Cellular Wireless

Modem Primer
EMEA Headquarters
Multi-Tech Systems (EMEA)
United Kingdom
Tel: +(44) 118 959 7774
World Headquarters Fax: +(44) 118 959 7775
Multi-Tech Systems, Inc
2205 Woodale Drive Multi-Tech Systems (EMEA)
Mounds View, MN 55112 U.S.A France
Tel: +(33) 1-64 61 09 81
Tel: (763) 785-3500 or (800) 328-9717 Fax: +(33) 1-64 61 09 71
Fax: (763) 785-9874
Technical Support: (800) 972-2439 Multi-Tech Computers Pvt. Ltd. (India)
Tel: +(91) 124-5010780 or 124-2340780
www.multitech.com Fax: +(91) 124-2340776

GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet

portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS

CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability

mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA

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GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless intern
86002052 08/05

portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS
Content

Introduction ............................................................................................................................. 1

History of Modems .................................................................................................................. 2

Over the PSTN ................................................................................................................................ 2
Over Wireless Networks ................................................................................................................. 2

Network Architecture .............................................................................................................. 3

Circuit-Switched Cellular Data ..................................................................................................... 3
Short Message Service ................................................................................................................... 3
Packet-Switched Cellular Data...................................................................................................... 4

Implementing Your Wireless Modem Solution ................................................................... 5

Determining Your Wireless Technology ....................................................................................... 5
Choosing a Carrier and a Plan ....................................................................................................... 5
Choosing the Type of Physical Modem Connectivity ................................................................... 6
Activating the Wireless Service ..................................................................................................... 7

Applications ............................................................................................................................. 7

Benefits ..................................................................................................................................... 8
Accessibility .................................................................................................................................... 8
Portability ........................................................................................................................................ 8
Mobility ........................................................................................................................................... 8
Cost Savings .................................................................................................................................... 8

Multi-Tech Wireless Modem Solutions ................................................................................. 9

Glossary of Terms .................................................................................................................... 10

 Cellular Wireless Modem Primer
Introduction
Cellular wireless modem technology can be a confusing topic. Especially as it relates to the transferring
of data over a cellular network. However, Multi-Tech is here to tell you that it is easier to comprehend
than you might think. In fact, we like to say a cellular modem is “just a modem!”

What do we mean? Well, to start, a cellular modem works much like a standard analog dial-up modem
in that it connects to your computer or host device through a serial interface and configures and dials
using AT commands. Where it differs is that it uses a wireless cellular network to make the connection
through its antenna as opposed to a physical connection to an analog phone line. Beyond the connection,
it acts and functions just like a regular modem.

The real learning curve, however, lies with cellular technology itself. After all, cellular wireless has really
only become mainstream in the last few years. Therefore, the goal of this primer is to educate you on
cellular wireless modem technology by comparing it to another technology that most of us are familiar
with: the analog modem.

We’ll start by comparing the history of modems over the Public Switched Telephone Network (PSTN)
and the wireless network. Next, we’ll illustrate the similar network architecture and primary modes
of connections. Continuing, we will explain the steps you’ll need to take in order to implement your
wireless solution. Lastly, we’ll familiarize you with the common applications and additional benefits
you’ll receive with wireless technology.

After reading this primer, you should have a good understanding of wireless data technology, how to
implement your Multi-Tech wireless modem solution, and the benefits of utilizing a Multi-Tech wireless
modem in your application.

Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved. 1

History of Modems
Over the PSTN
Modems came into existence as a way to allow terminals to connect
to computers over standard phone lines. The word “modem” is a
contraction of the words modulator-demodulator. The sending
modem modulates the data into a signal that is compatible with the
phone line, and the receiving modem demodulates the signal back
into digital data.

The first commercial modem was developed in 1970. Over the course Multi-Tech’s first modem, the Acoustic
Coupler began shipping in 1971.
of 30 years, advancements in technology brought analog dial-up
modem speeds from 300 bps to 56K bps. In the analog dial-up world, 56K is probably the fastest speed
we will achieve over the PSTN network.

Over Wireless Networks

Wireless modems work the same way as a dial-up analog modem, except they convert digital data into
radio signals and back. What’s interesting is that the evolution of the modem over a cellular wireless
network has occurred at a much more rapid pace. In fact, the first wireless modem was developed in the
1990’s and over the course of only 14 years speeds have gone from 9,600 bps to 240K bps. These speeds
are expected to get even better as the technology evolves.

