Performance analysis on channel capacity in cooperative MIMO system

Recent years,cooperative technology has taken a lot of attention since it can improve the bit error rate(BER) and lower the transmit power in radio mobile networks,especially when the direct channel between the source and the destination is poor.Cooperative multiple input multiple output(Co-MIMO) is a kind of MIMO technique,where the multiple inputs and outputs are formed via cooperation.The capacity of Co-MIMO system over wireless channel has been investigated a lot,however few papers pay attention to the locations of the channel that may affect the probability distributions of the variable and the effect of antenna spatial correlation.The results can be achieved by choosing sub-channels that is not related to other sub-channels.This paper focuses on this problem.The simulation results show that once we search the partner we should consider trade offs cooperation get optimum system performance.It further investigates that cooperation between different terminals can reduce antenna spatial correlation,thereby increase the capacity and throughput of the system,and even reach the ideal capacity of MIMO system.

Investigation into the Performance of a MIMO System Equipped with ULA or UCA Antennas: BER, Capacity and Channel Estimation

This paper reports on investigations into the performance of a Multiple Input Multiple Output (MIMO) wireless communication system employing a uniform linear array (ULA) at the transmitter and either a uni-form linear array (ULA) or a uniform circular array (UCA) antenna at the receiver. The transmitter is as-sumed to be surrounded by scattering objects while the receiver is postulated to be free from scattering ob-jects. The Laplacian distribution of angle of arrival (AOA) of a signal reaching the receiver is postulated. The performance of bit error rate (BER), capacity and channel estimation for a MIMO system are evaluated for the two cases that the receiver is equipped with ULA or with UCA antennas.

On the Capacity of CPM MIMO Systems over Band-Limited Channels

Capacity analysis is a fundamental and important issue for continuous phase modulation (CPM) signals. In the letter, we investigate the capacity formula of CPM MIMO systems. Using Finite State Machine (FSM), the CPM symbols can be modeled as Markov source by combining channel and CPM modulation. Thus the capacity of CPM signals can be derived in form of the erroneous probability and normalized CPM bandwidth. In addition, the capacity of CPM MIMO systems is derived over Gaussian channels and Rayleigh channels. Finally, numerical simulations are implemented according to various parameters such as modulation scheme, modulation index h, memory length L, and antenna configuration.

Analytical Investigation of Channel Capacity of UWB-MIMO Systems

Ultra-wide-band (UWB) technology combined with multiple input and multiple output (MIMO) provides a viable solution for achieving high data transmission rates of more than 1 Gb/s in wireless communications. UWB is typically applied to short-range indoor environments and is therefore characterized by dense multipath propagation. In this type of environment, MIMO systems allow for a substantial improvement in the spectral efficiency by exploiting the inherent array gain and spatial multiplexing gain of UWB systems. This paper investigates the channel capacity of UWB-MIMO wireless technology and shows that UWB and MIMO designs improve the spectral efficiency logarithmically and linearly, respectively.

A Correlation-Based Stochastic Model for Massive MIMO Channel

In this paper,the channel impulse response matrix(CIRM)can be expressed as a sum of couplings between the steering vectors at the base station(BS)and the eigenbases at the mobile station(MS).Nakagami distribution was used to describe the fading of the coupling between the steering vectors and the eigenbases.Extensive measurements were carried out to evaluate the performance of this proposed model.Furthermore,the physical implications of this model were illustrated and the capacities are analyzed.In addition,the azimuthal power spectrum(APS)of several models was analyzed.Finally,the channel hardening effect was simulated and discussed.Results showed that the proposed model provides a better fit to the measured results than the other CBSM,i.e.,Weichselberger model.Moreover,the proposed model can provide better tradeoff between accuracy and complexity in channel synthesis.This CIRM model can be used for massive MIMO design in the future communication system design.

ERGODIC CAPACITY FORMULA OF MIMO-OFDM SYSTEMS UNDER CORRELATED FREQUENCY SELECTIVE RAYLEIGH FADING CHANNELS

An explicit formula for the ergodic capacity of Orthogonal Frequency Division Multiplexing (OFDM)-based Multiple-Input Multiple-Output (MIMO) systems under correlated frequency selective Rayleigh channels is derived,by simplifying the channel response matrix in frequency domain into the so-called Kronecker model composed of three kinds of correlations,i.e.multipath tap gain correlation and spatial fading correlations at both transmitter and receiver.The derived formula is very simple and convenient for one to estimate the effects of all three kinds of correlations on MIMO-OFDM capacity.If taps are independent,there is a very simple expression for the ergodic capacity.In case of tap correlation,the capacity formula could be further given in an integral expression.The validity of the new formula is verified and the effects of correlations,delay spread as well as the number of subcarriers on the ergodic capacity are evaluated via Monte Carlo simulations.

