Adaptive radio parameter control considering QoS for forward link OFCDM wireless access

This paper proposes an adaptive radio parameter control scheme that utilizes the maximum number of retransmissions in hybrid automatic repeat request (ARQ) in addition to the data modulation and channel coding scheme (MCS) according to quality of service (QoS) requirements and propagation conditions such as the delay spread in the forward link of orthogonal frequency and code division multiplexing (OFCDM) broadband wireless access. We elucidate that for non-real time (NRT) class data transmission, it is appropriate to employ three MCSs, QPSK with the coding rate of R = 1/2, 16QAM with R = 1/2 and 3/4. Application of a much higher MCS set. 16QAM with R = 5/6 and 64QAM with R = 3/4, in addition to the three MCSs improves the throughput under much higher average received E_s/N₀ conditions in a short-delay spread environment. Meanwhile, for real time (RT) data transmission assuming the number of retransmissions of M = 2, it is appropriate to use five MCSs, QPSK with R = 1/3, 1/2 and 16QAM with R = 1/3, 1/2, and 3/4. Thus, we elucidate that the appropriate MCS associated with the maximum number of retransmissions, i.e., major radio parameters should be controlled according to the QoS requirements and the propagation channel conditions. Furthermore, the proposed adaptive radio parameter control scheme that considers the QoS requirements is unified by controlling the threshold value for selecting the appropriate MCS associated with the maximum number of retransmissions in the hybrid ARQ.