This paper presents a method of predicting the bit-error rate (BER) performance of the global system for mobile communications (GSM) system as a function of the wideband channel parameters obtainable from measured or assumed power delay profiles. Although delay spread is found to be the most useful parameter for the prediction of BER performance, it has been shown that in some conditions delay interval (15 dB) can provide a more accurate prediction mechanism. Thus, based on the delay spread and the delay interval (15 dB), empirical prediction formulas are derived.

Time dispersion measurements have been conducted in the urban city centre of Liverpool at 1800 MHz. The measurement setup is based on the swept time-delay cross-correlation technique and has a time-delay resolution of 33 ns. The use of automatic gain control (AGC) circuitry in the RF stage permitted the observation of the spatial variation of the multipath power delay profile and RMS delay spread. The experimental work investigated the dependence of RMS delay spread on base antenna height, gain, downtilt and distance in the LOS and non-LOS regions of the microcell. The results obtained indicate that (a) the RMS delay spread is less than or equal to 520ns/280ns in the LOS/non-LOS regions, (b) that the delay spread increases with antenna height and with the use of a directional antenna but decreases with downtilt. Furthermore, the RMS delay spread results are compared with theoretical results obtained using geometrical optics (GO) and the uniform theory of diffraction (UTD).>

Personal communication networks (PCN) have recently been put into operation in the UK. The PCN/DCS1800 is expected to be a very high capacity system because smaller cells are intended to be used. The data rate of 270 kbits/sec exceeds the reciprocal of the decay spread often measured in mobile radio environments. Hence PCN can be regarded as a wideband transmission system and therefore the frequency-selective fading behaviour of the radio channel cannot be ignored. This paper shows possible improvements that can be obtained if PCN systems employ 2-branch selection or equal gain diversity techniques. The diversity schemes implemented in this study are totally based on the received signal strength. The results show that, at a BER of 0.01, 2-branch selection diversity can provide a gain of 5-6 dB for the various channels specified for the DCS1800 system. A further 1 dB improvement can be obtained using equal-gain combining.>

The performance of an asynchronous DS CDMA system for communications over multipath fading mobile radio channels using an N-path Rake receiver is investigated. Multipath power delay profiles for typical urban, hilly terrain and rural areas which are derived from those specified for the GSM system have been used to assess the robustness of the CDMA system against frequency-selective fading. The effect of interference on the system performance is also investigated for the three multipath environments. Furthermore, the authors evaluate the performance of a single path-lock correlation receiver and compare the results obtained with that of the Rake multipath combining receiver for a spreading bandwidth of 1.27 MHz. The effect of spreading bandwidth allocation on the diversity performance of the Rake system in the urban channel has also been investigated. The criterion of the system performance is the average bit-error rate (BER) as a function of the signal-to-noise ratio (SNR).>

A comparative evaluation of the performance of Manchester coded PSK (MC-PSK), phase shift keying return to zero (PSK-RZ) and phase shift keying varied phase (PSK-VP) anti-multipath modulation techniques is presented. A two-ray propagation channel model using various delay spread values has been employed. The effect of spectral shaping of the transmitted signal on the BER performance of each of these modulation schemes, using Butterworth lowpass and square-root raised cosine premodulation filters, is investigated. The BER performance results obtained using these modulation techniques are compared with that of differential phase-shift keying (DPSK) modulation. It is shown that for a frequency non-selective fading channel, the performance of the anti-multipath modulation schemes is comparable to that of simple DPSK. However as the channel becomes frequency selective, the performance of the anti-multipath modulation systems improves beyond that provided by the DPSK system.>

This paper describes the results of an experimental investigation into wideband channel characterisation at 1.8 GHz. The experiments were undertaken in the City of Liverpool using a swept time-delay cross-correlation (STDCC) channel sounder. This was used to measure the complex impulse response of the channel. The inclusion of an automatic gain control in the RF stage allowed continuous measurements for up to 200 m. The results show smaller values for the time domain descriptors and only fades of about 1.5 dB in the frequency domain.>

The paper presents the results of a Monte-Carlo software simulation that evaluates the performance of a fixed channel allocation (FCA) scheme for four different conditions namely, traffic distribution, terminal mobility, mean call duration and minimum call duration. The performance of the system has been assessed by evaluating the carried traffic and the call blocking percentage (including forced call termination) as a function of each of the four parameters. It is shown that knowledge of channel propagation alone is nor sufficient enough for good frequency planning. Hence it is shown that the performance of a FCA scheme depends not only on channel propagation but also on traffic distribution, terminal mobility, mean call duration and minimum call duration. The performance of a hybrid dynamic channel allocation (HDCA) is also presented.>

A method is proposed for predicting the degradation in performance of FSK data communication systems subjected to impulsive noise. It involves overlaying a representation of the incoming noise, expressed in terms of the noise amplitude distribution (NAD), on a family of isodegradation curves drawn with BER as the parameter. A direct prediction of the BER to be expected in the presence of the noise can be obtained by reading off the value of BER corresponding to the point of tangency between the two sets of curves (termed the tangential BER), and multiplying this by a factor F, characteristic of the radio location. The value of F can be found either experimentally or analytically. The usefulness of the method has been demonstrated, using vehicle-born equipment, by a series of experiments designed to be representative of typical mobile radio reception conditions. The method is very powerful experimental assessment technique. It is simple in concept, easy to apply, and has the advantage of being readily generalized for applications with different modulation techniques.>

A new method is proposed for assessing the performance of a radio receiver in the presence of impulsive noise. It involves selecting a criterion of performance, appropriate for the system under consideration (e.g., BER in data communication systems), and measuring isodegradation curves with respect to that criterion. A direct estimate of system performance can then be obtained using the noise amplitude distribution (NAD), one method being via the overlay technique. To demonstrate the validity of the method, three VHF/FM receivers have been tested in the laboratory. Results show that isodegradation curves in the new form give a better insight into performance degradation than those using the established criterion 20 dB quieting. It is suggested that receiver specifications should include a parameter related to performance in impulsive noise.