Mesh Networks: Part 2

Military Perspective

Aside from efforts to tame mesh network technology for commercial deployment, the U.S. Government has spent significant time, money, and resources on the research, development, and field deployment of mesh networks for tactical military operations.  With any mesh network deployment, the addition or deletion of network nodes can alter the dynamic network topology, emphasizing the need for efficient network organization, link scheduling, and routing to contend with varying distance and power ratios between links. A military environment, however, imposes additional complications by enforcing low probability of intercept and/or low probability of detection requirements, which in turn pose stringent power and transmission requirements on every network node [4].

Tactical military operations must also contend with varying degrees of mobility that occur within the military’s echelon of four Divisions per Corp, four Brigades per Division, three Battalions per Brigade, four Companies per Battalion, and three Platoons per Company [13].  In this particular hierarchy, the often unpredictable nature of battle can dictate the need to merge and reconfigure sections of missing forces, disrupting the communication paths from node to node within Battalions, Companies, or other command structures. And while some engineers argue that alternatives to mesh networking exist to support communications in these battlefield conditions, others highlight the mesh network capability for instantly configurable, decentralized, redundant, and survivable communications in frontline battle areas or during amphibious or airborne operations where a clustered, ad hoc network configuration might consist of people, planes, ships, and tanks. In this military environment, mesh networks must contend with the military’s requirement for preservation of security, latency, reliability, intentional jamming, and recovery from failure [1], [4].

The Joint Tactical Information Distribution System (JTIDS) provides one example of a repeater-based, full mesh military network architecture that uses airborne relay to perform base station functions such as routing, switching, buffering multiple packet streams, and radio trunking. Developed for air-to-air and air-to-ground communications, JTIDS consists of up to 30 radio nets each sharing a communications channel on a time division multiple access (TDMA) scheme with most nodes in the network containing minimal hardware and processing power. In this configuration, the loss of any node within a radio net would have no negative impact on communications connectivity [1].

In another example, the Army’s Communications Electronics Command oversees ITT Industries’ development of the Soldier Level Integrated Communications Environment (SLICE). Designed for voice communications and troop mapping functions, SLICE represents the latest in military mesh network capabilities. Originally conceived as the DARPA Small Unit Operations Situational Awareness System, SLICE supports simultaneous networking of voice, video, and data transfer with a waveform and media access protocol that yields effective communications in urban canyons and dense jungle environments. In its present form, SLICE consists of a backpack-size computer with a headset display and built-in microphone. By 2005, ITT expects SLICE to shrink to the size of a PDA.  With respect to SLICE, JTIDS, or any other military radio architecture, the theme of digitized battlefield communications describes the warfighter landscape with requirements for wearable, ruggedized personal computers capable of flawless performance under harsh conditions [14], [15, [16].

Final Thoughts

With low transmission power requirements and a multi-hop architecture, mesh networks increase the aggregate spectral capacity of existing nodes, providing greater bandwidth across the network. And since mesh networks transmit data over several smaller hops instead of spanning one large distance between hops, mesh network links preserve signal-to-noise ratios and decrease reliance on bandwidth-pinching forward error correction techniques [17]. In terms of scalability, mesh networks can accommodate hundreds or thousands of nodes with control of the wireless system distributed throughout the network, allowing intelligent nodes to communicate with one another without the expense or complication of having a central control point. Furthermore, these networks can be installed in a manner of days or weeks without the necessity of planning and site mapping for expensive cellular towers. As with other peer-to-peer router-based networks, mesh networks offer multiple redundant communications paths, allowing the network to automatically reroute messages in the event of an unexpected node failure. Thanks in part to standards efforts underway in the Internet Engineering Task Force (IETF) MANET Working Group, the design and standardization of algorithms for network organization, link scheduling, and routing will help facilitate the commercial acceptance of mesh network technology.

Despite their potential to provide a more sophisticated WLAN alternative, mesh networks must effectively address security issues with end-device and router introduction, user data integrity, device control and authentication, and network authentication. Aside from security issues, the RF-independent, self-forming, and self-healing characteristics these networks display come at  the expense of complex and power intensive computer processing. Even in static environments with all nodes stationary, mesh network topologies remain dynamic due to variations in RF propagation and atmospheric attenuation. With mobile nodes, a mesh network’s constantly shifting topology dictates the need for dynamic routing allocation, resource management, and quality of service management – all of which must be precisely choreographed to ensure optimum performance and reliability. Other skeptics contend that as ad hoc multi-hop networks grow, performance tends to deteriorate due in part to excessive traffic control overhead required to maintain quality of service along a path with multiple hops besieged by inconsistencies in routing and connectivity as nodes are added and dropped. Also, the network must handle multiple access and collision problems associated with the broadcast nature of RF communications. Regardless of these technical hurdles, researchers at Intel continue to push the research and development envelop in an effort to design a 100 Mbps mesh network where every network element (PC, PDA, mobile phone, etc.) could act as a data relay and link itself to all the devices in an intelligent network [10], [12], [17], [19].

