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We introduce and demonstrate a method for expanding the field of view of a typical imaging system by multiplexing images encoded onto different polarization states and recovering them from a limited number of measurements. [c] 2010 Optical Society of America OCIS codes: 110.1758, 110.5405.

Recent theoretical investigations have shown important radiometric disadvantages of interferential multiplexing in Fourier transform spectrometry that apparently can be applied even to coded aperture spectrometers. We have reexamined the methods of noninterferential multiplexing in order to assess their signal-to-noise ratio (SNR) performance, relying on a theoretical modeling of the multiplexed signals. We are able to show that quite similar SNR and radiometric disadvantages affect multiplex dispersive spectrometry. The effect of noise on spectral estimations is discussed. OCIS codes: 300.0300, 300.6300, 060.4230, 170.1630.

This paper describes a new approach, based on self-assembled mixed monolayers, to the design and preparation of extrinsic Raman labels (ERLs). ERLs function as spectroscopic tags for the readout of sandwich-type immunoassays using surface-enhanced Raman scattering (SERS). They are created by coating gold nanoparticles with Raman reporter molecules and antibodies specific for the target analyte. Mixed-monolayer ERLs are formed by covering gold nanoparticles with a mixture of two different thiolates. One thiolate serves to covalently bind antibodies to the particles, imparting biospecificity to the ERLs, while the other thiolate produces a strong Raman signal. Mixed-monolayer ERLs can be prepared in a few relatively simple steps using readily available materials. The SERS intensity of each type of ERL can be tuned to match other ERLs by adjusting the mixed monolayer composition, greatly facilitating the generation of sets of ERLs for multiplexed applications. The work herein not only describes the new pathway for ERL production, but also demonstrates the simultaneous quantitative and quantitative multiplexed detection using a set of four mixed-mono-layer ERLs. 10.1021/ac901711f

Simultaneous detection of multiple independent fluorescent signals or signal multiplexing has the potential to significantly improve bioassay throughput and to allow visualization of concurrent cellular events. Applications based on signal multiplexing, however, remain hard to achieve in practice due to difficulties in both implementing hardware and the photophysical liabilities associated with available organic dye and protein fluorophores. Here, we used charge-transfer interactions between luminescent semiconductor quantum dots (QDs) and proximal redox complexes to demonstrate controlled quenching of QD photoemission in a multiplexed format. In particular, we show that, because of the ability of the Ru complex to effectively interact with CdSe--ZnS QDs emitting over a broad window of the optical spectrum, higher orders of multiplexed quenching can be achieved in a relatively facile manner. Polyhistidine-appended peptides were site-specifically labeled with a redox-active ruthenium (Ru) phenanthroline complex and self-assembled onto QDs, resulting in controlled quenching of the QD emission. Different QD colors either alone or coupled to Ru--phen--peptide were then mixed together and optically interrogated. Composite spectra collected from mixtures ranging from four up to eight distinct QD colors were deconvoluted, and the individual QD photoluminescence (PL) loss due to charge transfer was quantified. The current multiplexing modality provides a simpler format for exploiting the narrow, size-tunable QD emissions than that offered by resonance energy transfer; for the latter, higher orders of multiplexing are limited by spectral overlap requirements.

A particle-based multiplexed DNA assay based on encoded porous Si[O.sub.2] photonic crystal disks is demonstrated. A 'spectral barcode' is generated by electrochemical etch of a single-crystal silicon wafer using a programmed current-time waveform. A lithographic procedure is used to isolate cylindrical microparticles 25 [micro]m in diameter and 10 [micro]m thick, which are then oxidized, modified with a silane linker, and conjugated to various amino-functionalized oligonucleotide probes via cyanuric chloride. It is shown that the particles can be decoded based on their reflectivity spectra and that a multiple analyte assay can be performed in a single sample with a modified fluorescence microscope. The homogeneity of the reflectivity and fluorescence spectra, both within and across the microparticles, is also reported.

