Clustered-OFDM transmitter implementation

Abstract

An elegant means by which high-speed burst wireless transmission can be accomplished with small amounts of overhead is through a novel technique referred to as clustered-OFDM [I]. By using OFDM modulation with a long symbol interval, this scheme overcomes the complex and costly equalization requirements associated with single carrier systems. Moreover, the need for highly linear power amplifiers typically required in OFDM systems is alleviated through the use of multiple transmit antennas combined with nonlinear coding. The clustering technique also leads to a natural implementation of transmit diversity. This paper reports on the implementation of a clustered-OFDM transmitter which was constructed using off-the-shelf components in a relatively short period of time. Despite the limitations associated with the prototyped system, it can deliver 7.5 Mbps and it is expected that this data rate could be easily tripled with existing technology. In addition to providing a brief introduction to clustered-OFDM, we describe the various architectural trade-offs which were made in order to reduce the hardware complexity of the boards as well as some experimental results showing the operation of the transmitter.

Near-Instantaneously Adaptive HSDPA-Style OFDM Versus MC-CDMA Transceivers for WIFI, WIMAX, and Next-Generation Cellular Systems

“…Dinis and Gusmao [66]- [68] researched the employment of two-branch amplifiers, where each amplifier was fed with a near-constant-envelope signal. The clustered OFDM technique introduced by Daneshrad et al [69] employs a set of parallel partial FFT processors in conjunction with separate radio-frequency transmission chains. OFDM systems exhibiting increased robustness to nonlinear distortion have also been proposed by Okada et al [70] as well as by Dinis and Gusmao [71].…”

Adaptive multicarrier modulation: a convenient framework for time-frequency processing in wireless communications

“…Müller [25], Pauli [26], May [27], and Wulich [28] suggested different algorithms for postprocessing the time-domain OFDM signal prior to amplification, while Schmidt and Kammeyer [29] employed adaptive subcarrier allocation in order to reduce the Crest factor. Dinis and Gusmão [30]- [32] researched the use of two-branch amplifiers, while the so-called clustered OFDM technique introduced by Daneshrad et al [33] operates with a set of parallel partial fast Fourier transform (FFT) processors with associated transmitting chains. More explicitly, clustered OFDM allows a number of users to share a given bandwidth amongst a number of users on a demand basis, potentially supporting a peak data rate identical to that of a single-user OFDM system.…”

Adaptive redundant residue number system coded multicarrier modulation

“…Relying on the seminal idea of Kalet [11], Schmidt and Kammeyer [19] employed adaptive subcarrier allocation in order to reduce the crest factor. Dinis and Manuscript received September 23, 1999; revised May 4, 2000. Gusmão [20]- [22] researched the use of two-branch amplifiers, while the clustered OFDM technique introduced by Daneshrad, Cimini, and Carloni [23] invokes a set of parallel partial FFT processors. OFDM systems with increased robustness to nonlinear distortion have been proposed by Okada, Nishijima, and Komaki [24] as well as by Dinis and Gusmão [25].…”