Mario Huemer — Page 3

arXiv2010

Direct vs. Two-Step Approach for Unique Word Generation in UW-OFDM

Unique word OFDM is a novel technique for constructing OFDM symbols, that has many advantages over cyclic prefix OFDM. In this paper we investigate two different approaches for the generation of an OFDM symbol containing a unique word in its time domain representation. The two-step and the direct approach seem very similar at first sight, but actually produce completely different OFDM symbols. Also the overall system's bit error ratio differs significantly for the two approaches. We will prove these propositions analytically, and we will give simulation results for further illustration.

cs.IT↗

arXiv2010

Coded OFDM by Unique Word Prefix

In this paper we propose a novel transmit signal structure and an adjusted and optimized receiver for OFDM (orthogonal frequency division multiplexing). Instead of the conventional cyclic prefix we use a deterministic sequence, which we call unique word (UW), as guard interval. We show how unique words, which are already well investigated for single carrier systems with frequency domain equalization (SC/FDE), can also be introduced in OFDM symbols. Since unique words represent known sequences, they can advantageously be used for synchronization and channel estimation purposes. Furthermore, the proposed approach introduces a complex number Reed-Solomon (RS-) code structure within the sequence of subcarriers. This allows for RS-decoding or to apply a highly efficient Wiener smoother succeeding a zero forcing stage at the receiver. We present simulation results in an indoor multipath environment to highlight the advantageous properties of the proposed scheme.

cs.IT↗