Geometrical-based statistical macrocell channel model for mobile environments

In this paper, a generalized 3-D scattering model is presented for macrocellular land mobile radio cellular systems with a mobile station (MS) located at the center of a 3-D scattering semispheroid and a base station (BS) employing a directional antenna located outside of the semispheroid. The effect of the directional antenna is thoroughly observed on spatial and temporal characteristics of the proposed model. Closed-form expressions for joint and marginal probability density functions (pdf's) of the angle of arrival (AoA) seen at the MS and the BS in correspondence with azimuth and elevation angles are derived. Furthermore, closed-form expressions for propagation path delays and trivariate joint pdf's of the time of arrival (ToA) seen at the MS and the BS in correspondence with azimuth and elevation angles are derived. Moreover, the theoretical results, along with observations, are shown that illustrate the effect of the directional antenna on the spatiotemporal statistics of the proposed 3-D model. The proposed 3-D scattering model is shown to deduce all previously proposed 2-D and 3-D models that assume a uniform distribution of scatters with directional or omnidirectional antennas found in the literature for a macrocell environment. The obtained theoretical results are compared with some notable 2-D and 3-D scattering models to validate the generalization of the proposed model.

In this paper, a propagation model is presented for the land mobile radio cellular systems with 3-D Gaussian distributed scatterers around Mobile Station (MS). The Base Station (BS) equipped with a directional antenna is located outside of the scattering region. The effect of directional antenna is thoroughly observed on spatial and temporal characteristics of the proposed model. General expressions for joint and marginal probability density functions (PDFs) of Angle-of-Arrival (AoA) observed at MS and BS in correspondence with azimuth and elevation angles are derived. Novel expressions for the trivariate and the bivariate density functions for Time-of-Arrival (ToA) / AoA in correspondence with azimuth and elevation angles are derived. Exploiting the proposed model, the theoretical results along with observations are presented to illustrate the effect of directional antenna on the spatio-temporal characteristics of channel. Obtained theoretical results for spatial statistics at BS are compared with an empirical set of measured data, which also demonstrates the validity of proposed model.

Statistical cellular Gaussian scatter density channel model employing a directional antenna for mobile environments

This paper presents a geometrically based statistical channel model with scatterers that are randomly distributed around the base station within a circle that is determined by the coverage area of the base-station antenna. The joint probability density function (pdf) of time of arrival (TOA)/angle of arrival (AOA), the marginal pdf of AOA, and the marginal pdf of TOA are derived for a general distribution of scatterers around the base station. Rayleigh and exponential distributions are selected as special cases for discussion. Comparisons between our theoretical calculations and the empirical results, as well as the measurement data that are reported in the literature, show that the Rayleigh distribution scatterer model can be applied to an outdoor microcell propagation environment, while the exponential distribution scatterer model gives accurate results for an indoor office/laboratory propagation environment.

A new time variant wideband propagation channel model is presented for user location applications in third generation mobile environments. The model considers evolutionary angle of arrival (AOA) and evolutionary time of arrival (TOA), based on the real instantaneous relative user equipment and base station position. The channel model proposed is used also in a link level simulator (LLS) to estimate realistic delay and angle of arrival coherence time, that is, the time in which position and time delay and angle of arrival for the received signal remain almost constant. In order to increase the time integration period and consequently reduce the error in geographical positioning, the maximum coherence time has to be known in the time delay and angle estimating process. The new wideband propagation channel model will provide the delay and angle estimating process with realistic coherence time and Doppler spread. The model also provides spatial correlation matrices for different diversity base station (BS) antenna schemes and compares them with experimental results.

The 6-GHz unlicensed band (5.925 – 7.125 GHz) and the lower 37 GHz shared band (37 – 37.6 GHz) are low-cost spectra considered by fixed wireless access (FWA) services to provide high throughput for non-mobile users. The propagation channel limits the FWA coverage. In this paper, we report extensive empirical channel measurements on 227 links and statistical models in these 6 and 37 GHz bands in a rural/suburban residential environment. The transmitter is placed outdoors at 5 m above ground, mimicking a strandmount or pole-mount small-cell base station (BS). The receiver was placed in a single-family house in eighteen indoor positions and one outdoor position (backyard patio). It is observed that the indoor customer premises equipment (CPE) has a larger path loss than the outdoor CPE, being up to 21 dB and on average 12 dB at 6 GHz, and up to 32 dB with an average of 16 dB at 37 GHz. If the homeowner or CPE installer knows the BS location, placing CPE on the side of the house closer to the BS reduces on average 7 dB path loss at 6 GHz and 13 dB at 37 GHz compared to placing it on the opposite indoor side of the house. One aspen tree increases the loss by 8.5 – 10 dB and three bruce/maple trees increase the loss by on average 15 – 16 dB at both frequencies. By comparing 1000 channel impulse responses (CIRs) collected at each receiver position, small-scale fading, delay, and angle of arrival (AoA) of each multipath component (MPC) are extracted. The operator may balance the tradeoffs between different CPE positions and antennas to optimize user throughput.

