IT6601 MOBILE COMPUTING M.I.E.T. ENGINEERING COLLEGE€¦ · it6601 – mobile computing m.i.e.t./cse/iii yr/mobile computing department of computer science and engineering course

IT6601 – MOBILE COMPUTING

M.I.E.T./CSE/III YR/MOBILE COMPUTING

DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

COURSE MATERIAL IT6601-MOBILE COMPUTING

M.I.E.T. ENGINEERING COLLEGE (Approved by AICTE and Affiliated to Anna University Chennai)

TRICHY – PUDUKKOTTAI ROAD, TIRUCHIRAPPALLI – 620 007




SYLLABUS (THEORY)

Sub. Code : IT6601 Branch/Year/Sem : CSE/III/VI Sub Name : MOBILE COMPUTING Batch : 2016-2020 Staff Name : A.BARVEEN Academic Year : 2018-2019

L T P C 3 0 0 3

UNIT I INTRODUCTION 9 Mobile Computing – Mobile Computing Vs wireless Networking – Mobile Computing Applications –Characteristics of Mobile computing – Structure of Mobile Computing Application. MAC Protocols –Wireless MAC Issues – Fixed Assignment Schemes – Random Assignment Schemes – Reservation Based Schemes. UNIT II MOBILE INTERNET PROTOCOL AND TRANSPORT LAYER 9 Overview of Mobile IP – Features of Mobile IP – Key Mechanism in Mobile IP – route Optimization. Overview of TCP/IP – Architecture of TCP/IP- Adaptation of TCP Window – Improvement in TCP Performance. UNIT III MOBILE TELECOMMUNICATION SYSTEM 9 Global System for Mobile Communication (GSM) – General Packet Radio Service (GPRS) –Universal Mobile Telecommunication System (UMTS). UNIT IV MOBILE AD-HOC NETWORKS 9 Ad-Hoc Basic Concepts – Characteristics – Applications – Design Issues – Routing – Essential of Traditional Routing Protocols –Popular Routing Protocols – Vehicular Ad Hoc networks ( VANET) –MANET Vs VANET – Security. UNIT V MOBILE PLATFORMS AND APPLICATIONS 9 Mobile Device Operating Systems – Special Constrains & Requirements – Commercial Mobile Operating Systems – Software Development Kit: iOS, Android, BlackBerry, Windows Phone – M Commerce– Structure – Pros & Cons – Mobile Payment System – Security Issues. TOTAL: 45 PERIODS





TEXT BOOK:

1. Prasant Kumar Pattnaik, Rajib Mall, “Fundamentals of Mobile Computing”, PHI Learning Pvt.Ltd, New Delhi – 2012.

REFERENCES: 1. Jochen H. Schller, “Mobile Communications”, Second Edition, Pearson Education, New Delhi,2007. 2. Dharma Prakash Agarval, Qing and An Zeng, "Introduction to Wireless and Mobile systems", Thomson Asia Pvt Ltd, 2005. 3. Uwe Hansmann, Lothar Merk, Martin S. Nicklons and Thomas Stober, “Principles of Mobile Computing”, Springer, 2003. 4. William.C.Y.Lee,“Mobile Cellular Telecommunications-Analog and Digital Systems”, Second Edition,Tata Mc Graw Hill Edition ,2006. 5. C.K.Toh, “AdHoc Mobile Wireless Networks”, First Edition, Pearson Education, 2002. 6. Android Developers : http://developer.android.com/index.html 7. Apple Developer : https://developer.apple.com/ 8. Windows Phone Dev Center : http://developer.windowsphone.com 9. BlackBerry Developer : http://developer.blackberry.com/

SUBJECT IN-CHARGE HOD/CSE




COURSE OBJECTIVE

1. Understand the basic concepts of mobile computing

2. Be familiar with the network protocol stack

3. Learn the basics of mobile telecommunication system

4. Be exposed to Ad-Hoc networks

5. Gain knowledge about different mobile platforms and application development

COURSE OUTCOMES

1. Comprehend the basics of mobile Computing

2. Express the functionality of Mobile IP and Transport Layer

3. Classify different types of mobile telecommunication systems

4. Implement Adhoc networks with routing protocols

5. Use mobile operating systems in developing mobile applications

6. Synthesize new knowledge in the area of mobile computing by using

appropriate techniques.

Prepared by Approved by Verified By STAFF NAME PRINCIPAL HOD (A.BARVEEN)

Sub. Code : IT6601 Branch/Year/Sem : CSE/III/VI Sub Name : MOBILE COMPUTING Batch : 2016-2020 Staff Name : A.BARVEEN Academic Year : 2018-2019





UNIT- I

INTRODUCTION

1.1 Mobile Computing Introduction:

What is mobile Computing

• What is mobile computing?

Users with portable computers still have network connections while they move.

• A simple definition could be

Mobile Computing is using a computer (of one kind or another) while on the

move.

1.2 Mobile Computing Vs wireless Networking

Mobile computing means communication services on the move. Wireless

communication is the basis for mobile communication.

Wireless network is classified in to two types.

1) Fixed Infra structure Network.

2) Adhoc Network.

Fixed Infra structure Network: Wireless device connects to the access point to

connect to the network – Access point acts as a hub to connect two wireless

devices.

Adhoc Network: Collection of wireless mobile nodes (devices) dynamically

forming a temporary network without the use of any existing network

infrastructure





Wired Networks Mobile Networks

High bandwidth Low bandwidth

Low bandwidth

variability

High bandwidth

Variability

Can listen on wire Hidden terminal

Problem

High power

machines

Low power machines

High resource

machines

Low resource

machines

need physical

access

need proximity

1.3 Applications for mobile computing

There are several applications for mobile computing including wireless

remote access by travelers and commuters, point of sale, stock trading,

medical emergency care, law enforcement, package delivery, education, insurance

industry, disaster recovery and management, trucking industry, intelligence

and military.

Most of these applications can be classified into:

Wireless and mobile access to the Internet Wireless and mobile access to private Intranets Wireless and Adhoc mobile access between mobile computers.

1.4 Mobile Computing -Characteristics

Ubiquity Anywhere. Anytime.



Location Awareness: Current location of the user can be found out using GPS (Global

positioning system)

Ex: Personalized application to find car maintaining service, Traffic

control application, and Fleet management application when travelling by

car.

Adaptation Adjust the bandwidth fluctuation automatically without disturbing the user

Personalization: Services can be personalized according to the user need. Some type of information

can be obtained from the specific source.

1.5 Application Structure

The simple three tier architecture

Presentation tier:

User interface: request and response in a meaningful way. Needs web browser and client program for transfer of information.



Application tier: Logical decision and calculation is performed in this layer. Get the information from the user and makes the decision. Moves data between presentation and data layers. This layer is implemented using JAVA, .NET services, cold fusion etc. Data tier: Contains database in which information is stored and retrieved. 1.6 Wireless MAC Protocols – Issues

The medium access control or media access control (MAC) layer is the

Lower sub layer of the data link layer (layer 2) of the seven-layer OSI model.

