When users use 2G and 3G networks, their main requirement for network quality is whether the quality of calls is stable. However, with the popularity of LTE network technology, many network users are more concerned about the speed of network downloads. The download rate of the network can affect the user experience. Therefore, the download rate of the network can more directly reflect the awareness of LTE network users about the network. The main reasons for optimizing and analyzing the network for low download rate of LTE network are According to the statistics, problems and many factors in the LTE network may ultimately affect the download rate. Therefore, locating and handling the problem of low download rate in the LTE network is the key to optimizing the LTE network.
1. Analysis of the low download rate of LTE network
The low download rate of the LTE network is mainly manifested in two aspects: the first is the low transmission efficiency of each RB; the second is the low scheduling rate of the PRB. These two factors can affect the download rate of the LTE network individually or simultaneously. Among them, network problems can lead to low transmission efficiency per RB, so the optimization of network problems is also a focus. The main factors causing the low PRB scheduling rate include scheduling algorithms, concurrent users, etc. Network optimization does not play a big role in this type of factors, so this type of problem will be briefly explained. The factors causing low download rate are divided into two types: low transmission efficiency per RB and low PRB scheduling rate, and detailed analysis is conducted, focusing on the weak coverage and low SINR factors that affect the quality of wireless links. Finally, we find out The fundamental factors leading to low speed.
1.1 Factors causing low download rate Low transmission efficiency per RB LTE network relies mainly on terminal feedback channel quality, information RI, CQI and other data to configure the transmission mode TM and modulation coding scheme MCS, etc., and finally uses RRC signaling for transmission For the terminal, the high or low transmission efficiency of each RB is mainly affected by the wireless link selection of the transmission mode and modulation and coding method. A low dual-stream ratio and low MCS level will result in low transmission efficiency per RB, which means that this wireless transmission line is unstable. Therefore, when this unstable situation occurs, the downlink channel quality should be optimized in time to increase the download rate.
1.1.1 Low download rate caused by coverage factors Good network coverage is the basic condition for judging the quality of network performance. RSRP can measure the coverage of the network, and the coverage strength is measured by RSRP. RSRP is mainly the average signal rate received by all REs on the ReferenceSignal within a certain measurement frequency bandwidth within an individual Symbol. RSRP can reflect the coverage status of the rough LTE network. When RSRP is lower than a specific threshold, it is defined as weak coverage. Low RSRP leads to low SINR, which affects the selection of TM and MCS, thereby reducing the download rate. Therefore, the low download rate is mainly caused by weak coverage. Therefore, to increase the download rate, improving coverage becomes the primary choice. There are many factors that lead to low coverage, and a lack of base stations is one of the more common factors.
1.1.2 Problem Factors Leading to Lower Rate Interference Factor The ratio of effective signal power, interference signal and noise power is called downlink SINR. This ratio can intuitively reflect the current interference situation of the network. The downlink SINR at the user end is mapped It is converted into CQI and fed back to the network side. At a section of the network, the transmission mode and MCS level are determined based on the calculation method provided by the CQI to determine the download rate. Therefore, there is a direct relationship between the SINR value and the download rate.
When the SINR of a sampling point is low, the average download rate at that point is also relatively low. As the SINR value increases, the average download rate also increases accordingly, and the two data show a linear relationship as a whole. Therefore, if you want to increase the download rate, improving SINR becomes the primary consideration. Through analysis, it can be seen that low SINR is caused by interference with the network structure. In addition to low SINR caused by the above factors, factors such as overlapping coverage, redundant coverage, mobility issues and external interference can also cause low SINR. Overlapping coverage is also an important factor leading to low SINR. Overlapping coverage will occur due to various factors such as ultra-high stations, ultra-near stations, uneven distribution of base stations, etc. There are also some areas where there are very few signal sources and have not yet reached the level of overlapping coverage. However, if the cell signal segment is close to the signal value of the neighbor, it will cause interference to each other. At this time, the sINR of this area will also be #- /E is bad.
Looking at the relationship between overlapping coverage and download rate in the same city, it can be concluded from observing the curve that when the overlapping coverage is less than 3, the download rate reaches more than 15Mbit/s, so when the overlapping coverage continues to increase, the corresponding average download rate begins to decrease, and there is an inverse relationship between overlap coverage and average download rate.
Frequent movement can also cause low SINR. Unreasonable parameter settings for mobility management may cause the terminal to switch to the optimal area in time. At this time, even if the signal strength in this area can be maintained at a very good level, due to the current optimal cell emitted The signal will cause serious interference to the serving cell, which will also reduce its download rate.
1.2 Low PRB scheduling rate leads to low download rate PRB (physical resource module) refers to the basic unit of downlink physical resource allocation. The base station performs certain calculations by using information such as business priority, wireless link quality, number of concurrent users, and user data volume. Calculation to allocate physical resources to different users. At the same time, the quality of the wireless link can reduce the PRB scheduling rate, which will also cause a reduction in the RB transmission rate.
2. How to deal with low download rates
From the above analysis, it can be concluded that the main factors affecting the underground download rate include: weak coverage, low SINR and low PRB scheduling. Among them, weak coverage and low SINR are important indicators for measuring wireless link quality. We use the data from a road test in a certain city as the basis for analysis, and use the above three factors to collect data for statistical analysis. The factors causing low rates are classified by sampling points, and 27.9% of the factors causing low rates are caused by weak coverage. At the same time, by analyzing the factors causing weak coverage, it can be known that the proportion of comrades who lack base stations is 15.76%. For this factor, it is recommended to add base stations or adjust the antenna azimuth angle to improve the overall coverage of the base station, mobile Sexual problems accounted for 7.3%, and access room problems accounted for 4.83%; from the data point of view, the second largest factor causing the low rate of sampling points is low SINR, accounting for 24% of the proportion of low efficiency. 52%.
Through the analysis of the causes of low SINR, the factors causing low SINR of 11.69% are overlapping coverage and redundant coverage accounting for 1.47%. Factors in this aspect can be improved by optimizing the coverage area and adjusting its transmit power. . The proportion of mobility problems is 7.66%, and the proportion of other factors causing low SINR is 3.69%.
In addition, low PRB scheduling and low transmission efficiency per RB are also factors directly causing the low rate, accounting for 39.48% and 5.82% respectively. There are other factors that cause the proportion of low-rate comrades at the sampling point to be 2.13 %. Through the above summary, combined with the analysis method in the previous section, we can conduct classified cohabitation data analysis on all low-rate sampling points in the city, and specifically determine the proportion of each factor, and we can intuitively find out the reasons for the low speed of the LTE network. Download rate gets where the factors are.
3. Conclusion
The primary criterion for measuring LTE network user experience is the download rate. Currently, the overall load of the LTE network is still very low. As the number of LTE user groups increases, the data burden of the LTE network will increase rapidly, which will also have an impact on the download rate. More impact. This article proposes a method to analyze the problem location that causes low download rates in LTE networks, and uses actual drive test data to test the practicability of this method. In the future LTE network optimization, we can use low download rate factors to find out the factors causing low rates to improve the performance of the LTE network and improve the user experience.Related keywords: 4G industrial router
Author of this article: Han Yuanbin