manifest in two aspects: first, the new expression for updating the interference suppression filter coefficients vector relaxes paralleled projection fields and reduces computation complexity. In addition, the relaxation parameter in the updated process is adaptively determined to guarantee the interference suppression filter coefficients vector falling into fields containing the optimal filter coefficients vector after several iterations. Theoretical analysis and simulation results conclude that this algorithm has a fast convergence speed, steady interference suppression performance, low computation and low bit error rate.     

卫星通信系统中的多址接入协议

简述了卫星通信中多址协议的分类和影响多址协议性能的因素,重点介绍了三种预约多址协议PRMA-HS、PRMA/CDMA和Butst Reservation CDMA,并分析了它们的性能.     

Bit Error Probability for Baseband and Subcarrier Optical Communication Systems

Digital baseband and digital subcarrier noncoherent optical communication systems are considered in this paper. Expressions are developed for the bit error probability of optical subcarrier systems which use a nonliner polarization modulator and either a one-detector or a two-detector receiver, The expressions are evaluated numerically, and the results are used to compare the one- and two-detector subcarrier systems with the corresponding one- and two-detector baseband systems for a fLxed bit error probability.     

Erasure and Error-Correction Decoding Algorithm for Spread-Spectrum Systems with Partial-Time Interference

An erasure-control decoding algorithm is discussed for frequency-hopped spread-spectrum systems operating in the presence of pulsed or partial-time interference, and some properties of the resulting error probability which are useful in designing effective decoding algorithms are derived. Based on numerical results, specific decoding algorithms which correct both erasures and errors are then presented for use with block codes employing hard decisions.     

CDMA移动通信系统中的多址干扰及抑制技术

相对于FDMA及TDMA，CDMA具有一系列的优点，这些优点使得CDMA技术在日新月异的移动通信领域中所处的地位越来越重要，已经成为新一代移动通信以及未来个人通信中最具竞争力、最具发展前景的无线多址技术。但在CDMA已经成为第三代移动通信主流技术的时候，要真正达到预定的目标，还有许多关键技术要解决，其中最为关键的就是要突破克服CDMA系统中多址干扰(MAI)的技术。     

Error Rate Bounds for Digital PAM Transmission with Phase Jitter and Intersymbol or Cochannel Interference

A simple method is presented for computing upper and lower bounds for binary PAM signaling over channels with phase jitter. Other impairments to reliable communication are taken to be additive thermal noise and intersymbol or cochannel interference. The important cases of binary and quadrature phase shift keying are cases for which the analysis presented is valid. The method consists of finding upper and lower bounds conditioned on the phase jitter, φ, in a form in which the auguments of theQ-functions involved are linear incos phiandsin phi. When these functions are represented by a piecewise linear approximation, the average of these bounds can be given in closed form. In most cases 5 piecewise linear segments provides an error rate estimate that is accurate to at least 1 dB in system signal-to-noise ratio (SNR).     

Bounds and Approximations for Rapid Evaluation of Coherent MPSK Error Probabilities

The error probability for MPSK detection is expressed here as a sum of a familiar upper-bound approximation and a correction term which is well suited for numerical integration. An asymptotic expansion of the correction term is derived, from which simple and extremely tight upper and lower bounds are obtained. Relative errors in using these bounds and approximations of them are graphed for cases of practical interest.     

Error Performance of Binary NCFSK in the Presence of Multiple Tone Interference and System Noise

This paper presents a general solution to the problem of calculating the error performance of binary NCFSK systems in the presence of multiple tone interference and system noise. The development uses the concepts of circularly symmetric signals and expresses the results in terms of a Bessel integral. This integral is then evaluated using a rapidly converging Fourier-Bessel series. The error in this approximation to the integral is controlled by two parameters which may be adjusted so that the desired accuracy is attained. It is determined that, in the useful probability-of-error range and when the total tone power is constrained, the error rate increases for an increase in the number of interfering tones. In addition, for equal amplitude tones, the performance is independent of the distribution of the tones within the channel. The technique used is also applicable to other detection problems where the threshold is a random variable.     

New Simple and Efficient Bounds on the Probability of Error in the Presence of Interference and Gaussian Noise

The problem of determining or of bounding the probability of error in the presence of intersymbol interference and Gaussian noise is an important one in data communications. In this concise paper we describe new upper and lower bounds for the probability of error when the peak distortion is finite (in practice, when the eye is open) and the data are independent. Over a range ofS/Nof interest in data communications; these bounds compare favorably with previously published bounds of similar complexity, especially when the eye opening is small. They can be applied to multilevel AM and CPSK transmission.     

Error Probability Upper Bound for Coherently Detected QASK Signals with Cochannel Interference

A simple upper bound to the probability of error for a QASK system with additive Gaussian noise and cochannel interference has been derived using Cramer-Chernoff techniques. Numerical results for the QASK-16 system are given.     

Probability of Error in Binary Communication Systems with Causal Band-Limiting Filters--Part I: Nonreturn-to-Zero Signal

Upper and lower bounds to probability of error in binary communication systems with intersymbol interference are presented. Closed-form formulas are given for systems with filters having a finite number of lumped elements. Explicit results are given when the filters are Butterworth filters of orderN = 1, 2,..., 10. Four systems are considered: with a sample detector (SD), with an integrate-integrated-and-dump detector (IDD), with a filter in receiver only, and with filters in receiver and transmitter. The transmitted signal is assumed to be of the nonreturn-nonreturn-to-zero (NRZ) form.     

Probability of Error in Binary Communication Systems with Causal Band-Limiting Filters--Part II: Split-Phase Signal

The probability of error is computed in four binary communication systems withNth order (N = 1, 2,...,10) Butterworth filters and split-phase signals. The systems have either a sampling detector or an integrating-and-dumping detector; the filter is either in the receiver only or both in the receiver and transmitter. A lower bound to the probability of error is also computed for modified binary communication systems in which prior to the decision the contribution of the past transmitted symbols is eliminated. In all systems the sampling time is optimized and the effect of nonoptimal sampling time on probability of error is demonstrated.     

三种多址蜂窝系统的容量及性能分析

从理论上推导了 FDMA、TDMA、CDMA制式的容量表达式 ,计算了 3种典型系统 AMPS、GSM和 Q- CDMA的容量关系 ,分析比较不同系统的通信性能 ,指出了移动通信系统的发展趋势