Medium access control (MAC) is a fundamental and challenging problem in networking. This problem is at the data link layer which interfaces the physical layer and the upper layers. A solution to this problem in a particular network thus needs to factor in the characteristics of the physical layer and the upper layers, which makes the MAC problem both a challenging and evolving problem. Medium access control in distributed wireless networks is one of the most active research areas in networking because distributed wireless networks are diverse and evolving fast. One of the most well-known problem in medium access control in distributed wireless networks is the hidden terminal problem. Hidden terminals are interesting but problematic phenomena in distributed wireless networks. Basically, even if two nodes in a wireless network cannot sense each other, they may still cause collisions at the receiver of each other (1). If the hidden terminal problem is not well addressed, a wireless network may have a significantly degraded performance in every aspect, since frequent packet collisions consume all types of network resources such as energy, bandwidth, and computing power but generate no useful output. There are basically two existing approaches to the hidden terminal problem. One is the use of an out-of-band control channel for signaling a busy data channel when a packet is in the air (2; 3; 4; 5). This approach is effective in dealing with hidden terminals but requires an additional control channel. The more popular approach to the hidden terminal problem is the use of in-band control frames for reserving the medium before a packet is transmitted (6; 7; 8; 9; 10). The popular IEEE 802.11 standard (11) uses this approach in its distributed coordination function (DCF). Basically, before an IEEE 802.11 node in the DCF mode transmits a packet to another node, it first sends out a Request to Send (RTS) frame after proper backoffs and deferrals. If the receiver successfully receives the RTS frame and the channel is clear, the receiver responds with a Clear to Send (CTS) frame, which includes a Duration field informing its neighbors to back off during the specified period. In an ideal case, the hidden terminals of the initiating sender will successfully receive the CTS frame and thus not initiate new transmissions when the packet is being transmitted. However, control frames have limited effectiveness in dealing with hidden terminals because they may not be able to reach all the intended receivers due to signal attenuation, fading, or interference (12). In addition, control frames have considerably long airtimes
