OGMAD: Optimal GTS-Allocation Mechanism for Adaptive Data Requirements in IEEE 802.15.4 Based Internet of Things

Future Internet of Things (IoT) will utilize IEEE 802.15.4 based low data rate communication for various applications. In the IEEE 802.15.4 standard, nodes send data to their Personal Area Network (PAN) coordinator using the Guaranteed Time Slot (GTS). The standard does not meet the adaptive data requirements of GTS requesting nodes in an efficient manner. If requesting GTSs in an active period are more or less than the available limit, either the requested nodes will not be entertained or GTSs remain underutilized. Consequently, it may cause unnecessary delay or poor GTS utilization. In this paper, an Optimal GTS allocation Mechanism for Adaptive Duty cycle (OGMAD) is proposed that adapts the active period of the superframe in accordance with the requested data. OGMAD also reduces GTS size to improve link utilization as well as accommodate more GTS requesting nodes. Simulation results verify that OGMAD improves link utilization, reduces network delay and offers more nodes to transmit their data as compared to the standard

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

Doubly Orthogonal Wavelet Packets for Multi-Users Indoor Visible Light Communication Systems

Visible Light Communication (VLC) is a data communication technology that modulates the intensity of the light to transmit the information mostly by means of Light Emitting Diodes (LEDs). The data rate is mainly throttled by the limited bandwidth of the LEDs. To combat, Multi-carrier Code Division Multiple Access (MC-CDMA) is a favorable technique for achieving higher data rates along with reduced Inter-Symbol Interference (ISI) and easy access to multi-users at the cost of slightly reduced compromised spectral efficiency and Multiple Access Interference (MAI). In this article, a multi-user VLC system is designed using a Discrete Wavelet Transform (DWT) that eradicates the use of cyclic prefix due to the good orthogonality and time-frequency localization properties of wavelets. Moreover, the design also comprises suitable signature codes, which are generated by employing double orthogonality depending upon Walsh codes and Wavelet Packets. The proposed multi-user system is simulated in MATLAB software and its overall performance is assessed using line-of-sight (LoS) and non-line-of-sight (NLoS) configurations. Furthermore, two sub-optimum multi-users detection schemes such as zero forcing (ZF) and minimum-mean-square-error (MMSE) are also used at the receiver. The simulated results illustrate that the doubly orthogonal signature waveform-based DWT-MC-CDMA with MMSE detection scheme outperforms the Walsh code-based multi-user system

New methods of partial transmit sequence for reducing the high peak-to-average-power ratio with low complexity in the ofdm and f-ofdm systems

The orthogonal frequency division multiplexing system (OFDM) is one of the most important components for the multicarrier waveform design in the wireless communication standards. Consequently, the OFDM system has been adopted by many high-speed wireless standards. However, the high peak-to-average- power ratio (PAPR) is the main obstacle of the OFDM system in the real applications because of the non-linearity nature in the transmitter. Partial transmit sequence (PTS) is one of the effective PAPR reduction techniques that has been employed for reducing the PAPR value 3 dB; however, the high computational complexity is the main drawback of this technique. This thesis proposes novel methods and algorithms for reducing the high PAPR value with low computational complexity depending on the PTS technique. First, three novel subblocks partitioning schemes, Sine Shape partitioning scheme (SS-PTS), Subsets partitioning scheme (Sb-PTS), and Hybrid partitioning scheme (H-PTS) have been introduced for improving the PAPR reduction performance with low computational complexity in the frequency-domain of the PTS structure. Secondly, two novel algorithms, Grouping Complex iterations algorithm (G-C-PTS), and Gray Code Phase Factor algorithm (Gray-PF-PTS) have been developed to reduce the computational complexity for finding the optimum phase rotation factors in the time domain part of the PTS structure. Third, a new hybrid method that combines the Selective mapping and Cyclically Shifts Sequences (SLM-CSS-PTS) techniques in parallel has been proposed for improving the PAPR reduction performance and the computational complexity level. Based on the proposed methods, an improved PTS method that merges the best subblock partitioning scheme in the frequency domain and the best low-complexity algorithm in the time domain has been introduced to enhance the PAPR reduction performance better than the conventional PTS method with extremely low computational complexity level. The efficiency of the proposed methods is verified by comparing the predicted results with the existing modified PTS methods in the literature using Matlab software simulation and numerical calculation. The results that obtained using the proposed methods achieve a superior gain in the PAPR reduction performance compared with the conventional PTS technique. In addition, the number of complex addition and multiplication operations has been reduced compared with the conventional PTS method by about 54%, and 32% for the frequency domain schemes, 51% and 65% for the time domain algorithms, 18% and 42% for the combining method. Moreover, the improved PTS method which combines the best scheme in the frequency domain and the best algorithm in the time domain outperforms the conventional PTS method in terms of the PAPR reduction performance and the computational complexity level, where the number of complex addition and multiplication operation has been reduced by about 51% and 63%, respectively. Finally, the proposed methods and algorithms have been applied to the OFDM and Filtered-OFDM (F-OFDM) systems through Matlab software simulation, where F-OFDM refers to the waveform design candidate in the next generation technology (5G)