A method to expand the viewing window for the integral floating display by twofold through time multiplexing is proposed. The viewing window of the integral floating display can be expanded by enlarging the elemental image area for each elemental lens, by which the viewing angle of the integral imaging system is determined. Also, the difference between the effects of elemental image area expansion on the viewing characteristics of images reconstructed by the integral floating display and the integral imaging system is investigated. The experimental results verify the enhancement of the viewing window for the three-dimensional images displayed by the proposed scheme. OCIS codes: 100.6890, 110.2990.

The performance and design of collaborative spatial multiplexing methods for IEEE 802.16e-based systems are investigated. Average sector throughput can be improved by up to 60% using collaborative uplink multiple input-multiple output.

A new microfluidic electrophoresis device and technique is described that is designed specifically for multiplexed, high-throughput separations. The device consists of an array of short (3 mm) capillaries connecting individual sample reservoirs to a common buffer reservoir. Each capillary in the array functions as both a separation channel and as a conductivity-based detection cell. The new technique is based upon the recently described gradient elution moving boundary electrophoresis (GEMBE) technique, which uses a combination of an electric field and buffer counterflow to achieve electrophoretic separations in short capillaries or microfluidic channels. A high voltage drives electrophoresis of the sample analytes through each separation channel. At the start of a separation, the bulk counterflow of buffer through the channel is high, and none of the analytes of interest can enter the channel. The counterflow is then gradually reduced until each analyte, in turn, is able to enter the channel where it is detected as a moving boundary or step. With very short capillaries, only one step at a time is present in each capillary, and the electric current through the channels can then be used as the detector signal, without any extra detector hardware. The current vs time signal for each channel is then smoothed and differentiated to produce a set of simultaneous electropherograms. Because there is no light source or other added hardware required for detection, the system is simple and can be easily and inexpensively scaled up to perform large numbers of simultaneous analyses. As a first demonstration, a 16-channel array device is used for high-throughput, time-series measurements of enzyme activity and inhibition.

The multiplex ligation-dependent probe amplification (MLPA) technique is a sensitive technique for relative quantification of up to 50 different nucleic acid sequences in a single reaction, and the technique is routinely used for copy number analysis in various syndromes and diseases. The aim of the study was to exploit the potential of MLPA when the DNA material is limited. The DNA concentration required in standard MLPA analysis is not attainable from dried blood spot samples (DBSS) often used in neonatal screening programs. A novel design of MLPA probes has been developed to permit for MLPA analysis on small amounts of DNA. Six patients with congenital adrenal hyperplasia (CAH) were used in this study. DNA was extracted from both whole blood and DBSS and subjected to MLPA analysis using normal and modified probes. Results were analyzed using GeneMarker and manual Excel analysis. A total number of 792 ligation events were analyzed. In DNA extracted from dried blood spot samples, 99.1% of the results were accurate compared to 99.9% of the results obtained in DNA from whole blood samples. This study clearly demonstrates that MLPA reactions with modified probes are successful and reliable with DNA concentrations down to 0.3 ng/[micro]L (1.6 ng total). This broadens the diagnostic perspectives of samples of DBSS allowing for copy number variation analysis in general and particularly testing for CAH.

We propose a multichanneling encryption method by using multiple random-phase mask apertures in the input plane based on a joint transform correlation scheme. In the proposal, this multiple aperture arrangement is changed as different input objects are inserted and stored. Then, during the decryption step, the appropriate use of the random-phase mask apertures can ensure the retrieval of different information. This approach provides different access levels. Computer simulations show the potential of the technique and experimental results verify the feasibility of this method. OCIS codes: 100.1160, 090.4220.

Multi-channel high speed ADCs with a serial output interface operating at several hundred Mbps have been introduced several years ago. Interfacing to these high speed devices poses new challenges to the designer. Existing techniques usually rely on delay locked loops, require several milliseconds to reach stable operation, and do not guarantee a fixed latency making the accurate synchronization of several multi-channel ADCs difficult to achieve. A new interface technique is introduced to overcome these limitations. We detail the proposed method and show an implementation where a single field programmable gate array is used to collect data from twenty four 12-bit ADC channels clocked at 20 MHz. Index Terms--Field programmable gate arrays, high speed analog to digital converters, source synchronous interfaces.

