Network planning and design is an iterative process, encompassing topological design, network-synthesis, and network-realization, and is aimed at ensuring that a new network or service meets the needs of the subscriber and operator. The process can be tailored according to each new network or service. This is an extremely important process which must be performed before the establishment of a new telecommunications network or service.
A traditional network planning methodology involves four layers of planning, namely:
Each of these layers incorporates plans for different time horizons, i.e. the business planning layer determines the planning that the operator must perform to ensure that the network will perform as required for its intended life-span. The Operations and Maintenance layer, however, examines how the network will run on a day-to-day basis.
The network planning process begins with the acquisition of external information. This includes:
It should be borne in mind that planning a new network/service involves implementing the new system across the first four layers of the OSI Reference Model. This means that even before the network planning process begins, choices must be made, involving protocols and transmission technologies.
Once the initial decisions have been made, the network planning process involves three main steps:
Topological design: This stage involves determining where to place the components and how to connect them. The (topological) optimisation methods that can be used in this stage come from an area of mathematics called Graph Theory. These methods involve determining the costs of transmission and the cost of switching, and thereby determining the optimum connection matrix and location of switches and concentrators.
Network-synthesis: This stage involves determining the size of the components used, subject to performance criteria such as the Grade of Service (GoS). The method used is known as "Nonlinear Optimisation", and involves determining the topology, required GoS, cost of transmission, etc., and using this information to calculate a routing plan, and the size of the components.
Network realization: This stage involves determining how to meet capacity requirements, and ensure reliability within the network. The method used is known as "Multicommodity Flow Optimisation", and involves determining all information relating to demand, costs and reliability, and then using this information to calculate an actual physical circuit plan.
These steps are interrelated and are therefore performed iteratively, and in parallel with one another. The planning process is highly complex, meaning that at each iteration, an analyst must increase his planning horizons, and in so doing, he must generate plans for the various layers outlined above.