Experience with an implementation of the Idle Sense wireless access method

Abstract

An overwhelming part of research work on wireless networks validates new concepts or protocols with simulation or analytical modeling. Unlike this approach, we present our experience with implementing the Idle Sense access method on programmable off-the-shelf hardware-the Intel IPW2915/abg chipset. We also present measurements and performance comparisons of Idle Sense with respect to the Intel implementation of the 802.11 DCF (Distributed Coordination Function) standard.Implementing a modified MAC protocol on constrained devices presents several challenges: difficulty of programming without support for multiplication, division, and floating point arithmetic, absence of support for debugging and high precision measurement. To achieve our objectives, we had to overcome the limitations of the hardware platform and solve several issues. In particular, we have implemented the adaptation algorithm with approximate values of control parameters without the division operation and taken advantage of some fields in data frames to trace the execution and test the implemented access method. Finally, we have measured its performance to confirm good properties of Idle Sense: it obtains slightly better throughput, much better fairness, and significantly lower collision rate compared to the Intel implementation of the 802.11 DCF standard.

Hashing Backoff: A Collision-Free Wireless Access Method

“…where α and β are the parameters of the AIMD scheme chosen for the implementation of Idle Sense after tuning and measurements [9] (the parameters result in the best tradeoff between accuracy and convergence speed):…”

“…The simulator focuses on the MAC layer performance and takes into account the influence of an imperfect physical layer by simulating frame losses at a given frame error rate. Before the present study, we validated the simulator by comparing its results with other simulators [10] and measurements on a 802.11b platform [9]. A simulation runs for 10 6 transmissions to obtain a relative precision of the order of 10 −3 (confidence intervals are too small to show in figures).…”

“…Consequently, Hashing Backoff also performs better than DCF, because Idle Sense provides shorter delays than DCF (cf. measurement based comparisons [9]). Figure 3 presents collision probability.…”

How to Improve CSMA-Based MAC Protocol for Dense RFID Reader-to-Reader Networks?

“…Our objective is to use protocols such as Idle Sense [9], Sift [14] and Reverse Backoff [13] to perform channel access through broadcasting message with almost zero-collision or in collision-free fashion. Once the channel is reserved by a reader, it can communicate with tags located in its interrogation area in collision-free fashion.…”

A MPSoC Prototyping Platform for Flexible Radio Applications

“…This means that when studying wireless networking, experimentations are often limited to simulations. In a few particular cases, finding and modifying an existing device is possible, which is very time-consuming in any way, as in [3] for example. To really validate new wireless networking propositions, it is necessary to experiment with real devices in real conditions.…”