In the cellular world, there are two competing standards: GSM and CDMA. EDGE and GPRS are based on
the GSM standard. Recently, the convergence era has driven wireless technology to continue to evolve
new standards that provide higher data rates and greater system capacity making wireless broadband
possible. As these standards are implemented, you can rest assured Multi-Tech will have a solution to
meet your needs. To see how the different standards compare, take a look at our technology comparison
chart:

Cellular Wireless Data Technology Comparison

* U.S. National carriers listed. Carriers vary by country. For more detailed carrier support, go to www.gsmworld.com (GPRS)
or www.cdg.org (CDMA).
† Maximum theoretical data throughput rates are affected by environmental and network capabilities. Typical data rates are
normally about half of the maximum theoretical data rate.

2 Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved.

Network Architecture
There are three primary modes of cellular wireless modem connections: Circuit-Switched Data, Short
Message Service and Packet-Switched Data. All three share common characteristics to analog dial-up
modem connections as illustrated in the following chart:

Primary Modes of Connection

Circuit-Switched Cellular Data (CSD)

Circuit-switched cellular data connections work the same way dial-up modem-to-modem communication
works, except they use the air interface to access wireless network resources. To illustrate, let’s review
a typical modem-to-modem circuit-switched data connection. First, you dial out using a modem
connected via a phone line to the PSTN. The call is then routed through the switch at your local central
office (CO) to the modem you are connecting to, opening the circuit. During the call, the routed line is
dedicated to the two modems.

In a circuit-switched cellular data connection, the cellular transmission replaces the phone line
connection to the PSTN. Therefore, you dial out via any analog cellular network, and are connected
to a receiving modem pool that also resides on the wireless network. A circuit-switched cellular data
connection allows you to connect from almost anywhere with a connection speed of up to 14.4K bps.
CSD cellular wireless connections are ideal for applications that require a quick wireless replacement
of an existing point-to-point analog dial-up connection. They integrate seamlessly with your current
application requiring little infrastructure change.

Circuit-Switched Data Communication

Short Message Service (SMS)

Short Message Service is analogous to Instant Messaging in the Internet world. It allows you to send text
messages of up to 160 characters to mobile devices. SMS is similar to paging, however, SMS messages do
not require the mobile device to be active and within range and will be held for a number of days until
the device is ready to receive them. SMS messages are transmitted within the same cell or to anyone
with roaming service capability.

Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved. 3

 SMS provides mobile-to-mobile, mobile-to-email, and email-to-mobile communication. The messages
are sent to an SMS server. The server then forwards them to their mobile endpoint or to an SMTP mail
server for Internet delivery. A good example of an SMS data application would be notifying a driver of
the address of their next pickup.

SMS Data Communication

Packet-Switched Cellular Data

Packet-Switched cellular data involves overlaying a packet based air interface onto existing circuit-
switched networks. This gives the user an option to use a packet-based data service. The Internet is an
example of a packet data network.

Packet switching is a technique where the information (voice or data) to be sent is broken up into
packets, of a few Kbytes each, which are then routed by the network between different destinations
based on addressing data within each packet. Use of network resources is optimized as the resources
are needed only during the handling of each packet.

In the cellular world, this efficient use of scarce radio resources means that large numbers of users can
potentially share the same bandwidth and be served from a single cell. The actual number of users
supported depends on the application being used and how much data is being transferred.

To illustrate, let’s look at an analog dial-up modem-to-Internet connection. First, your modem
connects to an Internet service provider (ISP), and the ISP connects you to the Internet. In order to do
this, the modem routes packets between you and your ISP. The ISP receives each packet and routes it
appropriately onto the Internet. The same process occurs to get data from the ISP to your computer.

Packet-switched cellular data works exactly the same way. It enables mobile Internet functionality by
allowing interworking between the existing Internet and the cellular network. Any service that is used
over the fixed Internet today – File Transfer Protocol (FTP), web browsing, chat, e-mail, telnet is available
over the cellular network as well.

Packet-switched cellular modem connections also facilitate instant connections whereby information
can be sent or received immediately as the need arises, subject to radio coverage. In fact, cellular modem
connections are often referred to as being “always connected”. High immediacy is a very important
feature for time critical applications such as remote credit card authorization where it would be
unacceptable to keep the customer waiting for even thirty extra seconds.

Packet-Switched Data Communication

4 Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved.

