Caballero Jambrina, Antonio

Jensen, Jesper Bevensee

Rodes, Roberto

Tafur Monroy, Idelfonso

We propose and experimentally demonstrate a high speed impulse radio ultra wide-band (IR-UWB) wireless link for in-home network signal distribution. The IR-UWB pulse is distributed over a multimode fiber to the transmitter antenna. Wireless transmitted bit-rates of 1 Gbps at 2 m and 2 Gbps at 1.5 m have successfully been demonstrated, with a simple envelope detection scheme. This system is remarkably simple and robust; this makes it very attractive for low-cost applications in short range high-speed wireless links with low radiated power

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Downloaded from orbit.dtu.dk on: Dec 17, 2017Impulse radio ultra wide-band over multi-mode fiber for in-home signal distributionCaballero Jambrina, Antonio; Rodes, Roberto; Jensen, Jesper Bevensee; Tafur Monroy, IdelfonsoPublished in:International Topical Meeting on Microwave Photonics, 2009. MWP '09Publication date:2009Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Caballero Jambrina, A., Rodes, R., Jensen, J. B., & Tafur Monroy, I. (2009). Impulse radio ultra wide-band overmulti-mode fiber for in-home signal distribution. In International Topical Meeting on Microwave Photonics, 2009.MWP '09 (pp. 1-2). IEEE.Impulse Radio Ultra Wide-Band over Multi-Mode Fiber for In-Home Signal Distribution   Antonio Caballero, Roberto Rodés, Jesper B. Jensen, Idelfonso Tafur Monroy DTU Fotonik, Department of Photonics Engineering  Technical University of Denmark  Kgs. Lyngby, Denmark acaj@fotonik.dtu.dk   Abstract— We propose and experimentally demonstrate a high speed impulse radio ultra wide-band (IR-UWB) wireless link for in-home network signal distribution. The IR-UWB pulse is distributed over a multimode fiber to the transmitter antenna. Wireless transmitted bit-rates of 1 Gbps at 2 m and 2 Gbps at 1.5 m have successfully been demonstrated, with a simple envelope detection scheme. This system is remarkably simple and robust; this makes it very attractive for low-cost applications in short range high-speed wireless links with low radiated power. I. INTRODUCTION Wireless communication using ultra wide-band (UWB) modulation formats is a promising technology for delivering high data rates with low power emission [1]. This feature allows its coexistence with other radio signals working in the same frequency region. As stated in the requirements of the Federal Communication Commission (FCC) for UWB transmission [2], the Effective Isotropic Radiated Power (EIRP) has to be below -41.3 dBm/MHz in the band from 3.1 to 10.6 GHz, which limits the transmission to a few meters. The two common approaches for generating UWB are orthogonal frequency division multiplexing (OFDM) and impulse radio (IR) based on nth order Gaussian pulse generation. The latter method has the advantage of simplicity in generation and detection. The frequency range used for UWB transmission allows the use of small antennas, which increases the flexibility in system design, in terms of equipment selection and placement options; therefore the IR generator can be set in the home gateway. As a transmission medium, optical fiber offers a great advantage over copper cable, due to low losses and high bandwidth, and is a natural choice for extending the distance between signal generation point and the wireless antenna node. Cost is also an issue for in-home optical signal distribution, but this may be decreased using low-cost optical equipment, such as vertical cavity surface emitting LED (VCSEL) sources and multimode fibers (MMF) [3].  