Bit Rate Efficiency Research Articles

A Scalable High Utilization Itemset Mining Technique for Large Datasets Using A Bit-Based Model

Objectives: Utility-list based algorithms have gained a lot of traction due to their efficiency and the ease with which they may be modified. While there have been some enhancements, the problem of inefficiency persists. This research presents a solution to this issue by enhancing the utility-list building process, a crucial function that has received little attention in previous studies. Also, the research aims at reducing memory complexity and better performance than existing approaches. Methods: To expedite building, a new set of bitwise operations termed Bit combine construction (BCC) is proposed. In addition, BCC is supported by a unique data format called EBP (Efficiency Bit Partition). An innovative EBP-Miner algorithm is developed with this framework in mind, and it uses many techniques to narrow the search field. Findings: On widely used baseline methods, experimental findings reveal that EBP-Miner outperforms numerous state-of-the-art techniques, including FEACP as well as CLH-Miner approaches. The experiments were conducted with utilization value ranging from 20% to 100% of the nodes. The proposed system achieves an average of 390s runtime and utilization value of 90.25% which are outperformed the existing methods. Also, the approach has proven 20% lesser memory complexity than of the existing algorithms. Novelty: In the field of data mining, high utility itemset mining (HUIM) is an important challenge. The idea is to discover groups of data in a database that are particularly significant or profitable in order to unearth information that can aid in making decisions. The novelty of this study is on developing a better method for building algorithms for HUIM that make use of a bitwise data structure, and on suggesting a more time- and effort-effective strategy for building utility-lists. Keywords: High Utility Itemsets; Data Mining; Optimization Model; Bitwise Operations; Pattern Mining

A Bit-Interleaved Sigma-Delta-Over-Fiber Fronthaul Network for Frequency-Synchronous Distributed Antenna Systems

Cell-free massive multiple-input multiple-output (MIMO) has attracted wide attention as wireless spectral efficiency has become a 6G key performance indicator. The distributed scheme improves the spectral efficiency and user fairness, but the fronthaul network must evolve to enable it. This work demonstrates a fronthaul network for distributed antenna systems enabled by the bit-interleaved sigma-delta-over-fiber (BISDoF) concept: multiple sigma-delta modulated baseband signals are time-interleaved into one non-return-to-zero (NRZ) signal, which is converted to the optical domain by a commercial QSFP and transmitted over fiber. The BISDoF concept improves the optical bit-rate efficiency while keeping the remote unit complexity sufficiently low. The implementation successfully deals with an essential challenge—precise frequency synchronization of different remote units. Moreover, owing to the straightforward data paths, all transceivers inherently transmit or receive with fixed timing offsets which can be easily calibrated. The error vector magnitudes of both the downlink and uplink data paths are less than 2.8% (–31 dB) when transmitting 40.96 MHz-bandwidth OFDM signals (256-QAM) centered around 3.6 GHz. (Optical path: 100 m multi-mode fibers; wireless path: electrical back-to-back.) Without providing an extra reference clock, the two remote units were observed to have the same carrier frequency; the standard deviation of the relative jitter was 9.43 ps.

HyperSight: A Precise Decoding Algorithm for VLC With Mobile-Phone Camera

In this paper, we propose and experimentally demonstrate HyperSight, which is a precise image decoding algorithm for the mobile-phone camera based visible light communication (VLC) system. The conventional algorithms have to select an appropriate column matrix, and then decode the image according to the fitting curve. The selection of the column matrix and the fitting of the function are not only time-consuming but also error-prone, leading to low decoding efficiency and high bit error rate (BER). While HyperSight calculates characteristic grayscale matrix to avoid column matrix selection and uses critical grayscale to replace the function fitting to decode the image. As expected, our algorithm not only reduces the BER, but also improves the processing performance. The experimental results show that, the BER can be reduced by two orders of magnitude on average compared with the conventional scheme. For the $4.8\,$ kbps data rate, our algorithm can achieve the transmission distance of $50\,$ cm under the $7\%$ forward error correction (FEC) threshold with the low illuminance of $702\,$ lux.

