Downlink Massive MIMO Systems: Reduction of Pilot Contamination for Channel Estimation with Perfect Knowledge of Large-Scale Fading

Massive multiple-input multiple-output (MIMO) technology is considered crucial for the development of future fifth-generation (5G) systems. However, a limitation of massive MIMO systems arises from the lack of orthogonality in the pilot sequences transmitted by users from a single cell to neighboring cells. To address this constraint, a proposed solution involves utilizing orthogonal pilot reuse sequences (PRS) and zero forced (ZF) pre-coding techniques. The primary objective of these techniques is to eradicate channel interference and improve the experience of end users who are afflicted by low-quality channels. The assessment of the channel involves evaluating its quality through channel assessment, conducting comprehensive evaluations of large-scale shutdowns, and analyzing the maximum transmission efficiency. By assigning PRS to a group of users, the proposed approach establishes lower bounds for the achievable downlink data rate (DR) and signal-to-interference noise ratio (SINR). These bounds are derived by considering the number of antennas approaches infinity which helps mitigate interference. Simulation results demonstrate that the utilization of improved channel evaluation and reduced loss leads to higher DR. When comparing different precoding techniques, the ZF method outperforms maximum ratio transmission (MRT) precoders in achieving a higher DR, particularly when the number of cells reaches . &nbsp

Downlink Massive MIMO Systems: Reduction of Pilot Contamination for Channel Estimation with Perfect Knowledge of Large-Scale Fading

Massive multiple-input multiple-output (MIMO) technology is considered crucial for the development of future fifth-generation (5G) systems. However, a limitation of massive MIMO systems arises from the lack of orthogonality in the pilot sequences transmitted by users from a single cell to neighboring cells. To address this constraint, a proposed solution involves utilizing orthogonal pilot reuse sequences (PRS) and zero forced (ZF) pre-coding techniques. The primary objective of these techniques is to eradicate channel interference and improve the experience of end users who are afflicted by low-quality channels. The assessment of the channel involves evaluating its quality through channel assessment, conducting comprehensive evaluations of large-scale shutdowns, and analyzing the maximum transmission efficiency. By assigning PRS to a group of users, the proposed approach establishes lower bounds for the achievable downlink data rate (DR) and signal-to-interference noise ratio (SINR). These bounds are derived by considering the number of antennas approaches infinity which helps mitigate interference. Simulation results demonstrate that the utilization of improved channel evaluation and reduced loss leads to higher DR. When comparing different precoding techniques, the ZF method outperforms maximum ratio transmission (MRT) precoders in achieving a higher DR, particularly when the number of cells reaches . &nbsp

A New All-Optical Signal Regeneration Technique for 10 GB/S DPSK Transmission System

The transmission of high power inside the optical fiber, produce amplitude noise, phase noise and other transmission impairments that degrade the performance of optical communication system. The signal regeneration techniques are used to mitigate these nonlinear impairments in the electrical or in the optical domain. All-optical signal regeneration techniques are one of the solutions to mitigate these nonlinear transmission impairments in the optical domain without converting the signal from optical to electrical domain. The existing techniques are not capable enough to attain the Bit Error Rate (BER) less than 10-10 with the power penalty less than – 9dBm. In this paper, a new all-optical signal regeneration technique is developed that mitigate amplitude and phase noises in the optical domain. The new optical signal regeneration technique is developed by combining the two existing technique one is 3R (Reshaping, Reamplification and Retiming) regeneration and other is Phase Sensitive Amplification (PSA). The 10Gb/s Differential Phase shift Keying (DPSK) noisy transmission system is used to verify the features of developed technique. The developed technique successfully mitigates the nonlinear impairments from the noisy DPSK system with significant improvement in BER at low power penalty with the additional feature of high Q-factor and an eye open response for the regenerated signal. It is determined that BER of 10-12 is achieved at the power penalty of -14 dBm with Q-factor of 42 and an eye opened response. The developed technique in the DPSK system is realized using commercial software package Optisystem. The designed technique will be helpful to enhance the performance existing high-speed optical communication by achieving the minimum BER at low power penalty

Mitigated Pilot Contamination to Achieve Higher Downlink Data Rate in 5G Massive MIMO Systems

Massive multiple-input, multiple-output (M-MIMO) is an important knowledge for fifth-generation (5G) wireless cellular networks. The pilot contamination (PC) is an issue in massive MIMO due to interference between adjacent cells. We proposed that the number of pilot sequence inside a cell could become smaller than or equal to the number of users (UEs), taking into account the different number of UEs that transmitted the same pilot sequence in the same cell. In addition, the pilot sequence became mutually orthogonal for different cells to prevent PC among cells. In this paper, we analyzed a channel estimation for time division duplex (TDD) and improved the achievable data rate by reducing the PC for limiting user capacity and using channel orthogonality for minimum mean square error (MMSE) precoding. From the simulation results, the proposed scheme provided a data rate for two several situations, with and without interference PC for an increased number of antennas. Consequently, increasing the number of coherence intervals made the channel estimation critical and provided a small data rate due to increased noise and interference at increased transmit pilot sequence

