Rician Fading Channel Model Research Articles

Least Square Estimation-Based Different Fast Fading Channel Models in MIMO-OFDM Systems

In cellular wireless communication systems, channel estimation (CE) plays a pivotal role as a crucial technique applied in orthogonal frequency division multiplexing (OFDM) modulation. CE utilizes a variety of methods, including decision-directed channel estimation, pilot-assisted channel estimation (PACE), and blind channel estimation. Among these options, PACE is widely favored for its remarkable stability and consistent superior performance. The idea of massive multiple-input multiple-output (MIMO) shows tremendous potential for the future of wireless communications. However, existing massive MIMO systems face challenges with their high computational complexity and intricate spatial structures, preventing efficient utilization of channel and sparsity features in these multiantenna systems. In communication channels, the signal received is often influenced by the characteristics of the channel and noise present at the receiver. To address this issue, an efficient dataset is utilized, employing the least square (LS) algorithm for minimization. OFDM is a commonly and widely used modulation method in communication systems utilized to specifically combat resonance fading in wireless channels. In wireless communication systems employing OFDM-MIMO, frequency selectivity and time-varying attributes due to multipath channels cause Intercarrier Interference (ICI) among symbols. Channel estimation is a vital aspect for mitigating the effects of fading channels. This investigation focuses on the application of a method examined in the study, which involves a block-type pilot symbol-assisted estimation technique for Rayleigh and Rician fading channel models. The research assesses the performance of the least square (LS) channel estimators in fast-fading channel models while employing various symbol mapping techniques focusing on bit error rate, throughput, and mean square error. The results indicate that the LS estimator exhibits excellent performance in Rayleigh and AWGN channels within the pedestrian A (PedA) model for both uplink and downlink scenarios. It outperforms the PedA model without channel estimation.

Task Completion Time Minimization for UAV-Enabled Data Collection in Rician Fading Channels

In wireless sensor networks, unmanned aerial vehicles (UAVs) can be employed to collect data from sensor nodes (SNs) efficiently. In this article, we consider a dual-UAV-enabled (long-distance) data collection system, where one UAV is dispatched to collect data from distributed SNs, while the other UAV is employed to relay data from the data-collection UAV to a fusion center (FC) that locates far from the SNs. To shorten the time duration for the FC to collect all data, we propose to minimize the completion time of the data collection task by jointly optimizing the transmit power and bandwidth of all SNs and the UAVs, as well as the three-dimensional trajectories of the two UAVs. Instead of assuming the simplified line-of-sight UAV-ground channel model as in most existing works, we model the channels between the UAVs and SNs as well as that between the UAVs and FC by applying the practically more accurate elevation-angle-dependent Rician fading channel model. The resulting optimization problem is nonconvex and thus is difficult to solve in general. Nevertheless, we propose an algorithm to solve it efficiently by using the techniques of block coordinate descent, slack variable substitution, and successive convex approximation. Simulation results show that our proposed algorithm can achieve higher communication efficiency than other benchmark schemes and greatly reduce the task completion time for data collection.

Frequency Permutations for Joint Radar and Communications

This paper presents a new joint radar and communication technique based on the classical stepped frequency radar waveform. The randomization in the waveform, which is achieved by using permutations of the sequence of frequency tones, is utilized for data transmission. A new signaling scheme is proposed in which the mapping between incoming data and waveforms is performed based on an efficient combinatorial transform called the Lehmer code. Considering the optimum maximum likelihood detection, the union bound and the nearest neighbour approximation on the communication block error probability is derived for communication in an additive white Gaussian noise channel. The results are further extended to incorporate the Rician fading channel model, of which the Rayleigh fading channel is presented as a special case. Furthermore, an efficient communication receiver implementation is discussed based on the Hungarian algorithm which achieves optimum performance with much less operational complexity when compared to an exhaustive search. From the radar perspective, two key analytical tools, namely, the ambiguity function and the Fisher information matrix are derived. Furthermore, accurate approximations to the Cramer-Rao lower bounds on the delay and Doppler estimation errors are derived based on which the range and velocity estimation accuracy of the waveform is analysed.

Latency Optimization of UAV-Enabled MEC System for Virtual Reality Applications Under Rician Fading Channels

This letter considers an unmanned aerial vehicle (UAV)-enabled mobile edge computing (MEC) system, where UAV base stations (UBSs) are deployed to cache, process, and deliver virtual reality (VR) content from a cloud server to VR users (VRUs). Under Rician fading channel model, we optimize various resource allocation parameters, e.g., association of VRUs with UBSs, caching policy, computing-capacity allocation, and location of UBSs, with the objective of minimizing the maximum latency, subject to computing, caching, and power constraints at the UBSs. The problem is non-convex and solved by using alternating optimization and successive convex approximation techniques. Our simulation results clearly show the importance of the proposed joint optimization algorithm, in terms of performance improvement, over different benchmark schemes.

