Abstract: This invention is generally concerned with methods, apparatus and processor control code for decoding a signal received over a MIMO (multiple input-multiple output) channel.

Abstract: In a MIMO system the bit error rate floor caused by time dispersion is reduced by employing a joint minimum mean square error (MMSE) equalizer for all of the respective transmit antenna—receive antenna pairings that are possible in the MIMO system. The resulting joint equalization compensates not only for the impact of the channel on the transmit antenna—receive antenna pairings but also for the interference of the other transmit antennas on any given receive antenna. The joint equalization outperforms simply replicating the prior art minimum mean square error (MMSE) equalizer for each transmit antenna—receive antenna pairings.

Abstract: In a lattice-reduction-aided receiver based wireless communications system, soft estimates of transmitted bit values are determined from a received signal by applying lattice reduction to the channel estimate and equalising the received signal in accordance with the reduced basis channel, and determining probabilities of transmitted bits having particular values by selecting a core candidate vector in the reduced basis, determining a set of mapping functions between the core vector in the reduced basis and transmitted symbol vectors from which a set of candidate transmitted symbol vectors can be generated, generating a set of transmitted symbol vectors based on the mapping functions and, on the basis of the received signal determining the probability of each transmitted bit value having been transmitted.

Abstract: In a lattice-reduction-aided receiver based wireless communications system, soft estimates of transmitted bit values are determined from a received signal by applying lattice reduction to the channel estimate and equalising the received signal in accordance with the reduced basis channel, and determining probabilities of transmitted bits having particular values by generating a set of candidate vectors in the reduced basis based on nearest candidate vectors, determining a corresponding transmitted symbol vector for each candidate vector and, on the basis of the received signal determining the probability of each transmitted bit value having been transmitted.

Abstract: This invention relates to methods, apparatus, and processor control code for signal detection in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexed (MIMO-OFDM) communications systems. A method for determining outputs from a received signal in a lattice-reduction-aided receiver based multi-carrier wireless communications system having a plurality of sub-carriers divided into a plurality of sets of sub-carriers, the method comprising performing a detection method for each of said sets, the detection method comprising the step of applying lattice reduction to said set of sub-carriers thereby generating a reduced basis channel response.

Abstract: Information is detected in a signal received from a transmission over a MIMO channel from a plurality of transmit antennas. The information is encoded as QAM symbols over space and time and/or frequency.

Abstract: In a wireless communications system, an inverse of a lattice reduction matrix can be obtained at the same time as performance of the LLL algorithm to determine the lattice reduction. This is achieved by interposing in the LLL algorithm corresponding steps applied to a running calculation of the inverse matrix. Similarly, a row-wise sum of the inverse matrix can be calculated, if this is all that is required in subsequent processing.

Abstract: This invention relates to apparatus, methods, processor control code and signals for channel estimation in OFDM (Orthogonal Frequency Division Multiplexed) communication systems with a plurality of transmitter antennas, such as MIMO (Multiple-input Multiple-output) OFDM systems. An OFDM signal is transmitted from an OFDM transmitter using a plurality of transmit antennas. The OFDM signal is adapted for channel estimation for channels associated with said transmit antennas by the inclusion of orthogonal training sequence data in the signal from each said antenna. The said training sequence data is derived from substantially orthogonal training sequences of length K for each said transmit antenna, said orthogonal training sequences being constructed such that a minimum required sequence length K needed to determine a channel estimate for at least one channel associated with each said transmit antenna is linearly dependent upon the number of said transmit antennas.

Abstract: The present invention relates to estimating and correcting for frequency offset errors in wireless receivers, and is particularly but not exclusively related to MIMO WLAN applications. The present invention provides an improved method of tracking receiver frequency offsets in a receiver for MIMO systems. These receiver based frequency offset components are caused by errors or inaccuracies in various receiver sub-systems such as phase lock loops or carrier frequency oscillator error, and sampling clock rate errors. The frequency offsets due to each of a number of receiver sub-systems are estimated by monitoring frequency offsets on a number of channels or subcarriers (such as OFDM pilot channels) on different frequencies. These channel frequency offsets are preferably estimated by detecting the phase rotation between adjacent pilot symbols on each respective channel. They are then weighted according to a quality parameter of the estimates, which corresponds to their accuracy.

Abstract: A method of estimating channel response in a communications system comprising a transmitting device having a plurality of transmit antennas and a receiving device having at least one receive antenna, the method comprising: (a) Superimposing training sequences onto transmit data to be transmitted by the transmit antennas in order to form a composite message, wherein the training sequences for each transmit antenna are arranged such that they are non-overlapping in the frequency domain; (b) Transmitting the composite message from step (a); (c) Receiving data at the receiving device and then performing the following steps across all channels i. Equalising received data to remove channel distortion; ii. detecting an estimate for the transmit data; iii. using the estimate of the transmit data from step (c)(ii) in order to derive an estimate of the received training sequences as modified by the channel response from the received data; iv.

