A different look on cyclic prefix for SC/FDE

Abstract

In this work we investigate the use of a known symbol sequence -a so-called unique word (UW) -instead of the well-known cyclic prefix (as it is used in OFDM (Orthogonal Frequency Division Multiplexing) systems) for a single carrier system with fiequency domain equalization (SCFDE). The considered SCFDE system is similar to the one proposed in the IEEE 802.16.3~ target group. It is shown that the UW fulfils the theorem of cyclic convolution required for the eacient implementation of the SC/FDE structure. We will elaborate on the advantages that result for equalization, channel estimation, and synchronisation. Compared to the advantages, the disadvantages in terms of BER behaviour and bandwidth efficiency are rather modest.

Block synchronization using a unique word for a generalized unitary rotation based communication system

“…UWs traditionally are used for the synchronization in single carrier (SC) communication systems [10]. Recently UW based padding has gained interest in context of MC communications [11].…”

Single-carrier frequency domain decision feedback equalization with carrier-selection in 3GPP LTE MISO systems

“…The other is that the UW is part of the FFT processing period, whereas the CP is not. Not just for avoiding the error propagation, due to the deterministic nature of UW extensions, the UW can be also applied to other purposes at a little expense of bandwidth efficiency, such as channel estimation, noise variance computation, and synchronization [6], [8], [9]. Furthermore, the UW-based system possesses better BER performance against the CP scheme [10].…”

“…Placing the UW into the SC block transmission as an alternative to the well-known cyclic prefix (CP) technique was first investigated in [6]. The UW blockwise extension can make error propagation impossible beyond one FFT-block due to the deterministic nature for the UW [7], [8].…”

Parallel Multistage Decision Feedback Equalizer for Single-Carrier Layered Space-Time Systems in Frequency-Selective Channels

“…Moreover, the complexity of this scheme does not increase with RMS delay spread. Results in [7] show that the fixed CP can be used for channel estimation and synchronization.…”