wireless communication systems - western michigan …bazuinb/swradio.pdf · · 2009-12-23the...

November 14, 2003 ECE 460 Guest Lecture 1

Wireless Communication Systems:Software Radio Architecture and

Advanced Signal Formats

Dr. Bradley J. BazuinAssistant Professor

Western Michigan UniversityDept. Of Electrical and Computer Engineering


The Wireless World

There is an incredible range of wireless communications systems available with more products and services available every day.

Satellite

Satellite dish

Video

Video

Mobile

Satellite

Wireless

Computers/Workstations

INTERNET

Radio Tower

Telephony

Aircraft


Wireless Communications Developments• Communications systems have experienced rapid advancement

due to the demand created for mobile and local wireless communications devices.– Reliable, small, low cost consumer communication products..– Cost effective infrastructure to provide local competition or provide new

telecommunication installations.• Evolving signal formats support higher capacity and more

stringent bandwidth restrictions and requirements.– Historical formats: AM, FM, PSK, FSK, SSB, VSB, QAM, AMPS.– Modern formats: NAMPS, GSM, CDMA, DSSS, frequency hop, etc.– Developing formats: 3rd and 4th generation wireless, theoretically

optimized signals (OFDM?).• Device and component technologies have been been driven to

support the commercial demand.– RF and microwave devices for wireless voice and data access.– High sample rate, high dynamic range digital sampling and filtering.– Digital components to support advanced signal structures and formats.


Communications Systems ElementsThe message type that the system will transmit

– Voice, Music, Video, Television (merged formats)– Continuous digital data– Data Packets

The signal modulation scheme used for the message– AM, FM, PM, OOK, M-PSK, QAM, OFDM, CDMA

The frequency and frequency band available– FM radio, Aircraft Comm, CB radio, Military Comm., TV– Cellular telephone, PCS, MMDS, ISM

The radio wave signal environment, “channel effects”– Attenuation, interference, multipath,etc.

They all combine to define a unique communications systems, the operational requirements for success, and

the specifications/standards that must be followed.


Radio Frequency Bands

The Radio Frequency Spectrum extends from 3kHz to 300GHz. Spectrum use internationally and nationally regulated.

– International Telecommunications Union (ITU)– Federal Communication Commission (FCC)


FCC Allocation Chart

Adobe Acrobat Document

http://www.ntia.doc.gov/osmhome/allochrt.html

http://www.ntia.doc.gov/osmhome/allochrt.pdf


AM, FM and TV

http://wireless.fcc.gov/auctions/data/bandplans.html


Common RF Bands

• Cell Phones: 824-849 MHz and869-894 MHz

• PCS Bands: 1850-1910 MHz and1930-1990 MHz

• FCC Part 15 Unlicensed BandsInstrumentation, Scientific and Medical (ISM):

902 - 928 MHz and 2400 - 2483.5 MHz5725 – 5850 MHz

• Unlicensed National Information Structure (U-NII) bands:

5150 – 5350 MHz5725 – 5850 MHz


IEEE 802.11b

• Frequency Band Plan– unlicensed band from 2.4000 to 2.4835 GHz– up to 11 channels spaced at 5 MHz available

• Capacity– 11 Mbps wireless Ethernet connection

> Degraded performance options for 5.5 Mbps, 2 Mbps, and 1 Mbps– DSSS modulation with a required signal bandwidth of 22 MHz

From: ANSI/IEEE Std 802.11, 1999 Edition, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, p. 219.


Frequency Band Assignment

From: IEEE Std 802.11b-1999, (Supplement to ANSI/IEEE Std 802.11, 1999 Edition), Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band, p. 49.

• Overlapping Channels May Interfere– Three clear channels: 1, 6, and 11– Others shown at 10 MHz spacing: 1, 3, 5, 7, 9, and 11


Site Planning

• Optimal Coverage of a space by alternating the three non-overlapping frequencies. – Notice that there are significant regions of dual

coverage– In many cases overlapping of the same band will occur– Range and data rate considerations


Friis Transmission Formula

Wireless Range Equation

where trP / is the received (or transmitted) signal power trG / is the effective antenna gain

R is the distance between the transmitter and receiver, andλ is the wavelength ( ωλ ⋅=c )

( )2

2

4 RGGPP rt

tr ⋅⋅⋅⋅⋅=

πλ

r

rtt

r

rtt

PGGP

fc

PGGPR ⋅⋅⋅

⋅⋅=⋅⋅⋅

⋅=

ππλ

44

where c is the speed of light and f is the frequency


Wireless Range Example

Assumptions:Tx Power (Pt):

+23 dBm (200 mW)Tx Antenna Gain (Gt):

0 dBRcv Antenna Gain (Gr):

-20 dB

WiFi Receiver Sensitivity:11 Mbps: -87 dBm (1000 ft.)5.5 Mbps: -90 dBm (1500 ft.) 2 Mbps: -93 dBm (2000 ft.)1 Mbps: -95 dBm (2600 ft.)

