INTERWORKING ISSUES IN INTEGRATION OF WLANS, PAN, LAN AND GSM IN HMANETS
KEY TO SYMBOLS OR ABBREVIATIONS
AP Access Points
AMASS Architecture for Mobile Ad-hoc Systems and Services
AODV Ad Hoc on Demand Distance Vector Routing
BS Base Station
BNEP Bluetooth Network Encapsulation Protocol
CDMA Code-Division Multiple Access
CGSR Cluster-head Gateway Switch Routing
CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
CTS Clear to Send
DBTMA Dual Tone Multiple Access
DSDV Destination Sequenced Distance Vector Routing
DSR Dynamic Source Routing
GEO-TORA Geographical Temporally Ordered Routing Algorithm
GPRS General Packet Radio Service
GPS Global Positioning System
GRDL Grid Resource Description Language
GSM Global System for Mobile Communication
HF High Frequency
HMANET Heterogeneous Mobile Ad Hoc Network
HOLSR Hierarchical Optimized Link State Routing
IP Internet Protocol
LBR Location Based Routing
LLC Logical Link Control
MAC Medium Access Control
MACA Multi Hop Collision Avoidance
MACAW Medium Access Protocol for Wireless LAN
MAN Metropolitan Area Network
MANET Mobile Ad Hoc Network
MPR Multipoint Relays
NAT Network Address Translation
NFS Network File System
OLSR Optimized Link State Routing
OSI Open Systems Interconnection
PDA Personal Digital Assistant
QoS Quality of Service
RREP Route Reply
RREQ Route Request
RERR Route Error
SCTP Stream Control Transmission Protocol
SDR Software-Defined Radio
TBRPF Topology Broadcast Based on Reverse Path Forwarding
TC Topology Control
TCP Transmission Control Protocol
TDMA Time Division Multiple Access
TORA Temporally Ordered Routing Algorithm
VHF Very High Frequency
WAN Wide Area Network
WLAN Wireless Local Area Networks
WPAN Wireless Personal Area Network
WSDL Web Services Description Language
WSN Wireless Sensor Network
ZRP Zone Routing Protocol
Recent developments in wireless communications have taken possible applications from simple voice services in early cellular networks to newer integrated data applications. IEEE 802.11 family i.e. Wireless Local Area Networks (WLANs) have become popular for allowing low cost data transmissions . The most common and approachable places, such as airports, hotels, shopping places, university campuses and homes have been provided with WLAN Access Points (AP) which provide hotspot connectivity . The future advances in modern radios like Software-Defined Radio (SDR) and cognitive radio technologies will surely facilitate the need of multi-mode, multi-interface and multi-band communication devices. This heterogeneous networking paradigm will certainly enable a user to enjoy better service quality, ease of use and mobility, while keeping in view the application needs and types of available access networks e.g. cellular network, WLAN, wireless personal area network (WPAN) etc.
Mobile Ad hoc Networks
The Mobile Ad hoc Network (MANET) is a network formed by mobile wireless hosts without (necessarily) using a pre-existing infrastructure and the routes between these hosts may potentially contain multiple communication hops . The autonomous nature of participating mobile nodes enables MANETs to have dynamic and frequently changing network topology. The nodes are self-organizing and behave as routers. The ease and speed of deployment and decreased dependence on infrastructure have made ad hoc networks popular within very short span of time. MANET variations include Personal area networking (e.g. cell phone, laptop, ear phone), Military environments (e.g. soldiers, tanks, aircraft), Civilian environments (e.g. cab network, meeting rooms, sports stadiums), and foremost Emergency operations (e.g. search-and-rescue, policing and fire fighting). MANET’s rapid deployment, ease of use and subsequent properties make them a hot choice for many important applications.
One of the intended aspects of MANETs is that it will facilitate the sharing of resources. These include both technical and information resources. Technical resources like bandwidth, Quality of Service (QoS), computational power, storage capacity and information resources include any kind of data from databases. Resource sharing among mobile devices require the devices to agree on communication protocols without the existence of any dedicated servers.
Mechanisms that enable the sharing of resources between different mobile devices, i.e. different coordination system is necessary for sharing dissimilar resources. Examples of such mechanisms are Samba, Network File System (NFS) for sharing disk space and the distributed dot net client for sharing processor cycles.
Before nodes start sharing any resource, they demand a certain amount of trust between them or systems with which they share resources. The level of trust depends on the kind of information or resources that is to be shared. For instance, sharing processor cycles require less trust than the sharing of personal information. Similarly, sharing of profit-making or highly sensitive information can require another level of trust establishment. There are systems currently in operation that can provide a certain amount of trust like the public key infrastructure that makes use of certificates.
Before any node starts communicating with other node, that node must be discovered. When a node enters the network, it has to be capable of communicating to the other nodes about its capabilities e.g. it is a Personal Digital Assistant (PDA) and it has a camera, Global Positioning System (GPS) capabilities and Global System for Mobile Communication (GSM) capabilities etc. When a node is detected, other users can send a query to the new device to find out what it has to offer. Commercial service providers can advertise the resources they have to offer through Internet Protocol (IP) multicasts. There is a myriad of standards that include resource description protocols like Standards Grid Resource Description Language (GRDL), the Web Services Description Language (WSDL) for telling all offer devices a way to describe and publish their specific resources and needs. There are also various different systems currently available that can gather these resource descriptions and structure them for other devices to use.
