System and method for applying transmit windowing in ADSL+networks
View Patent ↗A system and method for formatting and transmitting DMT symbols. For each symbol to be transmitted, the last L cp samples of the symbol are prepended to the symbol as a cyclic prefix. Next, of the samples contained within the cyclic prefix, the first Î 2 samples are appended to the symbol as a cyclic suffix. By providing the above described cyclic prefix and suffix, sharp PSD transitions are provided in the first overlapped RFI band (1.8–2 MHz) and out of band PSD. Upon formatting, each symbol is transmitted so that its transmission overlaps the prior symbol by Î 2 samples. This results in the output signal being shaped by a raised cosine function for the duration of the Î 2 overlap.
1. A method for applying transmit windowing to DMT symbols, comprising the steps of: receiving, into a windowing application, an initial DMT transmit symbol having 2N samples therein; extracting a last Lcp samples from the initial transmit symbol; prepending the extracted Lcp samples to the initial transmit symbol, to create an initial transmit symbol+cyclic prefix transmit symbol; extracting a first Î 2 of the extracted Lcp samples; appending the Î 2 samples to the initial transmit symbol+cyclic prefix transmit symbol as a cyclic suffix Lcs to create a final transmit symbol k; and placing the final transmit symbol in a transmission channel, wherein N, Lcp, Lcs, Î 2 , and k are all integer values.
2. The method of claim 1 , wherein N=512.
3. The method of claim 1 , wherein Lcp=64.
4. The method of claim 1 , wherein Lcs=16.
5. The method of claim 1 , further comprising the steps of: transmitting a first 2N+Lcp time domain samples of the final transmit symbol k; determining whether all available symbols have been transmitted; performing the following steps if it is determined that all available symbols have not been transmitted: summing the remaining Lcs samples of symbol k with the first Î 2 samples of symbol k+1 and incrementing the value of k; transmitting the summed samples; transmitting a next 2N+Lcp−Î 2 samples of symbol k; and determining whether all available symbols have been transmitted; and transmitting a last Lcs samples of symbol k if it is determined that all available symbols have been transmitted.
6. A computer-readable medium having memory storage incorporating instructions for applying transmit windowing to DMT symbols, the instructions comprising: one or more instructions for receiving, into a windowing application, an initial DMT transmit symbol having 2N samples therein; one or more instructions for extracting a last Lcp samples from the initial transmit symbol; one or more instructions for prepending the extracted Lcp samples to the initial transmit symbol, to create an initial transmit symbol+cyclic prefix transmit symbol; one or more instructions for extracting a first Î 2 of the extracted Lcp samples; one or more instructions for appending the Î 2 samples to the initial transmit symbol+cyclic prefix transmit symbol as a cyclic suffix Lcs to create a final transmit symbol k; and one or more instructions for placing the final transmit symbol in a transmission channel, wherein N, Lcp, Lcs, Î 2 , and k are all integer values.
7. The method of claim 6 , wherein N=512.
8. The computer-readable medium of claim 6 , wherein Lcp=64.
9. The computer-readable medium of claim 6 , wherein Lcs=16.
10. The computer-readable medium of claim 6 , further comprising: one or more instructions for transmitting a first 2N+Lcp time domain samples of the final transmit symbol k; one or more instructions for determining whether all available symbols have been transmitted; one or more instructions for performing the following instructions if it is determined that all available symbols have not been transmitted: one or more instructions for summing the remaining Lcs samples of symbol k with the first Î 2 samples of symbol k+1 and incrementing the value of k; one or more instructions for transmitting the summed samples; one or more instructions for transmitting a next 2N+Lcp−Î 2 samples of symbol k; and one or more instructions for determining whether all available symbols have been transmitted; and one or more instructions for transmitting a last Lcs samples of symbol k if it is determined that all available symbols have been transmitted.
11. A system for applying transmit windowing to DMT symbols, comprising: means for receiving, into a windowing application, an initial DMT transmit symbol having 2N samples therein; means for extracting a last Lcp samples from the initial transmit symbol; means for prepending the extracted Lcp samples to the initial transmit symbol, to create an initial transmit symbol+cyclic prefix transmit symbol; means for extracting a first Î 2 of the extracted Lcp samples; means for appending the Î 2 samples to the initial transmit symbol+cyclic prefix transmit symbol as a cyclic suffix Lcs to create a final transmit symbol k; and means for placing the final transmit symbol in a transmission channel, wherein N, Lcp, Lcs, Î 2 , and k are all integer values.
12. The system of claim 11 , wherein N=512.
13. The system of claim 11 , wherein Lcp=64.
14. The system of claim 11 , wherein Lcs=16.
15. The system of claim 11 , further comprising: means for transmitting a first 2N+Lcp time domain samples of the final transmit symbol k; means for determining whether all available symbols have been transmitted; means for performing the following steps if it is determined that all available symbols have not been transmitted: summing the remaining Lcs samples of symbol k with the first Î 2 samples of symbol k+1 and incrementing the value of k; transmitting the summed samples; transmitting a next 2N+Lcp−Î 2 samples of symbol k; and determining whether all available symbols have been transmitted; and means for transmitting a last Lcs samples of symbol k if it is determined that all available symbols have been transmitted.