Abstract: Techniques to process data for transmission over multiple transmission channels. The available transmission channels are segregated into one or more groups, and the channels in each group are selected for use for data transmission. Data for each group is coded and modulated based on a particular coding and modulation scheme to provide modulation symbols, and the modulation symbols for each selected channel are weighted based on an assigned weight. The weighting “inverts” the selected channels such that they achieve similar received SNRs. With selective channel inversion, only “good” channels in each group having SNRs at or above a particular threshold are selected, “bad” channels are not used, and the total available transmit power for the group is distributed across the good channels in the group. Improved performance is achieved by using only good channels in each group and matching each selected channel's received SNR to the required SNR.

Abstract: A transmission apparatus used in a radio communication system adopting the OFDM scheme is disclosed. The transmission apparatus includes: a dividing inverse Fourier transform part including plural transform parts, wherein the dividing inverse Fourier transform part divides a signal to be transmitted into plural signals, and each of the plural transform parts performs inverse Fourier transform on one of the plural signals; a peak control part for outputting a peak control signal based on peaks that are detected from output signals of the dividing inverse Fourier transform part; and a peak reducing process part for adjusting a weight or an arranging order of an output signal of the dividing inverse Fourier transform part according to the peak control signal to output an adjusted signal, and synthesizing the adjusted signal with other signal so as to output a synthesized signal.

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: A method for fine timing synchronization is provided. The method comprises: detecting an end point of the short preamble; delivering the samples after the end point to a matched filter to generate a plurality of correlation peaks; searching the correlation peaks generated from the samples of the first LTS for a first maximal peak point which is the correlation peak with a first maximal intensity, and obtaining the first time index of the first maximal peak point; searching the correlation peaks generated from the samples of the first LTS for a pre-peak point which is the correlation peak forming a peak intensity appearing before and nearest to the first maximal peak point, and obtaining the second time index of the pre-peak point; estimating a third time index of the start point of the second LTS according to the first and second time indexes.

Abstract: Transmission waveforms are synthesized from orthogonal subcarriers using appropriate combinations of complex sub-carrier codes. This allows conventional single-carrier signaling (such as GSM and CDMA transmission protocols) to be generated and received using a multicarrier platform that is similar to OFDM. Carrier interferometry provides unprecedented bandwidth efficiency and enables substantial improvements in interference rejection, power efficiency, and system versatility.

Abstract: A physical layer (PHY) module includes NT radio frequency (RF) channels and a mapping module. The NT RF channels each include N subcarriers. The mapping module includes Ns inputs receiving corresponding ones of NS data streams. The mapping module further includes NT outputs communicating with corresponding ones of the NT RF channels. Each of the NT outputs includes N outputs. The mapping module further includes a mapping matrix that maps the NS data streams to the NT outputs. NT, NS, and N are integers greater than or equal to 2. The NT RF channels include NT gain modules that apply NT different complex gains to the NT outputs, respectively. One of the NT different complex gains is applied to each of the N outputs of a corresponding one of the NT outputs. The NT different complex gains correspond to NT transmit antennas of the NT RF channels, respectively.

Abstract: A communication device for receiving and transmitting OFDM signals in a wireless communication system, in which each OFDM signal is composed of a plurality of subcarrier signals each being assigned to a respective transmission channel of a communication system, comprising a diversity antenna; an examination unit for examining, individually for each antenna element, at least one subcarrier signal of an OFDM reception signal received by a respective antenna element and for gaining, from the result of such subcarrier signal examination, attenuation information on attenuation properties of at least some of the transmission channels associated to the respective antenna element; and an amplitude adjustment unit adapted for adjusting, individually for each antenna element, the amplitude of at least one subcarrier signal of an OFDM transmission signal to be transmitted from a respective antenna element in accordance with attenuation information.

Abstract: An information processing apparatus and a communication apparatus for accurately recognizing at the base station the current receiving quality of the mobile terminals for improving the throughput of the base station. A mobile terminal determines its own receiving quality based on the signal received from the base station for generating the receiving quality message indicating the receiving quality and generates the power control information requesting the transmission power of the base station. The receiving quality message is transmitted at a frame rate and power control information is transmitted at the slot rate to the base station. Based on both the receiving quality message and power control information, the base station estimates the current receiving quality of the mobile terminal and adaptive modulation and coding is performed based on the estimated value.

