Abstract:
Abstract - One of the most effective techniques to mitigate multipath fading and inter-cell interference at a downlink wireless channel in WCDMA systems for achieving high capacity is transmitter power control. In this case, system increases the power of the subscriber when its interference increases in order to satisfy the requested signal qualities. However, when the requested signal qualities are infeasible, the power control algorithms might diverge as a result of power limitation. Another way to mitigate multipath problems is using diversity techniques. Space-time diversity offers an advantage in the forward link of the WCDMA system. In this paper, three environments for forward link power control, together with space-time diversity, are examined. These are indoor office, indoor-outdoor pedestrian and vehicular environments. The simulator takes into account 19 hexagonal cells with spatially uniform user distribution and a propagation channel characterized by distance attenuation, fast Rayleigh fading and inter-cell interference. Computer simulations are given to evaluate the effect of space-time diversity on convergence of downlink power control algorithms. Simulation results show that space-time diversity together with downlink power control have very good performance, especially in the vehicular environments with high mobile speed.
Machine summary:
R. of Iran Abstract - One of the most effective techniques to mitigate multipath fading and inter-cell interference at a downlink wireless channel in WCDMA systems for achieving high capacity is transmitter power control.
Simulation results show that space-time diversity together with downlink power control have very good performance, especially in the vehicular environments with high mobile speed.
Signal fading and ISI arise from multipath propagation while interference is generally caused by January/ June, 2006 Iranian Journal of Information Science & Technology, Volume 4, Number 1 co-channel or unknown jammer systems.
January/ June, 2006 Iranian Journal of Information Science & Tech nology, Volume 4, Num her 1 In this paper, we use downlink power control algorithm and space-time diversity technique simultaneously.
p Downlink power control and space-time coding with RAKE receiver are used to alleviate the effects of multipath fading, co-channel interference and propagation loss.
84Mcps Maximum MS TX power, 2 ldbm Maximum total BS TX power, 43dbm MS sensitivity, -l00dbm Power control dynamic, 30db Power control step size, FSAPC: Idb VSAPC: according to algorithm used in power control process BS antenna height, 30m Antenna gain(Ga), 1 I db Carrier frequency, 2150Mhz Data modulation, QPSK Channel multiplexing, Time multiplexing of data and control channels Power control, Fast power control operates at the rate of and SIR-based Antenna correlation, Uncorrelated Speed of MS, 3km/h (for indoor environment) 3km/h (for pedestrian environ) l20km/h (for vehicular environ) Simulation length, 500 frames Diversity, RAKE and Space-time In this system each cell is supposed to be in hexagonal shape like that illustrated in Figure 1.