Performance of IEEE 802.16e OFDMA in Tight Reuse Scenarios

Mobile networks based on the IEEE 802.16e standard are promising candidates for providing broadband wireless access to mobile users. Due to the flexibility of the physical layer definition based on Orthogonal Frequency Division Multiple Access (OFDMA), it is possible to adjust the networks according to IEEE 802.16e to meet different requirements, e.g., system bandwidth. However, these networks cannot guarantee a reliable transmission in scenarios with frequency reuse of 1 to users at the cell border which achieve only poor Signal to Interference plus Noise Ratio (SINR) conditions due to the high amount of interference from neighbouring cells. Link level simulations provided in this paper show that transmission with a sufficiently low block error probability is achieved for SINR conditions above 4 dB. To improve the SINR conditions at the cell border, a system design is proposed that coordinates the resource allocation among the cells. The available subcarriers shall not be used in an omnidirectional way within the cell, but instead shared among the sectors of a cell that neighbouring sectors do not utilise the same subcarriers and interference can be reduced. System level simulations show that the sector and user throughput can be double with the proposed system design compared to an omnidirectional transmission, although the average amount of allocated radio resource units to each user is equal in both scenarios.