research article baseband transceiver design of a high...

Research ArticleBaseband Transceiver Design of a High DefinitionRadio FM System Using Joint Theoretical Analysisand FPGA Implementation

Chien-Sheng Chen1 Chyuan-Der Lu2 Ho-Nien Shou3 and Le-Wei Lin4

1 Department of Information Management Tainan University of Technology Tainan 710 Taiwan2Department of Finance Tainan University of Technology Tainan 710 Taiwan3Department of Aviation and Communication Electronics Air Force Institute of Technology Kaohsiung 820 Taiwan4Department of Electrical Engineering National Cheng Kung University Tainan 701 Taiwan

Correspondence should be addressed to Chien-Sheng Chen t00243mailtutedutw

Received 3 January 2014 Accepted 3 March 2014 Published 16 April 2014

Academic Editor Chung-Liang Chang

Copyright copy 2014 Chien-Sheng Chen et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Advances in wireless communications have enabled various technologies for wireless digital communication In the field of digitalradio broadcasting several specifications have been proposed such as Eureka-147 and digital radiomondiale (DRM)These systemsrequire a new spectrum assignment which incurs heavy cost due to the depletion of the available spectrumTherefore the in-bandon-channel (IBOC) system has been developed to work in the same band with the conventional analog radio and to provide digitalbroadcasting services This paper discusses the function and algorithm of the high definition (HD) radio frequency modulation(FM) digital radio broadcasting system Content includes data format allocation constellation mapping orthogonal frequencydivision multiplexing (OFDM) modulation of the transmitter timing synchronization OFDM demodulation integer and fractioncarrier frequency (integer carrier frequency offset (ICFO) and fractional CFO (FCFO)) estimation and channel estimation ofthe receiver When we implement this system to the field programmable gate array (FPGA) based on a hardware platform boththeoretical and practical aspects have been considered to accommodate the available hardware resources

1 Introduction

With advances in wireless communication many schemeshave been developed and are currently available In thedigital radio broadcasting area several specifications arecurrently in use for example the Eureka-147 in Europe [1]This is known as digital audio broadcasting (DAB) [2ndash4]and has been adopted by many European countries one ofits early commercial adopters was the British BroadcastingCorporation (BBC) which went into digital broadcasting in1995 This system utilizes the orthogonal frequency divisionmultiplexing (OFDM) technology Another digital radiobroadcasting proposition is called digital radio mondiale(DRM) which was developed in France and is able to operateat frequencies below 30MHz [3 5] Both of these digitalradio broadcasting technologies require a new spectrum

assignment for their proprietary use which is costly dueto limited spectrum availability Therefore an in-band on-channel (IBOC) system has been developed and it allowsthe conventional radio and the digital signal to broadcastsimultaneously in the same channel allocation [6ndash11]

IBOC has been adopted by the United States (US) asits digital radio broadcasting standard including two sets ofspecifications high definition (HD) radio frequencymodula-tion (FM) and HD radio amplitude modulation (AM) bothof which share identical working frequencies as conventionalFM and AM spectrums [11ndash13]The HD radio FM system is adigital radio broadcasting system developed by the iBiquityDigital Corporation and it can simultaneously broadcastanalog and digital audio signals in the same FM spectrumThe benefit of adopting this system is that the listeners whohave digital receivers can receive compact disk- (CD-) like

Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2014 Article ID 580479 9 pageshttpdxdoiorg1011552014580479

2 International Journal of Antennas and Propagation

400kHz200 kHz

Analog FM signal

Primary mainPrimary main

10 frequencypartitions


1 frequencypartition

minus198402 minus129361 129361 198402

Frequency (Hz)

1 referencesubcarrier 18 data

subcarriers

0

Figure 1 HD radio FM spectrum

quality programs and those with the conventional receiverscan still receive the same analog programs

This system specifies two broadcasting modes the hybridmode and the all-digital mode A station occupies 400 kHzbandwidth to transmit in parallel its analog and digital signalsto the hybrid mode meanwhile it can utilize the whole400 kHz bandwidth to transmit the pure digital signal in theall-digital mode [14] As this system restrains itself from theanalog FM station spectrum allocation it has less bandwidthto transmit the digital signal to the hybrid mode whichis 140ndash200 kHz In the future as soon as broadcasting istransferred to full digital the all-digital mode will be appliedinstead In this mode the HD radio FM system utilizes thecomplete 400 kHz bandwidth in digital transmission eventhough it occupies less bandwidth than other digital radiobroadcasting standards do Since the located spectrum is thesame as the conventional analog FM the broadcast stationdoes not need to drastically change its equipment and thelisteners do not need to adjust to the new station allocationfrequency Due to the spectrum attribution this system isvery suitable for a limited spectrum environment

