Root Mean Square Delay Research Articles

3GPP Standardized 5G Channel Model for IIoT Scenarios: A Survey

Industrial Internet of Things (IIoT) is an emerging area that fifth-generation (5G) mobile communication system penetrates industrial manufacturing applications. The indoor factory has larger space and there are a lot of metal machine tools distributed in it, which makes its radio propagation characteristics and corresponding channel models significantly different from those of the indoor office and indoor hotspot. To support the design and the evaluation of the IIoT techniques, the 3rd Generation Partnership Project (3GPP) released the first 5G IIoT standard model in October 2019. In this article, we give a detailed explanation of this IIoT model and compare it with other indoor models. First, we introduce the standardization of 3GPP IIoT channel model and its motivation. Second, four IIoT subscenarios, which are classified according to the clutter density and antenna height, are described. Third, the potential frequency bands of 5G IIoT are summarized. Fourth, the models of channel parameters, including the path loss and the line-of-sight (LOS) probability, the root mean-square (RMS) delay spread, and the angular spread, are given. Among them, the models of path loss and LOS probability take the antenna height and clutter density into consideration. The model of RMS delay spread changes from frequency-dependent to volume-dependent in order to catch the size variation of factories. Finally, two newly added key channel characteristics, dual mobility and absolute time of arrival, which help to describe the robot movement and positioning, are also presented.

Wireless Channel Measurements and Modeling of LTE Broadband System for High‐Speed Railway Scenarios

In high-speed scenarios, channel model is of vital importance in Long term evolution (LTE) systems. By extensive measurements on Beijing-Tianjinrailway, this paper proposes a distance-dependent channel model. Both large-scale and small-scale channel characteristics are presented in detail. The large-scale path loss is modeled under the hierarchical network structure. Small-scale channel characteristics that include channel impulse response, power delay profile and Doppler spectrum are deduced and analyzed. In particular, a new stage-wise K-factor model is proposed. Combined with the cumulative distribution function of Root-mean squared (RMS) delay spread and the number of paths, they clearly illustrate the distancedependent variances of the channel. Finally, the integrated distance-dependent channel models are proposed to give a comprehensive description of broadband LTE channel in high-speed railway scenario.

On Indoor Millimeter Wave Massive MIMO Channels: Measurement and Simulation

The millimeter wave (mmWave) communications and massive multiple-input multiple-output (MIMO) are both widely considered to be the candidate technologies for the fifth generation mobile communication system. It is thus a good idea to combine these two technologies to achieve a better performance for large capacity and high data-rate transmission. However, one of the fundamental challenges is the characterization of mmWave massive MIMO channel. Most of the previous investigations in mmWave channel only focus on single-input single-output links or MIMO links, whereas the research of massive MIMO channels mainly focus on a frequency band below 6 GHz. This paper investigates the channel behaviors of massive MIMO at a mmWave frequency band around 26 GHz. An indoor mmWave massive MIMO channel measurement campaign with 64 and 128 array elements is conducted, based on which, path loss, shadow fading, root-mean-square (RMS) delay spread, and coherence bandwidth are extracted. Then, by using our developed ray-tracing simulator calibrated by the measurement data, we make the extensive ray-tracing simulations with 1024 antenna elements in the same indoor scenario, and get insights into the variation tendency of mean delay and the RMS delay with different array elements. It is observed that the measurement and the ray-tracing-based simulation results have reached a good agreement.

Simulation and Analysis of Indoor Visible Light Propagation Characteristics Based on the Method of SBR/Image

The indoor visible light propagation characteristics are simulated and analyzed using the method of SBR/Image (shooting and bounding ray tracing/Image). A good agreement is achieved between the results simulated and the results given in published literature. So the correctness of the method has been validated. Some propagation parameters are obtained in the simulation, such as the indoor received power distribution, statistical distribution of phase angle of received power, RMS (root mean square) delay spread, direction of arrival, and Doppler shift. The foundation for the wireless network coverage of indoor visible light communication system is provided by the analysis of the above results.

Planning the Number of Taps in a Delay Line for Negative Exponential Delay Profile

In real radio-communication systems, information about the time-varying channel is required for planning tasks. From such information, tapped delay lines are used to model the impulse response of the channel. This letter analyzes the relative error between the theoretical RMS (Root Mean Square) delay spread of negative exponential power delay profiles and that obtained from the tapped delay line. A method using a closed expression for calculating this error is then proposed for the planning of the number of taps in different environments.

Performance enhancement of differential UWB autocorrelation receivers under ISI

The autocorrelation receiver (AcR) is a suboptimum, low-complexity receiver architecture particularly suited to ultra-wideband (UWB) communication systems. As the bit rate increases, interference among pulses due to multipath propagation causes serious impairments of the AcR's performance. To mitigate this effect, we propose an appropriate design of the chip code and of the delay hopping (DH) code. We provide conditions to be satisfied by the DH code in order to reduce the nonlinear intersymbol interference (ISI) and the bias term, which are peculiar nuisance parameters of autocorrelation receivers. By extending the length of the chip code, we show that N/sub p/ transmitted pulses per symbol can be employed to suppress the average linear ISI of N/sub p/-1 previous symbols. Simulated results confirm the performance improvement in terms of bit-error rate. However, in previous work it has been shown that the noise power linearly increases with N/sub p/. Although a large number of pulses per symbol is favorable for ISI mitigation, we show that the transmission of a single pulse minimizes the probability of error, for bit rates lower than an upper bound depending on the channel root mean-square delay spread and on the noise power.