Slide môn Mạng Giảng viên Đỗ Trọng Tuấn
-
Upload
nguyen-duy-cong -
Category
Documents
-
view
230 -
download
0
Transcript of Slide môn Mạng Giảng viên Đỗ Trọng Tuấn
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
1/20
1
1. Mt s khi nim
Tnh ton dung lng
trong mng GSM
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
2/20
2
Khi nim lu lng
Lu lng - traffic:
L thng tin (ngi s dng/bo hiu) mang trncc knh truyn dn
Lu lng gi bn (Busy hour traffic):
Thi gian chim knh trong gi bnA = C*t/T = C*t/3600
[Erlangs = (Calls/busy hour)*(mean call holding time) ]
Trong : A: lu lng [Erl]C: s cuc gi trong gi bn
t: thi gian trung bnh ca mt cuc gi (s)
T: thi gian kho st = 1h = 3600 s
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
3/20
3
Gi bn B.H - Busy Hour
B.H l gi c lu lng trao i qua cc knh ln nht trong ngy v
c xc nh theo s liu thng k.(Busy hour is that continuous 60 minutes time span of the day during
which the highest usage occurs).
Note:
may not occur at the same time every day
weekly variation
week day /weekend variation
seasonal variation
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
4/20
4
V d
Cho bit ti lu lng ca MS l bao nhiu khi thu bao di ng
tin hnh 2 cuc gi trong gi bn vi thi gian trung bnhl 90 s.
Ti lu lng Lu lng gi bn (Busy hour traffic):
A = C*t/T = C*t/3600 = 2*90/3600 = 50 mErl
ngha: thi gian chim knh ti gi bn ca MS l 180 s
tng ng vi ti lu lng 50 mErl
Thi gian trung bnh 1 cuc gi ca MS trong gi bn khong50 s90 s
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
5/20
5
Traffic Density / Intensity
Mt lu lng - Traffic Density is defined as the number
of simultaneous calls at a given moment.
Cng lu lng - Traffic Intensity represents the
average traffic density (occupancy) during any one hour
period.
Chim knh- occupancy is any use of of a traffic resource
regardless of whether or not a connection (call) is completed.
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
6/20
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
7/207
Quan h gia cc loi lu lng
Thit lp cuc gi
(knh bo hiu)
Knh
lu lng
Ao
Ab
Ac= Ao Ac
Ab
Ao= Ac+ Ab
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
8/208
Cp dch v GoS (Grade of Service)
Khi nim:GoS l thng s nh gi xc sut lu lngnghn (Ab) i vi mt s knh xc nh:
GoS = Ab/ Ao
Quan h gia lu lng v cp dch v GoS:Ab= GoS * Ao
Ac= (1 - GoS) * Ao
Gi tr GoS in hnh ca mng PLMN = 2%
-> lu lng nghn = 2% ; lu lng thc hin = 98%
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
9/209
Quan h gia lu lng v GoS
Thit lp cuc gi
(knh bo hiu)
Knh
lu lng
Ao
Ab
Ac= Ao Ac
Ab
A
c= f(Ao) = ?
Ac= (1-GoS)Ao = (1-GoS)*(1-GoS)*Ao
GoS GoS
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
10/2010
Loss and Delay Systems
H thng tn tht- A Loss System is one in which a callattempt is rejected when there is no idle resource to serve
the call. (GSM system)
Blocked callscuc gi b nghn
Resource = signalling channels + traffic channels
H thng tr- A Delay System is one in which call
attempts are held in a waiting queue until resource are
available to serve the calls.
Delayed calls
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
11/2011
M hnh Erlang B
L m hnh h thng thng tin theo kiu tn tht.
M hnh Erlang B c s dng tnh ton dung lng cho mng
thng tin di ng GSM.
Bng Erlang B: tra cu thng s theo m hnh Erlang B
* Th hin mi quan h gia 3 i lng:- S knh c s dng N
- Cp dch v GoS
- Lu lng yu cu Ao
* Khi bit 2 thng s => tra cu thng s th 3
[*] V d:
Hy xc nh lu lng thc hin ca 6 knh c GoS = 2%
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
12/2012
Bng Erlang B
Ao = 2,2759 Erl
Ac = (1-GoS)Ao = (1 - 0,02)*2,2759 = 2,2304 (Erl)
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
13/2013
Hiu sut s dng knh
Khi nim: L t s gia lu lng p ng v s knh
c s dng:
= Ac*100/ N (%)
Vi v d trn: N = 6, GoS = 2% ; Ac = 2,2304 Erl
= Ac/ N = 2,2304*100/6 = 37%
= ? Khi GoS = 10%
= Ac/ N = 3,3826*100/6 = 56%
Nhn xt: Hiu sut s dng knh thp -> xc sut nghn
nh -> GoS nh -> cht lng tt.
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
14/2014
2. Tnh ton vng ph sng
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
15/2015
Bi ton
Cn quy hoch vng ph sng cho th trn C, s dng cng ngh
GSM900, dng 3 cp tn s cho mi cell vi cu hnh cp pht knh
bo hiu chun. Yu cu GoS = 2% vi mc lu lng d on c
th hin nh hnh v. Gi thit mi thu bao tin hnh 2 cuc gi
trong gi bn vi thi gian trung bnh ca mt cuc gi l 90 s.[*] Hy xc nh:
- Lu lng gi bn d kin trn 1 km2
- Dung lng ca 1 cell.
- Bn knh cc i ca cell (din tch cell hnh lc gic S = 2,6 R2)
- S cell cn thit ph sng cho c th trn C.
- Lp li cc php tnh trn khi cp pht 4 tn s cho mi cell.
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
16/2016
Mc lu lng d on th trn C
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
17/2017
Li gii
1. T hnh v ta c MS tch cc trong B.H l: 40 MS/km2
- Ti lu lng ca 1 MS l A = 2*90/3600 = 0,05 (Erl) Lu lng d kin trn 1 km2 trong gi bn l:
40 MS/km2* 0,05 Erl/MS = 2 Erl/km2
2. Mi cell c cp pht 3 cp tn s, s dng cu hnhknh bo hiu chun ti C0 , nh sau:
TS1TS0 TS3TS2 TS5TS4 TS7TS6
BCCH/CCCH SDCCH/8 TCH
TS1TS0 TS3TS2 TS5TS4 TS7TS6
TS1TS0 TS3TS2 TS5TS4 TS7TS6
RFC1
RFC2
RFC3
Sngmang
C0
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
18/2018
Bng Erlang B
Ao = 14,896 Erl
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
19/2019
- S knh lu lng ti mi cell l: 3*8 2 = 22 (TCH)
- Khi GoS = 2%, lu lng yu cu ca 1 cell l: 14,896 Erl
- Khi ti lu lng ca 1 MS l 33 mErl, s thu bao c th c
phc v trong 1 cell l: 14,896/0,033 451 MS
3. Din tch 1 cell l:
S = lu lng c cell / lu lng trn 1 km2
= 14,896 (Erl) / 2 (Erl/km2) = 7,448 (km2)
=> Bn knh cc i ca cell : R = (7,448/2,6)0,5 = 1,69 (km)
4. S cell ph sng c th trn C:
Ncell = Din tch th trn/Din tch 1 cell=35/7,448 5 (cell)
-
8/10/2019 Slide mn Mng Ging vin Trng Tun
20/20
B mnK thut Thng tin
H ni, 9 - 2007
Email: [email protected]
Ging vin Trng Tun
Trng i Hc Bch Khoa H NiKhoa in t -Vin thng
Mn hc:Thng tin di ng
( Mobile Communications )