Mahmoud M. Elmesalawy

Adaptive Resource Sharing Algorithm for Device-to-Device Communications Underlaying Cellular Networks

Device-to-device (D2D) communication underlaying cellular networks allows closely located user equipments (UEs) to communicate directly by sharing the radio resources assigned to cellular UEs (CUEs). The case of multiple D2D-UEs (DUEs) sharing the same channel while each DUE can reuse multiple channels is considered. In this letter, two phases-based resource sharing algorithm is designed in such a way that its computational complexity can be adapted according to the network condition. The initial set of candidate channels that can be reused by each DUE is adaptively determined in the first phase. In the second phase, Lagrangian dual decomposition is used to determine the optimal power for DUEs that maximizing the network sum-rate. Simulation results show that the proposed algorithm can offer near-optimal performance and outperforms the comparable algorithms especially in terms of achievable throughput even with markedly reduced complexity levels.

New Forensic ENF Reference Database for Media Recording Authentication Based on Harmony Search Technique Using GIS and Wide Area Frequency Measurements

In forensic sciences, verification of digital media recordings is an important aspect. Electrical network frequency (ENF) criterion is a promising technique for media recording authentication. The ENF reference database is recorded from a single point on the power grid based on the fact that the ENF variation is the same across all points on the grid. This fact is not valid in case of system disturbances, whereas the ENF as a reference database varies in time and space. Post-disturbance ENF recorded from a single point is mismatched with the ENF extracted from media recorded at any other point on the grid. This will lead to judicial errors in the forensic examination of recordings. A new method for establishing a robust ENF reference database using geographical information system (GIS) and wide area frequency measurements is proposed. The method is based on building the ENF reference database from a number of frequency sensors deployed over multipoint on the grid rather than single point. The minimum number of sensors required is determined according to the frequency sensitivity of the ENF extraction algorithm and the estimation accuracy of the frequency sensor. The sensors locations are decided based on partitioning the power grid to a set of geographical frequency coherent areas. A novel harmony search algorithm using GIS data and wide area frequency measurements is proposed to identify the geographical frequency coherent areas for different disturbance scenarios. Results showed that the proposed method can be used to enhance the accuracy of the ENF database matching process.

A Game Theoretic Framework for Device Association in Heterogeneous Cellular Networks With H2H/IoT Co-Existence

In this letter, a device association algorithm is proposed to consider the diverse association requirements for human-to-human devices (H2HDs) and Internet of Things devices (IoTDs) coexisted in heterogeneous cellular network. The association strategy was developed to jointly maximize downlink (DL) sum rate and minimize total uplink (UL) transmit power for H2HDs while maximizing UL energy efficiency for IoTDs. The association problem is formulated as a cooperative Nash bargaining game. We first develop a two-player bargaining algorithm for two base stations to bargain their associated devices. Then, based on this algorithm and the Hungarian method, a multi-player bargaining algorithm is developed. Simulation results show that the proposed algorithm outperforms the comparable schemes, especially in terms of DL rate distribution for H2HDs, device side energy efficiency for IoTDs, as well as fairness performance among devices.

Joint channel selection and optimal power allocation for multi-cell D2D communications underlaying cellular networks

Device-to-device (D2D) communication underlaying cellular networks can improve the spectrum efficiency as a result of sharing the radio resources allocated to cellular user equipments (CUEs). However, the severe interference between D2D and CUEs communications may lead to performance degradation of cellular system if not coordinated properly. In this study, a joint channel assignment and power allocation algorithm is proposed, which addresses the intra-cell and inter-cell interference management problems for D2D communication underlaying cellular network. The case of multiple D2D-user equipments (DUEs) sharing the same channel while each DUE can reuse multiple channels is considered. The proposed algorithm is designed with two complementary steps in such a way that its computational complexity can be adapted according to the network condition. The preliminary set of CUEs candidate channels that can be reused by each DUE is adaptively decided in the first step. In the second step, the optimal power allocation for each DUE is determined using Lagrangian dual decomposition to maximise the network sum-rate. Simulation results show that the proposed algorithm outperforms the current comparable algorithms especially in terms of achievable throughput. Moreover, the effect of various system parameters on the performance of the proposed technique is also investigated.

Efficient WMMSE Beamforming for 5G mmWave Cellular Networks Exploiting the Effect of Antenna Array Geometries

Millimetre wave (mmWave) transmission is considered as one of the potential technologies in fifth generation (5G) cellular networks that could allocate more bandwidth to support the rapid growth of mobile data services. However, mmWave signals experience large path loss which can overcome by employing directional beamforming with high-dimensional antenna arrays. In this study, a downlink multiuser multiple-input multiple-output beamforming optimisation problem is considered for maximising the system utility subject to per-user quality-of-service constraint as well as per-antenna and base station transmit power constraints. The difficulty of this problem lies in its non-convex nature. To address this challenge, a weighted minimum mean square error (WMMSE)-based solution is proposed to reformulate the non-convex problem into equivalent convex one. Then, the block coordinate descent method is used to determine beamforming vectors. Moreover, the different antenna array geometries either two-dimensional (2D) such as planar array and circular array (CiA), or 3D such as conformal array and conical array (CoA) are designed at the base station and their effect on the system performance is exploited. Extensive simulations show that the performance of the proposed WMMSE-based solution with CiA and CoA geometries outperforms the comparable algorithms in terms of system throughput, system power consumption and access rate.

