A method and arrangement for decoding n-dimensional codes in which the alphabet of codewords is selected from the points of a lattice comprised of a union of cosets of the lattice D.sub.n, the latter being comprised of those n-dimensional integer-valued-coordinate points which have a predetermined parity.
In a system where a signal constellation is used for data communications, signal points in the signal constellation are selected to represent incoming data. The signal points, thus selected, are transmitted through a channel. The signal constellation is divided into a plurality of regions each including an equal number of signal points. A coding scheme is employed to ensure that signal points within any one region are selected equiprobably, and the probability of selecting any signal point in one region is different from that in another region.
An improved system and method for communicating information at variable data rates over in-phase (I) and quadrature phase (Q) communication channels in a CDMA spread spectrum communication system is disclosed herein. In an exemplary implementation an input information signal is transmitted over either an I or Q communication channel using a direct sequence spread spectrum communication signal. The information signal is initially divided into first and second subsignals, which are respectively provided to first and second coset-encoding networks. The first coset-encoding combines the first subsignal with a first coset code, while the second coset-encoding network combines the second subsignal with a second coset code orthogonal to the first coset code. In this way the first and second coset-encoding networks are operative to produce first and second coset-encoded signals, respectively. A composite coset-encoded signal formed from the first and second coset-encoded signals is then modulated by an orthogonal function signal to provide a first modulated signal. In-phase pseudorandom noise (PN.sub.I) and quadrature phase pseudorandom noise (PN.sub.Q) signals of predetermined PN codes are used for spreading the first modulated signal for transmission to a receiver over either the I or Q communication channel, respectively. The receiver is operative to produce an estimate of the input information signal on the basis of the modulated carrier signal received over either the I or Q communication channel.
An analog baseband signal modulates a reference-frequency carrier signal to provide a double-sideband, suppressed-carrier DSB-SC signal. The DSB-SC signal is converted in a voltage-to-frequency converter to a series of pulses, which are demodulated to produce a digitally formatted version of the baseband signal. A notch filter for rejecting an undesired analog signal includes a voltage-to-frequency converter and a selective feedback path which demodulates the undesired signal from a frequency-encoded domain back to the analog domain for a cancellation in a summer preceding the voltage-to-frequency converter.
