A Light-Weight Wireless Handshake

摘要

In many wireless systems, it is desirable to precede a data transmission with a handshake between the sender and the receiver. For example, RTS-CTS is a handshake that prevents collisions due to hidden terminals. Past work, however, has shown that the overhead of such handshake is too high for practical deployments. We present a new approach to wireless handshake that is almost overhead free. The key idea underlying the design is to separate a packet's PLCP header and MAC header from its body and have the sender and receiver first exchange the data and ACK headers, then exchange the bodies of the data and ACK packets without additional headers. The header exchange provides a natural handshake at almost no extra cost. We empirically evaluate the feasibility of such lightweight handshake and some of its applications. Our testbed evaluation shows that header-payload separation does not hamper packet de-codabilty. It also shows that a light handshake enables hidden terminals, i.e., nodes that interfere with each other without RTS/CTS, to experience less than 4% of collisions. Furthermore, it improves the accuracy of bit rate selection in bursty and mobile environments producing a throughput gain of about 2x.