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Hidden terminal management for uplink traffic in rate-controlled WiFi networks

This paper exposes several problems in managing hidden terminals for uplink traffic in rate-controlled environments, and presents solutions to mitigate them. In particular, we focus on scenarios, in which, clients are associated with an access point (AP). The main challenge stems from the negative interactions between rate-control protocols and hidden terminals. To expose the problems, we use a recent channel estimation approach (CEA) to differentiate the reason for packet losses into three categories, noise, congestion and hidden terminals. Our testbed and simulation-based experiments show that the accuracy of hidden terminal estimations using the CEA degrades as MAC-layer ACK frames are sent with relatively high transmission rates. To improve the accuracy of the CEA, the results demonstrate the necessity and cost of making the AP send ACKs based on the minimum ACK rate of all clients. We propose an adaptive scheme that combines both the CEA and RTS/CTS messages. The proposed scheme increases the overall throughput of Minstrel rate-control algorithm by 60% in case of light congested environments. We also proposed a threshold-based adaptive RTS/CTS scheme based on the prior scheme to handle the highly congested environments. The threshold-based adaptive RTS/CTS scheme improves the overall throughput of the adaptive RTS/CTS scheme and Minstrel algorithm between 20-35%. Finally, we propose and evaluate an opportunistic burst scheme, which enforce fairness among clients. Simulation results show that opportunistic bursting outperforms the prior schemes and Minstrel algorithm in Jain's fairness metric (between 0.11 and 0.38) for a realistic given scenario. It also keeps a relatively high overall throughput.