Abstract: The present invention provides a method and system for reducing the peak to average power ratio (PAP) of a signal with low computational complexity. According to one embodiment, the present invention is applied to reduce the PAP of an OFDM signal. According to an alternative embodiment, the present invention is applied to reduce the PAP of a CDMA signal. Rather than seeking the optimum solution, which involves significant computational complexity, the present invention provides for a number of sub-optimal techniques for reducing the PAP of an OFDM signal but with much lower computational complexity. In particular, according to one embodiment utilizing the PTS approach, an iterative technique is used to assign phase factors to each of a set of partial transmit sequences from a set of possible phase factors. Experimental results using the iterative technique showed only a slight degradation (1 dB) from the optimal approach using the same number of subblocks and subcarriers.

Abstract: Proposed is a method and apparatus for reducing interference in a frequency hopping wireless communications system. In one embodiment of the present invention, a base station and a terminal station each using an orthogonal frequency division multiplexing (OFDM) technique to simultaneously measure an interference level for each system frequency and to enable high speed frequency hop pattern changes which can follow changes in desired and interfering signal levels due to changes in co-channel interference or shadow fading. The terminal station interference level measurement values are then transmitted to the base station. Next, the base station identifies each frequency hop pattern currently in use by each terminal station communicating with that base station.

Abstract: This invention provides wireless resource allocation techniques where the wireless network resource allocation is based on maximum system gain. System gain may be the difference between a maximum performance (e.g., throughput rate) for a requested link and a performance loss of all currently active links affected by the requested link. A currently active link is affected if the requested link is within its link neighborhood. Wireless network resources are allocated to optimize system performance. Inter-base communication may be used to facilitate information exchange among base stations to optimize system performance. The performance loss experienced by any currently active link is called damage to that link. Damage may be determined in a pair-wise fashion based on a nominal performance which may be defined as the performance of a link if interference is experienced only from links which are outside the link neighborhood of the link or as a system parameter.

Abstract: A method of locating a mobile telephone includes steps of receiving, transmitting, increasing and determining. In the receiving step, a first base station receives a call from a mobile telephone, the call including a dialed number and a TDMA signal. In the transmitting step, the base station transmits a control message to the mobile telephone when the dialed number meets a predetermined criterion, such as being 911. The control message instructs the mobile telephone to transmit the TDMA signal at a maximum power. In the increasing step, the mobile telephone increases the TDMA signal to maximum power in response to the control message. Then in the determining step, location information for the mobile telephone is determined based on at least one characteristic of the TDMA signal received at at least one of the first base station and other base stations.

Abstract: An efficient method for providing both dedicated and simulcast services over a common wireless infrastructure is described. The services can be available to a single terminal as well as to a multiplicity of terminals simultaneously. The method uses time division multiplexing and orthogonal frequency division multiple access for simulcasting information and transmitting dedicated message information from a plurality of base stations forming a cellular pattern over the same wireless frequency channel. The method comprises the steps of constructing frames for transmission by the plurality of base stations comprising control information, simulcast information and dedicated message information within predetermined time slots of the frames and allocating the simulcast information and the dedicated message information to time slots of the same frame predetermined by the control information of the frame. The underlying modulation technology used is OFDM and thereby the channel delay-dispersion is minimized.

Abstract: A high-speed wireless transmission system is employable in a macro-cellular environment. In the system multiple transmit antennas are employed. Multiple carrier tones are used to transmit the data. The carrier tones can be assigned to the respective transmit antennas in such a manner as to provide each antenna with a subset of carrier tones with each subset being spread over the transmission spectrum. In addition, operation is enhanced by providing Reed-Solomon coding of the data across consecutive time intervals.

Abstract: A method of locating a mobile telephone includes steps of receiving, transmitting, increasing and determining. In the receiving step, a first base station receives a call from a mobile telephone, the call including a dialed number and a TDMA signal. In the transmitting step, the base station transmits a control message to the mobile telephone when the dialed number meets a predetermined criterion, such as being 911. The control message instructs the mobile telephone to transmit the TDMA signal at a maximum power. In the increasing step, the mobile telephone increases the TDMA signal to maximum power in response to the control message. Then in the determining step, location information for the mobile telephone is determined based on at least one characteristic of the TDMA signal received at at least one of the first base station and other base stations.

Abstract: A MIMO OFDM system includes a plurality of space-time encoders for encoding respective data blocks with independent space-time codes. The transformed data block signals are transmitted by a plurality of transmit antennas and received by a plurality of receive antennas. The received data is pre-whitened prior to maximum likelihood detection. In one embodiment, successive interference cancellation can be used to improve system performance. Channel parameter estimation can be enhanced by weighting the channel impulse response estimates based upon a deviation from average.

Abstract: A method and apparatus provide channel estimation for multicarrier systems. A minimum mean-square-error (MMSE) channel estimator makes full use of time-and frequency-domain correlations of the frequency response of time-varying dispersive fading channels. A robust channel estimator that is insensitive to the channel statistics is provided. The robust channel estimator can significantly improve the performance of a multicarrier system such as an orthogonal frequency division multiplexing (OFDM) modulation system in a rapid dispersive fading channel. In addition, the estimation process can employ a new reference generator which can select the source of the reference signal as being a decoded or undecoded signal depending on the correction success rate of the decoder.

