Expecting 56k (V.90/X2/K56)?
Disappointed?
Welcome to the club.
If you find, as many others have, that you're unable to achieve full speed connections and/or your new high-speed modem sometimes even behaves erratically, the likely reason is a telephone line "impairment" somewhere along the way.
No, I am not implying nor even suggesting that you have a "bad" phone line. I'm merely saying your phone line simply may not be capable of providing what your modem is demanding from it.
Usually the problem is not enough bandwidth. It could also be any one of a half dozen other technical things such as group or phase delay, poor signal to noise ratio, an impedance mismatch, imbalance in the phone lines causing a slight hum or any combination thereof. This "impairment" could be in your phone line, in the phone lines of the system you are calling, or in the lines and telephone switching equipment -anywhere- along the way.
Experience has shown that the usual culprit is what some in the industry refer to as "the last mile" meaning that portion of the phone line between the subscriber (you) and your telephone company's central office. As I said above, the most common problem is not enough bandwidth. The most common reason for this is that YOU are simply too far from your telephone company's switching office. Okay, how far is too far? This is not an absolute number, but in general, anything beyond about 3½ miles (by car, not as the crow flies) is too far. Phone line bandwidth is inversely proportional to its length and the frequency applied. The longer the line, the less usable bandwidth there is and the slower your modem goes.
How do you find the location of your telephone company switching office? Well, you can always ask the Telephone Company, but http://www.dslreports.com/r3/dsl/coinfo will get you within 1,000 feet of it. No, not precisely, but close enough most of the time. Using the map location as a reference point, calculate the STREET MILES by car from there to your location and then add another 20% more as a fudge factor to allow for the fact that phone lines usually don't follow the most direct route.
Here are the approximate phone line bandwidth requirements for various modem speeds:
56,000 BPS requires 3600 Hz bandwidth, from 150 - 3750 Hz.
33,600 BPS requires 3429 Hz bandwidth, from 244 - 3674 Hz.
31,200 BPS requires 3200 Hz bandwidth, from 359 - 3559 Hz.
28,800 BPS requires 3200 Hz bandwidth, from 320 - 3520 Hz.
26,400 BPS requires 3000 Hz bandwidth, from 375 - 3375 Hz.
24,000 BPS requires 2800 Hz bandwidth, from 467 - 3267 Hz.
The problem with the above numbers is the Telephone Company guarantees and is only obligated (by regulatory tariffs) to furnish you with a line that has 2700 Hz of bandwidth, from 300 - 3000 Hz. Anything more than that is free extra bandwidth that you're not paying for. Okay, so what can we do in that guaranteed 2700 Hz of bandwidth? Well, besides the ability to talk on the phone and hear each other clearly, a 14,400 BPS modem should also work quite well. You might even achieve speeds as high as 19,200 and perhaps even 21,600. However, in only 2700 Hz of phone line bandwidth (the "guaranteed" minimum) you are not going to be achieving any of the high modem speeds you hear folks talking about. You're not even going to achieve 28.8k.
Alas, while virtually all U.S. domestic phone lines can easily support the requirements of the old 14.4 modems (even on most rural country lines), many fall short of meeting the minimum technical specifications REQUIRED for V.90/56k (and even V.34) to function at their "advertised" speeds. This, in a nutshell, is what you and I and many, many others are experiencing. Listen closely folks, this is not the telephone company's fault!
What's wrong? The bottom line is simply that the modem manufacturers have succeeded in building a product that requires more from the phone line than the phone line was designed to deliver.
Okay, what about those people I hear about who are getting the good speeds? They're not lying and I doubt they're even exaggerating. What's the deal?
Well, someone who is able to achieve a modem speed of 24,000 BPS or greater is merely someone fortunate enough to live close to their phone company's switching office and therefore have a telephone line that exceeds the phone company's "design minimums". The actual speeds they are able to achieve over and above 24,000 BPS are merely testament to how great a degree their line exceeds the minimum specifications. Lucky them, unlucky you, unlucky me. What can we do? Move!
According to FCC tariff # 260, the Telephone Company is only obligated to provide you with a VOICE grade telephone line that provides only 2700 Hz of VOICE bandwidth over a frequency range of 300 to 3000 Hz with a flat response within +4 and -8 dB. This doesn't mean the Phone Company has to necessarily limit you to those parameters, merely those are what they have to guarantee and design for as minimums when building their voice network. This minimum bandwidth is also all that you and I are technically paying for. Anything more is gratis. It is bandwidth over and above the guaranteed minimum and which you're not being charged for. Thus, if your modem is already doing 24,000 BPS or better, you can rest assured that your phone line meets the minimums (and virtually all do).
