Abstract: Embodiments described herein include methods for improving the SINR, and therefore communication quality or rate, in the downlink of a cellular communication system. In an embodiment, the system is an orthogonal-frequency-division multiple-access (OFDMA) system. In an embodiment, a set of terminals is designated a coordinated-transmission group. The set of terminal is chosen such that the slot-allocations of the set are given special treatment to alleviate interference from other sectors or cells. All terminals within a coordination group generally use the same slot, but embodiments are not so limited.

Abstract: The disclosed embodiments relate to a centralized buffer architecture for an Orthogonal Frequency Division Multiplexing (OFDM) receiver. In this architecture, a central buffer is shared by the main functional blocks or modules of the OFDM receiver. A state machine enables access to the buffer by the functional blocks to maintain buffer coherency.

Abstract: An arrangement is disclosed where in a multi-carrier communication system, the modulation scheme, coding attributes, training pilots, and signal power may be adjusted to adapt to channel conditions in order to maximize the overall system capacity and spectral efficiency without wasting radio resources or compromising error probability performance.

Abstract: Techniques and apparatus for identifying the target mobile stations for data transmission in a wireless communication network. Techniques and apparatus can include generating a first N-symbol bi-orthogonal sequence from Walsh functions based on a first portion of a MACIndex and generating a complex preamble signal based on a second portion of the MACIndex. Generating the complex preamble signal can include applying the first N-symbol bi-orthogonal sequence between an In-phase branch and a Quadrature branch channel of a complex signal, which can include switching between the In-phase and Quadrature branch channels based on the second portion of the MACIndex to communicate information.

Abstract: The present invention provides apparatus and methods for carrier frequency offset and phase compensation, which can compensate the phase rotation of an OFDM symbol resulted from carrier frequency offset between the receiver and transmitter of an OFDM System. The apparatus and method for carrier frequency offset compensation generates an estimated carrier frequency offset according to a phase error between estimated frequency responses of two consecutive received OFDM symbols within the pilot subchannel, and calculates an accumulated phase rotation, according to the estimated carrier frequency offset, for compensating the received OFDM symbol.

Abstract: The present invention relates to a method for gaining channel quality information at a base station of a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers. According to the present invention, the method comprises the steps of: measuring a Channel Frequency Response at a user terminal of said multi-carrier radio communication channel; extracting samples of said Channel Frequency Response represented in the frequency domain at a predefined oversampling factor; sending said samples on a signaling channel from said user terminal to said base station; performing a windowing operation on the received samples in the time domain; determining a channel quality information for each of said sub-carriers on a representation in the frequency domain of said received samples after windowing operation.

Abstract: A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system is provided. In one embodiment, a system includes: a host unit including a demodulator that simultaneously demodulates upstream information modulated on a plurality of tones within an OFDM waveform, and a plurality of remote units for transmission of upstream information, each remote unit including a modem, the remote units modulating a plurality of tones with upstream information so that when received at the host unit the tones are orthogonal within the OFDM waveform.

Abstract: An OFDM receiver includes a timing error detection unit that determines error information based on a difference between receiving timing of a desired signal from a counterpart transmitter and receiving timing of an undesired signal from a non-counterpart transmitter. The timing error detection unit includes a pilot signal detection unit configured to detect a pilot signal of the desired signal and a pilot signal of the undesired signal from an FFT-processed received signal; a first converting unit configured to convert a frequency-domain channel estimate derived from the pilot signal of the desired signal to a first time-domain channel impulse response; a second converting unit configured to convert a frequency-domain channel estimate derived from the pilot signal of the undesired signal to a second time-domain channel impulse response; and an error information determination unit configured to determine the error information based on the first and second channel impulse responses.

