Gsm Fundamentals By Dr. Hatem Mokhtari

GSM RF Design and Planning Fundamentals

Dr. Hatem MOKHTARI Cirta Consulting LLC

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A. Introduction to Wireless Telephony During the 1980s, in Europe, Many Systems were used without any Regulation, Standards, or Compatibilities. Most of them were Analog. As a result : * No Roaming between Countries * Major Capacity Problems and Congestions * Limited Market for each Technology * Very high subscriber equipment cost...Further growth difficult ! In The USA and Canada DAMPS (Digital Advanced Mobile Phone Service) : Cheaper handsets, roaming, easy subscribing, etc ® Cirta Consulting LLC

A. Introduction to Wireless Telephony Modern Systems are : * Digital : The signal is Digitized through A/D Converters, Modulated, and then sent via the Antenna * High Capacity : They are able to simultaneously serve a large number of customers * Encrypted : Due to the fact that they are digital, they have full protection against fraud. Also, they are highly securised * High Speech Quality : Due to Technology advance and electronics improvements * Spectrum Efficient : They offer optimised frequency spectrum use * Possibility to roam within the GSM Community Networks (provided a signed Roaming Agreement) ® Cirta Consulting LLC

A. Introduction to Wireless Telephony „

Role of the RF Design Engineer : ‹ Design the Network Architecture ‹ Select type of Antennas ‹ Analyze the Links : Downlink and Uplink ‹ Propose Solutions to Enhance the Capacity of a Base Station ‹ Consider Marketing Inputs and Propose Design accordingly ‹ Perform Drive Test to ensure Quality of the Link ‹ Use Radio Planning rules to install Antennas in different sites ‹ Use Radio Planning tools to assess the Coverage using Simulation ‹ Perform RF Propagation Model Tunning using measurements ‹ Selects the RF Infrastructure to fullfil the Link Budget requirements ‹ Calculates Propagation, Site Clearance, Link Quality using different Hardware and Software Tools ® Cirta Consulting LLC

A. Introduction to Wireless Telephony „

„

A GSM subscriber (Mobile) Should be able to : ‹ Receive and Transmit within a given geographical area ‹ Roam to other countries (If a Roaming Agreement exists) ‹ Have a continuous Quality of Service (QoS) A Mobile Station should be able to : ‹ Change the Serving Base Station (BS) if the link is bad (or going to become bad) on the actual BS. This is the Handover (or Hand-off) ‹ Recognize which country, Network, or Base Station the user is attached to ‹ Inform the actual Network about the Identity of the User ‹ Prevent forthcoming Drop Calls, Quality Problems due to Interference, or Signal Level (shadowing by obstacles) ® Cirta Consulting LLC

B. RF Fundamentals „

Notation in dBm, dBW, dBi, dBd, dB ‹

P (dBm) = 10Log10(P mW/1mW) ) Example : 100 mW power results in 10Log10(100)=20 dBm

‹

P dBW = 10Log10(P W/1W) )

‹

Example : 15 W power results in 10Log10(15)= 11.76 dBW

Relation between dBW and dBm : dBm = dBW + 30 ) Example : 100 mW = 20 dBm = -10 dBW )

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B. RF Fundamentals : DC CIRCUITS I E

U

•Voltage R •Power

If an internal resistor is to be considered: I •Voltage r R U E •Power ® Cirta Consulting LLC

U = RI U2 P = UI = R

R U= E R+r R 2 P= E 2 (r + R)

B. RF Fundamentals : AC CIRCUITS •Voltage u = Ri • If e(t ) = E cos ωt • Then

i e

R

u

r

R e(t ) = E cos ωt ≡ U m cos ωt R+r •Power

U m2 cos 2 ωt p (t ) = u (t )i (t ) = R •RMS Notion = Root Mean Square T

1 2 U= u (t )dt ∫ T 0 ® Cirta Consulting LLC

B. RF Fundamentals : Exercise „

Suppose we have a voltage :

T=

u (t ) = U m cos ωt

2π

„

With a period of

„

Compute the RMS Voltage for Um = 50 V

„

Is the RMS dependent of the frequency ?

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ω

Complex numbers

B.RF Fundamentals

* z1 = x1 + jy1

z1 ± z 2 = ( x1 ± x2 ) + j ( y1 ± y2 )

* z 2 = x2 + jy2

z1 × z 2 = ( x1 x2 − y1 y2 ) + j ( x1 y2 + y1 x2 z1 z1 z 2 1 = = × {( x1 x2 − y1 y2 ) + ( x1 y2 − y1 x2 )} 2 2 2 z2 z2 x2 y 2

 y1    * If Θ1 = arg( z1 ) = tg  x1   y2  −1   Θ 2 = arg( z 2 ) = tg  x2  −1

Given Exercise Compute ® Cirta Consulting LLC

arg( z1 z 2 ) = Θ1 + Θ 2 z1 arg( ) = Θ1 − Θ 2 z2

Θ1 = arg(z1 )

z1 = 1 + j 2

Θ 2 = arg(z 2 )

z 2 = −1 + j 3

z1 + z 2 z1 − z 2 z1 z 2

z1 z2 Θ1 Θ2

 z1  Θ 3 = arg   z2  Θ 4 = arg(z1 z 2 )

B.RF.Fundamentals Exercise Ζ1 = 2e

Given

j

Compute 1) Ζ1 + Ζ 2 , Ζ1 + Ζ 2 and arg(Ζ1 + Ζ 2 )

π

 Ζ1  Ζ1 Ζ1 and arg  2) , Ζ2 Ζ2  Ζ2 

3

Ζ2 = 2 − j 3

Ζ = Χ + jΥ

Given

3) Ζ1Ζ 2 , Ζ1Ζ 2 and arg(Ζ1Ζ 2 ) Υ Show that log Ζ = log Χ 2 + Υ 2 + jtg −1  

U = Ζ• I

> Impedance e

~

U

where Ζ = jLω

ω = 2π f Ζ=−

j

for

Cω Ζ = jLω for

a capacitor an inductor

Ζ®=Cirta R Consulting for a LLCpure resistor

Χ

(rad • s ) −1

B. RF Fundamentals : Complex numbers Imaginary Part Y

ρ

Z θ X

Z = X + jY = ρe

X = ρ cosθ Y = ρ sin θ ® Cirta Consulting LLC

jθ

Real Part

B. RF Fundamentals : Impedance A

I

ε U

Zin

U=Z I U, Z and I are all Complex Numbers Z

B Z : The Impedance of the Load and Zin internal to the Generator Z = R for a Resistor Z = jLω for an Inductive Component

Z = − j / Cω for a Capacitor In Low Frequencies, all the power delivered to Z is absorbed or dissipated into heat ® Cirta Consulting LLC

B. RF Fundamentals „

„

„

Vertical Polarization Refers to the direction of the Electric Field Horizontal Polarization would be to configure the dipole horizontally Horizontal Polarization Refers to the direction of the Electric Field

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r E

Dipole Antenna

r H

r Π

r Π is the Poynting Vector (Power) r r r E×H Π=

η

B. RF Fundamentals : High Frequency considerations A

I

ε U

Zin

Z

At RF domain, Energy flows from the generator to the Load. It can be fully absorbed by Z, or Partly reflected and partly absorbed.

