Energy-aware Resource Allocating Mechanism Based on MAC/PHY for Wireless Network

针对无线网络服务能耗较高的问题,提出了一种基于机会主义的能量感知调度方案(OEARS)。首先,该方法将资源分配过程中的能耗和其他自然因素同时考虑; ,采用一种称为MAC/PHY机会主义方法对系统吞吐量进行优化;然后,利用唤醒-休眠模式和信道条件进行实现能耗最小化,并利用物理层信息提高系统容量; ,最大化能量效率。仿真实验结果表明,在保持接近的系统性能的前提下,OEARS的能耗低于现有的其他调度方案。Aimed at the problem of high energy consumption of wireless network; service, an energy-aware resource scheduling scheme-OEARS based on the; opportunism is proposed. Firstly, this method considers the energy; consumption and other natural factors in the process of resource; allocation. An opportunistic approach called MAC/PHY is used to optimize; the system throughput. Then, the energy consumption is minimized by; using the wake-sleep mode and the channel condition, and the physical; layer information is used to improve the system capacity and maximize; the energy efficiency. The simulation results show that the energy; consumption of OEARS is lower than that of other existing scheduling; schemes on the premise of keeping the close system performance.国家自然科学基金面上项目; 广东省教育部科技部中国科学院产学研结合项

A channel estimation method for MIMO-OFDM Mobile WiMax systems

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.In this paper, channel estimation for Space-Time Block Code (STBC) - Orthogonal Frequency Division Multiplexing (OFDM) is investigated for Mobile WiMax systems. A new channel estimation approach is proposed using the dedicated pilot subcarriers defined at constant intervals by the WiMax standard. The estimation method has low computation as only linear operations are needed due to orthogonal pilot coding. The performances of the proposed method have been demonstrated by extensive computer simulations. For the OFDM system with two transmit antennas and one to four receive antennas and using QPSK modulation, the simulated results under different Stanford University Interim (SUI) channels show that the proposed method has only a 4dB loss compared to the ideal case where the channel is known at the receiver

Robustness of space-time codes in the presence of channel estimation errors in OFDM systems

Many space-time codes (STC) have been proposed to enhance the performance of wireless communications in flat fading channels. All of them rely on the knowledge of the channel, and are hence affected by the channel estimation errors. In this paper, we investigate STC robustness under imperfect channel knowledge. We first define the concept of "closeness" by comparing the BER under channel estimation errors with that under perfect channel knowledge, aiming to characterize STC performance degradation due to imperfect channel knowledge. Then the robustness of STC can be compared by their "closeness" to perfect results. We find that for systems with two and three transmit antennas, the space time block codes (STBC) are always more robust to channel estimation errors than space time trellis codes (STTC). With the increase of receive diversity, all STCs become more robust to the channel estimation errors. For STTC, as the number of trellis states increases, the codes become less robust to the channel estimation errors. We also compare the BER performance of STC in the presence of channel estimation errors. For the two-transmit-antenna system, the performance of STBC is always better than that of the 4-state STTC, but is always worse than 16-state STTC. For systems with three transmit antennas, the BER performance of STTC is much better than that of STBC.published_or_final_versio

A Detailed Study of Channel Estimation and BER Optimization in presence of AWGN and Rayleigh Channel of OFDM System

Orthogonal Frequency Division Multiplexing is an important one field communication and that uses parallel information series. Contrast and single carrier adjustment are basic aspects of this technique where OFDM has many favourable circumstances are risky to work on this technique. It is robust, easy to use, and strength to safe the processing channel from distortions. It provides safety from multipath, much lesser computational many-sided characteristic. OFDM has some significant to execute it in commonly using media transmission frameworks. OFDM standard tolerate Packet misfortune, Bit trouble, Bit Error Rate (BER), Signal to Noise Ratio (SNR), Calculation of PAPR, Power Spectrum estimation. This dissertation is targeted to show the comparison of AWGN and Rayleigh channel by using fading process for particularity in superior performance with individual values of spectrums as well as by their scattering plots. In this dissertation each and every signal of these terms are examined and all the four parameters are thought about utilizing AWGN and Rayleigh fading channel by changing the period of a portion of the subcarriers utilizing QPSK in OFDM regulation. The representation of outputs is finished through MATLAB programming

A CME based channel estimation approach for MIMO-OFDM systems

A pilot-assisted, conditional model-order estimation (CME) based channel estimation algorithm is presented. The algorithm is proposed for MIMO-OFDM systems and can detect both channel frequency responses and number of multi-path taps. In addition, the modified CME estimator is also verified its capacity in determining the nonzero taps. The performance of the proposed approach is compared to the popular minimum description length (MDL) algorithm for estimation of the number of channel paths, by means of simulation in the context of a 2x2 MIMO-OFDM transceiver system. Result indicates that the new algorithm is superior in channel order estimation to the MDL algorithm in MMO-OFDM system over a noisy frequency selective fading channel. ©2009 IEEE