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As software products increasingly become part of larger ecosystems, research and development (R&D) units of software producers organize themselves around projects to become more responsive to the environment. Organizations participating in software ecosystems must continuously adapt and adjust their software development and maintenance processes to drive both medium-term and long-term innovation. Agile methods and practices are widely adopted to guide the collaboration within and between project teams in software development. Moreover, when successfully attained, agility can drive innovation by enabling software development organizations to cope with technological changes and exploit emerging opportunities in software ecosystems. In this article, we focus on how organizations attain agility in the maintenance and development of software products. To answer this question, we conduct a longitudinal case study of Agile Scrum implementation in the R&D unit of a major supplier of telecommunication equipment. We investigate the emerging tensions and highlight practices used to balance these tensions in the Agile Scrum implementation. We identify four capabilities and ten practices that support effective collaboration and coordination in the development and maintenance of software products. The study offers practical guidance for R&D managers to attain agility in software ecosystems. [ABSTRACT FROM AUTHOR]

In this article, an event-triggered distributed state estimation mechanism is proposed for general linear systems that comprise several subsystems. Two distributed moving horizon estimation (MHE) algorithms that can handle constraints on disturbances and noise are proposed. An event scheduler is exploited to govern the evaluation of the estimators and networked information exchange between the plant and the estimators, such that good estimates can be provided while both the usage of processors and networked communication frequency can be reduced. The estimation error provided by the event-triggered estimation mechanism is proven to be convergent and bounded. A numerical example and a chemical process example are used to verify the effectiveness and applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Environmental pollutants are a source for reliability issues across data center and telecommunications equipment. A primary driver of this is the transport and deposition of particle matter (PM2.5, PM10) on printed circuit boards, electronic components, and heat exchange surfaces. This process is enhanced by turbulent air flows generated from cooling fans. Particle pollutants can persist after contemporary filtering, highlighting the importance of elucidating particle transport mechanisms and utilizing this information to design robust equipment. This study investigates particle transport behavior arising from axial fans operating under varied aerodynamic conditions. Transient, multiphase numerical simulations were performed to model the flow of millions of microscale particles in air and determine their fate. Across a comprehensive range of fan operation conditions, from aerodynamic stall to free delivery, nondimensional deposition velocities spanned an order of magnitude. Deposition profiles vary from monotonic to nonmonotonic behavior, influenced by local flow impingement, blade tip vortices, and shear velocity. A simple flow control solution that mitigates the factors influencing deposition has been demonstrated for equipment already deployed. The findings and numerical methods can be applied for the optimization of fan-cooled equipment intended for indoor and outdoor environments where air quality is poor, or pollution levels are high. [ABSTRACT FROM AUTHOR]

This article addresses the minimum-loss control of the dual voltage-source inverter (VSI) and doubly fed induction generator (DFIG) system connected to a dc link. The minimum-loss operating conditions for field-oriented control based on the airgap flux are obtained analytically using Lagrange multipliers and validated with numerical optimization. As the main contribution of this article, the analysis accounts for core and VSI losses, providing the optimal stator frequency law and rotor/stator d-axis current split ratio, and an implicit expression for the optimal flux trajectory formulated as equality between suitable d-axis and q-axis loss functions. In the proposed implementation, this implicit condition is enforced by using a proportional-integral controller and avoiding look-up tables. Furthermore, the stator and rotor VSI controls are implemented in two independent digital signal processors with no communication, which may ease the use of off-the-shelf VSI units. The optimal conditions and control strategy are fully validated by simulations and experiments on a prototype. The main scope of application is wind-energy dc-grid technology. [ABSTRACT FROM AUTHOR]

