WipAir Series

RF Planning &
Link Budget Calculation
Link Budget Calculation

Gain
Gain it simply a ratio - Input x (Gain) = output

Frequently in RF and electronics, gains and attenuations are very

big or very small numbers. dB is used to simplify the calculations:

dB = “deci” + “Bell”

• It has no units

• To calculate Gain in dB: dB = 10 x log(output / input)

• To calculate effect: Gain = 10(dB/10)

Link Budget Calculation

Why do we use the logarithmic scale / dB?

• Conveniently represent very large or small numbers

For example:
50dB= gain of 100,000
-50dB= Gain of 0.00001

• Carry out multiplication of ratios by simple addition and subtraction

For example:
Gain=> 1,000x1000=1,000,000
or 30dB+30dB=60dB
Link Budget Calculation

Interpreting Gain: Positive dB

Rule of thumb:
Multiples of +10dB express magnitude (number of zeros).

• gain of 1 is +0dB (input = output)

• gain of 2 is +3dB (2*input = output)
• gain of 10 is +10dB
• gain of 100 is +20dB
• gain of 1,000 is +30dB
• gain of 10,000 is +40dB
• gain of 100,000 is +50dB
Link Budget Calculation

Interpreting Gain: Negative dB

Rule of thumb:

Multiples of -10dB express magnitude (number of places to shift

the decimal point to the left).

• gain of 1 is 0dB (input = output)

• gain of 0.5 is -3dB (2*input = output)
• gain of 0.1 is -10dB
• gain of 0.01 is -20dB
• gain of 0.001 is -30dB
• gain of 0.0001 is -40dB
• gain of 0.00001 is -50dB
Link Budget Calculation

dB Gain
A little dB trick 0 1.00
Since it’s a log function it can be simplified. 0.5 1.12
By remembering few basic dB gain 1 1.26
relationships, most others can be estimated
2 1.58
through some very simple math.
3 2.00
4 2.51
7dB = 3dB + 3dB + 1dB 5 3.16
 6 3.98

or 2 * 2 * 1.26 = 5.01 7 5.01

8 6.31
9 7.94
10 10.00
Link Budget Calculation

Basic Path of Wireless connection

• Radio (MU)
• Coax
• Antenna  (free space)  Antenna
• Coax
• Radio (SU)

Radio Wave Path

Free Space & Fresnel Zone
Antenna Antenna

Coax
Coax

Radio "Radio"

Earth Bulge
Link Budget Calculation

Line of Sight

LOS is what you can ”see”. Right?

• True for you.
• Almost true for radio systems.
Link Budget Calculation

Free Space Loss:

The amount of lost energy when the signal is going through free
space (air).

Free space loss can be easily calculated using the free space loss
formula:

Lp = 32.4 + 20log(f) + 20log(d)

f = Frequency [MHz]
d = Distance [km]
Link Budget Calculation

Transmit Power:
The amount of energy that the radio generates at the RF interface
(Antenna connector).
Receiver Sensitivity:
The minimum signal power that the radio receiver requires.
If the signal power is lower than the RX sensitivity, the radio will not
“see” the data and a physical link will not be established.

Both Tx power and Rx sensitivity are measured in dBm.

dBm: Decibels referenced to 1mW.

To convert between dBm and mW a simple formula is used:

dBm = 10log[P] P = power [mW]

Link Budget Calculation

Antenna Gain:
Antenna does not “amplify” the signal. It only concentrates it in a
particular direction or pattern.

The strength of the radiated field in a particular direction is

measured relative to an isotropic reference antenna and is called
Antenna gain (measured in dBi).
Link Budget Calculation

Before deploying any wireless link make sure the ‘Link Budget’ enables
RF connectivity with the required margin. Here is the “Go no go” test:

Pr = Tx + Gt + Gr - Lt – Lr- - Lp

Pr - Signal power available at the receiver input (dBm).

Tx - Transmitter power output (dBm). Radio Wave Path
Free Space & Fresnel Zone
Antenna Antenna

Gt - Antenna gain at the transmitter side (dBi). Coax

Coax

Gr - Antenna gain at the receiver side (dBi). Radio "Radio"

Lt - Transmission line loss at the transmitter side (dBm). Earth Bulge

Lr - Transmission line loss at the receiver side (dBm).

Lp - Free space loss (dBm).

