Network optimization of CDMA

In general, the process of CDMA network optimization is divided into three stages: single base station configuration confirmation, community optimization and system-wide optimization (or global optimization), each phase completes different tasks.

Single Base station configuration confirmation

The goal is to confirm the installation integrity of the BTS and the accuracy of the data. The verification parameters include:

(1) The Base station equipment debugging: the base station equipment debugging includes the base station initial data loading, the base station equipment launch parameter test and the equipment basic performance parameter test and so on.

(2) Mutual interference between systems: the majority of CDMA base stations and GSM base station common site construction, at this time the mutual interference between different system sites must exist, so that the receiver sensitivity reduction, overload or intermodulation interference, and ultimately lead to the degradation of the system performance. Therefore, we must consider the antenna isolation between the two base stations.

(3) Antenna configuration: First of all, if the use of space diversity to receive the antenna, should consider the space between the antenna can meet the requirements, the general use of horizontal diversity, the distance of about 2-5 meters; Secondly, the height and azimuth angle of the antenna is also the focus of the inspection, the verification is consistent with the design; Some antennas may be blocked by buildings, the antenna height and inclination should be adjusted in time, and the planning database should be updated. After calibration of the above parameters, we need to open the base station for spectrum monitoring and simple test-call function to verify that the spectrum is clean enough, the hardware and software, configuration and transmission of each base station is incorrect. The verification work mainly includes the following contents: Fixed → mobile call, mobile → fixed call, mobile → mobile call, sector and PN Bias Index, reception signal strength, signal-to-noise ratio and the switch between the base station sector and adjacent base station fan zone. (Computer science)

Local area optimization

The local area should have at least one central cell with a two-layer surround cell to provide sufficient forward channel interference and can generate actual switching boundaries near the central cell and the first layer surrounding the cell. The goal of local area optimization is to optimize the neighborhood table and switch relationship of the Central District, and confirm the coverage. The adjustment parameters are as follows:

Antenna adjustment

The antenna pattern can be either omnidirectional or directional on both horizontal and vertical planes. The antenna gain can compensate for the power loss of the transmitted and received signals, and the base station antenna height will affect the area and shape of the area covered areas, and the downward tilt of the antenna can reduce the interference to the adjacent cell and increase the coverage of some blind spots in the community, The basic idea of the antenna tilting is to tilt the radiation main lobe of the antenna to a specific angle to reduce the power level of the site to reach the multiplex, thereby reducing the interference of the fellow.

Toggle Threshold

Changing the switching threshold parameter can increase or decrease the proportion of the switching region, it mainly includes four parameters: T-add (when switching to add pilot signal to noise ratio threshold), t-drop (switching to discard the pilot signal to noise ratio threshold), t-tdrop (switch when the pilot dropped timer length), t-com ( The pilot strength of the switch is compared with the threshold value.

Overhead channel transmit power

Overhead channel transmitting power refers to pilot channel power, synchronous channel power and paging channel power. The power of pilot channel has a direct effect on the size of the forward cell radius. In the initial stage of construction, due to less traffic, the large CDMA network coverage radius is required. At this point, we can consider increasing the total transmit power, and also consider increasing the percentage of the overhead channel transmitting power to the total power.

Full-Domain optimization

After the optimization of the last stage, the whole domain optimization is basically determined by the blind area and the switching region, at this time, all the cells are activated and the system optimization is started. It is in a full set of sites in the antenna and RF parameters in a more realistic environment for the final optimization, all sites use OCNS (Orthogonal channel noise source) simulation forward link business. There is a new understanding of overlay and switching, at the same time, to solve the problem of system-wide interference. After optimization, the neighborhood and switch parameters are finalized, the hardware configuration changes are defined, and the network is ready for acceptance testing.

CDMA network optimization is a repetitive cycle process, in the formal commercial operation of CDMA network, it is necessary to continue to debug system parameters to adapt to unbalanced traffic distribution (such as business volume concentration area, special traffic pattern, etc.) and other dynamic effects which are not easy to be predicted or imitated by simulation business load.