Is-95 Air Interface Standard

7/31/2019 Is-95 Air Interface Standard

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IS-95 Air Interface Standard

CDMA Standards

A standard is an agreement as to how a theory or technology will be practiced. It

contains the "rules of interoperability" and becomes the guidelines by whichdifferent vendors design and manufacture their equipment.

It is the job of the standards committee, whose members come from within theindustry, to spell out the "rules" in just enough detail to guarantee interoperability.Committee members typically avoid over specification to encourage continuingadvances in technology and to foster healthy competition in the marketplace. TIAand ANSI have defined several standards that apply to CDMA at cellular and atPCS frequencies. These are shown in the table below.

Subsystem

Cellular

Frequencies PCS FrequenciesMobile TIA / IS-98 ANSI / J-STD-019

Base Station TIA / IS-97 ANSI / J-STD-018

Speech Coding TIA / IS-96

Air Interface TIA / IS-95 ANSI / J-STD-008

TIA Standards for the cellular frequencies are called interim standards (IS). ANSIStandards for the PCS frequencies are called joint standards (J-STD). Thecellular and PCS standards for a particular subsystem are written to be as similaras possible - differing only when the frequency differences make it necessary.

Although the constraints imposed by standards are not always welcome ones,telecommunication companies remain highly motivated to conform with them.Why?

Quite simply, people do not buy non-compliant systems.

Products must be built to standard to have any chance of being viable in themarketplace. Outside of the market, there is no enforcement of standards.

Now let's take a closer look at the air interface standards.

Air Interface Standards: IS-95

TIA established its TR-45.5 subcommittee in March 1992 with the charter ofdeveloping a spread-spectrum digital cellular standard. In July of 1993, TIAapproved the Mobile Station - Base Station Compatibility Standard for Dual-


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Mode Wideband Spread Spectrum Cellular System standard, better known as IS-95.

IS-95 is the formal definition of the cellular CDMA air interface. It defines theproperties that CDMA signals must have at transmission and, subject to

propagation changes, the nature of the signal you might expect to pick up at theantenna of a receiver.

For example, you've seen that IS-95 specifies a 1.23 MHz bandwidth for thecarrier. It also defines quadrature spreading, quadrature modulation and powercontrol strategies.

The industry is currently operating under revision A of the cellular air interfacestandard.

Although IS-95A differs only slightly from the prior version, it has added:

13 kbps speech coding.

International mobile station identifier (IMSI) addressing.

Extended system parameters.

Air Interface Standards: J-STD-008

As PCS technology came on the scene, ANSI developed its PCS air interfacestandard using IS-95A as a template.

ANSI's J-STD-008, the Personal Station - Base Station Compatibility Standardfor Dual-Mode Wideband Spread Spectrum PCS System standard, controls theopen-air interface in CDMA PCS systems.

This standard serves the same purpose for CDMA PCS that IS-95A serves forCDMA cellular.

Air Interface Standards: Comparison

Although very similar, the primary differences between IS-95A and J-STD-008

are, as you would expect, found in the frequency plan. Signal processing,including spreading and coding, is identical in the two standards.

As this course progresses, a great deal of focus will be placed on the CDMA airinterface. Because of the substantial similarities between the cellular and PCS airinterface standards, we will not distinguish between the two unless the situationwarrants doing so.


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Air Interface Standards: IS-95B

TIA is currently working on a next version of the IS-95 standard.

IS-95B will bring together IS-95A and J-STD-008. It will also:

Add new or enhanced algorithms that improve handoffs both within cellsand to other carriers.

Enable mobiles to be brought up in handoff state (when in a handoffregion).

Add DTMF messages.

Documents

Is-95 Air Interface Standard