754 results about "Transmit diversity" patented technology

Communication is performed for a first communication device having a set of antenna elements. A quality-indication signal is received from a second communication device (e.g., a basestation). A complex weighting is calculated based on the quality-indication signal. A pre-transmission signal is modified based on the complex transmit diversity weighting to produce a set of modified-pre-transmission signals, wherein the modifications are symmetric by making approximately half the magnitude of the transmit diversity modification to one signal in a first direction, and approximately half the magnitude of the transmit diversity modification to the other signal in a second direction, opposite the first direction. Each modified pre-transmission signal from the set of modified-pre-transmission signals is uniquely associated with an antenna element from the set of antenna elements. The set of modified-pre-transmission signals is sent from the set of antenna elements to produce a transmitted signal.

A duplex polarization adaptive system is described. The system provides polarization diversity for base station antennas under both receive and transmitting conditions. Since the base station provides polarization diversity in both transmit and receive modes, no polarization diversity is needed in the handheld unit. Even though the handheld unit does not provide polarization diversity, a duplex communication system, that uses polarization diversity for both the uplink and the downlink is provided, because the base station provides polarization diversity for the uplink and the downlink paths. By installing the two-way diversity at the base station, the overall cost of implementing diversity is reduced because one base station can typically serve many handsets. The base station antenna determines the polarization state of signals received from a remote unit, such as a handheld unit, using a polarization diverse antenna system. The base station then transmits using the same polarization state. The system is compatible with time-division duplex systems.

Wireless communications for frequency-selective fading channels is realized by employing a system including orthogonal frequency division multiplexing (OFDM) in combination with an at least two antenna transmit diversity arrangement. Specifically, OFDM converts a multipath channel into a plurality of narrowband subchannels each having flat fading. Then, the signals on the same frequency subchannels of the at least two antennas are grouped together. Considering a first frequency subchannel, during a first OFDM time interval, a first signal and a second signal are transmitted on the first frequency subchannel from a first antenna (0) and from a second antenna (1), respectively. During a second OFDM time interval, a reverse sign (−) complex conjugate of the second signal and a complex conjugate of the first signal are transmitted from the first antenna and the second antenna, respectively. In a specific embodiment of the invention, reduced complexity in the implementation is realized by a reverse order complex conjugate and a reverse order, reverse sign (−) complex conjugate and judicious selection of the processed data signals in order to transmit the appropriate ones of the signals during the first and second OFDM intervals. Again, if the channel remains constant over the two OFDM intervals, diversity combination is realized for each frequency subchannel. In another embodiment of the invention, antenna-group hopping is employed in conjunction with pairing in time of the OFDM frequency subchannel signals to realize increased transmit diversity without rate loss.

A method of transmitting data in a wireless communication system comprises receiving feedback data on an uplink data channel, the feedback data comprising a precoding matrix indicator (PMI), wherein the value of the PMI corresponds to an index in a codebook, transmitting a precoding scheme for downlink data on a downlink control channel, wherein the preceding scheme is determined as one of at least two of a transmit diversity irrespective of the received PMI, an acknowledgement indicating preceding according to the received PMI and a new PMI indicating that it is used in precoding downlink data to be transmitted, and transmitting the downlink data on a downlink data channel after applying precoding according to the determined preceding scheme.

Disclosed is a method in a base station for providing a network access service to terminals. Where one of the terminals is selected as a source terminal and at least one of the other terminals is used as a relay node for relaying communication between the base station and the source terminal. Parameters for relay communication are initialized. A relay communication request message including that the parameters is transmitted. In response to the message, a terminal independently sets and performs the relay communication between the base station and the source terminal. Uplink signals are received from the source and relay terminals. The uplink signals received from the source and relay terminals are combined and decoded. A transmit diversity gain is obtained in uplink transmission of a terminal with a single antenna because relay nodes retransmit the source terminal's signal.

Methods and circuits for assigning pilot boosting factors and calculating traffic to pilot ratios in a wireless communication system. The data to be transmitted is first modulated to generate a plurality of data modulation symbols. The plurality of data modulation symbols and a plurality of reference signal symbols are mapped into transmission resources of each of a plurality of antennas in accordance with a transmit diversity scheme. The transmission resources of each of the antennas are divided into a plurality of subcarriers in a frequency domain and a plurality of time units in a time domain. Then, a power scaling factor are assigned for data modulation symbols on each of the antennas in dependence upon power levels of the reference signal symbols to maintain a fixed power level across the plurality of antennas in each time unit. Finally, the data modulation symbols and the reference signal symbols are transmitted via the plurality of antennas in accordance with the mapping scheme and the assigned scaling factors.

