Abstract: System and method for detecting multiple direct sequence spread spectrum signals using a multi-mode searcher. A preferred embodiment comprises the specification of a hypothesis for a particular communications network. The hypothesis can then be used to generate a pseudo-random number (PN) sequence that is provided to a searcher. The searcher can then make adjustments to the PN sequence to bring the PN sequence to conformity with requirements of the particular communications network. The adjustment to the PN sequence permits the use of a multi-mode searcher to perform searches for signals of various communications networks with minimal hardware dedicated to each communications network.

Abstract: Transmit diversity (TD) has become a common technique used in modern wireless communications systems to improve performance. TD uses multiple antennas (e.g., 110 and 111 ) at a transmitter (e.g., 105) to transmit multiple encoded datastreams and a single (or multiple) antenna (e.g., 116) at a receiver (e.g., 115) to receive the datastreams. Preferred embodiments of the present invention provide a general architecture (e.g., 705) that can support different TD schemes and even non-TD, simplifying receiver design and minimizing hardware usage.

Abstract: Search scheduling circuitry for use with a wireless communication device, such as a mobile telephone, includes a search time calculator, a search period calculator, a queue circuit, and a search time circuit. The search scheduler generates a prioritized list of cells to be adaptively searched in response to the network requirements and the capability of the search hardware. If there are very few “handoff” possibilities the search hardware may be turned off and then back on in time to meet the search rate requirements. However, if there is an excessive number of possibilities, the searcher list is prioritized and pared to assure the most likely candidates are searched. This search scheduling minimizes battery power consumption while meeting the search rate requirement and maximizes use of the search hardware for measuring signal quality from multiple neighboring cells and estimating the delay profile of active cells.

Abstract: A method and apparatus are provided that uses the feedback information from an ARQ signal that is received to control the transmit diversity of a transmitter. The method provides for improved performance over some existing ARQ plus open loop transmit diversity schemes in terms of bit-error rate for a given Eb/No. Furthermore, the method does not require extra signaling used by closed loop TD schemes.

Abstract: Gain and phase imbalance is estimated by using an IQ-swapped spreading sequence in addition to a regular spread pilot signal. The IQ-swapped spreading sequence is the spreading sequence whose real and imaginary components are the imaginary and real components of the regular spreading sequence. The gain imbalance can be estimated by a function of the difference between the real component of a regular despread pilot signal and the imaginary component of the IQ-swapped pilot signal. In a similar fashion, the phase imbalance is estimated by a function of the difference between the imaginary component of a regular despread pilot signal and the real component of the IQ-swapped despread pilot signal. A controller such as a DSP (102) uses the gain and phase imbalance estimates to control a gain and phase correction circuit (104). In one embodiment, the correction circuit (104) includes a plurality of multipliers (202-212) and a ROM look-up-table (202) in order to perform the imbalance correction.

Abstract: A Hybrid Automatic Retransmission Request (H-ARQ) technique is provided for Multi-Input Multi-Output (MIMO) systems. The technique changes the basis (V) upon retransmission, which helps reduce the error probability upon retransmission. This basis hopping technique provides for improved performance gain without significant increase in design complexity. In one embodiment, communication device (100) includes a receiver section (114) for receiving an acknowledgment (ACK) or a non-acknowledgment (NACK) signal in response to information transmitted by the transmitter section of the communication device. If a NACK is received, a new basis is selected from a set of basis stored in a basis set unit (110). The new basis that is selected is then used by a linear transformation unit (106) in the retransmission of the information.

Abstract: Method and system for carrier recovery and estimation of Doppler shift from a signal source that is moving relative to a signal receiver. A pure carrier preamble for the received signal is processed through each of two stages of a linear predictor to obtain a successively more accurate estimation of a Doppler frequency offset for the carrier. The received signal is downconverted by each stage estimation of the Doppler frequency offset, and the downconverted signal is processed through a decision feedback phase locked loop to provide a signal in which substantially all of the Doppler offset and/or phase angle are identified and removed. The system has low complexity, is fast, and is accurate to within an estimated few tens of Hertz and will work with signals having relatively low signal-to-noise ratios. The invention is useful for receipt of signals from satellites in low earth orbits (LEOs) and other non-geosynchronous orbits, and wherever a transmitter and receiver are moving relative to each other.

Abstract: A method and apparatus for reducing the average number of iterations in an iterative decoding technique includes the step of at the end of each decoding iteration or sub-iteration estimating the transmitted bit sequence by processing the available information. A signature for the estimation is then generated of reach iteration or sub-iteration. If this signature is the first signature generated, the decoder proceeds to the next process. When there exists a signature generated for the previous decoding iteration or sub-iteration step, the new signature for the current iteration is compared with the signature (old signature) for this previous iteration. If the two signatures match, the decoding iteration stops. Otherwise, the decoding iteration process continues.

Abstract: A method for prioritizing protection in the symbol mapping of selected information includes the steps of supplying information bits and overhead bits. Interleaving the information bits and overhead bits to supply a plurality of interleaved data blocks. And selectively mapping the plurality of interleaved data blocks into a modulation symbol.

Abstract: A method for prioritizing protection in the symbol mapping of selected information includes the steps of supplying information bits and overhead bits. Interleaving the information bits and overhead bits to supply a plurality of interleaved data blocks. And selectively mapping the plurality of interleaved data blocks into a modulation symbol.

Abstract: A method and apparatus for processing modulation symbols for soft input decoders using an efficient method of calculating an accurate log-likelihood ratio without relying on approximations is described. In contrast to other techniques that calculate distance metrics based on the individual constellation points, the method of the invention analyzes distances based on different groupings of points, where a given group (e.g., one of the II+k or II−k sets) is defined by the same bit (1 or 0) in the same bit position. A recursive scheme is preferably used where previous computations are saved and used for subsequent computations or iterations and the decoupled processing of real and imaginary components associated with the I and Q components.