Low-Overhead Feedback Topology Design for the K-User MIMO Interference Alignment

( Jin Jin ),( Xiang-chuan Gao ),( Xingwang Li ),( Charles C. Cavalcante ),( Lihua Li ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.11

Since designing a feedback topology is a practical way to implement interference alignment at reduced cost of channel state information (CSI) feedback, six feedback topologies have been presented in prior works for a K-user multiple-input multiple-output interference channel. To fully reveal the potential benefits of the feedback topology in terms of the saving of CSI overhead, we propose a new feedback topology in this paper. By efficiently performing dimensionality-decreasing at the transmitter side and aligning interference signals at a subset of receivers, we show that the proposed feedback topology obtains substantial reduction of feedback cost over the existing six feedback designs under the same antenna configuration.

Outage Analysis of Multi-Antenna Rate Adaptive Systems With Outdated Feedback

Jin Whan Kang,Min Jang,Sang-Hyo Kim,Dong In Kim IEEE 2014 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.13 No.10

<P>The effect of imperfect channel state information (CSI) on rate adaptation in time-varying multi-antenna fading channels is studied. In the presence of feedback delay and channel estimation error, we analyze the outage probability (OP), defined as the average probability that the achievable rate in the current channel state is lower than data rate scheduled based on outdated feedback, for maximum ratio combining receivers in single-input multiple-output channels and zero-forcing (ZF) receivers in multiple-input multiple-output (MIMO) channels. In particular, for temporally correlated MIMO channels, the conditional distribution of SNR at the output of ZF detection in the current channel state is unknown; hence we apply a Gaussian approximation to obtain a closed-form expression for the average OP of the MIMO-ZF receiver. Simulation results show that our derivations are well-matched to the actual OP and throughput of multi-antenna rate adaptive systems. Also, based on our analysis results, we propose a simple rate adaptation scheme that maximizes the average throughput under a target OP constraint. The proposed schemes optimize the scheduled rate according to a given CSI condition, and effectively maximize the average outage-constrained throughput.</P>

나카가미 페이딩 채널에서 궤환채널의 잡음을 고려한 ARQ 기법의 정보전송율 분석

황재문,박진수 한국정보통신학회 2002 한국정보통신학회논문지 Vol.6 No.8

본 논문에서는 ARQ 기법의 성능을 정확히 분석하기 위해 궤환채널의 잡음을 고려하여 시스템의 성능을 분석하였다. 상태도를 이용하여 ARQ 메카니즘을 표현하였고, 신호흐름 그래프에 대한 생성함수를 이용하여 ARQ 기법의 정보전송율을 수학적으로 유도하였다. 채널은 광범위한 채널환경에 적용할 수 있는 나카가미-m 페이딩 채널모델을 사용하였으며, BPSK 및 BFSK 시스템에 ARQ 기법을 적용하여 궤환이득과 페이딩 지수 m에 따른 시스템의 정보전송율을 컴퓨터 시뮬레이션을 통해 분석하였다. 분석결과, 궤환채널의 잡음이 증가할수록 ARQ 기법의 정보전송율은 감소하지만 궤환이득과 페이딩 지수 m이 증가할수록 ARQ 기법의 정보전송율이 증가됨을 확인하였다. 또한 비트에러확률의 차이로 BFSK에 비해 BPSK의 정보전송율이 우수함을 확인하였다. In this paper, the throughput performance of an ARQ scheme is analyzed with noisy feedback channel, in order to exactly analysis for performance of an ARQ scheme. An ARQ mechanism is presented by state diagram, and the throughput of an ARQ scheme is mathematically derived using generation function for a signal flow graph. The channel is modeled by the Nakagami-m fading channel which is distributed over far and wide, and the throughput performance of an ARQ scheme, which is applied in BPSK and BFSK systems, according to feedback gain and fading index m is analyzed through computer simulation. In the results, It is shown conformed that the throughput of an ARQ scheme decreased according to the increase of the noise for feedback channel, but it increased according to the increase of the feedback gain and fading index m. Also, it is shown that the throughput of an ARQ scheme using BPSK system is superior to BFSK system because of the difference of bit error probability between BPSK and BFSK systems.

Distributed Compressive Sensing Based Channel Feedback Scheme for Massive Antenna Arrays with Spatial Correlation

( Huanqin Gao ),( Rongfang Song ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.1

Massive antenna array is an attractive candidate technique for future broadband wireless communications to acquire high spectrum and energy efficiency. However, such benefits can be realized only when proper channel information is available at the transmitter. Since the amount of the channel information required by the transmitter is large for massive antennas, the feedback is burdensome in practice, especially for frequency division duplex (FDD) systems, and needs normally to be reduced. In this paper a novel channel feedback reduction scheme based on the theory of distributed compressive sensing (DCS) is proposed to apply to massive antenna arrays with spatial correlation, which brings substantially reduced feedback load. Simulation results prove that the novel scheme is better than the channel feedback technique based on traditional compressive sensing (CS) in the aspects of mean square error (MSE), cumulative distributed function (CDF) performance and feedback resources saving.

