GPS System Could Fail Next Year, Report Warns

[poltergeisty]

737-700's have FMC's.. What is you point?

Referring to 737-200's Might Janet be sht up a creek? :lol:

IDK, if all VOR's,etc will be removed, it would be prudent not to. Just my take, especially for Red Cross, etc transport.

...anyway, back to this "POS" GPS. :lol:

N467RX = Mexicana?

 

[radio9]

Oh and another thing that leads me to believe that this is a BS story is that Verison, Telus Mobility and Bell Mobility will all need GPS to have proper timing for CDMA (and any other CDMA based network)

Almost all commercial wireless systems rely on GPS based timing to derive their master oscillator timing. This is done to synchronize all base station transmitters to the same exact frequency. Using the same timing source for all system transmitter sites keeps the receivers from heterodyning.

From Nextel to Cingular and Verizon, all of the wireless carriers use GPS to derive their master oscillator frequencies. If for some reason you notice that the time or occasionally the day and year are incorrect on your cell phone, there is a distinct possibility that the cell site that is serving you at the present time is experiencing technical difficulties.

If you make a call on that cell it is likely that your call will either fail prematurely or drop during the handoff process. Why you may ask? It’s because the cell that you originated on is off in timing from the rest of the cells in the network. For the network providers, it is imperative that these problems are identified immediately so that it does not become wide-spread and affect many customers.

During the first gulf war, and again during the Iraq conflict, the governmental agency that operates the GPS system intentionally injected an error into the timing algorithm. This error affected some systems and not others. When they intentionally caused the error, it only affected one of the satellites. If that was one of the satellites that were in view to your local “cell site” the timing got out of sync. This caused many lost calls because it did not affect all of the sites. The cell site with the timing problem becomes an "island" cell. You can;t originate and hand out of it, nor can you originate somewhere else and hand into the "island" cell site. The master oscillators at the local cell sites affected by the error needed to be reset, and everything cleared up.

A loss of a single satellite is relatively minor and this occurs occasionally for military exercises. The loss of many satellites can severely affect the performance of most of today’s state-of-the-art digital wireless communications systems.

Even one of my local townships uses VHF repeaters that use GPS synchronized transmitters to cover their public safety and police communications. Without the GPS timing these several transmitters are not locked to a common timing source. This immediately causes a constant whining noise as the free-running, un-stabilized oscillators even with their tightest tolerances will begin heterodyning. Can you imagine what this can do to today’s modern digital modulation systems.

 

[shaft]

Most telco's now days either wireless or wireline uses timing source from GPS which it gets its source from the master clock. I've never seen a total cell site lost just because it lost its timing source. What does happen is circuit errors which cause static, jitter, choppy audio and sometimes a call can be dropped, but your talking a severe timing mismatch. Theres too much redundancy involved to lose entire sites due to timing, but a single circuit loss does happen.

 

[N_Jay]

GPS is used for lots of things on different systems, and the loss of signal has different effects on each of those systems.

In addition to the loss of GPS signal you can have signal errors. Those symptoms are different.

Making broad based assumptions as to whether a particular event is significant or not to some unspecified systems, like all overly broad generalizations is more likely to be wrong than right.

Examples, CDMA uses GPS for critical timing to allow hand-offs to occur.
Simulcast uses GPS to align transmitter frequency reducing simulcast carrier beat issues.
Some (but not all) simulcast also used GPS timing for audio phase alignment.

Some systems are backed up with secondary GPS, others Rubidium, others, network generated time sources.

Each of these fails in different manner.

 

[poltergeisty]

NIST Internet Time Service clock



Why GPS? Use the lanline for sync.

Or WWV? :lol: My atomic clocks are matched to satellites...

I live 15 miles from WWV where the signal actually isn't as good as it would be father away.

 

[N_Jay]

NIST Internet Time Service clock



Why GPS? Use the lanline for sync.

