专业英语论文.doc

专业英语论文.docHandoffs in Fourth Generation works
As mobile works increase in popularity and pervasiveness, we are faced with the challenge bining a diverse number of works. The fourth generation of munications is expected to integrate a potentially large number of heterogeneous wireless technologies in what could be considered a huge step forward toward universal seamless access. Efficient handoff schemes enhance quality of service and provide flawless mobility. This article presents different and novel aspects of handoff and discusses handoff related issues of fourth generation systems. Desirable handoff features are presented. Handoff decisions, radio link transfer, and channel assignment are described as stages of plete handoff process.
First, second- and third-generation mobile systems depended on the employment of the radio spectrum that was either unlicensed (available for public use) or licensed for use by a very small number of service providers work operators in each region. Differences in bandwidth and coverage areas have led to the necessity of developing work interface devices (terminals) that are capable of using the variety of work services provided.
The fourth generation (4G) of munications is expected to integrate a potentially large number of different heterogeneous wireless technologies in what could be considered a huge step forward toward universal wireless access an