Abstract: From the Publisher: Orthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channels at different frequencies. CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimising the use of available bandwidth. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. Multi-Carrier (MC) CDMA is a combined technique of Direct Sequence (DS) CDMA (Code Division Multiple Access) and OFDM techniques. It applies spreading sequences in the frequency domain. Wireless communications has witnessed a tremendous growth during the past decade and further spectacular enabling technology advances are expected in an effort to render ubiquitous wireless connectivity a reality. This technical in-depth book is unique in its detailed exposure of OFDM, MIMO-OFDM and MC-CDMA. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context. Divided into three main parts: Part I provides a detailed exposure of OFDM designed for employment in various applications Part II is another design alternative applicable in the context of OFDM systems where the channel quality fluctuations observed are averaged out with the aid of frequency-domain spreading codes, which leads to the concept of MC-CDMA Part III discusses how to employ multiple antennas at the base station for the sake of supporting multiple users in the uplink Portrays theentire body of knowledge currently available on OFDMProvides the first complete treatment of OFDM, MIMO(Multiple Input Multiple Output)-OFDM and MC-CDMAConsiders the benefits of channel coding and space time coding in the context of various application examples and features numerous complete system design examplesConverts the lessons of Shannon's information theory into design principles applicable to practical wireless systemsCombines the benefits of a textbook with a research monograph where the depth of discussions progressively increase throughout the book This all-encompassing self-contained treatment will appeal to researchers, postgraduate students and academics, practising research and development engineers working for wireless communications and computer networking companies and senior undergraduate students and technical managers.

Abstract: The paper studies the problem of finding an optimal subcarrier and power allocation strategy for downlink communication to multiple users in an orthogonal-frequency-division multiplexing-based wireless system. The problem of minimizing total power consumption with constraints on bit-error rate and transmission rate for users requiring different classes of service is formulated and simple algorithms with good performance are derived. The problem of joint allocation is divided into two steps. In the first step, the number of subcarriers that each user gets is determined based on the users' average signal-to-noise ratio. The algorithm is shown to find the distribution of subcarriers that minimizes the total power required when every user experiences a flat-fading channel. In the second stage of the algorithm, it finds the best assignment of subcarriers to users. Two different approaches are presented, the rate-craving greedy algorithm and the amplitude-craving greedy algorithm. A single cell with one base station and many mobile stations is considered. Numerical results demonstrate that the proposed low complexity algorithms offer comparable performance with an existing iterative algorithm.

Abstract: We consider multiple-input - multiple-output (MIMO) systems with reduced complexity. Either one, or both, link ends chose the "best" L out of N available antennas. This implies that only L instead of N transceiver chains have to be built, and also the signal processing can be simplified. We show that in ideal channels, full diversity can be achieved, and also the number of independent data streams for spatial multiplexing can be maintained if certain conditions on L are fulfilled. We then discuss the impact of system nonidealities, like noisy channel estimation, correlations of the received signals, etc.

Abstract: We investigate the use of optical differential phase-shift keying (DPSK) as the downstream modulation format in a low-cost upstream data remodulation scheme for a wavelength-division multiplexing (WDM)-based passive optical network. A 2.5-Gb/s upstream data transmitter is realized by directly modulating a Fabry-Perot (FP) laser, injection-locked with a 10-Gb/s downstream optical DPSK signal. A simple polarization-offset technique is proposed to largely minimize the induced power penalty.

Abstract: A random beamforming technique for multiple-input multiple-output (MIMO) systems that simultaneously obtains downlink multiuser diversity gain, spatial multiplexing gain and array gain by feeding back only effective signal-to-noise ratios (SNRs) is described. In addition, power control using waterfilling is employed to improve the throughput of our method in correlated channels. In a slow fading channel, we prove that the throughput of the proposed method converges to that of eigen beamforming when many users are in a cell. The number of users required to achieve capacity bound increases with the number of antennas and SNR was determined. However, the capacity bound is achieved even with a small number of users, e.g., 16 users in a cell, when the SNR is low, e.g., 0 dB, and the number of transmit and receive antenna is small, e.g., two. We also find that the effect of waterfilling is more noticeable in correlated channels.

