Mobile Computing

Lecture (2)

Evolution of Computing

Mobile Computing Functions A computing environment is defined as

mobile if it supports one or more of these characteristics:

User mobility: User should be able to move from one physical location to another location and use same service

Network mobility: User should be able to move from one network to another network and use same service

Mobile Computing Functions (Cont.) Device mobility: User should be able to move

from one device to another and use same service

Session mobility: A user session should be able to move from one user-agent environment to another.

Service mobility: User should be able to move from one service to another

Host mobility: The user should can be either a client or server.

Mobile Computing Functions (Cont.) Mobile computing functions can be logically divided

into the major segments:1- User with device: fixed, portable2- Network: different networks: GSM, CDMA, Ethernet,

Wireless LAN, …etc.3- Gateway: Interfacing different transport bearers4- Middleware: handling the presentation and

rendering of the content on a particular device.5- Content: it is the domain where the origin server

and content is.

Mobile Computing Functions (Cont.)

Device Adaptation FrameworkOrigin Server

User with device

Networks & Gateways

Datastore

Middleware Framework

Application Server

Content

Networks

Mobile computing will use different types of networks: fixed telephone network, GSM, GPRS, ATM, …etc.

1- Wireline Networks: designed over wire. It is called fixed network. Copper or fiber optic cables.

2- Wireless Networks: mobile networks 3- Ad-hoc Networks: for this purpose only. 4- Bearers: transport bearers: TCP/IP, http,

protocols for dialup connection.

Middleware and Gateways

Middleware: A software layered between a user application and operating system.

Examples: communication middleware, object oriented middleware, message oriented middleware, database middleware, …etc.

In mobile computing we need different types of middleware components and gateways at different layers of the architecture. These are:

Types of Middleware 1- Communication middleware The application will communicate with different nodes and

services through different communication middleware. Examples could be NT3270 for IBM mainframe or Javamail connector

2- Transaction processing middleware In many cases a service will offer session oriented dialogue

(SoD). For a session to maintain over the stateless Internet. This is done through an application server. The user may be using a device, which demands a short transaction whereas the service at the backend offers a SoD. In such cases a separate middleware component will be required to convert a SoD to a short transaction. Management of the Web components will be handled by this middleware as well.

Types of Middleware (cont.0 3- Behavior management middlewareFor different devices we need different types of rendering. We

can have applications which are developed specially for different types of rendering. For example, we can have one application for Web, another for WAP, and a different for SMS.

4- Communication gatewaysBetween the device and the middleware there will be network of

networks. Gateways are deployed when there are different transport bearers or network with dissimilar protocols. For example, we need an IVR gateway to interface voice with a computer, or a WAP gateway to access internet over a mobile phone.

Mobile Computing Applications Enable the business initiatives by supporting mobility of

Customers Suppliers and Businesses Employees

Mobile computing applications Wireless messaging (e.g., SMS) Mobile ecommerce (M-Commerce) and its variants

Positional commerce (p-commerce) . Voice commerce (v-commerce). Television commerce (T-Commerce)

Mobile ebusiness applications (MEBAs), e.g., M-CRM, M-portal Specialized applications

Location sensitive apps Wireless sensor network apps Mobile agent apps

Two views: Mobile applications are fundamentally new applications. Mobility is another dimension of the existing applications

Mobile Computing Applications Categorization

Consumer

Citizens

Business Employees

EmployeesGovernment

C2G, G2C

C2B, B2C

E2G, G2E

B2E, E2B

B2G, G2B

G2G

B2B

Mobile Computing PlatformsM o b ile D ev ice (C e ll P h o n e , P D A , P o ck e t P C )

S e rv e r (W eb S e rv e r, eM a il se rv e r,M a in fra m e)

A p p lica tio n

P h ys ica l W ire le ss N e tw o rk

(A n te n n a s , T ra n sce iv e rs , B a se S ta tio n s , C e llu la r N e tw o rks , 8 0 2 .1 1 L A N s , S a te llite s )

M id d lew are S e rv ice s

N e tw o rkT ran sp o rt S e rv ice s

L o ca lP la tfo rmS erv ice s

A p p lica tio n

M o b ile C o m p u tin gP la tfo rm N etw o rk

T ran sp o rt S e rv ice s

L o ca lP la tfo rmS erv ice s

M id d lew are S e rv ice s

Internet as the Network Platform

IP

WAN1

(Typically

ATM,

Frame Relay,

X.25)

