Abstract: Pilot transmission and channel estimation techniques for an OFDM system with excess delay spread are described. To mitigate the deleterious effects of excess delay spread, the number of pilot subbands is greater than the cyclic prefix length. This “oversampling” may be achieved by using more pilot subbands in each symbol period or different sets of pilot subbands in different symbol periods. In one example, a first set of pilot subands may be received in a first symbol period, and a second set of pilot subands may be received in a second symbol period. The first set of pilot subands and the second set of pilot subbands may be staggered in frequency.

Abstract: A method for providing repeater communication in a wireless repeater deployed in a multi-repeater environment includes inserting a message signal into the transmit signal of the repeater. The message signal may be a unique or quasi-unique low power spreading sequence uniquely identifying the repeater from other repeaters in the environment. The message signal may also contain information relating to the operational characteristics of the repeater. The message signal may be detected by another repeater or by an end-user wireless communication device.

Abstract: A method for computing a gain control metric used in controlling gain in a wireless repeater operates to store correlation and normalization values associated with the gain control metric for the previous N samples in registers. For each new sample of the gain control input signal, the correlation and normalization values are computed by discarding the multiplication terms of the obsolete sample and adding the multiplication terms of the new sample to the stored correlation and normalization values. In this manner, the complexity of the computation is greatly reduced and the complexity of the computation does not increase with the integration length.

Abstract: A wireless repeater has a receiving antenna for receiving an input signal and a transmitting antenna for transmitting an amplified signal where the input signal is a sum of a remote signal and a feedback signal. The repeater includes an echo canceller receiving the input signal and generating an echo cancelled signal by estimating a feedback channel between the transmitting antenna and the receiving antenna and cancelling a feedback signal estimate from the input signal, an amplifier for amplifying the echo cancelled signal and providing the amplified signal to the transmitting antenna, and a variable delay element receiving the echo cancelled signal and introducing a first delay to the echo cancelled signal. The first delay is selected to optimize the estimation of the feedback channel, thereby optimizing the cancellation of the feedback signal. The delayed echo cancelled signal is coupled to the echo canceller as a reference signal for estimating the feedback channel.

Abstract: A wireless repeater includes an echo canceller to cancel an estimated feedback amount from an input signal and a delay to delay the input signal. The delay may be selected to decorrelate a remote signal from a signal to be transmitted by the repeater.

Abstract: A wireless repeater having a receiving antenna for receiving an input signal and a transmitting antenna for transmitting an amplified signal includes first and second front-end circuits and a repeater baseband block coupled between the first and second front-end circuits. The repeater baseband block includes a channel estimation block, an echo canceller implementing time domain echo cancellation, a variable gain stage controlled by a gain control block implementing digital gain control, a first variable delay element introducing a first delay before or after the echo canceller, a second variable delay element introducing a second delay to the output signal. The delayed output signal is coupled to the channel estimation block as a reference signal for estimating the feedback channel, to the echo canceller as a reference signal for estimating the feedback signal, and to the gain control block for monitoring the stability of the repeater.

Abstract: A method for controlling gain in a wireless repeater includes using two or more gain control metrics indicative of stability of the repeater, at least two of the gain control metrics having different integration lengths, where the integration length is the sum of the coherent integration time and the non coherent integration time, and controlling a variable gain value of the repeater based on one or more of the selected gain control metric(s) where the gain control metric(s) to use is selected based on the stability of the repeater.

Abstract: A method for monitoring feedback loop stability in a wireless repeater includes measuring a gain control metric in the feedback loop of the repeater periodically for a given time period where the gain control metric is indicative of a loop gain of the feedback loop of the repeater; and monitoring the magnitude of the gain control metric to determine the stability of the feedback loop of the repeater. In operation, a large magnitude of the gain control metric indicates instability in the feedback loop of the repeater.

Abstract: A method for controlling gain in a wireless repeater includes providing one or more gain control metrics where the gain control metrics is indicative of a loop gain of the repeater; measuring the one or more gain control metrics; and adjusting a variable gain of the repeater using a gain adjustment step size being a function of at least the loop gain of the repeater as measured by the one or more gain control metrics. In another embodiment, the gain control algorithm block is configured to divide the loop gain of the repeater into multiple gain adjustment control zones. The gain adjustment control zones may include a first zone having a loop gain in a stable operating region and a second zone having a loop gain outside the stable operating region.

Abstract: In one embodiment, a method for providing echo cancellation in a wireless repeater includes: adding the pilot signal to a transmit signal; receiving a receive signal being the sum of a remote signal, a feedback pilot signal and a feedback transmit signal; cancelling the feedback transmit signal from the receive signal using a currently available feedback channel estimate and generating a first echo cancelled signal; generating an updated feedback channel estimate using the first echo cancelled signal and the pilot signal as a reference signal; cancelling the feedback transmit signal and the feedback pilot signal from the receive signal using the updated feedback channel estimate and generating a second echo cancelled signal; and amplifying the second echo cancelled signal as the transmit signal. In another embodiment, the feedback pilot signal is cancelled from the first echo cancelled signal using the updated feedback channel estimate to generate the second echo cancelled signal.

