Variable Bit Research Articles

An empirical approach towards characterization of encrypted and unencrypted VoIP traffic

VoIP traffic classification plays a major role towards network policy enforcements. Characterization of VoIP media traffic is based on codec behaviour. With the introduction of variable bit rate codecs, coding, compression and encryption present different complexities with respect to the classification of VoIP traffic. The randomness tests do not extend directly to classification of compressed and encrypted VoIP traffic. The paper examines the applicability of randomness tests to encrypted and unencrypted VoIP traffic with constant bit rate and variable bit rate codecs. A novel method Construction-by-Selection that constructs a test sequence from partial payload data of VoIP media session is proposed in this paper. The results based on experimentations on this method show that such construction exhibit randomness and hence allows differentiation of encrypted VoIP media traffic from unencrypted VoIP media traffic even in the case of variable bit rate codecs.

Reduction of Padding Overhead for RLNC Media Distribution With Variable Size Packets

Random linear network coding (RLNC) can enhance the reliability of multimedia transmissions over lossy communication channels. However, RLNC has been designed for equal size packets, while many efficient multimedia compression schemes, such as variable bitrate (VBR) video compression, produce unequal packet sizes. Padding the unequal packet sizes with zeros to the maximum packet size creates an overhead on the order of 20%–50% or more for typical VBR videos. Previous padding overhead reduction approaches have focused on packing the unequal packet sizes into fixed size packets, e.g., through packet bundling or chaining and fragmentation. We introduce an alternative padding reduction approach based on coding macro-symbols (MSs), whereby an MS is a fixed-sized part of a packet. In particular, we introduce a new class of RLNC, namely MS RLNC which conducts RLNC across columns of MSs, instead of the conventional RLNC across columns of complete packets of equal size. Judiciously arranging the source packets into columns of MSs, e.g., through shifting the source packets horizontally relative to each other, supports favorable MS RLNC coding properties. We specify the MS RLNC encoding and decoding mechanisms and analyze their complexity for a range of specific MS arrangement strategies within the class of MS RLNC. We conduct a comprehensive padding overhead evaluation encompassing both previous approaches of packing the unequal size packets into fixed size packets as well as the novel MS RLNC approaches with long VBR video frame size traces. We find that for small RLNC generation sizes that support low network transport delays, MS RLNC achieves the lowest padding overheads; while for large generation sizes, both the previous packing approaches and the novel MS RLNC approaches effectively reduce the padding overhead.

Power Control for Wireless VBR Video Streaming: From Optimization to Reinforcement Learning

In this paper, we investigate the problem of power control for streaming variable bit rate (VBR) videos over wireless links. A system model involving a transmitter (e.g., a base station) that sends VBR video data to a receiver (e.g., a mobile user) equipped with a playout buffer is adopted, as used in dynamic adaptive streaming video applications. In this setting, we analyze power control policies considering the following two objectives: 1) the minimization of the transmit power consumption, and 2) the minimization of the transmission completion time of the communication session. In order to play the video without interruptions, the power control policy should also satisfy the requirement that the VBR video data is delivered to the mobile user without causing playout buffer underflow or overflows. A directional water-filling algorithm, which provides a simple and concise interpretation of the necessary optimality conditions, is identified as the optimal offline policy. Following this, two online policies are proposed for power control based on channel side information (CSI) prediction within a short time window. Dynamic programming is employed to implement the optimal offline and the initial online power control policies that minimize the transmit power consumption in the communication session. Subsequently, reinforcement learning (RL) based approach is employed for the second online power control policy. Via simulation results, we show that the optimal offline power control policy that minimizes the overall power consumption leads to substantial energy savings compared to the strategy of minimizing the time duration of video streaming. We also demonstrate that the RL algorithm performs better than the dynamic programming based online grouped water-filling (GWF) strategy unless the channel is highly correlated.