Switch/Gateway

IP

WAN2

IP

WAN3

Switch/Gateway

Switch/Gateway

83.13.17.3

83.13.17.4

Bank1.co..uk

Level3.co..uk

75.10.17.1

75.10.17.3

www.IBM.com

www.sun.com

108.2.11.5

108.2.11.7

cs.um.edu

arts.um.edu

•DNS (Domain Name Services) translates cs.um.edu to 108.2.11.5•Telnet cs.um.edu = Telnet 108.2.11.5•FTP cs.um.edu = FTP 108.2.11.5

The Figure shows a conceptual and partial view of the Internet. This Internet shows three networks (a university network with two computers, a commercial company network, and a network in UK). Each computer (“host”) on this network has an IP address and has been assigned a domain name as well. The Internet is very heterogeneous (i.e., different computers, different physical networks). However, to the users of this network, it provides a set of uniform TCP/IP services (TCP/IP hides many details). Once a device (mobile device or a laptop) has an IP address, then it can send messages to any other device with another IP address.

Wireless Web

WebServer

Content(XML/HTML)

Back-endSystemsandDarabases

httpoverwired Internet

WirelessGatewayWireless

Network

http

WirelessBrowser

WebBrowser

WebGateway

1

2

3

4

5

1. Access from Web browser to Web Server over wired Internet 2. Access to Web contents from HTML/XML files 3. Access to non-Web content through a Web gateway4. Access from cellular phone over a wireless network5. Access from wireless gateway to Web Server over wired Internet

Wireless Middleware and Wireless Gateways (WAP, i-mode, J2ME, MMIT, BREW)Wireless middleware, also known as mobile computing middleware, smoothes over the mobile computing issues, as much as possible, so that the same applications can run on wired as well as wireless networks. It performs the following functions:

Establishes connections between mobile clients and servers over wireless networks and delivers messages over the connection.

Transforms data from one format to another (e.g., one type of markup to another).

Detects the mobile device characteristics and optimizes the wireless data output according to device attributes.

Compresses data to minimize the amount of data being sent over a slow cellular wireless link.

Encrypts/decrypts data for security. Allows monitoring and troubleshooting of wireless devices and networks.Naturally not all these features are needed for every mobile computing

application. Some applications need less middleware support than others.

WAP(Wireless Application Protocol)

•Intended for data entry/display on cellular phones•“An open, global specification that empowers mobile users with wireless devices toeasily access and interact with information and services instantly.” www.wapforum.org•Complete protocol stack similar to Internet protocols but optimized for wireless information pull and push transport layer and above; across multiple wireless technologies

Web Server

WAPGateway

Wirelessnetworkwith WAPProtocol

WAP Phone

Internet

WAP and WAE

WAP is a set of protocols to enable the presentation and delivery of wireless information and telephony services on mobile phones and other wireless devices. The WAP model, shown in Figure, is based heavily on the existing Web; i.e., a WAP gateway translates between the Web server and the WAP

clients. WAP provides a Wireless Application Environment (WAE) for creating WAP applications and services.

The main elements of WAE are: A markup language called Wireless Markup

Language (WML) that is similar to XML but that has been optimized for wireless links and devices. A scripting language (WMLScript) is also provided.

Specification of a microbrowser in the wireless terminal. This is analogous to the standard Web browser – it interprets WML and WMLScript in the handset and controls presentation to the user.

A framework, the Wireless Telephony Applications (WTA) specification, to allow access to telephony services such as call control, messaging, etc. from within the WMLScript applets.

WIRELESS NETWORKS

Different type of wireless networks support mobile computing applications and platforms

Wireless networks, as the name implies, interconnect devices without using wires – instead they use the air as the main transmission medium. Wireless networks are enjoying widespread public approval with a rapidly increasing demand. The unique features of the wireless networks are:

The bandwidths, and consequently data rates, of communication channels are restricted by government regulations. The government policies allow only a few frequency ranges for wireless communications.

The communication channel between senders/receivers is often impaired by noise, interference and weather fluctuations.

The senders and receivers of information are not physically connected to a network. Thus the location of a sender/receiver is unknown prior to start of communication and can change during the conversation.

The next Figure displays an overall classification of wireless networks in terms of distance covered, from very short range (10 meters) to very long range (thousands of miles).

Wireless LANs (WLANs) allow workstations in a small area (typically less than 100 meters) to communicate with each other without using physical cables. The most popular example of Wireless LANs are the IEEE 802.11 LANs that deliver between 11Mbps to 54 Mbps data rate. Another example is the Bluetooth LANs (for the data rates in the 1 Mbps range over 10 meters). Very short range LANs such as Bluetooth are also known as Wireless Personal Area Networks (WPANs)

Wireless metropolitan area networks (WMANs) have been used in traditional packet radio systems often used for law-enforcement or utility applications. An interesting area of growth for wireless MANs is the wireless local loop (WLL) that is quite popular with long distance telephone companies. WLLs are fixed wireless networks where the devices being connected are stationary.

