Procedure Followed -1 Always start from Rx End. Find Out What BER Required. To calculated BER, Mod Type Required. Both BER & Mod Type will give what Eb/No Required. Now find out what data rate is required. Now find out what FEC is required. Now calculate What Spectrum BW is being used. Now calculate to achieve this BER for above parameters what C/N is required. Up to this its called digital base band calculation. This point is also to join analog parameters with digital parameters

.

Procedure Followed -2

Now to get C/N, we will first calculate C/No at Rx End. For this, lets start from TX End. Now, Take all parameters details as per link parameters required. Calculate C/No (uplink, measured at satellite) & C/No (downlink, measured at Rx earth station). Now calculate overall C/No at Rx earth station. Now co- relate this C/No with digital base band calculation.

Digital base band Explained -1 BER = bit error ratio means error bits accepted per total bits transfer. Eb/No = Eb divided by No. Eb = Energy per bit at the receiver after complete signal processing, doesn't matter what else. No = Noise power density means noise power per Hz.total noise is divided by total no of Hz & what noise is being experienced by per Hz. At Rx end, we are not interested in C/No, C/N, Mod Scheme, Noise Power, FEC, TX Power, Satellite Parameters etc. but we are very much interested in BER & in turn minimum bit energy required for demodulation & all. Eb/No = 13.2dB means one bit is having 13.2 dB more energy than noise energy being experienced by per one Hz.

Digital base band explained-2

Now, because we are not sending one single bit over one Hz bcos its not practical. We have limited spectral BW & any how we try to manage to maintain Eb/No by other parameters e.g. FEC, Mod, Data rate, BW. Now, What is transmitting WAN connectivity, its not our concern, our net requirement is what Data Rate is being Transmitted from modulator & what Eb/No we are getting by TX medium at receiver whether we are managing with Less BW & more BW, FEC & SR doesn't matter at all.

Digital Base band derivation Eb/No = Signal Energy per bit / Noise Energy per Hz To calculate energy attained by One bit , we have to divide total energy by total no of bits. To calculate energy attained by one Hz , we have to divide total noise power by total no of Hz. It means total signal power = energy per bit * total no of bits Total Noise power = energy per Hz * total no of Hz. Total energy / Total Noise power = Eb * Bit rate / No * BW Total signal Energy means total carrier power means C. Total Noise power means N. C/N= Eb/No * BR/BW

Digital Base band derivation 2 C/No = Total Carrier power / Noise power density . C/No = How much dB carrier power is more than noise power attained by per Hz. Or in other words, One Hz is having how much signal power more than noise power. E.g. C/No = 60 dB/Hz means in this link one Hz is having 60 dB more carrier power than noise power. Now, If we divide this carrier power by total no of Hz consisting a total no of HZs called BW then total power is divided among total no of HZs. C/No / BW = C/ No * BW but No * BW = N = Noise power hence C/N = C/No / BW. C/N = C/No 10log ( BW )

Sure Shot Digital Formulae If we say channel is of 8 Mb data. Its our actual information which needs to be transmitted. Its Called Information Rate(IR). Now divide it by FEC. It will be called your Transmission Rate (TR). TR = IR/FEC ( Viterbi) If we use reed solomen FEC also, then it will be TR = IR/ (FEC*188/204) TR is the total bits needs to be sent over spectrum. We use symbols to send these bits. If each symbol is carrying one bit, its called BPSK, if two bits, its called QPSK & so on. SR = TR/ Mod Sometimes, SR is also called noise bandwidth. If we multiply SR by roll off factor. Its our required bandwidth BW = SR* Roll Off factor

Explanation for Carrier Parameters

Lets calculate for following inputs. Eb/No = 7 , IR = 8 Mbps , FEC =3/4 , Mod = QPSK, BW = ? Now calculate, TR = 8 Mbps / .75 = 10.66 Mbps TR = 10.66 Mbps/ (188/204) = 11.56 Mbps Now S/R = 11.56 Mbps / 2 (Each Symbol carrying 2 bits) = 5.78 Msps Roll Off factor = 1.25, Then, BW = 5.78 Msps * 1.25 = 7.225 Mhz

Interpretation of C/N with power level

Up to C/N calculation , we dont know what is the power level & carrier level in dBm. We only know that there should be a ratio of carrier power to noise power to achieve required BER or Eb/No. In fact , up to C/No level calculation we are not dealing with noise which can affect Eb/No , this was the loss in signal power during transmission from TX site Satellite Rx site. Then, we should calculate our TX power in dBm only with loss in signal but we are calculating it with respect to noise C/No why?