Two-dimensional (crossed) diffraction gratings with sinusoidal or truncated pyramidal (trapezoidal) profiles are proposed to have diffraction efficiency almost independent of the incident polarization inside the optical communication spectral window 1.5-1.6 [micro]m The gratings are characterized by different periods in the two orthogonal directions, chosen to support only one dispersive diffraction order in addition to the zeroth (specular) one. OCIS codes: 060.4230, 050.1950, 050.2770.

This paper introduces a family of bandwidth efficient modulation schemes called quadrature multiplexed continuous phase modulation (QM-CPM). QM-CPM can be thought of as an alternative to smooth pulse-shaped quadrature amplitude modulation (QAM). Like pulse-shaped QAM, QM-CPM modulates smooth continuous signals onto the in-phase (I) and the quadrature-phase (Q) channels, but these signals are derived from CPM signals instead of being filtered to attain their desired smoothness and spectral properties. QM-MSK (QM-minimum shift keying) is developed and is shown to double the bits/Hz over MSK while maintaining MSK's normalized minimum distance of [d.sup.2.sub.min] = 2.0. Classes of [M.sup.2]-ary QM-CPFSK (QM-continuous phase frequency shift keying) signals are derived from constant envelope M-ary CPFSK signals to construct bandwidth efficient modulation schemes which are comparable to and offer advantages over pulse-shaped QAM. Index Terms--CPM, modulation, error probability, bandwidth efficient, trellis, constellation, phase state.

The identification (ID) data reproduction was computationally examined for the compatibility with the aperture multiplexing and the telecentric system. The mask for the multiplexing caused shade in the reproduced ID data cell. The shading tolerance was improved by modulating the phase of the original image so that the ID data holograms diffract the light in the oblique direction or with the concentrating. The telecentric system reproduced all ID data cells in the same position of the image sensor and made a distinction among the cells impossible. This was solved by reproducing the cell point symmetrically from the corresponding ID data hologram in each 3 x 3 ID data block. OCIS codes: 210.2860, 090.1760.

A family of detectors that exploit signal constraints is developed for maximum-likelihood detection for multiple-input-multiple-output (MIMO) systems. Real constrained detectors and decision-feedback detectors are proposed for real constellations by forcing the relaxed solution to be real. A generalized minimum mean square error (GMMSE) and constrained least squares MIMO detectors are also developed for unitary and nonunitary signal constellations. Using these constrained detectors, we propose a new ordering scheme to achieve a tradeoff between interference suppression and noise enhancement. Moreover, to mitigate the inherent error propagation, the decision-feedback MIMO detectors are integrated with signal constraints. The simulation results show that our combined detector achieves a significant performance gain over vertical Bell Laboratories layered space-time (V-BLAST) detection. Index Terms--Decision-feedback detector (DFD), linear detector, maximum likelihood, multiple-input-multiple-output (MIMO).

This paper considers low-complexity coded multiple-input-multiple-output transmission in Rayleigh channels with correlation between antennas at both the transmitter and receiver. We consider statistical beamforming (SB) and spatial multiplexing (SM) with a zero-forcing receiver. We calculate the link-level capacity of both schemes with bit-interleaved coded modulation and derive accurate closed-form approximations to the bit error rate. We then show how the resulting expressions can be used in an adaptive algorithm to select the best combination of code rate, modulation format, and transmission scheme (SB or SM) in order to maximize throughput. Unlike other mode-switching schemes that require empirical lookup tables, this approach applies to any correlation scenario. Numerical studies are used to demonstrate the performance as a function of signal-to-noise ratio and correlation parameters. Index Terms--Adaptive coding, modulation, multiple-input-multiple-output (MIMO) communications, spatially correlated channels.

