Making preamble shorter in OFDM real-time wireless control systems
Making preamble shorter in OFDM real-time wireless control systems
复制标题
DOI：
10.1109/apcc.2016.7581437
复制
发表时间：
2016-08
期刊：
影响因子：
--
通讯作者：
Theerat Sakdejayont;Chun-Hao Liao;Makoto Suzuki;H. Morikawa
中科院分区：
文献类型：
--
作者：
Theerat Sakdejayont;Chun-Hao Liao;Makoto Suzuki;H. Morikawa
实时和健壮的通信对于无线控制系统（WCS）至关重要。在有效载荷通常很小的WCS中，序言被认为是重要的通信开销。为了缩短OFDM系统的开销，以往的研究采用固定子载波采样获得子载波固定短前馈（SFSP），并采用频率方向插值（FDI）进行信道估计。尽管它在快速衰落信道中具有优势，但在频率选择性衰落信道中性能较差。在这项工作中，我们提出了一种子载波可选的短前导（SSSP），它通过几个前导传输提供所有子载波的完整采样覆盖。利用WCS中传输的周期性，SSSP方案通过FDI和时间方向外推（TDE）获得非选择子载波的信道估计，在频率选择衰落中具有鲁棒性。此外，为了使信道估计在快速衰落和频率选择衰落中都具有鲁棒性，我们采用了在FDI或TDE模式之间切换的自适应算法。通过对快速频率选择衰落下的符号误码率（SER）进行评估，验证了该方法的可行性。仿真结果表明，与SFSP方案不同，自适应SSSP方案在信道频率选择性衰落时，在SER曲线上没有误差层，在信道快速衰落时，其性能与SFSP方案相似。
Real-time and robust communication is essential for wireless control systems (WCS). Preambles are considered as significant communication overheads in WCS where payloads are typically small. To shorten the overhead in OFDM systems, previous works have considered fixed subcarrier sampling to obtain subcarrier-fixed short preambles (SFSP) and adopted frequency-direction interpolation (FDI) for channel estimation. Despite of advantage in fast fading channel, it results in poor performance in frequency-selective fading channel. In this work, we propose a subcarrier-selectable short preamble (SSSP) which provides full sampling coverage of all subcarriers with several preamble transmissions. By exploiting the periodicity of transmissions in WCS, the SSSP scheme obtains the channel estimation of non-selected subcarriers by not only FDI but also the time-direction extrapolation (TDE), which is robust in frequency-selective fading. In addition, in order to make the channel estimation robust in both fast fading and frequency-selective fading we adopt an adaptive algorithm altering between FDI or TDE mode. The feasibility of the proposed method is validated by evaluating symbol error rate (SER) in fast frequency-selective fading. Simulation results verify that unlike the SFSP the adaptive SSSP scheme shows no error floor in SER curve when the channel is frequency-selective fading, and performs similar to the SFSP scheme when the channel is fast fading.