Grouping strategy for solving hidden node problem in IEEE 802.15.4 LR-WPAN

The medium access control (MAC) protocol defined in IEEE 802.15.4 standard is able to achieve low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). The modified CSMA/CA protocol used to minimize power consumption does not have the hidden-node protection mechanism, such as RST/CTS mechanism, for the sake of reducing the control overheads. Referring to previous research results, which proved that the probability of any two nodes in infrastructure network unheard each other is about 41%, the hidden-node problem (HNP) could result in inefficient data transmission in WPAN and quick power consumption. In this paper, we propose a simple and efficient grouping strategy to solve the IEEE 802.15.4 HNP without needing extra control overheads in data transmissions. The proposed strategy groups nodes according to their hidden-node relationships and then separates the periodic transmission period into several non-overlapping sub-periods, one for each group. The WPAN coordinator is responsible for detecting the hidden-node situation and performing the grouping procedure if necessary. In this paper, we also prove that the maximal number of groups in a WPAN is five. Simulation results demonstrate that the proposed strategy is able to improve the standard transmission efficiency and to conserve energy by eliminating the unnecessary collisions.