B 2

The % of Reflected Energy is

 VSWR − 1  ρ =  × 100  VSWR + 1 

VSWR : Voltage Standing Wave Ratio ( 1:1 is ideal ) Acceptable VSWR = 1.5 : 1 Impedance Match : Z* = Zin ® Cirta Consulting LLC

B. RF Fundamentals „

EIRP or Equivalent Isotropic Radiated Power : „ The Power to supply to an antenna to obtain the same power in all directions at a distance d :

PE (θ , ϕ ) = P + G − Lr (θ , ϕ ) „

We always consider the main lobe direction where no losses exist

PE = P + G „

dBi : Refers to an Isotropic antenna and dBd to the Dipole : „ „

dBi = dBd + 2.15 dB EIRP = ERP + 2.15 dB

Example : G = 16 dBi, so G = 13.85 dBd and if P = 33 dBm (2 W) „ Then PE = 16 + 33 = 49 dBm in the main Lobe ® Cirta Consulting LLC „

B. RF Fundamentals 60

60 32.5

32.5

0

0

10

10 - 32,5

3 0 dB

- 60

Horizontal Diagram ® Cirta Consulting LLC

3 0

- 32,5 - 60

dB Vertical Diagram

20.00 0. 00-20. 00 0.00 -1. 05 -20.00

-0. 60

-20. 00-0. 00 -40. 00--20. 00 -60. 00--40. 00

-0. 15 0.30 0.75

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-40. 00 -60.00

B. RF Fundamentals „

Directivity : Figure of Merit to quantify the ability of an antenna to concentrate the Energy in a particular Direction

Wmax D= MeanPowerDensity @ d „

„

„

„

Where Wmax is the Power Density at a distance d in the main lobe direction Generally, we use the Gain instead :

G

=

W

max

PT 4π d

2

Where PT is the supplied power to the antenna, commonly known as the output power (minus the cable and connector losses) Given PT and G, we can compute the Power Density Wmax

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B. RF Fundamentals „

Relation Between W and E (The Electric Field) :

E2

E2 E2 W= = = η 120π 377 „

Besides :

30 PT GT ⇒ E= d

E2 PT GT = 120π 4πd 2 „

Maximum Useful Power : 2

λ E  Eλ  G R . GR =  P= A=  η 120π 4π  2π  120 ® Cirta Consulting LLC E

2

2

2

B. RF Fundamentals „

„ „

Effective Area of an Antenna (Reception) :

λ2 A= G 4π

Received Power : P = WA W : Power Density (Per Unit Area)

PT GT W= 2 4πd

PT GT λ2 PR = GR 2 4πd 4π

„

Finally, the received power reads :

„

Free Space Loss Between Isotropic Antennas (GR=GT = 1) :

PR L(dB ) = 10 Log10 = −32.44 − 20 Log10 f MHz − 20 Log10 d km PT ® Cirta Consulting LLC

B. RF Fundamentals „

Propagation Over a Plane Reflecting Surface (Flat Earth Model) :

Tx Ht

Rx Hr d

E = Ed − Ed e „

− jkδ

Assuming d >> Ht and Hr, the Path Loss (Iinear) :

PR  Ht Hr  = GT GR  2  PT  d  ® Cirta Consulting LLC

2

B. RF Fundamentals „

Reflection :

Tx Ht

Rx Hr d

E = ΓE d e

− jkδ

Γ is the Complex Reflection Coefficient The value of Γ depends upon frequency, Polarization and Electric Characteristics of the reflecting surface ® Cirta Consulting LLC

B. RF Fundamentals A

B

C

P

B

C Shadow region

A

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B. RF Fundamentals „

Diffraction :

Tx Ht

h D1 D2

Rx Hr

d

E = DEd e

− jkδ

D is the Complex Diffraction Coefficient The value of D depends upon frequency, Polarization, Geometry, and Angles of the structure ® Cirta Consulting LLC

B. RF Fundamentals „

The Diffraction Loss is shown to be :

20 Log (0.5 − 0.62v ) − 0 .8 < v < 0   20 Log (0.5 exp(−0.95v)) 0 < v <1  L (v ) =  2 − − − 20 Log ( 0 . 4 0 . 1184 ( 0 . 38 0 . 1 v ) ) 1 < v < 2 .4   20 Log (0.225 / v ) v > 2 .4 „

Where v, the Fresnel Parameter is given by :

2( D1 + D 2) v=h λD1D 2 ® Cirta Consulting LLC

B. RF Fundamentals

Hp

Hb

Compute L(v) for : Hb = 20 m Hp = 5 m Ho = 15 m Hm = 1.5 m A = 1250 m B = 4.5 m Frequency = 900 MHz

Ho Hm A

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B

02 01 H

T

h2

h1 Ht

R

D1 d1

D2 d2

Bullington Model : “equivalent” Knife - edge ® Cirta Consulting LLC

d3

Hr

Test : Bullington Diffraction Loss Model „

Compute H, D1, D2, and then L(v) the Diffraction Loss given the following data : ‹ Ht

= 25 m ‹ Hr = 1.5 m ‹ d1=d2=d3=1000 m ‹ h1 = 30 m, h2 = 15 m ‹ Frequency = 1880 MHz ‹ Compare L(v) to the Free Space Loss ‹ Please Conclude

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Propagation over irregular terrain 02 01 03

R

T

d1 x d2 x d3 x d4 The Epstein – Petersen diffraction construction ® Cirta Consulting LLC

Propagation over irregular terrain 02 01 03

R

T

d1

x

d2

x

d3

x d4 Main edge

The Deygout diffraction construction ® Cirta Consulting LLC

B. RF Fundamentals : Receiver Theory Receiver Input

BS / MS Demodulation & Selective Filtering

Receiver

Receiver Output

To operate properly the receiver has to receive a minimum power : Sensitivity The Sensitivity depends on the technology involved ® Cirta Consulting LLC

B. RF Fundamentals : Receiver Theory „

„

„

Receiver Sensitivity : ‹ Is the minimum acceptable input signal level in dBm, at the receiver‘s low noise amplifier, required by the system for reliable communication Carrier to Noise Ratio CNR or C/N : ‹ For a given BER (Bit Error Rate) of about 10-3 for example, C/N is the required minimum signal to noise ratio Thermal/Environment Noise : ‹ Is a combination of ) Antenna Noise (dBm) ) Receiver Noise Figure (NF) in dB ) Temperature and System Bandwidth ® Cirta Consulting LLC

B. RF Fundamentals : Receiver Theory

Receiver NF (S/N)in

S S   =   + NF  N in  N  out S S in − N in =   + NF  N  out S S in = N in +   + NF  N  out ® Cirta Consulting LLC

(S/N)out

Nin : Thermal Noise, NF : Noise Figure

RECEIVER SENSITIVITY :

S Sin = 10 Log10 (k .T .B) + NF +    N  out

B. RF Fundamentals : Receiver Theory S S in = 10 Log10 (k .T .B) + NF +    N  out

k : Boltzmann Constant ( 1.38 * 10-23 J/°K) T : System Operating Temperature (°K) B : System Bandwidth (Hz) T : 290 °K typical value Exercise : Compute Sin (dBm) for a GSM signal of 200 kHz Bandwidth, with a receiver NF=6 dB and C/N = 9 dB

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B. RF Fundamentals : Intermodulation IM is a non-linear process that generates an output signal Containing frequency components not present in the input signal

x

Non-Linear Device

a0 +a1x+a2x2 +a3x3 +...