Effect of FEC If everything is same what will be change in Eb/No by changing FEC. First Calculate ratio = New FEC value / Old FEC value. Change in Eb/No = 10 log ( New FEC / Old FEC). E.g FEC changes from to 7/8 then .. Eb/No Change = 10 log ( 7/8 / ) = .67 dB will be down.

Interpretation of BW & DR DR is basically can be considered from following two ways: If any channel is saying that its content is of 8 MB. It may that somebody can announce its their channel DR. But as far our calc concerned, its IR. What TR we use in our calc, its basically DR. Given BW or Available BW can transfer maximum DR= TR= BW * Mod Factor.

Calculation Of Power Level -1 First Calculate what C/N is required. Now Find followings about Receiver , Noise bandwidth , Gain , Noise floor. Now Calculate as follows: Noise Power + C/N = Carrier Power. Noise power = Thermal Noise + gain + NF Thermal Noise = Noise Density + 10 log ( Receiver BW ) Noise Density = Noise at One Hz (No) No = kT = -174 dBm.

Calculation Of Power Level -2 Lets more discuss on power level. Noise power means level of noise. Measured in dBm or dBW. Every equipment/component when gets power up for processing's. Its get heated. As a result, a temperature is there. Which in turn increase the noise. This temperature needs to be taken in account when we measure power level. Lets say we give some signal as an input to LNB. LNB process signal. Add some gain & output is there. Lets assume, there is no gain. Then input signal will be little bit down due to its won temp. This difference in i/p & o/p level due to temp is measured as a ratio. This ratio is called noise factor. Log value of which in turn is called Noise Figure, measured in dB.

Calculation Of Power Level -3 What signal we are receiving from satellite is having . Noise power means level of noise. Measured in dBm or dBW. Every equipment/component when gets power up for processing's. Its get heated. As a result, a temperature is there. Which in turn increase the noise. This temperature needs to be taken in account when we measure power level. Lets say we give some signal as an input to LNB. LNB process signal. Add some gain & output is there. Lets assume, there is no gain. Then input signal will be little bit down due to its won temp. This difference in i/p & o/p level due to temp is measured as a ratio. This ratio is called noise factor. Log value of which in turn is called Noise Figure, measured in dB.

LB - 1 Link Budget is the calculation to get the exact C/N within our permissible range. During a signal setup, we are given maximum allowed power from our HPA towards satellite by the satellite operator. Accordingly, we are given downlink EIRP which we will receive from satellite towards our earth station to lock the IRD. We need to maintain our signal within this permissible limits. To check our signal strength or link feasibility within this permissible limits, we need to calculate link budget.

LB - 2 Link Budget has two section a) Input of Data b) Calculations. Input of Data Satellite parameters. Carrier Parameters Tx ES Parameters Rx ES Parameters Misc Losses Calculations Uplink calculations. Downlink calculations Overall Calculations

LB -3 Satellite ParametersSatellite Name Orbital Location G/T SFD Input BO Output BO Saturation EIRP Transponder BW Uplink Frequency Downlink Frequency IM Product Sat.Ant.Rx.Gain/m2 Intelsat 10 68.500 -12.000 -79.400 5.000 3.500 32.000 54.000 6.148 3.923 18.000 37.200 deg.E dB/K dBW/m2 dB dB dBW MHz Ghz Ghz dB dB/m2

LB - 4 Link Parameters

Carrier Info Rate FEC Code Rate Modulation No.of Bits per Symbol Transmission Rate Noise BW Noise BW Factor Allocated BW Eb/No Required Cl Sky C/No Required Cl Sky C/N Required Link Availability

9750.000 0.750 QPSK 2.000 13000.000 6500.000 1.250 8125.000 6.000 77.139 8.041 99.700

Kbps

Kbps

KHz dB dB-Hz dB %

LB 5 Tx ES ParametersTx Antenna Dia 9.000 m

Tx Ant. Efficiency

70.000

%

Tx Gain

53.710

dB

Tx Ant. Pointing Losses

0.500

dB

Feeder Loss

0.500

LB -6 Rx ES ParametersRx Antenna Diameter Rx Ant. Efficiency Rx.Ant.Pointing Losses Pre LNA Losses LNA Noise Temp Ant. Noise Temp Clear Sky Noise Temp Clear Sky G/T Antenna Gain 2.400 50.000 0.300 0.200 65.000 35.000 100.000 16.365 36.865 m % dB dB K K K dB/Deg K dBi

LB 7 Misc LossesUplink Rain Attenuation 0.000 dB

Dnlink Rain Attenuation

0.000

dB

Uplink Free Space Loss

199.620

dB

Dnlink Free Space Loss

195.717

dB

Uplink Atm.Attn.

0.000

dB

Dnlink Atm. Attn.