Capacity and Spatial Correlation Measurements of Compact MIMO Antennas

The dual-port compact multiple-input multiple-output(MIMO)dipole antennas with close spacing d of 0.5λand 0.3λare designed,and some electromagnetic band gap(EBG)structures are inserted between them to reduce mutual coupling.Those MIMO antennas with d=0.5λand 0.3λ,and with different mutual couplings are fabricated and measured,the channel capacity and correlation coefficient(CC)are analyzed and compared in a rich multipath reverberation chamber(RC),an office and a conference room.Results show that if d is reduced from 0.5λto 0.3λ,in the RCs,channel capacities of all the antennas are very close to that of the i.i.d.Rayleigh channel,although the average CCs are increased from 0.168 in the nonlossy RC to 0.269 in the lossy RC.In the office and conference rooms,compared with the RC,the average capacities of those antennas get a slight reduction,however,in most cases,the capacity of d=0.5λis larger than that of d=0.3λ,and the antennas with EBG have a larger capacity compared with the antennas without EBG,with a corresponding reduction of CC.A non-line-of-sight(NLOS)scenario of through-the-wall is also investigated.

Investigations into Capacity of MIMO Ad Hoc Network Including Effects of Antenna Mutual Coupling

This paper reports on investigations into capacity of ad hoc network whose nodes are equipped with multiple element antennas (MEAs). The investigation of this multi-user Multiple Input Multiple Output (MIMO) system takes into account mutual coupling (MC) in addition to spatial correlation that is present in array antennas. A closed-form expression for an upper bound of mutual information (capacity) of MIMO ad hoc network is derived. An optimal signal transmission scheme is proposed to maximize the MIMO ad hoc network capacity. Simulation results for capacity of non-optimized and optimized cases of signal transmission are presented.

HIGH SNR SUM CAPACITY ANALYSIS OF BD MIMO BC SYSTEMS WITH IMPERFECT CSI

We investigate the sum capacity of Block Diagonalization precoding Multiple Input Mul-tiple Output Broadcast Channels(BD MIMO BC) with imperfect Channel State Information(CSI) at the base station.Since it is difficult to obtain the exact expression,a lower and an upper bounds of the sum capacity under Gaussian channel estimation errors are drived instead.Analyses show that the gap between two bounds is considerably tight at all Signal to Noise Ratio(SNR) region.From the lower bound of the sum capacity,we can see that the multiplexing gain tends to be zero at high SNR region,which indicates that the BD MIMO BC system with channel estimation errors is interference-limited at high SNR.

基于莱斯信道的大规模MIMO协作中继网络设计与优化

随着移动通信技术的不断发展,大规模多输入多输出(Multiple Input Multiple Output,MIMO)系统被广泛应用于提高网络容量和性能。而协作中继网络作为一种有效提高通信覆盖能力和网络容量的手段,也受到越来越多的关注。文章基于莱斯信道模型,针对大规模MIMO协作中继网络进行设计与优化,旨在提升网络的可靠性和传输效率。通过对信道特性的分析和系统参数的优化,可以实现更好的性能表现。

Power optimization for maximum channel capacity in MIMO relay system

Introducing multiple-input multiple-output（MIMO） relay channel could offer significant capacity gain. And it is of great importance to develop effective power allocation strategies to achieve power efficiency and improve channel capacity in amplify-and-forward relay system. This article investigates a two-hop MIMO relay system with multiple antennas in relay node （RN） and receiver （RX）. Maximizing capacity with antenna selection（MCAS） and maximizing capacity with eigen-decomposition （MCED） schemes are proposed to efficiently allocate power among antennas in RN under first and second hop limited scenarios. The analysis and simulation results show that both MCED and MCAS can improve the channel capacity compared with uniform power allocation （UPA） scheme in most of the studied areas. The MCAS bears comparison with MCED with an acceptable capacity loss, but lowers the complexity by saving channel state information （CSI） feedback to the transmitter （TX）. Moreover, when the RN is close to RX, the performance of UPA is also close to the upper bound as the performance of first hop is limited.