Assuming x to be a two-carrier f1 and f2 sine wave :

x(t ) = A cos(2πf1t ) + B cos(2πf 2t )

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B. RF Fundamentals : Intermodulation y (t ) = a0 + a1 x + y2 + y3 y2 =

(

)

[

]

a2 2 a A + B 2 + 2 A2 cos(2π (2 f1 )) + B 2 cos(2π (2 f 2 )) + a2 AB[cos(2π ( f1 + f 2 )) + cos(2π ( f1 − f 2 ))] 2 2 3630 MHz 1800 MHz

1830 MHz 3600 MHz

0 30 MHz

DC

f2-f1

f1

f2

3660 MHz

2f1 f2+f1 2f2

Cellular Band Spectral Characteristics of y2 Using f1 = 1800 MHz and f2 = 1830 MHz, A=B=1, and a2 = 1 ® Cirta Consulting LLC

B. RF Fundamentals : Intermodulation y (t ) = a0 + a1 x + y2 + y3 Six Different Frequencies are generated in IM3 :

3f1, 3f2, 2f1-f2, 2f1+f2, 2f2-f1, 2f2+f1 1800 MHz 0

DC

1830 MHz

1770 MHz

2f1-f2

1860 MHz

f1

f2

2f2-f1

Cellular Band Spectral Characteristics of y3 Using f1 = 1800 MHz and f2 = 1830 MHz, A=B=1, and a2 = 1 ® Cirta Consulting LLC

B. RF Fundamentals : Fade Margin R

 ( x − m )2  1  exp − p ( x) = 2  2 σ σ 2π  

x : is the received level m: Mean value of x σ : Standard Deviation of x • Due to shadowing and terrain effects the signal level measured on a circle around the BS shows radom behaviour around the predicted value given by the Propagation Model • This Random Signal level through the cell boundary has a Log-Normal distribution • Log-Normal variable is in fact a Gaussian Process when expressed in dB ® Cirta Consulting LLC

B. RF Fundamentals

PDF-Gaussian 0.06 0.05

0.03

PDF-Gaussian

0.02 0.01 -50.00

-56.00

-62.00

-68.00

-74.00

-80.00

-86.00

-92.00

-98.00

-104.00

0 -110.00

 ( x − m )2  1  exp − p( x) = 2  2 σ σ 2π  

0.04

Theory shows that to ensure 90 % of Surface Reliability, One may push the received signal level requirement to Higher values than m (50%). This leads to a notion called : Fade Margin : the additional margin to fullfil y % of surface Covered. ® Cirta Consulting LLC

Fade Margin 50% is the median value. To achieve higher %, one may add a Fade Margin to fullfil X% > 50% The Probability that a Field Strength Exceeds a Threshold E0 is : ∞

p E 0 = p ( E ≥ E0 ) =

∫ p( E )dE

E0

p E0

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1  E m − E0   = 1 − erf    2  σ 2 

Fade Margin „

The Lognormal Margin is defined as : ‹ Mlog

„

= Em – E 0

Hata Model has a general form :

E0 ( r ) = Em − 10γ log10 ( r / R ) „

The Contour Probability can be written as :

p E0

1 = 2

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 r    1 − erf  a + b ln   R   

Fade Margin

Em − E0 a = σ 2 10 log 10 e b = σ 2

„

The parameters a and b are :

„

The Area Coverage Probability over a Circle of Radius R is :

Pcov „

1 = 2 πR

∫∫ p

E0

(r ,θ )rdrdθ

The contour probability depends only upon the radius r, which simplifies the computation and leads to :

Pcov

1  ab + 1    2ab + 1  = 1 + erf (a ) − exp 1 − erf    2 2  b   b  

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Probability (% )

Contour and Area Coverage Probability Versus the Fade Margin

100 90 80 70 60

Cell Edge % Area %

50 40 30 20 10 0 0

1

2

3

4

5

6

Fade Margin (dB)

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7

8

9

10

Ms Antenna Gain Loss ERP

Gains and losses in uplink

Body Loss In-Building Car Penetration Loss Fade margin

GA

LCCC

Path Loss

RX Base = PAm + Gm − Lbody − LBldg − M Fade − Plup

+ GB − LCCC

Plup = PAm + Gm − LBody − LBldg − M fade − RX Base

+ GB − LCCC

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Combiner Cable & Connector Losses

RY

Gains and Losses in Down Link PA

LCCC

ERP

Fade margin Path Loss

GB

Power Amplifier

In-Building Car Penetration Loss Body Loss

Combiner Cable & Connector Losses

MS Antenna Gain Loss

RXMobile = PAB − LCCC + GB − MFade − MDown − LBldg − LBody + GM PAB = RXMobile+ LCCC − GB + MFade + PLDown + LBldg + LBody − GM ® Cirta Consulting LLC

RX

Maximum Allowable Path Loss Starting with the reverse link UL •Find the maximum Allowable Path Loss (MAPL) - Start from MS maximum power - Subtract all the losses in due to, RF components - Subtract all the margins due to fading and interference for a given target loading - Add all the gains in the path e.g. antenna and diversity gains - Subtract the receiver sensitivity of the base station for a given FER - The result is MAPL

MAPL = PLUp − AllLosses + AllGains − RX base ® Cirta Consulting LLC

Balance Equation: PLUp = PAm + GM − LBody − LBldg − MFade − RXBase + GB + GDiv − LCCC PLDown = PAB − LCCC + GB − MFade − RXMobile − LBldg − LBody + GM PLDown = PLUp •Write the balance equation and see which terms get cancelled •Find the Base station and EIRP that results in balanced paths. •Changing which parameter jeopardizes the path balance? - Antenna Gain - Antenna Height -® PA Cirta output Consulting LLC

Cell Size / Count Estimation

• Objective - To determine the number of cells required to provide coverage for a given area

• Required Input:

- Maximum Allowable Path Loss (MAPL) - Propagation Loss Model

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From MAPL to Cell Size Path Loss

Propagation Loss Model

MAPL

Distance from TX Range or Cell Radius ® Cirta Consulting LLC

Cell Size Information With Hata Model •Using Hata’s Empirical Formula PL = 69.55+ 26.16log10 fc −13.82log10 hb + (44.9 − 6.55log10 hb ) log10 R − a(hm ) − CF

•Solve it backward to find cell radius estimate

MAPL + CF − 69.55 − 26.16 log10 f c + 13.82 log10 hb + a ( hm ) log10 R = 44.9 − 6.55 log10 hb

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H. Guidelines for interference Minimisation „

„

BS Installation Requirements : ‹ A certain isolation has to be present between Tx and Rx antennas ‹ Radiation Patterns must not be distorted by obstacles or reflections nearby the antennas

Isolation : ‹ Between 2 antennas : Attenuation from the connector of one antenna to the connector of the other antenna when both antennas are in their installation positions ‹

To avoid unwanted signals into the receiver Rx, the following isolation values are required : ) )

40 dB Between a Tx Antenna and a Rx Antenna 20 dB Between 2 Tx Antennas

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H. Guidelines for interference Minimisation „

Isolation : ™

™

™

™

To obtain the Isolation values the antennas have to be placed at certain minimum distance from each other The distance depends on : Antenna types, configuration Omnidirectional antennas require greater horizontal distance than directional antennas Vertical separation requires less distance than horizontal separation

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H. Guidelines for interference Minimisation : Vertical Separation Pre-condition : a > 1 m Tx-Tx : 0.2 m minimum Tx-Rx : 0.5 m minimum k