Traffic-Based Side-Channel Attack in Video Streaming

Video streaming takes up an increasing proportion of network traffic nowadays. Dynamic adaptive streaming over HTTP (DASH) becomes the de facto standard of video streaming and it is adopted by Youtube, Netflix, and so on. Despite of the popularity, network traffic during video streaming shows an identifiable pattern which brings threat to user privacy. In this paper, we propose a video identification method using network traffic while streaming. Though there is bitrate adaptation in DASH streaming, we observe that the video bitrate trend remains relatively stable because of the widely used variable bit-rate (VBR) encoding. Accordingly, we design a robust video feature extraction method for eavesdropped video streaming traffic. Meanwhile, we design a VBR-based video fingerprinting method for candidate video set which can be built using downloaded video files. Finally, we propose an efficient partial matching method for computing similarities between video fingerprints and streaming traces to derive video identities. We evaluate our attack method in different scenarios for various video content, segment lengths, and quality levels. The experimental results show that the identification accuracy can reach up to 90% using only three-minute continuous network traffic eavesdropping.

Coverless Text Steganography Based on Maximum Variable Bit Embedding Rules

As a carrier of information hiding, text is difficult to hide secret because of its less redundancy. The robustness and security of some traditional methods based text are not high. Based on Markov chain model, a coverless text steganography algorithm was proposed in this paper. According to the characteristic and value of transition probability in the model, the algorithm used the maximum variable bit embedding instead of the usual fixed bit embedding. In order to verify the effectiveness of the algorithm, different datasets and algorithms were selected to test. By comparing with results, the proposed model had higher concealment and hidden capacity.

Performance Analysis and FPGA Prototype of Variable Rate GO-OFDMA Baseband Transmission Scheme

To fulfill the increasing demand for high speed Variable Bit Rate (VBR) broadcast services with reliable Quality of Service, Group Orthogonal-Orthogonal Frequency Division Multiple Access (GO-OFDMA) and Variable Spreading Length Multicarrier Code Division Multiple Access transmission schemes are examined over Land Mobile Satellite (LMS) channel. This paper presents the performance analysis of aforementioned multiple access transmission schemes in terms of computation complexity, Peak-to-Average-Power-Ratio (PAPR) and the average Bit Error Rate (BER) performance over L-band LMS channel. Minimum Mean Square Equalizer (MMSE) equalizer is employed at the receiver. Based on the simulation results, GO-OFDMA stems out to be a better variable rate transmission scheme in respect of both PAPR and BER performance for higher data rate users. Further, GO-OFDMA based VBR transmitter and MMSE equalizer are prototyped on commercially available virtex5 xc5vlx110t–1ff1136 Field Programmable Gate Array (FPGA) device. A block-by-block analysis of hardware resource utilization and power dissipation for the VBR GO-OFDMA transmitter is provided. The achieved baud rate for VBR GO-OFDMA transmission scheme on FPGA is 103.874 Msps. Thus, GO-OFDMA transmission scheme could be appropriate for VBR communication over LMS channel.

Analysis of Variable Bit Rate SOFDM Transmission Scheme Over Multi-Relay Hybrid Satellite-Terrestrial System in the Presence of CFO and Phase Noise

