An OFDMA-Based Next-Generation Wireless Downlink System Design with Hybrid Multiple Access and Frequency Grouping Techniques

This paper discusses how to effectively design a nextgeneration wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design. So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence bandwidths and by harmonizing the channel condition and OCI of the grouped sub-carriers.This work was supported in part by Samsung Advanced Institute of Technology

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201

JTP: An Energy-conscious Transport Protocol for Wireless Ad Hoc Networks

Within a recently developed low-power ad hoc network system, we present a transport protocol (JTP) whose goal is to reduce power consumption without trading off delivery requirements of applications. JTP has the following features: it is lightweight whereby end-nodes control in-network actions by encoding delivery requirements in packet headers; JTP enables applications to specify a range of reliability requirements, thus allocating the right energy budget to packets; JTP minimizes feedback control traffic from the destination by varying its frequency based on delivery requirements and stability of the network; JTP minimizes energy consumption by implementing in-network caching and increasing the chances that data retransmission requests from destinations "hit" these caches, thus avoiding costly source retransmissions; and JTP fairly allocates bandwidth among flows by backing off the sending rate of a source to account for in-network retransmissions on its behalf. Analysis and extensive simulations demonstrate the energy gains of JTP over one-size-fits-all transport protocols.Defense Advanced Research Projects Agency (AFRL FA8750-06-C-0199

Multiple access and coding method for wireless ATM.

by Cheng Siu Lung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 81-86).Abstracts in English and Chinese.ABBREVIATION --- p.3INTRODUCTION --- p.9Chapter 1.1 --- Wireless ATM for multimedia application --- p.9Chapter 1.2 --- Challenges in Wireless ATM --- p.11Chapter 1.3 --- Outline of thesis --- p.14PREDICTIVE QUEUING MULTIPLE ACCESS --- p.17Chapter 2.1 --- Introduction --- p.17Chapter 2.2 --- Protocol for Mobile to Base --- p.20Chapter 2.3 --- Scheduling Protocol at the Base Station --- p.23Chapter 2.4 --- Rate Compatible Punctured Turbo code --- p.27Chapter 2.5 --- FEC and ARQ methodologies --- p.30Chapter 2.6 --- Experimental Results --- p.32Chapter 2.7 --- Conclusion --- p.34FUNDAMENTALS OF THE WIRELESS COMMUNICATION MEDIUM --- p.36Chapter 3.1 --- Introduction --- p.36Chapter 3.2 --- Error control and channel capacity --- p.38Chapter 3.3 --- Capacity of fading channel --- p.39ITERATIVE CHANNEL ESTIMATION FOR TURBO CODE FOR FREQUENCY HOPPED MULTIPLE ACCESSING --- p.45Chapter 4.1 --- Introduction --- p.45Chapter 4.2. --- Turbo code structures --- p.47Chapter 4.3 --- System Model --- p.49Chapter 4.4 --- Iterative Channel Estimator --- p.53Chapter 4.5 --- Turbo decoding with iterative channel estimation --- p.56Chapter 4.6 --- Simulation Results --- p.58Chapter 4.7 --- Conclusion --- p.63DUMMY BITS INSERTED TURBO CODE --- p.64Chapter 5.1 --- Introduction --- p.64Chapter 5.2 --- Weight Distribution of turbo codes --- p.66Chapter 5.3 --- Encoding with dummy bit insertion --- p.69Chapter 5.3.1 --- Dummy bit insertion methodology --- p.69Chapter 5.3.2 --- Hybrid Periodic Random Interleaver --- p.70Chapter 5.3.3 --- Dummy bit removal before transmission --- p.71Chapter 5.4 --- Decoding with dummy signal enhancement --- p.73Chapter 5.5 --- Weight distribution of dummy bit inserted turbo coding --- p.76Chapter 5.6 --- Simulation results --- p.77Chapter 5.7 --- Summary --- p.79REFERENCES --- p.8

