A Frame Design for MIMO UW based Systems: Overhead Analysis &amp; Channel Estimation

Ehsanfar, Shahab; Chafii, Marwa; Fettweis, Gerhard

doi:10.1109/5gwf.2019.8911738

Cited by 6 publications

(7 citation statements)

References 12 publications

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“…Considering a doubly-dispersive channel condition, we analyze the overhead requirements of a UW-based system from synchronization and channel estimation perspectives-i.e. partially published in [14]and we compare its energy and spectral efficiency with respect to an equivalent pilot-aided CP-OFDM system design.…”

mentioning

confidence: 99%

On UW-Based Transmission for MIMO Multi-Carriers With Spatial Multiplexing

Ehsanfar

Chafii

Fettweis

2020

IEEE Trans. Wireless Commun.

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In this paper, we design a frame structure for unique word (UW) based transmission of multiple-input-multiple-output (MIMO) systems under doubly-dispersive wireless channel conditions. We elaborate an energy and spectral efficiency analysis of a MIMO UW-based system vs. a conventional MIMO cyclic prefix (CP)-based system. Considering the UW-based transmission for a MIMO multi-carrier, we derive its signal processing algorithms for channel estimation and joint channelequalization-and-demodulation. Through theoretical derivations as well as extensive simulations, we show that the proposed MIMO UW-based system significantly outperforms the state-ofthe-art approaches. I. INTRODUCTION T OWARDS the sixth generation (6G) cellular networks, new applications and use-cases are being enabled for the vertical markets, while also new challenges for a holistic approach and more efficient service provisioning are being defined. Thanks to the flexible physical layer definitions in latest release of fifth generation (5G) New Radio (NR) [1], diverse services namely enhanced-mobile-broadband, ultrareliable-low-latency-communication, and massive machinetype-communication are envisioned to coexist within the same time interval and the same frequency band. A major advancement for realizing this coexistence is the massive multipleinput multiple-output (MIMO) technology which can be used for three key concepts, i.e., beamforming, spatial diversity and spatial multiplexing. While employing the MIMO technology for spatial diversity or spatial multiplexing, the mobility of the users becomes limited because a large number of channel parameters requires a long training sequence that together with the data packet, must fit within the channel coherence time. Unique-word (UW) transmission is a promising candidate that facilitates per-block synchronization and channel estimation [2], [3], [4]. The main concept is to replace the cyclic prefix (CP) of random nature by a deterministic sequence that is known to both transmitter and receiver. Hence, maintaining the advantages of CP in terms of robustness against multipath channels, UW allows fast channel tracking in highly mobile Manuscript

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confidence: 99%

On UW-Based Transmission for MIMO Multi-Carriers With Spatial Multiplexing

Ehsanfar

Chafii

Fettweis

2020

IEEE Trans. Wireless Commun.

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“…In this paper, a UW-based channel estimation approach [16], [17] is considered, where the deterministic UW signal is always transmitted before and after the data blocks. In addition, we consider two different transmission modes, namely, with and without the addition of a CP before each sub-block x m .…”

Section: A Transmittermentioning

confidence: 99%

“…This signal is commonly used for channel estimation [13], [17]. Note that x UW has a length of N CPuw + N UW regardless of the transmission mode, and it is different from the size of x m in general.…”

Section: A Transmittermentioning

confidence: 99%

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A Robust Baseband Transceiver Design for Doubly-Dispersive Channels

Bomfin

Chafii

Nimr

et al. 2021

IEEE Trans. Wireless Commun.

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In this paper, we investigate three different concepts for robust link-level performance under doubly-dispersive wireless channels, namely, i) channel estimation, ii) cyclic prefix (CP)free transmission, and iii) waveform design. We employ a unique word-based channel estimation, where we decouple the channel related errors into channel estimation error (CEE) and Doppler error (DE). Then, we show that a trade-off between CEE and DE emerges in the frame design, where the system can be optimized to achieve the minimum composite channel error. Another strategy to improve the link-level performance is to suppress the CP of the sub-blocks. This allows for better channel estimation due to the reduced transmission time, with the penalty of requiring the CP-restoration processing at the receiver. Furthermore, we propose the waveform design based on the equal-reliability criterion (ERC), leading to the block multiplexing-orthogonal chirp division multiplexing (BM-OCDM). This waveform is advantageous in the CP-free transmission mode, where the data symbols have equally distributed interference from adjacent sub-blocks. Our framework is a generalization of the recently proposed orthogonal time frequency space (OTFS), which fails to achieve the ERC. The link-level simulations show that at high modulation and coding scheme, the proposed BM-OCDM provides superior link-level performance than OTFS.

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“…We therefore provide a generic UW-OFDM signaling framework that enables pilot symbols in both time (i.e., UWs) and frequency domain (i.e., pilot tones). However, the utilization of UWs for actual estimation tasks is beyond the scope of this work 2 , and the interested reader is e.g., referred to [19], [22], [23], [30], [31] for details. Instead, we show that due to its specific structure, the UW-OFDM signaling scheme provides a better estimation performance than conventional CP-OFDM, even for an estimator solely based on pilot tones.…”

Section: Introductionmentioning

confidence: 99%

On the Inclusion and Utilization of Pilot Tones in Unique Word OFDM

Hofbauer,

Haselmayr,

Bernhard

et al. 2020

Preprint

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Unique word-orthogonal frequency division multiplexing (UW-OFDM) is known to provide various performance benefits over conventional OFDM using cyclic prefixes (CP). Most important, UW-OFDM features excellent spectral sidelobe suppression properties and an outstanding bit error ratio performance. Current research has mainly focused on principle performance bounds of UW-OFDM, with less attention on challenges aside from idealized communication scenarios, such as system parameter estimation tasks. In this work we present an approach for including frequency pilots tones into the UW-OFDM signaling scheme, which can then be utilized for these estimation tasks. Suitable optimization criteria are presented and interactions of pilots with data symbols are highlighted. Pilot tone based estimation of a carrier frequency offset (CFO) is conducted as an estimation example, revealing considerable differences to conventional OFDM. Simulation results in a multipath environment demonstrate a significantly increased estimation accuracy in UW-OFDM over CP-OFDM, which becomes even more dominant with an increasing CFO. This performance difference is due to the inherent redundancy present in an UW-OFDM signal.

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A Frame Design for MIMO UW based Systems: Overhead Analysis & Channel Estimation

Cited by 6 publications

References 12 publications

On UW-Based Transmission for MIMO Multi-Carriers With Spatial Multiplexing

On UW-Based Transmission for MIMO Multi-Carriers With Spatial Multiplexing

A Robust Baseband Transceiver Design for Doubly-Dispersive Channels

On the Inclusion and Utilization of Pilot Tones in Unique Word OFDM

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