In this paper, the exact closed-form signal-to-interference-noise ratio (SINR) expression, for the joint impact of carrier frequency offset (CFO) and phase noise (PHN), is derived for each channel link in a multi-relay hybrid satellite-terrestrial broadcast system, employing the Walsh Hadamard (WH) based spread-orthogonal frequency multiplexing (S-OFDM) and OFDM transmission scheme at satellite terminal and terrestrial repeaters (relays) respectively. Additionally, bit error rate and spectral efficiency are analyzed for such hybrid system with $M$ -relay, based on the obtained SINR expressions. To examine that, an adaptive decode and forward (ADF) strategy is employed at relay terminals. Also, three-state Fontan Land Mobile Satellite and six-path typical urban terrestrial channel models are considered. This analysis is performed to support variable bit rate (VBR) quality of service at the physical layer of Digital Video Broadcast Satellite Handheld (DVB-SH)-A architecture, the provision of which is absent in the DVB-SH standard. VBRs are assumed for S-OFDM. The results illustrate that both single-relay and three-relay ADF-based VBR WH-SOFDM yield an identical performance in the presence of the combined effect of CFO and PHN, under both performance measures. However, the improvement in performance for the three-relay strategy is observed in the presence of CFO only. Further, a pilot-based channel estimation technique is performed at the receiver, and the estimated error variance is evaluated for every channel link. Later, the block-by-block system computational complexity of single-relay and $M$ -relay ADF-based VBR WH-SOFDM is evaluated. It is shown that the complexity of the $M$ -relay ADF strategy is rate dependent and almost $M-1$ times the single-relay strategy. Hence, an increase in the number of relays would not yield any significant performance gain, but would enhance the system computational complexity considerably. Therefore, for high data rate transmission, the single-relay ADF-based WH-SOFDM scheme could be a suitable candidate for hybrid satellite-terrestrial communication systems in future.

Elastic QoS Scheduling with Step-by-Step Propagation in IEEE 802.11e Networks with Multimedia Traffic

The spreading diffusion of wireless devices and the crowded coexistence of multimedia applications greedy of bandwidth and with strict requirements stress the service provisioning offered by wireless technologies. WiFi is a reference for wireless connectivity and it requires a continuous evolution of its mechanism in order to follow increasingly demanding service needs. In particular, despite the evolution of physical layer, some critical contexts, such as industrial networks, telemedicine, telerehabilitation, and virtual training, require further refined improvements in order to ensure the respect of strict real-time service requirements. In this paper an in-depth analysis of Dynamic TXOP HCCA (DTH) MAC enhanced centralized scheduler is illustrated and it is further refined introducing a new improvement, DTH with threshold. DTH and DTH with threshold can be integrated with preexisting centralized schedulers in order to improve their performances, without any overprovisioning that can negatively impact on the admission control feasibility test. Indeed, without modifying the centralized scheduler policy, they combine together the concepts of reclaiming transmission time and statistical estimation of the traffic profile in order to provide, at each polling, an instantaneous transmission time tailored to the variable traffic requirements, increasing, when necessary, the service data rate. These mechanisms can coexist with advanced physical layer-based solutions, providing the required service differentiation. Experimental results and theoretical analysis, based on elastic scheduler theory, show that they are effective especially in the case of Variable Bit Rate traffic streams in terms of transmission queues length, packets loss, delay, and throughput.

Analysis of Variable Bit Rate WH/CI‐Spread OFDM based Integrated Satellite‐Terrestrial Broadcast System

In this study, the exact closed-form signal-to-interference-noise ratio (SINR) expression, for the impact of Doppler frequency shift on minimum mean square error receiver is derived for Walsh Hadamard (WH) and polyphase carrier interferometry (CI) code based multicarrier spread orthogonal frequency division multiplexing (SOFDM) transmission scheme over integrated satellite–terrestrial broadcast system. Additionally, bit error rate and spectral efficiency are analysed based on the obtained SINR expression. To examine that, three-state Fontan land mobile satellite, and six-path typical urban and rural area terrestrial channel models are employed. This analysis is performed to substantiate variable bit rate (VBR) quality of service at the physical layer of digital video broadcast satellite handheld (DVB-SH)-A architecture, the provision of which is absent in DVB-SH standard. VBR is assumed for SOFDM. The results illustrate that WH-SOFDM outperforms CI-SOFDM under both performance measures in all the three channel environments. Further, pilot-based channel estimation technique is performed and the estimated error variance is evaluated for VBR WH/CI-SOFDM. Later, block-wise system computational complexity of WH/CI-SOFDM schemes is evaluated. It is shown that, CI-SOFDM is a relatively more complex system than WH-SOFDM. Thus, a trade-off is present between the achieved performance gain and system complexity.

