Very efficient wireless frequency usage system using convolutional spread time signals based on multipath estimation in correlation domain

Abstract

For future mobile systems, frequency usage efficiency is most important as demand for the wireless frequency band increases. Because both TDMA and FDMA use sine wave, it is very difficult to divide the faded sine wave into original sine wave and the multipath sine waves. On the other hand, because CDMA uses sequences of "chips", where each chip has its "address" in the sequence, their may be some method to divide the original signal and the multipath signals. In fact, when we use a pilot signal, both of whose frequency and time are the same as the signals which bear the data, we can divide the original signal and the multipath signals by using clever codes and modulation. Different signal design methods have been proposed using complete complementary code. In this paper, we propose a new simple method for using the complete complementary code. When we use a complementary code composed of 16 auto-complementary codes, where each auto-complementary code is composed of 16 binary sequences of length 256, we can assign 1 auto-complementary code to pilot signals and 15 auto-complementary codes to information transmission signals. Using the new method on convoluted QPSK signals, 40 Mbit/sec information transmission is realizable on 26 MHz bandwidth.