Multiple Wireless Research Articles

Edge Caching in Multi-UAV-Enabled Radio Access Networks: 3D Modeling and Spectral Efficiency Optimization

Unmanned-aerial-vehicle (UAV) enabled radio access is an effective technology to improve the wireless coverage, in particular for remote and disaster-struck areas. It will become a key enabler in the forthcoming 5G heterogeneous cellular networks to provide improved and resilient coverage. In this article, we study edge caching for multiple UAV-enabled radio access networks (UAV-RANs) and investigate how the overall spectral efficiency (SE) can be improved by efficient edge caching. In this context, UAV base stations (UBSs) may not serve the immediate close-by users, but serve the users based on the requested contents, which brings the service contents closer to users. Based on analyses of the SE achieved by the content-centric UAV-RAN, a hybrid caching strategy is proposed to further improve the SE. In order to cache more files with limited cache resources while guaranteeing the quality-of-service, the contents are divided into two subsets, a popular set and a less popular set, based on their popularity profile that follows Zipf distribution. The popular files, according to the proposed hybrid caching strategy, are cached at all the UBSs, while each less popular file is cached at one UBS only. The overall SE is maximized by finding an optimal popularity threshold between the two subsets. By relaxing the formulated problem, analytical expression for the optimized threshold is derived. The effectiveness of the proposed method is verified by numerical examples where existing benchmark schemes are compared and outperformed.

Cost-effective routing as a service in sensor-cloud

Sensor-cloud is a collaborative platform which allows multiple wireless sensor networks (WSN) to pull their resources together for better utilisation and efficiency. In this work, we consider a set of applications, each characterised by the set of targets it intends to cover and our aim is to provide routing as a service (RaaS) to all these applications in the sensor-cloud. We should be able to run data gathering for each application in parallel with the minimum use of sensor-cloud resources. This is achieved by creating a collection of data gathering trees. We have proposed an algorithm which selects a minimal set of sensors to cover the required targets and obtains a spanning forest connecting them so that, the total energy cost of all the trees in the forest is minimised. Experimental results demonstrate the advantages of serving the applications by a sensor-cloud over standalone WSNs in terms of the usage of resources.

Dynamic Block-Based HTTP Adaptive Streaming Scheme in Multiple Wireless Networks

Multipath-based hypertext transfer protocol (HTTP) adaptive streaming (MPHAS) has been studied due to the increasing use of mobile devices equipped with multiple network interfaces and the prevalence of high-quality video streaming services. However, the existing MPHAS schemes undergo a degraded quality of experience (QoE) in multiple wireless networks. The segment request-based MPHAS (SR-MPHAS) encounters frequent quality switching, and the block request-based MPHAS (BR-MPHAS) causes results in playback stalling and inefficient bandwidth utilization, according to slow responsiveness. In this paper, we propose a dynamic block-based MPHAS (DBAS) to improve the QoE by overcoming the limitations of the existing schemes in multiple wireless networks. We propose buffer-based block length adaptation and QoE-based block quality adaptation to reduce the frequency of quality switching and to improve the responsiveness to network changes. Moreover, we propose a partial request-based block scheduler to mitigate segment reordering. The experimental results show that the DBAS improves the QoE by reducing the quality switching frequency and rapidly adapting to abrupt changes in the bandwidth.

Low-Cost S-Band Reconfigurable Monopole/Patch Antenna for CubeSats

The development of reconfigurable antennas compatible with a CubeSat form factor can aid several space missions. Often, satellite missions require multiple wireless links with the same radio, but the design of such antennas is challenging due to the mechanical constraints and the limited power aboard a CubeSat. In this article, we present a unique reconfigurable antenna concept enabled by adhesive polyimide tapes. The presented antenna can switch from a conventional patch to a monopole-like antenna with minimal actuation complexity. This reconfiguration provides choices for polarization, pattern, and gain without use of active components for size, cost and power consumption reductions. The frequency of operation is S-band (2.4 GHz), and the antenna achieves $S_{11} <; -10$ dB for both reconfiguration states. Measurements compare well with simulations in both states.

