Showing papers on "Phase-shift keying published in 2005"
10 Jan 2005
TL;DR: Differential-phase-shift keying has recently been used to reach record distances in long-haul lightwave communication systems and theoretical as well as implementation aspects of DPSK are reviewed.
Abstract: Differential-phase-shift keying (DPSK) has recently been used to reach record distances in long-haul lightwave communication systems. This paper will review theoretical, as well as implementation, aspects of DPSK, and discuss experimental results.
949 citations
18 Sep 2005
TL;DR: The micro-modem is a compact, low-power, underwater acoustic communications and navigation subsystem which has the capability to perform low-rate frequency-hopping frequency-shift keying, variable rate phase-coherent keying and two different types of long base line navigation, narrow-band and broadband.
Abstract: The micro-modem is a compact, low-power, underwater acoustic communications and navigation subsystem. It has the capability to perform low-rate frequency-hopping frequency-shift keying (FH-FSK), variable rate phase-coherent keying (PSK), and two different types of long base line navigation, narrow-band and broadband. The system can be configured to transmit in four different bands from 3 to 30 kHz, with a larger board required for the lowest frequency. The user interface is based on the NMEA standard, which is a serial port specification. The modem also includes a simple built-in networking capability which supports up to 16 units in a polled or random-access mode and has an acknowledgement capability which supports guaranteed delivery transactions. The paper contains a detailed system description and results from several tests are also presented
548 citations
TL;DR: It is shown that the TAS/MRC scheme outperforms some more complex space-time codes of the same spectral efficiency and channel estimation errors based on pilot symbols have no impact on the diversity order over quasi-static fading channels.
Abstract: In this paper, we investigate a multiple-input-multiple-output (MIMO) scheme combining transmit antenna selection and receiver maximal-ratio combining (the TAS/MRC scheme). In this scheme, a single transmit antenna, which maximizes the total received signal power at the receiver, is selected for uncoded transmission. The closed-form outage probability of the system with transmit antenna selection is presented. The bit error rate (BER) of the TAS/MRC scheme is derived for binary phase-shift keying (BPSK) in flat Rayleigh fading channels. The BER analysis demonstrates that the TAS/MRC scheme can achieve a full diversity order at high signal-to-noise ratios (SNRs), as if all the transmit antennas were used. The average SNR gain of the TAS/MRC is quantified and compared with those of uncoded receiver MRC and space-time block codes (STBCs). The analytical results are verified by simulation. It is shown that the TAS/MRC scheme outperforms some more complex space-time codes of the same spectral efficiency. The cost of the improved performance is a low-rate feedback channel. We also show that channel estimation errors based on pilot symbols have no impact on the diversity order over quasi-static fading channels.
415 citations
TL;DR: The proposed MDC-QO-STBC has several desirable properties, such as a more even power distribution among antennas and better scalability in adjusting the number of transmit antennas, compared with the coordinate interleaved orthogonal design (CIOD) and asymmetric CIOD (ACIOD) codes.
Abstract: In this paper, we consider a quasi-orthogonal (QO) space-time block code (STBC) with minimum decoding complexity (MDC-QO-STBC). We formulate its algebraic structure and propose a systematic method for its construction. We show that a maximum-likelihood (ML) decoder for this MDC-QO-STBC, for any number of transmit antennas, only requires the joint detection of two real symbols. Assuming the use of a square or rectangular quadratic-amplitude modulation (QAM) or multiple phase-shift keying (MPSK) modulation for this MDC-QO-STBC, we also obtain the optimum constellation rotation angle, in order to achieve full diversity and optimum coding gain. We show that the maximum achievable code rate of these MDC-QO-STBC is 1 for three and four antennas and 3/4 for five to eight antennas. We also show that the proposed MDC-QO-STBC has several desirable properties, such as a more even power distribution among antennas and better scalability in adjusting the number of transmit antennas, compared with the coordinate interleaved orthogonal design (CIOD) and asymmetric CIOD (ACIOD) codes. For the case of an odd number of transmit antennas, MDC-QO-STBC also has better decoding performance than CIOD.
252 citations
TL;DR: Analysis will be performed to show the tradeoff between bit rate of the data in secondary constellation and the penalty to the performance of receiving the basic constellation.
