IPv6 Mobile Ad Hoc (MANETs) and Sensor Networks

Mobile Ad Hoc Networks (MANETs) are composed of nodes that can operate without a fixed network infrastructure. The network nodes act as both hosts and routers which form an ad hoc network connected by wireless links. Because of these characteristics, a MANET is considered to be self-organizing and highly dynamic due to each node's ability to dynamically determine routes and form ad hoc networks.

MANETs provide specific capabilities that typical fixed infrastructure networks are unable to match. Without the necessity for a fixed infrastructure, the nodes in a MANET are able to be mobile and flexible. Not only do the self-organizing nodes provide the ability to operate in environments without a fixed infrastructure, they reduce the time, complexity, cost, and economic impacts of network deployment.

A wireless sensor network is composed of small nodes that each consist of a battery powered sensor, CPU, and radio. In order to increase the lifetime of the nodes, the wireless sensor nodes are designed to use a limited amount of power, which results in low computational and transmission capabilities. Typically, a wireless sensor network will be deployed using a large number of nodes which form a self-configuring ad hoc network. The ability of wireless sensor network nodes to dynamically form ad hoc routes among available nodes allows these networks to be characterized as self-organizing, self-healing and highly dynamic.

Sensor networks offer capabilities beyond the capabilities of typical wireless networks. The network is simple to deploy, due to the ability of each node to dynamically join the network. In addition, the efficient design of the nodes extends each node's lifetime and will eventually result in a reduction of battery sizes. The sensor network nodes are designed to be inexpensive, which allows a large network deployment. Each node can be considered a disposable resource once its battery reaches the end of its lifetime.

Wireless MANET and sensor networks are seen as drivers that will revolutionize current and future DoD initiatives and programs. MANETs can be designed for Warfighter communications, emergency preparedness, and unmanned aerial vehicle (UAV) communications, as well as many programs that are required to operate without a fixed infrastructure environment. Department of Defense (DoD) programs such as the Joint Tactical Radio System (JTRS) and the Air Force Communications Agency are currently designing MANETs and sensor networks to enhance the Warfighter capability. Sensor networks will become critical for surveillance and remote area monitoring. A large number of densely populated nodes can be spread across a battlefield region and dynamically form an ad hoc network in order to transmit sensor data such as acoustic, temperature, light, and Warfighter movement intelligence back to a central command in order to provide area awareness and threat assessments.

In a policy memorandum released by the Assistant Secretary of Defense, Networks and Information Integration (ASD NII), the DoD is mandated to transition all enterprise-wide networks from Internet Protocol version 4 (IPv4) to Internet Protocol version 6 (IPv6). This effort will affect MANET and sensor networks, which will require modification of the existing MANET and sensor network protocol stacks in order to support the emerging protocol.

The inherent characteristics of the IPv6 protocol will enhance the future capabilities of MANETs and sensor networks. The protocol will enable the networks to improve mobile IP efficiency, enhance security capabilities, and provide support for Quality of Service (QoS) mechanisms in MANETs and interconnections between sensor networks and other fixed and wireless networks. In current MANETs, challenges exist for providing QoS capabilities and adequate security mechanisms. Extensive research has been conducted for providing QoS support for MANETs. IPv4 mechanisms suffer from issues such as fragmentation. IPv6 will enable MANETs to provide support for QoS mechanisms by providing the 8-bit traffic class field and the 20-bit flow label. In addition, IPv6 does not fragment packets while in transit between end hosts, which reduces the network load on the intermediate ad-hoc nodes.

IPv6 provides support for security mechanisms that can enhance MANETs. Most notably, encryption and authentication mechanisms via IP security (IPSec) will become critical in protecting the data transferred between MANETs and the integrity of the nodes within the network. In addition, the inherent mobile IP capabilities of IPv6 will allow complete ad hoc networking between different MANETs. The ability to travel between networks that do not have a fixed infrastructure allows complete information exchange between far-reaching networks.

The integration of the IPv6 protocol with MANET and sensor networks will present challenges that will require further investigation. While some obstacles need to be addressed at the fundamental design level of the devices and networks, others can be addressed at the implementation and deployment level.

Resource management will become a critical consideration in sensor networks and IPv6 MANETs. Resources such as battery life and CPU utilization must be monitored and managed in these networks. The computational complexity of QoS and security mechanisms in sensor networks and IPv6 MANETs will affect the lifetime of the network nodes as a result of increased power and CPU utilization.

As wireless MANET and sensor network technologies evolve, scalability will become a significant challenge. The throughput and performance of the network can reach bottlenecks as network and control traffic increases. As the network grows, data is routed between an increasingly larger number of nodes, which increases the probability of packet loss. In addition, as the size of ad hoc networks increases, more power will be utilized as additional packets are forwarded and IPv6 security and QoS mechanisms are implemented in IPv6 MANETs and wireless sensor gateways that interconnect to IPv6 networks. Some ongoing ad hoc network scalability research projects include Intel's Ecosense research project and the Heterogeneous Sensor Network project.

Wireless MANETs and sensor networks are emerging as technologies that will serve as drivers that will enhance the capabilities of today's networks. The ability to operate without fixed infrastructures and create ad hoc networks provides economic, deployment, and resource utilization benefits over infrastructure based networks. As the IPv6 protocol becomes integrated with the wireless MANET and sensor networks, its mobile IP capabilities, QoS, and security features are expected to revolutionize commercial and defense communications.