Abstract: An apparatus for transmitting a signal in a communication system includes: MT number of transmission antennas; a space-time encoder for generating MT number of transmission symbol streams by space-time encoding MT number of modulation symbol streams in accordance with a space-time encoding scheme determined by a predetermined control, and transmitting each of the MT transmission symbol streams through a corresponding transmission antenna from among the MT transmission antennas; and a controller for determining the space-time encoding scheme based on an iteration number of transmission, which indicates the number of times by which an information data bit stream corresponding to the MT modulation symbol streams has been transmitted.

Abstract: An apparatus is provided for transmitting a signal in a communication system. Upon receipt of an information vector, the apparatus includes converting the information vector into a plurality of sub-information vectors; performing coding and modulation on each of the sub-information vectors according to a corresponding mode thereby generating a modulation symbol; interleaving the modulation symbol generated for each of the sub-information vectors; allocating power to the interleaved modulation symbol for each individual mode; and beamforming the modulation symbols power-allocated for each individual mode, and transmitting the beamforming symbols.

Abstract: A method is provided for ordering retransmissions in a Multi-Input Multi-Output (MIMO) system using N×M antennas. A transmitter splits a coded data stream into N sub-packets, and transmits the N sub-packets to a receiver via N transmission antennas. The receiver removes interferences of the N sub-packets received via M reception antennas, and independently decodes the interference-removed sub-packets. The receiver transmits an acknowledgement (ACK) or a negative acknowledgement (NACK) to the transmitter based on errors included in the decoded sub-packets. Upon receipt of the NACK, the transmitter retransmits to the receiver a sub-packet retransmission using ordering based on an Alamouti space-time coding scheme.

Abstract: Embodiments of methods and/or systems for reducing PAPR are disclosed.

Abstract: A signal scrambling method is provided for peak-to-average power ratio (PAPR) reduction of STBC MIMO-OFDM signals in a MIMO-OFDM system having Y transmit antenna. In general terms the OFDM sequence of symbols in said signal for each transmit antenna is divided into M sub-blocks of equal size and subclockwise rotation and inversions are performed across all transmit antennas to generate [2Y]M permuted sequence sets from the original OFDM sequence. Based on a predetermined criteria, there is then selected from the resulting sets of OFDM sequences the one with the best PAPR properties for transmission. The predetermined criteria preferably comprises identifying maximums for all [2Y]M sequence sets, by calculating the largest PAPR value of Y sequences in each set and selecting a set with the minimum maximum for transmission.

Abstract: A signal scrambling method based on combined symbol rotation and inversion (CSRI) for the peak-to-average power ratio (PAPR) reduction of OFDM signals. By dividing OFDM sequences into subblocks and performing symbol rotation and inversion in each subblock, high degrees of freedom are available to offset the possibility of encounting poor sequences with large PAPR. In order to reduce the complexity of this scheme, two suboptimal CSRI schemes are disclosed, one based on a successive approach combined with symbol grouping, and the other based on a random approach combined with threshold control.

Abstract: A phase noise mitigation method which mitigates phase noise for MIMO-OFDM. A criterion is provided which jointly optimizes both spectral efficiency and receiver performance by determining the best number of pilots.

Abstract: For a given decision order, MMSE successive interference cancellation (MMSE-SIC) can simultaneously maximize SIRs of all users. To further increase its efficiency, a power control (PC) algorithm, under equal BER criterion, is disclosed for uplink MC-CDMA. In frequency-selective Rayleigh fading channels, the MMSE-SIC integrated with the equal BER PC suppresses multiple access interference (MAI) effectively, resulting in a performance very close to the single user bound (SUB).

Abstract: Practical transmission power adaptation in multicarrier code division multiple access (MC-CDMA) communications is using either a frequency domain technique or a time domain technique or a combined frequency and time domain technique in response to channel variations. With frequency domain power adaptation, the transmission power is allocated over the N? (1?N??N) strongest subcarriers rather than over all possible N subcarriers, where the strongest subcarriers are understood to exhibit the highest channel gains. A substantially optimal N? can be chosen so that the average bit error rate (BER) is minimized. In the time domain power adaptation technique, transmission power is adapted so that the desired signal strength at the receiver output is maintained at a fixed level.

Abstract: Transmit power adaptation for DS/CDMA systems is disclosed for a CDMA system that utilizes a successive interference cancellation receiver on fading channels. The transmission power is adapted in response to channel variations to achieve an arbitrary power profile for received signal powers at the system base station. That is, the received signal powers are distributed with some factor xi's given as: SRi=SR(l)xi, (i=2,3, . . . , K and xl=1) where K is the number of users and SR(i) is the received signal power of the user having the ith strength, and wherein user strengths are ranked in the order of estimated channel gains. The factor xi gives a measure of the disparity between the received power levels. The channel is estimated at both the transmitter and receiver. In one embodiment, the factors, xi, for distributing the signal powers are selected such that the average BER for each user is minimized.

Abstract: Optimum usage of time diversity and significantly higher data rates are achieved by utilizing an adaptive Ultra-wideband impulse radio (UWB IR) transmission scheme based upon information about the channel state at a particular time instant. Through the use of channel state information, the transmission scheme is adjusted for the particular channel state. In particular, the system is adapted dynamically for each user by varying the number of pulses transmitted per bit in response to the channel state. The channel state is a dynamic parameter of the transmission system that is typically measured or estimated by the receiver. An adaptation element responds to the channel state information to determine a desired number of pulses per bit to be utilized in a transmission channel for subsequent UWB IR communication. This desired number of pulses per bit is then supplied to and used by an adaptive transmitter for subsequent transmission by a particular mobile station.

Abstract: Orthogonal frequency division multiplexing (OFDM) has been specified by IEEE 802.11a standard as the transmission technique for high-rate wireless local area networks (WLANs). Performance of an OFDM system, however, is heavily degraded by random Wiener phase noise, which causes both common phase error (CPE) and inter-carrier interference (ICI). A method and algorithm is disclosed for efficiently eliminating the effect of phase noise in OFDM based WLANs.

Abstract: This invention relates to a system and method utilizing a receiver architecture with a set of at least two antennae followed by a Rake demodulator at a mobile station for interference cancellation and diversity combining. Such a structure can work well only when the channel vector of desired signal is correctly estimated. The present invention makes use of the identifying spreading codes (as in IS-95 for example) to provide an adaptive channel vector estimate, to thereby cancel cochannel interference and improve the system capacity.