Client-Centric Access Device Selection for Heterogeneous QoS Requirements in Beyond 5G IoT Networks

The expected manifolds increase in the traffic and the massive number of connected Internet of Things (IoT) devices would be a challenge to ensure a certain Quality of Service (QoS) in Beyond 5G (B5G) networks. Due to the increased availability of processing and energy resources and heterogeneous QoS requirements in modern IoT nodes, a client-centric access device selection approach for QoS provisioning in multiple Radio Access Technologies (RATs) scenario is proposed in this paper. The proposed algorithm provides the ability to specify node-specific QoS requirements at each node, a better access device selection, and improved network scalability. For experimental evaluation, a hybrid indoor network consisting of Wireless Fidelity (WiFi) and Light Fidelity (LiFi) RATs has been considered. Experimental results show that the proposed technique outperforms several conventional client-based access device selection approaches by up to 32.66% in network emulation experiments and up to 50% in hardware experimentation. The contribution of this paper includes the proposed algorithm, its complexity and game-theory based convergence analyses, evaluation of the proposed algorithm using network emulation and hardware-based setups, and LiFi channel analysis. The analyses and results imply that the proposed algorithm could be utilized in next-generation IoT networks as it performs better than conventionally used access device selection techniques for QoS provisioning.

Enabling DSRC and C-V2X Integrated Hybrid Vehicular Networks: Architecture and Protocol

Emerging Vehicle-to-Everything (V2X) applications such as Advanced Driver Assistance Systems (ADAS) and Connected and Autonomous Driving (CAD) requires an excessive amount of data by vehicular sensors, collected, processed, and exchanged in real-time. A heterogeneous wireless network is envisioned where multiple Radio Access Technologies (RATs) can coexist to cater for these and other future applications. The primary challenge in such systems is the Radio Resource Management (RRM) strategy and the RAT selection algorithm. In this article, a Hybrid Vehicular Network (HVN) architecture and protocol stack is proposed, which combines Dedicated Short-Range Communication (DSRC) technology-enabled ad hoc network and infrastructure-based Cellular V2X (C-V2X) technologies. To this end, we address the design and performance evaluation of a distributed RRM entity that manages and coordinates Radio Resources (RR) in both RATs. Central to distributed RRM are adaptive RAT selection and Vertical Handover (VHO) algorithms supported by two procedures. (1) Measurement of Quality of Service (QoS) parameters and associated criteria to select the suitable RAT according to the network conditions. (2) Dynamic communication management (DCM) via implementing RR-QoS negotiation. The simulation results show the effectiveness of the proposed architecture and protocol suite under various parameter settings and performance metrics such as the number of VHOs, packet delivery ratio, and throughput, and latency.

ROF系统中基于单个调制器的多射频操作

ROF系统中基于单个调制器的多射频操作

An adaptive interference‐aware and traffic‐aware channel assignment strategy for backhaul networks

SummaryThe transformation of traditional networks is being done by incorporating billions of daily life devices to provide service centric facilities. With such transformation, the major traffic load will be shifted toward the backhaul networks, for which guaranteed bandwidth and low latency are the basic requirements. In order to meet varying and dynamic requirements of each service, the development of a traffic aware network is unavoidable. For achieving last mile connectivity, wireless mesh is considered among the best of the backhaul networks. Additionally, classical single radio mesh routers restrict the whole network on a single channel and hence the full potential of available multiple channels is not achieved. Mesh routers plugged with multiple radios allow parallel transmissions and increase the capacity of the whole network. To utilize network resources more efficiently, the key issue of channel assignment for wireless mesh networks is explored by incorporating the concept of time‐based traffic in a distributed environment. This paper discusses the problem of assigning a limited number of channels to a large number of radios while keeping in view the restrictions involved in maintaining a minimal level of interference and preservation of network topology. Bayesian estimation approach is used to gather knowledge from surroundings to determine the high‐interfered region and hence a distributed solution is proposed where mesh routers can find a more suitable alternative channel for respective region. The proposed algorithm is evaluated through traces on multiple flows, collected from simulations. Results show that the proposed algorithm performed better than existing ones in the presence of interference.

Fair Self-Adaptive Clustering for Hybrid Cellular-Vehicular Networks

Due to the increasing number of car-centered connected services, making efficient use of limited radio resources is critical in vehicular communications. Hybrid vehicular networks dispose of multiple Radio Access Technologies (RATs) like cellular and vehicle-to-vehicle (V2V) networks, with complementary characteristics that allow for developing smarter network traffic distribution methods. This paper proposes a self-adaptive clustering system for ensuring a suitable trade-off between data aggregation (over the cellular network) and communication congestion due to cluster management (within the V2V network). The system's algorithms use a distributive justice approach for selecting cluster heads, to improve fairness among car drivers and hence help the social acceptability of self-adaptive clustering. Simulation results show that this approach significantly improves fairness over time without affecting network performance. This solution can thus optimize the usage of radio resources, reducing cellular access costs, without the need for uniformization among different mobile operators' access plans.

