High Speed Design Of Adsl Using Modified Split Radix Algorithm

In telecommunication, the DSL is widely understood as ADSL. In ADSL, „A‟ stands for Asynchronous” which means that the data stream are not going at the same data rate. Asymmetric Digital Subscriber Line (ADSL) is a high speed internet access over an existing telephone line. To increase the spectral efficiency of the available bandwidth, ADSL provides services for customers to receive internet access in passive mode. It can able to use higher speed direction for minimum guaranteed download from internet at available bandwidth. There are two computing standards for DMT that is ADSLANSI and G-DMT. To increase the spectral efficiency of the available bandwidth, ADSL employs a G-DMT transmission technique based on Multicarrier modulation method. This technique separates the ADSL signal into 255 carriers centered on multiples of 4.3125 kHz. The ADSL uses two separate frequency at which the band from 25.875 kHz to 138 kHz used for upstream communication, while 138 kHz–1104 kHz is used for downstream communication. ADSL is capable of delivering broad-band data at rates up to 8 Mb/s for downlink (from central offices to customer premises) and 1 Mp/s for uplink (reverse direction). The widespread adoption of ADSL supports G.LITE service at full rate connect speed and signal loss through the line combined with noise sources at both near and far ends, tends to limit the connection in the available bandwidth. G-LITE means splitter-less version of ADSL which can be selected on a DSLAM port by an ADSL provides larger resistance to noise and tolerates longer loop lengths for a given bandwidth. The advantage of G.LITE is that the need for the installation of splitter is eliminated by reducing the output level of the ADSL signal enough not to interfere with analog voice signals. A technical issue disturbing the implementation of ADSL transceiver is the complexity of the DMT modem. The modulation and demodulation scheme of DMT are identical to the inverse discrete Fourier transform (IDFT) and discrete Fourier transforms (DFT), respectively. Although, the use of the fast Fourier transform (FFT) algorithm can greatly reduce computational complexities in practical implementations, Abstract: This paper proposes a high speed FFT processor for Asymmetric Digital Subscriber Line ( ADSL) system. The ADSL uses FDM and Echo Cancellation techniques to divide the available bandwidth into three band group for services. This is done by Discrete Multi-tone modulation technology (DMT) in maximizing the throughput of every single sub channel. The most existing system of an ADSL transceiver use MR-FFT processor where the speed is limited in the upstream direction. To overcome this problem we have proposed a modified ADSL transmitter architecture with an optimized parallel pipeline implementation based on 512 point Split Radix L-Shaped dragon fly FFT Processor. The modified SR-FFT algorithm has less number of complex multiplication and addition than MR-FFT which reduces the Latency and thereby increases the speed of upstream ADSL. The designed modem has been coded in VHDL and synthesized by XILINX 8.2. The computational speed of the proposed system results in the Minimum period of 6.204ns (Maximum Frequency: 161.188MHZ).