Capacity Enhancement in 60 GHz Based D2D Networks by Relay Selection and Scheduling

Millimeter-wave or 60 GHz communication is a promising technology that enables data rates in multigigabits. However, its tremendous propagation loss and signal blockage may severely affect the network throughput. In current data-centric device-to-device (D2D) communication networks, the devices with intended data communications usually lay in close proximity, unlike the case in voice-centric networks. So the network can be visualized as a naturally formed groups of devices. In this paper, we jointly consider resource scheduling and relay selection to improve network capacity in 60 GHz based D2D networks. Two types of transmission scenarios are considered in wireless personal area networks (WPANs), intra and intergroup. A distributed receiver based relay selection scheme is proposed for intragroup transmission, while a distance based relay selection scheme is proposed for intergroup transmission. The outage analysis of our proposed relay selection scheme is provided along with the numerical results. We then propose a concurrent transmission scheduling algorithm based on vertex coloring technique. The proposed scheduling algorithm employs time and space division in mmWave WPANs. Using vertex multicoloring, we allow transmitter-receiver (Tx-Rx) communication pairs to span over more colors, enabling better time slot utilization. We evaluate our scheduling algorithm in single-hop and multihop scenarios and discover that it outperforms other schemes by significantly improving network throughput

Enabling Millimeter Wave Communication for 5G Cellular Networks: MAC-layer Perspective

Data traffic among mobile devices increases dramatically with emerging high-speed multimedia applications such as uncompressed video streaming. Many new applications beyond personal communications involve tens or even hundreds of billions wireless devices, such as wireless watch, e-health sensors, and wireless glass. The number of wireless devices and the data rates will continue to grow exponentially. Quantitative evidences forecast that total data rate by 2020 will be 1000 times of current 4G data rate. Next generation wireless networks need fundamental changes to satisfy the overwhelming capacity demands. Millimeter wave (mmWave) communication with huge available bandwidth is a very promising solution for next generation wireless networks to overcome the global bandwidth shortage at saturated microwave spectrum. The large available bandwidth can be directly translated into high capacity. mmWave communication has several propagation characteristics including strong pathloss, atmospheric and rain absorption, low diffraction around obstacles and penetration through objects. These propagation characteristics create challenges for next generation wireless networks to support various kinds of emerging applications with different QoS requirements. Our research focuses on how to effectively and efficiently exploit the large available mmWave bandwidth to achieve high capacity demand while overcoming these challenges on QoS provisioning for various kinds of applications. This thesis focuses on MAC protocol design and analysis for mmWave communication to provide required capacity and QoS to support various kinds of applications in next generation wireless networks. Specifically, from the transmitter/receiver perspective, multi-user beamforming based on codebook is conducted to determine best transmission/reception beams to increase network capacity considering the mutual interferences among concurrent links. From the channel perspective, both interfering and non-interfering concurrent links are scheduled to operate simultaneously to exploit spatial reuse and improve network capacity. Link outage problem resulting from the limited diffraction capability and low penetration capability of mmWave band is addressed for quality provisioning by enabling multi-hop transmission to replace the link in outage (for low-mobility scenarios) and buffer design with dynamic bandwidth allocation among all the users in the whole coverage area (for high-mobility scenarios). From the system perspective, system structure, network architecture, and candidate MAC are investigated and novel backoff mechanism for CSMA/CA is proposed to give more transmission opportunity to faraway nodes than nearby nodes in order to achieve better fairness and higher network capacity. In this thesis, we formulate each problem mentioned above as an optimization problem with the proposed algorithms to solve it. Extensive analytical and simulation results are provided to demonstrate the performance of the proposed algorithms in several aspects, such as network capacity, energy efficiency, link connectivity and so on

