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6 Mobile communication routing
Business Research Methods (DMS 502)
University of Nairobi
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MOBILE COMMUNICATION ROUTING
Mobile computing is one of the most important technologies supporting pervasive computing. Advances in both hardware and software techniques have enabled the spread of mobile hosts and wireless networking to masses. Generally, there are two modes in which wireless mobile nodes can communicate: 1. Infrastructured : In this mode, all the communication among the mobile nodes goes through a base station. A Base station is also known as an access point. These base stations are connected to the fixed infrastructure or wired networks. 2. Infrastructureless : This mode of communication is known as a mobile ad hoc network. A MANET is a collection of wireless nodes that can dynamically form a network to exchange information without using any pre-existing fixed network infrastructure. A typical example of this mode of communication is people sitting in the conference room and exchanging data among them without any fixed infrastructure.
Infrastructured and Infrastructureless wireless networks
Mobile ad hoc network (MANET) is an autonomous system of mobile nodes connected by wireless links.
MANET is a collection of wireless nodes that can dynamically form a network to exchange information without using any pre-existing fixed network infrastructure.
In a MANET, each node or device is expected to serve as a router, and each router is indistinguishable from another in the sense that all routers execute the same routing algorithm to compute paths through the entire network.
Each node operates not only as an end system, but also as a router to forward packets. The nodes are free to move about and organize themselves into a network. These nodes change position frequently. To accommodate the changing topology special routing algorithms are needed. There is no single protocol that fits all networks perfectly. The protocols have to be chosen according to network characteristics, such as density, size and the mobility of the nodes. MANET does not require any fixed infrastructure, such as a base station, therefore, it is an attractive option for connecting devices quickly and spontaneously. Mobile ad hoc networks can be used alone (for example in the military) or as a hybrid together with the Internet or other networks. Different MANET applications have different needs, and hence the various Mobile Ad Hoc Network routing protocols may be suitable in different areas. The size of the network and the frequency of the change in topology are factors that affect the choice of the protocols. There is no best protocol for all applications. There is still ongoing research on mobile ad hoc networks and the research may lead to even better protocols and will probably face new challenges.
Mobile ad hoc network
is typically the norm rather than the exception i. aggregate application demand will likely approach or exceed network capacity frequently. 6. Energy-constrained operation : Some or all of the nodes in a MANET may rely on batteries or other means for their energy. Such devices need optimized algorithms and mechanisms that implement the computing and communicating functions. 7. Limited physical security : MANETs are generally more prone to physical security threats than are fixed cable networks. The increased possibility of eavesdropping, spoofing and denial-of-service attacks should be carefully considered.
The following are the desirable properties of MANET routing protocol: 1. Distributed operation : Since there is no central point like a wired network, each and every node in the MANET performs routing. 2. Loop-freedom: Though, if not incorporated in the routing protocol, the Time-to-live (TTL) value could be used to prevent the packet from roaming in the network for arbitrarily long periods of time. But, still, this property is desirable for efficient use of resources and better overall performance. 3. Demand-based operation : Instead of assuming a uniform traffic distribution within the network and maintaining routing information between all nodes at all times, routing algorithm should adapt to the traffic pattern on a demand or need basis. It should be done in such a way so that it could utilize mobile nodes energy and network bandwidth more efficiently at the cost of increased route discovery delay. 4. Proactive operation : This is the opposite of demand-based operation. It certain contexts, the additional latency demand-based operation are unacceptable. If bandwidth and energy resources permit, the proactive operation is desirable in these contexts. 5. Security : Without some form of network-level or link layer security, a MANET routing protocol is vulnerable to many forms of attack. It may be relatively simple to snoop network traffic, manipulate packet headers and redirect routing messages, within a wireless network without appropriate security provisions. 6. Sleep period operation : As a result of energy conservation, or some other need to be inactive, nodes of a MANET may stop transmitting and/or receiving for arbitrary time
periods. A routing protocol should be able to accommodate such sleep periods without overly adverse consequences. 7. Unidirectional link support : Bi-directional links are typically assumed in the design of routing algorithms, and many algorithms are incapable of functioning properly over unidirectional links. But, unidirectional links can and do occur in wireless networks.
Routing Routing is the process of finding the best path for traffic in a network, or across multiple networks. The role of routing is similar to the road map for a hotel. In both cases, we need to deliver messages at proper location and in an appropriate way. Routing in a mobile ad-hoc network depends on many factors such as: o Modeling of the topology, o Selection of routers, o Initiation of a route request, o And specific underlying characteristics that could serve as heuristics in finding the path effectively.
Need for Routing o Since centralized routing in a dynamic and even for small networks is impossible therefore routing computation must be distributed. o Route computation should not add many more nodes. o If any host demands for the route, they must have quick access. o Maintenance of a global state should not involve in the route computation. o Each node should care about their destination node to its route and should not be involved in frequent topology updates for those portions of the network that have no traffic. o Since broadcast can be time consuming for MANETs, it must be avoided as much as possible. o In routing there must have a backup route when the primary route has become stale.
3. Hybrid Protocols Hybrid protocols attempt to take advantage of best of reactive and proactive schemes. The basic idea behind such protocols is to initiate route discovery on demand but at a limited search cost. One of the popular hybrid protocols is zone routing protocol (ZRP).
4 Routing Protocols
With this type of protocol, the choice of proactive and of reactive routing depends on the hierarchical level in which a node resides. The routing is initially established with some proactively prospected routes and then serves the demand from additionally activated nodes through reactive flooding on the lower levels. The choice for one or the other method requires proper attribution for respective levels. The main disadvantages of such algorithms are:
- Advantage depends on depth of nesting and addressing scheme.
- Reaction to traffic demand depends on meshing parameters.
Assignment Read on:
Geographical routing protocols Power-aware routing protocols
Routing protocols may also be categorized as follows: 1. Table-driven protocols 2. Source initiated on -demand protocols
1. Table-driven routing protocol o These protocols are called table-driven because each node is required to maintain one or more tables containing routing information on every other node in the network. o They are proactive in nature so that the routing information is always consistent and up to date. o The protocols respond to changes in network topology by propagating the updates throughput the network so that every node has a consistent view of the network. The table-driven routing protocols are categorized as: Destination - sequenced distance vector routing, Cluster Head gateway switch Routing, Wireless routing protocol (WRP)
2. Source initiated on -demand protocols o Source - initiated on demand routing is reactive in nature, unlike table driven routing. This type of protocols generates routes only when a source demands it. o In other words, when a source node requires a route to a destination, the source initiates a route discovery process in the network. This process finishes when a route to the destination has been discovered or all possible routes have been examined without any success. o The discovered route is maintained by a route maintenance procedure, until it is no longer desired or the destination becomes inaccessible. The source initiated on demand routing is categorized as follows: Ad hoc on demand distance vector routing (AODV), Dynamic Source Routing (DSR)
6 Mobile communication routing
Course: Business Research Methods (DMS 502)
University: University of Nairobi
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