Probabilistic model checking of IEEE 802.11 IBSS power save mode

The IEEE 802.11 standard for wireless local area network defines a power management algorithm for Independent Basic Service Set (IBSS). The wireless stations that form an IBSS communication mode create ad-hoc connections between themselves and communicate with each other through a contention based channel access mechanism. The wireless stations in IBSS are typically battery enabled low power devices. In the power management for IBSS, time is divided into Beacon Intervals (BIs) and each BI is divided into an Announcement Traffic Indication Message (ATIM) window and a data window. The stations that have successfully transmitted an ATIM frame within the ATIM window will compete to transmit a data frame in the date window. The rest of the stations go to sleep mode during the data window, thus saving power. The power management algorithm for IBSS mode, based on a randomized exponential backoff procedure, is defined in the IEEE 802.11 standard for wireless LANs. The probabilistic behavior of the MAC mechanism enable us to design a probabilistic model suitable for model checking. This paper presents a finite state Markov Decision Process (MDP) and uses the tool PRISM to compute the performance of the IEEE 802.11 IBSS in PSM. A set of performance properties, such as expected delay and energy consumption are specified as queries in the probabilistic temporal logic PCTL and computed using PRISM.