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Nataraju A B natarajuab.tech at gmail.comThanks for the useful info, Is there some reference doc which deals in details on this timings... ? 2011/1/8 Fadil Berisha <f.koliqi at 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 at 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 at 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/openbsc/attachments/20110109/102c5b2b/attachment.htm>