Implementing Your Wireless Modem Solution
The process of implementing your wireless modem solution is fairly straightforward, and can be broken
down into four basic steps: determining your wireless technology, choosing a carrier and a plan, choosing
the type of physical modem connectivity, and activating the service.

Determining Your Wireless Technology

Before you begin looking at wireless modem technology, you must first decide whether you are going
to go with EDGE, GPRS or CDMA (See the Wireless Data Technology Comparison chart on page 2). The
wireless modem you choose is designed specifically to support one technology or the other.

Choosing a technology should really be based on the coverage of the carrier, the application where
it is being used, and whether you have (or prefer) a relationship with one carrier over another. For
more detailed information on EDGE, GPRS and CDMA technologies visit the following web sites at
www.gsmworld.com (GPRS) and www.cdg.org (CDMA).

Choosing a Carrier and a Plan

After you’ve chosen your technology, then you need to choose a carrier that offers it. There are many
carriers out there offering wireless data service. You need to find one that meets your needs based on
their network coverage.

In addition to looking at coverage, you also need to look at the wireless data plans the individual carriers
offer. These plans vary widely in how the service is billed. Speaking in generalities, the following chart
outlines the types of costs associated with a dial-up analog modem application as compared to the
plans available for wireless data applications.

Carrier Plans

Note: Plans vary widely per carrier. These costs are for example only.

To further explain, let’s look at a common application: using your cellular wireless modem to connect to
the Internet. To do this, you can use Dial-up Networking in Windows just like you would with an analog
modem. The difference is that instead of paying a monthly charge for the analog line and a monthly
charge to an ISP you simply set up a wireless data account with a wireless carrier. In this case, your
wireless carrier becomes the ISP as they provide the connection to the Internet.

Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved. 5

Choosing the Type of Physical Modem Connectivity
Once you’ve chosen your technology and a carrier, then you can begin to look at your specific application
and how you want to physically connect the modem to your host device or system. Multi-Tech wireless
modems, for example, are designed around a broad range of interface options including RS-232, Universal
Serial Bus (USB), Bluetooth®, and Ethernet. Multi-Tech wireless modems also support GPS for vehicle
tracking and fleet management applications. Each interface option offers unique features and benefits
related to the technology it supports.

Serial Connectivity. RS-232/USB Application

A serial interface utilizes RS-232 or USB to
connect to any serial device to provide access to
the Internet. An RS-232 interface supports DTE
speeds of up to 460K bps and typically provides
a DE-15 voice/data interface. A USB interface
provides for the easiest modem installation.It
features a 12M bps serial connection and typically
utilizes an RJ-9 jack for voice connectivity. In
addition, with a host-based USB powered wireless modem, no external power supply is required.

Bluetooth Connectivity. Bluetooth Application

A Bluetooth interface provides any Bluetooth-
enabled peripheral device such as a POS
terminal, vending machine, or PDA with cellular
wireless access to the Internet. Providing secure,
standards-based wireless data transfer up to
100 meters, a Bluetooth interface completely
eliminates the need for serial cable connections.
A Class 1 Bluetooth V1.2 compliant wireless
modem utilizes 56-bit encryption and 10
alphanumeric Personal Identification Number
(PIN) authentication. In addition, it utilizes error correction schemes for guaranteed packet delivery.

Ethernet Connectivity. Ethernet Application

A wireless modem utilizing an Ethernet
interface, and built-in routing capabilities,
enables shared Internet access with just one
IP address. It can provide DHCP services and
firewall security utilizing Network Address
Translation and Stateful Packet Inspection
making it ideal for sharing Internet access
among networked PCs. In addition, its ability
to support an “always-on” network connection
allows for around the clock surveillance, monitoring or real-time data acquisition of any remote
Ethernet device such as a Web camera. If the data link is dropped in the event of poor reception or a
complete loss of service, it will automatically re-establish the data link. It can also be configured for
“dial-on demand” so that the wireless modem only accesses the Internet when data is present.

6 Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved.

Activating the Wireless Service
Before you use your wireless modem, you will need to activate the wireless data service. This process is
different depending on the technology.

With EDGE or GPRS, the process of activating the cellular data service is much like activating a cell
phone. Once you have set up an account with your carrier, they (the carrier themselves or a third party
agent) will provide you with a SIM (Subscriber Identity Module) card. This SIM card contains all of the
access rights including identification for billing. The card also contains storage space for SMS and a
phone book. It is plugged into a slot in the front of your wireless modem. The SIM card can be swapped
out easily with new hardware providing you with more flexibility and mobility.

