Backward Compatibility Research Articles

DCache - joining the noWORM storage club

For over a decade, dCache.ORG has provided robust software, called dCache, that is used at more than 80 universities and research institutes around the world, allowing these sites to provide reliable storage services for the WLCG experiments and many other scientific communities. The flexible architecture of dCache allows running it in a wide variety of configurations and platforms - from all-in-one Raspberry-Pi up to hundreds of nodes in multi-petabyte infrastructures. The life cycle of scientific data is well defined - collected, processed, archived and finally deleted, when it’s not needed anymore. Moreover, during all those stages the data is never modified: either the original data is used, or new derived data is produced. With this knowledge, dCache was designed to handle immutable files as efficiently as possible. Data replication, HSM connectivity and data-server independent operations are only possible due to the immutable nature of stored data. Nowadays many commercial vendors provide such write-once-read-many or WORM storage systems, as they become more and more demanded with grown demand of audio, photo and video content in the web. On the other hand by providing standard NFSv4.1 interface dCache is often used as a general-purpose file-system, especially by new communities, like photon scientists or microbiologists. Although many users are aware of data immutability, some applications and use cases still require in-place updates of stored files. To satisfy new requirements some fundamental changes have to be applied to dCache’s core design. However, new developments must not compromise any aspect of existing functionality. In this presentation we will show new developments in dCache to turn it into a regular file system. We will discuss the challenges to build a distributed storage system, ‘life’ with POSIX compliance, handling of multiple replicas and backward compatibility by providing WORM and noWORM capabilities within the same storage system.

Reverse Cooperatively Routed Wi-Fi Direct in the Advent of 5G Driven Designs

In this article, the instantiation of the logic behind the so-called “Multi-Connect” mode of Wi-Fi Direct is advocated for and prescribed in order to make it possible to increase, if not multiply, the data throughput attainable by a given P2P Device thanks to traffic aggregation. In general, the described extension to the existing standard, defined by the Wi-Fi Peer-to-Peer (P2P) Technical Specification, enables the reversal of the logical roles of a P2P Group Owner (P2P GO) and its respective P2P Clients, while ensuring that the general architectural framework of Wi-Fi Direct should remain unchanged for backward compatibility reasons. This is achieved with the aid of a number of specifically tailored modifications including: new P2P Attribute allocation, extended Group Owner determination, modified P2P State Machine operation, enhanced Concurrent and Non-Concurrent operation, as well as expanded Reverse Operation Logic definition. The concept is illustrated with and verified through the analysis of cumulative virtual channel capacity and, therefore, the expected data throughput gain.

Reducing the Codeword Search Complexity of FDD Moderately Large MIMO Beamforming Systems

It is of great interest to develop larger scale multiple-input multiple-output (MIMO) technology based on frequency division duplexing (FDD) for backward compatibility with existing standards and already deployed cellular networks. One hindrance to the FDD approach is the complexity of the codeword search performed by the receiver, which is known to scale with the number of transmit antennas $N_{t}$ in a system. The codeword search complexity does not scale linearly and soon becomes infeasible even for the not-so-massive MIMO systems expected in the very near future. We address this problem by proposing a natural sequence-based orthogonal codebook and an intra-array interference magnitude (IIM) framework for MIMO beamforming based on quantized equal gain transmission that altogether tremendously simplifies the codeword search problem. We also present an assessment on the quality of the codeword selected by the proposed framework that explains it’s near optimal performance, and, provide detailed codeword search complexity quantification. Finally, we provide simulation analyses of beamforming gain under time selective fading channels and an FDD MIMO system transmit delay model. Our analyses indicate that despite significantly reducing complexity, the proposed IIM framework executed by already commercialized processors is capable of approaching the ideal performance of an static system even in the presence of time-selectivity inherent to high-speed mobile communications. Our analyses also quantify the impact of feedback delay on average beamforming gain of moderately large transmit arrays.

