New Technologies - Software Radios

An Easy Definition

A software-defined radio (SDR) system is a radio communication system which uses software for the modulation and demodulation of radio signals. (Wikipedia)

The Industry Definition

A software radio is a wireless communications device in which all of the signal processing is implemented in software. By simply downloading a new program, a software radio is able to interoperate with different wireless protocols, incorporate new services, and upgrade to new standards. (An Introduction to Software Radio, Vanu Inc.)

Technical Definition.

Software defined radios are elements of a wireless network whose operational modes and parameters can be changed or augmented, post-manufacturing, via software. Software defined radios are a collection of hardware and software technologies that enable reconfigurable system architectures for wireless networks and user terminals.

(Software Defined Radio Forum, “Overview and Definition of Software Download for RF Reconfiguration”, Aug 2002,www.sdfforum.org)

Regulatory Definition

A radio that includes a transmitter in which the operating parameters of frequency range, modulation type or maximum output power (either radiated or conducted) can be altered by making a change in software without making any changes to hardware components that effect the radio frequency emissions. (US, Federal Communications Commission, First Report And Order, “Authorization and Use of Software Defined Radios”, Sep 2001, www.fcc.gov )

Keywords

• Modulation, Demodulation – Signal Processing in software.

• Interoperability between different wireless protocols, different frequencies.

• Upgradeable and reconfigurable via software

What are we looking for:

Software Architecture Reconfigurabl

e

Generic HardwareFlexible

Multiple Protocols

Upgradeable

Multiple Frequencies

Interoperable

Wireless Devices in Use

• Cell Phone – GSM, CDMA etc.

• Cordless Phone

• Wireless PDA

• Wireless Email device

• Pager

• GPS navigation system

• Car Phones

• Ham radios

• FM Radios

• Walkie-Talkies

Need for Software Radios

Scenario 1:Communication required between personnel from different departments of Public Safety and Emergency Services at a disaster recovery area. Police – use 800 MHz 2-way analog radioFirefighters – use Digital VHF band radios

Problem: Incompatibility between communication devices

Solution: Bring in thousands of new radio devices and distribute to all departments?

Better Solution: Software patch – download a patch and reconfigure all radios to communicate with each other.

Need for Software Radios

Scenario 2:

Commercial wireless network standards continuously evolving from 2G to 2.5G/3G and then further onto 4G. Significant difference in link-layer protocol standards. Cellular Service Provider – needs to upgrade to new technology.

Problem:Customer base using 2G. As need for data services arises among customers – provider needs to upgrade to 2.5 or 3 G.

Solution : Providers -Spend millions and billions to replace expensive equipment.Subscribers – buy new handsets.

Better solution : Software upgrade – software changed to upgrade from old to new technology.

Need for Software Radios

Scenario 3:A day in the life of an ordinary individual – cell phone, cordless phone, pager, internet enabled PDA, Navigation

System in car, TV Remote, Music System remote, FM Radio, Garage Door opener.

So many wireless devices !!!!!

A single Software radio device could • Act as a cell phone when he is traveling.• Switch to performing as a cordless phone from his office desk.• Accept GPS (global positioning system) signals in his car.• Act as a wireless Internet device to download e-mail.• Act as a garage-door opener when the user gets home.

Brief History

• SDR technology was first demonstrated in a Department of Defense project in 1995.

• SpeakEasy Phase I – 2 MHz to 2 GHz– Ground force radios (frequency-agile VHF, FM, and SINCGARS)– Air Force radios (VHF AM),– Naval Radios (VHF AM and HF SSB teleprinters) – Satellites (microwave QAM).

• SpeakEasy Phase II– 4 MHz to 400 MHz range – more quickly reconfigurable architecture (i.e. several conversations at

once)– cross-channel connectivity (i.e "bridge" different radio protocols). – Air ForceTactical Air Control Party (TACP) Personnel, using a VHF/AM

Radio communicated with an F-16 operating on a UHF Radio.

Brief History … contd.

• Joint Tactical Radio Systems - 1998– based on an internationally endorsed open Software Communications

Architecture (SCA). – CORBA on POSIX operating systems to coordinate various software

modules.– First known use of FPGAs

• Amateur Software Radio– GNU Radio - free software toolkit for learning about, building, and

deploying Software Defined Radios. (1998)– The goal is to give ordinary software people the ability to 'hack' the

electromagnetic spectrum - to understand the radio spectrum and think of clever ways to use it.

Quick Recap - Radio

Source - Wikipedia

The Superheterodyne Receiver

Source - Wikipedia

Software Radio

Change from Hardware to Software Radio

• Move analog/digital (A/D) conversion as close to the receiving antenna as possible.

