Channel Sounding System Research Articles

Investigation of cross-correlation characteristics for multi-link channels in high-speed railway scenarios

This paper investigates the cross-correlation characteristics of large-scale parameters (LSPs) and small-scale fading (SSF) for high-speed railway (HSR) multilink propagation scenarios, based on realistic measurements conducted on Beijing to Tianjin HSR line in China. A long-term evolution-based channel sounding system is utilized in the measurements to obtain the channel data. By applying a proposed time-delay based dynamic partition method, multi-link channel impulse responses are extracted from the raw channel data. Then, the statistical results of LSPs, including shadow fading, K-factor, and root-mean-square delay spread are derived and the cross-correlation coefficients of these LPSs are calculated. Moreover, the SSF spatial correlation and cross-correlation of SSF are analyzed. These results can be used to exploit multi-link channel model and to optimize the next-generation HSR communication system.

Channel Sounding System for MM-Wave Bands and Characterization of Indoor Propagation at 28 GHz

The aim of this work is to present a vector network analyzer based channel sounding system capable of performing measurements in the range from 2 to 50 GHz. Further, this paper describes an indoor measurement campaign performed at 26–30 GHz. The sounding system is capable of receiving two channels and transmitting one. Using this feature a channel measurement has been performed using both a directional horn antenna and a virtual uniform circular array (UCA) at the same time. This allows for comparative studies of measured channels with two different antennas in a simultaneous way. The measurement has been conducted with 42 measurement positions distributed along a 10 m long path through an indoor laboratory environment. The transmitter was positioned such that measurements were conducted both in line-of-sight and non-line-of-sight scenarios. The measurements showed good agreement between the measurement data collected with the horn antenna and the data collected with the UCA. The propagation environment was found to be sparse both in delay and angular domain for the given scenario. Based on the performed measurement campaign together with validation measurements of the system stability, it is found that the system works as expected.

Virtual Large-Scale Array Beamforming Analysis Using Measured Subarray Antenna Patterns

An accurate and reliable massive MIMO channel model is crucial for supporting design and performance evaluation of such systems in the future. However, massive MIMO channel sounding systems are cost prohibitive and complicated, where a large number of antenna elements and associated radio frequency transceiver chains are needed. Virtual large-scale arrays have been extensively utilized as an alternative for massive MIMO channel characterization. In this paper, we investigate virtual large-scale array systems formed by repositioning a real subarray system for channel characterization. With this scheme, we have the flexibility to scale between system cost and system channel sounding capability. Based on this scheme, general beampatterns of subarrays and subarray-based virtual large-scale arrays are derived, based on measured complex antenna patterns of antenna elements on the subarray. Three real subarray antenna systems, i.e., a 16-element uniform rectangular array (URA) at 3.5 GHz, an 8-element uniform circular array at 3.5 GHz, and an 8-element uniform linear array (ULA) at 10 GHz, were utilized to form the respective large-scale virtual arrays, i.e., a 128-element URA, a 48-element uniform cylinder array, and a 64 element ULA, respectively. Beamforming analysis based on the measured complex radiation patterns of the real arrays is provided to demonstrate that virtual large-scale arrays can significantly improve the capability of multipath parameter detection compared with the subarrays. Therefore, such cost-effective systems are promising for characterization massive MIMO propagation channels.

3D heart sound source localization via combinational subspace methods for long-term heart monitoring

Abstract Heart sound is a key mean for heart monitoring and a common known early diagnosis modality. In this paper, by employing a multiple channel sound recording system and implementing a spatiotemporal information extraction process, a powerful approach is proposed for heart monitoring. Use of the extracted spatiotemporal information of the heart sound, which in turn could lead to detection of the time duration and the heart abnormalities source locations, gives a clinical contribution to the diagnosis of heart valvular diseases. Since the heart valves have very small distances from each other and are located in a reverberant environment of chest and its surrounding muscles, we take the advantages of the group-delay information of the Recursively Applied and Projected-MUltiple SIgnal Classification (RAP-MUSIC) method to localize the active heart valves in the S1, systole, S2, and diastole phases of the heart sound. The proposed algorithm is applied to a simulated database and compared with the MUltiple SIgnal Classification (MUSIC), RAPMUSIC and group delayed MUSIC algorithms. The comparison shows the proposed combinational method has the highest resolution in the simulated environment and more accuracy when sources are very close. In the following, the proposed algorithm is applied to some normal and abnormal heart sounds recorded by the employed microphone array. The obtained results indicate that the proposed method can localize the heart valves in real conditions. Moreover, it is shown that via this approach, the extra abnormal sound sources in the heart of the patients, if exist, could be properly detected and localized. This 3D heart valve localization method is an appropriate approach suitable to be employed in long-term heart monitoring instruments.