Wireless Channel (Wireless medium) is shared among multiple neighboring

nodes.

If more than one MS transmit at a time on the shared media, a collision occurs

How to determine which MS can transmit?

Access Control protocols define rules for orderly access to the shared medium

It should have the following features

Fairness in sharing Maximize the utilization of the channel Support different types of traffic Should be robust for equipment failures and changing network condition. There are two types of basic classification to avoid medium access problem

1) Contention protocols 2) Conflict-free protocols

Contention protocols:

Contention protocols resolve a collision after it occurs or try to avoid it. These

protocols execute a collision resolution protocol after each collision.

https://en.wikipedia.org/wiki/Data_link_layerhttps://en.wikipedia.org/wiki/OSI_model



Conflict-free protocols:

Conflict-free protocols (e.g., TDMA, FDMA, and CDMA) ensure that a

collision can never occur

Hidden Terminal Problem

A hidden node is one that is within the range of the intended destination but out

Of range of sender

Node B can communicate with A and C both A and C cannot hear each other When A transmits to B, C cannot detect the transmission using the carrier

sense mechanism

C falsely thinks that the channel is idle If C transmits, collision will occur at node B

Exposed Terminal Problem

• An exposed node is one that is within the range of the sender but

out of range of destination.

• B sends to A, C wants to send to D.

• C has to wait, CS signals a medium in use.

• since A is outside the radio range of C waiting is not necessary

• C is “exposed” to B.



1.7 Fixed-assignment schemes

FDMA

FDMA is the process of dividing one channel or bandwidth into multiple

individual bands, each for use by a single user. Each individual band or channel

is big enough to hold the signal to be propagated

For full duplex communication each user is allotted two channel

One channel for sending the data (forward link) other channel for receiving the

data (reverse channel).When the channel is not in use no one is permitted to use

that channel.

Advantages of FDMA

• Channel bandwidth is relatively narrow (30 kHz)

• FDMA algorithms are easy to understand and implement.

• Channel Operations in FDMA are simple.

• No need for network timing

• No restriction regarding the type of baseband or type of modulation



Disadvantages to using FDMA

If channel is not in use, it sits idle. No high channel utilization.

The presence of guard bands

• Need right RF filtering to reduce adjacent channel interference

• Maximum bit rate per channel is fixed

TDMA – Time Division Multiple Access

FDMA – Frequency Division Multiple Access

CDMA – Code Division Multiple Access

TDMA

TDMA allocates each user a different time slot on a given frequency. TDMA Divides each cellular channel into three time slots in order to increase the amount of data that can be carried. Each user occupies a cyclically repeating time slot.

All the nodes use the same channel but in different time given to them in Round Robin Fashion.



Advantages of TDMA

Flexible bit rate

• No frequency guard band required

• No need for precise narrowband fi lters

• Easy for mobile or base stations to initiate and execute hands off

• Extended battery life

• It is very cheap.

Disadvantages to using TDMA

Unused time slot is wasted. So it will lead to less channel utilization. Has a predefined time slot. When moving from one cell site to other, if all the time

slots in the moved cell are full the user might be disconnected.

Multipath distortion Code division Multiplexing Access: CDMA

Many users can use the channel to send the data. Collision can be avoided

using code. Each user is allotted different codes .when sending a data the users

can multiplex their data with the code and send the data in the same channel.so

different users use the same channel at the same time by using the coding

technique. The code can be generated by using a technique called m bit pseudo-

noise code sequence.by using m bits 2m codes can be obtained. From these each

user can use one code.

Advantages of CDMA

Many users of CDMA use the same frequency, TDD or FDD may be used

• Multipath fading may be substantially reduced because of large signal

bandwidth.

• No limit on the number of users.

• Easy addition of more users.

• Impossible for hackers to decipher the code sent.



Disadvantages to using CDMA

As the number of users increases, the overall quality of service decreases

• Self-jamming.

• Near-Far- problem arises.

1.8 Random Access Scheme

• ALOHA

• CSMA

Simple ALOHA

“Free for all”: whenever station has a frame to send, it sends. It does not check if the channel is free or not. Station listens for maximum RTT for an ACK. If no ACK, re-sends frame. If two or more users send their packets at the same time, a collision occurs

and the packets are destroyed it does not work well when many nodes are

ready to send.

In pure ALOHA, frames are transmitted at completely arbitrary times

Pure ALOHA: Performance Vulnerable period for the shaded frame.



S=Ge-2G, where S is the throughput (rate of successful transmissions) and G is

the offered load.

• S = Smax=1/2e = 0.184 for G=0.5.

Slotted Aloha

• Divide time up into small intervals, each corresponding to one packet.

• At the beginning of the time slot only data will be sent.

• It sends a signal called beacon frame. All the nodes can send the data only

at the starting of the signal.

• This also does not work well if many nodes are there to send the data.

• Vulnerable period is halved.

• S = G e-G.

• S = Smax = 1/e = 0.368 for G = 1.



Carrier Sense Multiple Access (CSMA)

• Station that wants to transmit first listens to check if another transmission

is in progress (carrier sense).

• If medium is in use, station waits; else, it transmits.

• Collisions can still occur.

• Transmitter waits for ACK; if no ACK, retransmit.

Two types of Transmission:

CSMA/CA

CSMA/CDCSMA/CA Protocol

• If the channel is sensed as busy, no station will use it until it goes free

• If the channel is free the node can start transmitting the data.

• This is the basic idea of the Carrier Sense Multiple Access (CSMA)

protocol.

• There are different variations of the CSMA protocols:

• 1-persistent CSMA

• No persistent CSMA

• p-persistent CSMA

• 1-persistent CSMA (IEEE 802.3)

– If medium idle, transmit; if medium busy, wait until idle; then transmit

with p=1.

– If collision, waits random period and starts again.

• Non-persistent CSMA: if medium idle, transmit; otherwise wait a

random time before re-trying.

– Thus, station does not continuously sense channel when it is in use.

• P-persistent: when channel idle detected, transmits packet in the first

slot with p,if the channel is not idle wait for thr the probability(1-p)and

the sense the channel.

CSMA/CD

• CSMA with collision detection. Stations can sense the medium

while transmitting



• A station aborts its transmission if it senses another transmission is

also happening (that is, it detects collision) in the same time.

CSMA/CD Protocol

1. If medium idle, transmit; otherwise 2.

2. If medium busy, some time and then sense the medium again, then transmit

with p=1.

3. If collision detected, transmit brief jamming signal and abort transmission.

4. After aborting, wait random time, try again.

Summary

CSMA (Carrier Sense Multiple Access) Improvement: Start transmission only if no transmission is

ongoing.

CSMA/CA (CSMA with Collision Avoidance) Improvement: Wait a random time and try again when carrier is

quiet. If still quiet, then transmit.

CSMA/CD (CSMA with Collision Detection) Improvement: Stop ongoing transmission if a collision is

detected.

