ful tool in computing good solutions far be- yond a paper-and-pencil analysis. Often the graph representation of a problem is direct (for example, warehouses are nodes and trucking routes are arcs), and other times the relationship can be more subtle. 4 In our case, the base stations and the MSC are nodes, and the transport links are the arcs. The easiest solution to visualize is a star graph, where all the arcs share a common node, as shown in Fig. 26.2. This is the solution where the wireless service provider calls the telephone company and leases separate transport links from the MSC to each base station. Even if we never plan to build a star-graph solution for a backhaul net- work, the star-graph is a useful starting point for a computational algorithm to work its way to a less expensive network solution. The graph that contains every possible arc between every pair of nodes is the com- plete graph shown in Fig. 26.3. If there are n nodes, then there are n(n 2 + 1) arcs in a com- plete, fully-connected, graph. We would not deploy a complete transport network, but we would use the complete graph to enumerate all the route possibilities. If nodes are 1In conventional reuse, a cell can have every radio channel of every sector in use because sec- tors do not share the same frequencies. In CDMA, however, the sectors of a cell share a carrier frequency and interfere with each other. A well-designed CDMA cell will have enough capacity on each antenna face so that its sector has low blocking, and the total capacity of all the antenna faces should be more than the cell as a whole can handle. 2The plural of vertex is vertices just as the plurals of index and simplex are indices and simplices. The grammatical waters are muddied, however, because the plural of the noun complex is com- plexes. 3This is not to be confused with the (x, y) plot of points, lines, and curves also called a graph. 4We recall one optimization model where the airline flights were nodes and the connections at the airports were arcs. This is contrar