Bitrate maximizing time-domain equalizer design for DMT-based systems

IEEE Trans. Signal Process.

Ysebaert²,

Vanbleu³

2007

Cyclic prefixed communications, such as multicarrier communications, first became widely used in the context of digital subscriber lines (DSL). In DSL, bit loading is allowed at the transmitter, and the performance metric is the bit rate that can be provided without exceeding a given bit error rate (BER). Wireless cyclic prefixed systems are now becoming increasingly popular, and in such systems the appropriate performance metric is the BER for a given bit loading at the transmitter. Cyclic prefixed systems perform well in the presence of multipath, provided that the channel delay spread is shorter than the guard interval between transmitted blocks. If this condition is not met, a channel shortening equalizer can be used to shorten the channel to the desired length. Previous work on channel shortening has largely been in the context of DSL, thus it has focused on maximizing the bit rate. In this paper, we propose a channel shortener that attempts to directly minimize the BER for a multiple-input multiple-output channel model. We simulate the performance of the resulting channel shortener and compare it to existing designs and the matched filter bound.

Section: B Multicarrier Subchannel Snr Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bit Error Rate Minimizing Channel Shortening Equalizers for Cyclic Prefixed Systems

IEEE Trans. Signal Process.

Ysebaert²,

Vanbleu³

2007

“…In DSL, the system performance is measured by bit rate without exceeding a given bit error rate (BER). With this in mind, the previous works have attempted to maximize the bit rate [8], [9], [10]. In contrast, OFDM systems have a fixed bit loading algorithm at the transmitter, and the performance metric is said as minimizing the BER.…”

Section: Introductionmentioning

confidence: 95%

Adaptive MIMO channel shortening with post-FEQ diversity combining

Altin

2008 42nd Asilomar Conference on Signals, Systems and Computers

2008

Cyclic prefixed communication systems are generally called Discrete MultiTone (DMT) for wireline systems, and Orthogonal Frequency-Division Multiplexing (OFDM) for wireless systems. A cyclic prefix should be as long as the channel impulse response (channel delay spread) to combat inter symbol interference (ISI). If this requirement is not met, a channel shortening equalizer is used to shorten the channel. In time varying channels, it is more sensible to use an adaptive channel shortener. In literature, adaptive channel shorteners and frequency domain equalizers (FEQ) have been well studied. But on the other hand, in wireless communication systems the performance metric is the bit error rate (BER) and minimizing the BER is the primary concern of the designing a system. In this paper we reviewed the adaptive channel shortener which uses recursive least squares algorithm (RLS-MERRY), and proposed an adaptive FEQ with different post combining techniques in order to get a lower BER than existing adaptive TEQ-FEQ architectures.

“…Starting in the mid-1990's, it was used to shorten the long impulse responses of twisted pair telephone lines to enable frequency-domain equalization in DSL [5], [6]. While initial designs were based on heuristic cost functions, more recent designs have considered maximizing the bit rate for a given bit error rate (BER) [7], [8], [9], which is appropriate for wireline systems that allow bit allocation.…”

Section: Introductionmentioning

confidence: 99%

Unit Tap Constrained Adaptive Channel Shortening Equalization

Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.

Orthogonal frequency division multiplexing (OFDM) is a popular transmission format for emerging wireless communication systems. Single-carrier cyclic-prefixed (SCCP) modulation is similar to OFDM, but with all frequency-domain operations performed at the receiver. Systems employing OFDM and SCCP perform well in the presence of multipath provided that the channel delay spread is shorter than the guard interval between transmitted blocks. If this condition is not met, a channel shortening equalizer can be used. Existing adaptive channel shorteners require re-normalization to restrain the channel shortener away from zero. In this paper, we study the use of a unit-tap constraint rather than a unit-norm constraint. We use this constraint to manipulate existing algorithms into a framework analogous to the recursive least squares algorithm, and we develop adaptation rules for blind and semi-blind frequency domain equalizers for SCCP receivers. Simulations show an order of magnitude improvement in convergence speed and reduced asymptotic bit error rate.