Azzam Al-nahari

Relaying techniques for enhancing the physical layersecrecy in cooperative networks with multipleeavesdroppers

Physical layer security has recently attracted considerable attention in the context of information-theoretic point of view. In this paper, we investigate relay selection schemes for security-constrained half-duplex cooperative wireless networks with multiple eavesdroppers, which have the ability to cooperate to overhear the source transmission. The proposed techniques select a trusted decode-and-forward relay to assist the source transmission and maximize the achievable secure rate for different eavesdropper policies cooperation or not; for the two cases, we assume that the channel is always available. In addition, a jamming method that selects two relay nodes to create an intentional interference at both phases of the decode-and-forward protocol to confound the eavesdropper nodes is also considered. Both the source-destination and source-eavesdroppers links are taken into account in the proposed analysis. Secrecy rate and secrecy outage probability are the two performance metrics that are used to verify the effectiveness of the proposed schemes while asymptotic approximations of the secrecy outage probability are also derived. Simulation and analytical results demonstrate the performance improvement of the proposed schemes. Copyright

SC-FDMA for Mobile Communications

SC-FDMA for Mobile Communications examines Single-Carrier Frequency Division Multiple Access (SC-FDMA). Explaining this rapidly evolving system for mobile communications, it describes its advantages and limitations and outlines possible solutions for addressing its current limitations.The book explores the emerging trend of cooperative communication with SC-FDMA and how it can improve the physical layer security. It considers the design of distributed coding schemes and protocols for wireless relay networks where users cooperate to send their data to the destination.Supplying you with the required foundation in cooperative communication and cooperative diversity, it presents an improved Discrete Cosine Transform (DCT)-based SC-FDMA system. It introduces a distributed spacetime coding scheme and evaluates its performance and studies distributed SFC for broadband relay channels. Presents relay selection schemes for improving the physical layer Introduces a new transceiver scheme for the SC-FDMA system Describes spacetime/frequency coding schemes for SC-FDMA Includes MATLAB codes for all simulation experiments The book investigates Carrier Frequency Offsets (CFO) for the Single-Input Single-Output (SISO) SC-FDMA system, and Multiple-Input Multiple-Output (MIMO) SC-FDMA system simulation software. Covering the design of cooperative diversity schemes for the SC-FDMA system in the uplink direction, it also introduces and studies a new transceiver scheme for the SC-FDMA system.

Physical layer security using massive multiple-input and multiple-output: passive and active eavesdroppers

Physical layer security is considered as a promising technique that exploits the channel properties in order to send confidential messages to the legitimate receiver even in the presence of a powerful eavesdropper and the absence of its channel information. In this study, the authors consider the effect of massive multiple-input and multiple-output (MMIMO) system operating in TDD mode in improving the physical layer security in the presence of multi-antennas eavesdropper. The channel state information (CSI) of the eavesdropper is assumed not known at the transmitter side, and also imperfect CSI of the legitimate receiver is assumed. The first important finding is that MMIMO is a valuable technique to combat passive eavesdropping, where it is shown that the achievable secrecy rate increases logarithmically with the number of transmit antennas. However, the eavesdropper can be active and attack the training phase of the legitimate transmitter. As a consequence, this dramatically reduces the achievable secrecy rate. The second contribution of this study is a simple protocol that can effectively detect this attack so that a countermeasure can be taken. Closed-form expressions for the detection and false-alarm probabilities are derived. Moreover, the authors analyse the intercept probability and show that asymptotically exponential diversity is achieved.

Detection of active eavesdroppers in massive MIMO

We consider physical layer security of massive MIMO systems in TDD mode. We show that with massive MIMO a passive eavesdropper is not very dangerous and must therefore be active and attack the training phase. An attack on the training phase is potentially very harmful to the physical layer security, and we therefore investigate three different schemes for detecting the presence of an active eavesdropper. The three schemes differ in the location where the detection is done (base station, intended user, or jointly), and also in the level of system parameters that are assumed known to the base station and/or intended user.

