摘要:
A spread-spectrum communication system provides an effective signal-to-noise ratio (SNR) of received orthogonal frequency division multiplex (OFDM) slots in the presence of timing errors. Effective SNR can serve as a diagnostic tool for determining whether there was a timing error when a measured packet error rate (PER) remains high, and a predicted PER from the effective SNR remains low. A loop can use the effective SNR to control a time reference used by an OFDM decoder.
摘要:
Noise variance estimation in wireless communications. Noise variance estimation includes receiving a signal including an OFDM symbol having, in-band tones including in-band pilot tones, and band-edge tones including band-edge pilot tones and guard tones, estimating an effective noise variance for the in-band tones using the in-band pilot tones and channel estimates for the in-band pilot tones, and estimating an effective noise variance for the band-edge tones using the band-edge pilot tones, channel estimates for the band-edge pilot tones, and the guard tones.
摘要:
A pilot assisted channel estimation process. A receiver may be configured to estimate the impulse response of a channel from a signal having pilot tones and spread-spectrum pilot signals. The receiver estimates the response of the channel from the pilot tones, and adapts the length of delay the channel response is estimated based on the spread-spectrum pilot signals.
摘要:
Synchronized broadcast transmits a same broadcast content using a same waveform from multiple transmitters. Transmitters each apply a same spreading code for broadcast transmissions. In a spread-spectrum communication system having a time division multiplexed forward link, a synchronized broadcast transmission is inserted into a broadcast slot. One embodiment employs an Orthogonal Frequency Divisional Multiplex (OFDM) waveform for the synchronized broadcast. An OFDM receiver is then used to process the received synchronized broadcast transmission. An alternate embodiment implements a broadcast Pseudo-random Noise (PN) code for use by multiple transmitters. An equalizer is then employed to estimate the synchronized broadcast transmission.
摘要:
A method and an apparatus for scaling demodulated data symbols contained in a packet to generate scaled log-likelihood ratios for Turbo decoding are disclosed. A packet consists of one or more subpackets depending on the type of packet. Each subpacket is identified by a subpacket identification number. The payload size of the packet and the subpacket identification number may be determined by decoding a reverse rate indicator (RRI) channel. A scale factor which is associated with a specific subpacket identification number and a specific payload size results in a performance measure that is closest to an expected performance measure. The scale factor is used for scaling the demodulated data symbols to generate scaled log-likelihood ratios for Turbo decoding.
摘要:
In one embodiment, the invention comprises a channel estimation method, comprising determining a FFT window position, and calculating a delay spread. In another embodiment, the step of determining a FE window position comprises setting an initial position of the FFT window, computing an energy for each tap, time averaging said energy for each tap, comparing an average energy of each tap with a first threshold multiplied by the average energy of all taps, comparing the average energy of each tap with a second threshold multiplied by a maximum average energy in alias components, updating the set of paths if the average energy of the tap is greater than said second threshold multiplied by the maximum average energy in alias components; and refining the FFT window position.
摘要:
An apparatus may be configured to generate document data representing a document for use in providing a service comprising a number of different activities that are to be carried out in providing the service. The apparatus may enable a user to retrieve previously stored document portions in accordance with the activity to which the document portion relates so that it is not necessary for the user to identify a specific document portion, a specific filename or an inventory part number allocated to that document portion. In one embodiment, an apparatus may be configured to generate a document that enables a user to assemble a document in accordance with the activities to which the document relates rather than to the actual content of the document. Thus, the user wishing to assemble a document may be concerned with the activities instead of which precise document portions to include in the document.
摘要:
A method and an apparatus for waveform quality measurement are disclosed. An actual signal, representing a waveform channelized both in time and in code is generated by, e.g., an exemplary HDR communication system. Test equipment generates an ideal waveform corresponding to the actual waveform. The test equipment then generates an estimate of offsets between parameters of the actual waveform and the ideal waveform, and the offsets are used to compensate the actual waveform. The test equipment then evaluates various waveform quality measurements utilizing the compensated actual waveform and the corresponding ideal waveform. Definitions of the various waveform quality measurements as well as conceptual and practical examples of processing of the actual waveform and the corresponding ideal waveform by the test equipment are disclosed. The disclosed method and apparatus may be extended to any waveform channelized both in time and in code regardless of the equipment that generated the waveform.
摘要:
A transmitter directed, distributed receiver using multi-user diversity provided by the distribution of the receiver. Advantage is taken of the uncorrelated variations over time in the condition of communication links between a common transmitter and several users. The greater the variation in the quality of a particular link over time, the greater the increase in total system throughput provided. A scheduler metric (or scheduler metric) represents the instantaneous quality of the communication link between each user and the transmitter with respect to the average quality of the link. Alternatively, the scheduler metric represents the instantaneous channel condition with respect to the average data throughput over that channel. The common transmitting station uses the scheduler metric to directly compare the desirability of granting each channel access with the desirability of granting each other channel access. The users with links that have the greatest scheduler metric are provided access to the channels.
摘要:
In a data communication system capable of variable rate transmission, high rate packet data transmission improves utilization of the forward link and decreases the transmission delay. Data transmission on the forward link is time multiplexed and the base station transmits at the highest data rate supported by the forward link at each time slot to one mobile station. The data rate is determined by the largest C/I measurement of the forward link signals as measured at the mobile station. Upon determination of a data packet received in error, the mobile station transmits a NACK message back to the base station. The NACK message results in retransmission of the data packet received in error. The data packets can be transmitted out of sequence by the use of sequence number to identify each data unit within the data packets.