Distributed Antenna System Using Sigma-Delta Intermediate-Frequency-Over-Fiber for Frequency Bands Above 24 GHz

The fifth generation (5G) cellular network is expected to include the millimeter wave spectrum, to increase base station density, and to employ higher-order multiple-antenna technologies. The centralized radio access network architectures combined with radio-over-fiber (RoF) links can be the key enabler to improve fronthaul networks. The sigma-delta modulated signal over fiber (SDoF) architecture has been proposed as a solution leveraging the benefits of both digitized and analog RoF. This work proposes a novel distributed antenna system using sigma-delta modulated intermediate-frequency signal over fiber (SDIFoF) links. The system has an adequately good optical bit-rate efficiency and high flexibility to switch between different carrier frequencies. The SDIFoF link transmits a signal centered at a 2.5 GHz intermediate frequency over a 100 m multi-mode fiber and the signal is up-converted to the radio frequency (24–29 GHz) at the remote radio unit. An average error vector magnitude (EVM) of 6.40% (−23.88 dB) is achieved over different carrier frequencies when transmitting a 300 MHz-bandwidth 64-QAM OFDM signal. The system performance is demonstrated by a 2 × 1 multiple-input single-output system transmitting 160 MHz-bandwidth 64-QAM OFDM signals centered at 25 GHz. Owing to transmit diversity, an average gain of 1.12 dB in EVM is observed. This work also evaluates the performance degradation caused by asynchronous phase noise between remote radio units. The performance shows that the proposed approach is a competitive solution for the 5G downlink fronthaul network for frequency bands above 24 GHz.

AV1: Implementation, Performance, and Application

With the finalization of the AVI specification, the Alliance for Open Media (AOM) has set high expectations for it. The prospect of a royalty-free alternative to high efficiency video coding (HEVC) has many supporters in the industry, particularly those seeking a standard for streaming applications that is optimized for over-the-top (OTT) delivery quite excited. Fundamental to AV1’s success will be the transfer of a toolset of efficient software implementations that can deliver the expected performance over existing compression standards within the constraints of future server provision. Efficient implementations of AV1 will require a careful balance between utilizing bespoke processor features to offload demanding processor-intensive functions and the desire to have a platform-agnostic compression standard that can be applied across a wide range of infrastructures. As with all complex compression schemes, realizing a software mapping of the toolset is crucial. This is true for AV1, which, being royalty-free, utilizes algorithms and methods that are different from those used in the Motion Picture Experts Group (MPEG) suite of standards. This article will look at the application challenges facing AV1 and compare its objective performance to that of the HEVC in terms of bitrate efficiency and encode time.

Hybrid Pre-Coding Based on Minimum SMSE Considering Insertion Loss in mmWave Communications

Hybrid pre-coding design is a promising research direction in large antenna array millimeter wave (mmWave) systems. The insertion loss is an inherent and significant feature of hybrid pre-coding, resulting in lower energy efficiency and inferior bit error rate (BER) performance. This paper takes the minimum sum-mean-square-error (Min-SMSE) considering the insertion loss as the optimization objective function, which aims at increasing the sum-rate and improving the BER performance. Then a hybrid pre-coding is designed based on this criterion with an adaptive overlapped subarray (OSA) architecture. It is proved that the optimization problem is non-convex. Thus, we decompose the optimization problem into two sub-optimum ones. One is to design the digital pre-coding based on the Min-SMSE criterion under the equivalent channel condition. The other one is to design the analog pre-coding based on the simplified Min-SMSE with the insertion loss objective function. Theoretical analyses of the proposed scheme are conducted, including the upper bound of the average BER, the lower bound of the average sum-rate, and the computational complexity. Simulation results show that our proposed scheme outperforms three representative hybrid pre-coding schemes with different architectures in both BER and sum-rate, when the numbers of the phase shifters and combiners are relatively small.