Received Signal Power from +23 dBm Trasnmitter

-110

-100

-90

-80

-70

-60

-50

-4010.0 100.0 1000.0 10000.0

Distance (ft)

Pow

er (d

Bm)

916 MHz2.4 GHz5.2 GHz

Power and Sensitivity values based on: Surf and Sip’s Supercharged WiFi Card www.surfabdsip.com/ps_superchargedcard.htm


Network Planning

Wireless Relative Range and Application

The phony conflict: IEEE 802.11 and Bluetooth wireless technology, Brent Miller ([email protected]), Sr. software engineer, IBM, October 2001, http://www-106.ibm.com/developerworks/library/wi-phone/

WWAN:Wireless Wide Area Network

WLAN: Wireless Local Area Network

WPAN: Wireless Personal Area Network


Defining a Common ArchitectureWith all the variations in communications systems, can a common transmitter or receiver architecture be defined that can support all the different signal formats?

– One universal communications device that can be a pager, cell phone, wireless modem, GPS receiver, or whatever else you need.

What if?– You could digitize the entire radio spectrum with an analog-to-digital

converter or use a digital-to-analog converter to output it.– Microprocessors were fast enough to perform digital signal

processing on the digital data at the sample rate required.– Then, all communications can be done in software!

How close are we?


Receiver Architecture History

Pre-selector

NarrowbandIF Bandpass

Filter

LowpassFilter

1st LOSynthesizer

2nd LOPLO

ADCLNA

DigitalOutput

Demodulator

Super-heterodyne Receiver

Digital Demodulation Receiver

Pre-selector

IF BandpassFilter

LowpassFilter

1st LOSynthesizer

2nd LOPLO

ADCLNA

DigitalOutput

Demodulator

Digital SignalProcessor


Pre-selecto

r

IF BandpassFilter

LowpassFilter

1st LOSynthesizer

2nd LOPLO

ADCLNA

DigitalOutput

Demodulator

Digital Signal Processor


DigitalOutput

Receiver Architectures

Multi-channel Receiver

Zero IFDigital Receiver

Pre-select

LowpassFilter

1st LOSynthesizer

ADC

LNA

DigitalOutput

Complex Demodulator

Digital SignalProcessor

LowpassFilter

ADC

90 deg. Digital SignalProcessor

DigitalOutput


Enabling Technologies• RF and microwave commercial components

– Flexible amplifiers, mixers, filters, and oscillators are available• High speed, high dynamic range ADC and DAC

– Digitization of entire spectral bands– Dynamic range to handle both weak and strong signals

• DSP Algorithms and Devices to perform all-digital down conversion and up conversion– CIC Filter-Decimation and Filter-Interpolation

• Advanced Digital Signal Processors supporting GOPS rates– VLIW parallel floating-point processing

• Software Algorithms for common data handling and communications processing

• Algorithmic simulation tools for validation of concepts and implementations


Quadrature Demodulators

www.analog.com web site – AD8347 Data Sheet


ADC

www.analog.com web site – AD10226 Data Sheet



www.ti.com - DSP Selection Guide 4Q 2003


SW Signal Processing Flow

FEAST SW processing flow based on TI’s TMS320C6701 audio tutorial

AudioLine-In

AudioLine-Out

Audio Codec

DDR DXR

DMA0

McBSP0Serial Port

AudioDMA ISR

Receiver DDCOutput

TransmitDUC Input

DDR DXR

DMA1

McBSP1SerialPort

BasebandDMA ISR

Demodulation

Audio InMemory

Audio OutMemory

BasebandIn

Memory

BasebandOut

Memory

ModulationCommand andControl

Display andStatus

Main Program Loop Routines

Watch DogTimeout

Watch DogISR


Signals: Real or complex waveforms in time

Symbols: Encoded representation of underlying digital data bitsConstellation Modulations (M-PSK or QAM), Direct Sequence Spread Spectrum (DSSS), Discrete Multitone Packing, etc. with or without error correction codes

Bits: The digitized components of the data communicatedRaw data bits to be rendered into the information; voice, video, text, file transfers, etc.