Consider this: a modem speed of 24,000 already requires 4% more bandwidth than the Telephone Company is obligated to provide. No, a mere 4% is not much over the minimum (which is why 24,000 probably works), but let's look at the rest of the picture as we start increasing the speed;
26,400 requires 7% more than the required minimum bandwidth
28,800 requires 10% more
33,600 requires 27% more and... Here's the big one,
56k/V90 requires a whopping 33% more, along with some extremely
High tolerances normally only associated with very expensive "Conditioned" lines.
Folks, I'm not pulling your leg and I'm not in here as a schill for the Telephone Company. This additional bandwidth has to be there from end to end, all the way from your modem to the modem at the other end of the call. Either you have that extra free, untariffed bandwidth or you don't have it and your modem is simply telling you how much or how little of that extra free untariffed (but needed) bandwidth you have via its performance.
Before you start screaming at your phone company, remember that Telephone Company tariffs on file with the FCC and state Public Utility Commissions only guarantee a VOICE grade bandwidth of 300 to 3000 Hz. What this means is that if 14.4/v.32bis works ok and you're already achieving a modem speed of 24,000 BPS or better with your 28.8 (or faster) modem, then we know with absolute certainty that your telephone line at least meets the minimums. Unfortunately, what this also means is that the phone company is under no regulatory obligation whatsoever to provide you with anything better. They might be willing to work with you out of a spirit of cooperation and desire to give good service, but my point is that you have no leverage to force them. Fortunately most of us do enjoy considerably better than bare minimum spec lines, although many users are not enjoying the advertised speeds of this funky new breed of modems over standard dial-up connections. Did we buy something we cannot use? More modem than our phone line can handle? In my opinion, yes!
Here are the hard numbers. In actual performance testing, the new "56k" modems can,
---- DEPENDING ON TELEPHONE LINE CONDITIONS ----
operate at speeds which on average, yield about 42-48k for less than 65% of the total user base. Okay, sure there are some exceptions where 5 to 7 percent of users report 50-56k, but I need to emphasize that those are highly unusual exceptions where the user's dumb luck affords them access to a near "laboratory grade" telephone line. These are often those instances where both the user and the ISP are served out of the same telco switching office and/or the user is located very near to his local telco office, typically less than a mile or so, i.e., just down the block.
If you think the problem might be at home, here are a few things you can TRY for improving your high-speed modeming:
Go throughout the house and disconnect EVERYTHING attached to the phone line. This includes extension phones, answering machines, fax machines, caller-id boxes, line-in-use indicators, cordless phone base units, demon dialers and voltage spike protectors or line filters like those commonly found in PC Desktop master-switch power directors and power line conditioning units. Don't overlook the less obvious things like remote utility meter reading devices and BURGLAR ALARMS that may be attached to the phone line. If you find disconnecting any of this helps, then start plugging things back in one by one, making modem test calls each time until the culprit is identified. It could even be a combination of things. At the office you're apt to discover that your modem will perform better when provisioned with an outside "1FB" or "POTS" line, i.e., one which does not go through the office PBX or a multi-line key system.
If your telephone wiring is a rat's nest, and/or you've strung some extension lines yourself and not used genuine twisted-pair telephone wiring, please consider having a professional replace your haywired additions. Your telephone wiring should also be well away from the AC power wiring in walls, ceilings & floors. AC power wiring should be crossed only at right angles. The old (non-twisted) 4-conductor "cloverleaf" phone wire (red/green/yellow/black) should never be used for 2-line service since the parallel conductors will cause crosstalk. If you have to make a vertical drop down a wall that also has electrical wires in it, a good rule of thumb is to allow at least 24-inches horizontal separation. Never-ever put telephone lines inside an electrical conduit with A/C power wiring. Never-ever coil up excess phone cord length together with excess AC cord length from your cordless phone base unit. One of the most serious cases of hum I ever found was getting into the line in just this fashion.
INSTALLING NEW WIRE: Don't waste money installing shielded wire or
"Category-5" data grade cable - that's overkill. It is not required,
even for ISDN or ADSL lines. However, twisted-pair phone wiring (the right
stuff) can sometimes be hard to find whereas 'Cat-5' wire is often plentiful, so
use Cat-5 if you can't find anything else. When using 'twisted pair' wire, never
split a "pair". Your first phone line should use the white/blue
"pair". If you have more than one phone line, connect your 2nd phone
line wires to the white/orange pair, and if still more put line 3 on the
white/green and line 4 on the white/brown pair.
PAIR GAIN: If your phone service arrives in your area via a small neighborhood hut inside which is a subscriber loop carrier system or remote terminal or other "PairGain" device such as the ubiquitous SLC-96 ("SLICK") or DMS-1/Urban or Dis*Cus, etc, then my friend, you're in trouble! In this case you're going to have to be content with a modem speed between 24,000 and 26,400, with 28,800 being a rare treat, indeed. What can you do in this case? Either order ISDN service or move. Chances are that ADSL isn't in the cards either if your phone service is on a pair gain system.
