Showing papers on "Bit error rate published in 2004"

Digital Communication over Fading Channels

Abstract: noncoherent communication systems, as well as a large variety of fading channel models typical of communication links often found in the real world, including single- and multichannel reception with a large variety of types. The book gives many numerical illustrations expressed in large collections of system performance curves, allowing the researchers or system designers to perform trade-off studies of the average bit error rate and symbol error rate. This book is a very good reference book for researchers and communication engineers and may also be a source for supplementary material of a graduate course on communication or signal processing. Nowadays, many new books attach a CD-ROM for more supplementary material. With the many numerical examples in this book, it appears that an attached CD-ROM would be ideal for this book. It would be even better to present the computer program in order to be interactive so that the readers can plug in their arbitrary parameters for the performance evaluation. —H. Hsu

Coded cooperation in wireless communications: space-time transmission and iterative decoding

Abstract: When mobiles cannot support multiple antennas due to size or other constraints, conventional space-time coding cannot be used to provide uplink transmit diversity. To address this limitation, the concept of cooperation diversity has been introduced, where mobiles achieve uplink transmit diversity by relaying each other's messages. A particularly powerful variation of this principle is coded cooperation. Instead of a simple repetition relay, coded cooperation partitions the codewords of each mobile and transmits portions of each codeword through independent fading channels. This paper presents two extensions to the coded cooperation framework. First, we increase the diversity of coded cooperation in the fast-fading scenario via ideas borrowed from space-time codes. We calculate bounds for the bit- and block-error rates to demonstrate the resulting gains. Second, since cooperative coding contains two code components, it is natural to apply turbo codes to this framework. We investigate the application of turbo codes in coded cooperation and demonstrate the resulting gains via error bounds and simulations.

A transmit preprocessing technique for multiuser MIMO systems using a decomposition approach

Abstract: We introduce a transmit preprocessing technique for the downlink of multiuser multiple-input multiple-output (MIMO) systems. It decomposes the multiuser MIMO downlink channel into multiple parallel independent single-user MIMO downlink channels. Some key properties are that each equivalent single-user MIMO channel has the same properties as a conventional single-user MIMO channel, and that increasing the number of transmit antennas of the multiuser system by one increases the number of spatial channels to each user by one. Simulation results are also provided and these results demonstrate the potential of our technique in terms of performance and capacity.

Digital Communications Over Fading Channels

Abstract: : In this report, the probabilities of bit error for the most commonly used digital modulation techniques are analyzed. Analytic solutions are developed for the probability of bit error when the signal is affected by the most commonly encountered impairment to system performance for a wireless channel, the transmission of the signal over a fading channel. In this report, the effect of a slow, flat Ricean fading channel on communications systems performance is examined. Since channel fading significantly degrades the performance of a communication system, the performance of digital communication systems that also use forward error correction channel coding is analyzed for hard decision decoding and, where appropriate, for soft decision decoding. Diversity, another technique to mitigate the effect of fading channels on digital communication systems performance, is also discussed. Also included is a discussion of the effect of narrowband noise interference, both continuous and pulsed, on digital communication systems. We then discuss the analysis of the probability of bit error for the combination of error correction coding and diversity. Following this, we briefly discuss spread spectrum systems. Next, we examine the link budget analysis and various models for channel loss. Finally, we examine in detail the second generation digital wireless standard Global System for Mobile (GSM).

A low complexity algorithm for proportional resource allocation in OFDMA systems

Abstract: Orthogonal frequency division multiple access (OFDMA) basestations allow multiple users to transmit simultaneously on different subcarriers during the same symbol period. This paper considers basestation allocation of subcarriers and power to each user to maximize the sum of user data rates, subject to constraints on total power, bit error rate, and proportionality among user data rates. Previous allocation methods have been iterative nonlinear methods suitable for offline optimization. In the special high subchannel SNR case, an iterative root-finding method has linear-time complexity in the number of users and N log N complexity in the number of subchannels. We propose a non-iterative method that is made possible by our relaxation of strict user rate proportionality constraints. Compared to the root-finding method, the proposed method waives the restriction of high subchannel SNR, has significantly lower complexity, and in simulation, yields higher user data rates.

