ABSTRACT
Operators, which enable services to mobile users over Wireless Wide Area Networks (WWAN) broadband networks, are faced with constantly raising challenges to provide enough capacity at the network access level, in environments characterized with ever increasing users' demands. Following some of the ideas and results achieved with wireless local area networks, orthogonal frequency division multiplexing (OFDM) based relaying has been proposed as a logical solution to increase capacity of WWAN networks with the simultaneous extension of theirs coverage areas. IEEE 802.16j is the first standard for broadband wireless access systems which includes deployment of relay stations. The relay solutions in both accepted IMT-Advanced systems have reduced many of the relay functionalities defined in the IEEE 802.16j standard. When mobile station leaves the coverage area of a certain base station, handover is realized in a manner standard for traditional cellular networks. Relay stations are also foreseen for the next generation of WiMAX systems, formulated through the IEEE 802.16m standard.
