Abstract
Pilot symbol assisted modulation (PSAM) is widely used to obtain the channel state information (CSI) needed for coherent demodulation. It allows the density of pilot symbols to be dynamically chosen depending on the channel conditions. However, the insertion of pilots reduces the spectral efficiency, more severely when the channel is highly time-variant and/or frequency-selective. In these cases a significant amount of pilots is required to properly track the channel variations in both time and frequency dimensions. Alternatively, non-coherent demodulation does not require any CSI for the demodulation independently of the channel conditions. For the particular case of up-link (UL) based on massive single input - multiple output (SIMO) combined with orthogonal frequency division multiplexing (OFDM), we propose to replace the traditional reference signals of PSAM by a new differentially-encoded data stream that can be non-coherently detected. The latter can be demodulated without the knowledge of the CSI and subsequently used for the channel estimation. We denote our proposal as hybrid demodulation scheme (HDS) because it exploits both the benefits of a coherent demodulation scheme (CDS) and a non-coherent demodulation scheme (NCDS) to increase the spectral efficiency. The mean squared error (MSE) of the channel estimation, bit error rate (BER), achieved throughput and complexity are analyzed to highlight the benefits of this differential data-aided channel estimation as compared to other approaches. We show that the channel estimation is almost as good as PSAM, while the BER performance and throughput are improved for different channel conditions with a very small complexity increase.
Highlights
N EW DEMANDING applications have emerged in the last years, which require a tremendous increase in the capabilities of the communications networks
For an UL massive single input - multiple output (SIMO)-Orthogonal frequency division multiplexing (OFDM) system, we have proposed a differential data-aided channel estimation scheme, where the traditional reference signals are replaced by a differential data stream
By proposing a hybrid scheme denoted as hybrid demodulation scheme (HDS), the channel can be accurately estimated to perform coherent demodulation of the coherent demodulation scheme (CDS) stream, while the resources typically occupied by pilots are leveraged for transmission of the non-coherent demodulation scheme (NCDS) data stream
Summary
N EW DEMANDING applications have emerged in the last years, which require a tremendous increase in the capabilities of the communications networks. Alternatives to PSAM exist, such as blind channel estimation [7], [8] It requires no reference signals and the spectral efficiency is increased, at the expense of sacrificing the complexity and/or the quality of the CSI. The spectral efficiency is increased at the expense of degrading the quality of the channel estimates due to the presence of data self-interference All these techniques, blind, semi-blind or ST, are appropriate for time-invariant and/or flat-fading environments, since they need to average a significant number of samples to obtain an acceptable quality of the CSI. These non-coherently detected symbols are used for channel estimation to produce the CSI to coherently demodulate the main data stream.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
