Opportunistic spectrum sharing for D2D-based URLLC

A device-to-device (D2D) ultra-reliable low latency communications network is investigated in this paper. Specifically, a D2D transmitter opportunistically accesses the radio resource provided by a cellular network and directly transmits short packets to its destination. A novel performance metric is adopted for finite block-length code. We quantify the maximum achievable rate for the D2D network, subject to a probabilistic interference power constraint based on imperfect channel state information. First, we perform a convexity analysis that reveals that the finite block-length rate for the D2D pair in short-packet transmission is not always concave. To address this issue, we propose two effective resource allocation schemes using the successive convex approximation based iterative algorithm. To gain more insights, we exploit the monotonicity of the average finite block-length rate. By capitalizing on this property, an optimal power control policy is proposed, followed by closed-form expressions and approximations for the optimal average power and the maximum achievable average rate in the finite block-length regime. Numerical results are provided to confirm the effectiveness of the proposed resource allocation schemes and validate the accuracy of the derived theoretical results

Relaying in the Internet of Things (IoT): A Survey

The deployment of relays between Internet of Things (IoT) end devices and gateways can improve link quality. In cellular-based IoT, relays have the potential to reduce base station overload. The energy expended in single-hop long-range communication can be reduced if relays listen to transmissions of end devices and forward these observations to gateways. However, incorporating relays into IoT networks faces some challenges. IoT end devices are designed primarily for uplink communication of small-sized observations toward the network; hence, opportunistically using end devices as relays needs a redesign of both the medium access control (MAC) layer protocol of such end devices and possible addition of new communication interfaces. Additionally, the wake-up time of IoT end devices needs to be synchronized with that of the relays. For cellular-based IoT, the possibility of using infrastructure relays exists, and noncellular IoT networks can leverage the presence of mobile devices for relaying, for example, in remote healthcare. However, the latter presents problems of incentivizing relay participation and managing the mobility of relays. Furthermore, although relays can increase the lifetime of IoT networks, deploying relays implies the need for additional batteries to power them. This can erode the energy efficiency gain that relays offer. Therefore, designing relay-assisted IoT networks that provide acceptable trade-offs is key, and this goes beyond adding an extra transmit RF chain to a relay-enabled IoT end device. There has been increasing research interest in IoT relaying, as demonstrated in the available literature. Works that consider these issues are surveyed in this paper to provide insight into the state of the art, provide design insights for network designers and motivate future research directions

Multiple resource reuse for device-to-device communication in future cellular networks

