Keskeiset käsitteet
This paper proposes a two-stage channel estimation scheme and a modified low-complexity maximum ratio combining (MRC) detection algorithm for OTFS systems operating in overspread wireless channels with very large delay spread.
Tiivistelmä
The paper addresses the challenge of channel estimation and detection for OTFS systems in overspread wireless channels, where the delay spread exceeds the block duration in the transmission frame.
The key highlights are:
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Proposed a two-stage channel estimation (CE) scheme:
- The first stage uses an embedded pilot in the delay-Doppler (DD) domain to estimate the aliased delays and Doppler shifts, and identifies underspread paths not coinciding with overspread ones.
- The second stage employs time-domain dual chirp correlation to estimate the actual delays and Doppler shifts of the remaining paths, resolving ambiguity in estimating delays and Doppler shifts for paths sharing the same aliased delay.
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Presented a modified low-complexity MRC detection algorithm for reduced zero-padded OTFS (RZP-OTFS) in overspread channels.
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Analyzed the complexity of the proposed CE and MRC detection schemes.
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Evaluated the performance of the proposed CE and MRC detection in terms of normalized mean square error (NMSE) and bit error rate (BER) for different synthetic and practical overspread channel models.
The proposed two-stage CE and modified MRC detection demonstrate reliable performance in overspread channels, outperforming existing methods designed for underspread channels.
Tilastot
The delay spread of the channel exceeds the block duration in the OTFS frame.
The maximum normalized delay lmax = 2400.
The maximum normalized Doppler shift kmax = 16.
Lainaukset
"In low latency applications and in general, for overspread channels, channel delay spread is a large percentage of the transmission frame duration."
"Increasing the duration of a block (or decreasing subcarrier spacing) to meet the underspread condition on maximum delay spread of the channel would require to increase the number of subcarriers. As a consequence, the number of blocks must decrease to satisfy the low latency constraint on the fixed frame duration. However, decreasing such a number reduces the maximum allowable channel Doppler spread."