The structure of this paper is as follows Section 2describes the transmitter design based on the system speci-fications Section 3 specifies the receiver design and discussesthe algorithms of each receiver module including its specificfunction and the simulation results Section 4 presents theimplementation of the system to the FPGA hardware plat-form Finally the conclusion is given in Section 5

2 Transmitter Design

21 HD Radio FM System Parameters The technical doc-ument released by iBiquity details the specification of theHD radio FM The subcarrier spacing is 3634Hz the cyclicprefix (CP) width is 7128 and the FFT size is 4096 Thesethree parameters result in the OFDM symbol duration of2902ms In the 400 kHz bandwidth assigned to each stationthe central 200 kHz is for analog use only while the othertwo remaining sidebands of total 200 kHz are for digital useThe spectrum allocation is shown in Figure 1 The digitalsignal occupies up to 534 subcarriers In this paper thespectrum distribution is compatible with the hybrid mode 1described by the Spec There are 10 frequency partitions oneach sideband of the digital FM Each partition consists of19 OFDM subcarriers with the combination of 1 referencesubcarrier for controlsynchronization and the remaining 18subcarriers for digital audio transmission Each frame lastsfor 1486 seconds which consists of 16 blocks and 32 OFDMsymbols per block In addition the OFDM symbol durationand the CP length are also specified in the Spec as 2902milliseconds and 7128 respectively

22 Transmitter Design In this subsection the transmittedblock structure defined in the Spec will be introduced Thephysical layer architecture of the HD Radio FM systemis shown in Figure 2 The data stream at first enters thescrambling block which randomizes the digital data in each

International Journal of Antennas and Propagation 3

Channel

encoding Interleaving Mapping IFFT Cyclicprefix

FFT

Channel

estimation

estimation

STOestimation

Deinterleaving Decoding Descrambling

Scrambling Channel +

AWGN

Removecyclicprefix

+

FMmodulator

FMreceiver

FCFO FCFOcompensation

Frame

ICFO estimation

Equalizer

Binarysequence

Binarysequence

Audio sourceTransmitter

Receiver

Audio source

Upconversion

Downconversion

Demapping

synchronization

Figure 2 HD radio FM transceiver block diagram

logical channel Afterward the scrambled data is encoded byusing the convolutional code to add redundancy to the digitaldata in each logical channel Later the channel encoded bitsare interleaved in the time and frequency domains tomitigatethe effects of burst errors

The HD radio FM system utilizes quadrature phase shiftkeying (QPSK) mapping in the data subcarriers and BPSKmapping in the reference subcarriersOFDMsubcarriermap-ping converts the interleaved data to the frequency domainPairs of adjacent columns within an interleaver partitionare mapped to individual complex QPSK-modulated datasubcarriers in the frequency partitionThe transmission sub-system formats the baseband IBOC FM waveform for trans-mission through the very high frequency (VHF) channelTheconcatenation functions include symbol concatenation andfrequency upconversion The concatenation functions areexecuted in the IFFT block In this block frequency domaindata is transformed to time domain and the transformeddata is concatenated into OFDM symbols Afterward CP isadded to the OFDM symbols The frequency upconversion isexecuted in the upconversion block after the CP blockWhentransmitting the hybrid or extended hybrid waveformsthis function modulates the baseband analog signal beforecombining it with the digital waveforms Figure 3 shows thehybrid transmission subsystem block diagram The input tothis module is a complex baseband time-domain OFDMsignal 119910(119905) After implementing the diversity delay 119879dd thebaseband analog signal 119898(119905) is input from an analog source119879dd is adjustable to account for the processing delays betweenthe analog and the digital chains In the IBOC system theanalog and digital signals carry the same audio program

The analog signal119898(119905) is transmitted by the conventionalFM modulation that is

119886 (119905) = cos(2120587119891119888119905 + 2120587119891

119889int

119905

minusinfin

119898(120591) 119889120591) (1)

Analog FMAnalog

OFDMsignal

audio

Upconversion RF IBOC FM waveform

source modulator+

m(t)

y(t)

a(t)

s(t)

z(t)

Figure 3Hybrid transmission subsystem functional block diagram

where 119891119888denotes the FM carrier frequency max

119905|119898(119905)| = 1

and 119891119889= 75 kHz is the maximum frequency deviation The

FM radio frequency (RF) signal is then combined with thedigitally modulated RF OFDM signal which passes throughupconversion producing the IBCO FM hybrid waveform119904(119905)