Al-enabled spectrum technology: What's next? - [Spectral Lines

You've graduated from the school of spectral hard knocks, Paul Tilghman, a U.S. Defense Advanced Research Projects Agency program manager, told the teams competing in DARPA's Spectrum Collaboration Challenge (SC2) finale on 23 October. The three-year competition had just concluded. ¶ Hard knocks wasn't an exaggeration—the 10 teams that made it to the finale, as well as others who were eliminated in earlier rounds of the competition, had been tasked with doing something that had never been done before. Their challenge was to see if AI-managed radio systems could work together to share wireless spectrum more effectively than static, preallocated bands. They had spent three years battling it out in matchups in Colosseum, an RF emulator that DARPA built specially for the competition.¶ By the end, the top teams had demonstrated that their systems could transmit more data over less spectrum than is possible using existing standards like LTE; they also showed an impressive ability to reuse spectrum over multiple radios. In some matchups, the radio systems of five teams were transmitting 200 or 300 percent more data than is possible with today's rigid spectrum band allocations. And that's important, given that we're facing a looming wireless-spectrum crunch. _ But, as Tilghman also stressed during SC2, when a DARPA Grand Challenge ends, it doesn't mean the technology is ready to go to market. These challenges are more about proving that a new technological idea is possible. So the contest showed that AI-controlled radios can work together to share spectrum among themselves, and pack more data into a given amount of spectrum. But where does the technology go from here, now that the DARPA challenge is finished?

Advanced User Association in Non-Orthogonal Multiple Access-Based Fog Radio Access Networks

Non-orthogonal multiple access (NOMA) is promising to further improve spectral efficiency (SE) and decrease transmit latency in fog radio access networks (F-RANs) through serving multi-users in the same frequency-time resource block simultaneously, while the complexity of user association is challenging to exploit the corresponding performance gains. In this paper, a performance analysis framework for the user association in NOMA based F-RANs is proposed and the closed-form analytical results are developed by using stochastic geometry tool. In particular, we propose two user association algorithms based on evolutionary game and reinforcement learning, respectively. The performance model jointly considering quality of service, delay cost, and power consumption is formulated as a payoff function, and the corresponding performance expressions are derived for these two user association algorithms. Numerical and simulation results demonstrate that the derived expressions are accurate, and the NOMA based F-RAN can provide over 50% performance gains on SE compared to the orthogonal multiple access scheme. Furthermore, these two proposed user association algorithms work well with high convergence, which can effectively enhance the overall performance and the fairness of users.

Low-Delay Scheduling for Internet of Vehicles: Load-Balanced Multipath Communication With FEC

The proliferation of devices with multiple wireless interfaces and (automobile) manufacturers’ interest in implementing reliable connectivity for vehicles create an ideal scenario for multipath transmission control protocol (MPTCP) over vehicular networks. Next generation vehicular networks will be highly dynamic and exploit MPTCP over various wireless technologies including WiFi and 5th generation (5G) cellular networks to form the Internet of vehicles (IoV). However, the probability of packet loss can be high and/or packets arrive at the destination out-of-order due to time-varying heterogeneous wireless paths. Further, the IoV traffic is delay sensitive, which urges the need to investigate MPTCP algorithms for reliable communication over heterogeneous lossy networks, while satisfying delay constraints. We approach these challenges by jointly using load balancing and forward error correction (FEC) for performing coupled congestion control inside MPTCP. As a result, the proposed MPTCP-IoV is TCP-friendly by design, and provably stable and convergent to a unique equilibrium point. In addition, a comprehensive mathematical analysis (developed to approximate the reordering delay) is carried out and shown that the delay penalty for MPTCP-IoV over such networks becomes insignificant when considering the potential gains obtained by the convergence of multiple networks. Experiments are carried out and the results demonstrate these characteristics.

