Rician Factor Research Articles

A Study on the Performance Characteristics of a Chirp RTLS over Wireless Channel with Gaussian Noise

The chirp signaling has been mainly used in radar systems due to its good correlation characteristics, and nowadays it is applied to real time locating system(RTLS). The RTLS with chirp signaling was chosen as a standard such as ISO/IEC 24730-5 and IEEE 802.15.4a. In this paper, the performance of a real time locating system with chirp signaling was evaluated and simulated with relative distance error rates. We considered three cases of S/I = -30[dB], -20[dB], and -10[dB] with Rician factor K=10 and K=20. The performance was enhanced with K factor improvement by 25%, 27% and 50% for respective three cases of S/I. As results, in case of S/I -20[dB], as the line of sight component is stronger the better performance is obtained.

A Novel Spatial Modulation Scheme Over Correlated Fading Channels

A novel spatial modulation (SM) scheme suitable for correlated Rician fading scenario is proposed with the help of the key idea of Ungerboeck's set partitioning. The motivation is based on the fact that the different error performance exists between the antenna domain and modulation signal domain in the traditional SM scheme. And the total system error performance is mainly determined by the worse case. We analyze the unequal error protection (UEP) performance and find that the error performance of the antenna selection is mainly determined by the correlation coefficient and Rician factor. If the correlation coefficient or Rician factor is large, the error performance will be bad. Considering the error performance of the modulation signal domain is mainly determined by the minimum Euclidean distance between pair of signal points, the error performance of two domains will differ significantly over the fading channels with strong correlation or large Rician factor. The main idea of the novel scheme is to establish the relationship between the antenna domain and modulation signal domain by expanding the signal constellation to carry all the input information bits. The expanded constellation is then partitioned into subsets by using Ungerboeck's set partitioning. The bits mapping to the antenna index are also used to select the partitioned subset, while the remaining bits are used to determine the transmit signal in the selected partitioned subset. In this way, the error performance of the bits mapping to the antenna index is improved, while the error performance of the other bits is preserved by maximizing the minimum Euclidean distance between any pair of signal points in the partitioned subset. Performance analysis and simulation results show that the novel SM scheme could improve the error system performance greatly when the correlation coefficient or Rician factor become larger.

MIMO Stochastic Model and Capacity Evaluation of On-Body Channels

The improvement in terms of channel capacity provided by using a MIMO antenna system in personal area networks is investigated. Two on-body channel models derived in the 2.45 GHz frequency band are also presented and applied to two on-body links. The first proposed model uses, for each spatial subchannel, the same average values for the Rician factor, received power, and shadowing deviation. The second model encompasses the polarization loss in the on-body channels by utilizing different values of these parameters per each spatial subchannel. Furthermore, the joint correlation matrix is used instead of the classical Kronecker product. It is shown that the second model results in a better agreement of the achievable capacity with the measured channel. Also, the equal power and waterfilling power allocation schemes are compared in such on-body channels and it is shown that, adopting waterfilling instead of the equal power provides a higher capacity in the low SNR range while yielding the same achievable capacity in high SNR.

Throughput Scaling in Cognitive Multiple Access With Average Power and Interference Constraints

This paper derives tight ergodic sum-rate capacity scaling limits for cognitive radio secondary networks under five different communication environments (CoE) for two different network types when secondary users' (SUs) transmission powers are optimally allocated. The network types studied are power-interference limited (PIL) networks and interference limited (IL) networks. In PIL networks, SUs' transmissions are limited by both an average total power constraint and a constraint on the average interference that they cause to primary users (PUs). In IL networks, SUs' transmissions are only limited by an average interference constraint. The capacity scaling results in PIL networks are derived for three different CoEs in which secondary transmitter to secondary base station (STSB) channel gains are Rayleigh distributed while secondary transmitter to primary base station (STPB) channel gains are Rayleigh, Rician or Nakagami distributed. It is shown that secondary network capacity scales according to log log(N) in these three CoEs, where N is the number of SUs. In addition to these three CoEs, two more CoEs are also studied for IL networks: Rician or Nakagami distributed STSB channel gains and Rayleigh distributed STPB channel gains. It is shown that the secondary network capacity scales according to log(N) for all live CoEs in IL networks. This result implies exponential capacity gains in IL networks over PIL networks. The same capacity scaling results are shown to hold even for heterogeneous cognitive radio networks in which different SUs experience statistically different channel conditions. In some cases, our analysis leads to a new notion called effective number of users, which signifies the effective number of users contributing to multiuser diversity in cognitive radio networks. For example, effective number of users is given by K+1/e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sup> N when STSB channel gains are Rayleigh distributed and STPB channel gains are Rician distributed with a Rician factor K.