A method of achieving transmit diversity in a wireless communication system is disclosed. The method comprises encoding and modulating data stream based on feedback information, demultiplexing symbols to at least one encoder block, encoding the demultiplexed symbols by the at least one encoder block, transforming the encoded symbols by at least one inverse fast Fourier transform (IFFT) block, and selecting antennas for transmitting the symbols based on the feedback information.

A method for transmitting data via multiple antennas by modulating data to be transmitted into a plurality of modulated symbols, encoding each pair of modulated symbols from among said plurality of symbols in accordance with a transmission diversity scheme to result in a plurality of N by N matrices, with each N by N matrix corresponding to each pair of modulated symbols, generating a M by M code matrix comprised of the plurality of N by N matrices, orthogonally spreading the M by M code matrix to generate an output matrix, generating a plurality of row-permuted matrices by exchanging at least one pair of rows in the output matrix, and transmitting the symbols in the plurality of row-permuted matrices via a plurality of antennas by using either a space time transmission diversity scheme, a space frequency transmission diversity scheme, or a combination of a space time transmission diversity scheme and a space frequency transmission diversity scheme.

In a mobile communication system, receivers measure channel characteristics using a received reference channel signal. The receivers determine a weight which has orthogonality with respect to each of a preset number of weight vectors in the mobile communication system and has the highest signal-to-interference-and-noise ratio, and feedback the weight and the corresponding signal-to-interference-and-noise ratio to the transmitter. The transmitter interprets the feedback information output from the receivers and determines receivers having feedback information which are orthogonal to each other and have the maximum throughput as an addition capacity when transmitted simultaneously, and determines weights based on the feedback information of the receivers having the maximum throughput. By applying the determined weights to the antennas using a well-known beam forming scheme, data can be transmitted to each of the determined receivers. Therefore, the present invention can maximize the efficiency in transmission capacity even with a simple transmitting and receiving structure.

The technique of amplifier sharing is implemented in a system designed to accommodate transmit diversity. In one embodiment of the invention, the amplifiers are shared 1) to amplify a first and a second diversity-encoded signal, each of which represents the information a first signal that is to be transmitted using transmit diversity, and 2) to amplify a second signal to be transmitted without using transmit diversity. The first and second diversity-encoded signals are used to form a first and a second composite signal. Each composite signal is amplified in a different one of two power amplifiers. Each amplified composite signal is then used to form an amplified first diversity-encoded signal and an amplified second diversity-encoded signal. The first and second composite signals can also be formed using the second signal. Each composite signal is then amplified in a different one of the two power amplifiers and the two amplified composite signals are used to form an amplified second signal. In another embodiment of the invention, the first and second composite signals can be formed in the digital domain. Each composite signal is digitally pre-distorted and then modulated onto a transmission frequency signal, such as an RF signal. Each pre-distorted composite signal is then amplified in the respective amplifier.

A method of transmitting acknowledgement/nonacknowledgement (ACK/NACK) signals including multiplexing ACK/NACK signals; and repeatedly transmitting for predetermined times the multiplexed signal with each of repetitions of transmitting the multiplexed signal being spread in a frequency domain and being mapped to a plurality of discrete resource units each having a pair of neighboring subcarriers and a predetermined number of Orthogonal Frequency Division Multiplexing (OFDM) control symbols.

A method for transmitting Category 0 bits, including modulating the Category 0 bits; repeatedly transmitting the modulated Category 0 bits with each of repetitions of transmitting the modulated Category 0 bits being spread in a frequency domain and being mapped to a plurality of discrete resource units each having a pair of subcarriers and a predetermined number of OFDM control symbols; and mapping the modulated Category 0 bits by a frequency selective transmit diversity (FSTD).

A method and apparatus for providing hopped delay diversity for multiple antenna transmissions. In the method and apparatus, an input symbol stream is offset in time by M symbol periods to generate or offset symbol stream. The offset input stream may be offset so as to lead or lag the original input symbol stream. The original input symbol stream is then transmitted on a first set of N antennas and the offset input symbol stream is transmitted on a second set of N antennas, with transmit diversity techniques applied to the transmissions from the first and second set of N antennas.

Interference cancellation is performed in a CDMA receiver by projecting a received signal onto a subspace that is orthogonal to a signal selected for removal. An interference matrix or a combined interference vector is used to construct an interference-canceling projection operator. Confidence weights may be provided to components of the interference matrix or the interference vector based on estimation errors or relative strengths of interfering signals. Complexity reduction of the orthogonal projection operator may be achieved by providing for simplifying approximations that remove terms and operations. A linear transformation operator may be applied to the rows and/or columns of the interference matrix or the interference vector prior to construction of the orthogonal projection. Interference cancellation techniques may be configured for processing signals in a transmit-diversity system or a receive-diversity system using time and/or frequency-domain implementations and space and/or wave-number implementations of the transceiver.