BUT DARN IT, THE MODEM BOX SAYS "56K!" What about this new modem I bought? Well, unless you read closely or listened closely, the advertising hype might have us all suckered in, hook, line and sinker, believing that the new V90/X2/K56Flex modems will operate at twice the normal speed of our old 28.8/V34 modem. Folks, that's nonsense! The fact is that although these new modems might indeed be "capable" of those speeds, the hard reality is they most often won't achieve anything close to those implied speeds over the average "real world" telephone line. If you bothered to read the ad or press release closely, you may have noticed that those statements were all couched in very vague and ambiguous terms. In close analysis no one really "promised" anything. Words like "nearly" and "almost" and a deliberately vague reference to "standard modem speeds" are used to lead the unwary buyer into expecting something that the new modems simply did not promise and for many users fall considerably short of delivering. You must realize that you did not buy a 56k modem. What you bought was a V.90 modem that is capable of speeds up to 56k. Compare to buying a car. You do not buy a 150 MPH car, although you might very well buy a car that is "capable" of achieving speeds up to 150 MPH.
For you technical types, here are some of the phone line bandwidth, frequency response and related technical parameters expected by the new 56k modems:
3600 Hz of usable bandwidth between 150 - 3750 Hz with
-Less than 10 dB rolloff at the low end between 150 and 300 Hz
-Less than 24 dB rolloff at the high end between 3450 and 3750 Hz
-Better than -50 dB receive level at 3750 Hz
-No load coils
-No bridge taps
-No wire gauge changes
-Less than 43 dB attenuation end-to-end
-Maximum of one (1) digital-to-analog transition
Any telephone company engineer will tell you these are some really extraordinary parameters to expect from the average subscriber's phone line. Yes, a few will, but many won't meet these parameters.
MY OTHER ISP WAS FASTER: Yes, I've heard that one before. Can a different modem or different service provider (ISP) help? Yes, very often in fact. Why? It's because not all modems are created equal and not all service providers use the same brand. That's not to suggest that one ISP is necessarily "better" than the other, it's just that certain brand modems work best when dialing into a host (service provider) that uses the same or a specific brand. For example, we know that in the past, the USR Sportster modem generally "preferred" to connect with a USR central site host system and often had difficulty establishing and/or holding a connection to an Ascend host. By contrast, modems based on the Conexant/Rockwell chipset had a strong tendency to favor the Ascend host and not the USR. This still holds some truth, but over the past 2 years, the major modem chipset manufacturers have fixed most of their v.90 interoperablity problems. This means that the USR modem can now work well with the Ascend host and that Conexant/Rockwell modem can work well with a USR host. Making sure you have the newest drivers usually assures you of getting the best connect speed and throughput.
What do I use and recommend? If cost is no object, my favorite is still the external desktop model of the 3Com/USRobotics "Courier V.Everything". Yes, it's big but it sure works! No, it cannot compensate for poor bandwidth. Nothing can help if the bandwidth just isn't there. However, the Courier has a lot of horsepower under the hood and therefore can often overcome certain other problems that the low-end modems cannot. If cost or size is a factor, then my favorites are the Diamond SupraMax and SupraExpress modems.
GETTING DROPPED? Having trouble connecting or staying connected? Try disabling 56k on your end. 56k/V.90 has jokingly been called "VeeDot Unreliable" by some communications professionals. You know what? I think they're right. The problem is that in order to make the customer feel better about his modem, too many of the mediocre and low-end models are just too doggoned aggressive about trying to establish too high of a speed that the phone line cannot actually sustain. The customer is impressed by the connect speed report, but then complains to the ISP that he can't stay connected. It is far better to connect solidly and stay connected at 28.8 or 26.4 than it is to keep getting dropped, or keep locking up at some higher speed or otherwise fight the connection. Come to grips with the fact that any smooth data movement at all is better than jerkiness or frequent disconnects. Learn to accept what your modem can do and what it cannot do considering the telephone line you have been given to work with. If disabling V.90 is what you have to do, then that's what you have to do. Again, Making sure you have the newest drivers usually assures you of getting the best STABLE connect speed.
NEED HELP? If you know someone else in your neighborhood with a high-speed modem, do not hesitate to ask what modem speeds they encounter. Try making the connection with your modem from their location or see if you can borrow their modem or perhaps loan them yours. If your neighbor encounters the same low connection rates as you, the problem could be resulting from the fact that your neighborhood is too far from the central office. If the neighbor reports good connection rates (much better than yours) then the problem is possibly right there within your home or office. If your neighbor's modem works well at your house, then it might be time to dump yours and purchase one like the neighbor has. Your telephone company or a private consultant may also be able to help.
Good luck!
See the original version at http://www.hal-pc.org/~wdg/56k.html
This page was last updated on Sunday, December 03, 2000 .
If you have any comments, suggestions or questions Email: [email protected] or [email protected].