Abstract: An apparatus and method for switching between a first and a second Orthogonal Frequency Division Multiplexing (OFDM) communication mode includes a first step of determining an operational modulation scheme. A next step includes estimating a first performance factor for the modulation scheme in the first communication mode and a second performance factor for the modulation scheme in the second communication mode. A next step includes comparing the first and second performance factors against at least one selection criterion. A next step includes selecting the communication mode in response to the selection criterion and the modulation scheme. A next step includes transmitting on the selected communication mode using the modulation scheme.

Abstract: A pilot (or reference) transmission scheme is utilized where different transmitters are assigned pilot sequences with possibly different cyclic time shifts. A pilot signal is transmitted concurrently by the transmitters in a plurality of pilot blocks, and a receiver processes the plurality of received pilot blocks to recover a channel estimate for at least one of the transmitters while suppressing the interference due to the pilot signals from the other transmitters.

Abstract: Various embodiments are described which can serve to mitigate interference between the control channel signaling of adjacent sectors/cells. Potentially, these techniques may have the benefit of reducing the system resource drain caused by control channels, particularly control channels in high frequency-reuse, OFDMA systems. A transmitting device (101) transmits primary control channel information to a plurality of user devices (102). The primary control channel information includes an indication that a first OFDMA resource region (e.g., 320 or 330) is assigned to at least one user device of the plurality of user devices. The transmitting device correspondingly transmits secondary control channel information to the at least one user device using the first OFDMA resource region.

Abstract: In an OFDM system the same Walsh code is used at the same time for a plurality of transmitters. The multiple transmitters can be from the same, or different devices (e.g., different base stations on the downlink, different terminals on the uplink). Each subcarrier/antenna combination will share a similar pilot Walsh code, except for the fact that the scrambled spread pilot signals will be phase shifted on some subcarriers of some antennas, based on the subcarrier/antenna combination.

Abstract: A method for communicating channel estimates on a plurality of subcarriers between a transmitting device and a receiving device. The transmitting device determines a channel estimates on a plurality of subcarriers and then encodes the channel estimates into at least one encoded channel waveform. Then the transmitting device transmits the at least one encoded channel waveform to the receiving device.

Abstract: Mobile units in a multicarrier, multidimensional communications system can assess their own channel coherence time attributes (base stations can also access such dynamics for mobile units as well). This information is utilized (either by the mobile unit itself or by an infrastructure component such as a base site) to determine a level of trustworthiness for other channel quality data as might be measured by the mobile unit. Different modulation and coding schemes, along with responsive frequency and time diversity resource allocations, are adaptively selected as a function of this level of trustworthiness.

Abstract: Narrowband remote units will scan over frequencies within a wideband channel spectrum, evaluating frequency-selective channel characteristics. The best sub-channel(s) for communication will be determined and reported back to a base station via a channel-quality report message. The base station will then utilize only a narrowband portion (e.g., one sub-channel comprised of a plurality of OFDM subcarriers) of the wideband channel for transmitting data to the narrowband unit.

Abstract: A downlink frame (401) is divided in to similar sized resource blocks (403, 405, 407) with each co-channel sector scheduled to transmit from the beginning of its respective assigned resource block. Transmissions to remote units within the particular sector will occur only within the particular resource block, up to a point where all N resource units have been utilized. Beyond that point, additional transmissions are scheduled to be transmitted at the end of the resource blocks assigned to the other sectors.

Abstract: A staggered spread OFCDM scheme is utilized that improves channel estimation. In a first embodiment, each chip stream is time shifted by a predetermined amount and then transmitted on a predetermined subcarrier. This results in time-spread symbols being staggered (time-offset) on different subcarriers allowing for more frequent sampling of the channel. In a second embodiment a staggered spreading approach is applied in the frequency dimension to improve the performance of a system with spreading in the frequency dimension.

Abstract: An apparatus (300) for and method of synchronizing OFDM signals utilizes a single baud to provide synchronization in time, frequency, and per-subcarrier rotation (201). Timing and fractional subcarrier frequency synchronization may be obtained from either a known or unknown (e.g., data symbol) baud having known symmetry properties. Because all three synchronization tasks may be accomplished utilizing a single sync baud, the present invention is spectrally efficient. A differential correlation metric is utilized to efficiently provide integer subcarrier frequency synchronization and per-subcarrier rotation synchronization.

Abstract: A method includes the steps of receiving (402), by a first receiver (102), a first received signal comprising a first signal (110) and a second signal (120), and receiving (402), by a second receiver (104), a second received signal comprising the first signal (110) and the second signal (120). A branch weight associated with the first receiver (102) and at least one other branch weight associated with the second receiver (104) are determined (406). The branch weight associated with the first receiver (102), the at least one other branch weight associated with the second receiver (102), the first received signal, and the second received signal are combined, forming a combined signal. Channel state information is determined for the combined signal, and the channel state information of the combined signal is restored (412).

