Adaptive transmission and multiple-access for sparse-traffic sources

M2M/online gaming are considered as key applications in LTE and LTE-advanced networks. However, for most of these applications whose traffic is sporadic and some of them require very low latency, they are not well supported by the current LTE and LTE-advanced systems due to the large signaling overhead. This paper proposes two methods to address this problem. The first method provides a co-optimization method for AMC and HARQ when CQI is outdated or unavailable and there is a latency constraint. The second method presents a contention based access method to reduce uplink channel access latency. Simulation results show that with these two methods a significant improvement in spectral efficiency can be achieved while greatly reducing latency or maintaining a latency constraint.