Demand For Wireless Capacity Research Articles

Analyzing the impact of medium access control protocol design and control-plane uplink in asymmetric RF/OWC networks with RF congestion

As the demand for wireless capacity continues to grow, highly directional wireless communication technologies have the potential to provide massive gains in area spectral efficiency. However, novel challenges arise when considering bidirectional connectivity and multi-cell/multi-user systems with highly directional links. Some of these challenges can be alleviated with the introduction of asymmetric connectivity where the highly directional links are used solely for downlink transmission. As an example, we consider asymmetric links with an optical wireless communication (OWC) downlink and sub-6 GHz RF uplink. More specifically, we consider visible light communication as an instance of OWC, although the presented analysis and validation are applicable to alternative OWC technologies and other simplex downlink transmission technologies. While asymmetric connectivity has been previously demonstrated in scenarios like this, the impact of control-plane asymmetry has not been explored, to our knowledge. In this paper, we first introduce the novel challenges related to local handshaking in wireless networks with control-plane asymmetry. We then develop a theoretical framework for throughput analysis in a network where the sub-6 GHz RF channel is shared between a conventional RF link and an asymmetric RF/OWC link. This analysis is validated via simulation and verified in a testbed system using Mango WARP3 software defined radios and a commercially available RF access point. Finally, we use the derived throughput equations to analyze the impact of various protocol parameters and demonstrate one potential use of the derived equations to evaluate sum throughput in the presence of an unreliable OWC link.

Model-free machine learning of wireless SISO/MIMO communications

Machine learning is a highly promising tool to design the physical layer of wireless communication systems, but the training usually requires an explicit model of the signal distortion as it undergoes transmission over a wireless channel. As data rates, number of MIMO streams and carrier frequencies increase to satisfy the demand for wireless capacity, it becomes difficult to design hardware with few imperfections and to model the imperfections that there are. New machine learning schemes for the physical layer do not require an explicit model but can implicitly learn the end-to-end link including channel characteristics and non-linearities of the system directly from the training data. In this paper, we present a novel neural network architecture that provides an explicit stochastic model for both SISO and MIMO channels, by learning the parameters of a Gaussian mixture distribution from real channel samples. We use this channel model in conjunction with an autoencoder to learn a suitable modulation scheme. We experimentally validate our proposed model in an FPGA-based millimeter-wave testbed for both SISO and MIMO channels, showing that it is able to reproduce the channel characteristics with good accuracy.

Multi-Tier Heterogeneous Beam Management for Future Indoor FSO Networks

To meet the growing demand for wireless capacity, communications in the Terahertz (THz) and optical bands are being broadly explored. Communications within these bands provide massive bandwidth potential along with highly directional beam steering capabilities. While the available bandwidth offers incredible link capacity, the directionality of these technologies offers an even more significant potential for spatial capacity or area spectral efficiency. However, this directionality also implies a challenge related to the network’s ability to quickly establish a connection. In this paper, we introduce a multi-tier heterogeneous (MTH) beamform management strategy that utilizes various wireless technologies in order to quickly acquire a highly directional indoor free space optical communication (FSO) link. The multi-tier design offers the high resolution of indoor FSO while the millimeter-wave (mmWave) system narrows the FSO search space. By narrowing the search space, the system relaxes the requirements of the FSO network in order to assure a practical search time. This paper introduces the necessary components of the proposed beam management strategy and provides a foundational analysis framework to demonstrate the relative impact of coverage, resolution, and steering velocity across tiers. Furthermore, an optimization analysis is used to define the top tier resolution that minimizes worst-case search time as a function of lower tier resolution and top tier range.

On the Fundamental Characteristics of Ultra-Dense Small Cell Networks

In order to cope with the forecasted 1000 increase in wireless capacity demands by 2030, network operators will aggressively densify their network infrastructure to reuse the spectrum as much as possible. However, it is important to realize that these new ultra-dense small cell networks are fundamentally different from the traditional macrocell or sparse small cell networks, and thus UDNs cannot be deployed and operated in the same way as in the last 25 years. In this article, we systematically investigate and visualize the performance impacts of several fundamental characteristics of UDNs that mobile operators should consider when deploying UDNs. Moreover, we also provide new deployment and management guidelines to address the main challenges brought by UDNs in the future.