Impact of Depolarization Phenomena on Polarized MIMO Channel Performances

The performance and capacity of multiple-input multiple-output (MIMO) wireless channels are limited by the spatial fading correlation between antenna elements. This limitation is due to the use of mono polarized antennas at receiver and transmitter sides. In this paper, in order to reduce the antenna correlation, the polarization diversity technique is employed. Although the spatial antenna correlation is attenuated for multi-polarization configurations, the cross-polar components appear. This paper highlights the impact of depolarization effect on the MIMO channel capacity for a 4×4 uniform linear antenna array. We assume that the channel is unknown at the transmitter and perfectly known at the receiver so that equal power is distributed to each of the transmit antennas. The numerical results illustrate that for low depolarization and spatial correlation, the capacity of single-polarization configuration behaves better than that of multi-polarization configuration.

Investigations into the Effect of Spatial Correlation on Channel Estimation and Capacity of Multiple Input Multiple Output System

The paper reports on investigations into the effect of spatial correlation on channel estimation and capacity of a multiple input multiple output (MIMO) wireless communication system. Least square (LS), scaled least square (SLS) and minimum mean square error (MMSE) methods are considered for estimating channel properties of a MIMO system using training sequences. The undertaken mathematical analysis reveals that the accuracy of the scaled least square (SLS) and minimum mean square error (MMSE) channel estimation methods are determined by the sum of eigenvalues of the channel correlation matrix. It is shown that for a fixed transmitted power to noise ratio (TPNR) assumed in the training mode, a higher spatial correlation has a positive effect on the performance of SLS and MMSE estimation methods. The effect of accuracy of the estimated Channel State Information (CSI) on MIMO system capacity is illustrated by computer simulations for an uplink case in which only the mobile station (MS) transmitter is surrounded by scattering objects.

Channel Simulation of Non-imaging Optical MIMO Communication

This paper reports a channel simulation of an indoor optical wireless multiple-input-multiple-output (MIMO) system with non-imaging receivers. The system consists of a 2×2 array of white light-emitting diodes (LEDs) and 2×2 array of PDs. An overview of the model specifications, channel impulse response and channel capacity are demonstrated in this paper. The distribution of the first reflection is analyzed. The effect of SNR and the location of receivers on non-imaging optical MIMO communications are investigated. In addition, by moving the receivers, the optimal location of the communication is found.

Analytical Expression for the MIMO Channel Capacity

This paper presents analytical expressions for the multiple-input multiple-output （MIMO） channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capacity for single-input multiple-output （SIMO） channels. The analysis shows that the SIMO channel capacity can be approximated by a Gaussian random variable and that the MIMO channel capacity can be approximated as the sum of multiple SIMO capacities. The SIMO channel results are used to derive approximate closed-form expressions for the MIMO channel ergodic capacity and the complementary cumulative distribution function （CCDF） of the MIMO channel capacity （outage capacity）. Simulations show that these theoretical results are good approximations for MIMO systems with an arbitrary number of transmit or receive antennas. Moreover, these analytical expressions are relatively simple which makes them very useful for practical computations.

Channel modeling and influenced factor analysis of the broadband dual-orthogonal polarized MIMO land mobile satellite channel

An accurate, complete and realistic channel model is re- quired to accurately analyze the system performance of a multiple input multiple output （MIMO） broadband satellite mobile commu- nication system with dual-orthogonal polarized antennas （DPAs）. In most current studies, the channel characteristic matrix （CCM） is always formed by an independent identical distribution （i.i.d） model of Rayleigh or Rice distribution and nevertheless incomplete and inaccurate to describe a broadband dual-orthogonal polarized MIMO land mobile satellite （BDM-LMS） channel. This paper fo- cuses on establishing the BDM-LMS channel statistical model, which combines the 4-state broadband LMS channel model, the time selective fading features, the channel covariance information （CCI） channel model and polarization correlations between an- tennas. The modeling steps of the channel model are introduced. The main emphasis is placed on the effects of the factors, such as antenna numbers, temporal correlations, terminal environments, elevation angles and polarization correlations between the DPAs, on the channel capacity in the BDM-LMS system. Many simulation results are provided to illustrate the effects of these factors through comparisons of the transmit rate, ergodic capacity and outage capacity with different factor values. Besides, the MIMO outage capacity advantages, which indicate the benefits of MIMO com- pared with a single input single output （SISO） system under the same channel condition, are also studied under i.i.d or BDM-LMS channel.