Geometric Modeling and Manufacturing Method for a few Teeth Involute Gear with Bilateral Modification

Aiming at the issue of undercutting and machining difficulties caused by gear with a few teeth, the geometric modeling method and processing method of bi-directional displacement less tooth number were studied. Based on the calculation formula of the involute cylindrical gear and the characteristics of the bi-directional gear, the calculation formula of the diameter of the variable tooth top circle is derived, and the modeling of the gear pair with bi-directional variable bit number is carried out. The research shows that the bidirectional displacement can solve the root cutting problem well and improve the transmission quality. In view of the problem that machining efficiency is not high at present, a method of machining with tangent and radial gear is proposed, and the same gear cutter is used to process different cutting and radial gears, and the feasibility of the above method is verified by the processing test. The research work laid a foundation for further promotion and application of small tooth number gear transmission.

Adaptive Scheduling Mechanism with Variable Bit Rate Traffic in EPON

Abstract In Ethernet Passive Optical Network, with Load Adaptive Polling Sequence Arrangement (LASA) method, the Optical Line Terminal assigns delayed polling sequence arrangement for a set of Optical Network Units (ONUs) over the cycles. This arrangement has resulted in identical cycle time with Constant Bit Rate traffic. In addition, the LASA through its arrangement provides sleep mode to different set of ONUs over the cycles and provides maximum sleep time for ONUs. With these advantages of LASA and keeping the scenario with different cycle times for the ONUs, in this work, the Variable Bit Rate (VBR) based LASA method is analyzed. The variation in the cycle times has resulted in two cases and in each case by varying the maximum (Mxi) and the minimum (Mni) idle times, a maximum of 40.6% reduction in power consumption is observed in LASA with VBR scheduling method than traditional one.

Resource Provisioning for a Multi-Layered Network

Given the growth, complexity, and size of the Internet, new methodologies are needed to support cost-effective resource provisioning. This paper provides a cost-based polynomial-time heuristic algorithm for resource provisioning optimization called multi-layered market algorithm (MMA). The MMA is solvable for multi-layered, multi-technology, and practical-sized networks, where the traffic is modeled as a combination of constant bit-rate and variable bit-rate (VBR) traffic streams. A VBR stream is modeled either by a Gaussian process or by a Poisson Pareto burst process (PPBP) which under certain parameter values is long-range dependent – a known characteristic of the Internet traffic streams. The consideration of VBR traffic models in a multi-layered network optimization is a key novel aspect of MMA. The MMA considers a range of transport technologies operating in layers and traffic sharing schemes. The MMA implements flow-size-based routing where flows according to their sizes are routed independently. As routing affects resource requirement, such considerations are important for resource provisioning by the given cost models. The complexity resulting from these considerations, including layering and PPBP traffic, requires a simplified design philosophy which in this paper, is based on adopting the shortest path routing in each layer. This is achieved by MMA which is based on an iterative algorithm, and resource provisioning that is performed link-by-link in all layers. As a benchmark for MMA, we provide an integer linear programming (ILP) formulation for a multi-layered network optimization problem with fixed end-to-end demands. The MMA is validated by comparing its solutions to those ILP results in different variants of a six-node network, and its software is verified using double-entry bookkeeping – a method commonly used in accounting systems. The MMA runs on a platform called network mark-up language, which enables visualization and further validation of the results.

FastScan: Robust Low-Complexity Rate Adaptation Algorithm for Video Streaming over HTTP

