Literature Review on Wireless Technology in Mobile Ad-Hoc Networks

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

LITERATURE REVIEW

Introduction

The literature available on heterogeneous MANETs has suggested different combination of access technologies but no comprehensive solution comprising of maximum access technologies has been suggested yet. Some of the suggested techniques will be discussed in succeeding paragraphs.

Service Architecture for Heterogeneous IP Networks

It was presented by Joe C. Chan and Doan B. [14]. This proposal is presented to resolve two main issues i.e. universal connectivity and MANET location management in heterogeneous networks. The new architecture suggested for Mobile Ad-hoc Systems and Services (AMASS) introduces a new abstraction layer called Mobile P2P overlay in order to cater for the problems such as transparency, dynamic routing, unique addressing, association, and application independence. Mobile users can associate local resources from neighboring devices, build wireless on-demand systems which is independent of location, hardware devices, networking technology and infrastructure availability. Five key design considerations considered were Mobile Peer-to-Peer Overlay, Internet Interworking, Intelligent Overlay Routing, Infrastructure-free Positioning and Application Layer Mobility. Three enhanced mobility models offered in this approach are Personal Mobility (using different IP devices while keeping the same address), Session Mobility (keeping the same session while changing IP devices) and Service Mobility (keeping personal services while moving between networks).

The architecture is built on a peer-to-peer communication model to integrate MANETs seamlessly into heterogeneous IP networks. Mobile Peer-to-Peer System(P2P) is a distributed Middleware addresses the demand of direct communication needs by creating spontaneous community. Whenever the Mobile P2P system has global connectivity, it works with its peer system and other applications systems by generic P2P signaling. It consists of Ad-hoc Network layer and Mobile P2P Overlay. The former layer includes wireless hardware and MANET routing software offering homogeneous connectivity among nodes with same wireless interfaces. These nodes act as a router forwarding traffic toward its destination. The later layer includes the following core services: (i) Membership Services offers single sign-on, naming, profile and identity features; (ii) Discovery Services for peer/resource discovery and caching; (iii) Communication Services for Internet interworking, intelligent routing, session control, presence and service delivery; (iv) Location Services for infrastructure-free positioning, and user mobility management functions; (v) Adaptation Services for application and network services adaptation.

Members of the Mobile P2P system should first sign-in a “common group” with their exclusive name and password. Some stationary nodes may also join to offer its resources such as Internet connection, printer, video conferencing. Whenever these client devices are within range of each other, they would work together as a team leading to a wireless adhoc service community where local resources could be shared by individual at its will. These members will then be available by intimating their capabilities and location information to the central location server. Information regarding physical location is also essential to offer spatial locality relationships and enable mobile content customization.

The results which were achieved through this process can be summarized as first, it maximizes the synergies of MANETs and P2P for building wireless on-demand systems and services. MANETs provide dynamic physical connectivity while P2P offers dynamic associations of entities (users, devices, and services) for direct resources sharing. Second, its Mobile P2P overlay unites mobility, user-centric connectivity, and services for universal communications. This allow dynamic service adaptations pertinent to user location, application requirements, and network environments. Third, it presents a flexible network structure stimulating fixed and wireless networks convergence. The result is an “Integrated Mobile Internet” which makes our future environment lot better.

Transparent Heterogeneous Mobile Ad hoc Networks

The idea was suggested by Patrick Stuedi and Gustavo Alonso[3]. The paper discussed that performance issues in a personal area network (PAN) or wireless sensor network (WSN) may have less priority than an office network. In contrast, battery life and low cost is vital to PANs and WSN while most probably it is not an issue in an office network. Consider a scenario where in a certain university campus the students carry variety of personal devices like mobile phones, PDA or laptops equipped with different communication technologies tailored to their capabilities. The mobile phones or PDA will be using Bluetooth whereas laptops have 802.11 as well as a Bluetooth interface built in technology. Ubiquitously combining all these devices into one mobile ad hoc network could invite new applications and services such as location based services or VoIP. So there may be an occasion where a personal device of one particular PAN might communicate with a personal device of another PAN in a multi-hop fashion with the underlying MAC scheme changing per hop.