Integration of unidirectional technologies into wireless back-haul architecture

This thesis was submitted for the degree of Docter of Philosophy and awarded by Brunel University.Back-haul infrastructures of today's wireless operators must support the triple-play services demanded by the market or regulatory bodies. To cope with increasing capacity demand, the EU FP7 project CARMEN has developed a cost-effective heterogeneous multi-radio wireless back-haul architecture, which may also leverage the native multicast capabilities of broadcast technologies such as DVB-T to off-load high-bandwidth broadcast content delivery. However, the integration of such unidirectional technologies into a packet-switched architecture requires careful considerations. The contribution of this thesis is the investigation, design and evaluation of protocols and mechanisms facilitating the integration of such unidirectional technologies into the wireless back-haul architecture so that they can be configured and utilized by the spectrum and capacity optimization modules. This integration mainly concerns the control plane and, in particular, the aspects related to resource and capability descriptions, neighborhood, link and Multi Protocol Label Switching (MPLS) Label-Switched Path (LSP) monitoring, unicast and multicast LSP signalling as well as topology forming and maintenance. During the course of this study we have analyzed the problem space, proposed solutions to the resulting research questions and evaluated our approach. Our results show that the now Unidirectional Technology (UDT)-aware architecture can readily consider Unidirectional Technologies (UDTs) to distribute, for example, broadcast content

Thirty Years of Machine Learning: The Road to Pareto-Optimal Wireless Networks

Future wireless networks have a substantial potential in terms of supporting a broad range of complex compelling applications both in military and civilian fields, where the users are able to enjoy high-rate, low-latency, low-cost and reliable information services. Achieving this ambitious goal requires new radio techniques for adaptive learning and intelligent decision making because of the complex heterogeneous nature of the network structures and wireless services. Machine learning (ML) algorithms have great success in supporting big data analytics, efficient parameter estimation and interactive decision making. Hence, in this article, we review the thirty-year history of ML by elaborating on supervised learning, unsupervised learning, reinforcement learning and deep learning. Furthermore, we investigate their employment in the compelling applications of wireless networks, including heterogeneous networks (HetNets), cognitive radios (CR), Internet of things (IoT), machine to machine networks (M2M), and so on. This article aims for assisting the readers in clarifying the motivation and methodology of the various ML algorithms, so as to invoke them for hitherto unexplored services as well as scenarios of future wireless networks.Comment: 46 pages, 22 fig

An Adaptive Packet Aggregation Algorithm (AAM) for Wireless Networks

Packet aggregation algorithms are used to improve the throughput performance by combining a number of packets into a single transmission unit in order to reduce the overhead associated with each transmission within a packet-based communications network. However, the throughput improvement is also accompanied by a delay increase. The biggest drawback of a significant number of the proposed packet aggregation algorithms is that they tend to only optimize a single metric, i.e. either to maximize throughput or to minimize delay. They do not permit an optimal trade-off between maximizing throughput and minimizing delay. Therefore, these algorithms cannot achieve the optimal network performance for mixed traffic loads containing a number of different types of applications which may have very different network performance requirements. In this thesis an adaptive packet aggregation algorithm called the Adaptive Aggregation Mechanism (AAM) is proposed which achieves an aggregation trade-off in terms of realizing the largest average throughput with the smallest average delay compared to a number of other popular aggregation algorithms under saturation conditions in wireless networks. The AAM algorithm is the first packet aggregation algorithm that employs an adaptive selection window mechanism where the selection window size is adaptively adjusted in order to respond to the varying nature of both the packet size and packet rate. This algorithm is essentially a feedback control system incorporating a hybrid selection strategy for selecting the packets. Simulation results demonstrate that the proposed algorithm can (a) achieve a large number of sub-packets per aggregate packet for a given delay and (b) significantly improve the performance in terms of the aggregation trade-off for different traffic loads. Furthermore, the AAM algorithm is a robust algorithm as it can significantly improve the performance in terms of the average throughput in error-prone wireless networks

