Showing papers on "Pulse-position modulation published in 2013"
TL;DR: Compared with OFDM, the CAP scheme shows competitive performance and provides an alternative spectrally efficient modulation for next generation optical wireless networks.
Abstract: We experimentally demonstrate a visible light communication (VLC) system based on a single commercially available RGB-type LED. High spectrally efficient carrierless amplitude and phase (CAP) modulation and orthogonal frequency-division multiplexing (OFDM) are adopted in the intensity-modulation and direct-detection VLC system of limited bandwidth. In order to achieve higher capacity of the uneven-frequency-response LED-based VLC system, OFDM signals are combined with the bit- and power-loading techniques, and CAP signals of various modulation are pre-emphasized to modulate one of the RGB chips. To reach the BER of less than 10-3, CAP and OFDM signals demonstrate the maximum data rates of 1.32 and 1.08 Gb/s, respectively, employing the blue chip. In addition to spectrally efficient formats, the wavelength-division-multiplexing (WDM) scheme is applied to further increase the capacity. After individually optimizing RGB chips, the maximum aggregate data rates of CAP and OFDM are 3.22 and 2.93 Gb/s, respectively, in our RGB-LED-based WDM VLC system. Hence, compared with OFDM, the CAP scheme shows competitive performance and provides an alternative spectrally efficient modulation for next generation optical wireless networks.
168 citations
TL;DR: In this paper, the Bussgang theorem is employed to characterize the impact of nonlinear distortions on normally distributed signals in an intensity modulation and direct detection optical wireless communication system based on orthogonal frequency division multiplexing.
Abstract: This paper presents a complete analytical framework for modeling memoryless nonlinear effects in an intensity modulation and direct detection optical wireless communication system based on orthogonal frequency division multiplexing. The theory employs the Bussgang theorem, which is widely accepted as a means to characterize the impact of nonlinear distortions on normally distributed signals. This paper proposes a new method to generalize this approach, and it describes how a closed-form analytical expression for the system bit error rate can be obtained for an arbitrary memoryless distortion. Major distortion effects at the transmitter stage such as quantization and nonlinearity from the light emitting diode are analyzed. Four known orthogonal-frequency-division-multiplexing-based modulation schemes for optical communication are considered in this paper: direct-current-biased optical OFDM, asymmetrically clipped optical OFDM, pulse-amplitude-modulated discrete multitone modulation, and unipolar orthogonal frequency division multiplexing.
164 citations
TL;DR: In this article, a high-dimensional quantum key distribution (QKD) protocol that employs temporal correlations of entangled photons is proposed, which relies on measurements by Alice and Bob in one of two conjugate bases, implemented using dispersive optics.
Abstract: We propose a high-dimensional quantum key distribution (QKD) protocol that employs temporal correlations of entangled photons. The security of the protocol relies on measurements by Alice and Bob in one of two conjugate bases, implemented using dispersive optics. We show that this dispersion-based approach is secure against collective attacks. The protocol, which represents a QKD analog of pulse position modulation, is compatible with standard fiber telecommunications channels and wavelength division multiplexers. We describe several physical implementations to enhance the transmission rate and describe a heralded qudit source that is easy to implement and enables secret-key generation at $g4$ bits per character of distilled key across over 200 km of fiber.
139 citations
TL;DR: The GSSK transmitter is much simpler than that of an equivalent regular pulse amplitude modulation (PAM) system with similar spectral efficiency and the receiver is based on the maximum likelihood criterion and using multiple photodetectors in the receiver improves the error performance.
