초록 ▼

A method and apparatus for carrying out synchronous co-division multiple access (SCDMA,) communication of multiple channels of digital data over a shared transmission media such as a cable television system coaxial cable, a fiber optic or copper conductor telephone link, terrestial microwave, satell

A method and apparatus for carrying out synchronous co-division multiple access (SCDMA,) communication of multiple channels of digital data over a shared transmission media such as a cable television system coaxial cable, a fiber optic or copper conductor telephone link, terrestial microwave, satellite link, local or wide area network, wireless including cellur network or some combination of these media using suitable interface circuitry. The system includes modems at remote units and a central unit to receive time division multiplexed digital data arranged into timeslots or channels and uses orthogonal codes to encode each channel of multiple data and spread the energy of each channel data over a frame of data transmitted in the code domain. Spreading the data this way makes the system less susceptible to impulse noise. Frames are synchronized as between remote and central units using a ranging scheme which is also useful in any other system transmitting data by frames in a distributed system where synchronizing the frames as between all units regardless of differences in propagation delays is necessary. Each frame in the SCDMA modulation scheme includes a gap or guardband containing no other data. The ranging process involves training each remote unit to impose enough delay prior to re-transmission of a barker code received from the CU such that a barker code sent by the RU arrives at the CU during the gap. The process of setting the delay in each RU is a trial and error process, and each RU starts the ranging process asynchronously. Contention resolution protocols such that only one RU is aligning to the gap at any particular time are taught.

대표청구항 ▼

[ What is claimed is:] [1.] A method for transmitting multiple channels of digital data simultaneously over a cable television media carrying cable television programming, comprising:receiving multiple channels of digital data;selecting portions of said digital data from each channel and organizing

[ What is claimed is:] [1.] A method for transmitting multiple channels of digital data simultaneously over a cable television media carrying cable television programming, comprising:receiving multiple channels of digital data;selecting portions of said digital data from each channel and organizing said portions as an information vector having n elements;performing code division multiplexing by performing a matrix multiplication of said information vector times a code matrix comprised of n orthogonal spreading codes, each code comprising one row or one column of said code matrix and having n elements, said matrix multiplication generating a result vector having n elements, each element comprised of the sum of the partial products of multiplication of each of the n elements of said information vector times the n elements of one of said orthogonal spreading codes;modulating the n elements of said result vector onto one or more radio frequency carriers and transmitting the resulting radio frequency carriers on a cable television media carrying cable television programming while limiting the overall bandwidth of the resulting radio frequency signals so as to not interfere with said cable television programming.