When simulating SSCH in QualNet [5], we made two technical choices that seem to be relatively uncommon based on our reading of the literature. The first technical choice relates to how we added SSCH to an existing system, and the second relates to a little-utilized part of the IEEE 802.11 specification.
In order to implement SSCH, we had to implement new packet queuing and retransmission strategies. To avoid requiring modifications to the hardware (in QualNet, the hardware model) or the network stack, SSCH buffers packets below the network layer, but above the NIC device driver. To maintain control over transmission attempts, we configure the NIC to buffer at most one packet at a time, and to attempt exactly one RTS for each packet before returning to the SSCH layer. By observing NIC-level counters before and after every attempted packet transmission, we are able to determine whether a CTS was heard for the packet, and if so, whether the packet was successfully transmitted and acknowledged. All the necessary parameters to do this are exposed by the hardware model we used in QualNet. This also prevents head-of-line blocking from interfering with our desire to implement the SSCH transmission strategy.
For efficiency reasons, we choose to use the IEEE 802.11 Long Control Frame Header format to broadcast channel schedules and current offsets, rather than using a full broadcast data packet. The most common control frames in IEEE 802.11 (RTS, CTS, and ACK) use the alternative short format. The long format was included in the IEEE 802.11 standard to support inter-operability with legacy 1-Mbps and 2-Mbps DSSS systems [8]. The format contains 6 unused bytes; we use 4 to embed the 4 (channel, seed) pairs, and another 2 to embed the offset within the cycle (i.e., how far the node has progressed through the 530 ms cycle).
Lastly, we comment that the beaconing mechanism used in IEEE 802.11 ad-hoc mode for associating with a Basic Service Set (BSS) works unchanged in the presence of SSCH. A newly-arrived node can associate to a BSS as soon as it overlaps in the same channel with any already-arrived node.