Abstract: A hierarchical modulation scheme is proposed to upgrade an existing digital broadcast system, such as satellite TV, or satellite radio, by adding more data in its transmission. The hierarchical modulation consists of a basic constellation, which is the same as in the original system, and a secondary constellation, which carries the additional data for the upgraded system. The upgraded system with the hierarchical modulation is backward compatible in the sense that receivers that have been deployed in the original system can continue receiving data in the basic constellation. New receivers can be designed to receive data carried in the secondary constellation, as well as those in the basic constellation. Analysis will be performed to show the tradeoff between bit rate of the data in secondary constellation and the penalty to the performance of receiving the basic constellation.
248 citations
TL;DR: This synchronous quadrature-phase-shift keying (QPSK) receiver concept allows us to process signals in parallel after electronic demultiplexing.
Abstract: This synchronous quadrature-phase-shift keying (QPSK) receiver concept allows us to process signals in parallel after electronic demultiplexing. An automatic electronic polarization control with a control time constant in the low microsecond range is provided. It is followed by a phase-locked loop free carrier recovery. An intermediate frequency linewidth tolerance of up to 10/sup -3/ times the QPSK symbol rate is expected. Commercially available distributed feedback lasers shall, therefore, suffice.
203 citations
TL;DR: A fully integrated binary phase-shift keying (BPSK) demodulator, which is based on a hard-limited COSTAS loop topology, dedicated to such implantable medical devices, which may improve the controllability and observability of the overall implanted system.
Abstract: During the past decades, research has progressed on the biomedical implantable electronic devices that require power and data communication through wireless inductive links. In this paper, we present a fully integrated binary phase-shift keying (BPSK) demodulator, which is based on a hard-limited COSTAS loop topology, dedicated to such implantable medical devices. The experimental results of the proposed demodulator show a data transmission rate of 1.12 Mbps, less than 0.7 mW consumption under a supply voltage of 1.8 V, and silicon area of 0.2 mm/sup 2/ in the Taiwan Semiconductor Manufacturing Company (TSMC) CMOS 0.18-/spl mu/m technology. The transmitter satisfies the requirement of applications relative to high forward-transferring data rate, such as cortical stimulation. Moreover, the employment of BPSK demodulation along with a passive modulation method allows full-duplex data communication between an external controller and the implantable device, which may improve the controllability and observability of the overall implanted system.
182 citations
TL;DR: In this paper, a feed forward carrier recovery scheme based on regenerative intradyne frequency dividers was proposed for synchronous optical quadrature phase-shift keying (QPSK)/BPSK transmission.
Abstract: Quadrature phase-shift keying (QPSK) is attractive to increase transmission lengths and capacity, especially when it is combined with polarization division multiplex. Baseband processing at the symbol rate allows to keep the required electronic bandwidth low. So far, external cavity lasers seemed to be indispensable for such transmission systems due to linewidth requirements. We propose a feedforward carrier recovery scheme based on regenerative intradyne frequency dividers, i.e., the well-known regenerative frequency divider is extended to process baseband in-phase and quadrature (I and Q) signals. An IF linewidth tolerance of up to 0.001 times the QPSK symbol rate is predicted, 2 decades more than for an optical phase locked loop with a realistic loop delay. This means that commercially available DFB lasers shall suffice for synchronous optical QPSK/BPSK transmission.
177 citations
TL;DR: In this article, a time-reversal communication system is proposed to improve data telemetry in the ocean by taking advantage of the focal properties of time reversal, which mitigates channel fading, reduces the dispersion caused by the channel, and increases the signal strength.
