The use of an ultra-wideband (UWB) radio technique is proposed as a viable solution for the distribution of high-definition audio/video content in fiber-to-the-home (FTTH) networks. The approach suitability is demonstrated by the transmission of standards-based UWB signals at 1.25 Gb/s along different FTTH fiber links with 25 km up to 60 km of standard single-mode fiber length in a laboratory experiment. Experimental results suggest that orthogonal frequency-division-multiplexed UWB signals exhibit better transmission performance in FFTH networks than impulse radio UWB signals

Alves, Tiago

Beltran, Marta

Cartaxo, Adolfo

Llorente, Roberto

Marti, Javier

Morant, Maria

Perez Soler, Joaquin

English

Morant, María

Beltrán, Marta

Pérez Soler, Joaquín

Martí Sendra, Javier

Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura

This paper must be cited as: Llorente, R.; Alves, T.; Morant, M.; Beltran, M.; Perez, J.; Cartaxo, A.; Martí Sendra, J.(2008). Ultra-Wideband Radio Signals Distribution in FTTH Networks. IEEE Photonics Technology Letters. 20(11):945-947. https://doi.org/10.1109/LPT.2008.922329Publication avaailable at : https://doi.org/10.1109/LPT.2008.922329© 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—The use of ultra-wide band (UWB) radio technique is proposed as a viable solution for the distribution of high-definition audio/video content in fiber-to-the-home (FTTH) networks. The approach suitability is demonstrated by the transmission of standards-based UWB signals at 1.25 Gbit/s along different FTTH fiber links with 25 km up to 60 km of standard single-mode fiber length in a laboratory experiment. Experimental results suggest that orthogonal frequency division multiplexed UWB signals exhibit better transmission performance in FFTH networks than impulse radio UWB signals. Index Terms— Optical communications, Fiber-To-The-Home access networks, Ultra-Wide Band (UWB). I. INTRODUCTIONltra-Wide Band (UWB) has been indicated as one of the most promising techniques to be used in wireless communication networks. The growing interest in this technique is due to its low self-interference, tolerance to multi-path fading, low probability of interception and capability of passing through walls while maintaining the communication [1]. Nowadays, UWB is appointed for high bit-rate wireless communications at picocell range, namely as a replacement of high definition (HD) video/audio cabling [2]. This paper proposes to extend this application to the distribution of HD audio/video content by the optical modulation and transmission of UWB signals in their native format through fiber-to-the-home (FTTH) access networks. This approach exhibits several advantages: (i) FTTH networks provide bandwidth enough to distribute a large number of UWB signals, as each one of them can occupy up to 7 GHz in current UWB regulation [3]. (ii) No trans-modulation is required at user premises. HD audio/video content is transmitted through the fibers in UWB native format. (iii) No frequency up-conversion is required at customer premises. The UWB signals are photo-detected, filtered, amplified and radiated directly to establish the wireless connection. (iv) FTTH networks are transparent to the specific UWB implementation Manuscript received 6th December 2007. This work has been partly funded by the FP6-IST-33615 UROOF project. Tiago Alves’ work was supported by FCT from Portugal under contract SFRH/BD/29871/2006. Marta Beltran’s work is supported by Spain MEC grant BES-2006-12066. The E-Photon ONe+ NoE is also acknowledged.  R. Llorente, M. Morant, M. Beltran, J. Perez, and J. Marti are with Fibre-Radio Group, Nanophotonics Technology. Centre, Universidad Politécnica de Valencia, Camino. de Vera s/n , 46022 Valencia, Spain (phone: +34-963879768; fax: +34-963877827; email rllorent@dcom.upv.es). T. Alves, and A. Cartaxo are with Optical Communications Group, Instituto de Telecomunicações, Dep. Electrical and Computer Engineering, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal (email: tiago.alves@lx.it.pt). employed. This flexibility is of special interest for operators as UWB regulation is still evolving. II. FTTH DISTRIBUTION OF UWB SIGNALSHFC networkHeadEndFTTHUWBon fibreUWBon fibreUWBon fibre!