[EVO 4G General] bitbang3r:
Another unpleasant oddity I've noticed while driving around: Sprint/Clear 4G doesn't handle moving users well. I don't mean wildly-changing signal conditions, I'm talking about TCP/IP routing and IP address assignment. I've noticed that if I'm driving through an area with rock-solid coverage, it drops and re-establishes a 4G connection at almost PRECISELY the point where the signal is the strongest, and seems to do it every 2-3 miles.

It's kind of like each tower does its own DHCP and assigns its own pool of IP addresses, and the network will route and let you keep that address as long as you're within 1 or 2 towers of the one that gave it to you, but forcibly reassigns it as soon as you get into an area that's more than 1-2 hops away that has strong coverage.

Who here hasn't noticed (while driving around, watching Sensorly and the 4G icon like a hawk & wantonly endangering everyone driving/walking nearby) that the 4G connection is most likely to drop when you're almost close enough to spit on the next tower, and that if you stop and either force a reconnect or wait, it will reconnect with solid 3-bar coverage at almost precisely the point where it dropped the previous connection?

Direct, personal example:

2 days ago, I was stuck in traffic on southbound 95. Around Sunrise Blvd, I toggled 4G and ran speedtest. Rock-solid. Ditto, at Broward Boulevard. I launched a video on Youtube (really, just using it as a free source of audio entertainment). Guess where it dropped the 4G connection? About a hundred feet north of the Sprint tower west of 95 at the New River Bridge. I could almost read the writing on the backhaul antennas, and when I toggled 4g off and on to force an immediate reconnect, got a nearly-instant connection with 8mbit down and 1.1mbit up, moving about 250 feet between the time I lost the connection and launched speedtest.

More historical evidence (I haven't formally tested the theory in these spots yet): If I obtain a 4G connection near Pines & Flamingo, it's pretty much GUARANTEED that I'll lose it right around Palm if I'm heading east on Pines. But if I establish the 4G connection as I'm turning left onto Pines from Flamingo, I usually sail past the police station tower with a solid 4G connection just fine... until I get to University, and it drops.

Heading in the opposite direction, if I have an active 4G connection as I'm getting off the Turnpike, I'm almost guaranteed to have it drop about a half mile east of Univeristy. But if I don't establish the connection until I'm roughly halfway between the Turnpike and University, it sails fine through the intersection, and drops as I'm approaching Douglas (usually, when I'm almost NEXT to the police station tower).

More anecdotal evidence that the system allows you to hold on to your IP and connection through at most one or two hops, and tends to force a reconnection when you move into a more distant area with solid coverage: the corner of Hiatus and Johnson street has just about the worst coverage in the area. If I'm stopped at the light, I can only bring up a 4G connection about 60% of the time, and when I do... it tends to be slow (1-2mbit down, 400-500k up). However, if I establish my 4G connection near Johnson Street & Flamingo, I can sail through the intersection without a single 4G hiccup, and keep the connection as I turn right onto Hiatus and left onto Pines. Then promptly lose it as I approach the big tower near Palm & Pines.

Here's where it gets nailed, though... heading in the opposite direction, establishing 4G near Palm & Pines and zig-zagging west on Pines, north on Hiatus, and west on Johnson Street, guess where it drops the 4G connection? No, not in the big tower-free void known as Johnson Street between Flamingo & Hiatus. It drops the connection right smack at the corner of Johnson & Flamingo, in plain view of TWO towers within about 1/2 mile (one at the western edge of CB Smith Park, one at the corner of Taft & Flamingo). Yep, an area that if I were to initiate the connection, has rock-solid 3-bar 9mbit down, 1.1mbit up 4G.

If this behavior is by design (and not just an artifact of the network still being under construction), that really sucks, because it means 4G is basically useless in moving vehicles (at least, in any context where having an IP address that changes every minute or two is a problem, like most corporate VPNs). It basically means that if you're someplace with trains (like the NEC), Sprint 4G will be useless regardless of how solid the coverage is because it'll be dropping and reconnecting every minute or two. :(

Actually, there might also be a bug in Sprint's radio. The main reason I became aware of this behavior is because when 4G drops, the phone doesn't even TRY to immediately reconnect (FYI, it's an Epic, not an Evo). To force an immediate reconnection, you have to toggle 4G off and on. At first, I just thought it was dropping in areas without coverage. But after a while, I realized I was always reaching over to toggle 4G in almost the EXACT SAME places, day after day... and more often than not, when I toggled it, it would instantly connect with a solid connection. It's almost like their towers are the ones deciding to terminate the connection because my phone has an alien IP address and a 3-bar signal, but my phone's radio firmware is too stupid to bother trying to reconnect immediately when it happens. For what it's worth, I'm probably still running the original radio firmware (my phone's rooted, but the only OTA I'm aware of getting from Sprint is the voicemail one; it seems like at least half the guerrilla firmware updates lately have completely borked the Epic's GPS even more than it was to begin with. More disturbingly, nobody really seems to know why).