Resource Allocation with Adaptive Spread Spectrum OFDM Using 2D Spreading for Power Line Communications
- PDF / 1,004,669 Bytes
- 13 Pages / 600.03 x 792 pts Page_size
- 101 Downloads / 198 Views
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 Mois´es 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 J.-Y. Baudais and M. Crussi`ere. 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 data rate communication access. One of these possible techniques is power line communications (PLC) which exploits the power supply grid for indoor and outdoor communication purpose. Recently, orthogonal frequency division multiplexing (OFDM) has been retained as a good modulation able to ensure high data rates in this frequency selective medium [1, 2]. The power line channels essentially offer quasistatic impulse responses, like in other wireline channels, which implies that the channel state information (CSI) can be made available at the transmitter by sending adequate feedback information from the receiver. Under this assumption, the channel knowledge is exploited by bit-loading algorithms to increase the capacity of the transmission systems, as done with the well-know discrete multitone (DMT) system in the digital subscriber line (DSL) applications. This adaptive loading approach results in substantial improvements in terms of system throughput or robustness [3]. In a general approach, each subcarrier can be assigned a given energy and be loaded with a given modulation, such as quadrature am-
plitude modulations (QAM). In order to ensure reliable communicat
Data Loading...
