초록 ▼

The OCDMA waveform of the present invention uses hi-phase PN modulation (BPSK PN chip modulation) in conjunction with MPSK or MQASK data modulation (QPSK data modulation is one preferred embodiment) to increase bandwidth efficiency. The number of orthogonal users that can be placed on a single carri

The OCDMA waveform of the present invention uses hi-phase PN modulation (BPSK PN chip modulation) in conjunction with MPSK or MQASK data modulation (QPSK data modulation is one preferred embodiment) to increase bandwidth efficiency. The number of orthogonal users that can be placed on a single carrier is equal to, at most, the length of the orthogonal binary sequence. The Radamacher-Walsh (RW) sequence chip rate must be 4″times the symbol rate (where n is a positive integer) since the symbol transitions must be synchronized to the RW period to guarantee orthogonality of the multiple users when data transitions are present. The symbol rate for QPSK modulation is one-half that for BPSK modulation. As a result, twice as many orthogonal functions are available for a given clock rate for QPSK as for BPSK modulation. That is, an OCDMA system with QPSK data can support twice as many users in a given bandwidth as an OCDMA system with BPSK data.

대표청구항 ▼

In a spread spectrum OCDMA communication system in which a set of orthogonal Radamacher-Walsh (RW) functions are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal, each orthogonal function of said set carries voice/data for a single user in said

In a spread spectrum OCDMA communication system in which a set of orthogonal Radamacher-Walsh (RW) functions are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal, each orthogonal function of said set carries voice/data for a single user in said system, a source of selected carrier signals and means to modulate said information signal onto said selected carrier signals to form a transmit signal and said coded spreading sequence on said transmit signal for radio broadcasting, the improvement comprising: modulator means wherein MPSK modulation is used and where M is selected from 4, 8, 16, etc. for modulating said voice/data on said carrier and form said transmit signal, and BPSK modulation means for modulating said coded spreading sequence on said transmit signal.