Abstract
Mobile WiMAX is one of the candidate technologies for 4G wireless systems, promising high data rates and affluent multimedia services. The mobile WiMAX standard (IEEE802.16e-2005)is based on Orthogonal Frequency Division Multiple Access (OFDMA), which allows a very efficient use of bandwidth in a wide frequency range, this is due to the fact that OFDMA uses multi-channel OFDM approach and provides subcarrier access in the time and the frequency domains. In this paper the impact of downlink distributed (FUSC, PUSC) and adjacent (AMC) subcarrier permutation modes used in mobile WiMAX system are investigated using simulation under various modulation and coding schemes (link speeds)with the support of optimum value of the Cyclic Prefix (CP) for the OFDMA symbol duration. The results are expressed in terms of the maximum achievable throughput and operating distance from base station in pedestrian multipath fading channel (ITU-R Ped. B at 3Km/h speed) under a UDP-based application (video streaming), which is the proper application for multimedia services. The results show the optimum cyclic prefix valve for the FUSC, PUSC and AMC subcarrier permutation modes to achieve the best system performance, also the results show differences in PER performance atvarious modulation and coding schemes for the three subcarrier permutation modes (FUSC, PUSC and AMC). These differences in performance are exploited in the present work to show the best threshold SNR to switch from link speed to another link speed in terms of throughput and operating distance. Key words: IEEE802.16e-2005, OFDMA, FUSC, PUSC, AMC, ITU-R Ped. B channel, PER.
Highlights
Wireless Metropolitan Area Network (Wireless MAN) or worldwide interoperability for Microwave Access (WiMAX), which is mainly based on the IEEE standard is the leading technology for delivering wireless internet services and offers high-throughput broadband connections over long distances
The results show that the optimum cyclic prefix valve for the Full Usage of Sub channels (FUSC), Partial Usage of Sub channels (PUSC) and AMC subcarrier permutation modes that achieve the best performance is Tb/16 of the Orthogonal Frequency Division Multiple Access (OFDMA) symbol time
The results show a slight differences in the PER performance between the FUSC, PUSC and AMC subcarrier permutation modes at the lower modulation and coding schemes (QPSK1/2, QPSK3/4, 16QAM1/2)
Summary
2.2 Downlink Partial Usage of Sub channels (PUSC) Permutation Mode: PUSC is similar to FUSC except that all the subcarriers are first divided into six groups. Some useful terms specific to the DL PUSC: Physical Cluster: It is a set of 14 adjacent subcarriers (12data+2pilot). These clusters are contiguous in the frequency band. By allocating disjoint subsets of the six available groups to neighboring transmitters, it is possible to separate their signals in the subcarrier space, enabling a tighter frequency reuse at the cost of data rate. Such usage of subcarriers is referred to as segmentation
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