NOMA Schemes for Multibeam Satellite Communications

Non-orthogonal multiple access (NOMA) schemes are being considered in 5G new radio developments and beyond. Although seminal papers demonstrated that NOMA outperforms orthogonal access in terms of capacity and user fairness, the majority of works have been devoted to the wireless terrestrial arena. Therefore, it is worth to study how NOMA can be implemented in other types of communications, as for instance the satellite ones, which are also part of the 5G infrastructure. Although communications through a satellite present a different architecture than those in the wireless terrestrial links, NOMA can be an important asset to improve their performance. This article introduces a general overview of how NOMA can be applied to this different architecture. A novel taxonomy is presented based on different multibeam transmission schemes and guidelines that open new avenues for research in this topic are provided

A Survey on Cross-Layer Design Frameworks for Multimedia Applications over Wireless Networks

In the last few years, the Internet throughput, usage and reliability have increased almost exponentially. The introduction of broadband wireless mobile ad hoc networks (MANETs) and cellular networks together with increased computational power have opened the door for a new breed of applications to be created, namely real-time multimedia applications. Delivering real-time multimedia traffic over a complex network like the Internet is a particularly challenging task since these applications have strict quality -of-service (QoS) requirements on bandwidth, delay, and delay jitter. Traditional IP-based best effort service will not be able to meet these stringent requirements. The time-varying nature of wireless channels and resource constrained wireless devices make the problem even more difficult. To improve perceived media quality by end users over wireless Internet, QoS supports can be addressed in different layers, including application layer, transport layer and link layer. Cross layer design is a well-known approach to achieve this adaptation. In cross-layer design, the challenges from the physical wireless medium and the QoS-demands from the applications are taken into account so that the rate, power, and coding at the physical layer can adapted to meet the requirements of the applications given the current channel and network conditions. A number of propositions for cross-layer designs exist in the literature. In this paper, an extensive review has been made on these cross-layer architectures that combine the application-layer, transport layer and the link layer controls. Particularly the issues like channel estimation techniques, adaptive controls at the application and link layers for energy efficiency, priority based scheduling, transmission rate control at the transport layer, and adaptive automatic repeat request (ARQ) are discussed in detail.Comment: 16 pages, 9 figure

Maplets: An Efficient Approach for Cooperative SLAM Map Building Under Communication and Computation Constraints

This article introduces an approach to facilitate cooperative exploration and mapping of large-scale, near-ground, underground, or indoor spaces via a novel integration framework for locally-dense agent map data. The effort targets limited Size, Weight, and Power (SWaP) agents with an emphasis on limiting required communications and redundant processing. The approach uses a unique organization of batch optimization engines to enable a highly efficient two-tier optimization structure. Tier I consist of agents that create and potentially share local maplets (local maps, limited in size) which are generated using Simultaneous Localization and Mapping (SLAM) map-building software and then marginalized to a more compact parameterization. Maplets are generated in an overlapping manner and used to estimate the transform and uncertainty between those overlapping maplets, providing accurate and compact odometry or delta-pose representation between maplet's local frames. The delta poses can be shared between agents, and in cases where maplets have salient features (for loop closures), the compact representation of the maplet can also be shared. The second optimization tier consists of a global optimizer that seeks to optimize those maplet-to-maplet transformations, including any loop closures identified. This can provide an accurate global "skeleton"' of the traversed space without operating on the high-density point cloud. This compact version of the map data allows for scalable, cooperative exploration with limited communication requirements where most of the individual maplets, or low fidelity renderings, are only shared if desired

Discovery Signal Design and Its Application to Peer-to-Peer Communications in OFDMA Cellular Networks

This paper proposes a unique discovery signal as an enabler of peer-to-peer (P2P) communication which overlays a cellular network and shares its resources. Applying P2P communication to cellular network has two key issues: 1. Conventional ad hoc P2P connections may be unstable since stringent resource and interference coordination is usually difficult to achieve for ad hoc P2P communications; 2. The large overhead required by P2P communication may offset its gain. We solve these two issues by using a special discovery signal to aid cellular network-supervised resource sharing and interference management between cellular and P2P connections. The discovery signal, which facilitates efficient neighbor discovery in a cellular system, consists of un-modulated tones transmitted on a sequence of OFDM symbols. This discovery signal not only possesses the properties of high power efficiency, high interference tolerance, and freedom from near-far effects, but also has minimal overhead. A practical discovery-signal-based P2P in an OFDMA cellular system is also proposed. Numerical results are presented which show the potential of improving local service and edge device performance in a cellular network.Comment: arXiv admin note: text overlap with arXiv:1112.1990, arXiv:1207.0557 add reference in page 5 add text in page 5 for explainatio

Performance Analysis of Multi-Service Oriented Multiple Access Under General Channel Correlation

