Blocked Call Vs Dropped Call

A Blocked Call and a Dropped Call are two very common terms used in telecommunications (Cellular Communications) world these days. These two are completely different phenomena, but the impact they create on a customer is the same, annoyance. In this post I am going to discuss what the differences between these two events are, and briefly explain how they can be handled by the mobile service provider.

Blocked Call:

A Blocked Call is an event that can occur only before the call is completed between the called and the calling parties. Completion of the call here implies the connection being complete for either party to exchange talks. Any call you place on a cellular network, the service provider has to find all the resources necessary to connect the call between the two parties. As I mentioned in my previous post about a wireless call, it is not wireless in entirety and it has to access the wire-line network in order to reach the destination cell phone. In case of a long distance call, a service provider should make sure that there is sufficient network capacity all through the intermediate network hops to carry the call from one end to the other.

If there is not sufficient capacity to carry the call through, this results in a blocked call. When you are in a stadium watching a Baseball match or a Cricket match, when you attempt to make a call, you might hear a voice recording saying “the network is currently busy please try after sometime” or the call may just give three beeps and not connect. This is mainly because of insufficient bandwidth availability (Wireless Channels or the Wire-Line Channels) compared to the number of people attempting to access the network. In one of my posts about Why Sprint Nextel has more dropped calls than AT&T and Verizon? I mentioned that Sprint has an advantage of selecting the higher frequency range of (1900 MHz). If Sprint can tackle the dropped calls issue by installing more cell sites to cover the same area as that of its competitors, this automatically provides higher number of wireless channels in the same geographical area thereby reducing the chances of blocked calls. It still has to build the backbone wire-line network to support the calls but for now let us assume that this matter has been taken care. As the customer base keeps increasing in a geographic area, AT&T and Verizon have to eventually invest to tackle the increasing capacity requests from the customers. But Sprint, already has the wireless network to handle increasing capacity which is definitely an advantage but this is not a great situation to be in. Gradual investment as the customer base grows is always a better situation to be in than investing heavily at once expecting the customer base to rise. So this is a catch 22 situation where the decision has to be made by the service provider depending on the traffic analysis and customer growth analysis made over the years.

This is where traffic management comes into picture. A traffic management team makes sure that the network is always ready to handle the calls at any moment of time including the busiest hour of the day. During events like American Idol or on auspicious days like Christmas Day, Mother’s Day, Father’s Day or New Years Day, the network has to be ready to handle the avalanche of calls that can hit the network. Even in events like the baseball matches, the service provider takes necessary actions to provide more wireless channels by process called Cell Sectoring or another process of turning on smaller and more cellular base station towers to cover the same area.

To summarize things, a Blocked Call is something which occurs before the connection is complete between the called party and the calling party. This phenomenon depends on the entire network, the wireless channels on the calling end, the wire-line backbone network, the wireless channels on the destination end.

Dropped Call:

This is an event that can occur only after the call is connected and the exchange of talks has started. This implies that the network has the capacity to handle this call and the resources necessary for the call have already been allocated to the call. In my previous post I mentioned about the various factors that influence and contribute towards dropping of a call. The dropped call is a result of improper R.F. planning or some of the natural phenomena that cellular signals undergo while travelling in the environment surrounding us. Even as the mobile moves from one coverage area to another coverage area, there might be a dead zone resulting in a dropped call. The co-channel interference also can influence a dropped call but this is more evident in GSM network than CDMA network. A blocked call only depends on the wireless part of the network, i.e. the wireless signal power on the calling side and the wireless signal power on the receiving side.

I tried to explain the difference between a Blocked Call and Dropped Call in simple terms and there might be something that you can add to understand the process better. Please add any comments or suggestions on the blog.

Thank you very much for reading the blog.

Sincerely,

Krishna Chaitanya Emani.