The exposure schedule for partially coherent hologram multiplexing, in which data pages are multiplexed by multiple signal beams and a single reference beam, is investigated in detail for the case of a [pi]/2 phase-shifted photorefractive medium. We found that the optimum recording schedule for partially coherent multiplexing cannot be determined by the classical recording schedule theory because of timeconstant errors induced by partially coherent interaction between a reference beam and self-diffraction signal beams. To overcome the issue, we derive a modified recursion equation that accounts for the time-constant errors, and we also propose a novel iterative recording-schedule correction algorism for finding the optimum solution. In the calculation with hologram multiplicity of 30 and photorefractive coupling strength of 3.0, we could successfully obtain a flat diffraction-efficiency profile aider the second recursion. OCIS codes: 190.5330, 090.4220, 210.2860.

A paradigm is developed for decentralized inference that exploits the multiple-access channel (MAC) structure from a joint source-channel coding perspective. A new type-based-multiple-access (TDMA)-based protocol has established its significant performance gain when compared to the identical mapping approach.

We replace the traditional grating used in a dispersive spectrometer with a multiplex holographic grating to increase the spectral range sensed by the instrument. The multiplexed grating allows us to measure three different, overlapping spectral bands on a color digital focal plane. The detector's broadband color filters, along with a computational inversion algorithm, let us disambiguate measurements made from the three bands. The overlapping spectral bands allow us to measure a greater spectral bandwidth than a traditional spectrometer with the same sized detector. Additionally, our spectrometer uses a static coded aperture mask in the place of a slit. The aperture mask allows increased light throughput, offsetting the photon loss at the broadband filters. We present our proof-of-concept dispersion multiplexing spectrometer design with experimental measurements to verify its operation. OCIS codes: 120.620, 090.1970.

A new analytical model is presented to study nonlinear distortion due to cross-phase modulation in dispersive and nonlinear wavelength-division-multiplexing microwave fiber-optic links. The model is not based on the pump-probe approach. Hence, it can be used to analyze a larger variety of links, including, in particular, electrooptical upconversion links. Our simulations and experiments show that the model predicts the nonlinear distortion due to cross-phase modulation quite accurately, even when the modulating microwave frequency is in tens of gigahertz and the fiber length is in tens of kilometers. Detailed analyses of the distortion due to cross-phase modulation for links with optical single-sideband modulation are presented. Measured results for optical single-sideband are shown to match our theoretical predictions very well. Our results show that the nonlinear distortion due to cross-phase modulation can be a limiting factor for optical launch power in wavelength-division-multiplexing microwave fiber-optic links; moreover, the maximum possible nonlinear distortion level for a higher frequency may be lower than that for a lower frequency. Also presented are some simple approximations for a quick estimate of the level of the nonlinear distortion. Index Terms--Cross-phase modulation, electrooptical upconversion, fiber dispersion, fiber nonlinearity, microwave fiber-optic link, wavelength division multiplexing.

This paper proposes a new switched MIMO system where the MIMO includes both diversity-based MIMO and spatial multiplexing MIMO (SM-MIMO). The proposed scheme is a closed-loop system where the feedback bits are sent back to the transmitter to indicate the channel quality. The switching operation is employed among groups of a certain number of transmit antennas. For diversity-based MIMO systems, the switching operation aims to improve the link performance, while the goal of the switching for the SM-MIMO systems is to increase the data rate. The authors analyze and optimize the proposed systems and show that there is considerable benefit in terms of performance and practical use. Index Terms--Diversity techniques, fading channels, MIMO, performance analysis, switched diversity, transmit diversity.

