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Using WiMAX To Replace a Phone?
vigmeister writes "I've decided to explore the possibility of using a netbook/MID as a phone while eschewing the services of a cellphone provider. Now that Atlanta (where I live) has WiMAX from Clear, I ought to be connected to the Internet everywhere within the city (once I sign up). Theoretically, this should mean that I will be able to use my netbook as a cell phone. Of course, there are some very real issues to overcome and I am simply putting this experiment together to see if it is something that is realistically possible.
This could possibly extend to uncapped 3G connections (if they exist any more) as well. Are there any obvious problems you would foresee? Is there anything I have missed or any other questions I should attempt to answer in this 'experiment' of mine? A major issue is, of course, the fact that my pseudo-netbook has to be carried everywhere and always left on."
You don't *honestly* think that you're going to get WiMAX coverage everywhere you go, do you? WiMAX isn't magic. It has most of the same limitations that regular 802.11 b/g has. It's an *improvement*, but you still aren't going to get good signal inside of most public buildings.
Are there any obvious problems you would foresee?
How are you going to dial 911?
Unless you barely use your cellphone, you'll find that the netbook's battery is
your biggest limiting factor. Particularly if you use a bluetooth headset so you aren't walking around
with a cabled headset plugged into the netbook. There are 802.11 based SIP phones that can serve the same purpose.
I think an important thing to consider is the ability to forward your number. I'm thinking of doing that in general. If I have one number which I can forward different places, I can give that out to people who want to call me and I can have it forwarded to a prepaid cell phone, my work phone or other devices as needed at any particular time. It makes your idea much more practical and I think it's how people will do things in the future. It also helps enable more competition in the market for mobile phone devices.
Because they're not ubiquitous. You will end up somewhere where coverage isn't so great for your new protocol. If you can handoff to an older protocol, you will keep your connection. So this is why even a few years ago you could get Verizon phones that still supported AMPS, why every phone that supports EV-DO also supports 1X (and older standards), and why every phone with WCDMA/HSDPA/HSUPA/etc still supports plain old GSM/GPRS/EDGE.
It's also why it doesn't make a lot of sense to have a WiMAX only phone. You need at least WiMAX+GSM, or WiMAX+CDMA1X. You need to be able to hand off to the older interfaces. And probably you want to support everything... WiMAX when it's available, HSDPA or WCDMA when that's available but WiMAX isn't, or GSM/GPRS/EDGE when that's all that's available.
Or maybe you never leave downtown Atlanta. Then maybe WiMAX-only would be fine, assuming you trust the reliability of the relatively new network.
-- Erich
Slashdot reader since 1997
I use Clearwire's regular wireless internet here in Seattle. They block Skype traffic to promote their own VIOP plan for an extra $10-15/month. They might not let you use your netbook as a cell phone without ponying up extra $$.
Funtime Candy Wow! - my plan for eventually conquering Japan.
Problem solved...
http://www.thinkgeek.com/gadgets/cellphone/8928/
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The CP Lawn Bowling Club in Victoria, BC has done this. WiMAX -> Buffalo AP -> Linksys PAP2T -> SIP provider. Bringing the monthly bill from $54/month with Telus on copper pair, to $35/month for unlimited long distance and broadband/wifi as well. http://cplawnbowling.org/
Are there any obvious problems you would foresee?
"Oh my god, someone call 9-1-1!"
"Hang on, let me get my computer out of suspend...
And put my headset on...
Ok, I am dialing...
Hello, yes, emergency-- What? You are the 9-1-1 dispatch center where? Tulsa?"
Portland, Oregon, also has WiMax through Clear. There are decently large sections of Portland (including my house,) that do not have WiMax coverage; and larger sections with very spotty coverage. Admittedly, Portland is a much "hillier" city than Atlanta, but it only stands to reason that some parts of Atlanta would have coverage that leaves much to be desired, as well.
The 911 problem others mention can be resolved by picking a VoIP provider that has 911 service; or by manually bookmarking your local phone number for emergency dispatch.
Another non-functioning site was "uncertainty.microsoft.com."
The purpose of that site was not known.
If you're mobile, you wouldn't care if 911 is supported - the operator wouldn't have your location. You'd carry around your old cell phone with no contract or service for that job.