Distributed device association for multiservice heterogeneous cellular networks with QoS provisioning

Heterogeneous cellular network offers a promising architecture for supporting multiservice traffic generated by Internet of thing (IoT) paradigm and human-to-human (H2H) communications. In this paper, a distributed device association algorithm is proposed to consider the diverse quality of service requirements for H2H devices and IoT devices coexisted in heterogeneous cellular network. In this context, the traffic generated by H2H devices and IoT devices is categorized into 2 main classes, ie, primary service class (PSC) requiring low outage probability and secondary service class (SSC) with a minimum long-term rate requirement. Primary service class is principally used to model H2H traffic, while SSC is mainly used to model IoT traffic. The association problem is formulated to maximize the system revenue in terms of the number of devices belonging to the SSC while minimizing the global outage probability for devices modeled to PSC under quality of service guarantee. Since the proposed optimization problem is an NP combinatorial problem, an efficient solution is derived by relaxing the association constraints and adopting the Lagrange dual decomposition method. Simulation results show that our proposed algorithm outperforms the comparable schemes especially on outage performance for PSC-modeled devices and number of accommodated SSC-modeled devices.

BPSK based SIM-FSO communication system with SIMO over log-normal atmospheric turbulence with pointing errors

In this paper, we analyze a bit error rate (BER) as well as outage probability in a free-space optical (FSO) link. Log-normal atmospheric turbulence with an effect of pointing errors (PE) is used to model the FSO channel. Binary phase shift keying based on subcarrier intensity modulation is employed. The BER degradation due to the effect of PE is improved by applying single-input multiple-output (SIMO) technique using maximal ratio combining. The outage probability and BER closed-form expressions are derived for all cases which are confirmed by integral expressions. The numerical results show that the BER can be improved by using SIMO technique. For instance, the BER is 1.884×10−6 at 0 dBm transmitted power in the case of without using SIMO, while the BER become 3.223×10−21 at 0 dBm in the caseof applying the SIMO technique.

Opportunistic Device Association for Heterogeneous Cellular Networks With H2H/IoT Co-Existence Under QoS Guarantee

The integration of Internet of Things (IoT) and heterogeneous cellular networks (HCNs) forms a promising paradigm for next generation mobile systems. In this paper, a new association algorithm with quality of service provisioning is proposed to consider the diverse association requirements for human-to-human (H2H) communications and IoT devices (IoTDs) coexisted in HCN. In this context, the devices are categorized into two main classes; rate oriented devices (RODVs) and power oriented devices (PODVs). RODVs are primarily used to model H2H devices while PODVs are mainly used to model IoTDs during the association process. Then, the device association is formulated as an adaptive optimization problem that considers DL rate only, UL transmit power only or both of them according to devices orientations. Since the formulated optimization problem is hard to solve due to the combinatorial device association indicators, we reformulate the proposed optimization problem into a better tractable problem by relaxing the combinatorial indicators. Then, Lagrange dual decomposition method is adopted to find the optimal solution. Moreover, a radio channel distribution mechanism is proposed as a subsequent step to the device association phase for RODVs where the remaining resources after device association phase are distributed among the RODVs. Simulation results show that our proposed algorithm outperforms the comparable schemes especially in terms of power distribution for PODVs and rate distribution for RODVs with a significant rate gain.

Egyptian Wide Area Monitoring System (EWAMS) Based on Smart Grid System Solution

Wide-area measurement systems (WAMS) in smart grid can be defined as a system that captures measurements in the power grid over a wide area and across traditional control boundaries, and then uses those measurements to improve grid stability and events through wide-area situational awareness and advanced analysis.Authors have achieved Wide Area Monitoring System (WAMS) based on Frequency Disturbance Recorders (FDRs) as a family of the PMUs deployed on Egyptian Power grid for mapping and visualization of all system parameters. The FDRs are deployed on live 220kV/500kV Egyptian grid system in cooperation with the Egyptian Electricity Transmission Company (EETC). The project is funded from the National Telecommunication Regulatory Authority (NTRA). The Egyptian Wide Area Monitoring System (EWAMS) achieved at the Helwan University can gather information from many FDR units geographically dispersed throughout the boundary of the Egyptian power grid and data manipulated at a data center contains many servers at Helwan University. The Synchrophasor system with wide deployment of using (FDRs) phasor measurement units and high-speed communications to deliver and collect synchronized high-speed grid operating data, along with analytics and other advanced on-line applications will improve real-time situational awareness and decision support tools to enhance system stability. The EWMS is a good environment for many applications that can help the EETC to enhance the Egyptian Grid. This manual Guide explains the remote access for the EWAMS established at Faculty of Engineering through the EETC. The access will be for displaying the FDRs’ parameters with different configuration through web service.

Wide area synchronized frequency measurement system architecture with secure communication for 500kV/220kV Egyptian grid

Continuous and reliable supply of electricity is required for Egypts socio-economic development. With a highly urbanized population and a high growth electricity demand, a systematic expansion of the electricity generation facilities and other infrastructure developments are imperative to cope with household demand. At the same time, economic growth will hinge on the provision of adequate and reliable power to vital sectors like industry, agriculture, tourism and transport sectors. Against this background, the Egyptian power system has had to confront some major operating problems in voltage regulation, power flow control, protection, and stability. Wide-area monitoring systems (WAMSs) utilizing synchrophasor measurements can help with understanding, forecasting, or even controlling the status of power grid stability in real-time. This paper introduces infrastructure to cape with the world in solving the wide area power system from the protection to coordination and then control action. The architecture of the wide-area synchronized measurement used for on-line monitoring and application is discussed. The paper introduces real time structure of a number of Frequency Disturbance Recorders (FDRs) devices deployed across various locations in the Egyptian power grid and connected to a server through a secure communication infrastructure for collecting data, displaying many of parameters such as voltage, current, phases, etc. and provide some data analysis for future control and analysis. It has served utilities, academics, and policy makers with reliable and valuable synchrophasor data from 500kV/220kV Egyptian grid.