Precoding for multiple-input multiple-output (MIMO) spatial multiplexing generally requires high feedback overhead and/or high-complexity processing. Simultaneous reduction in transmitter complexity and feedback overhead is proposed by imposing a diagonal structural constraint to precoding, i.e., power allocation. Minimum bit-error rate (MBER) is employed as the optimization criterion, and an approximate MBER (AMBER) power-allocation algorithm is proposed for a variety of receivers, including zero-forcing (ZF), successive interference cancellation (SIC), and ordered SIC (OSIC). While previously proposed precoding schemes either require ZF equalization for MBER, or use a minimum mean-squared error (MMSE) criterion, we provide a unified MBER solution to power allocation for ZF, SIC, and OSIC receiver structures. Improved error-rate performance is shown both analytically and by simulation. Simulation results also indicate that SIC and OSIC with AMBER power allocation offer superior performance over previously proposed MBER precoding with ZF equalization, as well as over MMSE precoding/decoding. Performance under noisy channels and power feedback is analyzed. A modified AMBER algorithm that mitigates error propagation in interference cancellation is developed. Compared with existing precoding methods, the proposed schemes significantly reduce both transmit processing complexity and feedback overhead, and improve error-rate performance. Index Terms--Minimum bit-error rate (MBER), multiple-input multiple-output (MIMO), power allocation, precoding, spatial multiplexing, successive interference cancellation (SIC).

Space-time code (STC) designs classically rely on the assumption of independent and identically distributed (i.i.d.) Rayleigh channels. However, poor scattering conditions may have detrimental effects on the performance of STCs. In this letter, we derive code-design criteria leading to robust STCs in a large variety of slow-fading propagation conditions. No channel knowledge is assumed at the transmitter. Codes satisfying these criteria are shown to perform much better on real-world channels than codes designed only for i.i.d, channels. As examples, the robustness of various spatial multiplexing schemes, linear dispersion codes, and space--time trellis codes is discussed based on those criteria. Index Terms--Correlated channels, multiple-input multipleoutput (MIMO), space-time coding, spatial multiplexing (SM).

In recent years, the remarkable ability of multiple-input--multiple-output (MIMO) wireless communication systems to provide spatial diversity or multiplexing gains has been clearly demonstrated. For MIMO diversity schemes, it is well known that antenna selection methods that optimize the postprocessing signal-to-noise ratio (SNR) can preserve the diversity order of the original full-size MIMO system. On the other hand, the diversity order achieved by antenna selection in spatial multiplexing systems, especially those exploiting practical coding and decoding schemes, has not thus far been rigorously analyzed. In this paper, a geometrical framework is proposed to theoretically analyze the diversity order achieved by transmit antenna selection for separately encoded spatial multiplexing systems with linear and decision-feedback receivers. When two antennas are selected from the transmitter, the exact achievable diversity order is rigorously derived, which previously only appears as conjectures based on numerical results in the literature. If more than two antennas are selected, we give lower and upper bounds on the achievable diversity order. Furthermore, the same geometrical approach is used to evaluate the diversity-multiplexing tradeoff in spatial multiplexing systems with transmit antenna selection. Index Terms--Antenna selection, diversity order, diversity and multiplexing tradeoff, multiple-input--multiple-output (MIMO), spatial multiplexing.

A nonasymptotic framework is presented to analyze the diversity-multiplexing tradeoff of a multiple-input--multiple-output (MIMO) wireless system at finite signal-to-noise ratios (SNRs). The target data rate at each SNR is proportional to the capacity of an additive white Gaussian noise (AWGN) channel with an array gain. The proportionality constant, which can be interpreted as a finite-SNR spatial multiplexing gain, dictates the sensitivity of the rate adaptation policy to SNR. The diversity gain as a function of SNR for a fixed multiplexing gain is defined by the negative slope of the outage probability versus SNR curve on a log-log scale. The finite-SNR diversity gain provides an estimate of the additional power required to decrease the outage probability by a target amount. For general MIMO systems, lower bounds on the outage probabilities in correlated Rayleigh fading and Rician fading are used to estimate the diversity gain as a function of multiplexing gain and SNR. In addition, exact diversity gain expressions are determined for orthogonal space--time block codes (OSTBC). Spatial correlation significantly lowers the achievable diversity gain at finite SNR when compared to high-SNR asymptotic values. The presence of line-of-sight (LOS) components in Rician fading yields diversity gains higher than high-SNR asymptotic values at some SNRs and multiplexing gains while resulting in diversity gains near zero for multiplexing gains larger than unity. Furthermore, as the multiplexing gain approaches zero, the normalized limiting diversity gain, which can be interpreted in terms of the wideband slope and the high-SNR slope of spectral efficiency, exhibits slow convergence with SNR to the high-SNR asymptotic value. This finite-SNR framework for the diversity--multiplexing tradeoff is useful in MIMO system design for realistic SNRs and propagation environments. Index Terms--Finite signal-to-noise ratio (SNR), multiple antennas, outage probability, random matrices.

