Xiupei Zhang

Chungbuk National University, Chinsen, North Chungcheong, South Korea

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Publications (8)1.11 Total impact

  • Xiupei Zhang, Heung-Gyoon Ryu, Jin-up Kim
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    ABSTRACT: OFDM (Orthogonal Frequency Division Multiplexing) has been chosen as the air interface technique for LTE (Long Term Evolution) standard. Furthermore, CA (Carrier Aggregation) is defined by 3GPP (the 3rd Generation Partnership Project) to support wide-bandwidth transmission. However, OFDM system is sensitive to synchronization errors generated by multipath delay, Doppler shift and oscillator instability. In this paper, we address the synchronization problem in non-continuous CA scenario and propose a block type pilot based synchronization algorithm to suppress the STO (Sampling Timing Offset) and CFO (Carrier Frequency Offset). The pilot pattern used here is CAZAC (Constant Amplitude Zero Autocorrelation) sequence, which is also exploited in LTE-Advanced standard. Since the proposed method is a parallel processing, different bands could experience different synchronization errors. Simulation results show the proposed method can significantly improve system performance and has smooth performance when synchronization errors vary.
    Communications (APCC), 2010 16th Asia-Pacific Conference on; 12/2010
  • Xiupei Zhang, Heung-Gyoon Ryu
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    ABSTRACT: In this paper, we address the ICI (intercarrier interference) problem and compensation in MIMO (multiple input multiple output) SC-FDMA (single carrier frequency division multiple access) system that exploits SC-SFBC (single carrier-space frequency block coding) scheme. Recently, SC-FDMA technique has received more attention due to the low PAPR (peak to average power ratio) property. However, SC-FDMA system is sensitive to phase noise and CFO (carrier frequency offset) which is unavoidable in wireless communication systems. Phase noise and CFO introduce CPE (common phase error) as well as ICI into the received signal and seriously degrade the system performance. Therefore, analysis and suppression of these interferences are of great importance. In this paper, we analyze the interferences in MIMO SC-FDMA system with SC-SFBC. Then a new ICI estimation and suppression method is proposed to suppress the interferences. Instead of directly estimating the CFO and phase noise, which is pretty difficult and complex, this algorithm exploits block-type pilots, which is a common pilot pattern in wireless communication systems, such as LTE standard, to estimate the interferences. After that the interferences are suppressed by the inverse matrix method. Simulation results show that the system performance is significantly improved. Copyright © 2010 John Wiley & Sons, Ltd.
    International Journal of Communication Systems 01/2010; 23:1521-1536. · 1.11 Impact Factor
  • Xiupei Zhang, Heung-Gyoon Ryu, J. Gao
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    ABSTRACT: In orthogonal frequency division multiple access (OFDMA) uplink system, orthogonal multiple subcarriers are assigned to different users for parallel high data rate communications. However, carrier frequency offset (CFO), which is mainly due to oscillator mismatches and/or Doppler shift, will destroy the orthogonality among subcarriers and introduce intercarrier interference (ICI) as well as multiple-access interference (MAI) in uplink scenario. Thus, system performance will be seriously degraded. To overcome this problem, it is of great importance to do research on suppression of the interferences caused by CFO. In this paper, we proposed a novel time domain inverse matrix receiver to suppress the interference of multiple CFOs. Compared with the conventional frequency domain direct ZF inverse matrix method, which has high complexity in obtaining the ICI matrix and its inverse matrix, the proposed method has very low complexity in obtaining the interference matrix. Furthermore, the signal after interference suppression is a frequency domain signal. Thus the receiver complexity can be simplified. Simulation results show that this algorithm has almost the same performance to the frequency domain direct ZF inverse matrix method.
    Proceedings of the 71st IEEE Vehicular Technology Conference, VTC Spring 2010, 16-19 May 2010, Taipei, Taiwan; 01/2010
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    Xiupei Zhang, Heung-Gyoon Ryu, Yingshan Li
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    ABSTRACT: MIMO (multiple input multiple output) system has been used to for communication capacity enhancement. Also, the single carrier frequency division multiple access (SC-FDMA) has very low PAPR (peak to average power ratio) property. However, SC-FDMA system is very sensitive to phase noise (PN) and carrier frequency offset (CFO), so that CPE (common phase error) and ICI (inter-subcarrier interference) in the received signal degrade the system performance seriously. Therefore, the suppression of influences from CFO and phase noise is of great importance. In this paper, we analyze the interference effects caused by phase noise and CFO in MIMO SC-FDMA system with SC-SFBC (single carrier-space frequency block coding). Next, a new ICI suppression method is proposed to overcome the ICI by block type pilot that is very suitable for SC-FDMA. The computer simulations show that the system performance is significantly improved by the proposed method.
