GPS timing receivers have long been relied upon by various communications networks for achieving synchronization among the network nodes. Cellular networks, particularly CDMA cellular networks, actively employ GPS timing receivers for making their time critical decisions, particularly handoff. Operations and parameters which set the network quality of service (QoS) require that these GPS receivers provide timing solution up to nano-second accuracy. Therefore, GPS timing receiver are required to provide a disturbance free solution. However, as all GPS receivers communicate with GPS satellites over the air interface; these are inevitably vulnerable to RF interference. This interference disturbs the timing receiver¿s performance, degrading its solution. This paper appreciates this issue, identifies the problems caused and discusses in detail the performance degradations of cellular networks due to instability of timing signals from GPS.