Passive two-phase cooling systems are an efficient and viable alternative to conventional air-cooling schemes for thermal management of electronics due to their capability of dissipating higher power densities with lower power consumption and noise levels. This article aims to assess the performance of a novel two-phase air-cooled thermosyphon for cooling shelf-level telecommunications equipment that is designed with 18 line cards. In particular, the main objective is to investigate the effect of the condenser technology on the thermal-hydraulic performance of the cooling system. The thermosyphon consists of a multimicrochannel evaporator with 18 individual microchannel zones (one per card) connected to an air-cooled condenser via riser and downcomer tubes. The total height of the loop, from midevaporator to midcondenser, is approximately 50 cm. Two different condenser designs have been tested: a single-pass louvered-fin flat-tube condenser, and a multipass wavy-fin, circular-tube condenser. An extensive experimental campaign is performed to evaluate the performance of these two air-cooled condensers in a front-to-back airflow configuration. The experiments are carried out with R134a as the working fluid, varying filling ratios from 45% to 60%, and heat loads from 102 to 1023 W under uniform and nonuniform conditions. The influence of the air-side fan configuration is also investigated by varying the fans speed from 10 548 to 15 480 min−1 and by increasing the fan-tray height from 65 to 103 mm. The results demonstrate that the single-pass louvered-fin flat-tube condenser provides lower liquid-side frictional pressure drops and consequently higher refrigerant mass flow rate in the loop. This leads to a higher critical heat flux value, which is ideal for increasing power densities and limiting dry-out occurrence. On the other hand, the multiple-pass wavy-fin, condenser offers lower thermal resistances over a larger range of dissipated heat loads. This is mainly attributed to its lower air-side pressure drop. [ABSTRACT FROM AUTHOR]

In Europe, market access for radio equipment is governed through the Radio Equipment Directive (RED), which replaced the Radio Equipment and Telecommunications Terminal Equipment (R&TTE) Directive in 2016. The essential requirements were introduced by RED and subsequently processed by European standards organizations: the European Telecommunications Standards Institute, the European Committee for Electrotechnical Standardization, and the European Committee for Standardization, in order to develop harmonised standards (HSs). These HSs may be used by manufacturers in order to achieve self-declaration of conformity of radio equipment. Compared to the previously applicable R&TTE Directive, RED contains a set of new Articles, including RED Articles 3(3)(a) to 3(3)(i) and Article 4, which were not enacted when RED was originally published. This article discusses the process for "activating" the corresponding articles, and provides commentary on related ongoing activities in European Commission Expert Groups and detailed implications on radio equipment design. Indeed, new requirements need to be met in order to achieve market access, such as reconfigurability, privacy, and security features. Finally, implications such as time to market and RED compliance certification cost are assessed, and a comparison to other regulation regimes is given, including those in the United States, Korea, and Russia. [ABSTRACT FROM AUTHOR]

Bloom filters have been used to reduce the delay in networking and computing applications when a set membership check is to be applied. Error sources can affect the behavior of Bloom filters resulting in a wrong outcome of this membership test and a possible effect in the system's output. Single event transients are a type of temporary errors altering the operation of combinational logic. A single event transient affecting the hash generation logic of a hardware-implemented Bloom filter can produce errors such as false negatives. This paper presents different approaches to build Bloom filters that are tolerant to single event transients occurring in the hash generation circuitry. They are compared to the use of traditional Modular Redundancy approaches. The results show that the new schemes can reduce significantly the circuit area needed to implement the Bloom filter. [ABSTRACT FROM AUTHOR]

We investigate the design of a new instruction set for the Keccak permutation, a cryptographic kernel for hashing, authenticated encryption, keystream generation and random-number generation. Keccak is the basis of the SHA-3 standard and the newly proposed Keyak and Ketje authenticated ciphers. We develop the instruction extensions for a 128-bit interface, commonly available in the vector-processing unit of many modern processors. We examine the trade-off between flexibility and efficiency, and we propose a set of six custom instructions to support a broad range of Keccak-based cryptographic applications. We motivate our custom-instruction selections using a design space exploration that considers various methods of partitioning the state and the operations of the Keccak permutation, and we demonstrate an efficient implementation of this permutation with the proposed instructions. To evaluate their performance, we integrate a simulation model of the proposed ARM NEON vector instructions into the GEM5 micro-architecture simulator. With this simulation model, we evaluate the performance improvement for several cryptographic operations that use the Keccak  permutation. Compared to a state-of-the-art NEON software implementation, we demonstrate a performance improvement of 2.2x for SHA-3. Compared to optimized 32-bit assembly programming, we demonstrate a performance improvement of 2.6x, 1.6x, and 1.4x for River Keyak, KetjeSR and KetjeJR respectively. The proposed instructions require 4,658 gate-equivalent (GE) in 90 nm, which represents only a tiny fraction of the hardware cost of a modern processor. [ABSTRACT FROM AUTHOR]

