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Enhanced spectrum sensing using a combination of energy detector,matched filter and cyclic prefix

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Digital Communications and Networks 2020年第4期6卷 534-541页

作者： Ghassan Alnwaimi Hatem Boujemaa King Abdulaziz University Saudi Arabia COSIM Lab SUPCOMTunisia

In this paper,we propose a sensing scheme based on energy detection,matched filter and cyclic prefix.Both Equal Gain Combining(EGC)and optimal combination of the aforementioned detectors are investigated in cooperative and non-cooperative spectrum sensing scenarios.In packet transmission systems such as OFDM(Orthogonal Frequency Division Multiple access)systems,the proposed scheme takes advantage of utilizing more samples than individual detectors,i.e.,cyclic prefix,training or pilot samples,and data payload samples.The proposed combine-sensing scheme offers higher detection probability and lower false alarm probability,as compared with the performance of individual detectors over the same frame duration.Simulation results are congruent with the theoretical curves and confirm the validity of our derivations.

关键词： Cooperative spectrum sensing Energy detector Matched filter cyclic prefix CFAR CDR Cognitive radio networks False alarm probability Detection probability

A novel OFDM transmission scheme with length-adaptive cyclic prefix

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2004年第11期5卷 25-31页

作者：张朝阳赖利峰 Hangzhou 310027 Institute of Information and Communication Engineering China Zhejiang University

Conventional OFDM transmission system uses a fixed-length cyclic prefix to counteract Inter-Symbol Inter- ferences (ISI) caused by channel delay spreading under wireless mobile environment. This may cause considerable per- formance deterioration when the CP length is less than the channel RMS delay spread, or may decrease the system power and spectrum efficiency when it is much larger. A novel Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme is proposed in this paper to adapt the CP length to the variation of channel delay spread. AOFDM-VCPL utilizes the preamble or pilot sub-carriers of each OFDM packet to estimate the channel RMS delay spread; and then uses a criterion to calculate the CP length , which finally affects the OFDM transmitter. As illustrated in the simulation section, by deploying this scheme in a typical wireless environment, the system can transmit at data rate 11.5 Mb/s higher than conventional non-adaptive system while gaining a 0.65 dB power saving at the same BER performance.

关键词： Adaptive OFDM cyclic prefix RMS delay spread

Hybrid prefix OFDM with spatial modulation toward terahertz broadband transmission

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Science China(Information Sciences) 2020年第8期63卷 53-55页

作者： Tiebin WANG Weipeng JING Wenlong SONG Information and Computer Engineering College Northeast Forestry University

Dear editor,In the development of 6G, terahertz communications [1] have attracted much attention owing to their potential for providing wireless broadband connections with even higher frequency resources. Furthermore, new transmission technologies have been widely considered for supporting future 6G systems [2]. Specifically, the spatial

关键词： spatial modulation ofdm cyclic prefix terahertz multiple path fading

Blind estimation of multipath delays in OFDM systems

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Science China(Information Sciences) 2012年第6期55卷 1397-1401页

作者： SHENG Bin & YOU XiaoHu National Mobile Communications Research Laboratory,Southeast University,Nanjing 210096,China National Mobile Communications Research Laboratory Southeast University Nanjing China

In order to coherently detect the transmitted data symbols,an orthogonal frequency division multi-plexing (OFDM) receiver requires reliable identification and equalization of the experienced wireless multipath fading channels.The information of path delays plays an important role in the procedure of identification and equalization.The need for high data rates motivated the search for blind identification and equalization methods because they save bandwidth by avoiding the use of training sequences.In OFDM systems,multipath fading channels introduce interference between adjacent symbols which can be prevented by inserting a cyclic prefix (CP) before each symbol.In this paper,we find that the power of the interference in the CP interval can be estimated by using the circular convolution and based on the variations of the interference power,the time delay of each path can be estimated blindly.

关键词： multipath delay cyclic prefix OFDM

Equivalent Time-Domain Representation and Uplink Channel Estimator for Multicarrier CDMA Systems

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Journal of Systems Engineering and Electronics 2003年第3期14卷 1-7页

作者：吴晓军殷勤业曾明 School of Electronics and Information Engineering Xi' an Jiaotong University Xi' an 710049 P. R. China

Many blind channel estimation methods have been proposed for direct sequence (DS) code-division multiple access (CDMA) systems, so we can certainly use them to estimate the finite impulse response (FIR) channel for the multi-carrier (MC-) CDMA system. In this paper, the MC-CDMA system is interpreted as an equivalent time-domain DS-CD-MA system with specific spreading codes. Then, an equivalently time-domain blind channel estimator is derived for the uplink MC-CDMA, which is based on second-order statistics of the received data. By exploiting singular value decomposition (SVD) and the finite alphabet property of transmitted symbols, the time-domain channel impulse response (CIR) for the uplink MC-CDMA can be accurately identified. Computer simulations illustrate both the validity and the overall performance of the proposed estimator.

关键词： Multicarrier code-division multiple access Channel impulse response Multiple access interference Intersym-bol interference cyclic prefix Blind channel estimation Multiuser detection.

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A Method for OFDM Timing Synchronization Estimation

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A Method for OFDM Timing Synchronization Estimation