Optimized Layered/Enhanced ACO-SCFDM for Short-Reach Optical Interconnects

This letter is the first experimental demonstration of layered/enhanced asymmetrically clipped optical single-carrier frequency-division multiplexing (L/E-ACO-SCFDM) in short-reach optical interconnects. An optimized method is employed to significantly improve the performance of L/E-ACO-SCFDM. L/E-ACO-SCFDM has higher spectral efficiency than ACO-SCFDM, and it also has lower peak-to-average power ratio and computational complexity than L/E-ACO orthogonal frequency-division multiplexing (L/E-ACO-OFDM). In the experimental system, the low-cost electrical and optical devices are utilized, which induce serious high-frequency distortion caused by bandwidth limitation. Under the same spectral efficiency and net bit rate, the optimized L/E-ACO-SCFDM has about 4-dB and more than 3-dB receive sensitivity improvement at 7% forward error correction limit compared with the optimized L/E-ACO-OFDM and the optimized ACO-SCFDM, respectively. Therefore, L/E-ACO-SCFDM is a promising scheme for the future short-reach optical interconnects.

High energy efficiency for low error rate in wireless relay networks

A new method to increase energy efficiency (EE) and decrease bit error rate (BER) in amplify-and-forward (AF) relay networks is presented in this study. In this network, the source transmitted signal through flat fading channel to a set of intermediate relay nodes which amplify and then forward the signal to the destination through a set of independent flat fading channels. The proposed EE is derived in a balanced scheme with spectral efficiency (SE), when relay nodes locations are taken into consideration. This balance between EE and SE is achieved by minimising power consumption. The BER for this balance is analysed and the relationship between BER and EE is derived. All analytical expressions are validated by numerical analysis and simulation. It is found that only a small increase in EE leads to a reduction in BER.

Self-Coherent OFDM With Undersampling Downconversion for Wireless Communications

In this paper, we introduce self-coherent orthogonal frequency-division multiplexing (OFDM), a well-known non-coherent technique in optical communications, for wireless radio frequency communications. Self-coherent OFDM provides complete immunity against phase noise (PN) using a non-coherent receiver and a significantly higher spectral efficiency than self-heterodyne (self-het) OFDM, which utilizes at most 50% of the available spectrum for communications. We present the performance analysis of self-coherent OFDM over additive white Gaussian noise and frequency selective fading channels, and show by simulations that self-coherent OFDM provides both higher spectral efficiency and better bit error rate performance than self-het OFDM. Considering that filter realization in high-frequency bands is challenging, we adopt the undersampling downconversion technique in conjunction with self-coherent OFDM. We show that with the self-coherent demodulation, the additional PN introduced by undersampling downconversion can be significantly reduced. We compare analytically the system performance of self-coherent OFDM using undersampling downconversion with two other conventional OFDM systems: one with super-heterodyne receiver and the other with undersampling downconversion. We show theoretically and by simulations that both in AWGN and frequency selective fading channels, self-coherent OFDM with undersampling downconversion outperforms the two conventional OFDM systems even when intercarrier interference compensation schemes are applied.

The case for random access in OFDMA femtocells

Data services in current cellular networks are growing exponentially, due to the proliferation of high-end mobile devices (smartphones, tablets, ereaders) supporting ever increasing multimedia applications. Clearly, availing of new spectrum (as with 4G allocations) is a necessary part of meeting this challenge, but so are improved network architectures that achieve enhanced spatial spectral efficiency (bits per second per Hertz per area). 4G network operators are moving toward a heterogeneous architecture consisting of overlaid cells of various sizes. A variety of low-power, small-cell base stations and relays are being deployed to increase capacity around local, typically indoor hotspots. The primary concern in such scenarios is understanding the nature and impact of inter-cell interference in dense deployments of such unmanaged small cells, and arriving at solutions for its mitigation. Resource allocation in traditional wide-area cellular networks usually assume a fully loaded network (i.e. many simultaneous active users in a cell) where the system performance is insensitive to the activity of a single user. This assumption is not suitable for femtocells which are designed to serve very few (indoor) users and thus lacks the presumed traffic aggregation. This article provides a fresh look at the femtocell interference problem from a multiple access perspective. It first compares the multi-channel features inherent to OFDMA with traditional multi-channel MAC designs for wireless LANs and highlights how the ability to schedule users in both time and frequency as afforded by OFDMA, can be exploited to achieve more effective (distributed) random access. A simplified MAC model that hides the complexity of LTE protocol stack is proposed to facilitate the design and analysis of random access MAC algorithms in the context of OFDMA femtocells.