Abstract: A wireless communication system includes first and second wireless terminals capable of performing transmission by at least one of a first transmission scheme and a second transmission scheme. The first wireless terminal performs transmission of a first frame to the second wireless terminal by using the second transmission scheme. The second wireless terminal communicates with the first wireless terminal to notify the first wireless terminal of information associated with a status of the reception of the first frame transmitted from the first wireless terminal by using the first transmission scheme.

Abstract: Systems and methods for an orthogonal frequency division multiplexing multipoint-to-point communications system are provided. In one embodiment, a method comprises establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration; transmitting up to a plurality of tones from the first remote unit, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing; modulating the up to a plurality of tones using a first modulation scheme when transmitting a first type of upstream information; and modulating the up to a plurality of tones using a second modulation scheme when transmitting a second type of upstream information.

Abstract: When data is transmitted on a burst basis, a symbol having a higher modulation level is inserted into parts of a burst on a symbol basis and this burst is transmitted. When the data including this burst is received on a burst basis, it is determined which symbol positions are inserted by the symbols having the higher modulation level and which symbol positions are inserted by the other symbols. This method allows increasing a communication capacity while retaining the reliability of the communication.

Abstract: A network troubleshooting framework is described. In an implementation, a method includes generating a first estimation of network performance by a simulator based on network settings obtained from a network, estimating the new performance under an alternative setting by providing the alternative setting to the network simulation and observing the simulation output, repeating the procedure for other alternative settings, and suggesting the alternative setting that improves network performance.

Abstract: The subject invention relates to a method and apparatus for multiplication of numbers. In a specific embodiment, the subject invention can be used to perform sequential multiplication. The subject invention also pertains to a method and apparatus for modular reduction processing of a number or product of two numbers. In a specific embodiment, sequential multiplication can be incorporated to perform modular reduction processing. The subject method and apparatus can also be utilized for modular exponentiation of large numbers. In a specific embodiment, numbers larger than or equal to 2128 or even higher can be exponentiated. For example, the subject invention can be used for exponentiation of number as large as 21024, 22048, 24096, or even larger.

Abstract: An enhanced 8-VSB reception system and E8-VSB data demultiplexing method, by which an E8-VSB signal can be stably received as well as a previous ATSC 8VSB signal, is disclosed. Herein, the enhanced data are coded at ½ code rate and ¼ code rate in the new E8-VSB transmission system compatible with the conventional ATSC 8VSB system, respectively. The ½ and ¼ enhanced data are multiplexed by 164-byte packet unit according to the previously determined multiplexing format and further pre-processed to output as the format of the MPEG transport packet. And, the pre-processed enhanced data and the main data are multiplexed again by 188-byte packet unit according to the previously determined multiplexing format. The E8-VSB map information, which was inserted in the field sync section in the E8-VSB transmission system to be transmitted, is extracted to generate the information indicating the attributes of the respective E8-VSB data.

Abstract: A high-speed communications system utilizes approximate bit-loading during data transmission in a channel. In one embodiment, a plurality of parallel data preparation circuits in a data transmission circuit receive respective subsets of a data stream, each of the respective subsets of the data stream having a data rate that is less than a data rate of the data stream. Converters in the data preparation circuits convert the respective subsets of the data stream into respective analog signals. Multipliers in the data preparation circuits multiply the respective analog signals by respective vectors to produce respective sub-channel signals. At least a frequency band in the spectrum corresponding to one of the respective sub-channel signals partially overlaps at least a frequency band for at least one other of the respective sub-channel signals. The respective sub-channel signals are combined prior to transmission.

Abstract: Methods and devices of the invention relate to sending information over a wireless communications channel using an adaptive frame structure (AFS) having unequal error protection. Unequal error protection relates to a first data region of the frame being modulated with a first modulation and coding scheme (MCS) and a second data region of the frame being modulated with a different MCS typically with a higher modulation order. The first data region, modulated with a lower order MCS, may include critical data such as error checking and header/router information while the second region may include data payload for loss tolerant applications such as voice over Internet protocol (VoIP).