A recent result of Zheng and Tse states that over a quasi-static channel, there exists a fundamental tradeoff, referred to as the diversity-multiplexing gain (D-MG) tradeoff, between the spatial multiplexing gain and the diversity gain that can be simultaneously achieved by a space--time (ST) code. This tradeoff is precisely known in the case of independent and identically distributed (i.i.d.) Rayleigh fading, for T [greater than or equal to] [n.sub.t] + [n.sub.r], - 1 where T is the number of time slots over which coding takes place and [n.sub.t], [n.sub.r] are the number of transmit and receive antennas, respectively. For T < [n.sub.t] + [n.sub.r], - 1, only upper and lower bounds on the D-MG tradeoff are available. In this paper, we present a complete solution to the problem of explicitly constructing D-MG optimal ST codes, i.e., codes that achieve the D-MG tradeoff for any number of receive antennas. We do this by showing that for the square minimum-delay ease when T = [n.sub.t] = n, cyclic-division-algebra (CDA)-based ST codes having the nonvanishing determinant property are D-MG optimal. While constructions of such codes were previously known for restricted values of n, we provide here a construction for such codes that is valid for all n. For the rectangular, T > [n.sub.t] ease, we present two general techniques for building D-MG-optimal rectangular ST codes from their square counterparts. A byproduct of our results establishes that the D-MG tradeoff for all T [greater than or equal to] [n.sub.t] is the same as that previously known to hold for T [greater than or equal to] [n.sub.t] + [n.sub.r] - 1. Index Terms--Cyclic division algebra, diversity-multiplexing gain tradeoff, explicit construction, space-time codes.

Opportunity driven multiple access (ODMA), a cellular multihop method proposed for Universal Mobile Telecommunications Systems, potentially allows reduction in power consumption of user equipment (UE), extending Node B's coverage and supporting higher user data rate. However, ODMA requires extra power for discovering relaying nodes and introduces additional transmission latency in data transfer. This paper offers enlightenment to these ODMA implementation problems. A power-efficient routing (PER) mechanism is proposed to identify a minimum-power path for ODMA communication. Prior to the route (or path) discovery, the PER mechanism utilizes an analytical solution to estimate the total power and number of intermediate UEs required in the minimum-power path. With the estimation, route discovery procedures originating from nonattainable ODMA requests can be prevented. For those attainable ODMA requests that require a route discovery procedure to locate intermediate UEs, the PER mechanism further provides a method to set the transmission power and maximum hop count. Hence, the power consumption of each UE during route discovery is significantly reduced. Simulation results coincided with the analysis, and the results demonstrate the performance improvement of PER over dynamic source routing. Index Terms---Opportunity driven multiple access (ODMA), power-efficient routing (PER).

The incorporation of the orthogonal frequency-multiplexing (OFDM) with the space-time or space-frequency coding is a robust and effective method to achieve a transmit-diversity gain and to suppress an intersymbol interference for the broadband wireless transmissions. This paper is concerned with the downlink-performance improvement using multiple transmit antennas for the OFDM systems with a large delay spread. A delay-spread reduction method using space-frequency block coding and statistical prefiltering (SPF) was proposed, which combines signal prealignment and multiple transmit beamformers designed with the statistical knowledge of the downlink channel state information. The proposed method, which is called the SPF-OFDM, transforms a large delay-spread channel into multiple channels, each with small delay spread. Thus, it does not only shorten the effective excess delay but also preserves the path diversity through the use of the space-frequency coding. Computer simulations have evaluated the effectiveness of the proposed scheme, and comparisons have been made with the conventional solutions. Index Terms--Antenna array, delay-spread reduction, orthogonal frequency-division multiplexing (OFDM), transmit beamforming.

