Bit error simulation for π/4 DQPSK mobile radio communicationsusing two-ray and measurement-based impulse response models

An accurate software/hardware bit-by-bit error simulator for mobile radio communications is described. Simulation results in indoor and outdoor channels are compared with theoretical results. Bit error rate (BER) results in simulated frequency-selective fading channels generated by several channel models such as two-ray, constant amplitude, and simulated indoor radio channel impulse models (SIRCIMs) are presented. It is shown that BER is not only dependent on the RMS delay spread, but also on the distribution of temporal and spatial multipath components in local areas. An important result is that a two-ray Rayleigh fading model is a poor fit for indoor wireless channels and, if used, can underestimate the BER by orders of magnitude. A real-time bit error simulation of video transmission using the bit-by-bit error simulator is described. The simulator, called BERSIM, is shown to be a useful tool for evaluating emerging data transmission products for digital mobile communications     

RMS delay and coherence bandwidth measurements in indoor radiochannels in the UHF band

A study of time dispersion in different indoor line-of-sight radio channels in the 492-862 MHz band is presented in this paper. A combined method to filter the noise in the measured impulse response is described. The effect of frequency windowing on the impulse responses and the root mean square (rms) delay spread is also investigated. It has been found that, in general, the use of windows with lower side-lobe levels yields larger values of the rms delay spread. The relation between the mean delay and the rms delay spread has also been studied for copolar and crosspolar channels. The dependence of the coherence bandwidth on the rms delay spread has been considered, and an inverse relation has been tested for both components     

Adaptive equalization for high-speed indoor wireless data communication

The performance of a 4-QAM indoor wireless data communication system with adaptive equalizer is investigated. The effectiveness of using linear and decision-feedback equalizer for Rayleigh and Rician frequency-selective indoor channels is evaluated, and contrasted to the performance of a 4-QAM modem without equalizer. The effects of some important channel and system parameters (multipath spreads up to 200 ns, data rates up to 25 Mbit/s, signaling pulse rolloff factor between 0.5 and 1.0, and additive, white Gaussian noise) on the indoor communication system performance are examined and presented in the paper. The indoor propagation measurements, carried out in a research laboratory, provided data to be used for BER performance assessments of the system with and without equalizer. The performance results based on computer generated channels are then compared with those obtained for measured channel impulse responses.     

A Statistical Model for Indoor Multipath Propagation

The results of indoor multipath propagation measurements using 10 ns, 1.5 GHz, radarlike pulses are presented for a medium-size office building. The observed channel was very slowly time varying, with the delay spread extending over a range up to about 200 ns and rms values of up to about 50 ns. The attenuation varied over a 60 dB dynamic range. A simple statistical multipath model of the indoor radio channel is also presented, which fits our measurements well, and more importantly, appears to be extendable to other buildings. With this model, the received signal rays arrive in clusters. The rays have independent uniform phases, and independent Rayleigh amplitudes with variances that decay exponentially with cluster and ray delays. The clusters, and the rays within the cluster, form Poisson arrival processes with different, but fixed, rates. The clusters are formed by the building superstructure, while the individual rays are formed by objects in the vicinities of the transmitter and the receiver.     

A novel 3-D indoor ray-tracing propagation model: the pathgenerator and evaluation of narrow-band and wide-band predictions

A novel three-dimensional (3-D) ray-tracing model capable of supporting detailed representation of the indoor environment, as well as external building structures, is presented in this paper. The developed algorithm uses a hybrid imaging technique where the two-dimensional (2-D) image generations in vertical and horizontal planes are combined to produce 3-D paths. It also employs the concept of “illumination zones” of the images which greatly simplifies the image map and allows the evaluation of complex indoor scenarios. In order to investigate the accuracy of the presented model, comparisons of predictions with narrow-band and wide-band measurements are performed in line-of-sight (LOS), non-LOS (NLOS), and deep shadow areas, both for co- and cross-polarized antennas. The analysis shows that accurate power predictions can be achieved for both antenna polarizations with rms errors less than 7 dB, even when long sections of the test route are in deep shadow areas. There is a trend agreement between the simulated and measured channel impulse responses, while the rms delay spread in NLOS areas is predicted with less than 5-ns rms error (or better than 13% normalized mean error). The paper provides an insight into the real and the modeled radio channel     

