What's interesting about WiMax

My opinion: very secure wireless, inexpensive, good speed, and non line-of-sight. What else can one ask for!

EW

What frequency are they planning to operate it on ? I heard it's around the

400Mhz area.. that right ?

Frank hath wroth:

Clearwire, Nextel and Sprint own most of the 2.3/2.7GHz MMDS/ITFS licenses. At this time, Sprint has some MMDS systems:

existing customers that will need to be "transitioned" before they can deploy a WiMax system. Nextel isn't doing anything, but will probably follow whatever Sprint does. There's rumors of conglomerated Cellular and WiMax phones, but I haven't seen anything real.

Clearwire is currently using 2.5 - 2.7GHz. They're using a slightly proprietary version of WiMax. In Europe, Clearwire and MAC Telecom have licenses for 3.5GHz.

TowerStream uses the 5.8GHz unlicensed band.

The newly allocated unlicensed 3.6GHz band doesn't seem to be getting much attention due to lack of equipment and location restrictions.

50MHz is not enough and it should have been the same as the European 3.5GHz band, which is 200MHz wide. The goofy protocol requirements and restrictions are rather excessive. I'm sure the telcos will do everything they can to insure that the FCC makes life miserable for WiMax service providers. Still, it's the only band that isn't already auctioned or polluted. | | There are some small local providers doing WiMax on 2.4Ghz. I don't have the names handy. Seems to work fairly well from mountain tops.

The public safety groups are looking into WiMax on their 700Mhz and

4.9GHz bands. Most of the vendors are doing everything they can to avoid industry standards and are trying to lock in the public safety users into proprietary technology. This is traditional in the public safety market and is the major reason why standards based technologies such as Project 25 have rotted in place for 15 years.

two licensed bands 3.3-3.8 GHz and 2.3-2.7 GHz One license exempt band 5.725-5.85 GHz.

Long:-

|

surely one of the benefits of Wimax was portability and roaming.. Not exactly workable if you have to keep LOS with thos freqs.

Doz hath wroth:

In my never humble opinion, NLOS (non-line of sight) is not reliable. OFDM is a giant step in that direction, but you must recognize that such post processing has its limitations. What ODFM and WiMax do is combine the reflections into a useable signal through heavy duty DSP (digital signal processing). That works fairly well but is not 100% reliable. What happens is that the reflections tend to change rapidly as the user moves. The result is dropouts and fades at points where the reflections don't quite combine into something useable. It also produces rather drastic changes in thruput as one moves. In other words, it's not perfect and tends to unreliable. The result is that you can probably get an NLOS connection, but staying connected is not easy or guaranteed. How often you want your WiMax VoIP call to be dropped is the question.

As for roaming, that has only recently been recognized as a problem worth solving. The result are alliances such as WISPr and WGRA dedicated to making it work.

think WGRA is defunct (not sure) and WISPr has been implimented in at least 4 different ways that will eventually become 802.11r for Wi-Fi in perhaps 3 years, and is being worked on for "Mobile WiMax" as part of 802.16e. standard is scheduled for publication at the end of Jan and things should hopefully progress rapidly after that.

As for frequencies, a hertz, is a hertz, is a hertz. Propogation is completely independent of modulation, protocol, and political influence. Propogation is similar to 1.9Ghz PCS cell phones, except that instead of about 30KHz of bandwidth per user, WiMax bandwidth is MUCH larger. All other things being equal (tx power, rx sensitivity, antennas, and losses), the larger bandwidth has a proportionatly smaller range. It's not exactly linear but close enough for a crude approximation. If your 30KHz PCS phone can talk reliably over a 5 mile radius cell, then WiMax at 2.3/2.5Ghz, running 1000Kbits/sec will work over: 30Kbits/sec / 1000Kbits/sec * 5 miles = 0.15 miles radius. In other words, if you want speed, you gotta either have more signal to play with, or install more "cell" sites to cover the area. Again, this is an oversimplification and should not be used for calculating coverage or range. However, it does illustrate the principle and limitations of WiMax.

One nice thing about WiMax is that it's more resistant to interference that other protocols. This is important because at the present growth of wireless everything, interference will probably be the limiting factor in deployements and service reliability.

Thanks for the info Jeff,

In your opinion (highly valued on here I might add!) do you think standard wifi, ie. g,b modes could be replaced by Wimax (all be it with lower power for shorter ranges) ?

Regards,

Doz

Doz hath wroth:

I try to stay away from predicting the future, but I'm also not very good at resisting temptation. I'll try to be coherent.

Without dedicated frequencies, WiMax will not function. Without a major service provider pushing for deployments, it will not be adopted. Without economical hardware, it will not be affordable. As long as the telcos consider WiMax to be competition for their EV-DO and HSPDA, it will not have regulatory backing. I don't see adoption of WiMax for small scale networks because WiMax doesn't offer much that 802.11b/g/r/n/etc does today. Too many obstacles, methinks. There will be deployments, but only in areas that make sense (i.e. where there's no competing infrastructure).

Also, consider that 802.11 has only been a specification since 1997.

802.11 didn't really become cheap commodity technology until about 2003. That's 6 years from spec to commodity. 802.16 has only recently been approved. Bluetooth took about 5 years. Wanna wait 5-6 years for WiMax?

Personally, I think UWB (wireless USB) will be the next big thing. That's because it fills needs (very high speed local wireless data and removal of the cable tangle) that can't be done any other way, and that there are no regulatory obstacles. It also doesn't interfere with existing wireless technologies. If you're looking for indoor WiMax to replace 802.11, I suggest you consider wireless USB as a possible alternative.

Disclaimer: This is my opinion which should not be confused with reality.

Shame then that IEEE has abandoned the UWB standard, but has moved forward on 802.11n.

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The most exciting thing to me is that WiMax could become something that's offered commercially but can still be deployed by individuals. That means I can get WiMax service from someone like Sprint but still have my own WiMax stations at my home, farm, campus, wherever.

It's much like WiFi except at more usable distances. I get *really* excited thinking about WiMax VoIP handsets. Make this one WiMax and the possibilities are amazing.

--kyler

The problem is that interference tends to increase with range. Spectrum is finite.

David Goodenough hath wroth:

Forward? You mean final approval predicted for Sept 2007?

has been in process since Sept 2003. My guess(tm) is we'll have UWB chips and systems before 802.11n is approved.

Yes I agree.. roll on UWB.. I'll have a bag of dongles instead of a nest of wires any day!