Abstract: A modem unit inputs a combination, of control signal and data signal, which is to use a plurality of subcarriers. Among a plurality of combinations inputted, the modem unit performs interleaving with a size defined by the first number of subcarriers on a control signal and performs interleaving with the size defined by the second number of subcarriers on a data signal. The modem unit appends additional signals to control signals contained in the second and the subsequent combinations in a plurality of combinations interleaved. The modem unit appends additional signals whose number of subcarriers is equal to the difference between the first number of subcarriers and the second number of subcarriers.

Abstract: A phase mismatch compensation system includes a first summer that has a first input that communicates with a first phase of a received signal and an output. A second summer has a first input that communicates with a second phase of the received signal and an output, wherein the second phase is offset from the first phase. A first filter selectively filters the output of the first summer. An adaptive control module determines a predicted shift between the first and second phases of the received signal based on an output of the first filter and an actual shift between the first and second phases of the received signal. A correction module communicates with an output of the adaptive control module and the first phase and second phase of the received signal. The correction module outputs a mismatch correction to second inputs of the first and second summers respectively.

Abstract: A transmitter determines a number of available bits (Navbits) in a minimum number of orthogonal frequency division multiplex (OFDM) symbols in which a data field of a packet may fit, by Navbits=(NCBPS*(1+USTBC))*ceil(Npld/(NCBPS*R*(1+USTBC))), where USTBC equals 1 when Space-Time Block Code (STBC) is used and 0 otherwise, where Npld=LENGTH*8+16, where NCBPS is the number of coded bits per symbol, where R is the code rate, and where LENGTH is a number of bytes in a Physical Layer Convergence Protocol (PLCP) PLCP Service Data Unit (PSDU); and determines an integer number of Low-Density Parity-Check Code (LDPCC) codewords to be transmitted, NCW, and the length of the codewords to be used, LLDPC, from information capable of being expressed in a table format.

Abstract: The present invention provides a wireless terminal apparatus, including a reception unit for receiving a multi-carrier signal generated by applying an N-point (where N is a natural number) inverse fast Fourier transform (IFFT) to a plurality of sub-carriers to which transmission information for a plurality of wireless terminal apparatuses is allocated; a fast Fourier transform unit for extracting a plurality of the sub-carriers from the multi-carrier signal; a thin-out unit, being placed at the front stage of the fast Fourier transform unit, capable of changing, from the N points, a sampling number of the multi-carrier signals which are digitalized; and a judgment unit for discerning, based on sub-carrier allocation information accompanying the multi-carrier signal, whether or not the sub-carrier of another wireless terminal apparatus overlaps with that of the wireless terminal apparatus itself in the case of changing the sampling number from the N points, and determining a sampling number for the thin-out un

Abstract: Disclosed is a coded orthogonal frequency-division multiplexing (OFDM) system and method for reducing a peak-to-average power ratio (PAPR). The system and method include a modulator configured to modulate (e.g., using quadrature amplitude modulation (QAM)) coded bits into symbols. The system and method also include an inverse discrete fourier transform (IDFT) module to perform an IDFT on the symbols to produce an OFDM signal. The system and method measure the PAPR of the OFDM signal and transmit the signal to a receiver if the PAPR of the signal is less than a threshold PAPR.

Abstract: A system and method for dynamically varying traffic channel sectorization within a spread spectrum communication system is disclosed herein. In a preferred implementation the system is operative to convey information to at least one specified user in a spread spectrum communication system and includes multiple antennas, each having an associated coverage area, and each coupled to an antenna driver. The antenna drivers each include a delay element and an input summation node. A switching transmission network is disposed to selectively transmit via antennas. Selective transmission of signals results in variation in size of a given user sector. In another aspect, the system may be configured to selectively receive, and coherently combine, signals from different coverage areas.

Abstract: A method and apparatus for modulating an input signal comprised of an ordered series of samples separated by a substantially constant period T comprising the steps of providing a carrier signal, the carrier signal comprised of a series of samples separated by a substantially constant period T, wherein one of the carrier samples corresponds to each of the input signal samples, selecting a plurality of N successive samples from the series of input signal samples, the series of samples having an input order, for each of the N selected samples in parallel, multiplying the selected sample by the corresponding carrier sample and recombining the N multiplied samples while maintaining the input order.