As a General Rule : Isolation :

k AV = 28 + 40 Log10   λ a

For GSM 900, λ = 0.33 m

AV = 47 + 40 Log10 k With A = 35 dB, k = 0.5 m ® Cirta Consulting LLC

dB

dB

H. Guidelines for interference Minimisation : Horizontal Separation G1 : Gain of antenna 1 in dBd G2 : Gain of antenna 2 in dBd

d

d  AH = 22 + 20 Log10   − (G1 + G2 ) dB λ AH = 31 + 20 Log10 d − (G1 + G2 ) dB ® Cirta Consulting LLC

General @ 900 MHz

H. Guidelines for interference Minimisation : Horizontal Separation Omni Antenna Gain (dBd)

Tx-Rx distance Tx-Rx distance (40 dB) (20 dB)

0

3.0 m

1.0 m *

3

5.5 m

1.0 m *

6

11.0 m

1.0 m

9

22.0 m

2.5 m

10

28.0 m

3.0 m

Could be less for Tx-Tx but 1.0 m is a conservative option to avoid shadowing effects ® Cirta Consulting LLC

H. Guidelines for interference Minimisation : Combined H/V Separation α k

d

A ≈ ( AV − AH ). ® Cirta Consulting LLC

α° 90°

+ AH

H. Guidelines for interference Minimisation

h D

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H. Guidelines for interference Minimisation Antenna height 4 Step function

3

First Fresnel zone

2 1

5

10

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15

20

25

30

35

40

45 distance(m)

H. Guidelines for interference Minimisation

The mast is allowed Mast to swing 1° at a wind velocity of 30 m/s

±1 a 2 m is recommended ® Cirta Consulting LLC

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H. Guidelines for interference Minimisation

k

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H. Guidelines for interference Minimisation d

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o Max. 15

o 90

Forward direction ® Cirta Consulting LLC

H. Guidelines for interference Minimisation α k

d

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H. Guidelines for interference Minimisation RxB

H

Axis

Maximum diversity

RxA

a ® Cirta Consulting LLC

Ground level

H. Guidelines for interference Minimisation

h D

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H. Guidelines for interference Minimisation Antenna height (m) 4 Step function

3

First Fresnel zone

2 1

5

10

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15

20

25

30

35

40

45 distance(m)

H. Guidelines for interference Minimisation Top view Forward direction

Wall

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Top view

Forward direction

Maximum 15° Cell sector including safety margin ± 75°

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Top view

Forward direction

More than 15°

Cell sector including safety margin

Wall ® Cirta Consulting LLC

± 75°

H. Guidelines for interference Minimisation : Diversity „

Definition ‹

Diversity is the statistical improvement of the received signal when more than one signal is used.

‹

To improve the overall received signal level, due to multipath phenomenon, it is interesting to use more than one antenna and consider internally the best received signal.

‹

Diversity in cellular is used only at the Base Station end, although it is theoretically possible for mobiles, it is quite cumbersome to have two antennas moving with the subscriber !

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H. Guidelines for interference Minimisation : Diversity

Mobile Station (MS)

Base Station (BS) Antenna #1 d Antenna #2 The Receiver uses different combining techniques. The most popular is the Maximum Combining Ratio Technique

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Received signal

H. Guidelines for interference Minimisation : Diversity

Signal Level Received by Antenna 1 (RxA) Signal Level Received by Antenna 2 (RxB) Improvement due to Antenna Diversity

Time

Typical Diversity Gains : 3.5 dB for Cross-Polarised antennas, 4.5 dB for Space Diversity. The maximum theoretical value is 6 dB. ® Cirta Consulting LLC

H. Guidelines for interference Minimisation : Correlation vs distance

αJ (k .d ) Correlation Function

Antenna #2

Antenna #1

2 0

d

0.7

10λ

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40λ

Normalized Distance

H. Guidelines for interference Minimisation : Diversity Requirements a≥

H 10

a = distance between Rx antennas

RxA

a

RxB

H = height of mast plus building (Effective antenna height) H

Ground level ® Cirta Consulting LLC

H. Guidelines for interference Minimisation

Maximum diversity

RxA

Minimum diversity

a 90°

® Cirta Consulting LLC

RxB

H. Guidelines for interference Minimisation

Coverage area

RxB Optimum diversity RxA

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Market Boundaries

•Usually a midsize market covers heterogeneous areas,e.g. - Downtown,Urban or dense urban areas - Suburban, Light residential areas - Rural, open areas, farmland…

Urban Suburban Rural ® Cirta Consulting LLC

Radio Planning Methodology Define Design Rules and Parameters

Set Long Term Plans and Performance Targets Coverage Requirement & Demand Forecasts from Marketing

Design Nominal Cell Plan

Acquire Sites and Implement Cell Plan Computer-Based Modelling

Produce Frequency Plan

Optimise Network ® Cirta Consulting LLC

Design Iteration

Business Planning

Market Boundaries

® Cirta Consulting LLC

Hata RF Propagation Model for Urban Environments Lu = 69,55 + 26,16Log( f ) −13,82Log(hb ) − a(hm ) + [44,9 − 6,55Log(hb )]Log(d ) a(hm ) = [1,1Log( f ) − 0,7]hm − [1,56Log( f ) − 0,8] a(hm ) = [3,2Log(11,75hm )] hm − 4,97 2

Lsu = Lu − 2[Log( f / 28)] − 5,4 2

For a Midium Size City

For a Big Size City and f > 400 MHz

For Suburban Environments

2 Lro = Lu − 4,78[Log( f )] +18,33Log( f ) − 40,94 For Rural Environments

2 Lrqo = Lu − 4,78[Log( f )] +18,33Log( f ) − 35,94 For Semi-Rural Environments

® Cirta Consulting LLC

Hata RF Propagation Model for Urban Environments „

„ „ „ „

„

Hata Model is valid under certain conditions : Frequencies between 150 and 1000 MHz Base Station Antenna Height between 30 an 200 m Mobile Station Antenna Height between 1 and 20 m BS-MS Distance between 1 and 20 km As a Result, it is suitable for GSM900 only and NOT GSM1800 or PCS1900 !!!

® Cirta Consulting LLC

COST231-Hata RF Propagation Model for Urban Environments

Lu = 46,33 + 33,9 Log ( f ) − 13,82 Log (hb ) − a (hm ) + [44,9 − 6,55 Log (hb )]Log (d ) + Cm a (hm ) = [1,1Log ( f ) − 0,7]hm − [1,56 Log ( f ) − 0,8]

Cm = 0 dB

For Medium Size Cities and Suburbs

Cm = 3 dB

For Big Metropolitan Centers

Validity : Frequencies between 1500 MHz and 2000 MHz

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Table of Penetration Losses In Building penetration (dB) In Car penetration (dB) Body Loss (dB)

For all receiving environments a loss associated with the effect of users body on propagation has to be included. This effect is in the form of a few dB loss in both uplink and downlink directions.

