In recent years, wireless communication systems have a high demand for high data throughput, high quality and spectrum efficiency. Massive MIMO is one of the new ideas in 5G. The idea is to expand the conventional MIMO system by installing large number of antennas in the base station to make better use of spatial diversity in order to provide higher throughput while using the same spectrum. However, in order to separate users and data streams and eliminate interference, an effective channel estimation technique with minimum overhead is crucial. In this paper, we propose a channel estimation technique to estimate the channel state information based on Kalman Filter. The received predetermined data is used by Kalman filter to estimate the channel, which is then used to detect the following data symbols in the same frame. The effectiveness of the proposed scheme is compared to the well-known Least square (LS) and Minimum Mean square Error (MMSE) schemes. The performance of the proposed scheme is assessed using computer simulation, and the obtained results for the proposed channel estimation demonstrate improved bit error rate performance in time-varying Rayleigh fading channels.

 Cognitive radio (CR) is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use. Upon the result of the detection, the system instantly moves into vacant channels while avoiding occupied ones. To improve the capacity of CR systems, the unused sub-channels by primary user (PU) could be aggregated. However, when secondary user (SU) system aggregates more channels, more collisions may occur. This collision occurs due to the PU backto reuse its channels during SU transmission on them. Moreover, there are other reasons for collisions as misdetection which happens when wrongly detected absence of PU may occur as well.

In this paper a Proposed Channel Aggregation Algorithm is introduced in which the CR data rate is maximized by aggregating multiple channels for the SU while satisfying the minimum collision requirements. Moreover, channel capacity is maximized under collision constraints. Matlab simulation is conducted to implement the proposed algorithm and the rustles showed that, very low collision probability was observed as compared to previous work. The capacity of CR was also improved as well.

MANETs is a type of Mobile Ad Hoc Networks and it contains a set of nodes that do not need central management to communicate with each other because each node can act as a sender, receiver and router at the same time. All these nodes can perform self-configuration. The ad hoc stationary or mobile networks face many challenges such as limited bandwidth, congestion and data transfer speed. Therefore, it is extremely important to develop an intelligent routing protocol to encounter these challenges. An evaluation study is also important to perform the backoff contention window effectively in order to know the obstacles and avoid them. This paper concentrates on the performance of backoff contention window using the main routing protocols such as DSR, DSDV and AODV for MANETs networks in crowded areas with random movement. The important parameters which include network throughput …

Voice in IP networks is transmitted as packets over IP (VoIP), the voice signals are converted to IP packets after beingdigitized and compressed for transmission. However, some packets can be missed in their way to the receiving side, due to network congestion. The loss of these packets degrades the speech quality in the listener side at VoIP system transmission. Since voice is transmitted is real time, the receiver cannot request a retransmission for any lost packets. Voice and data multiplexing in VoIP network always face problems when huge TCP traffic is transmitted resulting the voice packet to be stuck in the network during congestion. Therefore, VoIP packets will be delayed. Since delay and loss are the main parameters that affect the quality of a voice signal in a VoIP network.

This paper presents a design and a simulation study of voice and data integration in a VoIP network and analyses which scenario will suite the best performance for voice packets in traffic congestion to have a high voice quality rating when using a single data TCP source and a multiple TCP sources when multiplexed with a UDP voice source. This is accomplished by using NS-2 network simulator (version 2), and M/D/1 queue type with various queuing systems such as First in First out (FIFO), Fair queue (FQ) and Deficit Round Robin (DRR), which represent the technique mechanism to serve voice and data packets in a queueing system. Then loss and delay are measured for each scenario to determine the quality of voice.

