Release date：2021-12-28Author source：KinghelmViews：264
With the continuous development of mobile communication network, operators have different frequency band resources of high, medium and low. Radio band resources are valuable strategic resources. How to make rational and efficient use of spectrum resources is the primary problem for operators.
At present, 2.1g and 3.5G bands are the mainstream bands for 5g network deployment. This paper compares the coverage performance of 2.1g and 3.5G from two aspects of link budget and field test, analyzes their differences in coverage performance and service bearing in detail, and demonstrates the defects of independent networking in 3.5G band and the improvement of subsequent networking efficiency by replanting 2.1g band. Combined with the current network situation of Shandong Unicom, this paper puts forward the corresponding construction strategy. It provides an important basis for the follow-up 5g network construction.
With the promulgation of 5g license, China's 5g network commerce began. The Ministry of industry and information technology authorizes China Unicom to use 3.5 GHz as 5g band. The 3.5G band has the best industrial support in the world. However, the 3.5G band has high frequency and faster signal attenuation. The deployment of 5g network based on 3.5G frequency band will need to add more base stations, and the corresponding base station equipment investment and supporting investment will also be greatly improved. How to build a high-quality and competitive 5g network at low cost has become an important issue in front of China Unicom.
With China Unicom and China Telecom starting to build and share 5g network, this opportunity has brought opportunities for the construction of 5g network. At present, China Unicom 3G network has 15 MHz bandwidth in 2.1g band, 4G network has 10 MHz bandwidth in 2.1g band, and China Telecom 4G network has 20 MHz bandwidth in 2.1g band. China Unicom and China Telecom have 45 MHz bandwidth in the 2.1g band. In addition, the remaining 10 MHz bandwidth in the domestic 2.1g band has not been allocated. If approved for use, China Unicom and China Telecom will have 55 MHz bandwidth in the 2.1g band. Radio band resources are valuable strategic resources. How to make rational and efficient use of 2.1g band and 3.5G band in 5g network is the primary problem considered by operators. Combined with link budget and field test, this paper compares and analyzes the coverage performance and service bearing of 2.1g and 3.5G frequency bands, analyzes their differences in coverage performance and service bearing in detail, and demonstrates the defects of independent networking in 3.5G frequency band and the improvement of subsequent networking efficiency by replanting 2.1g frequency band, Combined with the current network situation of Shandong Unicom, this paper puts forward the corresponding construction strategy, which provides an important basis for the follow-up 5g network construction.
Theoretical analysis of 2.1g and 3.5G band coverage
3GPP protocol stipulates that b42 band is 3.5G band, B1 band is 2.1g band, B3 band is 1.8g band and B41 band is 2.6g band. The wavelength of the 3.5G band is shorter than that of the 2.1g band, and the natural penetration, diffraction and diffraction capabilities of the 3.5G band are worse than those of the 2.1g band, resulting in insufficient uplink coverage on the terminal side.
Taking the B3 band (1.8g band) of the existing network as the reference point, calculate the link budget theoretical values of 1.8g, 3.5G, 2.1g and 2.6g bands respectively. Through the comparison of uplink budget results, it can be found that the uplink capacity of 3.5G band is 7.7 DB worse than that of 2.1g band (4t4r) and 4.2 DB worse than that of 2.6g band.
It can be seen that the uplink coverage of 5g network independently deployed in 3.5G band is poor compared with that in 2.1g band.
Measured uplink coverage capacity of 2.1g and 3.5G frequency bands
The base station in Gude square, Weifang Development Zone is selected for the test. Since there is no NR terminal supporting 2.1g at present, during the field test, 2.1g 4t4r LTE equipment and 3.5g 64tr NR equipment are deployed at the same station to conduct the field comparison test on the uplink coverage capacity of 3.5G and 2.1g frequency bands.
3.1 test parameter setting
a）2.1g 4t4r LTE equipment and 3.5g 64tr NR equipment are deployed in the same station, and the same hanging height, direction angle, downward inclination and other parameters are set. During the test, the coverage of the main test cell is expanded to more than 500 m by temporarily closing the surrounding base stations and adjusting the transmission power.
Table 2 physical parameters of test base station
3.2} test description
Test the coverage of 2.1g and 3.5G frequency bands. Select sectors with the same normal direction, hanging height, direction angle, downward inclination (including electronic downward inclination) and power spectral density of the main lobe of 2.1g and 3.5G frequency bands for testing. The relevant CQT and DT test route diagram is as follows:
Outdoor network road survey in continuous coverage area(DT test) requirements are as follows:
a）Two terminals are placed side by side on the table or seat in the vehicle, locked at 3.5 and 2.1 GHz respectively, and each initiates and maintains full buffer FTP uplink service.
b）The network management side records the uplink bottom noise and other information of the main test cell in real time during the test time.
c）The test vehicle shall carry the test terminal and road test tools to move slowly along the predetermined route (no more than 5 km / h), traverse the roads in the main test area, and the test time shall not be less than 1 h.
d）If the service drops, record the drop information, restart the data service nearby and continue the road test.
e）The road test software records the log data in the whole test process in real time as required.
During the deep coverage CQT test, no less than 7 buildings are selected as CQT test buildings from near to far in the normal direction of the main lobe of cells 3.5G and 2.1g according to figure 2 until the buildings are 500 m away from the base station or cannot be accessed.
a）Each building to be tested shall be tested on the high, medium and low floors respectively, preferably on the 1st, 3rd and 5th floors.
b）Two terminals are placed side by side. After frequency locking of 3.5 GHz and 2.1 GHz respectively, initiate full buffer FTP uplink service at the test points in each building, traverse the roads in the building and maintain the service for at least 1 min; If the access cannot be completed in the test building, record the test phenomenon in detail.
c）Keep the station height and dip angle unchanged, and rotate the two main survey cells clockwise by 30 DEG; (adjust the adjacent cell as needed), repeat step (b) at the original test location according to the same test route.
