A mobile mesh is a self-organizing wireless communications network in which every mobile device becomes a network router and can connect with other devices in the network. Mobile mesh networks configure themselves instantly and automatically and are inherently survivable because of the availability of alternate paths. Meshed devices can utilize when fixed infrastructure is available (e.g. 802.11 access points), which, however, is not required to create a mesh network.

Figure 1 shows the difference between a conventional hub-and-spoke network topology versus a multi-hop mobile mesh. Traditional hub-and-spoke networks, as in wireless local area networks (WLANs), require all data to be sent to a centralized access point before it is sent to its destination - even if the destination is a mere few feet away. In contrast, in a mobile mesh network, data distribution takes place in a peer-to-peer manner with multiple hops if needed and an access point is used only to reach a fixed private network or Internet.

Building on a Foundation of Proven Technology and Standards
PacketHop’s mobile mesh technology has a legacy of more than 30 years of research and development at SRI International, tracing back to the early Packet Radio Network (PRNET) program sponsored by the Defense Advanced Research Project Agency (DARPA) of the Department of Defense in the 1980's. Also, the DARPA Global Mobile Information Systems (GloMo) program during 1995-2000 advanced the state of the art in wireless mobile mesh networks, including new radios and antennas, network protocols, security techniques, network management tools, and adaptive applications.

PacketHop is taking an open standards approach to solving the hard problems of mobile mesh networking by delivering a technology that is based on established IEEE and Internet Engineering Task Force (IETF) standards. Its routing protocol, called Topology Broadcast with Reverse Path Forwarding (TBRPF), licensed from SRI International, is an Experimental RFC (RFC 3684) within the Mobile Ad hoc Networking (MANET) Working Group of the IETF. PacketHop's software builds on available standards on quality of service, security, and management from IEEE and IETF to ensure interoperable connections to existing infrastructure.

Mobile mesh network protocols
A mobile mesh routing protocol has to adapt instantly to changing multi-hop topology and variable link bandwidth caused by mobility. Today’s fixed Internet routing algorithms are based on the critical assumption that the network topology changes slowly compared to the time it takes to discover topology changes. In contrast, PacketHop's routing protocols are designed to respond quickly to highly dynamic mobile environments. Every node in the mobile mesh maintains a routing table and forwards incoming packets toward the destination as shown in Figure 2, based on number of hops, network congestion, and link bandwidth. Alternate routing paths are immediately established to provide seamless connectivity as topology changes occur due to mobility or a node in the network cloud going offline.

Scalable, secure, and robust mobile mesh networking requires a comprehensive set of network capabilities beyond simple connectivity. To meet the needs of demanding network applications, PacketHop is addressing the complete set of mobile mesh networking challenges with appropriate solutions. These include:

Security—distributed encryption, key management, and authentication methods to ensure that the mobile mesh can continue to operate securely even if all connections to centralized management entities are lost.

Roaming—self-contained dynamic Internet Protocol (IP) addressing and rendezvous technologies to enable devices to join and leave a mobile mesh and/or connect to public or private fixed infrastructure, retaining connectivity to critical services.

Quality of Service (QoS)—standards-based QoS protocols with innovative enhancements that include layer 2-aware routing techniques, optimizations to multicast protocols, and application-level control to permit management of multimedia data flows.

Network Management—a unique combination of distributed and centralized methodology to enable coherent management and policy control of a mobile mesh.

Interoperability—interoperate with existing WLAN infrastructure as is, with no upgrades or replacement of wireless access points.

With PacketHop’s mobile mesh networking software loaded onto a variety of IP compatible radio (e.g. 802.11) equipped devices—laptops, tablets and PDAs—a wireless broadband network can be formed instantly. This is done by functionally turning each device into a router that proactively keeps track of other devices in the highly dynamic and changing wireless mesh. Each device is then capable of communicating with one another as well as with any traditional fixed IP infrastructure (e.g. 802.11 access points). In this manner, highly secure, mobile, interoperable, and survivable broadband communications are enabled instantaneously. PacketHop's mobile mesh broadband solution is a complete network system, including the network client software (installed on each wireless device), network controller (a secure high-performance appliance that interconnects multiple mesh networks), and network management system (real-time control for both distributed and centralized operations). In addition, PacketHop developed a suite of applications that operate in a peer-to-peer, server-less environment over any network and any IP device.

Mobile mesh networking is applicable to several markets as illustrated in Figure 3. In all these markets, mobile mesh enables mobility beyond what is feasible with WLANs and supports applications more reliably.

PacketHop applications to Homeland security
PacketHop’s initial market focus is on Homeland security and first responders. The PacketHop system is IP-based, radio agnostic and integrates easily with standards-based, commercial off-the-shelf equipment. It is invaluable to public safety because it delivers a network that is survivable, instantaneous, interoperable, and secure.

In February 2004, PacketHop conducted a field exercise in association with the Golden Gate Safety Network (GGSN), which is a San Francisco-based coalition made up of federal, state and local public safety agencies, including the California Governor's Office of Emergency Services (CAL OES), California Highway Patrol, FBI, San Francisco Fire and Police, Sheriff's Department Marin County, National Park Service and U.S. Coast Guard, among others. Focusing its efforts on San Francisco's landmark Golden Gate Bridge and surrounding waterways and national parks, the GGSN team and PacketHop demonstrated for the first time a mobile broadband communications system that enables interoperable data communications.

The GGSN exercise successfully tested the ability of multiple agencies to communicate, coordinate and respond using PacketHop's broadband mobile mesh network technology. Dozens of first responders from 13 multi-jurisdiction agencies participated in the field exercise with a wide variety of command and operations vehicles and marine patrols. CAL OES was linked via a virtual private network from the State Capital in Sacramento. Figure 4 gives a schematic of the covered geographical area and deployment during the exercise.

As each first responder arrived on the scene, an icon with an individual's vitals such as name, rank, agency, etc., appeared on the GIS map and automatically tracked their movement on foot, car, or boat. For example, first to the scene, was the Marin County Office of Emergency Services to secure the north anchor of the Golden Gate Bridge. Members of the San Francisco Fire Department arrived next at the south anchor, followed by marine units from the San Francisco Police and the U.S. Coast Guard, securing the waterways in and around the Bridge. All of this information was available instantly to all participants without the need for multiple voice calls that could have risked overloading the voice system. Figure 5 shows a typical screen on a laptop with various application windows concurrently running.

Across dissimilar networks, difficult terrain and diverse devices, the GGSN exercise achieved mobile broadband connectivity, effectively solving the communication barriers that exist between first responder agencies today. The ability to create survivable, packet switched, mobile broadband networks on the fly will change the face of interoperable communications for public safety, and in doing so, will extend valuable resources and save lives.

Dr. Ambatipudi Sastry has 35 years of involvement in the research and development of telecommunications and networking technologies, particularly in wireless networks and protocols. As CTO at PacketHop, he is responsible for developing strategy for PacketHop's mobile mesh networking and systems solutions. Prior to that, at SRI International, Dr. Sastry supervised the group that developed protocols for mobile ad hoc network protocols, which provide the foundation for PacketHop's core technology. He received his Ph.D. in Electrical Communications Engineering from the Indian Institute of Science, Bangalore, India.