TM HIU V QU TRNH QUY HOCH TN S TRONG H THNG DI NG

TNG CNG TY VIN THNG QUN ICNG TY IN THOI DI NG VIETTEL MOBILEPHNG THIT K TI U KHU VC I

BAN THIT K TN S

NI DUNGPHN 1FREQUENCY PLANNING.PHN 2FREQUENCY HOPPING

PHN 1- THIT K TN S Thit k tn s: Qu trnh n nh tn s cho mi cell trong h thng GSM.

Yu cu: Nhiu gia cc cells phi c gim ti mc ti thiu.

MC CH n nh sng mang cho cc cell nhm to knh kt ni.

Thay i tn s nhm gim thiu nhiu trong mng di ng. Nng cp cu hnh trm bi vn lu lng.

S LNG KNH TRONG P-GSM900 1 knh sng mang (carrier) c rng 200KHzK hiu: ARFCN Absolute Radio Frequency Channel Number, n

ng xung: Fl(n)= 890 + 0.2 * n (MHz)

ng ln: Fu(n)= Fl(n) + 45 (MHz)

Tng s knh trong P-GSM900: 1 n 124

VIETTEL: 44 n 82

QU TRNH S DNG LI TN S Nhm gii quyt vn v gii hn ph tn.

Khong cch s dng li tn s D/R, c tnh da vo kch thc cm (N)

Nhiu ng knh (Co-channel) ph thuc vo khong cch s dng li tn s.

(D/R) = 6 * (C/I)Vi l h s truyn sng, c gi tr t 2 n 4 (thng thng: = 3.5).

YU CU THIT KGSM 05.05

Nhiu ng knh (co-channel): C/Ic 9 dB

Nhiu knh ln cn th nht:C/Ia1 -9 dB

Nhiu knh ln cn th hai:C/Ia2 -41 dB

QUY HOCH TN S Chia tng bng tn c php thnh 2 nhm nh

VIETTEL: BCCH: 44 n 63 TCH: 65 n 82 Guardband: n = 43,64,83.

Vic s dng li tn s phi khc nhau i vi c hai nhmBCCH:Mu 4x3, C/I 12dBTCH:Mu 3x3, C/I 9 dB

QUY HOCH BSIC M nhn dng trm gc (BSIC: Base Station Identify Code), c n nh km theo knh tn s.

Tc dng:+ Nhm loi tr kh nng xc nhn cell khng chnh xc.+ Cho php quy hoch cu trc cell trong tng lai.

Cu trc:+ NCC (Network Colour Code), c gi tr t 0 n 7NCC uc gn cho mt nh vn hnh mng.+ BCC (Base station Colour Code), c gi tr t 0 n 7BCC xc nh s hiu cm (cluster)

QU TRNH THIT K TN S Qu trnh thit k tn s bng tay (Manual Frequency Planning)ENTERPRISE - AIRCOMMCOM - ERICSON. Qu trnh thit k tn s t ng (AFP: Automatic Frequency Planning) hot ng da trn thut ton phc tp, ph thuc vo:+ D liu bng nhiu (Interference Table Data)+ Bng phn b lu lng (Traffic Distribute Table)ENTERPRISE AICOM

Tc dng:+ y nhanh cng vic thit k.+ Rt tin dng i vi cc mng ln v phc tp.

PHN 2 FREQUENCY HOPPING GII THIU

U IM

PHNG THC NHY TN

THUT TON NHY TN

CC THNG S KHC

KHAI BO TRONG H THNG

KHI NIM Mt tp hp cc tn s c s dng trong mi cell, v MS c th thay i cc tn s ngay trong mi khung TDMA c gi l nhy tn. Thng s HOP nh ngha c tnh nhy tn:HOP = ON: hopping.HOP = OFF: not hopping.

U IM Gim nh hng ca pha inh a ng (multipath fading).

Cht lng thoi c ci thin.

a ra quy trnh s dng li tn s (reuse) cht ch v hiu qu.

PHNG THC NHY TN (1) Baseband hopping:Mi b pht c n nh mt tn s.S dng filter combiner, iu chnh di hp.RBS2000: 12 u vo.

PHNG THC NHY TN (2)Cu hnh knh cho cc b thu pht:

Nhy tn ch c th c thc hin trn cc knh:TCHsSDCCHsPDCHs

PHNG THC NHY TN (3)Synthesized hopping:Mi b pht c n nh nhiu tn s.S dng hybrid combiner, iu chnh di rng.

PHNG THC NHY TN (4)Cu hnh knh cho cc b thu pht:

Mi cell c n nh vi mt vi nhm knh (CHGRs)

PHNG THC NHY TN (5) Thng s FHOP ch ra phng thc nhy tn:FHOP = BB: Baseband hopping.FHOP = SY: Synthesized hopping.

THUT TON NHY TN Cyclic hopping:Cc tn s b thay i theo 1 chui vng lin tip.Ch c mt chui vng duy nht vi ARFCN tng dn. Random hopping:Cc tn s b thay i theo 1 chui gi ngu nhin.C 63 chui c nh ngha (3GPP TS45.002). Thng s HSN ch ra thut ton nhy tn c s dng:HSN = 0: cyclic hopping.HSN = 1 63: random hopping.

CC THNG S KHC Thng s COMB ch ra loi combiner s dng:COMB = HYB: hybrid combiner.COMB = FLT: filter combiner. Thng s MAIO (Mobile Allocation Index Offset) phn bit cc b thu pht c cng HSN.MAIO = default: Chun GSM quy nh.MAIO =0 n N-1: Do cc operators nh ngha(N l s tn s nhy tn)S lng MAIO c dng ph thuc vo s TRXs s dng cho mi nhm knh.

D LIU THC TCc thng s HSN, HOP, MAIO, FHOP, COMB c khai bo trong h thng hin ti.

Mt s khai bo cn xem xt nh sau:

KT LUNTHIT K TN S (FREQUENCY PLANNING) L MT QUY TRNH KHNG TH THIU TRONG QU TRNH THIT K V TI U MNG THNG TIN DI NG.

CN NM VNG CNG C THIT K V TI U TN S C NHNG THAY I PH HP LM TNG CHT LNG MNG HIN C.