Interference testing on CPRI links at wireless cell sites: Page 4 of 4

July 04, 2016 //By Cyril Noger, Anritsu
A key economic aim for wireless network operators is to reduce the amount of money spent in deploying the network in the field while maximising the cell coverage and ensuring better quality of service despite the impact of interference on the quality of reception.

In addition, having the ability to observe the behaviour of the interferer over time using the spectrogram display allows the technician to better emphasise the frequency and amplitude stability of the interfering signal. By colour coding the amplitude level, it becomes easy to see at a glance what occurs in the chosen frequency carrier and channel band (Figure 4).


Figure 4: Spectrogram of a LTE 10 MHz channel without and with a zooming capability highlighting an interferer’s behaviour.

Once the interferer has been seen from the ground level and the frequency identified by using markers on the plot, the technician can then use a conventional RF spectrum analyser to hunt for the interferer’s location on the basis that its amplitude will become higher closer to the source. However, as interferers may occur randomly, it is not always easy or fast to locate them in dense environments. In this case, it may sometimes be useful to drive to a neighbouring site to determine if this new site gets more disturbed by the same interferer or not.

 

Conclusion

Mobile phone subscribers all expect good Quality of Service from their cellular network operator including the ability to connect anytime, anywhere. Having deployed CPRI technology in the field, network operators need to work hard to prevent any network communication drops or failures caused by interference within the system. CPRI testing is therefore becoming more and more important, and the latest handheld instruments offer new ways of investigating interference problems and showing the test results.

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