radio technologies passanger...

2017. október 9.,

Budapest

RADIO TECHNOLOGIES ON AIRCRAFTS

PASSENGER AIRCRAFT- UAV

Dr. István Koller

Department of Networked Systems and

Services

Budapest University of Technology

and Economics

Radio technologies – passanger aircraft

• Communication systems

• Air traffic control (mainly voice)

• Digital data communication

• Collision avoidance

• Navigation technologies non satellite

• NDB (Non Directional Beacon) – flight orientation (bearing)information on the aircraft (in aircraft coordinate system)

• VOR (VHF Orientation Radio range) orientation in ground coordinate system

• DME (Distance Measuring Equipment)

• Navigation technologies satellite

• GPS: Global Positioning System

• GLONASS

• Galileo

• BeiDou: 北斗衛星導航系統• Landing systems

• ILS: Instrument Landing System

• MLS: Microwave Landing System

10/9/2017 BME HIT 2

Radio Communication bands used

in aviation

MF: 0.3-3MHz (wavelength: 1000m-100m)

HF: 3-30MHz (wavelength: 100m-10m)

VHF: 30-300MHz (10m-1m)

UHF: 300-3000MHz ( 1m -1dm)

SHF: 3GHz-30GHz (1dm - 1cm)

10/9/2017 3BME HIT

Communication – voice

Voice communication (telephony)

• 118-137MHz (aeronautical VHF band)

• Analog Amplitude Modulation,

• ~3 kHz baseband,~ 6kHz RF RF bandwidth

• 8.33 kHz channels (25/3kHz)

• 1,5-30 MHz: rarely used

• SSB (single side band) AM

• Primary role: air traffic control

• Digital voice communication standard has never became

widespread, however it exists in VDL (ICAO International

Civilian Aviation Organization VHF Data Link) Mode 3 (118-

137MHz)

10/9/2017 BME HIT 4

Communication – digital data

Data communication between ground-air stations

• ACARS: Aircraft Communications Addressing and Reporting System, since 1978

• 118-137 MHz: MSK or ICAO VDL Mode 2 (VHF Data Link)

• 3-30 MHz: HFDL (High Frequency Data Link)

• AMSS: Aeronautical Mobile Satellite System

– IRIDIUM, INMARSAT

• CPDLC: Controller-Pilot Data Link Communication

• 2 major implementations:

– FANS-1/A (Future Air Navigation System): developed by Boeing and Airbus, deployed in North-Atlantic and South Pacific routes

– Eurocontrol’s system in many European Flight Information Regions

• 118-137MHz: ICAO VDL Mode 2

• AMSS Aeronautical Mobile Satellite System

– IRIDIUM, INMARSAT

10/9/2017 BME HIT 5

Communication – digital data

Data communication between ground-air stations (cont’d.)

• ADS-B: Automatic Dependent Surveillance – Broadcast

• ADS-C: Automatic Dependent Surveillance – Contract

• Both use SSR transponders on 1090MHz (USA: 978MHz too)

Data communication between air-air stations

• TCAS/ACAS: Traffic/Airborne Collision Avoidance System

• Based on SSR transponders (see later)

Special communication need: Emergency

Emergency frequencies - Emergency Locator Transmitter

(ELT)

• 121,5MHz, 243MHz Analog frequencies are NOT monitored

by Satellite sysetems

• 406MHz new Satellite monitored digital systems

10/9/2017 BME HIT 6

ACARS PHY

Created in 1978

VHF (118-137MHz ) system (aeronautical VHF band)

• MSK: 1200 and 2400Hz tones, 2.4kbps, amplitude modulated

carrier

• VDL Mode 2: 8PSK, 10500 symbols/s, gross bitrate: 31.5kbps

HF (3-30 MHz) system

• HFDL: 1800 symbols/s, BPSK, QPSK or 8PSK, with different

FEC

• 300, 600, 1200 or 1800 bps speed

• Used where VHF coverage is not present

• Global coverage with 17 ground stations operating on 145

frequencies

10/9/2017 BME HIT 7

ACARS HFDL Coverage

10/9/2017 BME HIT 8

ACARS HFDL routes

Source:

Rockwell-Collins10/9/2017 BME HIT 9

ACARS Usage Main message types:

• Air Traffic Control – Pilot communication

• Aeronautical Operational Control

• Airline Administrative Control

Examples:

• OOOI: Out of gate, Off the ground, On the ground, Into the gate

• FMS (Flight Management System) Interface: updating flight plans

• Engine status reports

• Position data

• E-mail like communication between the flight crew and the ground stations (clearances, information requests, connecting flights)

• NOT optimal for fast air traffic control, because of the possible long delay!