1.9 Reservation based scheme:

CONCEPT:

MACAW: A Media Access Protocol for Wireless LANs is based on MACA (Multiple Access Collision Avoidance) Protocol



MACA • When a node wants to transmit a data packet, it first transmit a

RTS (Request to Send) frame.

• The receiver node, on receiving the RTS packet, if it is ready to

receive the data packet, transmits a CTS (Clear to Send) packet.

• Once the sender receives the CTS packet without any error, it

starts transmitting the data packet.

• If a packet transmitted by a node is lost, the node uses the binary

exponential back-off (BEB) algorithm to back off a random

interval of time before retrying.



MACAW

Variants of this method can be found in IEEE 802.11 as DFWMAC (Distributed Foundation Wireless MAC),

MACAW (MACA for Wireless) is a revision of MACA. • The sender senses the carrier to see and transmits a RTS

(Request to Send) frame if no nearby station transmits a RTS.

• The receiver replies with a CTS (Clear to Send) frame.

• Neighbors

• See CTS, then keep quiet.

• See RTS but not CTS, then keep quiet until the CTS is

back to the sender.

• The receiver sends an ACK when receiving a frame.

• Neighbors keep silent until see ACK.

• Collisions

• There is no collision detection.

• The senders know collision when they don’t receive CTS.

• They each wait for the exponential back off time.



UNIT II

MOBILE INTERNET PROTOCOL AND TRANSPORT LAYER

2.1 Overview of Mobile IP

Mobile IP (or MIP) is an Internet Engineering Task Force

(IETF) standard communications protocol that is designed to allow mobile

device users to move from one network to another while maintaining a

permanent IP address.

MOBILE IP Terminology.



https://en.wikipedia.org/wiki/Internet_Engineering_Task_Forcehttps://en.wikipedia.org/wiki/Protocol_%28computing%29



Mobile Node (MN)

A system (node) that can change the point of attachment to the

network without changing its IP address. The Mobile Node is a device such

as a cell phone, personal digital assistant, or laptop which has roaming

capabilities.

Home Network

Home Network is the network of a mobile node where it gets its

original IP Address.

Home Agent (HA)

• Stores information about all mobile nodes and its permanent address.

• It maintains a location directory to store where the node moves.

• It acts as a router for delivering the data packets.

Foreign Agent (FA)

ds the packet to the MN

Care-of Address (COA)

Care-of address is a temporary IP address for a mobile node

(mobile device) that helps message delivery when the device is connected

somewhere other than its home network. The packet send to the home

network is sent to COA.

COA are of two types

Foreign agent COA: It is the static IP address of a foreign agent on a visited

network

Co-located COA: Temporary IP address is given to the node visited the

new network by DHCP.

Correspondent Node (CN)

Node communicating to the mobile node.

Foreign Network

The foreign network is current subnet to which the mobile node is visiting.

http://csetube.weebly.com/http://csetube.weebly.com/http://csetube.weebly.com/http://csetube.weebly.com/http://csetube.weebly.com/



Tunnel

It is the path taken by the encapsulated packets.

2.2 Features of Mobile IP

Transparency mobile end-systems keep their IP address Continuation of communication after interruption of link.

Compatibility Compatible with all the existing protocols

Security Provide secure communication in the internet

Efficiency and scalability only little additional messages to the mobile system required

(connection typically via a low bandwidth radio link)

World-wide support of a large number of mobile systems in the whole Internet.

2.3 Key Mechanism in Mobile IP

To communicate with a remote host, a mobile host goes through three

phases:

Agent discovery, registration, and data transfer.

• Agent Discovery A Mobile Node discovers its Foreign and Home Agents during its move. • Registration

The Mobile Node registers its current location with the Foreign Agent

and Home Agent during registration.

http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gif



• Tunneling

A Tunnel(like a pipe) is set up by the Home Agent to the care-of

address (current location of the Mobile Node on the foreign network) to

send the packets to the Mobile Node as it roams.

PACKET DELIVERY

1) Agent discovery

A mobile node has to find a foreign agent when it moves away from its

home network. To do this, mobile IP describes two methods:

Agent advertisement. Agent solicitation.

Agent advertisement:

The Home Agent and Foreign Agent advertise their services on the network

by using the ICMP Router Discovery Protocol (IRDP). The Mobile Node

listens to these advertisements to determine if it is connected to its home

network or foreign network.

http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gif



Home agents and foreign agents broadcast advertisements at regular

intervals by using the packet format given below.

Type: 16: agent advertisement.

Length: depends on number of care-of addresses advertised.

Sequence number: Number of advertisement sent since the

agent was initialized.

Lifetime: Lifetime of advertisement.

Address: Number of address advertised in this packet.

Addresses: Address of the router.

Registration Lifetime: Maximum lifetime a node can ask during

registration.

R: Registration with this foreign agent is required (or another foreign agent

on this network). Even those mobile nodes that have already acquired a

care-of address from this foreign agent must reregister.

B: Busy...

H: home agent on this network.

F: foreign agent on this network.

M: minimal encapsulation

G: This agent can receive tunneled IP datagrams that use Generic Routing

Encapsulation (GRE),

Y: This agent supports the use of Van Jacobson header compression

Care-of address: The care-of address or addresses supported by this agent

on this network.



Type: 19, indicates that this is a prefix-length advertisement

Length: N, where N is the value of the Numb Address field in the ICMP

router advertisement portion of this ICMP message.

Agent Solicitation: If the MN doesn’t receive any advertisement by the

agent, then the MN must ask its IP by means of solicitation.

2) Registration

Mobile nodes when visiting a foreign network, informs their home agent of

their current care-of address, renew a registration if it expires.

Diagram:

The mobile node when travels to the foreign network and gets the care of

address from the foreign network it has to inform this to the home network.

This is done using the registration process.

The process are

1) It first sends the registration request message to the foreign network .This

is the registration process with the foreign network. The registration request

message consists of mobile node’s Permanent IP Address and the home

agent’s IP address.

2) The foreign agent will send the registration request message to the home

agent.



3) The home agent will store this information in its routing table. This is

called mobility binding

4) The home agent then sends an acknowledgement to the foreign agent.

5) The foreign agent passes this reply to the mobile node

6) The foreign agent updates its visitor list.

3) Tunneling and encapsulation

This process forward IP datagram (packet) from the home

agent to the care-of address.

Tunnel makes a virtual pipe for data packets between a tunnel

entry and a tunnel endpoint.

Packets entering a tunnel travel inside the tunnel and comes out

of the tunnel without changing.

When a home agent receives a packet for a mobile host, it forwards that packet to the care of address using IP-within-IP encapsulation.

IP-in-IP encapsulation means the home a get inserts a new IP header (COA address) added to the original IP packet.

The new header contains HA address as source and Care of Address as destination.

Tunneling, i.e., sending a packet through a tunnel is achieved by using

encapsulation.

