Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast and the system is highly complex due to random and unpredictable movement of mobile users continuously. The complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control is an efficient technique to mitigate the effect of interference under fading conditions, combat the Near-Far problem and conserve the battery life. Several remedial measures-like space diversity, frequency diversity, route diversity, increase in antenna height, antenna tilting, etc.-have been tried by many operators to overcome the debilitating effect of multipath fading in fixed line-of-sight microwave and mobile communication links. Among these remedial measures, diversity techniques have been extensively studied in terms of improvement factor, whereas the concept of antenna tilting is relatively less explored compared with other remedial measures. In this study, the effect of antenna tilting on fixed and mobile communication links is investigated to find out the optimum tilting angles in terms of design parameters, as well as on quality of service (QoS). The paper established that a deviation of more than 1.5˚ in antenna elevation angle would impact on QoS requirements and seriously affect the quality of signal to be received by the mobile systems.
Radiolocation has been previously studied for CDMA networks, the effect of Multiple Access Interference has been ignored. In this paper we investigate the problem of Radiolocation in the presence of Multiple Access Interference. An extensive simulation technique was developed, which measures the error in location estimation for different network and user configurations. We include the effects of lognormal shadow and Rayleigh fading. Results that illustrate the effects of varying shadowing losses, number of base stations involved in position location, early-late discriminator offset and cell sizes in conjunction with the varying number of users per cell on the accuracy of radiolocation estimation was presented.
i b q k~-~~~t VMF sfatiorts Spread(% of national) I J t l r 11, 5 -\\l,.G+ b -t T C r u t 4 7 . 4 28 2 4 . 6 100 16 I + 57 0-780327145/95/541)00 1995 IEEE ,1968 Reqional UHF stations North S-West S-East Total 6 6 5 ~ 17 1969 Spread(% of national) 35.3 35.3 29.4 100L S under-utilisation of VHF/UHF spectrum due to either the spread to uninhabitable areas like the sea, the desert, the thick forest or, the multiple-systems phenomenon, or the low daily average hours of transmission. In order to optimise VHF and UHF spectrum utilisation, technically articulated plans should be made to enable private broadcasters share time with existing services by 'utilising' the spectrum during normal "idle" periods of existing stations-Modified antenna structures and specially designed ones may also be used to reduce spectrum under-utilisation in any locality.ACKNOWLEDGEMENT.
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