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WiMax Guide

Light Reading
1/5/2005
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Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an alternative to wire technologies (such as cable modems, DSL, and T1/E1 links) to provide broadband access to customer premises. This application is often called wireless last/first-mile broadband because the transmission distances involved are typically of this order and the engineering problem is to bridge the final gap between the customer premises and the telco’s or service provider’s main network. The technology is specified by the Institute of Electrical and Electronics Engineers Inc. (IEEE), as the IEEE 802.16 standard.

More strictly, WiMax is the Worldwide Microwave Interoperability Forum, a non-profit industry body dedicated to promoting the adoption of this technology and ensuring that different vendors’ products will interoperate. WiMax will do this through developing conformance and interoperability test plans, selecting certification laboratories, and hosting interoperability events for 802.16 equipment vendors. But WiMax is such a convenient term that people tend to use it for the 802.16 standard and technology themselves, although strictly it applies only to systems that meet specific conformance criteria laid down by the WiMax Forum.

The 802.16 standard is large, complicated, and evolving, and offers many options and extensions, so interoperability is a major issue that must be addressed. In particular, one extension known as 802.16a became the focus of a lot of industry attention because it should be the easiest and most useful to implement. So it is likely that when people talk loosely of WiMax they are referring to the technology for fixed wireless specified by 802.16a and its later version 802.16d.

802.16 is one of a family of technologies being standardized by the IEEE (with other bodies, such as the European Telecommunications Standards Institute (ETSI), whose Hiperman standard is harmonized with 802.16) to create wireless versions of Ethernet that can operate over distances from a few meters to tens of kilometers -- from personal area networks (PANs), through local area networks (LANs) and metropolitan area networks (MANs), to wide area networks (WANs). 802.16 is the MANs member of the family.

 
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fgoldstein
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fgoldstein,
User Rank: Light Sabre
12/5/2012 | 3:30:40 AM
re: WiMax Guide
A lot of the press reports on WiMax, and I'm afraid including this one, are apparently written by people who are somewhat familiar with data networking, but are not skilled in the art of microwave radio. So they overstate the case, making it sound simpler than it really is. WiMax is good technology: It is a smarter spec than, say, WiFi (which to be sure is optimized for a lower price point and reflects implementation capabilities of some years ago) and it may well be the best hope for a mass-produced data radio. But it's still a radio.

Think of cellular. CDMA is, like WiMax, very efficient, even more so than analog or GSM. But in most areas it either has lots of cell sites or lots of dead spots. WiMax is similar: Path loss cannot be overcome by clever modulation or even fancy signal processing. Shannon's Law applies with a vengeance; it is not trumped by Moore's Law.

WiMax will find markets; it will find applications. But it won't run DSL and fiber out of business. It won't be the magic bullet that creates Gilder's phantasmagorical Telecosm. It won't widely replace the local loop. It will require careful path engineering, or it will work on an opportunistic basis, like many hot spot services do now.
Peter Heywood
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Peter Heywood,
User Rank: Light Beer
12/5/2012 | 3:30:35 AM
re: WiMax Guide
In explaining Wimax, we need to explain its potential, and I guess this is what you're describing as over optimistic.

Take a closer look: We actually start the report saying that 2005 could be the year when Wimax sinks or swims and then go on to quote a poll that indicates that the industry is evenly split on which way it will go.

I don't call this overly optimistic. I call it giving both sides of the argument.

hills@lightreading.com
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[email protected],
User Rank: Light Beer
12/5/2012 | 3:30:35 AM
re: WiMax Guide
I'm not sure I would describe the report as "overly optimistic". There is no intention to suggest that WiMax will sweep away wired/fibred broadband - clearly, it won't. No freespace radio system can match the space-division multiplex capabilities of wires and fibres (nor the THz frequencies of optics, for that matter), without even considering all the propagation and similar issues the posting points out.

The point is rather that the broad industry (telecoms, IT and consumer electronics) has understandably got very interested in the idea of wide-area wireless broadband access as a new capability, service and revenue opportunity - and so there is a lot of pressure to try to make this one fly. How it will turn out is anyone's guess at the moment (the report points out a fair number of issues), but it is all part of the technical innovation needed to keep telecoms advancing. It seems a bit unfair to write off a technology just because it doesn't offer the peformance of another technology - aircraft have not yet replaced cars.