Abstract: An apparatus is provided for high frequency multiplexed electrical line communication for cable TV, telephone, internet, security and other control applications over the mid and low voltage power lines and directly through the transformers. The apparatus includes a transmitter, a receiver, a modem (14), a multiplexer and multiple couplers (28) at each of two or more locations along an electrical line (18). The couplers have capacitive circuits serially connected with an air-core or dielectric-core transformer (22). The capacitive circuits resonate with the transformer (22) at a preselected frequency. The coupler (28) eliminates noise and is matched to the characteristic impedance of the line at the preselected frequency, which linearizes communication on the line and allows high speed data and voice communication over long distances. Multiple modulators and demodulators are used to produce multiple modulated carrier frequencies.

Abstract: We study channel estimation for orthogonal frequency-division multiplexing (OFDM) systems utilizing transmitter diversity and operating over multipath fading channels. Two expectation-maximization (EM)-type algorithms are introduced and compared with each other in terms of convergence rate. At each iteration and for every OFDM link, the EM-type algorithms partition the problem of estimating a multi-input channel into independent channel estimations for each transmit-receive antenna pair, therefore avoiding the matrix inversion encountered in the joint least-square estimation. The EM-type algorithms can also be used to efficiently implement a recently proposed algorithm, termed the significant-tap-catching estimator, so that the system performance is more robust to different multipath channel delay profiles.

Abstract: Disclosed is a multiplexing method and apparatus that allows holograms to be spatially multiplexed with partial spatial overlap between neighboring stacks of holograms. Each individual stack can additionally take full advantage of an alternate multiplexing scheme such as angle, wavelength, phase code, peristrophic, or fractal multiplexing, for example. An amount equal to the beam waist of the signal beam writing a hologram separates individual stacks of holograms. Upon reconstruction, a hologram and its neighbors will all be readout simultaneously. An filter is placed at the beam waist of the reconstructed data such that the neighbors that are read out are not transmitted to the camera plane. Alternatively, these unwanted reconstructions can be filtered out with an angular filter at an intermediate plane in the optical system that has a limited angular passband.

Abstract: This paper describes a method for realizing the efficient utilization of wavelength resources in wavelength-division multiplexing networks with centralized light sources. Using a deeply saturated semiconductor optical amplifier (SOA) modulator located in a remote node (RN), we erase the data on a downstream signal with a low extinction ratio and modulate it with new data to generate an upstream signal. Thus, we use only one wavelength for bidirectional transmission between a center node and an RN, without placing lasers at the RN. In this paper, we analyze the data suppression characteristic of the SOA using a large signal model. We also estimate the bit error rate degradation in the presence of an unsuppressed downstream bit pattern in an upstream signal. We then report experimental results that confirm the basic characteristics of the wavelength channel data rewriter, which we constructed using a linear amplifier and an SOA. Finally, we provide the results of a data transmission experiment that we undertook using the data rewriter.

Abstract: Spatial multiplexing multiple-input multiple-output (MIMO) wireless systems are of both theoretical and practical importance because they can achieve high spectral efficiencies by demultiplexing the incoming bit stream into multiple substreams. It has been shown that sending fewer substreams than the number of transmit antennas by linear precoding can provide improved error rate performance. Methods for designing linear precoders using perfect channel knowledge have previously been proposed. In many wireless systems, the assumption of complete channel knowledge is unrealistic because of the lack of forward and reverse channel reciprocity. To overcome this difficulty, we propose a precoding scheme that does not require transmit channel knowledge. The precoder is designed at the receiver and conveyed to the transmitter using a limited number of bits. The limited feedback represents an index within a finite set, or codebook, of precoding matrices. The receiver selects one of these codebook matrices using a modified version of a previously proposed full channel knowledge precoder selection criterion. A precoder codebook design method for maximizing the average effective channel power is shown to relate to chordal distance Grassmannian subspace packing. Simulation results show this technique outperforms antenna subset selection spatial multiplexing.