스마트 그리드를 위한 전력선 통신의 신뢰성 향상 기법 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 8. 김성철.지구 온난화, 증가하는 에너지 요구 및 최대 부하에 따른 위험 문제 등을 해결하기 위해, 스마트 그리드 구축을 위한 많은 노력들이 진행 중이다. 스마트 그리드를 구현하기 위해서는 향상된 정보통신 기술이 필요하며, 이는 통신 네트워크를 통한 안정성 있는 데이터 전송 여부에 달려있다. 스마트 그리드를 위한 여러 통신기술 후보 중 전력선통신 (PLC), 특히 중전압 (MV) 전력선 상의 고속 PLC에 집중하였다. 전력선 통신 네트워크의 신뢰성은 전력선이 스마트 그리드의 통신 매체로 올바르게 동작하기 위한 선결 조건이다. 본 논문에서는 전력선 통신을 보다 신뢰성 있고 강건하게 만들기 위한 방안에 대하여 연구한다. 이를 위해 OFDM 기반의 전력선 통신 시스템에서 최대비합성 (MRC) 다이버시티 구조를 고안한다. 이러한 시스템에서 최대비합성 다이버시티 이득을 최대화하기 위한 최적의 부반송파 페어링 (subcarrier pairing) 기법을 제안한다. 모의실험을 통해 제안하는 기법의 성능 향상 여부를 검증한다. 다이버시티 이득은 주파수 효율의 감소를 유발한다. 앞의 제안된 부반송파 페어링 기법으로 인해 본질적으로 발생하는 주파수 효율 감소를 해결하기 위해, 무선 MIMO 채널의 전처리 (precoding) 기법을 적용한다. 모의실험 결과를 통해, 높은 변조 지수로 페어링 기법을 이용하는 것이 매우 많은 계산량이 필요한 전처리 기법과 비교하여 유사한 성능을 나타냄을 알 수 있다. 다음으로 최대비합성 기반 최적 부반송파 페어링 기법을 전력선/무선 다이버시티 시스템에 확장한다. 이 시스템에서 전력선과 무선시스템의 각 부반송파들은 짝을 이루어 최대비합성을 수행한다. 전체 데이터 전송률을 최대화하기 위해 앞과 유사한 최적 부반송파 페어링 기법을 제안한다. 모의실험 결과를 통해 제안된 기법이 데이터 전송률과 아웃티지 확률 측면에서 상당한 성능 향상을 나타낸다.To solve the problems of global warming effects, rising energy-hungry demands, and risks of peak loads, many efforts to build a Smart Grid system are underway. A smart grid requires advanced information, and communication technologies to support its intelligent features, and it depends on the reliable data transmission via a communication network. Among the candidates of communication technology for smart grid, we focus on a power line communications (PLC), especially a broadband PLC over a medium voltage (MV) powerline network. The reliability of the PLC network are prerequisite for an appropriate communication medium for smart grid. This dissertation considers a strategy to make the PLC network more reliable and robust. We consider a maximal ratio combining (MRC) diversity scheme for a power line orthogonal frequency division multiplexing (OFDM) system. An optimal subcarrier pairing scheme is proposed to maximize the MRC gain. Numerical results are presented to verify that the proposed scheme provides enhanced performance. Diversity gain comes at the expense of spectral loss. We adopt the precoding scheme proposed for wireless MIMO system to compensate the spectral loss due to the inherent transmission mechanism of the above subcarrier pairing scheme. It is shown that the proposed pairing scheme with higher modulation order achieves a comparable performance to the precoding scheme which requires high computational cost. We extend the optimal subcarrier pairing with MRC approach to powerline/wireless diversity system, where the powerline and wireless subcarriers are paired to perform maximal ratio combining (MRC). An similar optimal subcarrier pairing scheme is proposed to maximize the data rate for MRC reception in powerline/wireless diversity OFDM systems. Numerical results show that, by using the proposed optimal subcarrier pairing, significant performance enhancement can be achieved in terms of Ergodic data rate and outage probability.1 Introduction 1 1.1 Smart Grid 1 1.2 Communication and Networking in the Smart Grid 5 1.2.1 Network Topologies 6 1.2.2 Communication Technologies for the Smart Grid 8 1.3 Dissertation Outline 11 2 Power Line Communications for Smart Grid 12 2.1 Power Line Channel Characteristics 15 2.2 PLC Channel Modeling 15 2.3 PLC Channel Noise Characteristics 17 2.4 MV Channel Description for This Dissertation 19 2.4.1 Implementation of Powerline Channel 19 2.4.2 Typical Topology 22 2.5 MV Powerline Noise 25 3 Optimal Subcarrier Pairing for Maximal Ratio Combining in OFDM Power Line Communications 27 3.1 Motivation 27 3.2 Optimal Subcarrier Pairing for Maximal Ratio Combining 28 3.2.1 System Model 28 3.2.2 Optimal Subcarrier Pairing 31 3.3 Numerical Results 33 3.3.1 Simulation Environments 33 3.3.2 SER Performance Analysis 35 3.3.3 Performance Comparison with Equal Gain Combining 38 3.4 Precoding Scheme to Compensate Spectral Loss Due to Diversity Transmission 40 3.4.1 Review of the Minimum Distance-Based Precoder for MIMO Spatial Multiplexing Systems 41 3.4.2 Optimal Minimum Distance-Based Precoder for QPSK Constellation 41 3.4.3 Application to PLC OFDM System 44 3.4.4 Performance Comparison of max-dmin Precoder for QPSK Modulation 44 3.4.5 Performance Comparison of max-dmin Precoder for 16-QAM Modulation 49 3.4.6 Complexity Analysis 53 3.5 Conclusion 53 4 Optimal Subcarrier Pairing for MRC in Powerline/Wireless Diversity OFDM Systems 55 4.1 Motivation 55 4.2 Powerline/Wireless Diversity OFDM Systems 57 4.3 Optimal Subcarrier Pairing for Powerline/Wireless Diversity 60 4.4 Numerical Results 62 4.4.1 Channel Models 63 4.4.2 Performance Comparison 67 4.5 Conclusion 76 5 Concluding Remarks 77 5.1 Summary 77 5.2 Future Works 78Docto