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Orthogonal time frequency space (OTFS) is a recently proposed modulation scheme which multiplexes information symbols in the delay-Doppler domain to combat severe Doppler shifts in high mobility wireless communications. In this paper, we classify all the OTFS variants depending on whether a cyclic prefix (CP) or zero padding (ZP) is added to each block or to the entire frame. We then present the general input-output relations for integer and fractional delays and Doppler shifts. Further, we present a low-complexity universal maximum ratio combining (MRC) detector for all OTFS variants, which has the lowest complexity among other known OTFS detection schemes at no loss of performance. Finally, we derive the input-output relation for overspread channels, where the channel delay spreads can exceed the OTFS block duration. Simulation results demonstrate that the MRC detection offers same performance for all OTFS variants and can also be effectively used for overspread channels.

In the successive cancellation (SC) list decoding, the tree pruning operation retains the L best paths with respect to a metric at every decoding step. However, the correct path might be among the L worst paths due to the imposed penalties. In this case, the correct path is pruned and the decoding process fails. shifted pruning (SP) scheme can recover the correct path by additional decoding attempts when decoding fails, in which the pruning window is shifted by κ≤L paths over certain bit positions. A special case of the shifted pruning scheme where κ=L is known as SCL-flip decoding, which was independently proposed in 2019. In this work, a new metric that performs better in particular for medium and long codes is proposed, and nested shift-pruning schemes are suggested for improving the average complexity.

This paper proposes a curve fitting technique for fast and accurate estimation of the perceived quality of streaming media contents, delivered within a wireless network. The model accounts for the effects of various network parameters such as congestion, radio link power, and video transmission bit rate. The evaluation of the perceived quality of service (PQoS) is based on the well-known VQM objective metric, a powerful technique which is highly correlated to the more expensive and time consuming subjective metrics. Currently, PQoS is used only for offline analysis after delivery of the entire video content. Thanks to the proposed simple model, we can estimate in real time the video PQoS and we can rapidly adapt the content transmission through scalable video coding and bit rates in order to offer the best perceived quality to the end users. The designed model has been validated through many different measurements in realistic wireless environments using an ad hoc WiFi test bed.