10/9/2017 BME HIT 10

CPDLC usage

Classical Controller-Pilot: voice

Controller - Pilot Data Link Communication: text

• Data link between Air Traffic Controller and pilot

• Alternative to voice communication in busy airspaces

• Messages are displayed on the flight deck

• Standard (clearance, information, request) messages and

free text

• Eg. Runway cleared, request altitude, speed, etc.

• No worldwide deployment yet

• FL380 – Flight level: 38 000 Feet

10/9/2017 BME HIT 11

ICAO VDL mode2 ACARS, CPDLC,

GBAS 118.. 137MHz (aeronautical VHF band) 25 kHz bandwith,

channel spacing

D8PSK 10500 symbol/s, 31.5 kbit/s modulation

Half duplex – communication on the same frequency for

uplink, downlink

Common Signaling Channel: 136.975 MHz for initial link

establishment

Media access: CSMA

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CPDLC spreading

10/9/2017 BME HIT 13

Cockpit of 787 DreamlinerInstructions from the controller can be accepted, rejected or

cancelled by the pilot, altitude, speed, heading, etc. values can be

transferred in the appropriate windows by XFR buttons

Messages are displayed in the AUX

window

10/9/2017 BME HIT 14

Radio navigation

NDB: Non-directional Beacon

• The oldest technology which is still in operation, and aircrafts

still able use it

• 255-495kHz, 505-1606.6kHz (Long and Medium waves)

• AM transmission with only one modulation content: the

station’s identifier in Morse code

• Omnidirectional antennas on the ground, radio direction finder

aboard the aircraft (ADF: Automatic Direction Finder)

Example: Mar Del Plata – Argentina 385 kHz MDP(--|-..|.--.)

10/9/2017 BME HIT 15

(-- -.. .--.)

http://ourairports.com/navaids/MDP/

Radio navigation

VOR: VHF Omnidirectional Radio Range

• 108-118 MHz

• Basically AM signal

• Identifier in Morse code (sometimes in telephony)

• FM subcarrier containing a reference signal (30Hz)

• AM subcarrier transmitted by a directional antenna containing

the navigation signal (30Hz)

• The phase of the navigation signal is depending on the position

of the reception

• The phase difference between the two signals is the bearing

• Direction finding is not necessary on the aircraft!

• More accurate than NDB, however its range is shorter

10/9/2017 BME HIT 16

VOR operation

𝑟 𝑡 = cos(𝜔𝑐𝑡)(1 + 𝑐 𝑡 + 𝑔 𝐴, 𝑡 )

𝑐 𝑡 = Xid(t) + 0.3cos 0

𝑡

𝜔𝑠 + 𝜔𝑑 cos 𝜔𝑛𝜏 𝑑𝜏

Consider the signal at the receiver at azimuth angle A:

where

𝑔 𝐴, 𝑡 = 0.3 cos(𝜔𝑛𝑡 − 𝐴)

𝜔𝑐 is the carrier angular frequency

𝑋𝑖𝑑 𝑡 is the identifier baseband signal (Morse code + voice)

𝜔𝑠 is the subcarrier angular frequency 2𝜋 ⋅ 9960𝐻𝑧𝜔𝑑 is the subcarrier deviation 2𝜋 ⋅ 480𝐻𝑧𝜔𝑛 is the navigation tone angular frequency 2𝜋 ⋅ 30𝐻𝑧Note that 𝑐 𝑡 is independent from the azimuth angle 𝑔 𝐴, 𝑡 is dependent!

The VOR receiver demodulates the reference signal (FM) and compares the

phase of the navigation signal with the reference. The phase difference between

the two is the bearing.

AVOR

TX

Aircraft

10/9/2017 BME HIT 17

VOR receiver block diagram

10/9/2017 18BME HIT

108.. 118MHz

𝑟 𝑡 = cos(𝜔𝑐𝑡)(1 + 𝑐 𝑡 + 𝑔 𝐴, 𝑡 ) 𝑐 𝑡 = Xid(t) + 0.3cos 0

𝑡

𝜔𝑠 + 𝜔𝑑 cos 𝜔𝑛𝜏 𝑑𝜏

𝑔 𝐴, 𝑡 = 0.3 cos(𝜔𝑛𝑡 − 𝐴)

NDB vs. VOR

AVOR

TX

Aircraft

ANDB

TX

Aircraft

Apart from being more accurate, VOR has another advantage. Let us consider

the following case: an aircraft is flying towards a given navigation point

(VOR/NDB station), the pilot sets up the instruments (VOR and ADF receivers)

to point right at the station. Both receivers should indicate the same until

there is no crosswind at all.

