AQAM under high time delay spread conditions

An analysis process is described for adaptive quadrature amplitude modulation(AQAM)of constant-power constant-symbol-rate over frequency-selective Rayleigh fading channels with inter symbol interference(ISI)and Gaussian noise.The delay spread resistance of the AQAM scheme is put forward by studying its average throughput and average bit-error-rate(BER),both of which can be expressed as functions of two variables,the ratio of root mean square(RMS)delay spread to symbol period and the ratio of average symbol energy to noise.Average throughput reacts regularly to the latter,whereas it does not react to the former.The AQAM scheme is highly superior in the delay spread resistance in comparison with the fixed modulation modes.Gains of the AQAM scheme over the fixed modes become more significant as the delay spread becomes severer or the average throughput decreases.

Propagation characteristics of wideband high-speed railway channel in viaduct scenario at 2.35 GHz

In order to obtain accurate characteristics of wireless channels in the viaduct area of China, a channel meas- urement was taken in a railway viaduct scenario of the Zhengzhou-Xi＇an passenger dedicated line with a bandwidth of 50 MHz at 2.35 GHz. The single-slope log-distance model is used to analyze the path-loss （PL）, and the distribution of shadow fading （SF） is obtained by statistical methods, which shows that the normal distribution fits the samples well. Ricean K-factor is analyzed by the method of moments, and the variation of K-factor is given along the measured route. Small scale such as delay spread and Doppler behavior are parameterized. Based on empirical channel measurement, this paper provides parameters for the evaluation and simulation work on viaduct scenarios of high-speed railway.

Measurements and analysis at 400MHz and 2600MHz in corridor radio channel

A propagation measurement campaign was performed at the 10 th floor corridor of Xingjian Building,Shanghai University,China.The channel was sounded by pseudo noise( PN) sequence at carrier frequencies of 400-and 2600-MHz respectively.In order to obtain large scale and small scale propagation characteristics in the corridor,the receiver was moved along the corridor every 1.02 meter to record the impulse response.More than 280,000 impulse responses were recorded in the campaign.This work first describes the principle of the measurement,and then how the recorded raw data are processed.The results show that path loss exponent is related to frequency.The relationship between the root-mean squared( RMS) delay spread and the T-R separation distance is analyzed.The RMS delay spread and the mean excess delay spread against path loss are also given,which explain why the 2600 MHz RMS delay spread is larger than that of 400 MHz.

Novel uncertainty relations associated with fractional Fourier transform

In this paper the relations between two spreads, between two group delays, and between one spread and one group delay in fractional Fourier transform （FRFT） domains, are presented and three theorems on the uncertainty principle in FRFT domains are also developed. Theorem 1 gives the bounds of two spreads in two FRFT domains. Theorem 2 shows the uncertainty relation between two group delays in two FRFT domains. Theorem 3 presents the crossed uncertainty relation between one group delay and one spread in two FRFT domains. The novelty of their results lies in connecting the products of different physical measures and giving their physical interpretations. The existing uncertainty principle in the FRFT domain is only a special ease of theorem 1, and the conventional uncertainty principle in time-frequency domains is a special case of their results. Therefore, three theorems develop the relations of two spreads in time-frequency domains into the relations between two spreads, between two group delays, and between one spread and one group delay in FRFT domains.

Indoor massive multiple-input multiple-output channel characterization and performance evaluation

We present a measurement campaign to characterize an indoor massive multiple-input multiple-output (MIMO) channel system, using a 64-element virtual linear array, a 64-element virtual planar array, and a 128-element virtual planar array. The array topologies are generated using a 3D mechanical turntable. The measurements are conducted at 2, 4, 6, 11, 15, and 22 GHz, with a large bandwidth of 200 MHz. Both line-of-sight (LOS) and non-LOS (NLOS) propagation scenarios are considered. The typical channel parameters are extracted, including path loss,shadow fading, power delay profile, and root mean square (RMS) delay spread. The frequency dependence of these channel parameters is analyzed. The correlation between shadow fading and RMS delay spread is discussed. In addition, the performance of the standard linear precoder—the matched filter, which can be used for intersymbol interference (ISI) mitigation by shortening the RMS delay spread, is investigated. Other performance measures,such as entropy capacity, Demmel condition number, and channel ellipticity, are analyzed. The measured channels,which are in a rich-scattering indoor environment, are found to achieve a performance close to that in independent and identically distributed Rayleigh channels even in an LOS scenario.

Empirical study on directionalmillimeter-wave propagation in vehicle-to-infrastructure communications between road and roadside

With the increased demand for unmanned driving technology and big-data transmission between vehicles,millimeter-wave(mmWave)technology,due to its characteristics of large bandwidth and low latency,is considered to be the key technology in future vehicular communication systems.Different from traditional cellular communication,the vehicular communication environment has the characteristics of long distance and high moving speed.However,the existing communication channel tests mostly select low-speed and small-range communication scenarios for testing.The test results are insufficient to provide good data support for the existing vehicular communication research;therefore,in this paper,we carry out a large number of channel measurements in mmWave vehicle-toinfrastructure(V2I)long-distance communication scenarios in the 41 GHz band.We study the received signal strength(RSS)in detail and find that the vibration features of RSS can be best modeled by the modified two-path model considering road roughness.Based on the obtained RSS,a novel close-in(CI)model considering the effect of the transmitter(TX)and receiver(RX)antenna heights(CI-TRH model)is developed.As for the channel characteristics,the distribution of the root-mean-square(RMS)delay spread is analyzed.We also extend the twosection exponential power delay profile(PDP)model to a more general form so that the distance-dependent features of the mmWave channel can be better modeled.Furthermore,the variation in both RMS delay spread and PDP shape parameters with TX-RX distance is analyzed.Analysis results show that TX and RX antenna heights have an effect on large-scale fading.Our modified two-path model,CI-TRH model,and two-section exponential PDP model are proved to be effective.