Abstract: A system, an apparatus and a method for transmitting/receiving data coded by a low density parity check matrix code are provided. The apparatus for transmitting data coded by a low density parity check code includes: a low density parity check encoder for encoding input data based on the low density parity check code; and a bit puncturer for puncturing columns in an order of columns which least degrade a performance caused by puncturing in the low density check code according to a code rate of an output data. Accordingly, the low density parity check code having superior performance can be implemented to the next generation mobile communication system supporting various code rates.

Abstract: A technique for an equalizer filter with dynamically configurable convolution filter is described. The input to a transmitter chain is modified by an equalizer filter, prior to being applied to the transmitter. The equalizer filter modifies and smoothen the amplitude of the signal. The modified and smoothen signal has its peaks reduced which results in lower Crest Factor. The input to the reconditioning equalizer filter could be a baseband, an intermediate frequency (IF) or radio frequency (RF) signal. In the case of an IF or RF signal, it needs to be down converted to baseband before applied to the equalizer filter.

Abstract: A receiving method receiving an OFDM signal including a first OFDM symbol having first and second pilot signals allocated to first and second subcarriers positioned symmetric on the frequency axis, and a second OFDM symbol having third and fourth pilot signals allocated to the first and the second subcarriers, a difference between a product of the first pilot signal and a complex conjugate of the fourth pilot signal and a product of the third pilot signal and a complex conjugate of the second pilot signal being non-zero, estimating a first coefficient representing a change components of an amplitude and a phase, and a second coefficient representing an interference component, using first and second received pilot signals corresponding to the first and third pilot signals, estimating from the first and second coefficients IQ imbalance, and compensating the influence of amplitude and phase errors in accordance with the IQ imbalance.

Abstract: A technique for an equalizer filter with dynamically configurable code domain filter is described. The input to a transmitter chain is modified by an equalizer filter with dynamically configurable code domain filter, prior to being applied to the transmitter. The equalizer filter with dynamically configurable code domain filter modifies and smoothen the amplitude of the signal. The modified and smoothen signal has its peaks reduced which results in lower Crest Factor with negligible degradation of Error Vector Magnitude of individual codes. The input to the equalizer filter with dynamically configurable code domain filter could be a baseband, an intermediate frequency (IF) or radio frequency (RF) signal. When the signal is an IF or RF signals it needs to be down converted to baseband before applied to the equalizer filter.

Abstract: Apparatus and systems comprise a forward error correction (FEC) encoder to encode a data block to produce an encoded data block in a radio link control media access control (RLC-MAC) module. The EFC encoder may be coupled to a punctured subset selector to select a punctured subset of the encoded data block for transmission across a communication link. The punctured subset selector may be coupled to a modulator to modulate the punctured subset of the encoded data block using a selectable modulation type selected by a modulation selector coupled to the modulator. Hybrid automatic repeat request (HARQ) logic may be coupled to the modulation selector to receive at least one of an acknowledgement (ACK) or a no-acknowledgement (NACK) that a previously-transmitted punctured subset of the encoded data block was successfully decoded at a receiving end of the communication link. Additional apparatus, systems, and methods are disclosed.

Abstract: The present invention relates to a method and a device for data extraction from a data stream containing at least one data packet. First, comparing a bit stream derived from a received digital data stream with an expected bit sequence is performed by packet detector to determine a correlation value (CorrVal) for detecting a data packet. Then, a data extraction unit is started for data extraction when the correlation value (CorrVal) exceeds a threshold value (CorrThres) indicating that a data packet has been detected. Therefore, comparing the received bit stream with the expected bit sequence to determine a new correlation value (CorrVal) is continued by the packet detector. Finally, restarting data extraction is initiated by a sync-control module when the new correlation value (CorrVal) exceeds the form correlation value (MaxCorrVal).