Wireless WANs (WWANs) provide wireless support over long distances. Traditional examples of wireless WANs are paging networks and satellite systems. However, a great deal of wireless WAN activity at present revolves around the cellular networks that provide support for cellular phones and other handheld devices such as PDAs and laptops.

Wireless Networks

SatelliteSystems

CellularNetworks

Wireless LANs

Example1: GSM, 9.6 Kbps, wide coverage

Example2: 3G, 2 Mbps, wide coverage

Example1:802.11b 11 Mbps, 100 Meters

Other examples:802.11g, HiperLAN2

Wireless WANs

PersonalArea Networks

BusinessLANs

Example1:Bluetooth1 Mbps, 10 Meters

Other examples:wireless sensor networks, UWB

Example1: Motorola Iridiumup to 64 Mbps globally

Example 2:Deep space communication

WirelessLocal Loops(Fixed Wireless)

Wireless MANs

Example1: LMDS37 Mbps, 2-4 Km

Example2:FSO 1.25 Gbps 1-2 KM

Paging Networks

Example1:FLEX, 1.2 Kbps

Example2:ReFLEX, 6.4Kbps

Issues unique to wireless•Frequency allocation•Multiple Access•Location

Local Area Networks (LANs) Metropolitan Area Networks (MANs)

Wide Area Networks (WANs)

Wired Wired LANs

Ethernet (10-100 Mbps, 150 to 500 meters)

Token Ring (4 -16 Mbps, 200 to 500 meters)

Wired MANs

FDDI (100 Mbps, 50 Kilometers)

Wired WANs

ATM (44 Mbps to 140 Mbps)

Frame Relay (44 Mbps)

Wireless Wireless LANs

Bluetooth (1 Mbps, 10 meters)

IEEE 802.11 LANs (2-11 Mbps, 100 meters)

Wireless MANs

wireless local loops (10 Mbps, 100 Kilometers)

Wireless WANs

Current GSM systems at 9.6Kbps, future 3G systems at 2 Mbps

A sample environment that supports wireless Ethernet LANs The next Figure shows a sample environment

that supports wireless Ethernet LANs so that the students can access the school server as well as the public Internet. In this configuration, several wireless access points are connected to a wired LAN that is connected to the Internet and an internal server. Each access point supports mobile computers with wireless Ethernet cards in a wireless cell that spans around 100 meters.

A Sample Wireless School

Wireless LAN Cell

Wireless LAN Cell

Wireless LAN Cell

CentrexRouter

Link to

Public Ethernet

T1orDSL

X

Y Z

LAN Server

Wired Ethernet LAN

•X, Y, Z are access points for the wireless Ethernet LANs

A B

C D

•A, B, C, D arestudent laptops

Wireless Personal Area Networks (WPANs), Bluetooth and UWB Wireless Personal Area Networks (WPANs) are short-range (10

meter or less) radio networks for personal, home, and other special uses. Within the WPAN family, several specifications such as Bluetooth, wireless sensor networks, and UWB (Ultra Wideband) have emerged.

Bluetooth is a wireless cable replacement standard that provides a 1 Mbps data rate over 10 meters or less. It typically consists of a group of linked devices, such as a computer wirelessly connecting to a set of peripherals, known as as a “piconet.” Multiple piconets can be formed to provide wider coverage. Due to its relatively low data rates and very short distances,

Bluetooth is being used in home appliances, “Bluetooth-enabled” cars, and other such applications.

Bluetooth Founders: Ericsson, IBM, Intel, Nokia, Toshiba; May 98 Currently: Over 850 companies, V1.0 spec issued 7/99 Small form factor, low-cost, short range radio link between

mobile PCs, phones and other portable devices Relatively fast, short packets Software for service and device discovery Typical application: cellular phone to PDA or earphone

The next Figure shows a simple Bluetooth was designed to allow low-bandwidth wireless connections to become so simple to use that they seamlessly mesh into your daily life. A simple example of a Bluetooth application is updating your cellular phone directory. The main idea is that this could happen automatically as soon as the phone is within the range (10 meters) of your desktop computer where your directory resides.

Bluetooth

Cellular Network

PSTN

AccessPoint

WiredLAN Bluetooth Piconet

(1 Mbps, 10 meters)

Cellular Communication Networks The next Figure shows a high-level view of a cellular

communication network used in wide areas. The cellular network is comprised of many “cells” that typically cover 1 to 25 miles in area.

