Although 4G has been licensed in China, the large-scale network construction has just begun. Facing the explosive growth trend of mobile data, it is necessary to continuously improve network capacity and network construction quality. However, the dispersion of 4G frequency, the increase of interference, and the need to share the site with 2G and 3G base stations are driving the development of base station antenna to the direction of higher integration, wider bandwidth and more flexible adjustment.
4G network coverage capacity
A good network coverage layer and a certain thickness of capacity layer are the two bases to determine the network quality.
A new national network should consider the construction of network capacity layer while completing the coverage target. "Generally speaking, there are only three ways to improve the network capacity," Wang Sheng, sales director of China wireless network solutions of CommScope's wireless business unit, told China electronic news
One is to use more frequencies to make the bandwidth wider. For example, GSM initially only had 900MHz frequency. Later, users increased and 1800MHz frequency was added. Now 3G and 4G frequencies are more. China Mobile's TD-LTE frequency has three bands, and the frequency of 2.6GHz has been used. Some people in the industry believe that this is the limit, because the high-frequency attenuation will be more and more severe, and the input and output of equipment are out of proportion. The second is to increase the number of base stations, which is also the most commonly used method. At present, the density of base stations in large and medium-sized cities has been reduced from an average of one base station per kilometer to one base station of 200-300 meters. The third is to improve the spectrum efficiency, which is the direction of every generation of mobile communication technology. At present, the spectrum efficiency of 4G is the highest, and it has reached the downlink rate of 100m in Shanghai.
Having good network coverage and a certain thickness of capacity layer are two important foundations of a network. Obviously, China Mobile's positioning for TD-LTE is to create a high-quality network and stand at the top of 4G market with high-quality user experience. "We are involved in the construction of most of the 240 LTE networks in the world." "From the experience of CommScope, there are five elements in LTE network construction. The first is to manage the network noise; the second is to plan and control the wireless sector; the third is to modernize the network; the fourth is to do a good job in the return signal, that is, the bandwidth of the uplink signal and downlink signal should be wide enough; the fifth is to do a good job of indoor coverage and coverage under the special environment of venues
Technical details of noise management test
It is a real problem to manage the noise level and make the network edge users have high-speed access.
Different from 3G signal enhancement by increasing the transmission power, 4G network will bring new noise with the enhancement of signal. "The characteristic of 4G network is that the noise not only affects the sector covered by the antenna, but also affects the surrounding sectors. For example, it will cause more soft handoffs, resulting in a high packet loss rate. The performance is that the data transmission rate is reduced, the user experience is reduced, and the revenue is decreased." Wang Sheng said, "the farther the 4G network is from the base station, the lower the data rate is, and the closer the 4G network is to the transmitter, the more resources users can get. We need to manage the noise level, so that the network edge can get high-speed access, which is the problem we really need to solve." To solve this problem, there are several requirements: first, the bandwidth of the RF part should be wide enough; second, the equipment performance of the entire radio frequency network should be good enough; third, the bandwidth of the uplink signal returned should be wide enough.
In the traditional 2G network, the network coverage overlap of adjacent base station cells is relatively large. Mobile phones can receive signals from different base stations. 2G mobile phones will automatically lock in the base station with the strongest signal, ignoring others. Because it will not switch frequently, it will not cause any interference to the next cell. Therefore, in GSM network, there are 9 to 12 overlapping areas that can be tolerated. However, in the 3G period, the overlapping coverage of the network will have a greater impact on the processing capacity of the system. Now, the antenna with 65 degree horizontal half angle is used for three sector coverage. The three sector coverage of LTE needs high-performance antenna to be done in the same way as 3G. "The so-called high-performance antenna means that when doing 65 degree antenna coverage, the coverage on both sides of the network shrinks very fast, making the overlapping area between networks smaller. Therefore, we can clearly see that LTE networks have higher and higher requirements for equipment." Wang Sheng said.
Frequency division independent electrically tunable antenna is becoming more and more important
It is necessary to control the edge of network waveform accurately to reduce inter station interference. The best way is to realize remote antenna control.
To solve the interference control of the network, mainly depends on several aspects: first, network planning, leaving enough margin in frequency; second, device level, each construction process should be well controlled; third, installation level. "We entered China in 1997 and made a lot of practical cases. At Andrew college, which specializes in antennas, we will do training to teach them how to install and use our wireless products. At the same time, we also have a team to make connectors and antennas. " Wireless products, especially outdoor products, have the worst working environment in the whole communication system, facing wind, sun, rain, high temperature and low temperature, so the requirements for it are very high. "Our products can stand there for 10 to 30 years. It's really not easy." Wang Sheng said.
In addition to self interference, there is also inter station interference. In order to reduce the inter station interference, the network wave should be