Abstract: This paper contains theoretical and experimental results on the application of the time-reversal process to acoustic communications in order to improve data telemetry in the ocean. A coherent underwater acoustic communication system must deal with the inter-symbol interference caused by the time-varying, dispersive, shallow-water ocean environment. An approach is demonstrated that takes advantage of the focal properties of time reversal. The spatial and temporal compression available at the time-reversal focus mitigates channel fading, reduces the dispersion caused by the channel, and increases the signal strength. Thus, a time-reversal communication system does not require spatial diversity at the receiver, i.e., an array of receiving sensors, but takes advantage of spatial diversity at the transmitter. The time-reversal communications system concept is demonstrated using experimental data collected in shallow water. Data telemetry bit rates of 500 bps (BPSK) and 1000 bps (QPSK) with bit error rates of 0 out of 4976 bits and 254 out of 9953 bits, respectively, were obtained when transmitting to a receiver at a distance of 10 km, with a carrier frequency of 3500 Hz, and a 500 Hz bandwidth. In a shallow-water upslope region, bit error rates of 15 out of 4976 bits and 14 out of 4976 bits were achieved over the same distance. In neither case was complex processing at the receiver used (i.e., channel equalization, error correction coding). Time-reversal transmissions are intercompared with single source and broadside transmissions and shown to have superior results in both range independent and dependent bathymetries. The time-reversal performance appears limited by self-generated inter-symbol interference. In addition, an initial look at the application of a single channel adaptive channel equalizer to received time-reversal communication sequences is presented. The same properties that are beneficial to a single channel receiver are also beneficial to adaptive channel equalization. A single channel RLS DFE equalizer is cascaded with the received time-reversal sequences and shown to further reduce scatter in the I/Q plane. The bit error rate decreased in all but one of the cases
165 citations
TL;DR: Simulation results show that by using the proposed likelihood function generation scheme for soft-decision Turbo decoding following QRM-MLD in 4-by-4 MIMO multiplexing, the required average received signal energy per bit-to-noise power spectrum density ratio is significantly reduced.
Abstract: This paper proposes likelihood function generation of complexity-reduced Maximum Likelihood Detection with QR Decomposition and M-algorithm (QRM-MLD) suitable for soft-decision Turbo decoding and investigates the throughput performance using QRM-MLD with the proposed likelihood function in multipath Rayleigh fading channels for Orthogonal Frequency and Code Division Multiplexing (OFCDM) multiple-input multiple-output (MIMO) multiplexing Simulation results show that by using the proposed likelihood function generation scheme for soft-decision Turbo decoding following QRM-MLD in 4-by-4 MIMO multiplexing, the required average received signal energy per bit-to-noise power spectrum density ratio (E b /N 0 ) at the average block error rate (BLER) of 10 -2 at a 1-Gbps data rate is significantly reduced compared to that using hard-decision decoding in OFCDM access with 16 QAM modulation, the coding rate of 8/9, and 8-code multiplexing with a spreading factor of 8 assuming a 100-MHz bandwidth Furthermore, we show that by employing QRM-MLD associated with soft-decision Turbo decoding for 4-by-4 MIMO multiplexing, the throughput values of 500 Mbps and 1 Gbps are achieved at the average received E b /N 0 of approximately 45 and 93 dB by QPSK with the coding rate of R= 8/9 and 16QAM with R = 8/9, respectively, for OFCDM access assuming a 100-MHz bandwidth in a twelve-path Rayleigh fading channel
145 citations
TL;DR: It is shown that direct-sequence binary phase-shift keying outperforms time-hopping Binary phase- shift keying for medium and large values of signal-to-noise ratio, which contradicts some previous results obtained using a Gaussian approximation.
Abstract: An exact analysis is derived for precisely calculating the bit error probability of time-hopping and direct-sequence ultra-wideband systems with multi-user interference in an additive white Gaussian noise environment. The analytical expressions are validated by simulation and used to assess the accuracy of the Gaussian approximation proposed for estimating the performance of ultra-wideband communication systems. The Gaussian approximation is shown to be inaccurate for predicting the bit error rate for medium and large signal-to-noise ratio values. The performances of time-hopping and direct-sequence modulation schemes are accurately compared for different numbers of users and frame widths. It is shown that direct-sequence binary phase-shift keying outperforms time-hopping binary phase-shift keying for medium and large values of signal-to-noise ratio, which contradicts some previous results obtained using a Gaussian approximation.
TL;DR: The capacity and error probability of orthogonal space-time block codes (STBCs) are considered for pulse-amplitude modulation/phase shift keying/quadrature-amPLitude modulation (PAM/PSK/QAM) in fading channels and the results are extended to obtain the capacity and probability of error for a multiuser direct sequence code-division multiple-access system employing space- time block coding.
