Comments on: LTE at 50 Mbps? Don’t hold your breath

By: Paul Kapustka

Paul Kapustka — Tue, 16 Jun 2009 05:42:20 +0000

@Chris the math is not that simple. As Ken states there are questions about network load and app performance. As Brett notes the real-world performance of other wireless technologies makes the LTE claims suspect.

My main point is — Verizon and AT&T really don’t have enough spectrum *depth* right now to run anything bigger than 5 MHz channels. And if you look at the Motorola chart in this post:

http://www.sidecutreports.com/2009/03/24/motorola-mobile-lte-demos-coming-at-ctia/

You see 5 MHz channels at best will deliver about 7.85 Mbps on the download. At best. So — PLEASE don’t hold your breath for 50 Mbps over LTE. It isn’t going to happen soon enough to save you if you try.

By: Chris

Chris — Tue, 16 Jun 2009 00:33:11 +0000

So if we look at a best case of “172.8 Mbit/s for 2×2 antennas for every 20 MHz of spectrum” (from an Agilent whitepaper) and then divide that into 3 channels,per the author, and then divide by 3 per Ken Biba’s comment, we’re looking at 19Mb down in the best case of a 5km cell, quickly falling to 10mb if the cells are further apart. That sound about right?

@Ken Biba: how many users/cell does your divide by 3 rule hold? just 3 as it might imply?

By: Ken Biba

Ken Biba — Sun, 22 Feb 2009 23:03:29 +0000

In any case, these speeds are the raw bit rate of the channel, not the net, loaded performance of a user application.

Our tests of 3G cellular suggest that no more than a third of the channel rate is really delivered to a give user on average. I see no reason to believe we will see better numbers from LTE.

Or WiMax for that matter.

Also, the bit rate is closely coupled to the cell size as well as the channel size.

By: Brett Glass

Brett Glass — Sun, 22 Feb 2009 22:02:30 +0000

There’s this little, minor law of Information Theory called Shannon’s Law which governs how fast you can transmit data reliably over a given amount of spectrum. And it makes it rather doubtful that you could get 50 Mbps out of LTE. On the other hand, private (not municipal) wireless ISPs like myseif are doing 50 Mbps right now. And we can continue to do it so long as municipal networks don’t eat up the available spectrum and interfere.

By: Paul Kapustka

Paul Kapustka — Sun, 22 Feb 2009 19:11:59 +0000

@Arnon I think you have some good points about nomadic/mobile use but not sure I agree with the second part; Towerstream is already doing pretty well using WiMax to replace or undercut T-1 lines; not only is it usually cheaper it’s faster to install and more scalable/flexible if you need to move offices.

It also looks like Clearwire may offer more products along the lines of their prototype WiMax/Wi-Fi router — a portable answer to the distinction in your first point. The tradeoff may be whether the mobility is more attractive than the reliability/speed of a wired connection.

By: Arnon Kohavi

Arnon Kohavi — Sun, 22 Feb 2009 16:14:58 +0000

I think we need to separate between “nomadic” and “mobile”. Even in an iPhone, one “consumes” high data rate usually when one is stationary (difficult to walk/run staring at screen). So I, at least see a distinction between true mobile usage, that likely needs lower data rates, and nomadic usage, where WiFi & Femto Cells can do the trick.
People/offices will not replace their DSL/Cable/Fiber with 4G because it will always be slower/more expensive and less reliable than a wireline+wifi solution. And the wireless carriers don’t have capacity for that.

By: bulk

bulk — Fri, 20 Feb 2009 19:24:20 +0000

60 mbps shared among all users of the tower. heh

By: Paul Kapustka

Paul Kapustka — Thu, 19 Feb 2009 00:57:45 +0000

@Arnon femtos may be a point solution but they don’t address the market need for fast mobile wireless, which users would likely want to see as a *replacement* for their current landline broadband.

I could see power users wanting a femto but at what cost… if Verizon’s current femto is any evidence that means a few hundred for the femto, a couple hundred for an LTE device… and how much for LTE services? With data caps?

Clearly… we need more details.

By: Arnon Kohavi

Arnon Kohavi — Thu, 19 Feb 2009 00:51:57 +0000

Paul, I think Femtocells may allow higher data rates, as the channels can be re-used more efficiently. It will be interesting to see if that will be the case: obviously, my cable service will need to support 50mbps in the backhaul…