With the ability to deploy a wide-spread coverage network without towers, mesh networks pose a viable alternative to traditional cellular architectures. Labeled as a potentially disruptive fourth-generation technology, QDMA-based mesh networks aren’t alone in their quest for the ultimate radio communications system capable of operating in unlicensed spectrum. Though technologically disparate from QDMA-based networks, ultra wideband (UWB) mesh networks present one alternative to MeshNetworks, Inc. proprietary QDMA-based software, thanks in part to recent FCC rulings approving limited usage of UWB devices. Several companies are championing the development of UWB networks, which promise data rates of 100 Mbps at very low power levels over a wide bandwidth from 1 to 10 GHz. By employing time-modulated digital pulses in lieu of continuous sine waves, mesh networks with UWB technology can send signals at very high rates in wireless communication environments that suffer from severe multipath, noise, and interference. Whether UWB mesh networks or QDMA-based mesh networks will prevail remains to be seen. Some analysts give the edge to UWB as an open standard, which is steadily gaining support in commercial and military markets. Either way, the continued development of mesh networks for military and commercial markets holds promise for a radical shift in the way we view the world of wireless communications [18], [20].

References

1      “Alternative Architectures for Future Military Mobile Networks,” Obtained April  7, 2003 from URL: http://www.rand.org/publications/MR/MR960/MR960.chap3.pdf

2      Poor, Robert, “Wireless Mesh Networks,” Sensors [on-line], February 2003. http://www.sensorsmag.com/articles/0203/38/main.shtml.

3      Braunschweig, Carolina, “Wireless LANs Could Turn Into a Big Mesh,” Private Equity Week [on-line], February 3, 2002. http://www.ventureeconomics.com/vec/1031551158703.html

4      “Project: Wireless Ad Hoc Networks,” NIST.  Obtained April 8, 2003 from URL: http://w3.antd.nist.gov/wctg/manet/

5      “QDMA and the 802.11b Radio Protocol Compared,” MeshNetworks: Technology, [on-line]. Obtained April 9, 2003 from URL: http://www.meshnetworks.com/pages/technology/qdma_vs_80211.htm

6      Blackwell, Gerry, “Mesh Networks: Disruptive Technology?” 802.11 Planet [on-line].  Obtained April 8, 2003 from URL: http://www.80211-planet.com/columns/article.php/961951.

7      Black, Uyless (1993). Computer Networks: Protocols, Standards, and Interfaces. Second Edition. New Jersey: Prentice Hall.

8      Stroh, Steve, “MeshNetworks – From the Military Battlefield to the Battlefield of Modern Mobile Life,” Shorecliff Communications [on-line], Vol. 2, No. 2, February 2001. http://www.shorecliffcommunications.com/magazine/print_article.asp?vol=10&story=85

9      Morrissey, Brian, “The Next 802.11 Revolution,” Internet News [on-line], June 13, 2002. http://www.internetnews.com/wireless/article.php/136561

10   Rubin, Izhak, and Patrick Vincent, “Topological Synthesis of Mobile Backbone Networks for Managing Ad Hoc Wireless Networks,” Electrical Engineering Department, University of California Los Angeles, 2001.

11   Krane, Jim, “Military Networks Trickling into Civilian Hands,” The Holland Sentinel [on-line], December 8, 2002. http://www.thehollandsentinel.net/stories/120802/bus_120802072.shtml

12   Fowler, Tim, “Mesh Networks for Broadband Access,” IEE Review, January 2001.

13   Graff, Charles et al., “Application of Mobile IP to Tactical Mobile Internetworking,” IEEE Magazine, April 1998.

14   “ITT Industries Awarded $44 Million to Develop Advanced Soldier Communications System,” PR Newswire [on-line], November 25, 2002. http://www.cnet.com/investor/news/newsitem/0-9900-1028-20696617-0.html

15   “Mesh Networks Keep Soldiers in the Loop,” Associated Press [on-line], January 27, 2003. http://www.jsonline.com/bym/Tech/news/jan03/113806.asp

16   Omatseye, Sam, “The Connected Soldier,” RCR Wireless News, March 17, 2003.

17   Krishnamurthy, Lakshman et al, “Meeting the Demands of the Digital Home with High-Speed Multi-Hop Wireless Networks,” Intel Technology Journal, Volume 6, Issue 4 [on-line], November 15, 2002. http://developer.intel.com/technology/itj/index.htm

18   Smith, Brad, “Smell the Coffee: Disruptive Technologies on the 2002 Horizon,” Wireless Internet Magazine, January 7, 2002. http://www.wirelessinternetmag.com/news/020107/020107_opinion_brad.htm

19   Ward, Mike, “Promise of Intelligent Networks,” BBC News [on-line], February 24, 2003.  http://news.bbc.co.uk/2/hi/technology/2787953.stm

20   Barr, Dale, “Ultra-Wideband Technology,” Office of the Manager, National Communications System Technical Notes, Volume 8, Number 1, February 2001

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