Abstract: A receiver for implementing a training prefix modulation method in response to a reception of a signal propagating through a channel is disclosed. The signal as received includes training blocks with each training block having a data inter-block-interference therein, and data blocks with each data block having a training inter-block-interference therein. The signal is selectively reconstructed to provide a circular appearance of the channel over the data blocks. Specifically, an estimate of the training inter-block-interferences is generated and subtracted from the data blocks. And, an estimate of the data inter-block interferences is generated and added to the data blocks.

Abstract: A downlink frame (401) is divided in to similar sized resource blocks (403, 405, 407) with each co-channel sector scheduled to transmit from the beginning of its respective assigned resource block. Transmissions to remote units within the particular sector will occur only within the particular resource block, up to a point where all N resource units have been utilized. Beyond that point, additional transmissions are scheduled to be transmitted at the end of the resource blocks assigned to the other sectors.

Abstract: A receiver for implementing a training prefix modulation method in response to a reception of a signal propagating through a channel is disclosed. The signal as received includes training blocks with each training block having a data inter-block-interference therein, and data blocks with each data block having a training inter-block-interference therein. The signal is selectively reconstructed to provide a circular appearance of the channel over the data blocks. Specifically, an estimate of the training inter-block-interferences is generated and subtracted from the data blocks. And, an estimate of the data inter-block interferences is generated and added to the data blocks.

Abstract: Mobile units in a multicarrier, multidimensional communications system can assess their own channel coherence time attributes (base stations can also access such dynamics for mobile units as well). This information is utilized (either by the mobile unit itself or by an infrastructure component such as a base site) to determine a level of trustworthiness for other channel quality data as might be measured by the mobile unit. Different modulation and coding schemes, along with responsive frequency and time diversity resource allocations, are adaptively selected as a function of this level of trustworthiness.

Abstract: An apparatus (30) for and method of synchronizing OFDM signals utilizes a single baud to provide synchronization in time, frequency, and per-subcarrier rotation (201). Timing and fractional subcarrier frequency synchronization may be obtained from either a known or unknown (e.g., data symbol) baud having known symmetry properties. Because all three synchronization tasks may be accomplished utilizing a single sync baud, the present invention spectrally efficient. A differential correlation metric is utilized to efficiently provide integer subcarrier frequency synchronization and per-subcarrier rotation synchronization.

Abstract: A method includes the steps of receiving (402), by a first receiver (102), a first received signal comprising a first signal (110) and a second signal (120), and receiving (402), by a second receiver (104), a second received signal comprising the first signal (110) and the second signal (120). A branch weight associated with the first receiver (102) and at least one other branch weight associated with the second receiver (104) are determined (406). The branch weight associated with the first receiver (102), the at least one other branch weight associated with the second receiver (102), the first received signal, and the second received signal are combined, forming a combined signal. Channel state information is determined for the combined signal, and the channel state information of the combined signal is restored (412).

Abstract: A family of methods for interference averaging in orthogonal frequency division multiplexing (OFDM) systems is provided. The methods can provide interference averaging in situations where an interfering co-channel is either partially or fully loaded. For partially loaded systems, subcarrier puncturing, frequency domain repetition, time domain repetition, and hybrid time-frequency repetition schemes are provided. For systems using adaptive modulation/coding rates, lower rates and transmit power can be selected in order to perform interference averaging in time-spread and frequency-spread OFDM schemes. In systems with downlink power control, frequency domain mixing can be used to perform interference averaging.

Abstract: A communication system (100) that includes a base unit (101) and a subscriber unit (e.g., 103) employs a method (400) and apparatus (101) for mitigating interference (135) therein. The base unit (101) receives an uplink communication signal from the subscriber unit (103) at an uplink frequency and conveys a downlink communication signal to the subscriber unit (103) at a downlink frequency. Upon receiving (403) an uplink communication signal from the subscriber unit (103), the base unit (101) determines (405) a quality metric for the uplink frequency. When the quality metric is below a quality threshold (407), the base unit (101) and the subscriber unit (103) transfer (415) the communication signal to an alternate uplink frequency, while the downlink frequency remains unchanged.

Abstract: A method and device in a communication system including a receiver having a plurality of receiving antennas for receiving a plurality of information bursts transmitted by at least one transmitting user device where the information bursts contain a number of data symbols and a pilot symbol sequence of content known at both the transmitting user device and the receiver. The method provides for computing a channel transfer function between the transmitting user device at each of the plurality of receiving antennas, by computing a simulated received pilot signal for each receiving antenna, computing an error signal between the simulated received pilot signal and the received pilot symbol sequence, computing a channel modeling sequence, wherein the power of the error signal is minimized, and computing the channel transfer function by weighting predetermined basis functions by the channel modeling sequence.