Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Adaptive modulation

Analysis of the Capacity, Spectral Efficiency and Probability of Outage of Adaptive Mobile Channel for WiMAX System

Hadi T. Ziboon; Wasan S. Rasheed

Engineering and Technology Journal, 2014, Volume 32, Issue 9, Pages 2248-2267

This paper presents an analysis of the channel capacity, spectral efficiency and probability of outage for the 4th generation adaptive modulation ofWiMAX system. The adaptive modulation techniquesare Variable rate-Variable power, Variable rate-Constant power and Constant rate by using truncated channel inversion in the presence of Additive White Gaussian Noise (AWGN), Rayleigh fading and Nakagami fading.
The growing demand for wireless communication requires determining the capacity, spectral efficiency and probability of outage of these channels to evaluate the performance time varying channels.
The analysis results show the advantage of using WiMAX system with adaptive MQAM modulation techniques. Analytical results have proved that the channel capacity is improved by (38) M bit/sec when increasing the bandwidth fromMHz to 20MHz in the presence of AWGN, the capacity channel is improved by (35) Mbit/Secwhen increasing the bandwidth from 1MHz to 20MHz in the presence of Rayleigh fading with Variable rate-Variable power, the capacity channel is improved in the presence of Nakagami fading (m=2)which is (37) Mb/sec and improved (38) when (m=3) due to severe effect of Nakagami when increasing the 1MHz to 20MHz for a given SNR. However, the analysis of spectral efficiency shows that maximum spectral efficiency is accrues in Shannon capacity.The spectral efficiency decreases when Bit Error Rate (BER) increases. The analysis results show the spectral efficiency decreases (0.5) when BER=〖10〗^(-3)is used than when BER=〖10〗^(-6) is used. The probability of outage increases when the BER increase.

Design and Implementation of Adaptive Modulation Modem Based on Software Defined Radio(SDR) for WiMAX System

H. T. Ziboon; Zeinah Tariq Naif

Engineering and Technology Journal, 2010, Volume 28, Issue 14, Pages 4730-4749

This paper presents design and implementation of adaptive
modulation modem for WiMAX system. (BPSK, QPSK, 8QAM, 16QAM,
32QAM and 64QAM) are used in this work. Software Defined Radio(SDR)
is used for implementing this modem. This work examines the benefits of
using adaptive modulation in terms of probability of bit error and spectral
efficiency. It specifically examines the performance enhancement made
possible by using linear prediction along with channel estimation in
conjunction with adaptive modulation. Simulation results proved that the
adaptive system performance with estimator and predictor is better than
other modulation alone. The simulation results for adaptive modulation in
compared to each modulation technique alone show that for BER=10-3 with
(fd=50Hz -200Hz)system the improvement occurs by decreasing S/N by 2-
3dB. As for BER=10-4 with same Doppler frequency, the system
improvement takes place by decreasing S/N by 1.3dB- 4dB. Recarding
BER=10-5 with same Doppler frequency, the improvement is by decreasing
S/N by 1.5dB-5 dB. Simulation results also show the flexibility of the
adaptive system to operate with different level of modulation based on
switching of S/N. Matlab7.8(R2009a) used for simulation of adaptive
modulation system with AWGN and fading channel.