Abstract: A turbo decoder control comprises an address generator for addressing systematic data, parity data, and systematic likelihood ratios according to a pre-determined memory mapping. The systematic data samples are accessed in the order required by the MAP decoding algorithm such that interleaving and de-interleaving functions in the MAP decoding algorithm are performed in real-time, i.e., without delay. Such memory-mapping in combination with data handling functions (e.g., multiplexing and combinatorial logic) minimizes memory requirements for the turbo decoder and allows for use of programmable interleavers, variable block lengths, and multiple code rates.

Abstract: In this letter, we address the antenna subset selection problem in spatially correlated multiple-input multiple-output (MIMO) channels. To reduce the severe performance degradation of the traditional antenna selection scheme in correlated channels, we propose to embed fast Fourier transform operations in the RF chains. The resulting system shows a significant advantage both for diversity schemes and for the capacity of spatial multiplexing, while requiring only a minor hardware overhead.

Abstract: We discuss the implementation of a time-division superconducting quantum interference device (SQUID) multiplexing system for the instrumentation of large-format transition-edge sensor arrays. We cover the design and integration of cryogenic SQUID multiplexers and amplifiers, signal management and wiring, analog interface electronics, a digital feedback system, serial-data streaming and management, and system configuration and control. We present data verifying performance of the digital-feedback system. System noise and bandwidth measurements demonstrate the feasibility of adapting this technology for a broad base of applications, including x-ray materials analysis and imaging arrays for future astronomy missions such as Constellation-X (x-ray) and the SCUBA-2 instrument (submillimeter) for the James Clerk Maxwell Telescope.

Abstract: Microparticles (8, 72) includes an optical substrate (10) having at least one diffraction grating (12) disposed therein. The grating (12) having a plurality of colocated pitches A which represent a unique identification digital code that is detected when illuminated by incident light (24). The incident light (24) may be directed transversely from the side of the substrate (10) with a narrow band (single wavelength) or multiple wavelength source, in which case the code is represented by a spatial distribution of light or a wavelength spectrum, respectively. The code may be digital binary or may be other numerical bases. The micro-particles (8, 72) can provide a large number of unique codes, e.g., greater than 67 million codes, and can withstand harsh environments. The micro-particles (8) are functionalized by coating them with a material/substance of interest, which are then used to perform multiplexed experiments involving chemical processes, e.g., DNA testing and combinatorial chemistry.

Abstract: A random beamforming technique for MIMO systems that simultaneously obtains downlink multiuser diversity gain, spatial multiplexing gain, and array gain by feeding back only effective SNRs is described. In addition, power control using waterfilling is employed to improve the throughput of our method. In a slow fading channel, we prove that the throughput of the proposed method converges to that of eigen beamforming when many users are in a cell. The number of users required to achieve capacity bound increases with the number of antennas and SNR. However, the capacity bound is achieved even with a small number of users, e.g. 16 users is a cell, when the SNR is low, e.g., 0 dB, and the number of transmit and receive antenna is small, e.g., 2.

Abstract: This paper studies the performance of TCP transport protocol over an optical burst-switched (OBS) wavelength division multiplexed (WDM) wide-area network. Typically, an OBS network consists of optical core routers and electronic edge routers connected by WDM links. At the network ingress nodes, IP packets are assembled into bursts that are routed through the core network and disassembled at the network egress nodes. This paper studies the effects of OBS network characteristics and parameters on TCP's delay and throughput performance: (i) burstification (burst-assembly and disassembly) delays, (ii) data-burst scheduling and (iii) variation of burst packet parameters (i.e. burst size, burst time-outs), and (iv) burst drop probability. Detailed results based on an ns2-based simulator, that has been extended to incorporate WDM and OBS networking, are presented.