A wideband frequency-shift keying wireless link for inductively powered biomedical implants

Abstract: A high data-rate frequency-shift keying (FSK) modulation protocol, a wideband inductive link, and three demodulator circuits have been developed with a data-rate-to-carrier-frequency ratio of up to 67%. The primary application of this novel FSK modulation/demodulation technique is to send data to inductively powered wireless biomedical implants at data rates in excess of 1 Mbps, using comparable carrier frequencies. This method can also be used in other applications such as radio-frequency identification tags and contactless smartcards by adding a back telemetry link. The inductive link utilizes a series-parallel inductive-capacitance tank combination on the transmitter side to provide more than 5 MHz of bandwidth. The demodulator circuits detect data bits by directly measuring the duration of each received FSK carrier cycle, as well as derive a constant frequency clock, which is used to sample the data bits. One of the demodulator circuits, digital FSK, occupies 0.29 mm/sup 2/ in the AMI 1.5-/spl mu/m, 2M/2P, standard CMOS process, and consumes 0.38 mW at 5 V. This circuit is simulated up to 4 Mbps, and experimentally tested up to 2.5 Mbps with a bit error rate of 10/sup -5/, while receiving a 5/10-MHz FSK carrier signal. It is also used in a wireless implantable neural microstimulation system.

How accurate channel prediction needs to be for transmit-beamforming with adaptive modulation over Rayleigh MIMO channels?

Abstract: Adaptive modulation improves the system throughput considerably by matching transmitter parameters to time-varying wireless fading channels. Crucial to adaptive modulation is the quality of channel state information at the transmitter. In this paper, we first present a channel predictor based on pilot symbol assisted modulation for multiple-input multiple-output Rayleigh fading channels. We then analyze the impact of the channel prediction error on the bit error rate performance of a transmit-beamformer with adaptive modulation that treats the predicted channels as perfect. Our numerical results reveal the critical value of the normalized prediction error, below which the predicted channels can be treated as perfect by the adaptive modulator; otherwise, explicit consideration of the channel imperfection must be accounted for at the transmitter.

Optimal insertion of pilot symbols for transmissions over time-varying flat fading channels

Abstract: Two major training techniques for wireless channels are time-division multiplexed (TDM) training and superimposed training. For the TDM schemes with regular periodic placements (RPPs), the closed-form expression for the steady-state minimum mean square error (MMSE) of the channel estimate is obtained as a function of placement for Gauss-Markov flat fading channels. We then show that among all periodic placements, the single pilot RPP scheme (RPP-1) minimizes the maximum steady-state channel MMSE. For binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) signaling, we further show that the optimal placement that minimizes the maximum uncoded bit error rate (BER) is also RPP-1. We next compare the MMSE and BER performance under the superimposed training scheme with those under the optimal TDM scheme. It is shown that while the RPP-1 scheme performs better at high SNR and for slowly varying channels, the superimposed scheme outperforms RPP-1 in the other regimes. This demonstrates the potential for using superimposed training in relatively fast time-varying environments.

Optimal minimum distance-based precoder for MIMO spatial multiplexing systems

Abstract: We describe a new precoder based on optimization of the minimum Euclidean distance d/sub min/ between signal points at the receiver side and for use in multiple-input multiple-output (MIMO) spatial multiplexing systems. Assuming that channel state information (CSI) can be made available at the transmitter, the three steps ( noise whitening, channel diagonalization and dimension reduction), which are currently used in investigations on MIMO systems, are performed. Thanks to this representation, an optimal d/sub min/ precoder is derived in the case of two different transmitted data streams. For quadrature phase-shift keying (QPSK) modulation, a numerical approach shows that the precoder design depends on the channel characteristics. Comparisons with maximum signal-to-noise ratio (SNR) strategy and other precoders based on criteria, such as water-filling (WF), minimum mean square error (MMSE), and maximization of the minimum singular value of the global channel matrix, are performed to illustrate the significant bit-error-rate (BER) improvement of the proposed precoder.

