Hidden-Node Detection in IEEE 802.11n Wireless LANs

The demand for wireless local area networks (WLANs) has drastically increased due to the prevalence of mobile devices, such as smartphones and tablet personal computers. In such an environment, a large number of basic service sets (BSSs) can overlap with each other, causing the well-known hidden-node problem to occur more frequently. Solutions to alleviate the hidden-node problem, such as the request-to-send/clear-to-send (RTS/CTS) exchange, often contain protocol overhead that may lead to throughput degradation when there is no hidden node. Therefore, it is necessary to develop a hidden-node detection (HD) mechanism that can be used to trigger a resolution mechanism for hidden nodes. By utilizing frame aggregation, block acknowledgment (ACK), and fast link adaptation (FLA) in IEEE 802.11n, we propose a novel HD mechanism that takes three main causes of frame losses, which are collisions, hidden nodes, and channel impairments, into consideration. The proposed HD mechanism detects hidden nodes based on measurable medium access control (MAC) layer statistics and the received block ACK frame and determines whether or not to use the RTS/CTS exchange. We show in a simulation study that the HD mechanism can detect hidden nodes well under various circumstances and that the network throughput can be improved by using the RTS/CTS exchange adaptively in conjunction with the HD mechanism.