Indian Institute of Science

Beceem Communications Inc.

Indian Institute of Science at Bangalore

Balaji Sundar Rajan

Ananthanarayanan Chockalingam

Saif Khan Mohammed

Djordje Tujkovic

Arogyaswami J Paulraj

Shashidhar Vummintala

Erik David Lindskog

Srinidhi Nagaraja

Tanumay Datta

Pavan Koteshwar Srinath

Susinder Rajan Gulasekaran

Vummintala Shashidhar

Kalepalli Vishnu Vardhan

Sreenath Ramanath

Ashok Kumar N

A device and method for precoding vectors in a communication system is provided. A transmitter may precode a data vector using information regarding a communication channel prior to transmitting the data vector. The transmitter may precode the data vector in a manner that reduces an energy value of a resulting transmit data vector so as to minimize interference in a received signal at a receiver. The transmitter may perturb entries of the data vector one-by-one in an iterative fashion until a minimum in an energy value of the transmit data vector is obtained.

Device and method for precoding vectors in a communication system

Techniques for enabling an estimate of a transmittal signal vector, given a received signal vector and a channel matrix to be computed, are provided. An initial solution signal vector for the estimate is calculated, and based on the initial estimate, a pool of possible solutions is generated. Methods described herein may be iterative in nature, and may cycle through possible estimates of the transmitted signal vector so as to continually improve the estimates and the pool of possible estimates. The methods may terminate once stopping criteria are reached. In some example methods, solutions may be marked at taboo and a taboo period can be established that indicates a number of subsequent iterations for which the current solution signal vector cannot be considered.

Techniques for decoding transmitted signals using reactive taboo searches (RTS)

A method of determining a transmitted vector (x) in a MIMO receiver includes the steps of receiving a received vector (y) representative of the transmitted vector (x), generating a first random number and forming, in a first iteration, a first symbol of a first candidate vector, the candidate vector representing a potential solution vector. The step of forming is based on a first approach if the first random number is greater than a first predetermined value (q), but is based on a second approach if the random number is less than or equal to the first predetermined value (q). The first approach randomly selects the first symbol from a uniform distribution of symbols in the transmission alphabet. The second approach selects the first symbol based on Gibbs sampling. The method represents a randomized Markov Chain Monte Carlo (RMCMC) sampling technique.

Multiple input multiple output (MIMO) transmitted signal vector estimation employing Monte Carlo sampling techniques

A receiver of a multiple-input multiple-output (MIMO) system performs QR decomposition of the channel matrix to enable detection of a transmitted vector in a layered manner. In each layer, a sub-vector of the transmitted vector is estimated. A reactive tabu search is performed if an estimated symbol differs from a nearest symbol in the alphabet by a predetermined value. The receiver may order the entries of the channel matrix prior to QR decomposition to enable estimation in an optimum order. In another embodiment, a receiver performs multiple reactive tabu searches to estimate a transmitted vector. The receiver employs a fixed threshold or a variable threshold for a cost function used in the multiple reactive tabu searches depending on whether the MIMO system is under-determined or not. The techniques enable low bit-error rate (BER) performance in MIMO systems with large number of antennas and when higher-order modulation techniques are used.

Techniques for detection of signals in multiple-input multiple-output communication systems

Disclosed is a method and system to detect data transmitted by multiple transmit antennas. The method comprises selecting a starting data block that is either a random data block or an output data block from known detectors. Also, the method comprises changing each symbol of the starting data block one symbol at a time to identify a data block which has minimum euclidean distance from the starting data block as detected data block. Next, changing two symbols of the detected data block at a time to identify a data block which has minimum euclidean distance from the starting data block as second data block and assigning the second data block as the starting data block. Repeating the above steps, if the minimum euclidean distance of second data block is better than that of the detected data block, and determining the detected data block as the data transmitted.

Method to detect data transmitted by multiple antennas

Techniques for enabling an estimate of a transmitted signal vector, given a received signal vector and a channel matrix to be computed, are provided. An initial solution signal vector for the estimate is calculated, and based on the initial estimate, a pool of possible solutions is generated. Methods described herein may be iterative in nature, and may cycle through possible estimates of the transmitted signal vector so as to continually improve the estimates and the pool of possible estimates. The methods may terminate once stopping criteria are reached. In some example methods, solutions may be marked at taboo and a taboo period can be established that indicates a number of subsequent iterations for which the current solution signal vector cannot be considered.