• Substitute software for hardware processing

• Transition from dedicated to general-purpose hardware – from ASICs to FPGAs and DSPs and even general purpose processors.

Software functions

• Signal generation • Waveform modulation and demodulation • Baseband and digital signal processing functions • Use of intermediate frequencies (such as for frequency hopping) • Use of multiple link-layer protocols • Security and encryption

Dynamic selection of parameters.

Components

Software collected in libraries:

• Signal processing modules: – Basic functions such as coding and modulation.

• Real-time control modules: – Supervise the processing flow, perform the scheduling of the signal

processing and hardware interface modules.

• Hardware interface modules: – Manage the data input/output flow from and toward the IF stage.

Difficulties

• Antennas and LNAs serving bandwidths ranging from 100s of MHz to 10s of GHz

• Jitters in A/D conversion at RF

Software Architecture of SDR

Software Download

SMART CARD LOADING (SIM)

• Advantages– Error free, faster, no

overhead on network

• Disadvantages– Memory and processing

power– Sale points of smart

cards

AIR INTERFACE DOWNLOAD

• Advantages– Easy for user.– Better managed

• Disadvantages– Network overhead –

dedicated channel, defined download procedure.

– Error control– Speed – Security

Software Radios in Wireless Networking

• Mobile computing device with wide range of connectivity options.– Cellular– Wireless LAN– Satellite systems

• Spectrum Ware software radio system– All physical layer functions implemented in software.

• Contribution– Flexible easy to use software radio research platform/ testbed.

• Components– Signal acquisition– I/O subsystem – A/D/A converter to memory and vice versa– Programming environment – Signal Processing Environment for Continuous Real-

Time Applications (SPECTRA)– Radio Specification model – Next slide

Data link - Link Framing, MAC, Coding, Modulation,

Software Radio Layering Model

Virtual Radios

• Does all the Digital Signal Processing in off-the-shelf workstation (e.g PC).– Experimentation– Integration with other applications.– Rapid deployment– Current work stations have enough processing power

• Implemented as– A software cellular receiver– A software network interface “card”.

Flavours of Software Radio• Tier 1 - Software-Controlled Radios (SCR).

– multiple transceivers– software control functions activate transceiver as required– e.g. dual mode cell phones – support CDMA and GSM

• Tier 2 – Reconfigurable Software Defined Radios (SDR)– what is available now– software controls modulation techniques, wideband and narrowband

operation, security, and the waveform requirements.– Software starts from IF processing

• Tier 3 – Ideal Software Radio – The future– A/D conversion at antenna– Software starts from RF onwards

• Tier 4 – Ultimate Software Radio– Hypothetical – only for comparisons.

Advantages

• Reconfigurability • Interoperability • Low cost solutions – software cheaper than hardware, mass

production• Time to market• Easy to fix bug – once shipped.• Quick evolution of end user equipment, communication and

network infrastructures.• Easier upgrade for evolving link-layer communication protocol

standards.• Increase product lifetime – reduce obsolescence.

Future-proof!!

Issues

• Security – of downloading an upgrade.

• Fast, easy to perform, error-free download despite mobility of end user terminals

• Higher processing power required.

• Battery/power consumption – with all the increased processing load.

• Licensing issues with FCC

Some bits of info…..

• Industry support for SDR on the network/base station side.– Cost and battery power of handset are limitations.

• FCC introduced special licensing process for software radio – “permissive change” – Sep 2004

• FCC approved the Vanu Software Radio GSM Base Station – Supports multiple cellular technologies and frequencies at the

same time.– Can be modified in the future without any hardware changes.– Runs on an off-the–shelf server and standard OS.

Cognitive Radios On the Horizon

• “Cognitive" - being aware of and making judgments about something.

• A cognitive radio will be able to sense its surroundings and the presence of other signals.

• Use that information, and adapt, without user intervention, to its user’s communication needs.

• Sense unused range of the unlicensed spectrum and switch to a frequency that will give better performance.

• Select the correct radio interface, channel, data rate, etc., to provide maximum data throughput to the user's application

Discussion

What could be the possible impact on higher layers of networking?

• Adverbs and adjectives.• • •

Links of interest

• SDR Forum -http://www.sdrforum.org/faq.html• SDR resources page –

http://www-sop.inria.fr/planete/SoftwareRadio/

• GNU software radio project - http://www.gnu.org/software/gnuradio/

• SDRadio - http://www.sdradio.org/• Vanu Inc. - http://vanu.com/

Thank You.