Symbol-level detection: A new approach to silencing hidden terminals

Hidden terminals are typical interference sources that can significantly reduce the throughput of a wireless network if it adopts the CSMA/CA MAC protocol. The RTS/CTS mechanism is a well-known solution to this hidden terminal problem. However, it only works well under the assumption that all hidden terminals can decode the CTS packets correctly. In the real world, the CTS packets might not be correctly received all the time due to either the CTS packets are unable to be decoded at remote hidden terminals or the CTS packets are collided with other packets at the hidden terminals. Both of these drawbacks can make the standard RTS/CTS mechanism fail to silence all hidden terminals, and deteriorate the throughput of the wireless network. In this paper, we present the RTS/S-CTS mechanism, a novel symbol-level detection mechanism that combats these two drawbacks. The RTS/S-CTS frames make slight changes to the standard RTS/CTS frames, and can be compatible with the standard 802.11 MAC layer. We design the symbol-level detection decoder (SLDD) and NAV decision algorithm that enable the S-CTS frame to be correctly detected from collisions and by remote hidden terminals. We build a testbed of RTS/S-CTS with GNURadio/USRP2 software radio to demonstrate its feasibility and run ns-2 simulations to evaluate its performance. The results show that the RTS/S-CTS can achieve up to 63% throughput improvement in the random topology network scenario compared with the standard RTS/CTS.