Wind Wind

To compensate the effect of wind, the pilot must fly with a yaw angle different

from the bearing. This must be taken into account on the ADF, but not on the

VOR. VOR indicates the bearing from the station, NDB is always pointing right

at the station

Reading is

in the earth

coordinate

system

Reading is in

the aircraft

coordinate

system

10/9/2017 BME HIT 19

Radio navigation

DME: Distance Measuring Equipment

• The aircraft can measure the distance from a given station

• The ground speed can also be estimated from the doppler

shift (if flying straight to or from a station)

• Typically deployed together with VOR stations

• Interrogator (aircraft): 1025-1150MHz

• Transponder (ground station): (interrogator +-63MHz ) 962-

1213MHz – 50us delay

• 126 pcs. of 1MHz channels

• Accuracy: app. +-0.1NM (+-180m)

10/9/2017 BME HIT 20

VOR DME – unambiguous position

10/9/2017 21BME HIT

Pusztaszabolcs VOR, NDB

From: Kállai Tibor (Panoramio)

NDB

antenna

(386kHz)

VOR

antenna

(117.1MHz)

DME

antenna

10/9/2017 BME HIT 22

Pusztaszabolcs VOR

From: Kállai Tibor (Panoramio)

10/9/2017 BME HIT 23

Radio navigation - landing

ILS: Instrument Landing System

• Localizer

• 108,1-111,95MHz

• Indicates the deviation from the runway centerline

• Based on a phased array

• Glideslope

• 330,95-334,7 MHz, paired with localizer frequencies

• Indicates the deviation from the ideal glideslope

• Based on a phased array

• The stations transmit AM signals, and the localizers identify themselves with Morse code

MLS: Microwave Landing System

• Never became widespread, due to advanced GNSS technologies (with GBAS)

10/9/2017 BME HIT 24

Radionavigation – Landing

Localizer

phased

array

Glideslope

phased

array

Glideslope

phased

array

The green lobe is a carrier modulated with

90Hz, the blue lobe is the same carrier

modulated with 150Hz.

When the plane is flying on the desired path

(runway centerline and descending with the

desired rate) all signals will have the same

amplitude.

If the plane deviates from the path, the signal

which is stronger in that direction will have

larger amplitude, and this can be indicated.

10/9/2017 BME HIT 25

Phase array

10/9/2017 26BME HIT

ILS receiver

10/9/2017 27BME HIT

Hannover Airport Localizer

Source: Wikipedia

10/9/2017 BME HIT 28

Hannover Airport Glideslope

Source: Wikipedia

10/9/2017 BME HIT 29

ILS on the headup display

10/9/2017 30BME HIT

Budapest Airport

VOR/DME

117,3

„BUD”NDB

357kHz

„L”

LOC

109,5

„BPR”

GP/DME

SSR

10/9/2017 BME HIT 31

Airport Surveillance Radar (ASR)

systems

Primary Surveillance Radar - PSR (2700.. 2900MHz)

• Detects targets (aircraft) based on the reflected waves

• Capable of detecting targets, and can measure the speed

• The range is limited by the effective radiated power density

and the effective radar cross section of the target

Secondary Surveillance Radar -SSR (1030MHz, 1090MHz)

• A transmitter-receiver (transponder) is necessary aboard the

aircraft, which responds to interrogation requests

• The transponder can also transmit data (identifier, altitude,

speed, etc.)

• The power of the transponder is orders of magnitude greater

than the reflected power, therefore the range can be

considerably longer

10/9/2017 BME HIT 32

SSR Transponder

Common system for military a civilian aircraft

Originating from IFF (Identification Friend or Foe, World

War II)

5+1 modes of operation for military aircraft, 3 modes for

civilian

ADS-B is based on Mode-S transponders, but it is

transmitted without interrogation

Interrogation frequency 1030MHz, transmission frequency

1090 MHz

The peak pulse power available at the antenna end of the

transmission line of the transponder shall be at least 21 dB

and not more than 27 dB above 1 W

10/9/2017 BME HIT 33

SSR Transponder Modes

Military

Mode

Civilian

ModeDescription

1 Provides 2-digit 5-bit mission code (cockpit selectable)

2Provides 4-digit octal unit code (set on ground for fighters, can be

changed in flight by transport aircraft)

3 AProvides a 4-digit octal identification code for the aircraft, set in the

cockpit but assigned by the air traffic controller.

