Descriptions
"High speed" modem
56K Modems
ISDN
ADSL
T1 Line
Ethernet
Wireless Cable Modems
Cable Modems
Either a 56 kilobits per second Modem or a Dedicated "56k Line"
56 K Modems suffer from a lack of standardization and the fact the they haven't been able to successfully deliver on that data rate. Test show that most of them actually deliver somewhere in the 40-45 Kbps range.
Normal copper twisted pair line, changed to digital from analog. Allows simultaneous voice
and data
Asymmetrical
Digital Subscriber
Line. Requires an ADSL modem. Uses existing twisted-pair, copper phone lines. Meant to compete with "cable modems." While cable modems could be slowed greatly when many people are logged on, 1.5 Megabits/sec. for ADSL is pretty much guaranteed. (ADSL-2 = 3 Mbps and ADSL-3 = 6 Mbps) Technical performance is greater over phone lines than coaxial cable lines which are susceptible to a range of service problems (i.e. outages and RF interference problems). Also, Telcos don't have to
make the major upgrades that cable companies would need to undergo to get into the cable modem business.
Fancy Phone Line-more twists/Lower limit of low-quality MPEG-1 compressed video
(Not used to deliver the Internet over distances. For comparison purposes only)
The system operates in the 2-gigahertz range reserved for MMDS (multichannel-multipoint distribution system...essetially small microwave receiving dishes on a rooftop used to receive only). The rooftop receiver is connected to a cable modem. The system sends Ethernet-like packets over the air to homes. However, phone lines must be used to send user-originated requests "upstream." Because these are "connection based," a phone line is tied up the entire time of the connection. In contrast, cable's bi-directional
systems offer connection-less, session-based transmissions, meaning
that headend demodulators can juggle multiple incoming requests in a
way that's transparent to the user.
Your standard cable TV coaxial cable. Will utilize a switching technology called ATM (asnychronous transfer mode). Data speeds up to 155 mbps from national internet sites to regional data centers, 45 mbps from regional data centers to cable head ends, and 27 mbps from head ends to the home (128 kbps from home to head end). Phone technology such as ISDN & ADSL are dedicated while cable modems could be slowed markedly if many others are also online. If many users are logged on, the effective speed may be much lower than 10 Megabits/sec. At peak times you may get no more than 200-300 Kilobits/sec. This means that telephone based technology such as ADSL could result in an effective higher data rate than cable modems. Also, cable modems have signal quality problems. In engineering parlance, it must be "locked down tight." In essence, RF (radio frequency) interference could disrupt service. Also, cable companies don't have much experience with the delivery of data, lack supporting personnel and will have to undergo expense plant upgrades to get into the business.
