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## Traffic Calculation - Yola

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Traffic Calculation

For this we have to define some parameters1. Erlang2. GOS3. TCH4.SDCCH5. Site Type
Erlang
AnErlangis a unit ofGSMtrafficmeasurement.an Erlang represents the continuous use of one voicepath.it is used to describe the total traffic volume of one hour.
GOS means Grade of serviceprobability of call blocking, probability of callfailure.2% blocking means 2 calls could be blocked out of 100.
TCH
TCH stands for traffic channelThe traffic channel carries speech or data information. The different types of trafficchannel are listed below:Full rateTCH/FS: Speech (13 kbit/s net, 22.8 kbit/s gross)TCH/EFR: Speech (12.2 kbit/s net, 22.8 kbit/s gross)TCH/F9.6: 9.6 kbit/s – dataTCH/F4.8: 4.8 kbit/s – dataTCH/F2.4 2.4 kbit/s – dataHalf rateTCH/HS: speech (6.5 kbit/s net, 11.4 kbit/s gross)TCH/H4.8 4.8 kbit/s – dataTCH/H2.4 2.4 kbit/s –data
SDCCH
It is also a traffic channel namedStand-alone DedicatedControl Channel.Itsupports the transferof Datato and from the MS during call setup and validation.
Site Types
We will consider here two types of sites.Type 2 siteType 4 siteIn case of Type2 sites we have only 900 band.Each sector have 2 TRX’S means total 6 TRX’s of 3 sectors of a site.In case of Type4 sites we have 900 and 1800 bands both. Each sector have 4 TRX’s means total 12 TRX’s of 3 sectors of a site.
Procedure For Type2(900 only) sites
For one sector we haveTotal no’s of TRX = 2Which implies TS = 16From 16 TS one is used for BCCH, then we left 15 TS.GOS = .02 or 2%Using erlang Calculator we got 9 erlang traffic.As we know total traffic allowed/ subscriber is 15merlang. So we can calculate total number of subscriber/sector.Divide the total erlang i.e. 9erlang/ 15m erlang = 600 subsNow for all sectors we have 27 erlang traffic and 1800 subs.To calculate the actual trafficActual traffic = total – SDCCH usageSDCCH traffic = 1800 *3.56 m erlang= 6.408 erlangSo actual traffic = 27 – 6.408 = 20.59 erlang
Procedure ForType4(900 and 1800) sites
For one sector we haveTotal no’s of TRX = 4Which implies TS = 32From 32 TS one is used for BCCH, then we left 30 TS.GOS = .02 or 2%Using erlang Calculator we got 21.9 erlang traffic.As we know total traffic allowed/ subscriber is 15merlang. So we can calculate total number of subscriber/sector.Divide the total erlangi.e21.9erlang/ 15m erlang = 1460 subsNow for all sectors we have 65.7 erlang traffic and 4380 subs.To calculate the actual trafficActual traffic = total – SDCCH usageSDCCH traffic = 4380 *2*3.56 m erlang= 31.185 erlangSo actual traffic = 65.7 – 31.185 = 34.515 erlang

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