Packet Size Variability Affects Collisions and Energy Efficiency in WLANs

Wireless Local Area Networks (WLANs) support a wide range of applications, with various packet sizes. This diversity is set to increase in 802.11e WLANs which effectively allow very large packets controlled by a Transmission OPportunity (TxOP) parameter. This paper presents a new phenomenon which occurs as a result of this diversity: When a network carries some large packets and many small packets, the collision probability after a large packet is much larger than predicted by previous models. This can be important because collision probability determines the number of packet transmissions, and hence the energy consumption. The authors propose a candidate model which captures this effect.