Mobile WiMax applied in a Coastal Environment

Abstract

In this thesis the wireless broadband standard 802.16e-2005, also known as mobile WiMAX is used for simulation purposes. WiMAX is a system that use an OFDM system in addition to using subcarrier permutation modes to cope with multipath fading effects. The channel conditions will be what you may find in a calm sea communication scenario, although many simplifications have been done. Scheduling is done on the basis of those subchannels created by the subcarrier permutation mode, where each subchannel contains a logical collection of subcarriers, where subcarriers can be both adjacent to each other or spread throughout the entire broadband channel. Mobile stations(assuming one user per mobile station) placed at different locations will experience different channel conditions, different path loss due to their distance from the base station and they also may have different QoS demands. All of these things matter when choosing a scheduling algorithm, and a few such algorithms are presented in this thesis resulting in vastly different capacity distributions amongst users and system throughput. The concept of waterfilling is considered to be the optimal distribution of power in many wireless communication systems with time varying channel conditions. In this thesis waterfilling will be carried out in frequency, allocating power to subcarriers according to their SNR. WiMAX systems however do not support giving subcarriers individual power, but each subcarrier is allocated the same amount of power. The thesis will investigate the effect this technique may bring, and whether it would be worthwhile implementing it in WiMAX. The results show that the capacity gain is close to nothing, but it is affected by the choice of permutation mode and the use of single user diversity, done in this thesis. Simulations where carried out using Matlab.