This paper proposes and evaluates a novel algorithm for streaming video over HTTP. The problem is formulated as a non-convex optimization problem which is constrained by the predicted available bandwidth, chunk deadlines, available video rates, and buffer occupancy. The objective is to optimize a QoE metric that maintains a tradeoff between maximizing the playback rate of every chunk and ensuring fairness among different chunks for the minimum re-buffering time. We propose FastScan, a low complexity algorithm that solves the problem. The online adaptations for dynamic bandwidth environments are proposed with imperfect available bandwidth prediction. The results of experiments driven by variable bit rate (VBR) encoded video, video platform system (dash.js), and cellular bandwidth traces of a public dataset reveal the robustness of the online version of FastScan algorithm and demonstrate its significant performance improvement as compared to the considered state-of-the-art video streaming algorithms. For example, on an experiment conducted over 100 real cellular available bandwidth traces of a public dataset that spans different available bandwidth regimes, our proposed algorithm (FastScan) achieves the minimum re-buffering (stall) time and the maximum average playback rate in every single trace as compared to Bola, Festive, BBA, RB, FastMPC, and Pensieve algorithms.

Algorithm for Enhancing the QoS of Video Traffic over Wireless Mesh Networks

One of the major issues in a wireless mesh networks (WMNs) which needs to be solved is the lack of a viable protocol for medium access control (MAC). In fact, the main concern is to expand the application of limited wireless resources while simultaneously retaining the quality of service (QoS) of all types of traffic. In particular, the video service for real-time variable bit rate (rt-VBR). As such, this study attempts to enhance QoS with regard to packet loss, average delay, and throughput by controlling the transmitted video packets. The packet loss and average delay of QoS for video traffic can be controlled. Results of simulation show that Optimum Dynamic Reservation-Time Division Multiplexing Access (ODR-TDMA) has achieved excellent utilization of resource that improvised the QoS meant for video packets. This study has also proven the adequacy of the proposed algorithm to minimize packet delay and packet loss, in addition to enhancing throughput in comparison to those reported in previous studies.

UNPU: An Energy-Efficient Deep Neural Network Accelerator With Fully Variable Weight Bit Precision

An energy-efficient deep neural network (DNN) accelerator, unified neural processing unit (UNPU), is proposed for mobile deep learning applications. The UNPU can support both convolutional layers (CLs) and recurrent or fully connected layers (FCLs) to support versatile workload combinations to accelerate various mobile deep learning applications. In addition, the UNPU is the first DNN accelerator ASIC that can support fully variable weight bit precision from 1 to 16 bit. It enables the UNPU to operate on the accuracy-energy optimal point. Moreover, the lookup table (LUT)-based bit-serial processing element (LBPE) in the UNPU achieves the energy consumption reduction compared to the conventional fixed-point multiply-and-accumulate (MAC) array by 23.1%, 27.2%, 41%, and 53.6% for the 16-, 8-, 4-, and 1-bit weight precision, respectively. Besides the energy efficiency improvement, the unified DNN core architecture of the UNPU improves the peak performance for CL by 1.15 $\times$ compared to the previous work. It makes the UNPU operate on the lower voltage and frequency for the given DNN to increase energy efficiency. The UNPU is implemented in 65-nm CMOS technology and occupies the $4 \times 4$ mm2 die area. The UNPU can operates from 0.63- to 1.1-V supply voltage with maximum frequency of 200 MHz. The UNPU has peak performance of 345.6 GOPS for 16-bit weight precision and 7372 GOPS for 1-bit weight precision. The wide operating range of UNPU makes the UNPU achieve the power efficiency of 3.08 TOPS/W for 16-bit weight precision and 50.6 TOPS/W for 1-bit weight precision. The functionality of the UNPU is successfully demonstrated on the verification system using ImageNet deep CNN (VGG-16).

Reversible AMBTC-Based Data Hiding With Security Improvement by Chaotic Encryption

Social networking and cloud computing are being extensively used, and in this era, the frequency of sending information or images to each other is increasing. The prevention of private information leakage during communication over the Internet has become a concern in the past decades. Several data protection methods, such as cryptographic, watermarking, and steganography techniques, have been proposed to protect private data. In this paper, an embedding method is proposed based on an absolute moment block truncation coding (AMBTC)-compressed image. High and low mean tables are extracted from a compressed image and are divided into non-overlapping blocks. An adaptive variable N-bit bit plane truncation image embedding method is proposed to embed the secret data in each block. In this method, at the receiver end, the secret data are extracted, and the original AMBTC image could be recovered by recalling the stored peak and zero points. In addition, a chaotic encryption scheme is integrated into the proposed system to improve robustness against security vulnerability. The results show that the proposed method has superior performance and higher payload compared with the reference methods.

