Techniques are described for carrier frequency offset (CFO) and channel estimation of orthogonal frequency division multiplexing (OFDM) transmissions over multiple-input multiple-output (MIMO) frequency-selective fading channels. A wireless transmitter forms blocks of symbols by inserting training symbols within two or more blocks of information-bearing symbols. The transmitter applies a hopping code to each of the blocks of symbols to insert a null subcarrier at a different position within each of the blocks of symbols, and a modulator outputs a wireless signal in accordance with the blocks of symbols. A receiver receives the wireless signal and estimates the CFO, and outputs a stream of estimated symbols based on the estimated CFO.

A radio frequency transmission system and methods for mitigating multipath radio frequency interference are disclosed. Embodiments include a first helical antenna having a first radius and operable to receive a first electromagnetic signal, and a second helical antenna having a second radius and operable to receive a second electromagnetic signal. Further embodiments include a phase adjuster configured to receive the first electromagnetic signal as an input signal, apply an adjustable phase delay to the input signal, and output an adjusted electromagnetic signal. Still further embodiments include a signal combiner configured to receive the adjusted electromagnetic signal and the second electromagnetic signal and output a combined electromagnetic signal.

The method includes configuring a first CLI-RS configuration at a first UE (200a). Further, the method includes configuring a second CLI-RS configuration at a second UE (200b). Further, the method includes generating a CLI-RS sequence using a common CLI-RS reference point known to the first UE (200a) and the second UE (200b). Further, the method includes filling the CLI-RS sequence in the first set of CLI-RS resources indicated in the first CLI-RS configuration. Further, the method includes transmitting the CLI-RS sequence filled in the first set of CLI-RS resources indicated in the first CLI-RS configuration to the second UE (200b). Further, the method includes receiving the CLI-RS sequence transmitted by the first UE (200a). Further, the method includes processing the received CLI-RS sequence based on the second CLI-RS configuration.

Filtering for sampled data representing uplink wireless RF signals monitored by a pair of antennas is provided to improve accuracy in determining an angular location of an identified UE. An extracted portion of the filtered sampled data is used to improve accuracy in determining an angular location of the identified UE. The extracted portion represents direct path uplink wireless RF signals that have traveled by a line of sight between the pair of antennas and the identified UE. Another portion of the filtered sampled data is cancelled, which represents multiple path (multipath) uplink wireless RF signals that have traveled a longer distance than the direct path signals due to reflection from one or more surfaces on multiple paths between the identified UE and the pair of antennas.

Filtering for sampled data representing uplink wireless RF signals monitored by a pair of antennas is provided to improve accuracy in determining an angular location of an identified UE. An extracted portion of the filtered sampled data is used to improve accuracy in determining an angular location of the identified UE. The extracted portion represents direct path uplink wireless RF signals that have traveled by a line of sight between the pair of antennas and the identified UE. Another portion of the filtered sampled data is cancelled, which represents multiple path (multipath) uplink wireless RF signals that have traveled a longer distance than the direct path signals due to reflection from one or more surfaces on multiple paths between the identified UE and the pair of antennas.

A radio frequency transmission system and methods for mitigating multipath radio frequency interference are disclosed. Embodiments include a first helical antenna having a first radius and operable to receive a first electromagnetic signal, and a second helical antenna having a second radius and operable to receive a second electromagnetic signal. Further embodiments include a phase adjuster configured to receive the first electromagnetic signal as an input signal, apply an adjustable phase delay to the input signal, and output an adjusted electromagnetic signal. Still further embodiments include a signal combiner configured to receive the adjusted electromagnetic signal and the second electromagnetic signal and output a combined electromagnetic signal.

Techniques are described for carrier frequency offset (CFO) and channel estimation of orthogonal frequency division multiplexing (OFDM) transmissions over multiple-input multiple-output (MIMO) frequency-selective fading channels. A wireless transmitter forms blocks of symbols by inserting training symbols within two or more blocks of information-bearing symbols. The transmitter applies a hopping code to each of the blocks of symbols to insert a null subcarrier at a different position within each of the blocks of symbols, and a modulator outputs a wireless signal in accordance with the blocks of symbols. A receiver receives the wireless signal and estimates the CFO, and outputs a stream of estimated symbols based on the estimated CFO.

Using a phase interferometry method which utilizes both amplitude and phase allows the determination and estimation of multipath signals. To determine the location of an object, a signal that contains sufficient information to allow determination of both amplitude and phase, like a packet that includes a sinewave portion, is provided from a master device. A slave device measures the phase and amplitude of the received packet and returns this information to the master device. The slave device returns a packet to the master that contains a similar sinewave portion to allow the master device to determine the phase and amplitude of the received signals. Based on the two sets of amplitude and phase of the RF signals, the master device utilizes a fast Fourier transform or techniques like multiple signal classification to determine the indicated distance for each path and thus more accurately determines a location of the slave device.

The present disclosure provides a radio communication apparatus, a radio communication system, a radio communication method, and a program capable of demodulating signals at appropriate reception timings. A radio communication apparatus 11 includes: a measurement unit 111 configured to measure delay profiles of a plurality of frequency bands; and a determination unit 112 configured to determine a path timing of a first frequency band f.sub.1 based on a time difference between a first time t.sub.m1 indicating a time of a maximum amplitude in the first frequency band f.sub.1 of the plurality of frequency bands and a second time t.sub.m2 indicating a time of a maximum amplitude in a second frequency band f.sub.2 of the plurality of frequency bands.

Different numerologies may be used to communicate orthogonal frequency division multiplexing (OFDM)-based signals over different frequency sub-bands of a given carrier. This may allow the OFDM-based signals to efficiently support diverse traffic types. In some embodiments, the numerology of OFDM-based signal depends on a bandwidth of the frequency sub-band over which the OFDM-based signals are transmitted. In some embodiments, the OFDM-based signals are filtered OFDM (f-OFDM) signals, and the pulse shaping digital filter used to generate the f-OFDM signals allows the receiver to mitigate interference between adjacent f-OFDM signals upon reception, thereby allowing f-OFDM signals to be communicated over consecutive carriers without relying on a guard band.