Voice clarity on Vodacom

[leonb]

I know it is a bit off topic, but can anyone with the real facts please comment on this.

In the MTN EDGE forum:

http://www.mybroadband.co.za/vb/showthread.php?t=18350

[Edinetz]

Which real facts are you looking for - information about half rate or speculation about why half rate is being used.

Half rate is where one full rate channel is split into two half rate channels resulting in a decrease in voice quality but an increase in battery life. Enable the mobile operators to carry more calls at your expense.

[kvi]

... who cares so long as they dont slow my data transfer rate down....:)

[ScrnScrm]

half rate usage stems back to the whole 900/1800mhz frequency licensing debacle. basically, vodacom and mtn were not allowed to use the 1800mhz frequency band, and as the networks grew, their base stations started reaching capacity. to grow with the demand, they had no option but to switch the base stations to half rate so that they could carry more calls. (its on demand, so only switches to half rate when all time slots are full). Hence - during peak times, when the bse stations operate at half rate, you will notice poorer voice quality.
me thnks this has effected voda more than mtn simply because they have more subscribers.
the fix for this of course is UMTS networks (3g). its basically a totally seperate network, and can carry substantially more users than TDMA (GSM). me thinks that as more 3g handsets become available, combined with more 3g basestations, load on the gsm infrastructure will decrease and half rate connections will become a thing of the past.

going a bit off topic here - its interesting to note that some european operators have permanently set their base stations to half rate AFTER 3g rollouts, and are offering reduced call rates over this old infrastructure. wonder if our local networks are considering this... cheap (albeit poor quality) calls for the masses over already paid for infrastructure...

[ajax]

half rate usage stems back to the whole 900/1800mhz frequency licensing debacle. basically, vodacom and mtn were not allowed to use the 1800mhz frequency band, and as the networks grew, their base stations started reaching capacity. to grow with the demand, they had no option but to switch the base stations to half rate so that they could carry more calls. (its on demand, so only switches to half rate when all time slots are full). Hence - during peak times, when the bse stations operate at half rate, you will notice poorer voice quality.
me thnks this has effected voda more than mtn simply because they have more subscribers.


ScrnScrm, if I take your post literally, you typed "WERE not allowed". They are allowed now to use 1800 MHz, right? Everywhere I go nowadays I see on my Vodacom phone (with Netmonitor) 1800 MHz channels in use. So why then use half rate still? Have they not had time to switch the towers back?

Are data speeds in any way affected?

[ScrnScrm]

correct. i did say "were", as in past tense. Not sure how they got around it, but they can now use 1800mhz. maybe vodacom3g can comment on this?
my guess, and i must re-iterate, my GUESS, is that Vodacom piggy backed off the Cell C license for 1800mhz as part of their roaming agreement.
as for the half rate thing, i guess it still boils down to capacity issues. 1800mhz doesnt automatically add capacity. the key difference between 900 and 1800 is that 900mhz base stations can be spaced further apart, whereas 1800mhz is ideal for congested city/urban areas, where the base stations can be closer together. to add capacity, the networks still have to build additional base stations in an area to cater for the load. until this is done, capacity stays as is. i dont think we will see a massive addition of "legacy" gsm basestations now - the networks will rather be investing in UMTS (3G) networks where capacity is no longer a major issue. As users move to 3G, GSM will become a lot less congested negating the need for additional 1800mhz base stations.

as for data speeds - they are effected by congestion. each base station has 8 time slots, and when they are all full, data queues... the cell phone network is first and foremost a voice network!

if you need more info on how the whole data thing works, please search for some previous posts that i have made - i have explained it in detail elsewhere on this forum! not trying to shirk answering the question, but me fingers are getting a little tired :-)
or you can PM me. thinking of setting up a workshop in cape town sometime to explain the fundamentals of wireless technology for anyone that is interested.
later -

[vodacom3g]

Half rate is used in cells (900 or 1800) where there is such a load that with normal full rate, you would not be able to make a call.

Switching from full rate to half rate is automatic and transparent to the end user, i.e. when the cell gets congested it will automatically switch to half rate. As soon as congestion eases it will switch back.

Most people cannot tell the difference in voice quality between full rate and half rate, it's very subtle.

I personally have used handsets that give worse voice quality than halfrate cells on a good mobile.

[Edinetz]

Does this mean Vodacom network is completly congested? What is Vodacom doing about increasing capacity? 3G is going to do nothing as the old mobile is going to end up with a prepaid simm back on the network. During the day my mobile always goes into HR even in the suburbs. At home In the CBD after setting up a call I always get handed over to the same "congensted cell" and the voice quality is bad. I even took it in to be repaired but Nokia could find nothing wrong (according to the test printout they didn't test HR) Maybe its just bad radio planning where everybody is being handed over the same cell.

Previously you could disable the half rate codec but this is not possible anymore. Is this part of Vodacom certification process, that the software is not allowed to disable the HR codec?

[vodacom3g]

No, not at all. Capacity planning is done with extreme care and as soon as required, radios and transmission links are added to the network to ease congestion.

Edinetz, if you're interested, PM me, and I'll put you directly in contact with the radio planning guys in Cape Town. Sounds like you guys can have a constructive conversation.

[ScrnScrm]

Hi Edinetz - sure, oldhandsets will go back onto the market as prepaid, but call volumes will be a lot less. GSM is fast becoming "legacy" technology worldwide - 3g is gaining momentum. I think that you will see within a year most handsets on contract will be 3g capable - and contracts is where the bulk of the network's high volume usage is.
with regards to call voice quality - i have both vodacom and mtn (one is for work, one is for private) and i never have quality problems on either network in cape town or surrounding suburbs. now sandton is a different story... (although with 3g it has got a lot better!!!)