LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Evolution of Wireless Networks

Table 1.1. summarizes the history of cellular networks. Through the generations, emphases have been made on different design objectives, ones that best served the requirements of the time.

Interest in the First Generation (1G) cellular, for example, focused on mobilizing landline telephony. The outcome networks, Advanced Mobile Phone Systems (AMPS) and Total Access Communication Systems (TACS), were circuit switched with analog voice transmission over the air. A definite drawback of analog transmission was a generally degraded quality and an extreme sensitivity to basic mobility and medium conditions. Hence, the main design objective in Second Generation (2G) cellular networks was to enhance voice quality. The standards responded by replacing analog voice transmission with digital encoding and transmission, immensely improving voice communication. Improvements to the network core also facilitated the introduction of basic digital messaging services, such as the Short Messaging Service (SMS). The two main standards comprising 2G networks were Global System for Mobile Communications (GSM) and Interim Standard 95 (IS-95), commercially called (cdmaOne). GSM relied mostly on Time Division Multiple Access (TDMA) techniques, while cdmaOne, as the name suggests, utilized Code Division Multiple Access (CDMA). Such division, in addition to variation in the spectrum bands utilized for deployments in different regions, would mark a characteristic interoperability ...