Software Radio Processing

( ) ( ) ( )( ) ( ) ( )tntittftAts kkkkkk +++⋅⋅⋅= θπ2cos

( ) ( ) ( )titstsp spk

k +=∑

SignalDemodulation

Signals

SymbolDecoding

Symbols

BitRendering

Bits

Information


Digital Signals

Digitized Analog Modulations– AM to OOK (On-Off Keying) – amplitude is 0 or 1– AM to ASK (Amplitude Shift Keying) – amplitude takes discrete levels– PM to M-PSK (Phase Shift Keying) – phase takes discrete angles– FM to FSM (Frequency Shift Keying) – frequency takes discrete values

Basic Advanced Modulations– AM with PM to QAM (Quadrature Amplitude Modulation)

> Discrete amplitude and phases constellation points> Described in terms of a real-imaginary (In-phase and Quadrature-phase)

plot of points that define a magnitude and phase

A.B. Carlson, Communications Systems, 3rd Ed., Chapter 14


Advanced Signal (1)Basic Spread Spectrum Techniques

Frequency Hopping– Conventional signal moves from frequency to frequency in a pre-defined

pseudo-random sequence– Signal energy is spread out (in time) across a frequency band– Bluetooth peer-to-peer communications– Capabilities exist within CDMA cell phones

Direct Sequence Spread Spectrum– A high rate pseudo-random digital “chipping” sequence is used to

multiply the data symbol (typically BPSK) being sent, effectively spreading the original signal spectrum.

– Convolution receiver needed to “find” chipping sequence and thendetermine the data symbol that was sent. These systems may have negative signal to noise ratios!

– Deep space satellite communications, CDMA cell phones, the Global Positioning System.


GPS Signal Characteristics

• Two Principal Frequencies– L1 Band at 1575.42 MHz with C/A and P(Y) codes– L2 Band at 1227.60 MHz with P(Y) code– (L5 Band at 1176.45 MHz with “new” C/A code)

• Direct Sequence Spread Spectrum Communications– Data Message at 50 bps consisting of 1500 bit pages (30 sec.)– C/A-code spreads the data using 1023-bit Gold codes at a chipping rate of

1.023 Mcps (C/A – coarse-acquisition code)– P(Y)-code spreads the data using a code that does not repeat at a chipping

rate of 10.23 Mcps (P – precision code)• Code Transmission

– The C/A- and P(Y)-codes are transmitted in quadrature on L1– The P(Y)-code only is transmitted on L2


GPS Receiver Characteristics

• Receive up to 12 satellites simultaneously• User Minimum received power

– L1 C/A-Code: –130 dBm– L1 P-Code: –133 dBm– L2 P-Code: –136 dBm– kTB (20 MHz): –101 dBm

-10 -5 0 5 10-160

-150

-140

-130

-120

-110

-100

dBm

/ H

z

F re qua nc y (MHz )

The rm a l Nois e P owe rC/A Code P (Y) Code


GPS Code Correlation

• Code Lock to Satellite Vehicle’s Pseudo Random Sequence (acquisition process)• GPS satellites have highly accurate atomic clocks on board to maintain an

absolute reference.• When a GPS receiver locates one satellite, it can download all satellite location

information, and find the remaining needed satellites much more quickly.

Tc

ττττ

A2

Tc-Tc

NTc-NTcR(ττττ) = A2 (1 - | ττττ | / Tc) for | ττττ | <=<=<=<= Tc

= - A2 /N elsewhere


Advanced Signal (2)Discrete Wavelet Multitone (DWMT)

– A technique that was widely used for telephony to create FDM (frequency division multiplexed) communication channels from TDM inputs. Original systems were referred to as Transmultiplexers.

Orthogonal Frequency-Division Multiplexing (OFDM) or Discrete Multitone (DMT) Systems

– Individual FFT bins are loaded with complex symbols. An inverse-FFT generates a wide bandwidth real signal. The received signal goes through an FFT and the “spectral bin” data symbols are extracted.