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15 - 25 3 - 10 2- 5

Tower Mounted Amplifier : Effect on Coverage and Quality

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TMA

4 dB Gain in the UL

3 dB cable loss

BTS

BTS

Static Sensitivity=-110 dBm

Static Sensitivity=-110 dBm

S(without TMA) = -110 + 3 = -107 dBm*

* Body ® Cirta Consulting LLC

S(with TMA) = -110 + 3-4 = -111 dBm*

Loss and Lognormal Fading have to be added

Overview on Linkbudget Impact (1/2) „

Cell Range R computed using : ‹ MAPL=A+B*log(R) ‹ MAPL : Maximum Allowed Path Loss ‹ MAPL = EIRP-Effective Sensitivity ‹ Example : ) Given EIRP=Pout+Gant-CableLoss ) with Pout=40 dBm; Gant=18 dBi; Cable Loss=3 dB ) EIRP=40+18-3=55 dBm ) MAPL = • 55 - (-107+7+5) = 150 dB without TMA • 55 - (-111+7+5) = 154 dB with TMA ‹

MAPL : The higher the bigger the cell radius )

log(R) = (MAPL-A)/B ⇒ R = 10^((MAPL-A)/B)

® Cirta Consulting LLC

Overview on Linkbudget Impact (2/2) „

Numerical Example : ‹ Assume we use a Rural Propagation Model PL = 135 + 30*log(R) ‹

Cell Radius R= ) 10^( (150-135)/30 )= 3.2 km without TMA ) 10^( (154-135)/30 )= 4.3 km with TMA !

Path Loss (dB)

135+30*lod(d)

MAPL=154 dB with TMA

4 dB due to TMA MAPL=150 dB without TMA

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3.2 km

4.3 km

Distance (km)

Uplink Coverage Downlink Coverage

Directional Antenna Due to linkbudget imbalance

TMA Improves Uplink vs Downlink: To balance the Linkbudget the BTS output power has to be raised by 4 dB ! (the TMA gain) ® Cirta Consulting LLC

Measurements and Propagation Model Calibration Three Types of measurement equipment are commonly used : 1. Narrowband measurements (CW) a) b) c)

Prior to starting the design For calibrating the prediction model For verification of critical and borderline coverage areas

2. Test Mobile Measurements a) b) c)

Once the Network has been built For analysis of System Parameters and Handover behavior For Network Optimization

3. Reflection Measurements (channel sounder) a) b) c)

As a research tool For analysis of Multipath Propagation and Delay Spread Normally only necessary in mountainous regions

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Measurements and Propagation Model Calibration Measurement requirement for Tool Calibration To measure out to the cell radius, requires typically 145 dB (MAPL) To measure out to the point where interference is significant, requires typically another 20 dB (i.e. a total of 165 dB dynamic range) The measuring equipment should handle this range easily, i.e. should have a dynamic range of the order of 175 dB To achieve this dynamic range, narrowband CW measurements are necessary

Wideband Receivers and Test Mobiles (Based on a modified subscriber handset – measuring GSM RXLEV) are unsuitable for model calibration but may be used later for confirmation of coverage

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Measurements and Propagation Model Calibration Tx Antenna

Rx Antenna

Trigger

MS

BTS Amplifier

Rx/Computer

Transmitter

Navigation

Trigger Wheel ® Cirta Consulting LLC

Antenna

Storage

Measurements and Propagation Model Calibration For CW measurements it is important to record an averaged value of instantaneous measurements 1. Rayleigh Fading makes instantaneous measurement unrepresentative a) b)

Aim to eliminate the Rayleigh fading, but not the shadow fading Average over an interval which is less than the magnitude of streets and buildings. Some refereneces speak about a distance of 40λ

2. Averaging interval should be greater than the Rayleigh Fading interval, but shorter than the building interval a) b)

13 m outdoors 6.5 m indoors

3. Separation of instantaneous measurements should be : a) b)

More than 36 per interval to reduce averaging variation to less than 1 dB Corresponds to 0.36 m (1.1λ at 900 MHz)

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Measurements and Propagation Model Calibration Sampling Rates RMS Error (dB)

Number of averaged samples in 13 m

Resulting Sampling Interval (λ)

0.50

144

0.28

0.75

64

0.63

1.00

36

1.11

1.25

23

1.74

1.50

16

2.50

1.75

12

3.40

2.00

9

4.44

® Cirta Consulting LLC

Measurements and Propagation Model Calibration Guidelines for CW Measurements 1. The Survey Route should include various road directions and street widths in built up areas 2. Special features relevant to propagation such as tunnels, bridges, etc. should be clearly marked in the case of calibration measurements 3. If possible, measurement antennas should be the same as the planned antenna in type and installation 4. Measurements must be conducted and documented accurately, especially regarding antenna installation and transmitter height 5.

Only measure within 3 dB beamwidth (antenna aperture) The pattern outside the main beam may not correspond to the stored antenna pattern, due to local obstructions, such as the mast and other antennas

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Measurements and Propagation Model Calibration * To effectively calibrate a propagation model, many measurements are needed : 1. 2. 3.

About 10 different base stations in each city At least 75 km of survey route for each city At least 1000 km of route in total

* Measurements at each point are compared to the predictions at each point and the error statistics analyzed Errors may be broken down by : 1. 2. 3. 4.

Clutter class LOS/NLOS Within a given range Outside a given range

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Measurements and Propagation Model Calibration •

Error Analysis Statistics • The Error is commonly defined as the difference between the predicted value (Propagation Model) and the measured value. At a given distance of index i, the error is noted εi •

Root Mean Square Error and Mean Error are given by : N

2 ε ε − ( ) ∑ i

RMS =

i =1

N

N

ε=

∑ε i =1

i

N

® Cirta Consulting LLC

The target is to ensure a mean error=0 and an RMS < 9 dB (The Lower the Better)

Non-uniform Propagation Types • Each area has a different correction factor. • Also the coverage objectives are usually different for urban, suburban and rural areas. • Therefore MAPL and the corresponding cell size has to be calculated for each region and cell count is: • For each area: A = 2.6 R 2 where R is the cell radius and A is the area of the corresponding hexagon. UrbanArea( Km 2 ) SuburbanArea( Km 2 ) RuralArea( Km 2 ) CellCount = + + 2 2 AUrban ( Km ) ASuburban ( Km ) ARural ( Km 2 )

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Introduction

•Definition of Outdoor signal level design threshold to be used in prediction tool. •Insure good quality communications. •Threshold important because it is the basis for the design, and cell size and no. of cells depend on this. •Aim: understand the different elements in the determination of the threshold.

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Introduction 2 • Receiver Sensitivity (from vendor or standard)

Use of Different Margins

• Outdoor coverage design threshold ® Cirta Consulting LLC

Receiver sensitivity margin (1) •Sensitivities defined in GSM Rec. 05.05

Portable: -104 dBm Handheld: -102 dBm DCS1800: -100 dBm

•Sensitivity : Min required signal level at receiver to meet performance requirements •Sensitivities defined for mobiles in an urban environment traveling at 50 km/h (TU 50) •These sensitivities with a C/I of 9dB correspond to error rate of 10% or RxQual =6 •These values include a margin for Rayleigh Fading

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Receiver sensitivity margin (2) •Today many handsets used at walking pace or static •At 50 km/h effect of fading is averaged but”static” mobiles will remain in fading “holes” longer. •Measurements show that for a handheld moving at 3 km/h (TU3) then for an acceptable audio quality we need: - RxQual = 4 ( system without frequency hopping) - RxQual = 5 ( system with frequency hopping) Quality margin must be introduced

® Cirta Consulting LLC

Receiver sensitivity margin (3) • Measurements campaign by CNET to link C/N, C/I and Rxqual • With no interference, without frequency hopping a Rxqual = 4 is obtained with C = -97 dBm • Quality margin = 5 dB • (FT 3 dB, Cellnet 4 dB)

5 dB 3 Km/h

® Cirta Consulting LLC

50 Km/h

Prediction/Lognormal Margin (1) • Propagation model predicts mean signal level

(σ )

• Characteristics: Mean error (0) and standard deviation • Shadow fading (obstacles) not taken into account • Model this shadow fading by a probability following a lognormal law • Introduce Margin to guarantee a certain percentage of cell surface area is covered

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Prediction/Lognormal Margin (2)

Standard Deviation of Prediction model

Level of guarantee Required (probability)

Lognormal Margin

• To calculate the margin we use coverage probability at cell border which corresponds to the required coverage probability over the surface of the cell.