    Communications and Information Technology, 2009. ISCIT 2009. 9th International Symposium on; 10/2009
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    ABSTRACT: Recently, FH-OFDM (frequency hopping orthogonal frequency division multiplexing) system has been widely used in communication system. However, FH-OFDM system is sensitive to frequency offset and timing offset, which are inherently unavoidable in wireless mobile communication systems and can seriously degraded system performance. So, research on estimation and compensation of these offsets is of great importance. In this paper, a novel joint method for estimating carrier frequency offset and timing offset is proposed. This algorithm exploits pilots to estimate the offsets, and compared with other methods, the processing can be completed in one symbol time period. Thus, this method can be used in both static and ergodic channel. The estimation can be divided into frequency offset estimation and timing offset estimation. Also, both frequency offset and timing offset estimation are divided into two steps: coarse frequency offset estimation step, fine frequency offset estimation step, fraction timing offset estimation step and integer timing offset estimation step. Through the computer simulations, the suggested algorithm shows very good performance results both in AWGN and multipath environments.
    Advances in Satellite and Space Communications, 2009. SPACOMM 2009. First International Conference on; 08/2009
  • Xiupei Zhang, Heung-Gyoon Ryu
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    ABSTRACT: In order to improve the throughput, the water filling algorithm is considered in the FH- OFDM (frequency hopping - orthogonal frequency division multiplexing) system which combines frequency hopping technique and OFDM technique. This system may be seriously degraded in the multipath and jamming channel. Adaptive bit loading technique using water filling[1] algorithm is used in FH-OFDM system. Via the computer simulation, it is confirmed that FH-OFDM system using the adaptive bit loading technique shows better BER performance and system throughput than the ordinary FH-OFDM system in the multipath propagation and jamming the environment.
    Advanced Communication Technology, 2009. ICACT 2009. 11th International Conference on; 03/2009
  • Xiupei Zhang, Jangsu Kim, Heung-Gyoon Ryu
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    ABSTRACT: For the 3G-LTE (long term evolution) up-link, SC-FDMA (single carrier frequency division multiple access) system was adopted by the 3GPP (Third Generation Partnership Project) as standard method. However, similar to the other OFDM-based systems, SC-FDMA system is also very sensitive to frequency synchronization errors, especially in the uplink communications, where different users always have different CFOs (carrier frequency offset). When multiple CFOs exist, the orthogonalities between the subcarriers are lost. ICI (inter carrier interference) as well as MAI (multi-access interference) are generated to degrade the quality of received signals. A novel suppression method based on block type pilots is proposed to overcome the interferences simultaneously. It is confirmed that the proposed suppression algorithm can significantly improve the performance by simulation results.
    01/2009;
  • Xiupei Zhang, Heung-Gyoon Ryu
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    ABSTRACT: Nowadays, OFDMA (Orthogonal Frequency Division Multiple Access) technique has been used in WiMAX communication system to achieve very high data rate as well as multi-user service. However, similar with other OFDM-based systems, OFDMA system is very sensitive to frequency synchronization errors, especially in the uplink communications where different users always have different CFOs (Carrier Frequency Offset). When multiple CFOs exist, the orthogonality which separates different subcarriers will be lost, and ICI (Inter Carrier Interference) as well as MAI (Multi-Access Interference) will be generated to disturb the received signals. Then, the system performance will be highly degraded. To overcome this problem, it is of great importance to do research on the suppression to the interferences caused by multiple CFOs. In this paper, we first analyze the interferences, including ICI and MAI, caused by multiple CFOs in the uplink communications of OFDMA system. Next, the suppression method based on block type pilots is proposed to overcome the interferences simultaneously. Compared with other interference suppression methods, the proposed method could directly get the interference components from inverse matrix, thus it doesn’t need to do the CFO estimation. From the simulation results, it can be seen that the multiple CFOs will make serious degradation to the system performance. But through the proposed suppression algorithm, the system performance can be significantly improved.
    Access Networks, 4th International Conference, AccessNets 2009, Hong Kong, China, November 1-3, 2009, Revised Selected Papers; 01/2009

Publication Stats

6 Citations
1.11 Total Impact Points

Institutions

  • 2009–2010
    • Chungbuk National University
      • Department of Electronic Engineering
      Chinsen, North Chungcheong, South Korea