Spread spectrum techniques are well known. In a typical spread-spectrum communication system, transmitted bits are replaced by a spreading sequence, which are stored in a receiver. During transmission, received samples are correlated with the stored sequence to determine the transmitted bits. For a spread-spectrum system using Walsh Codes, the receiver would typically correlate the received samples with all possible Walsh Codes of the same length. Such an operation can be efficiently implemented using a Fast Hadamard Transform.
In another trend, OFDM transmission systems are becoming ubiquitous. The major processing elements in an OFDM communication system are the IFFT and FFT blocks at the transmitter and receiver. Considerable processing power and hardware resources are required to compute the FFT/IFFTs to make the communication system run in real-time.
FFT and FHT are usually implemented in hardware to meet the real-time processing requirements for high data throughput communication systems. Typically these are implemented as separate hardware blocks. Such separate hardware takes up chip real-estate. Moreover, having separate FFT and FHT hardware increases power consumption.
USPTO Backgrounds
USPTO Backgrounds