S.A. Filin, S.N. Moiseev, M.S. Kondakov
The fast QoS-guaranteed adaptive transmission algorithm in the Mobile WiMAX system with multiuser diversity frame structure and time division duplex is proposed. The proposed algorithm selects position of the boundary between downlink and uplink subframes and performs adaptive coding and modulation, allocation of transmit power and frequency subchannels to the downlink and uplink service flows. The proposed algorithm maximizes sector capacity subject to satisfying QoS requirements for all the downlink and uplink service flows scheduled for transmission in the current frame. The proposed algorithm takes into account MAC and PHY layers processing of data blocks. Hence, the proposed algorithm uses a cross-layer approach to determine the minimum transmission power value for which QoS requirements are satisfied. Moreover, the proposed algorithm enables QoS-guaranteed transmission of multiple downlink and uplink service flows having different QoS requirements. This feature of the proposed algorithm is essential to enable transmission of multimedia traffic. Adaptive transmission in the Mobile WiMAX system is a conditional optimization task. Its optimal solution has exponential complexity. Hence, the computational complexity of practical algorithms is of great interest. In the proposed practical adaptive transmission algorithm we use our OFDMA system load concept. This results in a very fast and efficient algorithm. The proposed algorithm is evaluated by performing system level simulation of the Mobile WiMAX system. The proposed algorithm gains a higher spectral efficiency and requires considerably fewer computational resources as compared to the previously developed algorithms.