Bandwidth-efficient modulation for wireless communications

As wireless technologies have evolved, the available radiofrequency spectrum has become an important commodity. The current crowding of the spectrum leads to the investigation of more efficient uses of allocated bandwidth. Quadrature-vestigial-sideband (QVSB) is a bandwidth-efficient modulation scheme that doubles the data capacity of conventional VSB. By superimposing two VSB-modulated, independent data streams, QVSB can achieve data rates equivalent to conventional, Nyquist-filtered, double-sideband (DSB) schemes, using half the bandwidth. Efficient, high-rate, turbo-product-codes (TPCs) are used in conjunction with QVSB modulation, to achieve a system which is both power and bandwidth efficient. In particular, capacity performance is about 4 to 5.5 dB from the Shannon bound, up to approximately 5 bits/s/Hz, the highest capacity simulated thus far.