Self-Interference Channel Training for Full-Duplex Massive MIMO Systems.

Full-duplex (FD) is a promising technology for increasing the spectral efficiency of next-generation wireless communication systems. A major technical challenge in enabling FD in a real network is to remove the self-interference (SI) caused by simultaneous transmission and reception at the transceiver, and the SI cancellation performance depends significantly on the estimation accuracy of the SI channel. In this study, we proposed a novel partial SI channel training method for minimizing the residual SI power for FD massive multiple-input multiple-output (MIMO) systems. Based on an SI channel training framework under a limited training overhead, using the proposed scheme, the BS estimates only a part of the SI channel vectors, while skipping the channel training for the other remaining SI channel vectors by using their last estimates. With this partial training framework, the proposed scheme finds the optimal partial SI channel training strategy for pilot allocation to minimize the expected residual SI power, considering the time-varying Rician fading channel model for the SI channel. Therefore, the proposed scheme can improve the sum-rate performance compared with other simple partial training schemes for FD massive MIMO systems under a limited training overhead. Numerical results confirm the effectiveness of the proposed scheme for FD massive MIMO systems compared with the full training scheme, as well as other partial training schemes.

Characterizing Packet Losses in Vehicular Networks

To enable testing and performance evaluation of new connected and autonomous driving functions, it is important to characterize packet losses caused by degradation in vehicular (V2X) communication channels. In this paper we suggest an approach to constructing packet loss models based on the so-called Pseudo-Markov chains (PMC). The PMC-based model needs only short training sequences, has low computational complexity, and yet provides more precise approximations than known techniques. We show how to learn PMC models from either empirical records of packet receptions, or from analytical models of fluctuations in the received signal strength. In particular, we validate our approach by applying it on: 1) V2X packet reception data collected from an active safety test run, which used the LTE network of the AstaZero automotive testing site in Sweden, and 2) variants of the Rician fading channel models corresponding to two models of correlations of packet losses. We also show that initializing the Baum-Welch algorithm with a second order PMC model leads to a high accuracy model.

Performance Analysis of Dense Small Cell Networks With Practical Antenna Heights Under Rician Fading

In this paper, we examine the combined impacts of distance-dependent Rician fading channel model and the absolute difference between the heights of base station (BS) and user equipment (UE) antennas on the coverage probability and the area spectral efficiency in an interference-limited ultra-dense (UD) small cell network (SCN). Exploiting distance dependent models for both path loss and multi-path fading, we show that in interference-limited UD-SCNs, Rician fading with variant Rician $K$ factor aggravates the performance loss caused by the difference between the heights of the BS and UE antennas in comparison to Rayleigh fading. In particular, we demonstrate that due to presence of the specular line-of-sight component in the Rician fading, both the coverage probability and the area spectral efficiency experience a steeper decline towards zero as the BS density increases. Our performance analysis has a prominent impact on the deployment of UD-SCNs in the 5th-generation of mobile networks, as it indicates that the right modeling of multi-path fading makes a significant difference when assessing the performance of UD-SCNs with non-identical UE-BS antenna heights.

Performance Analysis of Rayleigh and Rician Fading Channel Model

Performance Analysis of Rayleigh and Rician Fading Channel Model

Dual-Polarized Spatial Modulation Over Correlated Fading Channels

We address multiple-input multiple-output (MIMO) communication employing spatial modulation (SM) with dual-polarized (DP) antennas. The proposed architecture adds the polarization dimension to the conventional SM mappings and offers performances, which are comparable to or under certain conditions even better than those of the uni-polarized systems while occupying half as much space. We consider the generalized spatially correlated Rayleigh and Rician fading channel models and present an average bit-error probability upper bounding framework for the proposed DP SM-MIMO system. The theoretical error analysis is also extended to the case where the channel coefficients are estimated with Gaussian estimation errors. This upper bounding method is also used to determine the conditions in which the dual-polarized SM is better than equivalent systems with uni-polarized antennas. Theoretical derivations are also validated by extensive simulations, both corroborating that SM combined with dual-polarization forms an attractive alternative not only for its improved multiplexing gains and space efficiency but also for performance gains over correlated channels.