® Cirta Consulting LLC

Prediction/Lognormal Margin (3) •Typical values: - Urban environment (Typical distance exponent = 3.5 ) - Standard Deviation of prediction model = 7 dB Margin in dB

Coverage probability on cell bordure %

Coverage Probability Over cell surface %

0 5

50 75

77 90

7

84

95

9

90

97

12

95

99

® Cirta Consulting LLC

- GSM Rec

3.30

Head Effect

•The human body creates loss for handheld mobile. •Loss due to distortion of antenna diagram •Some suggested values : •Recommendations GSM 03.30 = 3 dB. •Dr. Lee proposes 5 dB in worst case ( mobile on belt) •Most operators use 6 dB. •Motorola proposes 9 dB head effect, 15 dB at belt. •Telemate suggested value is 5 dB. ® Cirta Consulting LLC

Other Margins • Hand – Over: Some Operators use a 2 dB margin to ensure a good HO to neighboring cell • Material imperfections: we take a 1 dB margin to account for the tolerance in MS and BTS output power • Interference Margin: Some vendors use an interference margin to overcome interference impairments

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Example Calculation of Outdoor coverage threshold for 2W GSM handheld Sensitivity ( GSM Rec. 5.50 )

- 102 dBm

Sensitivity margin

5 dB

Lognormal margin ( for 90% area coverage probability)

7 dB

Head Effect Margin

5 dB

Outdoor Coverage Threshold

- 85 dBm

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Indoor Threshold (1) • Different types of Indoor Threshold corresponding to different services - Indoor Window: Near to window - Indoor: In room with windows - Indoor Deep : In corridor (loss through 2 walls) • Penetration loss varies greatly. Depends on type of materiel, architecture (no. of windows…), floor within building etc. • Mean penetration loss must be determined from extensive measurement campaigns ® Cirta Consulting LLC

Indoor Threshold (2) •To determine an Indoor threshold from the penetration loss there are two methods: - Use the distribution function of the measurements to find the loss corresponding to 90 % of the samples - Use the mean penetration loss and increase the lognormal margin to take into account the standard deviation of the indoor measurements.

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Use of margins • Understand what goes into the determination of coverage thresholds. • Make sure that all margins are included but only once! • Translate the clients requirements for service quality into margins • Thresholds must be validated by the client.

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TEST : Link Budgets Balanced link budgets show Maximum Allowable Path Losses for the coverage objectives shown below. Drive tests have shown the following propagation equations are valid. Determine the cell radius for each coverage objective. Coverage objectives:

Rural on-street MAPL = 147 dB Suburban in-car MAPL = 135 dB Urban in-building MAPL = 125 dB

Propagation equations: Rural: path loss = 110 + 32 log d Surburban: path loss = 115 + 37 log d Urban: path loss = 120 + 48 log d ® Cirta Consulting LLC

The Cellular Concept „

Urban Areas : High Interference Amounts ‹ C/(N+I)=C/I,

The System is Interference-Limited ‹ Coverage is not a problem (in General) ‹ Service Criterion : C > I „

Rural Areas : Low Interference Profile ‹ C/(N+I)=C/N,

The System is Noise-Limited ‹ Interference is not a problem (in General) ‹ Service Criteria : C > N ® Cirta Consulting LLC

The Cellular Concept „

Frequency Planning aims at : Optimising the Allocated Spectrum ‹ Guaranteeing a seamless coverage ‹ Ensuring minimum interference ‹

„

Main Difficulty of Frequency Planning is : ‹

„

Limited Number of TRXs (Available Channels)

The concept of Frequency Re-Use overcomes the Spectrum Limitations. Caution has to be made concerning the risk of generating co-channel and adjacent channel interference ® Cirta Consulting LLC

GSM Spectrum „

Allocated GSM1800 Band comprises two sub-bands : ‹ 1710 – 1785 MHz for Uplink (MS->BTS) ‹ 1805 – 1880 MHz for Downlink (BTS->MS) ‹ Each Sub-band = 375 Channels of 200 kHz associated to a given carrier ‹ 95 MHz are necessary to ensure the isolation between Up and Down Links Duplexing ‹ Each Operator is allocated a DL/UL band ‹ GSM uses TDMA (Time Division Multiple Access) ) 1 Physical Channel = 8 Logical Channels ) 1 Logical Channel = TCH or Signalling Channel (SDCCH, FCCH, SCCH, AGCH, RACH, etc...)

® Cirta Consulting LLC

Interference „

„

Definition of the Signal to Noise Ratio irrespective to the coor adjacent channels ‹ C/I = Puseful/Pharmfull Co-Channel Interference ‹ Interference Due to a Signal using the same Frequency :

C C  = 0   0  I  co −channel I1 + I 2 ‹C

is the useful Signal, I1 and I2 are co-channel interferers using the same frequency as C ‹ C, I1 and I2 are linear units (i.e. Watts or mW) ® Cirta Consulting LLC

Interference „

„

Adjacent Channel Interference are due to out-of-band spurious transmission GSM RF Mask is based upon the GMSK Modulation Scheme (GMSK = Gaussian Minimum Shift Keying)

C C =0 1 2    I Resulting I +I +I +...+N

0.5 dB

-30 dB -60 dB

GMSK RF Mask f-400 kHz f-200 kHz ® Cirta Consulting LLC

f

f+200 kHz f+400 kHz

Interference „

„

Interference = Impossible to identify and extract the wanted and interfering signal (noise included) GSM Specifications require C/I to be higher than 9 dB GSM

Recommendation

Protection

C/I (dB)

C/I

Protection

CoChannel

9

7.94

0

1st Adjacent

-9

0.125

18

2nd Adjacent

-41

0.0000794

50

3rd Adjacent

-49

0.0000125

58

® Cirta Consulting LLC

Traffic Theory : Erlang B „ „ „ „ „

Poisson Input with mean of λ arrivals/sec. Mean Service Time = 1/µ Traffic Intensity = A = λ. 1/µ Number of Serving Trunks (Channels) = S Blocked Calls Abandoned

AS Pb = B( S , A) = S S! k A ∑ k = 0 k! ® Cirta Consulting LLC

Traffic Theory : Erlang B Nb Carriers 1 2 3 4 5 6 7 8 Etc. ® Cirta Consulting LLC

Nb TCH 7 14 22 29 37 45 52 59

Erlang 2.3 8.2 14.9 21.0 28.3 34.7 42.1 48.7

Traffic Theory : Erlang C „ „ „ „ „

Poisson Input with mean of λ arrivals/sec. Negative Exponential Service Time with mean = 1/µ Traffic Intensity = A = λ. 1/µ Number of Serving Trunks (Channels) = S Blocked Calls held until served