3 Receiver Design

31 Signal Synchronization The CP delay correlation isdesigned in this system to detect the symbolic timing offset(STO) and the fractional carrier frequency offset (FCFO)[8 15] The ICFO can be solved by using the control dataplaced in the reference subcarrier Since the HD radio FMsystem adopts the OFDM modulation technique the CP ofthe OFDM symbol allows the receiver to utilize the periodicfeature of signals to estimate the starting point of one symbolThe algorithm is shown in

Λ (119899) =

119873119892minus119898minus1

sum

119896=0

119903 (119899 minus 119896) times 119903(119899 minus 119896 minus 119873)lowast

Λ1015840

(119899) = 2 |Λ (119899)| minus 120588119864 (119899)

120588 equiv1205902

119904

1205902119904+ 1205902119899

119864 (119899) equiv

119899+119871minus1

sum

119896=119899

|Λ (119896)|2

+ |Λ (119896 + 119899)|2

(2)


Table 1 FM band channel models

Ray CM1lowast (119891119889

+ = 01744Hz) CM2lowastlowast (119891119889= 52314Hz) CM3lowastlowastlowast (119891

119889= 130785Hz) CM4lowastlowastlowastlowast (119891

119889= 52314Hz)

Delay (ms) Attenu (dB) Delay Attenu Delay Attenu1 00 20 00 40 00 1002 02 00 03 80 10 403 05 30 05 00 25 204 09 40 09 50 35 305 12 20 12 160 50 406 14 00 19 180 80 507 20 30 21 140 120 208 24 50 25 200 140 809 30 100 30 250 160 50lowastCM1 channel model 1 represents the Urban Slow Rayleigh Multipath ProfilelowastlowastCM2 channel model 2 represents the Urban Fast Rayleigh Multipath ProfilelowastlowastlowastCM3 channel model 3 represents the Rural Flow Rayleigh Multipath ProfilelowastlowastlowastlowastCM4 channel model 4 represents the Terrain-Obstructed Fast Rayleigh Multipath Profile119891119889

+ represents the Doppler frequency

where 119903(119899) is the received complex signal ( sdot )lowast is the complexconjugate119873

119892is the cyclic prefix length119898 is the summation

correction 120588119864(sdot) is energy correction 1205902119904is the signal energy

and 1205902119899is the noise energy

The peak value in the autocorrelation indicates that thestarting point of the OFDM is a symbol with the highautocorrelation feature in one symbol Correction functionsmust be added to compensate for the influence induced bythe multipath channel Nevertheless it is still difficult todistinguish the peak value from the surrounding noises suchas AWGN noise AWGN noise is a basic noise model thatpresents random noise in nature Except for AWGN thesimulation channels considered in this paper are shown inTable 1 and the frequency responses of CM1 to CM4 areshown in Figures 5 to 8 respectively Thus we might suggestthat averaging the cumulative autocorrelation values of onesymbol length is applied to increase the decision reliability

There are two main sources of the CFO First the relativespeed between the transmitter and the receiver results in theDoppler shift The second source is the mismatch betweenthe oscillator of the transmitter and that of the receiver Theworking carrier frequency of the HD radio FM can reach ashigh as 108MHzThe channel model defined in [16] specifiesthat the receiver is moving at the speed of 141 kmh resultingin 13Hz of Doppler shift This value is still less than half ofthe subcarrier spacingAccording to the SystemTransmissionSpec [8] the mismatch of broadcasting stations that is thelocal oscillator (LO) mismatch is limited to less than 1 ppmThus the LO mismatch of the receiver is the main concernof the CFO issue Therefore the following discussion mainlyfocuses on the LO mismatch Assume that the LO mismatchis 20 ppm and the carrier frequency is 108MHz the CFO canreach to 2160Hz As a result the ICFO can cover up to 6 typesof subcarrier spacing

As discussed above the CFO which affects this systemcan be divided into the FCFO and the ICFO When a CFOis greater than a half of subcarrier spacing it is customary toexpress it as an ICFO plusminus an FCFO The FCFO can

be estimated via the CP delay correlation method mentionedpreviously as shown in

Δ119891119891=minus1

2120587angΛ(argmax

119899

(Λ1015840

(119899))) (3)

As for the ICFO it can be resolved by using the evenlyspacing reference subcarriers in the frequency domainAccording to the Spec the length of the system control datasequence is 32 bits and each time 1 bit is transmitted in oneOFDM symbol at a time In this sequence there exists an 11-bit synchronization patternwhich is designed for the purposeof frame synchronization

Based on this property the receiver is able to cross-correlate the received subcarriers to the 11-bit synchronizedpattern upon receiving the OFDM signal If a highly corre-lated subcarrier combination in each 19 subcarriers apart isfound then the position of the reference subcarrier is reachedand the ICFO is acquired The frame and synchronizationmethodology is shown in Figure 4 In Figure 4 the allocationof the 11-bit synchronization pattern is displayed in frequencydomain The 11-bit synchronization pattern is used to searchand locate the ICFO