Abstract: The capacity and error probability of orthogonal space-time block codes (STBCs) are considered for pulse-amplitude modulation/phase shift keying/quadrature-amplitude modulation (PAM/PSK/QAM) in fading channels. The approach is based on an equivalent scalar additive white Gaussian noise channel with a channel gain proportional to the Frobenius norm of the matrix channel for the STBC. Using this effective channel, capacity and probability of error expressions are derived for PSK/PAM/QAM modulation with space-time block coding. Rayleigh-, Ricean-, and Nakagami-fading channels are considered. As an application, these results are extended to obtain the capacity and probability of error for a multiuser direct sequence code-division multiple-access system employing space-time block coding.
TL;DR: A nondata-aided, envelope-based estimator that can be applied to nonconstant modulus constellations, which is a feature not found in existing approaches to estimate the signal-to-noise ratio (SNR) over the flat-fading channel is proposed.
Abstract: We propose a new technique to estimate the signal-to-noise ratio (SNR) over the flat-fading channel. This is a nondata-aided, envelope-based estimator that can be applied to nonconstant modulus constellations, which is a feature not found in existing approaches. We also analyze the performance of our estimators for both phase-shift keying (PSK) and non-PSK constellations by deriving their asymptotic variances and comparing with the Crame/spl acute/r-Rao Bounds (CRBs). Moreover, we discuss how the SNR estimates can be used to approximate the bit error rate (BER) and how the accuracy of the SNR estimate is related to that of the BER estimate, which justifies the necessity for the accurate estimation of SNR. The analytical performance is shown for both PSK and non-PSK constellations, such as 8 quadrature amplitude modulation (QAM) and 16 QAM. Monte Carlo simulation results corroborate our analysis.
TL;DR: In this article, a reliability-based mapping strategy was proposed for LDPC-coded modulation systems with gray and natural labeling, which gave a 0.15 dB - 0.2 dB performance improvement with no added complexity.
Abstract: In this paper, we propose a reliability-based mapping strategy in LDPC-coded modulation systems. Compared to conventional mapping methods, this strategy gives a 0.15 dB - 0.2 dB performance improvement with no added complexity. Extrinsic information transfer (EXIT) chart analyses are used to explain the reason for this improvement. LDPC-coded modulation systems with gray and natural labeling are studied. We show that the performances of gray-labeled systems are always superior.
TL;DR: It is shown that the labeling optimization problem falls into the category of quadratic assignment problems for constellations of any shape and with an arbitrary number of transmit and receive antennas, and is proposed to achieve the largest asymptotic coding gain inherited in the constellation labeling.
Abstract: We consider the design of iteratively decoded bit-interleaved space-time coded modulation (BI-STCM) over fast Rayleigh-fading channels with N/sub t/ transmit and N/sub r/ receive antennas. We propose the design criterion to achieve the largest asymptotic coding gain inherited in the constellation labeling. In particular, for orthogonal space-time block codes, the labeling design criterion reduces to maximizing the (-N/sub t/N/sub r/)th power mean of the complete set of squared Euclidean distances associated with all "error-free feedback" events in the constellation. Based on this power mean criterion, we show that the labeling optimization problem falls into the category of quadratic assignment problems for constellations of any shape and with an arbitrary number of transmit and receive antennas. For a set of practical values of N/sub t/ and N/sub r/, we present optimal labeling maps for 8-PSK, 16-QAM, and 64-QAM constellations.
TL;DR: Regardless of the number of constellation points, all quadrature-amplitude modulation (QAM) signals can be generated using a single dual-drive Mach-Zehnder modulator.
Abstract: Regardless of the number of constellation points, all quadrature-amplitude modulation (QAM) signals can be generated using a single dual-drive Mach-Zehnder modulator. When the general method is applied to quadrature-phase-shift-keying (QPSK) signals, three different QPSK transmitters are shown with drive signals having four, three, or two levels. The usage of only one dual-drive modulator greatly simplifies the design of QAM and QPSK transmitters.
DOI•
01 Jan 2005
TL;DR: In this article, the feasibility of using both singlemode and multimode fibres to distribute high-frequency microwave signals to simplified remote radio antenna units was investigated, and it was shown that optical frequency multiplication (OFM) can be used to generate pure high frequency microwave signals with very narrow linewidth and low SSB phase noise.