Abstract: Methods and systems for training sequences are provided. In one embodiment, a bi-directional communication system comprises: a multipoint-to-point host unit; and a plurality of remote units communicatively coupled to the multipoint-to-point host unit through an orthogonal frequency division multiplexing waveform. The multipoint-to-point host unit is configured to receive the orthogonal frequency division multiplexing waveform, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by the plurality of remote units. The plurality of remote units each transmit a training pattern to the host unit on at least one of the plurality of tones; and the multipoint-to-point host unit is configured to adjust demodulation of upstream information from the plurality of tones based on the training pattern.

Abstract: The present invention provides a unique feedback system in a wireless communication system wherein the transmission channel is always overloaded with data, which is configured and modulated at a select order of modulation. Based on the channel conditions, only a portion of the data can be successfully received. As such, the receiver will attempt to receive the data using demodulation techniques corresponding to the different levels of modulation used to encode the data transmitted. The receiver will determine the data that is recovered, or the highest order of modulation at which the data is recovered, and provide feedback to the transmitter. The transmitter will then retransmit the data that was not properly received. By overloading the channel at all times, the maximum amount of data capable of being transmitted over the channel is optimized without requiring or heavily relying on the receiver feeding back channel condition information to the transmitter.

Abstract: Certain embodiments of the present disclosure relate to a method to determine appropriate values of cyclic delays applied at a transmitter with multiple antennas in order to provide accurate estimation of channel gains in a multiple-input single-output (MISO) system or multiple-input multiple-output (MIMO) system.

Abstract: An apparatus for generating a 2D spreading code and method for the same are proposed. The apparatus for generating the 2D spreading code includes a column counter, a row counter, a codeword selector, and a logic unit. The logic unit performs logic operations on the output of the column counter, the row counter, and the codeword selector to generate the 2D spreading code of desired order designated by the codeword selector. The 2D spreading code includes 4 2×2 initial matrixes for generating 4i codes for 4i users in the ith order. The apparatus for generating the 2D spreading code according to the present invention is advantageously used in OFDM system to increase the number of subscribers with reduced interference.

Abstract: A method and apparatus for reducing the peak to average power ratio of an OFDM signal. The method involves operating on the signal only after it is converted to the time domain where the signal is compared to a power threshold and any signal above the power threshold is considered undesirable. A reduced signal is produced by reducing the magnitude to the power threshold whenever it exceeds that threshold. The delta between the original signal and reduced signal is the clipped signal. The clipped signal is multiplied by a g-function, and then subtracted from the original signal to produce a first iteration of a peak-reduced signal. The process can then be repeated using the first peak-reduced signal in place of the original signal to produce the second iteration of a peak-reduced signal. This process can be repeated each time bringing the peaks closer to the power threshold.

Abstract: An apparatus and a system, as well as a method and article, may operate to send a selected data type without self-definition information to a receiver if a state capable of interpreting the selected data type has been maintained by the receiver, and to send the selected data type with the self-definition information to the receiver if the state capable of interpreting the selected data type has not been maintained by the receiver.

Abstract: A secondary source of dispatch information is provided in the event of a failure of a primary source of dispatch information. The second source of dispatch information can be accessed electronically by service technicians in the field when the primary source of dispatch information fails so that service technicians do not have to contact operators in a central office to obtain the dispatch information. The secondary source of dispatch information can distribute the dispatch information in a number of ways including e-mail, web and other methods.

Abstract: Of systematic bits (S) and parity bits (P1, P2) generated by coding (coding rate R=1/3) transmission bits, subcarriers to which parity bits are mapped are designated as candidates for transmission cancellation and subcarriers not to be transmitted are selected from among those candidates. When this selection is made, a selection pattern which corresponds to minimum peak power of an OFDM symbol is used based on values of parity bits and phase relationship between subcarriers.

Abstract: A method of improving frequency diversity of a signal that includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols comprises receiving an input data sequence, mapping the input data sequence to a transmission data sequence, wherein the mapping includes performing a mapping operation and generating an OFDM symbol using the transmission data sequence. An orthogonal frequency division multiplexing (OFDM) transmitter comprises an interface configured to receive an input data sequence, and a processor configured to perform a mapping operation, to map the input data sequence to a transmission data sequence wherein the mapping includes performing the mapping operation, and to generate an OFDM symbol using the transmission data sequence.

