RoXOR: Re-thinking retransmissions in WiFi

It is widely believed that future small-cell unmanaged wireless networks will be dominated by interference caused by packet collisions and not by signal-to-noise issues. In such a network, a large fraction of the collisions are caused by hidden terminals. Here we present the design and evaluation of RoXOR, a system that can effectively combat random collisions caused by bursty traffic from hidden terminals. RoXOR relies on jointly using both the amount of redundancy and the structure of the redundancy, as expressed by a code. Using these degrees of freedom, we design and experimentally evaluate an iterative rateless code that with high probability achieves better performance as compared to methods such as ZigZag. The mean improvement, as measured by the per packet delay, is 12-18% for values typically used for a 802.11× protocol.