Dropped call

Dropped call is the common term for a wireless mobile phone call that is terminated unexpectedly as a result of technical reasons. Areas where users experience a large number of dropped calls are commonly referred to as dead zones.

One reason for a dropped call is when the mobile phone moves out of range of a wireless network. An active call cannot usually be maintained across a different company's network (as calls cannot be re-routed over the traditional phone network while in progress), resulting in the termination of the call once a signal cannot be maintained between the phone and the original network. Another common reason is when a phone is taken into an area where wireless communication is unavailable, interrupted, interfered with, or jammed. From the network's perspective, this is the same as the mobile moving out of the coverage area.

Occasionally calls are dropped upon handoff between cells within the same provider's network. This may be due to an imbalance of traffic between the two cell sites' areas of coverage. If the new cell site is at capacity, it cannot accept the additional traffic of the call trying to "hand in." It may also be due to the network configuration not being set up properly, such that one cell site is not "aware" of the cell the phone is trying to hand off to. If the phone cannot find an alternative cell to move to that can take over the call, the call is lost.

Co-channel and Adjacent channel interference can also be responsible for dropped calls in a wireless network. Neighbor cells with the same frequencies interfere with each other, deteriorating the quality of service and producing dropped calls. Transmission problems are also a common cause of dropped calls. Another problem maybe a faulty transceiver (TRX) inside the base station.

A great amount of money and time is invested by wireless operators in order to improve the network quality of service (QOS) to acceptable values. Dropped calls along with congestion are the two most important customer perceived problems that affect the quality.

Calls can also be dropped if a mobile phone at the other end of the call loses battery power and stops transmitting abruptly. Sun spots and solar flares are rarely blamed for causing interference leading to dropped calls.

Experiencing too many dropped calls is a common customer complaint received by wireless service providers. They have attempted to address the complaint in various ways, including expansion of their home network coverage, increased cell capacity, and offering refunds for individual dropped calls.