Abstract: Wireless coverage of the end-user domain, be it outdoors or indoors (in-building), is poised to become an essential part of broadband communication networks. In order to offer integrated broadband services (combining voice, data, video, multimedia services, and new value added services), these systems will need to offer higher data transmission capacities well beyond the present-day standards of wireless systems. Wireless LAN (IEEE802.11a/b/g) offering up-to 54 Mbps and operating at 2.4 GHz and 5 GHz, and 3G mobile networks (IMT2000/UMTS) offering up-to 2 Mbps and operating around 2 GHz, are some of today’s main wireless standards. IEEE802.16 or WiMAX is another recent standard aiming to bridge the last mile through mobile and fixed wireless access to the end user at frequencies between 2 – 66 GHz. The need for increased capacity per unit area leads to higher operating frequencies (above 6 GHz) and smaller radio cells, especially in in-door applications where the high operating frequencies encounter tremendously high losses through the building walls. To reduce the system installation and maintenance costs of such systems, it is imperative to make the radio antenna units as simple as possible. This may be achieved by consolidating signal processing functions at a centralised headend, through radio-over-fibre technology. The research in this thesis focussed on the feasibility of using both single-mode and multimode fibres to distribute high-frequency microwave signals to simplified remote radio antenna units. An alternative radio-over-fibre technique, termed Optical Frequency Multiplication (OFM) has been investigated. OFM entails the periodic filtering of a swept optical signal at the headend followed by photodetection at the radio access unit. A low sweep frequency (e.g. 3 GHz) is used. After photodetection at the remote radio access unit, high-frequency (>21 GHz) harmonic components of the sweep signal are generated. The desired microwave signal is selected by means of bandpass filtering, amplified, and radiated by the antenna. Modulated microwave carriers are generated by intensity modulating the frequency-swept optical signal. Through modelling, simulations, and extensive experiments, the behaviour and performance of a radio-over-fibre downlink employing OFM was investigated. Simulation and comprehensive experimental results showed that OFM can be used to generate pure high-frequency microwave signals with very narrow linewidth and low SSB phase noise. This is because in the OFM process laser phase noise is inherently suppressed. The low-phase noise capability of OFM enables it to support the delivery of carriers modulated not only by the simple ASK data format, but also by complex multilevel modulation formats such as BPSK, QPSK, and x-level QAM. Multicarrier signals such as Subcarrier Multiplexed signals, and OFDM signals used in wireless LANs are also supported. Low Error Vector Magnitudes (below 5%) were obtained for x-QAM modulation formats, including 64-QAM. BER measurements showed a modal dispersion penalty of about 1 dB for a 4.4 km MMF link under restricted launch condition. It was established that OFM is chromatic dispersion tolerant and can support more than 10 times longer single-mode fibre transmission links (exceeding 50 km) than IMDD systems, which suffer from the chromatic-dispersion-induced amplitude suppression. OFM also enables the delivery of microwave carriers exceeding the modal bandwidth of MMFs, by using the higher transmission passbands of the fibre response. Silica glass MMF links of more than 4 km are feasible. The maximum link length, which can be bridged with Polymer Optical Fibre (POF) is significantly shorter, owing to its higher attenuation values. Thus POF may be more attractive for in-building applications where link lengths of 500m are often sufficient. Several different implementations of the Mach Zehnder Interferometer, and the Fabry Perot Interferometer filters were considered to determine their simplicity, performance, and applicability within the end-user environment. It was established that the wavelength of the optical FM source needs to be carefully aligned to the characteristics of the periodic optical filter. Therefore, it is preferred that both the source and the filter are co-located. This makes it easier to employ electronic tuning control of the filter (e.g. a fibre Fabry Perot Interferometer), so as to automatically track the alignment with the optical source, resulting in remarkable improvement of the OFM system stability. The ability to achieve high frequency multiplication factors, good phase noise performance, the support for all modulation formats, and the ability to operate on both single-mode and MMFs, all make OFM ideal for use in high-frequency (>5 GHz) broadband wireless system applications.
TL;DR: This work investigates the performance of BPSK and QPSK with coherent detection and matched filtering in the presence of both time and phase asynchronous cochannel interfering signals and shows that the Gaussian approximation is accurate not only in the (obvious) case of a large number of interferers, but also when the desired signal is subject to fading.