Abstract: In this paper the error performance analysis of a low complexity, multiple transmitter generalised space shift keying (GSSK) signalling technique for short range indoor visible light communications is presented. In an N_t transmitter system, this signalling technique is capable of achieving a spectral efficiency of N_t bits/s/Hz. The GSSK system has a higher spectral efficiency than the conventional on-off keying (OOK) and pulse position modulation (PPM) techniques. The GSSK transmitter is much simpler than that of an equivalent regular pulse amplitude modulation (PAM) system with similar spectral efficiency. An analytical expression for the symbol error rate (SER) is presented and verified using simulations. The receiver is based on the maximum likelihood criterion and using multiple photodetectors (PDs) in the receiver improves the error performance. Within the room and the transmitter-receiver configuration under consideration, with four PDs, a gain of 6 dB is attainable over the single PD system for the case of 2 and 3 bits/s/Hz. Considering a fixed link range with N_t = 2 and at a symbol error rate of 10-6, using wide half angle LEDs with Φ1/2= 60° requires about 12 dB less in electrical signal-to-noise ratio compared with Φ1/2 = 30°. The beam directivity is however of much lower effect when the room under consideration is equiped with sufficient LEDs to provide full coverage. The GSSK technique can also support dimming control by using different pulse widths. This, however, is at a price of reduced spectral efficiency.
117 citations
TL;DR: A detailed investigation on the digital filters in CAP modulation system is presented and the feasibility of the CAP16 modulation for the short range transmission systems is demonstrated experimentally.
Abstract: Carrier-less amplitude and phase (CAP) modulation can be a good candidate for short range optical communications for considerable computational complexity reduction and simple system structure. In this paper, a detailed investigation on the digital filters in CAP modulation system is presented. An adaptive equalizer based on cascaded multi-modulus algorithm (CMMA) is used for the demodulation at the receiver. The impact of digital filter taps on system performance is investigated through comprehensive simulations and a 10 Gb/s CAP16 modulation system is demonstrated experimentally. The BER performance for different length of fiber link is measured. Compared with back-to-back (BTB) transmissions, 2 dB and 3.5 dB receiver power penalty are observed at BER of 10(-3) for 20 km and 40 km fiber link respectively. It clearly demonstrates the feasibility of the CAP16 modulation for the short range transmission systems.
91 citations
TL;DR: This paper showed that for similar SNR, L-PPM scheme offered improved performance, and their performance in terms of power and bandwidth efficiencies and the Bit Error Rate versus Signal-to-Noise Ratio (SNR) are compared analytically.
Abstract: As wireless communication systems become ever-more important and pervasive parts of our everyday life; system capacity and quality of service issues are becoming more critical. In order to increase the system capacity and improve the quality of service, it is necessary that we pay closer attention to bandwidth and power efficiency issues. In this paper, the bandwidth and power efficiency issues in Free Space Optics (FSO) transmissions are addressed under Pulse Position Modulation (L-PPM) and Pulse Amplitude Modulation (M-PAM) schemes, and their performance in terms of power and bandwidth efficiencies and the Bit Error Rate (BER) versus Signal-to-Noise Ratio (SNR) are compared analytically. The comparative study of the L-PPM and MPAM schemes is discussed, and showed that for similar SNR, L-PPM scheme offered improved performance. For FSO communication systems, although the power efficiency is inferior to L-PPM scheme, On-Off Keying (OOK) modulation scheme is more commonly used due to its efficient bandwidth usage, but M-PAM is the bandwidth efficient modulation scheme in this research for more than “2” bits of information can be sent, while L-PPM is the power efficient modulation scheme for more number of bits can be sent, and it may be able to improve performance by increasing the number of bits in L-PPM scheme. General Terms Optical Communications, Modulation schemes, Bit Error Rate (BER), Signal to Noise Ratio (SNR), Bandwidth Efficiency, Power Efficiency.
80 citations
TL;DR: The performance of pulse amplitude modulation, carrierless amplitude/phase modulation, and direct detection orthogonal frequency- division multiplexing for short reach optical communication systems is discussed and their possible use for future high-capacity short reach Optical Communication Systems is explored.
Abstract: The use of advanced modulation formats helps to reduce the number of components required for short reach optical communication modules at 100 Gb/s and beyond. Unlike long haul optical communication systems where externally modulated high order modulation formats with coherent detection receivers are used, direct modulated lasers with direct detection are likely to be employed for short reach system implementation. Here we discuss the performance of pulse amplitude modulation, carrierless amplitude/phase modulation, and direct detection orthogonal frequency- division multiplexing for short reach optical communication systems. Their possible use for future high-capacity short reach optical communication systems is explored.
