Abstract: An automatic gain control mechanism with high-frequency detection. During a predetermined period, the cumulative strength of the real part of a complex-valued input signal is compared with that of the imaginary part of the complex-valued input signal. The zero crossings in either the real part or imaginary part of the complex-valued input signal are selectively totaled contingent upon which part of the complex-valued signal possesses the larger cumulative strength. If the zero crossings total exceeds a predetermined threshold, the automatic gain control mechanism starts detecting a normal packet signal and activating gain control over the detected normal packet signal.

Abstract: A mechanism for frequency tracking and channel estimation in multi-carrier systems. First, two training symbols are pre-compensated for an effect of frequency offset. Then an average of the two pre-compensated symbols is calculated. Meanwhile, a correlation between the two pre-compensated second symbols is evaluated by performing a differential operation. By means of a tracking loop, a frequency tracking value is calculated from the correlation and a loop coefficient. After that, the average of the two pre-compensated symbols is further compensated with a fine frequency offset estimate derived from the frequency tracking value. Accordingly, a channel response is estimated by performing a Fourier transform on the compensated average.

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: An OFDM detection apparatus and method for networking devices. First, a sample sequence is taken from the beginning of a newly arrived network packet. Next, a first correlation sequence between the complex conjugate of the sample sequence and the sample sequence with a lag of N samples is formed. In the meantime, a second correlation sequence between the complex conjugate of the sample sequence and the sample sequence with a lag of M samples is also formed. The first and the second correlation sequence are then normalized. Depending on a comparison between the first normalized correlation sequence and a first predetermined threshold as well as another comparison between the second normalized correlation sequence and a second predetermined threshold, the newly arrived network packet is determined accordingly whether it is an OFDM modulated packet.

Abstract: A frequency offset estimation apparatus for intersymbol interference channels. A storage area having M elements is provided to shift a received sample sequence by M samples to generate a lagged sample sequence. A sequence of preliminary values is calculated by differential operation between the received sample sequence and the lagged sample sequence. Next, a summation of the power of the preliminary value sequence over M? samples is taken to obtain an accumulative sum. Finally, the angle of the accumulative sum is derived and then scaled by a factor. A frequency offset estimate for the received sample sequence is thus obtained.

Abstract: A selective hopping method for hit avoidance in a frequency hopping spread spectrum communication system utilizing an original hopping sequence, having a plurality of available channels for receiving signal packet traffic utilizing a plurality of receiving signal slots are disclosed. The plurality of available channels all are available for use in frequency hopping. The method includes the steps of dividing the plurality of available channels into a plurality of partitions; distributing the available channels in each of the plurality of partitions into a predetermined distribution; forming a partition sequence by assigning a predetermined number of channels to a plurality of selected receiving signal slot sets; generating a generated hopping sequence by partition mapping, in which the partition mapping is responsive to the partition sequence; and managing the receiving signal packet traffic, in which the receiving signal packet traffic is transmitted only in the selected receiving signal slot sets.

Abstract: A method and an apparatus for determining a hopping sequence for selecting a channel from a plurality of channels divided into a plurality of partitions to reduce probability of data collision in a frequency hopping spread spectrum (FHSS) communication system are provided. The communication system stores multiple predetermined partition sequences and receives a first sequence generated by a convention sequence generator.

Abstract: This invention provides a method for bit detection of the GFSK signals at the receiver end. The bit detection is done digitally after the carrier is removed. It employs differential detection incorporated with decision feedback, which uses previous one (so-called on-bit differential detection), or two (so-called two-bit differential detection) bits as correcting information. In addition, synchronization for bit timing and frequency offset resulted from clocks between the transmitter and receiver are also performed with or without preamble as prior information. If preamble is available, the bit timing and frequency-offset bias are estimated from the preamble, which is the case of this present invention. If preamble is not available, this information is estimated directly from the unknown received signals. Once the information about the bit timing and frequency offset is obtained, it is used for the following bit detection.

Abstract: A channel quality assessment with short assessment time and good frequency resolution is disclosed. Some channels are grouped and their detecting results are collected as whale to determine the channel quality. The channel quality is determined by interference collision ratio, which is the ratio of the number of interference events to the sum of the number of interference events and interference-free events. Interfered channels are disabled form the group. The Channel quality of each of plurality of channels is determined from detection results of each of plurality of groups so as to have a short assessment time and meanwhile a good frequency resolution may be retained.