Aufgrund der stärkeren Verbreitung neuer mobiler Anwendungen, z.B. Autonomes Fahren, automatisierte Prozesssteuerung, intelligente Städte / Wohnen und taktiles Internet, nimmt - die Anzahl und Dichte von Geräten, die drahtlose Verbindungen erfordern, immer weiter zu. Dies erfordert effizientere Verfahren zur Nutzung des verfügbaren Frequenzspektrums für zellulare Netze. Um dieser Herausforderung zu begegnen, wurden Ansätze, wie die gemeinsame Nutzung von Frequenzen, vorgeschlagen, um die gesamte spektrale Effizienz zu verbessern. Die Device-to-Device Kommunikation (D2D) mit paralleler Übertragung zu einem zellularen Netz bietet eine Verbesserung der spektralen Effizienz durch die verstärkte gemeinsame Nutzung des verfügbaren zellularen Spektrums. Mit D2D kommunizieren Geräte in unmittelbarer Nähe direkt miteinander ohne oder mit nur einer minimalen Kontrolle über das Mobilfunknetz. Das 3rd Generation Partnership Project (3GPP) unterstützt durch Standardisierung die Integration von D2D in Mobilfunknetze, um die spektralen Effizienzgewinne bei der gemeinsamen Nutzung von Frequenzen unter Gewährleistung der Quality of Service (QoS) zu realisieren. Die Interferenzen zwischen D2D und zellularen Benutzern müssen jedoch während der gemeinsamen Nutzung des Spektrums kontrolliert werden, um diese Gewinne im Netzwerk zu erhalten. Die vorliegende Arbeit untersucht Lösungen, mit denen das Frequenzspektrum des Mobilfunknetzes mit D2D-Benutzern geteilt werden kann, welche sowohl die spektrale Effizienz maximieren als auch die QoS-Anforderungen aller Benutzer erfüllen (in Bezug auf das Signal-zu-Rausch-plus-Interferenz Verhältnis (SINR)). Die vorliegende Arbeit gliedert sich in zwei Teile: eine analytische und eine algorithmische Studie. Zunächst untersucht die analytische Studie den Ansatz für ein Interferenzmanagement, in welchem mehrere D2D-Benutzer das zellulare Spektrum gemeinsam nutzen. Dabei wird die Zuteilung einer einheitlichen Interferenzleistung (UIP) vorgeschlagen - ein Verfahren, bei dem alle D2D-Benutzer mit gleicher Interferenz an der Basisstation (BS) beitragen. Dieses Schema wird auf ein Szenario einer einzelnen Zelle angewendet, welches sehr positive Ergebnisse bei der Verbesserung der spektralen Effizienz erzielt, obwohl einige D2D-Benutzer ihre SINR-Schwellenwerte nicht erreichen können. Eine wesentliche Erkenntnis aus der analytischen Studie ist, dass eine räumliche Trennung zwischen Benutzern, die das Spektrum gemeinsam nutzen, wichtig ist, um ihre gegenseitige Beeinflussung zu minimieren. Die algorithmische Studie konzentriert sich daher auf die Auswahl geeigneter D2D-Benutzern. Zunächst werden räumliche Auswahlkriterien formuliert mit dem Ziel, mehrere D2D-Benutzer zu identifizieren, die das Spektrum eines bestimmten Mobilfunkbenutzers gemeinsam nutzen können, um die spektrale Effizienz zu maximieren, während alle Benutzer ihre SINR-Schwellenwerte erreichen. Danach werden basierend auf diesen Kriterien zwei Auswahlalgorithmen entwickelt. Der erste Algorithmus wählt opportunistisch D2D-Benutzer aus, die bei bestimmten Auswahlinstanzen die geringste Störung für andere das Spektrum gemeinsam nutzende Benutzer verursachen. Der zweite Algorithmus wählt zufällig alle D2D-Benutzer aus, die räumliche von anderen Benutzern getrennt sind, jedoch das Spektrum gemeinsam nutzen. Beide Algorithmen werden mit sehr positiven Ergebnissen durch Simulationen in einem Szenario einer einzelnen Zelle mit einer unterschiedlichen Anzahl von Benutzern vorgestellt. In einem Szenario mit mehreren Zellen, in welchem die Interferenz zwischen den Zellen die Leistungsfähigkeit beeinträchtigt, werden Verbesserungen an beiden Algorithmen vorgestellt, um die festgelegten Ziele zu erreichen. Diese Verbesserungen passen die Auswahlkriterien an, um: 1) keine D2D-Benutzer mit Zellenkante auszuwählen und 2) die Auswirkungen der gemeinsamen Nutzung des Frequenzspektrums zwischen benachbarten Zellen zu berücksichtigen. Die Arbeit zeigt deutlich, dass mithilfe eines geeigneten Auswahlkriteriums mehrere D2D Nutzer in der Lage sind, die gemeinsame Frequenzressource mit zellularen Nutzern zu teilen mit Erhöhung der gesamten spektralen Effizienz und Beibehaltung der QoS Anforderungen aller Nutzer. Die hierbei erbrachten Erkenntnisse können zusammen mit den vorhandenen Ergebnissen als Ausgangspunkt für weitere akademische Forschung sowie einer praktischen Anwendung dienen.Owing to the further proliferation of new mobile applications, e.g. autonomous driving, automated process control, smart cities/homes, and tactile internet, the number and density of devices requiring wireless connectivity continue to increase. This demands ever more efficient methods for utilizing the available frequency spectrum for cellular networks. To counter this challenge, approaches like spectrum sharing have been proposed as enablers to improve the overall spectral efficiency. Device to device communication (D2D) as an underlaying transmission to the cellular network presents spectral efficiency improvements through the increased sharing of the available cellular spectrum. In D2D, devices in close proximity communicate directly with each other having either minimal or no control from the cellular network. The third generation partnership project (3GPP) supports, through standardization, the integration of D2D within cellular networks in order to realize the spectral efficiency gains during spectrum sharing and user quality of service (QoS) guarantees. However, the interference between D2D and cellular users during spectrum sharing must be controlled to get these gains in the network. This thesis studies the solutions through which the cellular network's frequency spectrum can be shared with D2D users to concurrently maximize the spectral efficiency and achieve all users' QoS requirements (in terms of threshold signal-to-interference-plus-noise ratio (SINR)). The thesis is divided into two parts: an analytical study and an algorithmic study. First, the analytical study evaluates the framework for interference management when several D2D users share the cellular network's spectrum. Therein, uniform interference power (UIP) allocation -- a scheme where all D2D users contribute equal interference at the base station (BS), is proposed. This scheme is applied to a single-cell scenario with very positive results in improving spectral efficiency although some D2D users are unable to achieve their threshold SINRs. The main lesson from the analytical study is that spatial separation between users sharing spectrum is important to minimize their mutual interference. So the algorithmic study focuses on D2D-users selection. First, spatial selection criteria are formulated with the objective of identifying multiple D2D users that can share a given cellular user's spectrum to maximize spectral efficiency while all users achieve their threshold SINRs. Thereafter, based on these criteria, two selection algorithms are developed. The first algorithm opportunistically selects D2D users causing the least interference, at given selection instances, to other users sharing the spectrum. The second algorithm randomly selects any D2D users meeting the minimal required spatial separation from other users sharing the spectrum. Both algorithms are presented with very positive results in simulations that consider a single-cell scenario with varying number of users. In a multi-cell scenario, where the experienced inter-cell interference degrades performance, enhancements to both algorithms are applied to achieve the set objectives. These enhancements adapt the selection criteria to: $1$) not select cell-edge D2D users and $2$) take into account the effects of spectrum sharing between neighbouring cells. The thesis studies clearly showed that, using appropriate selection criteria, multiple D2D users can share a specific cellular user's spectrum resources to improve the network's spectral efficiency and achieve all users' QoS requirements. These findings together with other existing results on D2D spectrum resource reuse can be the starting point for further academic research and practical implementation

