In this Section we discuss alternative designs for SSCH within the constraints that we enumerated in Section 2. We will discuss prior work related to SSCH in detail in Section 6.
SSCH distributes the rendezvous and control traffic across all the channels. One straightforward alternative scheme, which still only requires one radio, is to use one of the channels as a control channel, and all the other channels as data channels (e.g., [21]). Each node must then somehow split its time between the control channel and the data channels.
Such a scheme will have difficulty in preventing the control channel from becoming a bottleneck. Suppose that two nodes exchange RTS/CTS on the control channel, and then switch to a data channel to do transmission. Unless all other nodes were also on the control channel during the RTS/CTS exchange, these two nodes will still need to do an RTS/CTS on this channel in order to avoid the hidden terminal problem. The two nodes should wait to even do the RTS/CTS until after an entire packet transmission interval has elapsed, because another pair of nodes might have also switched to this channel, orchestrating that decision on the control channel during a time that the first pair of nodes were not on the control channel. In order to amortize this startup cost, the nodes should have several packets to send to each other. However, while any one node remains on a data channel, any other node that desires to send it a packet must remain idle on the control channel waiting for the node it desires to reach to re-appear. If the idle node on the control channel chooses not to wait, and instead switches to a data channel with another node for which it has traffic, it may repeatedly fail to rendezvous with the first node, leading to a significant imbalance in throughput and possibly a logical partition.
The problems with a dedicated control channel may be solvable, but it is clear that a straightforward approach with un-synchronized rendezvous presents several difficulties. If one instead tried to synchronize rendezvous on the control channel, the control channel could again become a bottleneck simply because many nodes simultaneously desire to schedule packets on that channel.