3 CProvides the aircraft's pressure altitude in 4-digit octal code (Gilham

Code)

4 Provides a 3-pulse reply, delay is based on the encrypted challenge

5Provides a cryptographically secured version of Mode S and ADS-B

GPS position

S SProvides multiple information formats to a selective interrogation.

Each aircraft is assigned a fixed 24-bit address.

10/9/2017 BME HIT 34

SSR Transponder Operation

Interrogation, on 1030MHz radiated by ground station radar:

• P2 pulse is the sidelobe suppression pulse, transmitted by an

omnidirectional antenna with at least the same power as the strongest

sidelobe.

• Aircraft in the main lobe will receive P1 stronger than P2, while aircraft in the

sidelobe will receive P2 as strong as (or even stronger than) P1.

• If P1 is not stronger than P2, the transponder will not answer

10/9/2017 BME HIT 35

SSR Transponder Operation

Response on 1090MHz

• The modulation is PAM (Pulse Amplitude Modulation): no pulse = 0, pulse = 1

• The response contains 2 framing pulses (F1, F2) and 12 data bits, which

correspond to a 4 digit octal value, meaning either altitude or identification

code (squawk code). The SPI (Special Purpose Identification) pulse is the

„IDENT” pulse, which can be transmitted upon pilot request. Pulse X is

reserved

10/9/2017 BME HIT 36

SSR Transponder Response Example

Mode A or C

response from a

passing airplane

captured at the

University

A4, A2, A1: 000 = 0

B: 101 = 5

C: 110 = 4

D: 000 = 0

Octal Code: 0540

F. e.:

7700 means general

emergency as A

7700 means 20 000

feat altitude as C

(7700 can easily be

detected)

10/9/2017 BME HIT 37

Mode A, Mode C summary

10/9/2017 38BME HIT

Mode S SSR

10/9/2017 39BME HIT

Mode S is an enhanced SSR technology from A and C

S mode transponders can de addressed by a unique 24 bit

address, which is assigned to the aircraft itself ( better info

than Mode A answer)

Can send information f. e.:

• aircraft type and aircraft ID

• altitude,

• latitude,

• longitude

• airborne velocity…

http://www.radartutorial.eu/13.ssr/sr80.en.html

Mode S

How do we discover Mode S capable aircraft?

• Mode S transponders use a fixed 24 bit unique address

• Mode A uses 12 bit address assigned by the ATC

A Mode S All Call interrogation is necessary, which tells Mode S

capable transponders to respond with their unique 24 bit address

This pulse must not confuse A or C interrogations

The solution is the use of P4 (1.6us long) pulse, which is discarded by

non-mode S transponders

10/9/2017 BME HIT 40

Mode S

Mode S uses the sidelobe suppression pulse followed by a

56 or 112 bit data block

• Non Mode S transponders will not respond, since they treat it

as a sidelobe interrogation

• Mode S transponders will decode the data block and decide

whether they have to answer to it or not

• The interrogation data block uses DPSK (Differential Phase

Shift Keying)

10/9/2017 BME HIT 41

Mode S

Mode S responses contain a 2x2 pulses as preamble

followed by 56 or 112 bit data block

The data block uses PPM (Pulse Position Modulation)

10/9/2017 BME HIT 42

Mode S

-30 dBm

-40 dBm

-50 dBm

-60 dBm

-70 dBm

-80 dBm

-90 dBm

-100 dBm

-110 dBm

M1[1] -61.73 dBm

6.000000000 µs

D2[1] 0.00 dB

0.000000000 s

Att 0 dB

*

*

*

RBW

VBW

SWT

3 MHz

10 MHz

40µs

1Pk

Clrw

Ref -20.00 dBm

Trg

IFP

4.0 µs/CF 1.09 GHz

SGL

M1D2

Date: 31.AUG.2017 17:14:46

Beginning of a Mode S

transponder response

10/9/2017 BME HIT 43

Mode S Downlink Frames

DF

5 bits

Data block

27 or 83 bits

Parity

24 bits

56 or 112 bits

Data Format - DF field defines the downlink frame format

The parity field is generated from the DF and data block

10/9/2017 BME HIT 44

TCAS

Traffic Collision Avoidance System

Based on SSR transponders

The interrogation signal is sent by the airplane

Aircraft equipped with TCAS can detect nearby airplanes

• Informs the pilot about traffic (Traffic Advisory) if the intruder

is within 3.3NM, ±850ft up or down

• Issues a Resolution Advisory if the intruder is within 2.1NM

±600ft up or down: Instruction to the pilots:fly higher alt or

lower alt

TCAS-2 allows the use of Mode S, which provides

significantly more information - world wide used now

10/9/2017 BME HIT 45

ADS-B

Automatic Dependent Surveillance – Broadcast

• Automatic: needs no operator input, nor interrogation

• Dependent: depends on the aircraft’s navigation system

• Based on SSR transponders (1090MHz S mode)

