This document provides an overview of key concepts in mobile communications, including: - Wireless communications can be divided into mobile communications, which requires non-tethered connectivity for roaming, and fixed wireless, which provides alternative connectivity from fixed locations. - Personal Communications Service (PCS) networks were designed to meet needs for anytime, anywhere connectivity and initially used smaller cell sites than cellular, operating at 1900MHz versus 800MHz for cellular. - Common digital radio frequency protocols for mobile communications include TDMA-based IS-136 and CDMA-based IS-95, which have largely replaced analog protocols. - Mobile networking protocols like ANSI-41 and GSM MAP facilitate roaming and services between

1. Introduction
This module provides a brief introduction to the basic concepts and technologies
associated with mobile communications.
Wireless vs. Mobile Communications
Wireless telecommunications can be divided into two broad categories: mobile
communications and fixed wireless communications. Each category has its own unique
market in terms of customer needs and technology requirements. The mobile
communications market requires mobility or non-tethered communications.
The goal of mobility is anytime, anywhere communications. Mobile communications
technology must be able to allow roaming - the ability to provide service to a mobile
phone users while outside their home system. On the other hand, fixed wireless is
simply an alternative to wired communications. The fixed wireless user does not need
mobility. Instead, the fixed wireless user needs cost effective telecommunications from
fixed locations. Wireless is an alternative means of providing service. It is sometimes
the only means. When the customer is in a remote location, satellite is the only
alternative.
Cellular and PCS
The personal communications concept arose after cellular networks were deployed.
Personal Communications Service (PCS) technologies were designed to meet the
needs of anytime, anywhere personalized communications. PCS networks were
deployed utilizing cellular RF designs similar to cellular. However, many PCS carriers
initially deployed larger groupings of smaller cell sites to cover densely populated urban
areas. PCS also uses a higher portion of the RF spectrum (1900 MHz in the US versus
800 MHz for cellular). Being deployed after the initial cellular networks, PCS networks
also initially had more advanced technologies than PCS, including SS7 network
infrastructure for services such as calling number identification. However, cellular would
soon catch up due to competitive pressures. In aggregate, there are now no substantive
differences between the initial "cellular" networks and "PCS". In fact, they both utilize
the same underlying technologies.
Mobile Communications Protocols
Radio Frequency Protocols
Interim Standard 136 (IS-136) is a specific Time Division Multiple Access (TDMA) based
radio frequency (RF) standard.
IS-95 is a specific Code Division Multiple Access (CDMA) based radio frequency (RF)
standard. With TDMA, multiplexing occurs within time slots within dedicated frequency
band for each call or data session. On the other hand, CDMA is a "spread spectrum

2. technology", utilizing all available frequency and time slots within an allocated service
band.
It is important to be aware that TDMA and CDMA are digital RF protocols. There are
various analog RF protocols that are still in commercial service, but they are being
replaced with TDMA and CDMA as mobile operators upgrade their networks.
Mobile Networking Protocols
IS-136 and IS-95 based networks both utilize ANSI-41 as a protocol for mobile
networking. ANSI-41 based networks are deployed primarily in the Americas and parts
of Asia.
Global System for Mobility (GSM) is a global standard based on TDMA. GSM utilizes
the GSM Mobile Application Part (MAP) as a mobile networking protocol.
Mobile Networking
Cellular/PCS networks can use different type of mobile networking protocols that allow
for roaming – the use of a mobile phone while away from the home area – and
advanced services.
Global System for Mobility (GSM) networks deployed in Europe and throughout the
world utilizes a protocol called the GSM Mobile Application Part (MAP), standardized by
the European Telecommunications Standards Institute (ETSI). Other TDMA based
networks and CDMA networks utilize a protocol called ANSI-41, a protocol standardized
by the Telecommunications Industry Association (TIA) and the American Standards
Institute (ANSI).
Mobile networking entails communication between Home Location Registers (HLR) and
Visiting Location Registers (VLR) - databases used to store information about
subscribers. Communication between these databases allows roaming.
ANSI-41 and GSM MAP
GSM MAP and ANSI-41 are key protocols that utilize SS7 to allow roaming and
advanced as well as more advanced capabilities. Communication between the VLR in
the serving system and the HLR of the home area is facilitated by these mobile
networking protocols and signaling based on a signaling protocol called Signaling
System number Seven (SS7).
In GSM networks, the MAP rides on top of SS7, allowing VLR to HLR (and HLR to VLR)
communications.
In non-GSM networks (such as many of those found in the United States), ANSI-41 is
deployed (which also uses SS7) for HLR/VLR communications.

3. Mobile IN for GSM & ANSI-41
While there are various proprietary-based mobile intelligent network (IN) technologies,
the standards based technologies are often of most value to the mobile network
operator and their customers. These standards based technologies are referred to as
Customized Applications for Mobile Enhanced Logic (CAMEL) and Wireless Intelligent
Network (WIN) and are used in GSM and ANSI-41 based networks respectively.