Co-channel interference or CCI is crosstalk from two different radio transmitter using the same frequency There can be several causes of co-channel (communications) radio interference four examples are listed here. *Cellular Mobile Networks In Cellular network (GSM & 3GPP Long Term Evolution Systems, for instance), frequency spectrum is a precious resource which is divided into non-overlapping spectrum bands which are assigned to different cells (In cellular communications, a cell refers to the hexagonal/circular area around the base station antenna). However, after certain geographical distance, the frequency bands are re-used, i.e. the same spectrum bands are re-assigned to other distant cells. The co-channel interference arises in the cellular mobile networks owing to this phenomenon of Frequency reuse Thus, besides the intended signal from with in the cell, signals at the same frequencies (co-channel signals) arrive at the receiver from the undesired transmitters located (far away) in some other cells and lead to deterioration in receiver performance. *Adverse weather conditions During periods of abormally anticyclone weather VHF signals which would normally exit through the atmosphere can instead be reflected by the troposphere This tropospheric ducting will cause the signal to travel much further than intended; often causing interference to local transmitters in the areas affected by the increased range of the distant transmitter. *Poor frequency planning Poor planning of frequencies by broadcasters can cause CCI, although this is rare. A very localised example is Listowel in the south-west of Ireland The RTÉ Network Limited UHF television transmitter systems in Listowel and Knockmoyle (near Tralee are on the same frequencies but with opposite polarisation. However in some outskirts of Listowel town, both transmitters can be picked up causing heavy CCI. This problem forces residents in these areas to use alternative transmitters to receive RTÉ programming. *Overly-crowded radio spectrum In many populated areas, there just isnt much room in the radio spectrum. Stations will be jam-packed in, sometimes to the point that one can hear loud and clear two, three, or more stations on the same frequency, at once. In the USA, the FCC propagation models used to space stations on the same frequency are not always accurate in prediction of signals and interference. An example of this situation is in some parts of Fayetteville, Arkansas the local 99.5 FM KAKS-FM is displaced by KXBL-FM 99.5 FM in Tulsa, particularly on the west side of significant hills. Another example would be of Cleveland, Ohio s WKKY-FM 104.7 having interference from Toledo, Ohio s WIOT-FM 104.7 FM on the Ontario shore of Lake Erie, as well as Woodstock, Ontario s CIHR-FM (on rare occasions), which is also on 104.7 FM, due to the signals travelling very far across Lake Erie Co-channel interference may be controlled by various radio resource management schemes.

See also

* Adjacent-channel interference * Crosstalk (electronics) * Signal-to-interference ratio (SIR or S/I), also known as Carrier-to-interference ratio (CIR or C/I) * Frequency coordination

External links

http://www.youtube.com/watch?vDmwFda51SqA An example of analog TV co-channel interference.] Principles of mobile communication]‎ by Gordon L. Stüber Category:Interference Category:Radio frequency propagation Category:Electronics terms Category:Radio resource management