Optimizing Unlicensed Spectrum Sharing for LTE-U and WiFi Network Coexistence

Long-term evolution in unlicensed spectrum (LTE-U) is an emerging technology for expanding cellular network capacity without additional spectrum cost. This paper investigates effective spectrum sharing for coexisting Wi-Fi and LTE-U services. Based on a novel hyper access point (HAP) we introduced for effectively embedding LTE-U in unlicensed Wi-Fi band, LTE-U can directly take advantage of the Wi-Fi point coordination function protocol. To facilitate the coexistence, our HAP dedicates a contention-free period to LTE-U users and allows a contention period (CP) for traditional Wi-Fi users. We investigate the optimization of joint user association and resource allocation to further improve system throughput and user fairness. We formulate a network utility maximization problem based on the Nash bargaining solution (NBS), for which we derive a closed-form expression for the optimal CP length under a given user association. We analyze this NBS-based utility maximization and the performance of the proposed algorithm under log-normal fading, Rayleigh fading, and Rician fading channel models, respectively. Our numerical results corroborate our analysis and demonstrate effective improvement of the system performance by the proposed HAP algorithm against traditional LTE-U deployment.

Tri‐orthogonal polarization diversity for 5G networks

AbstractMillimetre‐waves offer the possibility of wide bandwidth and consequently high‐data rate for wireless communications. For both uni‐polarised and dual‐polarised systems, signals sent over a link may suffer severe degradation because of antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple‐input multiple‐output polarisation diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high‐path loss is often considered to limit millimetre‐wave propagation, thereby reducing any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole at a frequency of commercial interest provides antenna orientation robustness in this setting, as well as improved performance in a rich scattering environment, by means of a Ricean fading channel model. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis of millimetre-wave polarization diverse multiple-input multiple-output capacity.

Millimetre-waves offer the possibility of wide bandwidth and consequently high data rate for wireless communications. For both uni- and dual-polarized systems, signals sent over a link may suffer severe degradation due to antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple-input multiple-output polarization diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high path loss at millimetre-wave frequencies may limit any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole provides orientation robustness in this setting, as well as in a rich scattering environment, by means of a Rician fading channel model covering all orientations for a millimetre-wave, tri-orthogonal, half-wave dipole transmitter and receiver employing polarization diversity. Our simulation extends the analysis into three dimensions, fully exploiting individual sub-channel paths. In both the presence and absence of multipath effects, capacity is observed to be higher than that of a dual-polarized system over the majority of a field of view.

Optimality of Transmit Beamforming in Spatially Correlated MIMO Rician Fading Channels

This work exploits the algorithm for the "rate-optimum beamformer" in spatially correlated MIMO Rician fading channels and proposes a probabilistic analysis for the "optimality of transmit beamforming condition", (the necessary and sufficient condition when beamforming achieves ergodic capacity). The proposed analysis allows now for simulations to be performed in order to study the effects of the channel and system parameters on the optimality of transmit beamforming condition. Results demonstrate that the spatially correlated MIMO Rician fading channel model incorporates known characteristics from the corresponding spatially uncorrelated model, while they also reveal new and unique characteristics, not observed or discussed in the open literature previously: (a) the optimality condition is affected by the angle between the dominant eigenvector of the channel mean matrix and the dominant eigenvector of the channel covariance matrix, (b) the manner that the optimality condition is affected by the transmit antenna correlation varies with respect to the remaining channel distribution parameters.

Ship to Ship Maritime Communication for e-Navigation Using WiMAX

Maritime wireless communication is different from terrestrial wireless communication, due to difference of environments. Nevertheless technologies based on WiMAX (IEEE 802.16j) for ship to ship maritime communication promised to deliver high data rates over large distances and deliver multimedia services and are expected to use e-Navigation system. This paper focuses to simulate on IEEE 802.16j for ship to ship maritime communication under various sea states. We describe BER level according to sea states under Rician fading channel model. BER patterns are designed using MATLAB.

Performance Analysis of Rayleigh and Rician Fading Channel Models using Matlab Simulation

An effort has been made to illustrate the performance comparison of the Rayleigh and Rician fading channel models by using MATLAB simulation in terms of source velocity and outage probability. We have developed algorithms for the Rayleigh and Rician fading channels, which computes the envelop and outage probability. The parameters such as source velocity and outage probability play very important role in the performance analysis and design of the digital communication systems over the multipath fading environment.