Encapsulation means taking a packet consisting of packet header and data

and putting it into the data part of a new packet.



The new header is also called the outer header for obvious reasons. Old header is called inner header .There are three methods of

encapsulation

IP-in-IP encapsulation: The figure shows the format of the packet

The packet consists of outer header and inner header

Outer header fields

The version field : 4 for IP version 4 IHL: DS (TOS) is just copied from the inner header.

The length field covers the complete encapsulated packet. TTL must be high enough so the packet can reach the tunnel

endpoint.

The next field, here denoted with IP-in-IP, is the type of the protocol used in the IP payload. This field is set to 4, the protocol type for IPv4

because again an IPv4 packet follows after this outer header.

IP checksum is calculated as usual. The next fields are the tunnel entry as source address (the IP address

of the HA) and the tunnel exit point as destination address (the

COA).



Inner header fields

It starts with the same fields as outer header. The only change is TTL

which is decremented by 1. This means that the whole tunnel is considered

a single hop from the original packet’s point of view. Finally, the payload

follows the two headers.

2.4 Route Optimization

Triangle Routing: Tunneling forwards all packets go to home network (HA) and then sent to MN via a tunnel.

(CN->HNMN) Two IP routes that need to be set-up, one original and the

second the tunnel route.

It causes unnecessary network overhead and adds Delay. Route optimization: allows the correspondent node to learn the current

location of the MN and tunnel its own packets directly. Problems arise with

Mobility: correspondent node has to update/maintain its cache. Authentication: HA has to communicate with the

correspondent node to do authentication.

Message transmitted in the optimized mobile IP are

1. Binding request:

Correspondent Node (CN) sends a request to the home Agent to know

the current location of mobile IP.

2. Binding Update:

The Home agent sends the Address of the mobile node to CN

3. Binding Acknowledgement:

The correspondent node will send an Acknowledgement after

getting the address from the HA.

4. Binding Warning:

When a correspondent node could not find the Mobile node it

sends a Binding Warning message to the HA.



DHCP.

It is Dynamic Host Configuration Protocol Administrator manually assigns the IP address to the system. Manual configuration is difficult and error-prone. Dynamic Host Configuration Protocol (DHCP) is used to configure IP automatically.

Using DHCP server.

DHCP provides static and dynamic address allocation that can be manual or automatic.

In static allocation, a DHCP server has a manually created static database that binds

Physical addresses to IP addresses.

Dynamic address allocation

The DHCP server maintains a pool (range) of available addresses .This address wil l be allocated to the system if it wants.

1. A host which is joined newly in the network sends a DHCPDISCOVER

message to Broadcast IP address (255.255.255.255) to all the server. In

the fig given below two servers receive the broadcast message.

2. Servers reply to the client’s request with DHCPOFFER and offer a list of

configuration parameters Client can now choose one of the configurations

offered.

3. The client in turn replies to the servers, by accepting one of the

configurations and rejecting the others using DHCPREQUEST.

4. If a server receives a DHCPREQUEST with a rejection, it can free the

reserved configuration for other clients.



5. The DHCP server will say ok by giving a command called DHCPACK.

6. The new system will take the new IP address assigned by the DHCP server.

7. The addresses assigned from the pool are temporary addresses.

8. The DHCP server issues that IP address for a specific time when the time

expires, the client must renew it. The server has the option to agree or

disagree with the renewal.

9. If a client leaves a subnet, it should release the configuration received by

the server using DHCPRELEASE. Now the server can free the context

stored for the client and offer the configuration again.

Origins of TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP)

effort by the U.S. Department of Defense

(DOD).

Advanced Research Projects Agency (ARPA).

.

.

.

.

inclusion of the TCP/IP protocol with Berkeley UNIX (BSD UNIX).



2.5 Overview of TCP/IP

The TCP/IP model explains how the protocol suite works to

provide communications

layers: Application, Transport, Internetwork, and Network Interface

Requests for Comments (RFCs)

describe, and standardize the implementation and

configuration of the TCP/IP protocol suite.

2.6 TCP/IP Architecture



Application Layer

Protocols at the TCP/IP Application layer include: File Transfer Protocol (FTP) Trivial File Transfer Protocol (TFTP) Network File System (NFS) Simple Mail Transfer Protocol (SMTP) Terminal emulation protocol (telnet) Remote login application (rlogin) Simple Network Management Protocol (SNMP) Domain Name System (DNS) Hypertext Transfer Protocol (HTTP)

Transport Layer Performs end-to-end packet delivery, reliability, and flow

control.

Protocols: TCP provides reliable, connection-oriented

communications between two hosts

Requires more network overhead UDP provides connectionless datagram services between two hosts Faster but less reliable Reliability is left to the Application layer Ports TCP and UDP use port numbers for communications between hosts Port numbers are divided into three ranges: Well Known Ports are those from 1 through 1,023 Registered Ports are those from 1,024 through 49,151 Dynamic/Private Ports are those from 49,152 through 65,535



TCP three-way handshake

Establishes a reliable connection between two points TCP transmits three packets before the actual data transfer occurs Before two computers can communicate over TCP, they must

synchronize their initial sequence numbers (ISN)

A reset packet (RST) indicates that a TCP connection is to be terminated without further interaction.



2.7 Adaption of TCP Window

TCP sliding windows

Control the flow and efficiency of communication Also known as windowing A method of controlling packet flow between hosts



Allows multiple packets to be sent and affirmed with a Single acknowledgment packet

The size of the TCP window determines the number of acknowledgments sent for a given data transfer

Networks that perform large data transfers should use large window sizes

TCP sliding windows (continued)

Other flow control methods include Buffering Congestion avoidance

Internetwork Layer

Four main protocols function at this layer

Internet Protocol (IP) Internet Control Message Protocol (ICMP) Address Resolution Protocol (ARP) Reverse Address Resolution Protocol (RARP) ARP A routed protocol Maps IP addresses to MAC addresses ARP tables contain the MAC and IP addresses of other devices on the

network

When a computer transmits a frame to a destination on the local network

It checks the ARP cache for an IP to MAC Address mapping for the destination node

ARP request If a source computer cannot locate an IP to MAC address mapping in

its ARP table

It must obtain the correct mapping



ARP request (continued)

A source computer broadcasts an ARP request to all hosts on the

local segment

Host with the matching IP address responds this request

ARP request frame See Figure 3-7 ARP cache life Source checks its local ARP cache prior to sending packets on the

local network

ARP cache life (continued)

Important that the mappings are correct Network devices place a timer on ARP entries



ARP tables reduce network traffic Reverse Address Resolution Protocol (RARP) Similar to ARP Used primarily by diskless workstations Which have MAC addresses burned into their network cards but no IP

addresses

Client’s IP configuration is stored on a RARP Server RARP request frame RARP client Once a RARP client receives a RARP reply, it configures its

IP networking components

By copying its IP address configuration information into its local RAM

ARP and RARP compared ARP is concerned with obtaining the MAC address of other clients RARP obtains the IP address of the local host

ARP and RARP compared (continued)

The local host maintains the ARP table A RARP server maintains the RARP table The local host uses an ARP reply to update its ARP table and to send

frames to the destination



The RARP reply is used to configure the IP protocol on the local host Routers and ARP ARP requests use broadcasts Routers filter broadcast traffic Source must forward the frame to the router

ARP tables

Routers maintain ARP tables to assist in transmitting frames from one network to another.