WiMAX was designed to handle VoIP traffic, and has specific traffic categories on the airlink for isochronous flows, like RTP and other VoIP payload streams. Unlike something like Ethernet, which is CSMA/CD (carrier sense multiple access, with collision detection), traffic is scheduled by the carrier network. For uplink data, your WiMAX card goes through a process of requesting bandwidth on what amounts to a hailing channel, and then gets a bandwidth allocation it can use. In theory, a small but constant amount of bandwidth can be allocated for VoIP at the airlink level, resulting in low jitter, low latency, and low frame loss.
There are a couple of problems with this.
The first problem is that not all WiMAX cards on the market today (in fact, quite possibly none of them) have sufficient sophistication in their device drivers and microcontrollers to send the RTP (or Skype, or whatever VoIP protocol you're using) packets on an isochronous service flow while the balance of the packets travel on a general-purpose service flow. As a result, the RTP (etc) packets have to compete with whatever else your machine is doing, either stuff you're initiating with the browser, or background things like checking email or updating the Vista weather widget, or checking for updates of one kind or another. It doesn't help matters that no operating system has a network stack that implements the service flow concept.
The second problem is that low-speed isochronous flows over the WiMAX OFDMA airlink depend upon sharing a fairly large timeslot with other users transmitting simultaneously on the uplink using a different set of carriers, at least if the system is going to be economically feasible for the carrier. Allocating an entire timeslot often enough to keep the delay below half a second or so would result in considerable wasted bandwidth, so the idea is to have users share a timeslot by have each one use only a fraction of the available carriers. Decoding the resulting burst at the base station then depends upon maintaining orthogonality between OFDM carriers, which means that exact frequency synchronization is required between multiple users. While each user's WiMAX card synchronizes its clock with the base station, doppler shift due to changes in speed or direction or a changing multipath environment can change the received frequency at the base station enough to compromise orthogonality and make the burst impossible to decode.
The result of all this is, from your perspective, is that your VoIP traffic could be jittery and have long delays and high packet loss, especially when the carrier's network is heavily loaded.
It seems like the arguments against this can be put in 3 categories. 911, battery life and coverage.
I would think that if you are viewing this as a "cell"phone replacement then it would obviously fail on all 3.
I remember being able to live without a cellphone. In fact, I miss it. I find it very annoying that in our cellphone enamoured society my friends and relatives feel "entitled" to talk to me whenever, wherever I might be. I don't want to talk to someone as I go through the checkout line in the grocery store. I find it annoying to try to understand someone who will not speak up when I am driving my Jeep. It's loud in there. Let alone the safety issues! I'd rather call people back when it's convenient for me. Just like I would have with an answering machine and a landline about 12 years ago. Does this make me old? I am only 29.
That in mind I too have considered what the author is asking though I would use a more portable form, some sort of PDA rather than a netbook.
I would keep separate power adapters in my office at work, one at home and a third in my car. Most of the time I would be in one of those places and could plug it in. Don't want to be tethered to the plug? Use bluetooth! If I don't get a signal in my car then oh-well. I know how to change a tire! That about takes care of the power problem. It just doesn't have to be on every moment I am not in one of those places. If I need to make a call, that's when I would turn it on and use the battery.
As for coverage... wifi at home and work are easy. Your mileage will vary at work but I doubt many on this site don't have it at home. Anywhere else it works... that's just a bonus.
Think you have too much of a social life to not be always connected? Do you think you will miss too much because you're out? I think not... you are on Slashdot! Seriously though, I was a college student with one of the busiest lives I knew just before I got my first cellphone. Missing calls didn't stop me, if I missed it then I was already busy! If I missed too many calls then maybe I would have ended up at home, but then I wouldn't miss the next call. See how that works?!
Now, 911. This issue has been brought up against every form of VoIP since the begining. I have to ask... does it really matter that much? Honestly, I don't know the answer to this but don't the 911 operators have the ability to transfer to one another quickly? If not then this is a problem the public should be crying to see addressed! What if a call was coming in via radio or some other third party method where the person making the call is not in the same local as the emergency. Hasn't there always been a need for 911 calls to be transfered?