摘要:
A system and method for enabling a transmitter employing signal spreading techniques to increase the data rate of the transmitted modulated signal without reducing the multi-path delay spread. Specifically, the system and method use concatenated spreading sequences to provide data modulated spread signals having increased data rates with extended multi-path delay spread. The system and method therefore removes the one-to-one relationship between the repetitive spreading code length and maximum multi-path delay spread of a data modulated spread signal, to thus increase the data rate for a given multi-path delay spread while preserving the autocorrelation and cross-correlation properties of the individual spreading sequences.
摘要:
Operational parameters for transmitting a signal over a communication channel of a network are selected by first determining RF conditions on the communication channel from a received signal transmitted over the communication channel. An initial set of parameter values is selected for transmitting the signal based on RF conditions determined from the received signal. The initial set of parameter values is used to identify other sets of parameter values as other potential candidates for transmitting the signal. The parameter values in the other sets of parameter values differ from parameter values in the initial set of parameter values by less than a predetermined amount. The expected performance of the candidate sets of parameter values is compared to determine which set of parameter values has the best expected performance among the candidate sets of parameter values. The signal is transmitted on the communication channel using the selected set of parameter values.
摘要:
Disclosed is a digital pulse shaping circuit for reducing undesirable frequency components in subsequent data modulated transmissions, which circuit can be easily manufactured as a monolithic integrated circuit. In a preferred embodiment, the pulse shaping circuit employs an edge detector circuit to detect data transitions of an incoming serial data stream. Upon a data edge detection, the edge detector provides a control signal to a digital counter to enable the counter to begin counting applied clock pulses and generate a linear count. The linear count is provided to a decoding circuit, which generates an output word as a nonlinear function of the value of the count. The decoded output word then drives a digital modulator which modulates an RF carrier to provide wireless data transmission with improved spectral efficiency.
摘要:
A modulator device is disclosed for a spread spectrum communication system which generates a modulated signal from incoming data. The device includes a QPSK portion for separating the incoming data into two data channels and for further spreading the two channels over a wide bandwidth according to a predetermined spreading code. A phase mapping element coupled to the QPSK portion for processing both channels in order to minimize spectral regrowth of the modulated signal by preventing the RF envelope deviation from going close to zero. Pulse shaping elements coupled to the phase mapping element for further processing each channel in order to improve the modulator spectral efficiency and minimize adjacent channel interference. A quad-mixer coupled to the pulse shaping elements for combining both channels into a recombined signal and for further modulating the recombined signal according to a predetermined carrier frequency.