In one embodiment, an apparatus includes: a radio frequency (RF) front end circuit to receive and downconvert a RF signal to a second frequency signal, the RF signal comprising an orthogonal frequency division multiplexing (OFDM) transmission; a digitizer coupled to the RF front end circuit to digitize the second frequency signal to a digital signal; and a baseband processor coupled to the digitizer to process the digital signal. The baseband circuit comprises a first circuit having a first plurality of correlators having an irregular comb structure, each of the first plurality of correlators associated with a carrier frequency offset and to calculate a first correlation on a first portion of a preamble of the OFDM transmission.

This application discloses a reference signal transmission method and apparatus. The method includes: generating one or more OFDM symbols, where at least one OFDM symbol includes a PTRS resource block, the PTRS resource block includes at least two of three sequences: a PTRS sequence of Y elements, X elements after the PTRS sequence, and Z elements before the PTRS sequence, and the PTRS resource block occupies a plurality of consecutive resource elements REs, where X, Y, and Z are all integers; and sending the one or more OFDM symbols. According to the foregoing method and apparatus, inter-carrier interference is reduced, thereby improving spectral efficiency.

DM-RS symbols may be inserted in the beginning of a subframe, or in two parts of the subframe. In one aspect, a method, a computer-readable medium, and an apparatus for dynamically conveying DM-RS information are provided. The apparatus may be a base station. The apparatus may determine the number of DM-RS symbols and/or the locations within a subframe for transmission of the DM-RS symbols. The apparatus may transmit the number of the DM-RS symbols and/or the locations within the subframe for transmission of the DM-RS symbols to a UE. In another aspect, a UE may receive the number of DM-RS symbols and/or the locations within a subframe for transmission of the DM-RS symbols from a base station. The UE may decode the DM-RS symbols from the subframe based on the number of the DM-RS symbols and/or the locations within a subframe for transmission of the DM-RS symbols.

A jitter measuring setup (10) comprises a signal generator (14), a sample-and-hold circuit (15), and the inventive all stochastic jitter measuring device (1) comprising signal acquisition means (2) and calculation means (3). The input signal of the sample-and-hold circuit (15) is generated by the signal generator (14). Furthermore, the output signal of the sample-and-hold circuit (15), respectively the input signal of the measuring device (1), is comprised of a superposition of the sampled input signal of the sample-and-hold circuit (15) and a cyclostationary random process.

In one aspect, a method for estimating residual carrier frequency offset (CFO) in a phase-modulated wireless signal having pseudo noise (PN) spreading is provided. The method includes receiving, at a digital transceiver, a plurality of PN spread blocks of in-phase and quadrature (I/Q) samples of the phase-modulated wireless signal and performing sample-level de-rotation, symbol-level de-spreading, and sign alignment. The method also includes estimating a phase difference and determining an estimated residual CFO based on the phase difference.

Systems and methods are disclosed herein to provide improved clock synchronization between wireless data communication transmitters and receivers, including Orthogonal Frequency Division Multiplexing (OFDM) communication systems. In accordance with one or more embodiments, a clock synchronization system is disclosed that includes an adaptive threshold function operative in conjunction with a synchronizer that adjusts the frequency and phase of a receive clock oscillator. Such a synchronization system may offer improved capabilities such as resistance to radio frequency (RF) channel impairments and noise, rejection of mis-decoded clock synchronization signals, and handling of multiple transmitters.

Flexible employment of frame configuration in light of the Doppler frequency change is proposed. According to the present invention, frame configuration for a predetermined frequency band may be changed. Changing frame configuration in the present invention may include changing the number (≧0) of zero-power subcarriers which alternate with nonzero-power subcarriers.

This application discloses a reference signal transmission method and apparatus. The method includes: generating one or more OFDM symbols, where at least one OFDM symbol includes a PTRS resource block, the PTRS resource block includes at least two of three sequences: a PTRS sequence of Y elements, X elements after the PTRS sequence, and Z elements before the PTRS sequence, and the PTRS resource block occupies a plurality of consecutive resource elements REs, where X, Y, and Z are all integers; and sending the one or more OFDM symbols. According to the foregoing method and apparatus, inter-carrier interference is reduced, thereby improving spectral efficiency.

The present invention concerns a method for correcting a frequency shift on symbols received by a receiver, each symbol being composed of N samples and of a cyclic prefix of a predetermined number Δ samples, the Δ samples being a copy of Δ samples of the N samples. The receiver: —calculates for each symbol, a correlation between at most the Δ samples of the cyclic prefix and the at most Δ samples among the last samples, —averages the correlations over a number of symbols and determines one smooth frequency shift estimation for each averaged correlation, —calculates an exponential from the smooth frequency shift estimation, delays the received symbols by a delay, —multiplies the exponential by the delayed received symbols.

Interference (I.sub.1, I.sub.2) is mitigated in a waveform received at the input of a receiver in a wireless network, the interference comprising passive intermodulation PIM products of at least a first signal (C.sub.1). A first stream of time samples (5) is generated of a simulated first PFM product of at least the first signal (C.sub.1), and a second stream of time samples (6) is generated of the simulated first PIM product. The second stream has a delay with respect to the first stream. A replica (8) is generated of the interference by processing (7) at least the first stream and the second stream, the processing comprising reducing a degree of correlation between the first stream and the second stream, and the replica of the interference is combined with a stream of time samples of the received waveform (40) to reduce the interference in the received waveform.