Papers by Azzam Al-nahari
Relay selection schemes for secure transmission in cognitive radio networks
Wireless Networks, 2016
Detection of active eavesdroppers in massive MIMO
2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), 2014
Relay selection scheme for Improving the physical layer security in cognitive radio networks
2015 23nd Signal Processing and Communications Applications Conference (SIU), 2015
Cooperative space-time/frequency coding for uplink single carrier FDMA systems
Journal of Central South University, 2012
The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
2010 5th International Conference on Future Information Technology, 2010
Cooperative diversity using distributed space-time codes has been recently proposed to form virtu... more Cooperative diversity using distributed space-time codes has been recently proposed to form virtual antennas in order to achieve diversity gain. In this paper, we propose a distributed space-time coding with amplify-and-forward relaying. Motivated by protocol (III) presented in [1], we propose a distributed space-time code for an arbitrary number of relay nodes. The pairwise error probability (PEP) is derived and the theory analysis demonstrates that our protocol achieves a diversity of order 1 N + where N is the number of relay nodes.
ISRN Communications and Networking, 2011
The single carrier-frequency division multiple access (SC-FDMA) system is a new system that was a... more The single carrier-frequency division multiple access (SC-FDMA) system is a new system that was adopted in the standardization of the upcoming 3GPP long-term evolution (LTE). Designing diversity-achieving schemes for the SC-FDMA system is a challenging task. The codes adopted should not affect the peak-to-average power ratio (PAPR) among other constraints. In this paper, we consider the design of cooperative diversity schemes for SC-FDMA systems in the uplink direction. Specifically, two relay-assisted distributed space-time/frequency codes are proposed. The proposed distributed space-frequency code (SFC) achieves full spatial diversity in the uplink fast-fading channels, where a diversity of order three can be achieved. The proposed code keeps a low PAPR, which is a good feature of the system. A minimum mean square error (MMSE) decoder is used at the receiver of the destination node. Moreover, we propose a bandwidth-efficient distributed space-time code (STC) for slow-fading relay channels. A decodeand-forward (DF) protocol is used at the relay node, and the possibility of erroneous decoding is taken into account. Simulation results demonstrate the performance improvement of the proposed schemes.
2010 IEEE 18th Signal Processing and Communications Applications Conference, 2010
In this paper, we propose a distributed space-time coded cooperative protocol with amplify-and-fo... more In this paper, we propose a distributed space-time coded cooperative protocol with amplify-and-forward relaying. Motivated by protocol (III) presented in [1], we propose a distributed space-time coding for an arbitrary number of relay nodes. The pairwise error probability (PEP) is derived and the theory analysis demonstrates that our protocol achieves a diversity of order 1 N + where N is the number of relay nodes.
2008 National Radio Science Conference, 2008
Wideband code division multiple access (WCDMA) systems are interference-limited. When a WCDMA sys... more 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 its stability. Therefore, 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 tradeoff 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 distribution scenarios are also considered. Simulation results reveal that the MC-AC algorithm has many advantages over single cell admission control in terms of the overall stability of the system and the total system throughput.
Progress In Electromagnetics Research B, 2008
This paper develops a new approach to the detection of the emergency locator transmitter (ELT) si... more This paper develops a new approach to the detection of the emergency locator transmitter (ELT) signal using an adaptive line enhancer (ALE). The input signal to the ALE is replaced by its autocorrelation function (ACF) because noise affects the central samples of the autocorrelation function only while it affects all samples of the noisy signal. This gives the ALE the ability to get rid of noise, easily. The output ACF is then used in the spectral estimation and detection of the ELT signal. This approach is related to the signal processing using Higher Order Statistics (HOS) since the ACF is the used input. The paper also compares the results of the new approach to other different previously used methods foe ELT signal detection. The first method uses the signal x k as an input to the ALE, and the second method uses x 2 k . Results illustrate the superiority of the proposed method over the other two methods. A comparison study between the performance of two types of ALE; Fixed pole radius and variable pole radius ALEs in detecting the ELT signal, is introduced.
Transactions on Emerging Telecommunications Technologies, 2012
Physical layer security has recently attracted considerable attention in the context of informati... more 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.
International Journal of Speech Technology, 2014
This paper studies the process of speaker identification over Bluetooth networks. Bluetooth chann... more 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.
2009 International Conference on Computer Engineering & Systems, 2009
In this paper, a new distributed space-frequency coding (DSFC) scheme, for broadband fading relay... more In this paper, a new distributed space-frequency coding (DSFC) scheme, for broadband fading relay channels is presented. This scheme exhibits a spatial and a multipath diversity in a distributed fashion. An upper-bound on the pairwise error probability (PEP) is derived. From this PEP bound, it is shown that the proposed coding scheme achieves a diversity of order NL , where N is the number of relay nodes and L is the channel memory length. A decode-and-forward (DAF) protocol and erroneous decoding at the relay nodes are considered. To compensate for the diversity loss due to potential error detection at the relay nodes, additional coding at the source node is proposed.
SC-FDMA for Mobile Communications
Journal of Signal Processing Systems, 2012
The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
Current and next generation wireless networks including 3 rd generation (3G) and beyond are expec... more Current and next generation wireless networks including 3 rd generation (3G) and beyond are expected to provide a wide range of multimedia services with different QoS constraints. Call admission control (CAC) and resource reservation (RR) for mobile communication are of the most important issues that guarantee system efficiency and QoS required for different services in a very scarce resource as the radio spectrum. As forced call termination due to the handoff call dropping are generally less desirable than blocking a new one, handoff calls should have a higher priority than new calls. This paper investigates the concepts of sharing resources and reservation for WCDMA systems with the unique feature of soft capacity. Voice and data traffic are considered, and further classified into handoff and new requests. The reservation thresholds are dynamically adjusted according to the traffic pattern and mobility prediction in order to achieve maximum channel utilization while guaranteeing d...
IEEE Communications Letters, 2000
In this paper, we analyze the performance of regularized channel inversion (RCI) precoding in mul... more In this paper, we analyze the performance of regularized channel inversion (RCI) precoding in multiple-input single-output (MISO) broadcast channels with confidential messages under transmit-side channel correlation. We derive a deterministic equivalent for the achievable per-user secrecy rate which is almost surely exact as the number of transmit antennas and the number of users grow to infinity in a fixed ratio, and we determine the optimal regularization parameter that maximizes the secrecy rate. Furthermore, we obtain deterministic equivalents for the secrecy rates achievable by: (i) zero forcing precoding and (ii) single user beamforming. The accuracy of our analysis is validated by simulations of finite-size systems.
Digital Signal Processing, 2011
The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Computers & Electrical Engineering, 2010
Wideband code division multiple access (WCDMA) systems are interference-limited. When a WCDMA sys... more 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. (S.A. El-Dolil), dr_moawad@yahoo.com (M.I. Desouky), fathi_sayed@ yahoo.com (F.E.A. El-samie).
IEEE Transactions on Vehicular Technology, 2000
Multipath fading is one of the main challenges in transmission over wireless broadband relay chan... more 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.
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Papers by Azzam Al-nahari