A router uses ARP just as other hosts use ARP. Routers have multiple network interfaces and therefore also include the

port numbers of their NICs in the ARP table.

The Ping utility. Packet Internet Groper (Ping) utility verifies connectivity between two

points.

Uses ICMP echo request/reply messages.



The Trace utility

Uses ICMP echo request/reply messages Can verify Internetwork layer (OSI-Network Layer) connectivity shows

the exact path a packet takes from the source to the destination

Accomplished through the use of the time-to-live (TTL) counter Several different malicious network attacks have also been created using

ICMP messages

Example: ICMP flood

Network Interface Layer

Plays the same role as the Data Link and Physical layers of the OSI model

The MAC address, network card drivers, and specific interfaces for the network card function at this level



No specific IP functions exist at this layer Because the layer’s focus is on communication with the network

card and other networking hardware Assume congestion to be the primary

cause for packet losses and unusual delays

Invoke congestion control and avoidance algorithms, resulting in significant degraded end-to-end performance and very high interactive

delays

TCP in Mobile Wireless Networks Communication characterized by sporadic

high bit-error rates (10-4 to 10-6) disconnections intermittent connectivity due to

handoffs low bandwidth

Mobile Networks Topology

TCP Performance with BER



Classification of Schemes

End-to-End protocols

loss recovery handled by sender Link-layer solutions hide link-related losses from sender TCP sender may not be fully shielded Split-connection approaches hide any non-congestion related losses from TCP sender since the problem is local, solve it locally End-to-End Protocols

Make the sender realize some losses are due to bit-error, not congestion.

Sender avoid invoking congestion control algorithms if non-congestion related losses occur.

E.g. Reno, New-Reno, SACK Link-Layer Protocols Hides the characteristics of the wireless link from the

transport layer and tries to solve the problem at the link layer

Uses technique like forward error correction (FEC) Snoop, AIRMAIL(Asymmetric Reliable Mobile Access In Link-layer)

Pros:

The wireless link is made more reliable Doesn’t change the semantics of TCP Fits naturally into the layered structure of network protocols

Cons:

If the wireless link is very lousy, sender times-out waiting for ACK, and congestion control algorithm starts Split Connection

Split the TCP connection into two separate connections.

1st connection: sender to base station 2nd connection: base station to receiver The base station simply copies packets between the connections in both

directions.



Pros:

Sender shielded from wireless link. Better throughput can be achieved by fine tuning the wireless protocol link.

Cons:

Violates the semantics of TCP Extra copying at the Base station

Classification of Schemes

2.8 Improving TCP/IP Performance over Wireless Networks

Snoop-TCP

A (snoop) layer is added to the routing code at BS which keep track of packets in

both directions

Packets meant to MH are cached at BS, and if needed, retransmitted in the wireless link

BS suppress DUPACKs sent from MH to FH BS use shorter local timer for local timeout Changes are restricted to BS

and optionally to MH as well

E2E TCP semantics is preserved



I-TCP: Indirect TCP for Mobile Hosts



I-TCP –LAN Performance

I-TCP –LAN Performance

Normal and overlapped – effective reaction to high BER. Non-Overlapped – No congestion avoidance algorithm I-TCP –LAN Performance



I-TCP – WAN Performance Disadvantages End-to-end semantics is not followed MSR sends an ack to the correspondent but loses the packet to the mobile

host Copying overhead at MSR Conclusion: I-TCP particularly suited for applications which are throughput intensive

Slow Start Sender starts by transmitting 1 segment On receiving Ack, congestion window is set to 2. On receiving Acks, congestion window is doubled. Continues until Timeout occurs After thresh, the sender increases its window size by [current window]on

receiving Ack.(Congestion Avoidance phase)



Fast Recovery

After Fast retransmit, perform congestion avoidance instead of slow start. Why? Duplicate ACK indicates that there are still data flowing between the two ends → Network resources are still available. TCP does not want to reduce the flow abruptly by going into slow start.

End to End Protocols Tahoe: Original TCP Slow start, Congestion avoidance, fast retransmit Reno: TCP Tahoe + Fast Recovery Significant Improvement - single packet loss. Suffers when multiple packets are dropped. New-Reno: Reno + Stay in Fast Recovery The first non-duplicate ACK but not the expected one. SACK: Reno + SACK option When multiple packets are dropped Packet Loss Scenario Fast Retransmission ssthresh = 0.5 x current window size congestion window = 1 Reno, New-Reno and SACK Fast Retransmission Fast Recovery congestion window = 0.5 x current window size +3 x segment size Increase window size by 1 on receiving a dup ACK



UNIT III

MOBILE TELECOMMUNICATION SYSTEM

Cellular Network Organization

Use multiple low-power transmitters (Base station) (100 W or less) Areas divided into cells

Each served by its own antenna Served by base station consisting of

transmitter, receiver, and control unit

Band of frequencies allocated Cells set up such that antennas of all neighbors are equidistant (Hexagonal pattern)

Cellular systems implements Space Division Multiplexing Technique

(SDM). Each transmitter is called a base station and can cover a fixed area called

a cell. This area can vary from few meters to few kilometres.

Mobile network providers install several thousands of base stations each

with a smaller cell instead of using power full transmitters with large cells



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Basic concepts:

High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell

Same frequencies/ timeslots/codes are reused by spatially separated base station

A switching technique called handoff enables a call to proceed uninterrupted when one user moves from one cell to another

Neighboring base stations are assigned different group of channels so as to minimize the interference

By systematically spacing base station and the channels group may be reused as many number of times as necessary

As demand increases the number of base stations may be increased thereby providing additional capacity

Frequency Reuse

adjacent cells assigned different frequencies to avoid interference or crosstalk

Objective is to reuse frequency in nearby cells 10 to 50 frequencies assigned to each cell

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Advantages

1. Higher capacity

Smaller the size of the cell more the number of concurrent user’s i.e. huge cells

do not allow for more concurrent users.

2. Less transmission power

Huge cells require a greater transmission power than small cells.

3. Local interference only

For huge cells there are a number of interfering signals, while for small cells

there is limited interference only.

4. Robustness

As cellular systems are decentralized, they are more robust against the failure of

single components.

Disadvantages:

Infrastructure needed: Cellular systems need a complex infrastructure to connect all base stations

Handover needed: The mobile station has to perform a handover when changing from one cell to another.