32 Channel Estimation In designing the receiver attentionshould be paid to the timingfrequency synchronization aswell as the channel effects In the receiver these harmfuleffects should be estimated and compensated The pilotsignals which are located in the reference subcarriers canbe used in the channel estimation In each transmissionall subcarriers except for bit 20 and bit 21 are transmit-ted as the same data in one OFDM symbol These twobits are transmitted in a predefined order Upon receivingthese two signals the system control data sequence can bedecoded correctly by using the signalsrsquo redundancy featureThe decoded signal is then used as the known pilot signalto assist the channel estimation The channel response ofeach reference subcarriers is estimated by using the leastsquares (LS) channel estimation method Consequently the


0

Subcarrier group

Differential BPSK demodulation

Cross-correlation withBPSK timing pattern

Mark correlation ofsuccessful subcarriers

Frame synchronization is successful and ICFO is found

198402Hz129361Hzminus129361Hzminus198402Hz

(minus9sim0sim9)

middot middot middotmiddot middot middot

If gt threshold

Figure 4 HD radio FM frame and ICFO synchronization

Frequency (kHz)Symbol number

Mag

nitu

de

4

2

0100

8060

4020

600

200

Channel response under simulation channel model 1

minus200

minus600 quency (kHz)ymbol number

8060

4020

6

200

minus200

Figure 5 The frequency response of CM1

channel response of each data subcarrier is estimated by usingthe linear interpolation as shown in (4) and (5) Equation(4) explains the approach of using the transmitted pilotsignals and the received ones to search for the frequencyresponse of the communication channel Equation (5) is touse the result of (4) to perform the interpolation of the extrasubcarriers

119867119890(119896) =

119884119901(119896)

119883119901(119896)

119896 = 0 1 119873119901minus 1 (4)


Mag

nitu

de

4

2

0100

8060

4020

600

200

quency (kHz)Symbol number

8060

4020

60

200


minus200

minus600


where 119884119901(119896) is the received pilot signal at the 119896th pilot

subcarrier119883119901(119896) is the transmitted pilot signal at the 119896th pilot

subcarrier119873119901(119896) is the number of pilot subcarriers Consider

119867119890(119896) = 119867

119890(119898119871 + 119897) 0 le 119897 lt 119871

= (119867119901(119898 + 1) minus 119867

119901(119898))

1

119871+ 119867119901(119898)

(5)

where 119867119901(119896) 119896 = 0 1 119873

119901 is the frequency response

of the channel at pilot subcarriers 119871 is the number ofcarriers119873

119901

The FM band channel model proposed by ElectronicsIndustries Association (EIA) in 1993 [16] is used in the



Mag

nitu

de 46

20

10080

6040

20

600

200


minus200

minus600



Mag

nitu

de

10

5

0100

80

60

40

20

600

200

minus200

minus600



simulations of the proposed channel estimation methodThis method can be conducted to reach the bit error rateof 10minus4when the convolution code and the interleaver areapplied as shown in the simulation charts below Theresponse characteristics of all of the four channel modelsare listed in Table 1 The four figures (Figures 5 6 7 and8) correspond to the frequency responses of CM1simCM4 inTable 1 respectively

The robustness of different coding schemes under thesechannel models is shown in Figure 9

Note that a convolutional code with the code rate 25 isimplemented in this system Besides a three-element slidingwindow is applied to execute the averaging operation Thatis the final outcome of each symbol in each subcarrier isthe weighted sum of the current symbol and the two mostadjacent ones as shown in Figure 9When averaging is incor-porated with the channel estimation system performancewill be modified The main reason for this improvement isthat more pilot data are used to estimate the correspondingchannel responseThe averaging process used in this paper isshown in Figure 10

10minus6

10minus4

10minus5

10minus3

10minus2

100

10minus1

BER

0 1 2 3 4 5 6 7 8 9 10

Compare 4 CMs with or without average

CM1 averageCM2 averageCM3 averageCM4 average

CM1 no averageCM2 no averageCM3 no averageCM4 no average

EbN0

Figure 9 BER performance under FM band channel models

4 Implementation of the FPGAHardware Platform

After careful examination of the parameters defined in theSpec and the available hardware resources the followingparameters are chosen in the hardware implementation

FFT size 2048CP length 112sampling rate 78125 kHzsubcarrier spacing 3815Hzsymbol rate 3619Hztransmission rate 1042 kbps (code rate 25)

