• Journal of Communications and Networks
• /
• v.9 no.1
• /
• pp.67-74
• /
• 2007

The performance of dual diversity receivers operating over correlated Ricean fading channels is analyzed. Using a previously derived rapidly converging infinite series representation for the bivariate Ricean probability density function, analytical expressions for the statistics of dual-branch selection combining, maximal-ratio combining, and equal-gain combining output signal-to-noise ratio (SNR) are derived. These expressions are employed to obtain novel analytical formulae for the average output SNR, amount of fading, average bit error probability, and outage probability. The proposed mathematical analysis is used to study various novel performance evaluation results with parameters of interest the fading severity, average input SNRs, and the correlation coefficient. The series convergence rate is also examined verifying the fast convergence of the analytical expressions. The accuracy of most of the theoretical performance evaluation results are validated by means of computer simulations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.7
• /
• pp.648-656
• /
• 2009

We perform an analysis of the characteristics of the time-reversal pulse in Rayleigh or Ricean fading channel environments. We verify it by using Monte Carlo simulation. In a time-reversal system, each antenna in the time-reversal array receives signals from the transmitter and reverse the received signal in the time axis and then resend it to the original transmitter. We assume that the channel characteristics varies very slowly and the spatial separation between the antennas is not large. Hence the signals received by each antenna are correlated. In this paper, the effect of the correlation on the time-reversed pulse is examined, which includes the spatial properties of the time-reversal pulse such as the focus size, and spatial power distribution.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.2A
• /
• pp.110-118
• /
• 2006

In part-I of the paper, two sub-channel structures, either contiguous or distributed, were considered. Modeling the SNR distribution over a sub-channel as Ricean in general, the statistical chracteristics were investigated. In this part of the paper, we develop a generalized two step channel/resource allocation algorithm, which incorporates the two statistical measurements, and analyze the spectral efficiency of OFDMA in terms of average frequency utilization for the two sub-channel structures. In OFDMA with distributed structure, the key design parameter would be the sub-channel bandwidth. To give an insight into the impact on this parameter, we show in the numerical results the frequency utilization as a function of sub-channel bandwidth normalized to coherence bandwidth. As confirmed by numerical results, for contiguous sub-channel structure, we obtain the nominal multiuser diversity gain when the sub-channel bandwidth is smaller than the coherence bandwidth and lose the gain as it is getting larger.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.2A
• /
• pp.119-127
• /
• 2006

In this two-part paper, we consider dynamic resource allocation in orthogonal frequency division multiple access(OFDMA). To reduce the reverse link overhead for channel quality information(CQI) feedback, a set of sub-carriers are tied up to a sub-channel to be used as the unit of CQI feedback, user-multiplexing and the corresponding power/rate allocation. Specifically, we focus on two sub-channel structures, either aggregated or distributed, where the SNR distribution over a sub-channel is modeled as Ricean in general, and the channel quality of a sub-channel is summarized as the mean and variance of channel gain envelop divided by noise standard deviation. Then, we develop a generalized two step channel/resource allocation algorithm, which uses the two statistical measurements, and analyze the spectral efficiency of the OFDMA system in terms of average frequency utilization. An extension to proportional fair algorithm will also be addressed. As confirmed by numerical results, the aggregated structure is preferred especially when intending aggressive link adaptation.