IEEE Transactions on Communications

The authors comment that the probability density function (PDF) of the signal-to-noise ratio (SNR) for third-order selection combining (SC3) given by Eng, Kong and Milstein (see ibid., vol.44, p.1117-29, 1996) is incorrect. A correction is given by presenting a more efficient method of deriving the generalized PDF of the SNR essential in the analysis of Nth-order selection combining. View full abstract»

Based on the observation of Kim, Kwon, Hong and Whang (see ibid., vol.46, no.9, p.1109-10, 1998), we discovered that in our derivation (see ibid., vol.44, p.1117-29, 1996), a factor of one-half in the exponent of one of three exponentials was inadvertently dropped and this, in turn, affected two other equations. View full abstract»

Pilot-channel-assisted binary phase-shift keying (PCA-BPSK) in direct-sequence code-division multiple-access (DS-CDMA) systems is investigated. The loss due to imperfect channel estimation is calculated, and the pilot-to-data channel power ratio is optimized analytically. The results show the effects of the various parameters and provide a suitable tool for system design View full abstract»

The asynchronous transfer mode (ATM) adaptation layer type 1 (AAL1) segmentation and reassembly (SAR) are designed and implemented by the field programmable gate array (FPGA). The SAR header is generated and processed in the FPGA and the SAR payload is stored in an external first-in-first-out (FIFO) device. A method to recover the source clock, called synchronous residual time stamp (SRTS), is imp... View full abstract»

The general condition for the optimality of the Viterbi algorithm (VA) as a method for implementing maximum-likelihood sequence detection (MLSD) is described. It is shown that this folding condition is not met for the fading linear Gaussian channel. This clarifies previously published results and allows approaches for approximate MLSD to be viewed as an attempt to force the VA as a suboptimal solu... View full abstract»

A method for broadcasting digital audio simultaneously with existing analog frequency modulation (FM) radio is presented. The method is based on precomputing the response of the host analog FM signal at the digital receiver and precanceling it at the transmitter. As a result, the digital transmission is free from interference from analog FM. We select the rate and power level of the digital transm... View full abstract»

We present Walsh-quadrature phase-shift keying (Walsh-QPSK) pseudonoise (PN) modulation schemes for both coherent and noncoherent direct-sequence code-division multiple-access (DS-CDMA) systems, wherein the PN spreading sequences for in-phase and quadrature data in a conventional QPSK PN modulation scheme are coded by Walsh sequences indexed by a special rule to reduce the envelope variation of th... View full abstract»

A new alternative is proposed for reducing the power consumption of the portable (battery-powered) units operating in a mobile packet-data network. First, a review of the current power-saving protocols is given. It is shown that the most common means for conserving power is the intermittent operation of the receivers (at the portable units) and a central administration authority that synchronizes ... View full abstract»

The bit-error probability is determined for a binary antipodal diversity system with an adaptive receiver using decision-directed channel estimation. The diversity channels are assumed to be nonselective Rayleigh-fading channels with additive white Gaussian noise (AWGN). The analysis is valid for all linear estimators which use a finite-impulse-response (FIR)-type estimation filter. Numerical resu... View full abstract»

A new methodology for the determination of an objective metric for still image coding is reported. This methodology is applied to obtain a picture quality scale (PQS) for the coding of achromatic images over the full range of image quality defined by the subjective mean opinion score (MOS). This PQS takes into account the properties of visual perception for both global features and localized distu... View full abstract»

We examine adaptive equalization and diversity combining methods for fast Rayleigh-fading frequency selective channels. We assume a block adaptive receiver in which the receiver coefficients are obtained from feedforward channel estimation. For the feedforward channel estimation, we propose a novel reduced dimension channel estimation procedure, where the number of unknown parameters are reduced u... View full abstract»

For pt.I see ibid., vol.46, no.8, p.1027-37 (1998). Four-wave mixing (FWM) in dispersion-shifted optical fiber is a major problem associated with low optical input power levels in optical wavelength-division multiplexed (WDM) systems. To reduce the crosstalk caused by FWM, a generalized suboptimum unequally spaced channel allocation (S-BISCA) technique has been proposed. While the S-USCA technique... View full abstract»

Recursive systematic convolutional encoders have been shown to play a crucial role in the design of turbo codes. We recall some properties of binary convolutional encoders and apply them to a search for good constituent convolutional codes of turbo codes. Tables of the “best” recursive systematic convolutional encoders found are presented for various rates, together with the average bi... View full abstract»

The asymptotic performance of Reed-Solomon (RS)-coded M-ary orthogonal signaling with ratio-threshold test (RTT) type demodulation in a Rayleigh-fading channel is considered. We show that the minimum E¯b/N0 needed for error-free communication is eln2 (2.75 dB) with RTT, and 4.79 (6.8 dB) with hard decisions. The optimum code rate that minimizes the required E¯b... View full abstract»

Combined free/demand-assignment multiple-access (CFDAMA) schemes are suitable for broad-band packet satellite communications systems serving a finite number of bursty data sources. The performance analysis of the CFDAMA using piggy-backed (PB) reservation is presented. The probability generating function (PGF) of the packet delay is developed. The performance is evaluated in terms of three perform... View full abstract»

This paper handles the simultaneous suppression of narrow-band and multiaccess interference in code division multiple-access (CDMA) direct-sequence spread-spectrum (DSSS) systems. The basic structure we refer to is reminiscent of the decorrelating detector, but here the design strategy relies on the concept of combating jointly the two interference sources-precisely, a decision as to the bit trans... View full abstract»

The spectral occupancy and composition of a chosen digital signaling technique when the data pulse stream is nonideal, due, for instance, to implementation imperfections, are important considerations in the design of a practical communication system. One source of imperfection is timing jitter where the rising and falling transitions do not occur at the nominal data transition time instants; never... View full abstract»

Spectral-amplitude-coding optical code-division multiple-access (OCDMA) systems are limited by interference between incoherent sources. A detailed analysis of this limit for a system with a balanced receiver is presented. Additional pulse-position modulation (PPM) coding is proposed as a method to improve the system performance beyond this limit. A simple and robust PPM decoding structure is propo... View full abstract»