Embodiment of the disclosure set forth methods for transmitting data in a wireless communication system. Some example methods include converting a data stream to a symbol set; selecting a first plurality of symbols from the symbol set, wherein the first plurality of symbols includes at least a first symbol, a second symbol, a third symbol, and a fourth symbol; generating a second plurality of symbols having at least a fifth symbol and a sixth symbol, wherein the fifth symbol includes a first part of the first symbol and a second part of the second symbol and the sixth symbol includes a first part of the third symbol and a second part of the fourth symbol; weighting the sixth symbol to form a first weighted symbol; and transmitting in a first time slot the fifth symbol with a first antenna and the first weighted symbol with a second antenna.

Data transmission in wireless communication system

A method to detect data transmitted from multiple antennas, said method comprising steps of: selecting a starting data block and calling it as previous data block; defining a set of indices of bits to be checked for possible flip in the previous data block as a check candidate set; applying update rule to obtain updated data block using the previous data block and the check candidate set, wherein the update is made in such a manner that change in likelihood is positive; checking if the updated data block and several consecutive previous data blocks are the same; if yes, declare the updated data block as the detected data block; if no, make updated data block as previous data block and repeat updation of data block.

Method to detect data transmitted from multiple antennas and system thereof

Embodiments of the disclosure set forth methods for transmitting data in a wireless communication system. Some example methods include converting a data stream to a symbol set and selecting a first plurality of symbols from the symbol set. The first plurality of symbols includes at least a first symbol, a second symbol, a third symbol, a fourth symbol, a fifth symbol, a sixth symbol, a seventh symbol, and a eighth symbol. The methods include generating one or plurality of symbols of a second plurality of symbols based on interleaving two symbols selected from the first plurality of symbols. The methods further include weighting some symbols of the second plurality of symbols and generating a matrix based on symbols selected from the second plurality of symbols and the weighted symbols. The methods also include encoding the data stream based on the matrix.

In a training cycle, a source node transmits at least one pilot symbol to relay nodes in a training cycle. The relay nodes each amplifies and forwards the pilot symbol to a destination node in an assigned time slot in the training cycle. The destination node sequentially receives multiple versions of the pilot symbol from the relay nodes and estimates channel information based on the multiple versions of the pilot symbol. In data transmission cycles that follow the training cycle, the nodes apply coherent distributed space-time block code (DSTBC) with the estimated channel information to communicate data symbols. The power allocation between training and data cycles may be adjusted to improve the error performance. The nodes may also apply orthogonal frequency division multiplexing (OFDM) based DSTBC when timing errors are not known.

Leveraging coherent distributed space-time codes for noncoherent communication in relay networks via training

Methods and systems for determining a Log-Likelihood Ratio (LLR) corresponding to each bit of a symbol are provided. The symbol comprises a predefined number of bits based on a predetermined constellation. The methods and systems include expanding the predetermined constellation. The predetermined constellation comprises a plurality of constellation-points wherein each constellation-point has a unique X co-ordinate and Y co-ordinate. Also, the expanded predetermined constellation further comprises points corresponding to each combination of the X co-ordinate and the Y co-ordinate of the constellation-points. The methods and systems further include calculating the LLR corresponding to each bit of the symbol based on the expanded predetermined constellation.

Method and system for determining a log-likelihood ratio (LLR) corresponding to each bit of a symbol

A communication system is provided that includes signal encoding in a multiple input multiple output system. The communication system includes wireless communication networks. The communication system includes methods of encoding and transmitting symbols in a rate-1 complex symbol per second per Hertz transmission system while achieving maximum diversity. The communication further includes methods of interleaving the complex symbols such that each interleaved symbol comprises information of at least two complex symbols where the complex symbols obtain values from a rotated constellation.

Method and system for maximum transmit diversity

Signal encoding in a multiple input multiple output system in a wireless communication network is provided. The communication system provides a method of encoding and transmitting symbols in a rate-2 complex symbol per second per Hertz transmission system that achieves a maximum diversity of four for a four transmit antenna system and a diversity of three on a three transmit antenna system. The communication system further provides a method of interleaving the complex symbols such that each interleaved symbol comprises information of at least two complex symbols where the complex symbols obtain values from a rotated constellation.

Method and system for rate-2 transmission

The invention relates generally to the field of signal encoding in a multiple input multiple output system in a wireless communication network. This invention specifically relates to a method of encoding and transmitting symbols in a rate-2 complex symbol per second per Hertz transmission system that achieves a maximum diversity of four for a four transmit antenna system and a diversity of three on a three transmit antenna system. The invention discloses a method of interleaving the complex symbols such that each interleaved symbol comprises information of at least two complex symbols where the complex symbols obtain values from a rotated constellation.

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Bengaluru, India

Balaji Sundar Rajan