Signal Handoff Could Mean Roaming VoIP over WiFi

wassup writes "According to this article in MIT tech review (and here), researchers at University of California San Diego have developed a technology called SyncScan that will reduce handoff delay in WiFi networks to a few milliseconds. VoIP roaming will be here soon!"

Comments

just wait...

[jleq]

... until the wireless providers find out. We will finally break the speed of light when all of their lawyers run crying to the FCC and FTC. "OmG, unfair competition!" This, combined with municipal wi-fi, could lead to a much less expensive wireless future for us all. Yay!

What about TCP/IP handoff?

[hgilde]

Last I checked, VOIP uses TCP sockets. When you move between WiFi base stations, you first must discover your new DHCP server, then get a new local IP address, then reconnect to the VOIP server.

This will definitely be an annoying delay.

Re:What about TCP/IP handoff?

[jleq]

True... unless, of course, the access points are all on the same network (and therefore use the same DHCP server)

Re:What about TCP/IP handoff?

[c_g_hills]

This is why IPv6 is a much better network (layer 3) protocol for VoIP as it supports mobility natively, allowing TCP and UDP sessions to be maintained when roamning from one network to the next.

In fact, the Internet Society point out that IPv6 is necessary for mobile and wireless internet.

Re:What about TCP/IP handoff?

[LordoftheFrings]

VOIP does use TCP sockets for the initial data setup but UDP for actual voice streaming. This problem could be solved with some overlap of the wireless access point ranges and two network interfaces. One could get a DHCP lease on the upcoming network while the other still streams, and then once the first network is out of range instantly switch over to the other interface. Just a thought.

Re:What about TCP/IP handoff?

[templeton008]

sip can go over tcp or udp, it's most often used over udp though. The actual rtp audio stream goes exclusively over udp to minimize delay/complexity (it doesn't matter if some packets get dropped).

Re:What about TCP/IP handoff?

[Anonymous Coward]

You are correct about the TCP/IP issues, but the design for multi-AP networks
is to have them all on the same subnet. Then the act of roaming between APs
is scoped to L2.

That leaves a couple different sources for delay/glitch:

One is if the wireless client were to set the WiFi interface "down" upon
dissassociating with the initial AP, then setting the interface back "up"
once it associates with the next AP. This may have the affect of triggering
the IP stack to release it's address information, and then restart a DHCP
transaction when the interface comes up. This sort of thing should be easy
to avoid in a WiFi VoIP client though.

The other stickler is WiFi authentication. Most WiFi users are used to WEP
with Open authentication, which is more or less instant. But a modern,
enterprise-level network with modern authentication features (802.1x/RADIUS)
makes the authentication step not-so-instant. Cisco has some proprietary
features in their APs to make roaming in such an environment a much faster
operation (they basically use an authentication "proxy" of sorts). I follow
this stuff because I'm helping develop a competing AP at the company I work for.

I'm glad to see some new ideas come out, but from looking at the article, it
doesn't look like this new research is taking the full context of the wireless
network - including the authentication scheme - into account.

I just hope

[Pinefresh]

this research wasn't randomly generated

Don't worry...

[wingsofchai]

I'm sure the FCC will step in and protect us from this innovative and helpful new technology with plenty of arbitrary regulations that make little or no sense...

Re:Don't worry...

[Saeger]

It's just greedy human nature. Machiavelli put it best 500 years ago:

"Innovation makes enemies of all those who prospered under the old regime, and only lukewarm support is forthcoming from those who would prosper under the new."

I've had that quote up on my wall for a number of years, since it helps to remind me how consistantly people -- and especially the cashcow status quo -- resist any disruptive change that shifts net benefit/power to a greater number of people.

NO thanks

[Timesprout]

I will stick with my current approach of having a team of engineers follow me around 24/7 laying cat5 cable for my skype connection.

WiMax will break the cell operators backs

[cpeterso]

Cell operators like Verizon spend BILLIONS on proprietary "3G" networks. Their networks require lots of towers, yet have poor coverage and lots of "signal shadows". WiMax access points have ranges from 30-50 MILES and don't have the same signal shadow problems. WiMax phone networks will steamroll cell operators with cheap networks yet better coverage and service.

Actually

[bluGill]

Actually VOIP over WiFi is more likely to be useful in deserts and other remote areas because those who care can setup their own network. It might not be worthwhile for a cell phone company to put up a cell tower, but a farmer can put a WiFi station on his silo and get pretty good coverage of his ranch. Sure it won't have a large coverage areas, but it covers his needs.