We present a solution for IR-UWB distribution for broadband (~Gigabit/s) in-home data networks, in which the pulse generator implements a part of the home gateway, and broadcasts a stream of data pulses to wireless access points via a multimode optical access infrastructure. Our implementation achieves significant simplification in wireless transceiver node hardware, and provides a level of ‘future-proofing’ of the network for supporting next-generation wireless networking protocols. After the fiber transmission, only filtering and amplification is needed for FCC-mask compliance. This scheme also avoids the limitations of copper cables for long-distance high-frequency links. II. UWB SIGNAL GENERATION AND DEMODULATION To fit the frequency spectrum of a pulse into the FCC requirements of bandwidth different order Gaussian pulses are generally used. The 5th derivative of the Gaussian pulse has been demonstrated [4] to be the optimal in fitting the mask. Moreover it concentrates the energy in the lower part of the spectrum, which is less affected by the high-frequency attenuation during air-transmission. The pulse can be written as:  ⎟⎟⎠⎞⎜⎜⎝⎛−⎟⎟⎠⎞⎜⎜⎝⎛−+−= 227931152exp2152102)(σσπσπσπttttAty  (1) where A is the amplitude and σ represents the standard deviation of the pulse, which is chosen to better place the spectrum peak of the signal. In this paper σ=55 ps is set for both bitrates. In the design of the pulse shape, it is also necessary to take into account the frequency response of the transmit antenna, as FCC mask refers to EIRP [5]. In our experiment an omnidireccional UWB antenna is used and included in the modified mask. To fully accommodate the spectrum to the requirements, high pass filtering at 3.1 GHz is needed to avoid exceeding the mask in the band from 960 MHz to 1.61 GHz. Figure 1 shows the FCC mask, the modified mask and the spectra of the 1 Gbps and 2 Gbps signals. As specified in the FCC regulation, the peaks due to Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on August 03,2010 at 07:58:06 UTC from IEEE Xplore.  Restrictions apply. 0 2 4 6 8 10 12-80-70-60-50-40-30-20  Power [dBm/MHz]Frequency [GHz] FCC mask Modified mask 1 Gbps signal 0 2 4 6 8 10 12-80-70-60-50-40-30-20Power [dBm/MHz]Frequency [GHz] FCC mask Modified mask 2 Gbps signal Figure 1. Spectra of transmitted 1Gbps and 2 Gbps signals before transmission. Compliance with FCC regulation is clearly seen. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.15-0.10-0.050.000.050.100.15Amplitude [V]0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.15-0.10-0.050.000.050.100.150.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.03-0.02-0.010.000.010.020.03Amplitude [V]0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.03-0.02-0.010.000.010.020.030.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.03-0.02-0.010.000.010.020.03Amplitude [V]Time [ns]0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.03-0.02-0.010.000.010.020.031 GbpsTime [ns]2 Gbps Figure 3. Examples of 1 Gbps (left) and 2 Gbps (right) pulses transmitted from AWG (upper) and its distortion due to air link (middle) and  100 m fiber plus air link (bottom)  Figure 2. Experimental setup the pattern speed should not be considered in the EIRP. The pulses are generated using a high speed Arbitrary Waveform Generator (AWG) at 24 Gsamples/s. Envelope detection is used to demodulate the received signal. The signal processing is done offline. The signal is squared and low-pass filtered. Fixed decision point and threshold is used to simplify the receiver. However, due to changes of power because of Inter-Symbol-Interference (ISI), variable threshold should improve the performance, especially for higher bitrates, where the tails from consecutive pulses add up. III. SETUP DESCRIPTION The setup description is shown in figure 2. The signal generated by the AWG, on-off keying with a PRBS length of 27-1, directly drives the 850 nm VCSEL in balance mode with a Vpp of 0.35 V. The VCSEL, designed for 10 Gbps data communications gives the best response in terms of bandwidth with balance direct modulation. The bias current offset is set to 9 mA to operate in the linear zone of the VCSEL. The output optical power is -2 dBm. The fiber used is 100 m of standard 50/125 μm silica Multi-Mode Fiber (MMF), with 2 dB of losses. On the receiver side, after the photodiode a wide-band amplifier and high-pass filter are used to better accommodate the signal to the transmission mask before driving the antenna. On the receiver side, a 10 dBi gain bowtie phased-array antenna is used to obtain higher gain in the reception. After that a 3.1 GHz high-pass pre-filter removes the noise accumulated from air transmission and interferences. A