Handsets are commanded to transmit at a higher power level when their received power is low, such as when they are far from the base station. Additionally, handsets are commanded to transmit at a lower power level when their received power is high, such as when they are near the base station. The traditional design process for many new products, such as cellular equipment, often starts with the creation of a high-level diagram or schematic for the whole system. Specifications for each component and the interfaces between them are usually documented on paper. Low-level tools such as PSpice products are slow in terms of development and simulation, and as a result, engineers only perform limited testing of the components before implementing prototypes.
Problems can arise due to ambiguous and miscommunicated specifications.
In particular, unforeseen interactions can occur among the analog, digital, or control logic components, and can prevent the whole system from meeting its specifications. Designers can split the design into components to be worked on by each team member. With system-level design, designers can perform global optimizations by trying many different solutions. Block diagrams let designers accurately model the concurrency of the multiple components and the complex timing relationships present in any real system. Once the components have been designed and tested individually, engineers can integrate them together and test the whole system to create a validated design.