Abstract: Aspects of a method and system for selective equalization enablement based on modulation type may be found in a method for processing a radio frequency (RF) signal that comprises receiving a Bluetooth signal via an RF channel, detecting a modulation type of the received Bluetooth signal, and selecting an equalization circuit for processing the received Bluetooth signal based on the detected modulation type. The method may also comprise determining a data rate based on the detected modulation type.

Abstract: The present invention relates to a communication system comprising a plurality of terminals each having an uplink transmission unit (1) for transmitting radio frequency OFDM signals at a radio frequency and an access point having an uplink receiving unit (4) for concurrently receiving said radio frequency OFDM signals from at least two terminals, said OFDM signals being Orthogonal Frequency Division Multiplex (OFDM) modulated, wherein the bandwidth of said uplink transmission units and of the transmitted radio frequency OFDM signals is smaller than the bandwidth of said uplink receiving unit, that the bandwidth of at least two uplink transmission units and of their transmitted radio frequency OFDM signals is different and that the uplink transmission unit is adapted to assign different connections for concurrently transmitting radio frequency OFDM signals to different sub-carriers in the same time slots or to the same or different sub-carriers in different time slots.

Abstract: A correlation signal generating circuit generates a duplicate signal for correlation processing based on a multiplex duplication signal. An autocorrelation circuit performs autocorrelation processing through sliding processing of the duplicate signal with respect to a received signal. An Nd detecting circuit detects the length of the data symbol by detecting a correlation value peak obtained based on the guard interval symbols. A data correlation circuit performs mutual correlation processing on the extracted data through the sliding processing by changing the window sizes. An Ng detecting circuit detects the length of the guard interval symbol by detecting the correlation value peak which is obtained when the guard interval symbol length and the window size become consistent.

Abstract: Systems and methods are disclosed for detecting and mitigating temporary high-level impairments, in a communications channel, and subsequently, mitigating the deleterious effects of the dynamic impairments. The system includes a transmitter and a receiver. The transmitter is adapted to transmit at least one set of modulated signals. The receiver is adapted to receive the at least one set of modulated signals and mitigate temporary high-level impairment in the at least one set of modulated signals using at least one error vector received during the temporary high-level impairment.

Abstract: Method of communicating digital data in which frames (8) are transmitted cyclically whereby a first number of symbols is transmitted according to a first keying mode (II) using a first constellation, and a second number of symbols is transmitted according to a second keying mode (L) using a second constellation. The first and second keying modes (H, L) are used at predetermined positions in the frame, whereby both the symbols according to the first and second keying mode carry information under at least an operative traffic phase.

Abstract: A transmitter transmits data to a communicating opponent with a better channel condition with use of one or more frequency blocks including one or more carrier frequencies. The transmitter includes a communicating opponent selection unit evaluating the channel condition for each frequency block for each of plural communicating opponents and selecting one or more communicating opponents from the plurality of communicating opponents, a modulation scheme determination unit determining at least a modulation scheme depending on the evaluated channel condition, a control channel generation unit generating a control channel indicative of the determined modulation scheme and one or more frequency blocks available for the selected communicating opponents to receive a data channel, and a channel transmission unit providing the selected communicating opponents with the control channel and the data channel modulated in accordance with the modulation scheme.

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: The invention is a process and system for controlling selection of which MS is to receive the next packet data transmission on a forward channel and selection of which plural MCS is to be used for the packet data transmissions on the forward channel. A process for controlling selection of MCS method to be used by a BTS (10) to transmit data packets over a forward shared channel to a MS (12) in accordance with the invention stores information at the BTS, the information containing MCS methods which may be selected to transmit data packets over the forward shared channel to the MS; receiving from the MS at the BTS a quality indication of transmission of data packets over the forward channel to the MS; and selecting a MCS method from a plurality of MCS methods which may be used to transmit data packets on the forward channel dependent upon the received quality indication.

Abstract: Described is a communication system including mobile communication devices. In the described system, the mobile devices may be wrist-worn watches such as are in common use today, except that the watches are specially configured to receive data in a “broadcast” mode and transmit and/or receive data in a “localcast” mode. The localcast mode includes the ability to transmit and receive data in a peer-to-peer fashion, allowing mobile devices to communicate directly with each other. The ability to combine two of these communication modes in a small, integrated and hence inexpensive and low-power package provides many advantages over existing personal communication device solutions.