Secure Relay Beamforming With Imperfect Channel Side Information

In this paper, we study the robust relay beamformer design problem in the relay-eavesdropper network with imperfect knowledge of the eavesdropper's channel. In this network, the half-duplexing relay is equipped with multiple antennas and employs the amplify-and-forward (AF) relaying protocol. Assuming static legitimate links, we consider the relay beamforming problem under two models for the eavesdropper's channel: 1) the Rician fading channel model, where only statistical information of the eavesdropper's channel is known by the legitimate nodes; and 2) the deterministic uncertainty model, where the uncertainty region of the eavesdropper's channel vector is modeled as a sphere. As for the optimization criteria, we use an approximation of the ergodic secrecy rate under the Rician fading model and the worst-case secrecy rate under the deterministic uncertainty model. Under both models, the optimal rank-1, match-and-forward (MF), and zero-forcing (ZF) beamformers are developed, and the equivalence of the optimal rank-1 beamformer and the optimal MF beamformer is also established. Under the Rician fading model, it is shown that the optimal ZF beamformer may have a rank greater than 1 and, therefore, could outperform the optimal MF beamformer, whereas under the deterministic uncertainty model, the optimal ZF beamformer must be rank-1. Numerical results are presented to verify the effectiveness of the proposed relay beamformers.

4S 해상 통신을 위한 채널 추정 알고리즘 비교 연구

In this paper, we compare the existing channel estimation technique for 4S (Ship to Ship, Ship to Shore) maritime communications under AWGN channel model, Rician fading channel model, and Rayleigh fading channel model respectively. In general, the received signal is corrupted by multipath and ISI (Inter Symbol Interference). The estimation of a time-varying multipath fading channel is a difficult task for the receiver. Its performance can be improved if an appropriate channel estimation filter is used. The simulation is performed in MATLAB. In this simulation, we use the popular estimation algorithms, LMS (Least Mean Square) and RLS (Recursive Least-Squares) are compared with respect to AWGN, Rician and Rayleigh channels.

Link Analysis of Mobile Nodes in Ad Hoc Network Using Ricean Fading Channel Model

Communication channels are one of the important components of the wireless mobile ad hoc network. The link connectivity among mobile nodes moving in these channels can be measured through various performance metrics. This paper analysis the link connectivity of mobile nodes in one of the well known channel model, the Ricean fading channel, in which a strong dominant signal component is always present among several multipath signals received by receiver. Two performance matrices have been used to evaluate the link analysis of nodes. These are Link duration and Link ratio. It is discovered that the link duration is dependent on Ricean Factor K where as Link ratio shows irregular results, which represent true picture of link connectivity in the presence of fading.

Performance Analysis of Subspace Based Downlink Channel Estimation for W-CDMA Systems Using Chaotic Codes

This paper presents blind channel estimation for downlink W-CDMA system that employs chaotic codes and Walsh codes for spreading information bits of the multiple users. In a W-CDMA system, while transmitting over multipath channels, both intersymbol interference (ISI) as a result of Inter Chip Interference and multiple access interference (MAI) cannot be easily eliminated. Although it is possible to design multiuser detectors that suppress MAI and ISI, these detectors often require explicit knowledge of at least the desired users' signature waveform. Earlier work focused on a subspace based channel estimation algorithm for asynchronous CDMA systems to estimate the multiple users' symbols, where only AWGN channel was considered. In our work, we study a similar subspace-based signature waveform estimation algorithm for downlink W-CDMA systems, which use chaotic codes instead of pseudo random codes, that provide estimates of the multiuser channel by exploiting structural information of the data output at the base station. In particular, we show that the subspace of the (data+noise) matrix contains sufficient information for unique determination of channels, and hence, the signature waveforms and signal constellation. We consider Rayleigh and Rician fading channel model to quantify the multipath channel effects. Performance measures like bit error rate and root mean square error are plotted for both chaotic codes and Walsh codes under Rayleigh and Rician fading channels.

Accurate multiple-input multiple-output fading channel simulator using a compact and high-throughput reconfigurable architecture

This article presents an ultra-compact and high-throughput reconfigurable fading channel simulator that supports a relatively large number of propagation paths. To closely reflect actual radio channels, the authors used a recently improved Rayleigh and Ricean fading channel model based on the sum-of-sinusoids technique. The improved model is optimised for hardware compactness. To achieve a fast fading variate generation rate with much less hardware and no significant loss in accuracy, the new scheme first generates fading samples at a lower rate using a time-multiplexed datapath that can be fit into a small fraction of a field-programmable gate array (FPGA). In the second step, the simulator uses a compact multiplication-free linear interpolator to produce the fading samples at the full symbol rate. Implementing a 64-path fading channel simulator on a Xilinx Virtex-4 XC4VLX200-11 FPGA requires only 13 044 (14%) of the configurable slices, 10 (2%) of the block memories and one (1%) of the dedicated DSP blocks, while generating 64 × 191 million complex-valued fading samples per second. The simulated paths can be readily combined to form high path count models for multiple-input multiple-output systems as well as frequency-selective channels.