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The multiple-input multiple-output (MIMO) technology is intensively developed and used in wireless data transmission systems to improve channel capacity and to provide reliable transmission. Therefore, the creation of an educational system based on the MIMO technology is necessary to understand the MIMO concepts and to accelerate scientific research in this domain. In this work, an ultrasonic MIMO system is proposed for communication over short distances. Eight antennas are used both in the transmitter and receiver to form 8 × 8 MIMO system. Linear frequency modulation (LFM) signals are used as pilot signals to construct the channel matrix. The determination of the delay of the pilot and data signals is achieved using matched filtering. 4-QAM modulation scheme is considered, and the experimental results show that data transmission and reception is achieved with the ability to track propagation channel changes since pilot signals are sent in each data frame. [ABSTRACT FROM AUTHOR]

This paper considers the link-level and network-level performance of code division multiple access (CDMA) pilot interference cancellation (pilot IC) technology, a low-complexity advanced receiver technology being considered for use in commercial third generation (3G) CDMA cellular systems. The concept behind this technology is to estimate and cancel at the handset receiver the interference effects associated with CDMA downlink pilot signals broadcast from the base stations of the network. The canceling of interference at the receiver improves the signal-to-interference/noise ratio (SINR), which enables increased cell capacity or throughput. In this paper, we derive SINR expressions for evaluating the probability of error performance of both the RAKE and pilot IC handset receivers, under conventional random spreading code assumptions. The approach can easily and accurately model a wide variety of transmitter, channel, and receiver conditions, including the effects of channel estimation. We also utilize radio network simulations to illustrate and quantify the capacity gains available for 3G CDMA networks through the use of pilot IC handsets. Network simulations are also used to examine the reduced level of soft-handoff found to be possible in pilot IC-based networks and the increased flexibility available in setting pilot power levels. We further consider the impact of using stronger pilot signals for improving the demodulation performance of sensitive higher-order modulation constellations that are needed to support spectrally efficient high-rate data services. [ABSTRACT FROM AUTHOR]

A chromatic‐dispersion‐free transmission using a time‐reversal optical parametric amplifier (OPA) for 10 Gbit/s data over 25 km of standard single‐mode fibre is demonstrated. The time‐reversal was achieved using optical phase conjugation in the OPA. A pilot signal was first sent to estimate the optical channel, which would be reshaped by the OPA and then retransmitted with data through the same fibre. The dispersion is compensated automatically through the transmission. Experimental results showed that around 1 dB improvement can be obtained at a bit error rate of <10−9 compared to the traditional return‐to‐zero on–off keying link. [ABSTRACT FROM AUTHOR]

In cellular CDMA, the implementation of pilot channels on the forward link enables accurate coherent detection and synchronous transmission. In conjunction with concatenated Walsh sequences, this results in significant capacity gain. However, the undesirable co-channel interference introduced by these intercell pilot signals is seldom addressed. Our analysis indicates that ignoring its effect can overestimate the capacity by as much as 15%. A partial implementation of multiuser detection is proposed to recover most of the degradation. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To reduce irreducible error floors that disturb digital mobile satellite links, a pilot tone-based technique (TCT) has been presented in recent years. Although TCT performs well against the error floors, it is necessary for the TCT to make a null point at the transmitted data spectrum for carrying a pilot tone. This spectrum zero itself, however, usually degrades error performance. Further, the implementation of a narrowband pilot-extracting BPF at the receiver is difficult. This paper presents a time domain TCT which can overcome these defects. Theoretical analysis and numerical results are given which verify the effectiveness of the presented system. [ABSTRACT FROM AUTHOR]

This paper analyzed the problem of the existed chaotic masking secure communication, gave a new chaotic communication method with the separation between chaos synchronization control signal and chaos modulated signal. It used a chaotic pilot signal independently to synchronize the chaos of the communication transceiver, it was a better solution for the original chaotic communication systems in which the information signal was much smaller than the chaotic modulation signal and anti-noise performance was poor. It built the circuit simulation based on Sprott system to verify the new method of chaotic communication. Simulation results show that it is more flexible to achieve synchronization between communication terminals, more accurate for chaos synchronization, high performance of anti-noise, and the strength of the information signal is no affected by the chaotic signal. [ABSTRACT FROM AUTHOR]

Pilot contamination is the reuse of pilot signals, which is a bottleneck in massive multi-input multi-output (MIMO) systems as it varies directly with the numerous antennas, which are utilized by massive MIMO. This adversely impacts the channel state information (CSI) due to too large pilot overhead outdated feedback CSI. To solve this problem, a compressed sensing scheme is used. The existing algorithms based on compressed sensing require that the channel sparsity should be known, which in the real channel environment is not the case. To deal with the unknown channel sparsity of the massive MIMO channel, this paper proposes a structured sparse adaptive coding sampling matching pursuit (SSA-CoSaMP) algorithm that utilizes the space–time common sparsity specific to massive MIMO channels and improves the CoSaMP algorithm from the perspective of dynamic sparsity adaptive and structural sparsity aspects. It has a unique feature of threshold-based iteration control, which in turn depends on the SNR level. This approach enables us to determine the sparsity in an indirect manner. The proposed algorithm not only optimizes the channel estimation performance but also reduces the pilot overhead, which saves the spectrum and energy resources. Simulation results show that the proposed algorithm has improved channel performance compared with the existing algorithm, in both low SNR and low pilot overhead. [ABSTRACT FROM AUTHOR]