ICT | Software Defined Radio : enjeux et perspectives par Sylvain Azarian et Jonathan Pisane | Liege Creative, 13.12.11

Parole d’expert

Ir Jonathan PISANE, Doctorant ULg - INTELSIG Ir Sylvain AZARIAN, Ingénieur de Recherche - SUPELEC

Software Defined Radio : enjeux et perspectives

Avec le soutien de :

Software Defined Radio: Enjeux et perspectives – Sylvain AZARIAN et Jonathan PISANE 1

Sylvain AZARIAN - Supélec Jonathan PISANE – Ulg / INTELSIG - Supélec

Software Defined Radio : Challenges and Opportunities


Talk outline

•  Part I – Introduction to SDR –  Need for new system architectures –  SDR as a potential solution –  Basics to understand how it works –  Demos

•  Part II – SDR in OUFTI-1 Satellite •  Part III – Radar applications

–  What is radar ? –  “Active” and “passive” radars –  Using passive radar techniques to collect RCS

•  Introduction to J. Pisane PhD work •  System presentation •  Live demo •  Results

•  Part IV– Challenges –  Balancing technical constraints –  Possible issues –  Consumer Electronics and product life-cycle

•  Part V – Future mobile Networks –  Quick presentation on active research topics for future mobile networks


Part I

1 – Introduction to Software Defined Radio


Communication system

Osc.

Modulator

time

0 1 0 1 ….. 1

Message A

Osc.

Demodulator

time

0 1 0 1 ….. 1 Message A

A communication system takes input message A at transmitter side and delivers it at receiver side. On transmit side, a modulator is used to “encode” the information to be transmitted by the carrier. This information is then “extracted” using a demodulator at the receiver. This message can be analogical (voice, image) or digital (data).


Frequency allocation plan (USA)


Spectrum allocation… spectrum saturation

Currently, spectrum is allocated on a « per usage » basis. Ideal for broadcasting systems, this scheme is no longer efficient when spectrum is saturated and new « point to point » communication is required.

Dynamic spectrum Access is a possible solution to this saturation. New allocation rules… new techniques… new challenges


The limits of « classical hardware design »

One technology => one chip

• GSM • GPRS • UMTS • 4G • WiFi • BlueTooth • WiMAX • …

Does not fit !


Lack of space for new wideband telecoms

HF VHF

Allocated band : not available

Need for more throughput => need for more bandwidth … where ????

One solution : “bandwidth aggregation” •  Design modulations and RF chains able to transmit on sparse spectrum


Stacking RF technologies – Cell. phones

RF modules – Nokia X6 •  Phone CDMA •  WiFi •  BlueTooth •  GPS

•  Close in frequency, but completely different systems ►one chip by function ► cost and battery life…


Stacking RF technologies – Broadcast radio receivers

One sub-circuit by modulation type… Adding a new modulation means redesigning the hardware


Using applications to replace hardware

SDR technologies bring a new approach to have ‘one hardware for all’

•  Wide bandwidth •  High resolution AD & DA converters •  Sample signals from 1µVolt to 50 mVolt with constant linearity… •  Tunable power, tunable gain, … •  Unlimited speed to main application..


Sampling signal to process it by software

0010101010101000 0111010101111010 0100010010001001 … 0100010011011100

Sampling clock (defines the “zoom level” on the incoming signal)

RF signal Continuously varying voltage from the antenna

Bit stream

Analog to digital converter (ADC) : at each ‘top’ given by sampling clock, a ‘picture’ of the incoming signal is taken and delivered as a binary word.


Basic SDR system architecture

CPUADCDAC

Software Defined Radio equipment : •  Antenna and basic filtering, •  Analog to Digital conversion, •  CPU + applications.

Digital world Analog world


Communication system - Modulation Signal modulation involves changes made to sine waves in order to encode information. The mathematical equation representing a sine wave is as follows:

We see we have two “variables” we can use separately : amplitude and angle. Each modulation technique (AM,FM,…) uses a different scheme to change these variable depending on the information to send. In a digital communication system, the information transmitted is called the baseband.


