This specification is to be used for the two way interworking between fixed and portable radio devices operating in the unlicensed frequency band allocated for personal communications services (Unlicensed PCS or U-PCS). The equipment is intended to convey digitally-encoded speech and data with associated digital signaling, via a radio channel, to and from a nearby fixed station, or network of fixed stations.

Applications of the equipment include wireless access to business and residential services. The specification is intended to allow a user to migrate from one personal communications environment (domestic, private branch exchange, key system, Centrex) to another with a single portable device.

This air interface specification outlines the technical requirements considered necessary to ensure that :

- minimum interference is created to other users of the shared unlicensed radio spectrum and the interference from other systems has a minimum effect on the operation of equipment so that co-existence is possible; and

- there exists a defined degree of interworking between the portable and fixed devices following this specification, allowing users in possession of compliant portable devices, to make and receive telephone calls from compliant fixed devices.

To these ends, this specification specifies the essential requirements for:

- monitoring, accessing and relinquishing an RF channel;

- the means by which the specified data structures are modulated onto the channel;

- the means by which the two ends of a radio link become and remain synchronized;

- the provision of signaling or marker channels;

- generation and interpretation of digital control; and

- generation and interpretation of digital speech and data.