– High definition digital television, ADSL modems, IEEE 802.11 a&gImpulse Radios or Ultrawideband (UWB) Spread SpectrumSingnaling

– Using impulses and pulse-position modulation techniques


IEEE 802.11a

• Unlicensed national information structure (U-NII) bands– 5150 – 5350 MHz and 5725 – 5850 MHz– 12 non-overlapping channels available

• Signaling– OFDM Modulation: Orthogonal Frequency Division Multiplexed

(Hybrid signal using QAM symbols in FFT bins)– Mandatory rates 6, 12, and 24 Mbps– Optional rates 9, 18, 36, 48, or 54 Mbps


OFDM Modulation

From: IEEE Std 802.11a-1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications High-speed Physical Layer in the 5 GHz Band, p. 27.

Inverse FFT Bins

•••

•••

QAM Constellation


Frequency Bands• IEEE 802.11a: 12 non-overlapping bands

From: IEEE Std 802.11a-1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications High-speed Physical Layer in the 5 GHz Band, p. 27.


Wireless Communication Systems

• Why have these systems come about?– The inevitable push of technology … yes but …

• Technological Advancements– Signal Processing Developments– Communications Protocols– Microwave, RF, and Digital ICs– Microprocessors and Microcontrollers– Software Radio Architectures (All-Digital Radios)


WMU Resources and Research

• RF Prototyping, Test, and Measurement Lab– Acquisition of RF test equipment and prototyping modules

> CEAS startup funds> Donations from BAE Systems> Michigan Space Grant Consortium with WMU matching

• Projects– FEAST: Flexible Electrical and Software Programmable

Transceiver– Chaotic Carrier Communications– Wireless Smart Sensor Systems– Bluetooth Prototype Monitoring System and IP Development– Various GPS based projects– Incorporation of simple wireless communications into multiple

Senior Design Projects


RF Chamber Lab Space

• Kohrman 3059 RF Chambers: – Two 10x10 metal boxes


RF Test Equipment• Agilent 4396B Spectrum/Network Analyzer (10 Hz to 1.8 GHz)• Two RF Synthesized Signal Sources (to 990 MHz and 2.2 GHz)• Power Supplies (Agilent 2 dual and 2 single supplies)• Misc. older equipment


Components• Minicircuits: Amplifiers, mixers, splitters, VCOs, Filters, and

attenuators• Cables: SMA cables with terminators• Custom designed and constructed modules:

– SAW BP Filter, test fixtures, VCO control circuitry


• Projects– FEAST: Flexible Electrical and Software Programmable

Transceiver– Chaotic Carrier Communications– Wireless Smart Sensor Systems– Bluetooth Prototype Monitoring System and IP Development– Various GPS based projects– Incorporation of wireless communications into multiple Senior

Design Projects> Flowserve Pump and Motor Monitor, Low Cost Local Area

Differential GPS, etc.

Research Projects


MSGC Research: FEAST• Provide the nucleus and resources to define, develop, and demonstrate an initial

prototype of the flexible, electrical and software programmable transceiver(FEAST) for wireless communications.

• Seed Grant and Student Research http://homepages.wmich.edu/~bazuinb/BJB_Research.htm


Chaotic Communication• Dr. Damon Miller and Dr. Giuseppe Grassi

– Reference: http://homepages.wmich.edu/~miller/


Wireless Smart SAW Sensor Systems• Dr. Massood Atashbar and Sridevi Krishnamurthy

This work is partially funded by an NSF grant, 02-039 Integrated Smart Wireless SAW Sensors and Systems.

IDTInput/Output Antenna Reflectors

Piezoelectric Crystal

Reflectedresponse

Burst Input

BurstModulator

PowerAmplifier

BurstGenerator

RF to IFReceiverADC

IntelligentM icro-

ControllerSAW

Sensor

T/RSwitch

SampleBuffer

Low NoiseAmplifier

Netw

orkInterface


Future Wireless Directions

• RF-ID, Bluetooth, or WiFi based material tracking and position location

• 3G and 4G Telephony– Novel signal generation– Smart antenna system integration– Bandwidth on demand

• RF Interference Mitigation– Temporal narrowband cancellation– Smart antenna spatial cancellation


Wireless Communication Systems:Software Radio Architecture and Advanced Signal Formats

Dr. Bradley J. BazuinWestern Michigan University, CEAS

Dept. of Electrical and Computer [email protected]

http://homepages.wmich.edu/~bazuinb

wireless communication systems - western michigan …bazuinb/swradio.pdf · · 2009-12-23the...

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