3.1 GSM ARCHITECTURE

GSM is a digital cellular system designed to support a wide variety of services, depending on the user contract and the network and mobile

equipment capabilities.

formerly: Group Special Mobile (founded 1982) now: Global System for Mobile Communication

GSM offers several types of connections voice connections, data connections, short message service There are three service domains

Bearer Services Telematics Services Supplementary Services



3.1.1 GSM SERVICES AND FEATURES

Bearer Services

Telecommunication services to transfer data between access points Specification of services up to the terminal interface (OSI layers 1-3) Different data rates for voice and data (original standard) Data Service (circuit

switched)

synchronous: 2.4, 4.8 or 9.6 kbit/s asynchronous: 300 - 1200 bit/s

Data service (packet switched)

synchronous: 2.4, 4.8 or 9.6 kbit/s asynchronous: 300 - 9600 bit/s

Tele Services

Telecommunication services helps for voice communication via mobile phones

Offered voice related services electronic mail (MHS, Message Handling System, implemented in

the fixed network)

ShortMessageServiceSMS alphanumeric data transmission to/from the mobile terminal using

the signaling channel, thus allowing simultaneous use of basic

services and SMS (160 characters)

MMS Supplementary services

Important services are identification: forwarding of caller number automatic call-back conferencing with up to 7 participants locking of the mobile terminal (incoming or outgoing calls)

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Architecture of the GSM system

GSM is a PLMN (Public Land Mobile Network) several providers setup mobile networks following the GSM

standard within each country

components MS (mobile station) BS (base station) MSC (mobile switching center) LR (location register)

subsystems RSS (radio subsystem): covers all radio aspects NSS (network and switching subsystem): call forwarding,

handover, switching

OSS (operation subsystem): management of the network

3.1.3 GSM SYSTEM ARCHITECTURE

Winter 2001ICS 243E - Ch4. Wireless

Telecomm. Sys.

4.12

GSM: elements and interfaces

NSS

MS MS

BTS

BSC

GMSC

IWF

OMC

BTS

BSC

MSC MSC

Abis

Um

EIR

HLR

VLR VLR

A

BSS

PDN

ISDN, PSTN

RSS

radio cell

radio cell

MS

AUCOSS

signaling

O

GSM Network consists of three main parts:

Radio subsystem RSS Base Station Subsystem BSS Network and Switching Subsystems NSS



Radio subsystem:

The Radio Subsystem (RSS) contains three main parts Base Transceiver Station (BTS) Base Station Controller (BSC) Mobile Stations (MS)

Base Transceiver Station (BTS) defines a cell and is responsible for radio link protocols with the Mobile Station

Base Station Controller (BSC) controls multiple BTSs and manages radio channel setup, and handovers. The BSC is the connection between the

Mobile Station and Mobile Switching Center.

A mobile station (MS) is a hand portable and vehicle mounted unit It contains several functional groups

SIM (Subscriber Identity Module) personalization of the mobile terminal, stores user parameters PIN IMEI Cipher key Location Area Identification It also has Display, loudspeaker, microphone and programmable keys.

Base Station Subsystem Consists of:

Base Transceiver Station (BTS) defines a cell and is responsible for radio link protocols with the Mobile Station

Base Station Controller (BSC) controls multiple BTSs and manages radio channel setup, and handovers. The BSC is the connection between

the Mobile Station and Mobile Switching Center.

Network and Switching Subsystems

It consists of

Mobile Switching Center (MSC) Home Location Register (HLR) Visitors Location Register (VLR) Authentication Center (AuC)

http://www.pulsewan.com/data101/gsm_basics.htm#Mobile Station#Mobile Stationhttp://www.pulsewan.com/data101/gsm_basics.htm#Base Transceiver Station (BTS)#Base Transceiver Station (BTS)http://www.pulsewan.com/data101/gsm_basics.htm#Mobile Station#Mobile Stationhttp://www.pulsewan.com/data101/gsm_basics.htm#Mobile Switching Center (MSC)#Mobile Switching Center (MSC)



Mobile Switching Center (MSC) is the central component of the NSS.

Its functions:

Manages the location of mobiles Switches calls Manages Security features Controls handover between BSCs Resource management Interworks with and manages network databases Collects call billing data and sends to billing system Collects traffic statistics for performance monitoring

Home Location Register (HLR)

Contains all the subscriber information for the purposes of call control, and

location determination. There is logically one HLR per GSM network.

Visitors Location Register (VLR)

Local database for a subset of user data - data about all users currently visiting in

the domain of the VLR.

Operation subsystem

The OSS (Operation Subsystem) used for centralized operation, management, and maintenance of all GSM subsystems

The main Components of OSS are

Authentication Center (AUC) Equipment Identity Register (EIR) Operation and Maintenance Center (OMC)

Authentication Center (AUC)

It is a protected database that stores the security information for each subscriber (a copy of the secret key stored in each SIM).

Equipment Identity Register (EIR)

It contains a list of all valid mobile equipment on the network. Operation and Maintenance Center (OMC)

It has different control capabilities for the radio subsystem and the network subsystem



Radio spectrum is very limited resource and this is shared by all users. Time- and

Frequency-Division Multiple Access (TDMA/FDMA) is used to share the

frequency. FDMA divides frequency bandwidth of the (maximum) 25 MHz into

124 carrier frequencies. Each Base Station (BS) is assigned one or more carrier

frequencies.

Time Division Multiple Access (TDMA) - the users take turns (in a round robin),

each one periodically getting the entire bandwidth for a little time.

Frequency Division Multiple Access (FDMA) - the frequency spectrum is

divided among the logical channels, with each user using some frequency band.

Mobile unit can be in two modes

Idle - listening Dedicated: sending/receiving data

There are two kinds of channels: Traffic channels (TCH) and Control channels

Organization of bursts, TDMA frames, and multi frames for speech and data.

The fundamental unit of time in TDMA scheme is called a burst period and it

lasts 15/26 msec. Eight bust periods are grouped in one TDMA frame (120/26

msec), which forms a basic unit of logical channels. One physical channel is

one burst period per TDMA frame. Traffic channels. It is used to transmit data.

It is divided to Full rate TCH and Half rate TCH.

In GSM system two types of traffic channels used:

Full Rate Traffic Channels (TCHF): This channel carries information at rate of 22.8 Kbps.

Half Rate Traffic Channels (TCHH): This channels carries information at rate of 11.4 Kbps.

http://www.pulsewan.com/data101/gsm_basics.htm#Time Division Multiple Access (TDMA)#Time Division Multiple Access (TDMA)



Control channels : carries control information to enable the system to operate

correctly.

1. BROADCAST CHANNELS (BCH)

Broadcast Control Channel (BCCH) Frequency Correction Channel (FCCH) Synchronization Channel (SCH) Cell Broadcast Channel (CBCH)

2. DEDICATED CONTROL CHANNELS (DCCH)

Standalone Dedicated Control Channel (SDCCH) Fast Associated Control Channel (FACCH) Slow Associated Control Channel (SACCH)

3. COMMON CONTROL CHANNELS (CCCH)

Paging Channel (PCH) Random Access Channel (RACH) Access Grant Channel (AGCH)

GSM Protocol:

GSM architecture is a layered model used to allow communications

between two different systems. The GMS protocol stacks diagram is shown

below:

MS Protocols

GSM signaling protocol is divided in to three layers:

Layer 1: The physical layer. It uses the channel structures over the air interface.



