Closed-form BER (bit error rate) expressions are derived for Gray-encoded QPSK (quadrature phase shift keying) and 8-PSK schemes using coherent detection in a slow Rayleigh fading narrowband channel with fading cochannel interference. Earlier work has been limited to deriving the approximate BER using the canonical Stein (1961) receiver concept. The symbol error rate (SER) for the QPSK scheme is also derived. The desired signal and the cochannel interferer are both PSK signals, modulated by different baseband pulses with identical signaling rate.>

The spectrum overlay of a CDMA PCN on a preexisting narrowband, analog, corrupted by AWGN FM channel is considered. This overlay can increase communications capacity, within a geographical area, and spectral efficiency. The overlayed PCN is assumed to employ DS spreading, using maximal length pseudorandom sequences. The interference the FM channel experiences is estimated, and an extremely severe test is simulated using a PCN overlayed on a preexisting 600-channel SSSC-FM FDM microwave line-of-sight radio link. It is found that the interference caused by the PCN depends on the carrier frequency separation between the two systems, the power of the EM system, the length of the SS system pseudorandom sequences, and the data rate and power of the PCN users.>

Various parametric receivers such as the maximum likelihood and the hard-limiter have been analyzed for their performance in decoding the frequency hopped multilevel FSK (FH-MFSK) messages in mobile environment. Here, some nonparametric receivers such as the maximum rank sum receiver (MRSR) and the reduced rank sum receiver (RRR) are considered. RRR and MRSR are nearly identical in performance but the former is much simpler to implement. The results indicate that RRR is a competing alternative to the parametric receivers.

Random phase tracking of discrete time signals perturbed by an additive White Gaussian Noise channel (AWGN) and also a fading channel is presented in this paper. The zero-crossing sampling detector employed causes the sampling of the incoming signal to be non-uniform. The fading channel assumed is a Log-Normal channel and causes random pertubations in both amplitude and phase of the incoming signal. Mathematical description of the phase detector with a second order digital filter is presented and its performance is characterized by the phase error process statistics. Under the assumption of weak amplitude fluctuations and for a frequency step-input an approximate analytic solution in the steady state has been obtained by solving the corresponding Chapman-Kolmogorov (C-K) equation. These results have been verified by numerical and simulation methods.

Recently, various frequency-hopping schemes have been proposed for possible application to digital mobile radio telephony. While the advantage of the inherent frequency diversity against fading is well known, the improvement in the system performance due to the use of space diversity has not been studied. In this paper we analyze the performance of FH-MFSK under the influence of Rayleigh fading and log-normal shadowing due to the combined use of frequency and space diversities. It is shown by analysis that the system capacity can be increased from the corresponding nondiversity figure by 26.3 percent relative to the full system capacity (i.e., 209 users) with the use of two diversity branches at channel condition of 10 dB normalized area mean and worst case of shadowing\sigma = 12dB. Also, graphical results are given for different channel environments, and required signal-to-noise ratio.

The performances of three receivers, namely, the hardlimited, the linear, and the maximum-likelihood combiners for the detection of frequency-hopped multilevel frequency-shift keyed signals transmitted from mobiles to base have been reported earlier [11]. Only the hard-limited combiner has been analyzed with respect to base-to-mobile link [1]. Here, we give new results on the performance of the likelihood and the linear combining receivers operating at the mobiles. Whereas it is possible to find exactly the union bound on the probability of bit error for a linear combiner, for a likelihood receiver, bounding and approximation techniques such as simple Chernoff bound and saddle point integration were employed. We also observe the asymptotic (SNR \rightarrow \infty) equivalence of the hard-limited and the likelihood receivers. This, together with the approximate error estimates at finite SNR, leads us to believe that the likelihood receiver is only marginally superior to a hard-limited combiner. As expected, the linear combiner performs poorly.

In this paper an analytical method is developed to determine the performance of a system with two types of customers and "cutoff" priority. A completely recursive solution and a solution involving matrix inversion are provided. Some examples from the mobile radio communication system are considered to illustrate applications of the method. This paper is an extension of the case for equal service rate for the two classes.

The probability of cochannel interference is evaluated for a mobile radio system operating in Rayleigh fading and log-normal shadowing environment. All cochannel cells surrounding the base station are taken into consideration in this evaluation. The results obtained are used to calculate the reuse distance and the cluster size (number of cells in a group). The blocking probability, the number of channels in each cell, the protection ratio, and the standard deviation are taken as parameters in this evaluation. The results show that shadowing has a severe effect on the interference level and on the channel reuse distance ratio.

Extended Kalman filter algorithms are used to obtain a digital phase lock loop structure for demodulation of angle modulated signals. It is shown that the error variance equations obtained directly from this structure enable one to predict threshold if one retains higher frequency terms. This is in sharp contrast to the similar analysis of the analog phase lock loop, where the higher frequency terms are filtered out because of the low pass filter in the loop. Results are compared to actual simulation results and threshold region results obtained previously.

This paper considers digitized Weaver modulators for single-sideband modulation that can be used in radio communications and telemetering. A system of 12 such modulators to process 12 analog signals digitally is replaced by six multiplex modulators at the cost of additional computation at the input but with an overall reduction in computation time and a higher degree of accuracy. A unique digital filter is developed that can interpolate and output samples at multiples of the input sampling rate and exhibits a passband that occurs above the Nyquist frequency with no apparent distortion effects. A discussion of the Fortran simulation of a combined modulator-demodulator structure is included to verify the effectiveness of this scheme.