[Motorola Photon 4G] bitbang3r:
Strictly speaking, LTE is neither better nor worse. The problem with Sprint's 4G wasn't wimax itself, it's the half-assed way Clear deployed it, and the way Sprint decided to handle switch-overs between 3G and 4G (fully breaking one connection before attempting to make the next).

There *are* semi-decent reasons for not trying to simultaneously do wimax and EVDO (EVDO is TDMA, and the harmonics & front end overload from both radios would screw each other up without major additional logic to interleave the transmissions and keep them from stomping each other), but Sprint *should* have treated the wimax handoff like this:

(phone has EVDO data session through proxy. EVDO's IP is 10.1.19.73, phone's public IP is 64.18.24.9)

(phone breaks EVDO data session, and establishes 1xRTT data session. 1xRTT's IP is 10.3.55.4, public IP is still 64.18.24.9 because it's routed behind the scenes through a proxy that tracks your phone through a region and funnels all of your traffic through that public IP)

(phone attempts to establish wimax connection to Clear)

If success, wimax IP is 192.55.74.180; public IP is still 64.18.24.9, running through Sprint's same proxy. The phone keeps the 1xRTT data session active the whole time, because it doesn't consume power beyond that needed for polling the tower for incoming calls & SMS when actual outbound data isn't being sent over it.

If failure, phone tries to establish wimax a few more times. If it keeps failing, or totally moves out of wimax range, the phone breaks the 1xRTT data session, and replaces it a fraction of a second later with EVDO. As long as the user had an EVDO session active within the past 5 minutes or ~5-tower radius, the session is still active and can be brought back up almost instantly. In fact, if the phone kept both 1xRTT and EVDO data sessions live, it could even jump back to EVDO for a few seconds between wimax connection attempts if it had lots of data to send, or seemed to be busily receiving data. The outside world would never know the difference... the phone's IP doesn't change, and inbound data gets buffered and throttled briefly when the phone goes offline for a quarter-second or so to physically switch modes.

Why does 1xRTT play nicely with wimax, but not EVDO? EVDO is actually TDMA and transmits in bursts. 1xRTT is "pure" CDMA, and works by spraying bits across a wide chunk of spectrum in a way that interferes with everything nearby, but doesn't usually interfere enough to make a difference. 1xRTT transmits at lower power, and in a way that makes it look like background noise to the wimax radio. In contrast, EVDO produces somewhat square-wave harmonics (not really, but close enough for illustration) that would overload the wimax radio, just like a CB operator who interferes with TV reception. Different frequencies, but the harmonics and front end overload cause problems anyway.

So, why DIDN'T Sprint do something like this? Interface cards. Basically, Sprint deployed 1xRTT in an era when few people used data, and instead of increasing their 1xRTT capacity, they added EVDO in parallel. Thus, a typical tower site has more or less the same 1xRTT data session capacity it had back around 2003. If every Android phone doing wimax consumed a 1xRTT interface at all times, Sprint's tower sites would have started maxing out right around the time the Epic4G came out... and never, EVER would have survived the iPhone onslaught.

Part of the problem is also that 1xRTT development pretty much ended in the early 2000s, so nobody ever made high-capacity 1xRTT interfaces that Sprint could easily swap into their existing equipment racks to enable simultaneous wimax + 1xRTT. Since no market existed for them, there was nobody for Sprint to even buy hypothetical 1xRTT high-density cards from, even if they were willing to spend the cash. Sprint wasn't about to spend millions deploying coture 1xRTT cards that would have probably required significant tower site upgrades as well.

Plus, nobody thought Clear's wimax would end up sucking as badly as it did. Sprint probably didn't think it would even be necessary to have a fallback plan to prevent thrashing, and it didn't sink in how dire things were until they were well underway with the wimax deployment.

Now, for the bad news. I don't have much faith that Sprint's LTE will suck less in real urban mobile use than wimax does now. They'll probably have marginally better cell density in places that were semi-abandoned when they were only 2/3 built out (like Broward County, Florida), but for the most part, everything that's a problem with wimax is likely to STILL be a problem with LTE. Clear uses Sprint's tower sites, and in the areas where they're deployed, there aren't many Sprint/Nextel sites that DON'T have Clear wimax as well.

To really make LTE work as well as 3G, Sprint's going to need about 2-8 TIMES as many urban cell sites as they have now. Sprint has lots of spectrum, but there's basically one way to get more total bandwidth out of a finite chunk of spectrum: deploy more towers, and reduce the RF footprint of both the towers and phones so more people can use the same frequencies in a given region.

Remember, Sprint is deploying LTE into spectrum where they currently do EVDO. The total spectrum isn't really changing, and LTE isn't much more efficient than EVDO. The only reason Sprint even has headroom to do LTE is because right now, even post-"Network Vision" upgrade, they still have more RF spectrum than they have backhaul capacity (in other words, if lots of people connect to a tower site and run speedtest, their backhaul to the rest of the internet will saturate LONG before they run out of radio spectrum in most places besides San Diego). And ultimately, they're going to have to secure more tower sites.

Truth be told, Sprint's LTE is more about marketing than actual service. If they bought a ton of fractional T3 lines (where necessary) and fully-utilized Clear's wimax for backhaul so they had enough upstream bandwidth to fully saturate their 1900MHz spectrum, we'd be getting more or less the same throughput that urban T-Mobile users enjoy today. Unfortunately, saying "We have rock-solid 10-megabit EVDO that works reliably everywhere, indoors and out, at home and on the go" isn't sexy. Saying "our advanced LTE network supports speeds up to 50mbit/sec (but rarely pokes about 12 under any conditions you're likely to ever see)" does. So, we're all stuck with a data mess for another year or two that really wouldn't even be *necessary* if they just fully-utilized the network (with upgraded backhaul) that they have *now*.

Anyway, enough griping about 4g. The main thing to take from this is that LTE isn't the second coming of Marconi. It's basically the same radio transmission scheme as wimax, and differs from it mainly in terms of higher-level protocol (think: NetBEUI vs TCP/IP). LTE (the abstract standard) has the POTENTIAL, when FULLY and IDEALLY DEPLOYED (using hardware neither Sprint nor Verizon are actually using) to spank wimax, but the minimal subset both Sprint and Verizon are deploying for marketing reasons have more in common with wimax than real differences.

That also brings up my other gripe about Sprint... their premature discontinuation of wimax capabilities. I fully support making new phones support LTE... but I think that for at least 2012, they should have had them made their highest-end Android phones using dual-mode chipsets that can do BOTH wimax AND LTE. Why didn't they? Because Sprint has to pay Clear $5/month for every active phone on their network with wimax capabilities in perpetuity, and Sprint wants to quit paying them at the first possible opportunity. The faster they can replace their wimax phones with LTE-only phones, the sooner they can pocket $60/year extra per customer instead of forking it over to Clear. I have a hunch that next year (once LTE is more widely deployed), Sprint will run a one-time deal offering early upgrades for $100 above the normal upgrade price to anyone replacing a wimax-capable phone with a LTE-only phone IF you physically trade in the old wimax phone (so they can take it out of service and destroy it, and not risk that you'll sell it to someone else who'll activate it).