Browsing by Author "Lei, Xianfu"

Now showing 1 - 4 of 4

Citation - WoS: 13
Citation - Scopus: 17
Conditional Power and Rate Adaptation for Mqam/Ofdm Systems Under Cfo With Perfect and Imperfect Channel Estimation Errors
(IEEE-INST Electrical Electronics Engineers Inc, 2015) Dong, Zhicheng; Fan, Pingzhi; Panayırcı, Erdal; Lei, Xianfu
In this paper a new conditional power and rate adaptation scheme for orthogonal frequency-division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO) with perfect and imperfect channel state information (CSI). The conventional adaptive scheme is shown to be a special case of the conditionally adaptive scheme technique that enables the resulting nonconvex optimization problem which is solved in a feasible way. It leads to a solution for optimal power adaptation that maximizes the spectral efficiency of an OFDM system using M-ary quadrature amplitude modulation (MQAM) under average power and instantaneous bit error rate (BER) constraints. Closed-form expressions for the average spectral efficiency (ASE) of adaptive OFDM systems are derived for perfect and imperfect CSI cases. The theoretical results and computer simulations show that range of the conditional adaptation becomes narrow and the performance of constant power and continuous rate is very close to that of the conditionally adaptive power and continuous rate for higher CFO or high signal-to-noise ratio (SNR) values.
Multi-Satellite Collaboration for Integrated Satellite Remote Sensing, Communications and Computing Networks: Usage Scenarios and Challenges
(IEEE-Inst Electrical Electronics Engineers Inc, 2026) Xiao, Ming; Lei, Lei; Panayirci, Erdal; Ma, Zheng; Lei, Xianfu; Zhang, Zhengquan
With the booming demands for real-time integrated space information services and the advanced satellite direct-to-X technology, it is a promising future to integrate satellite remote sensing, communications and computing in the form of integrated satellite networks (ISN), which directly provide space information services for users even without terrestrial networks. In this article, we firstly present typical usage scenarios and discuss the requirements for ISN. Subsequently, we present ISN architecture by considering heterogeneous satellites, homogeneous integrated satellites and their hybrid deployments. Furthermore, we study the key parts of designing ISN, including integrated satellite sensing and communications, and multi-satellite collaborative computing. To reduce computing delay, we propose a multi-satellite and satellite-terrestrial collaborative computing scheme together with partial offloading, which fully utilizes the computing capabilities of satellite edge computing, terrestrial cloud computing and user computing. Request and push modes are studied for ISN's satellite remote sensing services, where the former satisfies the personalized user service requests, while the latter actively distributes public information to users for such scenarios as public safety services. Finally, we highlight some technical challenges and future research directions.
Partial Power and Rate Adaptation for Mqam/Ofdm Systems Under Cfo
(IEEE, 2014) Dong, Zhicheng; Fan, Pingzhi; Panayırcı, Erdal; Lei, Xianfu
In this paper a new partial power and rate adaptation scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO). The conventional adaptive scheme is shown to be a special case of the partially adaptive scheme technique which enables the resulting non-convex optimization problem solved in a feasible way. It leads to a solution for optimal power adaptation that maximizes the spectral efficiency of an OFDM system using M-ary quadrature amplitude modulation (MQAM) under average power and instantaneous BER constraints. Closed-form expressions for the average spectral efficiency (ASE) of adaptive OFDM systems are derived. The theoretical results and computer simulations show that the range of the partial adaptation becomes narrow and the performance of constant power and continuous rate is very close to that of the partially adaptive power and continuous rate for higher CFO or high signal noise ratio (SNR) values.
Citation - WoS: 5
Citation - Scopus: 7
Power and Rate Adaptation Based on Csi and Velocity Variation for Ofdm Systems Under Doubly Selective Fading Channels
(IEEE-INST Electrical Electronics Engineers Inc, 2016) Dong, Zhicheng; Fan, Pingzhi; Lei, Xianfu; Panayırcı, Erdal
In this paper a novel joint continuous power and rate adaptation scheme is proposed fordoubly selective fading channels in orthogonal frequency division multiplexing (OFDM) systems based on terminal velocity and perfect or imperfect channel state information (CSI). The analysis and simulation results show that the continuous power and rate adaptation scheme is very effective and improve the performance of OFDM systems substantially under time-varying fading channels as compared with the traditional adaptation schemes operating without a priori knowledge of velocity and mobility adaptation without CSI.