74 citations
TL;DR: Higher-order modulation is being studied for future 100G, 400G, and faster client optics and greater sensitivity to link impairments require use of DSP algorithms implemented in advanced CMOS nodes to close the link budget.
Abstract: Higher-order modulation is being studied for future 100G, 400G, and faster client optics. Amplitude, phase, and multi-subcarrier modulation approaches, used separately and in combination with each other, are being considered. Increased penalties due to higher-order modulation greater sensitivity to link impairments require use of DSP algorithms implemented in advanced CMOS nodes to close the link budget. DSP also enables programmability to reconfigure the optics for different applications and link conditions.
72 citations
TL;DR: In this article, a multi-LED phase-shifted OOK (MP-OOK) modulation was proposed for parallel transmission of visible-light communication with DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM).
Abstract: The limited modulation bandwidth and the non-linearity nature of LEDs are the key challenges to visible light communication. In general, one LED lamp consists of multiple LED chips. In this letter, these LED chips are used for parallel transmission though multi-LED phase-shifted OOK (MP-OOK) modulation. For MP-OOK, the bandwidth efficiency is approximate N times that of conventional OOK ( N is the number of LED chips). For each branch, the modulation format is OOK. Hence, MP-OOK has a better anti-nonlinearity performance than other high-order modulation formats, such as DC-biased optical orthogonal frequency-division multiplexing (DCO-OFDM). The simulation comparisons between MP-OOK and DCO-OFDM verify these.
56 citations
09 Jun 2013
TL;DR: It is shown that a combined usage of multipath routing and flexible distance-adaptive modulation format assignment can reduce blocking ratio while consuming portions of spectrum comparable to single path routing.
Abstract: Elastic optical path networks have been proposed as a promising approach to flexibly use the optical spectrum (hence the name flexi-grid) thus overcoming the rigidness of traditional WDM networks where optical channel spacing is equidistant irrespectively of the type of signal transmitted. Past research effort in spectrum allocation focused on single transmission paths with a uniform modulation format in the network. However, by using optical OFDM technologies, the flexi-grid networks can benefit from multipath routing with parallel transmission that uses flexible modulation format assignment. In this paper, we propose novel multipath routing and spectrum assignment (RSA) algorithms with distance-adaptive modulation format assignment and analyze the effectiveness in dynamic traffic scenarios. We show that a combined usage of multipath routing and flexible distance-adaptive modulation format assignment can reduce blocking ratio while consuming portions of spectrum comparable to single path routing. Our results also show that a careful dimensioning of guard-band size is a critical factor, and that the full benefits of parallel transmission can be better achieved in networks requiring a small guard-band size.
56 citations
01 Dec 2013
TL;DR: The BER performance under BPSK modulation is better compared to OOK, RZ-OOK, PAM, 2-P PM, 4-PPM, DPSK, and QPSKModulation techniques, and for FSO communication systems, although the power efficiency is inferior to PPM.
Abstract: In this paper, we are interested in more efficient modulation techniques that achieve a good Bit Error Rate (BER) performance, bandwidth and power efficiencies for Free Space Optics (FSO) Communication Systems. The theoretical expressions of the BER versus the Signal-to-Noise Ratio (SNR), the bandwidth efficiency, and the normalized power requirements for NRZ-OOK, RZ-OOK, PPM, PAM, DPSK, BPSK, and QPSK modulation schemes for FSO communication systems are introduced, and a comparison between these modulation techniques is presented. The comparative study of the PPM and PAM schemes is also discussed and showed that for similar SNR, PPM offered improved BER performance. In addition, the BER performance under BPSK modulation is better compared to OOK, RZ-OOK, PAM, 2-PPM, 4-PPM, DPSK, and QPSK modulation techniques. And for FSO communication systems, although the power efficiency is inferior to PPM, OOK is more commonly used due to its efficient bandwidth usage, but PAM scheme is the bandwidth efficient modulation scheme in this research for more than two bits of information sent, while the PPM scheme is the power efficient modulation scheme for more than two bits of information sent.