…SCM group 1 SCM group 2…SCM group N…Ch1-1Ch1-2Ch1-MCh2-1Ch2-2Ch2-MChN-1ChN-2ChN-M(a)(b)UCEf !PD(c)SSMFUCEUWBUWBUCEUWBAntennaOpt. Group SelectionUWB Antenna Amp. Elect. Channel SelectionFigure 1. (a) Concept of UWB on FTTH for distribution of high definition audio/video. (b) Proposed sub-carrier multiplexing (SCM) channelisation. (c) Proposed UWB channel extractor (UCE) architecture. The proposed technique is depicted in Fig. 1(a). This figure shows a central node (head-end) which generates UWB signals transporting HD content. These signals are distributed through the FTTH network to a number of subscribers. At the subscriber premises, the received UWB signals are photo-detected, filtered, amplified and radiated to broadcast the HD content to an UWB-enabled TV set or computer. This technique benefits from the high bit-rate capabilities of UWB, supporting bit-rates up to 1 Gbit/s at a few meters range [4], which can be extended to 30 m by multiple-input multiple-output processing techniques [5] covering a whole home. UWB is defined as a radio modulation technique with 500 MHz of minimum bandwidth or at least 20% greater than the center frequency of operation. The modulated signal must meet stringent equivalent isotropic radiated power (EIRP) limits [3] shown by the dashed line of Fig. 2, inset (b).       Ultra Wide-Band Radio Signals Distribution in FTTH Networks R. Llorente, T. Alves, M. Morant, M. Beltran, J. Perez, A. Cartaxo, J. MartiU > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) <  2 OFDM-UWB 3CHNRZPRBSCW laserAWG(ECMA368 OFDM)BER, EVMReceiver!=1559 nmOBPFMZ-EOMOFDM-UWB SCM TransmitterDelayLineRFAmpPINAgilent 6030 AWGCH2OSC (fOL2)OSC (fOL1)OSC (fOL3)AttCH1CH3AttFTTH paths:Path #1: L=25 km SSMFPath #2: 25km (L1) + 25km (L2) = 50 km SSMFPath #3: 25km (L1) + 35km (L2) = 60 km SSMFOSC (fOL,RX)EDFAHP83486AIR-UWB SCM TransmitterLPFLPFL1 L2EDFAL(1)UWB pulse shaping filterSHF EA44OSC (fOL)MLL10 GHzMZ-EOM PIN Gaussian Tfwhm =2.8 psAttIR-UWB(3)LPF(2)(1a)(1b)(4)LPF: low-pass filter; BPF: band-pass filter; OBPF: optical band-pass filter; Att: attenuator; OSC: oscillatorCW: continuous wave; MZ-EOM: Mach-Zehnder electro-optical modulator; PIN: positive-intrinsic-negativeEDFA: erbium doped fibre amplifier; RF Amp: radio–frequency amplifier; MLL: mode-locked laser0.5                        2                      4.51(a)510  MHzCH1CH3-75-70-65-60-55-50-45-40-35-30-25Normalized PSD (dB/MHz)3.51  GHzFrequency (GHz)CH2Normalized PSD (dB/MHz)(b)BW-10dB=3.2 GHz0                         6.6                   13.2Frequency (GHz)-85-80-75-70-65-60-55-50-45-40-9048 49-6-4-20246Amplitude(V)Time(ns)(c)283 pspulse profile50(HP83480)×10-2 Figure 2. UWB on FTTH demonstration set-up. Both IR-UWB and OFDM-UWB signals have a total bit-rate of 1.25 Gbit/s. Both UWB signals are transmitted through three different FTTH paths with reach from 25 km to 60 km. The receiver emulates the UWB channel extractor, including downconverting and filtering. (a) OFDM-UWB electrical spectrum at point (1a) of transmitter; (b) IR-UWB RF spectrum, and (c) Electrical IR-UWB signal and pulse profile at point (1b).  Two specific UWB implementations are mainstream nowadays: impulse-radio (IR-UWB), which transmits data by short impulses (monopulses), and orthogonal frequency division multiplexing (OFDM-UWB), which divides the UWB spectrum into 14 channels of 528 MHz bandwidth. Each channel is occupied by one OFDM signal composed by 128 carriers. Each carrier can be BPSK- or QPSK-modulated. Fig. 1(b) shows the sub-carrier multiplexing (SCM) channelisation proposed for the FTTH transmission. The channelisation consists in several 528 MHz-wide channels (each one in accordance with [3]) forming a SCM group which modulates an optical carrier. Different optical carriers can be wavelength division multiplexed (WDM) to increase the number of UWB channels delivered by each fibre of the FTTH network. Each UWB channel bears one HD audio/video stream, which is extracted at the customer premises by an UWB channel extractor (UCE). Fig. 1(c) shows the proposed architecture for the UCE. Operation is as follows. A given SCM group is first selected by optical filtering, and then the group is photo-detected and filtered in electrical domain to select the specific UWB channel transporting the desired HD contents. The selected UWB channel is then amplified and radiated. The proposed UCE architecture does not require demodulation or frequency translation of the UWB signal, and is transparent to the specific modulation employed. Other UCE architectures can be used, but their analysis is out of the scope of this paper. III. EXPERIMENTAL SET-UP AND RESULTS In this section, the