Branch : Computer Science and Engineering
Subject : Wireless Communication
AMPS and ETACS Air Interface
Introduction:
AMPS and ETACS use different physical rate channels for transmission of voice and control information
Types of Channels
Control channels
- Reverse and forward control channels
- Control channels are used for call set up
- Registration
- Paging ( Notification of an incoming call to a mobile)
Voice channels (Reverse and forward control channels)
- Voice signals
- Supervisory audio tone (SAT)
- Signaling tone (Used for sending a signal from a mobile indicating call termination)
- Blank and burst ( The voice transmission is suspended, and data is sent may be to effect a hand-off)
Some of the air interface specifications for AMPS and ETACS are listed in Table 1
Table 1 |
Blank and Burst Encoding
AMPS Control and blank and burst channels transmit data at 10 Kbits (8 Kbps for ETACS)
The data stream uses Manchester coding
- The advantage is that the energy is concentrated at 10 KHz, and a little energy leaks into 4 KHz
- So burst of data over a voice channel can be easily detected within a 30 KHz RF channel and barely audible to the user
- Can use phone lines which have DC blocking