Abstract: A signal processor includes an in-phase and quadrature (I/Q) detection module that generates I/Q components based on baseband signals. An analog to digital converter converts the I/Q components to digital I/Q components. An I/Q imbalance compensation module generates compensated I/Q components based on the digital I/Q components and maximum likelihood estimates of gain imbalance and phase imbalance. A frequency converting module converts the compensated I/Q components to first subcarrier signals. A channel estimating module generates initial channel estimates based on second subcarrier signals. The second subcarrier signals are based on the first subcarrier signals. A phase error and I/Q imbalance module generates the maximum likelihood estimates of the gain imbalance and the phase imbalance based on the initial channel estimates and the second subcarrier signals.

Abstract: A transmitting method of OFDM signal includes allocating first and second channel estimation preamble signals for channel response estimation respectively to +kth and ?kth subcarriers from center frequency of first OFDM signal, allocating first and second pilot signals for residual phase offset estimation respectively to +kth and ?kth subcarriers from center frequency of second OFDM signal, transmitting first and second OFDM signals respectively in different time zones using at least one antenna, where, first product of complex conjugate of first channel estimation preamble signal and second pilot signal is equal to second product of second channel estimation preamble signal and complex conjugate of first pilot signal.

Abstract: Angle estimation for modulated signal. A novel compensation technique is presented by which angle estimation may be performed for a modulated signal. More specifically, the angle between a constellation corresponding to a received signal and a constellation corresponding to a received signal may be very efficiently estimated using any one of the possible embodiments corresponding to various aspects of the invention. After this angle has been estimated, the received signal or the expected constellation may be rotated (or de-rotated) to compensate for this angular difference. In doing so, better estimates of the information bits that are demodulated and decoded from the received signal may be made.

Abstract: Apparatus, and an associated method, for recovering the informational content of data in an MIMO-OFDM communication system. Different data sets are communicated upon different subcarriers to a receiving station. Apparatus at the receiving station performs data value estimations based upon the communication conditions on the different subcarriers upon which the data is communicated. Separate path length estimations are performed upon the data communicated upon the different subcarriers, at complexity levels responsive to the communication conditions of the subcarriers.

Abstract: A method is provided for receiving a received signal corresponding to a multicarrier signal transmitted by at least one transmitter via a transmission channel. The multicarrier signal is formed by a temporal succession of symbols consisting of a set of data elements including informative data elements with real values, and pilots for at least some of the symbols. Due to groups of at least two pilots being respectively located in an adjacent region in the time/frequency space, the reception method includes a step of extracting at least two complex values corresponding the pilots of the group of the adjacent region, once they have passed through the transmission channel, and a step of estimating the transmission channel in the adjacent region on the basis of the complex values. The modulation used is the type of OFDM OQAM.

Abstract: An IS-OFDM system for point-to-point wireless communications that suppresses narrow-band interference comprises an IS-OFDM transmitter and an IS-OFDM receiver, wherein a transmitted signal comprises a plurality of subcarriers, and further wherein each subcarrier contains more than one and potentially all symbols transmitted in a given frame. The IS-OFDM transmitted signal is at a data rate that is equal to the data rate of the input data stream via the use of P/S converters.

Abstract: Method and apparatus for peak-to-amplitude ratio reduction are described. A data carrying signal waveform with sub-carrier signals (S1-1 through S1-M) is obtained. An initial peak reduction waveform (S2(m)) is obtained by selection of a portion of the sub-carrier signals (S1-1 through S1-M) for non-data carrying. The initial peak reduction waveform (S2(m)) is refined by at least one recursive iteration which combines the initial peak reduction waveform (S2(m)) with a circularly time-shifted version thereof to obtain a resultant peak reduction waveform having a peak side lobe amplitude less than that of the initial peak reduction waveform (S2(m)).

