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Australian WiMax Pioneer Calls It a Disaster
Anonymous Coward writes "Garth Freeman, CEO of Australia's first WiMax operator, sat down at the recent International WiMax Conference in Bangkok and unleashed a tirade about the failings of the technology, leaving an otherwise pro-WiMax audience stunned. His company, Buzz Broadband, had deployed a WiMax network over a year ago, and Freeman left no doubt about what conclusions he had drawn. He claimed that 'its non-line of sight performance was "non-existent" beyond just 2 kilometres from the base station, indoor performance decayed at just 400m and that latency rates reached as high as 1000 milliseconds. Poor latency and jitter made it unacceptable for many Internet applications and specifically VoIP, which Buzz has employed as the main selling point to induce people to shed their use of incumbent services.' We've previously discussed the beginnings of WiMax as well as recent plans for a massive network in India.
I am no RF expert either, but I have been on the receiving end of WiMax-ish technology, and the jitter was so bad, it was completely unusable for VoIP and even made ssh annoying at times.
This was kit designed to work for up to 10 km (6 miles) and I had line-of-sight to the base station, which was about 150m (500 ft) away.
Sky.. sky.. SkySomething. SkyPilot? Some kind of wierd meshy-network, I was also connected to the "master" tower, not a leaf.
The problem, as it was explained to me, was that it has a collision/backoff algorithm not unlike that of 10-base-2 ethernet ("thin net"). So, the 50 (or so) neighbours I had, plus the leaf towers (2 of them, I think) were causing me to not get "slots" with the master on a timely basis. Hence, introducing jitter.
So, your L2 protocol hypothesis is reasonable from my perspective, although we can eliminate poor radio performance as a direct cause. Changing the radio from broadcast to something like time or code division multiplexing would be a good solution for reducing jitter, but probably causes other problems (like decreased burst bandwidth and range).
My solution? "*sigh* - cancel the wireless link and order me a up a T1"
Wireless is nice because it's easy. But it sure ain't there yet.
Do daemons dream of electric sleep()?
AM radio spans roughly 1 MHz (IE: approx 530KHz to 1.6 MHz.) You CANNOT fit a broadband wireless service into that space ... furthermore, the resonant antenna length for 1/4 wave varies between (approx) 150 metres to 40 metres. Like to see you stick that out of the back of your Laptop.
... okay for Laptop, (easy)
...)
doubtful if you could effectively get one 54mbit channel in that space, plus, because it is NOT line of sight, someone a few miles away WILL interfere with your local transmissions.
Low frequencies (below about 2 MHz) hug the ground, this means AM does not have line of sight issues. Some AM broadcast stations have service areas of hundreds of miles (kilometers) (radius)
FM is 88.. 108 MHz. 1/4 wave here is roughly around 1 metre. Still a thumping huge antenna! These frequencies are considered line of sight, however, there is a small area extending beyond line of sight. Enough bandwidth for a few 54mbit channels.
WiFi is generally at 2.4 GHz. Same band as Microwave ovens use. Has to do with the frequency of maximum absorbance of water. (Thus used in ovens!) 1/w wavelength approx 4 cm
To get sufficient bandwidth, only UHF and up is really useful. But, get too high in the microwave band and the signal wont even get through a thin wall.
So, there are trade offs that genuinely make sense for wireless broadband. (lots more reasons as well
Lots of people seem to be confused about whether Clearwire is WiMax.
My Clearwire device has an FCC ID of PHX-RSU2510F. The FCC docs say that it operates on 2.496-2.690Ghz. The chipset leads me to believe that it is an implementation of the Motorola Expedience Wireless Broadband CPE.
The Motorola RDM specs say that the device can operate in Expedience (up to 2W) or WiMax (up to 0.5W) modes. They also say that in Expedience mode it is a layer 2 smart bridge, while in WiMax mode it is a router with NAT, DHCP and firewall functions.
Since my device acts like a layer 2 bridge, I conclude that it is in Expedience mode. Having just checked the Wikipedia article, I see that the first paragraph agrees:
"Clearwire currently uses Expedience wireless technology, dubbed Pre-WiMax, transmitted from cell sites over licensed spectrum of 2.5-2.6 GHz in the U.S. and 3.5 GHz in Europe."
So no, they use the WiMax frequency range, but they can transmit a stronger signal. That seems to be the main difference between the technologies.
