Loss probabilities for circuit-switched networks

Abstract

Consider a circuit-switched network where several source switches are connected to a destination switch via a tandem switch. Circuit-switched networks traditionally employ a Blocked Calls Cleared ( BCC) admission rule: a call is rejected if all circuits from the originating switch to the tandem switch are busy, or if all circuits from the tandem switch to the destination switch are busy. This paper investigates a simple extension to the BCC rule. Rather than reject all blocked calls, the Blocked Calls Held (BCH) rule holds some blocked calls by storing their call signalling information in a buffer at the tandem switch. These calls will later be connected when circuits become available. The BCH system is modeled by a MSCCC loss queue. The stationary distribution for the MSCCC loss queue is presented and an efficient recursive calculation of the queue performance measures is derived . The model reveals that, under moderate overload conditions, the BCH rule achieves a substantially lower loss probability than the BCC rule, at the expense of a small increase in the connection delay.