• Transmissions are not requested -> broadcast

• ADS-B messages are always 112 bit long, contains info:

• Identification (24 bit aircraft address, aircraft identification)

• Altitude (barometric),

• Heading,

• Speed,

• Position (latitude, longitude)

• …

10/9/2017 BME HIT 46

ADS-B summary

Aircraft determines position

using GPS

Broadcasts position, identity,

altitude and velocity (ADS-B

out)

Ground stations and

satellites receive, broadcasts

and relay information to ATC

Other aircraft receive

broadcasts & display to pilot

(ADS-B in)

10/9/2017 47BME HIT

ADS-C (Also known ADS-A)

Automatic Dependent Surveillance – Contract (Addressed)

• Similar data as in ADS-B, but for a specific ground control station

• The ground station agrees with the aircraft upon

• The data content of the messages

• Events triggering reports

• Contract types:

• Periodic Contract

• Demand Contract

• Event contract

– Waypoint change event (when passing a waypoint and heading for a new one)

– Level range deviation event

– Lateral deviation event

– Vertical rate change deviation event

10/9/2017 BME HIT 48

Radio navigation – Satellite Based

GNSS: Global Navigation Satellite System

• GPS: Global Positioning System

• US system

• Project launched in 1973, fully operational since 1995

• Full global coverage

• GLONASS: Глобальная навигационная спутниковая

система

• Russian system

• Launched in 1976, completed in 1995

• Full global coverage since 2010

10/9/2017 BME HIT 49

Radio navigation – Satellite Based

• Galileo

• EU system

• Launched in 2005, Early Operational Capability since 15.

December 2016., full operation: ~2019

• BeiDou: 北斗衛星導航系統

• Chinese system

• Launched in 2000

• Covering China, India, Indonesia, Philippines, Australia since

2012

• Expected to provide global coverage in 2020

10/9/2017 BME HIT 50

GNSS Basics

Satellites orbiting the Earth contain atomic clocks, therefore

every satellite can transmit data with the exact* same

timing

Radiovawes travel with the same* speed

Each satellites’ signal will arrive to the receiver with

different timing

The receiver can decode the data coming from the

satellites, and determine the time difference of arrival of

each satellites’ signal

Satellites broadcast their exact* position (Almanac data)

From the time difference and the satellite almanac data, the

receiver position can be calculated

The problems are due to the *-ed items

10/9/2017 BME HIT 51

GNSS Basics

Atomic clocks are very-very precise devices, but they still

drift away

Speed of light: 299 792 458 m/s in vacuum

• Earth has atmosphere, waves must penetrate this, and the

speed of light is not exactly the same as in vacuum

• 1ns temporal error corresponds to ~30cm spatial error

GNSS satellites deviate from their desired orbit

A ground control segment is necessary

• Verify the integrity of the navigation data

• Make adjustments, and corrections if necessary

The achievable accuracy with these measures, is in the

order of 10 meters

10/9/2017 BME HIT 52

GNSS Augmentation

The accuracy of satellite based navigation can be improved by augmenting satellite data

The positions of well known ground stations are measured, and from the error, augmentation data can be derived and sent to the receiver

The data can be sent in two ways:• Satellite Based Augmentation System (SBAS)

• WAAS (Wide Area Augmentation System) in USA

• EGNOS (European Geostationary Navigation Overlay Service) in Europe

– Precision: ~3m

– 3 Geostationary satellites transmits the augmentation data

– GPS, GLONASS, GALILEO

• Ground Based Augmentation System (GBAS)• Augmentation data is transmitted in VHF band in the vicinity of the

airport (108.. 118MHz, 25 kHz Bandwith D8PSK)

• Can be used for precision approach (instead of ILS)