Abstract: There is provided a multi sub-carrier communication system for providing improved performance of a frequency equalizer and a method thereof. The multi sub-carrier communication system includes a frequency equalization coefficient (vector) calculation unit that receives an equalized signal outputted from a frequency equalizer and periodically calculates a new frequency equalizer coefficient (vector) which is used to update the frequency equalizer coefficient (vector) used by the frequency equalizer. The multi sub-carrier communication system periodically updates the frequency equalization coefficient (vector) (after an initialization interval for initially estimating a channel characteristic) by periodically calculating the frequency equalization coefficient (vector) during a data receiving interval and thus, it is possible to dynamically adapt to changes of the channel characteristic over the passage of time, thereby improving performance of the frequency equalizer.

Abstract: A transceiver in an N×N MIMO (Multiple-In-Multiple-Out) system includes a mode selection module to select a spatial multiplexing rate and a coding module to space frequency code OFDM (Orthogonal Frequency Division Multiplexing) symbols in response to the selected spatial multiplexing rate. The coding module maps data symbols to the transmit antennas for all data tones in the OFDM symbol. The tones may be mapped using different mapping permutations, which may be applied to the tones in a cyclical manner.

Abstract: Systems and methods are presented for transmitting additional data over preexisting differential COFDM signals by modulating existing data carriers with a phase and an amplitude offset. In exemplary embodiments of the present invention, additional data capacity can be achieved for an COFDM signal which is completely backwards compatible with existing satellite broadcast communications systems. In exemplary embodiments of the present invention additional information can be overlayed on an existing signal as a combination of amplitude and phase offset from the original QPSK symbols, applied for each information bit of the overlay data. With two additional levels of modulation, a receiver can demodulate the information from each of the previous stages and combine the information into a suitable format for soft decoding. The first stage of demodulation will be recovery of overlay data from the amplitude modulated D8PSK.

Abstract: A coarse estimate of a location of an information carrying part of a symbol in a received signal in a telecommunication system is generated. This involves generating correlation values by correlating the received signal with a delayed received signal. A maximum correlation value of the correlation values is identified, and a duration in time during which the correlation values are greater than or equal to a predetermined percentage of the maximum correlation value is identified, wherein the duration in time begins at a first moment in time and ends at a second moment in time. The coarse estimate of the location of the peak correlation value is set equal to a moment in time between the first moment in time and the second moment in time, for example, a midpoint between the first moment in time and the second moment in time.

Abstract: A modified preamble is used by extended devices that operate at higher rates, MIMO or other extensions relative to strict 802.11a-compliant devices. The extended devices might use multiple antenna techniques (MIMO), where multiple data streams are multiplexed spatially and/or multi-channel techniques, where an extended transmitter transmits using more than one 802.11a channel at a time. Such extensions to IEEE 802.11a can exist in extended devices. The modified preamble is usable for signaling, to legacy devices as well as extended devices, to indicate capabilities and to cause legacy devices or extended devices to defer to other devices such that the common communication channel is not subject to unnecessary interference. The modified preamble is also usable for obtaining MIMO channel estimates and/or multi-channel estimates.

Abstract: A time division duplex (TDD) user equipment (UE) is configured to synchronize to a TDD base station. The UE includes a receiver configured to receive a primary synchronization code along with a plurality of secondary synchronization codes from a TDD base station. The TDD base station is associated with having a code group out of N code groups. The plurality of secondary synchronization codes number less than (log2N)+1 and are quadrature phase shift keying modulated. The UE also includes a corresponding matched filter to each of the received secondary synchronization codes. The UE is configured to identify the code group of the TDD base station by the received plurality of secondary synchronization.

Abstract: Systems and methods are disclosed for providing reverse signals from a plurality of DHCTs to a downstream modulator that is located in the headend facility. The present invention includes a single wire return device (SWRD) that receives RF modulated signals, dynamically determines the address of the associated modulator, and converts the signals into Ethernet signals. The Ethernet signals are subsequently provided to the headend facility via fiber cable.

