PERFORMANCE OF PERSONAL PORTABLE RADIO TELEPHONE SYSTEMS WITH AND WITHOUT GUARD CHANNELS

We present and compare three call handling schemes for a base station which can handle both originating calls (OC's) and prioritized handoff calls (HC's), and which serves these calls under the blocked-call-del ayed basis. Delayed calls are assumed to be stored in a finite storage buffer. One scheme (Scheme I) exclusively allows handoff calls to be stored and to use a fixed number of guard channels. The other two sche mes without guard channels (Scheme II-using the last-in/first-out poli cy for OC's, and Scheme III-using the first-in/first-out policy for OC 's) allow both types of calls to be stored, and allow prioritized hand off calls to pushout originating calls if the buffer is full. For thes e three schemes, the blocking probabilities and delay distributions of both types of calls are numerically obtained, and a boundary for call handling schemes between with and without guard channels is found. Fr om the numerical results, the schemes without guard channels reduce th e call blocking probability of originating calls without a severe pena lty on handoff calls, and thus provide higher total grade of service t han the scheme with guard channels. For the two schemes without guard channels, Scheme II provides shorter average waiting time of calls tha n Scheme III. Thus, Scheme II can be a good candidate for a call handl ing scheme for microcellular systems.