For any device to be able to use any resource, a way to identify and describe the resource has to be agreed upon by all available devices. If, for instance, storage capacity is to be shared, it first has to be clear what the capacity of each device is, and, what the storage need is. Although there are techniques to describe certain resources but not one technique that is able to provide this service for all resources. The available techniques combined, however, cover most of what is needed.
Mobile Ad hoc Networks are usually categorized as Homogeneous MANETs and Heterogeneous MANETs.
When MANETs operate in fully Symmetric Environment whereby all nodes posses identical capabilities in terms of battery, processing powers, responsibilities and hardware and software capabilities, thus having no diversity, the network is Homogenous MANET.
In certain environments, mobile nodes may have asymmetric capabilities in terms of transmission ranges, Medium Access Control (MAC), battery life, processing powers, speed of movement and software variations etc. Mobility rate may also differ in ad hoc networks due to varying traffic characteristics, transmission ranges, reliability requirements and communication needs. Similarly, addressing and traffic flows like host-based addressing, content-based addressing or capability-based addressing patterns may be defined in certain scenarios; for example, people sitting at an airport lounge, metro taxi cabs, sportsmen playing and military movements etc
Homogenous MANETs do not allow for the heterogeneity in the network, which is seriously required in many scenarios, for instance, in a military battlefield network, where soldiers usually carry light portable wireless devices and more powerful equipment like High Frequency (HF) or Very High Frequency (VHF) is installed on vehicles. So, heterogeneous mobile nodes may co-exist in a single ad hoc network making it a Heterogeneous MANET.
Criterion for Heterogeneous MANETs
The integration of different communication networks like cellular networks, WLANs, and MANETs is not straightforward due to various communication scenarios, different interface capabilities and dynamic mobility patterns of mobile nodes. This exhibits many possible application scenarios where devices may unexpectedly interact, create and receive random data streams (video and music etc), or request different network services. The drawback is that each network type typically uses its own protocol stack especially in the case of medium access. In fact, frequency allocation becomes more complicated since different wireless technologies like IEEE 802.11 a and IEEE 802.15.4 may possibly operate in the same frequency band, which makes coexistence mechanisms increasingly important. A heterogeneous MANET paradigm needs to be capable of providing subsequent characteristics.
The network should be capable of providing seamless end-to-end communication among mobile nodes i.e. the MANET user must not be informed about the route followed or network interfaces traversed by a communication session .
Integration among dissimilar communication networks must facilitate mobile nodes via some mobility management framework that can manage flow of information through different medium access techniques .
Most of the IP based networks consider each communication interface as an independent network device running under its own protocol stack . However, this mechanism makes it difficult to remember destinations by IP addresses. So, there must be some mechanism similar to domain name service to recognize mobile nodes with more logical and easy to remember names.
Various configuration options like network ID, willingness for cooperative communications, desired mobility level and intended services shall be provided to mobile users for their convenience .
End to End security
Integration between various networks and data transfer over multiple wireless hops can even expose data to malicious nodes. Security mechanisms must take care of end-to-end data security as well as route security .
Transmission Power and interference of Nodes
MANET routing protocols must take care of issues arising due to various communication ranges like communication gray zones  and issues arising because of various communication technologies like Bluetooth and WLAN working in same frequency band .
Utilization of Resources
In heterogeneous networking paradigm, there may arise situations where some or most of the mobile nodes are installed with different kind of resources. For example, there may be some nodes installed with location monitoring devices like GPS. Now it is the responsibility of routing protocol to benefit from such capabilities in order to facilitate location aided routing and similar services .
Current research efforts in mobile ad hoc networks are mainly converging towards inclusion of dissimilar communication technologies like IEEE 802.11  and IEEE 802.15.4  to a single mobile ad hoc network. Integrations of different networks like Wide Area Networks WANs (1G, 2G, 2.5G, 3G) and Metropolitan Area Networks MANs (IEEE 802.16) wherein users can access the system through a fixed base station (BS) or AP connected to a wired infrastructure in single hop fashion are also extending towards multihop communication environment using the new and revolutionary paradigm of a mobile ad hoc networks (MANETs), in which nodes constituting MANET serve as routers.
Comprehensive research efforts have been done to address the issues related to infrastructure-less multihop communications among nodes installed with dissimilar communication capabilities [3, 11, 12, 13]. However, an investigation needs to be made in order to analyze and address the issues arising from such integrations. Such problems relate to both end user’s convenience (For example, remembering each destination with its IP address is a cumbersome job specially when every destination may carry multiple IP addresses and any communication interface may optionally be connected or disconnected) as well as network’s performance; for example, routing to the best possible interface when there are multiple interfaces installed at destination. Likewise, optimized neighborhood sensing and position based routing can help to improve heterogeneous ad hoc network’s performance and scalability.
The objective of this thesis is to study the integration of different technologies like WPAN, WLAN and GSM having different capabilities and protocol stacks to mobile ad hoc networks. Performance improvement issues relating to network configuration, human understandable naming mechanism and sophisticated location aided routing mechanisms will also be discussed and evaluated on an actual ad hoc network testbed.
Chapter 2 describes the different design and technological challenges arising from integration of multiple communication interfaces. Chapter 3 includes an overview of famous heterogeneous routing protocols architectures, interworking issues encountered, the limitation and solution suggested. Chapter 4 specifically discusses the adopted solution. Chapter 5 presents the details about solution implementation, protocol evaluation testbed, proposed test cases for evaluation of the proposed mechanisms and results obtained, whereas; chapter 6 concludes the research work.
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