4 ms·

i know in Ireland, most of our Unlimited providers have a limit of 45000 min a month... which is grand, given there are only 44640 min in a normal 31 day month.

i know in Ireland, most of our Unlimited providers have a limit of 45000 min a month... which is grand, given there are only 44640 min in a normal 31 day month... but GSM is a lot more limited in bandwidth than standard POTS: old GSM Modems would top out at 9.6kbps, with some having a 14.4kbps option... it wasnt till GPRS that you got faster speeds (packet switched, not Modem).

jsjohnst 7y ago
> old GSM Modems would top out at 9.6kbps, with some having a 14.4kbps option Uhm, you are off on your numbers. GSM channel size is 200khz, but TDMA is used on top of that only leaving ~20khz for voice traffic (remember analog modems are “voice” traffic). So naively one might assume since 14,400 is under 20,000, it would be theoretically possible to achieve, but that’s not true in reality due to losses in the digital to analog to digital conversion due to noise. In the case of POTS, which has a max channel size of 64k, the theoretical maximum is roughly 38k (the reason 56k modems worked is due to the removal of the ADC conversion on the ISP side). Using a similar conversion for GSM, that gives you a theoretical maximum of 12k. If nothing else was a factor, then 9600 would be doable, but due to other issues with GSM, the real world experience usually was closer to 2400, sometimes getting 9.6k when everything was working great. Source: I owned a dialup ISP in the 90s and routinely logged in from remote to manage user accounts from my 386 Thinkpad connected to a GSM phone. After selling the ISP, I worked for multiple years in the telco field, on the RBOC side (Southwestern Bell and later SBC), the cell carrier side (Voicestream and later T-mobile), and LDDS side (MCI and later MCI Worldcom).
jsjohnst 7y ago
> it wasnt till GPRS that you got faster speeds Forgot to mention, GPRS uses the same time slots as voice calls do over GSM. Each time slot is still limited to about 9.6k useable data rate as with using a modem, but GPRS allows bonding to use more than one time slot. As such, using three time slots would get you 28.8k, using six gets you 57.6k, etc.
- tiernano 7y ago
  both comments are very handy to know! thanks. i remember trying to get internet access on my Nokia 7650 back in the day, and been given HSDCA and GPRS as options... larger downloads usually worked out cheaper on HSDCA (it was charged per min, no bandwidth limit, bar the standard limits) but GPRS worked out handier for "browsing" which, back then, was not standard either... big difference between now and then...
  - jsjohnst 7y ago
    Back when I had an ISP in the mid 90s, I felt like I was king of the world as I had a T1 going to my place (as I only had to pay for the local loop, bandwidth was “free” by owning the ISP). My dream back then was to have those speeds everywhere I went. Fast forward 25 years and my watch can get 20x that speed even in a random rural area.

jsjohnst 7y ago

> old GSM Modems would top out at 9.6kbps, with some having a 14.4kbps option Uhm, you are off on your numbers. GSM channel size is 200khz, but TDMA is used on top of that only leaving ~20khz for voice traffic (remember analog modems are “voice” traffic). So naively one might assume since 14,400 is under 20,000, it would be theoretically possible to achieve, but that’s not true in reality due to losses in the digital to analog to digital conversion due to noise. In the case of POTS, which has a max channel size of 64k, the theoretical maximum is roughly 38k (the reason 56k modems worked is due to the removal of the ADC conversion on the ISP side). Using a similar conversion for GSM, that gives you a theoretical maximum of 12k. If nothing else was a factor, then 9600 would be doable, but due to other issues with GSM, the real world experience usually was closer to 2400, sometimes getting 9.6k when everything was working great. Source: I owned a dialup ISP in the 90s and routinely logged in from remote to manage user accounts from my 386 Thinkpad connected to a GSM phone. After selling the ISP, I worked for multiple years in the telco field, on the RBOC side (Southwestern Bell and later SBC), the cell carrier side (Voicestream and later T-mobile), and LDDS side (MCI and later MCI Worldcom).

jsjohnst 7y ago

> it wasnt till GPRS that you got faster speeds Forgot to mention, GPRS uses the same time slots as voice calls do over GSM. Each time slot is still limited to about 9.6k useable data rate as with using a modem, but GPRS allows bonding to use more than one time slot. As such, using three time slots would get you 28.8k, using six gets you 57.6k, etc.

tiernano 7y ago
both comments are very handy to know! thanks. i remember trying to get internet access on my Nokia 7650 back in the day, and been given HSDCA and GPRS as options... larger downloads usually worked out cheaper on HSDCA (it was charged per min, no bandwidth limit, bar the standard limits) but GPRS worked out handier for "browsing" which, back then, was not standard either... big difference between now and then...
- jsjohnst 7y ago
  Back when I had an ISP in the mid 90s, I felt like I was king of the world as I had a T1 going to my place (as I only had to pay for the local loop, bandwidth was “free” by owning the ISP). My dream back then was to have those speeds everywhere I went. Fast forward 25 years and my watch can get 20x that speed even in a random rural area.