文档介绍：全球無線通訊技術分析與未來趨勢
Yi-Bing Lin
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Doubts on 4G
At first glance, discussing 4G works seems ridiculous.
works are in a very painful phase of their development, with early trials yielding disappointing results, costs ballooning, technical glitches, work operators being forced to deflate expectations based on unrealistic buildup.
So why are we already talking about the next generation of works?
7/22/2017
2
WLAN & 3G Interworking: An Example (1)
Much is being made of the possibility of WLAN/3G interoperability.
Already we are moving toward a model in which WLANs in public and private "hotspots" will provide one to ten megabit/second bandwidth at very low cost, while works will cover wide areas with 30-100 kilobit/second bandwidth at fairly high cost.
The theory is bining the strengths of works will result in a range of services available to mobile users in all environments.
7/22/2017
3
WLAN & 3G Interworking: An Example (2)
But would today's work operators see a business justification to either invest in public-space WLANs, or open works to interoperability with WLANs owned and operated by others?
What sort of device would be reasonably usable on both a WLAN and a mobile work? Would end-users find this valuable and sensible?
 In other words, the engineering problems of this may be solvable, but the economic and business justifications for such work are plex.
7/22/2017
4
What is 4G – One View
works are only a concept. There are no standards under development, no real definition of what 4G will be.
Current consensus indicates that 4G will be a unification of different works, including wireless LAN technologies (IEEE , HiperLAN/2, HomeRF), public works (, 3G), and even personal works such as Bluetooth.
Under this umbrella, 4G calls for a wide range of mobile devices roaming across different types works - some using licensed spectrum and some not.
7/22/2017
5
What is 4G (1)
The roots of 4G lie in the concepts of "pu