Discussion on Measures for Increasing Efficiency of CDMA Wireless Network Resources

1 CDMA wireless network resource efficiency ideas

Improving the utilization rate of wireless system resources is to fully tap the potential of the network, make full use of the existing channel resources, equipment resources and network capacity without reducing the quality of service, try to reduce the proportion of super busy cells and super idle cells, and absorb more To increase the input-output ratio.

The general idea of ​​network resource efficiency is as follows:

(1) In the network planning stage, according to the forecast of market traffic, reasonably plan the site and configuration;

(2) Eliminate the faults in the network and ensure the normal operation of the network;

(3) Closely integrate with market development, balance cell load, and dynamically "remove idle to supplement busy" on the network to activate the idle resources of the existing network;

(4) In view of the characteristics of the current distribution system with low utilization rate, the existing distribution system, repeaters, RRU and other network resources are transformed and optimized to expand coverage and improve the utilization rate of existing sources;

(5) Monitor and analyze the existing wireless network resources, and regularly report the distribution of network traffic to the front-end department to provide a reference for marketing strategies.

2 CDMA wireless network resource efficiency key points

CDMA network resources are divided into core network resources and wireless network resources. The wireless network resources mainly include transmission resources, BSC resources, and wireless air interface resources. The efficiency of wireless network resources is based on eliminating network equipment failures, transmission resource bottlenecks and BSC resource allocation, etc., in-depth, detailed analysis and optimization of wireless air interface resources.

(1) Transmission resources

There are three main transmission links for transmission resources, namely: Abis link between BTS and BSC, A1 / A2 link between BSC and MSC, and A3 / A7 link between BSC.

(2) BSC resources

BSC resources are mainly reflected in signaling processing capabilities and traffic processing capabilities. BSC resources include CPU load of each processing board, vocoder and PCF configuration, signaling link configuration, etc.

(3) CDMA wireless air interface resources

CDMA wireless air interface includes: paging channel resource, access channel resource and service channel resource of CDMA 1X wireless air interface; control channel resource, access channel resource, service channel resource and time slot resource of CDMA EV-DO wireless air interface.

3 CDMA wireless network resource efficiency implementation process

3.1 General implementation process

The overall process of CDMA wireless network resource efficiency implementation:

3.2 Implementation of sub-process

(1) Transmission resource enhancement process

(2) BSC resource efficiency process

(3) Wireless air interface resource efficiency process

4 CDMA wireless network resource efficiency measures

4.1 Optimize paging channel resources

(1) Abnormal paging channel caused by unreasonable paging mechanism

Optimize the paging mechanism, which can be combined with Cluster Paging and IS Paging, optimize the paging strategy or optimize the registration cycle and other parameters, reduce the paging channel load, and solve congestion.

(2) Paging channel congestion caused by SMS

Reduce the trigger threshold of the MSC side SMS to go to the service channel, thereby reducing the occupation of the paging channel by SMS; for the SP group to send SMS, the MSC side can be used to alleviate congestion by SMS flow control; when the traffic is not high, it can be passed GPM message merge mode or configure multiple paging channels according to the actual situation, but consider adding the paging channel to other resources (forward power, Walsh code, etc.), which must be used with caution.

(3) Abnormal paging channel caused by high traffic

The paging channel load is abnormally high due to the excessive traffic volume of the carrier frequency, and the traffic of the carrier frequency can be reduced through cell traffic balancing or capacity expansion, thereby reducing the load of the carrier frequency paging channel.

(4) Paging channel abnormality caused by unreasonable LAC area planning

The planning of the LAC area should not be too large. Its borders should avoid high traffic areas or high-traffic traffic arteries. At the same time, it should avoid nesting in the LAC area. For paging channel congestion caused by unreasonable LAC area planning, the size and boundary of the LAC area should be readjusted to solve the congestion.

4.2 Optimize access channel resources

(1) Unreasonable REG_ZONE planning causes access channel congestion

The planning of REG_ZONE should not be too small, and its borders should not be located in high traffic areas or high-traffic traffic arteries, and REG_ZONE nesting should be avoided. For access channel congestion caused by unreasonable REG_ZONE planning, the size and boundary of REG_ZONE should be readjusted.

(2) Unreasonable registration mechanism setting causes access channel congestion

The access channel is used for signaling interaction when users access or register. Too many users access or register at the same time (it is generally believed that when the access channel load exceeds 60%), the access channel will be congested. This can be solved by optimizing the registration mechanism, such as adjusting parameters such as TOTAL ZONE and ZONE TIMER to improve the phenomenon of frequent registration at the junction of multiple locations; or optimizing parameters such as REG_PRD to optimize the registration cycle and resolve congestion.

