Mobile phone range offshore

[gogecko]

How far out will a standard GSM mobile phone work? For the Gold Coast area, will it work 2 miles out? Further? I assume it wont work at 24s, and yes, I have a VHF on order, but it wont be here for 2 weeks. Just curious as to the range, because I couldnt find any old threads on this. Is range better East of Surfers than North of the seaway?

regards
Andrew

[Cruiser]

Theoretically, a GSM phone has a maximum range of 35km from a base station. This limit is applied by the system due to timing issues (prevents a call in one timeslot from interfering with the adjacent timeslots). On land, this limit is not realised due to terrain blocking the signal but they have more bases to cover that. However, at sea (or in the air) you should be able to get close to the 35km although you can get some interference if you are getting strong signals from multiple base stations. This is because every second base re-uses the same frequencies but are normally blocked from interference due to terrain. Out at sea you could get good signal from 4 or 5 base stations (which is a bad thing).

I know a GSM won't work at the Barwons (45km out) but you should get 30km or so out from the Gold Coast. Anyone had more practical experience?

A CDMA phone will get you a bit further out.

Chris.

[Mantaray]

Theoretically, a GSM phone has a maximum range of 35km from a base station. This limit is applied by the system due to timing issues (prevents a call in one timeslot from interfering with the adjacent timeslots). On land, this limit is not realised due to terrain blocking the signal but they have more bases to cover that. However, at sea (or in the air) you should be able to get close to the 35km although you can get some interference if you are getting strong signals from multiple base stations. This is because every second base re-uses the same frequencies but are normally blocked from interference due to terrain. Out at sea you could get good signal from 4 or 5 base stations (which is a bad thing).

I know a GSM won't work at the Barwons (45km out) but you should get 30km or so out from the Gold Coast. Anyone had more practical experience?

A CDMA phone will get you a bit further out.

Chris.

Now not many would know the 35km GSM limit is a system "restriction"

CDMA will go the distance but CDMA won't see much past 2008 eventhough there is money going into upgrading CDMA, yes announce CDMA is getting the chop, then upgrade it before it gets the chop! makes a lot of sense doesn't it?

[adamleah]

Andrew ,

I have been onboard foxys rig "DFox" and when nearing 100km offshore he still has range on his mobile ..
He has installed a large aerial that mounts on the cabin that allows such distances... I think he mentioned that one of his pro mates up North gets even huger coverage from these such aerials...

He is on holidays at the moment so if you want further info. you better PM him ..

Cheers

Adam

[bay_firey]

Mantaray

the 35km is not a "restriction" bit a "limitation"

The system is not restricted by anybody or thing but IS limited by the technology

GSM call switching is a time based system and that is what limits the range.

CDMA - CODE DEVISION MULTIPLE ACCESS - is a different switching system not reliant on time, which in theory (theory not practice) with a powerfull enough transmitter and pretty much line of sight to a base station/repeater/cell (call it what you will) you could expect well in excess of the 100km metioned above.

BUT all must be just right to achieve this. Including the fact that Telstra position and aim the antenna's toward the majority of the population - on dry land.

With an antenna at sea it is not uncommon to achieve 100km but the signal does drop off pretty quick after that.

[Mantaray]

restriction / limitation has the same result doesn't it, don't work and it is quite canny how it knows the difference between 35km and 36km ? now CDMA as you mentioned is something quite different but then it is on its way out in favour of 3gsm

[Cruiser]

Mantaray,

Just by way of explanation... GSM mobiles use TDMA (Time Division Multiple Access) which means each call occupies a particular time slot in a particular frequency and is not allowed to stray into adjacent timeslots. To prevent this the system instructs the handset to adjust exactly when to transmit it's timeslot to compensate for the distance it is away from the base station (the signals travel at close to the speed of light). The handset will send it's data in advance of the start of the timeslot by an amount proportional to the distance. However, it can't determine this distance until a call is already established so it reserves a special timeslot for the purpose of establishing calls. Your mobile will attempt to connect with the base by sending a short message (not a whole timeslot) at the start of this special timeslot. If the message arrives at the base station prior to the end of that timeslot then it will be accepted. However, if the message arrives in the neighbouring timeslot it will be ignored and the call won't proceed. The timeslot length multiplied by the speed of light comes out at 35km. So (assuming sufficient radio signal strength) up to 35km will work fine but 36km won't work at all as the base can't "see" the connect message. No amount of bumping up power or raising antenna heights or gains will overcome this issue with GSM.

The telco's could have used a concept called "extended cell" whereby every 2nd timeslot is not used and the range could have been doubled to a theoretical 70km. But this would have halved the call capacity of each base station - so guess what?

Probably more than you wanted to know but there you are.

From what I understand 3G should have similar range to CDMA and is not restricted to this 35km limit.

Regards,
Chris.

[DaneCross]

I've had mobile reception on the 24s. We were at the limit the other week when we were (at a guess) 20km due east of the Jumpinpin Bar. Reception was dropping in/out. SMS will go better when you're low on coverage.
DC