4G communication Technology----Series (2)
In March 2008, a set of requirements for the 4G standard was assigned to the International Telecommunication Union-Radiocommunication Sector (ITU-R), dubbed the IMT-Advanced specification, setting the peak speed of 4G services to require high-speed mobile communications Trains and cars) to 100 Mbit / s and fixed or low speed mobile communications (pedestrians and fixed-point users) up to 1 Gbit / s.
The first release of LTE (3GPP Release 8) and WiMAX (IEEE 802.16e) support peak bit rates much less than 1 Gbit / s, which are not fully IMT-Advanced standards, but many telecom service providers often advertise their 4G The internet. On December 6, 2010, ITU-R recognition, the two technologies, and other 3.9 technologies that do not match the requirements of IMT-Advanced can still be considered as "4G" provided they are pioneers that the IMT- The standard version of Advanced and improved performance and functionality point to just the equivalent of the 3G network now deployed.
Compared to previous generations, 4G systems do not support traditional circuit-switched telephony services, but full Internet protocol (IP) communications such as VoIP. As will be seen below, spreading the radio technology used in 3G systems discards all 4G candidate systems and replaces them with OFDMA heavy-carrier transmission and other frequency-domain equalization (FDE) schemes, potentially shifting very high The bit rate despite wide-spread multipath propagation. The peak bit rate is multiple-input multiple-output (MIMO) communication through a further refined smart antenna array.
However, the traditional telephone service (voice call) system business is also an important part. In the technology of 4G operators in Taiwan, all adopt the Circuit Switched Fallback (CSFB) technology to roll back the 4G LTE network to the 2G / 3G switched network Circuit-Switch Domain a mechanism. The technological evolution of equipment vendors, the availability of commercially available handsets and the coverage of network signals can be upgraded to VoLTE voice technology to provide the proper quality of 4G voice telecommunication services with clearer voice and video call quality, faster recall Continued speed.
Requirements for IMT-Advanced