If Pr is lower than the Rx sensitivity, the wireless connection cannot be established !

Link Budget Calculation

SNR – Signal to Noise Ratio

The SNR is measured:

SNR = RSSI (Pr) - Noise Wave

In congested areas, the SNR defines the Signal

modulation (not the sensitivity levels):
Noise
Modulation BPSK QPSK QPSK 16QAM 16QAM 64QAM 64QAM 64QAM
1/2 1/2 3/4 1/2 3/4 2/3 3/4 5/6 Low High
SNR [dB] 7 12 13 16 17 23 24 25 SNR SNR

Without sufficient SNR the wireless link will not be stable or not work at all !
Link Budget Calculation

WipAir Throughput Specification

Link Budget Calculation

Radio Specifications

WipAir WipAir WipAir WipAir WipAir

1000 2000 3000 6000 8000
Net Throughput 20 Mbps 50 Mbps 135 Mbps 200 Mbps 310 Mbps
2.3-2.7, 4.8-6.0 GHz 700, 900 MHz, 2.0-2.3, 2.3-2.7, 2.3-2.7, 4.4-4.7, 4.8-6.0, 6.x, 10.5GHz
3.3-3.8, 4.8-6.0 GHz
PPS >100,000 Packets Per Second
Waveform Advanced OFDM Advanced OFDM 2x2 dual polarization MIMO
Channel Size Configurable – 3.5/ 5/ 7/ 10 / 14/ 20 / 28/ 40/ 50 MHz
Range > 130 Km
Output Power Configurable up to 30 dBm, 40 dB dynamic range
Handling Interference AIS – Automatic Interference Sensibility
Hitless ACM – Adaptive Coding & Modulation
ACS – Automatic Channel Selection
FEC – Forward Error Correction, k = 1/2, 2/3, 3/4, 5/6
Fast ARQ – Automatic Retransmit reQuest

Encryption & Security 128 AES & MAC level authentication 256 & 128 AES & MAC level authentication
Modulation BPSK QPSK 16QAM 64QAM
FEC 1/2 1/2 3/4 1/2 3/4 2/3 3/4 5/6
Sensitivity @ 20 MHz (dBm) -87 -85 -83 -80 -78 -72 -70 -67
Link Budget Calculation

Noise Levels
Link Budget Calculation

Exercise: Real life Link budget analysis

Test conditions:
1) TX power = 25 dBm
2) RF frequency = 5.8 GHz
3) Noise level = -75 dBm

Questions:
1) What will be the RSSI @ 1, 5 and 10 Km?
2) Will the link be stable at QPSK3/4 modulation?
3) Will the link be stable at 16QAM3/4 modulation?

Tested Solutions:
1) Competitor with integrated antenna of 15.5 dBi (MIMO)
2) WipAir with integrated antenna of 23 dBi (SISO)
Link Budget Calculation

What will be the RSSI @1, 5 and 10 Km of competitor 15.5 dBi antenna?

Tx - Transmitter power output  25dBm

Gt - Antenna gain at the transmitter side  15.5dBi
Gr - Antenna gain at the receiver side  15.5dBi
Lt - Transmission line loss at the transmitter side  0dBm
Lr - Transmission line loss at the receiver side  0dBm
Lp - Free space loss 1, 5, 10 Km  108, 122, 128 dBm
Pr - Signal power available at the receiver input  -52, -66, -72 dBm

Lp = 32.4 + 20log(f) + 20log(d)

Pr = Tx + Gt + Gr - Lp - Lt - Lr
Link Budget Calculation

What is the required SNR per modulation?

Modulation Required SNR [dB]

(+/- 2dB)
BPSK 1/2 7
QPSK 1/2 12
QPSK 3/4 13
16QAM 1/2 16
16QAM 3/4 17
64QAM 2/3 22
64QAM 3/4 24
64QAM 5/6 26

Without sufficient SNR the wireless link will not be stable or not work at all !
Link Budget Calculation

Will competitor link be stable at QPSK ¾ modulation?

SNR SNR for Noise Rx sensitivity RSSI Distance

Margin QPSK 3/4 Floor @ QPSK 3/4 (dBm) (Km)
(dB) (dB) (dBm) (dBm)

10 13 -75 -83 -52 1

-4 13 -75 -83 -66 5
-10 13 -75 -83 -72 10

Competitor link equipped with 15.5dBi Antenna:

• Works at 1KM
• Will not work above 5KM
• Will not work above 10KM, not even with noise level of –85dBm
Link Budget Calculation

What will be the RSSI @1, 5 and 10 Km for WipAir 23 dBi antenna?