Abstract: We investigate the performance of BPSK and QPSK with coherent detection and matched filtering in the presence of both time and phase asynchronous cochannel interfering signals. More precisely, we analyze the role played by different channel statistics on the distribution of the decision variable at the output of the matched filter. The results show that the Gaussian approximation is accurate not only in the (obvious) case of a large number of interferers, but also when the desired signal is subject to fading, whatever the number of interferers is. For example, when the desired signal is subject to Rayleigh fading, even in the presence of only one unfaded interferer the Kullback-Leibler distance between the exact distribution of the decision variable and that obtained with the Gaussian approximation on the interference is lower than 0.01 [nats] for all cases of practical interest.
31 Oct 2005
TL;DR: This paper constructs a family of space-time trellis codes for BPSK modulation scheme that is characterized to possess the full cooperative diversity order without the synchronization assumption, and generalizes this family to higher order QAM and PSK modulation schemes based on the unified construction proposed by Lu and Kumar.
Abstract: In current cooperative communication schemes, to achieve cooperative diversity, synchronization between terminals is usually assumed, which may not be practical since each terminal has its own local oscillator. In this paper, based on the stack construction proposed by Hammons and El Gamal, we first construct a family of space-time trellis codes for BPSK modulation scheme that is characterized to possess the full cooperative diversity order without the synchronization assumption. We then generalize this family of space-time trellis codes from BPSK to higher order QAM and PSK modulation schemes based on the unified construction proposed by Lu and Kumar. And also, simplified decoding methods are discussed. Simulation results are given to illustrate the performance of the newly proposed codes
TL;DR: This paper presents a simple, but effective method of enhancing and exploiting diversity from multiple packet transmissions in systems that employ nonbinary linear modulations such as phase-shift keying (PSK) and quadrature amplitude modulation (QAM).
Abstract: In this paper, we present a simple, but effective method of enhancing and exploiting diversity from multiple packet transmissions in systems that employ nonbinary linear modulations such as phase-shift keying (PSK) and quadrature amplitude modulation (QAM). This diversity improvement results from redesigning the symbol mapping for each packet transmission. By developing a general framework for evaluating the upper bound of the bit error rate (BER) with multiple transmissions, a criterion to obtain optimal symbol mappings is attained. The optimal adaptation scheme reduces to solutions of the well known quadratic assignment problem (QAP). Symbol mapping adaptation only requires a small increase in receiver complexity but provides very substantial BER gains when applied to additive white Gaussian noise (AWGN) and flat-fading channels.
TL;DR: In this article, a phase shift-keying (PSK) self-homodyne detection scheme using a polarization-multiplexed pilot-carrier with an inverse return-to-zero (RZ) intensity modulation signal for 2-bit/symbol transmission at 20 Gb/s was demonstrated.
Abstract: Phase-shift-keying (PSK) self-homodyne modulation and demodulation using a polarization-multiplexed pilot-carrier with an inverse-return-to-zero (RZ) intensity modulation signal for 2-bit/symbol transmission at 20 Gb/s was demonstrated. The pilot-carrier was generated by polarization-modulation in an orthogonal polarization state with respect to a PSK signal in the transmitter, while its polarization state was rotated by 90/spl deg/ in a LiNbO/sub 3/-based hybrid module for homodyne detection in the receiver. We confirm that the proposed self-homodyne detection scheme is insensitive to cross-modulation degradation by an inverse-RZ signal with high extinction ratio, thanks to an intensity-noise reduction capability of more than 15 dB in the homodyne-balanced receiver. The proposed scheme offers robust PSK homodyne detection for multibit per symbol formats without using a complex optical phase-locked loop.
TL;DR: A novel maximum a posteriori (MAP) estimation approach is employed for error correction of arithmetic codes with a forbidden symbol, which improves the performance in terms of error correction with respect to a separated source and channel coding approach based on convolutional codes.