• Precision: ~1m

10/9/2017 BME HIT 53

SBAS Systems

Source: Wikipedia

10/9/2017 BME HIT 54

GBAS System

Source: FAA

10/9/2017 BME HIT 55

GPS system frequencies

10/9/2017 56BME HIT

https://en.wikipedia.org/wiki/GPS_signals#cite_note-handbook-pent-43

Radio antennas on a passanger aircraft

10/9/2017 57BME HIT

Cockpit of 787 Dreamliner

Communication

and navigation

radio panels

Transponder

control

10/9/2017 58Department of Networked Systems and Services BUTE

Digital data communication between the GCS and UAV

• Control

• Telemetry

• Payload

Navigation

• GNSS ~15 m - outdoor

• SBAS - EGNOS ~3m

• GBAS - RTK ˇ~1dm

• Based on UWB technology – indoor 1dm

Collision Avoidance

• ADS-B

• FAA: below 5,500 m use the 978MHz instead of 1090MHz

• Receiver

• Transmitter

Dr. Istvan Koller

AMOR

ES

59

Department of Networked Systems and Services BUTE

UAV radio electronic systems

Typical UAV mission

UAV flies autonomously

• Flight plane uploaded on the

ground

• Auto takeoff – or manual

• Autonomous flight according

to the plan

• Autolanding – or manual

During operation

• Continuous supervision of

the UAV

• GCS

– Radio link

Dr. Istvan Koller

AMOR

ES

60


UAV Digital Data Communication

No global standards

• No standardized frequency bands in Europe for UAVs

• China has: 840.5 – 845MHz, 1430-1444MHz, 2408 – 2440MHz (ISM)

Communication solutions nowadays

• Cellular solutions

• 2G GPRS, EDGE – can be used for telemetry

• 3G, 4G LTE can be used for f.e. video stream too

• Telecom Satellite solution

• L1 Iridium

• Custom radio solutions operating

• ISM bands

• Hired bands

• WiFi solutions (ISM band)

• 2.4GHz Band

• 5.8GHz Band

10/9/2017 61BME HIT

Connection the GCS – UAV

MAVLINK protocol for Telemetry/control

MAVLINK (Micro Aerial Vehicle Link) protocol

• Standard protocol between the GCS and

autopilot

• Can be used

• Send commands to the UAV

• Receive telemetry and other data from the

autopilot

62BME HITDr. Koller István

Public Cellular Service

The UAV can be sent very far away equipped by cellular

communication modem

Moving Cellular modems at high altitude: potential UAVs

• G2

• 900MHz

• 1800MHz

• G3

• 2100MHz

• G4 LTE

• 800MHz

• 1800MHz

• 2600MHz

64Dr. Koller István Department of Networked Systems and Services BUTE

2G coverage of Hungary by

Hungarian Telekom

65Department of Networked Systems and Services BUTEDr. Koller István

LTE coverage of Hungary by

Hungarian Telekom


Cellular data service features

General Packet

Radio Service

GPRS

Enhanced Data

rate Gsm

Evolution

EDGE

Universal

Mobile

Telecom.

System

UMTS

High-Speed

Packet Access

HSPA

HSDPA

HSUPA

HSPA+ LTE

Telecommunication

generation

2.5G 2.75G 3G 3.5G 3.75G 4G

Max downlink

speed

bps

35k.. 171k 120.. 184k 384k 14M 28M 100M

Max uplink speed

bps

35k.. 171k 120.. 184k 128k 5.7M 11M 50M

Latency

round trip time

approx.

700ms, 1s 20ms 150ms 100ms 50ms 10ms

UAV application Telemetry

Control

Low speed pilot

camera

Telemetry Control

Low speed pilot

camera

Telemetry

Control

Low speed pilot

camera

Telemetry

Control

HD camera

Telemetry

Control

HD camera

Telemetry

Control

HD camera

Frequency band

numbers

and frequencies

Hz

EUROPE

E-GSM 900 MHz

Digital Cellular System DCS 1800

MHz

Band 8 (900 MHz)

Band 1 (2100 MHz)

Band 31 (450MHz)

(MVM NET)

Band 20 (800 MHz)

Band 8 (900 MHz)

Band 7 (2600 MHz)

Band 3 (1800 MHz)

Band 1 (2100 MHz)


Devices to utilize LTE on a UAV

OEM device TOBY-L2 module

• Multi-mode LTE Cat 4 module

• with HSPA+ and/or

• 2G fallback

• 152-pin LGA (Land Grid Array):

24.8 x 35.6 x 2.6 mm, 4.8 g

• USB 2.0 interface

Commercial solution Huawei

E3372

• USB 2.0 stick

• TS5 antenna connector for

external MIMO antennas


ISM bands for Telemetry, Control,

Payload

69BME HIT

ISM bands – no need of licencse

• 169,4.. 169,475 MHz – Automatic Metering – low speed

(telemetry/control)

• 433,05.. 434,79 MHz - telemetry

• 868,7.. 869 MHz - telemetry

• 2400.. 2483.5 MHz – (WiFi, microwave ovens..) telemetry,

payload video (analog, digital)

