Tham khảo tài liệu 'mobile and wireless communications physical layer development and implementation part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Joint Cooperative Diversity and Scheduling in OFDMA Relay System 211 rates expanded range and more features. 2G networks saw their first commercial light of day on the global system for mobile GSM standard. In addition to GSM protocol 2G also utilizes various other digital protocols including CDMA TDMA iDEN and PDC. Afterwards wireless technology was established as a stepping stone that bridged 2G to 3G wireless technology. 3G technology was introduced to enable faster data-transmission speeds greater network capacity and more advanced network services. The first precommercial 3G was launched by NTT DoCoMo in Japan in May 2001. Actually wireless mobile communications have become very persistent. The number of mobile phones and wireless internet users has increased significantly. The growth of the number of mobile subscribers over the last years led to a saturation of voice-oriented wireless telephony. From a number of 214 million subscribers in 1997 to 4 billion cellular mobile subscribers in 2008 Acharya 2008 . However modern cellular networks need to provide not only high quality voice service for users but a large amount of data transfer services as well. Users want to be connected with the networks not only for making voice conversations anytime and anywhere with people but also for data downloading uploading. It is now time to explore new demands and to find new ways to extend the mobile wireless concept. The evolution of 3G mobile networks will be followed by the development of next generation mobile networks called 4th generation 4G or beyond 3G mobile phone technology. 4G refers to the entirely new evolution in wireless communications and will support extremely high-speed packet data service 100M-1Gbps Adachi Kudoh 2007 as shown in Fig. 1. Fig. 1. Wireless mobile communication network evolution. Although 4G wireless communication systems are expected to offer considerably higher data-rate services and larger coverage areas compared to these older .
