Wireless mesh networks gain traction

Wireless mesh networks gain traction
Manhasset, N.Y. - Startup Ember Corp. will announce today an IEEE 802.15.4-based wireless transceiver with mesh-networking software, the third distinct boost for wireless ad hoc mesh networking in a week. Earlier, startup PacketHop Inc. unveiled a routing protocol and Zensys A/S announced a business partnership with Intel Corp.

The separate announcements bring into sharp relief the intense work now under way to achieve an efficient, scalable wireless network that is more robust than the centralized architectures now used for Wi-Fi and cellular local- and wide-area networks. They also bring to the fore a longstanding debate over a Layer 3 protocol's ability to ensure, by itself, robust connectivity for mesh networking in an RF environment.

Derived from military-funded research into mobile networks, mesh networking eliminates the need for a central controller and its associated reliability and efficiency issues. Instead, mobile ad hoc mesh networks use peers in the network to transmit data from source to destination by means of multiple hops.

While the Internet-like concept and its advantages are straightforward, a problem arises in deriving an optimum routing protocol to minimize the number of hops while ensuring security and seamless mobility, as well as quality-of-service (QoS). Fewer hops mean lower latency and overall power consumption.

So far, companies like MeshNetworks Inc. (Maitland, Fla.) have dominated mobile ad hoc networking. The company's mesh-enabled architecture includes an air-interface-agnostic multihopping routing protocol and a proprietary QDMA radio.

Ember (Boston) similarly uses a proprietary radio, the EM2420, which debuts this week. Chief technology officer Robert Poor said the chip is based on the IEEE 802.15.4 low-power physical layer and is the first device to cater to all three frequencies outlined in that standard-915 MHz, 2.4 GHz and 868 MHz, the last for Europe. This integrated transceiver has a serial interface to a variety of 8-bit host processors; the antenna interface is a simple LC network. Other features of the 0.18-micron CMOS design are hardware encryption and an on-chip Tx/Rx switch in a 7 x 7-mm package. The chip is available now, priced at $3.50 each in volume. It comes with EmberNet software, which includes libraries for mesh, star and hybrid implementations.

While MeshNetworks and Ember offer combination protocol/radio solutions, PacketHop last week entered the fray with a protocol implementation. Michael Howse, president and CEO of the Belmont, Calif., spin-off of SRI International, said an emphasis on enhanced security, QoS, device management, dynamic addressing and session management, as well as the integration of both centralized and distributed control, has created a solution that surpasses previously available offerings.

PacketHop's routing protocol was earlier used as a way to overcome line-of-sight issues associated with fixed wireless access. Since then, Howse said, the Pentagon mandated an infrastructureless network that did not need proprietary radios but had an ability to do Layer 3 routing. The PacketHop protocol is based on TBRPF, one of two mobile ad hoc networking (Manet) protocols specified by the Internet Engineering Task Force. AODV is the other.

Eye on Wi-Fi
Embedded within a wireless client, the software decreases infrastructure dependency by letting users carry and retransmit data to other users. Should a connection fail, Howse said, "the proactive protocol can dynamically re-create routes, with the ability to ensure application and session maintenance and QoS for data and multicast video." Wi-Fi is the company's initial target.

Though no product is available, Howse said the protocol is "in trial" with a major commercial operator and will debut in the first quarter of 2004.

MeshNetworks, for its part, "doesn't use Manet protocols because we don't believe they work in real-world applications," said Rick Rotondo, vice president of technical marketing. Instead, "we do Layer 2 routing, as you need to employ cross-layer optimization to ensure operation over asymmetric wireless connections," Rotondo said.

Charles E. Perkins, a member of the research staff at Nokia and an authority in this area, agreed in part with Rotondo's assessment. "TBRPF isn't a complete solution, but then again no routing protocol by itself can [be]," Perkins said. Though he called AODV a more-scalable option, "that's not complete either," he said. "QoS in ad hoc networks is a famously difficult problem. It's even hard just in [centralized] wireless IP networks [like Wi-Fi], unless some strong assumptions are made."

But Howse said PacketHop has already solved the problem, and proved it in real-world implementations. Howse said he could not describe the core enhancements for intellectual-property reasons, but "The fact is we're much better off riding the cost curve of established radios-such as Wi-Fi and cellular-rather than trying to implement a proprietary radio. The protocols will all converge at some stage on a workable solution that everyone's happy with."

Meanwhile, Zensys' deal with Intel targets low-data-rate, low-cost wireless ad hoc networking, specifically for home automation. In the deal announced last week, Zensys (Berkeley, Calif.) and Intel will develop a universal platform for seamless home control based on Zensys' Z-Wave mesh-networking scheme. The system will include Universal Plug-and-Play (UPnP) drivers.

The goal is to enable everyday devices such as light switches, thermostats, alarms and appliances to be networked along with TVs, PCs, PDAs and cell phones via a low-cost wireless connection. "The deal validates our technology," said Michael Dodge, vice president of marketing at Zensys.

The technology is based on a low-cost mixed-signal ASIC that integrates an 8051 processor with a proprietary narrowband radio operating at 868 MHz (for Europe) or 908.4 MHz (for the United States) and the company's routing protocol. It can support up to 254 nodes and costs $6.50 for a full package on a pc board as small as 2 x 3 cm.

Dodge said the radio and mesh protocol eliminate the high processing overhead associated with other proposed radios for automation and control. "Unlike Zigbee [based on the IEEE 802.15.4 physical layer], we're here and now," Dodge said.

The Intel partnership will allow Z-Wave-enabled devices to interact and will extend the capabilities of UPnP to small devices that do not support TCP/IP stacks. Founded in 1999, Zensys lists Sylvania, IBM's HomeDirector, ACT and Intermatic among its customers.

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