suitability of the proposed UWB-on-FTTH technique for HD content distribution is evaluated. We analyze the signal degradation due to the fiber transmission impairments experienced in the FTTH link. Fig. 2 shows the experimental set-up to evaluate the UWB signal degradation due to fiber transmission. The two UWB versions are implemented for performance comparison: IR-UWB and OFDM-UWB as in ECMA regulation [6]. The UWB signal bit-rate is 1.25 Gbit/s in both cases, adequate for uncompressed 1920×1080i×18bpp×60 Hz video [7]. The UWB signals are transmitted along different standard single-mode fiber (SSMF) links, ranging from 25 km to 60 km corresponding to conventional FTTH transmission paths. The OFDM-UWB transmitter consists in three OFDM channels with an aggregated bit-rate of 1.25 Gbit/s, forming a SCM group. Each OFDM channel has 128 carriers, each QPSK-modulated, including pilots. Separation between carriers is 4.11 MHz. The channel under study (labeled CH2 in Fig. 2) is located at fOL2= 2.5 GHz and is surrounded by two adjacent channels centered at frequencies fOL1= 1 GHz and fOL3= 4 GHz. The bandwidth (BW) at "10 dB of the OFDM-UWB SCM group is 3.51 GHz [see Fig. 2, inset (a)]. The average optical power after modulation and before transmission [point (2) in Fig. 2] is "2 dBm. The three OFDM channels are generated by an AWG6030 arbitrary waveform generator with 1.25 Gsamples/s. The IR-UWB signal is generated as shown in Fig. 2, in accordance with the FCC UWB spectral mask between 3.1 and 10.6 GHz. The IR-UWB monopulses are obtained from a 10 GHz Gaussian pulse (Tfwhm=2.8 ps) train generated by a mode-locked laser. The pulse train is gated by a Mach-Zehnder electro-optical modulator (MZ-EOM) with 1.25 Gbit/s PRBS NRZ data. The gated optical pulses are photo-detected, shaped to monopulses with Tfwhm=283 ps by a pulse-shaping filter and up-converted to fOL=6.6 GHz for fiber transmission. The overall "10 dB bandwidth of IR-UWB signal is 3.2 GHz [see Fig. 2, inset (b)] and occupies the band from 5 GHz to 8.2 GHz, following FCC regulation [3]. The average optical power at point (2) in Fig. 2 is adjusted to "2 dBm.  The two UWB versions modulate a 20 GHz BW MZ-EOM at quadrature-bias point and are transmitted through the three FTTH paths shown in Fig. 2. After transmission, the signals are filtered by a 0.8 nm @ -0.5 dB optical filter (SCM group selection) and photo-detected by a PIN photodiode (0.65 A/W, 50 GHz BW) as in the UCE architecture proposed in Fig. 1(c). In order to evaluate the performance of the UWB channel under study, the photo-detected signal is converted to baseband and sampled by an HP83486A module (20 GHz BW). Performance is evaluated with received optical power ranging 0 – 10 dBm at the photodiode. These levels translate to -51.8 – -31 dBm/MHz (50 ") power spectral density over the 3.2 GHz BW. These > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 3 values would meet the wireless EIRP limits [3] employing a 0 dBi antenna. In the OFDM-UWB case, after sampling the received channel, the channel under study is equalized from pilot information, demodulated and the error vector magnitude (EVM) is measured. Bit-error ratio (BER) is calculated as ( )BER Q 1 EVM=  [8]. In the IR-UWB cases, the monopulses are demodulated, low-pass filtered and the Q-factor is measured by the HP83480 instrument in Fig.2. Under Gaussian noise assumption BER is given by ( )BER 0.5 erfc 2Q= × . Themeasurements have been done in back-to-back and for three FTTH SSMF transmission paths: Path#1=25 km SSMF, Path#2= 25 km SSMF + amplification + 25 km SSMF (50 km reach) and Path#3= 25 km SSMF + amplification + 35 km SSMF (60 km reach). These paths are depicted in Fig. 2. Inline amplification is realized by a 23 dB gain, 4 dB noise figure EDFA (Keopsys BT2C-13). The receiver includes a 4.5 dB noise figure, 19 dBm saturation power EDFA (Exelite SFA-19). In-PhaseQuadrature(a) (b)-1.5 -1 -0.5 0 0.5 1 1.5-1.5-1-0.500.511.5(a)In-PhaseQuadrature22.732Time (ns)23.732(b)Amplitude (mV)21018Figure 3. (a) Received OFDM-UWB (QPSK carriers) constellation (784 symbols shown) after pilot compensation, at point (4) of Fig. 2. Aggregated bit-rate 1.25 Gbit/s. (b) IR-UWB received eye diagram, at point (4).  