Abstract: The outage probability in an under-addressed optical MIMO system may be reduced by configuring a spatial-mode coupler at a transmitter and/or a spatial-mode separator at a receiver to dynamically change its spatial-mode configuration on a time scale that is shorter than the channel coherence time. Provided that the MIMO system employs an FEC code that has a sufficient error-correcting capacity for correcting the amount of errors corresponding to an average state of the MIMO channel established between the transmitter and receiver, this relatively fast dynamic change tends to reduce the frequency of events during which the number of errors per FEC-encoded block of data exceeds the error-correcting capacity of the FEC code.

Abstract: The outage probability in an under-addressed optical MIMO system may be reduced by configuring an intra-link optical mode mixer to dynamically change the spatial-mode mixing characteristics of the link on a time scale that is faster than the channel coherence time. Provided that the MIMO system employs an FEC code that has a sufficient error-correcting capacity for correcting the amount of errors corresponding to an average state of the MIMO channel, this relatively fast dynamic change tends to reduce the frequency of events during which the number of errors per FEC-encoded block of data exceeds the error-correcting capacity of the FEC code.

Abstract: In a representative embodiment, a multipath channel and an optical subcarrier modulation scheme are designed in concert to cause different modulated subcarriers of the optical communication signal to become substantially uncorrelated over the aggregate signal bandwidth. Provided that the employed FEC code has sufficient error-correcting capability for average channel conditions, breakdowns in the operation of the FEC decoder and the corresponding system outages can substantially be avoided.

Abstract: In a system of MIMO communications in a wireless network, a number of wireless units are logically divided into a plurality of user groups, through operation of a semi-orthogonal user selection sub-system. For example, the user selection sub-system may implement a heuristic user selection algorithm based on near-orthogonality. Each user group is assigned a discrete transmission channel, which may be orthogonally defined in terms of frequency, time, or code. Data is transmitted over the channels (e.g., from network base stations) in a coherently coordinated manner, according to a zero-forcing beamforming operation. The system may be configured for operation in a time/frequency selective manner, e.g., over time/frequency selective fading channels. The wireless units may be allocated to the time/frequency slots based on prioritization of channel strength and considerations of fairness, in conjunction with the application of a semi-orthogonal user selection algorithm.

Abstract: Techniques are disclosed for interference coordination in communication networks. For example, a method comprises the following steps. Input information is obtained from a communication network. The input information comprises existing power levels associated with transmitting nodes in the communication network, and existing channel information associated with receiving nodes in the communication network. A coordinated resource set of future transmitting times and future power levels associated with the transmitting nodes and future decoding times associated with the receiving nodes that reduce interference in the communication network is determined. The coordinated resource set determination comprises evaluating a cost function for a given range of interference values based on at least a portion of the input information. In a downlink scenario, the transmitting nodes may comprise base stations and relays, and the receiving nodes may comprise user equipment.

Abstract: In a system of MIMO communications in a wireless network, a number of wireless units are logically divided into a plurality of user groups, through operation of a semi-orthogonal user selection sub-system. For example, the user selection sub-system may implement a heuristic user selection algorithm based on near-orthogonality. Each user group is assigned a discrete transmission channel, which may be orthogonally defined in terms of frequency, time, or code. Data is transmitted over the channels (e.g., from network base stations) in a coherently coordinated manner, according to a zero-forcing beamforming operation. The system may be configured for operation in a time/frequency selective manner, e.g., over time/frequency selective fading channels. The wireless units may be allocated to the time/frequency slots based on prioritization of channel strength and considerations of fairness, in conjunction with the application of a semi-orthogonal user selection algorithm.

Abstract: The outage probability in an under-addressed optical MIMO system may be reduced by configuring an intra-link optical mode mixer to dynamically change the spatial-mode mixing characteristics of the link on a time scale that is faster than the channel coherence time. Provided that the MIMO system employs an FEC code that has a sufficient error-correcting capacity for correcting the amount of errors corresponding to an average state of the MIMO channel, this relatively fast dynamic change tends to reduce the frequency of events during which the number of errors per FEC-encoded block of data exceeds the error-correcting capacity of the FEC code.