Abstract: In this paper, a novel maximum a posteriori (MAP) estimation approach is employed for error correction of arithmetic codes with a forbidden symbol. The system is founded on the principle of joint source channel coding, which allows one to unify the arithmetic decoding and error correction tasks into a single process, with superior performance compared to traditional separated techniques. The proposed system improves the performance in terms of error correction with respect to a separated source and channel coding approach based on convolutional codes, with the additional great advantage of allowing complete flexibility in adjusting the coding rate. The proposed MAP decoder is tested in the case of image transmission across the additive white Gaussian noise channel and compared against standard forward error correction techniques in terms of performance and complexity. Both hard and soft decoding are taken into account, and excellent results in terms of packet error rate and decoded image quality are obtained.
TL;DR: A new signaling scheme that overlays phase-shift keying on ON-OFF keying is proposed and shown to be optimally efficient in the low-power regime.
Abstract: Transmission of information over a discrete-time memoryless Rician fading channel is considered, where neither the receiver nor the transmitter knows the fading coefficients. The spectral-efficiency/bit-energy tradeoff in the low-power regime is examined when the input has limited peakedness. It is shown that if a fourth-moment input constraint is imposed, or the input peak-to-average power ratio is limited, then in contrast to the behavior observed in average-power-limited channels, the minimum bit energy is not always achieved at zero spectral efficiency. The low-power performance is also characterized when there is a fixed peak limit that does not vary with the average power. A new signaling scheme that overlays phase-shift keying on ON-OFF keying (OOK) is proposed and shown to be optimally efficient in the low-power regime.
TL;DR: A novel direct sequence/spread spectrum (DS/SS) communication system is proposed that exploits the two-dimensional complex valued chaotic Ikeda map as the spreading sequences and significantly outperforms the Gold code DS/SS-BPSK system in synchronous channel conditions.
Abstract: In this paper, a novel direct sequence/spread spectrum (DS/SS) communication system is proposed. This scheme exploits the two-dimensional complex valued chaotic Ikeda map as the spreading sequences. With this double spreading DS/SS system, the effect of multiple access interference can be mitigated by choosing the spreading sequences with appropriate cross-correlation properties. The performance of the system is assessed and demonstrated in a multiuser environment by means of computer simulation with additive white Gaussian noise, Rayleigh fading, and selective fading channel conditions. These studies reveal that the proposed system significantly outperforms the Gold code DS/SS-BPSK system in synchronous channel conditions. In asynchronous case, the improvement is substantial for low signal-to-noise ratios.
TL;DR: In this article, a homodyne phase-diversity receiver followed by carrier-phase estimation through digital signal processing is demonstrated for unrepeatered optical transmission of 20 Gbit/s quadrature phase-shift keying (QPSK) signals over 210 km.
Abstract: Unrepeatered optical transmission of 20 Gbit/s quadrature phase-shift keying (QPSK) signals over 210 km, using a homodyne phase-diversity receiver followed by carrier-phase estimation through digital signal processing is demonstrated. The advantage of the coherent detection with phase estimation leads to significant improvement of the receiver sensitivity compared with differential demodulation. It also enables the observation of the distortion of the complex amplitude due to fibre nonlinearity, offering new tools to monitor the transmission quality.
TL;DR: This paper introduces multidimensional mapping for BICM-ID, where a group of bits is mapped to a vector of symbols, rather than a single symbol, which allows for more flexibility and potential performance improvements.
Abstract: In recent years, it has been recognized that bit-interleaved coded modulation with iterative decoding (BICM-ID) achieves excellent performance on virtually any channel, provided the signal mapping is carefully designed. In this paper, we introduce multidimensional mapping for BICM-ID, where a group of bits is mapped to a vector of symbols, rather than a single symbol. This allows for more flexibility and potential performance improvements. Our analysis shows that multidimensional mapping leads to an increase in Euclidean distance, thus boosting the performance compared to conventional mapping schemes. We derive a design criterion for optimal mappings and we provide such optimal mappings for BPSK and QPSK constellations.
TL;DR: By setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hotspot cell configurations assuming various channel conditions.