Modulation – one example ASK (OOK) – Amplitude Shift Keying – playing with amplitude

In this modulation scheme, we change Ac depending on the bit value to transmit. We can use two levels or “on off keying” (OOK).

Modulator

Osc. time

Demodulation is quite easy but this method is very sensitive to parasites.


Quick introduction to the theory… why I & Q ? Signal spaces and basis functions

Basis : Two orthogonal functions chosen as basis set : sine and cosine.

Signal space : Let’s define our message M(t) as a two-dimension vector M(t)={x(t) ; y(t) } We can represent our message on a 2D plane using Cartesian or polar coordinates.

M(t) M(t) Q

I

In our signal space, we have the horizontal axis called “I” (in phase) and vertical axis called “Q” (in quadrature). We can also use complex numbers to represent our messages : M(t) = S.ejɸ


Digital modulation

0 1 0 1 ….. 1

Using a predefined “dictionary” (constellation), each sub-block of bits is mapped in IQ plane :

Ex: QAM16

The corresponding I and Q values are then used to generate baseband “time” signal. Of course the “dictionary” must be shared by transmitter and receiver…

One can imagine a complete set of constellations to map bits to symbols :


Digital transmitter architecture Back to our RF chain…

“Polar modulator”, quite complex to realize in hardware because requires evaluation of :


Digital transmitter architecture Quadrature modulator

Quadrature modulator is the most common design used in digital communications. To increase communication throughput, this scheme can also be parallelized on multiple frequencies simultaneously. OFDM uses multiple carriers, carefully chosen, to transmit bursts of data.


Digital receiver architecture Quadrature receiver

Minimalistic architecture for quadrature signals recovery: Incoming signal is “projected” (multiplied) with our two basis functions (sin & cos) to retrieve projections over I and Q axis in our signal space.

CPU


Introducing demo #1 – SDR Dongle from Microsat

USB bridge

Analog to Digital converter

RF Tuner

RF amplifier

Antenna socket

No signal processing is done ‘aboard’ : Samples are sent to host PC via USB and need to be processed to extract information.


HDSDR : Software Defined Receiver application

Waterfall display

frequency

time

spectrum display

Zoom area


Demo #1 : Ingredients

•  See it working…

easySDR USB dongle From microsat

PC

WinRAD : Multimode SDR decoding freeware


Part II

2 - SDR In OUFTI-1 Satellite


MS Thesis A. Dedave •  Implementation of FM, AX.25 and D-STAR radiocommunication protocols on SDR •  Feasibility study for future nanosats

•  Develop SDR experience @ULg – Montefiore


Analog RF front-end: Rx


Analog RF front-end: Tx


Digital back-end: Tx & Rx


Application (1): D-STAR – Rx & Tx


Application (2): AX.25


MS Thesis A. Dedave: Demos


Part III

3 - Radar applications


Definition and application

Military air surveillance (surveillance and tracking ) maritime surveillance battlefield surveillance missile seeker guidance & interception imagery

Civilian air traffic control (ATC) maritime navigation control collision avoidance satellites tracking road traffic control & ERP archaeological & geologic research

RADAR = RAdio Detection And Ranging

transmit & receive E.M. waves

detect the target

provide localization (range, angle, velocity)

can provide classification, identification of target


Radar in the day to day life Air Traffic Control and

monitoring Weather Radar

http://www.meteox.com/h.aspx?r=&jaar=-3&soort=loop1uur

Maritime Surveillance

Radar Presence Detection (Domotic)

Road Traffic Control

360km

200 to 400km

10 to 40km

10 to 30 m

200 to 400km

10 to 40 m


Less popular but so useful… Fighter control radar AWACS

Early Warning Surveillance

Imaging & remote Sensing from the earth

Air Defence Radar

Through the wall radar

50 to 140km

> 400km

700 to 1000 km

200 to 400 km

1 to 10 m


Radars you haven’t imagined…

Very Long range skywaves radar

Passive Radar

1000 to 3000 km

1 to 80 km


Radar principle Peak power : Pe (~ 1 kW à 1 MW ) Average power : Pm (~ 100 W à 10 kW )