Layer 2: The data-link layer. Across the Um interface, the data-link layer is LAP-D protocol is used. Across Abs interface (LAP-Dm) is used. Across

the A interface, the Message Transfer Part (MTP) is used.

Layer 3 : GSM protocol’s third layer is divided into three sub layers: o Radio Resource Management (RR),

o Mobility Management (MM), and

o Connection Management (CM).

THIRD LAYER (RR, MM, AND CM):

The RR layer (radio resource) is the lower layer that manages both radio

and fixed link, between the MS and the MSC. The work of the RR layer is to

setup, maintenance and release of radio channels .

The MM layer is above the RR layer. It handles the functions of the

mobility of the subscriber, authentication and security and Location

management...

The CM layer is the topmost layer of the GSM protocol stack. This layer

is responsible for Call Control, Supplementary Service Management, and Short

Message Service Management call establishment, selection of the type of service

(including alternating between services during a call), and call release.

SECOND LAYER:

To Signal between entities in a GSM network requires higher layers. For

this purpose, the LAPDm protocol is used at the Um interface for layer two.

LAPDm is called link access procedure for the D-channel (LAPD. LAPDm gives

reliable data transfer over connections, sequencing of data frames, and flow

control.

PHYSICAL LAYER:

The physical layer handles all radio-specific functions. It multiplexes the bursts into a TDMA frame, synchronization with the BTS, detection of idle

channels, and measurement of the channel quality on the downlink.

The physical layer at Um uses GMSK for digital modulation and performs encryption/decryption of data.

The main tasks of the physical layer comprise channel coding and error



detection/correction.

It uses forward error correction (FEC) schemes. The GSM physical layer tries to correct errors, but it does not deliver

erroneous data to the higher layer.

The physical layer does voice activity detection (VAD)

CONNECTION ESTABLISHMENT

Mobile Terminated Call

1: call ing a GSM subscriber

2: forwarding call to GMSC

3: signal call setup to HLR

4, 5: request MSRN from VLR

6: forward responsible MSC to GMSC

7: forward call to current MSC

8, 9: get current status of MS

10, 11: paging of MS

12, 13: MS answers

14, 15: security checks

16, 17: set up connection

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Security in GSM

Security services

Access control/authentication User SIM (Subscriber Identity Module): secret

PIN (personal identification number)

SIM network: challenge response method Confidentiality voice and signaling encrypted on the wireless link (after

successful authentication)

Anonymity temporary identity TMSI (Temporary Mobile Subscriber

Identity)

newly assigned at each new location update (LUP) encrypted transmission

3 algorithms specified in GSM

A3 for authentication (“secret”, open interface) A5 for encryption (standardized) A8 for key generation (“secret”, open interface)



AUTHENTICATION

Authentication key Ki,, the user identification IMSI, and the algorithm

used for authentication A3 is stored in the sim. This is known only to the MS

and BTS. Authentication uses a challenge-response method: The access

control AC (BTS) generates a random number RAND this is called as

challenge, and the SIM within the MS reply with SRES (signed

response) .This is called as SRES response.

N/W side:

BTS send random number RAND to MS.

MS side:

MS prepares SRES response by giving the random number RAND and

Ki, to the algorithm A8.The output is the SRES which is sent to the BTS.

BTS side:

BTS also prepares the same SRES and the output from the MS is compared

with result created by the BTS.

If they are the same, the BTS accepts the subscriber, otherwise the

subscriber is rejected.

ENCRYPTION

To maintain the secrecy of the conversation, all messages are encrypted

in GSM. Encryption is done by giving the cipher key Kc with message to the

algorithm A5 .Here the key is generated separately.



Kc is generated using the Ki which is stored in SIM and a random

number RAND given by BTS, by applying the algorithm A8. Note that the SIM

in the MS and the network both calculate the same Kc based on the random value

RAND. The key Kc itself is not transmitted over the air.

MOBILITY MANAGEMENT

Handover or Handoff:

Handover basically means changing the point of connection while

communicating.

Whenever mobile station is connected to Base station and there is a need to

change to another Base station, it is known as Handover

A handover should not cause a cut-off, also called call drop. handover duration is 60 ms.

There are two basic reasons for a handover: The mobile station moves out of the range. The received signal level

decreases. Error rate may increase. all these effects may lower the

quality of the radio link

The traffic in one cell is too high and shift some MS to other cells with a lower load (if possible). Handover may be due to load balancing.

Four possible handover scenarios in GSM:



Intra-cell handover: Within a cell, narrow-band interference could make transmission at

a certain frequency impossible.

The BSC could then decide to change the carrier frequency (scenario 1).

Inter-cell, intra-BSC handover: The mobile station moves from one cell to another, but stays within

the control of the same BSC.

The BSC then performs a handover, assigns a new radio channel in the new cell and releases the old one (scenario 2).

Inter-BSC, intra-MSC handover:



As a BSC only controls a limited number of cells; GSM also has to perform handovers between cells controlled by different BSCs.

This handover then has to be controlled by the MSC (scenario 3). Inter MSC handover: A handover could be required between two cells

belonging to different MSCs. Now both MSCs perform the handover

together (scenario 4).

Whether to take handover or not HD depends on the average value of received signal when MS moves away

from BT sold to another closer BTS new

BSC collects all values from BTS and MS calculates average values Values are then compared with threshold (HO_MARGIN_ hysteresis to

avoid ping-pong effect)

Even with the HO_MARGIN, the ping-pong effect may occur in GSM-a value which is too high could cause too many handovers

Typical signal flow during an inter-bsc, intra-msc handover.

The MS sends its periodic measurements reports to BTS old, the BTSold forwards these reports to the BSC old together with its own measurements.

Based on these values and, e.g., on current traffic conditions, the BSC old may decide to perform a handover and sends the message HO_required to

the MSC.

MSC then checks if the resources available needed for the handover from the new BSC, BSC new.

This BSC checks if enough resources (typically frequencies or time slots) are available and allocates a channel at the BTS new to prepare for the arrival

of the MS.

The BTS new acknowledges the successful channel activation to BSC new, BSC new acknowledges the handover request.

The MSC then issues a handover command that is forwarded to the MS. The MS now breaks its old connection and accesses the new BTS.



The next steps include the establishment of the link (this includes layer two link

Establishment and handover complete messages from the MS).

the MS has then finished the handover, release its old resources to the old BSC and BTS

3.2 GPRS NETWORK ARCHITECTURE:

GPRS is the short form of General Packet Radio Service. It is mainly used

to browse internet in mobile devices. GPRS is GSM based packet switched

technology. It needs MS (mobile subscriber) or user to support GPRS, network

operator to support GPRS and services for the user to be enabled to use GPRS

features.