An adaptive subcarrier allocation and an adaptive modulation for multiuser orthogonal frequency-division multi-plexing (OFDM) are considered. The optimal subcarrier and hit allocation problems, which are previously formulated as nonlinear optimizadious, are reformulated into and solved by integer programming (IP). A suboptimal approach that performs subcarrier allocation and bit loading separately is proposed. It is shown that the subcarrier allocation in this approach can be optimized by the linear-programming (LP) relaxation of UP, while the bit loading can be performed in a manner similar to a single-user OFDM. In addition, a heuristic method for solving the LP problem is presented. The LP-based suboptimal and heuristic algorithms are considerably simpler to implement than the optimal IP, plus their performances are close to those of the optimal approach. Index Terms--Integer programming (IP), linear programming (LP), multiuser orthogonal frequency-division multiplexing (OFDM), subcarrier and hit allocation.

We propose a channel state information (CSI) feedback scheme based on unquantized and uncoded (UQ-UC) transmission. We consider a system where a mobile terminal obtains the downlink CSI and feeds it back to the base station using an uplink feedback channel. If the downlink channel is an independent Rayleigh fading channel, then the CSI may be viewed as an output of a complex independent identically distributed Gaussian source. Further, if the uplink feedback channel is an additive white Gaussian noise channel, and the downlink CSI is perfectly known at the mobile terminal, it can be shown that UQ-UC CSI transmission (that incurs zero delay) is optimal in that it achieves the same minimum mean-squared error distortion as a scheme that optimally (in the Shannon sense) quantizes and encodes the CSI, while theoretically incurring infinite delay. Since the UQ-UC transmission is suboptimal on correlated wireless channels, we propose a simple linear CSI feedback receiver that can be used to improve the performance of UQ-UC transmission while still retaining the attractive zero-delay feature. We provide bounds on the performance of such UQ-UC CSI feedback and study its impact on the achievable information rates. Furthermore, we explore its application and performance in multiple-antenna multiuser wireless systems, and also propose a corresponding pilot-assisted channel-state estimation scheme. Index Terms--Autoregressive (AR) process, channel state information (CSI), correlated wireless channels, distortion, minimum mean-squared error (MMSE) receiver, multiple-input single-output (MISO) systems, spatial prefiltering.

Optimal and suboptimal multiuser noncoherent detection for square-law receivers is studied in this paper. Great potential is found for the multiuser square-law detector when compared with the conventional single-user square-law detector. We study the optimal detector and two detectors with simpler structures: the asymptotically optimal detector and the pairwise linear detector. The saddle-point approximation method is used to study the error performance and its asymptotic behavior as noise reduces. Due to difficulty in optimizing the detectors at an arbitrary noise level, we propose to use the asymptotic efficiency for detector optimization. For a low-error-rate system like a fiber optic communication system, the asymptotic efficiency is found to be an efficient way to design detectors. Numerical results show that the asymptotically optimized detectors perform as well as the optimal detector, even for nonzero noise levels of practical interest. Despite their exponential complexity, these detectors are applicable to wavelength-division multiplexed systems in which only a few neighboring channels produce strong interference. Index Terms--Multiuser detection (MUD), optical fiber communication, wavelength-division multiplexing (WDM).