In this scenario two issues needs to be solved i.e. broadcast emulation and handover. Broadcast emulation is not directly supported in Bluetooth (nor on nodes comprising both Bluetooth and 802.11). Handover is an issue because, in the case of heterogeneous MANETs, a handover might include a change in how the medium is accessed. A handover can be caused by node mobility, a change in user preferences (where due to energy constraints the user chooses to use Bluetooth instead of 802.11), or performance reasons. [15]

Any device or node supporting multi interface though having different protocol stack will be specific to the interface at lower level. This characteristic will deteriorate the ability of a device to switch from one network to the other. The objective of such network is to provide an end-to-end communication abstraction that hides heterogeneity. The different possible design differs from each other with regard to application transparency, performance and mobility. There is another issue of handover which includes route changes as well as MAC switching. In principle, there are three possible scenarios

Horizontal Handover

The horizontal handover between the participating nodes take place when the route changes and underlying MAC technology remains the same.

Vertical Handover

The route does not change but the given neighbor is now reached through a new physical interface.

Diagonal Handover

The diagonal handover takes when the MAC technology and route between the participating nodes change simultaneously.

To address all these issues an IP based heterogeneous mobile ad hoc test bed using Bluetooth and IEEE 802.11 that implements a virtual interface approach as the end-to-end abstraction is presented.

Stream Control Transmission Protocol

Another approach presented by R. Stewart, Q. Xie, and K. Morneault is [16] Stream Control Transmission Protocol, a transport protocol defined by the IETF providing similar services to TCP. It ensures reliable, in-sequence delivery of messages. While TCP is byte-oriented, SCTP deals with framed messages. A major involvement of SCTP is its multi-homing support. One (or both) endpoints of a connection can consist of more than one IP addresses, enabling transparent fail-over between hosts or network cards.

Each interface could be separately cond and maintained (AODV-UU [17] e.g., supports multiple interfaces). This solution seems to be quite valuable in terms of performance since SCTP optimizes the transmission over multiple links. In fact, if one particular node can be reached through several interfaces, SCTP switches transmission from one interface to another after a predefined number of missing acknowledgements. Unfortunately, the solution lacks transparency. Applications running traditional unix sockets would have to be changed to use SCTP sockets instead. Another problem arises with the connection oriented nature of Bluetooth. In Bluetooth, interfaces appear and disappear dynamically depending on whether the connection to the specific node is currently up or down. Therefore, this is something that both the ad hoc routing protocol as well as SCTP would have to cope with.

Global connectivity for IPv6 Mobile Ad Hoc Networks

R. Wakikawa, J. T. Malinen, C. E. Perkins, A. Nilsson, and A. J. Tuominen, in 2003 through IETF Internet Draft, 2003 presented “Global connectivity for IPv6 Mobile Ad Hoc Networks,” suggested one of the solutions for connecting heterogeneous MANETs. Before this work, the issue was solved by the traditional Internet model. But by adopting the approach presented by them the non structured MANETs were made to operate in structured environment, and inevitably limit the extent of flexibility and freedom that an evolving Mobile Internet can offer. Current mobile positioning and network mobility solutions are mainly infrastructure-driven which is contradictory to infrastructure-less MANETs. Without a flexible and user-centric network structure, existing solutions are generally insufficient to handle the dynamic and on-demand requirements of MANETs.

Conclusion

Heterogeneous MANET service architectures and routing protocols have been talked about and it is established that lots of enhancements need to be introduced to the heterogeneous ad hoc networks. First of all, different issues like IP addresses to hostname mapping and seamless communication need to be addressed. Secondly, ad hoc networks must seamlessly utilize all underlying interfaces. Finally, research efforts need to converge towards real-world network deployment as very few MANET service architectures have been evaluated on actual network testbeds.