科研之友
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摘要
Channel state information (CSI) is defined as the signal-to-noise ratio (SNR) for a sub-carrier position. In white noise channels it is proportional to magnitude of the channel frequency response (CFR). However, if the channel introduces frequency selective interference such as interference from existing analogue TV systems (PAL/SECAM/NTSC) and narrowband interference due to inter-modulation distortions in receiver, magnitude of CFR does not represent SNR values and system performance is significantly degraded. On the other hand, conventional methods for SNR estimation (using received data) do not give good results in white noise channels. To improve the reliability of the channel state measurements, we propose an adaptive technique for coded OFDM receiver, particularly for Digital Video Broadcasting-terrestrial and handheld ((DVB-T/H) receiver. In this paper, two methods are employed for CSI generation. The first method is based on channel frequency response provided by channel equalizer, whereas in the second method, channel state is obtained by measuring distance between received and de-mapped values for each sub-carrier of the OFDM signal. In most situations the first method provides better results, except in situations when frequency selective co-channel inference (CCI) is present in the received signal. In order to improve channel state measurements, CCI detector is used, and based on its decisions appropriate method for channel state measurements is selected. Extensive simulation results verify that the proposed technique has good performance in channels with CCI and no performance loss in white-noise channels(1).
- 出版日期2010-8