Multi-Dimensional Space–Time Shift Keying for Wireless Communications

In this paper, we introduce the concept of multi-dimensional (MD) space-time shift keying (STSK) for improving conventional STSK schemes, while still maintaining the general STSK structure for backward compatibility. Firstly, we design two transmission modes for three-dimensional (3-D) STSK schemes, referred to as R2 3-D STSK and R3 3-D STSK, with the incorporation of 3-D constellations. In addition, we devise a joint optimization mechanism utilizing the modified simplified conjugate gradient (SCG) algorithm to enhance the achievable system performance of R3 3-D STSK, through a harmonized design of the constellation and the dispersion matrix set. Furthermore, we derive the optimal combinations of the 3-D constellation coordinates for R2 3-D STSK by maximizing the minimal determinant of the difference matrices. Then, we extend 3-D STSK to the MD STSK family, offering a flexible and efficient performance enhancement mechanism for STSK systems. Extensive simulation results are provided to show the tradeoffs among link performance, diversity order and signal dimensionality of the proposed MD STSK scheme, illustrating a good way to upgrade conventional STSK systems.

Design and implementation of a real‐time software receiver for BDS‐3 signals

The BeiDou Navigation Satellite System (BDS) is currently building its third phase (BDS-3), which will provide services to users around the world. In addition to backward compatibility with BDS-2, BDS-3 satellites are equipped with the B1C and B2 interoperable signals for compatibility with GPS and Galileo systems. To evaluate performance and optimize processing methods, we designed and implemented a real-time software receiver with the ability to process all BDS-3 signals in parallel. A complete description of all signal processing aspects is given. To reduce the reliance on high-performance hardware while maintaining the independent analysis capabilities of acquisition performance in real-time software receivers, a B1I-aided acquisition method for reducing the search space of other signals from the same satellite is applied. An unambiguous tracking method is proposed to solve the ambiguity problem of the Quadrature Multiplexed Binary Offset Carrier (QMBOC) signal that can be used for matching reception of the pilot component of the B1C signal.

THE PROGRAMMING LANGUAGE FOR EMBEDDED REAL-TIME DEVICES WITH REDUCING ERRORS AND WITHOUT REDUCING THE PERFORMANCE OF PROGRAMS

Background. C or C ++ languages are most commonly used for programming of embedded systems. The main drawbacks are: lack of updates, difficulty in use, limited backward compatibility and potentially a large number of possible programmer errors. Therefore, it is important to provide developers of low-level software of embedded systems, operating systems and systemutilities with fast, productive, reliable and stable language on the basis of modern programming theory.Objective. The aim of the paper is to create a new productive and reliable programming language for embedded systems using the principles and approaches of modern programming theory.Methods. Analyzing well-known publications devoted to programming languages used for embedded systems allowed identifying their main advantages and disadvantages. Comparing of modern approaches to the implementation of programming languages allowed determining the requirements for the developed language.Results. A new programming language for embedded devices has been developed. The following compiler modules are described: lexer, parser, semantic analyzer, intermediate code generator. A detailed description of the developed programming language is presented.Conclusions. In this paper, we propose to use a new programming language for embedded devices. An analysis of existing programming languages and typical developer errors was performed to ensure the reliability of the proposed language.

Q-FRPML: QoS-Centric Fault-Resilient Routing Protocol for Mobile-WSN Based Low Power Lossy Networks

Considering the significance of mobile-Wireless Sensor Networks (WSNs) under Low Power Lossy Network (LLN) Conditions, in this paper a highly robust and QoS-Centric Fault-Resilient Routing Protocol for Mobile-WSN in LLN (Q-FRPML) has been proposed. Unlike classical routing approaches such as Routing Protocol for 6LowPAN based LLNs (RPL), our proposed Q-FRPML protocol contributes multiple novelties including received signal strength indicator (RSSI) based mobile node positioning for fault-resilient communication, proactive node management, RSSI and ETX objective functions based best parent node selection, link layer adaptive fault-resilient alternate path formation for QoS centric communication over mobile-WSNs. Q-FRPML protocol is implemented in parallel to the link layer of the classical RPL IEEE 802.15.4 protocol stack that once detecting any link-outage executes best parent node selection and alternate path formation to assure reliable data delivery. In this process, Q-FRPML avoids continuous network discovery that significantly reduces signaling overheads and energy consumption. Contiki-Cooja based simulation results have revealed that the proposed Q-FRPML protocol outperforms state-of-art native RPL or S-RPL protocol in terms of higher packet delivery ratio, lower packet loss ratio and end-to-end delay under varying network or load conditions. Though, Q-FRPML protocol has been applied in parallel to the native RPL, it preserves backward compatibility and hence can be applied in real-time mobile-WSN based QoS centric communication purposes.