Abstract: Techniques to estimate the frequency response of a wireless channel in an OFDM system. In one method, an initial estimate of the frequency response of the wireless channel is obtained for a first group of subbands based on a pilot transmission received via the subbands in the first group. An estimate of the impulse response of the wireless channel is then derived based on the initial frequency response estimate. An enhanced estimate of the frequency response of the wireless channel is then derived for a second group of subbands based on the impulse response estimate. The first and second groups may each include all or only a subset of the usable subbands. Subband multiplexing may be used to allow simultaneous pilot transmissions by multiple terminals on their associated groups of subbands.

Abstract: The paper introduces to orthogonal frequency-division multiplexing (OFDM) systems a novel pseudo-orthogonal carrier interferometry spreading code which spreads each parallel data stream over all the OFDM carriers. Pseudo-orthogonal carrier interferometry (PO-CI) spreading codes are carefully selected to introduce the following benefits to OFDM: up to 2N parallel data streams can be coded onto N carriers, with little degradation in performance; when rate 1/2 channel coding is applied in addition to PO-CI spreading codes, the resulting binary phase-shift keying OFDM systems demonstrate the performance of coded OFDM and the throughput of uncoded OFDM; PO-CI codes are carefully selected to spread in a manner which eliminates the peak-to-average power ratio problems characteristic of traditional OFDM.

Abstract: With relatively simple standard transmission equipment, we achieved a wavelength-division-multiplexing transmission with a record-high spectral efficiency of 1.6 b/s/Hz using return-to-zero differential quadrature phase-shift keying and polarization multiplexing over 200-km standard single-mode fiber with a 40-Gb/s capacity per wavelength but 10-GSymbol/s rate.

Abstract: A new multiplexing method demonstrating the separation of two series of geometrically arranged fiber-optic distributed sensors in a Michelson interferometer (MI) configuration has been developed. This method can acquire data from two sensors, then propagate the data into one channel, and finally separate the data by determining their working point, which is essential for some remote measurements. The working point of one sensor was deflected from the normal MI by introduction of two reference arms. The deflection was extracted electrically and employed to label the sensor. Verification with commercial piezoelectric transducers proves the efficiency of the method.

Abstract: Disclosed is a method for changing channels in a digital television transport stream, which comprises accessing the digital television transport stream, itself comprising a plurality of multiplexed channels, by using a first tuner, displaying a first program channel from the digital television transport stream, detecting and storing in a buffer memory recent video data from a second channel while displaying the first channel by using a second tuner, immediately recalling and presenting a complete video frame from the stored video data of the second channel for display when the second channel is selected by the user, and displaying real-time video from the second channel when decodable real-time video data is available from the transport stream.

Abstract: The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme.

Abstract: A method of preparing data streams to facilitate seamless switching between such streams by a switching device to produce an output data stream without any switching artifacts. Bi-directional switching between any plurality of data streams is supported. The data streams are divided into segments, wherein the segments include synchronized starting points and end points. The data rate is increased before an end point of a segment, to create switch gaps between the segments. Increasing the data rate can include increasing a bandwidth of the plurality of data streams, for example by multiplexing, or compressing the data. The present invention can be used, for example, with MPEG or AC-3 encoded audio and MPEG encoded video segments that are multiplexed into MPEG-2 transport streams. Also included are specific methods for preparing MPEG video streams and multiplexing MPEG video with MPEG or AC-3 audio streams to allow a receiver to create seamless transitions between individually encoded segments.

Abstract: Promising to eliminate just about all of a home's signal cables, ultrawideband very-low-power wireless technology, when finally standardized, will be a carrier-based system most likely incorporating frequency hopping and orthogonal frequency-division multiplexing (OFDM). Its purpose: to replace almost every data cable in the home, even the ones going in and out of the television set, a job that requires moving hundreds of megabits of data per second. That' s faster than all but the speediest of wired networks. The speed is achieved, however, over distances of only 10 meters or so. Ultrawideband (UWB) handles anything from high-speed streams carrying real-time HDTV programs to images downloaded from a digital camera to low-speed timing signals for keeping clocks accurate.