01 Dec 2013
TL;DR: Numerical results show that for modest code rates in low signal-to-noise ratio regions, the normalized throughputs of FQAM basedCM systems are close to the theoretical channel capacity limit compared to that of QAM and FSK based CM systems.
Abstract: We analyze the performance of bit interleaved coded modulation (BICM) and coded modulation (CM) systems with frequency and quadrature amplitude modulation (FQAM), which is a combination of frequency shift keying (FSK) and quadrature amplitude modulation (QAM). Numerical results show that for modest code rates in low signal-to-noise ratio regions, the normalized throughputs of FQAM based CM systems are close to the theoretical channel capacity limit compared to that of QAM and FSK based CM systems. Also, we analyze the performance of downlink cellular LTE systems [10] using FQAM and compare it with that using QAM, especially for cell-edge users. Numerical results show that, unlike QAM, the statistical distribution of inter-cell interference (ICI) incurred with FQAM highly deviates from the Gaussian distribution and has a heavier tail. The results also show that due to the non-Gaussian nature of the ICI incurred with FQAM, the transmission rate of a cell-edge user using FQAM is significantly higher than that using QAM.
TL;DR: The proposed differential decoder enables the SIM DPSK scheme to outperform the non-coherent decoding based pulse position modulation scheme and theoretically analyze the bit error rate (BER) performance of the SIM differential binary phase shift keying modulation scheme with differential decoding over FSO MIMO links which follow the Gamma-Gamma distribution.
Abstract: In this paper, we derive a differential decoder for the subcarrier intensity modulation (SIM) based differential phase shift keying (DPSK) scheme in free space optical (FSO) multiple-input multiple-output (MIMO) communication system. The proposed differential decoder avoids requirement of the knowledge of irradiance fluctuations in the receiver contrary to the existing selection combining (SC) based decoder of SIM DPSK. Moreover, the proposed differential decoder enables the SIM DPSK scheme to outperform the non-coherent decoding based pulse position modulation scheme. We theoretically analyze the bit error rate (BER) performance of the SIM differential binary phase shift keying modulation scheme with differential decoding over FSO MIMO links which follow the Gamma-Gamma distribution. On the basis of the analytical BER, the analytical diversity order of the proposed differential decoder is obtained.
TL;DR: The experimental results show that using the modulation, the data rate of 120 Mbit/s with BER 1 × 10(-3) can be achieved with an optical blue filter and RC post-equalization.
Abstract: We propose and experimentally demonstrate a novel modulation scheme called superposed pulse amplitude modulation (SPAM) which is low-cost, insensitive to non-linearity of light emitting diode (LED). Multiple optical pulses transmit parallelly from different spatial position in the LED array and overlap linearly in free space to realize SPAM. With LED arrangement, the experimental results show that using the modulation we proposed the data rate of 120 Mbit/s with BER 1 × 10−3 can be achieved with an optical blue filter and RC post-equalization.
17 Mar 2013
TL;DR: The experimental transmission of 4-D coded modulation formats based on set-partitioning of two 16QAM 2-D constellations over long-haul distance and compared with PDM-16QAM is reported.
Abstract: We report the experimental transmission of 4-D coded modulation formats based on set-partitioning of two 16QAM 2-D constellations. Using Nyquist-pulse-shaping, 32SP-DP-16QAM and 128SP-DP-16QAM signals are transmitted over long-haul distance and compared with PDM-16QAM.
TL;DR: The transmitter, optical wireless channel, and receiver structure of VPPM were modeled mathematically, and their error performance for examining the communication performance according to dimming level and data rate was analyzed.
Abstract: Variable pulse position modulation (VPPM) is a new modulation scheme that supports simultaneously illumination with dimming control and communication. In this paper, the transmitter, optical wireless channel, and receiver structure of VPPM were modeled mathematically, and their error performance for examining the communication performance according to dimming level and data rate was analyzed. The results highlight the need for careful consideration of the tradeoff between the dimming flexibility and communication performance according to the channel condition in VPPM.
