Downlink Capacity Analysis of Distributed Antenna Systems with Imperfect Channel State Information

( Weiye Xu ),( Min Lin ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

In this paper, considering that perfect channel state information (CSI) is hard to achieve in practice, the downlink capacity of distributed antenna systems (DAS) with imperfect CSI and multiple receive antennas is investigated over composite Rayleigh fading channel. According to the performance analysis, using the numerical calculation, the probability density function (PDF) of the effective output SNR is derived. With this PDF, accurate closed-form expressions of ergodic capacity and outage probability of DAS with imperfect CSI are, respectively, obtained, and they include the ones under perfect CSI as special cases. Besides, the outage capacity of DAS in the presence of imperfect CSI is also derived, and a Newton`s method based practical iterative algorithm is proposed to find the accurate outage capacity. By utilizing the Gaussian distribution approximation, another approximate closed-form expression of outage capacity is also derived, and it may simplify the calculation of accurate outage capacity. These theoretical expressions can provide good performance evaluation for downlink DAS for both perfect and imperfect CSI. Simulation results verify the effectiveness of the theoretical analysis, and the system capacity can be improved by increasing the receive antennas, and decreasing the estimation error or path loss. Moreover, the system can tolerate the estimation error variance up to about 0.01 with a slight degradation in the capacity.

Interference Tolerant Based CR System with Imperfect Channel State Information at the CR-Transmitter

Asaduzzaman,Hyung-Yun Kong 한국전자파학회JEES 2011 Journal of Electromagnetic Engineering and Science Vol.11 No.2

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.

CoMP Transmission for Safeguarding Dense Heterogeneous Networks with Imperfect CSI

( Xu Yunjia ),( Huang Kaizhi ),( Hu Xin ),( Zou Yi ),( Chen Yajun ),( Jiang Wenyu ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.1

To ensure reliable and secure communication in heterogeneous cellular network (HCN) with imperfect channel state information (CSI), we proposed a coordinated multipoint (CoMP) transmission scheme based on dual-threshold optimization, in which only base stations (BSs) with good channel conditions are selected for transmission. First, we present a candidate BSs formation policy to increase access efficiency, which provides a candidate region of serving BSs. Then, we design a CoMP networking strategy to select serving BSs from the set of candidate BSs, which degrades the influence of channel estimation errors and guarantees qualities of communication links. Finally, we analyze the performance of the proposed scheme, and present a dual-threshold optimization model to further support the performance. Numerical results are presented to verify our theoretical analysis, which draw a conclusion that the CoMP transmission scheme can ensure reliable and secure communication in dense HCNs with imperfect CSI.

Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI

Hung Nguyen-Le,Vien Nguyen-Duy-Nhat,Chien Tang-Tan,Vo Nguyen Quoc Bao 한국통신학회 2016 Journal of communications and networks Vol.18 No.5

This paper studies the problem of precoding and post-coding design for multicellmultiuser downlink transmissions in theabsence of perfect channel state information (CSI). Using statisti-cal information of imperfect CSI, an iterative multiuser multicelltransceiver design is formulated by minimizing the mean squarederror (MSE) cost function of signal and leakage interference underper-base station power constraint (PBPC). The convergence of theiterative precoding and postcoding algorithm is verified by analyt-ical and empirical results. The proposed precoding and postcodingalgorithm offers a low computational complexity and robustnessagainst CSI imperfection.

Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI

Nguyen-Le, Hung,Nguyen-Duy-Nhat, Vien,Tang-Tan, Chien,Bao, Vo Nguyen Quoc The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5

This paper studies the problem of precoding and post-coding design for multicell multiuser downlink transmissions in the absence of perfect channel state information (CSI). Using statistical information of imperfect CSI, an iterative multiuser multicell transceiver design is formulated by minimizing the mean squared error (MSE) cost function of signal and leakage interference under per-base station power constraint (PBPC). The convergence of the iterative precoding and postcoding algorithm is verified by analytical and empirical results. The proposed precoding and postcoding algorithm offers a low computational complexity and robustness against CSI imperfection.

A Robust Closed-Loop Transmit-Diversity Scheme with Unknown CSI Reliability

YOON, Eunchul,KIM, Joon-Tae,HWANG, Taewon The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.9

<P>In a closed-loop scenario, the performance of transmit-diversity schemes for a multiple antenna system depends on the reliability of the channel state information (CSI). However, estimating the reliability of the instantaneous CSI at the transmitter is a challenging task. In this paper, we propose a robust transmit-diversity scheme for the case when the instantaneous CSI available at the transmitter is imperfect and its reliability is unknown to the transmitter. We show by simulation that our proposed scheme is efficient when the CSI reliability varies arbitrarily in every channel realization.</P>