Wireless technology is expected to undergo considerable transformation because of the numerous services offered by 6G communication networks, which virtually entirely encompass every part of everyday life and use a variety of devices. Channel modeling is an essential factor in designing 6G communication networks. To meet the channel requirements of future 6G communication networks, it is crucial to measure the channel to consider path loss, multi-band, fading, blocking effect, multipath clustering, transmitter, and receiver moving speed/direction/time. The goal of this paper is to design and evaluate a 6G communication network in Banda Aceh City using a statistical channel model. The channel model is associated with environmental conditions such as rainfall and humidity. The method is then based on computer simulation using the NYUSIM simulator to complete the channel modeling using an operating frequency of 95 GHz with a bandwidth of 800 MHz. In the simulator, the designed 6G channel model is evaluated in both line-of-sight (LOS) and non-line-of-sight (NLOS) network environments. In addition, the designated network parameters, such as the coverage area, angle of arrival (AoA), angle of departure (AoD), and power delay profile (PDP), are simulated. The results, at AoA, the value of received power for LOS conditions ranges from -86 dBm to -101 dBm, while the value for NLOS conditions ranges from -91 dBm to -111 dBm. Under LOS conditions, the received power for AoD ranges from -86 dBm to -101 dBm, whereas under NLOS conditions, it ranges from -91 dBm to -111 dBm. In the omnidirectional PDP, the pathloss value for the LOS condition is 99.8 dB and the delay is 17.9 ns, while the pathloss value for the NLOS condition is 104.2 dB with a delay of 28.1 ns. For the directional PDP, the LOS condition yields a path loss of 106.4 dB and a delay of 2.9 ns, while the NLOS condition yields a path loss of 110.5 dB and a delay of 3 ns. Conclusions. The simulation indicated that the AoA, AoD, and PDP in terms of received power, pathloss, and propagation delay are in acceptable conditions for a 6G network in Banda Aceh City in the two observed environments. Therefore, it is conceivable to establish a 6G network in Banda Aceh City in the future.

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. In multi-path environments, the received signal frequency constantly varies as a result of the relative motion between the receiver and transmitter. In this paper, we bridged a novel 3D geometric channel model and the multiple-input and multiple-output (MIMO) antenna array, analyzed deeply the probability density functions (PDFs) of the Doppler shift (DS), its variance, and characteristic function and etc. For the particular channel model, analytical expressions for PDFs of the channel model and the DS of mobile station (MS) due to its motion, have been derived. Based on the analysis, we investigated MIMO receiving performance. Also developed a geometric channel model, and was firstly in the asymmetric geometry literature due to a directional antenna array employed at base station. For this channel model, it was assumed that each multi-path component of the propagating signal undergoes one bounce. It was also assumed that the scattering objects around MS, could be expressed as Gaussian and exponential density models, which are more suitable to simulate outdoor and indoor environments.

Dilution of precision (DOP) for time-of-arrival (TOA) or time-difference-of-arrival (TDOA) positioning systems has been thoroughly investigated. This is not the case for angle-of-arrival (AOA) positioning systems, especially three dimensional AOA systems. However, the recent increase in deployment of antenna arrays and multipath mitigation techniques make AOA systems more attractive. In this paper, the DOPs for position systems using range measurements are reviewed and an expression for 3D AOA DOP is derived. The average values of DOPs for different deployments of base station geometries are examined. It is found that for a 3D AOA system, unlike TOA or TDOA systems, vertical DOP (VDOP) is generally smaller than horizontal DOP (HDOP), and the best VDOP can be achieved when the base stations are at the same height as the user. Moving the base stations away from the plane of the user may decrease the HDOP and Geometric DOP (GDOP) slightly, but it also increases the VDOP. For applications that the height of the user changes frequently, the base stations should be deployed with height close to half the height of the area of interest.