Abstract: Information is decoded from a signal received from a transmission over a MIMO channel from a plurality of transmit antennas, by means of a decoder and a corresponding decoding method. The signal is received on a plurality of receive antennas, and the information is encoded as a string of symbols over space and time and/or frequency. Each transmitted symbol has one of a plurality of values The decoding method comprises the steps of identifying a predetermined number of sets of symbol values, the sets being the most likely combinations of symbol values to be presented at the transmit antennas at a given time instant, and, for each symbol permitted for transmission, determining and outputting the probability of received information corresponding to the transmission of the symbol at a given antenna, on the basis of the other transmit antennas transmitting the symbol values of one of the identified sets.

Abstract: The invention relates to apparatus, methods, processor control code and signals for channel estimation in MIMO (Multiple-input Multiple-output) OFDM (Orthogonal Frequency Division Multiplexed) communication systems. An OFDM signal is transmitted from an OFDM transmitter using a plurality of transmit antennas but has one or more nulled subcarriers, corresponding to windowing in the frequency domain. The OFDM signal is adapted for channel estimation for channels associated with said transmit antennas by the inclusion of orthogonal training sequence data in the signal from each said antenna. The training sequence data is derived from substantially orthogonal training sequences for each said transmit antenna, the training sequences being constructed based upon sequences of values Xmk=exp(?j2?km/M) where k indexes a value in a said sequence, m indexes a transmit antenna, and M is the number of transmit antennas.

Abstract: In the GPRS, a method of decoding uplink status having reduced interleaving depth in a RLC/MAC block is proposed; for RT-EGPRS users, all of the uplink flag bits are provided in the first burst of the four bursts; and for EGPRS users, nine bits of the uplink status flags are provided in the first burst of the RLC/MAC block and the remaining bits in the next three bursts. On receiving the first nine bits, a mobile performs an autocorrelation to identify the USF whether it belongs to the EGPRS or to the RT-EGPRS group.

Abstract: A channel scrambler for use in a transmitter employing a plurality of transmit antennas comprises at least two signal inputs for inputting a signal and a processor for applying a time-varying scrambling matrix to each input signal to produce a scrambled signal. An output stage is provided for outputting each scrambled signal to an antenna. The scrambling matrix is preferably different for each symbol period of a channel block.

Abstract: This invention is generally concerned with methods, apparatus and processor control code for decoding a signal received over a MIMO (multiple input-multiple output) channel.

Abstract: This invention relates to apparatus, methods, processor control code and signals for channel estimation in OFDM (Orthogonal Frequency Division Multiplexed) communication systems with a plurality of transmitter antennas, such as MIMO (Multiple-input Multiple-output) OFDM systems.

Abstract: In the GPRS, a method of decoding uplink status having reduced interleaving depth in a RLC/MAC block is proposed; for RT-EGPRS users, all of the uplink flag bits are provided in the first burst of the four bursts; and for EGPRS users, nine bits of the uplink status flags are provided in the first burst of the RLC/MAC block and the remaining bits in the next three bursts. On receiving the first nine bits, a mobile performs an autocorrelation to identify the USF whether it belongs to the EGPRS or to the RT-EGPRS group.

Abstract: In a MIMO system the bit error rate floor caused by time dispersion is reduced by employing a joint minimum mean square error (MMSE) equalizer for all of the respective transmit antenna—receive antenna pairings that are possible in the MIMO system. The resulting joint equalization compensates not only for the impact of the channel on the transmit antenna—receive antenna pairings but also for the interference of the other transmit antennas on any given receive antenna. The joint equalization outperforms simply replicating the prior art minimum mean square error (MMSE) equalizer for each transmit antenna—receive antenna pairings.

Abstract: A method of estimating channel impulse response in a signal transmitted over a channel in a communication system is described. The channel estimator obtains a priori knowledge about the transmitted signal, and then uses the transmitted signal and the a priori knowledge to choose an estimate of channel impulse response which minimizes the expected distance between the transmitted signal and a reconstructed signal. The expected distance that is minimized is a cost function, represented by E{∥r−Bh∥2r}. By using soft decision feedback, the invention minimizes erroneous decision feedback which can cause error propagation. The decisions are usually in the form of log likelihood ratios (LLR).

Abstract: A time division multiple access cellular radio telecommunications network is disclosed, in which physical channels may be reused in the same cell. Reused channels on the up link are differentiated by a time shift between them. Same cell reuse (SCR) can thus be implemented in a TDMA (GSM) system without assigning different signatures to SDMA users sharing the same physical channel.