Crosstalk is a major issue in modern ADSL and VDSL systems. Static spectrum management (SSM), the traditional way to guarantee spectrum compatibility, employs spectral masks which can be overly restrictive and result in poor performance. In this paper, fixed margin iterative water-filling algorithm is investigated in downstream VDSL and ADSL2+ scenario when they are in the same binder. The algorithm can minimize the transmission power and at the same time the overall high-quality service is guaranteed for all the users of the same binder. Simulation results show that ADSL2+ can realize performance gains of up to 80% compared with SSM techniques or ADSL.

In this paper, a weighted element-wise block adaptive frequency-domain equalization (WEB-FDE) is proposed for a single-carrier system with the cyclic-prefix. In the WEB-FDE, the one-tap equalizer corresponding to a frequency-bin first preserves input DFT elements (element-wise block). Its coefficient in each block is then calculated by minimizing a weighted squared norm of the a posteriori error. Simulation results in a time-varying typical urban (TU) channel show that the bit-error-rate (BER) performance of the WEB-FDE outperform that of the normalized least-mean-square (NLMS)-FDE and recursive-least-square (RLS)-FDE.

We propose a new cyclic postfix based orthogonal frequency division multiplexing (OFDM) system. The proposed system shows superior performance in symbol time synchronization while achieving channel estimation performance comparable to that of conventional cyclic prefix based OFDM system. In the proposed system, an identical postfix is generated at the end of each OFDM symbol by inserting pilot values amongst the data symbols in a frequency domain and performing Inverse Fast Fourier Transform (IFFT) operation on it. Robust time synchronization is achieved by auto- and cross-correlating the postfix. Also, time or frequency domain channel estimation can be realized by using properly designed postfix according to channel estimation method.

A cell search technique utilizing a known postfix for OFDM (orthogonal frequency division multiplexing) cellular systems is described. The known postfix is generated in the time domain by inserting pilots in the frequency domain and plays the role of the cyclic prefix in general OFDM systems. Since it demonstrates good correlation properties, it can be facilitated to synchronize each symbol with an identified postfix. In this paper, two different known postfixes are allocated to each cell. One is used for cell identification and symbol synchronization, which is designed to be different among neighboring cells. The other is used for frame synchronization and is the same for all cells. In the simulation, the cell search is accomplished with a probability greater than 10-3 at -27 dB in a vehicular channel. Even at -30 dB, the cell search probability is greater than 10-2 in a pedestrian channel as well as 10-3 in the AWGN (additive white gaussian noise) channel.