VoIPowering Your Office: VoIP Can Do Wi-Fi!
October 22, 2007
Despite a slow start—and a bad reputation—voice over that other kind of wireless is gaining a foothold.
Last week we pondered the question "Can VoIP Do Wi-Fi?", and the answer was a resounding Yes. Today we're going to examine the technologies and where they are headed, and next week look at some devices and vendors that make it happen. As you will see, there is a lot more to it that waving your hand and saying "Make it so."
CDMA, GSM, Wi-Fi, and WiMAX, Oh My!
I'm experiencing increasing nostalgia for the olden days. My grandmother had a single phone in her entire three-story house. It was black and it had an actual dial. That's right, not a touchpad, but an actual rotary dial. So making a phone call was an Event. You had to journey through this big old house to the phone table in the entry hall and then wait for the dial to return to '0' before you could dial the next number—none of this modern hyperactive speed-dialing, which isn't really dialing anyway. When your call was completed, you went about your business, and if you were in a part of the house (or outside) where you couldn't hear the phone, oh well, too bad so sad; you were not interrupted.
But that was then, and in a remarkably short period of time we have unchained ourselves from the stationary black rotary phone in the entry hall, and are wired for telephony no matter where we are. But we're still well entrenched in the "growing pains" phase, so it's gotten complicated with different technologies and gadgets:
- First there were analog cell phones
- These have been mostly, but not entirely, replaced by digital cell networks
- But all is not harmonious, as there are two incompatible digital standards: GSM and CDMA
- GSM is dominant outside the United States, while the U.S. relies mostly on CDMA
- Cell networks are incompatible with each other, and CDMA phones are tied to a single vendor. Many of us have experienced the "joy" of buying new phones every time we change carriers, and having to retire a perfectly good, functional phone.*
- Network incompatibility is mitigated somewhat by carriers making roaming contracts with each other. Which typically costs the user a premium
- GSM supports Subscriber Identity Module (SIM) cards. The SIM cards are tied to networks, rather than phones, so swapping SIM cards allows your phone to connect to different networks
- The CDMA equivalent of the SIM is the Re-Usable Identification Module (R-UIM), which is not yet available in the US, but has been rolled out in other countries
Thanks to Asterisk and other VoIP technologies, all you need to integrate cell phones into your IP voice network is PSTN integration. And then you can create clever hacks that let you use a single phone number to reach all of your phones and devices—home, office, cell, pager, Blackberry, whatever.
So at first glance it might appear that cell phone integration is the way to go, and we don't even need to worry about newfangled sillinesses like Wi-Fi (IEEE 802.11) telephony. But Wi-Fi offers a number of advantages that cell phones don't have.
A chronic problem with cell phone networks is customers want seamless, perfect coverage no matter where they are, but they don't want the planet carpeted with ugly cell phone towers. (Disguising them might help.) Wireless Internet doesn't need tall ugly towers, but rather deploys small, tasteful transmitters that don't need towers, like this one.
Both CDMA and GSM have weak support for high data transfer speeds, which is not a problem for voice and texting, but it does limit streaming sound and video, which of course are becoming must-haves whether we really want them or not. CDMA2000, also called EVDO, offers a theoretical 2.4 megabits per second. GSM's counterpart, EDGE (Enhanced Data Rates for GSM Evolution), offers a relatively puny theoretical 384 kbps. Naturally in the real world you'll see significantly lower speeds, depending on your proximity to a phone tower, interference, and whether you are moving or stationary, and of course you must purchase phones that support these—not to mention paying a premium for data service. Both of these fall under the 3G standard, which is the wireless broadband standard: 384 kbps for a stationary or slow-moving device, 128 kbps in motion, and 2 Mbps for fixed devices.
Ordinary Wi-Fi promises network speeds up to 54 Mbps, and as much as 108 Mbps with various vendor-specific tweaks. Of course in the real world it's a lot less, due to Ethernet overhead and less-than-ideal conditions, but you still get genuine LAN speeds. The downside is limited range, typically a few hundred feet. So the answer to this is WiMAX, the IEEE 802.16 standard, which aims to provide broadband wireless at ranges up to 30 miles.
WiMAX joins 3G
WiMAX has, until now, been a competing standard to the 3G technologies. But now it has been officially welcomed into the 3G family. This should mean that future development will be standardized and beneficial to us poor beleaguered customers.
Cell phones and Wi-Fi offer a limited amount of overlap. Neither one yet offers complete, seamless coverage of everywhere. So an increasing number of vendors are combining both in single devices. We'll look at these in more detail next week.
*You can donate your old cell phones to battered women's shelters and other charitable groups, because they can be programmed to call 911 for free.