"Raqueeb Hassan" <wideangle@[EMAIL PROTECTED]
> wrote in message
news:1150297865.356668.204420@[EMAIL PROTECTED]
> Hi,
>
> I have been using EDGE for sometimes here in Bangladesh with Siemens
> MC75 EDGE card which claims to have a maximum bit rate of 474 kbps
> compared to GPRS with 171 kbps. I've been using Nokia GPRS phone
> before this EDGE card.
Where did you find this claim?
Siemens' webpage
(http://www.siemens.com/index.jsp?sdc_p=ft15mls4u1436o1299267i1300522pWMENcz2&sdc_bcpath=1300522.s_4,&sdc_sid=26181128089&)
states the following:
"Thanks to EDGE, users can easily conduct their business activities on the
Internet or on the company intranet using their smartphone, PDA or laptop
PC - in fact, this can be done three times faster than when using GPRS;
EDGE
theoretically has a maximum bit rate of 474 kbps compared to GPRS with 171
kbps."
(I don't know where they got the 474 kbps from...)
and further down "The main features of the MC75 include: ... EDGE (E-GPRS)
Multislot Class 10 ".
With simple calculation (and knowing that multislot class 10 means max 4.
slots downlink, max. 2 slots uplink, and maximum sum of timeslots is 5 at
any given moment), we get the following maximum speeds (with 8-PSK MCS9)
for
this Siemens device :
downlink : 59,2 kbps/timeslot * 4 timeslots = 236,8 kbps
uplink : 59,2 kpbs/timeslot * 2 timeslots = 118,4 kbps
>
> Yes, GSM can deliver 14.4 CS data on a single slot. Which turns out to
> be maximum of 64 kbit/s. So, in real life scenario it should be often
> 3*14.4 kbit/s (43.2) or at most 4*14.4 kbit/s (57.6).
> As someone mentioned in the newsgroup, Nokia GPRS phones, those are
> limited to 3
> downlink CS slots in most of the networks - even if the model sup****ted
> more slots with GPRS. When it comes to downlink speed, it provides
> maximum of 3*14.4 or 43.2 kbit/s. Since the data is checksummed, what
> would be the actual payload?
How come do you mix between CS data and GPRS/EGPRS? Here are the facts:
- most Nokia models suppot HSCSD (High-Speed Circuit-Switched Data), i.e.
multislot connections for CS data with multislot class 6 (max. 3 slots
downlink, max. 2 slots uplink, max. 4 simultaneous timeslots).
- Siemens MC75 only sup****ts CS data with 1 timeslot
- Siemens MC75 sup****ts EGPRS multislot class 10, and GPRS multislot class
12 (max 4 timeslots, max 4 uplink timeslots, with extended dynamic
allocation or fixed allocation - I don't know for sure which, but fixed
allocation is not sup****ted by any live networks out there!)
- most Nokia phones sup****t EGPRS and GPRS multislot class 10.
>
> As I understand, getting 474 kbps would be a dream when there's
> bottleneck with Internet gateway at EDGE provider. Does that mean that
> this speed will remain when I try connecting local networks, i.e.
> cor****ate networks?
>
Well, I don't know about the gateway but as described above, the maximum
bitrates achievable over the radio interface with EGPRS multislot class 10
are what were described above (downlink 236,8 bkps ; uplink 118,4 kbps).
Also, bear in mind that the maximum bitrates possible over the radio
interface are far and distant from what is the real case, especially when
looking from the application level and also depending on the distance to
the
basestation and the amount of traffic in the network.
Actually, this point alone would merit for a lenghty discussion, but
typically e.g. throughput "over" TCP protocol depends on bandwidth,
latency
and packet loss. When considering this, it is im****tant to realise that
even
with significant increase in bandwidth, the overall throughput gains are
moderate if the latency of the system is high - as it is in GPRS/EDGE.
Therefore, increasing bandwidth without improvements to (read: reduction
of)
latency (or round-trip-time, if you will) is a game of dimini****ng
returns.
Improvements to GPRS/EGPRS in terms of latency have been standardised, but
many of them require sup****t from both the network and the mobile device.
I
do not know whether the network you are using in Bangladesh sup****ts these
enhancements (most im****tantly, the extended uplink TBF mode ; delayed
downlink TBF release is likely sup****ted, as it works with all GPRS and
EGPRS -capable terminals), and also I can't say this for the Siemens card
in
question (the data sheet states that the card is GSM release 99, which
suggest the extended uplink TBF mode is not sup****ted as it is a GSM Rel-4
*) feature ; *) Rel-4 comes after R99). What I do know is that most
(relatively new, e.g. models introduced to the markets in 2005 or later)
Nokia EGPRS-capable devices do sup****t these enhancements.
I'm not saying all this in order to bash or advertise anything, I'm just
trying to say that Internet rumors and speculations may be just that -
rumors and speculation.
> How would I know the number time-slots allotted to this device from my
> EDGE provider?
You don't, unless you have a network monitor or other engineering tools at
your disposal.
Besides, the amount of timeslots does not directly equal to the available
data throughput due to the fact that in GPRS/EGPRS the radio resources
(i.e.
timeslots) can be shared between several mobile stations. Therefore, e.g.
having 2 timeslots for one mobile may actually result in faster connection
speed than having 4 timeslots allocated but shared with some other
mobiles.
> Can providers limit number of time slots to the devices
> used?
Depends, but chances are that the radio network sup****ts multislot class
operation (up to multislot class x), but depending on traffic conditions ,
the negotiated QoS parameters for the packet data traffic, and the quality
of the radio connection, the amount of allocated timeslots and used
(modulation &) coding scheme is continuously changed.
> Is that true that providers configure their network to knock-off
> the data service when voice calls are prioritized to use more
> bandwidth?
In most cases, yes. This is logical as users require certain (low)
blocking
rates for CS connections - and would be very dissatisfied if more call
attempts would be blocked. Also, speech calls may bring more profit to the
operator than packet data services.
> Shouldn't be they using some threshold levels for data
> service?
>
Which thresholds are those?
> Thanks in advance for any pointer.
>
You're welcome.
>
> --
> Raqueeb Hassan
> Bangladesh
>
Antti
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