Practical multiple scattering for rough surfaces

Microfacet theory concisely models light transport over rough surfaces. Specular reflection is the result of single mirror reflections on each facet, while exact computation of multiple scattering is either neglected, or modeled using costly importance sampling techniques. Practical but accurate simulation of multiple scattering in microfacet theory thus remains an open challenge. In this work, we revisit the traditional V-groove cavity model and derive an analytical, cost-effective solution for multiple scattering in rough surfaces. Our kaleidoscopic model is made up of both real and virtual V-grooves, and allows us to calculate higher-order scattering in the microfacets in an analytical fashion. We then extend our model to include nonsymmetric grooves, allowing for additional degrees of freedom on the surface geometry, improving multiple reflections at grazing angles with backward compatibility to traditional normal distribution functions. We validate the accuracy of our model against ground-truth Monte Carlo simulations, and demonstrate its flexibility on anisotropic and textured materials. Our model is analytical, does not introduce significant cost and variance, can be seamless integrated in any rendering engine, preserves reciprocity and energy conservation, and is suitable for bidirectional methods.

An Enhanced Fast Multi-Radio Rendezvous Algorithm in Heterogeneous Cognitive Radio Networks

In this paper, we propose a fast rendezvous algorithm for a heterogeneous cognitive radio network (CRN), where each user might have more than one radio. One of the well-known problems for most multiradio rendezvous algorithms in the literature is that they are not backward compatible to users with only one radio. To tackle this backward compatibility problem, our approach is a hierarchical construction that groups several time slots into an interval and proposes a novel algorithm to emulate two radios with a single radio in an interval. By doing so, at the interval level, each user behaves as if it had (at least) two radios. For the two-user rendezvous problem in a CRN with ${N}$ commonly labelled channels, the interval length is chosen to be ${M}$ time slots, where ${M=2\lceil \text {log}_{2} (\lceil \text {log}_{2} N \rceil)\rceil +7}$ . We show that the maximum time-to-rendezvous (MTTR) of our algorithm is bounded above by ${9 M \lceil n_{1}/m_{1} \rceil \cdot \lceil n_{2}/m_{2} \rceil }$ time slots, where ${n_{1}}$ (resp. ${n_{2}}$ ) is the number of available channels to user 1 (resp. 2), and ${m_{1}}$ (resp. ${m_{2}}$ ) is the number of radios for user 1 (resp. 2). For the setting that each user is equipped with only one radio and two available channels, our MTTR bound is only ${M}$ and that improves the state-of-the-art bound $16(\lceil \log _{2} \log _{2} N \rceil +1)$ in the literature. By conducting extensive simulations, we show that for the expected time-to-rendezvous, our algorithm is also better than several existing multiradio algorithms.

Protocol Design for Enabling Full-Duplex Operation in Next-Generation IEEE 802.11 WLANs

Full-duplex (FD) technology is under consideration for adoption in various legacy communications standards. The IEEE 802.11ax working group has been considering a simultaneous transmit and receive (STR) mode for the next-generation wireless local area networks (WLANs). Enabling STR mode (FD communication mode) in 802.11 networks creates bidirectional FD (BFD) and unidirectional FD (UFD) links. The key challenge is to integrate STR mode with minimal protocol modifications, while accounting for the coexistence of FD and legacy half-duplex (HD) stations (STAs) and backward compatibility. This paper proposes a simple and practical approach to enable STR mode in 802.11 networks while explicitly accounting for the peculiarities of BFD and UFD links along with the coexistence of FD and HD STAs. Key aspects of the proposed solution include FD capability discovery, handshake mechanism for channel access, node selection for UFD, adaptive acknowledgment timeout, and contention unfairness mitigation. A comprehensive analytical model has been developed to evaluate the gain of STR. Performance evaluation demonstrates the effectiveness of the proposed solution in realizing the gains of FD technology for next-generation WLANs.