Abstract: The outage probability in an under-addressed optical MIMO system may be reduced by configuring an intra-link optical mode mixer to dynamically change the spatial-mode mixing characteristics of the link on a time scale that is faster than the channel coherence time. Provided that the MIMO system employs an FEC code that has a sufficient error-correcting capacity for correcting the amount of errors corresponding to an average state of the MIMO channel, this relatively fast dynamic change tends to reduce the frequency of events during which the number of errors per FEC-encoded block of data exceeds the error-correcting capacity of the FEC code.

Abstract: In a representative embodiment, a multipath channel and an optical subcarrier modulation scheme are designed in concert to cause different modulated subcarriers of the optical communication signal to become substantially uncorrelated over the aggregate signal bandwidth. Provided that the employed FEC code has sufficient error-correcting capability for average channel conditions, breakdowns in the operation of the FEC decoder and the corresponding system outages can substantially be avoided.

Abstract: The outage probability in an under-addressed optical MIMO system may be reduced by configuring a spatial-mode coupler at a transmitter and/or a spatial-mode separator at a receiver to dynamically change its spatial-mode configuration on a time scale that is shorter than the channel coherence time. Provided that the MIMO system employs an FEC code that has a sufficient error-correcting capacity for correcting the amount of errors corresponding to an average state of the MIMO channel established between the transmitter and receiver, this relatively fast dynamic change tends to reduce the frequency of events during which the number of errors per FEC-encoded block of data exceeds the error-correcting capacity of the FEC code.

Abstract: The outage probability in an under-addressed optical MIMO system may be reduced by configuring an intra-link optical mode mixer to dynamically change the spatial-mode mixing characteristics of the link on a time scale that is faster than the channel coherence time. Provided that the MIMO system employs an FEC code that has a sufficient error-correcting capacity for correcting the amount of errors corresponding to an average state of the MIMO channel, this relatively fast dynamic change tends to reduce the frequency of events during which the number of errors per FEC-encoded block of data exceeds the error-correcting capacity of the FEC code.

Abstract: Techniques are disclosed for interference coordination in communication networks. For example, a method comprises the following steps. Input information is obtained from a communication network. The input information comprises existing power levels associated with transmitting nodes in the communication network, and existing channel information associated with receiving nodes in the communication network. A coordinated resource set of future transmitting times and future power levels associated with the transmitting nodes and future decoding times associated with the receiving nodes that reduce interference in the communication network is determined. The coordinated resource set determination comprises evaluating a cost function for a given range of interference values based on at least a portion of the input information. In a downlink scenario, the transmitting nodes may comprise base stations and relays, and the receiving nodes may comprise user equipment.

Abstract: To reduce intercell interference, a method of coherently coordinated downlink transmission in a wireless network involves coordinating transmissions from a plurality of base stations to a plurality of wireless units, for coherent, reinforced reception of the transmitted signals at the wireless units. Thus, transmissions from the base stations are coordinated such that signals received at each wireless unit's particular location constructively add, but cancel out at other locations. The signals are generated based on a zero-forcing operation, e.g., by applying zero-forcing complex antenna weight vectors to data symbols designated for transmission to the wireless units. For fairness, the signals are transmitted at no less than a guaranteed common rate. A convex optimization problem (which incorporates a per-base station power constraint or a per-transmission antenna power constraint) is solved to maximize the guaranteed common rate. Dirty paper coding may also be employed.

Abstract: An example method includes modulating an optical signal using a Phase Shift Keying (PSK) signal constellation, wherein signal points of the PSK signal constellation are located on at least two rings. The first ring has a first radius r1 and a second ring has a second radius r2, wherein the first radius and second radius differ, and wherein the signal points are not located on a regular n-dimension lattice, where n is an integer. The regular n-dimension lattice is formed from a minimum number of lines parallel to an axis for each of the n-dimensions that connect ones of the signal points of the PSK signal constellation on either side of an origin of the axis. The second radius may be greater than the first radius, with the second radius a non-integer multiple of the first ring radius.