TL;DR: In this paper, the performance of a non-return-to-zero, pulse-amplitude modulation (PAM), and carrierless amplitude phase (CAP) modulation was tested under the different conditions, including various link lengths and fiber-coupled power.
Abstract: An experimental comparison of multilevel modulation schemes for polymer optical fiber (POF) transmission systems is shown in this letter. The performance of a non-return-to-zero, pulse-amplitude modulation (PAM), and carrierless amplitude phase (CAP) modulation was tested under the different conditions, including various link lengths and fiber-coupled power. As an optical transmitter, the commercial laser diode operating at 655 nm was used. A maximum bit rate of 5 Gb/s over 50-m 1-mm step-index POF link was achieved with 16-CAP modulation format at +6 dBm fiber-coupled power and a bit-error ratio of 10-3. Over 100 m, a maximum bit rate of 3.4 Gb/s was realized with 4-PAM.
TL;DR: In this paper, three carrier-based randomized pulse position modulation schemes are proposed for an indirect matrix converter (IMC), which, to date, have not been discussed in existing literatures.
Abstract: To attenuate the peaks of harmonics, three carrier-based randomized pulse position modulation schemes are proposed for an indirect matrix converter (IMC), which, to date, have not been discussed in existing literatures. In the first scheme, to avoid commutation of a rectifier stage at instants of carrier transition, one of four different pulse positions of the rectifier stage is selected randomly based on the Markov chain. The second scheme randomly places the center of the pulse position with a limited degree of freedom, which has a lower harmonic spectrum but higher commutation frequency. The maximum degree of freedom is achieved in the third scheme, which randomly varies the pulse position by delaying its edge along entire carrier cycle, resulting in a continuous and flat harmonic spectrum, but the maximum commutation frequency in three proposed schemes. An alternative carrier of an inverter stage is applied in all the schemes to maintain smooth operation at instants of carrier transition. Effectiveness of the proposed schemes is validated through experimental tests on an IMC prototype.
01 Dec 2013
TL;DR: It is shown that in a mobile scenario with variable receiving power, depending on the availability and strength of the LOS-path, optimization of both the symbol rate and the modulation format will be the key parameters enabling efficient and reliable highspeed transmission using block-based PAM-FDE.
Abstract: In this paper, we analyze block-based pulse amplitude modulation with frequency domain equalization (block-based PAM-FDE) for visible light communications (VLC) in realistic application scenarios. Typical effects of the VLC-channel, such as different frequency responses of the LED together with the wireless optical propagation channel are included. We consider a measured LED response from our experimental system reaching a noticeable extended 3 dB cutoff freqeuncy of 60 MHz. Further simulations are then based on a 60 MHz low-pass approximation. To consider multipath propagation, two common models for diffuse and non-directed line-of-sight (LOS) conditions are used. We illustrate the influence of the transmitter and propagation characteristics and observe in general significant gains by using a higher system bandwidth while the modulation order is increased only if the received power is very high. We show that in a mobile scenario with variable receiving power, depending on the availability and strength of the LOS-path, optimization of both the symbol rate and the modulation format will be the key parameters enabling efficient and reliable highspeed transmission using block-based PAM-FDE.
28 Oct 2013
TL;DR: In this paper, several 8-dimensional modulation formats for coherent fiber-optic communications were proposed for spectral efficiencies of 1.75 and 2 b/s/Hz/pol/pol.
Abstract: We propose several 8-dimensional modulation formats for coherent fiber-optic communications. For spectral efficiencies of 1.75 and 2 b/s/Hz/pol, the proposed modulations offer up to 1 dB gain over DP-QPSK.
TL;DR: In this paper, a hybrid binary phase shift keying-modified multi-pulse pulse position modulation (hybrid BPSK-modified MPPM) scheme is proposed as a new modulation technique to improve the performance of both conventional binary phase-shift keying (BPSK) and MPPM in optical fiber communications systems.