Dt - Pulse delay, used to retreive the range D Dt = 2D/c

Tr - Pulse period (~100 ms à 10 ms )

t - Pulse duration (~1 à 100 ms)

Emitted signals

Received

The antenna beam is narrow and scanning all directions

This allows for measuring the target direction

1 to 3°

Scanning 10rpm


Passive radar

Passive radar relies on existing transmitters (donors). By processing reflected and direct path signal, it is possible to compute target position and speed. For this specific application, SDR offers the possibility to receive any type of donor.


Introduction to J. Pisane PhD work SN533, A320

transponder on

? Unknown aircraft transponder off

Goal of Ph. D. thesis: Identify the ?’s

?

SN533, A320

Radar


Introduction to J. Pisane PhD work

Receiver 2 Emitters of opportunity

Receiver 3

Receiver 1

GSM

DVB-T

•  Operate at "low frequencies" (<1GHz) •  Data = RCS of targets •  No image reconstruction


Using passive radar techniques to collect RCS System overview

USB or remote

Network (direct or Internet)

Network (direct or Internet)

Donor(VOR, FM station, …)

Donor(VOR, FM station, …)

Geo databaseDonors & Receivers

Software Defined Receiver


SDR controller

ADSB-B decoderKinetic SBS-1

ADSB Receiver

Apache Tomcatsupervision

MySQL

remote

Central systemData collection / storage / analysis


RCS Data collection: System overview

Position given by ADSB receiver




Receiver tuned on a “quiet” area of the spectrum to have good SNR



Old samples New samples

Decimation

shift

We keep around

1second of signal

FFT

Samples

Axe

YFrequency (FFT bin)

‘Direct Path’ signal : spectrum of original transmitted signal

‘Echo path’ : same signal delayed and

shifted (Doppler effect)

SNR !



Live demo ! (if it works )


Typical spectrogram


Recovered RCS of plane


Part IV

4 - Software Defined Radio: challenges


Market driven by « Consumer Electronics »

Each iPhone® gives $300 operational profit… More than 8MILLIONS units sold in 2010 => 300x8000000 = 240 Million$

Current designs are “Keep it simple, Keep it low cost” new models every 6 month, design driven by marketing team


Balancing a set of constraints

Wideband signals => Wide bandwidth

High frequency => High sampling rate

Huge amount of data to process in real-time

System design is complex

=


Processing power

•  SDR system to process WiFi signals •  One channel is 22MHz wide, sampled at 44 MSPS at 16 bits (I

and Q) gives : –  44M * 4 bytes / seconds ➜ 176 MBytes/seconds

➜ Too much data to be processed by a « PC » processor ➜ Specific pre-processing hardware required (FPGA, DSP…) ➜ Such system require hardware + software + radio engineers to work

together


Analog front-ends must be designed with care Effect of imperfections on transmitted symbols

Any difference with ideal characteristic will degrade RF signal generation and… make signal demodulation more difficult.

Imperfection


Part V

5 – Research at Alcatel Lucent Chair in Flexible Radio @ Supélec


« Small cells » as a solution to densification

•  Many small, low-cost, low-power BSs (50 to 150 meter range) as additional capacity/coverage layer under a macro cell deployment

•  Use existing backhaul infrastructure •  Collocated with existing street furniture (in-street cabinets/telephone booth, lamp posts,

etc.) ➜ no cell site acquisition •  Self-organizing/maintaining (plug & play) ➜ no planning

Current mobile networks cannot follow customer bandwidth requirements… need for new network solutions






Future of mobile networks – ALU Chaire @ Supélec

We dream to have…

The challenges we have to face…

Technology

ICT | Software Defined Radio : enjeux et perspectives par Sylvain Azarian et Jonathan Pisane | Liege Creative, 13.12.11