The built-in CP2102 USB-UART bridging chip on theFPGA board is used as the communication interface betweenthe board and the computer as shown in Figure 11 The firstFPGA board is linked to the other FPGA board through theUSB transmission interface

41 Constellation Mapping The Agilent 89600 vector signalanalyzer is used to monitor the QPSK constellation mapgenerated by the transmitter as shown in Figure 12 It can beseen that all the constellation points are mapped into the fourcorresponding clusters of QPSK

42 The Transmitter Spectrum Diagram The OFDM wave-forms generated by the transmitter are fed into the Agilent89600 vector signal analyzer to analyze its spectrummapTheresult is shown in Figure 13 The simulation frequency mapgenerated by MATLAB is shown in Figure 14 It is found thatthese two spectrum distributions are basically similar


Frequency

Tim

e

18 data subcarriers

11 reference subcarriers

1 frequency partition

10 frequency partitions

middot middot middot



















Figure 10 Time domain averaging by using a 3-element slidingwin-dow

PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB

Figure 11 Diagram of the communication interface between thecomputer and the FPGA

Figure 12Using theAgilent 89600 vector signal analyzer tomonitorthe constellation points of the transmitter

Figure 13 Real transmitting spectrum of the HD radio FM imple-mentation

0 100 200Frequency (kHz)

Mag

nitu

de

HD radio FM digital signal spectrum

minus200 minus100

106

104

102

100

10minus2

Figure 14 Simulated transmitting spectrum of the HD radio FMimplementation

43 Receiver Signal Synchronization This system utilizesthe OFDM technology to achieve symbol synchronizationthrough the autocorrelation property First upon receivingthe signal it uses a FIFO memory to temporarily storethe signal so as to extract the two sampling points ofthe intervals OFDM length of symbol for autocorrelationcalculations This autocorrelation calculation value will bestored in another FIFO memory having the CP length inorder to sum up the entire CP length actions The summedvalue will be stored in another FIFO memory having thelength of an entire OFDM length of symbol adding this tothe autocorrelated value having the length of a symbol Theposition of the largest value in the memory storage will bethe standard time for time synchronization which is then fedinto the FFT The flow chart is shown in Figure 15

44 Channel Estimation Circuit Design The channel estima-tion scheme contains twomain stepsThe first one is to detectthe channel response of the subcarrier while the second one


Compute angle

2049 OFDM samples FIFOOFDM signal

112 correlation values FIFO

Sum FCFO

2160 summation values FIFO(reset after 16 OFDM symbol

intervals)

Find max index STO

minus( )

( )lowast

Figure 15 Flow chart of time synchronization and fractional fre-quency offset

is the division of complex numbers signals needed to beprocessed in this area Through (6) the hardware can beimplemented through the addition tool and the real numberdivision tool Consider

119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)

=(119860 times 119862 + 119861 times 119863) + (119861 times 119862 minus 119860 times 119863) 119895

1198622 + 1198632

(6)

After that the channel response will be estimated Thisstep is derived by interpolation from the preamble Thecircuit of this matter is shown in Figure 16 The FPGAimplementation provides a prototype baseband systemwhichis compatible with the HD radio FM specifications Thesynthesis software ISE 9103i is used to synthesize thetransmitter and the receiver The synthesized gate count ofthe transmitter is about 1938975 while the highest operationclock is 96375MHz the synthesized gate count of thereceiver is about 1788016 while the highest operation clockis 81264MHz

5 Conclusion

In this paper the HD radio FM structure and algorithms oftheir transmitter and receiver are presented The transmitterdesign is fully complied with the HD radio FM specification

DividerReceived pilot signal n

Estimated channel response n

DividerReceived pilot Estimated channel

Linear interpo-

lationdivider

adderand

Data subcarrier channel response

Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1

Figure 16 The circuit diagram of channel estimation

In the receiver algorithms the timing and frequency synchro-nization issues are studied and discussed As for the chan-nel impairments a channel estimation and compensationalgorithm is presented and performed in different channelmodels From the simulation results it can be seen that thesystem performance still maintains in a descent range undervarious channel environments A hardware prototype systemis realized on FPGA and a PC platformThe system is capableof processing signals at a fast pace due to the nature ofFPGA and also adding flexibility for the future algorithmconfiguration

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] C Faller B-H Juang P Kroon H-L Lou S A Ramprashadand C-E W Sundberg ldquoTechnical advances in digital audioradio broadcasting in theUnited StatesrdquoProceedings of the IEEEvol 90 no 8 pp 1301ndash1302 2002

[2] ETS 300 401 Radio Broadcasting Systems Digital Audio Broad-casting (DAB) toMobile Portable and Fixed Receivers EuropeanTelecommunications Standard Valbonne France 1995