This Motorola promotional video talks about some of the infrastructure and business justifications for using their Expedience gear:
I chose as my ISP in Mexico City E-go, co-owned by Alestra, the Mexican AT&T subsidiary. It started offering WiMax connection in 2003 in limited areas of Mexico City (I understand nowadays it covers most of the Central, Western and Southern parts), before even WiMax was standardized. Clients get a NextNet RSU unit, which is basically a network bridge. :) E-go owns 20MHz of spectrum, which allows it to give a theoretical maximum of 70Mbps to a given area. If many too people were to subscribe, each client would have much less effectibe bandwidth alloted.
The latency complaints you state are simply not true - I get consistent ping response times of 100ms in average (with minimum response times of around 50ms) to hosts in Mexico City, 200ms to hosts in the USA. Yes, this is about 80ms higher than wired equivalents - but it's not so much of a killer. What I do get, of course, is way higher packet loss - About 5% when things are optimal, and it sometimes gets up to 50%. But yes, I'm located at a relatively poor reception area, at one of the lower-income (this means, no incentive to place many antennas nearby) neighbourhoods in the South of the city, where the mostly flat valley where most of the city is located begins to become quite hilly. The RSU unit does not provide any means (for the client) for monitoring connection, to help choose the best possible location. It only has five LEDs (and no, they are not blue, just an unfashionable old green. Bummer.) indicating signal strength, and I always get one or two of them. I have seen signal quality significantly better when at a five-leds connection.
Prices and speed are more or less in-par with Mexico's near-monopoly TelMex; I'm paying about US$40 for a nominal 1Mbps/128Kbps connection (512K guaranteed, whatever that means). The upstream data flow _is_ shaped to 128k, but the downstream speed is not - when the network smiles on me, I get up to 2Mbps. It is not common, though.
I understand E-go (back then called I-go, don't ask me why) was praised as the world-first massive WiMax deployment - Even before the standard was finalized. There are several aspects of the installed network that show clearly the gear is pre-standard (i.e. extreme sensibility to position changes - If I move my RSU over two centimeters, it has to resynchronize with the antenna. This process takes around two seconds, so no big deal).
To me, clearly, the reason it hasn't got more popular is because it is owned by a relatively small company, and has not had the muscle to stand in front of Telmex's publicity machine.
Of course, we benefit more than DSL users from having a low client density
Medium-Wave broadcasting in the U.S. evolved when the country was still significantly rural.
Distances in the U.S. can defeat the European imagination.
The 50,000 watt "clear channel" station could be heard across several states - and to istances of 1,000 miles under favorable conditions.
AM radio had a distinct local or regional identity which persists to this day.
Minor nitpick: 2.4 GHz is not the frequency of maximum aborbance of water. The frequency of the maximum is temperature dependent, and the absorbance peak is very broad. Thus there is no need to use any special frequency. 2.4 GHz is used in microwave ovens due to that it was free to use, being an ISM band, and that the penetration depth is useful for cooking.
This is WiMax, not Wi-fi. Despite the first two letters, and the fact they're both 802.x standards, these are completely unrelated technologies, which for some reason geeks in particular tend to get overly excited and confused about conflating the features of one with the other. WiMax is generally run on licensed spectrum, and is about as useful as Wi-fi on unlicensed spectrum, if you can even get certified equipment. So far as I'm aware there are no commercial operators trying to run it on unlicensed spectrum: there's no point, Wifi is cheaper and just as effective for non-LoS use.
Again, you're assuming WiMax is generally run on unlicensed frequencies. But your point is worth addressing because the bands WiMax is generally licensed in to tend to be greater than 2GHz, though it is being considered by a number of operators for use on the 700MHz spectrum recently auctioned.
Anyway: 2-3GHz has roughly the same characteristics as PCS, the 1900MHz spectrum used by Sprint PCS and T-Mobile USA, and it's in this area that WiMax is usually offered - though I have heard of it being deployed in the 3.5GHz range. It's generally pretty strong outside, while indoor coverage generally deteriorates relatively quickly, though not to the point of unusability.
WiMax is an interesting technology but it suffers from being "first" and from being designed by the computer industry with almost no input from the telecoms industry. The latter may be a bunch of Luddites but they do put a premium on reliability, something our industry is absolutely abysmal at. Which is partially why I'm betting on LTE being the path forward to universal internet connectivity.
You are not alone. This is not normal. None of this is normal.