When there is non-line-of-sight (NLOS) path between the mobile station (MS) and base stations (BSs), it is possible to integrate many kinds of measurements to achieve more accurate measurements of the MS location. This paper proposed hybrid methods that utilize time of arrival (TOA) at five BSs and angle of arrival (AOA) information at the serving BS to determine the MS location in NLOS environments. The methods mitigate the NLOS effect simply by the weighted sum of the intersections between five TOA circles and the AOA line without requiring priori knowledge of NLOS error statistics. Simulation results show that the proposed methods always give superior performance than Taylor series algorithm (TSA) and the hybrid lines of position algorithm (HLOP).

Location estimation in wireless communications systems experiencing purely non-line-of-sight propagation paths is an open problem. In this paper, a novel least squares algorithm is presented to estimate the location of a mobile station (MS) experiencing purely non-line-of-sight communication with at least one base station (BS) by using the time of arrival (TOA), angle of arrival (AOA), and Doppler-shift (DS) measurements collected at the BS. Simulation results are provided to demonstrate the estimation accuracy and improvement over existing methods.

Intelligent reflecting surface (IRS) has emerged as a cost-efficient technique to improve the wireless network’s capacity and performance. Existing works on IRS have mainly considered IRS being deployed in the environment to dynamically control the wireless channels between the base station (BS) and its served users in favor of their communications. In contrast, we propose in this paper a new integrated IRS-BS architecture by deploying IRSs inside the BS’s antenna radome to directly reconfigure the signal radiation to/from the BS’s antennas. In other words, the IRSs can be considered as auxiliary passive arrays with real-time reconfigurability equipped at the BS to enhance its communication performance cost-effectively. Since the distance between the integrated IRSs and BS’s antenna array is practically small (in the order of several to tens of wavelengths), the path loss among them is significantly reduced as compared to conventional IRS deployed much farther away from the BS, while the real-time control of the IRS’s reflection by the BS becomes easier to implement. However, the resultant near-field channel model also becomes drastically different from its far-field counterpart for conventional far-away IRSs in the literature. Thus, we propose an element-wise channel model for IRS to characterize the channel vector between each single-antenna user and the antenna array of the BS, which includes the direct (without any IRS’s reflection) as well as the single and double IRS-reflection channel components. Based on this channel model, we formulate a problem to optimize the reflection coefficients of all IRS reflecting elements for maximizing the uplink sum-rate of the users. By considering two typical cases with/without perfect channel state information (CSI) at the BS, the formulated problem is solved efficiently by adopting the successive refinement method and iterative random phase algorithm (IRPA), respectively. Numerical results validate the substantial capacity gain of the integrated IRS-BS architecture over the conventional multi-antenna BS without integrated IRS. Moreover, the proposed algorithms significantly outperform other benchmark schemes in terms of sum-rate, and the IRPA without CSI can approach the performance upper bound with perfect CSI as the training overhead increases.

A novel positioning scheme based on the specific communication network for high-speed train (HST) with a single base station (BS) is presented. In order to improve the accuracy of TOA estimation, the proposed method utilizes the cumulative sum of time-of-arrival (TOA) estimation values, which are measured during the initial ranging (IR) and periodical ranging (PR) process of each mobile station (MS). When the HST gets close to the BS, a positioning algorithm based on angle- of-arrival (AOA) estimation is employed to guarantee the accuracy of positioning. Simulation results are implemented under the mobile worldwide interoperability for microwave access (WiMax) configuration, showing that the proposed scheme dramatically improves the accuracy and reliability of TOA estimation. Furthermore, by using the combined scheme of TOA and AOA estimation, real-time and accurate location information could be provided for HST.

Integrated sensing and communication (ISAC) in the Industrial Internet of Things (IIoT) presents unique challenges in terms of localization techniques. While three-dimensional (3D) environments offer extra challenges to enhanced accuracy and realism, research in this area remains limited. To bridge this gap, we propose a novel localization technique assisted by a single base station (BS) in 3D IIoT scenarios. Our approach employs the MUltiple SIgnal Classification (MUSIC) algorithm to jointly estimate the angle of arrival (AoA) in azimuth and elevation, as well as the time of arrival (ToA). Compared to conventional multi-BS-assisted or MUSIC-based algorithms, our technique offers flexibility, easy implementation, and low computational cost. To improve performance, we integrate the Taylor-series into the iterative process after a MUSIC-based joint azimuth, elevation angle and delay estimation (JAEDE), resulting in a significant 99% reduction in computational complexity compared to a two-step MUSIC-based approach utilizing coarse-fine grid searching. Through numerical simulations, we compare our algorithm with three other MUSIC-based joint or separate estimation approaches, demonstrating its superior performance in azimuth angle of arrival (AoAz), elevation angle of arrival (AoAe), TOA, and overall location estimation across varying signal-to-noise ratio (SNR) conditions.