With CDMA, the wireless modem, depending on the carrier, utilizes IP-based Over-The-Air (OTA) activation
technology. Upon installation, the modem immediately and securely registers onto a wireless network
via standard registration messaging. The wireless network automatically identifies the device (through
the Electronic Serial Number), collects user data, and completes the activation and provisioning. In
most cases, the wireless modem is pre-provisioned for the various carriers, which means you need to
order a specific model for your carrier of choice.

Applications
The applications for a cellular wireless modem are exactly the same as those for a standard dial-up
modem. In addition, EDGE, GPRS and CDMA facilitate new data applications that were previously not
available over dial-up connections, such as vehicle tracking and job dispatch.

Applications
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Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved. 7

Benefits
In general, wireless modems provide a seamless integration with your application. They connect to
your host device through an RS-232, USB, Bluetooth, or Ethernet interface, configure and dial using
AT commands, and connect to the cellular network through an antenna. What’s more, they provide
additional benefits above and beyond dial-up analog modem connectivity including better accessibility,
portability, mobility and an overall cost savings.

Accessibility
In some applications, or even some emerging markets, access to a standard PSTN line for a dial-up
connection can be difficult. With cellular wireless, you can install your device/machine and connect to
the Internet anywhere you can get a cellular connection.

Portability
With a dial-up modem, your device/machine is connected via a physical line providing limits to where it
can be located. With cellular wireless modems, you can locate your device/machine anywhere you can
get a cellular connection, which means you can easily move it around. This increased flexibility allows
you to move a vending machine, an ATM, or a convention kiosk to different locations with ease.

Mobility
Mobility is a completely new application that was previously not available to dial-up modems. Cellular
wireless modems, for example, are ideal for vehicle tracking as they can be paired with a Global
Positioning System (GPS) or utilize a built-in GPS module. In addition, nonvoice cellular wireless services
can be used to assign and communicate new jobs from office-based staff to mobile field staff. The 160
characters of a short message are sufficient for communicating most delivery addresses such as those
needed for pizza delivery or a courier package delivery.

Cost Savings
Utilizing cellular wireless technology can also eliminate the hassle and expense of running PSTN lines to
locations where they are not readily available. And, while the cost of cellular wireless modems might be
more expensive than traditional analog dial-up modems, the overall service plan is often less expensive.
In addition, with CSD applications, you save the cost of long distance charges otherwise accrued with
a traditional dial-up modem-to-modem connection. There is also savings associated with a wireless
solution’s quick time-to-market, providing you with rapid deployment of your application.

8 Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved.

Multi-Tech’s Wireless Modem Solutions
Multi-Tech’s wireless modems utilize EDGE, GPRS or CDMA technologies to communicate data and
voice over worldwide cellular communications networks. The external models are ideal for applications
needing a complete wireless modem equipped with an RS-232, USB, Bluetooth or Ethernet interface.
The embedded models are ideal for developers looking to add wireless communications capabilities
with a minimum of development time and expense.

MultiModem® EDGE, MultiModem® GPRS, MultiModem® CDMA

• External wireless modem

• RS-232, USB, Bluetooth, and Ethernet interfaces

• 12-channel GPS functionality

• Desktop or panel mounting

• Carrier approved

SocketModem® EDGE, SocketModem® GPRS, SocketModem® CDMA

• Embedded wireless modem

• Easy integration

• Space efficient Universal Socket Connectivity

• Carrier approved

ModemModule™ GPRS and ModemModule™ CDMA

• Embedded wireless modem

• Compact industrial chassis

• Board-to-board or board-to-cable mounting

• Carrier approved

Wireless Activation Agent

Multi-Tech is a certified national wireless activation agent for Cingular and Sprint. If you are not currently
working with an activation agent, Multi-Tech can simplify the process and setup your wireless account
for you. We offer the same competitive data and voice plans provided by Cingular and Sprint.

Since 1970, Multi-Tech has provided corporations in over 135 countries with superior modem technology,
delivering the most reliable and highest speed connections possible. By consistently exceeding customer
expectations in quality, performance and support, Multi-Tech has become the world’s most successful
maker of corporate modems. Cellular wireless modem technology is a logical next step that best matches
our customer needs and our experience.

