Defining Terms

Capacity

While Shannon originally defined capacity as the maximum data rate which permits error-free communication in a given environment, a looser interpretation is normally employed in wireless communication systems. Here capacity denotes the traffic density supported by the system under consideration normalized with respect to bandwidth and coverage area.

Multiple Access

denotes the support of simultaneous transmissions over a shared communication channel.

Duplexing

refers to the exchange of messages in both directions of a connection.

FDMA

In frequency-division multiple-access simultaneous access to the radio channel is facilitated by assigning non-overlapping frequency bands to different users.

TDMA

Time-division multiple-access systems assign non-overlapping time-slots to different users in a round-robin fashion.

CDMA

Code-division multiple-access systems use signals with very small cross-correlations to facilitate sharing of the broadcast radio channel. Correlators are used to extract the desired user's signal while simultaneously suppressing interfering, ``parallel'' transmissions.

Random-Access Channel

This up-link control channel is used by mobiles to request assignment of a traffic channel. A random access protocol is employed to arbitrate access to this channel.