Robust Relay Design for Two-Way Multi-Antenna Relay Systems with Imperfect CSI

Chenyuan Wang,Xiaodai Dong,Yi Shi 한국통신학회 2014 Journal of communications and networks Vol.16 No.1

The paper investigates the problem of designing themultiple-antenna relay in a two-way relay network by taking intoaccount the imperfect channel state information (CSI). The objectiveis to design the multiple-antenna relay based upon the CSIestimates, where the estimation errors are included to attain therobust design under the worst-case philosophy. In particular, theworst-case transmit power at the multiple-antenna relay is minimizedwhile guaranteeing the worst-case quality of service requirementsthat the received signal-to-noise ratio (SNR) at both sourcesare above a prescribed threshold value. Since the worst-case receivedSNR expression is too complex for subsequent derivationand processing, its lower bound is explored instead by minimizingthe numerator and maximizing the denominator of the worst-caseSNR. The aforementioned problem is mathematically formulatedand shown to be nonconvex. This motivates the pursuit of semidefiniterelaxation coupled with a randomization technique to obtaincomputationally efficient high-quality approximate solutions. Thispaper has shown that the original optimization problem can be reformulatedand then relaxed to a convex problemthat can be solvedby utilizing suitable randomization loop. Numerical results comparethe proposed multiple-antenna relay with the existing nonrobustmethod, and therefore validate its robustness against thechannel uncertainty. Finally, the feasibility of the proposed designand the associated influencing factors are discussed by means ofextensive Monte Carlo simulations.

Robust Relay Design for Two-Way Multi-Antenna Relay Systems with Imperfect CSI

Wang, Chenyuan,Dong, Xiaodai,Shi, Yi The Korea Institute of Information and Commucation 2014 Journal of communications and networks Vol.16 No.1

The paper investigates the problem of designing the multiple-antenna relay in a two-way relay network by taking into account the imperfect channel state information (CSI). The objective is to design the multiple-antenna relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. In particular, the worst-case transmit power at the multiple-antenna relay is minimized while guaranteeing the worst-case quality of service requirements that the received signal-to-noise ratio (SNR) at both sources are above a prescribed threshold value. Since the worst-case received SNR expression is too complex for subsequent derivation and processing, its lower bound is explored instead by minimizing the numerator and maximizing the denominator of the worst-case SNR. The aforementioned problem is mathematically formulated and shown to be nonconvex. This motivates the pursuit of semidefinite relaxation coupled with a randomization technique to obtain computationally efficient high-quality approximate solutions. This paper has shown that the original optimization problem can be reformulated and then relaxed to a convex problem that can be solved by utilizing suitable randomization loop. Numerical results compare the proposed multiple-antenna relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty. Finally, the feasibility of the proposed design and the associated influencing factors are discussed by means of extensive Monte Carlo simulations.

Outage Probability of Two-Way Full-Duplex Relaying With Imperfect Channel State Information

Dongwook Choi,Jae Hong Lee IEEE 2014 IEEE Communications Letters Vol.18 No.6

<P>In this letter, we investigate two-way full-duplex (TWFD) relaying with a residual loop interference (LI). In the TWFD relaying, two full-duplex users exchange data with each other via a full-duplex relay, and each node attempts to subtract the estimate of the residual LI from its received signal. We derive the exact integral and approximate closed-form expressions for the outage probability of the TWFD relaying in case of perfect and imperfect channel state information. Monte Carlo simulations verify the validity of analytical results.</P>

Robust Secure Transmit Design with Artificial Noise in the Presence of Multiple Eavesdroppers

( Xiaochen Liu ),( Yuanyuan Gao ),( Nan Sha ),( Guozhen Zang ),( Shijie. Wang ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.6

This paper studies secure wireless transmission from a multi-antenna transmitter to a single-antenna intended receiver overheard by multiple eavesdroppers with considering the imperfect channel state information (CSI) of wiretap channel. To enhance security of communication link, the artificial noise (AN) is generated at transmitter. We first design the robust joint optimal beamforming of secret signal and AN to minimize transmit power with constraints of security quality of service (QoS), i.e., minimum allowable signal-to-interference-and-noise ratio (SINR) at receiver and maximum tolerable SINR at eavesdroppers. The formulated design problem is shown to be nonconvex and we transfer it into linear matrix inequalities (LMIs). The semidefinite relaxation (SDR) technique is used and the approximated method is proved to solve the original problem exactly. To verify the robustness and tightness of proposed beamforming, we also provide a method to calculate the worst-case SINR at eavesdroppers for a designed transmit scheme using semidefinite programming (SDP). Additionally, the secrecy rate maximization is explored for fixed total transmit power. To tackle the nonconvexity of original formulation, we develop an iterative approach employing sequential parametric convex approximation (SPCA). The simulation results illustrate that the proposed robust transmit schemes can effectively improve the transmit performance.