In this communication, a frequency and pattern reconfigurable V–shaped printed antenna is presented. The proposed structure operates at two different frequency bands. The variation in the frequency of operation is achieved by individually extending the length of each of the two antenna arms. The directional behavior of the proposed antenna structure is improved through the incorporation of a triangular parasitic element within the empty space between the two antenna arms. More specifically, the antenna is able to steer its gain pattern to either the left or right directions based on which arm of the V–shaped printed structure is fed. A prototype structure is fabricated and tested to validate the proposed approach in achieving directional behavior over two distinct frequency bands. [ABSTRACT FROM PUBLISHER]

In this paper, a lightweight horn antenna array demonstrator is designed and fabricated by means of an additive manufacturing (AM) process that has been optimized for complicated passive radio-frequency (RF) components. The presented design comprises a complex waveguide feeding network (WFN) which aims to exploit the increased flexibility offered by this novel fabrication technique. This WFN concept could be easily extended to larger antenna arrays with higher gain for full-size telecommunication applications. The electromagnetic performance of the featured structure is validated by means of full-wave numerical simulations. Fabricated prototypes of the WFN and of the complete antenna array are tested and are found to exhibit a promising agreement with the simulation results. [ABSTRACT FROM AUTHOR]

The article focuses on cloud radio access network (C-RAN) systems. Topics include various end-to-end solutions offered by C-RAN for issues including design of power-effective signals and cost-effective hardware for remote radio heads (RRHs), conception of an elastic and flexible architecture, and distribution and design of data and control traffic for coordinated communications. It discusses the development and effectiveness of the load-controlled parasitic antenna array (LCPAA) for C-RANs.

The article offers information on device-to-device (D2D) proximity services (ProSe) for public safety communications. Topics include the service's mechanisms and physical channels in Release 12, priority control in Release 13, and user equipment (EU)-to-network relay. Also mentioned are the service's system-level performance in Release 13 D2D and the practice and incorporation into the state-of-the-art and future cellular network evolutions.

This paper describes the design and the architecture of symbiote coprocessor unit (SCU)—a programmable streaming coprocessor for a heterogeneous reconfigurable logic-assisted data stream management systems (DSMSs) such as symbiote. The SCU is intended for streaming applications with real-time event and data processing that have stricter deadlines, high-bandwidth, and high-accuracy requirements. To meet these requirements, the SCU exploits unique characteristics of DSMSs, such as single-pass tuple processing, windowed operators, and inherent data level parallelism, using a single-instruction multiple-data very large instruction word (SIMD-VLIW) microarchitecture and a novel inverted distributed register file. In order to better explain the instruction set, design, and functionality of the various units in the SCU, this paper also provides a brief overview of SymQL—a procedural query language that we developed to describe the queries that can be executed on the SCU. Finally, this paper presents the performance of SCU using four queries that represent common data stream processing use-cases, one of them being similar to a query found in the Linear Road Benchmark. Using these queries on SCU simulation, we show that the SCU outperforms a software-only DSMS running on an AMD Opteron 2350 quad-core processor by 1.5–42 times. [ABSTRACT FROM PUBLISHER]

The flexibility and programmability of an application-specific instruction-set processor (ASIP) come at the expense of reduced area and energy efficiency compared to application-specific integrated circuit (ASIC) solutions. Nevertheless, ASIPs are desirable for versatile application domains like wireless communications and software defined radio (SDR). Typically, ASIP designers reduce the ASIC-ASIP efficiency gap by increasingly complex architectures with decreasing flexibility and usability. This paper takes the opposite approach and presents concepts for a highly efficient, lightweight SDR ASIP. Efficiency enablers include simple but effective measures like a carefully chosen instruction set, optimized data access techniques for efficient utilization of functional units, and the use of flexible floating-point arithmetic with runtime-adaptive numerical precision. We present a conceptual processor core to show the impact of these measures and discuss its potential as well as limitations compared to tailored ASIC solutions. For demonstration, we choose the field of linear multiple-input multiple-output (MIMO) detection. We present synthesis results for several design versions in 90 nm CMOS technology and the corresponding energy benchmarks. Also, we show post-layout results for a selected design to demonstrate the feasibility of our concept. [ABSTRACT FROM AUTHOR]