[3] M C Rau ldquoOverview of digital audio broadcastingrdquo inProceed-ings of the IEEE MTT-S Symposium on Technologies for WirelessApplications pp 187ndash194 February 1995

[4] B Chen and C-E W Sundberg ldquoDigital audio broadcasting inthe FM band by means of contiguous band insertion and pre-canceling techniquesrdquo IEEE Transactions on Communicationsvol 48 no 10 pp 1634ndash1637 2000

[5] W Y Zou and Y Wu ldquoCOFDM an overviewrdquo IEEE Transac-tions on Broadcasting vol 41 no 1 pp 1ndash8 1995

[6] D D Kumar ldquoIn-band on-channel digital broadcastingmethodand systemrdquo Tech Rep 5949796 US Patent 1998

[7] D Kumar ldquoIn-band on-channel digital broadcasting methodand systemrdquo Tech Rep 5949796 US Patent 1999

[8] iBiquity Digital Corporation ldquoHD radio FM transmission sys-tem specificationsrdquo 2008


[9] P J Peyla ldquoThe structure and generation of Robust Waveformsfor FM in-band on-channel digital broadcastingrdquo iBiquityDigital Corporation 2006

[10] S A Johnson ldquoThe structure and generation of Robust Wave-forms for AM in-band on-channel digital broadcastingrdquo iBiq-uity Digital Corporation

[11] B W Kroeger and P J Peyla ldquoCompatibility of FM hybrid in-band on-channel (IBOC) system for digital audio broadcast-ingrdquo IEEE Transactions on Broadcasting vol 43 no 4 pp 421ndash430 1998

[12] H-L Lou D Sinha and C-E W Sundberg ldquoMultistreamtransmission for hybrid IBOC-AM with embeddedmulti-descriptive audio codingrdquo IEEE Transactions on Broadcastingvol 48 no 3 pp 179ndash192 2002

[13] S-Y Chung and H-L Lou ldquoMultilevel RSconvolutional con-catenated coded QAM for hybrid IBOC-AM broadcastingrdquoIEEE Transactions on Broadcasting vol 46 no 1 pp 49ndash592000

[14] iBiquity Digital Corporation ldquoHD radio air interface designdescription-layer 1 FMrdquo 2007

[15] J-J van de Beek M Sandell and P O Borjesson ldquoML esti-mation of time and frequency offset in OFDM systemsrdquo IEEETransactions on Signal Processing vol 45 no 7 pp 1800ndash18051997

[16] USA Digital Radio ldquoPetition for rulemaking-to the UnitedStates Federal Communications Commission for in-band on-channel digital audio broadcastingrdquo Tech Rep 1998

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VLSI Design



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Propagation




Navigation and Observation



DistributedSensor Networks



400kHz200 kHz

Analog FM signal

Primary mainPrimary main



1 frequencypartition

minus198402 minus129361 129361 198402

Frequency (Hz)

1 referencesubcarrier 18 data

subcarriers

0

Figure 1 HD radio FM spectrum

quality programs and those with the conventional receiverscan still receive the same analog programs

This system specifies two broadcasting modes the hybridmode and the all-digital mode A station occupies 400 kHzbandwidth to transmit in parallel its analog and digital signalsto the hybrid mode meanwhile it can utilize the whole400 kHz bandwidth to transmit the pure digital signal in theall-digital mode [14] As this system restrains itself from theanalog FM station spectrum allocation it has less bandwidthto transmit the digital signal to the hybrid mode whichis 140ndash200 kHz In the future as soon as broadcasting istransferred to full digital the all-digital mode will be appliedinstead In this mode the HD radio FM system utilizes thecomplete 400 kHz bandwidth in digital transmission eventhough it occupies less bandwidth than other digital radiobroadcasting standards do Since the located spectrum is thesame as the conventional analog FM the broadcast stationdoes not need to drastically change its equipment and thelisteners do not need to adjust to the new station allocationfrequency Due to the spectrum attribution this system isvery suitable for a limited spectrum environment

The structure of this paper is as follows Section 2describes the transmitter design based on the system speci-fications Section 3 specifies the receiver design and discussesthe algorithms of each receiver module including its specificfunction and the simulation results Section 4 presents theimplementation of the system to the FPGA hardware plat-form Finally the conclusion is given in Section 5