Abstract: The paper describes the new world-wide broadcasting system Digital Radio Mondiale/spl trade/ (DRM/spl trade/) for the long, medium and short wave bands It is originated by the goal of the consortium members to develop a flexible and efficient audio and data broadcasting standard Better sound quality, more reliable reception in combination with additional service information make DRM a promising successor to analogue AM Achieving good audio quality becomes a challenging task due to the limited bandwidth of 9 or 10 kHz, especially in often strongly impaired channels Many other requirements, which were the basis for the system development, are illustrated The article gives an overview of the system architecture, including the components for multiplexing, modulation, channel coding and source coding Important receiver aspects, such as synchronization and channel estimation, are also described

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 channelization code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. Computer simulation results elucidate that bit-interleaving in the frequency domain is superior to chip-interleaving especially for a full channel load because bit-interleaving exhibits a large randomization effect of burst errors, while still maintaining code orthogonality. In time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency f/sub D/ = 1500 Hz, becomes SF/sub Time/ = 16, and it should be decreased to SF/sub Time/ = 8 for such a very fast fading environment using 16QAM modulation. When the channel load is light such as C/sub mux//SF = 0.25 (C/sub mux/ and SF denote the number of multiplexed codes and total spreading factor, respectively), the required average received signal energy per symbol-to-background noise power spectrum density ratio (E/sub s//N/sub 0/) is reduced as the spreading factor in the frequency domain is increased up to say SF/sub Freq/ = 32 for QPSK and 16QAM modulation, respectively (Note that, nevertheless, 16QAm modulation under such a lighter channel load condition is replaced by QPSK modulation together with two fold the channel load as 16QAM to achieve the same information bit rate). Meanwhile, when the channel load is close to full such as when C/sub mux//SF = 0.94, the optimum spreading factor in the frequency domain is SF/sub Freq/ = 1 for 16QAM modulation and SF/sub Freq/ = 1 to 8 for QPSK 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 hot-spot cell configurations assuming various channel conditions.

Abstract: We demonstrate six-channel 160-Gb/s wavelength-division-multiplexed transmission over 20 100-km spans of nonzero-dispersion fiber, with a spectral efficiency of 0.53 b/s/Hz. We achieve this result using optical-time-division multiplexing with polarization bit interleaving and return-to-zero differential-phase-shift-keying modulation format. We also operate at 170.6 Gb/s per channel to emulate the use of forward error correction.

Abstract: Even in millimeter-wave-band (mm-wave-band) radio-on-fiber (ROF) systems, wavelength-division multiplexing (WDM) combined with subcarrier multiplexing (SCM) is a practical and attractive way to increase the channel capacity in existing optical-frequency-interleaved fibers. In this paper, we propose a channel selection scheme for interleaved dense WDM/SCM mm-wave-band ROF signals that use optical heterodyne detection with dual-mode local light. The principle underlying this scheme is explained theoretically, and channel selection of the DWDM/SCM ROF signal after transmission over a 25-km-long standard single-mode optical fiber has been experimentally demonstrated.

Abstract: We consider path-based protection methods for two-link failures in mesh optical networks. Two link-disjoint backup paths are pre-computed for each source and destination node pair. We identify the scenarios where the backup paths can share their wavelengths without violating 100% restoration guarantee (backup multiplexing). We use integer programming to optimize the total capacity requirement for both dedicated-and shared-path protection schemes. Our results indicate that backup multiplexing significantly improves the efficiency of total capacity utilization. For the randomly generated demand sets, the shared-path scheme provides up to 37.5% saving in total capacity utilization over dedicated-path scheme. Backup multiplexing provides more saving for the demand set that has connection requests distributed more evenly. For the double link failure recovery methods, path-based methods are more efficient in capacity utilization than link-based methods. Dedicated-path scheme performs better than shared-link scheme in total capacity utilization on average.