Laboratorium Telekomunikasi Radio dan Gelombang Mikro Departemen Teknik Elektro Institut Teknologi Bandung
SISTEM KOMUNIKASI SELULAR (ET-5005) Dr. Dr. Ir. Ir. Adit Kurniawan, Kurniawan , M.Eng.
[email protected] Minggu_3_dan_4: Propagasi Selular
ET-5005, Sistem Komunikasi Selular
Pendekatan Analitik dan Empirik • Mobile Mobile Radio Chan Channel nel Characteri Characterisatio sation n • Theor Theoreti etical cal app approa roach ch – Free space loss – Plane earth path loss – Diffraction loss • Empirical Empirical/pred /prediction iction approach approach – – Lee - Alsebrook – • Measurement Measurement of large scale and application in coverage prediction • Some Some exam exampl ples es
Pendekatan Analitik dan Empirik • Mobile Mobile Radio Chan Channel nel Characteri Characterisatio sation n • Theor Theoreti etical cal app approa roach ch – Free space loss – Plane earth path loss – Diffraction loss • Empirical Empirical/pred /prediction iction approach approach – – Lee - Alsebrook – • Measurement Measurement of large scale and application in coverage prediction • Some Some exam exampl ples es
MODEL PROPAGASI PROPAGASI SISTEM SELULAR
Model untuk memperkirakan redaman: • Model teoretis • • Model Lee • Persamaan Umum Redaman Propagasi • er raan t em t • Model Okumura-Hatta Okumura-Hatta • Faktor Koreksi Undulasi • Faktor Koreksi Kemiringan
Model Teoretis Sederhana
∆d
= d 1 - d0
h1 h2
Karakterisasi Propagasi
Mobile Radio Propagasi Large-scale propagation
Mean signal
Sma -sca e pr propagation
Signal Variation
•Theoretical approach •Empirical/prediction •Empirical/prediction approach •Statistical modelling ogno ognorm rma a or ar arge ge sca sca e pa loss)
ime spreading of si nal
ime variation of
Model Teoretis Sederhana aya yang
ter ma me a u ge om ang angsung: 2
1 or
Pt t Gt d
= = = = λ =
t
t
r
4πd / λ
Daya pancar a n antena pemacar Gain antena penerima (MS) Jarak emancar - enerima Panjang gelombang yang dipakai
gelombang pantul:
1 r
t
t
r
4πd / λ
2
cos
ω
sn
ω
2
Model Teoretis Sederhana engan menurun an persamaan a am tan a mut a , ma a diperoleh persamaan sederhana sebagai berikut: 2
Pr
Pt G t G r
1
2
d2
Persamaan tersebut menghasilkan dua kondisi yang sesuai dg percobaan, yaitu:
Path loss sebesar 40 dB/ dekade (sebanding dengan d -4) atau 12 dB/ oktaf. enam a an pat oss ar ara 1 e 2 = 40 og 2 1 Pertambahan gain sebesar 12 dB/dekade atau 6 dB/oktaf . Penambahan gain antena dari h1 ke h2 = 20 log h2/h1
Sedangkan hasil yang tidak sesuai dg percobaan dan perlu ,
Tidak terdapat faktor interferensi (pjg gel.) Rumus empiris: Pr = f -n dengan 2 < n < 3 Teoretis: penambahan tinggi antena pada MS: 6 dB/ oktaf. emp r s: pengurangan ngg an ena -nya: ga n er urang dB.
Theoretical approach • Received power density at distance t
• Received ower antenna gain G t is
when
Rx r
=
P
=
Wt G t 4π
λG 4π 2
WG 4πd 2 2
• Ratio of Rx/Tx power is
r
Wt
c
=G G ⎜ ⎟ =G G ⎜ ⎟ ⎝ 4πd ⎠ ⎝ 4πdf ⎠ t
r
t
r
• Free space path loss is Lp(FS) [dB] = 32.45 + 20 log f + 20 log d
2
Plane earth propagation x
Tx d h t
h r
Ratio of Rx/Tx power is
Wr
λ W hh ⎛ ⎛ ∆ϕ =G G ⎜ ⎟ ⎟ [1 - ρe ] = = G G ⎜ j
t
t
2
t
r
r
t
t
Path loss model plane earth is Lp(PE) = 120 + 40 log d – 20 log h t – 20 log h r
r
r
2
Diffraction Loss h ositif x
d2
1
d1
x
d2
x
h (negatif)
2
≈
h d 2
+d
d1d 2
x
Fresnel zone (path clearance) •
