Branch : Computer Science and Engineering
Subject : Wireless Communication
USDC Radio Interface
Introduction
To ensure smooth migration from AMPS to USDC the IS-136 is specified to operate in a dual mode, which makes roaming possible with a single phone.USDC supports 3 subscribers in a single FVC/RVC channel .USDC uses TDMA. As more efficient voice coding becomes available, it could potentially support more subscribers
USDC Radio Interface:
USDC Channels:
Supervisory/control channel
- AMPS specifies 42 control channels (21 each for provider A and provider B)
- IS-136 has specified additional 42 called secondary control channels
- The secondary control channels during transition can be allocated to USDC only, so AMPS does not have to monitor or decode these channels and the SMS and paging services may be introduced for USDC only
- After the transition is complete all the control channels will be used, to carry the signaling, paging and SMS traffic
Voice channels:
- Same as AMPS except converted to TDMA. Occupies 30 KHz bandwidth in forward as well as in reverse direction. Each Voice channel supports a max of 3 users, and has six time slots.
- For full rate speech coding a max of 3 users
- For half rate speech coding a max of 6 users
- User 1, may occupy slots 1 and 4, user 2 may occupy 3 and 5 slots, while user 3 may occupy 3 and 6 time slots
- A half rate user occupies only one slot