A Three-Layered Adjustable Frequency-Selective Surface for Wireless Applications

A three-layered adjustable frequency-selective surface (FSS) is proposed and investigated. The FSS consists of a main resonator in the middle layer and two subresonators in the upper and lower layers of a sandwich structure. The resonant frequency can be varied by shifting the upper and lower layers symmetrically. This has the advantages that the same frequency characteristics can be obtained in both vertical and horizontal polarizations and that its fabrication is easy, eliminating the need for electronic elements such as varactor diodes to control capacitance, although the FSS is not suitable for situations that require real-time tuning. This article confirms that the resonant frequency can be varied from $f_{0}$ to $1.7f_{0}$ in a microwave band which covers multiple wireless bands, with good angular stability in both vertical and horizontal polarizations, by shifting the upper and lower layer overlaps by up to 1.8 mm. Note that $f_{0}$ is the lowest resonant frequency, and the size of a unit cell is varied from $0.066\lambda $ to $0.125\lambda $ . Also, the adjustment capability and the angular stability of an FSS fabricated by using a silver inkjet printer are experimentally demonstrated, by simply stacking and shifting the three films.

Multiple access schemes for Cognitive Radio networks: A survey

Spectrum bands are the backbone of wireless networks. Every user is allocated a fraction of the spectrum from available fixed spectrum band. But, the fixed available spectrum band cannot accommodate the growing demands of wireless networks. To accommodate the growing demand of wireless networks, the different multiple access schemes and Cognitive Radio (CR) networks come to fulfill these demands. Multiple access schemes are nothing but the schemes that can multiplex the numbers of users then transmit over the medium, whereas CR networks allow using unutilized frequency bands of spectrum through dynamic or opportunistic way. Till now, OFDMA is well known and most successful multiplexing scheme among other schemes for advanced wireless networks. It can accommodate large number of users with higher data rates than others. Due to the popularity of smart devices having video and other applications, the data demand for additional frequency bands are continuously increasing. These further higher demands of spectrum by futuristic networks can be overcome by introducing Non-Orthogonal Multiple Access (NOMA) scheme. It has higher spectral efficiency than the other existing access schemes. NOMA works on the principle of superposition coding of signals at the transmitter and successive interference cancellation at the receiver. Hence, the spectrum demands due to the exponential growth in mobile data traffic can be solved by the use of optimal multiple access scheme for CR networks. Presently, there exists no detailed classification and comprehensive survey is available for multiple access schemes for CR networks. This paper provides comprehensive survey and a generic classification of the recent progress of the multiple access schemes for CR networks. The multiple access schemes are classified into various categories which provide an overview of the active research initiatives in the area of multiplexing. Finally, the paper discussed various challenges, research issues and some future aspects for research community.

Physical Layer Security in Nonorthogonal Multiple Access Wireless Network with Jammer Selection

The physical layer security of downlink nonorthogonal multiple access (NOMA) network is analyzed. In order to improve the secrecy probability, friendly jammers are jointed in the NOMA network. Two jammer schemes are proposed in the NOMA network. All the jammers transmit jamming signal without jammer selection in the first scheme (NO JS scheme). Jammers are selected to transmit jamming signal if their interfering power on scheduled users is below a threshold in the second scheme (JS scheme). A stochastic geometry approach is applied to analyze the outage probability and the secrecy probability. Compared with the NO JS scheme and traditional scheme (without jointing jammers), the jammer selection scheme provides a good balance between the user outage probability and secrecy probability. Numerical results demonstrate that the security performance of the two proposed schemes can be improved by jointing the jammers in the NOMA wireless network.

Truncated T parasite staircase fractal U‐slot antenna for multiple advance internet of things applications

AbstractThe internet of things (IoT) connects billions of smart heterogeneous modules in long‐term evolution (LTE) and LTE‐advance. The rapid growth of IoT has attracted typical wireless sensors designs for machine‐to‐machine communication. More action is required to improve quality, bandwidth, interfacing compatibility and efficiencies of such smart systems. This article presents an antenna design evolution to enhance compatibility, impedance matching and high bandwidth fidelity to smart wireless IoT sensors. A compact 12 × 18 × 1.6 mm3 staircase‐fractal slot antenna with truncated “T” parasites, gives promising characteristics for IoT applications in UWB and GSM/GPS range. Antenna is modeled and simulated on high frequency structure simulator. The prototype is fabricated and experimented to validate practical feasibility of antenna for wireless sensor based applications. The antenna resonates on 2.4, 5, and 9.55 GHz, exhibits complete UWB (3.1‐10.5 GHz). Additionally, offers GPS/GSM compatibility for real time applications. Therefore, the proposed antenna has novel utility of compatibility enhancement among multiple wireless sensors interface embedded in advance IoT based application.