Abstract: To reduce intercell interference, a method of coherently coordinated downlink transmission in a wireless network involves coordinating transmissions from a plurality of base stations to a plurality of wireless units, for coherent, reinforced reception of the transmitted signals at the wireless units. Thus, transmissions from the base stations are coordinated such that signals received at each wireless unit's particular location constructively add, but cancel out at other locations. The signals are generated based on a zero-forcing operation, e.g., by applying zero-forcing complex antenna weight vectors to data symbols designated for transmission to the wireless units. For fairness, the signals are transmitted at no less than a guaranteed common rate. A convex optimization problem (which incorporates a per-base station power constraint or a per-transmission antenna power constraint) is solved to maximize the guaranteed common rate. Dirty paper coding may also be employed.

Abstract: In a system of MIMO communications in a wireless network, a number of wireless units are logically divided into a plurality of user groups, through operation of a semi-orthogonal user selection sub-system. For example, the user selection sub-system may implement a heuristic user selection algorithm based on near-orthogonality. Each user group is assigned a discrete transmission channel, which may be orthogonally defined in terms of frequency, time, or code. Data is transmitted over the channels (e.g., from network base stations) in a coherently coordinated manner, according to a zero-forcing beamforming operation. The system may be configured for operation in a time/frequency selective manner, e.g., over time/frequency selective fading channels. The wireless units may be allocated to the time/frequency slots based on prioritization of channel strength and considerations of fairness, in conjunction with the application of a semi-orthogonal user selection algorithm.

Abstract: The present invention is directed to a formatter, a method of formatting encoded symbols and a wireless communication system employing the same. In one embodiment, the formatter includes a symbol generator that provides a plurality of encoded symbols from a bit stream. The formatter also includes a symbol mapping organizer that maps the plurality of encoded symbols into information cells, each having a unique space coordinate, time coordinate and degree of freedom within a frequency band. The information cells are arranged in a parallelopiped communication resource volume.

Abstract: A method and apparatus for increasing the capacity of a multiple-input and/or multiple-output system. Each sub-stream of a primary data stream is stratified to produce a processed sub-stream whose strata can be separated out and decoded with an acceptable error rate. A sub-stream can be stratified by dividing it into a plurality of sub-stream-components that are processed to obtain strata, with each stratum representing one of the sub-stream-components. The strata are then combined to obtain the processed sub-stream. Stratifying allows a particular processed sub-stream's strata have different transmit features from each other, such as different bit rates, or different power levels, or both. This reduces the interference for some of the strata of each processed sub-stream since as stratum are separated out and decoded they are no longer interference for the other strata. Thus, allowing for a higher overall bit rate for the processed sub-streams.

Abstract: When using four transmit antennas, conventional channel coding is employed for a decoupled space-time coding approach for each of a number, L, of data substreams derived from the overall source bit stream. The symbols of the data substreams, after any encoding, are processed and the resulting derivatives of the encoded data substreams, which includes at least the complex conjugate of one of the encoded symbols, are grouped to form four transmit time sequences each one spanning L symbol periods which form a transmission matrix B. Each row of the matrix corresponds to an antenna, and the elements of each row represent the samples of a temporal sequence that is emitted by the antenna in L symbol periods.

Abstract: A method and apparatus for assigning the data rate and/or power level to the mobile terminals without determining the highest theoretical system throughput, and without determining the highest weighted system throughput. An order is imposed on the terminals and the data rate and/or power covariance matrices are assigned such that the data rates of the terminals having a lower index in the order will not be decreased due to the presence of the terminals having a higher index in the order, and this is accomplished without changing the power covariance matrixes of the antennas involved in the communication with the lower index terminals. Thus, the assignment is made to the terminals based on the terminals requirements without regard to the interference introduced by the terminals with a higher index in the order since this interference will be compensated for by the compensation technique when the compensation technique process the terminals in accordance with the order.