Patent EA-002914-B1 (EA)
Title: Multiple access method and carrier-interference multiple access communication system
Inventor: SHATTIL STEVEN J
IPC: H04B1/7115
Filed: 1999-02-10
Abstract: 1. A method of communication between at least one transmitter and one receiver using carrier-interference multiple-access (CIMA) communication signals, the method comprising the steps of: providing for the generation of a plurality of electromagnetic carrier signals for use by at least one user, the carrier signals having a plurality of frequencies, providing a relative phase to the carriers to produce a predefined phase relationship at a predetermined time, providing modulation of the carrier signals by an information signal, providing for transmission of the modulated, phased carrier signals into a communications channel to produce CIMA transmit signals having carrier-signal components, and providing for reception of the CIMA transmit signals from the channel wherein the carrier-signal components are combined in phase to produce at least one constructive interference pulse that is indicative of the information signal. 2. The method of communication recited in Claim 1 wherein the carrier signals are incrementally spaced in frequency. 3. The method of communication recited in Claim 1 wherein the step of providing for the generation of a plurality of electromagnetic carrier signals includes the generation of a plurality of groups of carriers having identical sets of carrier frequencies, each group being assigned to one of a plurality of users, and the step of providing a relative phase to the carriers includes providing a unique relative phase to the carriers of each group wherein each group has a unique time offset in order to generate pulses that are received at different time intervals. 4. The method of communication recited in Claim 1 wherein the step of providing for the generation of a plurality of electromagnetic carrier signals includes the generation of a plurality of groups of carriers, each group having a unique set of carrier frequencies and being assigned to at least one user, and the step of providing a relative phase to the carriers includes providing a relative phase to each group such that a plurality of users receives pulses in the same time interval but each user uses different carrier frequencies. 5. The method of communication recited in Claim 1 wherein the step of providing for the generation of a plurality of electromagnetic carrier signals having a plurality of frequencies includes the step of providing variations to the carries frequencies with respect to time wherein the frequency variations for each carrier in a group of carriers corresponding to each user are substantially identical, thereby causing little or no change to the envelope of the pulse. 6. The method of communication recited in Claim 1 wherein the step of providing modulation of the carrier signals comprises pulse amplitude modulation being applied to a plurality of the carriers, the pulse amplitude modulation having a duration that is longer than the pulse width of the constructive-interference pulse. 7. The method of communication recited in Claim 1 wherein the step of providing modulation of the carrier signals comprises pulse amplitude modulation being applied to a plurality of the carriers, the pulse amplitude modulation having a duration that is shorter than the period of the constructive-interference pulse. 8. The method of communication recited in Claim 1 wherein the step of providing for the generation of a plurality of electromagnetic carrier signals includes tapering the frequency versus-amplitude window of the carries signals to reduce time-domain side-lobe energy of the constructive-interference pulse. 9. The method of communication recited in Claim 1 wherein the step of providing for reception of the CIMA transmit signals includes the step of providing a number of predetermined delays to each received carrier signal before combining to produce the constructive interference pulse where the number of predetermined delays is equal to the number of different phase space in which the received CIMA transmit signal is sample. 10. The method of communication recited in Claim 1 wherein the step of providing modulation of the cattier signals by an information signal is performed in a specific time interval relative to the phase of the carriers such that the resulting modulated carriers occupy one or more nonzero-phase spaces and do not combine constructively in zero-phase space to produce a pulse. 11. The method of communication recited in Claim 1 wherein the step of providing for reception of the CIMA transmit signals includes compensating for the relative phases of the carries in at least one of the nonzero-phase spaces in order to combine the carrier signals in phase. 12. The method of communication recited in Claim 9 wherein multi-user interference is sampled in the different phase spaces and then weighted and combined with an intended user signal to cancel contributions of the multi-user interference to the intended user signal. 13. The method of communication recited in Claim 1 wherein the step of providing for the generation of a plurality of electromagnetic carrier signals is performed by a frequency shifted feedback cavity. 14. The method of communication recited in Claim 1 wherein the step of providing for reception of the CIMA transmit signals is performed by a frequency shifted feedback cavity. 15. The method of communication recited in Claim 1 wherein the communications channel is a waveguide. 16. The method of communication recited in Claim 15 wherein the electromagnetic carrier signals are optical signals and the waveguide is an optical fiber. 17. The method of communication recited in Claim 15 wherein the step of providing fa the generation of a plurality of electromagnetic carrier signals and providing a relative phase to the carriers to produce a predefined phase relationship are performed to match the relative phases between the carriers to the cinematic dispersion profile of the carries in the waveguide such that the dispersion causes the carrier phases to have a predetermined phase relationship after propagating a predetermined distance in the waveguide. 18. The method of communication recited in Claim 1 wherein the step of providing for transmission of the modulated, phased carrier signals includes transmitting the carriers from a transmitter array wherein each carrier for a particular user is transmitted from a separate transmitter element of the array and an array beam pattern is generated from the superposition of transmitted carriers from each of the transmitter elements. 19. The method of communication recited in Claim 18 wherein a separation between the transmitter elements is selected with respect to the carrier frequency separation to control the shape of the array beam pattern and the period in which the array beam pattern scans. 20. The method of communication recited in Claim 1 wherein the step of providing a relative phase to the carries results in a train of pulses in the time domain and the step of providing modulation of the carrier signals results in modulating each of the pulses with a direct sequence chip such that the modulated train of pulses is a direct sequence code. 21. The method of communication recited in Claim 20 wherein the direct sequence chip is the product of an information signal and a chip of a pseudo-random CDMA spreading code. 22. The method of communication recited in Claim 1 wherein the step of providing for reception of the CIMA transmit signals includes multi-user detection in which user signals from an intended use and at least one interfering user are received where the interfering user signals are weighted and combined with the intended use's signal to cancel the interfering user signals to the intended user's signals. 23. The method of communication recited in Claim 1 wherein the step of providing a relative phase to the carriers to produce a predefined phase relationship at a predetermined time results in at least two received constructive-interference pulses that overlap in time. 24. The method of communication recited in Claim 1 wherein the stop of providing a relative phase to the carriers to produce a predefined phase relationship at a predetermined time includes a decision step that allows for at least two received constructive-interference pulses to overlap in time when the number of users or channel usage increases beyond a predetermined limit. 25. The method of communication recited in Claim 24 wherein the decision step includes a step of identifying the users and assigning a priority to each user that is used to determine which user signals are be selected to overlap in time. 26. The method of communication recited in Claim 1 wherein the carrier frequencies for each user are separated by an amount that is equal to or greater than the coherence bandwidth of the communication channel. 27. A carrier-interference multiple-access (CIMA) communication system for providing communication between at least one transmitter and one receiver comprising: a CIMA transmitter comprising: - a multicarrier generator for generating a plurality of electromagnetic carrier signals for use by at least one user where the carrier signals are incrementally separated in frequency, - a delay controller to cause a predefined phase relationship between the carriers at a predetermined time, - a carrier modulator to modulate the carrier signals with an information signal, and - an output coupler for coupling the modulated, phased carrier signals into a communications channel to produce CIMA transmit signals having carrier-signal components, and a CIMA receiver for receiving the CIMA transmit signals from the channel, providing a predetermined delay to each of the carrier signal components and combining the carrier-signal components in phase to produce at least one constructive-interference pulse that is indicative of the information signal. 28. The CIMA communication system claimed in Claim 27 wherein the CIMA receiver samples within at least case predetermined time interval