Fig. 3(a) shows the OFDM-UWB received constellation after equalization employing pilot tones information, at point (4) of Fig. 2. Fig. 3(b) shows the IR-UWB received eye diagram, at point (4) of Fig. 2. Constellation and eye diagram shown in Fig. 3 are obtained at point (3), at 9 dBm received power and 50 km of SSMF. Fig. 3 shows that the received signal presents good quality for both IR-UWB and OFDM-UWB signals; therefore, good performance is expected for both UWB implementations. The BER achieved by OFDM-UWB and IR-UWB are shown in Fig. 4 for all the FTTH paths between 25 km and 60 km and back-to-back versus the received power, measured at point (3) in Fig. 2. These experimental results demonstrate the feasible distribution of 1.25 Gbit/s UWB signals achieving BER<10-9 operation at 50 km with both IR-UWB and OFDM-UWB implementations. Fig. 4 shows that the IR-UWB technique exhibits performance degradation in comparison with OFDM-UWB. This is due to the different modulation schemes. OFDM-UWB channels are generated independently and up-converted to generate a SCM group. The IR-UWB signal does not follow this channelisation, and to provide a bit rate of 1.25 Gbit/s, a single IR-UWB signal with 3.2 GHz bandwidth @-10 dB was generated. IR-UWB suffers from the non-perfect operation of up- and down-converting mixers over such wide bandwidth. Fig. 4 also shows that OFDM-UWB degrades quickly with fiber length. We believe this is due to the carrier suppression effect originated from the SSMF chromatic dispersion [9]. The bandwidth occupied by the 3 channels in OFDM-UWB (3.51 GHz), that ensures the accumulated bit-rate of 1.25 Gbit/s, leads to an equivalent spectral efficiency of 0.36 bit/s/Hz. The IR-UWB bandwidth (3.2 GHz) for the same bit-rate gives a spectral efficiency of 0.39 bit/s/Hz. This similar spectral efficiency combined with the improved performance obtained for OFDM-UWB suggests that the UWB-over-fiber implementation should be accomplished with OFDM signals. Received Power (dBm)369121518-6 -4 -2    0          2         4        6  8  10OFDM-UWB QPSK back-to-backOFDM-UWB QPSK Path#1 25kmOFDM-UWB QPSK Path#2 50kmOFDM-UWB QPSK Path#3 60kmIR-UWB back-to-backIR-UWB Path#1 25kmIR-UWB Path#2 50kmIR-UWB Path#3 60kmFigure 4. Comparison of UWB implementations at 1.25 Gbit/s for the three FTTH SSMF paths. Dotted lines: OFDM-UWB three channels SCM group (QPSK per carrier); dashed lines: IR-UWB signal. OFDM-UWB signal achieves better performance at same received power for all FTTH paths. IV. CONCLUSIONThe distribution of IR-UWB and OFDM-UWB signals in FTTH networks for HD audio/video broadcasting has been proposed and experimentally demonstrated. Experimental results suggest that OFDM-UWB signals show better transmission performance than IR-UWB signals, although other detection techniques could lead to different results. Optimization of the generation schemes of each one of UWB flavors will provide a thorough conclusion. An improved spectral efficiency can still be achieved in IR-UWB and OFDM-UWB through generating monopulses with a narrower bandwidth and reducing of the channel spacing, respectively. REFERENCES [1] R. Kohno, “State of arts in ultra wideband (UWB) wireless technology and global harmonization”, in Proc. 34th European Microwave Conf, Netherlands, pp. 1093- 1099, 2004.[2] C. Duan, G. Pekhteryev, J. Fang, Y. Nakache, J. Zhang, K. Tajima, Y. Nishioka, H. Hirai, “Transmitting multiple HD video streams over UWB links”, in Proc. CCNC’06, Las Vegas, vol. 2, pp. 691-695, 2006.[3] FCC, “Revision of part 15 of the Commission’s rules regarding ultra-wideband transmission systems”, Report FCC 02-48, Apr. 2002.[4] T. Lunttila, S. Iraji, H. Berg, "Advanced Coding Schemes for a Multi-Band OFDM Ultrawideband System towards 1 Gbps", in Proc. CCNC’06, Las Vegas, vol. 1, pp. 553-557, 2006.[5] Qiyue Zou, A. Tarighat, A.H. Sayed, “Performance analysis of multiband OFDM UWB Communications with application to range improvement”, IEEE Trans. on Vehicular Technology, vol. 56, pp. 3864—3878, 2007. [6] ECMA International Standard, ECMA-368: “High rate ultra widebandPHY and MAC standard”, ECMA, Dec. 2005.[7] Y. Shoji , C. Choi, S. Kato, I. Toyoda, K. Kawasaki, Y. Oishi, K. Takahashi, H. Nakas, “Re-summarization of merged usage model definitions parameters”, IEEE doc. 802.15-06-0379-02-003c, 2006.[8] R. A. Shafik, M.S. Rahman, A.H.M.R. Islam, “On the extendedrelationships among EVM, BER and SNR as performance metrics” inProc. ICECE’06, Bangladesh, pp. 408-411, Dec. 2006.[9] H. Schmuck, “Comparison of optically millimeter-wave system con-cepts with regard to chromatic dispersion,” Electron. Lett., vol. 31, no.21, pp. 1848–1849, 1995.

