UBC Theses and Dissertations

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UBC Theses and Dissertations

Efficient routing of telephone calls in a circuit-switched network Braun, Darrel


Every year Telus invests tens of millions of dollars to increase the capacity of their circuit-switched network in response to growth in demand. Growth has accelerated in recent years due to rapid increases in data and Internet traffic, and the introduction of flatrate long-distance services. This in turn has forced Telus to accelerate their investments in the network to keep pace with demand. Circuit-switched technology is inefficient in comparison to newer packet-switched technology, especially for data, which constitutes a large and increasing portion of network traffic. In the near future Telus intends to begin the move away from a circuit-switched to a packet-switched network. Investments in the circuit-switched network will have very little value after the move to a packet-switched network. Therefore Telus is looking for ways to reduce the investments needed in their circuit-switched network. One possibility for reducing investments is to use the existing network more efficiently by improving the call routing. Every call has an origin switch and a destination switch. Most calls are routed on a circuit linking the two switches directly. Call routing concerns processing of calls where the direct circuit is either fully occupied or does not exist, in which case calls are routed indirectly through one or more intermediate switches. Presently Telus uses a method called Fixed-Hierarchical Routing. This is a fairly inflexible scheme that routes overflow calls through one of only two of the 33 lower mainland switches. The project team is investigating Sequential Alternate Routing which would allow calls to be routed through any of the 33 switches. A key tool in this investigation is a network simulator that was written for this project. The simulator will be used to compare the performance of various new routing schemes, and the simulation results will be used when recommending a scheme to Telus. The simulator was subjected to a number of tests to verify that it functions as intended. A key finding of those tests is that the simulator tends to underestimate the number of calls blocked due to network congestion, but that this effect can be managed through the judicious choice of the simulation run parameters. The tests also led to insights into the choice of appropriate measurement criteria comparing the performance of routing schemes.

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