Enhancing Physical Layer Security in AF Relay Assisted Multi-Carrier Wireless Transmission

In this paper, we study the physical layer security (PLS) problem in the dual hop orthogonal frequency division multiplexing (OFDM) based wireless communication system. First, we consider a single user single relay system and study a joint power optimization problem at the source and relay subject to individual power constraint at the two nodes. The aim is to maximize the end to end secrecy rate with optimal power allocation over different sub-carriers. Later, we consider a more general multi-user multi-relay scenario. Under high SNR approximation for end to end secrecy rate, an optimization problem is formulated to jointly optimize power allocation at the BS, the relay selection, sub-carrier assignment to users and the power loading at each of the relaying node. The target is to maximize the overall security of the system subject to independent power budget limits at each transmitting node and the OFDMA based exclusive sub-carrier allocation constraints. A joint optimization solution is obtained through duality theory. Dual decomposition allows to exploit convex optimization techniques to find the power loading at the source and relay nodes. Further, an optimization for power loading at relaying nodes along with relay selection and sub carrier assignment for the fixed power allocation at the BS is also studied. Lastly, a sub-optimal scheme that explores joint power allocation at all transmitting nodes for the fixed subcarrier allocation and relay assignment is investigated. Finally, simulation results are presented to validate the performance of the proposed schemes.Comment: 10 pages, 7 figures, accepted in Transactions on Emerging Telecommunications Technologies (ETT), formerly known as European Transactions on Telecommunications (ETT

DESIGN AND DEVELOPMENT OF CARRIER ASSIGNMENT AND PACKET SCHEDULING IN LTE-A AND Wi-Fi

The highly competitive environment in today's wireless and cellular network industries is making the management of systems seek for better and more advance techniques to keep masses of data, complexity of systems and deadline constrains under control with a lower cost and higher efficiency. Therefore, the management is getting significant attentions by researchers in order to increase the efficiency of the resource usage to provide high quality services. Two of the cornerstones of the management system in wireless and cellular network are carrier assignment and packet scheduling. Therefore, this work focuses on analysis and development of carrier assignment and packet scheduling methods in multi-band Wi-Fi and LTE-A networks. First, several existing carrier assignment methods which are developed by considering different strategists in LTE and LTE-A are analyzed. Secondly, a new technique for the carrier assignment methods for LTE and LTE-A is developed to improve the efficiency of carrier assignment methods. Thirdly, a novel carrier assignment method is proposed by considering the behaviors of mobile users for LTE and LTE-A. Then, a novel architecture with packet scheduling scheme is proposed for next generation mobile routers in multi-band Wi-Fi environment as similar to LTE-A. Finally, the scheme is improved based on energy awareness. Results show that the developed methods improve the performance of the systems in comparison to existing methods. The proposed methods and related analysis should help network engineers and service providers build next generation carrier assignment and packet scheduling methods to satisfy users in LTE, LTE-A and Wi-Fi

Hybrid Spectrum Sharing in mmWave Cellular Networks

While spectrum at millimeter wave (mmWave) frequencies is less scarce than at traditional frequencies below 6 GHz, still it is not unlimited, in particular if we consider the requirements from other services using the same band and the need to license mmWave bands to multiple mobile operators. Therefore, an efficient spectrum access scheme is critical to harvest the maximum benefit from emerging mmWave technologies. In this paper, we introduce a new hybrid spectrum access scheme for mmWave networks, where data is aggregated through two mmWave carriers with different characteristics. In particular, we consider the case of a hybrid spectrum scheme between a mmWave band with exclusive access and a mmWave band where spectrum is pooled between multiple operators. To the best of our knowledge, this is the first study proposing hybrid spectrum access for mmWave networks and providing a quantitative assessment of its benefits. Our results show that this approach provides major advantages with respect to traditional fully licensed or fully unlicensed spectrum access schemes, though further work is needed to achieve a more complete understanding of both technical and non technical implications

Carrier Aggregation in Multi-Beam High Throughput Satellite Systems

Carrier Aggregation (CA) is an integral part of current terrestrial networks. Its ability to enhance the peak data rate, to efficiently utilize the limited available spectrum resources and to satisfy the demand for data-hungry applications has drawn large attention from different wireless network communities. Given the benefits of CA in the terrestrial wireless environment, it is of great interest to analyze and evaluate the potential impact of CA in the satellite domain. In this paper, we study CA in multibeam high throughput satellite systems. We consider both inter-transponder and intra-transponder CA at the satellite payload level of the communication stack, and we address the problem of carrier-user assignment assuming that multiple users can be multiplexed in each carrier. The transmission parameters of different carriers are generated considering the transmission characteristics of carriers in different transponders. In particular, we propose a flexible carrier allocation approach for a CA-enabled multibeam satellite system targeting a proportionally fair user demand satisfaction. Simulation results and analysis shed some light on this rather unexplored scenario and demonstrate the feasibility of the CA in satellite communication systems

Adaptive video transmission for OFDMA systems

An adaptive framework is proposed for multi-user video transmission over orthogonal frequency division multiple access (OFDMA) systems. Utilizing the channel knowledge, a two-step heuristic sub-carrier assignment algorithm is proposed to achieve unequal error protection for the video data. The approach also solves the fairness issue among different users that may be caused by varying channel quality on different sub-carriers. Meanwhile, multi-user channel gain is also achieved. The proposed framework significantly improves the video transmission quality with little extra computational complexity and system overhead. ©2007 IEEE.published_or_final_versio

On the design of a wireless multi-antenna monitoring system

In this paper we investigate the design of a wireless monitoring system. This system consists of several wireless monitoring units, each transmitting data collected from sensors. This data is received and processed at a central control unit. The typical operating environment poses several challenges. The channel’s delay spread is substantial and the distance between receiver and transmitter is in the order of 400 meters. In order to guarantee reliable communication, we combine multi-antenna techniques (spacetime block coding) with strong coding (LDPC codes). The cost and complexity of the monitoring units is kept low, and most of the processing is performed on the central control unit. We present a system design for the monitoring units and show simulation results