GPRS network Architecture

Entire GPRS network can be divided for understanding into following basic

GPRS network



Serving GPRS Support Node (SGSN)- It is similar to MSC of GSM network. SGSN functions are outlined below.

Data compression Authentication of GPRS subscribers VLR.

Mobility management

Traffic statistics collections.

User database

Gateway GPRS Support Node(GGSN)- Packet delivery between mobile stations and external networks

Authentication



Packet data is transmitted from a PDN, via the GGSN and SGSN directly to the BSS and finally to the MS.

The MSC, which is responsible for data transport in the traditional circuit-switched GSM, is only used for signaling in the GPRS scenario.

Before sending any data over the GPRS network, an MS must attach to it,

following the procedures of the mobility management. A mobile station must

register itself with GPRS network.

GPRS attach GPRS detach

GPRS detach can be initiated by the MS or the network.

The attachment procedure includes assigning a temporal identifier, called a

temporary logical link identity (TLLI), and a ciphering key sequence number

(CKSN) for data encryption.

A MS can be in 3 states:

IDLE READY STANDBY In idle mode an MS is not reachable and all context is deleted. In the standby state only movement across routing areas is updated to the

SGSN but not changes of the cell.

In the ready state every movement of the MS is indicated to the SGSN



PROTOCOL ARCHITECTURE

Protocol architecture of the transmission plane for GPRS. All data within the GPRS backbone, i.e., between the GSNs, is transferred

using the GPRS tunneling protocol (GTP).

GTP can use two different transport protocols, either the reliable TCP (needed for reliable transfer of X.25 packets) or the non-reliable UDP

(used for IP packets).

The network protocol for the GPRS backbone is IP (using any lower layers).

Sub network dependent convergence protocol (SNDCP) is used between an SGSN and the MS. On top of SNDCP and GTP, user packet

data is tunneled from the MS to the GGSN and vice versa.

To achieve a high reliability of packet transfer between SGSN and MS, a special LLC is used, which comprises ARQ and FEC mechanisms for PTP

(and later PTM) services.

A base station subsystem GPRS protocol (BSSGP) is used to convey routing and QoS-related information between the BSS and SGSN.



BSSGP does not perform error correction and works on top of a frame relay (FR) network.

Finally, radio link dependent protocols are needed to transfer data over the Um interface.

The radio link protocol (RLC) provides a reliable link.

3.3 UMTS (Universal Mobile Telephone System

• Reasons for innovations

- new service requirements

- availability of new radio bands

• User demands

- seamless Internet-Intranet access

- wide range of available services

- compact, lightweight and affordable terminals

- simple terminal operation

- open, understandable pricing structures for the whole

spectrum of available services

UMTS Basic Parameter

• Frequency Bands (FDD : 2x60 MHz):

– 1920 to 1980 MHz (Uplink)

– 2110 to 2170 MHz (Downlink)

• Frequency Bands (TDD: 20 + 15 MHz):

– 1900 – 1920 MHz and 2010 – 2025 MHz

• RF Carrier Spacing:

– 4.4 - 5 MHz

• RF Channel Raster: – 200 KHz

• Power Control Rate:

– 1500 Cycles per Second



UMTS W-CDMA Architecture



UNIT 4

MOBILE AD HOC NETWORKS

HISTORICAL DEVELOPMENTS OF MANET

In early 1970s, the Mobile Ad hoc Network (MANET) was called packet radio

network, which was sponsored by Defense Advanced Research Projects Agency

(DARPA). They had a project named packet radio having several wireless

terminals that could communication with each other on battlefields. “It is interesting

to note that these early packet radio systems predict the Internet and indeed were part

of the motivation of the original Internet Protocol suite”. The whole life cycle of Ad hoc networks could be categorized into the First, second, and the third generation Ad hoc networks systems. Present Ad

hoc networks systems are considered the third generation.

The fi rst generation goes back to 1972. At the time, they were called

PRNET (Packet Radio Networks). In conjunction with ALOHA (Arial

Locations of Hazardous Atmospheres) and CSMA (Carrier Sense Medium

Access), approaches for medium access control and a kind of distance-vector

routing PRNET were used on a trial basis to provide different networking

capabilities in a combat environment.

The second generation of Ad hoc networks emerged in 1980s, when the

Ad hoc network systems were further enhanced and implemented as a part of

the SURAN (Survivable Adaptive Radio Networks) program. This

provided a packet-switched network to the mobile battlefield in an

environment without infrastructure. This Program proved to be beneficial in

improving the radios' performance by making them smaller, cheaper, and

resilient to electronic attacks.

In the 1990s (Third generation), the concept of commercial Ad hoc networks arrived with notebook computers and other viable communication equipment’s. At the same time, the idea of a collection of mobile nodes was Proposed at several researchers gatherings IEEE 802.11.





Had adopted the term "Ad hoc networks" and the research community had

started to look into the possibility of deploying Ad hoc networks in other

areas of application.

4.1 BASIC CONCEPTS OF MOBILE AD HOC NETWORKS

An Ad hoc network is a collection of mobile nodes, which forms a

temporary network without the aid of centralized administration or standard

support devices regularly available as conventional networks. These nodes

generally have a limited transmission range and, so, each node seeks the

assistance of its neighboring nodes in forwarding packets and hence the nodes

in an Ad hoc network can act as both routers and hosts. Thus a node may

forward packets between other nodes as well as run user applications. By

nature these types of networks are suitable for situations where either no fixed

infrastructure exists or deploying network is not possible. Ad hoc mobile

networks have found many applications in various fields like mili tary,

emergency, conferencing and sensor networks. Each of these application areas

has their specific requirements for routing protocols.

Since the network nodes are mobile, an Ad hoc network will typically

have a dynamic topology, which wi l l have profound effects on

network characteristics. Network nodes will often be battery powered, which

limi ts the capacity of CPU, memory, and bandwidth. This will require network

functions that are resource effective. Furthermore, the wireless (radio) media

will also affect the behavior of the network due to fluctuating link bandwidths

resulting from relatively high error rates. These unique desirable features pose

several new challenges in the design of wireless Ad hoc networking protocols.

Network functions such as routing, address allocation, authentication and

authorization must be designed to cope with a dynamic and volatile network

topology. In order to establish routes between nodes, which are farther than a

single hop, specially configured routing protocols are engaged. The unique

feature of these protocols is their ability to trace routes in spite of a dynamic

topology. In the simplest scenarios, nodes may be able to communicate directly

with each other, for example, when they are within wireless transmission

range of each other. However, Ad hoc networks must also support



communication between nodes that are only indirectly connected by a series

of wireless hops through other nodes. For example, in Fig 3.1, to establish

communication between nodes A and C the network must enlist the ai

Documents

IT6601 MOBILE COMPUTING M.I.E.T. ENGINEERING COLLEGE€¦ · it6601 – mobile computing m.i.e.t./cse/iii yr/mobile computing department of computer science and engineering course