From: Miguel Cruz on 13 Aug 2006 18:40
Mxsmanic <mxsmanic(a)gmail.com> wrote:
> Miguel Cruz writes:
>> I don't think the service would work without accurate clocks;
>> extremely accurate timekeeping is a key element of the system used
>> to select cells and hand off calls.
> If it works like GSM, it has to be relatively accurate, but not
> absolutely accurate with respect to time of day.
The most reasonable way to ensure they are relatively accurate is to
ensure they are absolutely accurate.
I find it hard to believe they would take any other, more complicated
>> You may want that, but I don't see why it's important or why 99.99%
>> of people would care.
> Since it has no disadvantages, why not use it?
For people who are already carrying around a cell phone, a watch has the
disadvantage of being another thing to carry/wear.
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From: Mxsmanic on 13 Aug 2006 19:01
Miguel Cruz writes:
> The most reasonable way to ensure they are relatively accurate is to
> ensure they are absolutely accurate.
Not necessarily. It may be cheaper to provide very stable time
references for the network for relative measurement rather than try to
derive those measures from an ultra-accurate time-of-day source. This
is especially true since the accuracy required might be microseconds
or better, and this is expensive to derive from the time of day.
For example, most time of day sources provide extremely high long-term
accuracy at low cost, but they provide poor short-term accuracy unless
a great deal of effort and money is expended. A radio source will
keep your network locked to the correct time of day with long-term
accuracy equal to that of the best atomic clocks, but the short-term
accuracy may be off by hundreds of milliseconds per day unless you
spend a great deal on either continuous synchronization or a local
reference that is extremely accurate when free-running. In the latter
case, you might as well skip the time-of-day reference.
In summary, for timing of protocols, you don't necessarily need
accurate time of day. However, for things like time stamps, and
synchronization of events with precision over long periods or
distances, time of day can be very useful.
One application that illustrates this is live television. In the days
when live television was common and nationally broadcast, sometimes
studios on one coast would pick up where another left off. If they
didn't have their clocks synchronized to within a fraction of a
second, either there would be a period of dead air or a period of
confusion whenever one location handed off to another.
Accurate time of day is important for things like electronic money
transfers and stock operations, too.
Transpose mxsmanic and gmail to reach me by e-mail.
From: Jim Ley on 13 Aug 2006 19:45
On Mon, 14 Aug 2006 00:19:53 +0200, Mxsmanic <mxsmanic(a)gmail.com>
>Jim Ley writes:
>> How does a chain make you remember to transfer it between clothes, or
>> remember to have it with you?
>When you put the clothing on, it's there. When you take it off, you
>can feel it dangling around. Pocket watches are heavier than
What happens to it in the intervening 8 hours whilst you're sleeping,
and how does feeling it dangling around 8 hours before remind you to
transfer it to the new clothes the next morning.
I concede it may not be an issue if you only have one set of clothes,
although rembering to remove it whilst you walk through a public
carwash to get clean might be another problem.
From: Jim Ley on 13 Aug 2006 19:48
On Mon, 14 Aug 2006 00:28:06 +0200, Mxsmanic <mxsmanic(a)gmail.com>
>Jim Ley writes:
>> How do you update it for leap-seconds?
>The radio signals to which it synchronizes cover leap years, leap
>seconds, and daylight saving time. No manual adjustment is ever
In any case, your watch is not accurate to what you claimed, as there
is more inaccuracy in the radio tranmission than your quoted figure,
there is also reportedly more accuracy with a GPS system.
So a GPS connection would be more reliable, so a CDMA phone would be
>> It's not a function of the phone, it's a function of the network -
>> anything that is CDMA based or the majority of the 3G methods (AIUI)
>> have clocks synchronised with the base-station, which are GPS sync'd.
>Which _can_ be GPS synchronized.
No all CDMA systems are, there's no other available clocks.
>GSM (the standard used everywhere else in the world) provides for time
Oops, have you not heard of 3G roll outs, GSM is not as ubiquitous as
it was - although they roll over to it obviously.
From: Jim Ley on 13 Aug 2006 19:50
On Mon, 14 Aug 2006 00:30:06 +0200, Mxsmanic <mxsmanic(a)gmail.com>
>Relatively accurate time measurement is required by the protocols I've
>seen, but the absolute time of day need not be as accurately kept.
no, obviously it does not need to be absolutely accurate (they could
all synchronise to 3 weeks ago last tuesday) however there are few
sources of accurate clocks you can synchronise base stations too other
than GPS signals, which are highly accurate atomic clock signals
giving the correct time. So they all have the right time.
>> Why? For what purpose?
>Why do I need to justify it?
because you're suggesting your experience would be relevant beyond
yourself, because of that, justification is kind of important.