Efficient Interconnection of IEEE802.15.4 WPANs with Internet and Extraneous Wireless Networks

Abstract

IEEE802.15.4 Low-Rate Wireless Personal Area Networks (LR-WPANs) are envisioned to play an important role in application centric ubiquitous networks such as Wireless Sensor Networks (WSN). Interconnection of these networks with Internet and with other WPANs in close proximity is essential for effectively organizing, managing and utilizing these networks. Ubiquitous role of WSN can be realized through interconnection with adjacent WSNs as well as with infrastructure networks which can be direct or hopping through bordering WSNs. An example scenario is environmental monitoring of large geographical area where clusters of WSN jointly ensure the ubiquitous presence of WSN. These clusters would require collaboration among themselves in addition to management through infrastructure network. Similarly in critical, mission oriented military applications multiple groups form WSN clusters which require reliable code update in addition to inter-cluster collaboration for information sharing. This thesis addresses challenges in interconnection of LR-WPANs with Internet and with other WPANs in close proximity. In addition to reliable and timely code dissemination to WSN from infrastructure network, there is a need for procedural details to carry out efficient cluster diffusion for inter-PAN communication when multiple PANs operating in distinct logical channels are in close proximity of each other. This work presents two innovative and comprehensive architectures that provide complete solutions for above mentioned research problems while covering all related design elements. A complete architecture for efficient TCP realization in IPv6 based Low-Power Personal Area Network (6LoWPAN) is presented as solution to Internet interconnection research challenge. The 6LoWPAN is a protocol specification that enables communication of Internet Protocol version 6 (IPv6) packets on top of IEEE802.15.4 so that Internet and WSNs can be inter-connected. In commercial and enterprise applications of WSNs reliable and timely multiple/repeated code updates are required from Internet hosts to sensor nodes. For such inbound data traffic which is in general heavy, time-sensitive and loss-intolerant, TCP as transport layer protocol is essential such that end-to-end TCP sessions from Internet node(s) to sensor nodes through a default gateway are set up. In this situation, a single gateway is likely to form the bottleneck of connection due to non-uniform connectivity to sensor nodes and is also susceptible to buffer overflow. The solution to this problem, Session layer-assisted Efficient TCP management architecture (SET) is a management architecture that establishes and manages multiple splitTCP sessions across a number of available gateways. SET performs multiple-TCP-sessions management and executes data striping through shim at session layer. Through analytical modeling and simulations using NS2, it is demonstrated that SET architecture optimizes communication for incoming bulk data transfer, at the same time offering related load balancing services. Multiple split-TCP sessions handled in parallel across a number of gateways results in reducing end-to-end latency for bulk data transfer and prevents absolute communication failure in case of gateway failure. For effective inter-WPAN association, a comprehensive architecture, COmmoN-iNterest basEd diffusion of Collocated PANs via gaTing at border nodes (CONNECT) is proposed that executes diffusion of neighboring PANs. In IEEE802.15.4 networks when multiple PANs are present in Personal Operating Space (POS), they function in non-interfering logical channels. This way, capacity of PANdirected broadcast is restricted, received-energy per PAN device is reduced and interference at physical layer is minimized. At the down side, under this type of configuration, inter-PAN communication is not possible because PANs in the same region remain unaware of each other’s presence. CONNECT architecture supports communication between multiple PANs in the same POS that might be operating in different logical channels. It enables neighboring PANs to communicate by diffusing into each other through “bordering nodes” called “connect nodes”. The main idea is to time share logical channels such that a gating operation is performed by nodes residing at the border of two non-interfering PANs. CONNECT architecture executes procedures; identification of border nodes by PAN coordinator, discovery of neighboring PAN(s), assigning duty cycle and gating command to border nodes, interest solicit from sensor nodes and data transfer across PANs. CONNECT framework is mathematically analyzed and NS2 simulations are performed to demonstrate communication aspects at connect nodes to show their usability for diffusion