Does Google’s Mountain View Network Fold Under Pressure? asks Sascha Meinrath and posted on MuniWireless.
This was recently sent to me and raises some serious questions about what’s really happening on the Google/Tropos Mountain View Network when load levels increase: Subject: Re: SF Wifi: How good is the coverage for Google’s Mountain View network?
This is typical with Tropos radios.
One of my closest friends is a contractor for FEMA and occupied an apartment in French Quarter of New Orleans. His balcony was located across the street from a node. He told me even sitting on the balcony and trying to check email, it was giving him about 28k best effort. It’s amazing to see what government, excuse me, taxpayers are paying for. The economics of the system deployment and monthly reoccurring is unbelievable.
The system described below uses single channel/frequency radios:
1. This architecture restricts load capacity on the systems ability to aggregate TX/RX traffic not just how much band-width is available. Once stressed, the system errors begin to compound at a rapid rate and ultimately crash.
2. The amount of nodes required to cover a square mile is about 25, based on the OEMs calculations. This limits the root to repeater ratio to 6:1. Meaning that for every 6 repeater nodes there has to be a gateway or root node…
Comments included:
…Take a look at Mesh Dynamics for a really good explanation of why Tropos needs to change their ways.
…This discussion mixes 2 issues, not necessarily related to one another:
(1) “Coverage” — this relates to the ability of a client device to connect to the network at an acceptable modulation rate and communicate back-and-forth reliably.
The comment regarding 25 nodes required per square mile is old news, Google’s network is upwards of 45 (and very well planned from an RF perspective) and I’m sure Tropos knows better than to suggest meaningful coverage from 25.
Even coming from a competitor (me/SkyPilot), Tropos’ Wi-Fi rate/reach is fairly typical, they are no better, but not really much worse…
(2) Larger issue, Is this really “mesh” networking and does the network behave well when loaded with user traffic? The answer, in practice, No…
Google’s Message Board in Mountain View has all the service reports from users.
The Mercury News put Google’s WiFi network to the test. GigOm explains the network covers 11.5 square miles and features 380 access points, all supplied by Tropos. One in six access points is an Alvarion gateway. There are also three bandwidth aggregation points connected to GooglePlex using point-to-point gear from GigaBeam, an equipment vendor of licensed 71-76 GHz and 81-86 GHz radios.
Tropos says their MetroMesh solutions are in use in more than 350 deployments around the world. It uses the purpose-built, infinitely scalable mesh routing algorithm, the Predictive Wireless Routing Protocol (PWRP™), which maximizes client-to-server-to-client throughput real-time.
The Tropos 5320 outdoor MetroMesh router is a dual-band Wi-Fi mesh router. Other products in the MetroMesh router family will include multi-radio routers combining a variety of wireless technologies including MIMO, WiMAX, 4.9 GHz, 3G/4G cellular and more.
The Tropos 5320 (pdf), which sports 802.11a and 802.11b/g radios, is said to be the first and only mesh router that can dynamically create multi-band paths through a mesh network.
WiFi Planet reports competitor BelAir Networks says the latest from Tropos is too little, too late.
BelAir co-founder and CTO Stephen Rayment says his company already delivers dynamically created multi-band paths, and that it already has three times the capacity at the same price as single-radio mesh products (namely, Tropos). “Tropos claims that in future software releases they might support clients on 5GHz, and that they expect to deliver 4.9GHz public safety band radios within the year, and that future devices could include directional antennas, and that they are ‘watching WiMAX,’” Rayment says. “Again, BelAir is already delivering all of the above.”
Tropos says the 5320 will cost 30 to 40 percent more than the current single-radio 5210 units — which they claim is still lower in cost than the competition.
The Oregonian’s Mike Rogoway tested the SkyPilot/MetroFi system in Sunnyvale, Cupertino and Santa Clara.
SkyPilot, which also favors the dual-radio approach, says their approach to 5 GHz backhaul is cheaper than Belair because it uses a single radio with switchable antennas. Their 8-antenna array for the backhaul claims ranges up to 10 miles/16 km. When multiple SkyGateway base stations are added to the network, the Synchronous Mesh Protocol automatically recalculates the optimal paths for the network and load balances the traffic across all of the base stations.
The proof is in the pudding. An objective study of the different approaches, using each companys’ best practices, should be funded by an objective third party like APCO.
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Tropos uses first generation(single radio) mesh and has only recently moved to second generation(2 radio). There are critical limitations for both first and second genartion mesh. Google mountain view is an example of these problems.
Companies like MeshDynamics who have third genartion mesh(multi-radio) solves these issues.
Left by technokarma on November 9th, 2006