Performance Analysis And Optimization For AF Two-Way Relaying With Relay Selection Over Mixed Rician And Rayleigh Fading

In this paper, we analyze the performance of an amplify-and-forward (AF) two-way relaying system, where two sources exchange information via the aid of an intermediate relay that is selected among multiple relays according to max-min criterion. We consider a practical scenario, where one source-relay link undergoes Rician fading, and the other source-relay link is subject to Rayleigh fading. To be specific, we derive a tight lower bound for the outage probability. From this lower bound, the asymptotic outage probability and average symbol error rate (SER) expressions are derived to gain insight into the system performance at high signal-to-noise ratio (SNR) region. Furthermore, we investigate the optimal power allocation (PA) with fixed relay location (RL), optimal RL with fixed PA and joint optimization of PA and RL to minimize the outage probability and average SER. The analytical expressions are verified through Monte Carlo simulations, where the positive impact of Rician factor on the system performance is also illustrated. Simulation results also validate the effectiveness of the proposed PA and relay positioning schemes.

Optimality of beamforming condition for multiple antenna systems with mean feedback

The necessary and sufficient condition for beamforming optimality for multiple-input multiple output (MIMO) systems with mean feedback has been derived and thoroughly investigated in this article. The condition is an inequality that contains parameters of the number of antennas, transmission power, and the singular values of channel mean matrix. When the beamforming optimality condition is satisfied, the Shannon capacity of MIMO system can be achieved by beamforming and hence scalar codes can therefore be used to achieve the maximum capacity. The channel is modeled as the sum of a scattering matrix of i.i.d zero mean, unit variance complex Gaussian random variables, and a mean matrix having its rank r ≥ 1. The beamforming condition inequality performance versus system parameters of signal-to-noise ratio and Ricean factor have thoroughly been investigated by numerical results. Computer simulations show that the beamforming strategy can be adopted on a relatively relaxed beamforming condition without the loss of capacity performance.

Throughput Performance of 2X2 MIMO LTE Downlink in a Spatial Correlation Based Microcellular Channel for Wireless Broadband Networks

Multiple Input Multiple Output (MIMO) technology is going to be a viable alternative for future generation wireless broadband services in order to meet the striving requirements for throughput and system robustness. In Long Term Evolution (LTE), MIMO technologies have been broadly used to get better downlink peak rate, cell coverage, as well as average cell throughput. In the present paper a 2x2 MIMO is taken as baseline configuration for a LTE downlink under a Microcellular propagation scenario considering a non physical correlation based channel with Poor and rich scattering environment. The throughput capacity of the downlink is obtained for poor and rich scattering environments. Besides, two vital aspects of MIMO technique viz Spatial Multiplexing (SM) and Transmit Diversity (TD) are investigated in order to see their effect on throughput of the system. The effect of parameters like Speed of mobile station, number of Multipath, Rician factor (K) on throughput of such systems is reported and discussed. The investigations reported in this paper helps in estimating the throughput capacity of LTE downlink under SM and TD mode.

Performance analysis and power allocation for decode‐and‐forward cooperative communications over Rician fading channel

ABSTRACTThis paper derives the asymptotic symbol error rate (SER) and outage probability of decode‐and‐forward (DF) cooperative communications over Rician fading channels. How to optimally allocate the total power is also addressed when the performance metric in terms of SER or outage probability is taken into consideration. Analysis reveals the insights that Rician factor has a great impact on the system performance as compared with the channel variance, and the relay–destination channel quality is of importance. In addition, the source–relay channel condition is irrelevant to the optimal power allocation design. Simulation and numerical evaluation substantiate the tightness of the asymptotic expressions in the high‐SNR regions and demonstrate the accuracy of our theoretical analysis. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Capacity Analysis of the VBLAST MIMO System in Fading Condition with MQAM Modulation

input multiple output (MIMO) system using multiple transmit and receive antennas are widely recognized as the vital breakthrough that will allow future wireless systems to achieve higher data rates and also to increase diversity to combat channel fading. Therefore, a MIMO system can provide capacity gain and diversity gain. In this paper, we investigate the channel capacity issue of the Vertical$Bell Laboratories Layered Spa ce$Time (V$ BLAST) multiple$input multiple$output (MIMO) system with minimum min square error (MMSE) receiver and zero$f orcing (ZF) receivers in fading channel condition. In this paper, the difference in capacity of MIMO system with the MMSE receiver and ZF receiver is validated by comparing the mathematical relation and the simulated results. KeywordsMMSE, ZF, Capacity, Rician factor.