A modified weighted bit-flipping decoding of low-density Parity-check codes

Abstract: In this letter, a modified weighted bit-flipping decoding algorithm for low-density parity-check codes is proposed. Improvement in performance is observed by considering both the check constraint messages and the intrinsic message for each bit.

A simple cooperative extension to wireless relaying

Abstract: In this paper, we propose and analyze a simple protocol that simultaneously exploits two potentials offered by wireless relay systems: diversity gains and pathloss savings. An intermediate decode-and-forward relay assists transmission from source to destination, and the destination combines the signals it receives from source and relay. The key feature of the proposed system is that the relay node decides independently whether or not to forward information to the destination, thereby minimizing the risk of error propagation while providing truly constructive diversity gains. In combination with pathloss savings, this leads to significant gains over both direct transmission and conventional relaying. The results are obtained from an analysis of the end-to-end bit error rate, which are confirmed by simulation.

Iterative multiuser joint decoding: optimal power allocation and low-complexity implementation

Abstract: We consider a canonical model for coded code-division multiple access (CDMA) with random spreading, where the receiver makes use of iterative belief-propagation (BP) joint decoding. We provide simple density-evolution analysis in the large-system limit (large number of users) of the performance of the BP decoder and of some suboptimal approximations based on interference cancellation (IC). Based on this analysis, we optimize the received user signal-to-noise ratio (SNR) distribution in order to maximize the system spectral efficiency for given user channel codes, channel load (users per chip), and target user bit-error rate (BER). The optimization of the received SNR distribution is obtained by solving a simple linear program and can be easily incorporated into practical power control algorithms. Remarkably, under the optimized SNR assignment, the suboptimal minimum mean-square error (MMSE) IC-based decoder performs almost as well as the more complex BP decoder. Moreover, for a large class of commonly used convolutional codes, we observe that the optimized SNR distribution consists of a finite number of discrete SNR levels. Based on this observation, we provide a low-complexity approximation of the MMSE-IC decoder that suffers from very small performance degradation while attaining considerable savings in complexity. As by-products of this work, we obtain a closed-form expression of the multiuser efficiency (ME) of power-mismatched MMSE filters in the large-system limit, and we extend the analysis of the symbol-by-symbol maximum a posteriori probability (MAP) multiuser detector in the large-system limit to the case of nonconstant user powers and nonuniform symbol prior probabilities.

Rapid discrimination preambles and methods for using the same

Abstract: A system, method and program are disclosed for achieving rapid bit synchronization in low power medical device systems. Messages are transmitted via telemetry between a medical device and a communication device. The synchronization scheme uses a portion of a unique preamble bit pattern to identify the communication device allowing for economical communications with a minimum expenditure of energy. A special set of preamble bit patterns are utilized for their unique synchronization properties making them particularly suited for rapid bit synchronization. These unique preamble bit patterns further provide simplification to the preamble error detection logic.

Coarse frame and carrier synchronization of OFDM systems: a new metric and comparison

Abstract: We propose a fast and reduced complexity frame and carrier acquisition scheme for orthogonal frequency-division multiplex systems which assumes either a continuous or a burst mode operation in additive white Gaussian noise and frequency-selective channels. By exploiting the repetitive structure of a training symbol, a robust frame synchronizer is obtained and shown to resume to finding the peak of a certain correlation metric that is obtained by invoking maximum likelihood principles. A modified carrier estimator that can correct frequency offsets up to two subcarrier spacings is also proposed. The efficiency of the proposed synchronization algorithms is illustrated by both theoretical performance analysis and computer simulations.

Performance analysis of IEEE 802.11 DCF in presence of transmission errors

Abstract: IEEE 802.11 is worldwide established and the most used protocol for wireless local area networks (WLANs). In this paper, we propose an improved analytical model that calculates IEEE 802.11 DCF performance taking into account both the packet retry limits and transmission errors for the IEEE 802.11a protocol. Validation of our new analytical performance model results is carried out by comparison with the simulation results using the OPNET/sup TM/ simulation package. We explore the effect of transmission errors, packet retry limits, data rate and network size on the performance of the basic access scheme, in terms of throughput, packet delay, packet drop time and drop probability.

