Closed-loop control of multiple MAC queues in multiservice wireless access networks

The real-time control of multiple queues, handling traffic of different nature, is getting increasing attention in both the uplink and downlink of wireless telecommunication networks, characterized by the presence of a central access point. Such is the case of satellite networks, with on-board processing or double-hop configuration, infrastructure Wireless LANs (WLANs), and WiMax (IEEE 802.16) networks. Given a certain amount of available bandwidth, the problem is that of deciding, within a certain time frame, the allocation of bandwidth partitions for each traffic queue, whose packets are awaiting transmission, i.e., ultimately, the transmission rates to be passed to the scheduler and to the physical layer Adaptive Coding and Modulation (ACM) devices. Whenever this task is accomplished by a master station, residing at the access point, it is possible to take such decisions by means of a centralized controller, based on real-time instantaneous (in the downstream direction) or delayed (in the upstream) information on the queues' state. The paper derives a control law to be used in this task, by adopting an approach based on optimal Linear Quadratic (LQ) regulation. Both cases of un-delayed and delayed information are considered. The control laws are tested in a geo-stationary satellite scenario of Digital Video Broadcasting - Return Channel via Satellite (DVB- RCS), and the queues are considered at the MAC (Medium Access Control) level. Simulation results under real-traffic traces are also presented, to highlight the effectiveness of the control and to compare alternative solutions.