With rising capacity demand in mobile networks, the infrastructure is also be-coming increasingly denser and complex. This results in collection of larger amount of raw data (big data) that is generated at different levels of network architecture and is typically underutilized. To unleash its full value, inno-vative machine leing algorithms need to be utilized in order to extract valuable insights which can be used for improving the overall network’s performance. Additionally, a major challenge for network operators is to cope up with increasing number of complete (or par-tial) cell outages and to simultaneously reduce operational expenditure. This paper contributes towards the aforementioned problems by ex-ploiting big data generated from the core net-work of 4G LTE-A to detect network’s anom-alous behavior. We present a semi-supervised statistical-based anomaly detection technique to identify in time: first, unusually low user activity region depicting sleeping cell, which is a special case of cell outage; and second, unusually high user traffic area corresponding to a situation where special action such as additional resource allocation, fault avoidance solution etc. may be needed. Achieved results demonstrate that the proposed method can be used for timely and reliable anomaly detection in current and future cellular networks.