Abstract: A frequency offset estimation based on state-based differential accumulation and the device thereof are disclosed. The concept of the sate-based operation is introduced by mathematical derivations. The knowledge of received data symbols and timing is utilized. Then the detailed operations are also given by both equations and conceptual descriptions. It is unnecessary to estimate the channel jointly or concurrently, while the differential operation over the received samples of the same state is performed. Such operation is obviously much simpler and easier to implement in VLSI than all the other techniques.

Abstract: A phase drift compensation scheme for multi-carrier systems. According to the invention, a timing offset compensator is provided to compensate for a timing offset in a current symbol after taking an N-point FFT. Then a phase estimator computes a phase estimate for the current symbol based on a function of a channel response of each pilot subcarrier, transmitted data on each pilot subcarrier, and a timing compensated version of the current symbol on the pilot subcarrier locations. From the phase estimate, a tracking unit can generate a phase tracking value for the current symbol. Thereafter, a phase compensator uses the phase tracking value to compensate the timing compensated version of the current symbol for the effect of phase drift.

Abstract: A robust timing offset compensation scheme for multi-carrier systems. According to the invention, a timing offset compensator is provided to compensate a current symbol in the frequency domain for the effect of timing offset with a timing offset prediction value. Then a timing error estimator calculates a timing error value for the current symbol based on a function of a phase tracking value, a channel response of each pilot subcarrier, transmitted data on each pilot subcarrier, and a timing compensated version of the current symbol on the pilot subcarrier locations. Furthermore, a timing tracking unit receives the timing error value of the current symbol to generate a shift amount of the DFT window and the timing offset prediction value for a next symbol.

Abstract: Disclosure is a device and a method for estimating frequency offset in radio receiver. Said device comprises: an analog-to-digital converter, a first storing means having M elements; a multiplication means for performing multiplication between a complex conjugate of delayed sampled element and a current sampled element; a second storing means having N elements; an accumulating means for accumulating output of said multiplication means; and a subtracting means for sequentially subtracting output of second storing means from output of said accumulating means; an estimating means for generating said estimated frequency offset based on an output of said subtracting means. Furthermore, said method is achieved by utilizing the above device in the same principle.

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: An apparatus and method for detection of direct sequence spread spectrum signals in 802.11b/g systems. First, a sample sequence is taken from a preamble of a newly arrived network packet. The next step is to calculate a sequence of correlation measures between the sample sequence and a pseudo-noise code sequence of length L. An accumulation sequence is then calculated in which each accumulation value thereof is obtained by summing N correlation measures that are selected at an interval of L from the sequence of correlation measures. Also, a statistic of the sample sequence is evaluated over a multiple of L number of samples. Based on a comparison between the statistic of the sample sequence and a predetermined threshold scaled by the maximum of the accumulation sequence, the presence of direct sequence spread spectrum signals can be determined accordingly.

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 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: An OFDM detection apparatus and method for networking devices. First, a sample sequence is taken from the beginning of a newly arrived network packet. Next, a first correlation sequence between the complex conjugate of the sample sequence and the sample sequence with a lag of N samples is formed. In the meantime, a second correlation sequence between the complex conjugate of the sample sequence and the sample sequence with a lag of M samples is also formed. The first and the second correlation sequence are then normalized. Depending on a comparison between the first normalized correlation sequence and a first predetermined threshold as well as another comparison between the second normalized correlation sequence and a second predetermined threshold, the newly arrived network packet is determined accordingly whether it is an OFDM modulated packet.

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: The present invention relates to a method and controlling apparatus for controlling AGC unit. The method provided by the present invention first starts to receive a packet. After starting to receive a packet, an average envelope level of a received symbol in the packet is calculated, and a gain of the AGC unit is adjusted for a first time period by looking up the average envelope level in a table to obtain a first adjustment value. After the first time period is past, the method calculates the average envelope level and adjusting the gain of the AGC unit for a second time period by looking up the average envelope level in the table to obtain a second adjustment value. Moreover, the average envelope level is calculated every time after a first duration is past in the first time period, and is calculated every time after a second duration is past in the second time period, and the first duration is different from the second duration.