Abstract
We address the efficient realization of a filtered multitone (FMT) modulation system and its orthogonal design. FMT modulation can be viewed as a Discrete Fourier Transform (DFT) modulated filter bank (FB). It generalizes the popular orthogonal frequency division multiplexing (OFDM) scheme by deploying frequency confined subchannel pulses. We compare three realizations that have been described by Cvetkovic and Vetterli (1998), and Weiss and Stewart (2000), and Tonello (2006). A detailed derivation of them is performed in the time-domain via the exploitation of different FB polyphase decompositions. We then consider the design of an orthogonal FMT system and we exploit the third realization which allows simplifying the orthogonal FB design and obtaining a block diagonal system matrix with independent subblocks. A numerical method is then presented to obtain an orthogonal FB with well frequency confined subchannel pulses for arbitrarily large number of subchannels. Several examples of pulses with minimal length are reported and their performance is evaluated in typical multipath fading channels. Finally, we compare the orthogonal FMT system with a cyclically prefixed OFDM system in the IEEE 802.11 wireless LAN channel. In this scenario, FMT with minimal length pulses and single tap subchannel equalization outperforms the OFDM system in achievable rate.
Highlights
Multicarrier (MC) systems deploy a transmission technique where a high rate information signal is transmitted through a wide band channel by simultaneous modulation of a set of parallel signals at low rate
It is found that even deploying minimal length pulses and with single tap equalization, in the considered scenario, the achievable rate of filtered multitone (FMT) is higher than that of orthogonal frequency division multiplexing (OFDM)
The results show that in the considered scenario, FMT significantly outperforms OFDM yet having similar complexity since single tap equalization is used in both systems, and the pulse used in FMT has minimal length
Summary
Multicarrier (MC) systems deploy a transmission technique where a high rate information signal is transmitted through a wide band channel by simultaneous modulation of a set of parallel signals at low rate. The most popular MC architecture is orthogonal frequency division multiplexing (OFDM) [2] It can be viewed as an exponentially modulated FB with a prototype pulse that has a rectangular impulse response. Another scheme is Filtered Multitone (FMT) modulation It differs from OFDM since it uses confined frequency response pulses. The performance in terms of average signal-tointerference power ratio of the orthogonal FMT system in typical multi-path fading channels is reported and compared to that obtained with a conventional truncated root-raisedcosine pulse. It is found that even deploying minimal length pulses and with single tap equalization, in the considered scenario, the achievable rate of FMT is higher than that of OFDM.
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