L2Relay: An Intelligent Layer 2 Wi-Fi Packet Relay Protocol
L2Relay is a novel packet relay protocol for Wi-Fi networks that can improve the performance and extend the range of the network. It is designed to be a layer 2 solution that has direct control over many layer 2 functionalities such as carrier sense. The device solves unique problems including link measurement, rate adaptation, relayer selection, and relayer collision detection.
Commercial range extenders that are easy to install are currently available on the market. However, they extend the range by capturing and rebroadcasting all transmitted packets, which is known to reduce network throughput in many cases because the node may be close to the Access Point (AP) and may be able to receive from the AP directly such that the rebroadcasting of the packets is completely unnecessary.
An L2Relay device runs an intelligent protocol that selectively repeats packets only when necessary, thus practically never degrades the network performance. L2Relay is designed for ubiquitous compatibility without the need of any modification to the nodes and the AP; as a result, an L2Relay device can be easily installed by simply plugging into a wall outlet in any Wi-Fi network and bring immediate benefits.
L2Relay has many distinct features due to the requirement of not modifying the AP and the nodes, as well as exploiting the Layer 2 information. Our solutions to link measurement, rate adaptation, relayer selection, and relayer collision detection are completely different from the academic prototype solutions that require the AP to act as a central controller, such as CoopMAC. In addition, our solutions are novel because they are based on the Layer 2 information. In wireless networks, Layer 2 is the data link layer which handles issues such as medium access. The existing academic prototype solutions are implemented above the Layer 2, such that they suffer many restrictions and do not have access to much useful infonnation such as the medium idle time. On the contrary, L2Relay functions within Layer 2 and has access to such information, which enables it to solve many problems very efficiently.