Statistical Analysis of MIMO Keyhole Channels under Double Rayleigh and Double Nakagami-Rice Fadings

This paper gives statistical analysis of double fading channels which are typically found in keyhole MIMO (multiple input multiple output) models. First, to investigate the potential of identically distributed double Nakagami-Rice MIMO keyhole channels including LOS (line of sight) environment, the density function of SNR (signal to noise ratio) which corresponds to the only one non-zero eigenvalue of channel correlation matrix is presented. In addition to the exact expression with an infinite series form, an approximation formula with a simple monomial form derived by substituting Nakagami m formula for Rician distribution is also considered. Next, similar equations are introduced for double Rayleigh channels which have correlated branches in both the transmitter and receiver sides (independent but nonidentical case is included here). Through computer simulations, the effectiveness of the proposed formulae is verified, and in double Nakagami-Rice fading case, the advantage of the approximated formula particularly for large array size and/or large Rician factor is demonstrated.

MIMO Channel Gain Mechanisms Relative to SISO Channel

In contrast to the rest of wireless communication technologies, multiple-input multiple-output (MIMO) technology enjoys different gain mechanisms that make it very attractive for reliable high data rate wireless communications. This paper presents a study on these gain mechanisms with particular emphasis on the case of high average received signal to noise ratio (SNR) where the MIMO system deployment is most promising. We write the MIMO channel capacity in terms of gains relative to a single- input single-output (SISO) wireless channel. Doing so, spatial multiplexing gain and power gain of MIMO wireless channels become more insightful. Based on this analysis a switching scheme between spatial multiplexing and transmit diversity is proposed. We support our discussion with numerical results which show that under a high data rate spatial multiplexing scheme the contribution of each gain mechanism to the total channel capacity depends on the channel Ricean factor, the average received SNR, and the MIMO system size. The proposed switching scheme gives about 2 dB gain in bit error rate performance relative to the spatial multiplexing mode.

Cross-layer design of multiple antenna multicast combining AMC with truncated HARQ

Combining adaptive modulation and coding with truncated hybrid automatic request, this paper presents a cross-layer design for multiple antenna multicast over a common radio channel. In the design, the modulation and coding scheme of a multicast packet is selected based on the minimum signal-to-noise ratio (SNR) in the multicast group in such a way that the constraint on the packet loss rate is satisfied for all users in the group. A general expression for the throughput of the proposed design is derived in frequency-flat fading channel environment and specific results in Rayleigh, Nakagami, and Rician fading channels are provided. It is shown that the proposed multicast design provides a significant throughput gain compared to the unicast counterpart, in particular, in the mid- to high SNR region. It is also shown that a larger value of the diversity order, Nakagami parameter, and Rician factor is more beneficial to multicast than to unicast.

On the Accuracy of the Gaussian Approximation With Linear Cooperative Spectrum Sensing Over Rician Fading Channels

Linear cooperative spectrum sensing has been proposed for cognitive radio networks which are often limited by the achievable complexity of the devices involved. The method is based on the Gaussian approximation of the summary statistics sent to the fusion center. The goodness of this approximation is investigated in this letter in the case of block Rician fading. The impact of the number of secondary users, sampling times, and the Rician factor are assessed by an analytic method proposed to calculate the false-alarm and the missed-detection probabilities.

Capacity fades analysis of MIMO Rician channels in mobile ad hoc networks

Multiple-input multiple-output (MIMO) mobile ad hoc networks have been receiving increased attention in both commercial and military applications. Just as in cellular networks, MIMO technologies can benefit ad hoc networks by providing the diversity and capacity advantages as well as the spatial degree of freedom in designing the media access control (MAC) protocol. However, one fundamental issue of MIMO mobile ad hoc networks is how to accurately model the impact of spatial/temporal channel correlation in the mobile-to-mobile communications environment. In such a channel, line-of-sight (LOS) components and different scattering environments will affect both ergodic capacity and average capacity fading duration of the MIMO system. In this paper, based on the double-ring scattering model with LOS components we suggest a sum-of-sinusoids MIMO mobile-to-mobile channel simulation method, which can characterize the spatial/temporal channel correlation and Rician fading effect. Our numerical results show the ergodicity of our proposed channel model, correctness of the analytical channel correlation, effect of spatial correlation on channel capacity, impact of the number of antennas and scatterers on capacity, capacity distribution, and level crossing rate (LCR) and average fading duration (AFD) of MIMO Rician channel capacity. We also show the impacts of Rician factor K on channel capacity, probability density function (PDF), LCR, and AFD.

