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Tropos sets mesh cat amongst WiFi pigeons with dual-radio hotzone

Some exciting firsts" are claimed for Tropos's new "multi-radio mesh" hotzone hardware - some of which are going to raise eyebrows with rivals.

The new hardware is detailed in the official PR  from Tropos. It quotes Bert Williams, director of marketing for Tropos, saying: "We expect customers to mix and match the new equipment with the older generation gear. San Francisco is a good example of how this could work. The new 5320 routers might be used to provide service in more densely populated regions, while the older 5210 routers could be used to offer service in less populated areas like near city parks."

The devices, called the Tropos 5320 outdoor MetroMesh router, "use two radios instead of one to transmit signals. One radio operates at 5GHz. This radio will be used exclusively to link routers in the mesh. Because the 5GHz spectrum works at a higher frequency, it offers more bandwidth. But it also has more difficulty penetrating through walls or dense foliage. As a result, 5GHz spectrum is used mostly in line-of-sight applications."

So much for the official line. Comment has been mostly enthusiastic. Silicon said: "The new routers may incorporate WiMax metropolitan-area wireless and even third-generation mobile data (3G) in addition to WiFi," attributing the quote to the same Bert Williams. "They will be able to figure out the highest-performing combination of links within the mesh at a given time," the quote concluded

More models will follow the 5320 over the next year and will incorporate other technologies, including WiMax and multiple in-multiple out (MIMO) multi-antenna wireless LAN, Williams said. Future products could have Evolution-Data Optimized (EV-DO) 3G capability, he said.

Silicon quotes a tame consultant, IDC analyst Godfrey Chua: "Tropos so far has sold mesh routers with just one radio for both client access and backhaul. That has landed Tropos behind some competitors in technology terms, but the company has led the market for municipal Wi-Fi gear anyway, probably because of cost." And he considers: "The citywide wireless Internet services so far have been aimed at the low-end and midrange consumer markets. Competitors such as Strix Systems Inc. and BelAir Networks Inc. already sell routers with more than one radio."

Here's the official line again: "The Tropos 5320, which sports best-of-breed 802.11a and 802.11b/g radios, is the first and only mesh router that can dynamically create multi-band paths through a mesh network," and:  "The MetroMesh OS intelligently manages multiple radio interfaces automatically, similar to the way a wireline router accommodates multiple Ethernet, Token Ring, WAN and other interfaces. The interfaces provide the patented Tropos Predictive Wireless Routing Protocol (PWRP) with additional paths from which it can choose when maximizing end-to-end, client-server throughput."

"Using this radio-independent approach, Tropos will quickly follow the introduction of the Tropos 5320 with additional multi-radio MetroMesh routers combining Wi-Fi, MIMO, WiMAX, 4.9 GHz, 3G/4G cellular and other unlicensed and licensed radio technologies."- press release ends.

Somewhat more restrained enthusiasm from Glenn Fleishman: "Combined with a recent improvement that allows per-packet power level controls, this change could produce a substantially more efficient use of spectrum; lack of efficiency has been one of the biggest criticism of single-radio mesh networks in general and Tropos’s system specifically."

But his analysis is a bit rigorous: "True mesh networks require all nodes in a cluster to use the same frequencies, which results in a single packet occupying network time slots usually at least once, but possibly several times, to reach a connection out of the cluster," he says. "With a second radio, packets could transit the mesh-only 5 GHz connections as need be, offering more time slots to clients. (In future software releases, Tropos might support clients on 5 GHz as well as mesh traffic.)"

And then the bit which may be over-generalising: "Tropos competitors—all of them—use a second band primarily as capacity injection, or the layer at which traffic from the user-facing radio in 2.4 GHz is offloaded to aggregated backhaul through point-to-multipoint connections. Now BelAir will say that they use intelligent switching in 5 GHz when they have two or more 5 GHz radios in a single box, and that’s just fine. Strix has similar statements. SkyPilot uses extremely high-gain antennas to create point-to-point limits that are isolated in frequency and time from adjacent networks."

The trouble with all the analyses online so far, is that they tend to ignore the market-leading mesh technology, LocustWorld, because of two major (irrelevant) factors. First, LocustWorld is not a standard corporate entity, supplying its mesh technology free and only building hardware for small customers - and second, it provides only a simplified version of the network for most sites, but behind the scenes, it has a very sophisticated routeing algorithm.

Mesh designer Jon Anderson told NewsWireless that a Locustworld mesh can, for example, use any link from any node for any purpose. "So we can link between wireless meshes using broadband between nodes, if that's what we have - and if we supply a two-radio meshbox, there's no inherent restriction on whether one radio channel is used for backhaul or for local meshing. The standard product out of the box does it that way, but it can be configured how you like."