Towards Deep Learning-aided Wireless Channel Estimation and Channel State Information Feedback for 6G

Kim, Wonjun,Ahn, Yongjun,Kim, Jinhong,Shim, Byonghyo 한국통신학회 2023 Journal of communications and networks Vol.25 No.1

Deep learning (DL), a branch of artificial intel-ligence (AI) techniques, has shown great promise in variousdisciplines such as image classification and segmentation, speechrecognition, language translation, among others. This remarkablesuccess of DL has stimulated increasing interest in applyingthis paradigm to wireless channel estimation in recent years. Since DL principles are inductive in nature and distinct fromthe conventional rule-based algorithms, when one tries to useDL technique to the channel estimation, one might easily getstuck and confused by so many knobs to control and smalldetails to be aware of. The primary purpose of this paper isto discuss key issues and possible solutions in DL-based wirelesschannel estimation and channel state information (CSI) feedbackincluding the DL model selection, training data acquisition, andneural network design for 6G. Specifically, we present several casestudies together with the numerical experiments to demonstratethe effectiveness of the DL-based wireless channel estimationframework.

Machine learning-based adaptive CSI feedback interval

Seunghui Hong,Sanguk Jo,Jaewoo So 한국통신학회 2022 ICT Express Vol.8 No.4

The channel state information (CSI) is essential for the base station (BS) to schedule user equipments (UEs) and efficiently manage the radio resources. Hence, the BS requests UEs to regularly feed back the CSI. However, frequent CSI reporting causes large signaling overhead. To reduce the feedback overhead, we propose two machine learning-based approaches to adjust the CSI feedback interval. We use a deep neural network and reinforcement learning (RL) to decide whether an UE feeds back the CSI. Simulation results show that the RL-based approach achieves the lowest mean squared error while reducing the number of CSI feedback transmissions.

Reducing Feedback Overhead in Opportunistic Scheduling of Wireless Networks Exploiting Overhearing

( Seung Jun Baek ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.2

We propose a scheme to reduce the overhead associated with channel state information (CSI) feedback required for opportunistic scheduling in wireless access networks. We study the case where CSI is partially overheard by mobiles and thus one can suppress transmitting CSI reports for time varying channels of inferior quality. We model the mechanism of feedback suppression as a Bayesian network, and show that the problem of minimizing the average feedback overhead is NP-hard. To deal with hardness of the problem we identify a class of feedback suppression structures which allow efficient computation of the cost. Leveraging such structures we propose an algorithm which not only captures the essence of seemingly complex overhearing relations among mobiles, but also provides a simple estimate of the cost incurred by a suppression structure. Simulation results are provided to demonstrate the improvements offered by the proposed scheme, e.g., a savings of 63-83% depending on the network size.

Quantized Channel State Information Feedback Scheme for Multi-carrier Systems

서희정,김세영,김낙명,김기호,Seo Hee-Jung,Kim Seayoung,Kim Nak-Myeong,Kim Kiho The Korean Institute of Communications and Informa 2005 韓國通信學會論文誌 Vol.30 No.12A

본 논문에서는 다중 반송파 통신시스템에서의 채널상태정보 피드백 기법에 관한 압축된 양자화 채널상태정보 피드백 기법을 제안한다. 각 단말기에서 순간순간의 채널 상태를 평가하되, 주파수 도메인의 채널평가치를 실효수준을 기반으로 양자화하고 이 정보에 압축 부호화 알고리듬을 적용하는 방법으로 채널상태정보를 코딩함으로써 피드백되는 채별 상태 정보량을 현저히 감소시켰다. 컴퓨터 시뮬레이션을 통해 채널상태정보 비트가 기존 시스템과 비교하여 $10\%$ 정도까지 감소됨을 확인하였다. 또한 주파수 선택적 페이딩이 강한 경우에 대처하기 위한 제한된 압축 양자화 피드백 기법을 제안하여 vehicular B 채널 모델을 바탕으로 검증하였다. In this paper, we propose a compressed quantized channel state information (CQCSI) feedback scheme for multi-carrier mobile communication systems. The proposed CQCSI figures out the contiguous subsequences of equal QCSI's as separate types of runs across the subcarriers, and then encodes the types of runs using a truncated Huffman coding algorithm. Computer simulation shows that the proposed algorithm can reduce the QCSI feedback up to one tenth of the uncompressed, while providing a comparable performance with the conventional QCSI feedback schemes. To cope with special cases when the frequency selective fading is very high, we also propose a restricted CQCSI feedback scheme. The restricted CQCSI feedback has been proved under vehicular B channel model.

Optimal Wireless Power Transfer with Distributed Transmit Beamforming

Rui Wang,D. Richard Brown III 한국통신학회 2017 Journal of communications and networks Vol.19 No.2

This paper considers the performance of wireless powertransfer (WPT) with distributed transmit beamforming (DTB) ina narrowband setting. One or more receive nodes, each equippedwith energy harvesting and storage capabilities, provide periodicchannel state feedback to a cluster of transmit nodes, each with anindependent local oscillator, to facilitate beamforming and passbandsignal alignment for efficient WPT. Without channel statefeedback, the transmit cluster can not align the passband signals atthe receivers and the receivers can only harvest incoherent power. Since feedback improves the beamforming gain but requires the receiversto expend energy, there is a fundamental tradeoff betweenthe feedback period and the energy harvesting efficiency. This paperanalyzes the optimal feedback period to maximize the weightedmean energy harvesting rate as a function of the oscillator parameters. An optimization problem is formulated and an explicitmethod to numerically calculate the globally optimal feedback periodis developed. Numerical results are provided to confirm theanalysis and demonstrate the sensitivity of the weighted mean energyharvesting rate with respect to the feedback period and theDTB system parameters.

다중 입출력 시스템의 부분적 채널 정보 궤환을 통한 빔포머 형성 방안

김윤수(Yoonsoo Kim),성원진(Wonjin Sung) 대한전자공학회 2014 전자공학회논문지 Vol.51 No.6