A first communication device determines that each second communication device in a plurality of second communication devices has respective data to be transmitted to the first communication device. The first communication device transmits a request to the plurality of second communication devices to transmit data to the first communication device simultaneously during a transmit opportunity period of the first communication device. The first communication device receives data transmitted simultaneously by the plurality of second communication devices during the transmit opportunity period of the first communication device.

Systems and methods are provided for estimating the flow velocity of a multi-phase flow using signals of different frequencies. The signals can correspond to any convenient type of signal that interacts with contrast agents in the multi-phase flow, such as acoustic signals or electromagnetic signals. The signal emitters can be located so that one emitter/receiver pair is downstream from a second pair by a separation distance. The receivers can preferably be located in sufficient alignment with the emitters to receive a transmitted portion of the emitter signal after any scattering or attenuation from the contrast agents in the multi-phase fluid. The emitters can be configured to generate signals of different frequencies. This can allow filters to be used on the received signals, so that the resulting filtered signal from the first receiver corresponds substantially to energy received from the first emitter, while the filtered signal from the second receiver corresponds substantially to energy received from the second emitter. The filtered signals can then be cross-correlated to determine a time shift that results in a maximum correlation. This time shift can be used in conjunction with the distance between the emitters to calculate an estimated flow velocity.

Systems and methods are provided for estimating the flow velocity of a multi-phase flow using signals of different frequencies. The signals can correspond to any convenient type of signal that interacts with contrast agents in the multi-phase flow, such as acoustic signals or electromagnetic signals. The signal emitters can be located so that one emitter/receiver pair is downstream from a second pair by a separation distance. The receivers can preferably be located in sufficient alignment with the emitters to receive a transmitted portion of the emitter signal after any scattering or attenuation from the contrast agents in the multi-phase fluid. The emitters can be configured to generate signals of different frequencies. This can allow filters to be used on the received signals, so that the resulting filtered signal from the first receiver corresponds substantially to energy received from the first emitter, while the filtered signal from the second receiver corresponds substantially to energy received from the second emitter. The filtered signals can then be cross-correlated to determine a time shift that results in a maximum correlation. This time shift can be used in conjunction with the distance between the emitters to calculate an estimated flow velocity.

Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.

Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.

Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.

Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.