Pr ob( Delay) = C ( S , A) = P[τ D > 0] AS S . S! S − A C (S , A) = s −1 AS S Ai + ∑ . S! S − A i! i=0 ® Cirta Consulting LLC

Traffic Theory : Erlang C „

Probability of Delay Greater than t :

P(τ D > t ) = C ( S , A)e „

Average Delay :

C ( S , A) E[τ D ] = (1 − A) Sµ ® Cirta Consulting LLC

− (1− A ) sµt

Traffic Theory : Poisson „ „ „ „ „

Poisson Input with mean of λ arrivals/sec. Negative Exponetial Service Time with Mean = 1/µ Traffic Intensity = A = λ. 1/µ Number of Serving Trunks (Channels) = S Blocked Calls Held ∞

k

A Pb = P( S , A) = e ∑ k = S k! −A

® Cirta Consulting LLC

Capacity Planning „

Aims of Capacity Planning 9 To allocated Sufficient Channels to support the expected traffic load 9 To ensure future sites are planned and implemented in time to meet subscriber growth (Business Plan) 9 To provide Traffic Loading Figures on which the fixed network can be based

„

Traffic Unit 9 9 9 9

„

Traffic is measured in Erlang : Etot = Esub*Nsubs Etot is the total Traffic Esub is the average traffic per subscriber Nsub Number of Subscribers

Example : Esub = 25 mE* and Nsub = 100, then Etot = 2.5 Erlangs *25 mE = 1.5 minutes of occupied TCH per Hour ® Cirta Consulting LLC

Capacity Planning „

Procedure for Calculating Number of Required Channels „

„

„

„

First Compute Busy Hour Traffic per Subscriber (Erlangs) : 9 Average Daily Number of Call Attempts × Average Call Length 9 Plus Number times length of Incoming Calls 9 Times Proportion of Total Calls made in the Busy Hour Then Calculate Total Traffic as Average Traffic Times Number of Subscribers Finally Use Erlang B Tables to determine the number of Channels required for a given Blocking Level Example : For GSM, 2 % is the typical blocking rate used

® Cirta Consulting LLC

Capacity Planning TEST ON DIMENSIONING USING CAPACITY DEMANDS „

Given a Dense Urban Area of about 35 km2 and a penetration rate estimated to 9 % over a total population of 500.000 inhabitants

„

Assuming 4 TRX 3-sector BTSs will be used,

„

Each sector (using 4 TRXs) has a cell radius of 0.45 km

„

Each Subscriber will require a 25 mE traffic

„

„

Compute the total required Traffic (Erlang) within this dense urban area, along with the required number of 3-sectorial BTSs What would be these numbers if the unit traffic increase to 40 mE ?

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Tower Mounted Amplifier : Effect on Coverage and Quality

® Cirta Consulting LLC

TMA

4 dB Gain in the UL

3 dB cable loss

BTS

BTS

Static Sensitivity=-110 dBm

Static Sensitivity=-110 dBm

S(without TMA) = -110 + 3 = -107 dBm*

* Body ® Cirta Consulting LLC

S(with TMA) = -110 + 3-4 = -111 dBm*

Loss and Lognormal Fading have to be added

Overview on Linkbudget Impact (1/2) „

Cell Range R computed using : ‹ MAPL=A+B*log(R) ‹ MAPL : Maximum Allowed Path Loss ‹ MAPL = EIRP-Effective Sensitivity ‹ Example : ) Given EIRP=Pout+Gant-CableLoss ) with Pout=40 dBm; Gant=18 dBi; Cable Loss=3 dB ) EIRP=40+18-3=55 dBm ) MAPL = • 55 - (-107+7+5) = 150 dB without TMA • 55 - (-111+7+5) = 154 dB with TMA ‹

MAPL : The higher the bigger the cell radius )

log(R) = (MAPL-A)/B ⇒ R = 10^((MAPL-A)/B)

® Cirta Consulting LLC

Overview on Linkbudget Impact (2/2) „

Numerical Example : ‹ Assume we use a Rural Propagation Model PL = 135 + 30*log(R) ‹

Cell Radius R= ) 10^( (150-135)/30 )= 3.2 km without TMA ) 10^( (154-135)/30 )= 4.3 km with TMA !

Path Loss (dB)

135+30*lod(d)

MAPL=154 dB with TMA

4 dB due to TMA MAPL=150 dB without TMA

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3.2 km

4.3 km

Distance (km)

Uplink Coverage Downlink Coverage

Directional Antenna Due to linkbudget imbalance

TMA Improves Uplink vs Downlink: To balance the Linkbudget the BTS output power has to be raised by 4 dB ! (the TMA gain) ® Cirta Consulting LLC

RF Repeater : Problem Statement (1/2)

Base Station High Penetration Loss added to propagation loss

In Car Coverage Threshold not reached No Coverage Tunnel

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RF Repeater : Problem Statement (2/2)

High Diffraction and Shadowing Loss : Hills, Blockings, etc.

Base Station ® Cirta Consulting LLC

MS

RF Repeater : Design Issues Repeater = Bidirectional Amplifier used to * Provide Coverage to “shadowed” rural areas * Provide Coverage to Tunnels * Provide Coverage to Indoor Areas where Capacity is not an issue Repeater comprises : * A High Gain Amplifier * A Duplex-filter for Up and Downlink Service * A Donor Antenna : From the Repeater to the Donor Site * A Re-Radiating Antenna : From the Repeater to the Area to be covered Repeater Features : * High Amplifier Gain * High Isolation Between the Repeater Ends to avoid oscillation ® Cirta Consulting * High LLC Channel or Band Selectivity

RF Repeater : Components Donor Antenna (BTS) High Gain, Very Directional To donor Cell

High Gain Amplifiers up to 85 dB

BPF BPF Band-Pass High Rejection Filters : Channel or Band Selective

® Cirta Consulting LLC

To poor area coverage

Re-Radiating Antenna (MS) Lower Gain, Wide Beamwidth

RF Repeater : Typical Antennae Mounting To donor cell

To donor cell

Uni- or Bidirectional High Gain Antenna

R

To Tunnel To a valley wide bandwidth antenna

R ® Cirta Consulting LLC

RF Repeater : Design Tricks 1. Donor Antenna should be : a. Preferably in LOS with the Donor Cell b. High Gain and High Directional c. Mounted in a location so that the RxLev > its static sensitivity d. Dip Fades have to be avoided : RF Measurements done prior to installation (Go or not Go) 2. To avoid interference between Donor and Re-Radiating antennas, an isolation is required : this should prevent the Repeater to oscillate. 3. Never have LOS between Re-Radiating antenna and Donor Cell 4. Depending on the application : Re-radiating antenna has to be chosen accordingly a. Tunnels : High gain (uni- or bidirectional) b. Valley or “shadow” : wide beamwidth and typical antenna gains ® Cirta Consulting LLC

RF Repeater : Antennae Location To donor cell

NOT RECOMMENDED

R

To a valley wide bandwidth antenna

To donor cell

R RECOMMENDED

To a valley wide bandwidth antenna

® Cirta Consulting LLC

RF Repeater : Powerbudget „

Allgon Indoor Repeater Technical Specs : ‹ ‹ ‹

„

Gain : 45 - 70 dB Noise Figure : 5 dB Maximum input power : +13 dBm

Assumptions : ‹ ‹ ‹ ‹ ‹

„

(1/3)

