SISTEM KOMUNIKASI NIRKABEL

Jati Fallat

Pendekatan Analitik dan Empirik Mobile Radio Channel Characterisation Theoretical approach

Free space lossPlane earth path lossDiffraction loss

Empirical/prediction approachOkumura-Hatta - Blomquist-LadelLee - AlsebrookEgli - Ibrahim Parson

Measurement of large scale and application in coverage prediction

Some examples

Karakterisasi Propagasi

Mobile Radio Propagasi

Large-scale propagation

Small-scale propagation

Mean signal

Signal Variation

Time spreading of signal

Time variation of channel

MODEL PROPAGASI SISTEM SELULAR

Model untuk memperkirakan redaman :• Model teoretis• Model empiris

• Model Lee• Persamaan Umum Redaman Propagasi• Perkiraan Titik demi Titik

• Model Okumura-Hatta• Faktor Koreksi Undulasi• Faktor Koreksi Kemiringan

Theoretical approachFree space formula Received power density at distance d when Tx antena

gain Gt is

Received power when Rx antenna gain Gt is

Ratio of Rx/Tx power is

Free space path loss is Lp(FS) [dB] = 32.45 + 20 log f + 20 log d

2tt

r d4GWP

4G

d4GWW r

2

2tt

r

2

rt

2

rtt

r

df4cGG

d4 GG

WW

Plane earth propagation

Path loss model plane earth is Lp(PE) = 120 + 40 log d – 20 log ht – 20 log hr

Tx Rx

ht hr

d

Diffraction Loss

The difference of path length between direct and diffracted ray is

TxRxd1 d2

h (positif)

Tx Rxd1 d2

h (negatif)

21

212

dddd

2h d

Fresnel zone (path clearance) The phase difference when h << d1 and h << d2 is

with v is diffraction parameter which can be expressed as

The n-th Fresnel zone is area between Tx and Rx inside the ellipsoide with radius of its cross section of rn where

2

21

212

v2dd

dd2h2d2

21

21

dddd2hv

21

21n dd

ddnhr

Empirical Prediction ApproachBased on signal measurement

Okumura - Blomquist-LadelLee - AlsebrookEgli - Ibrahim-Peterson

Mathematical Formulation based on signal measurementHatta (Japan)COST-231 (Europe)

Okumura –Hatta Model

Lp(open) = Lp(urban) –4.78(logf)2 + 18.33 log f – 40.94

For urban area:

Lpu [dB] = 69.55 + 26.16 log f – 13.82 log hb – a(hm) + (44.9 – 6.55 log hb) log d

Model Okumura – Hatta

KLASIFIKASIDAERAH

PELAYANANRUMUS REDAMAN PERAMBATAN

Urban Area

Lu = 69,55 +26,16 log fc – 13,82 log hb – a (hm) + (44,9– 6,55 log hb) log R……………..(dB)

Faktor koreksi untuk tinggi antena stasiun mobilyang bergantung kepada tipe daerah urban yangdibagi sebagai berikut :

Medium – small city :a (hm) = (1,1 log fc – 0,7) hm – (1,56 log fc – 0,8) ….(dB)Large City

a (hm) = 8,29 (log fc 1,54 hm)2 – 1,1 , fc < 200 MHza (hm) = 3,2 (log fc 11,75 hm)2 – 4,97 , fc > 400 MHz

Sub Urban Area Lsu = Lu (urban area) – 2 [log (fc/ 28)]2 – 5,4 ….(dB)Open Area Lo = Lu (urban area) – 4,78 (log fc)2 + 18,33 log fc –

40,94 ….(dB)

Keterangan :

fc = frekuensi kerja yang berharga : 150 MHz – 1500 MHzhb = tinggi antena stasiun tetap (RBS) : 30 m – 200 mhm = tinggi antena stasiun mobil (MS) : 1 m – 3 mR = jarak pemancar penerima : 1 km – 20 km

Lee Model

Lee formulated the path loss of beingLp[dB] = L0 + log d ; with L0 is path loss at d = 1 km

and is the path loss slope.Area L0 [dB] (dB/decade]

Free space 91.2 20

Open/rural area 90.4 43.5

Suburban area 104.3 38.4

New Ark 105.5 43.1

Philadelphia 112.8 36.8

New York City 117.5 48

Tokyo 128.1 30.5

Egli Model dan Blomquist-Laded Model EGLI MODELBased on Plane Earth Theoretical model with correction

factors

Lp [dB] = 120 + 40 log d – 20 log ht – 20 log hr +

Blomquist-Laded Model

Lp [dB] = Lfree space +{(Liplane earth – Lfree space)2 + (Ldiffraction)2}1/2

Alsebrook ModelFor flat areas Lp [dB] = Lplane earth +LB +

For hilly areas : Lp [dB] = Lfree space +{(Liplane earth – Lfree

space)2 + (Ldiffraction)2}1/2 + LB +

Ibrahim-Peterson Model

Lp [dB] = 40 log d – 20 log(hbhm) +