• 5800 MHz - telemetry, payload

Dr. Koller István

Telecommunication satellite systems

Satellite system IRIDIUM GLOBALSTAR INMARSAT THURAYA

Orbit LEO LEO GEO GEO

Altitude 780 km 1412 km ~36 000 km ~36 000 km

Number of

satellites

66 sats / 6 orbits 48 sats / 8 orbits 4 sats 2 sats

Frequency

bands

L (1.6GHz),

Ka (26..40GHz)

L,

Ku (12.. 18GHz)

L, Ku L, Ku

Services voice (2,4 kbps), voice (9,6 kbps), voice/VoIP (4

kbps)

voice (9,6 kbps),

data / ISP

(2,4 kbps)

Data (9,6 kbps) ISDN (64kbps),

IP (492 kbps)

data (9,6 kbps),

fax (9,6 kbps),

IP (144 kbps),

70Dr. Koller István Department of Networked Systems and Services BUTE

Iridium data modem

Your drone can be - anywhere on Earth - connected

Very low data speed

• Short Burst Message

• 300 byte packet - 6.. 22 seconds

Anybody can reach this technology

• 0.5 Ft/byte – expensive

L Band moving radio signal source

• It radiates to the satellite – hard to detect

71

A RockBlock Iridium modemje (76x52x19mm)

Dr. Koller István Department of Networked Systems and Services BUTE

ISM band telemetry / control

modems for UAVs

10/9/2017 72BME HIT

Custom Radio link - BBCOM

Ground > UAV control:

• Spread spectrum CHIRP modulation

• 17kbit/s

UAV > Ground Telemetry:

• Spread spectrum CHIRP modulation

• 108 kbit/s

UAV > Ground Payload:

• OFDM modulation

• 108kbaud/s - 1 symbol - 100bit: 10.8 Mbit/s

5GHzband – 20MHz bandwith


Timing of BBCOM operation

74BME HIT

CHIRP

OFDM

3.7ms

10 msec

1.0 ms 1.0 ms

UP Link

DOWN Link

3.7ms

CHIRP

OFDM

0.6ms

time

CHIRP

CHIRP

CHIRP

10 msec

UP Link

DOWN Link

Dr. Koller István

CHIRP modulation symbol

75BME HIT

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-1

-0.5

0

0.5

1

gs(n

)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-1

-0.5

0

0.5

1

Time (1 symbol interval)

hs(n

)

„1”:

„0”:

Dr. Koller István

CHIRP Generation of the CHIRP signal

76BME HIT

analog output

Memory

with UpChirp

D/A Up/down counter

clock

bit

Dr. Koller István

0 100 200 300 400 500 600 700 800 900 1000-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Sample

Diffe

rential outp

ut

CHIRP demodulator

10/9/2017 77BME HIT

A/D

Matched filter „1”

clock

databit

Differentialsignal

"1"Symbol

Matched filter „0”

„0"Symbol

input

Differentialsingnal -databit

OFDM transmitter

78BME HIT

Errorcorrectionencoder

Frequencydomainvectors

1 : 2

Input bits

Analogoutput

Time domain

Inverz Fourier trans-

formationD/A

FrequencydomainRedundant

bits

Dr. Koller István

OFDM receiver

79BME HIT

A/D

Fourier transformation

Bits from

Frequencysamples

Output bits

AnalogInput

Errorcorrectiondecoder

Viterbi

1:2

Dr. Koller István

OFDM parameters

80BME HIT

Sampling frequency: fs = 94 MHz

FFT point munber: NFFT = 256

Guard Time : NGUA = 64 (25 %)

Sample / symbol: NTOT = 320

Carrier number: M = 50 + 1 pilot

Frequency gaps: 1875.367256

94

FFT

s

N

ff kHz

Carriers: fk = k * fs / NFFT k = 39, 40, …..,88,89

Modulation: Differential QPSK (DQPSK )

1.

39.

14.32

MHz

40.

14.69

MHz

41.

42.

63

23.13

MHz

64.

23.50

MHz

65.

23.87

MHz

87.

88.

32.31

MHz

89.

32.68

MHz

. . . . . . . .

Pilot

fk

k

2. 3. 4. 25. 26. 50. 49. 48.