Experimental characterization of EHF multipath indoor radiochannels

This paper reports on experimental results and their interpretations for an indoor extremely high frequency (EHF) multipath channel. It is intended to help in establishing design guidelines for indoor wireless communications systems using millimeter waves. It deals with measurements obtained for the narrow and wideband indoor radio channels at 37.2 GHz within a typical concrete building at Laval University. Two kinds of transmission antennas, omnidirectional and directional, are used to investigate the propagation characteristics for the indoor channel. Under line-of-sight (LOS) conditions, the distance-power law exponent is found to be lower than the free space condition with walls playing a major role on the sustaining of high level signals. Large- and smallscale variations extracted from the original data are shown to follow log-normal and Rice distributions, respectively. The observed wideband impulse response has delay spread extending over a range up to 40 ns and a maximum root mean square (rms) value of about 16 ns. Both amplitude and phase behaviors of the signals are available for a better understanding of the various effects     

Analysis of Scattering in Mobile Radio Channels Based on Clustered Multipath Estimates

This paper presents the results of angle and delay measurements in physically nonstationary radio channels obtained in an outdoor urban environment. The multidimensional estimation data are obtained using a recently developed 3-D high-resolution channel sounder. The estimation results are compared with results obtained from a 3-D deterministic propagation prediction tool. For a better analysis, a hierarchical clustering method is presented that can separate and group the multidimensional estimation data into clusters. Measurements performed at a fixed position as well as along a trajectory are used to characterize the angular dispersion in both azimuth and elevation. The angular dispersion in terms of the rms cluster angular spread in both elevation and azimuth of the different clusters is analyzed over space and time and related to its physical scattering sources. Compared to the measurements, a large number of multipath clusters are missing in the predictions. Furthermore, it is observed from the measurements that different objects cause different angular spread values in azimuth and elevation. The results can be very helpful for the identification, improvement and calibration of deterministic propagation prediction models.     

Performance of Multiple-Access DCSK Communication over a Multipath Fading Channel with Delay Spread

The bit error rate (BER) performances of variant delay multiple-access differential chaos-shift keying (VDMA-DCSK) communication systems over a multipath fading channel with delay spread are investigated. The BER formula of the VDMA-DCSK over the fading channel is evaluated. A two-ray Rayleigh fading channel model is used to simulate the VDMA-DCSK system. The theoretical and simulation results are presented and they match each other, which supports the theoretical analysis. The multipath performance of the VDMA-DCSK is compared with that of a benchmark coherent MA-CSK system and with that of an invariant delay MA-DCSK system. The results show that in the multipath fading channel with delay spread environment the VDMA-DCSK system performance decreases least.     

Dual diversity combining and decision feedback equalizer in indoor millimetre‐wave channel

Wideband communication characteristics of wireless indoor millimetre‐wave channel for arched and rectangular buildings are investigated. The impulse responses of arched and rectangular buildings for any transmitter–receiver location are computed by shooting and bouncing ray/image (SBR/Image) techniques. By using the impulse responses of these multipath channels, the impact of shapes of building is presented and the bit error rate performance of binary phase shift keying (BPSK) system with phase and timing recovery circuits are also calculated. Moreover, dual space antenna diversity technique and decision feedback equalizer (DFE) with four forward and three feedback taps are used to combat the multipath fading. Numerical results show that the mean root mean square (rms) delay spread for the arched building is smaller than that for the rectangular building. In addition, it is also found that the transmission rate can be up to 20 Mbps for indoor millimetre‐wave channel of these two buildings by using dual space diversity and DFE. Copyright © 2002 John Wiley & Sons, Ltd.     

