WG: Why TDM time slot time duration is 577us ??
in addition: Traffic Multiframe Structures - The 26 traffic multiframe structure is used to send information on the traffic channel. The 26 traffic multiframe structure is used to combine user data (traffic), slow control signaling (SACCH), and idle time period. The idle time period allows a mobile device to perform other necessary operations such as monitoring the radio signal strength level of a beacon channel from other cells. The time interval of a 26 frame traffic multiframe is 6 blocks of speech coder data (120 msec). (http://www.althos.com/tutorial/GSM-tutorial-frame-structure.html) one encoded speech block lasts 20ms. 576,92307692307692307692307692308us per slot 4615,3846153846153846153846153846 per 8 slots (1 frame) 120ms per 26 frames (6 speech blocks)
Hi Andreas, Thanks for the speedy reply. The link which sent you is definitely useful. But the very basic question I wanted to get a clarification was that, what is the drive behind selection of burst time to be 577us. For example the audio frequency can range upto 4Khz. The sampling frequency should be 8Khz. If each sample is of 8 bit accuracy. This lead to 64K bits of data. ...... If we explore further on these lines we should be able to correlate to the time 577us for each burst. I wanted some more info these lines. What was/were the drives behind selection of this burst time. Otherwise what are the other end requirements led to selection of this burst time and in turn TDMA frame hierarchy. Thanks, Nataraju A B On Fri, Jan 7, 2011 at 7:01 PM, Andreas.Eversberg < Andreas.Eversberg@versatel.de> wrote:
in addition:
Traffic Multiframe Structures - The 26 traffic multiframe structure is used to send information on the traffic channel. The 26 traffic multiframe structure is used to combine user data (traffic), slow control signaling (SACCH), and idle time period. The idle time period allows a mobile device to perform other necessary operations such as monitoring the radio signal strength level of a beacon channel from other cells. The time interval of a 26 frame traffic multiframe is 6 blocks of speech coder data (120 msec). (http://www.althos.com/tutorial/GSM-tutorial-frame-structure.html)
one encoded speech block lasts 20ms.
576,92307692307692307692307692308us per slot 4615,3846153846153846153846153846 per 8 slots (1 frame) 120ms per 26 frames (6 speech blocks)
-- Thanks, Nataraju A B
On 7-1-2011 14:51, Nataraju A B wrote:
Hi Andreas,
Thanks for the speedy reply. The link which sent you is definitely useful. But the very basic question I wanted to get a clarification was that, what is the drive behind selection of burst time to be 577us.
From what I remember, the timing was derived from ISDN.
Bit rate duration is determined from physical channel throughput for particular modulation schema. GMSK modulation is used with constant BT = 0.3, where B is the 3dB bandwidth of the theoretical Gaussian filter and T is duration of input data bit. Knowing B, we calculate 1/T = 1625/6 ksymb/s or approximately 270.833 ksymb/s. From here bit duration is 3.69.. μ s. Voice signal is processed in time intervals of 20ms = s/50. For that period of time throughput is [(1625/6) x (1000/50)] symbols. Because this number is fractional, let look at 6 times longer time interval. For time interval 120ms throughput is [1625 x 20] symbols or [13 x 125 x 20] symbols or [26 x 1250] symbols or [26 x 8 x 156.25] symbols.
Thanks for the useful info, Is there some reference doc which deals in details on this timings... ? 2011/1/8 Fadil Berisha <f.koliqi@gmail.com>
Bit rate duration is determined from physical channel throughput for particular modulation schema. GMSK modulation is used with constant BT = 0.3, where B is the 3dB bandwidth of the theoretical Gaussian filter and T is duration of input data bit. Knowing B, we calculate 1/T = 1625/6 ksymb/s or approximately 270.833 ksymb/s. From here bit duration is 3.69.. μ s.
Voice signal is processed in time intervals of 20ms = s/50. For that period of time throughput is [(1625/6) x (1000/50)] symbols. Because this number is fractional, let look at 6 times longer time interval. For time interval 120ms throughput is [1625 x 20] symbols or [13 x 125 x 20] symbols or [26 x 1250] symbols or [26 x 8 x 156.25] symbols.
From last result we can identify: Number of symbols in a burst = 156.25 symbols, and burst time 156.25 x 3.69... = 576,92μs Number of symbols in TDMA frame is 8 x 156.25 = 1250 symbols, Number of symbols in Multiframe is 26 x 1250 symbols.
On Fri, Jan 7, 2011 at 8:51 AM, Nataraju A B <natarajuab.tech@gmail.com> wrote:
Hi Andreas, Thanks for the speedy reply. The link which sent you is definitely useful. But the very basic question
I wanted to get a clarification was that, what is the drive behind selection of burst time to be 577us.
For example the audio frequency can range upto 4Khz. The sampling frequency should be 8Khz. If each sample is of 8 bit accuracy. This lead to 64K bits of data. ...... If we explore further on these lines we should be able to correlate to the time 577us for each burst. I wanted some more info these lines. What was/were the drives behind selection of this burst time. Otherwise what are the other end requirements led to selection of this burst time and in turn TDMA frame hierarchy. Thanks, Nataraju A B On Fri, Jan 7, 2011 at 7:01 PM, Andreas.Eversberg < Andreas.Eversberg@versatel.de> wrote:
in addition:
Traffic Multiframe Structures - The 26 traffic multiframe structure is used to send information on the traffic channel. The 26 traffic multiframe structure is used to combine user data (traffic), slow control signaling (SACCH), and idle time period. The idle time period allows a mobile device to perform other necessary operations such as monitoring the radio signal strength level of a beacon channel from other cells. The time interval of a 26 frame traffic multiframe is 6 blocks of speech coder data (120 msec). (http://www.althos.com/tutorial/GSM-tutorial-frame-structure.html)
one encoded speech block lasts 20ms.
576,92307692307692307692307692308us per slot 4615,3846153846153846153846153846 per 8 slots (1 frame) 120ms per 26 frames (6 speech blocks)
-- Thanks, Nataraju A B
-- Thanks, Nataraju A B
participants (4)
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Andreas.Eversberg -
Fadil Berisha -
Nataraju A B -
Nordin