Abstract: An OFDM system embeds sequence information in the transmitted signal that reduces peak average power ratio (PAP) with minimal impact on the overall system efficiency. A marker is embedded onto the transmitted information that is used to identify the combining (inversion) sequence at the receiver. In one embodiment, selected tones in a cluster are rotated when the corresponding phase factor rotates the cluster.

Abstract: A system and method for generating a coherent reference signal for extracting desired user signals from received signals even after error propagation is underway, are presented. A data symbol preceding a sequence whose relative phases are known is used as an absolute phase reference. Since errors in detection of the phase reference symbol are usually caused by error propagation already underway, the sequence can be used to reacquire the desired signal with merely an absolute phase shift in detected data, which allows accurate differential detection of the desired user signal even in the absence of absolute phase knowledge.

Abstract: A high-speed wireless transmission system is employable in a macro-cellular environment. In the system multiple transmit antennas are employed. Multiple carrier tones are used to transmit the data. The carrier tones can be assigned to the respective transmit antennas in such a manner as to provide each antenna with a subset of carrier tones with each subset being spread over the transmission spectrum. In addition, operation is enhanced by providing Reed-Solomon coding of the data across consecutive time intervals.

Abstract: A system provides transmit diversity with feedback to enhance the reception of communication signals at a wireless communication terminal. Multiple antennae are provided at the base station. The multiple antennae transmit multi-carrier information signals such as OFDM including pilot tones. The wireless communication terminal receives the pilot tones and performs processing on those tones to detect the relationship between the information signals transmitted from the various antennae of the base station. A feedback signal, based on the comparison of the pilot tones communicates back to the base station information about the channels of the respective transmit antennae to the terminals. The base station modifies the transmission processing associated with the various transmit antennae based upon the feedback signal. The modified processing improves the reception of the information signals at the wireless communication terminal.

Abstract: An improvement of a digital wireless receiver comprises a processing circuit for processing a plurality of received signals, and providing a processed signal having an amplitude; and an adjusting circuit for adjusting the amplitude of the processed signal, the adjusting circuit coupled to the processing circuit, where the adjusting circuit adjusts the amplitude as a function of distortion of the plurality of received signals. The processing circuit can weight and combine the plurality of received signals. The distortion can be estimated from a squared error of the plurality of received signals, which can be averaged over a sliding window. The function can comprise multiplying the processed signal by square root of the averaged squared error. Such amplitude adjustment is useful to maintain the soft decision information for the processed signal that is fed to a base station having soft decision decoding, or can be used in the base station with soft decoding.

Abstract: A method and system for controlling media access in which a paging message is transmitted from a base station to a wireless station when a data packet is received for downlink transmission to the wireless station. The base station is one of a plurality of base stations and the wireless station is associated with the base station. In response to the paging message, a level of each of a plurality of pilot frequency signals is detected at the wireless station. Each pilot frequency corresponds to a downlink traffic channel and is transmitted by base stations to which the downlink traffic channel is assigned. The wireless station generates a list of preferred traffic channels based on a priority order of traffic channels and on detected levels of the pilot frequency signals, and transmits the list to the associated base station.

Abstract: An apparatus for performance improvement of a digital wireless receiver comprises a processing circuit for processing a plurality of received signals and providing a processed signal, wherein a plurality of weights is applied to the plurality of received signals producing a plurality of weighted received signals. The plurality of weighted received signals are combined to provide the processed signal. A weight generation circuit generates the plurality of weights, wherein weights are generated so as to solve a minimization problem that penalizes excessive time variability in the weights.

Abstract: A system and method for applying channel weights in a communication system are presented. The application of weights derived from a sample window is time-shifted into that sample window, decreasing the effects of channel variation and partially compensating for degradation due to differential detection.

Abstract: A high-speed wireless transmission system is employable in a macro-cellular environment. In the system multiple transmit antennas are employed. Multiple carrier tones are used to transmit the data. The carrier tones can be assigned to the respective transmit antennas in such a manner as to provide each antenna with a subset of carrier tones with each subset being spread over the transmission spectrum. In addition, operation is enhanced by providing Reed-Solomon coding of the data across consecutive time intervals.

Abstract: A technique for estimating parameters for adaptive antenna arrays in orthogonal frequency division multiplexing systems with co-channel interference is disclosed. Channel parameter estimation is preferentially performed using a two pass process that advantageously expands the temporal scope (relative to a single pass process) and considers past, present and future temporal channel estimations during parameter estimation. Channel parameters are estimated by processing the signals through fast Fourier transforms, temporal filters, and inverse fast Fourier transforms. The temporal filters optimize parameter estimation based upon instantaneous correlation of the received signals.

Abstract: A decision feedback equalizer receiver that assigns a number F of feedforward filter taps and optimizes digital receiver performance in multipath channel environments, where F is an integer less than a memory length of a radio channel. The feedforward filter taps are assigned to delay times corresponding to an optimum burst timing parameter delay time, d(0), and to F-1 time delays based on "tap SNR indices." For an Uncorrelated Inter-Symbol-Interference (UISI) case, the F-1 time delays are the first F-1 rank ordered time delays are selected as the feedforward tap delay times. For a general case, a combination of the UISI case and an analytical two cluster case is obtained by selecting the first F-2 rank ordered time delays and a 2D time delay, where D is the delay time corresponding to the largest estimated tap SNR index.