Dr. Koller István

Communication hardware


Communication mode numberUp

Chirp

Down

ChirpOFDM

1Near (0..12 km* )

Single Chirp,

OFDM - 1:2 Viterbi

12

kb/s

100

kb/s

5

Mb/s

2Far (12.. ~17 km)

Single Chirp,

OFDM - 1:4 Viterbi

12

kb/s

100

kb/s

2.5

Mb/s

3Farther

(~17.. ~30 km)

Chirp without OFDM

12

kb/s

200

kb/s-

4Very far

(~30.. ~40km)

Double chirp

5

kb/s

100

kb/s-

*:OFDM data, 5GHz, 250mW, 2dBi, 16dBi, measured by BHE on UAV82

Collision avoidance small UAVs

USA solution uAvionix PING2020

Detects commercial aircraft threats on 1090MHz and 978MHz within a 100 statute mile radius in real time

Transmits ADS-B on 978MHz (UAT) 20W nominal - Only in the US!

25x39x12mm, 20grams

10/9/2017 83BME HIT

ADS-B in Europe - now only in UK

10/9/2017 84BME HIT

uAvionix PING1090

Detects commercial aircraft threats on 1090MHz and 978MHz within a 100 statute mile radius in real time

Transmits ADS-B on 1090MHz, 20W nominal - Certification for UK

25x39x12mm, 20grams

ADS-B everywhere – just receiver

10/9/2017 85BME HIT

uAvionix PINGRX

Detects commercial aircraft threats on 1090MHz and

978MHz within a 100 statute mile radius in real time

Does NOT Transmits ADS-B signals

19x34x8mm, 5grams

Transponders on UAVs

10/9/2017 86BME HIT

uAvionix PING200S

Replies to Mode C and Mode S radar interrogations 250W

nominal

Transmits ADS-B on 1090MHz

57x91x17mm, 73 grams

Radio link parameters

Mostly Point to Point link – typical, and simplest

• Rarely Point to Multi point

• Typically Line of Site connection

Three communication channels

• Must be robust, reliable:

• Command channel – Ground to UAV

• Telemetry channel – UAV to ground

• Generally must be high-speed:

• Payload - UAV to ground

Dr. Istvan Koller 87Department of Networked Systems and Services BUTE

General radio technology knowledges

About the radio channel

Range of radio channel


Attennuation between teransmitter and receiver

Simplest model – one way propagation

Dr. Istvan Koller

AMOR

ES

89


Transmitter antenna Receiver antenna

:Transmitter antenna Gain

d: distance

:Transmitted Power

S: Transmitted Power density : Received Power

: Effective Receiver antenna Area – antenna Aperture

: Wavelength

:: Receiver antenna Gain

Attennuation between transmitter

reciver – free space model

In dB:


a0[dB]=10⋅lg(4πRλ)2

RTR

T

GGλ

π d

P

Patt

142

R

TdB

P

Patt lg10

RT

dB GGλ

π datt

4log20

http://wiki.ham.hu/index.php/Decibel

Free space attenuation –

satellite - satellite


λ

π dattdB

FreeSpace

4log20

Attenuation (dB) Distance

Wavelength Frequency 10m 100m 1km 10km 100km

300 m 1 MHz - - - 52 72

30 m 10 MHz - - 52 72 92

3 m 100 MHz - 52 72 92 112

0.3 m 1 GHz 52 72 92 112 132

3 cm 10 GHz 72 92 112 132 152

More realistic model: two way

propagation

: Transmitter and Receiver antenna height


RT

RT

dB GGhh

datt

2

log20

RT hh

Very long distances :RT hhd

Two way propagation


RT

dB

hh

datt

2

log20

Attenuation (dB) Distance - d (UAV is flying at 100m altitude

hR = 100)

Ground antenna

height - hT

1km 10km 100km 1000km

1m 80 120 160 200

10m - 100 140 180

100m - - 120 160

RT hhd

Link Budget

Signal level at receiver input:


attPP TXRX Minimum input power is defined by sensitivity

F.e. a 5GHz WISP station (WiFi) data:

• PTX=23dBm: 23=10log(p/1mW) > PTX = 200mW

• Sensitivity: (MCS1-QPSK 10Mbit/s) – 96dBm

• Zero gain antennas: 119 dB attenuation is possible: ~ 10km

range

Big problem: fading – variation of the transmission relatively

fast because of the moving device

ERP EIRP

ERP - It is the total power in watts that would have to be

radiated by a halfwave dipol antenna to give the same

radiation intensity as the actual source at a distant receiver

located in the direction of the antenna's strongest beam.

EIRP - Effective isotropic radiated power is the total power

that would have to be radiated by a hypothetical isotropic

antenna to give the same signal strength as the actual

source in the direction of the antenna's strongest beam.

Example: Transmitter power: 10W, antenna gain 12dBi,

ERP ?W, EIRP ?W

Halfwave dipol 2dBi, gain to halfwave dipol: 10dB: 10 times:

ERP 100W

Gain to izotropic ant.: 12dB: 16 times: EIRP 160W


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