Measurements and characterization of wideband indoor radio channel at 60 GHz

This paper presents the measurements, the statistical results and channel models extracted by impulse response measurements of an indoor 60 GHz radio channel. The measurements were based on the pulse sounding technique. Multipath parameters that characterize the channel have been extracted and analyzed statistically concerning corridors and offices locations. The mean excess delay is in the range of 3.84 to 8.18 ns for hallways and 3.52 to 14.69 ns for offices. Additionally, rms delay spread varies from 12.34 to 15.04 ns in corridors and from 12.56 to 21.09 ns inside the laboratory. The coherence bandwidth varies between 13.88 and 30.49 MHz in corridors with a mean value of 22.48 MHz. Inside offices the mean coherence bandwidth is 22.80 MHz for LoS locations and drops to 7.05 MHz for NLoS. Small-scale models for all the measured locations were developed using tapped delay lines. The maximum Doppler frequency of the modeled channel remains around 1 Hz, whereas the coherence time is calculated 1.04 s, which indicates that the channel remains, almost stationary, exhibiting very slow fading. Finally, from the models it is derived that the channel preserves WSS and US characteristics giving rise to a WSSUS representation.     

A comparison of two radio propagation channel impulse responsedetermination techniques

A comparison of two radio propagation channel impulse response determination techniques is described. Presented are typical impulse response and transfer functions obtained from each measurement system. Also included for comparison are average impulse response envelopes and cumulative probability distributions for the RMS delay spread of static indoor radio channels calculated from 120 measurements using each system. The comparisons show good agreement between results     

Indoor radiated-mode leaky feeder propagation at 2.0 GHz

This paper presents the results of narrow-band and wide-band propagation measurements carried out at 2.0 GHz in an indoor environment using a radiated-mode leaky feeder as the transmitting antenna. The narrow-band measurements were devised to measure attenuation of radio signals and the wide-band techniques to measure multipath impulse responses and their associated root mean square (RMS) delay spread. Analysis of the narrow-band data files shows that the received signal levels in the direction along the feeder generally decay exponentially due to the feeder-specific attenuation. The received signal levels in the direction radial to the feeder decrease slowly, and the distance-power law exponent is found to be smaller than one. The slow and fast variations of the received signal levels are also examined. The results reveal that the slow variations basically follow the log-normal distribution, while the fast variations fit the Rayleigh distribution in the direction parallel to the feeder and the Rician distribution in the direction radial to the feeder, respectively. Analysis of the wide-band data files reveals that the maximum value of the RMS delay spread is 60.6 ns and the RMS delay spread values are less than 42 ns 50% of the time. One therefore can conclude that the indoor channel excited by the radiated-mode leaky feeder has a broad coherent band-width and can support a data rate of up to 3.3 Mb/s without equalization     

A digital DS spread-spectrum receiver with joint channel andDoppler shift estimation

A digital spread-spectrum receiver design is presented for communication over multipath channels with severe Doppler shifts. The characteristics of the underwater channel relevant to spread-spectrum system design are discussed, and a channel model for short-range communications (less than 10 km) is defined. The receiver considered uses a digital coherent RAKE combiner, coupled with an extended Kalman filter (EKF)-based estimator for channel parameters and pseudonoise code delay. Receiver performance is evaluated by computing average bit-error rate (BER) versus iterations of the EKF joint estimator, using both fixed and time-varying channels. It is shown that the BER obtained using the EKF joint estimator closely tracks the optimum BER obtained when the channel, delay, and Doppler parameters are known exactly. Finally, the Cramer-Rao lower bound for time-invariant joint channel, delay, and Doppler estimation is derived, and compared with the ensemble averaged mean-squared error of the EKF estimator     

Non-Coherent Fourth-Order Detector for Impulse Radio Ultra Wideband Systems: Empirical Evaluation Using Channel Measurements

Low-complex and low-power non-coherent energy detectors (EDs) are interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems, but suffer from a loss in performance compared to coherent receivers. The performance of an ED also strongly depends on the integration interval (window size) of the integrator and the window position. This paper presents a non-coherent fourth-order detector (FD) which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. The performance of the detectors is evaluated using realistic channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed FD receiver is slightly better than the ED in low signal-to-noise ratio (SNR) region and its performance improves as the SNR increases. In addition, BER of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.     

