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Chapter 1 – Introduction

CDMA 1xEV-D0 AT Commands Reference Guide (Document S000482B) 9

When using IS 95, there is special handling of AT commands. For a detailed explanation, consult Appendix A

Where traditional wire line has only the local host and modem on one side, the CDMA IS-95 model requires

two modems on the local side: the IWF and the Wireless radio modem. These two modems must work as a

team to make a data connection.

For Internet connections, the interworking function can use a special feature called QNC (Quick Net

Connect). The IWF provides a link to the Internet without going through the PSTN.

Establishing a standard point-to-point call requires the cellular modem to configure a modem at the IWF. It is

the IWF modem that actually connects to the PSTN and dials the number. Call progress is not directly

available to the local modem, although some information can be exchanged. When the IWF has completed

the handshake with the remote modem, the local modem is advised and the connection is complete.

CDMA 1X

In areas where this service is provided, the modem can connect much like a local area network card. The

connection can be “always on” and only actively used when there is packet data to send or receive.

CDMA 1X offers higher speed data operations than are available with IS-95 service. IS 95 is limited to 14.4

kbps. The packet services of CDMA 1X use a fundamental channel at 9600 bps and can add supplemental

channels when needed to boost speed to as high as 153.6 kbps.

CDMA 1xEV-DO

In areas where this service is provided, the modem can provide packet data services at a much higher data

rate, as shown in the following table.

Data Service Theoretical Maximum

Data Rate

Typical Data Rate

1xEV-DO rev. 0 Upload 153 kbps 40–80 kbps

Download 2.4 Mbps 400–700 kbps

1xEV-DO rev. A Upload 1.8 Mbps 300–400 kbps

Download 3.1 Mbps 600–1300 kbps

Voice Service

Also added to the modem is the ability to make and receive voice calls. This allows the modem to serve as a

cellular telephone.

Host Connection Basics

The embedded modem provides a USB interface and optional serial port interfaces. To support the high data

rate of the 1xEVDO service the USB is highly recommended. The “Modem Port” presented is the interface

available for performing AT commands.

Modes, States, and Conditions

Discussion of the operation of the modem requires understanding the settings of the modem and just how it

is handling the data being sent to it. Describing the modem as being in a particular “mode” is not sufficient to

capture the various characteristics of the modem in any given case.

To improve clarity, this document uses the words “mode”, “state”, and “condition” to reflect different elements

of the modem’s configuration. This section describes the various modes, states, and conditions that are used

in the reference.

The CDMA 1X modems operate very much like a landline modem. There are, however, some differences in

that the modem supports multiple connection options.

One method of operation is to place a call just like a landline modem would (asynchronous serial). We call

this a CSC (Circuit Switched Cellular) call. This type of connection supports data communication, and is

available in IS-95 service areas.

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