Abstract: A hybrid binary phase shift keying-modified multi-pulse pulse position modulation (hybrid BPSK-modified MPPM) scheme is proposed as a new modulation technique to improve the performance of both conventional binary phase shift keying (BPSK) and multi-pulse pulse position modulation (MPPM) techniques in optical fiber communications systems. In conventional BPSK scheme, a consecutive stream of low power BPSK symbols are transmitted. However, in the proposed scheme, a less number of high power BPSK symbols are transmitted in a hybrid frame and their positions are exploited to transmit more bits. That is, the transmitted information is carried in both the positions and phases of the transmitted pulses. The transmission characteristics, transmitter and receiver block diagram, bandwidth-utilization, and optimum decoding process for the proposed scheme are all studied in this paper. Several performance measures are also derived and compared to those of conventional schemes in optical fiber channels. Our results reveal that, under an average power constraint, the proposed hybrid BPSK-modified MPPM scheme achieves much lower levels of bit-error rates and symbol-error rates than those of ordinary BPSK and ordinary MPPM schemes, respectively, for both moderate or high signal-to-noise ratios. In addition, the proposed modulation scheme achieves much higher bandwidth-utilization efficiencies than those of ordinary schemes.
TL;DR: Four Q-ary intensity modulation schemes satisfying high-order intensity modulation condition are proposed and can be used with shift-OSTBC to mitigate inter-symbol interference (ISI) and provide diversity gain in asynchronous FSO MIMO channels.
Abstract: Recently, Simon-Vilnrotter and Premaratne-Zheng modified the binary pulse-position modulation (PPM) to support free-space optical (FSO) multi-input multi-output (MIMO) systems with orthogonal space-time block coding (OSTBC) that requires the use of negative symbols. In this paper, we extend the investigation to optical OSTBC schemes with high-order intensity modulation. A necessary and sufficient condition for the high-order intensity modulation to maintain the orthogonality of the applied OSTBC is derived, and four Q-ary intensity modulation schemes satisfying this condition are proposed. In asynchronous FSO MIMO channels in which the signals from different transmitters arrive at the receiver with timing misalignment, the proposed modulation schemes can be used with shift-OSTBC to mitigate inter-symbol interference (ISI) and provide diversity gain.
TL;DR: This paper proposes a coding theoretic variation of PPM that allows for significantly more efficient symbol and frame synchronization as well as strong error correction, and develops a generalization of expurgated PPM suited for the modulation layer of the proposed self-synchronizing modulation scheme.
Abstract: Pulse position modulation (PPM) is a popular signal modulation technique which converts signals into M-ary data by means of the position of a pulse within a time interval. While PPM and its variations have great advantages in many contexts, this type of modulation is vulnerable to loss of synchronization, potentially causing a severe error floor or throughput penalty even when little or no noise is assumed. Another disadvantage is that this type of modulation typically offers no error correction mechanism on its own, making them sensitive to intersymbol interference and environmental noise. In this paper, we propose a coding theoretic variation of PPM that allows for significantly more efficient symbol and frame synchronization as well as strong error correction. The proposed scheme can be divided into a synchronization layer and a modulation layer. This makes our technique compatible with major existing techniques such as standard PPM, multipulse PPM, and expurgated PPM as well in that the scheme can be realized by adding a simple synchronization layer to one of these standard techniques. We also develop a generalization of expurgated PPM suited for the modulation layer of the proposed self-synchronizing modulation scheme. This generalized PPM can also be used as stand-alone error-correcting PPM with a larger number of available symbols.
TL;DR: The proposed Magnitude-Keyed Modulation (MKM) modulation provides SC-OFDM system immunity to ICI and with an easy implementation it significantly outperforms OFDM, SC- OFDM and MC-CDMA systems with Phase Shift Keying (PSK) modulation and Quadrature Amplitude Modulations (QAM) in severe ICI environment.