Multiple Antenna Channel Measurements for Car-to-Car Communication

In car-to-car (C2C) communication, it is very important to understand the channel behavior. To increase the channel capacity, multiple antennas might be used in the form of multiple-input–multiple-output (MIMO). The location of antennas on the car affects the capacity. A channel sounding system is used to study the vehicular channels in various environments, therefore it is important that the sounding system to be portable and of small form factor. We propose a sounding system based on software defined radio (SDR). The system was developed and used for measurement campaigns. The testbed was implemented, and two scenarios of measurements were performed with different street size and building proximity.

Research of the High-Precision Dual-Channel Sound Velocity of Seawater Measurement System

For single channel sound velocity measurement system accuracy was generally not high,a high-precision dual-channel sound velocity of seawater measurement system was designed.Based on ultrasonic speed of sound measurement in seawater with time-of-flight method,the system used ARM microcontroller to combine with high-precision time interval measurement chip,and the sound velocity measurement was translated into distance and time measurement. Then the influence of the time delay of the system was eliminated by method of difference.The paper introduced the modules of the system,and the high-precision time interval measurement method as the key technology of time-of-flight method for the velocity measurement system was expounded.It wasproved by experiment that the measurement accuracy of the system on the velocity reached 0.019m/s.

Real-Time MIMO Channel Sounder for Emulation of Distributed Ultrawideband Systems

This paper introduces an ultrawideband (UWB) channel sounding system. Its novel architecture allows real-time measurements of multiple time-variant radio propagation channels in different ultrawide frequency bands. Its architecture allows emulation of multiuser systems, sensor networks, localization systems, and distributed MIMO radar systems. The sounder uses a maximum length binary sequence (MLBS) excitation signal and correlation processing in the receiver. Its synchronous multichannel operation is supported by excellent timing stability and low power consumption of miniature size modules based upon custom integrated SiGe circuits. The paper describes the architecture, design, calibration, basic parameters, and application examples of the sounding system.

Measurement-Based Stochastic Cross-Correlation Models of a Multilink Channel in Cooperative Communication Environments

In this paper, stochastic models for the cross-correlation of multiple channels are established based on measurement data collected using a wideband multiple-input multiple-output relay Band Exploration and Channel Sounder system at 3.7 GHz. We propose models for the cross-correlation characteristics of large-scale parameters (LSPs) between two links, that is, the base station and mobile station (MS) link and the relay station and MS link. The LSPs include shadow fading, Rician K-factor, delay spread, angle spread of arrival, and angle spread of departure. Furthermore, models are established for the cross-correlation of the small-scale fading in the impulse responses of two links. The statistics of these model parameters are investigated as functions of geometrical features of the multilink. They are extracted from a large amount of cross-correlation observations, which are obtained in three measurement sites along more than one hundred measurement routes. These models can be used together with the standard single-link channel models for the generation of correlated components, for example, path clusters, in two separate channels.

A Wideband Frequency-Domain Channel-Sounding System and Delay-Spread Measurements at the License-Free 57- to 64-GHz Band

A channel-sounding impulse-response identification system using the swept-frequency method is presented for the 57- to 64-GHz band. The swept-frequency channel sounder offers high time and frequency resolution of 1 ns and 625 kHz, respectively. The high dynamic range (70 dB) and the constant power output enable the nonlinearities of the channel-sounding system to be overcome within the coverage range, which is on the order of a picocell. This paper also reports the measurements and the analysis of wideband propagation data for various indoor radio channels at the 57- to 64-GHz band. The propagation characteristics are assessed for six different propagation environments. The results of the measurements for four environments are compared when horn antennas are employed at both terminal stations, and also when a horn and an omnidirectional antenna are used at the Tx and Rx terminals, respectively. Examining the statistical distributions of the multipath dispersion, the 90th percentile is about the same for both antenna configurations. For all environments under investigation, it was observed that the static delay spread values at the 90th percentile were below 62 ns.

Channel Characterization for 700 MHz DSRC Vehicular Communication

Adapting OFDM for vehicular communication requires extensive knowledge of anticipated multipath and Doppler environments. We present a GPS‐enabled channel sounding system built and used to conduct a channel measurement campaign. Tests conducted at the 700 MHz band in and around downtown Ann Arbor, Michigan, explored various vehicle‐to‐vehicle and vehicle‐to‐roadside channel scenarios. The measured channel metrics are used to quantify the effects on guard interval, packet duration, and subcarrier spacing for a functional OFDM system at 700 MHz. This paper is one of the first to present vehicular‐based channel‐modeling results from measured data in the 700 MHz band.