(3) Access channel congestion caused by unreasonable access parameter settings

Optimize access channel parameters, such as initial access power offset, power increment, access trial number, maximum access message packet length and access channel prefix length, etc., to reduce access collision probability, increase access channel capacity and Performance and thus resolve congestion.

(4) Excessive traffic volume causes excessive cell access load

If the traffic volume of a single cell is too large, the cell coverage can be adjusted reasonably to balance the traffic between cells; if the regional traffic volume is too large, it can be solved by increasing the carrier frequency.

4.3 Optimize CE resources

CE (Channel Elements) resource utilization is unreasonable, and needs to be combined with Walsh code traffic, CE load, soft handover ratio, and forward power load to avoid congestion when other resources are insufficient. The specific means are as follows:

(1) By adjusting the antenna height, downtilt angle, transmit power, etc., the coverage of high-load base stations can be reduced, and the coverage of adjacent idle base stations can be expanded according to the actual situation, reducing the traffic load of base stations and solving congestion.

(2) If the soft handover area of ​​the base station cell is located in a traffic-intensive area, a large amount of resources will be occupied due to soft handover. You can adjust the coverage of the base station by adjusting the antenna azimuth and other methods to rationally configure resources.

(3) "Release idle to supplement busy", adjust existing base stations, and allocate excess CE resources of idle base stations to busy base stations, so that CE resources can be used more reasonably.

(4) If the soft handover ratio of the base station is too high, you can adjust the handover parameters of the base station cell and the neighboring base station cell or use a dynamic soft handover algorithm to reduce the soft handover ratio and solve the high load. However, lowering the ratio of soft handover usually weakens the cell's border coverage or resistance to signal abrupt changes, and must be used with caution.

(5) For areas with high base station density, new independent sources and indoor distribution systems can be used to absorb traffic to solve the imbalance of network CE.

4.4 Optimize Walsh code resources

The lack of Walsh code resources requires a comprehensive analysis of factors such as Walsh code traffic, CE load, soft handover ratio, and forward power load to avoid congestion of other resources.

(1) Walsh code local busy area

â—† If the soft handover ratio is too high, the cell boundary can be adjusted through coverage control, or parameters can be optimized or a dynamic soft handover algorithm can be used to reduce the soft handover ratio.

â—† If the load difference of Walsh code between each carrier frequency of the sector is large, the dynamic load balancing method between carrier frequencies can be used to balance the Walsh code.

â—† If the Walsh code load difference of each carrier frequency in the sector is not large, the coverage control function can be used to shrink the coverage of the high Walsh traffic cell, and expand the coverage of the neighboring idle cell according to the actual situation to reduce the high Walsh traffic Cell load to avoid congestion due to insufficient Walsh codes.

(2) 1X high-speed data services occupy too many Walsh code resources

â—† In the case of power limitation, the parameters can be optimized to limit the access of high-speed data services, while fully considering the balance between voice services and data services. You can set the number of reserved Walsh codes for voice services or the maximum rate of data services to increase the application threshold for high-speed data services and avoid excessive occupation of Walsh codes.

â—† When the power is not limited, you can consider using RC4 configuration mode or RC3 / RC4 adaptive mechanism. Recommendations for RC4 usage scenarios: RC3 is used for voice and data FCH, and RC4 is used for SCH.

4.5 Optimizing forward power resources

The lack of forward power resources requires a comprehensive analysis of factors such as Walsh code traffic, CE load, soft handover ratio, and forward power load to avoid congestion of other resources.

(1) The forward power of the base station is insufficient, and the load of other resources (Walsh code, CE, etc.) is also high

It can be solved by cell splitting, adding sites or increasing carrier frequency. For areas with high base station density, traffic can be absorbed by new independent sources plus indoor distribution systems to solve network congestion problems.

(2) The difference in the traffic volume of each carrier frequency of the base station is large, and the difference in forward power load is also large

First check whether there is equipment failure or interference, and secondly, dynamic load balancing between carrier frequencies can be performed to solve congestion.

(3) The traffic volume of each carrier frequency of the base station is not different, and the forward power load of adjacent base stations is not high

â—† You can shrink the coverage of congested cells by adjusting the height, downtilt, and transmit power of the antenna, and expand the coverage of neighboring idle base stations according to the actual situation, reduce the traffic load of the cell, and solve the lack of forward power.