Power comparison between high-speed electrical and optical interconnects for interchip communication

Abstract: An I/O bandwidth commensurate with a dramatically increasing on-chip computational capability is highly desirable. Achieving this goal using board-level copper interconnects in the future will become increasingly challenging owing to severe increase in high-frequency, skin-effect and dielectric loss, noise due to crosstalk, impedance mismatch, and package reflections. The solutions designed to overcome these deleterious effects require complex signal processing at the interconnect endpoints, which results in a larger power and area requirement. Optical interconnects offer a powerful alternative, potentially at a lower power. Prior work in comparing the two technologies has entailed overly simplified assumptions pertaining to either the optical or the electrical system. In this paper, we draw a more realistic power comparison with respect to the relevant parameters such as bandwidth, interconnect length and bit error rate (BER) by capturing the essential complexity in both types of interconnect systems. At the same time, we preserve the simplicity by using mostly analytical models, verified by SPICE simulations where possible. We also identify critical device and system parameters, which have a large effect on power dissipation in each type of interconnect, while quantifying the severity of their impact. For optical interconnect, these parameters are detector and modulator capacitance, responsivity, coupling efficiency and modulator type; whereas, in the case of electrical system, the critical parameters include receiver sensitivity/offset and impedance mismatch. Toward this end, we first present an optimization scheme to minimize optical interconnect power and quantify its performance as a function of future technology nodes. Next, on the electrical interconnect side, we examine the power dissipation of a state-of-the-art electrical interconnect, which uses simultaneous bidirectional signaling with transmitter equalization and on-chip noise cancellation. Finally, we draw extensive comparisons between optical and electrical interconnects. As an example, for bandwidth of 6 Gb/s at 100 nm technology node, lengths greater than the critical length of about 43 cm yields lower power in optical interconnects. This length becomes lower (making optics more favorable) with higher data rates and lower bit error rate requirement.

Iterative channel estimation for turbo equalization of time-varying frequency-selective channels

Abstract: We investigate turbo equalization, or iterative equalization and decoding, as a receiver technology for systems where data is protected by an error-correcting code, shuffled by an interleaver, and mapped onto a signal constellation for transmission over a frequency-selective channel with unknown time-varying channel impulse response. The focus is the concept of soft iterative channel estimation, which is to improve the channel estimate over the iterations by using soft information fed back from the decoder from the previous iteration to generate "extended training sequences" between the actual transmitted training sequences.

Forward error correction based on block turbo code with 3-bit soft decision for 10-Gb/s optical communication systems

Abstract: The first experimental demonstration of a forward error correction (FEC) for 10-Gb/s optical communication systems based on a block turbo code (BTC) is reported. Key algorithms, e.g., extrinsic information, log-likelihood ratio, and soft decision reliability, are optimized to improve the correction capability. The optimum thresholds for a 3-bit soft decider are investigated analytically. A theoretical prediction is verified by experiment using a novel 3-bit soft decision large scale integrated circuit (LSI) and a BTC encoder/decoder evaluation circuit incorporating a 10-Gb/s return-to-zero on-off keying optical transceiver. A net coding gain of 10.1 dB was achieved with only 24.6% redundancy for an input bit error rate of 1.98/spl times/10/sup -2/. This is only 0.9 dB away from the Shannon limit for a code rate of 0.8 for a binary symmetric channel. Superior tolerance to error bursts given by the adoption of 64-depth interleaving is demonstrated. The ability of the proposed FEC system to achieve a receiver sensitivity of seven photons per information bit when combined with return-to-zero differential phase-shift keying modulation is demonstrated.

Error rate performance of coded free-space optical links over strong turbulence channels

Abstract: Error control coding can be used over free-space optical (FSO) links to mitigate turbulence-induced fading. We present error rate performance bounds for coded FSO communication systems operating over atmospheric turbulence channels, which are modeled as a correlated K distribution under strong turbulence conditions. We derive an upper bound on the pairwise error probability (PEP) and then apply the union-bound technique in conjunction with the derived PEP to obtain upper bounds on the bit error rate. Simulation results are further demonstrated to verify the analytical results.