Power transformers, which perform the function of transforming the voltage levels, are one of the most important electrical equipments that are used in power transmission systems. Hence, it is mandatory to perform power transformermaintenance; as they are normally scattered geographically, it is impractical to do periodical monitoring due to insufficient manpower. As the reason above, transformer failure may occur which causes the transformer from network unexpectedly power shutdown. To overcome this shutdown from transformer failure of the adapter, a system for transformer monitoring and self- protection was proposed in case the maintenance is delayed. In this paper, the temperature and humidity within the transformer were monitored, in addition to monitoring the rate of loading on the transformer. By using the internet of things (IoT), a self-protection system is designed and implemented for thetransformer. Where, if the transformer is not serviced quickly, the transformer will separate loads of low-importance (workshops, Homes,….) and it will keep the loads of high importance (hospitals,…) .and if the transformer is unable to feed the loads of high importance, in this case the transformer will separates all loads and stay in no-load status where the transformer monitor its parameters by itself, if all parameters of the transformer return to the normal level, the transformer automatically returns the loads in order of priority. All these components have been grouped and combined into one device. In addition the device is powered using an AC-DC adapter by an external power source.

Abstract— The optimized methods for a forecasting demand have been discussed among researchers to overview the most sufficient need in a rapid expansion city. The methods developed test and compare between all interrelated issues. Many variables are involved in the calculation of energy future demand, the prediction makes aggressive result to achieved requirements. After discussing proposed research methods a suitable and accurate approach is elected to be applied for any city to satisfy the public demand. The objectives of this research are to overview all the methods of forecasting of the electrical demand using different approaches , and come out with the most optimum suitable procedure in the field of electrical network for long and short terms. The result indicates a brilliant analysis with high contribution in the electrical industry, will find its application in a global rapid expansion city. The methods show a tradeoff between cost, reliability and complexity of operations regardless of energy generated.

Energy flow bottlenecks in high voltage transmission lines known as congestions are one of the challenges facing power utilities in fast developing countries. Bottlenecks occur in selected power lines when transmission systems are operated at or beyond their transfer limits. In these cases, congestions result in preventing new power supply contracts, infeasibility in existing contracts, price spike and market power abuse. The “Superconductor Technology” in electric power transmission cables has been used as a solution to solve the problem of bottlenecks in energy transmission at high voltage underground cables and overhead lines. The increase in demand on power generation and transmission happening due to fast development and linked to the intensive usage of transmission network in certain points, which in turn, lead to often frequent congestion in getting the required power across to where it is needed

Dynamic loads of high capacity power grids under normal and severe conditions are the most concerns of system operators and dispatchers to maintain voltage stability. Reactive power (Q) are often drawn by loads from various generated sources disturbing the operational power factor. Compensating methods are used, depending on load types and their reactive power patterns, to continuously monitor and correctly counteract fast changes by extremely rapid VAR compensation especially during transient conditions. Using power electronics and combining both, power and control engineering, some FACTS devises equipped with selected power electronic switching are the appropriate methods to respond to system variations in almost no time. STATCOM regulates system voltages based on a voltage-source converters, by absorbing or generating reactive power. Contrary to a thyristor-based Static VAR

Ad hoc underwater acoustic networks represent a very challenging field in digital communications due to the extreme nature of the underwater acoustic channel and also the requirement to meet critical needs in order to establish long range propagation, decentralisation and reliability. As a fact the underwater acoustic communications speed is five times less than the magnitude of the radio waves, and this makes the underwater acoustic suffer from high propagation delay and minimum throughput. This paper discusses the influence of the backoff windows on the ad hoc on demand Destination Sequenced Distance Vector (DSDV) protocol. Underwater Acoustic Media Access Control (UAMAC) is implemented in a NS2 simulator to adopt the Multiple Access Collision Avoidance and Acknowledgment (MACAW) scheme. The simulation results for the developed system are presented.

In this paper, the performance of limited feedback precoded spatial multiplexing multiple-input multiple-output orthogonal frequency division multiplexing (MIMO - OFDM) systems is investigated in time varying fading channels. Most studies into limited feedback precoded (MIMO - OFDM) systems are based on the notion of time invariant channels throughout transmission. Therefore, the precoding matrix for each subcarrier can be designed at the receiver in terms of the current channel state, fed back to the transmitter, and used for the subsequent block of data symbols. However, in time varying channels, the feedback information becomes outdated, which results in significant system performance degradation. To mitigate this system performance degradation caused by outdated information due to a delay in the feedback channel, this paper considers a more practical system, where the channel varies from one block