OFDMA uplink frequency offset estimation via cooperative relaying
OFDMA uplink frequency offset estimation via cooperative relaying
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DOI：
10.1109/twc.2009.081525
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发表时间：
2009-09
影响因子：
10.4
通讯作者：
Zhongshan Zhang;Wei Zhang-;C. Tellambura
中科院分区：
文献类型：
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作者：
Zhongshan Zhang;Wei Zhang-;C. Tellambura
研究了放大转发（AF）中继和解码补偿转发（DcF）中继在正交频分多址（OFDMA）上行链路中的频偏估计问题。考虑多个中继，并且选择具有最佳S rrrrrrrr信道的中继来执行重传，其中S和R分别表示源节点和中继节点。考虑了由于发射机和接收机振荡器之间的失配而引起的频率偏移，并且在不考虑多普勒频移的影响的情况下，S_r_D和S_r_R_r_D链路具有相同的频率偏移，其中D表示目的地。因此，通过使用这两个传输，D生成两个频率偏移估计，其被组合以最小化均方误差（MSE）。在频偏误差方差方面，可以自适应地调整S和R之间的功率分配以优化协作方案。当每个移动的节点都有信道状态信息（CSI）时，提出了一种中继自适应地在协作传输和传统传输（无中继）之间切换的方案，以优化频偏估计。虽然DcF模式中的频率偏移估计精度比AF模式稍差，但是两种模式都优于传统传输。然而，DcF（或解码和转发（DF））中继优于AF中继的信道容量和误码率（BER）。
Frequency offset estimation for an orthogonal frequency-division multiple access (OFDMA) uplink for amplify-and-forward (AF) relays and a new type of relay (R) called decode-and-compensate-and-forward (DcF) relays are studied. Multiple relays are considered, and the relay with the best S rarr R channel is chosen to perform re-transmission, where S and R represent the source and relay nodes, respectively. Frequency offsets due to the mismatches between the transmitter and receiver oscillators are considered, and without considering the effect of Doppler shift, both S rarr D and S rarr R rarr D links have the same frequency offset, where D represents the destination. Thus, by using these two transmissions, D generates two frequency offset estimates, which are combined to minimize the mean square error (MSE). Power allocation between S and R can be adaptively adjusted to optimize the cooperative scheme in terms of frequency offset error variance. When channel state information (CSI) is available at each mobile node, a scheme where the relays adaptively switch between the cooperative and conventional (no relaying) transmissions is proposed to optimize the frequency offset estimation. Although the frequency offset estimation accuracy in the DcF mode is somewhat worse than the AF mode, both modes outperform the conventional transmission. However, DcF (or decode-and-forward (DF)) relays outperform AF relays in terms of channel capacity and bit error rate (BER).