Hybrid OFDM-Digital Filter Multiple Access PONs

Hybrid orthogonal frequency division multiplexing (OFDM) digital filter multiple access (DFMA) passive optical networks (PONs) are, for the first time, proposed and extensively investigated, where digital signal processing (DSP) based software-reconfigurable digital filtering is employed for each individual OFDM signal from various optical network units (ONUs), and a single fast Fourier transform operation and its following data recovery processes are implemented in a pipelined approach in the optical line terminal. As a direct result of combining both OFDMA and DFMA PON characteristics, the proposed hybrid OFDM-DFMA PON still maintains highly desirable features associated with DFMA PONs, more importantly, it also offers a number of unique advantages including great relaxation of digital filter DSP complexity and considerable reduction in transceiver cost, significantly enhanced upstream PON performance and its robustness and flexibility, as well as excellent backward compatibility with existing OFDM-based 4G networks. In this paper, an analytical hybrid OFDM-DFMA PON model is developed, and numerical simulations are performed to verify the validity of the proposed technique and also to examine the upstream hybrid OFDM-DFMA PON performance characteristics over representative 25-km standard single mode fibre IMDD PON systems. It is shown that in comparison with the DFMA PONs, the hybrid OFDM-DFMA PON can improve the upstream ONU EVM performance by >10 dB for relatively large received optical powers, and also increases the differential ONU launch power dynamic range by as large as 16 dB.

A Novel WLAN Vehicle-To-Anything (V2X) Channel Access Scheme for IEEE 802.11p-Based Next-Generation Connected Car Networks

To support a massive number of connected cars, a novel channel access scheme for next-generation vehicle-to-anything (V2X) systems is proposed in this paper. In the design of the proposed scheme, two essential aspects are carefully considered: backward compatibility and massive V2X support. Since IEEE 802.11p-based V2X networks are already being deployed and used for intelligent transport systems, next-generation V2X shall be designed considering IEEE 802.11p-based V2X networks to provide backward compatibility. Since all future cars are expected to be equipped with a V2X communication device, a dense V2X communication scenario will be common and massive V2X communication support will be required. In the proposed scheme, IEEE 802.11-based extension is employed to provide backward compatibility and the emerging IEEE 802.11ax standard-based orthogonal frequency-division multiple access is adopted and extended to provide massive V2X support. The proposed scheme is further extended with a dedicated V2X channel and a scheduled V2X channel access to ensure high capacity and low latency to meet the requirements of the future V2X communication systems. To demonstrate the performance of the proposed scheme thoroughly and rigorously, the proposed scheme is mathematically analyzed using a Markov model and extensive simulations are performed. In the dense V2X communication networks of the future, the proposed V2X communication scheme will provide high performance and reliability.

ARBAT: A flexible network architecture for QoE-aware communications in 5G systems

The expansion of the service scope of cellular networks to include a wide variety of services such as mobile broadband, Internet of Things, and mission-critical machine-type communications has significantly shaped the evolution towards 5G and beyond systems. All these services impose divergent and often mutually exclusive requirements in terms of data rate, latency, and energy efficiency. To satisfy heterogeneous requirements, 5G systems should have properties such as Quality-of-Experience awareness, adaptability and flexibility, scalability and reliability, support for multiple RATs, and backward compatibility, all at a low CAPEX and OPEX. To this end, software-defined networking and network function virtualization have been envisioned as key enabling technologies for 5G, and represent a major paradigm shift for 5G systems. In recent years, a plethora of software-defined mobile network architectures have been introduced worldwide, each with their unique features and drawbacks. Within this context, this paper introduces a new architecture called ARBAT which has been designed to satisfy and exceed the requirements put forth by 5G. ARBAT is characterized by many innovative features such as the Universal Network Device and Unified Cellular Network concepts, multi-slice modular resource management with the AirHYPE wireless hypervisor, network-user application interaction through the xStream platform, and simplified multi-tenant orchestration through ServiceBRIDGE. The novel features of the ARBAT infrastructure plane, data plane, control plane and Management and Orchestration entity are also explained in the paper in detail. Furthermore, a qualitative evaluation and feature comparison of ARBAT with other state-of-the-art architectures is conducted to demonstrate that ARBAT satisfies the aforementioned objectives of the 5G systems.

