Performance evaluation of an efficient reduced-complexity time synchronization approach for OFDM systems

This paper presents a performance analysis of a recently proposed preamble-based reduced-complexity (RC) two-stage synchronization technique. The preamble, composed of two identical subsequences, is first used to determine an uncertainty interval based on Cox and Schmidl algorithm. Then, a differential correlation-based metric is carried using a new sequence obtained by element wise multiplication of the preamble subsequence and a shifted version of it. This second step is performed to fine tune the coarse time estimate, by carrying the differential correlation-based metric over the uncertainty interval of limited width around the coarse estimate, thus leading to low computational load. In this paper, we first discuss some complexity issues of the RC approach compared to previously proposed algorithms. Then, we study the effect of the training sequence class and length choices on the synchronization performance in the case of multipath channels. The impact of the uncertainty interval width on the trade-off between performance and complexity is also studied. The two-stage approach was found to provide almost equal performance to those obtained by the most efficient differential correlation-based benchmarks. However, it has a very reduced computational load, equivalent to that of sliding correlation-based approaches.     

5G meets satellite: Non-terrestrial network architecture and 3GPP

With 3GPP Release-17, global 5G standards now support non-terrestrial mobile networks comprising radio access network, terminals, and core network. This enables multi-vendor interoperability as well as interoperability with 3GPP-compliant 5G systems. This paper describes the key features enabling the NG-RAN architecture defined for 5G to support non-terrestrial networks. Starting from a general overview of NG-RAN and of the new paradigms of NTN, we introduce the NTN functionality in NG-RAN specifications with respect to feeder link switchover, cell handling, terminal registration, and OAM aspects. We also discuss different scenarios combining satellite access with 3GPP-defined core networks. We also describe some further enhancements expected to be seen in the next 3GPP release (Rel-18). We believe current and upcoming 3GPP work for NTN represents a solid basis on which 5G satellite networks can be built in the upcoming future.     

Nonsinusoidal radar signal design for stealth targets

The detection of stealth point targets challenges the design of conventional radars using sinusoidal carriers since the objective of stealth technology is to reduce the radar cross section (RCS) of targets to a level where the radar receiver cannot detect the target. While there are a number of techniques employing different technologies to reduce the RCS of targets, shaping and coating the target with absorbing material are the most useful ones. The analysis and design of nonsinusoidal radar signals is based on modeling stealth point targets by a two-layer structure consisting of a metal surface covered with a coat of absorbing material. The design is presented for two classes of signals: uncoded signals and pulse compression signals using Barker codes. The relationship between target response, absorbing material time delay, time variation of transmitted pulses and coding features are determined and analyzed. While sliding correlators are used for detection and selection of various target responses, their output autocorrelation functions are determined analytically in terms of transmitted signal autocorrelation functions. Thumbtack range-velocity resolution functions are obtained for transmitted signal characters with a single pulse and characters with coded waveforms, for different pulse duration. It is shown that the range resolution can be improved by the proper choice of the transmitted signal duration relative to absorbing material time delay. Thumbtack range-velocity resolution functions similar to those of conventional point targets can also be realized     

Energy efficient scheduling in local area networks

Wireless Networks - In Wireless Local Area Networks (WLAN), portable devices such as notebooks, tabs, and smart phones are powered by batteries with limited energy. With the great increase of using...     

Computer and network security risk management: theory,challenges, and countermeasures

The need to secure information systems and networked infrastructures is now commonplace in most enterprises. The use of novel communication technologies has became a crucial factor that can considerably improve or affect productivity. This is essentially due to the importance of the information transmitted across communication networks and stored in servers. As a consequence, strong ties are being built between security and the enterprise business activity. Risk management, which is the discipline that deals with this aspect, integrates a litany of architectures, techniques, and models that are described in this paper. A global view is proposed to the reader through a presentation of the research activity that has been directed towards this field. Copyright © 2005 John Wiley & Sons, Ltd.     

ESSPR: an efficient secure routing scheme based on searchable encryption with vehicle proxy re-encryption for vehicular peer-to-peer social network

In this paper, we propose an Efficient Secure routing Scheme based on searchable encryption with vehicle Proxy Re-encryption, called ESSPR, for achieving privacy preservation of message in vehicular peer-to-peer social network (VP2PSN). Specifically, the proposed ESSPR scheme consists of six phases: system initializations phase, peer registration phase, document generation phase, document forwarding phase, vehicle proxy re-encryption phase, and document receiving phase. Based on rationale of QoS-based clustering strategy, public key encryption with keyword search, identity based aggregate signature, and proxy re-encryption, ESSPR provides privacy for keyword, privacy for resources, and authentication and data integrity of the demand’s source. In addition, ESSPR is robust against eavesdropping attack, wormhole attack, packet analysis attack, packet tracing attack, and replay attack. Through performance evaluation, we demonstrate the effectiveness of ESSPR in terms of delivery ratio, average delay, average fairness, and detection ratio under malicious peers proportions in VP2PSN.     

Design and Analysis of a Channel Assignment Scheme for CDMA/TDMA Mobile Networks

In this paper, a channel assignment scheme is proposed for use in CDMA/TDMA mobile networks carrying voice and data traffic. In each cell, three types of calls are assumed to compete for access to the limited number of available channels by the cell: new voice calls, handoff voice calls, and data calls. The scheme uses the movable boundary concept in both the code and time domains in order to guarantee the quality of service (QoS) requirements of each type. A traditional Markov analysis method is employed to evaluate the performance of the proposed scheme. Measures, namely, the new call blocking probability, the handoff call forced termination probability, the data call loss probability, the expected number of handoff and the handoff link maintenance probability are obtained from the analysis. The numerical results, which are validated by simulation, indicate that the scheme helps meet the QoS requirements of the different call types.     

A hierarchical design methodology for full-search block matching motion estimation

Many useful DSP algorithms have high dimensions and complex logic. Consequently, an efficient implementation of these algorithms on parallel processor arrays must involve a structured design methodology. Full-search block-matching motion estimation is one of those algorithms that can be developed using parallel processor arrays. In this paper, we present a hierarchical design methodology for the full-search block matching motion estimation. Our proposed methodology reduces the complexity of the algorithm into simpler steps and then explores the different possible design options at each step. Input data timing restrictions are taken into consideration as well as buffering requirements. A designer is able to modify system performance by selecting some of the algorithm variables for pipelining or broadcasting. Our proposed design strategy also allows the designer to study time and hardware complexities of computations at each level of the hierarchy. The resultant architecture allows easy modifications to the organization of data buffers and processing elements-their number, datapath pipelining, and complexity-to produce a system whose performance matches the video data sample rate requirements.     

Analyse de la stabilité spectrale d’un laser DFB à trois sauts de phase (3PS-DFB)

The aim of this article is to analyze the spectral stability of the three phase shift distributed feedback (3ps-dfb) laser by using Time domain model (tdm). We have developed a software that simulates static and dynamic properties of distributed feedback (dfb) multi-sections laser at large signal. The best single-mode stability operation up to 18mW of the 3ps-dfb is achieved for three phase shifts at (π, π, π) whatever the phase position. These results showed that the 3ps-dfb laser was a much more suitable structure to realize stable single-mode high-power operation for a coherent optical communication system.     

Resilient BBU placement in 5G C-RAN over optical aggregation networks

Photonic Network Communications - The huge data demand envisioned for the 5G requires radical changes in the mobile network architecture and technology. Centralized radio access network (C-RAN) is...