A Comparative Survey of Optical Wireless Technologies: Architectures and Applications

New high-data-rate multimedia services and applications are evolving continuously and exponentially increasing the demand for wireless capacity of fifth-generation (5G) and beyond. The existing radio frequency (RF) communication spectrum is insufficient to meet the demands of future high-datarate 5G services. Optical wireless communication (OWC), which uses an ultra-wide range of unregulated spectrum, has emerged as a promising solution to overcome the RF spectrum crisis. It has attracted growing research interest worldwide in the last decade for indoor and outdoor applications. OWC offloads huge data traffic applications from RF networks. A 100 Gb/s data rate has already been demonstrated through OWC. It offers services indoors as well as outdoors, and communication distances range from several nm to more than 10000 km. This paper provides a technology overview and a review on optical wireless technologies, such as visible light communication, light fidelity, optical camera communication, free space optical communication, and light detection and ranging. We survey the key technologies for understanding OWC and present state-of-the-art criteria in aspects, such as classification, spectrum use, architecture, and applications. The key contribution of this paper is to clarify the differences among different promising optical wireless technologies and between these technologies and their corresponding similar existing RF technologies

Combinatorial resource allocation in D2D assisted heterogeneous relay networks

Exponential increase in wireless capacity demands innovative network designs. Heterogeneous networks (HetNets) have been considered as a promising solution to ever increasing wireless capacity demand and efficient spectrum utilization. However severe interference scenarios exist in HetNets which hinder overall network performance. It is necessary to find optimal resource allocation strategies which can maximize capacity by mitigating interference to harvest the benefits of HetNets. This article formulates the problem of capacity maximization in device-to-device (D2D) assisted heterogeneous relay networks, using mixed integer nonlinear programming (MINLP). MINLP problems are NP-hard in general. Exhaustive search cannot be applied as search space of problem increases exponentially with number of users. Outer approximation algorithm (OAA) is proposed to solve capacity maximization problem. Proposed algorithm is evaluated by extensive simulation work which show that proposed approach is effective in terms of major key performance indicators (KPIs). KPIs considered for algorithm evaluation include user throughput (sum rate) and capacity in terms of number of users accommodated.

Streamlining Permitting Processes for Small Cells in the Right of Way

Increasing demand for wireless capacity and throughput is necessitating more widespread and variegated deployment of wireless infrastructure. Along with traditional cell towers, small cells, Distributed Antenna Systems (DAS), outdoor Wi-Fi, and Internet of Things nodes, increase capacity, but also require close and continuous proximity. As wireless communications is increasingly becoming treated as a necessary public utility, the industry is challenging municipalities and other government entities to streamline their processes for siting and modification of these facilities in the Right of Way. While permitting entities request well-integrated, context-appropriate, and secure facilities, wireless representatives respond that onerous requirements create a significant barrier in deployment. This paper describes existing issues within this conflict between local governments and the wireless industry based on comments submitted to the Federal Communications Commission proceeding titled “Streamlining Deployment of Small Cell Infrastructure by Improving Wireless Siting Policies” (docket 16-421). The goal of this paper is to present a fair and unbiased assessment of the issue from both sides, impart the complexity and emotional nuances of the situations in which contention or misunderstandings can arise, and describe preliminary administrative improvements. Eventually, this paper will be expanded to create materials to facilitate resolution of these issues and expedite permitting processes in a practical and concrete manner, including the analysis of various legal, administrative, architectural, and economic options. These recommendations and best practices will improve communication and negotiation procedures between municipalities and the wireless industry and result in cost-savings and diminished delays.

Coexistence of WiFi and LiFi toward 5G: concepts, opportunities, and challenges

Smart phones, tablets, and the rise of the Internet of Things are driving an insatiable demand for wireless capacity. This demand requires networking and Internet infrastructures to evolve to meet the needs of current and future multimedia applications. Wireless HetNets will play an important role toward the goal of using a diverse spectrum to provide high quality-of-service, especially in indoor environments where most data are consumed. An additional tier in the wireless HetNets concept is envisioned using indoor gigabit small-cells to offer additional wireless capacity where it is needed the most. The use of light as a new mobile access medium is considered promising. In this article, we describe the general characteristics of WiFi and VLC (or LiFi) and demonstrate a practical framework for both technologies to coexist. We explore the existing research activity in this area and articulate current and future research challenges based on our experience in building a proof-of-concept prototype VLC HetNet.

Increasing Opportunistic Gain in Small Cells Through Energy-Aware User Cooperation

To meet the increasing demand for wireless capacity, future networks are likely to consist of dense layouts of small cells. The number of users in each cell is thus reduced, which results in diminished gains from opportunistic scheduling, particularly under dynamic traffic loads. We propose a user-initiated base station (BS)-transparent traffic spreading approach that leverages user-user communication to increase BS scheduling flexibility. The proposed scheme can increase opportunistic gain and improve user performance. For a specified tradeoff between performance and power expenditure, we characterize the optimal policy by modeling the system as a Markov decision process and also present a heuristic algorithm that yields significant performance gains. Our simulations show that, in the performance-centric case, average file transfer delays are lowered by up to 20% even in homogeneous scenarios and up to 50% with heterogeneous users. Further, we show that the bulk of the performance improvement can be achieved with a small increase in power expenditure, e.g., in an energy-sensitive case, up to 78% of the performance improvement can be typically achieved at only 20% of the power expenditure of the performance-centric case.

