A context management system for wireless mesh networks

Abstract

Wireless Mesh Networks (WMNs) have become a promising technology for providing communication services in many applications where there are no network services available, such as (i) incident area networks for emergency and disaster relief, (ii) battlefields and; (iii) mining communications. “WMNs self-organize, self-configure” [176, pg. 618] and self-heal themselves and comprise of mobile clients and mostly static mesh routers connected wirelessly. Conventional layered protocols based upon the OSI model do not have the flexibility to handle the dynamics of WMNs such as labile wireless links, varying battery power and dynamic network topology, etc [38, 173]. “Most WMN cross-layer proposals to overcome these problems utilize a [narrow] … set of parameters from the concerned layers rendering them incapable of network and system wide optimizations as they do not consider global network context” [173, pg. 606]. Cross-layer protocols such as battery-aware or link-quality aware routing are “limited by the use-case[s,] … deployment scenarios [and] … technologies” [173, pg. 606] deliberated while designing them. Furthermore, multiple cross-layer adaptations operating at different protocol layers can lead to destructive interaction or interference between each other due to the lack of global view and communication between each other. There is an urgent need to overcome these problems and develop a lightweight Context Management System (CMS) for WMNs that gathers and manages numerous WMN context types gathered from sensors, network protocols, and user profiles as well as manages context-aware adaptations of the WMN protocol stack centrally (inside every WMN node) to coordinate protocol interactions. However, there has not been any comprehensive and suitable solution so far, although there are a few recent proposals of MANKOP and MOBCROSS, etc. These appear promising; however, there is a need for enhanced CMS for WMNs that is capable of managing context as well as WMN protocol’s context-aware adaptation. Furthermore, earlier WMN CMS designs have limitations such as not being easily extendable; do not have a simplified way of reasoning and managing about context, and they rely on generic context gathering mechanisms which can lead to high overhead in WMN as well as lacking higher-level situation reasoning models [173]. This thesis researches and presents a critical literature review of previous context management techniques developed for distributed computing and WMNs as well as context-aware routing protocols for WMN.communications. This research project makes several important research contributions. Firstly, a description is presented of the architectural and design requirements and challenges that have to be tackled to enable seamless context-awareness in WMN protocol stack adaptations. Secondly, an analysis and description is presented in this thesis of the wide-ranging context types which impact the performance of different WMN protocols. Thirdly, a proposal is presented of the design of an efficient CMS for WMN protocol adaption, named MESH-CMS. MESH-CMS resides within WMN terminals, and manages, collects and reasons context information as well as initiates adaptations of various WMN protocols to the changes in WMN context. MESH-CMS simplifies the development of context-aware WMN protocols by managing raw context information gained from multiple sources and enabling higher-level context abstractions. Fourthly, a novel WMN context-aware routing (MESH-CAR) protocol is proposed in this thesis that acts as a case study for MESH-CMS in addition to providing features such as route selection, route discovery, route optimization, route monitoring, and route repair as well as route life-time calculation in a context-aware fashion. Furthermore, it can collect context information and carry context subscription by piggybacking them onto routing control messages, thereby reducing the overhead of gathering context information. Finally, the thesis presents a few important case studies that evaluate a partial simulation-based implementation of the MESH-CMS architecture and MESH-CAR protocol and their underlying conceptual foundations. This involves the expansion of the simulation platform (NS-2) to implement MESH-CMS and MESH-CAR. The proof-of-concept prototype demonstrates the effectiveness of MESH-CMS and MESH-CAR protocol. NS-2 has been used widely for WMN protocol and CMS simulations. The case studies validate the architecture and performance enhancement achieved by the use of MESH-CMS and MESH-CAR and exemplifies the processes and issues involved during the design and implementation of WMN context-aware protocols and context management systems.