2 Transmitter Design

21 HD Radio FM System Parameters The technical doc-ument released by iBiquity details the specification of theHD radio FM The subcarrier spacing is 3634Hz the cyclicprefix (CP) width is 7128 and the FFT size is 4096 Thesethree parameters result in the OFDM symbol duration of2902ms In the 400 kHz bandwidth assigned to each stationthe central 200 kHz is for analog use only while the othertwo remaining sidebands of total 200 kHz are for digital useThe spectrum allocation is shown in Figure 1 The digitalsignal occupies up to 534 subcarriers In this paper thespectrum distribution is compatible with the hybrid mode 1described by the Spec There are 10 frequency partitions oneach sideband of the digital FM Each partition consists of19 OFDM subcarriers with the combination of 1 referencesubcarrier for controlsynchronization and the remaining 18subcarriers for digital audio transmission Each frame lastsfor 1486 seconds which consists of 16 blocks and 32 OFDMsymbols per block In addition the OFDM symbol durationand the CP length are also specified in the Spec as 2902milliseconds and 7128 respectively

22 Transmitter Design In this subsection the transmittedblock structure defined in the Spec will be introduced Thephysical layer architecture of the HD Radio FM systemis shown in Figure 2 The data stream at first enters thescrambling block which randomizes the digital data in each


Channel


FFT

Channel

estimation

estimation

STOestimation



AWGN

Removecyclicprefix

+

FMmodulator

FMreceiver


Frame

ICFO estimation

Equalizer

Binarysequence

Binarysequence


Receiver

Audio source

Upconversion

Downconversion

Demapping

synchronization





119886 (119905) = cos(2120587119891119888119905 + 2120587119891

119889int

119905

minusinfin

119898(120591) 119889120591) (1)

Analog FMAnalog

OFDMsignal

audio


source modulator+

m(t)

y(t)

a(t)

s(t)

z(t)



119905|119898(119905)| = 1



3 Receiver Design


Λ (119899) =

119873119892minus119898minus1

sum

119896=0


Λ1015840

(119899) = 2 |Λ (119899)| minus 120588119864 (119899)

120588 equiv1205902

119904

1205902119904+ 1205902119899

119864 (119899) equiv

119899+119871minus1

sum

119896=119899

|Λ (119896)|2

+ |Λ (119896 + 119899)|2

(2)






119889= 52314Hz)











Δ119891119891=minus1

2120587angΛ(argmax

119899

(Λ1015840

(119899))) (3)





0

Subcarrier group






(minus9sim0sim9)


If gt threshold



Mag

nitu

de

4

2

0100

8060

4020

600

200


minus200


8060

4020

6

200

minus200



119867119890(119896) =

119884119901(119896)

119883119901(119896)

119896 = 0 1 119873119901minus 1 (4)


Mag

nitu

de

4

2

0100

8060

4020

600

200


8060

4020

60

200


minus200

minus600





119867119890(119896) = 119867

119890(119898119871 + 119897) 0 le 119897 lt 119871

= (119867119901(119898 + 1) minus 119867

119901(119898))

1

119871+ 119867119901(119898)

(5)

where 119867119901(119896) 119896 = 0 1 119873



119901




Mag

nitu

de 46

20

10080

6040

20

600

200


minus200

minus600



Mag

nitu

de

10

5

0100

80

60

40

20

600

200

minus200

minus600






10minus6

10minus4

10minus5

10minus3

10minus2

100

10minus1

BER

0 1 2 3 4 5 6 7 8 9 10




EbN0









Frequency

Tim

e

18 data subcarriers
























PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB





Mag

nitu

de


minus200 minus100

106

104

102

100

10minus2





Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Channel


FFT

Channel

estimation

estimation

STOestimation



AWGN

Removecyclicprefix

+

FMmodulator

FMreceiver


Frame

ICFO estimation

Equalizer

Binarysequence

Binarysequence


Receiver

Audio source

Upconversion

Downconversion

Demapping

synchronization





119886 (119905) = cos(2120587119891119888119905 + 2120587119891

119889int

119905

minusinfin

119898(120591) 119889120591) (1)

Analog FMAnalog

OFDMsignal

audio


source modulator+

m(t)

y(t)

a(t)

s(t)

z(t)



119905|119898(119905)| = 1



3 Receiver Design


Λ (119899) =

119873119892minus119898minus1

sum

119896=0


Λ1015840

(119899) = 2 |Λ (119899)| minus 120588119864 (119899)

120588 equiv1205902

119904

1205902119904+ 1205902119899

119864 (119899) equiv

119899+119871minus1

sum

119896=119899

|Λ (119896)|2

+ |Λ (119896 + 119899)|2

(2)






119889= 52314Hz)











Δ119891119891=minus1

2120587angΛ(argmax

119899

(Λ1015840

(119899))) (3)





0

Subcarrier group






(minus9sim0sim9)


If gt threshold



Mag

nitu

de

4

2

0100

8060

4020

600

200


minus200


8060

4020

6

200

minus200



119867119890(119896) =

119884119901(119896)