Chaos assisted variable bit steganography in transform domain

An efficient variable bit data hiding scheme based on combined chaotic system (CCS) and integer wavelet transform (IWT) is proposed. With the aim to maximise the security level, CCS is developed by combining two 1D chaotic maps. The developed combined tent-logistic (CTL), combined sine-logistic (CSL) and combined sine-tent (CST) maps with improved chaotic behaviour are utilised to generate the key sequences. These chaotic key sequences from CTL, CSL and CST are then quantised to embed the secret bits in high-high, high-low and low-high sub-bands of the IWT transformed cover image, respectively. The main advantage of this scheme is that the number of bits to be embedded in each and every sub-band coefficients is highly chaotic and extremely sensitive to the initial seeds.

Experimental demonstration of quasi-omni-directional transmitter for underwater wireless optical communication based on blue LED array and freeform lens

Abstract In this paper, we propose a transmitter with 150odivergence angle and more than 90% uniformity of radiation intensity for quasi-omni-directional underwater wireless optical communication (UWOC) by applying freeform lens into LED array. We demonstrate its performance under different transmitting directions with 19Mbps data rate and 8m communication distance in an experimental tank whose volume is 20m × 20m × 14m and attenuation coefficient is about 0.40m−1. The result shows that the variation of bit error rate (BER) is about three orders of magnitude with the help of freeform lens when direction deviation angle is between -75oand +75o, which is reduced five orders compared with the situation without the lens. The presented result is useful to make it easier to establish communication link and improve the performance of UWOC system when transmitter direction shake exists. Also, it implies that we could apply different freeform lenses into LED array to reshape transmitting illumination according to different demands for UWOC application.

Non-uniform Quantized Data Fusion Rule for Data Rate Saving and Reducing Control Channel Overhead for Cooperative Spectrum Sensing in Cognitive Radio Networks

In this paper a pretty new concept of non-uniform quantized data fusion (N-QDF) rule reducing control channel data overhead has been proposed for energy detection based cooperative spectrum sensing scheme in cognitive radio networks. To strike a balance between efficient detection performance and less complexity, the network has to allow soften hard or quantized data fusion (QDF) technique though this technique incurs few bit overhead on the control channel from each user. Again lower bit QDF causes loss of more information, where as higher bit QDF increases detection probability at the cost of some extra bits per user. Here lies the beauty of NQDF scheme which uses variable number of bits: more number of bits for lower energy region—thus increases detection probability for a given false alarm, and less number of bits for higher energy region—thus data rate gets saved which in turn alleviates control channel overhead. A holistic simulation study has been done in this very paper where the performance of variable bit NQDF scheme is compared with different uniform bit i.e. 2, 3, 4, 5 QDF with respect to different parameters to validate our proposed scheme.

Noniterative Content-Adaptive Distributed Encoding Through ML Techniques

Distributed encoding is desirable for content preparation cloud workflows to reduce turnaround times. Content-adaptive bit allocation strategies have been proposed to achieve efficiencies in storage and delivery. Many of these methods tend to be iterative in nature and consume significant additional compute resources. There is a need to limit this increase in computational complexity. In this paper, we propose a noniterative codec-agnostic approach that employs machine learning techniques to achieve average bitrate savings and a target consistent quality by selecting a content-adaptive bitrate and resolution for each adaptive bitrate (ABR) segment within each ABR representation in a manner that makes it equally suitable for live and on-demand workflows. Test results are presented over a wide range of content types. Initial results indicate that the proposed approach can recover ~85% of the bit savings possible with more exhaustive techniques while its computational complexity is only 15%–20% of two-pass variable bitrate (VBR) encoding.