The users communicate within a cell through wireless communications. A base transceiver station (BTS) is used by the mobile units in each cell by using wireless communication. One BTS is assigned to each cell. Regular cable communication channels are used to connect the BTSs to the mobile telephone switching office (MTSO). The MTSO determines the destination of the call received from a BTS and routes it to a proper destination, either by sending it to another BTS or to a regular telephone network. Keep in mind that the communications is wireless within a cell only. The bulk of cell-to-cell communication is carried through regular telephone lines.

A Cellular Network

Public SwitchedTelephoneNetwork(PSTN)

MobileTelephoneSwitchingCenter(MTSC)

Base Transceiver Station (BTS) Mobile User

Cell 1

Cell 2

Cordless connection

Wired connection

HLR VLR

HLR = Home Location Register

VLR = Visitor Location Register

Two issues are of fundamental importance in this conceptual model: Cell sizes. The sizes of the cells can be small or large. In some

cases, such as cordless networks, the cell sizes are only a few feet. But in cellular networks, the cell sizes can be many miles (10 to 20 miles).

Location (“Roaming”) support. In some cases, the user is only covered for his “home cell”; in others, the user can roam between cells and still be covered adequately. For example, in a cordless phone, the user is only covered at the home cell, while roaming is typically supported in a wide coverage area where the user can travel through several cells.

Cellular networks: What is 3G Anyway?

1G: First generation wireless cellular: Early 1980s Analog transmission, primarily speech

2G: Second generation wireless cellular: Late 1980s Digital transmission Primarily speech and low bit-rate data High-tier: GSM, IS-95 (CDMA), etc Low-tier (PCS): Low-cost, low-power, low-mobility e.g. PACS

2.5G: 2G evolved to medium rate (< 100kbps) data 3G: future: Broadband multimedia

144 kbps - 384 kbps for high-mobility, high coverage 2 Mbps for low-mobility and low coverage

Evolution to 3G

1G(<1Kbps)

1 Kbps

10 Kbps

100 Kbps

2 Mbps

1 Mbps

Data Rates

1980 1990 2000 2010

2G(9.6Kbps)

2.5G(10-150Kbps)

3G(144Kbps to 2Mbps)

Years

Wireless LANs First generation of products at about 1-2 Mbps

Lucent’s WaveLAN, RadioLAN, etc. factor of 10 less bandwidth than current Ethernet

Next generation of products at 10-11 Mbps factor of 10 less bandwidth than 100 Mbps Ethernet

IEEE 802.11 standard – very successful at present (wi-Fi) Can deliver up to 64 mbps

Important niche and enterprise applications (e.g. hospitals)

Increasing horizontal market interest (e.g. SOHO)

Satellite Communications

UplinkDownlink

Satellite Communications (cont.) A satellite system consists of the following components: Earth Stations – antenna systems on or near the earth Uplink – transmission from an earth station to a satellite Downlink – transmission from a satellite to an earth

station (different from uplink, typically faster, can be broad)

Transponder – electronics in the satellite that convert/amplify uplink signals to downlink signals. There are typically 16 to 20 transponders per satellite, each with 36-50 MHz BW (bandwidth).

The Wireless Business

The next figure shows the main business sectors and illustrates one view of the complex and multidimensional aspects of wireless business in terms of the physical communication network, network transport and connectivity services, mobile computing platforms, and mobile computing applications. Some business sectors concentrate on higher level services such as mobile applications, while others provide the low-level network elements. As expected, one large business may be involved in many business sectors, and vice versa. Similarly, many small businesses may provide different elements of one business sector.

Reference Model

1. Physical

2. Data Layer

3. Network

4. Transport

5. Session

6. Presentation

7. Application

Call Switching

(Cellular networks,Wireless LANs, Satellites, Wireless Local Loops)

PSTN Routing

WirelessTelephoneBusiness

IP DataNetwork Routing

WirelessManagement Business

WirelessConsultingBusiness

WirelessTelephonyApplications and Services

Physical Network Elements

WirelessNetworkManagement

WirelessApplication and Platform Management

WirelessNetworkConsultingand EngineeringServices

SystemsConsulting

Applications(e.g., SMS, email,Wireless Web, Mobile EC/EB)

Wireless DataNetworkBusiness

Questions 1) In your view, what are the top 3 strengths and

weaknesses of wireless systems? Rank them in order of priority. What can be done to address the weaknesses?

2) What is a mobile computing platform, what are its main components and how do these

components support mobile computing applications? 3) What is wireless Internet and what role does

Mobile IP play in wireless Internet? 4) What is wireless middleware and how does it

differ from wireless gateways? Give an example. 5) What are the main elements of wireless

networks? What is the fastest wireless network and what is the slowest? Which wireless networks go the farthest and which ones are designed for the shortest distances