Downlink resource allocation in beyond 3G OFDMA cellular systems

Orthogonal Frequency Division Multiplex (OFDM) based wireless communication is becoming a standard for providing broadband wireless services. OFDM is already deployed in various WLAN systems such as 802.11 a/g/e and in the mobile WiMAX systems (802.16e). The OFDM physical layer is also considered by 3GPP for the Long Term Evolution (LTE) of UMTS. The OFDM based physical layer enables a so-called Orthogonal Frequency Division Multiple Access (OFDMA) where the total number of sub-carriers is divided in distinctive sets and consequently allocated to different users. This study evaluates several algorithms for allocation of the sub-carrier sets for the downlink direction. The performance comparison is based on the sector throughput, user throughput and the average user throughput versus the distance from the reference sector. We have performed the evaluations based on simulations of a UMTS-LTE system.