A short wavelength GigaHertz clocked fiber-optic quantum key distribution system

Abstract: A quantum key distribution (QKD) system has been developed, using a standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The QKD system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single photon avalanche diodes as the single photon detectors. A distributed feedback laser of emission wavelength 1.3 /spl mu/m, and a linear gain germanium avalanche photodiode was used to optically synchronize individual photons over the standard telecommunications fiber. The QKD system exhibited a quantum bit error rate (QBER) of 1.4%, and an estimated net bit rate (NBR) greater than 100 000 bits/sup -1/ for a 4.2-km transmission range. For a 10-km fiber range, a QBER of 2.1%, and an estimated NBR of greater than 7000 bits/sup -1/ was achieved.

Bit error rate analysis of DS-CDMA with joint frequency-domain equalization and antenna diversity combining

Abstract: To improve the DS-CDMA signal transmission performance in a frequency-selective fading channel, the frequency-domain equalization (FDE) can be applied, in which simple one-tap equalization is carried out on each subcarrier component obtained by fast Fourier transform (FFT). Equalization weights for joint FDE and antenna diversity combining based on maximal ratio combining (MRC), zero-forcing (ZF), and minimum mean square error (MMSE) are derived. The conditional bit error rate (BER) is derived for the given set of channel gains in a frequency-selective multipath fading channel. The theoretical average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Performance comparison between DS- and multi-carrier (MC)-CDMA both using FDE is also presented.

Robust noncoherent receiver exploiting UWB channel properties

Abstract: Most UWB radio receivers discussed in the literature are coherent receivers, which can offer high signal sensitivity and support high data rates but require precise timing clock recovery and complex RAKE structures. For UWB radio systems requiring only lower data throughput, noncoherent receiver architectures offer a good performance-complexity tradeoff. In this paper, we describe a noncoherent receiver for 2PPM UWB signals. The key design parameter, the duration of signal integration, can be chosen such that a target BER is achieved for each element of a preselected set of channel realizations. Although the proposed receiver works without channel state information and complex RAKE frontend, its performance compares favorably with that of a coherent 2PAM RAKE receiver of low order. The simple noncoherent receiver exploits most of the multipath diversity offered by the channel and is robust to clock timing errors.

Multipath-enabled super-resolution for rf and microwave communication using phase-conjugate arrays.

Abstract: We demonstrate experimentally that phase-conjugate techniques can be used to achieve super-resolution focusing of electromagnetic waves in a multipath indoor environment at 2.45 GHz. The focusing phenomena was used to direct independent signals to two locations separated by approximately one-half wavelength, thereby creating two simultaneous channels at the same frequency. An increase in channel capacity is shown to be achievable by an experimental transmission of a 1 Mbps signal over two channels created using a four element phase-conjugate array.

Link error prediction methods for multicarrier systems

Abstract: Multicarrier modulations such as OFDM with adaptive modulation and coding (AMC) are well suited for high data rate broadband systems that operate in multipath environments and are considered as promising candidates for future generation cellular systems (e.g., 4G). Cellular system performance is normally investigated with system level simulations that are computationally complex. For broadband multicarrier systems, incorporating a detailed physical layer emulator into the system simulator becomes impractical, so there is a need for simplified link performance predictors. However, due to the large variability of the channel in the frequency domain, two links with the same average SNR can experience drastically different performance, thus making it difficult to accurately predict the instantaneous link performance such as the frame error rate. In this paper, the accuracy of two FER prediction methods is studied: Packet error rate indicator (PER-indicator) and exponential effective SIR mapping (Exp-ESM). Both methods are shown to have accuracy within a few tenths of a dB under a wide range of modulation schemes, coding rates and channel types. These methods are then extended to handle more advanced link enhancements such as hybrid ARQ and Alamouti encoding. The Exp-ESM method has slightly better accuracy than the PER-indicator, and is the preferred link error predictor for a system simulator.

