摘要:
A method for identifying a leading edge time period of a received radio signal includes identifying a greatest energy time period in a sequence of time periods. The received radio signal has a greatest average energy in the greatest energy time period. The method also includes identifying a least energy time period in the sequence of time periods. The received radio signal has a least average energy in the least energy time period. Further, the method includes setting a threshold energy based on the greatest average energy and the least average energy, determining a number of window time periods based on a characteristic of a radio channel used by the received radio signal, and identifying as a leading edge time period an earliest time period that precedes the greatest energy time period within the number of window time periods. The received radio signal in the leading edge time period has an average energy greater than or equal to the threshold energy.
摘要:
A method and system (500) estimates a time of arrival of a signal received via a wireless communications channel. The energy in the received signal is conditioned at multiple different time scales to produce a conditioned signal (700). Then, a leading edge is detected in the conditioned signal (550). The leading edge corresponds to the time of arrival of the received signal (551).
摘要:
A method generates (200) a radio signal to be used for ranging. For each of one of multiple frames (501,505) to be transmitted as a ranging symbol, a first time interval (560) and a second time interval (580) are allocated. The ranging symbol is then transmitted as a set of pulses in each of the frames ((501,505)) only during the first time interval (560), and the second time interval (580) has a length to reduces inter-frame interference.
摘要:
An ad-hoc wireless communication network includes multiple nodes. Each node maintains a routing table. The routing table is constructed by broadcasting route request packets from a source node. The request packet includes an address of a destination node. Intermediate nodes in the network receiving the request packet, determine power and delay cost associated with the intermediate node participating in the route. If the cost is less than a threshold value, then the intermediate node participates in the routing of packets for other nodes. The intermediate node then sends a reply packet back to the source node. The reply packet includes the intermediate node addresses, as well as the power and delay costs. The source can thus construct the routing table. The source node can select a particular node for transferring application data packets based on either the power cost, the delay cost or both costs.
摘要:
A method locates a mobile node in a partially synchronized wireless network comprised of nodes with heterogeneous communication ranges. The time intervals it takes for messages to travel from stationary nodes at known location to a mobile node at an unknown location are measured and used to determine a set of possible coordinates of the mobile node. This time-based set of coordinates is in the form of a hyperbolic function. The received signal strengths of a message received from the mobile node is measured in two additional stationary nodes at known location. These RSS-based measurements provide two more sets of possible coordinates of the mobile node. The three sets are then intersected to estimate the location of the mobile node.
摘要:
A method for detecting unbalance in a 3-phase voltage signal is disclosed. The method includes determining an unbalance indicator as a value of a square of an amplitude of a positive sequence of the voltage signal; and comparing the unbalance indicator with a threshold to determine unbalance of the voltage signal.
摘要:
A method provides space-time adaptive processing (STAP) for target detection using adaptive matched filters (AMF). A generalized likelihood ratio test (GLRT) is determined where spatial and temporal correlation matrices Q and A are assumed. Then, the correlation matrices A and Q are replaced with maximum likelihood (ML) estimates obtained only from training signals subject to a persymmetric constraint.
摘要:
A method for detecting a target in a non-homogeneous environment using a space-time adaptive processing of a radar signal includes normalizing training data of the non-homogeneous environment to produce normalized training data; determining a normalized sample covariance matrix representing the normalized training data; tracking a subspace represented by the normalized sample covariance matrix to produce a clutter subspace matrix; determining a test statistic representing a likelihood of a presence of the target in the radar signal based on the clutter subspace matrix and a steering vector; and comparing the test statistic with a threshold to detect the target.
摘要:
A wireless network master node periodically broadcasts beacons that specify a structure of a following fixed length superframe. Slave nodes determine a channel condition between each slave and the master. Then, the set of slaves is partitioned into subsets of slaves according to the channel conditions. The master assigns, to each slave, a transmission rate in a low to high order according to the channel conditions, and the slaves transmit data to the master in the low to high order between two consecutive beacons, wherein the subsets of slaves with a higher transmission rate also receive the data from the subsets of slaves with a lower transmission rate, and wherein a slave with a higher transmission rate includes a part of or all the data from a slave with a lower transmission rate.
摘要:
A network includes a master node (master) and a set of slave nodes (slaves). The network uses orthogonal frequency-division multiplexing (OFDM) and time division multiple access (TDMA) symbols on sub-carriers. During a first downlink transmission from the master to the set of slaves using downlinks and all of the sub-carriers, a broadcast polling packet including data packets for each slave and sub-carrier assignments for the slaves is broadcast. Each slave transmits simultaneously to the master using uplinks and the assigned sub-carriers, a first response packet after receiving the broadcast polling packet. The master then broadcasts using the downlinks and all of the sub-carriers, a group acknowledgement packet, wherein the broadcast polling packet, the response packet, and the group acknowledgement packet include one superframe in one communication cycle, and wherein the broadcasting on the downlinks and the transmitting on the uplinks are disjoint in time.