Abstract: In one embodiment, a device for constructing a pilot signal for use in a wireless repeater where the pilot signal is added to a transmit signal includes one or more pilot generators. Each pilot generator generates a carrier pilot signal associated with a single carrier of the transmit signal and the carrier pilot signals generated by the one or more pilot generators are summed to generate the pilot signal. Each of the one or more pilot generators includes a pilot symbol unit providing multiple data symbols having a predetermined data structure as the carrier pilot signal, a pilot scrambler, a filter, a pilot power determination unit, and a cyclic prefix insertion unit for inserting a cyclic prefix, to the carrier pilot signal. In another embodiment, the pilot symbol unit providing multiple data symbols in frequency domain as the carrier pilot signal.

Abstract: A method for estimating a feedback channel for a wireless repeater uses frequency domain channel estimation on samples of a pilot signal and samples of a receive signal. The pilot signal samples may be delayed to align the largest channel tap to a given reference time. A time domain feedback channel is generated by retaining both the causal taps and the non-causal taps of the channel estimate.

Abstract: A method for estimating a feedback channel for a wireless repeater detects changes in a power of a remote signal. When a large power swing in the remote signal is detected, the method operates to discard samples or blocks of samples of the pilot and receive signals and a final channel estimate is generated using undiscarded samples of the pilot and receive signals. Alternately, sub channel estimates are generated using individual blocks of the pilot samples and receive samples. When a large power swing in the remote signal is detected, the method operates to discard one or more sub channel estimates and a final channel estimate is generated using undiscarded sub channel estimates.

Abstract: A method for controlling gain in a wireless repeater includes computing a gain control metric indicative of a loop gain of the repeater and detecting changes in a signal power of a gain control input signal where the gain control input signal is taken from any point in the feedback loop of the repeater. When a large power swing in the gain control input signal is detected, the method operates to discard at least a portion of each gain control metric measurement for a first duration before continuing with computing the gain control metric. In another embodiment, the method may include discarding samples of the gain control input signal used in computing the gain control metric for a first duration when a large power swing in the gain control input signal is detected.

Abstract: A wireless repeater includes a channel estimation block to estimate a feedback channel between the antennas of the repeater using frequency domain channel estimation. The repeater includes a pilot signal blanking circuit to blank out a selected number of samples of the pilot signal to improve the accuracy of the channel estimation. In another embodiment, the repeater replaces T samples of the pilot signal with a cyclic prefix.

Abstract: A method for controlling gain in a wireless repeater implementing echo cancellation determines a signal-to-interference-noise-ratio (SINR) of the input and output signals of the repeater and adjusts the gain of the repeater to optimize an achievable data rate and a coverage area of the repeater. The repeater gain may be decreased to increase the data rate and increase the achievable SINR of the output signal while the coverage area is reduced. Alternately, the repeater gain may be increased to decrease the data rate and decrease the achievable SINR of the output signal while the coverage area is increased.

Abstract: Estimation of channel characteristics and interference level in a time-varying multi-carrier multi-user systems is carried out concurrently. To perform the estimation, a multitude of data symbols and dedicated pilot symbols are transmitted over the channel. Next, an initial estimate value is selected for the interference level. The initial estimate value for the interference level is used together with the received pilot symbols to provide a first estimate of the channel. The first estimate of the channel is used to determine a new updated value for the interference level, which in turn, is used to update the value of the first estimate of the channel iteratively. The iterations continue until the iteratively updated values of the interference level and channel satisfy predefined limits. The data symbols and the final updated value of the channel are subsequently used to provide a second estimate for the channel.

Abstract: A channel structure has at least two channel sets. Each channel set contains multiple channels and is associated with a specific mapping of the channels to the system resources available for data transmission. Each channel set may be defined based on a channel tree having a hierarchical structure. To achieve intra-cell interference diversity, the channel-to-resource mapping for each channel set is pseudo-random with respect to the mapping for each remaining channel set. In each scheduling interval, terminals are scheduled for transmission on the forward and/or reverse link. The scheduled terminals are assigned channels from the channel sets. Multiple terminals may use the same system resources and their overlapping transmissions may be separated in the spatial domain. For example, beamforming may be performed to send multiple overlapping transmissions on the forward link, and receiver spatial processing may be performed to separate out multiple overlapping transmissions received on the reverse link.

Abstract: Accordingly, a method and apparatus are provided to convert received content into a first stream and a second stream, to transmit said first stream using a first tone and to transmit said second stream using an orthogonal scheme. A layering scheme is used to transmit the base stream covering a smaller area and an enhanced stream is used to cover a large utilizing orthogonal scheme.

Abstract: Accordingly, a method and apparatus are provided to convert received content into a first stream and a second stream, to transmit said first stream using a first tone and to transmit said second stream using an orthogonal scheme. A layering scheme is used to transmit the base stream covering a smaller area and an enhanced stream is used to cover a large utilizing orthogonal scheme.