Note: Multi-Tech wireless modems support all major wireless carriers. To activate any other plans, contact your local
carrier for details.

For more detailed information on Multi-Tech’s cellular wireless modem solutions, go to

www.multitech.com/PRODUCTS/Categories/External_Device_Networking or give us a call at
1-888-288-5470 (U.S./Canada) or +(763) 785-3500.

Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved. 9

Glossary of Terms
Cell - The geographical area served by a cellular tower.

CDMA (Code Division Multiple Access) - A digital cellular technology that uses spread-spectrum techniques. Unlike
competing systems, such as GSM, that use TDMA, CDMA does not assign a specific frequency to each user. Instead,
every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital
sequence.

CDMA2000 1xRTT - 2.5G CDMA, doubles the voice capacity of cdmaOne networks and delivers peak packet data
speeds of 307 kbps in mobile environments. Backward compatible with cdmaOne networks.

CO (Central Office) - The central office is the lowest, or most basic level of switching in the PSTN network.

CSD (Circuit-Switched Data) - Circuit-switched data provides a temporary connection of two or more communications
channels using a fixed, non-shareable path through the network.

EDGE (Enhanced Data GSM Environment) - A faster version of GSM wireless service. The standard is based on the
GSM standard and uses TDMA multiplexing technology.

FTP (File Transfer Protocol) - A protocol used to transfer files over a TCP/IP network (like the Internet).

GPRS (General Packet Radio System) - A standard for wireless communications which runs at speeds up to 85K bps.
GPRS, which supports a wide range of bandwidths, is an efficient use of limited bandwidth and is particularly suited
for sending and receiving small bursts of data, such as e-mail and Web browsing, as well as large volumes of data.

GSM (Global System for Mobile communications) - One of the leading digital cellular systems. GSM uses narrowband
TDMA, which allows eight simultaneous calls on the same radio frequency. GSM was first introduced in 1991. As
of the end of 1997, GSM service was available in more than 100 countries and has become the de facto standard in
Europe and Asia.

Packet-Switched Network - A method of transferring information in which data is broken into small pieces, called
packets, and transported over shared communications channels.

Provisioning - The process of expediting all the tasks between receiving a request for a service (for example: access
to a wireless network) and making that service available to the customer.

PSTN - The Public Switched Telephone Network that traditionally routes analog voice/data calls from one location
to another over copper wires.

OTA (Over-the-Air) - IP-based activation technology, used by CDMA networks, that utilizes the wireless network to
automatically identify the device, collect user data and complete provisioning.

SIM (Subscriber Identity Module) - A smart card, used by GSM/GPRS devices, that securely stores the key identifying
a mobile subscriber.

SMS (Short Message Service) - Similar to paging, SMS is a service for sending short text messages (up to 160
characters in length) to mobile phones/devices.

Telnet - The TCP/IP standard network virtual terminal protocol that is used for remote terminal connection service
and that allows a user at one site to interact with systems at other sites as if that user terminal were directly
connected to computers at those sites.

VPN (Virtual Private Network) - A private communications network that utilizes dedicated equipment and data
encryption to securely connect remote sites or users together over the public Internet.

Trademarks: ModemModule, MultiModem, SocketModem, Multi-Tech, and the Multi-Tech logo: Multi-Tech Systems, Inc.
All other products or technologies are the trademarks or registered trademarks of their respective holders.

10 Copyright © 2005 Multi-Tech Systems, Inc. All rights reserved.

 Cellular Wireless
Modem Primer
EMEA Headquarters
Multi-Tech Systems (EMEA)
United Kingdom
Tel: +(44) 118 959 7774
World Headquarters Fax: +(44) 118 959 7775
Multi-Tech Systems, Inc
2205 Woodale Drive Multi-Tech Systems (EMEA)
Mounds View, MN 55112 U.S.A France
Tel: +(33) 1-64 61 09 81
Tel: (763) 785-3500 or (800) 328-9717 Fax: +(33) 1-64 61 09 71
Fax: (763) 785-9874
Technical Support: (800) 972-2439 Multi-Tech Computers Pvt. Ltd. (India)
Tel: +(91) 124-5010780 or 124-2340780
www.multitech.com Fax: +(91) 124-2340776

GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet

portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS

CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability

mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA

wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility

GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless

internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility

GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless intern
86002052 08/05

portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS CDMA wireless internet portability mobility GSM/GPRS