Discrete-rate adaptation schemes in multi-channel systems with finite-length buffer

Assuming a single-user multi-channel system, we study the performance of joint adaptive modulation and finite-length buffer. For higher spectral efficiency and more efficient usage of channel resources, we introduce hybrid schemes using discrete-rate adaptation jointly with discrete-power adaptation and selection-diversity. To analyze the queuing operation, we characterize the channel state of each scheme and derive the transition probability of the queue state and its stationary distribution. Furthermore, we investigate the system performance, in terms of the spectral efficiency, the packet dropping rate and the average delay. Numerical results show that hybrid scheme offers noticeable performance gain over the conventional adaptive modulation.