Performance of M-PSK in mobile satellite communication over combined ionospheric scintillation and flat fading channels with MRC diversity

Combined scintillation and terrestrial fadings occur in mobile satellite communication channels as the signal passes through the ionosphere and the lower atmosphere. This results in a product fading channel, which negatively affects the performance of the system. The challenge is to evaluate the performance of the system, in terms of the average bit error probability (BEP). In this paper, through the use of the moment generating function, we derive expressions for the average BEP and an upper bound for M-ary phase-shift keying (M-PSK) modulation with maximal-ratio combining (MRC) diversity over the product RiciantimesRician channel. The results are expressed as double summations in terms of the generalized hypergeometric function, which can be computed using standard commercial software. For a large Rician factor, the expression is simplified to a single summation. Numerical results are obtained from the derived expressions and compared with simulation results. They show very good agreement for various Rician factors and the number of diversity branches. The upper bound is also evaluated and shown to be reasonably tight.

Performance analysis of the dual-hop asymmetric fading channel

In real wireless communication environments, it is highly likely that different channels associated with a relay network could experience different fading phenomena. In this paper, we investigate the end-to-end performance of a dual-hop fixed gain relaying system when the source-relay and the relay-destination channels experience Rayleigh/Rician and Rician/Rayleigh fading scenarios respectively. Analytical expressions for the cumulative distribution function of the end-to-end signal-to-noise ratio are derived and used to evaluate the outage probability and the average bit error probability of M-QAM modulations. Numerical and simulation results are presented to illustrate the impact of the Rician factor on the end-to-end performance. Furthermore, these results confirm that the system exhibits an improved performance in a Rician/Rayleigh (source-relay link/relay-destination link) environment compared to a Rayleigh/Rician environment.

Two hop amplify-and-forward transmission in mixed rayleigh and rician fading channels

The performance of a two hop amplify-and-forward relay system, where the source-relay and the relay-destination channels experience Rayleigh and Rician fading respectively, is investigated. We derive exact and lower bound expressions for the outage probability and average bit error probability, where the bounds become tight at high signal-to-noise ratios (SNR). Our results are verified through comparison with Monte Carlo simulations, where we also illustrate the positive impact of the Rician factor on the system performance.

Synthetic Aperture Imaging of Multiple Point Targets in Rician Fading Media

This paper presents a study of stability, resolution, and detection for broad-band synthetic aperture (SA) imaging in Rician fading media. The stability condition $BNK^2/(K+1)\gg M$ is derived, where $K$ is the Rician factor, $B$ is the effective number of coherence bands, $N$ is the effective number of array elements, and $M$ is the number of (widely separated) targets. The imaging method is tested numerically with randomly distributed discrete scatterers, and comparisons with the imaging with the full response matrix (RM) are made. The resolution study reveals several interesting effects: First, given the same measurement resources, SA imaging has better resolution performance, although less stable, than RM imaging; second, for both imaging methods, the cross-range resolution measure (i.e., “full width at half maximum”) decreases with the aperture ($N$ fixed) and the probe spacing (the total aperture fixed) while the range resolution increases with both parameters. A statistical scheme is introduced to reduce the uncertainty when the stability regime is not realized.

Weak Solar Scintillation Effects on Deep Space Communication

摘要: 行星聚合和太阳闪烁是影响深空通信的重要因素. 分析了行星聚合和太阳闪烁的物理特性, 建立了弱太阳闪烁条件下深空通信信道的Rician 模型, 并得出了当Rician 因子大于10 dB 时近似为高斯信道的结论. 对弱太阳闪烁下X 波段和Ka 波段的通信性能进行了仿真, 这对建立可靠的深空通信链路具有十分重要的意义. 关键词: 太阳闪烁 / 行星聚合 / 深空通信

BER Performance Evaluation in 2 x 2 MIMO Spatial Multiplexing Systems under Rician Fading Channels

In this paper, BER (Bit Error Rate) performance in 2 × 2 MIMO (Multiple-Input Multiple-Output) spatial multiplexing systems under Rician fading channels is evaluated. We examine BER performances employing inverse channel detection (ICD) under Rician fading channels, adding the phase of the direct path and Rician factor as a parameter. The results clearly indicate that the phase of the direct path and Rician factor have a great influence on BER performances employing ICD under Rician fading channels.