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

Honest Question

[Sonny Yatsen]

FTA:

“Instant messaging and Exchange are the worst offenders,” claiming that a smartphone with “always on” applications like Exchange - while doing very little - can produce the same signalling load on the network as a device making 1000 voice calls per day.

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?

Re:Honest Question

[kent_eh]

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?

Because signaling traffic and user traffic are handled differently.

A very rough analogy to TCP/IP:
Signaling traffic is similar to SYN, ACK, DNS, DHCP, STP, ARP, SMB and all the other stuff you see on a normal LAN that isn't user payload.
On a GSM/UMTS network, this stuff is running on a separate virtual channel from the user traffic (voice or data). Think of it like a separate VLAN which has a max bandwidth allocated to it. (by design)
Basically, the "overhead" packets clog the signaling channel, even though the traffic channel still has oodles of bandwidth available. SYN flood anyone?

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.

Re:Where to buy?

[sheddd]

AT&T is selling something like this for $99. I'd like to have in my office, but haven't purchased yet; limited to 5 phones and you have to register the phones on the device.

Re:Bandwidth?

[demiurg]

Home Node B devices are not repeaters. They will actually increase the available bandwidth for large number of users as they will be able to transmit with higher modulation on shorter distance, i.e. they will be more spectrum efficient.

Hurray for paying more to use my service

[Anaxagoras]

So let me get this straight. I already pay at&t over 100$ a month, but I can't use my cell phone in my new apartment because I have a crappy signal (other providers are fine, but I'm locked into my contract for another year), so I can PAY them for a device to make calls over MY internet connection so they don't have to upgrade their shoddy network! bah humbug!

Note I do have at&t and have no issues at home, but this is the situation a friend of mine is going through and they want him to buy this device to use a service he's already paying for.

AT&T sells one

[Muad'Dave]

AT&T's microcell uses your broadband connection to extend their coverage and has a GPS to validate that you're using it in an 'approved area'. Also, calls don't transfer in, so you'll lose calls as you approach your house. No thanks.

From this page:

"AT&T 3G MicroCell acts like a mini cellular tower in your home or small business environment. It connects to AT&T's network via your existing broadband Internet service (such as U-verse, DSL or cable) and is designed to support up to four simultaneous users in a home or small business setting."

Also,

"Calls transfer out, but don't transfer in. Calls seamlessly transfer from the 3G MicroCell to the strongest available AT&T cell tower signal. However, calls connected on the cell tower do not transfer to the 3G MicroCell."

Re:Where to buy?

[colfer]

The range is not great. ATT says 40 ft, which is about what we got. Other than that, works great.

The limit is 4 phones operating at one time, and you keep a list of up to 10 approved phones.

The weirdest thing is it has to get a GPS signal to activate.

And why microcell vs. femtocell?

Problems

[Mr_Silver]

The biggest problem with femtocells is that customers expect them to be free. This isn't unreasonable, after all they're paying a monthly fee to get a service and they expect that they can stand in the bathroom in their city centre flat and be able to make a call.

The problem is that building a business case for purchasing a tonne of femtocells and giving them away to customers for nothing isn't a pretty read and getting a director to sign off on such an endeavour has been tough.

They'd far rather that the money was spent solving the signal problems (which improves things for everyone, not just the femtocell owner - but at the cost of a slow resolution time) rather than publicly admit that their signal is rubbish in urban places and needs "boosting".

Re:Problems

[Ephemeriis]

The biggest problem with femtocells is that customers expect them to be free. This isn't unreasonable, after all they're paying a monthly fee to get a service and they expect that they can stand in the bathroom in their city centre flat and be able to make a call.

It isn't so much that they aren't free... It's that they cost so much, while costing me additional resources, and not really doing much for me except allowing me to use the device that I'm supposed to be able to use anyway.

I have a Verizon cell phone. According to all their coverage maps, I should be fine. I'm not. I routinely drop calls at home. Regardless of what they say, we're right on the edge of their coverage.

Verizon offers a femtocell for $250. This femtocell will use my electricity, it will use my bandwidth, and it will not save me any money at all. I still get charged for calls and data at the normal rate even though I'm having less of an impact on their infrastructure. All I get for my money is the ability to use my cell phone in an area where they swear I should be able to use it anyway.

I wouldn't complain if the femtocell was just $50... Or if they took $5/month off my bill... Or if calls/data/whatever were discounted while using the femtocell...

Re:Problems

[TheRaven64]

That depends, of course, on who is deploying them. An existing ISP, for example, could deploy a cellular network pretty much instantly by providing the femtocells to their customers and buying capacity on an existing network.

A good candidate for doing that here in the UK would be Virgin Mobile, a virtual operator owned by Virgin Media, the largest ISP in the UK. If Virgin Media provided cable modems with built-in femtocells, they'd reduce their operating costs, because most calls in urban areas would be made within range of one of their cells, rather than having to use the Everything Everywhere network, but they could still fall back onto the EE network when out of range. They could encourage their customers to leave them turned on by paying them when a call was made through it (effectively also giving you cheaper calls when in your house).

My phone has WiFi, so I make calls via SIP when I am at home, using their network for the bandwidth but someone else for the POTS bridging. If they provided femtocells and a sane price structure, I'd be tempted to switch.

Re:Where to buy?

[PitaBred]

Not really weird. It's probably a legal requirement to have a GPS location of every cell on the network. AGPS, cell phone tracking and all that. The police wouldn't be happy with you being able to make cell calls from any network connection without being traceable, and AT&T probably wants to prevent overseas use as well.