3:30, SPCOM-L1.1
SIGNAL PROCESSOR IMPLEMENTATION OF DMT BASED VDSL MODEMS
A. LAKHZOURI, M. RENFORS
The Discrete Multi Tone (DMT) modulation is considered a viable technique for high-speed digital transmission over subscriber loop. It was selected as the standard for ADSL modems and it is also a strong candidate in the VDSL area. This paper investigates a programmable solution for the DMT based VDSL modems using Texas Instrument processor family TMS320C62xx. A structure for both transmitter and receiver sides will be presented. Synchronization and equalization issues will be also discussed.

3:50, SPCOM-L1.2
OPTIMUM DESIGN OF DISCRETE WAVELET MULTITONE FILTER BANKS FOR DISGITAL SUBSCRIBER LINE CHANNELS
B. CLERKIN, C. HENEGHAN
In this paper, a new approach to the design of optimum transmultiplexer filter banks for discrete wavelet multitone (DWMT) multicarrier modulation is presented. DWMT has been proposed for use in high-speed data communications over twisted-pair copper wires such as digital subscriber lines (DSL), due to its ability to cope well with channel degradations and noise [1]. Previous techniques have concentrated on optimising the spectral compactness of a prototype filter and rely on a frequency domain analysis of intercarrier interference (ICI) and intersymbol interference (ISI). In this study, we also consider the effect of the time domain overlap between successive symbol waveforms by considering each modulation filter as a series of filter components in time. We also explicitly incorporate some knowledge of the digital subscriber line channel into our design technique, to account for the effects of time dispersion and frequency distortion. Numerical simulations show that the optimisation of the components in the mixed time-frequency domain leads to an increase in the signal-to-interference ratio of the order of 0.2–0.3 dB.

4:10, SPCOM-L1.3
BLOCK BASED DMT SYSTEMS WITH REDUCED REDUNDANCY
Y. LIN, W. WENG, W. WENG, S. PHOONG
There has been great interest in the design of DMT (discrete multitone) transceivers. An $M$-band DMT transceiver is called block based if the transmitter and the receiver consist of constant matrices. The commonly used DMT systems are mostly block based, e.g., the DFT based system used in transmission over digital subscriber lines. For an FIR channel of order $L$, it is known that redundancy of length $L$ enables the receiver to cancel ISI completely. Such a scheme allow us to trade bandwidth for ISI cancellation. In block based DMT (BDMT) systems, the redundancy $K$ is typically chosen to be the same as the order of the channel $L$. In this paper we will consider BDMT transceiver with redundancy $K\le L$. With the reduced redundancy better bandwidth efficiency can be obtained as will be demonstrated by examples. Furthermore minimum redundancy for BDMT systems will be derived and the transceivers will be parameterized whenever ISI solutions exist.

4:30, SPCOM-L1.4
OPTIMAL BLOCK BASED DMT TRANSCEIVERS
S. PHOONG, Y. LIN
The design of optimal DMT transceivers for distorted channel with colored noise has been of great interest. Of particular interest is the class of block based DMT (BDMT), where the transmitter and the receiver consist of constant matrices. For a given channel and channel noise spectrum, the optimal DBMT transceiver that minimizes the transmission power for a fixed probability of error and transmission rate will be derived. The optimal biorthogonal transmitter is in fact orthogonal. That is, there is no loss of generality in using the orthogonal transmitter for the design optimal BDMT.

4:50, SPCOM-L1.5
PER TONE ECHO CANCELLATION FOR DMT-BASED SYSTEMS
K. VAN ACKER, M. MOONEN, T. POLLET
A new echo canceller for discrete multitone (DMT) systems is presented where each used tone has its own per tone echo canceller (PT-EC) in addition to a per tone equalizer (PT-EQ). This enables us to optimize the Signal-to-Noise Ratio (SNR) for each tone separately by solving a Minimum Mean Square Error (MMSE) problem for each tone. Simulation results confirm improved performance over time domain echo cancellation.

5:10, SPCOM-L1.6
OPTIMAL TRANSCEIVERS FOR DMT BASED MULTIUSER COMMUNICATION
A. PANDHARIPANDE, S. DASGUPTA
This paper considers discrete multitone modulation (DMT) for multiuser communications where different users are supported by the same system. These users may have differing quality of service (QoS) requirements, as quantified by their respective bit rate and symbol error rate specifications. Our goal is to minimize the transmitted power given the QoS specifications for the different users, subject to the knowledge of colored interference at the receiver input. In particular we find an optimum bit loading scheme that distributes the bit rate transmitted across the various subchannels belonging to the different users, and subject to this bit allocation, determine an optimum transceiver.