What Is IS-136?
IS-136 is a mobile communications interim standard which extends the functions of the dual-mode system standard IS-54B. IS-54B is also known as NADC/TDMA (North American dual mode cellular, time division multiple access). NADC/TDMA is a dual mode, full duplex cellular communications system in which each voice channel can be defined by both a frequency and a time slot. In earlier cellular communications systems the voice channel was defined only by a frequency. Thus, more calls can be transmitted by sharing one transmission frequency. The dual mode system uses a digital traffic channel (DTC) or an analog voice channel (AVC). The dual mode system uses only an analog control channel (ACC) to control transmissions on the voice and traffic channels. IS-136 has the DTC, AVC, ACC, and adds a digital control channel (DCCH). IS-136 expands the capability of IS-54B to include:
- Sleep mode for decreased battery usage during non-talk times.
- Public, private, and semi-private cells such as picocells in office buildings and personal base stations
- Short Message Service (SMS) for both point-to-point and broadcast information
- Greatly improved security (using DCCH and authentication)
Basic Features of IS-136:
Time Slots per Channel: 6
Users per Channel: 3 (full rate), 6 (half rate), 9 (future)
Modulation: Digital: Pi/4 DQPSK, Nyquist Filter factor = 0.35
Data Structure: TDMA
Speech Coding: VSELP (vector sum excited linear predictive) 8 kbps
Modulation Data Rate: 24,300 symbols per second (1 symbol = 2 bits)
EIA/TIA Standards: IS-136.1 and IS-136.2 for system
IS-137 for mobile stations
IS-138 for base stations
The Control Channels:
IS-136 has both digital (DCCH) and analog (ACC) control channels.
The ACC controls the analog transmissions and guarantees backward compatibility with systems such as AMPS and IS-54B.
The DCCH controls digital transmissions and enables the specialized features of IS-136.
A mobile station (cell phone) on an ACC has an idle mode. During this state, the mobile waits for messages from the base station, or it can originate a call.
A mobile on a DCCH has a similar state, called camping. Refer to Transactions for transactions which can be processed during the idle and camping states.
For more info on IS-136, refer to the Keysight 83206A User's Guide (Keysight part number 83206-90002).
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