0.000

dB

LB -8 Uplink CalculationsTx of EIRP of E/S Uplink Path loss Power at Sat. Ant. Sat.Ant.Rx Gain/m2 Per Carrier FD @ SC SC pattern advantage @ES Per carrier BE FD arriving @ SC Input BO/Carrier Sat G/T Uplink C/No Uplink C/N 58.75 199.62 -140.87 37.20 -103.67 11.40 -92.27 24.27 -12.00 87.13 18.03 59.84 199.62 -139.78 37.20 -102.58 11.40 -91.18 23.18 -9.00 88.22 19.12 dBW dB dBW dB/m2 dBW/m2 dB dBW/m2 dB dB/K dB-Hz dB

LB -9 Downlink CalculationsSaturation EIRP Output Backoff CarrierDn EIRP Output BO/Carrier Downlink Path Loss Cl.Sky G/T SC pattern advantage @ES Downlink C/No Downlink C/N 32.00 3.50 20.63 11.37 195.72 16.37 8.20 78.08 8.98 32.00 3.50 19.54 12.46 195.72 16.37 8.20 77.17 8.07 dB dB dBW dB dB/K dB dB dB-Hz dB

LB -9 Downlink CalculationsSaturation EIRP Output Backoff CarrierDn EIRP Output BO/Carrier Downlink Path Loss Cl.Sky G/T SC pattern advantage @ES Downlink C/No Downlink C/N 32.00 3.50 20.63 11.37 195.72 16.37 8.20 78.08 8.98 32.00 3.50 19.54 12.46 195.72 16.37 8.20 77.17 8.07 dB dB dBW dB dB/K dB dB dB-Hz dB

LB- 10 Overall CalculationsUplink C/N 18.03 19.12 dB

Dnlink C/N

8.98

8.07

dB

IM Product

18.00

18.00

dB

Composite C/N

8.01

9.77

dB

Required C/N

8.04

8.04

dB

Link Margin

-0.03

-0.03

dB

LB -11 G/T G/T Its figure of merit for any receiving stations. Even for satellite, G/T matters. Gain in dB / Temperature in K. Gain 10 log (System Temp) System temp = Ant Noise Temperature + LNB Temperature + any other noise temp. Note: More G/T means good receiving & less G/T means less receiving of the signal.

LB-12 Saturation Flux Density If we send light via a torch, over a distance its visibility gets down. In the same way, what signal power we are sending from antenna towards satellite, being scattered & gets down. To measure this signal strength anywhere in the space, we denote it via flux density. If we send enough power that will be received by satellite & its HPA will get saturate, we will denote this flux density as SFD. It is the power from ES towards satellite which will saturate satellite HPA.

LB -13 EIRP Effective isotropic readiated power. It is the final power transmissting from ES towards satellite irrespective of HPA power, W/G losses, antenna size etc. If we have transmitted 10dBW from HPA & antenna gain is 54 dbi. Ignoring any losses from HPA to antenna, EIRP will be 10+ 54 = 64 dBW. EIRP = Power in dBW + Gain in dBi. Note: If our HPA shows 4 watt output. It means 6 dBW being transmiited from 54 dBi gain antenna, then EIRP will be 60 dBW But actual EIRP will be less due to further losses till antenna.

LB -14 Downlink EIRP It the power coming from Satellite towards ES. Its exactly same like HPA of satellite is sending signal towards ES.

LB -15 Link Budget Calculated If we need 9 MHz BW from satellite operator. He will provide us following data. 1) Operating PFD e.g. -79.4 dBW 2) Downlink EIRP e.g 32 dBW Note: Operating PFD means, this is the maximum allowed PFD from your ES towards satellite. Downlink EIRP means, this is the maximum EIRP received from satellite by your earth station.

LB -16 How to calculate Operating PFD. First find out SFD for the satellite. E.g -79.4 dBW/m2. Normally, SFD given by satellite is on Beam Edge. It may vary w.r.t contour. Now find out your contour values. Lets say, you are in contour of -2dB. So now SFD for your contour will be -81.4 dBw/m2 Now find our Transponder BW. Lets say its 54 MHz. Now Divide this TBW by your alloted BW. Lets Say you have been alooteed 9 Mhz. E.g 54/9 = 6. Now calculate = 10 log (6) =7.78. Now get IBO for satellite Transponder. E.g. 5 dB Now operating SFD will be as follows: SFD Contour value 10 Log ( TBW/ABW)- IBO = -79.4-2-7.78-5 = -94.18dBW/m2.

