EDGE Dropping

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mc721221

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My connection has dropped 7 times today (between 09:00 and 14:30)

Anybody else?
 
if someone tries to make a voice call and there aren't enough channels available, data channels are dropped and given to the person trying to make a voice call. you can contact MTN and ask for a dedicated channels...
 
Can you tell is more about dedicated channels? Costs? who to contact? speed? etc?
 
andres101 said:
if someone tries to make a voice call and there aren't enough channels available, data channels are dropped and given to the person trying to make a voice call. you can contact MTN and ask for a dedicated channels...
Click to expand...

Are you sure about that Andres101?
AFAIK the only dedicated data channels are CSD or HSCSD, but for that you pay normal voice (per minute) rates as long as you are connected.
Can you elaborate?
 
you cant get dedicated timeslots afaik on grps. there are 8 time slots per base station, of which 4 are provisioned for grps as well. ajax is correct - when all 8 time slots are being used for voice calls, data is placed on hold.
 
Please note that I am not an expert!! I mearly work in a GSM related field that uses these GSM technologies.

I am 99% sure.

A cell tower has a limited number of "channels" or "time slots" (see TDMA [edit]also see CDMA[/edit]). I think the limit is 200. When making a voice call or a CSD call, a channel (or maybe more) is used. When making a HSCSD call, up to 4 channels are used (in SA, I think). GPRS also uses channels, not sure how many. EDGE is GPRS but with more channels assigned to you.

More channels = more bandwidth

MTN makes much more from voice calls than they do from GPRS/EDGE, so they set the priority of voice calls higher. When you're surfing on a overloaded tower and someone tries to make a voice call, they take your channel and give it to the person making the voice call... aka "dropped connection"

MTN can dedicate GPRS/EDGE channels to you. You have to justify it by giving them the avg number of bytes transferred daily, peak time, tower, ...
 
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Yes, for CSD you pay normal rates. Same goes for HSCSD, but you have to actually register for it if you want to connect to MTN's "internet modem bank" (083123DATA).
 
mc721221, I think your best bet is to contact your MTN Service Provider.

If that fails, you could try to contact support at mtnns dot net.

Not sure about cost, but I don't think they will charge you if you can justify reserving the channel. If you use enough bandwidth, I think they will do it for you.
 
andres101 said:
A cell tower has a limited number of "channels" or "time slots"

I think the limit is 200.

GPRS also uses channels, not sure how many.

EDGE is GPRS but with more channels assigned to you.

More channels = more bandwidth

MTN can dedicate GPRS/EDGE channels to you. You have to justify it by giving them the avg number of bytes transferred daily, peak time, tower, ...
Click to expand...

Hi
Channels and time slots are not the same thing. Time Slots are contained within a channel.

GPRS uses 1 channel, and up to 4 time slots depending on the class of device. Class 10 devices support up to 4 time slots for download.

EDGE is not GPRS with more channels assigned. EDGE uses the same amount of time slots, but the time slots use a different modulation scheme that in effect allows 3 bits to be sent over the air at once as opposed to GPRS's one. This results in 3 times the throughput of GPRS on an equivalent coding/modulation scheme. Eg. On coding Scheme 4, which allows approx 20kbps, EDGE give you apprx 60Kbps on the equivelant EDGE modulation (MCS9).
More timeslots - more bandwidth. (but again, depending on the class of device - some devices only support 2 or 3 download time slots)

If a cell carrier were to dedicate a time slot for you, it would in effect drastically reduce the capacity of the base station. Eg. If you require 236Kbps, they would need to reserver 4 time slots for you. I dont ever see this happening as it is equivalent to half the slots on the channel!

Hope this helps -
 
ScrnScrm, thanks for the info... like I said, I'm no expert. Sounds like you are though?!? Do you work for MTN/... or is this general knowledge to you?

I know for a fact you can reserve channels OR slots OR something that will ensure that you always get maximum thoughput when you connect to GPRS / EDGE.
 
nah, don't work for any of the cell carriers, but i know the technology very well...

wrt reserving channels - are you not getting confused with a dedicated APN with a Quality of Service for MPLS on the backhaul network? That is the only guarantee u will get from the cell networks - but it doesnt apply to the time slots. those are still best effort depending on capacity...
 
ScrnScrm, thanks for that info, all is now clear in my mind. I now realize what I knew about channels and time slots was dangerous
 
The Cellular standards allow for bumping, but that is very much from a voice perspective. ie... if implemented of course...

The president could bump an ambulance which could in turn bump a normal user making a voice call. it is my assumption that this is passed for GPRS/EDGE data as well, but I haven't the time to check it up on the GRPS documentation.

This is coded onto the sim card and if the base supports it is allowed to drop lower priority call for higher ones. this excert is from ETSI standard (GSM 11.11 version 8.3.0 Release 1999)

10.3.24 EFeMLPP (enhanced Multi Level Pre-emption and Priority)
This EF contains information about priority levels and fast call set-up conditions for the enhanced Multi Level Preemption
and Priority service that which can be used by the subscriber.
Identifier: '6FB5' Structure: transparent Optional
File size: 2 bytes Update activity: low
Access Conditions:
READ CHV1
UPDATE ADM
INVALIDATE ADM
REHABILITATE ADM
Bytes Description M/O Length
1 Priority levels M 1 byte
2 Fast call set-up conditions M 1 byte
- Priority levels
Contents: The eMLPP priority levels subscribed to.
Coding: Each eMLPP priority level is coded on one bit. Priority levels subscribed to have their corresponding
bits set to 1. Priority levels not subscribed to have their corresponding bits set to 0. Bit b8 is reserved and set
to 0.
 
ScrnScrm, I am sure that it is on the base station that they reserve capacity for you.

MTN does implement "priority levels". You can get an premium SIM which will give you voice priority over anyone else.
 
Just thought you'd like to know that GSM 900 has a total of 125 Channels with 8 timeslots per channel.

MTN use 55 of these channels. Therefore theorectically you can have 440 calls at the same time. If you use half rate for voice, you can effectively double the number of calls at a time to 880.
 
ScrnScrm said:
maybe mtnbb can comment here then?
Click to expand...

Thanks ScrnScrm

First - about dropping the connection on EDGE:

This is not normal or common. I can see from the radius logs that some users have been connected for a couple of days.

To resolve this we need to know the radio location, device used, software version of device, application running etc. Best to drop me a private mail.

I will give some background about timeslot allocations in a new thread called Timeslots. I hope that is helpful.
 
correct crash. but not all base stations have all the channels active on them - the frequencies would clash with neighboring cells... And when you initiate your GPRS connection, you only use one channel. i suppose at the end of the day it all depends on distance between base stations (the closer the base stations, the less channels will be active on that base station to avoid conflicts with neighbors). again - i think that mtnbb should comment on the reservation of channels. afaik, it doesnt happen. the only priority that is given is to 112 calls.
One other thing to bear in mind is the backhaul switching network...
 
ScrnScrm said:
correct crash. but not all base stations have all the channels active on them - the frequencies would clash with neighboring cells... And when you initiate your GPRS connection, you only use one channel. i suppose at the end of the day it all depends on distance between base stations (the closer the base stations, the less channels will be active on that base station to avoid conflicts with neighbors). again - i think that mtnbb should comment on the reservation of channels. afaik, it doesnt happen. the only priority that is given is to 112 calls.
One other thing to bear in mind is the backhaul switching network...
Click to expand...

I did discuss most of these issues in a new thread called timeslots. I hope it answers most queries.
 
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