Methods, systems and devices for wireless communication are described. One method includes obtaining a two-dimensional delay-Doppler representation of a received wireless signal that is received over a wireless channel, determining an estimated channel response of the wireless channel from a portion of the delay-Doppler grid corresponding to a channel estimation portion, performing, using the estimated channel response, channel equalization in the delay-Doppler domain, generating, based on the channel equalization, a posteriori probability estimates of data symbols in the received wireless signal, wherein the a posteriori probability estimates are generated based on a priori feedback that is generated using an iterative process and further processing the a posteriori probability estimates of data symbols to recover information bits from the received wireless signal.

Multiple symbol noncoherent soft output detectors in accordance with embodiments of the invention are disclosed. In a number of embodiments, the multiple symbol noncoherent soft output detector uses soft metrics based on the Log Likelihood Ratio (LLR) of each symbol to provide information concerning the reliability of each detected symbol. One embodiment of the invention includes a receiver configured to receive and sample a phase modulated input signal, and a multiple symbol noncoherent soft output detector configured to receive the sampled input signal and to generate a soft metric indicative of the reliability of a detected symbol based upon observations over multiple symbols.

The present invention relates to a method of improving the performance in bandwidth constrained communication systems while reducing the complexity of the equalizer used for information retrieval, as well as to improving the capacity of communication systems. These properties are achieved by appropriate information encoding, prior to signal shaping before transmission, whereas the equalizer complexity is reduced by applying the intersymbol interference shortening filter prior to the information retrieving equalization. A proper combination of the recounted elements is capable of providing a qualitatively improved and previously unsuspected performance, as compared to its constituent elements.

A method, system, and apparatus are provided for computing soft bits in a non-linear MIMO detector which decodes a signal received at a plurality of receive antennas using channel estimate information and a decoding tree to produce output data for a bit estimation value which includes a maximum likelihood solution along with a naturally ordered vector identifying all explored node metrics and node indices, where soft bits are computed for each bit estimation value by determining a set of bit-masks through repetition and indexing operations applied on the explored node indices, masking the naturally ordered vector with the set of bit-masks to generate masked node metrics, determining candidate soft bit values by subtracting metrics of all nodes that form the maximum likelihood solution from the masked node metrics, and determining a final soft bit value by identifying which of the candidate soft bit values has a lowest value.

Systems and methods for underwater communication using a SISO acoustic channel. An acoustic receiver may receive a signal comprising information encoded in at least one transmitted symbol. Using a Bi-SDFE, the at least one transmitted symbol is estimated. The Bi-SDFE may include a SDFE and a time-reversed SDFE that each output bit extrinsic LLRs, which are combined into combined bit extrinsic LLRs. The estimated symbol is then mapped to the combined bit extrinsic LLRs, the result of which is de-interleaved. Iterative bit extrinsic LLRs are generated with a MAP and/or soft-decision decoder using the mapped, combined bit extrinsic LLRs as a priori LLRs for the Bi-SDFE in another iterative estimation. The iterative bit extrinsic LLRs are interleaved and transmitted for use by the Bi-SDFE in another iterative estimation. After a plurality of iterations, a hard decision of the transmitted symbol is generated with the MAP and/or soft-decision decoder.

Systems and methods for detecting collisions in radio frequency tags in accordance with embodiments of the invention are disclosed. In one embodiment, a receiver system includes a receiver configured to receive and sample a phase modulated input signal, and a multiple symbol noncoherent soft output detector configured to receive the sampled input signal and to generate a soft metric indicative of the reliability of a detected symbol based upon observations over multiple symbols, a collision detector configured to calculate a decision metric from a set of soft metrics generated by the multiple symbol noncoherent soft output detector and detect a collision when the decision metric satisfies a predetermined criterion.

The present invention relates to a method of improving the performance in bandwidth constrained communication systems while reducing the complexity of the equalizer used for information retrieval, as well as to improving the capacity of communication systems. The said properties are achieved by appropriate information encoding, prior to signal shaping before transmission, whereas the equalizer complexity is reduced by applying the intersymbol interference shortening filter prior to the information retrieving equalization. A proper combination of the recounted elements is capable of providing a qualitatively improved and previously unsuspected performance, as compared to its constituent elements.

Disclosed is a relay method including: receiving, as input, respective reception signals by two receive antennas, the reception signals each including a reception signal resulting from multiplexing respective transmission signals transmitted by two transmission antennas in a first frequency band; performing frequency conversion on the reception signal received by one of the receive antennas so as to obtain a signal of a third frequency band; and performing frequency multiplexing on the signal having the third frequency band and the reception signal received by the other of the receive antennas.

A method and system for maximizing throughput and minimizing latency in a communication system that supports heterogeneous links is presented. The communication system supports a primary link and an alternate link, and the method and system leverage the alternate link to reduce the overhead transmitted over the primary link, thereby increasing throughput and reducing end-to-end latency. The higher latency alternate link provides a delayed version of an information signal that corresponds to a portion of the information signal that is transmitted on the primary link. The received samples from the primary and alternate links may be used to equalize subsequent portions of the information signal received over the primary link, and may also be used for synchronization, timing recovery, DC offset removal, I/Q imbalance compensation, and frequency-offset estimation.

Disclosed is a precoding method for generating, from a plurality of baseband signals, a plurality of precoded signals that are transmitted in the same frequency bandwidth at the same time. According to the precoding method, one matrix is selected from among matrices defining a precoding process that is performed on the plurality of baseband signals by hopping between the matrices. A first baseband signal and a second baseband signal relating to a first coded block and a second coded block generated by using a predetermined error correction block coding scheme satisfy a given condition.