In this thesis, we cope with the fundamental mathematical and physical problems of the space-time-Doppler UWB system design for fading channels: multi-input multi-output (MIMO) wireless communication with adaptive filtering. The estimation algorithm from equalizer providing an accurate parameters estimate is investigated. UWB radio is a fast emerging technology with uniquely attractively features inviting major advances in wireless communications, networking, radar, imaging, and positioning systems. By its rule-making proposal in 2002, the Federal Communications Commission (FCC) in the United States essentially unleashed huge new bandwidth (3.6-10.6 GHz) at the noise floor, where UWB radios overlaying coexistence RF systems cerate using low-power ultra-short information bearing pulses. Right now, there are three basic types of UWB: multiband OFDM UWB (MB-OFDM UWB), impulse-UWB (I-UWB), and direct sequence UWB (DS-UWB). We focus on I-UWB and MB-OFDM-UWB, and compare their performance. A simple means for spreading the spectrum of low duty cycle pulse trains is time hopping (TH), with pulse position modulation (PPM) for data modulation at the rate of many pulses per data bit. The main contribution of this thesis for I-UWB is the design of leading edge detectors, coherent correlation detector (CCD), and pilot performance enhancement compared with different Rayleigh and Ricean fading conditions. For MB-OFDM UWB, we have considered the performance analysis and design criteria of MIMO OFDM UWB systems for high data-rate wireless transmission. The signal processing of frame detection, time synchronization, frequency synchronization, channel estimation, synchronization tracking using pilot subcarriers and 2-D MIMO detection algorithms is discussed. The main contributions of this thesis are 1) Compared with receiver employing the Maximum Likelihood (ML) detector, the receiver employing a low-complexity linear Minimum Mean Square Error (MMSE) demodulator can perform a limited performance loss in spatially uncorrelated channels. 2) Due to the operations of spreading and dispreading combined with MMSE-based frequency domain equalization, the adverse effects of the low-SNR subcarriers on the average BER performance are potentially improved. This is a direct consequence of spreading, because even if the signal corresponding to a specific chip is obliterated by a deep frequency domain channel fade, after dispreading these effects are spread over the Walsh-Hadamard Transform (WHT) length. Hence there is a high chance of still recovering all the partially affected subcarrier symbols without errors. 3) As a test case, the OFDM-based 200 Mb/s MB-UWB network (IEEE 802.15.3a) are considered, but the simulation results are shown above section. 4) The simulation channel can be easily applied to NOS and NLOS situation with WHT transformation from Simulink model. The fading channels of UWB with low/high signal to noise ratio (SNR), multipath effects, and multiuser interference may introduce large errors in location. The location engine performs the following tasks: █ Data fusion techniques: Different data fusion techniques are implemented using Time Of Arrival (TOA), Angle Of Arrival (AOA), or a combination of both. █ Channel modeling: A multipath, multiuser channel environment is created that models path loss, shadowing, Rayleigh fading, and Doppler frequency effects. █ Parameter estimation: TOA and AOA estimation algorithms are implemented as part of the location finding engine. Different variations of algorithms are implemented for performance and comparison purposes. █ Configuring the physical layer for different wireless networks. Among the programmable parameters are spreading factor, packet size, training length, constellation type, modulation technique, carrier frequency, level of transmitted signal power, and the number of antennas at the transmitter for both sides. █ Configuring the mobile user conditions. The wireless channel models depend on the Doppler frequencies present in the environment. The Doppler frequency depends on the mobile speed and carrier frequencies as input and generates a Rayleigh fading channel with the U-shape Doppler spectrum. █ Configuring the environmental parameters and network geographical structure. One of the factors affecting the performance of the wireless location system is the environment type (e.g., bad urban, urban, suburban, or rural area). For example, in a bad urban area with many blocking objects and buildings, non-line of sight (NLOS) effects plays an important role in the estimation accuracy.