C

Carrier, carrier frequency
Baseband signals, in general, will not propagate directly because of their low frequency. Using the baseband signal to modify a signal of a much higher frequency (a carrier) allows:

-The resulting modulated signal to be propagated over a radio link

-Where different carrier frequencies are used, the modulated signals may be combined together and separated at the receiver, this is called frequency division multiplexing

-The resulting signal is 'narrowband' which enables it to be more easily filtered out from other signals

C-band
The range of frequencies between 4GHz and 6GHz

CDMA
Code Division Multiple Access. A method of combining signals by scrambling them with a pseudo random bit sequence (PRBS) prior to transmission. The signals mix together, but can be separated by correlating them with the original PRBS. The PRBSs used must be carefully selected such that the signals can be successfully separated.

Churn
Especially in a large network, the number of sites each year that will move, be ceased, or be added to the network.

CIR
Committed Information Rate. In networks that allow access to a variable amount of throughput, the committed information rate is the minimum throughput that is guaranteed to be available to an application.

Clarke orbit
The Geostationary orbit, 22,237 miles from the Earth's surface, proposed by Arthur C Clarke in Wireless World Magazine 1945.

Codec
COder-DECoder; a system that converts analog quantities, like speech or video, into digital signals and back again.

Compression
A technique used to reduce the amount of data to be sent, but retain all, or most of its information content.

CPE
Customer Premises Equipment; equipment located on the customer's site