Modeling joint usage of random and deterministic channel access in Wi-Fi networks

The ability to provide Quality of Service in Wi-Fi networks to a considerable degree depends on a used channel access method. A number of access methods allow a Wi-Fi station to preliminarily reserve a set of time intervals inside which transmissions are protected from interference. However, fixed parameters assigned to such reservations make them not so flexible as needed for serving Variable Bit Rate (VBR) traffic. On the contrary, random channel access mandatory for Wi-Fi provides such flexibility though at cost of reliability because of collisions and interference. In order to achieve both the reliability and flexibility, we propose a joint access method based on both reservations and random access. In this pioneering work, we study a VBR flow transmission process with the joint method and build its mathematical model. The model can be used to find appropriate parameters of the method which guarantee that QoS requirements of the flow are satisfied while the amount of used channel time is kept as low as possible.