Donor BTS @ 4.5 km from the Repeater : Free Space and LOS assumed. BTS Donor Antenna EIRP : 48 dBm Donor Antenna to Repeater cable loss : 1.5 dB Re-radiating Antenna to Repeater cable loss : 0.5 dB Donor Antenna Gain : 18.5 dBi Re-radiating Antenna Gain : 14 dBi

Task : Balance the UL and DL, then compute the repeater cell radius

® Cirta Consulting LLC

RF Repeater : Powerbudget „

„

„

„

(2/3)

Received Power at the donor antenna connector : ‹ Pr(donor)=EIRP(donor BTS)-PL = -56.6 dBm ) PL = 32.44+20*log10(4.5*900) = 104.6 dB (free space loss) ) EIRP(donor BTS) = 48 dBm Input Power at the Repeater (Downlink) : ‹ Pin = Pr(donor) - Cable Loss(DL) + G(donor) ) Pin = -56.6 -1.5 + 18 = -40 dBm Repeater Output power (downlink) : ‹ Pout(min) = Pin + Gmin(Repeater) = -40 + 45 = 15 dBm ‹ Pout(min) = 15 dBm > 13 dBm (need a 2 attenuation) EIRP(Re-Radiating) = Pout - Cable(to antenna) + G(Re-Radiating) ‹ EIRP(Re-Radiating) = 13 - 0.5 + 14 = 26.5 dBm

Without a repeater the penetration loss of 15 dB leads to : ® Cirta LLC ‹ Consulting Rxlev (indoor) = -56.6 - 15 = -71.6 dBm !!! @ the vicinity of the lossy wall

„

RF Repeater : Powerbudget „

„

„

„

(3/3)

Received Power at the Re-radiating antenna connector : ‹ Pr(Re-Rad.)=EIRP(MS)-PL = 33 - 106.5 = - 73.5 dBm ) PL = 120 + 45*log(0.5) = 106.5 dB (e.g. Okumura-Hata Model) ) EIRP(MS) = 33 dBm (no Power control considered) Input Power at the Repeater (Uplink) : ‹ Pin = Pr(Re-Rad) - Cable Loss(UL) + G(Re-rad) ) Pin = -73.5 - 0.5 + 14 = -60 dBm Repeater Output power (Uplink) : ‹ Pout(min) = Pin + Gmin(Repeater) = -60 + 45 = -15 dBm ‹ Pout(min) = -15 dBm < 13 dBm (OK) EIRP(Donor) = Pout - Cable(to antenna) + G(Re-Radiating) ‹ EIRP(Donor) = -15 - 1.5 + 18 = 1.5 dBm ‹ Uplink Power Amp. Of repeater must be raised to maximum 75 dB ‹ EIRP (donor) = 1.5 + 30 = 31.5 dBm

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Hybrid Combiners : Possible Usage To Antenna

To Antenna

Matched Load 50 Ω

-3 dB

50 Ω

-3 dB

-3 dB

50 Ω

-3 dB

TX1 TX2 TX1 TX2 ® Cirta Consulting LLC

TX3 TX4

Hybrid Combiners : Features „

Hybrid Combiners : ‹ ‹

„

Disadvantage : ‹ ‹

„

4-Port Balanced Passive Devices Reciprocal : Tx/Rx

High insertion loss : 3 to 3.3 dB Not suitable for large Number of Transmitters : High Losses

Advantage : ‹ ‹ ‹

Linear Device : Sufficient isolation between Transmitters Cost-effective combining solution for small number of Transmitters Being relatively Wide-band, permits Transmitter Frequency Hopping : Synthesized or Baseband

® Cirta Consulting LLC

Slow Frequency Hopping „

Radio Propagation Channel : ‹ ‹

„

Dynamic : Mobility and Scattering problems Fast Fading : Frequency Selective (dispersive) ) Some frequencies are more or less affected by Multipath fast fading (Reighley Fading) ) Fast Moving mobiles less sensitive to Multipath : GSM Standard define TU3 and TU50 and a Sensitivity margin of 4 dB is considered. ) Effective Receive Sensitivity improved for Fast Mobiles

Slow Frequency Hopping (SFH) : ‹ ‹ ‹

Allows an effective “Frequency Diversity” SFH statistically improves the overall signal receive power SFH “diversity” gain : between 3 and 6 dB (ref. W.Y. Lee)

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Slow Frequency Hopping : Implementation „

„

Synthesized Frequency Hopping : ‹

The processor controlling the Tx retunes it to a new frequency on a per time-slot basis, according to a predetermined pattern or sequence

‹

The Output from the Tx varies across a wide range of frequencies : Handled by the Hybrid combiner (wide-band device)

Baseband Frequency Hopping : ‹ ‹ ‹ ‹

The Digital baseband signal is applied to what is effectively a fast electronic switch, which is controlled by a processor in the Tx. The Switch is connected to a number of Txs, each being fixed-tuned to a different frequency On a per time-slot basis, baseband digital signal is switched between different transmitters Cavity Filter Combiners or Hybrid Combiners can be used

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Synthesized and Baseband Frequency Hopping : Comparison „

Synthesized FH : ‹ Offers

a versatile solution for multiple channels ‹ Cost-effective : No Cavity Filter Combiners required ‹ Few Transmitters can be used for more channels hopped „

Baseband FH : ‹ Low

losses when Cavity Filter Combiners are used ‹ Hopping can only occur over the same number of frequencies as there are Transmitters ® Cirta Consulting LLC

Slow Frequency Hopping : Implementation Baseband Frequency Hopping Cavity Filters Baseband Data

TX Processor

0110110110

Varying Frequency

TX1

TX2

Electronic Switch

f1 TX1

To Antenna

Tunning Control

11001101110

Hybrid Combiner

f2

Baseband Data 11001101110

BPF

TX2

BPF

f3 Varying Frequency

Baseband Data

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TX Processor

TX3

BPF Matching Stub

To Antenna

Synthesized Frequency Hopping

Receiver Multicoupler Rx Antenna A

AC/DC POWER SUPPLY

Rx Antenna B

RECEIVER MULTICOUPLER

RX A ® Cirta Consulting LLC

RX B

RX1

RX A

RX B

RX2

DUPLEX FILTER Common TX/RX Antenna Passes DL Frequencies only

Passes UL Frequencies only

DUPLEX FILTER

From TX

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To RX

Typical Antenna Connection : X-POL Diversity Cross-Polarized Antenna Assembly

Tx/Rx A

Rx B

Bandpass Filter

Duplex Filter Rx B

Matched Load

Rx A Hybrid Combiner

Rx A

Tx ® Cirta Consulting LLC

Receiver Multicoupler

Tx

Rx Rx

Rx B

Rx A Rx B

Polarization Diversity Systems Using Separate Tx Antenna Without Duplex Filter

Top View of 3-sector site with Vertical Polarization Diversity

d

Tx

2 Rx

2 Rx Tx

Tx

RxA RxB

BTS Equipment ® Cirta Consulting LLC

Tx

2 Rx

Polarization Diversity Systems Vertical Tx/Rx Antenna

Horizontal Rx Antena Tx/Rx

Duplexer

Tx

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Rx A Rx B

Tx/Rx

Tx/Rx

Polarization Diversity Systems d1 d2

d2

Rx Tx

Tx

Rx Rx A

Tx

Rx

Rx B Rx

Tx

Horizontal separation d1 for diversity = 10λ Horizontal Separation d2 for 30 dB Isolation = 2λ ® Cirta Consulting LLC

Rx