Tim Hills
Peter Heywood
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Peter Heywood,
User Rank: Light Beer
12/5/2012 | 3:30:34 AM
re: WiMax Guide
We would prefer you post messages about this article on this public board, but if you want to send a private note about it, please email [email protected] and include "wimax guide" in the subject field.
Peter Heywood
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Peter Heywood,
User Rank: Light Beer
12/5/2012 | 3:30:33 AM
re: WiMax Guide
This note came in from someone working for a major carrier, who requested anonymity:


QUOTE
One question that the article did not answer was how many simultaneous users a typical WiMax implementation could handle. WLAN can handle up to 230 simultaneous users per node, at lower bandwidth speeds of course, but what is the theoretical limit of users and lower bandwidth constraints and what would be a better quality of service from a bandwidth and simultaneous user perspective (typical implementation)
UNQUOTE
Peter Heywood
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Peter Heywood,
User Rank: Light Beer
12/5/2012 | 3:30:33 AM
re: WiMax Guide
Tim Hills has taken a crack at addressing this issue:


As far as I understand it, from digging in the material I have:

-----

IEEE Std 802.16.2T-2004 (Revision of IEEE Std 802.16.2-2001)

IEEE Recommended Practice for Local and metropolitan area networks

Coexistence of Fixed Broadband Wireless Access Systems


Table 22-Parameters for 3.5 GHz systems with a PMP (point-to-multipoint) architecture (this is a brief sample only - the whole table is much bigger)

Number of terminal stations per megahertz per transceiver per cell - Up to 70.
Number of cells in a system - 1 to 25 (typical range).
Channel bandwidth - 1.5, 3, 6, 12, 25 MHz (North America). 1.75, 3.5, 7, 14 MHz (Europe) (use 7 MHz for coexistence calculations) Typical sector arrangements and frequencies - Typically 4 sectors per cell,
4 frequencies. Vertical and horizontal polarization both used. Some systems will use AAs, pointing at individual users. FDD and TDD used.

-----

This suggests that a single cell transceiver in a 3.5GHz system could support a theoretical maximum of between 105 and 1750 terminal stations per frequency channel for the range of channel bandwidths contemplated in North America. Multiply by 4 to give a cell maximum for the typical 4-sector 4-frequency cell - so 420 to 7000 terminal stations per cell.

But there are lots of complications arising from the highly specific nature of radio propagation in a given environment and the need to avoid interference between different WiMax service providers in the same area. And mesh WiMax architectures have different parameters - and so on.

And I am very prepared to be corrected. Perhaps someone else is better qualified to answer?
bdixon23
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bdixon23,
User Rank: Light Beer
12/5/2012 | 3:30:11 AM
re: WiMax Guide
In the section, "In these [unlicensed 2.4 and 5 GHz] bands, WiMax operates at a much lower wireless power and has a very limited range (roughly the same as for WLAN, which also uses these frequency bands)," do you mean to say that the effective range of WiMax in unlicensed bands is no greater than Wi-Fi?
ggoyal
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ggoyal,
User Rank: Light Beer
12/5/2012 | 3:29:36 AM
re: WiMax Guide
Hi,

What is the maximum inter-node distance/range in a WiMAX mesh mode theoretically and practically?

Has anybody compared the mesh part of the two technologies (WiFi & WiMAX?

vinay
djkstra
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djkstra,
User Rank: Light Beer
12/5/2012 | 3:29:34 AM
re: WiMax Guide
Question that has been unanswered in minds of carriers in West is whether market is ready for Wimax to the extent where they could gain a potential momentum in selling Wimax services and migrate to this technology.
Post bubble effects have changed ISPs' attitude towards technology and made them measure technology critically in terms of returns on equity, capital, and assets.They are to answer whether they intend to continue build up
debt based capital structure where take the risk of deploying new technology even with larger debt.

Whereas, in my personal opinion, Wimax seems to be perfect fit in eastern countries like India and China who are still in the process of expanding carrier networks and opt for the latest technology. Market is these countries price driven and at the Wimax does not answer whether it can be cost effective soln to ISPs in these countries.

Time to watch..
paolo.franzoi
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paolo.franzoi,
User Rank: Light Sabre
12/5/2012 | 3:29:32 AM
re: WiMax Guide

I guess my view is a bit different. The question is why would I want to build yet another broadband High Speed Internet infrastructure. In most places in the US (not ALL but MOST) DSL and Cable Modems are available. In virtually the entire US, either DSL or Cable is available.

So, introducing this technology would have to have an application that did not work today or in places that service was not available today. To build out a network to support commodity High Speed Internet seems highly unlikely, since there are already embedded competitors. The question is what is that application that requires a WiMAX buildout if you already have a significant penetration of broadband deployed. Mobility seems like a logical answer.

seven
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