low noise amplifier (28 dB gain and Noise Figure of 3 dB) is needed to raise the signal voltage to be saved in the sampling oscilloscope at 40 Gsamples/s. IV. RESULTS To evaluate the capacity of the link, the air link was set to obtain the best performance for 1 and 2 Gbps. The maximum distance achievable was 2 m line of sight, due to lab limited space. The system performance has been evaluated for the link with direct modulation of the AWG to the antenna, and after 100 m of MMF transmission. In both cases the spectra before the antenna have been measured to ensure they are inside the mask. For 2 Gbps the signal gets distorted after 2 m of wireless transmission, giving a BER of 7·10-3 with the optical link. Therefore, the length was decreased to 1.5 meters.  The evolution of the pulses is shown in figure 3. The transmitted pulse is a clear 5th order Gaussian pulse with four oscillations. Due to air transmission and overall non-linearities of the system the pulse gets distorted but can be clearly detected. For the optical plus wireless link the presence of the pulse is still recognizable.   Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on August 03,2010 at 07:58:06 UTC from IEEE Xplore.  Restrictions apply. Figure 4. Eye diagram evolution for 1 Gbps at 2 m (left) and 2 Gbps at 1.5 m (rigth) of electrical, optical back-to-back and 100 m MMF transmission Figure 4 shows the evolution of the eye diagram for both bitrates. The eye distortion is greater for 2 Gbps, mainly caused by ISI. However, the signal can still be demodulated, obtaining 2·10-4 of BER after fiber transmission, which is below forward error correction limit. For 1 Gbps, no errors were detected in the demodulated 5·105 bits. The eye looks open and the transitions between bits are clear. The major penalty for the link is the distortion due to the optical conversion but the fiber link does not affect in excess. V. CONCLUSSION We have successfully demonstrated the use of UWB impulse radio transmission for high bitrates over short distances and its application for an in-home scenario. Signals at 1 Gbps (up to 2 m) and 2 Gbps (up to 1.5 m) were successfully demodulated. To the best of our knowledge, these results define new records in bitrate-length product for UWB signaling over multimode fiber (2 Gbps·m and 3 Gbps·m). A simple demodulation method was used, decreasing the receiver complexity. The centralization of the pulse generation also reduces the requirements of the transmitting antenna node equipment, and therefore relaxes its location requirements. ACKNOWLEDGMENT The authors would like to thank Tektronix and Mr. Thomas Jul of Nortelco Electronics Denmark for allowing us to use the AWG700B for this experiment. We also thank the European Commission for funding through Project INFSO-ICT-212 352 Architectures for Flexible Photonics Home and Access networks (ALPHA). REFERENCES [1] D. Porcino and W. Hirt, “Ultra-wideband radio technology: Potential and challenges ahead” IEEE Commun. Mag., vol. 41, no. 7, pp. 66–74, July 2003. [2] Federal Communications Commission, “Revision of Part 15 of the Commission’s Rules regarding Ultra-Wideband Transmission Systems”, February 2002. [3] C. M. Tan, L. C. Ong, M. L. Yee, B. Luo, P. K. Tang, “Transmission of ultra wide band radio using multimode radio-over-fiber system” Asia-Pacific Conference Proceedings, APMC 2005, vol 2, pp. 4-7, December 2005  [4] Hongsan Sheng, “On the spectral and power requirements for Ultra-Wideband Transmission” IEEE Int. Conference on Communications, ICC '03, vol. 1, pp 738–742, May 2003. [5] M. Abtahi, M. Mirshafiei, S. LaRochelle, L.A. Rusch, “All-optical 500 Mb/s UWB Transceiver:an experimental demonstration” IEEE J. Lightwave Tech., vol. 26, n. 15, pp 2795–2802, August 2008.  Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on August 03,2010 at 07:58:06 UTC from IEEE Xplore.  Restrictions apply. 

Impulse radio ultra wide-band over multi-mode fiber for in-home signal distribution

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Impulse radio ultra wide-band over multi-mode fiber for in-home signal distribution

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