Mobile Handset Design

2

Problem Analysis in Mobile Communication System

2.1 Introduction to Wireless Channels

Apart from the transmitter and receiver circuit design issues, several other critical factors appear in the design of a mobile communication system, primarily due to the wireless channel and user mobility. A wireless channel is more complex than a traditional wired transmission channel, with lots of issues being involved in signal transmission through a wireless channel. Before discussing these issues in detail, first let us examine the basic working principles of a typical communication system. The information flow between two parties communicating is depicted in Figure 2.1. The information from the source is digitized, source coded (redundant bits are removed), passed through the protocol layers (where extra header bits are inserted), processed in the physical layer (channel coding, puncturing, interleaving, burst formation, etc.), modulated (converted into an analog signal), amplified, and sent via the channel. The signal propagates via the channel and finally reaches the receiver. The receiver receives the transmitted signal and reverses the operations to recover the source information. In this communication process, the channel plays a significant role, as its characteristics severely affect the signals that are propagated through it.

First let us try to understand how the signal transmission–reception process gradually becomes complex from a point-to-point – wire-line scenario to a multi-user ...