THE COMMUNICATION PRINCIPLE IN THE BLUETOOTH WIRELLES PAN NETWORK

U ovom radu objašnjen je princip povezivanja i komunikacije u Bluetooth bežičnoj mreži. Bluetooth bežična tehnologija najpoznatiji je predstavnik mrežnih tehnologija u sve popularnijim osobnim mrežama (PAN)This paper gives an explanation for connection and communication principles of the Bluetooth wirelles network. Bluetooth wireless technology is the most popular network technology for personal area networking (PAN)

Receiver Design and Security for Low Power Wireless Communications Systems

This dissertation focuses on two important areas in wireless communications: receiver design and security. In the first part of this dissertation we consider low data rate receiver design for ultra-wideband (UWB), a wideband radio technology that promises to help solve the frequency allocation problem that often inhibits narrowband systems. Reference-based receivers are promising candidates in the UWB regime, because the conventional rake receiver designs suffers from complexity limitations and inaccuracies in channel estimation. Many reference-based systems have arisen as viable solutions for receivers. We unify these systems as well as other systems into the general framework for performance analysis to suggest the optimal system for varying constraints. We improve the performance of frequency-shifted reference (FSR-UWB) for an average power constraint by halving the frequency offset and employing a sample-and-hold approach across the frame period. Also, we introduce a novel peak mitigation technique; tone reservation, for the multi-differential (MD) version of FSR-UWB, to reduce the high peak-to-average power ratio observed as the data carriers increase. The next part of this dissertation is about wireless security which is ubiquitous in modern news. Cryptography is widely use for security but it assumes limited computational abilities of an eavesdropper, is based on the unproven hardness of the underlying primitives, and allows for the message to be recorded and decrypted later. In this dissertation we consider an information-theoretic security approach to guaranteeing everlasting secrecy. We contribute a new secrecy rate pair outage formulation, where an outage event is based on the instantaneous rates of the destination and the eavesdropper being below and above desired thresholds, respectively. In our new secrecy rate pair outage formulation, two new unaccounted outage events emerge: secrecy breach, where the eavesdropper is above the targeted threshold; unreliable, where the destination is unable to successfully decode the message. The former case must be carefully avoided, while for the latter case we can exploit automatic retransmissions (ARQ) while maintaining the eavesdropper intercept probability below the target threshold. We look at both ``simple\u27\u27 receivers and also complex receivers that use a buffer to store previous messages to maximally combine signal-to-noise ratio (SNR). Then we extend these results to the two-hop case where we maximize the end-to-end secure throughput by optimizing the intercept probability at each eavesdropper given a total end-to-end intercept constraint. Lastly, we consider the difficult case in information-theoretic security: the near eavesdropper case, where we contribute an optimal power allocation algorithm that leverages nearby chatter nodes to generate noise to reduce the probability of intercept by the eavesdropper while minimally impeding the source-to-destination communication. As shown in both one-hop and two-hop cases, allowing a slight outage at the destination for cases of when the eavesdropper is above a specific threshold greatly improves secrecy performance

CROSSLAYER OPTIMIZATION IN AN LTE NETWORK TO REDUCE THE EFFECT OF CO-CHANNEL INTERFERENCE

In this thesis, synergy between the physical layer and the Medium Access Control (MAC) layer of a Long Term Evolution (LTE) network is exploited to reduce the co-channel interference in both the forward and reverse channels. By doing such cross-layer optimization analysis, physical and MAC layer control decisions reach their full potential when they are designed in an integrated manner. The proposed solution focuses on the integration of the concepts of orthogonal frequency-division multiple access (OFDMA), sectorization, and Latin Square to improve the signal-to-interference ratio (SIR) with the most effective resource utilization. Sectorization in the physical layer alone is able to improve the SIR, however, by also implementing OFDMA and Latin Square techniques to reduce the effect of co-channel interference, better SIR can be achieved. There is some impact on resource utilization, however. The solution seeks to achieve an optimum point of tradeoff between improvement in the SIR and the acceptable amount of the unutilized resources.Civilian, Defence Science and Technology Agency, SingaporeApproved for public release; distribution is unlimited