LB -17 How to calculate Downlink EIRP. First find out Downlink EIRP for the satellite. E.g 32 dBW Normally, Downlink EIRP given by satellite is on Beam Edge. It may vary w.r.t contour. Now find out your contour values. Lets say, you are in contour of -6dB. So now SFD for your contour will be 26 dBw Now find our Transponder BW. Lets say its 54 MHz. Now Divide this TBW by your alloted BW. Lets Say you have been alooteed 9 Mhz. E.g 54/9 = 6. Now calculate = 10 log (6) =7.78. Now get OBO for satellite Transponder. E.g. 3 dB Now operating Downlink EIRP will be as follows: Downlink EIRP Contour value 10 Log ( TBW/ABW)- OBO = -32 -6-7.78-3 = 15.22 dBW.

Calculation of constants Let power transmitted=Pt Gain of antenna=Gt Then EIRP=Pt*Gt Pr(Power received at satellite)=(EIRP/4 Pi R^2)*Aeff..(1) Antenna gain Gr=4 Pi Aeff/lambda^2

Calculation of constants-2 Hence Aeff=Gr lambda^2/4Pi(2) From eqn 1&2 Pr=Pt Gt Gr (lamda/4 Pi R^2).(3) We know that noise power(N)=KTB(4) From eqn 3&4 C/N=Pr/N= Pt Gt Gr (lamda/4 Pi R)^2 /KTB = EIRP (Gr/T) (lamda/4 Pi R)^2 (1/K) (1/B) Converting in dB scale we get C/N= EIRP +(Gr/T)+ 10 log(lamda/4 Pi R)^2 -10 log K-10 log B) (5) K=1.38*10^-23 J/K

Calculation of constants-3 Hence 10 log K=10log(1.38*10^-23)=-228.6 10 log(lamda/4 Pi R)^2 = -10 log(4 Pi R/Lamda)^2= -Free space loss= -FSL Now eqn 5 becomes C/N=EIRP + G/T - FSL +228.6 -10 log B(6)

Calculation of FSL FSL=10 log (4 pi R/lambda)^2 =20 log (4 Pi R f /C) Let R=36000 km=36*10^6 m C=3*10^8 m/s f=6 GHz=6*10^9 Hz Now FSL=20 log (4*3.14*36*10^6*6*10^9)/3*10^8=199

Compression - Introduction Compression means reduction in data rate. We are much interested in to understand the processing once A/V signal is given to encoder & output of Modulator is available. It means how we encode A/V signal. It means how we actually reduce its data. How we carry this compress data. E.g. MPEG-2/MPEG-4 SD/HD etc.

Compression Information & Signal Information means the content we want to transmit. It may be Audio/ Video/ Text/ Picture/ Fax etc. It may be data bits also. In digital communication, this information is first converted in bits. Once, every type of content is converted in bits, its ready to send over any link. E.g with wire or wireless. Then we generate a high sine frequency wave, called as pure carrier. ( thats why, modulator is also called as transmitter) Now, we superimpose this information over this high sine wave. The process of super imposing this information over sine wave is called modulation. Output of modulator which is in form of modulated sine wave is a signal. Information is in form of bits whereas signal is in form of Hz.

Information & Signals - Basics Digital information is in bits & measured in Mbps. 2 Mbps means, 2 mega bits are being transmitted in one sec. Signal is in form of Hz & measured in MHz. 2 MHz means 2 mega Hz are being transmitted in one sec. If one bit is being carried by one Hz, it means spectral density is 1:1. If two bits are being carried by one Hz, it means spectral density is 2:1. Compactness of spectral density is function of modulation scheme. Signal itself has 3 parameters e.g Amplitude, frequency & Phase. If we play with Amplitude ,its called amplification & done by HPA. If we play with Frequency, its called frequency conversion & done is by upconvertor. If we play with Phase, its called modulation scheme.

Bit Rate & Baud Rate Bit rate means total no of bits transmitted in one sec. Baud rate means total no of signalling units per sec. Lets understand by one example. On one six- lane highway, only vehicles e.g cars can travel. Its called Baud rate. Total no of signalling units in the allowed BW. If now, lets assume, each car has five passengers inside, then total passengers in 6 cars will be 30. 30 is the total bit rate. Bit rate will either equal to baud rate or more than of baud rate. But cant be lesser than Baud Rate. Symbol rate is also a one type of Baud Rate.

Compression Standards

Digital information is in bits & measured in Mbps.

Difference between MPEG-2 & MPEG -4

Digital information is in bits & measured in Mbps.

Meta Data with Compression

Digital information is in bits & measured in Mbps. .

Noise Factor & Noise Figure

Digital information is in bits & measured in Mbps.

VSWR Explained

Digital information is in bits & measured in Mbps.

Intermod

Digital information is in bits & measured in Mbps.

Return Loss

Digital information is in bits & measured in Mbps.

Roll- Off factor

Digital information is in bits & measured in Mbps.

Spectrum Inversion

Digital information is in bits & measured in Mbps.