(IJCSIS) International Journal of Computer Science and Information Security, Vol. 9, No. 1, 2011
we plot the Channel capacity (in total number of bits per second per hertz (b/s/Hz)) and the SNR of the downlink channel as a function of the number of transmitting (nt)and receiving antennas(nr), respectively. It should be noted that the use of multiple antennas has significant impact on the Channel Capacity. We have calculate the error probability achieved by the MRC, showing it to be much smaller than the one corresponding to the SISO channel, in which no spatial diversity exists. Next, we consider the multiple-input single-output (MISO, multiple transmit antennas, single receive antenna) channel, and we present some mechanisms that exploit the transmit diversity offered by this channel. Specifically, Alamouti’s schemes are analyzed. In Fig. 2 and 3, we plot SNR vs BER for 2 Transmitter &1Reciver and 2 Transmitter &2Reciver,it is evident from plot that BER is minimum in the case of MIMO system. The Alamouti-based scheme are shown to achieve full diversity, i.e., they take full advantage of both transmit and receive diversity provided by the MIMO channel.
Figure 3. BER Vs SNR(2 Transmitter &2Reciver) The scheduling performance of our algorithm under two different types of traffic mode are implemented: one is voice or web-browsing in that bursts of data rate happen in some time intervals, sometimes it occurs silently also. The other one is for data transfer and streaming data. The requirement of data is self-similar and constantly high or low with only few fluctuations. The former is modeled by Pareto distribution while the later one is modeled by Weibull distribution. In the following simulations, channel matrix change every 10 time index with a total 12 transmit antennas for 3 users, and the algorithm trigger threshold at 1.5 bits/Hz/sec. The data streaming traffic mode is modeled by Weibull distribution with given pdf,
f (x) = aBxB-1 e -axB Where a is the scale parameter and B is the shape parameter. The pdf distribution is shown is shown in Figure 6.3. Data rate request and indemnity curves for Weibull Distribution are shown in Figure 4, Figure 5, and Figure 6 respectively.
Figure 1. Channel Capacity versus SNR
Figure 4: Weibull Distribution Figure 2. BER vs SNR (2 Transmitter &1Reciver)
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