Abstract: Orthogonal Frequency Division Multiplexing (OFDM) has been considered as a strong candidate for next generation wireless communication systems. Compared to traditional OFDM, Single Carrier OFDM (SC-OFDM) has demonstrated excellent bit error rate (BER) performance, as well as low peak to average power ratio (PAPR). Similar to other multi-carrier transmission technologies, SC-OFDM suffers significant performance degradation resulting from intercarrier interference (ICI) in high mobility environments. Existing techniques for OFDM can be directly adopted in SC-OFDM to improve performance, however, this improved performance comes at costs such as decreased throughput. In this paper, we analyze the effect of ICI on an SC-OFDM system and propose a novel modulation scheme. The proposed Magnitude-Keyed Modulation (MKM) modulation provides SC-OFDM system immunity to ICI and with an easy implementation it significantly outperforms OFDM, SC-OFDM and MC-CDMA systems with Phase Shift Keying (PSK) modulation and Quadrature Amplitude Modulation (QAM) in severe ICI environment. Analysis also illustrates the proposed SC-OFDM system with MKM modulation maintains low PAPR compared to traditional OFDM and SC-OFDM systems with PSK and QAM modulations. Simulation results for different modulation schemes in various ICI environments confirm the effectiveness of the proposed system.
TL;DR: A low complexity elastic wave signaling and reception method to achieve high data rate communication on dispersive solid elastic media, such as metal pipes, using piezoelectric transducers of PZT (lead zirconate titanate).
Abstract: In this paper, we present and demonstrate a low complexity elastic wave signaling and reception method to achieve high data rate communication on dispersive solid elastic media, such as metal pipes, using piezoelectric transducers of PZT (lead zirconate titanate). Data communication is realized using pulse position modulation (PPM) as the signaling method and the elastic medium as the communication channel. The communication system first transmits a small number of training pulses to probe the dispersive medium. The time-reversed probe signals are then utilized as the information carrying waveforms. Rapid timing acquisition of transmitted waveforms for demodulation over elastic medium is made possible by exploring the reciprocity property of guided elastic waves. The experimental tests were conducted using a National Instrument PXI system for waveform excitation and data acquisition. Data telemetry bit rates of 10 kbps, 20 kbps, 50 kbps and 100 kbps with the average bit error rates of 0, 5.75 × 10(-4), 1.09 × 10(-2) and 5.01 × 10(-2), respectively, out of a total of 40, 000 transmitted bits were obtained when transmitting at the center frequency of 250 kHz and a 500 kHz bandwidth on steel pipe specimens. To emphasize the influence of time reversal, no complex processing techniques, such as adaptive channel equalization or error correction coding, were employed.
TL;DR: Variable-rate multi-pulse-position-modulation (VR-MPPM) is proposed, for LED based visible light communication system, to achieve joint brightness control and data transmission and eradicates the need for either pulse width modulation or pulse amplitude modulation and still achieves the brightness control.
Abstract: LED based lighting systems provide an opportunity for data transmission in addition to their traditional use as source of illumination. Brightness control is required to achieve either desired level of illumination or to achieve energy conservation. Conventionally, simultaneous data transmission as well as brightness control is achieved using two different modulation schemes. Either pulse width modulation or pulse amplitude modulation is used for brightness control and some variants of pulse position modulation are employed for data transmission. The need for two different modulation schemes, to meet the dual objective, makes the system design complex. In this paper we propose variable-rate multi-pulse-position-modulation (VR-MPPM), for LED based visible light communication system, to achieve joint brightness control and data transmission. The proposed approach eradicates the need for either pulse width modulation or pulse amplitude modulation and still achieves the brightness control. Encoder and decoder algorithms for VR-MPPM realization are developed and are implemented on the hardware testbed. Experimental results revealing the effect of brightness level variation on symbol error rate are also provided. Existence of an underlying trade-off between achievable resolution for brightness control and the corresponding successful data transmission rate is recognized. To exploit this trade-off, an optimization problem is formulated.
01 Dec 2013
TL;DR: This paper investigates the use of multiple LEDs to perform a space-time block coding using optical MIMO techniques, jointly with Pulse Position Modulation, to achieve data rates of the order of hundreds of Mb/s in indoor VLC systems, with no reduction of link reliability.