Track identification codewords having multiple bit error correction capability and generalized gray code property

Abstract: The present invention may be embodied in a disk drive comprising a rotating magnetic media having tracks identified by binary codewords, and in a related method. Each track codeword for a particular track within a contiguous band of tracks differs from a track codeword for an adjacent track within the contiguous band of tracks by a defined number of bits, and differs from a track codeword for a nonadjacent track within the contiguous band of tracks by at least the defined number of bits. The defined number N of bits is greater than four such that at least two bit errors may be corrected when reading a track codeword.

Orthogonal polynomials for complex Gaussian processes

Abstract: Power amplifiers are the major source of nonlinearity in communications systems. Such nonlinearity causes spectral regrowth as well as in-band distortion, which leads to adjacent channel interference and increased bit error rate. Polynomials are often used to model the nonlinear power amplifier or its predistortion linearizer. In this paper, we present a novel set of orthogonal polynomials for baseband Gaussian input to replace the conventional polynomials and show how they alleviate the numerical instability problem associated with the conventional polynomials. The orthogonal polynomials also provide an intuitive means of spectral regrowth analysis.

Transmitter and receiver

Abstract: A receiver informs a delay profile and CIR measured in an FDE or a Rake receiver, together with a bit error rate of a received signal that is required in a receiver, as quality information to a transmitter. In the transmitter, based on the delay profile and CIR contained in the notified quality information, a number of code division multiplex and a frame format are decided in a decision circuit such that a bit error rate of a received signal, which is necessary on the receiver side, can be obtained. In addition, a transmission selection switch selects one of a unique word insertion unit and a cyclic prefix insertion unit that create a frame format for FDE reception and a pilot insertion unit and a complex scrambling unit that create a frame format for Rake reception, and data is then transmitted.

Jitter models for the design and test of Gbps-speed serial interconnects

Abstract: We present a comprehensive analysis of jitter causes and types, and develops accurate jitter models for design and test of high-speed interconnects. The recent deployment of gigabit-per-second (Gbps) serial I/O interconnects aims at overcoming data transfer bottlenecks resulting from the limited ability to increase chip pin counts in parallel bus architectures. The traditional measure of a communication link's performance has been its associated bit error rate (BER), which is the ratio of the number of bits received in error to the total number of bits transmitted. When data rates increase, jitter magnitude and signal amplitude noise must decrease to maintain the same BER. As data rates exceed 1 Gbps, a slight increase in jitter or amplitude noise has a far greater effect on the BER.

A novel trellis-shaping design with both peak and average power reduction for OFDM systems

Abstract: A new trellis shaping design is proposed for reducing the peak-to-average power ratio of the bandlimited orthogonal frequency-division multiplexing (OFDM) signals. The approach is based on recursive minimization of the autocorrelation sidelobes of an OFDM data sequence. A novel metric in conjunction with the Viterbi algorithm is devised. The performance of the trellis shaping depends on signal mapping strategy, and the two types of mapping, referred to as Type-I and Type-II, are proposed. The Type-I mapping has no capability of reducing the average power, but it can achieve a significant reduction of the peak-to-average power ratio. On the other hand, the Type-II mapping is designed to achieve both peak and average power reduction. The bit error probability of the system over an AWGN channel is evaluated based on the simulations, which confirms the effectiveness of the proposed scheme.

Layered space-frequency equalization in a single-carrier MIMO system for frequency-selective channels

Abstract: Frequency-domain equalization (FDE) has been shown to be an effective approach to combat frequency-selective wireless channels. In this letter, we propose a layered space-frequency equalization (LSFE) architecture for a single-carrier (SC) multiple-input multiple-output (MIMO) system, where MIMO FDE is employed at each stage or (layer) of detection. At a particular stage, a group of the best data streams in the minimum mean square error sense are detected and are canceled from the received signals. Simulation results show that our proposed LSFE structures can outperform layered space-time equalization (LSTE) structures and uncoded orthogonal frequency division multiplex (OFDM), especially at a higher delay spread. Performance is enhanced further, by incorporating the FDE with time-domain decision feedback at each stage of LSFE. We also provide performance analysis for LSFE, in comparison with OFDM.