NOMA based CR for QAM-64 and QAM-256

Non-Orthogonal multiple access (NOMA) and Cognitive radio (Cr) are seen as one of the most promising techniques, which improves the utilization of the spectrum in 5G. The expanding number of wireless applications like new gadgets, IOT brought about developing a block in the ISM groups. The FCC requested to permit unlicensed clients to work in the void area without obstruction to an authorized guest. Cr gives an answer for an extra range prerequisite issue for productive spectrum usage. The foremost condition for permitting CRs to utilize spectrum is not causing obstruction to licensed users. Spectrum sensing permit secondary users (Su) to separately recognize the idle portions of the spectrum, and thus evade obstruction to licensed users. In existing spectrum sensing techniques, SU can only utilize the unused spectrum when PU is not present. Therefore, spectrum exploitation of the conventional system is very low. In recent times NOMA has been projected to utilize the spectrum in an efficient manner. The proposed work permits the SU to utilize a spectrum of PU, both at its absence. Spectrum sensing in NOMA is not explored so far. Hence, in this paper, NOMA based matched filter detection is designed for QAM-64 and QAM-256. Matlab simulation is applied to study the operation of the proposed detection technique in NOMA in respect of several parameters like bit error rate (BER) Vs signal to noise ratio (SNR), the probability of detection (Pd), and probability of false alarm (Pfa).

High diversity gain super‐wideband single band‐notch MIMO antenna for multiple wireless applications

A two-element super-wideband (SWB) MIMO antenna is proposed in this study. A step impedance microstrip feed line structure is introduced to achieve an SWB impedance bandwidth of 185%. This antenna is designed to be circularly polarised at 1.575 GHz (L 1 -band) and 26.0 GHz (K-band) by using closed ring resonator on the radiating patch. The EBG structures are used to improve FBR in lower (1.5-5 GHz) and higher bands (25-35 GHz). The proposed antenna is designed with compact size 55.6 × 50.5 × 1.6 mm 3 on FR-4 substrate including exotic diversity performance. This MIMO antenna is suitable for defence and handheld devices covering GPS/DCS/PCS/UMTS/Wi-BRO/ISM/IRNSS/LTE (M/HB)/BLUETOOTH/IoT/WiMAX/X/Ku/K/Ka-band and it is also suitable for 5G (sub-6 GHz/mm) applications with channel capacity of 11.34 bps/Hz. Simulated results of MIMO antenna like radiated power-based ECC and diversity parameters are also verified experimentally, which are in the acceptable range. Finally, this antenna is tested in a realistic environment for SAR application.

Joint User Pairing, Channel Assignment and Power Allocation in NOMA based CR Systems

The fifth generation (5G) wireless communication systems promise to provide massive connectivity over the limited available spectrum. Various new transmission paradigms such as non-orthogonal multiple access (NOMA) and cognitive radio (CR) have emerged as potential 5G enabling technologies. These techniques offer high spectral efficiency by allowing multiple users to communicate on the same frequency channel, simultaneously. A combination of both techniques may further enhance the performance of the system. This work aims to maximize the achievable rate of a multi-user multi-channel NOMA based CR system. We propose an efficient user pairing, channel assignment and power optimization technique for the secondary users while the performance of primary users is guaranteed through interference temperature limits. The results show that, at small values of the power budget or high interference threshold, optimizing channel allocation and user pairing proves to be more beneficial than optimal power allocation to the user pairs. The proposed joint optimization technique provides promising results for all values of the power budget, interference threshold and rate requirement of the communicating users.

A smart Internet of Things–based mechanism for wireless communications in NoC

With the development of silicon integration technology, the network-on-chip (NoC) proposes a scalable communication architecture that can improve system performance. Future multi-core chips are expected to be heterogeneous and hierarchical in nature. Inter-frequency interference will occur between various 2.4-GHz wireless network communication cores integrated on the same chip, resulting in lower network throughput and higher communication latency. This article solves the problem of wireless co-channel mutual interference from the two aspects of time domain and frequency domain and designs a heterogeneous platform based on NoC architecture to achieve more stable parallel communication of multiple wireless co-frequency networks without mutual interference. When the system detects the interference, this article uses the chirped fractional Fourier transform to filter out the interference signal before the signal arrives and then spreads the frequency. According to the results, the method improves the anti-interference ability of the network and the utilization of spectrum resources. Compared with the traditional carrier sense multiple access method, the spectrum-aware channel cooperation method proposed in this article reduces the data average transmission delay by 0.02 s and the data packet reception rate is increased by about 30%, which provides a certain reference value for future wireless multi-core communication.