Abstract: Visible light communication is a new frontier of communication allowing high data-rate Internet access specially in indoor environment. One of the key challenges is the limited modulation bandwidth of sources, that is typically around several MHz. As a room or coverage space would typically be illuminated by an array of Light Emitting Diode devices, there exists the potential for parallel data transmission. In this paper we investigate the use of multiple LEDs to perform a space-time block coding. By exploiting optical MIMO techniques, jointly with Pulse Position Modulation, we can achieve data rates of the order of hundreds of Mb/s (i.e., around 600 Mb/s) in indoor VLC systems, with no reduction of link reliability. Finally, the proposed approach has been compared to similar techniques, highlighting its effectiveness and robustness.
TL;DR: This paper presents an experimental demonstration of a visible light communications link with an light emitting diode and a low-bandwidth organic photodetector as transmitter and receiver that achieves sub 4 Mbits/s speeds.
Abstract: This paper presents an experimental demonstration of a visible light communications link with an light emitting diode and a low-bandwidth organic photodetector as transmitter and receiver, respectively, that achieves sub 4 Mbits/s speeds. An artificial neural network (ANN) equalizer is required in order to achieve such high data rates because of the influence of intersymbol interference. The digital modulation formats tested in this paper are nonreturn-to-zero on–off keying (OOK), and fourth-order pulse position modulation (4-PPM). Without equalization, data rates of 200 and 300 kbits/s can be achieved for 4-PPM and OOK, respectively. With ANN equalization, data rates of 2.8 and 3.75 Mbits/s can be achieved for the first time for OOK and 4-PPM, respectively.
12 May 2013
TL;DR: Simulation results show that single carrier modes in most cases outperforms OFDM modes in LOS and NLOS scenarios, and BPSK and QPSK modulation schemes with low density parity coding are relatively more robust, and present a good choice at the cost of data rate reduction.
Abstract: IEEE 802.11ad is the new Wi-Fi standard operating at 60 GHz. This paper investigate the performance of specified modulation and coding schemes in additive white Gaussian noise channel and realistic 60 GHz band multipath fading channel. Three 802.11 ad physical layers, namely orthogonal frequency division multiplex physical layer, Single Carrier and Low Power Single carrier physical layer, are designed and evaluated in terms of bit error rate and packet error rate performances. Simulation results show that single carrier modes in most cases outperforms OFDM modes in LOS and NLOS scenarios. QAM based modulation schemes are sensitive to marginal channel conditions and provide poor performance in NLOS case, while BPSK and QPSK modulation schemes with low density parity coding are relatively more robust, and present a good choice at the cost of data rate reduction.
TL;DR: This work analyzes the bit error performance of the proposed energy detectors for two scenarios of the propagation channel: when the channel is deterministic, and when it is Gaussian distributed.
Abstract: Compressive sampling (CS) based energy detectors are developed for ultra-wideband (UWB) pulse position modulation (PPM), in multipath fading environments so as to reduce the sampling complexity at the receiver side. Due to sub-Nyquist rate sampling, the CS process outputs a compressed version of the received signal such that the original signal can be recovered from this low dimensional representation. Using the principles of generalized maximum likelihood (GML), we propose two types of energy detectors for such signals. The first type of detectors involves the reconstruction of the received signal followed by a detection stage. Statistical properties of the reconstruction error have been used for the realization of such kind of detectors. The second type of detectors does not rely on reconstruction and carries out the detection operation directly on the compressed signal, thereby offering a further reduction in the implementation complexity. The performance of the proposed detectors is independent of the spreading factor. We analyze the bit error performance of the proposed energy detectors for two scenarios of the propagation channel: when the channel is deterministic, and when it is Gaussian distributed. We provide exact bit error probability (BEP) expressions of the CS based energy detectors for each scenario of the channel. The BEP expressions obtained for the detectors working on the compressed signal directly can naturally be extended to BEP expressions for the related energy detectors working on the Nyquist-rate sampled signal. Simulation results validate the accuracy of these BEP expressions.