values (one bit) is enough for discrimination in this case. As can be seen by the specification, the last three values all identify fragments of an MscSdu. Thus, these values are actually used to provide a segmentation service to the service access control element, not for discrimination. From an architectural point of view, it would have been better to define separate parame- ters for discrimination (always an integrator function) and segmentation (part of 5.5 The EIA553 Case Study a TAH function, not necessarily part of an integrator). That may have cost an extra bit in this case. Most likely this is not the reason for this solution, but rather that the protocol designers did not see the benefit of separating TAH func- tions from discrimination functions. 4. The integrator also performs an error detection function by including a 12-bit parity parameter (P) in both Ovh and Msc messages. 5. Another kind of error handling is represented by the DCC parameter. This parameter discriminates between different base-stations and MSs, considering the risk that signals from MSs and base-stations in different cells are received on the same radio channel. 5.5.4 The Broadcast Data-Handling Protocol The broadcast data-handling unit handles a full message protocol, since the integra- tor does no encoding on behalf of its users. We will therefore separate the protocol element into a message-handling unit (MEH) and a service object. The MEH han- dles the ENC and FOH functions, the service object the OPH function. Broadcast data handling Service object OvhMessTrain abstract service primitives OvhMessTrain specification END ::= $BITSTR SIZE (1) (FOH,ENC) last END ::= '1'B notLast END ::= '0'B NAWC :: $BITSTR SIZE (4) OvhSdu OHD ::= $BITSTR SIZE (3) spomi OHD ::= '110'B spom2 OHD ::= '111'B OHD :: '100'B OHD '000'B OHD '001'B OvhMess Train ::= $SEQ{Spom1, Cfm OPT, Spom2, $SEQ OF Word} Word ::= $CHOICE{Gaom Rim, Cfm OPTIONAL} Fig. 5.35 Message specification for the broadcast data-handling element The problem now is to identify the op