Backstepping controllers are obtained for distributed hybrid photovoltaic (PV) power supplies of telecommunication equipment. Grid-connected PV-based power supply units may contain dc–dc buck–boost converters linked to single-phase inverters. This distributed energy resource operated within the self-consumption concept can aid in the peak-shaving strategy of ac smart grids. New backstepping control laws are obtained for the single-phase inverter and for the buck–boost converter feeding a telecom equipment/battery while sourcing the PV excess power to the smart grid or to grid supply the telecom system. The backstepping approach is robust and able to cope with the grid nonlinearity and uncertainties providing dc input current and voltage controllers for the buck–boost converter to track the PV panel maximum power point, regulating the PV output dc voltage to extract maximum power; unity power factor sinusoidal ac smart grid inverter currents and constant dc-link voltages suited for telecom equipment; and inverter bidirectional power transfer. Experimental results are obtained from a lab setup controlled by one inexpensive dsPIC running the sampling, the backstepping and modulator algorithms. Results show the controllers guarantee maximum power transfer to the telecom equipment/ac grid, ensuring steady dc-link voltage while absorbing/injecting low harmonic distortion current into the smart grid. [ABSTRACT FROM AUTHOR]

This paper proposes a shared multiplier scheduling scheme (SMSS) for area-efficient fast Fourier transform (FFT)/inverse FFT processors. SMSS can significantly reduce the total number of complex multipliers up to 28%. The proposed mixed-radix multipath delay commutator processors can support 128/256 and 256/512-point FFTs using SMSS. The proposed processors have been designed and implemented with 90-nm CMOS technology, which can reduce the total hardware complexity by 20%. The proposed processors having eight-parallel data paths can achieve a high throughput rate up to 27.5 GS/s at 430 MHz. In addition, the proposed processors can support any FFT size using additional stages. [ABSTRACT FROM AUTHOR]

Outdoor optical fiber cabinets are generally installed along roadsides where environmental conditions, such as sun exposure, rain, and dust, can cause damage to the cabinets. Furthermore, high temperatures and unexpected impacts that cause cabinet deformation may damage the network equipment inside the cabinets, affecting the quality of communications. This paper developed an optical fiber sensing system for real-time monitoring of the temperature variation and external forces exerted on outdoor cabinets using fiber Bragg gratings (FBGs). This FBG sensing system was established in the network management center, and was linked to the outdoor cabinets at the remote end through optical fibers in order to monitor the impacts and temperature changes of the cabinets. Experimental results revealed that exerting an external impact force of 297 N on an outdoor cabinet severely dented the impacted cabinet surface. When the monitoring system detects external impacts exceeding 297 N or cabinet temperatures greater than 65 °C, the network management center can then immediately send maintenance personnel to check for any network impairments. [ABSTRACT FROM PUBLISHER]

Device-to-device (D2D) communications has attracted substantial research attention recently owing to its simplicity and its potential to improve spectrum and energy efficiency within the existing cellular infrastructure. This work presents a low complexity method for matching D2D links with cellular user equipments (CUEs) to form partners for spectrum sharing. The overall objective is to maximize well defined performance metrics of all D2D links and CUEs after successful pairing under power and QoS constraints. We begin by identifying a set of D2D link candidates for each CUE uplink for a requisite SINR level to reduce the number of potential pairing searches. More importantly, we present a simple pairing algorithm to reduce the computational cost well below the well known Hungarian (Kuhn-Munkres) algorithm used in the literature for the pairing problem. Our new algorithm exhibits low complexity and is effective in improving the sum rate of all spectrum sharing CUEs and D2D links with modest performance loss. [ABSTRACT FROM PUBLISHER]

Device-to-device (D2D) communication commonly refers to a type of technology that enable devices to communicate directly with each other without communication infrastructures such as access points (APs) or base stations (BSs). Bluetooth and WiFi-Direct are the two most popular D2D techniques, both working in the unlicensed industrial, scientific and medical (ISM) bands. Cellular networks, on the other hand, do not support direct over-the-air communications between users and devices. However, with the emergence of context-aware applications and the accelerating growth of Machine-to-Machine (M2M) applications, D2D communication plays an increasingly important role. It facilitates the discovery of geographically close devices, and enables direct communications between these proximate devices, which improves communication capability and reduces communication delay and power consumption. To embrace the emerging market that requires D2D communications, mobile operators and vendors are accepting D2D as a part of the fourth generation (4G) Long Term Evolution (LTE)-Advanced standard in 3rd Generation Partnership Project (3GPP) Release 12. [ABSTRACT FROM PUBLISHER]