The introduction of cellphones with poor receiver sensitivity, known as dirty devices, to the Code Division Multiple Access (CDMA) cellular network results in a reduction in cell edge coverage, degraded capacity, and higher drop-call rates. This poor network performance has a negative impact on customer experience and satisfaction, which may result in increased churn for CDMA wireless carriers. Previous research on the impact of dirty devices has used computer-based simulations. This paper demonstrates the influence of dirty devices on a live commercial CDMA network using two distinct approaches.
The first approach deploys dirty and non-dirty devices in a live commercial cell, and measures the impact on forward base transceiver station (BTS) power and forward link Ec/Io (Ec is the received pilot chip energy and Io is the spectral density of the total power seen by the device). A series of tests on a live CDMA network with known dirty devices shows an increase in BTS transmit power resources compared with non-dirty devices, leading to the degradation of forward link Ec/Io. The second approach uses a statistical study of the aggregated pilot strength measurement messages reported by the mobile to ascertain the impact of known dirty devices on the overall network Ec/Io of non-dirty devices.