Ultra-Wideband Radio Signals Distribution in FTTH Networks

Northumbria Research Link

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 11, JUNE 1, 2008 945Ultra-Wideband Radio Signals Distributionin FTTH NetworksR. Llorente, T. Alves, M. Morant, M. Beltran, J. Perez, A. Cartaxo, and J. MartiAbstract—The use of an ultra-wideband (UWB) radio tech-nique is proposed as a viable solution for the distribution ofhigh-definition audio/video content in fiber-to-the-home (FTTH)networks. The approach suitability is demonstrated by the trans-mission of standards-based UWB signals at 1.25 Gb/s alongdifferent FTTH fiber links with 25 km up to 60 km of standardsingle-mode fiber length in a laboratory experiment. Experimentalresults suggest that orthogonal frequency-division-multiplexedUWB signals exhibit better transmission performance in FFTHnetworks than impulse radio UWB signals.Index Terms—Fiber-to-the-home (FTTH), radio-over-fiber,ultra-wideband (UWB).I. INTRODUCTIONULTRA-WIDEBAND (UWB) has been indicated as one ofthe most promising techniques to be used in wireless com-munication networks. The growing interest in this technique isdue to its low self-interference, tolerance to multipath fading,low probability of interception, and capability of passingthrough walls while maintaining the communication [1]. Today,UWB is appointed for high bit-rate wireless communicationsat picocell range, namely as a replacement of high-definition(HD) video/audio cabling [2].This letter proposes to extend this application to the distribu-tion of HD audio/video content by the optical modulation andtransmission of UWB signals in their native format throughfiber-to-the-home (FTTH) access networks. This approachexhibits several advantages: 1) FTTH networks provide band-width (BW) enough to distribute a large number of UWBsignals, as each one of them can occupy up to 7 GHz in currentUWB regulation [3]. 2) No transmodulation is required at userpremises. HD audio/video content is transmitted through thefibers in UWB native format. 3) No frequency up-conversionis required at customer premises. The UWB signals are pho-todetected, filtered, amplified, and radiated directly to establishthe wireless connection. 4) FTTH networks are transparent tothe specific UWB implementation employed. This flexibilityManuscript received December 6, 2007; revised March 5, 2008. This workwas supported in part by the FP6-IST-33615 UROOF Project. The work ofT. Alves was supported by FCT from Portugal under Contract SFRH/BD/29871/2006. The work of M. Beltran was supported by Spain MEC Grant BES-2006-12066.R. Llorente, M. Morant, M. Beltran, J. Perez, and J. Marti are with Fibre-Radio Group, Nanophotonics Technology Centre, Universidad Politécnica deValencia, 46022 Valencia, Spain (e-mail: rllorent@dcom.upv.es).T. Alves and A. Cartaxo are with Optical Communications Group, Instituto deTelecomunicações, Department of Electrical and Computer Engineering, Insti-tuto Superior Técnico, 1049-001 Lisboa, Portugal (e-mail: tiago.alves@lx.it.pt).Color versions of one or more of the figures in this letter are available onlineat http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/LPT.2008.922329Fig. 1. (a) Concept of UWB on FTTH for distribution of HD audio/video.(b) Proposed SCM channelization. (c) Proposed UCE architecture.is of special interest for operators as UWB regulation is stillevolving.II. FTTH DISTRIBUTION OF UWB SIGNALSThe proposed technique is depicted in Fig. 1(a). This figureshows a central node (head-end) which generates UWB signalstransporting HD content. These signals are distributed throughthe FTTH network to a number of subscribers. At the subscriberpremises, the received UWB signals are photodetected, filtered,amplified, and radiated to broadcast the HD content to a UWB-enabled television set or computer. This technique benefits fromthe high bit-rate capabilities of UWB, supporting bit rates upto 1 Gb/s at a few meters range [4], which can be extended to30 m by multiple-input multiple-output processing techniques[5] covering a whole home.UWB is defined as a radio modulation technique with500 MHz of minimum BW or at least 20% greater than thecenter frequency of operation. The modulated signal must meetstringent equivalent isotropic radiated power (EIRP) limits [3]shown by the dashed line of Fig. 2, inset (b).1041-1135/$25.00 © 2008 IEEE946 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 11, JUNE 1, 2008Fig. 2. UWB on FTTH demonstration setup. Both IR-UWB and OFDM-UWB signals have a total bit rate of 1.25 Gb/s. Both UWB signals are transmitted throughthree different FTTH paths with reach from 25 to 60 km. The receiver emulates the UCE, including down-converting and filtering. (a) OFDM-UWB electricalspectrum at point (1a) of transmitter; (b) IR-UWB RF spectrum; and (c) electrical IR-UWB signal and pulse profile at point (1b).Two specific UWB implementations are mainstream today:impulse-radio (IR-UWB), which