Enhanced information throughput in multiple input multiple output orthogonal frequency division multiplexing based systems using fractional sampling and iterative signal processing

ABSTRACTHerein, we study the feasibility of enhanced information throughput capability of multiple input multiple output orthogonal frequency division multiplexing (MIMO‐OFDM) based wireless communication systems in the context of increasing wireless capacity demand. The concept of fractional sampling (FS) is exploited for this purpose to take advantage of diversity created because of it. Furthermore, a novel channel adaptive iterative sequence detector is proposed using the FS technique. The performance analysis of the proposed receiver is carried out, and a tighter performance bound is derived. It is found that the FS technique can improve bit error rate performance of MIMO and OFDM based systems provided that the noise samples are uncorrelated up to a certain level of FS rate. Moreover, it is observed that the performance improvement is a non‐linear function of the FS rate. Besides this, the simulation results show that the proposed iterative receiver can significantly enhance the information throughput of MIMO‐OFDM based wireless communication systems in comparison to conventional non‐iterative receivers. Copyright © 2013 John Wiley & Sons, Ltd.

LIGHTNETs: Smart LIGHTing and Mobile Optical Wireless NETworks — A Survey

Recently, rapid increase of mobile devices pushed the radio frequency (RF)-based wireless technologies to their limits. Free-space-optical (FSO), a.k.a. optical wireless, communication has been considered as one of the viable solutions to respond to the ever-increasing wireless capacity demand. Particularly, Visible Light Communication (VLC) which uses light emitting diode (LED) based smart lighting technology provides an opportunity and infrastructure for the high-speed low-cost wireless communication. Though stemming from the same core technology, the smart lighting and FSO communication have inherent tradeoffs amongst each other. In this paper, we present a tutorial and survey of advances in these two technologies and explore the potential for integration of the two as a single field of study: LIGHTNETs. We focus our survey to the context of mobile communications given the recent pressing needs in mobile wireless networking. We deliberate on key challenges involved in designing technologies jointly performing the two functions simultaneously: LIGHTing and NETworking.

Software Tool for Assessing the Viability of Secondary System Deployments in Whitespace Spectrum Access Scenarios

The increasing demand for wireless capacity has led to a depletion of unallocated spectrum resources in the popular sub-3 GHz frequency bands. In order to overcome this spectrum scarcity, various secondary spectrum access policies have been proposed. Especially for UHF bands where spectrum usage of the incumbent broadcasting system is comparably static, a move towards granting access on a non-interfering basis seems to be a plausible step. Regulators, governments, and industry alike are currently working on technically feasible and economically viable solutions for opening up more potential spectrum whitespaces. In order to allow coexistence between wireless systems in shared frequency bands, the effect of interference from secondary transmitters to primary receivers needs to be evaluated. Besides active practical testing which is conducted in large-scale field tests, regulatory policies are currently being developed that define rules for maximum power emission and minimum separation distances of secondary device installations. The most prominent example of such legislation is the TV whitespace ruling in the US, but other countries are catching up with scenario-dependent proposals. While the proposed rulings are still under evaluation, concerns have been raised as to whether they will scale for entire secondary systems with hundreds to thousands of deployed devices. Evaluation here is still in its infancy, as it encompasses a complex techno-economical eco-system with a large number of unknowns.To our understanding, the envisioned coexistence scenarios of primary and secondary systems need to be analyzed in a holistic manner. Only by jointly studying the technical, economic, and social effects of secondary deployments within potential whitespaces, can the real threats and potential of such deployments be revealed. In this demonstration we present a software tool that, for the first time, supports such studies by combining primary and secondary technology models, application of different regulatory rules, and derivation of key performance indicators. Information generated by our tool may subsequently be used for in-depth studies on the fitness of proposed whitespace policies, feasibility of technical implementation, and business aspects of secondary system deployments. Our tool deliberately goes beyond simple whitespace availability studies by providing extensive analysis opportunities and building on a large-scale primary spectrum usage database. This demonstration aims at raising awareness of the complexity of the required studies and presents a novel methodology that may be used for the necessary evaluations. As such, our tool can be of benefit to regulators, researchers, and industry in assessing the utility of secondary spectrum access.