Dynamic Relay Selection Method for Distributed MIMO Relay System

The research on distributed MIMO relay system has been attracting much attention. In this paper, a decode-and-forward scheme distributed MIMO relay system is examined. For upper bound of channel capacity, the distance between transceivers is optimized when the propagation loss is brought close to actuality. Additionally, the number of relay is optimized whether total antenna element is fixed or not. When the number of relay is assumed to be infinite, the dynamic relay selection method based on the transmission rate is proposed. We represent that with the proposed method, the transmit power and the number of relays are saving.

Channel Capacity Optimization Based on Riemannian Trust Region Algorithm in IRS-Aided Communication System

Intelligent Reflecting Surface (IRS) can offer unprecedented channel capacity gains since it can reconfigure the signal propagation environment. We decide to maximize the channel capacity by jointly optimizing the transmit-power-constrained precoding matrix at the base station and the unit-modulus-constrained phase shift vector at the IRS in IRS-assisted multi-user downlink communication. We first convert the resulting non-convex problem into an equivalent problem, then use the alternate optimization algorithm. While fixing the phase shift vector, we can obtain the optimal precoding matrix directly by adopting standard optimization packages. While fixing the precoding matrix, we propose the Riemannian Trust-Region (RTR) algorithm to solve this optimization problem. And the key of the RTR algorithm is the solution of the trust-region sub-problem. We first adopt the accurate solution based on Newton's (ASNT) method to solve this sub-problem, which can obtain the global solution but cannot guarantee that the solution is optimal since the initial iteration point is difficult to choose. Then, we propose the Improved-Polyline (IPL) method, which can avoid the difficulty of the ASNT method and improve convergence speed and calculation efficiency. The numerical results show that the RTR algorithm has more significant performance gains and faster convergence speed compared with the existing approaches.

Achievable Rate Regions for Orthogonally Multiplexed MIMO Broadcast Channels with Multi-Dimensional Modulation

In this work, we consider a multi-antenna channel with orthogonally multiplexed non-cooperative users, and present its achievable information rate regions with and without channel knowledge at the transmitter. With an informed transmitter, we maximize the rate for each user. With an uninformed transmitter, we consider the optimal power allocation that causes the fastest convergence to zero of the fraction of channels whose mutual information is less than any given rate as the transmitter channel knowledge converges to zero. We assume a deterministic space and time dispersive multipath channel with multiple transmit and receive antennas, generating an orthogonally multiplexed Multiple-Input Multiple-Output (MIMO) broadcast system. Under limited transmit power;we consider different user specific space-time modulation formats that represent assignments of signal dimensions to transmit antennas. For the two-user orthogonally multiplexed MIMO broadcast channels, the achievable rate regions, with and without transmitter channel knowledge, evolve from a triangular region at low SNR to a rectangular region at high SNR. We also investigate the maximum sum rate for these regions and derive the associated power allocations at low and high SNR. Furthermore, we present numerical results for a two-user system that illustrate the effects of channel knowledge at the transmitter, the multi-dimensional space-time modulation format and features of the multipath channel.

地铁隧道有限空间Massive MIMO性能研究

基于实际场景测量,对地铁隧道有限空间Massive MIMO性能进行了研究。采用复用天线阵列法实现收发同步切换分时虚拟MIMO测量。基于测量数据,主要分析了3.5 GHz和5.6 GHz频段Massive MIMO信道在隧道场景的性能,研究了信道矩阵的特征值分布和条件数,着重分析了不同收发天线距离对Massive MIMO信道容量的影响,考虑了基于信噪比的有效秩选择方法。研究结果表明,在3.5 GHz及5.6 GHz频段上,Massive MIMO信道矩阵条件数的范围处在30 dB至55 dB之间,信道容量有较大的提升,且信道矩阵的有效秩随收发机距离增大的衰减趋势明显。以上结果对隧道场景下一代无线通信系统的设计与部署提供了依据。