transmits data by short im-pulses (monopulses), and orthogonal frequency-division multi-plexing (OFDM-UWB), which divides the UWB spectrum into14 channels of 528-MHz BW. Each channel contains an OFDMsignal comprising 128 carriers binary or quaternary phase-shiftkeying (QPSK) modulated.Fig. 1(b) shows the subcarrier-multiplexing (SCM) chan-nelization proposed for the FTTH transmission. The chan-nelization consists of several 528-MHz-wide channels (eachone in accordance with [3]) forming an SCM group whichmodulates an optical carrier. Different optical carriers can bewavelength-division multiplexed to increase the number ofUWB channels delivered by each fiber of the FTTH network.Each UWB channel bears one HD audio/video stream, which isextracted at the customer premises by a UWB channel extractor(UCE). Fig. 1(c) shows the proposed architecture for the UCE.Operation is as follows. A given SCM group is first selectedby optical filtering, and then the group is photodetected andfiltered in the electrical domain to select the specific UWBchannel transporting the desired HD contents. The selectedUWB channel is then amplified and radiated. The proposedUCE architecture does not require demodulation or frequencytranslation of the UWB signal, and is transparent to the specificmodulation employed. Other UCE architectures can be used,but their analysis is out of the scope of this letter.III. EXPERIMENTAL SETUP AND RESULTSIn this section, the suitability of the proposed UWB-on-FTTHtechnique for HD content distribution is evaluated. We analyzethe signal degradation due to the fiber transmission impairmentsexperienced in the FTTH link.Fig. 2 shows the experimental setup to evaluate the UWBsignal degradation due to fiber transmission. The two UWB ver-sions are implemented for performance comparison: IR-UWBand OFDM-UWB as in current regulation [6]. The UWBsignal bit rate is 1.25 Gb/s in both cases, adequate for thetransmission of 1920 1080 i 18 bpp 60 Hz uncompressedvideo [7]. The UWB signals are transmitted along differentstandard single-mode fiber (SSMF) links, ranging from 25to 60 km corresponding to conventional FTTH transmissionpaths. The OFDM-UWB transmitter consists in three OFDMchannels with an aggregated bit rate of 1.25 Gb/s, formingan SCM group. Each OFDM channel has 128 carriers, eachQPSK-modulated, including pilots. Separation between car-riers is 4.11 MHz. The channel under study (labeled CH2 inFig. 2) is located at GHz and is surrounded by twoadjacent channels centered at frequencies GHz andGHz. The BW at 10 dB of the OFDM-UWB SCMgroup is 3.51 GHz [see Fig. 2, inset (a)]. The average opticalpower after modulation and before transmission (point (2) inFig. 2) is 2 dBm. The three OFDM channels are generatedby an AWG6030 arbitrary waveform generator at 1.25 Gsam-ples/s. The IR-UWB signal is generated as shown in Fig. 2,in accordance with the FCC UWB spectral mask between 3.1and 10.6 GHz. The IR-UWB monopulses are obtained from a10-GHz Gaussian pulse ( ps) train generated by amode-locked laser. The pulse train is gated by a Mach–Zehnderelectrooptical modulator (MZ-EOM) with 1.25-Gb/s pseudo-random binary sequence data. The gated optical pulses arephotodetected, shaped to monopulses with ps bya pulse-shaping filter and up-converted to GHz forfiber transmission. The overall 10-dB BW of IR-UWB signalis 3.2 GHz [see Fig. 2, inset (b)] and occupies the band from 5to 8.2 GHz, following actual UWB regulation [3]. The averageoptical power at point (2) in Fig. 2 is adjusted to 2 dBm.The two UWB versions modulate a 20-GHz BW MZ-EOMat quadrature-bias point and are transmitted through the threeFTTH paths shown in Fig. 2. After transmission, the sig-nals are filtered by a 0.8 nm at 0.5-dB optical filter (SCMgroup selection) and photodetected by a PIN photodiode(0.65 A/W, 50-GHz BW) as in the UCE architecture pro-posed in Fig. 1(c). In order to evaluate the performance ofthe UWB channel under study, the photodetected signal isconverted to baseband and sampled by an HP83486A module(20-GHz BW). Performance is evaluated with received opticalpower ranging 0–10 dBm at the photodiode. These levelstranslate to 51.8 to 31 dBm/MHz (50 ) power spectraldensity over the 3.2-GHz BW. These values would meet thewireless EIRP limits [3] employing a 0-dBi antenna. In theOFDM-UWB case, after sampling the received channel, thechannel under study is equalized from pilot information, de-modulated and the error vector magnitude (EVM) is measured.Bit-error ratio (BER) is calculated as BERLLORENTE et al.: UWB RADIO SIGNALS DISTRIBUTION IN FTTH NETWORKS 947Fig. 3. (a) Received OFDM-UWB (QPSK carriers) constellation (784 sym-bols shown) after pilot compensation, at point (4) of Fig. 2. Aggregated bit rate1.25 Gb/s. (b) IR-UWB received eye diagram, at point (4) in Fig. 2.