Cellular, Paging, PCS Overview

There are many Common-Air-Interface (CAI) standards in use throughout the world.“Old” standards that will die very slowly: AMPS, POCSAG.“New” standards that flopped: CT2.“Slow-to-Start” standards: CDPD, DECT, PACS, IS-54(USDC).Big winners of the near future: IS-95 (CDMA), GSM (TDMA), IS-136 (USDC TDMA).Big winner applications: Wireless Local Loop, Position Location, Cordless/Cellular.

Typical Cellular System

Base station provides radio access between mobile users and Mobile Switching Center (MSC).

Identically labeled channels in the two bands form a forward and reverse channel pair for duplex communication (45 MHz separation).

U.S. Cellular Channel Plan

Wide Area Paging

The paging control center dispatches pages received throughout several cities simultaneously.Wide area paging systems simulcast a page from base stations in the coverage areas.Transmit powers are generally high (kilowatt range) and data rates low to insure good indoor penetration.

Cordless telephones are becoming an integral part of the wireless infrastructure. Some cordless telephones are capable of operating in several modes: as a normal cordless at home, as a cellular phone while traveling, and as a wireless PBX in the office. Cordless phones may also include paging functions.

Example: The U.S. PCS Phenomenon

A and B Block MTA Licenses sold for $7.7 Billion (30 MHz).

C Block BTA licenses sold for $13 Billion (30 MHz).

Smaller D, E, and F Blocks to be auctioned

Two license-free bands in 1910 - 1930 MHz for voice (isochronous) and data (asynchronous)

Leading U.S. PCS winners:

Example: U.S. Mobile Radio Spectrum

Example: U.S. Mobile Radio Spectrum

CDMA Cellular/PCS System

How Cellular Systems Work

Two-Way Cellular Communication relies on a

variety of channels to ensure call connection and delivery.

Control Channels: Channels used as beacons for idle mobiles and access to traffic channels.

Traffic Channels: Channels used to support customer voice calls and messages.

Signaling Channels: Channels used to provide network and hand-off signals during customer communications.

How Cellular Systems WorkAnalog Mobile Phone System (AMPS)

The Forward Link: Forward Control Channel (FCC): Sends a continuous beacon message,

provides registrations, and issues pages to mobiles by sending MIN. Voice channels are assigned from this channel.

Forward Voice Channel (FVC): Handles the voice call - customer traffic from the PSTN to the mobile.

Supervisory Audio Tone (SAT): Nominal 6kHz audio tone. Handles base station call management and supervises the voice channel while in use.

The Reverse Link: Reverse Control Channel (RCC): Handles call originations, registration

acknowledgments, and brief response messages sent by mobile. Collision is avoided by monitoring busy-idle bits on the FCC.

Reverse Voice Channel (RVC): Handles the mobile side of the voice call from subscriber to PSTN.

Signaling Tone (ST): ST denotes end-of-call, originated by mobile. SAT tone received on FVC is echoed back on the RVC to keep the voice channel allocation.

How Cellular Systems WorkThe IS-95 CDMA System

Forward Channels (64 simultaneous channels orthogonal by Walsh functions): Pilot: Each Base Station (BS) is represented by a known 2^15 length PN code

word, where the timing offset specifies the BS location. Synch Channel: The BS provides a 1200 bps data signal which provides

timing information to the mobile, so it can synchronize to all other forward channels.

Paging Channel: Up to eight paging channels are provided by each BS to dispatch call requests and control information to mobiles.

Forward Traffic Control: Carries voice or data to the mobile from the PSTN. Up to 63 traffic channels may be provided by each base station.

Reverse Channels: Access Channel: Allows mobile to send brief 20ms messages to register,

originate calls, and respond to pages. Traffic Channel: Carries voice or data from the mobile to the PSTN.

How Cellular Systems Work

How Cellular Systems Work