Coupled PHY, MAC and repetition scheduling in IEEE 802.16 WiMAX systems

We address some issues related to the mutual influence between the PHY layer budding blocks (FEC blocks ), the MAC level allocations, and repetition, in IEEE 802.16e/WiMAX systems, in order to increase the overall combined efficiency. We suggest three methods to use repetition: two are based on the increased transmission success probability due to the transmission and decoding of several copies of the same data, and one is based on signal adding and the decoding of one copy with a larger SNR. The last method turned out to be the most efficient one. We show quantitatively that repetition is efficient mainly in low SNRs where otherwise transmissions are not possible, and in particular in negative SNRs. However, there are cases where using repetition is more efficient than using a stronger Modulation/Coding scheme without repetition. Finally, we also show that repetition shall be used with several Modulation/Coding schemes, and not just with QPSK-1/2 as the IEEE 802.16e/WiMAX standard mandates.