A Novel Transmit Scheme in CDM-Based MIMO Channel Sounding Systems

The code division multiplexing (CDM)-based MIMO channel sounder architecture is efficient at measuring fast fading MIMO channels. This paper examines loosely synchronous (LS), CAZAC, Kasami, and Chaotic sequences as probing signals in the CDM architecture. After comparing the performance of the channel measurement among the sequences, it is concluded that the LS sequences are the most appropriate codes for the probing signals. However, because LS sequences have a significant drawback in that the number of transmit antennas is limited to less than 4, we propose using a hybrid architecture combining CDM with TDM for supporting a greater number of transmit antennas. The simulation results show that the proposed scheme can improve the measurement performance when more than 4 transmit antennas are used.

Statistical Model for 4.5-GHz Narrowband On-Body Propagation Channel With Specific Actions

This letter presents the characterization of an on-body propagation channel with a specific activity of a body on the basis of the measurement results of a male subject in a radio anechoic chamber. In order to capture the dynamic behavior of the channel, a commercial real-time channel sounding system for the 4.5-GHz narrowband was used. The measurement scenarios included two repetitive actions of walking on the spot and standing up and sitting down at 10 different receive antenna locations where the fading caused by the action was observed and statistically modeled.

Optimization of Spatiotemporal Apertures in Channel Sounding

In this paper, we investigate the impact of the spatiotemporal aperture of a channel sounding system equipped with antenna arrays at the transmitter and receiver on the accuracy of joint estimation of Doppler frequency and bidirection. The contribution of this paper is threefold. First, we state a spatiotemporal model that can describe parallel as well as switched sounding systems. The proposed model is applicable for arbitrary layouts of the spatial arrays. To simplify the derivations, we investigate the special case of linear spatial arrays. However, the results obtained for linear arrays can be generalized to arbitrary arrays. Secondly, we give the necessary and sufficient conditions for a spatiotemporal array to yield the minimum Cramer-Rao lower bound (CRLB) in the single-path case and Bayesian CRLB in the multipath case. The obtained conditions amount to an orthogonality condition on the spatiotemporal array. Thirdly, we define the Doppler-bidirection ambiguity function and derive the necessary and sufficient conditions for a linear spatiotemporal array to be ambiguous. Based on the ambiguity function, we define the normalized side-lobe level, which we propose to use as a figure of merit in the design of spatiotemporal arrays.

A word from the editor

A word from the editor

Welcome

Welcome to the first anniversary issue of the ACM Computers in Entertainment! It has been a year since the magazine was launched in October 2003. In this anniversary issue we publish eight interesting papers on entertainment technologies, including games, audio media, user interface, live HD media streaming, and digital cinema. We also feature video interviews with two of our distinguished advisory board members, John Gage and Tomlinson Holman. John Gage, chief researcher and co-founder of Sun Microsystems, talks about the volunteer project NetDay, the wireless and broadband Internet, digital media, and the 2008 Beijing Olympics. Tom Holman, creator of the THX sound system and professor at USC, speaks of the history of THX, the 10.2 channel sound system, multichannel music, and digital cinema.

Estimating the RF attenuation rate via roadside trees with extraction techniques

AbstractModelings of the radio propagation channel are among the most important and fundamental issues. The levels of the desired signal and cochannel interference are associated with the measurement system. A new approach to estimate the RF attenuation rate (AR, dBm/m) with the extraction technique is introduced in this paper. Any changes due to an environmental disturbance or cochannel interference will cancel. The AR can be used to characterize the trees (or medium) with a linear expression. In practice, the attenuation rate results of four roadside trees are described based on data acquired from experiments employing an RF channel sounding system at 1800 MHz. It makes the estimations suitable for wireless communication systems. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 242–246, 2001.

Wide-band channel sounding at 24 GHz based on a novel fiber-optic synchronization concept

This paper describes a novel fiber-optic synchronization concept used in a versatile channel sounding system called the ETH channel sounder operating at 24 GHz (ECHO 24). ECHO 24 achieves a 2-ns path delay resolution and allows the measurement of complex channel impulse responses with Doppler frequencies <200 kHz based on a correlation method. Moreover, an antenna array together with an appropriate signal-processing scheme yields the angle of arrival of the impinging waves at the receiver (Ex) site. The intolerable frequency offset due to the operation of locally separated oscillators in the transmitter (Tx) and Rx can be overcome by a remote Tx and Rx supply with a common carrier generated in a control unit. The problem of line attenuation in coaxial cables at millimeter-wave frequencies is circumvented by the generation of appropriate optical signals, which are fed to the Tx and Rx via thin and flexible fibers. The absence of mixers and frequency multipliers yields rather small Tx and Rx modules and, therefore, reduces the deformation of the electromagnetic field to be investigated. ECHO 24 exhibits a dynamic range of 55 dB. Measurements are presented to demonstrate the versatility and precision of ECHO 24.