Abstract: A method and associated system for processing a plurality of replicas of a signal in a signal processing chain, the method includes receiving each of the plurality of replicas of the signal at one of a corresponding plurality of respective antenna elements and orthogonally multiplexing the replicas of the signal on to a single processing chain. The multiplexed replicas are down converted from RF to baseband and converted from an analog to a digital multiplexed signal. The digital multiplexed replicas are then demultiplexed into a plurality of separate signals that correspond to replicas of the signal received at respective ones of the plurality of antennas. In variations, the orthogonal multiplexing includes frequency spreading the replicas of the signal on the single processing chain in accordance with complex Walsh codes. In other variations, the signal replicas are offset in phase by 90 degrees and time multiplexed on the single processing chain.

Abstract: Provided is a method for reducing a PAPR (Peak-to-Average Power Ratio) of a transmit signal in a broadband wireless communication. The method includes the steps of: assigning information signals to remaining tones except L reserved tones that are previously appointed among N tones, and performing an IFFT operation on the tones; detecting peaks that are greater than a predefined reference value from the IFFT-ed signal; generating signals for removing the detected peaks using P-waveform having impulse characteristic, the P-waveform being produced using the L reserved tones; generating a clipping signal by accumulating the signals; and simultaneously removing the peaks by adding the IFFT-ed signal and the clipping signal.

Abstract: A system and method for time diversity uses interleaving. To simplify the operation at both transmitters and receivers, a formula can be used to determine the mapping from slot to interlace at a given OFDM symbol time.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) demodulator, an integrated circuit for OFDM demodulation and an OFDM demodulation method in which at least one of a predictive value generated by a low order symbol filter and a predictive value generated by a high order symbol filter interpolates the order of a high symbol direction, or a weighted composite value of the predictive values, is selected to accomplish waveform equivalence of a carrier outputted from a transform section.

Abstract: An apparatus and a method for estimating a carrier to interference and noise ratio (CINR) in a communication system. The CINR value is precisely estimated by removing the error floor value, which is caused by the inaccurate sliding average window SAW channel estimation value, from the CINR estimation value. Since the CINR value is precisely estimated, performance of the adaptive power control or the adaptive modulation and coding device is improved.

Abstract: Method, apparatus, and data packet format to implement transmit diversity in a multicarrier environment is disclosed. For diversity transmission operations, space frequency encoding techniques are employed creating distinguishable first and second time domain signals from a multicarrier frequency domain symbol bearing data of interest, which are then broadcast in parallel over first and second transmission units respectively. For diversity reception operations, complementary space frequency decoding is used to recover a corrected multicarrier frequency domain symbol from a time domain signal containing either this symbol, a space frequency modified symbol based on the multicarrier symbol, or a possible partial/complete combination of both. The data packet format includes portions defining a transmission diversity semaphore, a preamble enabling training of a receiver receiving the data packet, and a payload.

Abstract: For determining FFT and GI (guard interval) modes within a receiver, a correlation signal is generated from an in-phase and quadrature (I/Q) stream. An plurality of GI mode division signals are generated by processing the correlation signal delayed by different delays. For each of the GI mode division signals, a respective peak-value position and a respective peak-value is determined to be used for determining the GI and FFT modes of the I/Q stream. The correlation calculator generates the correlation signal dependent on the FFT mode to minimize memory capacity and cost of the receiver.

Abstract: There is provided a method, system and receiver for receiving data over a communication link. An energy of said signal in respect of an estimated guard interval position of said signal is defined. Based on said energy, a position for a time domain to a FFT window is selected. Trial positions can be formed in accordance with a predetermined schemes. The selected position can be selected from the trial positions in such a way that smallest amount of inter symbol interference is formed.

Abstract: Systems and methodologies are described that facilitate transmitting and receiving signals over I and Q branches of a communication channel to mitigate potential I/Q imbalance. In particular, a device can transmit a signal over the I and Q branches to distribute transmission power substantially evenly for a given channel. The device can demodulate the data with a code or matrix having real and complex modifiers resulting in an I and Q branch signal for transmission. Where the channel has multiple resources, the device can alternate or transmit over the I branch in one resource and the Q branch in another resource for a given signal to distribute power. Also, the device can apply a complex scrambling code to distribute a signal over both the I and Q branches. The device can also use QPSK or higher order modulation to send the signals meant for the same user.