A method and corresponding upgrade kit, for enhancing a base station (10) having a CDMA air interface and a passive antenna (12) with receive space diversity capability so as to provide the base station with transmit diversity capability. The method comprises attaching a radio frequency interface unit to an R.F. output of the base station to obtain a sample of a main R.F. signal, attaching a diversity unit (20) to the radio frequency interface unit to generate a transmit diversity signal, and connecting the diversity unit to the passive antenna to transmit the transmit diversity signal.

A method from transmitting data via multiple antennas. In this method, four information bits to be transmitted are multiplexed by using either one of a code division multiplexing scheme or a second code division multiplexing scheme combined with a real and imaginary multiplexing scheme, to generate a code division multiplexed symbol including four vectors. Then, the code division multiplexed symbol is repeatedly transmitted by alternatively applying two transmit diversity schemes via four transmission antennas.

Influencing the transmission of signals from a transmitting device to a receiving device in a communication system comprising at least one transmitting device and at least one receiving device is disclosed. In a receiving station received transmission signals are processed and a feedback signal to be transmitted to a transmitting device is generated on the basis of the processed signals. Then, transmit weights to be applied to transmission signals are determined in accordance with the feedback signal.

A wireless communication system includes a transmitter and a receiver. The transmitter includes multiple groups of transmit antennas. Input symbols are generated and then orthogonal space-time block is encoded to produce a data stream for each group of transmit antennas. Each data stream is adaptively linear space encoded to produce an encoded signal for each transmit antenna of each group according to feedback information for the group. The receiver includes a single receive antenna, a module for measuring a phase of a channel impulse response for each transmit antenna. The feedback information is determined independently for each group of transmit antennas from the channel impulse responses. The feedback information for each group of transmit antennas is sent to the transmitter.

Delay measurement and delay calibration methods and apparatus are described for use within distributed wireless base stations employing a remote radio head topology. The methods and apparatus are usable in any system that requires accurate delay measurement and/or constant delay through an electronic device. The methods and apparatus for measuring delay embody a highly accurate distributed delay measurement architecture that handles multiple delay paths within distributed wireless base stations employing a remote radio head topology. The method and apparatus are amenable to implementation with current integrated circuit technology. The methods and apparatus for calibrating electronic delay within distributed base stations employing a remote radio head topology are useful for implementing distributed wireless base stations where transmit diversity is desired. Using the methods disclosed herein, delay within a distributed wireless base station can be measured and calibrated to achieve very deterministic delay characteristics at the system level.

The present invention relates to a method of sending first and second signals to a plurality of user equipments, the method comprising the steps of providing of a dedicated channel for each one of the plurality of user equipments, providing of a code-multiplexed shared channel for the plurality of user equipments, assigning of an antenna of a set of antennas to each one of the user equipments, sending of one of the first signals to one of the plurality of user equipments on one of the dedicated channels on a carrier frequency by applying transmit diversity, sending of one of the second signals to one of the plurality of user equipments on the code-multiplexed shared channel on the carrier frequency by applying multi-user diversity.

A communication system's transmit configuration is reconfigured based on mobile station associated conditions such as the capability of the mobile receiver, carrier to interference or signal to noise ratios, and the degree of mobility associated with the mobile station. As a result, the transmit configuration is optimized for the conditions associated with a particular mobile receiver. In one embodiment, the transmit configuration may be selected to operate in configurations such as a single transmit antenna configuration, a space time spreading configuration, a selective transmit diversity, and a multi-output and multi-input configuration.

A mobile terminal reduces its power consumption by selectively switching between a diversity mode and a non-diversity mode. The mobile terminal monitors the total output power of two or more of its transmitters, and selectively switches between the diversity mode and the non-diversity mode based on the total output power. The mobile terminal may also selectively switch between the diversity and non-diversity modes based on a difference in output power levels between the two or more transmitters.

Methods and apparatus for providing channel diversity to wireless terminals (WTs) in a manner that reduces the latency between the time a WT encounters satisfactory channel conditions are described. A plurality of communications channels with different physical characteristics are maintained in a cell by a base station (BS). Each WT monitors multiple channels and maintains multiple channel estimates at the same time so that rapid switching between channels is possible. Channel quality information is conveyed from each WT to the BS. The WT or BS selects a channel based on the measured channel quality. By supporting multiple channels and by introducing periodic variations into the channels in various embodiments, the time before a WT encounters a channel with good or acceptable channel conditions is minimized even if the WT does not change location. Multiple antennas are used at the BS to support numerous channels simultaneously, e.g., by controlling antenna patterns.