On the trade-off between uncertainty and delay in UWB and 5G localization

Location-aware technologies in combination with emerging wireless communication systems\ua0have revolutionized many aspects of our daily lives by means of applications within\ua0the commercial, public and military sectors. Ultra-wideband (UWB) and 5G stand\ua0out as emerging radio frequency (RF) based technologies that tackle the limitations of\ua0Global Positioning System solutions. The thrive in search for better accuracy involves\ua0improved ranging algorithms, higher transmission powers, network densification, larger\ua0bandwidths, and the use of cooperation among nodes in the network. However, practical\ua0implementations introduce communication related constraints. In this thesis, we study\ua0the trade-off between localization accuracy and communication constraints in terms of\ua0delay. This trade-off is investigated and quantified for two of the most rapidly growing\ua0RF technologies for high precision positioning: UWB and 5G.In UWB, we investigate the trade-off between medium access control (MAC) delay and\ua0accuracy based on a two-way-ranging and a spatial time division multiple access scheme.\ua0We quantify this relationship by deriving lower bounds on localization accuracy and MAC\ua0delay during the measurements phase, which is often neglected in the analyses. We find\ua0that the traditional means to improve accuracy such as increased number of anchors,\ua0increased communication range, and cooperation among nodes, come at a significant cost\ua0in terms of delay, which can be mitigated by means of techniques such as selective ranging\ua0and eavesdropping. We summarize and generalize our findings by characterizing the\ua0position error and delay lower bounds by deriving asymptotic scaling laws. These scaling\ua0laws are presented for dense noncooperative and cooperative networks in combination\ua0with delay mitigation techniques. Moreover, we introduce a delay/accuracy trade-off\ua0parameter, which can uniquely quantify the trade-off as a function of the agent and\ua0anchor density. Finally, we consider the problem of fast link scheduling and propose an\ua0optimization strategy to perform robust ranging scheduling with localization constraints.\ua0We propose two MAC-aware link selection heuristic approximation approaches which\ua0show similar performance as the optimal solution, but alleviate the problem complexity.In 5G, we analyze the interplay between communication and positioning within the initial\ua0access procedure between a transmitter and a receiver in a millimeter-wave multipleinput\ua0multiple-output system. We exploit the ability of the receiver to determine its\ua0location during the beam selection process and thus, improve the subsequent selection\ua0of beams within initial access. First, assuming that only the transmitter has beamforming\ua0capabilities, we propose an in-band position-aided transmitter beam selection\ua0protocol for scenarios with direct line-of-sight and scattering. Then, we extend the work\ua0and propose an in-band position-aided beam selection protocol where we also allow for\ua0the receiver to perform beamforming in scenarios with line-of-sight, reflected paths, and\ua0possible beam alignment errors. Both protocols show similar performance compared to\ua0their conventional counterparts in terms of final achieved signal-to-noise ratio, but they\ua0are significantly faster and can additionally provide the position and orientation of the\ua0devices in an accurate manner

Belaidžio ryšio tinklų terpės prieigos valdymo tyrimas

Over the years, consumer requirements for Quality of Service (QoS) has been growing exponentially. Recently, the ratification process of newly IEEE 802.11ad amendment to IEEE 802.11 was finished. The IEEE 802.11ad is the newly con-sumer wireless communication approach, which will gain high spot on the 5G evolution. Major players in wireless market, such as Qualcomm already are inte-grating solutions from unlicensed band, like IEEE 802.11ac, IEEE 802.11ad into their architecture of LTE PRO (the next evolutionary step for 5G networking) (Qualcomm 2013; Parker et al. 2015). As the demand is growing both in enter-prise wireless networking and home consumer markets. Consumers started to no-tice the performance degradation due to overcrowded unlicensed bands. The un-licensed bands such as 2.4 GHz, 5 GHz are widely used for up-to-date IEEE 802.11n/ac technologies with upcoming IEEE 802.11ax. However, overusage of the available frequency leads to severe interference issue and consequences in to-tal system performance degradation, currently existing wireless medium access method can not sustain the increasing intereference and thus wireless needs a new methods of wireless medium access. The main focal point of this dissertation is to improve wireless performance in dense wireless networks. In dissertation both the conceptual and multi-band wireless medium access methods are considered both from theoretical point of view and experimental usage. The introduction chapter presents the investigated problem and it’s objects of research as well as importance of dissertation and it’s scientific novelty in the unlicensed wireless field. Chapter 1 revises used literature. Existing and up-to-date state-of-the-art so-lution are reviewed, evaluated and key point advantages and disadvantages are analyzed. Conclusions are drawn at the end of the chapter. Chapter 2 describes theoretical analysis of wireless medium access protocols and the new wireless medium access method. During analysis theoretical simula-tions are performed. Conclusions are drawn at the end of the chapter. Chapter 3 is focused on the experimental components evaluation for multi-band system, which would be in line with theoretical concept investigations. The experimental results, showed that components of multi-band system can gain sig-nificant performance increase when compared to the existing IEEE 802.11n/ac wireless systems. General conclusions are drawn after analysis of measurement results