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.

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 …

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

Conventional precoded spatial multiplexing multiple-input multiple-output (MIMO) systems using limited feedback are mainly based on the notion of time invariant channels throughout transmission. Consequently, the precoding matrix can be found during the training symbols and used over the subsequent data symbols. In this study, the authors consider a more practical system where the channel varies from one block of symbols to another. In such a scenario, the precoding matrix designed at the receiver based on the previous training symbols becomes outdated, which results in significant system performance degradation. In order to avoid this problem and reduce performance degradation, the authors propose the use of a Kalman filter linear predictor at the receiver to provide the transmitter with the precoding matrix for the next block of symbols. The performance of this method is assessed using computer …

Precoded spatial multiplexing multiple-input multiple-output (MIMO) systems using limited feedback are mainly based on the notion of delay-free feedback channels. In this paper, we take into account the time varying nature of the channel, and consider the feedback delay problem. In order to reduce performance degradation of spatial multiplexing systems in the presence of feedback delay, we propose the use of a Kalman filter linear predictor at the receiver to provide the transmitter with the predicted channel state information, and hence, mitigate the effect of feedback delay. The performance of this method is assessed using computer simulation, and the obtained results for the proposed channel prediction scheme demonstrate improved bit error rate performance for time varying Rayleigh fading channels.

Precoded spatial multiplexing multiple-input multiple-output (MIMO) systems using limited feedback have been extensively studied to reduce the feedback information based on the notion of delay-free feedback channel. In order to reduce performance degradation of precoded spatial multiplexing MIMO systems due to delay in the feedback channel, in this paper, we take into account the time varying nature of the channel, and consider the feedback delay problem. We propose the use of a linear predictor at the receiver to provide the precoder at the transmitter with predicted channel state information, and hence, mitigate the effect of feedback delay. The predictor is implemented using Kalman filter. The performance of this method is evaluated using computer simulation, and the achieved results demonstrate improved bit error rate performance in frequency selective Rayleigh fading channels.

In this paper a low complexity MIMO MC-CDMA receiver is proposed. We investigate the receiver performance and complexity in the case of despreading multicarrier code division multiple access signals (MC-CDMA) prior to V-BLAST detection in multiple input multiple output systems (MIMO). The proposed structure shows that for iterative detection, despreading before detection (DBD) reduces the effect of multiple access interference (MAI), and the reported results demonstrate improved bit error rate (BER) performance and user capacity of the system over despreading after detection (DAD). Furthermore, DBD results in reduced system complexity. The performance of both detectors is evaluated using computer simulations for a frequency selective slow Rayleigh fading channel.