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The GPRS service of the dynamic environment monitoring equipment on a base station interferes with the OptiX Metro 1000 and causes a large number of transient bit errors on the optical path

Publication Date:  2012-07-24 Views:  57 Downloads:  0
Issue Description
After a mobile operator started the air conditioning equipment in the equipment rooms of base stations, the OptiX Metro 1000 at certain base stations encountered the transient service interruption problem. In addition, the OptiX Metro 1000 reported the R_OOF, R_LOF, and SYN_BAD alarms transiently. The optical boards transiently reported a large number of regenerator section bit errors. The interruption period was about 20 minutes (the on/off period of the air conditioning equipment). After the mobile operator removed the monitoring and sampling lines of the air conditioning equipment, the fault was rectified.      
Alarm Information
ROOF, RLOF, SYN_BAD      
Handling Process
1) An operator went to the site and found that the SDH equipment of Huawei was located near the dynamic environment monitoring equipment. The operator connected the status sampling line of the air conditioner, and started and stopped the air conditioner repeatedly. The operator found that when the air conditioner was started, the services at the base station were transiently interrupted.
2) The operator stopped the dynamic environment monitoring equipment. The base station was then restored to normal. The operator then started the dynamic environment monitoring equipment but powered off the GPRS module of the dynamic environment monitoring equipment. In that case, the OptiX Metro 1000 was still operating normally. Hence, the operator concluded that the OptiX Metro 1000 was affected by the GPRS module.
3) The operator powered off the dynamic environment monitoring equipment, and then used different cell phones near the OptiX Metro 1000 to access the network by using the GPRS. The operator found that the services on the base station were transiently interrupted. Hence, the OptiX Metro 1000 was affected by the GPRS signals.
4) The dynamic environment monitoring equipment was installed above the OptiX Metro 1000. The operator suspected that the GPRS signals generated strong interference on the OptiX Metro 1000 because the dynamic environment monitoring equipment was too close to the OptiX Metro 1000. The operator then moved the Jiaxun dynamic environment monitoring equipment to a place 15 cm higher than the original place. After the operator connected the mutual-inductor and the GPRS module, the OptiX Metro 1000 operated normally regardless of how the operator powered on or off the air conditioner.
5) The operator tested certain other stations where the PDH equipment of other vendors was used, and found that the GPRS signals also caused transient signal interruptions.
6) The operator adjusted the installation position of the dynamic environment monitoring equipment of company X at the stations where similar faults occurred. After the adjustment, the faults were cleared.
Based on onsite experience, it is recommended that the distance between the dynamic environment monitoring equipment and the transmission equipment be more than 20 cm. If conditions permit, it is recommended that the dynamic environment monitoring equipment and the transmission equipment be installed in different cabinets.             
Root Cause
The dynamic environment monitoring system (provided by company X) adopts the radio transmission mode to form the network. The signals transmitted and received by the radio transmission modules (GPRS) interfere with the OptiX Metro 1000.      
Suggestions
1) The GPRS module of the dynamic environment monitoring equipment of company X directly communicates with the base station. When the power supply, access control system, air conditioner, or other environmental units in the equipment room become abnormal, the dynamic environment monitoring equipment actively sends the monitoring data such as alarms to the base station, which then transmits the monitoring data to the dynamic environment monitoring system in the NM center. At this time, the transmit power of the GPRS module increases, which may affect the normal operation of the transmission equipment.
2) In the case that the Jiaxun dynamic environment monitoring equipment and the OptiX Metro 1000 are installed in the same cabinet, it is recommend that you first power off the dynamic environment monitoring equipment if the optical board transiently reports a large number of regenerator section bit errors and the dynamic environment monitoring equipment also reports a large amount of monitoring data. In this way, the external interference generated by the monitoring equipment is eliminated.
3) In the case that the dynamic environment monitoring equipment of company X and the OptiX Metro 1000 are installed in the same cabinet, it is recommended that you adjust the distance between these two types of equipment to reduce the interference intensity.
4) The operator performed tests on the existing network, and found that the OptiX Metro 1000 V3 had a weaker capability in resisting the GPRS signals generated by cell phones than the OptiX Metro 1000 V2. Hence, during the field maintenance, do not use a cell phone to make calls or even use the GPRS service near the transmission equipment to avoid the generation of transmission bit errors.             

END