[8]. In the IR-UWB cases, the monopulses are demodu-lated, low-pass filtered, and the -factor is measured by theHP83480 instrument in Fig. 2. Under Gaussian noise as-sumption, BER is given by BER . Themeasurements have been done in back-to-back and for threeFTTH transmission paths: Path#1 km SSMF, Path#2km SSMF amplification km SSMF (50-km reach),and Path#3 km SSMF amplification km SSMF(60-km reach). These paths are depicted in Fig. 2. Inlineamplification is realized by a 23-dB gain, 4-dB noise figureerbium-doped fiber amplifier (EDFA) (Keopsys BT2C-13).The receiver includes a 4.5-dB noise figure, 19-dBm saturationpower EDFA (Exelite SFA-19).Fig. 3(a) shows the OFDM-UWB received constellation afterequalization employing pilot tones information, at point (4) ofFig. 2. Fig. 3(b) shows the IR-UWB received eye diagram, atpoint (4) of Fig. 2. The constellation and eye diagram shownin Fig. 3 are obtained at point (3), at 9-dBm received powerand after 50-km transmission on SSMF. Fig. 3 shows that thereceived signal presents good quality for both IR-UWB andOFDM-UWB signals; therefore, good performance is expectedfor both UWB implementations.The BER achieved by OFDM-UWB and IR-UWB are shownin Fig. 4 for all the FTTH paths between 25 and 60 km andback-to-back versus the received power, measured at point(3) in Fig. 2. These experimental results demonstrate thefeasible distribution of 1.25-Gb/s UWB signals achievingBER operation at 50 km with both IR-UWB andOFDM-UWB implementations. Fig. 4 shows that the IR-UWBtechnique exhibits a performance degradation compared tothe OFDM-UWB. This is due to the different modulationschemes. OFDM-UWB channels are generated independentlyand up-converted to generate an SCM group. The IR-UWBsignal does not follow this channelization, and to provide a bitrate of 1.25 Gb/s, a single IR-UWB signal with 3.2-GHz BW at10 dB was generated. IR-UWB suffers from the nonperfectoperation of up- and down-converting mixers over such wideBW. Fig. 4 also shows that OFDM-UWB degrades quickly withfiber length. We believe this is due to the carrier suppressioneffect originated from the SSMF chromatic dispersion [9].The BW occupied by the three channels in OFDM-UWB(3.51 GHz), that ensures the accumulated bit rate of 1.25 Gb/s,leads to an equivalent spectral efficiency of 0.36 b/s/Hz.The IR-UWB BW (3.2 GHz) for the same bit rate gives aspectral efficiency of 0.39 b/s/Hz. This similar spectral effi-Fig. 4. Comparison of UWB implementations at 1.25 Gb/s for the three FTTHSSMF paths. Dotted lines: OFDM-UWB three channels SCM group (QPSKper carrier); dashed lines: IR-UWB signal. OFDM-UWB signal achieves betterperformance at same received power for all FTTH paths.ciency combined with the improved performance obtained forOFDM-UWB suggests that the UWB-over-fiber implementa-tion should be accomplished with OFDM signals.IV. CONCLUSIONThe distribution of IR-UWB and OFDM-UWB signals inFTTH networks for HD audio/video broadcasting has been pro-posed and experimentally demonstrated. Experimental resultssuggest that OFDM-UWB signals show better transmission per-formance than IR-UWB signals, although other detection tech-niques could lead to different results. Optimization of the gen-eration schemes of each one of UWB flavors will provide athorough conclusion. An improved spectral efficiency can stillbe achieved in IR-UWB and OFDM-UWB through generatingmonopulses with a narrower BW and reducing of the channelspacing, respectively.ACKNOWLEDGMENTThe authors would like to thank the E-Photon ONe+ NoE.REFERENCES[1] R. Kohno, “State of arts in ultra wideband (UWB) wireless technologyand global harmonization,” in Proc. 34th Eur. Microwave Conf., TheNetherlands, 2004, pp. 1093–1099.[2] C. Duan, G. Pekhteryev, J. Fang, Y. Nakache, J. Zhang, K. Tajima,Y. Nishioka, and H. Hirai, “Transmitting multiple HD video streamsover UWB links,” in Proc. CCNC’06, Las Vegas, NV, 2006, vol. 2, pp.691–695.[3] Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wide-band Transmission Systems FCC, Report FCC 02-48, 2002.[4] T. Lunttila, S. Iraji, and H. Berg, “Advanced coding schemes for amulti-band OFDM ultrawideband system towards 1 Gbps,” in Proc.CCNC’06, Las Vegas, NV, 2006, vol. 1, pp. 553–557.[5] Q. Zou, A. Tarighat, and A. H. Sayed, “Performance analysis of multi-band OFDM UWB communications with application to range improve-ment,” IEEE Trans. Veh. Technol., vol. 56, no. 6, pt. 2, pp. 3864–3878,Nov. 2007.[6] High Rate Ultra Wideband PHY and MAC Standard, ECMA Int. Stan-dard, ECMA-368, Dec. 2005.[7] Y. Shoji, C. Choi, S. Kato, I. Toyoda, K. Kawasaki, Y. Oishi, K. Taka-hashi, and H. Nakas, Re-Summarization of Merged Usage Model Def-initions Parameters IEEE doc. 802.15-06-0379-02-003c, 2006.[8] R. A. Shafik, M. S. Rahman, and A. H. M. R. Islam, “On the extendedrelationships among EVM, BER and SNR as performance metrics,” inProc. ICECE’06, Bangladesh, Dec. 2006, pp. 408–411.[9] H. Schmuck, “Comparison of optically millimeter-wave system con-cepts with regard to chromatic dispersion,” Electron. Lett., vol. 31, no.21, pp. 1848–1849, 1995.

