Wideband Radio Channel Research Articles

Compound strategies of coding, equalization, and space diversity for wide-band TDMA indoor wireless channels

Compound strategies of equalization and space diversity in the form of an optimum baseband combiner are attractive for wideband time division multiple access (TDMA) portable communication radio links in order to combat dispersive fading and cochannel interference. The authors investigate the performance of such a scheme in conjunction with convolutional coding and soft-decision Viterbi decoding via a semianalytical technique based on the method of moments. Such an approach avoids a Gaussian characterization of interference and yields results for both ideal interleaving and no interleaving. With dual space diversity, three taps per forward filter, and a data rate of 10 Mb/s, it is shown that, although a third space diversity branch remains preferable in terms of performance, channel coding can be a viable alternative, particularly in terms of outage rate, to increasing the space diversity order, even in the absence of interleaving, provided the signal-to-interference ratio is sufficiently high. >

Coding and optimum baseband combining for wide-band TDMA indoor wireless channels

Optimum baseband combining with coherent BPSK/QPSK is an attractive technique for wide-band TDMA portable communication radio links in view of its ability not only to combat dispersive fading but also to cancel cochannel interference. The performance of such a scheme for data rates ranging from 1 to 20 Mbits/s is investigated. It is shown that convolutional coding with soft-decision Viterbi decoding can be a viable alternative to increasing the space diversity order even in the absence of interleaving if the effective diversity order is sufficiently large. A number of performance curves for various combinations of transceiver and channel parameters are presented.

Wideband radio channel characteristics in Alpine regions

Radio channel time dispersion parameters of three adjacent base stations located in a mountainous area have been measured. The measured paths, subdivided into 100 m segments, were evaluated with a 9 dB delay window. A substantial number of critical locations were observed. Coverage based on tolerable time dispersion turns out to be different to coverage prediction based on the field strength only

Wide-band Measurements on Mobile Radio Channels by SAW Convolvers

After the explanation of the wide-band mobile radio channel with its linear, time-variant transmission characteristics, a measuring system is described. The experimental set-up is demonstrated, where a SAW convolver acts a correlator. The measurement results taken from the urban areas of Kassel are interpreted clearly

Measurements of the wide-band radio channel characteristics for rural, residential, and suburban areas

A setup for impulse response measurement using short RF pulses and a wide-band receiver is described. The impulse response is measured for every 10 cm of displacement. Results are presented showing the delay spread and the average power delay profiles for rural, residential, and suburban areas. Also some tools are presented to estimate the impulse response, using the radar equation and a diffuse scattering model.

Measurements of impulse response of a wideband radio channel at 910 MHz from a moving vehicle

A set-up for impulse response measurement is described using short RF pulses and a wideband receiver. A fast wave form digitiser digitises the detected impulse response and a minicomputer stores the data on a hard disc. First results are presented showing the rapid change of the impulse response during vehicle movement.

Automatic protection switching for TD-2 radio system

Intercity transmission of television programs and telephone conversations is now provided via a network of TD-2 microwave radio relay equipment operating on a transcontinental basis. Whenever service interruption threatens because of equipment troubles or atmospheric disturbances in the transmission path, a switching system automatically and quickly substitutes a stand-by wide-band microwave radio channel for the defective channel. The circuits and operation of this switching equipment are described.