S.N. Moiseev, S.A. Filin, M.S. Kondakov
The IEEE 802.16 family of standards specifies the requirements to the physical and medium access control layers of the Mobile WiMAX broadband wireless access system. The standards include the most of modern data transmission technologies. This gives a lot of opportunities to optimize the Mobile WiMAX system performance. While optimizing the performance of the modern communication systems it is reasonable to use the adaptive transmission approach and the cross-layer optimization approach.
An important optimization problem is the minimization of the total downlink and uplink transmission power subject to satisfying QoS requirements for all users of the system. The minimization of the total transmission power results in the reducing the inter-sector interference, thus improving the receiving conditions and increasing the system capacity.
It the known literature it is shown that the total radiated energy and the system spectral efficiency are strongly determined by the average number of data block transmissions, when the ARQ (Automatic Repeat Correction) mechanism is used. Hence, the average number of data block transmissions shall be one of the adaptation parameters while minimizing the total transmission power in the system using the ARQ mechanism.
In the previous work we solved the total transmission power minimization problem subject to satisfying the QoS requirements for the given average number of data block transmissions, while the average number of data block transmissions is determined by the QoS requirement for the maximum average data block transmission delay. In this paper we find the optimal average number of data block transmissions that minimizes the total downlink and uplink transmission power subject to satisfying the QoS requirements.
Using our algorithm we calculate the optimal average number of data block transmissions for numerous coding and modulation schemes and coding block sizes, for several propagation channels, and for different numbers of coding blocks containing one data block. We show that the optimal average number of data block transmissions in the Mobile WiMAX system is almost independent of these parameters. Hence, we recommend setting the optimal average number of data block transmissions to 1.18 in the Mobile WiMAX system.