Broadband Channel Long Delay Cluster Measurements and Analysis at 2.4GHz in Subway Tunnels

Abstract

Abstract-The delay caused by the reflected ray in broadband communication has a great influence on the communications in subway tunnel. This paper presents measurements taken in subway tunnels at 2.4 GHz, with 5 MHz bandwidth. According to propagation characteristics of tunnel, the measurements were carried out with a frequency domain channel sounding technique, in three typical scenarios: line of sight (LOS), Nonline-of-sight (NLOS) and far line of sight (FLOS), which lead to different delay distributions. Firstly IFFT was chosen to get channel impulse response (CIR) h(t) from measured threedimensional transfer functions. Power delay profile (PDP) was investigated to give an overview of broadband channel model. Thereafter, a long delay caused by the obturation of tunnel is observed and investigated in all the scenarios. The measurements show that the reflection can be greatly remained by the tunnel, which leads to long delay cluster where the reflection, but direct ray, makes the main contribution for radio wave propagation. Four important parameters: distribution of whole PDP power, first peak arriving time, reflection cluster duration and PDP power distribution of reflection cluster were studied to give a detailed description of long delay characteristic in tunnel. This can be used to ensure high capacity communication in tunnels.

Channel Measurements and Models for High-Speed Train Communication Systems: A Survey

“…The proposed model, which is a hybrid model that combines the geometrical optical model and waveguide model, can characterize the wave propagation both in near and far regions of the source. However, the aforementioned model failed to discuss the far LoS (FLOS) phenomena observed inside tunnels [114] or provide a mechanism to determine the breakpoint for different propagation regions in tunnels [6]. A GBDM based on random propagation-graph was proposed in [95] to characterize time-variant HST channels in open space scenario.…”

Channel measurements and models for high-speed train wireless communication systems in tunnel scenarios: a survey

“…Although some HST channel measurements in tunnels have been conducted in recent years, this is still a very challenging task. Here, we will briefly review and classify some tunnel channel measurements [8], [9], [15], [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] according to the carrier frequency, tunnel parameters, antenna configuration, and channel statistics, as illustrated in Table 1. Moreover, some important analysis of tunnel channel measurements are summarized as follows.…”

Shadow fading cross-correlation of multi-frequencies in curved subway tunnels

“…There are many investigations of propagation channels in tunnel scenarios [2][3][4][5][6]. The propagation characteristics in circular tunnels at 450 MHz and 900 MHz, arched railway and road tunnels at 400 MHz, subway tunnels at 2.4 GHz, as well as 5.8 GHz are studied, respectively.…”