◆ If the soft and soft handover area of ​​the cell is located in a traffic-intensive area, it will occupy a lot of resources due to the soft and soft handover. The cell boundary can be adjusted by adjusting the antenna azimuth to solve the problem of insufficient forward power.

â—† If the soft handover ratio of the cell is too high, you can adjust the handover parameters of the cell and neighboring cells or use a dynamic soft handover algorithm to reduce the soft handover ratio and avoid insufficient forward power. However, lowering the ratio of soft handover usually weakens the cell's border coverage or resistance to signal abrupt changes, and must be used with caution.

(4) Unreasonable setting causes insufficient power of the forward traffic channel

Unreasonable setting of forward power control parameters (such as FPC_INIT_SETPT, FPC_MIN_SETPT, FPCMAX_SETPT, FPC_FER and FPC_SUBCHAN_GAIN) will cause excessive transmission power and waste forward power. In addition, the maximum power and minimum power settings for each FCH and SCH in the forward direction also affect the consumption of forward power resources, resulting in insufficient forward power. Therefore, it is possible to reduce unnecessary power consumption and avoid insufficient forward power by optimizing parameters such as power control and the maximum and minimum transmit power allowed by the traffic channel.

At the same time, the power ratio of the pilot channel, paging channel and synchronization channel can be adjusted appropriately, but this adjustment will affect the forward coverage radius and must be used with caution.

4.6 Optimizing reverse power resources

Whether the RSSI is normal is an important indicator of whether the reverse channel is working properly, and it has a significant impact on call quality, dropped calls, handovers, congestion, network coverage, and capacity. Therefore, in the actual network, it is necessary to eliminate the abnormal phenomenon of RSSI to ensure the normal operation of the network.

(1) Device hardware failure may cause the reverse channel to be disconnected or the device to generate self-excitation, making RSSI abnormal

Check the fault alarm through the network management to eliminate the device fault.

(2) The quality problem of the antenna feeder system engineering caused the RSSI anomaly

If the jumper connector is not made well, or the diversity connection cable is wrong, the main or diversity RSSI is very high throughout the day. You can solve the problem of excessive RSSI by re-making the connector or correctly connecting the diversity.

(3) The planning or parameter setting of the REG_ZONE zone is unreasonable, resulting in frequent terminal registration and other causes of RSSI abnormality

For the planning of REG_ZONE, see Section 4.2, Part 1.

Optimize the registration mechanism, such as adjusting parameters such as TOTAL ZONE and ZONE TIMER to improve the frequent registration phenomenon at the junction of multiple locations; or optimizing parameters such as REG_PRD to optimize the registration cycle and solve congestion.

(4) RSSI abnormality caused by external interference

The reason may be that the network frequency band is interfered with or the repeater interferes. For example, if it is close to or conflicts with the frequency band used by the military or administrative organs, the base station's reception noise level is increased and interference is formed. First, use a frequency scanner to test the interference at the base station to ensure that the upstream wireless environment is good; then, check whether the gain of the repeater is too large, whether the components are faulty, and whether the reverse radius is set too large, and the user cannot register normally , Causing an RSSI exception.

4.7 Optimize EV-DO forward time slot resources

When the average time slot occupancy rate is> 75%, and user perception decreases due to insufficient time slot resources, corresponding optimization measures can be taken according to different scenarios.

(1) Low single user throughput and fewer equivalent users

This phenomenon is mostly caused by a small number of users in a poor wireless environment. It should be considered to adjust the antenna feed or increase the base station to enhance the coverage of the relevant area, improve the wireless environment, and reduce the forward retransmission rate.

(2) Low single user throughput and large number of equivalent users

â—† Increase carrier frequency or adopt cell splitting method. For areas with high base station density, traffic can be absorbed by new independent sources plus indoor distribution systems to solve network congestion problems.

â—† Determine whether there is the possibility of over-region coverage. If there is cross-region coverage, you can consider adjusting the downtilt of the antenna feed. In areas with dense base stations, it is also possible to consider reducing the base station's transmit power without affecting coverage.

â—† If it is a multi-carrier area, and the slot occupancy rate among carriers is not balanced, you can consider using a hard assignment algorithm based on time slots.

â—† Using the multi-user package function, optimize the forward scheduling algorithm and improve the throughput of single time slot.

(3) Single user throughput is high and the number of equivalent users is small

It remains to be seen.

5 Conclusion

The utilization rate of wireless network resources is an important standard to measure the operation level of telecom operators, and also an important manifestation of the core competitiveness of enterprises. Increasing the efficiency of network resources is a long-term task that requires technicians to constantly optimize during normal network maintenance to maximize the utilization of wireless network resources.

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