A receiver signal is sampled at a sampling rate equivalent to a chip rate at which chips of a known signal are timed. The resulting receiver signal samples are segmented into receiver signal segments, which are filtered by respective matched filters that are matched to known signal segments segmented from the known signal. Indexes are assigned to elements of the resulting filter response sequences to define an array thereof. Frequency transforms are computed of elements of the filter response sequences in respective columns of the array. Indexes are assigned to elements of the resulting frequency response sequences to define another array thereof. Channel effects imparted on a radio signal are jointly estimated from characteristics of the other array at which at least one local maximum is located.

A transmitter broadcasts a signal having a different code characteristic for each of several directions. A receiver receives the broadcast signal from one of the directions and generates an expected signal for that direction based on the code characteristic for that direction. The receiver detects the broadcast signal from the direction based on the expected signal for that direction.

In an example, a circuit includes a first signal path including a first filter having a first number of taps and having an input and an output. The circuit also includes a combiner having first and second inputs, the first input coupled to the output of the first filter. The circuit includes a second signal path coupled to the input of the first filter and to the second input of the combiner. The second signal path includes a gain component, a delay component coupled to the gain component, and a second filter having a second number of taps and coupled to the delay component.

In an example, a circuit includes a first signal path including a first filter having a first number of taps and having an input and an output. The circuit also includes a combiner having first and second inputs, the first input coupled to the output of the first filter. The circuit includes a second signal path coupled to the input of the first filter and to the second input of the combiner. The second signal path includes a gain component, a delay component coupled to the gain component, and a second filter having a second number of taps and coupled to the delay component.

A system for trans-horizon tropospheric-based wireless communication is provided. The system provides high availability and capacity as compared to a line-of-sight (LOS) standard microwave radio link while using very low height antenna towers. The system includes nn MIMO transceiver circuitry and two or more antennas and adaptive modulation and demodulation in response to slow varying pathloss. Each of the two or more antennas is located at a vertical height above an average sea mean level within the evaporation duct. Availability percentage for different pathloss ranges along with adaptive modulation contributes to the overall availability according to the varying evaporation duct height.

A system for trans-horizon tropospheric-based wireless communication is provided. The system provides high availability and capacity as compared to a line-of-sight (LOS) standard microwave radio link while using very low height antenna towers. The system includes nn MIMO transceiver circuitry and two or more antennas and adaptive modulation and demodulation in response to slow varying pathloss. Each of the two or more antennas is located at a vertical height above an average sea mean level within the evaporation duct. Availability percentage for different pathloss ranges along with adaptive modulation contributes to the overall availability according to the varying evaporation duct height.

The present invention discloses a method for processing a preamble sequence and header for a data packet, comprising the following steps of: using a bit sequence of a fixed pattern to replace a scrambled pseudo-random bit sequence in a SYNC field in the preamble sequence, and spreading the SYNC field by a Barker code; extending a length of a spreading code and spreading an SFD field in the preamble sequence by the extended spreading code; and extending a length of a spreading code and spreading a header field by the extended spreading code. The present invention may significantly improve the performance of reception and detection for the preamble sequence (the SYNC field and the SFD field) and the PLCP header field, better overcome long-distance channel conditions, enhance the signal stability of transmission; and meanwhile the present invention is easy to implement and only requires little modifications to the circuit of a conventional Wi-Fi device.

The present invention discloses a method for processing a preamble sequence and header for a data packet, comprising the following steps of: using a bit sequence of a fixed pattern to replace a scrambled pseudo-random bit sequence in a SYNC field in the preamble sequence, and spreading the SYNC field by a Barker code; extending a length of a spreading code and spreading an SFD field in the preamble sequence by the extended spreading code; and extending a length of a spreading code and spreading a header field by the extended spreading code. The present invention may significantly improve the performance of reception and detection for the preamble sequence (the SYNC field and the SFD field) and the PLCP header field, better overcome long-distance channel conditions, enhance the signal stability of transmission; and meanwhile the present invention is easy to implement and only requires little modifications to the circuit of a conventional Wi-Fi device.

Methods and apparatuses are provided for searching for a cell by a communication processor (CP) of a wireless terminal having a plurality of antennas. One of the plurality of antennas is selected based on whether a secondary antenna is in a driving state and whether a finger of a rake receiver has been allocated. The plurality of antennas includes a primary antenna and the secondary antenna. A cell search is performed through the selected one of the plurality of antennas.

Methods and apparatuses are provided for searching for a cell by a communication processor (CP) of a wireless terminal having a plurality of antennas. One of the plurality of antennas is selected based on whether a secondary antenna is in a driving state and whether a finger of a rake receiver has been allocated. The plurality of antennas includes a primary antenna and the secondary antenna. A cell search is performed through the selected one of the plurality of antennas.