I think you may be missing a couple of variables in the multivariable equation that determines the actual throughput a client can achieve in a given time slice. When comparing access systems one must understand the differences between the capabilities provided by the systems and their result on these variables. You harp on throughput when the reality is that ISPs don't sell throughput; they sell capacity. The throughput of any given flow is variable based on a variety variables including RTT and congestion. Most applications that end users care about are TCP based, which means TCP's congestion algorithm comes into play most often. One important aspect of a TCP flow is slow start, which causes flows initially to have throughput less than the capacity of the transport layer. Considering that much of real world traffic never has time to get up to full speed, the capacity is rarely full utilized. However, when multiple flows operate on the same access layer at the same time all slow starting you are able get more efficient use of your capacity. Unfortunately, most end users simply do not have enough flows operating at the same time lasting long enough to fully utilize all of their capacity. The unused capacity is what allows for oversubscription. In other words, by sharing the capacity across a large enough number of end users you can get more efficient utilization of the overall available capacity.
Now the above may be nothing new to most of us, but how easily we forget that we sell capacity and leverage our client's inability to use all of that capacity because their throughput rarely achieves what is available capacity wise. This means we need access systems that very efficiently multiplex flows from an arbitrary number of end users. It is not about getting more throughput than the overall capacity of the system; it is about efficiently delivery the maximum available throughput when the end user actually needs it. Your basic 802.11 wireless system does not efficiently share capacity across multiple stations, which results in stranded capacity. Compare this to a WiMAX system that is extremely efficient at sharing capacity across all connected stations. No system can allow the aggregate throughput of all stations to exceed the total capacity of the system, which would violate the law of physics. In the real world, end users can't use all of their capacity all of the time. Therefore, the more efficiently you can share that capacity across multiple users the more users you can support on a given system without negatively impacting their throughput when they need it. Comparing a WiMAX system to a Wi-Fi system you will always find the following: * The WiMAX station will have a better signal-to-noise ratio * The better signal-to-noise ratio will allow the WiMAX station to operate at a higher modulation with less ARQs * The higher modulation with less ARQs will allow greater throughput per Mhz * The greater throughput reduces the number of time slots needed to complete a flow * The greater number of available time slots allows for more stations to participate -Matt On Mar 19, 2009, at 8:34 PM, [email protected] wrote: > Sheesh. How many times must this misinformation be posted before > the snake > oil gets poured down the drain? > > The better MAC allows you to use a very high percentage of > transmission time > for actual data throughput, and it manages spreading bandwidth > nicely among > the oversubscribed. HOWEVER... > > If you built a 300mbit 802.11 PTMP system, you'd get about 120 total > throughput. > > This means you're using massive amounts of spectrum, but the actual > throughput would be higher than ANY WIMAX setup to date. This > snake oil > about the MAC supposedly violating physics and putting 36mbit > through an 18 > mbit pipe is nonsense. 802.11 sucks because the MAC wastes well > over 50% > of the airtime doing nothing at all, has absolutely no means of > managing > bandwidth use or dividing use among the users. However, REAL > THROUGHPUT IS > REAL THROUGHPUT. > > If you have an 18 mbit WIMAX you can support 3 clients consuming a > little > less than 6 each. > > Add client #4 asking for 6mbit and the the other three MUST LOSE > BANDWIDTH > TO FEED IT. Get it? So, instead of just under 6 each, if they're > all > equal priority, all 4 get about 4. Duhh. That's it. You cannot > violate > physics. > > The MAC allows greater efficiency concerning airtime and modulation > types > improve throughput vs spectrum consumption. > > NOTHING VIOLATES THE LAWS OF PHYSICS. > > You cannot get 36 through an 18 knothole. Period. > > You guys are all WAY smarter than this, and it's about time the hype > based > on comparison of RADIO DATA RATES gets chucked down the toilet. > None of us > operate that way, and none of care a whit about radio data rates. > We're > all about real throughput and good management of our our required > business > model of oversubscription. > > > > > ++++++++++++++++++++++++++++++++ > <insert witty tagline here> > > ----- Original Message ----- > From: "Jeff Booher" <[email protected]> > To: "'WISPA General List'" <[email protected]> > Sent: Thursday, March 19, 2009 5:06 PM > Subject: Re: [WISPA] 2nd Look @ 3.65 ? > > >> Mike, >> >> It absolutely has nothing to do with throughput. It has to do with >> the >> scheduling mechanism of the MAC. The reason why 802.11x networks cant >> scale >> like this is the listen before talk protocol. Even basic polling >> doesn't >> work because the more subs you add, the more latency you add to the >> network. >> >> - >> >> Jeff >> >> >> -----Original Message----- >> From: [email protected] [mailto:wireless- >> [email protected]] On >> Behalf Of Mike Hammett >> Sent: Thursday, March 19, 2009 11:34 AM >> To: WISPA General List >> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >> >> Good efficiencies, not enough throughput per channel, however. >> >> In one thread in one list we have people complaining about not having >> enough >> bandwidth to serve their customers now much less next year or the >> next and >> in the other, we have people excited about an AP that only does 18 >> megabit. >> >> >> ----- >> Mike Hammett >> Intelligent Computing Solutions >> http://www.ics-il.com >> >> >> >> -------------------------------------------------- >> From: "Gino Villarini" <[email protected]> >> Sent: Thursday, March 19, 2009 1:24 PM >> To: "WISPA General List" <[email protected]> >> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >> >>> Not enough? You get 18 mbps in a 7 mhz channel >>> >>> >>> Gino A. Villarini >>> [email protected] >>> Aeronet Wireless Broadband Corp. >>> tel 787.273.4143 fax 787.273.4145 >>> >>> -----Original Message----- >>> From: [email protected] [mailto:[email protected]] >>> On Behalf Of Mike Hammett >>> Sent: Thursday, March 19, 2009 2:20 PM >>> To: WISPA General List >>> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >>> >>> More troll than substance but I wouldn't put more than 30 users on a >>> WiMAX AP anyway... not enough bandwidth. >>> >>> >>> ----- >>> Mike Hammett >>> Intelligent Computing Solutions >>> http://www.ics-il.com >>> >>> >>> >>> -------------------------------------------------- >>> From: "Jeff Booher" <[email protected]> >>> Sent: Thursday, March 19, 2009 11:28 AM >>> To: "'WISPA General List'" <[email protected]> >>> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >>> >>>> It is not the same gear by any means. Tranzeo's AP is a micro base >>>> station, that only supports 30 subscribers. >>>> >>>> - >>>> >>>> Jeff >>>> >>>> >>>> -----Original Message----- >>>> From: [email protected] [mailto:wireless- >>>> [email protected]] >>> On >>>> Behalf Of Marlon K. Schafer >>>> Sent: Wednesday, March 18, 2009 7:34 PM >>>> To: WISPA General List >>>> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >>>> >>>> I'm certainly interested in ptmp. >>>> >>>> The Tranzeo gear is the same as Aperto isn't it? >>>> marlon >>>> >>>> ----- Original Message ----- >>>> From: "Gino Villarini" <[email protected]> >>>> To: "WISPA General List" <[email protected]> >>>> Sent: Wednesday, March 18, 2009 6:35 PM >>>> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >>>> >>>> >>>>> Ligowave its ptp in 3.65... >>>>> >>>>> Might wanna look at tranzeo for 3.65 ptmp >>>>> >>>>> >>>>> Gino A. Villarini >>>>> [email protected] >>>>> Aeronet Wireless Broadband Corp. >>>>> tel 787.273.4143 fax 787.273.4145 >>>>> >>>>> -----Original Message----- >>>>> From: [email protected] [mailto:[email protected] >>>>> ] >>> On >>>>> Behalf Of Leon Zetekoff >>>>> Sent: Wednesday, March 18, 2009 9:32 PM >>>>> To: WISPA General List >>>>> Subject: Re: [WISPA] 2nd Look @ 3.65 ? >>>>> >>>>> Hi Marlon...I'd look at the Ligowave stuff similar in principle to >>> the >>>>> UBNT stuff but I think much better. That's what I'd do today. >>>>> >>>>> Take care leon >>>>> >>>>> Marlon K. Schafer wrote: >>>>>> I'm looking into this too. >>>>>> >>>>>> So far I can't find a solution for rural towers. A 3 sector >>>>>> install at $20k? Not to service the 20 people that will be >>>>>> able to >>>>>> even see that tower.... >>>>>> >>>>>> Anyone have any better ideas? >>>>>> marlon >>>>>> >>>>>> ----- Original Message ----- >>>>>> From: "Gino Villarini" <[email protected]> >>>>>> To: "Motorola Canopy User Group" <[email protected]>; "WISPA >>> General >>>>> List" >>>>>> <[email protected]> >>>>>> Sent: Wednesday, March 18, 2009 7:55 AM >>>>>> Subject: [WISPA] 2nd Look @ 3.65 ? >>>>>> >>>>>> >>>>>> >>>>>>> Fellow operators: >>>>>>> >>>>>>> Any updates on your experienes with 3.65 gear? PMP and PTP? >>>>>>> >>>>>>> Any updates on experiences with: >>>>>>> >>>>>>> Redline, Aperto, Tranzeo, Vecima, Alvarion, Ligowave, Solectek, >>>>>>> Airspan ??? >>>>>>> >>>>>>> >>>>>>> Gino A. Villarini >>>>>>> [email protected] >>>>>>> Aeronet Wireless Broadband Corp. >>>>>>> tel 787.273.4143 fax 787.273.4145 >>>>>>> >>>>> >>>>> >>>>> >>> ---------------------------------------------------------------------- >>> -- >>>>> -------- >>>>> WISPA Wants You! Join today! >>>>> http://signup.wispa.org/ >>>>> >>> ---------------------------------------------------------------------- >>> -- >>>>> -------- >>>>> >>>>> WISPA Wireless List: [email protected] >>>>> >>>>> Subscribe/Unsubscribe: >>>>> http://lists.wispa.org/mailman/listinfo/wireless >>>>> >>>>> Archives: http://lists.wispa.org/pipermail/wireless/ >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>> ---------------------------------------------------------------------- >>> -- >>> ---- >>>> ---- >>>>> WISPA Wants You! 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