Study Of Concurrent Transmissions In Multiple Radio Access Network Technology

In this paper,we consider the problem of concurrent transmissions in a wireless network consisting of multiple radio access technologies(multi-RATs).That is,a single stream of packets are dispatched over multiple RATs so that the complementary advantages of different RATs can be exploited.One of the challenging issues arising in concurrent transmissions is the packet out-of-order problem due to diverse wireless channel states and scheduling policies of different RATs,leading to substantial performance degradation to delay sensitive applications.To address this problem,we firstly consider the state-independent packet dispatching(SIPD)policy,which attempts to find the traffic splitting over multiple RATs to minimize the maximum average delay across different RATs in the long run.We further consider the state-dependent packet dispatching(SDPD)policy,which achieves fine-grained packet dispatching in the short-term.We adopt value function as a measure of the admittance cost for packet dispatching given the current queueing states,and formulate the SDPD problem as a nonlinear mix-integer programming problem.We derive the close-form solutions for both problems under the special condition of two RATs,and the dual decomposition technique is adopted as the solution for the general cases.Simulation results are presented to show the performance of the proposed schemes and compare with existing solutions.The SDPD scheme outperforms all other schemes under all traffic conditions.And packets passing through different RATs incur similar delays.As a result,even though the out-of-order problem can not be avoided entirely due to the statistical nature of packet arrivals and service times,the extra delay incurred for reassembling the whole batch of packets is very small using the proposed SDPD scheme.