SINR and Throughput Analysis for Random Beamforming Systems with Adaptive Modulation

In this paper, we derive the exact probability distribution of post-scheduling signal-to-interference-plus-noise ratio (SINR) considering both user feedback and scheduling. We also develop an optimized adaptive modulation scheme in orthogonal random beamforming systems with M transmit antennas and K single-antenna users. The exact probability distributions of each user's feedback SINR and the exact post-scheduling SINR are derived rigorously by direct integration and multinomial distribution. It is also shown that the derived cumulative distribution function (CDF) of the post-scheduling SINR happens to be identical to the the existing approximate CDF for SINR higher than 0 dB. The closed form expressions of system performance, such as average spectral efficiency (ASE) and average bit error ratio (A-BER), are derived using the CDF of the post-scheduling SINR. The optimal SINR thresholds that maximize the ASE with a target A-BER constraint are solved using the derived closed form CDF and a Lagrange multiplier. Key contributions of this paper include the derivation of the exact CDF of post-scheduling SINR by direct integration, and its application to an optimized adaptive modulation based on a Lagrange multiplier. Simulations show the correspondence between theoretical and empirical CDF's, and the performance improvement of the proposed adaptive modulation method in terms of ASE.

Bandwidth efficient bidirectional 5 Gb/s overlapped-SCM WDM PON with electronic equalization and forward-error correction

We demonstrate an improved overlapped-subcarrier multiplexed (O-SCM) WDM PON architecture transmitting over a single feeder using cost sensitive intensity modulation/direct detection transceivers, data re-modulation and simple electronics. Incorporating electronic equalization and Reed-Solomon forward-error correction codes helps to overcome the bandwidth limitation of a remotely seeded reflective semiconductor optical amplifier (RSOA)-based ONU transmitter. The O-SCM architecture yields greater spectral efficiency and higher bit rates than many other SCM techniques while maintaining resilience to upstream impairments. We demonstrate full-duplex 5 Gb/s transmission over 20 km and analyze BER performance as a function of transmitted and received power. The architecture provides flexibility to network operators by relaxing common design constraints and enabling full-duplex operation at BER ∼ 10(-10) over a wide range of OLT launch powers from 3.5 to 8 dBm.

Joint Adaptive Modulation and Distributed Switch-and-Stay for Partial Relay Selection Networks

In this letter, we propose a distributed switch-and-stay combining network with partial relay selection and show that the system spectral efficiency can be improved via adaptive modulation. Analytical expressions for the achievable spectral efficiency and average bit error rate of the proposed system over Rayleigh fading channels are derived for an arbitrary switching threshold. Numerical results are gathered to substantiate the analytical derivation showing that in terms of spectral efficiency, the system with single relay outperforms that with more than one relay at high signal-to-noise ratios (SNRs) and the optimal switching threshold can significantly improve the system performance at medium SNRs.

Bit-Rate Efficiency of H.264 Encoders Measured With Subjective Assessment Techniques

In this study we evaluated the bit-rate efficiency of current hardware H.264 encoders as compared to that of established MPEG-2 hardware encoders. To estimate bit-rate efficiency, we measured the subjective video quality of MPEG-2 encoded material processed at three bit rates: 8, 12, and 16 Mbps, and determined the bit-rate at which H.264 encoded material produced similar subjective video quality. The MPEG-2 and H.264 bit rates that resulted in the same perceived video quality were used to estimate bit-rate efficiency.

A novel method for increasing the spectral efficiency of optical CDMA

Given K simultaneously active users, an Optical CDMA (OCDMA) receiver needs to discriminate among K codes. Since the number of available codes C is always C Gt K at any given time for any truly asynchronous OCDMA system that employs quasi-orthogonal codes, there is always a set of unused codes. We here propose to exploit these unused codes to increase the spectral efficiency of the system. This can be accomplished by exclusively assigning to each user a set of M codes which represent a log2(M)-tuple of bits so that each user effectively uses a multi-dimensional modulation (multiple information bits per code are conveyed). In this paper, we analyze the performance of such a system and find in closed form an upper bound on the average probability of error. Moreover, we report for the first time that, under lightly loaded, non interference-limited conditions, the multi-dimensional OCDMA scheme here proposed allows us to obtain both higher spectral efficiency and lower bit- error probability (BEP) than a conventional OCDMA system, which employs one code only per user. The analysis here presented allow us to formulate a useful system design criterion that yields truly asynchronous OCDMA systems with very high spectral efficiency.

