Mobile Computing Functions (Cont.)

mashpeemoveMobile - Wireless

Nov 24, 2013 (3 years and 11 months ago)

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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, portable

2
-

Network: different networks: GSM, CDMA, Ethernet,
Wireless LAN, …etc.

3
-

Gateway: Interfacing different transport bearers

4
-

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 Framework

Origin

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 middleware

For 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 gateways

Between 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

Employees

Government

C2G, G2C

C2B, B2C

E2G, G2E

B2E, E2B

B2G, G2B

G2G

B2B

Mobile Computing Platforms

Mobile Device
(Cell Phone, PDA, Pocket PC)
Server
(Web Server,
eMail
server,
Mainframe)
Application
Physical Wireless Network
(Antennas, Transceivers, Base Stations,
Cellular Networks, 802.11 LANs,
Satellites)
Middleware
Services
Network
Transport
Services
Local
Platform
Services
Application
Mobile
Computing
Platform
Network
Transport
Services
Local
Platform
Services
Middleware
Services
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

Web
Server
Content
(XML/HTML)
Back
-
end
Systems
and
Darabases
http
over
wired Internet
Wireless
Gateway
Wireless
Network
http
Wireless
Browser
Web
Browser
Web
Gateway
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 gateway
4. Access from cellular phone over a wireless network
5. Access from wireless gateway to Web Server over wired Interne
t
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 to

easily access and interact with information and services instantly.” w
ww.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

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
Satellite
Systems
Cellular
Networks
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
Personal
Area
Networks
Business
LANs
Example1:
Bluetooth
1 Mbps,
10 Meters
Other examples:
wireless sensor
networks, UWB
Example1:
Motorola
Iridium
up to 64 Mbps
globally
Example 2:
Deep space
communication
Wireless
Local Loops
(Fixed Wireless)
Wireless
MANs
Example1:
LMDS
37 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 M
bps 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 sys
tems 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


Centrex

Router

Link to

Public Ethernet


T1

or

DSL

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 are

student 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

Access

Point

Wired

LAN

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

Switched

Telephone

Network

(PSTN)

Mobile

Telephone

Switching

Center

(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

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

Wireless

Telephone

Business

IP Data

Network

Routing



Wireless

Management
Business

Wireless

Consulting

Business

Wireless

Telephony

Applications

and

Services

Physical Network Elements


Wireless

Network

Management

Wireless

Application

and

Platform

Management

Wireless

Network

Consulting

and

Engineering

Services

Systems

Consulting

Applications

(e.g., SMS,
email,

Wireless Web,

Mobile EC/EB)



Wireless Data

Network

Business

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