Abstract: The present invention provides a method, a mobile terminal device and a system for determining a transmission power factor. During an uplink of data between a mobile terminal device and a base station via a code division multiple access (CDMA) system supported by automatic repeat request (ARQ) first transmission containing original data and re-transmissions of different order containing supplementary information are communicated. The i-th re-transmissions are based on the automatic repeat request (ARQ). The transmission power factor to be determined is operable with an i-th re-transmission. A first and a second error quantity are obtained from an evaluation of status information items received in accordance with the automatic repeat request (ARQ). The first error quantity and the second error quantity allow for deriving an i-th error ratio so as to calculate a transmission power correction factor.

Abstract: An OFDM demodulator that demodulates an OFDM signal includes an antenna that receives a signal including delayed signals, an estimation circuit that estimates the channel response of the received signal, and a control circuit that controls a length of a retention time interval based on the estimated channel response. The retention time interval includes a time period from the head of a delayed signal having a maximum delay time in the delayed signals to the tail of a preceding signal in the delayed signals based on the estimated channel response. The OFDM demodulator also includes a retention memory that retains a portion of the received signal corresponding to the retention time period, and a selection circuit that selects an OFDM symbol based on a calculation of a maximum likelihood that the retained received signal is equivalent to a signal replica based on the channel response.

Abstract: Using a network in which one master station modem 105 and multiple slave station modem 106, 107, 108 are physically connected by rudder connection or bus connection with a telecommunication line 121, the measurement result of the S/N ratio between the master station and slave stations is once collected in the master station at the initialization stage, pairs of the modulation method, by which all modems can demodulate at high probability, and transmission voltage are calculated based on this data, and the calculation is transmitted to all slave stations; and at a normal transmission stage, information regarding the coordination and control of the network is transmitted in accordance with this setting. Thus, one-to-multi communication is realized, guaranteeing an access right.

Abstract: A communication device converts a bit stream to multiple symbols and provides encryption at a physical layer by shifting a phase of each symbol of the multiple symbols to produce multiple encrypted symbols. Each encrypted symbol of the multiple encrypted symbols is modulated with an orthogonal subcarrier to produce at least one modulated subcarrier and the at least one modulated subcarrier is then transmitted via a wireless link. On a receive side, a receiving communication device receives the transmitted, encrypted symbols and provides decryption at a physical layer by shifting a phase of each encrypted symbol in correspondence with the phase used to encrypt the symbol at the transmit side.

Abstract: Improved techniques for estimating a channel (e.g., channel impulse response) in the time domain are disclosed. The improved techniques can be used to estimate time-domain channel taps in a digital communication system. An improved training sequence enables time-domain estimation and eliminates the need for correct frequency-domain channel estimation at every frequency. By utilizing the improved training sequence, the estimation of each of the time-domain channel taps can be decoupled from each other. This enables a channel estimate to be performed with not only a higher convergence speed but also lower complexity.

Abstract: For subband-based OFDM demodulation, a “partial” Fourier transform is performed on a sequence of N input samples for an OFDM symbol to obtain Nc received symbols for a group of Nc data subbands, where Nc·L=N and L>1. For the partial Fourier transform, the N input samples are rotated with a phasor to obtain N rotated input samples, which are accumulated (for each set of L samples) to obtain Nc time-domain values. An Nc-point FFT is performed on the Nc time-domain values to obtain the Nc received symbols. Channel gain estimates for the data subbands are also obtained, for example, by performing a partial Fourier transform to obtain received pilot symbols, an inverse FFT to obtain time-domain channel gain values, and an FFT to obtain channel gain estimates for the data subbands. The received symbols are processed with (e.g., equalized by) the channel gain estimates to obtain recovered data symbols.