When it comes to the high-speed data communication network, it is not possible to not mention the wireless LAN 802.11wLAN and the hot 3G currently speculated. The three representative systems are WCDMA, CDMA2000, and TD-SCDMA. Compared with the former, WiMAX has a larger coverage, compared to the latter, WiMAX can provide a higher transmission rate, no wonder it is so optimistic. So how does WiMAX achieve these two technical ideas? It is first to warm the principle of communication. According to the law of Shennong, any bandwidth is a channel of H Hertz, the signal-to-noise ratio is S / N, and its maximum data transmission rate is: maximum data transmission rate (b / s) = hlog2 (1 S / N) actual bandwidth should It is the maximum data transfer rate in multiplying bandwidth utilization. It can be seen from here that there are three methods for increasing the actual bandwidth: the first is to increase the utilization of bandwidth, such as from the pure Aloha system to the fragmentation ALOHA system in the carrier listening multi-channel access protocol CSMA / CD, its largest channel The utilization rate can reach 1 / 2E, 1 / E, and 0.85. WiMAX is useful to improve channel utilization with respect to the currently widely used CDMA technology. The second is to increase the frequency, and the telephone line is used as a transmission medium. The dial-up speed is only 56K, and the ADSL can reach a number M. The root cause is ADSL uses a higher frequency band. The third is to increase the signal-to-noise ratio, but it can be seen from the above, the signal-to-noise ratio is log operation, then increases the contribution of signal-to-noise for system bandwidth. It can be seen that the increase frequency is the most direct effective way to increase bandwidth. For example, the current mainstream WLAN uses 802.11b standard, the standard specifies that the WLAN operating frequency section is 2.4GHz ~ 2.2.4835GHz, and the data transfer rate reaches 11Mbit / s, and the WLAN operating frequency section is 5.15GHz ~ 5.825GHz, data transmission rate. Reach 54 Mbit / s or 72Mbit / s. In WiMAX technology, 802.16d standard uses in the wireless metropolitan area network, using less than 11G operating frequency band, data transfer rate reaches 75Mbit / s, and 802.16e standard, use in mobile wireless LAN, operating frequency segment is 2 ~ 6GHz, The data transfer rate reaches 30 mbit / s. Combined with mobile cellular technology, the main idea of WiMAX technology is more clear, it uses high frequency sections and high-emission power to achieve higher bandwidth than traditional mobile phones, larger coverage than WLAN technology. Of course, there must be a lot of technical problems that need to be resolved, but it seems that WiMAX technology is not as the sympathy of the epoch. So, how is this technology application prospect? One technique in the market is often not determined by the advanced nature of its technical, and the activities of the main body in the market may have more significant. For communication technologies, end users' needs, operators' attention, and equipment manufacturers' industrial chain, social factors, and social factors affect the application of the technology to produce decisive effects. Wide applications for WiMAX technology may encounter as follows: The first is the spectral problem. There are two main options, one is a 5G frequency band similar to WLAN, but the frequency band is used as a common channel, and the interference problem is relatively serious. In addition, Intel deliberates the frequency band of 2.5g to 2.69g, but this band and the frequency band expected to divide 3G are relatively close.