The Potential Short- and Long-Term Disruptions and Transformative Impacts of 5G and Beyond Wireless Networks: Lessons Learnt from the Development of a 5G Testbed Environment

The capacity and coverage requirements for 5 th generation (5G) and beyond wireless connectivity will be significantly different from the predecessor networks. To meet these requirements, the anticipated deployment cost in the United Kingdom (UK) is predicted to be between £30bn and £50bn, whereas the current annual capital expenditure (CapEX) of the mobile network operators (MNOs) is £2.5bn. This prospect has vastly impacted and has become one of the major delaying factors for building the 5G physical infrastructure, whereas other areas of 5G are progressing at their speed. Due to the expensive and complicated nature of the network infrastructure and spectrum, the second-tier operators, widely known as mobile virtual network operators (MVNO), are entirely dependent on the MNOs. In this paper, an extensive study is conducted to explore the possibilities of reducing the 5G deployment cost and developing viable business models. In this regard, the potential of infrastructure, data, and spectrum sharing is thoroughly investigated. It is established that the use of existing public infrastructure (e.g., streetlights, telephone poles, etc.) has a potential to reduce the anticipated cost by about 40% to 60%. This paper also reviews the recent Ofcom initiatives to release location-based licenses of the 5G-compatible radio spectrum. Our study suggests that simplification of infrastructure and spectrum will encourage the exponential growth of scenario-specific cellular networks (e.g., private networks, community networks, micro-operators) and will potentially disrupt the current business models of telecommunication business stakeholders - specifically MNOs and TowerCos. Furthermore, the anticipated dense device connectivity in 5G will increase the resolution of traditional and non-traditional data availability significantly. This will encourage extensive data harvesting as a business opportunity and function within small and medium-sized enterprises (SMEs) as well as large social networks. Consequently, the rise of new infrastructures and spectrum stakeholders is anticipated. This will fuel the development of a 5G data exchange ecosystem where data transactions are deemed to be high-value business commodities. The privacy and security of such data, as well as definitions of the associated revenue models and ownership, are challenging areas - and these have yet to emerge and mature fully. In this direction, this paper proposes the development of a unified data hub with layered structured privacy and security along with blockchain and encrypted off-chain based ownership/royalty tracking. Also, a data economy-oriented business model is proposed. The study found that with the potential commodification of data and data transactions along with the low-cost physical infrastructure and spectrum, the 5G network will introduce significant disruption in the Telco business ecosystem