Analysis of force variance for a continuous miner drum using the Design of Experiments method

Continuous miners (CMs) are excavating machines designed to extract a variety of minerals by underground mining. The variance in force experienced by the cutting drum is a very important aspect that must be considered during drum design. A uniform variance essentially means that an equal load is applied on the individual cutting bits and this, in turn, enables better cutting action, greater efficiency, and longer bit and machine life. There are certain input parameters used in the drum design whose exact relationships with force variance are not clearly understood. This paper determines (1) the factors that have a significant effect on the force variance of the drum and (2) the values that can be assigned to these factors to minimize the force variance. A computer program, Continuous Miner Drum (CMD), was developed in collaboration with Kennametal, Inc. to facilitate the mechanical design of CM drums. CMD also facilitated data collection for determining significant factors affecting force variance. Six input parameters, including centre pitch, outer pitch, balance angle, shift angle, set angle and relative angle were tested at two levels. Trials were configured using the Design of Experiments (DoE) method where 26 full-factorial experimental design was selected to investigate the effect of these factors on force variance. Results from the analysis show that all parameters except balance angle, as well as their interactions, significantly affect the force variance.

Coefficient grouping method for shape-adaptive DCT

A generalised transform scheme for arbitrarily shaped image segments for the purpose of image compression is presented. The main feature of the scheme is an adaptive coefficient grouping method used in the second stage of the DCT. Experimental results show that this transform scheme performs better in terms of transform efficiency and maximum reducible bits than the methods proposed in for all the image models used.

Performance Comparisons Among Digital Radio Techniques Subjected to Multipath Fading

A major source of impairment in microwave digital radio is multipath fading, a phenomenon sufficiently prevalent on many paths to frustrate, the attainment of reliability objectives. Performance during multipath fading depends on such system parameters as channel bandwidth and type of modulation, and on details of the receiver processing (e.g., adaptive schemes, synchronization schemes). This paper compares the performance of different digital radio techniques in the presence of multipath fading. The measure used is the expected fraction of time, conditioned on the occurrence of a fading event, that the eye pattern at the receiver detector is closed. This measure is plotted against spectral efficiency (bit rate/channel bandwidth) for various types of modulation (QPSK, offset QPSK, 8-PSK, 16-PSK, 16-QAM, and offset 16-QAM) and for various forms of carrier recovery, timing recovery, transmit/receive filtering, and adaptive equalization. The computations assume a multipath fading frequency response described by a first-order complex polynomial, where the coefficients obey an empirically derived probability law reported previously. The comparisons show clearly the superiority of high-level modulation and the inferiority of offset modulation. The comparisons also demonstrate significant improvements for each of two adaptive equalizers postulated here.

System Aspects of Remote-Data-Access Ocean Measurements

The influence of economics interacting with measurement requirements on the recent evolution of ocean measurement systems is noted, particularly with respect to the costs of operating ships. The logical future course of this evolution toward remote-data-access systems, i.e., unattended systems from which data are accessible during the observation period, is noted. The concept of program reliability is differentiated from system reliability. Two measures of system effectiveness are defined: data-acquisition cost efficiency (bits/$) and systemcost-access index (bits/$-day). A hypothetical measurement problem is approached through two unattended systems, one a remote-data-access concept and one a data-isolated concept. The various measures of merit derived illustrate the economic and operational superiority of the remote-data-access concept under the conditions defined.

Equivalent Quantum Efficiency and the Information Content of Photographic Images

AbstractNoise-equivalent quantum efficiency and responsive quantum efficiency of a photographic emulsion are explained and a definition of its information storage capacity at a given mean density level is formulated on the basis of Shannon's information theory. The definition involves the conventional assumption that the intensity distributions to be recorded by the emulsion are random and of low contrast. Some conventional assumption about these distributions is unavoidable because the Shannon information content of a received message does not depend only on the message itself. Currently available data about photographic emulsions only permit their information storage capacity to be evaluated over a restricted range of spatial frequencies. For photographic systems one can define the analogous concept of the informational equivalent quantum efficiency (bits per unit object-contrast density per photon). This concept provides a figure of merit for photographic systems which takes account in a physically sig...