After discussing the nature of the electromagnetic field in urban environments, and the use of diversity techniques in fading media, the paper presents a survey of these techniques as applied to mobile radio, with emphasis on systems designed for analogue communication. It includes a unified approach to systems based on the double-heterodyne phase-stripper principle. The discussion is not restricted to present-day receivers only, but includes considerations which may apply in future designs.

Diversity techniques for mobile radio reception

Multipath fading is one of the most serious problems for the signal transmission in mobile radio. To combat this problem, the application of transmitter diversity to a digital FM paging system is described. The method is to transmit two digital FM paging signals with different modulation indices, each of which is modulated by an identical binary signal, from separate antennas. It is shown that the same action obtained with the well-known selection diversity can be achieved when the difference between the modulation indices is equal to two. The diversity effect on the bit-error-rate (BER) performance is theoretically analyzed. The diversity effect on the BER performance in a 600-bit/s Manchester-coded digital FM system is verified by the laboratory simulation tests using a Rayleigh fading simulator.

Transmitter diversity for a digital FM paging system

Capacity Analysis of Base Station Diversity

The dispersed-carrier-wave format is proposed for the execution of simultaneous multistation transmission for mobile communications. Signals are transmitted by modulating the carrier wave, which is frequency-modulated by sinusoidal waves. The diversity effects of this format were calculated, and the results were confirmed for the case of simultaneous two-station transmission. In cellular zone systems, in the case when the transmission distance of the radio waves is sufficiently large compared with the radius of the zone, there would be areas where several radio zones overlap. Therefore, for the theoretical calculations, the maximum number of simultaneous transmission bases was considered to be up to six stations. Also, numerical calculations of the transmission diversity effects have been made in the case of simultaneous multiple-station transmissions for a base station network with configurations of regular hexagonal meshes. >

http://ieeexplore.ieee.org/iel2/832/1551/00040117.pdf

Transmitter diversity effect with dispersal oscillators for digital mobile radio

Fading due to multi-path propagation is a serious problem in mobile radio communications. Consideration is given to the theory of an effective means for combining the signals from a twin antennae space diversity arrangement using phase sweeping in opposite directions for the two antennae. An analysis is presented for various modulation methods. The resulting system should be compatible with existing receivers. Some experimental results for acommercial v.h.f. a.m. system are included.

A.J. Rogers

Papers

A double phase sweeping system for diversity reception in mobile radio