Relay selection scheme for Improving the physical layer security in cognitive radio networks

The security in cognitive radio networks (CRNs) has been attracting continuously growing attention, due to the open and dynamic nature of cognitive radio architecture. In this paper, we propose a new relay selection scheme to improve the physical layer security in CRNs. The trusted decode-and-forward (DF) relay is selected to help the source transmission and improve the secrecy rate in the presence of an eavesdropper, and taking into account the primary user quality of service constraint. The performance of the proposed system is analyzed in terms of the achievable secrecy rate and the intercept probability. Asymptotic approximation of the intercept probability at high signal to noise ratios is also derived. The performance comparison of the proposed scheme with the schemes proposed in the literature reveals the superior of the proposed scheme.

Power-based multi-cell call admission control scheme for wideband-CDMA systems

Wideband code division multiple access (WCDMA) systems are interference-limited. When a WCDMA system operates at nearly full capacity, admitting a new user may affect the stability of the system. Therefore, the proper call admission control (CAC) is crucial and should balance between quality of service (QoS) requirements for the new user as well as for the existing users and the required high capacity. In this paper, we investigate this trade-off in the uplink direction using a power-based multi-cell admission control (MC-AC) algorithm. Multimedia services are considered with different QoS requirements in this algorithm. Different traffic scenarios are also considered. Simulation results reveal that the proposed MC-AC algorithm has many advantages over single-cell admission control (SC-AC) in terms of the overall stability of the system and the total system throughput.

Relay selection schemes for secure transmission in cognitive radio networks

The security in cognitive radio networks (CRNs) has been attracting continuously growing attention due to the open and dynamic nature of cognitive radio architecture. In this paper, we propose new relay selection schemes to improve the physical layer security in CRNs. A trusted decode-and-forward relay is selected to help the secondary user (SU) transmission and improve the secrecy rate in the presence of multiple eavesdroppers and multiple primary users (PUs). The secrecy rate of the SU is characterized under both its own transmit power constraint as well as a set of interference power constraints imposed at each PU, in order to preserve its quality of service. The performance of the proposed schemes is analyzed in terms of the achievable secrecy rate and the intercept probability. Closed form expressions for the asymptotic intercept probability at high source-relays channel variances are also derived. Moreover, new derivations of some existing traditional schemes are presented and compared. The performance comparison of the proposed schemes with the schemes proposed in the literature reveals the superior of the proposed schemes.

Efficient speaker identification from speech transmitted over Bluetooth networks

This paper studies the process of speaker identification over Bluetooth networks. Bluetooth channel degradations are considered prior to the speaker identification process. The work in this paper employs Mel-frequency cepstral coefficients for feature extraction. Features are extracted from different transforms of the received speech signals such as the discrete cosine transform (DCT), signal plus DCT, discrete sine transform (DST), signal plus DST, discrete wavelet transform (DWT), and signal plus DWT. A neural network classifier is used in the experiments, while the training phase uses clean speech signals and the testing phase uses degraded signals due to communication over the Bluetooth channel. A comparison is carried out between the different methods of feature extraction showing that the DCT achieves the highest recognition rates.

Distributed Space-Frequency Coding for Cooperative Diversity Over Broadband Relay Channels With DF Relaying

Multipath fading is one of the main challenges in transmission over wireless broadband relay channels due to frequency selectivity, which may deteriorate the received signal. Exploiting the extra source of multipath diversity, aside from cooperative (user) diversity, is important when coping with these wireless channel limitations. In this correspondence, we propose a new distributed space-frequency code (SFC) for broadband fading relay channels that can exploit both the spatial and multipath diversities in a distributed fashion. An upper bound for pairwise error probability (PEP) is derived, and from this PEP bound, we show that the proposed code achieves a diversity of order NL, where N is the number of relay nodes, and L is the channel memory length. The decode-and-forward (DF) protocol and erroneous decoding at the relay nodes are considered. Moreover, it is shown that the proposed code structure achieves the maximum coding gain among the linearly coded systems over channels with uniform power delay profiles.