Verizon DSL vs Comcast Cable

[Mark J. Dulcey]

Rich Braun wrote:

> In between ISDN and RCN, I used
> a terrific 27-megabit service rolled out by CAI Wireless.  You can drive
> through Davis Square along Cutter Ave and still see the chimney-mount antenna
> I put up to receive that in 1997.)

We had the CAI Wireless setup here at The Buttery also, but we had a lot 
of troubles with it. They originally installed it in the late fall, and 
everything worked fine until spring when the trees got leaves; then we 
no longer had line of sight and the connection would intermittently go 
out depending on weather. (It would work well enough through dry leaves, 
but not wet ones.) So the installer came back out and raised the antenna 
another 10 feet, but they did it with a rather flimsy long mast 
arrangement, so high winds would bend it far enough out of position that 
the connection would stop working. We also had two failures of the 
wireless cable modems, which the company replaced without cost to us.

When it worked, it was OK, though. It was essentially cable modem 
technology over a radio connection on the MMDS band (a frequency area 
reserved for wireless cable television and TV distribution over a 
metropolitan area); the downlink, as Rich said, moved 27 Mbps (shared 
among all the subscribers in a sector), and the uplink was a 33.6Kbps 
modem connection (using a modem built into the cable modem, not a 
separate one). Yes, that meant that you had to tie up a phone line 
whenever you were online, and the upload speed was abysmal. Also, the 
best actual download speed I ever got was about 1.5Mbps - I think the 
limiting factor was the slow uplink, which restricted the rate at which 
your system could send back the ACK packets.

Near the end, CAI did tests of a two-way wireless system that would not 
have required the telephone uplink. The company's financial difficulties 
doomed them before they ever used it for actual customers. (They had 
evidently had a co-marketing deal with the company that was then NYNEX, 
but the phone company pulled out, leaving CAI with a lot of capital 
spent and very few customers to show for it.)

Our antenna is no longer on the roof; the flimsy mast bent, so we had it 
taken down. I still have the MMDS antenna, though, as well as two 
wireless cable modems, one of which would work if it had anything to 
communicate with.

I haven't heard of much activity with MMDS spectrum and equipment 
lately. It would seem to have potential for the right sort of city: 
moderate size, a high point available to put the master antennas, and 
mostly owner-occupied buildings (so they can put up antennas without 
hassles). It wasn't an ideal fit for Boston, because too many potential 
users didn't have line of sight to their central site because of being 
blocked by buildings or hills.