Implementing and evaluating improved MAC efficiency through payload extension in 802.11n networks

Currently, the default size of Internet packets is set at a legacy value of 1500 bytes, since Ethernet was the dominant connection technology. Increasing this size, and thus using larger frames, brings several advantages such as less header overhead and CPU processing. However, the transmission of larger frames also raises several issues impacting data transmission, such as packet loss. With the increase in performance gained from recent wireless technology advances, solutions, such as Frame Aggregation, begin to exploit this increased bandwidth. However, the legacy value is still the dominant one. This paper evaluates the feasibility of increasing the Maximum Transfer Unit for a more efficient data transfer and bandwidth consumption in wireless 802.11n networks. We focus particularly in the experimental implementation and evaluation of the usage of Jumbo-Frames between an Access Point and the connected nodes, featuring a modified kernel that allows the usage of larger payloads, via enhancements to the existing wireless kernel modules. Network performance parameters including bandwidth usage, delay and packet losses are used to assess the benefits and drawbacks of the usage of Jumbo Frames in the wireless medium. Obtained results show that a more efficient medium usage can be achieved by increasing the payload size, when compared with standardized aggregation mechanisms. In addition, the measured packet losses decrease due to a considerable reduction on the number of packets sent for the same bandwidth consumption. To conclude, we perform an evaluation of the proposed enhancement in wireless video streaming scenarios and evaluate the performance gains that such module enables.