Joint Transmit Antennas for Energy Efficiency in Downlink Massive MIMO Systems

Massive multiple-input-multiple-output (MIMO) systems are an exciting area of fifth-generation (5G) technology and very important in maximizing energy efficiency (EE) and saving battery technology.  Obtaining energy efficiency without sacrificing the quality of service (QoS) has become increasingly important for mobile devices. In this paper, we investigate the maximal EE for downlink massive MIMO systems using zero-forcing beamforming (ZFBF), dependent on the number of antenna elements and the optimal number of users inside the cell to optimize the transmit power. The linear precoding ZFBF is able to mitigate interbeam interference, in addition to noise, due to expanding the reception at low  power transmission.  The simulation results reveal that the maximal energy efficiency  can be obtained dependent on increasing the number of antennas M and choosing the  , where the number of antennas is greater than the critical number of antennas   , which minimizes the received interference due to increased transmit power

Reduction Pilot Contamination in Downlink Multi-Cell for Massive MIMO Systems

Massive multiple- input–multiple- output has become an important fifth-generation (5G) wireless communication system because it improves transmitted spectral efficiency. In this paper, we obtained the maximal spectral efficiency by improving transmission performance in cell edges. This was achieved by using pilot reuse sequences from all available pilots in order to mitigate the pilot contamination and to suppress interference between adjacent cells. In addition, we investigated the impacts of pilot contamination on the received signal-to-interference-noise ratios (SINR) of users and employed different pilot reuse. We propose a new method called cell-edge-aware maximum ratio transmission (MRT), zero forcing (ZF), and return zero forcing (R-ZF). These were the precoders that employed less spatial dimensions and were able to suppress adjacent cells interference of the maximally vulnerable active user. We conclude that the large pilot reuse value between neighboring cells increased the gain, avoided interference between adjacent cells, and gave the maximal spectral efficiency. Consequently, the R-ZF was better than ZF and MRT because it was able to suppress the SINR

Error Performance Analysis in Underwater Acoustic Noise With Non-Gaussian Distribution

There is a high demand for underwater communication systems due to the increase in current social underwater activities. The assumption of Gaussian noise allows the use of Traditional communication systems. However, the non-Gaussian nature of underwater acoustic noise (UWAN) results in the poor performance of such systems. This study presents an experimental model for the noise of the acoustic underwater channel in tropical shallow water at Desaru beach on the eastern shore of Johor in Malaysia, on the South China Sea with the use of broadband hydrophones. A probability density function of the noise amplitude distribution is proposed and its parameters defined. Furthermore, an expression of the probability of symbol error for binary signalling is presented for the channel in order to verify the noise effect on the performance of underwater acoustic communication binary signalling systems

Distributed power control for 5G millimeter wave dense small cell

The millimeter wave (mm-wave) is one of the key enabling elements in the fifth generation (5G) technology that uses highly directional beamforming to mitigate path loss by using antenna arrays. The mmwave for massive multiple-input-multiple-output (MIMO) is able to reduce the cross-tier interference between multiple antennas to assist the number of active users (UEs). The dense small cell is very important to increase the capacity and high coverage in cell edge. This paper focuses on achievable high data rate in a dense small cell based on the use of mm-wave. In order to perform the achievable high data rate, a novel distributed power allocation is proposed in this work that reduces the high path loss and suppresses cross-tier interference under constraint transmission power in mm-wave. The condition of the Nash Equilibrium is also applied to reduce the cross-interference by guiding every femtocell user equipment's to achieve the target signal-to-interference noise ratio (SINR). From the numerical results, reduction in the high path loss on the desired signal in the heterogeneous downlink networks can be achieved by spatially reducing the larger antenna arrays and occurred when the mm-wave for distributed transmit power is larger than the threshold power

Effect of Pump Dithering at Each Stage of Cascaded Fiber Optical Parametric Amplifier

Cascaded fiber optical parametric amplifier (FOPA) can enhance gain and bandwidth. The gain and bandwidth can be further enhanced by dithering the FOPA pump. However, to our knowledge, the effects of a pump dithering at every stage of cascaded FOPA have not been discussed. The study of performance at every stage of cascaded FOPA is quite interesting and beneficial in designing the system. Here, we analyzed, using OptiSystem software, each stage of a cascaded FOPA, when there was a pump dithering and not. The results showed that the pump dithering enhanced the gain and broaden the bandwidth at every stage. The gain and bandwidth obtained with the pump dithering were 27 dB and 20 nm, respectively. On the other hand, when there was no pump dithering, the gain and bandwidth were 9 dB and 12 nm, respectively