Frequency domain characterization of LoS nonfading indoor wireless LAN channel employing frequency and polarization diversity in the 63.4-65.4 GHz band

This paper presents results of frequency domain measurements conducted to characterize the distortionless transmission bandwidth (DTB) of indoor nonfading channels employing vertically and horizontally polarized antennas in the frequency band 63.4-65.4 GHz. The mean delay spread (/spl tau//sub mean/), root mean square (rms) delay spread (/spl tau//sub rms/), and the DTB of the channel are also presented as functions of distance between terminals and are compared for both polarizations. The dependence of DTB on the separation between terminals d is modeled as DTB=kd/sup -n/ where k is a constant. /spl tau//sub mean/ increases linearly with d, and its relationship with DTB is characterized as DTB=(1//spl alpha//spl tau//sub mean//sup n/)+c, where /spl alpha/ and c are constants. The effectiveness of frequency and polarization diversity in mitigating the effects of multipath fading in indoor channels has also been evaluated. The performance of both diversity techniques when modulated signals with high data rates for multimedia applications are utilized is presented for maximum selection combining. The performance of frequency diversity is also shown as a function of frequency separation between diversity branch signals to determine whether an optimal frequency separation exists.     

多径衰落信道下频域差分检测OFDM系统的误码率分析

在多径衰落信道条件下，分析了正交频分复用系统中频域差分检测的误码率性能，并进行了仿真验证。分析与仿真结果表明，信道相干时间和相干带宽均影响频域差分检测的误码率性能，信道相干带宽对频域差分检测的影响比信道相干时间的影响更大，频域差分检测适合于多径延迟扩展比较小的信道。     

The dependence of indoor radio channel multipath characteristics oftransmit/receiver ranges

The authors report experimental and modeling studies that investigate the dependence of indoor radio channel multipath characteristics on a transmit/receive range. Specifically, a simple model for estimation of the complex baseband equivalent impulse response for indoor channels is explained. Using this model, the relationship between RMS delay spread and range on static indoor channels is estimated. Results show that this relationship is nonmonotonic and has a maximum at a range that depends on the building dimensions and the electrical properties of reflecting surfaces. The model is used in infinite, as well as finite, resolution modes to supplement the measurements of impulse response characteristics in different buildings using a limited resolution channel sounder. Experimental and modeling results are combined to derive conclusions that confirm the anticipated nonmonotonic relationship exists in empty buildings. Measurement results demonstrate that furniture has the effect of destroying this relationship, making RMS delay spread almost independent of range     

Transmission of high rate ATM packets over indoor radio channels

The design and performance of a high data rate modem that transmits asynchronous transfer mode (ATM) packets over indoor radio channels is discussed. A discrete Fourier transform (DFT)-based multicarrier modulation technique is used to mitigate intersymbol interface (ISI) caused by a multipath spread of up to 250 ns. A rate one-half channel code is used to combat fading. Computer simulation is performed to investigate the system performance for five different multipath intensity profiles. The system performance is compared using a differentially coherent scheme and a coherent scheme based on channel estimation. The effects of carrier frequency offset and some of the hardware nonlinearities are discussed. Using various channel codes, an signal-to-noise ratio (SNR) of 14-21 dB is required at an average bit error rate (BER) of 10^-5 to transmit a total of 155 Mb/s data over a bandwidth of 280 MHz     

Channal Impulse Response: Measurements and Interpretations

This paper presents a selection of results obtained during an impulse responsemeasurement campaign undertaken in Hong Kong at 1.8 GHz. The chanel probingsignal bandwidth of 60 MHz was generated by a pseudorandom sequence clockedat 30 MHz. The results of the channel impulse response measurements in theHung Hom district of Kowloon, Hong Kong are presented. The measured resultsare analyzed for CIR parameters like delay spread, average delay and thesignificant number of paths. An attempt is made to relate the measured datawith the geometry of the environmental features that surround the transmitterand the receiver.