Achilles George Kogiantis

A Wideband Spatial Channel Model for System-Wide Simulations

A wideband space-time channel model is defined, which captures the multiple dependencies and variability in multicell system-wide operating environments. The model provides a unified treatment of spatial and temporal parameters, giving their statistical description and dependencies across a large geographical area for three outdoor environments pertinent to third-generation cellular system simulations. Parameter values are drawn from a broad base of recently published wideband and multiple-antenna measurements. A methodology is given to generate fast-fading coefficients between a base station and a mobile user based on the summation of directional plane waves derived from the statistics of the space-time parameters. Extensions to the baseline channel model, such as polarized antennas, are given to provide a greater variety of spatial environments. Despite its comprehensive nature, the models implementation complexity is reasonable so it can be used in simulating large-scale systems. Output statistics and capacities are used to illustrate the main characteristics of the model

Design and analysis of an IEEE 802.16e-based OFDMA communication system

IEEE 802.16e has emerged as a strong candidate standard for future wireless systems primarily because it offers the potential for high spectral efficiency, flexible spectrum options (e.g., 2–6 GHz), scalable carrier bandwidth options (e.g., from 1.25 MHz to 20 MHz), multiple duplexing options (time and frequency division duplex), various subchannelization options, and, unlike its IEEE 802.16 predecessors, mobility. Because of the recent emergence of IEEE 802.16e and the complexity it poses in system analysis, there is little published work in the literature regarding the actual system capacity/throughput performance of IEEE 802.16e for high data rate services. In this paper, we investigate the link and system level performance on the downlink of an IEEE 802.16e-based orthogonal frequency division multiple access (OFDMA) communication system and provide recommendations on high performance IEEE 802.16e system design and deployment configurations. We also propose dynamic resource allocation methods that may be used in OFDMA systems and investigate their performance.

Zone Based Resource Allocation for OFDMA Systems

This paper investigates the performance benefits of different resource allocation strategies that take advantage of permutation zones specified in IEEE 802.16e-based OFDMA systems. In particular, we propose and investigate the benefits of a sub-zone scheduling approach where each permutation zone is partitioned into sub-zones that are used for scheduling subsets of eligible users according to their prevailing link quality. In the scenarios considered, the proposed sub-zone scheduling approach allows improvements in sector throughputs as high as 80% relative to a baseline IEEE 802.16e-based OFDMA system while maintaining the system outage at acceptable levels.