Advanced coding schemes for a multi-band OFDM ultrawideband system towards 1 Gbps,” in

Comparison of optically millimeter-wave system concepts with regard to chromatic dispersion,”

On the extended relationships among EVM, BER and SNR as performance metrics,” in

Performance analysis of multiband OFDM UWB communications with application to range improvement,”

Re-Summarization of Merged Usage Model Definitions Parameters

Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission Systems FCC,

State of arts in ultra wideband (UWB) wireless technology and global harmonization,” in

Transmitting multiple HD video streams over UWB links,” in

Ultra-wideband radio signals distribution in FTTH networks

[EN] The use of an ultra-wideband (UWB) radio technique is proposed as a viable solution for the distribution of high-definition audio/video content in fiber-to-the-home (FTTH) networks. The approach suitability is demonstrated by the transmission of standards-based UWB signals at 1.25 Gb/s along different FTTH fiber links with 25 km up to 60 kin of standard single-mode fiber length in a laboratory experiment. Experimental results suggest that orthogonal frequency-division-multiplexed UWB signals exhibit better transmission performance in FFTH networks than impulse radio UWB signals.This work was supported in part by the FP6-IST-33615 UROOF Project. The work of T. Alves was supported by FCT from Portugal under Contract SFRH/BD/29871/2006. The work of M. Beltran was supported by Spain MEC Grant BES-2006-12066.Llorente, R.; Alves, T.; Morant, M.; Beltran, M.; Perez, J.; Cartaxo, A.; Martí Sendra, J. (2008). Ultra-Wideband Radio Signals Distribution in FTTH Networks. IEEE Photonics Technology Letters. 20(11):945-947. https://doi.org/10.1109/LPT.2008.922329945947201

Ultra-wideband radio signals distribution in FTTH networks

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