Efficient multicarrier communication on the digital subscriber loop

ِ Multi-Carrier Modulation (MCM) is attractive for copper wire access technology in high performan
ce communication networks e.g. Asymmetric Digital Subscriber Line (ADSL). In digital implementation of MCM, ِsubcarriers generation and data modulation are accomplished digitally using orthogonal transformation of data blocks and bits are assigned to subcarriers according to bit-loading. The work in this thesis can be divided into four parts. First, ADSL2plus is designed and simulated, focusing on the recent enhancements to the physical layer in discrete multitone (DMT) modulation systems. Second, an alternative way to model DMT modulator is proposed. It uses fewer blocks, so it loads and initializes more quickly. This leads to shorter compile times and smaller executable sizes. Third, Alternative Bit Loading (ABL) algorithm is proposed to assign the bits and available power to each subchannel even if the SNR in each subchannel is unavailable, in a manner don’t depends on the existence of channel characteristics. Fourth, study the viability of a wavelet-based multicarrier modulation scheme as an alternative to the current Fast Fourier Transform (FFT)-based system used in an ADSL. The resultant system is the Discrete Wavelet Multi-Tone (DWMT) system. Finally, ADSL2+ is designed based on the proposed alternative techniques, simulated in MATLAB R2008a. The telephone channel is simulated by using Finite Impulse response (FIR) filter with Additive White Gaussian Noise (AWGN) as a noise source. As a result, 14.72 Mbps was achieved with Bit Error Rate (BER) = 1.43 x at Signal to Noise Ratio (SNR) = 3 dB. This yields 19 dB of performance gain over the conventional ADSL.