A Comprehensive Study and Performance Evaluation of HDR Video Coding

With production side for the HDR video being standardized, the distribution phase is still in its infancy. Although a number of promising HDR video coding methods exist, the standardization efforts for HDR video distribution are hampered due to limited performance evaluations. This paper addresses this shortcoming by first reviewing the existing HDR video coding methods categorically. A comprehensive performance evaluation is then presented of five state-of-the-art HDR video coding methods, namely HDR-MPEG, HDR10 (PQ), HLG HDR-TV, AdaptRes and SHVC-based coding method. The evaluation was performed on a HDR video dataset considering two HDR display configurations with four objective quality measures including HDR-VDP-2.2 and HDR-VQM quality metrics. The results reveal novel observations regarding two-layer backward-compatible HDR video coding methods indicating that these methods can provide better or similar HDR quality as in single-layer backward-compatible HDR video coding method HLG HDR-TV. Furthermore, HDR10 (PQ), the single-layer method designed for only HDR content delivery, outperforms the other evaluated methods in this work, demonstrating that best HDR quality can be achieved only without the constraint of backward compatibility. Finally, a discrepancy revealed in the performance, in terms of the HDR-VQM metric when compared to the other quality measures, is presented and its implications are discussed.

Equilibrium Analysis for Platform Developers in Two-Sided Market with Backward Compatibility

We consider a dominant platform provider operating both legacy and new platforms that connects users with suppliers in a two-sided market context. In addition to the typical indirect network effects in the two-sided market, backward compatibility works on the new platform. Thus, users joining the new one can also enjoy the services provided by suppliers using the legacy platform. Users and suppliers are linearly differentiated between two platforms as in the Hotelling model and play a subscription game of choosing one platform at the lower level. The suppliers in the new platform may suffer from congestion, which can be alleviated by platform provider’s investment on the new one. The platform provider also determines price margins for the supplier sides. Our equilibrium (eq.) analysis in the subscription game identifies an interior eq. (coexistence of both platforms in both sides). Though the backward compatibility plays a stabilizing role for the interior eq., its stability is fragile due to the network effects. Rather, some boundary eq.’s, where at least one side tips to the legacy or the new platform, are more likely to be stable. The backward compatibility is a key factor that characterizes the stable boundary eq.’s. The upper stage game is led by the platform provider, which tries to maneuver the system toward one of the stable boundary eq.’s using price margins and investment. The platform provider prefers an all-new boundary eq. when the indirect network effect and the maximum price margin for the new platform are large; thus, it puts a significant investment in the new one. With a small indirect network effect for suppliers, however, the platform provider does not invest in the new platform and choose a separate boundary eq. where two sides split into different platforms. Whether the user side completely tips to the new one (completely separated eq.) or not (partially separated eq.) depends on the backward compatibility. The relative advantage of the all-new eq. over the separate eq.’s in terms of social welfare from both sides depends on the backward compatibility as well as the indirect network effects for the new platform.

A 120 fps High Frame Rate Real-time HEVC Video Encoder with Parallel Configuration Scalable to 4K

This paper describes a new 120 fps (frames per second) real-time HEVC (High Efficiency Video Coding) encoder for HFR (high frame rate) video encoding and transmission. HFR provides more immersive viewing experience features by solving the problems created by fast moving scenes. Temporally scalable encoding with backward compatibility for legacy non-HFR systems is suitable for the rapid spread of HFR content delivery, avoiding the need to distribute multiple bitstreams of the same video with different frame rates. Such temporal scalability requires flexible encoder control functionalities to support newly-customized reference picture structures and dual-stream bitrate control. In this paper, modification in the customizable software architecture of encoder LSIs makes it possible to achieve 120 fps temporally scalable HEVC encoding for existing 60 fps-based systems. The encoder also achieves ${4\mathrm{K}/ 120\;\mathrm{fps}}$ video encoding in real time through the synchronized operation of multiple ${2\mathrm{K}/ 120\;\mathrm{fps}}$ encoders working in parallel. Our evaluations show that the bitrate increase rate from 60 fps to 120 fps under the same objective image quality condition are within the range of less than 57.2 percent in all video sequences and its average value is 53.8 percent. Both values are lower than that of the HM (HEVC reference software). The proposed encoder systems will open the door to the next generation high frame rate UHDTV (ultra high definition television) services.