Tx - Transmitter power output

 25dBm
Gt - Antenna gain at the transmitter side
 23dBi
Gr - Antenna gain at the receiver side
 23dBi
Lt - Transmission line loss at the transmitter side
 0dBm
Lr - Transmission line loss at the receiver side
 0dBm
Lp - Free space loss 1, 5, 10 Km
 108, 122, 128 dBm
Pr - Signal power available at the receiver input
 -37, -51, -57 dBm

Lp = 32.4 + 20log(f) + 20log(d)

Pr = Tx + Gt + Gr - Lp - Lt - Lr
Link Budget Calculation

WipAir Performance
Same conditions, using WipAir equipped with integrated 23dBi Antenna

SN SNR for Noise Rx sensitivity RSSI Distance

Margin 16QAM 3/4 Floor @16QAM 3/4 (dBm) (Km)
(dB) (dB) (dBm) (dBm)
21 17 -75 -78 -37 1
7 17 -75 -78 -51 5
1 17 -75 -78 -57 10

At the same conditions:

• WipAir 8000 MIMO, integrated 23 dBi Antenna - delivers Net capacity of 185Mbps at 10Km.
• WipAir 8000 SISO, integrated 23 dBi Antenna - delivers Net capacity of 92Mbps at 10Km.
Link Budget Calculation

A wireless link will work under the following two physical conditions:

• Link Budget:

RSSI – higher than the equipment sensitivity level

• SNR - Signal to Noise Ratio:

Sufficient for the required modulation / capacity

Link Budget Calculation

RSSI

SNR

LOS

Good Installation

• Are these enough for unlicensed bands?

• Will the link be stable?
• Can constant throughput and latency be guarantied?

Yes for WipAir !

No for others !
 Link Budget Calculation

AIS - Automatic Interference Sensibility

WaveIP’s proprietary technology -
WipAir ignore all WiFi
The only efficient ‘non-interrupted reception’ packets at the PHY level

technology in the market

Low Latency

Low Jitter

10-50 times more Capacity

WipAir - the only unlicensed link that guarantees performance according to physical laws !
 AIS - Interference Rejection

- Sensitivity

Good SNR is not sufficient for stable operation in unlicensed bands

WipAir AIS is the only solution that guarantees stability in latency and throughput !
Link Budget Calculation

MIMO Modes

• Higher capacity and spectral

efficiency - 310 Mbps NET rate.
MIMO transmits 2 streams that double
the throughput using same channel
bandwidth.

• Diversity - transmitting 2 redundant

streams enables lower fade margins by
choosing the highest quality stream.

WipAir 8000 - The highest Capacity MIMO link !

310 Mbps net throughput !
Link Budget Calculation

MIMO Advantages
• High Capacity
• Antenna Diversity
• Better Multipath performance over water or
over flat terrain
• NLOS performance at short distance

MIMO Disadvantages
• Higher cost radios
• Higher cost Antennas
• Both Antenna polarization are used, blocking the Spectrum of
the used channel
Link Budget Calculation

Is MIMO Always better?

SISO Advantages
• Cost effective radios
• Cost effective Antennas
• Higher gain integrated Antennas
SISO - Single Input Single Output
• Only one Antenna polarization is used, the
other polarization is available for another link Single data stream, transmitted in a
single channel
SISO Disadvantages
• Limited capacity

WipAir 8000 – Up to 150Mbps

SISO link !
Link Budget Calculation

Summary
• Link Budget Calculation - critical for the success of the link.
• SNR - Operator must take into account the SNR for the required modulation / capacity.
• Size Does Matter – Higher system gain increases capacity and availability.
• AIS - The only technology that avoids false reception, guaranteeing link’s stability.
• NLOS – relevant mainly for short ranges
• MIMO or SISO – Depends on the needed capacity and ranges:
SISO is recommended for medium capacity links
MIMO is recommended for high capacity and long ranges

WipAir - the only stable unlicensed radio !

Link Budget Calculation

Budget Calculation using WaveIP’s Path Profiler

Thank you

Gracias!
Thank you!
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Sales@waveip.com