In C7 the TCH is identified by CIC. The CIC values are unique between two PCs. The C7 messages between 2 PCs carries CIC value for identifying the TCH for which the signaling info is. also the messages has Sequence Nos(FSN/BSN) for flow control. The signal data is in packet form. Incase of R2 the signaling info is transmitted strictly at the momemt of time when it is the turn for that TCH. More info on layer1/2 can be found on pt.com. However feel free for any thing.