Efficient and Low Complexity Surveillance Video Compression using Distributed Scalable Video Coding

Video surveillance has been playing an important role in public safety and privacy protection in recent years thanks to its capability of providing the activity monitoring and content analyzing. However, the data associated with long hours surveillance video is huge, making it less attractive to practical applications. In this paper, we propose a low complexity, yet efficient scalable video coding solution for video surveillance system. The proposed surveillance video compression scheme is able to provide the quality scalability feature by following a layered coding structure that consists of one or several enhancement layers on the top of a base layer. In addition, to maintain the backward compatibility with the current video coding standards, the state-of-the-art video coding standard, i.e., High Efficiency Video Coding (HEVC), is employed in the proposed coding solution to compress the base layer. To satisfy the low complexity requirement of the encoder for the video surveillance systems, the distributed coding concept is employed at the enhancement layers. Experiments conducted for a rich set of surveillance video data shown that the proposed surveillance - distributed scalable video coding (S-DSVC) solution significantly outperforms relevant video coding benchmarks, notably the SHVC standard and the HEVC-simulcasting while requiring much lower computational complexity at the encoder which is essential for practical video surveillance applications.

Production method for simulcast in 22.2 multichannel sound broadcasting

The 8K with 22.2 multichannel (22.2 ch) sound broadcasting is planned to be launched since December 2018 in Japan. NHK is going to simulcast 2-channel stereo and 5.1 surround together with the 22.2 ch sound for backward compatibility with existing home reproduction equipment, e.g., AV receiver and soundbar. However, individual production for each audio format is impractical because it needs many engineers and a lot of production equipment compared with a production in single format. Hence, an efficient production method for simulcast which does not demand additional production resources is required. The first proposal is a tone compensation for downmixing from the 22.2 ch sound to the other audio formats. The energy spectrum of the downmixed signal is compensated to harmonize with that of the 22.2 ch sound. The second proposal is a loudness chase to have the loudness level of the downmixed signal follow that of the 22.2 ch sound. The loudness level of the downmixed signal usually differs from that of the 22.2 ch sound, so that the loudness chase successively adjusts the loudness level without unnatural level change and matches them by the end of the program.

C: Adding modern programming language features to C

SummaryThe C programming language is a foundational technology for modern computing with millions of lines of code implementing everything from hobby projects to commercial operating systems. This installation base and the programmers producing it represent a massive software engineering investment spanning decades and likely to continue for decades more. Nevertheless, C, which was first standardized almost 30 years ago, lacks many features that make programming in more modern languages safer and more productive. The goal of the C project (pronounced “C for all”) is to create an extension of C that provides modern safety and productivity features while still ensuring strong backward compatibility with C and its programmers. Prior projects have attempted similar goals but failed to honor the C programming style; for instance, adding object‐oriented or functional programming with garbage collection is a nonstarter for many C developers. Specifically, C is designed to have an orthogonal feature set based closely on the C programming paradigm, so that C features can be added incrementally to existing C code bases, and C programmers can learn C extensions on an as‐needed basis, preserving investment in existing code and programmers. This paper presents a quick tour of C features, showing how their design avoids shortcomings of similar features in C and other C‐like languages. Experimental results are presented to validate several of the new features.

Two-Layer Lossless HDR Coding Using Histogram Packing Technique with Backward Compatibility to JPEG

An efficient two-layer coding method using the histogram packing technique with the backward compatibility to the legacy JPEG is proposed in this paper. The JPEG XT, which is the international standard to compress HDR images, adopts two-layer coding scheme for backward compatibility to the legacy JPEG. However, this two-layer coding structure does not give better lossless performance than the other existing methods for HDR image compression with single-layer structure. Moreover, the lossless compression of the JPEG XT has a problem on determination of the coding parameters; The lossless performance is affected by the input images and/or the parameter values. That is, finding appropriate combination of the values is necessary to achieve good lossless performance. It is firstly pointed out that the histogram packing technique considering the histogram sparseness of HDR images is able to improve the performance of lossless compression. Then, a novel two-layer coding with the histogram packing technique and an additional lossless encoder is proposed. The experimental results demonstrate that not only the proposed method has a better lossless compression performance than that of the JPEG XT, but also there is no need to determine image-dependent parameter values for good compression performance without losing the backward compatibility to the well known legacy JPEG standard.