As the density of transmitters from mobile telecommunication systems contin
ues to increase there is a greater risk of electromagnetic compatibility (E
MC) problems due to the ensemble electromagnetic field from multiple mobile
handsets. An analysis of the characteristics of the threat field from mult
iple handsets is presented allowing prediction of the statistics of the ens
emble field. A measurement system designed to detect electromagnetic interf
erence (EMI) from ensembles of cellular phones has been used to quantify th
e level of EMI on Ethernet cables from multiple global system for mobile co
mmunications (GSM) mobiles. The measurements are consistent with a simple s
tatistical model of ensemble signals from GSM sources and electromagnetic m
odeling of the system.