Mathematical Model for Scheduling in IEEE 802.11ad Networks
Wireless networks are replacing cables not only when providing Internet access, but also in such scenarios as multimedia transmission and high performance computing, which require extremely high data rates. Although millimetre waves open the door for multigigabit communications at the PHY layer, these rates do not guarantee an adequate Quality of Service (QoS) at the application layer. In order to improve QoS when serving multimedia flows in an IEEE 802.11ad network, a station (STA) can reserve a sequence of time intervals by means of a new reservation-based channel access mechanism. However, the IEEE 802.11ad amendment provides no recommendation on choosing such positions and durations of the reserved intervals which guarantee required QoS. This problem is significantly complicated by the erroneous nature of wireless channels so that the amount of the reserved channel time should account for possible retransmissions. To solve the problem, we develop a mathematical model of multimedia flow transmission with reserved time intervals over an erroneous channel in an IEEE 802.11ad network. We use the model as a basis for a scheduling method which allocates time intervals in such a way that the QoS requirements of the flow are satisfied with the minimum channel time consumption.