Optimization of CDMA network

Mobile communications network is a constantly changing network, network structure, wireless environment, users distribution and use of behavior is constantly changing. Meanwhile, the expansion of network size, the size of the complex network coverage planning, network traffic model and business model changes, can lead to network performance and operation of the current deviation from the original design requirements, which require network optimization to continually the network to adjust to the changes, so the network optimization is a long-term sustainability of systems engineering, need to constantly explore, the accumulation of experience; only solve the problems arising in the network, optimizing network resources, improve network operating environment, improve the network operation quality, to make the network run in the best condition for the rapid development of mobile communication services to provide strong technical support and network support. Therefore, the meaning of network optimization is to increase network investment returns and improve operational efficiency of the network to improve the operation of the network quality, improve network quality of service, in the original network is no longer based on the premise of large-scale investment to fully enhance the network quality and capacity. This is the actual network maintenance are very important practical significance, but also optimize the network conditions in the short term, an important method to improve network quality.


1 the basic concepts of network optimization, network optimization goals

1.1
the so-called network optimization, one is there to run on the network coverage is not good, and poor call quality, call in a difficult connected, dropped calls, network congestion, handover success rate is low and data services to be addressed such issues as poor performance, enabling network operators to achieve the best state; on the other hand, but also by optimizing the allocation of resources, network resources and reasonable allocation of the overall and use to meet the needs and development of the situation, play equipment, the maximum potential for maximum investment returns. Therefore, the main purpose of network optimization is put into operation through wireless networks for data collection and analysis, identify the impact of network resource utilization is not high quality and the reasons for, and then adjusting parameters through technical means or operating state of the network to achieve the best so get the best benefits of network resources; and we understand the network's growth trend, provide the basis for the expansion. Therefore, the network optimization is the actual operation of mobile communication systems is an important process of job content.


1.2 Content
network optimization network optimization is a network development throughout the whole process of long-term work, but also a system work, including a series of optimization methods, including coverage optimization, traffic optimization , equipment optimization, interference signal analysis and optimization of use of funds. To solve the problem of network optimization to improve the hardware environment and software environment. "Hardware optimized" mainly includes the antenna optimization and optimization of equipment failure and so on. "Software Optimization" mainly refers to the frequency optimization, wireless parameter adjustment and verification of configuration parameters and so on.


2

network optimization analysis of network optimization network optimization analysis is an important part of the work, only the drive test, system acquisition and other aspects of network access to a comprehensive test data analysis system to the operational status of the network to assess and measure of network fault diagnosis and location, so as to further provide the basis for the development of network optimization measures. Here are some routine maintenance in the analysis of the main contents of network optimization:

2.1
dropped calls dropped calls of mobile communication is interrupted, it is a serious network failure phenomenon, drop rate is to assess the performance of CDMA systems is an important indicator, usually caused by signaling analysis to determine the direct cause of dropped calls is not difficult, but to determine the underlying causes of dropped calls caused by the test data must be carefully analyzed.

Under the agreement, during a call between mobile stations and base stations need to close the signaling exchange, if for some reason caused by failure of signaling exchange, the mobile station to adjust its transmitter is not the correct result, or re-initialization or idle, the mobile Taichung maintains a timer to limit the permit so as to receive the bad frame of time duration. When the timer expires, the mobile station transmitter will be shut down and return to the initial state, so that had dropped calls.

2.1.1 Mechanism of the mobile station dropped calls or bad frame
mobile station: the mobile station receives a bad frame 12 will be closed after the launch, receive two consecutive good frames will re-activate the transmitter.

Decline of the mobile station timer: T5 timer to decline, the mobile station fired off, and before the announcement to the traffic channel is lost.

Mobile station confirmed that failure: the mobile station sending a message not received MIN times confirmed that the mobile station re-initialized.

2.1.2 Mechanism of the base station dropped calls
wireless equipment manufacturers could develop a bad frame and the mobile station and base station confirmed that failure mechanism is similar to the bad frame and confirmed failure mechanisms that the implementation of the decision by the manufacturer, in agreement in the absence of detailed provisions. CDMA2000 agreement, base stations need to continue to monitor each reverse traffic channel to determine whether the call is active. If the base station detects that the call is not activated, the base station to determine the reverse traffic channel is lost, the base station to send the release command to the mobile station, once the base station sends a release command, then all the call control instance to send the release command, and enter the release of sub-state .


2.2 Access Failure Analysis
when the mobile station when it is dialing a phone number to initiate a call; initiated by the wireless network users call into the mobile station to the fixed network and mobile station call to the mobile station call. If the specified time, call setup process could not connect the caller and the called party entering into this situation to become an access failure. Send a message from the mobile station after the call, through the following five key steps to complete the business connection.

Step 1: the base station must receive a message from the call to confirm that the paging channel to send the confirmation message.

Step 2: the base station must be allocated to the mobile station after the traffic channel, paging channel in the channel assignment message is sent, while the first business to business channel to send an empty frame.

Step 3: the mobile station receives the channel assignment message, it begins to identify forward traffic channel, typically the mobile station should receive the channel assignment message to identify the 200 ms prior to the traffic channel.

Step 4: After successfully identified prior to the traffic channel, the mobile station began to air in the business of sending reverse traffic channel frames, the base station reverse traffic channel in the identification and must send a certified message.

Step 5: Connect the base station sends a message to the mobile station business.

Above 5 steps to complete each step can be called a critical point, regardless of which step error will cause access failure. The possible reasons for each step are a lot of mistakes, which requires a certain variety of possible reasons for the collection and collation, so the process is not difficult to master. There is also a valid way of access failure is the manpower from the analysis of signaling, signaling through some of the key to quickly locate the problem 5 above a certain critical point in, and then combined with other test data to identify problems lies. In addition to the signaling flow, we also need to observe changes in other test indicators to accurately locate the problem. Need to observe the test indicators include: the mobile station received power, transmit power and pilot strength. Links to Research Papers Download http://www.hi138.com
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