3.3 coverage capacity CQT measurement
The comparison results of 2.1g and 3.5G single cell uplink coverage CQT tests are shown in Figure 3.
According to the test results in Figure 3, in the case of cell coverage edge (LTE rsrp < - 105 DBM), the approximate coverage probability of 2.1g frequency band is 94%, and the approximate coverage probability of 3.5G frequency band is 31%. Under the condition of deep coverage, the rsrp value of 3.5G band in CQT test is 6 ~ 7 dB less than that of 2.1g band, indicating that the performance of 3.5G band is worse than that of 2.1g band in terms of deep coverage.
3.4 coverage DT test
In the analysis of DT test data, LTE 2.1g mobile phone and NR 3.5G mobile phone are in the same location / at the same time. In order to facilitate comparative analysis, the NR and LTE rates at the same location are normalized according to LTE rsrp.
Test the 2.1g and 3.5G frequency bands with the actual road coverage of the existing network, and select the sectors with the same normal direction, hanging height, direction angle, downward inclination (including electronic downward inclination) and power spectral density of the main lobe of the 2.1g and 3.5G frequency bands. DT test track results are shown in Figure 4.
Through the comparative analysis of road test data rsrp, the average level value of 2.1g frequency band test is - 97 DBM; The average level of 3.5G band test is - 105 DBM, and some test areas are seriously disconnected.
With the increase of coverage distance, the signal fading of 3.5G in non line of sight scenario is greater than 2.1g, and the signal strength difference between the two continues to increase with the increase of coverage distance. The data analysis is shown in Figure 5.
According to the data analysis in Figure 5, when the coverage distance is close, the difference between the signal reception strength of 3.5G and 2.1g in the sight distance scene is about 7 dB, and when the coverage distance is far, the difference between the signal strength of the two in the non sight distance scene is 14 dB.
In addition, 3.5G and 2.1g are analyzed from the cell edge coverage, as shown in Figure 6.
According to the analysis in Figure 6, when the cell edge speed is 1 Mbit / s, the received signal of 2.1g is - 115 DBM, while the received signal of 3.5G is - 106 DBM, lte2 1g and NR3 5 in the actual environment of the current network, the uplink coverage difference is 9 dB.
The uplink rate is compared and analyzed. When the signal strength is - 98 DBM, the uplink rate of 3.5gnr is significantly higher than that of 2.1g band.
4t4r 2.1g NR voice support capability analysis
Under the premise of the general principle of joint construction and sharing between China Unicom and China Telecom, the voice bearer scheme is gradually evolving towards vonr. In the NSA networking stage, it is flexibly allocated to the LTE network of China Unicom or China Telecom through volte. In the SA networking stage, it can fall back to the LTE network through EPS at the initial stage, and then smoothly turn on the vonr function in the 2.1g frequency band.
The voice bearer of volte and WCDMA networks is compared and analyzed. By analyzing MOS value and rsrp data, it can be found that the voice quality of vonr in 2.1g band is stronger than that of WCDMA network.
2.1g and 3.5G application suggestions
According to the previous analysis, the 2.1g band can effectively enhance the capacity and coverage of the 3.5G band, but the 2.1g band bandwidth is not as rich as the 3.5G band bandwidth resources, and the 3.5gnr equipment industry chain is relatively mature. Through comprehensive analysis, the applications of 2.1g and 3.5G frequency bands are summarized and analyzed as follows.
a）Since the 2.1g NR equipment industry chain is not mature, it is recommended to take the 3.5G network as the base network at the initial stage of 5g network construction to realize continuous coverage. In the follow-up, accelerate the frequency reduction and de frequency of 2G and 3G networks, timely re cultivate the 2.1g frequency band, and cooperate with high and low frequencies to create differentiated 5g networks.
b）5g network adopts mixed networking of 2.1g and 3.5G frequency bands, which is an important idea for building high-quality 5g network. 2.1g band can provide uplink capacity supplement and in-depth coverage extension. It can flexibly network according to construction needs, improve user perception and enhance the brand influence of China Unicom.
c）3G / 4G / 5G hybrid module network can use the existing network equipment software to upgrade and open 5g service. While reducing the 5g network construction cost, it can deeply tap the existing network equipment capacity and maximize the utilization of resources. At the same time, it also provides preconditions for the subsequent network structure adjustment.
This paper compares and analyzes the coverage performance of 2.1g band and 3.5G band from two aspects of link budget and field test. The signal attenuation of 3.5G band is large, and the performance of 3.5G band is worse than that of 2.1g band in terms of deep coverage. At the same edge rate, the uplink coverage of 3.5G band is 9 dB worse than that of 2.1g band. Through theoretical analysis and field test, it is found that 2.1g band can effectively enhance the capacity and coverage of 3.5G band. 5g network can adopt the mixed networking of 2.1g and 3.5G bands, which can enhance the uplink coverage capacity and meet the uplink capacity and delay requirements of 5g industry applications. The 2.1g frequency band and equipment of the current network can be replanted to 5g, which can improve the construction speed of 5g network, reduce the investment of construction resources and reduce the construction difficulty. It is an important means to improve the construction efficiency of 5g network.
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