Array (Smart) Antennas Improve GSM Performance

As wireless data applications over cellular networks become more widespread, the pressure to increase capacity will become even more intense. Capacity in the 800 and 900 MHz bands, where bandwidth is restricted, is already becoming a limiting factor. This paper attempts to address how the application of smart antenna systems has brought about improvements in call quality and increased capacity through reduced Interference in Mobile Communication. The smart antenna may be in a variety of ways to improve the performance of a communications system. Perhaps most importantly is its capability to cancel co-channel interference. It helps in improving the system performance by increasing the channel capacity, spectrum efficiency, extending range coverage, speech quality, enabling tighter reuse of frequencies within a cellular network and economically, feasible increased signal gain, greater, reduced multipath reflection. It has been argued that Smart antennas and the Algorithms to control them are vital to a high-capacity communication system development.

Performance Analysis of Two Frequency Reuse Schemes in Fixed Relay Systems

An upsurge of interest in relay-augmented infrastructure-based networks has appeared in recent years.Radio resource management in such relay systems has great influence on the system performance.How to utilize the limited frequency resources efficiently in the system is a hot research topic.In this paper,performance of frequency reuse schemes has been studied in fixed relay systems.A novel scheme is achieved by modifying an existing one.Theoretical model is proposed for the performance analysis of two schemes.Both the theoretical analysis and simulation results show that the modified scheme outperforms the existing one not only in power consumption of mobile stations but also in cell carrier-to-interference ratio coverage.

Effects of Antenna Tilting on Transmitting Power in Mobile Cellular Communication Systems

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 1.5o in antenna elevation angle would impact on QoS requirements and seriously affect the quality of signal to be received by the mobile systems.

Inter-carrier Interference Analysis for MIMO-OFDM Systems in High-Speed Train Environment

The orthogonality between the subcarriers of multipleinput multiple-output orthogonal frequency division multiplexing( MIMO-OFDM) systems is destroyed due to the Doppler frequency offset,particularly in the high-speed train( HST) environment,which leads to severe inter-carrier interference( ICI). Therefore,it is necessary to analyze the mechanism and influence factor of ICI in HST environment. In this paper, by using a non-stationary geometry-based stochastic model( GBSM) for MIMO HST channels, ICI is analyzed through investigating the channel coefficients and the carrier-to-interference power ratio( CIR). It is a fact that most of signal energy spreads on itself and its several neighborhood subcarriers. By investigating the amplitude of subcarriers, CIR is used to evaluate the ICI power level. The simulation results show that the biggest impact factor for the CIR is the multipath number L and the minimum impact factor K; when the train speed υR> 400 km / h,the normalized Doppler frequency offset ε > 0. 35,the CIR tends to zero,and the communication quality will be very poor at this condition. Finally,bit error rate( BER) is investigated by simulating a specific channel environment.