Abstract: According to an image signal cancel-type heterodyne reception method, I-phase and Q-phase intermediate-frequency signals can be modulated using two orthogonal signals, superimposed one on the other, amplified by one amplifier, and modulated using two modulated orthogonal signals, thereby amplifying I-phase and Q-phase signals by one amplifier. Therefore, it is possible to obtain a high image signal cancellation ratio with no difference in gain for both of the phases. According to a direct conversion orthogonal frequency division reception method, on the other hand, two-phase base-band signals can be amplified respectively by one amplifier to eliminate a difference in gain between amplifications of the two-phase base-bands, thereby realizing high non-interference between sub-carriers.

Abstract: A first rate matching stage matches a number of input bits coming from a transport channel including a high-speed downlink shared channel (HS-DSCH) of a block of data bits to be transmitted from a base station of a communications network to one or more pieces of user equipment (UE) to a selected number of intermediate bits as determined by the buffer size management system. A virtual buffer stores the selected number of intermediate bits. A second rate matching stage matches the selected number of intermediate bits to a number of output bits equal to a maximum number of bits that is guaranteed to be transmitted by a set of high-speed physical downlink shared channels (HS-PDSCH) associated with the transport channel in a given time interval without adding bits.

Abstract: An arrangement and a method for minimizing intracell and/or intercell interference for a data transmission system comprises a scheduler (2). A first base station (BS) receives information from user equipments (UE1-UE4) in a first cell (1) by means of a first antenna system (Rx, Tx). The scheduler (2) identifies the position of each user and allots a first time slot (TS1) to at least one user equipment (UE1) in a first cell segment (CS1) in the first cell (1). The scheduler (2) also allots the first time slot to at least one user (UE3) equipment in a second cell segment (CS2) in the first cell (1). The antenna system (Rx, Tx) then sends information from the base station (BS) simultaneously to all user equipments (UE1, UE3) allotted to the first time slot.

Abstract: In a method and an apparatus (1) for transmission diversity mode detection in a mobile radio receiver using a decision function, the decision function which is used for detection of the transmission diversity mode is based on the coherent processing of two successive input signal data tuples {r(k);r(k+1)} and {r(k+2);r(k+3)} and recording of a phase offset between the two tuples.

Abstract: A method and system transmits an input stream of data symbols in a multiple-input/multiple-output wireless communications system that includes M subgroups of transmitting antennas. A stream of data symbols is provided to a combined switch and demultiplexer. The combined switch and demultiplexer selects a subset L of the M subgroups of antennas as active, where L<M. The demultiplexer then splits the data stream into L substreams, which are fed to the L subgroups of antennas. Before transmission, each of the L substreams is adaptively modulated and coded to a maximum data rate while achieving a predetermined performance on an associated channel used to transmit the substream. Space-time transmit diversity encoding is applied to each coded substream to generate multiple output streams, one output stream for each antenna of each of the L subgroups. The selection by the switch is based on channel conditions fed back by a receiver of the output streams.

Abstract: A receiving modem (20) including functionality for adjusting the synchronization of its timing relative to a transmitting modem (10), by recovering timing from a plurality of pilot tones transmitted by the transmitting modem (10) in a multicarrier modulation signal, is disclosed. For a subset of the pilot tones, the receiving modem (20) sums phase error differences, for example according to a weighted sum, to derive a phase error estimate relative to reference signals, in which noncoherent random noise cancels out, to correct for timing differences between the modems (10, 20). For another subset of the pilot tones not used in the phase error estimate, the receiving modem (20) analyzes the demodulated signal for those tones to adjust reference signals for each of those pilot tones. The adjusting is performed either by deriving an adjusted complex reference signal, or by adjusting coefficients in a frequency domain equalizer (28).

Abstract: A device (D) is dedicated to managing transmission of digital data blocks in High-Speed Downlink Shared Channel (HS-DSCH) downlink transport channel set up between a base station of a communications network and a user equipment. It comprises processing means (MT) adapted, each time that a given block must be transmitted to the user equipment via the transport channel, to select successive values of the redundancy parameter XRV in accordance with a selected sequence in which the value of the redundancy parameter XRV used for the first block transmission is selected to give priority to transmitting systematic bits.

