Abstract: A system and method of frequency-diversity OFDM with a sampling rate less than the Nyquist rate for ultra-wideband devices are described. The channel encoder is used to encode at least one input data stream to a plurality of codewords. The evaluation device coupled to the channel encoder and having a plurality of weighting coefficients are combined with the codewords to generate a plurality of matrix elements. One or more first transformation device coupled to the evaluation device convert the matrix elements into a plurality of OFDM symbols. In addition, a modulated device coupled to the first transformation device is able to modulate the OFDM symbols to expand a plurality of different frequency bands and form a received signal. The signal filter coupled to the modulated device for eliminating noise in the received signal. More importantly, the sampling device coupled to the signal filter sample the received signal by a sampling rate less than the Nyquist rate.

Abstract: A method and system are disclosed that provide a more efficient decoder for decoding block codes such as a complementary code keying (CCK) code. A receiver receives a signal containing at least one block codeword. A decoder decodes the block codeword contained in the received signal by finding a path in a trellis diagram with a calculated path metric that accounts for intersymbol interference (ISI). The path metric can be based on a branch metric that is calculated according to a decision feedback sequence estimation algorithm.

Abstract: A method for I/Q imbalance calibration of an OFDM system comprising the steps of initializing parameters Ap, Bp and ?p, estimating a loop delay factor L, generating a discrete-time test signal x[n], deriving a signal xcom[n] by compensating the test signal x[n] according to a function with parameters Ap, Bp and ?p, converting the signal xcom[n] to an analog signal x(t), applying I/Q modulation to the signal x(t) and outputting a modulated signal xmod(t), obtaining a characteristic signal xc(t) of the modulated signal, obtaining a signal xs[n] by sampling the characteristic signal xc(t) and obtaining statistics U1 and U2 of the signal xs[n], and updating the parameters Ap, Bp and ?p respectively by functions of L, U1, U2, and the current values of Ap, Bp and ?p.

Abstract: An apparatus and method for calculating bit metrics in data receivers. The apparatus of the invention includes a storage unit and a calculator. The storage unit is configured to store a number of modulation-dependent coefficients; it selects as output one of the coefficients in accordance with a modulation mode being used. The calculator receives the selected coefficient from the storage unit and takes a received signal and a channel response in the frequency domain. According to the selected coefficient, the received signal and the channel response, the calculator generates at least N number of bit metrics for an N-bit codeword in the received signal.

Abstract: A method for I/Q mismatch calibration of a receiver having an I/Q correction module with correction parameters, comprising the steps of generating a test signal containing a single tone waveform with frequency of a carrier frequency plus a predetermined frequency, applying I/Q demodulation to reduce the central frequency of the test signal and outputting a demodulated signal, converting the demodulated signal to a digital signal, obtaining measures of the digital signal respectively indicative of the frequency response of the digital signal at the plus and minus predetermined frequencies, and calculating the set of the correction parameters for the I/Q correction module based on the measures.

Abstract: A method for I/Q mismatch calibration of a transmitter. First, a discrete-time signal is generated. Next, a corrected signal based on the discrete-time signal and a set of correction parameters Ap and Bp is obtained. Next, the corrected signal is converted to an analog corrected signal. Next, I/Q modulation is applied to the analog corrected signal and outputs a modulated signal. Next, a first, second, and third desired component measures and a first, second, and third image component measures with the first, second and third sets of the correction parameters Ap and Bp are respectively obtained from the modulated signal. Next, a fourth and fifth set of correction parameters Ap and Bp are obtained based on the first, the second, and the third desired component measures as well as the first, the second, and the third image component measures.

Abstract: A link quality estimating method and apparatus adopts a fading value to modify an estimated link quality of a channel thereby obtaining a measure being very close to the real link quality. The method is implemented by utilizing two sequentially received long training symbols to derive two sets of subcarrier gain values Hk,1 and Hk,2. Based on the subcarrier gain values Hk,1 and Hk,2, parameters representing the estimated channel gain value (A), the fading value (F) and the noise quantity (B) of the channel are all calculable. With these parameters, the link quality (LQ) of said communication channel is derived.

Abstract: A method for I/Q mismatch calibration in a receiver. The receiver has an I/Q correction module using parameters Ap and Bp. The method comprises the steps of generating an analog test signal x(t), applying I/Q demodulation to reduce the central frequency of the signal x(t) by fc Hz and outputting a demodulated signal xdem(t), converting the analog signal xdem(t) to a digital signal xdem[n], sending the signal xdem[n] into the I/Q correction module using parameters Ap and Bp and outputting a corrected signal w[n], obtaining two measures U1 and U2 of the corrected signal w[n], and updating the parameters Ap and Bp of the I/Q correction module respectively by a first and second function of the two measures U1 and U2, and the current values of the parameters Ap and Bp.

Abstract: An avoidance method for co-channel interference in a wireless network. The first step of the method is to evaluate an interference measure on each subcarrier. Based on the interference measure of each subcarrier, a peak-to-average measure ratio of interference within the received symbol is then obtained. If the peak-to-average measure ratio of interference is greater than a predetermined threshold, a most interfered subcarrier at which the maximal interference measure occurs is detected. Accordingly, a downgrading factor is set for the most interfered subcarrier.

Abstract: A system and method for estimating channel characteristics in orthogonal frequency-division multiplexing (OFDM) systems with transmitter diversity is presented. The disclosed approach is compatible with the Institute of Electrical and Electronics Engineers (IEEE) “Wireless Local Area Network (LAN) Medium Access Control (MAC) and Physical Layer (PHY) Specification.” In the disclosed system and method, an additional training symbol is transmitted during the data period. This provides additional information that may be used to more accurately estimate channel characteristics.

Abstract: A system and method for transmitting data in multiple-branch transmitter-diversity OFDM systems is presented. In one embodiment, an approach is taken where an inverse Fourier transform (IFT) is performed on data prior to encoding the data for transmission in the multiple-branch transmitter-diversity system. In another embodiment an IFT is performed on data prior to encoding the data using a space-time block code (STBC) algorithm.

Abstract: A method is directed to recovering a digital data content in a communication system, wherein the digital data content has been converted into an analog signal based on a primary clock, at a transmitter for transmitting to a receiver. The method comprises receiving the analog signal by the receiver. The analog signal is converted into a digital signal, based on a clock of the receiver. The digital signal is interpolated at the desired interpolation point, if digital signal in time has been shifted by an amount equal to or larger than a predetermined time length. The interpolated digital signal is recovered back to the digital data content, with the assist of an estimated channel impulse response. The channel impulse response is retrained every time when the interpolation point is significantly changed.

Abstract: A method and a device for detecting a preamble type of a wireless data frame are provided The preamble has a synchronization (SYNC) field and a start frame delimiter (SFD) field, and the method comprises following steps. The wireless data frame is first received, and then determined whether the wireless data frame has a short preamble. When the wireless data frame has the short preamble, the wireless data frame is transmitted to a MAC device. In addition, if the wireless data frame does not have the short preamble, it determines whether the wireless data frame has a long preamble. When the wireless data frame has the long preamble, the wireless data frame is then transmitted to the MAC device.