Abstract: This paper proposes the optimum design for adaptively controlling the spreading factor in Orthogonal Frequency and Code Division Multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional orthogonal channelization code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. We first demonstrate the reduction effect of inter-code interference by the proposed two-dimensional orthogonal channelization code assignment. Then, computer simulation results show that in time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency of f D = 1500 Hz, becomes SF Time = 16. Furthermore, it should be decreased to SF Time = 8 for such a very fast fading environment using 16QAM data modulation. We also clarify when the channel load is light such as C mux /SF = 0.25 (C mux and SF denote the number of multiplexed codes and total spreading factor, respectively), the required average received signal energy per symbol-to-noise power spectrum density ratio (E s /N 0 ) is reduced as the spreading factor in the frequency domain is increased up to say SF Freq = 32 for QPSK and 16QAM data modulation. When the channel load is close to full such as when C mux /SF = 0.94, the optimum spreading factor in the frequency domain is SF Freq = 1 for 16QAM data modulation and SF Freq = 1 to 8 for QPSK data modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hotspot cell configurations assuming various channel conditions.
TL;DR: A novel precoding approach for single transmit/receiver antenna orthogonal frequency-division multiplexing (OFDM) systems that enables blind channel estimation and an optimal precoding scheme is pursued that results in minimum channel error and asymptotically minimum bit error rate.
Abstract: We propose a novel precoding approach for single transmit/receiver antenna orthogonal frequency-division multiplexing (OFDM) systems that enables blind channel estimation. A nonredundant nonunitary linear precoder is applied on each pair of blocks before they enter the OFDM system. The structure induced to the transmitted blocks allows for blind channel estimation at the receiver based on simple cross-correlation operations. At the same time, the multipath diversity of the system is increased. An optimal precoding scheme is pursued that, for quadrature phase-shift keying signals results in minimum channel error and asymptotically minimum bit error rate. Analytic performance evaluation of the proposed approach, and Cramer-Rao bound for the proposed channel estimate, are presented.
12 Jun 2005
TL;DR: In this article, a large-signal polar modulation transmitter allows the use of an efficient nonlinear power amplifier (PA) for both GMSK and 8PSK in all four cellular bands (850/900/1800/1900).
Abstract: The addition of 8PSK modulation to the GSM standard creates the need for architectural modifications to achieve necessary performance while maintaining a cost-effective solution. A large-signal polar modulation transmitter allows the use of an efficient nonlinear power amplifier (PA) for both GMSK and 8PSK. Digital interfaces are used for both receiver and transmitter, with analog options available for compatibility with older technology baseband systems. The receiver section of the transceiver is programmable to operate in direct conversion mode or multiple VLIF modes. All analog and digital filtering necessary to define the final channel is included. The transmit section of the transceiver uses an all digital system with a fractional-N digital modulator for the phase path. The amplitude path uses a Powerstar PA with both the ramp and the amplitude modulation applied to the collector. The transceiver meets or exceeds all specifications for both GMSK and 8PSK in all four cellular bands (850/900/1800/1900).
TL;DR: This paper analyzes the error probability performance of maximal-ratio combining (MRC), equal-gain combining (EGC), selection combining (SC), and generalized-selection combining (GSC) diversity schemes with coherent binary phase-shift keying (BPSK) signaling on Rayleigh fading channels with Gaussian channel-estimation errors.
Abstract: In this paper, we analyze the error probability performance of maximal-ratio combining (MRC), equal-gain combining (EGC), selection combining (SC), and generalized-selection combining (GSC) diversity schemes with coherent binary phase-shift keying (BPSK) signaling on Rayleigh fading channels with Gaussian channel-estimation errors. We first show that, with weighting errors, averaging the conditional probability of error with the density function of the instantaneous signal-to-noise ratio (SNR) at the output of the combiner yields a lower bound on the exact probability of error. Later, we derive the exact probability of error for MRC, EGC, SC, and GSC diversity schemes and show that, for the case of nonnegative values of the in-phase correlation coefficient between the actual and the estimated channel gains, the exact probability of error with weighting errors is the same as that of the case with perfect channel estimation, but with the average SNR per diversity branch /spl gamma/~, for the case of perfect channel estimation, replaced by the effective SNR /spl gamma/~/sub /spl rho//, due to weighting errors. The effective SNR is a function of both /spl gamma/~ and /spl rho/, the magnitude of the normalized cross correlation between the actual and the estimated channel gains. Finally, we show that, as /spl rho//spl rarr/0, the average probability of error approaches 0.5, irrespective of the order of diversity and the diversity-combining rule.