Mobile Networking Challenges 1

5.6 Mobile Ad Hoc Networks

Ad hoc network does not have any preexisting centralized server nodes t

o perform packet routing, directory assistance, service discovery, resource management, and signaling.

MANET is defined as including both fully mobile multihop ad hoc networks and hybrid ad hoc networks.

A variety of potential applications Rescue operations and disaster recovery

Military operations in a battlefield

Conferences and events

Remote monitoring and surveillance system

Vehicular communication system

Mobile Networking Challenges 2

5.6.1 MANET Categories A vast of research effort in the domain of mobile computing.

Topology control

Routing

Service discovery and access

Data acquisition and aggregation

Security and privacy

5.6.2 Topology Control in a MANET Two key issues of topology control in a MANET

1. neighbor discovery

2. network organization

The basic idea is described as follows: Given a transmission graph that models node connectivity of a MANET, find a distributed algorithm that generates a subgraph comprised of optimal paths between any nodes with respect to network throughput and power consumption.

Mobile Networking Challenges 3

5.6.3 Routing in MANET

Routing protocols for MANET

proactive hybrid reactive

DSDV OLSR 2RP

DSR AODV

FSR TORA

ABR

Mobile Networking Challenges 4

Table 5.2 Unicast Ad Hoc Routing Protocols

DSDV OLSR DSR AODV TORA

Routing method

Proactive Proactive On-demand On-demand On-demand

Neighbordiscovery

Periodical broadcast of

“hello” messages

Multipoint relay of link

state messages

N/A

Periodical broadcast of “hello” messages

N/A

Communi-cation

overheadHigh High Low Medium Medium

Routing delay No delay No delay

No delay if a route cache is available

No delay

No delay if a route cache is available

Mobile Networking Challenges 5

LAR Landmark Grid

Network organization Flat

Hierarchy based on well-known

root nodes

Hierarchical grid

Location discovery

N/APath to the root

nodesPosition in the

grid

Location maintenance On-demand

Location server for each node

Selected nodes in the grid hierarchy

Communication overhead

Low Medium High

Scalability Low Medium High

Table 5.3 Location Based Ad Hoc Routing Protocols

Mobile Networking Challenges 6

5.6.4 Service Discovery

To a mobile node, a MANET is a virtual server that provides a number of services.

Network services, such as point-to-point or group communication, mobile access proxying, network performance monitoring, or power alert.

Computational services, such as distributed job scheduling, distributed storage, or distributed caching.

Application services, such as printing, web caching, or web services.

Mobile Networking Challenges 7

Table 5.4 Service Discovery Protocols

Universal Plug and Play (uPnP) Jini Rendezvous

Service Location

Protocol (SLP)

Directory No Yes Yes Optional directory

AddressingDynamic host configuration

protocol (DHCP) or auto IP

Notspecified

Dynamic configuration of IPv4 link-local

address

Not specified

Service discovery

Simple service discovery

protocol (SSDP)

Directory-assisted remote

method invocation (RMI)

Multicast DNS service discovery (mDN

S-SD)Multicast lookup

Service locator and attributes

Standard Standard Standard Standard

Service invocation

Simple object access protocol

(SOAP)Java’s RMI Not

specifiedNot

specified

Communication method

Unicast and multicast

Unicast and multicast Multicast Multicast

Service event and status notification

Eventing and polling Notification Notification and

pollingNot

specified

Mobile Networking Challenges 8

5.7 Quality of Service in Mobile Computing

Quality of service (QoS) in a network refers to the capability of the network to prioritize traffic and guarantee performance of data communication.

5.7.1 An Overview of QoS Key elements of a QoS provisioning mechanism are listed as follows:

Traffic classification and marking - the process of classifying traffic into a set of classes

Traffic policing - the process of discarding traffic that exceeds a profile

Traffic scheduling and shaping - the process of controlling multiple queues and possibly delaying or dropping some packets according of some rules

Resource reservation and signaling protocols - the process of explicitly reserving and allocating network resources such as bandwidth for specific traffic

Admission control - the process of deciding if a packet stream should be allowed to enter a network

Mobile Networking Challenges 9

5.7.2 End-to-End QoS Support in Mobile Computing

QoS provision in wireless networks is performed in one of two ways: resource reservation before traffic begins to flow or per-hop differentiated treatment while the traffic is flowing in the network

Some fundamental differences between wireless and wired networks have created an array of challenging issues in providing QoS in wireless networks and interconnected wireless systems.

Link bandwidth on QoS

Link quality on QoS

Mobility on QoS

Mobile devices on QoS