초록 ▼

A method and apparatus for carrying out synchronous code division multiple access (SCDMA) communication of multiple channels of digital data over a shared transmission media. The system includes modems at remote units and a central unit to receive time division multiplexed digital data arranged into

A method and apparatus for carrying out synchronous code division multiple access (SCDMA) communication of multiple channels of digital data over a shared transmission media. 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 ▼

[ I claim:] [1.] A process for transmitting multiple channels of digital data in distributed systems having multiple units coupled by a shared transmission media by using synchronous code division multiple access, comprising:receiving a time division multiplexed digital data stream comprised of N ti

[ I claim:] [1.] A process for transmitting multiple channels of digital data in distributed systems having multiple units coupled by a shared transmission media by using synchronous code division multiple access, comprising:receiving a time division multiplexed digital data stream comprised of N time slots or channels, each of which contains one or more bits of digital data;reorganizing the digital data from said N time slots into a frame containing M consecutive symbols, each said symbol containing an element from each time slot, each element having at least one bit;spreading the spectrum of each said symbol by doing matrix multiplication to multiply an information vector having as elements said elements of said symbol by a code matrix embodying N orthogonal spreading codes to generate a resulting chips out array;using the chips of the resulting chips out array to modulate at least one radio frequency carrier in successive intervals according to the amplitude represented by successive corresponding chips of the chips out array;transmitting said at least one modulated radio frequency carrier on said shared transmission media.