Designing efficient yet flexible medium access controllers (MAC) for wireless protocols is a challenge. Not only are these protocols still evolving, they are also increasingly demanding in terms of throughput and real-time requirements. In order to support a careful application-driven architecture development, reference applications are required that expose the full system and enable the quantitative evaluation of performance-flexibility tradeoffs.For this purpose, we have captured the 802.11n MAC protocol in an executable reference application which comprises the system function and its environment including traffic scenarios. We model the reference in Click, a packet processing framework. The functionally-correct model captures performance-relevant aspects such as the wireless protocol timing exactly. Leveraging extensions to Click we can use the model for the development and deployment of embedded architectures. Our 802.11n MAC model comprises between 118 and 1238 functional elements and can be simulated in real time depending on the scenario. Due to its modularity, additional scenarios can be added productively.

No abstract

For ad-hoc home networks without central coordinator, IEEE 802.11 systems merely support service differentiation. In many usage scenarios of a typical home network with applications requiring a strict quality of service (QoS), this MAC functionality is not sufficient. In order to counteract this problem, we developed in previous works a modified MAC scheme based on the IEEE 802.11 enhanced distributed channel access (EDCA) function. This paper describes enhancements of the modified MAC scheme enforcing prioritized medium access for strict QoS applications. For the first time, the established concept is realized in a distributed way with in-band signaling. Our enhanced MAC is embedded into a comprehensive IEEE 802.11n reference application to demonstrate its effectiveness in combination with the latest amendments like frame aggregation. The reference application is modeled in SystemClick, a framework for describing and evaluating packet processing applications on resource constraint network nodes. This enables functional validation and provides a path to future, cost-efficient implementations on programmable devices. On this basis, the paper presents simulation results substantiating the significant improvement of QoS parameters like delay and throughput. Besides enforcing strict priorities, collisions can be reduced to zero and the average waiting time can be decreased by up to 33 % for typical usage scenarios.

No abstract

No abstract