Femtocells To Replace Parts of the 3G Network

sweetpea23 writes "Grown-up versions of femtocells — devices which beef up 3G network strength in the home — are set to take over parts of the outdoor cellular networks, according to technology vendor picoChip. Femtocells — such as Vodafone UK's Sure Signal device — are cut-down versions of mobile phone base stations, redesigned to operate inside buildings, using home broadband networks to route 3G data onto the Internet. Now, picoChip, which claims to provide 70 percent of the chips used to make femtocells, has unveiled a toughened up version, which takes the femtocell idea back out onto the streets."

Comments

Re:Honest Question

[tlhIngan]

I'm not trying to be facetious, but how does a phone with Exchange produce the same amount of load on a network as a device that's constantly making voice calls? I realize that the phone will be signaling to a server to keep data synced, but how does it produce that much load?

Quite easily, actually. It's also the reason why the iPhone is so horrible on the AT&T network.

Basically, when your phone is "attached" to the cell network, it's communicating with the base station on a control channel. Similar to ISDN control channels, it's use for call setup/termination, management and other things. To optimize for power, the mobile station "pings" the base station with presence information (basically saying "i'm here"). This keeps the power-hungry transmitter off and only turns it on for the briefest of times. The receiver is also kept off, but it consumes less power so it can be turned on more frequently to listen for network messages, perform signal analysis (is it getting weak? Does the phone need to find another tower?). This is why if you're in a marginal signal area, your phone will consume more power - the transmitter will have ot use higher power to talk to the tower, and worst case is if you're in a marginal area between cells where the phone has to be constantly doing the handoff between cells (consuming lots more transmitter time).

Now, back to the topic at hand. Making a data "call" is exactly the same way - the phone uses the control channel to set up the call (find an uplink and downlink frequency) as well as any other network parameters, like maybe where in the frame it can transmit and receive its data on. Of course, this keeps the receiver on and the transmitter has to be active, so it consumes more power than idle. So when you want to maximize endurance, you want to tear down the data connection ASAP, which requires another control message. Depending on the application, this can mean setting up and tearing down hundreds of times, which consumes valuable control channel bandwidth.

So now your phone is making hundreds of "calls" continually as it sets up and tears down the data connection, which consumes the control channel bandwidth leaving less for SMS, other call setup/teardowns, handoffs, and the like.

Most North American carriers have the problem because the control channel bandwidth is fixed. Most rest-of-world carriers don't because texting is hugely popular, and SMS ends up consuming a rather significant chunk of control channel bandwidth. So those carriers long ago upgraded to dynamic control channel sizing to ensure that there's enough spare bandwidth for calls, voice or data. Texting is only really taken off in North America the past few years, and the iPhone was really also the first phone that was extremely aggressive on power savings by practically tearing down the data connection during pauses. End result, control channel overload leading to dropped calls (hard to be handed off the target cell can't handle the handoff request), missed calls, delayed text messages, and slow data.

I'm guessing Exchange may use a protocol that allows for frequent bringups and teardowns, especially amongst the more aggressively power saving phones.

This is a problem with all the carriers, especially since iPhones and Android phones are popular. If the Verizon iPhone is as popular as everyone makes it out to be, VZ could be in for a world of hurt if they don't already have the ability to dynamically adjust control channel bandwidth. It's also why early AT&T phone bills were more like phone books - because every time the data "call" is made, it's logged for billing purposes. This could result in pages of log entries just over the course of a browsing session as the data connection is brought up and down each time.