Or WWV? :lol: My atomic clocks are matched to satellites...

I live 15 miles from WWV where the signal actually isn't as good as it would be father away.

You mean for radio/cellular networks?

Would be interesting but harder, more expensive, and less reliable.

 

[poltergeisty]

Have they always used GPS?

Oops, Never mind, AMPS doesn't need sync like CDMA.

Actually, be an interesting backup if its implemented.

 

[vabiro]

NIST Internet Time Service clock



Why GPS? Use the lanline for sync.

Or WWV? :lol: My atomic clocks are matched to satellites...

I live 15 miles from WWV where the signal actually isn't as good as it would be father away.

Probably due to network latency.

Routing on the Internet is not consistent. As a result the time that it takes to get from the time code source (NTP Server) to the NTP client will vary significantly.

GPS always has the same route.

Try pinging or doing a traceroute to time.nist.gov it will vary depending on demand, time of day, and network conditions. Additionally, it would make the site vulnerable to Denial of Service attacks that could wipe out a network.

Victor

 

[vabiro]

Have they always used GPS?

Oops, Never mind, AMPS doesn't need sync like CDMA.

Actually, be an interesting backup if its implemented.

When AMPS came on line GPS didn't exist. LORAN C was the standard we used for positioning. Big antennas, and big $

Victor

 

[N_Jay]

Probably due to network latency.

Among many other issues.

Routing on the Internet is not consistent.

Except that cell sites sit in private networks and not the Internet.

GPS always has the same route.

+/- multipath (Snicker)

Besides NTP did not exist when cellular was first deployed.

With systems like CDMA and most TDMA, the time synchronization issues are too strict for most network distributed or network generated time keeping systems.

For simulcast, the issue is more about a frequency reference not a time reference.
(yes, time references are used for the most recent generation of GPS synchronized simulcast systems, also)

 

[N467RX]

737-700's have FMC's.. What is you point?

Referring to 737-200's Might Janet be sht up a creek? :lol:

IDK, if all VOR's,etc will be removed, it would be prudent not to. Just my take, especially for Red Cross, etc transport.

...anyway, back to this "POS" GPS. :lol:

N467RX = Mexicana?

Yeah, Mexicana, but now flying with a different reg.

On a not-funnier sidenote, 4 VORs are out in Panama, and the Civil Aviation Authority dude claims that GPS is the future and those who are saying that the VORs shouldn't be turned off are still in the era of the telegraph, even though we are on the cellular phone era.

And I was like yeah.... and if the GPS fails what are u doing? no GPS and no VORs?

I'm glad he's getting replaced next month.

 

[poltergeisty]

+/- multipath (Snicker)

:lol:


..Or orbital drift, right? :lol:
Oops, WAAS would make up for that. Of course one of the component to WAAS is the space segment. So if you have a major satellite problem you wouldn't have WAAS either.

And I was like yeah.... and if the GPS fails what are u doing? no GPS and no VORs?

I'm glad he's getting replaced next month.

I'm with you on that one.

Plus, GPS takes the fun out of things. :lol:

 

[poltergeisty]

Probably due to network latency.

Routing on the Internet is not consistent. As a result the time that it takes to get from the time code source (NTP Server) to the NTP client will vary significantly.

GPS always has the same route.

Try pinging or doing a traceroute to time.nist.gov it will vary depending on demand, time of day, and network conditions. Additionally, it would make the site vulnerable to Denial of Service attacks that could wipe out a network.

Victor

Thought about this before I had made the post. But then I thought of orbital drift as well. :lol:

But sense they gave their own trunks, would it be an issue? For backup maybe, IDK.

Another thing that dawned on me about this. National Security. HEHE

I mean, what if a Bureaucrat can't call that special phone number? :lol:

 

[vabiro]

Thought about this before I had made the post. But then I thought of orbital drift as well. :lol:

But sense they gave their own trunks, would it be an issue? For backup maybe, IDK.