A preplanned path-protection scheme with sufficient spare bandwidth is appropriate for real-time fault restoration in multiprotocol label switching (MPLS) networks. In this case, however, it is important to reduce the amount of spare bandwidth to prevent degradation of network efficiency. A distributed label switched path (D-LSP) scheme is proposed to reduce the amount of spare bandwidth required for protecting against network faults in MPLS networks. The main idea of the proposed D-LSP scheme is to partition traffic into multiple LSPs, each of which is established on a distinct link-disjoint route between each pair of end nodes. The D-LSP scheme is evaluated in terms of the reduction ratio of total network cost in comparison with the conventional LSP scheme. Traffic partitioning in the D-LSP scheme can decrease the statistical multiplexing gain (SMG) obtained by aggregating IP packet flows into an LSP. The tradeoff between spare bandwidth reduction and degradation of SMG due to traffic partitioning is also investigated. The numerical results show that the proposed D-LSP scheme yields the network cost-reduction ratio (NCRR) of at least 29%, 27%, and 15% for the networks where average node degrees are 4.6, 4.4, and 3.2, respectively. The D-LSP scheme shows the similar performance of NCRR in both Markovian traffic and self-similar traffic environments. Index Terms--Distributed label switched path (D-LSP), label switched path (LSP) partitioning, network cost-reduction ratio (NCRR), spare bandwidth reduction, statistical multiplexing gain (SMG).

A reflection-type holographic disk memory system with random phase shift multiplexing is proposed. The experimental results show that a binary data page of 18 X 17 bits is recorded successfully at intervals of 4 [micro]m in a Fe:LiNb[O.sub.3] crystal with a thickness of 0.5 mm when six data pages are superimposed. Numerical results show that random phase modulation can improve the shift selectivity in shift multiplexing recording as well as in data security. Experimental and numerical results show that reflection-type holographic disk memory has a high potential for terabyte storage capacity as in transmission-type memory. OCIS codes: 210.2860, 090.7330.

In this contribution, the capacity of multiple-input multiple-output (MIMO) systems using multidimensional phase-shift keying/quadratic-amplitude modulation signal sets is evaluated. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and that of the additive white Gaussian noise channel. However, because this gap becomes narrower when the receiver diversity order is increased, for higher order receiver diversity, the performance advantage of transmit diversity diminishes. A MIMO system having full multiplexing gain has a higher achievable throughput than the corresponding MIMO system designed for full diversity gain, although this is attained at the cost of a higher complexity and a higher signal-to-noise ratio. The tradeoffs between diversity gain, multiplexing gain, complexity, and bandwidth are studied. Index Terms--Capacity, diversity, multiple-input multiple-output (MIMO), multiplexing.

We introduce new methods for increasing the performance of multiprogram digital audio broadcast systems, e.g., satellite digital audio broadcasting. Joint multiprogram encoding is an attractive possibility for parallel broadcasting of a large number of programs. Joint coding extended over multiple audio frames in time give further improvements. The benefits of this kind of statistical multiplexing yield improved audio quality and/or higher capacity in terms of number of programs. We describe the new Joint Multiple Program Encoding Technique in the context of the perceptual audio coding (PAC) type of algorithms. We also describe methods for multi-program transmission including Equal Error Protection (EEP) as well as Unequal Error Protection (UEP) and improved error concealment for multiple program transmission. Some of the techniques described in this paper, are currently being used in satellite digital audio broadcasting in the United States. Index Terms--Digital audio, digital audio broadcasting, source coding, statistical multiplexing.

A space-time code is proposed that exhibits the highest coding gain among competing full-rate full transmit diversity space--time codes for the two transmit and receive antenna coherent quasi-static fading channel. The proposed code is derived from a layered architecture with real rotation of quadrature amplitude modulation (QAM) information symbols in two dimensions. The existing codes of similar architecture concentrate on application of complex full modulation diversity rotations or asymmetric real rotations. An analytic evaluation illustrates the significant improvement in coding gain achieved with the proposed code. Moreover, the coding gain of the proposed code is independent of its rate. This implies that the proposed code achieves the optimal diversity--multiplexing tradeoff curve for the two transmit antenna system. A stacked extension of the proposed code offers a reduced complexity capacity optimal alternative to the full diversity codes for larger number of transmit antennas. Performance enhancement in several scenarios is verified through simulations. Index Terms--Capacity optimal codes, coding gain, diversity--multiplexing tradeoff, fading channel, real rotation, space--time coding, transmit diversity.