ZTE Aids China Telecom in CDMA Network Optimization

With the consolidation of telecom operators and the issue of 3G licenses in China in 2008, a new round of telecom network construction has begun in full swing. The competition in the telecom market becomes very fierce, and telecom operators will be more concerned about the network quality, user experience, and 3G network services.
In Phase 1 project of China Telecom, ZTE was tapped to construct over 15,000 sites in nearly 200 service areas, which includes both constructing new CDMA sites and swapping old CDMA sites of China Unicom. Constructing a top-quality CDMA network within a very short period for China Telecom is a challenge confronting ZTE.
Before China Telecom took over China Unicom’s CDMA business, the equipment was outdated and was unable to satisfy future service requirements, neither can it adapt to the network upgrade and evolution trend. Moreover, the network maintenance was very slack. After the takeover was completed, China Telecom encounters many problems: The chronic faults in some sites remain unsolved, affecting coverage of the corresponding area; the directional and downtilt angles of the antennas have changed after being exposed to the weather for a long time, weakening the coverage and resulting in pilot pollution in other areas; the parameter settings in several sites are incorrect, leading to site operation abnormalities.
During the network replacement, ZTE not only needs to solve various problems in the old network, but also has to construct a new 3G network. Providing network optimization service for 15,000 sites in more than 200 areas is a challenging task. It not only needs enormous human and material resources but also efficient network optimization skills.

Formulating the Network Optimization Policies
ZTE’s network optimization team divides the CDMA network optimization task based on the following several stages:
Stage 1: Collect information on the existing network and evaluate it. Collect and verify site information of the existing network, and check the configuration parameters of the existing network (involving nearly 30,000 sites and 2.5 million parameters). Test the existing network and analyze drive test data and OMC performance data to detect problems in the existing network and put forward corresponding solutions.
Stage 2: Plan the parameters of the new network. During this process, ZTE needs to guarantee smooth transition during network swapping and to revise the settings of parameters that had been wrongly configured in the original network.
Stage 3: Implement optimization after network swapping and commissioning of new sites. Implement engineering optimization immediately after the completion of network swapping, for example, single site check, and RF optimization, neighbor cell optimization, and network parameters optimization so that the KPIs of the new network are better than those of the original network. At the same time, optimize the newly commissioned sites so that the network capacity and coverage quality can be further improved.

Making Network Optimization Flows for Network Swapping and Capacity Expansion
A rational work flow can greatly minimize the risks of a project and reduce unnecessary workload. To guarantee the network optimization quality in the Phase 1 project, the network optimization team develops a unified project implementation flow based on the common attributes and special features of the network optimization tasks in the Phase 1 project, in order to ensure rapid and efficient network optimization in each province.
The project implementation flow created by the network optimization team consists of two main tasks: network swapping and capacity expansion. The network swapping task involves reconfiguration of the parameters of the original network before network swapping, and evaluation of the network before and after network swapping. The capacity expansion project involves the replacement of HIRS BSC and rearrangement of the PNs in overall network. However, the key flows of the two tasks are the same: parameters planning for newly-constructed sites (CDMA1X and EV-DO), new sites commissioning, and engineering optimization.

Separating Technical Coordinator from Management Coordinator
The project team separates the technical coordinator from the management coordinator and sets up a technical support team to collect and analyze problems and summarize technical experiences. On one hand, this mechanism improves technical problem handling speed and experience sharing; on the other hand, the mechanism clarifies the responsibility assignment among project coordinators and allows the project team to get better technical support from the headquarters. The project is divided into several regions and the daily project management and coordination is performed on the basis of a region. Each region is assigned a regional manager who is responsible for controlling the project progress and quality based on preset milestones. 

Developing and Utilizing Efficient and Secure Network Optimization Tools
During the project implementation, the project team has encountered a wide range of thorny problems, for example, how to quickly make a new plan for PNs in the expanded network; how to quickly and reliably implement the PN plan; how to plan parameters of newly constructed base stations and neighbor cells and how to import these parameters into the OMC. To tackle these problems, the network optimization team has developed tools to improve the network optimization efficiency. The tools allow many tasks to be finished off-site, guaranteeing quality and reducing risks involved in on-site operations.
Take the parameter conversion tool as an example. In China Telecom’s Phase 1 project, the first task was to substitute IP addresses of 164 HIRS BSCs in 86 areas. The substitution process involves conversion of more than 30,000 BTS parameters and neighbor cell parameters. If the project team finishes the task manually as was done in the past, the workload would be enormous. Furthermore, the data consistency cannot be guaranteed during the conversion process. To tackle the problem, the network optimization team has developed a parameter conversion tool, which can convert multiple parameters by using various algorithms. As a result, the parameter conversion in all areas proceeded quickly and securely.
After the use of the network optimization tools, the network optimization efficiency has been improved substantially.
Before the use of the tools, in a network swapping project in 2007, swapping 401 BTSs in five cities of China took nearly four months. The network optimization team had invested 265 person days in the project, averaging 1.51 BTS per person day.
After the use of the tools, in a network swapping project in Guangxi Province in 2008, swapping 1363 BTSs in seven cities took less than two months. The network optimization team had invested 274 person days in the project, averaging 4.97 BTSs per person day. The network optimization efficiency had improved by 3.29 times.
By the end of March 2009, after five month of nationwide CDMA network optimization, the project team had solved various problems found in the original network, and the network KPIs in all areas had improved significantly.
Take the network in Sichuan Province as an example. Before China Telecom’s Phase 1 project, there were more than 4,000 BTSs in the network in Sichuan Province. Within four months, the project team had swapped all the BTSs in the network, including swapping 2,000 Ericsson BTSs, upgrading HIRS BSCs into All IP BSCs, commissioning 2,500 new sites and over 1,000 EV-DO BTSs. The project team had finished BTSs swapping and new sites commissioning within merely four months, guaranteeing smooth network transition. After the network swapping, the network KPIs have been greatly improved:

The call success rate increases from 97.5% to 99.3%; the call drop rate decreases from 0.8% to 0.2%. Figure 1 and Figure 2 compare the network KPIs in Chengdu before and after network swapping and before and after network optimization. 

Through network optimization, ZTE has presented a brand new CDMA network to China Telecom and laid a sound foundation for China Telecom to attract and keep users amidst the fierce 3G competition.