Another thing that dawned on me about this. National Security. HEHE

I mean, what if a Bureaucrat can't call that special phone number? :lol:

In the 3GPP architecture everything is migrating to IP, but the legacy network architecture is frame relay and SS7 signalling. There isn't a TCP/IP network for the NTP signalling.

The voice path is directly onto the PSTN at the site (most often), but is now being backhauled using VoIP so the carriers can route LD on their own backbone. One more way that they can charge you for something that doesn't cost them anything (i.e. call waiting, CLID, 3-way calling).

Having said that, the move to IP-based architecture would allow them to maintain their own NTP servers, and as long as they are on the same WAN then the latency and other network issues would probably be tollerated.

The change to 3GPP could eliminate GPS from the wireless network, but probably wont.

Victor

 

[N_Jay]

In the 3GPP architecture everything is migrating to IP, but the legacy network architecture is frame relay and SS7 signalling. There isn't a TCP/IP network for the NTP signalling.

The voice path is directly onto the PSTN at the site (most often), but is now being backhauled using VoIP so the carriers can route LD on their own backbone. One more way that they can charge you for something that doesn't cost them anything (i.e. call waiting, CLID, 3-way calling).

Having said that, the move to IP-based architecture would allow them to maintain their own NTP servers, and as long as they are on the same WAN then the latency and other network issues would probably be tollerated.

The change to 3GPP could eliminate GPS from the wireless network, but probably wont.

Victor

I still don't think that NTP is going to be good enough for CDMA (and CDMA derivative systems) to hand-off properly.

But I have not done the math.

 

[poltergeisty]

In the 3GPP architecture everything is migrating to IP, but the legacy network architecture is frame relay and SS7 signalling. There isn't a TCP/IP network for the NTP signalling.

The voice path is directly onto the PSTN at the site (most often), but is now being backhauled using VoIP so the carriers can route LD on their own backbone. One more way that they can charge you for something that doesn't cost them anything (i.e. call waiting, CLID, 3-way calling).

Having said that, the move to IP-based architecture would allow them to maintain their own NTP servers, and as long as they are on the same WAN then the latency and other network issues would probably be tollerated.

The change to 3GPP could eliminate GPS from the wireless network, but probably wont.

Victor

Is going IP mostly due to fiber being laid out all over?

 

[N_Jay]

Is going IP mostly due to fiber being laid out all over?

No, going IP, is because almost all networks are going IP.

The change occurs with the change to an LTE core network from a GSM/UMTS/HSDPA network.

 

[vabiro]

Is going IP mostly due to fiber being laid out all over?

The fibre helps, but is not the big factor. Much of backhaul and messaging is done over microwave, but some fibre is used. It all depends on the philosophy of the network engineers, and whether the carrier has access to cheap last mile connectivity.

The real driver for the move to IP started with 2.5G networks. A path to the switch for the IP traffic needed to exist. For just mobile data traffic this didn't need to be too big for 2.5G technologies.

That was a water shed moment for a lot of people that were telco people that had made the move to wireless. They had brought their paradigm into the wireless world and were now forced to take a hard look at why they were clinging to the old telco models.

About that time the carriers got out of the "Wireless PSTN" frame of mind and realised that IP was cheaper to route and switch. It would also accomodate their legacy switching cheaper than their current methods.

The 3GPP was formed by the GSMA and ITU and they knew that their core had to be IP-based. Virtually all future revenue on the wireless network was going to be from Internet access, and it was more cost effective to migrate everything in that direction.

Victor

 

[poltergeisty]

Very interesting! Thanks.

 

[dracer777]

GPS System Could Fail Next Year, Report Warns...

... and Y2K brought the world to a screeching halt, Nostradamus predicted 9/11, SARS killed everyone, and the world is ending in 2012.

Sooo... no gps?... I was gonna get a 396XT to assist me when the world starts to end in 2012... looks like ill be getting a none gps model... oh well...