119883119901(119896)

119896 = 0 1 119873119901minus 1 (4)


Mag

nitu

de

4

2

0100

8060

4020

600

200


8060

4020

60

200


minus200

minus600





119867119890(119896) = 119867

119890(119898119871 + 119897) 0 le 119897 lt 119871

= (119867119901(119898 + 1) minus 119867

119901(119898))

1

119871+ 119867119901(119898)

(5)

where 119867119901(119896) 119896 = 0 1 119873



119901




Mag

nitu

de 46

20

10080

6040

20

600

200


minus200

minus600



Mag

nitu

de

10

5

0100

80

60

40

20

600

200

minus200

minus600






10minus6

10minus4

10minus5

10minus3

10minus2

100

10minus1

BER

0 1 2 3 4 5 6 7 8 9 10




EbN0









Frequency

Tim

e

18 data subcarriers
























PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB





Mag

nitu

de


minus200 minus100

106

104

102

100

10minus2





Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














119889= 52314Hz)











Δ119891119891=minus1

2120587angΛ(argmax

119899

(Λ1015840

(119899))) (3)





0

Subcarrier group






(minus9sim0sim9)


If gt threshold



Mag

nitu

de

4

2

0100

8060

4020

600

200


minus200


8060

4020

6

200

minus200



119867119890(119896) =

119884119901(119896)

119883119901(119896)

119896 = 0 1 119873119901minus 1 (4)


Mag

nitu

de

4

2

0100

8060

4020

600

200


8060

4020

60

200


minus200

minus600





119867119890(119896) = 119867

119890(119898119871 + 119897) 0 le 119897 lt 119871

= (119867119901(119898 + 1) minus 119867

119901(119898))

1

119871+ 119867119901(119898)

(5)

where 119867119901(119896) 119896 = 0 1 119873



119901




Mag

nitu

de 46

20

10080

6040

20

600

200


minus200

minus600



Mag

nitu

de

10

5

0100

80

60

40

20

600

200

minus200

minus600






10minus6

10minus4

10minus5

10minus3

10minus2

100

10minus1

BER

0 1 2 3 4 5 6 7 8 9 10




EbN0









Frequency

Tim

e

18 data subcarriers
























PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB





Mag

nitu

de


minus200 minus100

106

104

102

100

10minus2





Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

Subcarrier group






(minus9sim0sim9)


If gt threshold



Mag

nitu

de

4

2

0100

8060

4020

600

200


minus200


8060

4020

6

200

minus200



119867119890(119896) =

119884119901(119896)

119883119901(119896)

119896 = 0 1 119873119901minus 1 (4)


Mag

nitu

de

4

2

0100

8060

4020

600

200


8060

4020

60

200


minus200

minus600





119867119890(119896) = 119867

119890(119898119871 + 119897) 0 le 119897 lt 119871

= (119867119901(119898 + 1) minus 119867

119901(119898))

1

119871+ 119867119901(119898)

(5)

where 119867119901(119896) 119896 = 0 1 119873



119901




Mag

nitu

de 46

20

10080

6040

20

600

200


minus200

minus600



Mag

nitu

de

10

5

0100

80

60

40

20

600

200

minus200

minus600






10minus6

10minus4

10minus5

10minus3

10minus2

100

10minus1

BER

0 1 2 3 4 5 6 7 8 9 10




EbN0









Frequency

Tim

e

18 data subcarriers
























PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB





Mag

nitu

de


minus200 minus100

106

104

102

100

10minus2





Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Mag

nitu

de 46

20

10080

6040

20

600

200


minus200

minus600



Mag

nitu

de

10

5

0100

80

60

40

20

600

200

minus200

minus600






10minus6

10minus4

10minus5

10minus3

10minus2

100

10minus1

BER

0 1 2 3 4 5 6 7 8 9 10




EbN0









Frequency

Tim

e

18 data subcarriers
























PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB





Mag

nitu

de


minus200 minus100

106

104

102

100

10minus2





Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Frequency

Tim

e

18 data subcarriers
























PCMATLAB

FPGARX

CP2102

FPGATX

CP2102

PCMATLAB





Mag

nitu

de


minus200 minus100

106

104

102

100

10minus2





Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Compute angle



Sum FCFO


intervals)

Find max index STO

minus( )

( )lowast



119860 + 119861119895

119862 + 119863119895=(119860 + 119861119895) times (119862 minus 119863119895)

(119862 + 119863119895) times (119862 minus 119863119895)


1198622 + 1198632

(6)


5 Conclusion





Linear interpo-

lationdivider

adderand


Pilot signal n

signal n + 1

Pilot signal n + 1

response n + 1





References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









research article baseband transceiver design of a high...

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