tailieunhanh - Báo cáo hóa học: " Research Article Resource Allocation with Adaptive Spread Spectrum OFDM Using 2D Spreading for Power Line Communications"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Resource Allocation with Adaptive Spread Spectrum OFDM Using 2D Spreading for Power Line Communications | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2007 Article ID 20542 13 pages doi 2007 20542 Research Article Resource Allocation with Adaptive Spread Spectrum OFDM Using 2D Spreading for Power Line Communications Jean-Yves Baudais and Matthieu Crussiere Institute for Electronics and Telecommunications of Rennes IETR CS 14315 35043 Rennes France Received 31 October 2006 Revised 28 February 2007 Accepted 16 May 2007 Recommended by Moises Vidal Ribeiro Bit-loading techniques based on orthogonal frequency division mutiplexing OFDM are frequently used over wireline channels. In the power line context channel state information can reasonably be obtained at both transmitter and receiver sides and adaptive loading can advantageously be carried out. In this paper we propose to apply loading principles to an spread spectrum OFDM SS-OFDM waveform which is a multicarrier system using 2D spreading in the time and frequency domains. The presented algorithm handles the subcarriers spreading codes bits and energies assignment in order to maximize the data rate and the range of the communication system. The optimization is realized at a target symbol error rate and under spectral mask constraint as usually imposed. The analytical study shows that the merging principle realized by the spreading code improves the rate and the range of the discrete multitone DMT system in single and multiuser contexts. Simulations have been run over measured power line communication PLC channel responses and highlight that the proposed system is all the more interesting than the received signal-to-noise ratio SNR is low. Copyright 2007 . Baudais and M. Crussiere. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. 1. INTRODUCTION Different techniques are proposed to provide reliable and high .