In this article, we provide both analytical and numerical performance analysis of multi-service oriented multiple access (MOMA), a recently proposed non-orthogonal multiple-access scheme for scenarios with a massive number of concurrent connections originating from separate service classes with diverse quality-of-service (QoS) profiles and running on both handheld terminals and Internet-of-Things (IoT) devices. MOMA is based on both class dependent hierarchical-spreading transmission scheme and per-class reception structure. The performance analysis presented in this article is based on realistic channel and signal models for scenarios where the base station is equipped with a large number of antennas. It provides asymptotically exact approximations of the ergodic rates achievable by MOMA.Comment: 6 pages, 3 figures, accepted for publication in GLOBECOM 2017, Singapor

On Coordinating Ultra-Dense Wireless Access Networks: Optimization Modeling, Algorithms and Insights

Network densification along with universal resources reuse is expected to play a key role in the realization of 5G radio access as an enabler for delivering most of the anticipated network capacity improvements. On the one hand, neither the expected additional spectrum allocation nor the forthcoming novel air-interface processing techniques will be sufficient for sustaining the anticipated exponentially-increasing mobile data traffic. On the other hand, enhanced ultra-dense infrastructure deployments are expected to provide remarkable capacity gains, regardless of the evolutionary or revolutionary approach followed towards 5G development. In this work, we thoroughly examine global network coordination as the main enabler for future 5G large dense small-cell deployments. We propose a powerful radio resources coordination framework through which interference management is handled network-wise and jointly over multiple dimensions. In particular, we explore strategies for pairing serving and served access nodes, partitioning the available network resources, as well as dynamically allocating power per pair, towards optimizing system performance and guaranteeing individual minimum performance levels. We develop new optimization formulations, providing network scaling performance upper bounds, along with lower complexity algorithmic solutions tailored to large networks. We apply the proposed solutions to dense network deployments, in order to obtain useful insights on network performance and optimization, such as rate scaling, infrastructure density, optimal bandwidth partitioning and spatial reuse factor optimization.Comment: ART-COMP PE7/396 Research Project Technical Repor

A Survey on Non-Orthogonal Multiple Access for 5G Networks: Research Challenges and Future Trends

Non-orthogonal multiple access (NOMA) is an essential enabling technology for the fifth generation (5G) wireless networks to meet the heterogeneous demands on low latency, high reliability, massive connectivity, improved fairness, and high throughput. The key idea behind NOMA is to serve multiple users in the same resource block, such as a time slot, subcarrier, or spreading code. The NOMA principle is a general framework, and several recently proposed 5G multiple access schemes can be viewed as special cases. This survey provides an overview of the latest NOMA research and innovations as well as their applications. Thereby, the papers published in this special issue are put into the content of the existing literature. Future research challenges regarding NOMA in 5G and beyond are also discussed.Comment: to appear in IEEE JSAC, 201

In-Band Full-Duplex Wireless: Challenges and Opportunities

In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. Because one the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference caused by an IBFD node's own transmissions to its desired receptions, this tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems

Ray-of-Arrival Passing for Indirect Beam Training in Cooperative Millimeter Wave MIMO Networks

This paper is concerned with the channel estimation problem in multi-cell Millimeter (mmWave) wireless systems. We develop a novel Ray-of-Arrival Passing for Indirect (RAPID) Beam Training framework, in which a network consisting of multiple BS are able to work cooperatively to estimate jointly the UE channels. To achieve this aim, we consider the spatial geometry of the mmWave environment and transform conventional angular domain beamforming concepts into the more euclidean, Ray-based domain. Leveraging this model, we then consider the conditional probabilities that pilot signals are received in each direction, given that the deployment of each BS is known to the network. Simulation results show that RAPID is able to improve the average estimation of the network and significantly increase the rate of poorer quality links. Furthermore, we also show that, when a coverage rate threshold is considered, RAPID is able to improve greatly the probability that multiple link options will be available to a user at any given time

Sequential Joint Spectrum Sensing and Channel Estimation for Dynamic Spectrum Access

Dynamic spectrum access under channel uncertainties is considered. With the goal of maximizing the secondary user (SU) throughput subject to constraints on the primary user (PU) outage probability we formulate a joint problem of spectrum sensing and channel state estimation. The problem is cast into a sequential framework since sensing time minimization is crucial for throughput maximization. In the optimum solution, the sensing decision rule is coupled with the channel estimator, making the separate treatment of the sensing and channel estimation strictly suboptimal. Using such a joint structure for spectrum sensing and channel estimation we propose a distributed (cooperative) dynamic spectrum access scheme under statistical channel state information (CSI). In the proposed scheme, the SUs report their sufficient statistics to a fusion center (FC) via level-triggered sampling, a nonuniform sampling technique that is known to be bandwidth-and-energy efficient. Then, the FC makes a sequential spectrum sensing decision using local statistics and channel estimates, and selects the SU with the best transmission opportunity. The selected SU, using the sensing decision and its channel estimates, computes the transmit power and starts data transmission. Simulation results demonstrate that the proposed scheme significantly outperforms its conventional counterparts, under the same PU outage constraints, in terms of the achievable SU throughput