Abstract: A method for maintaining the quality of transmission from a head end to a service unit in a telecommunications system that uses a multi-carrier transmission scheme with dynamic bandwidth allocation is disclosed. The method involves allocating a first payload channel to a service unit in a subband of a transmission channel of the telecommunications system and monitoring the quality of the first payload channel. When the quality of the first payload channel drops below a threshold, the method allocates a second, different payload channel to the channel unit.

Abstract: Disclosed is a method for transmitting a pilot symbol from base stations (BSs) to a subscriber station (SS) in a communication system which includes the base stations located adjacent to each other, the method includes the steps of transmitting BS-identifying sub-carriers which represent sequences for identifying the base stations in a frequency domain of the pilot symbol; and transmitting PAPR (Peak to Average Power Ratio) sub-carriers which represent sequences for reducing a PAPR of the pilot symbol together with the transmission of the BS-identifying sub-carriers in the frequency domain.

Abstract: A method for communication includes receiving a composite signal, which carries data at a first data rate and includes multiple sub-signals that are interleaved in a time domain and are separated by boundary indicators. The received composite signal is demultiplexed into the sub-signals by automatically detecting the boundary indicators between the sub-signals in the composite signal. The sub-signals are demodulated using multiple respective demodulators operating at second data rates that are lower than the first data rate so as to generate respective output data streams. The output data streams are combined so as to reconstruct the data at the first data rate.

Abstract: An OFDM (Orthogonal Frequency Division Multiplexing) system may utilize pilot symbol structures including two or more pilot symbols with pilot information on alternate tones. The pilot information in one symbol is transmitted on mirror tones in another of the symbols. The pilot symbol structure may include a copy of one of the pilot symbols to aid in frequency offset estimation.

Abstract: A transmitting apparatus, receiving apparatus, communication system, and a signal processing method for each apply a suitable modulation method and transmission path estimation method in accordance with the characteristics of the transmission information and capable of improving the transmission efficiency. At the transmission side, the method of estimation of the transmission path and the modulation method are selected in accordance with an attribute of the data to be transmitted, for example, the size of a packet to be transmitted, the transmission data is mapped by the selected modulation method, the signal is processed in accordance with the transmission path estimation method, and a transmission signal is created by increase fast Fourier transform processing and transmitted.

Abstract: Various embodiments are described for adaptive puncturing techniques involving an adaptive bit loading block to select a modulation scheme and a puncturing pattern for each of a plurality of subcarriers or subcarrier bands based on subcarrier channel state information.

Abstract: This permits the transmission of signals over the electricity network in such a way that the spectral density of power is adjusted to the regulations in the current rules by means of the possibility of introducing notches in transmission in an efficient manner. It is characterised by the adjustment of the power in one or more carriers of an OFDM signal for generating these notches, through the use of IDFTs of at least 1024 points (if the IDFT is complex) or at least 2048 points (if the IDFT is real) and through the use of a window to multiply the symbols to be transmitted in time.

Abstract: Systems for multipoint-to-point communication using orthogonal frequency division multiplexing and identification codes are provided. In one embodiment, a system comprises: a host unit; and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using orthogonal frequency division multiplexing (OFDM); wherein the host unit allocates orthogonal tones within the system to the plurality of remote units; wherein the host unit sends an adjustment signal to at least one of the remote units instructing the at least one remote unit to adjust the timing of transmissions from the remote unit to improve orthogonality of an OFDM waveform received at the host unit, and wherein the host unit associates an address code with each of the plurality of remote units for designating downstream signals to the remote units.

Abstract: Methods and apparatus are provided for varying the number of pilot tones in a multiple antenna communication system. Data is transmitted in a multiple antenna communication system by selecting a number of pilot tones to be employed to transmit the data; and transmitting an indication of the selected number of pilot tones in a preamble of a packet containing the data. Data is received in a multiple antenna communication system by receiving a preamble having an indication of a number of pilot tones embedded in the data; and processing the received data based on the indicated number of pilot tones. The indication of the selected number of pilot tones can be transmitted, for example, in a SIGNAL field of an exemplary IEEE 802.11 preamble. The number of pilot tones can be selected, for example, based on one or more of (i) a delay spread of a channel; (ii) the SNR at the receiver; or (iii) a number of antennas at a receiver.