摘要:
A system and method for encrypting all channels of a wireless spread spectrum communication at the chip level. The PN sequence is encrypted with one or more encryption sequences and then used to spread the signal.
摘要:
A communication system (10), and a method executed by same, for allocating communications traffic through a plurality of satellites (12) of a constellation of low earth orbit satellites. Each of the plurality of satellites is oriented, at any given time when in view of a ground station (18), at a particular elevation angle. The method comprises the steps of: (a) providing each of the plurality of satellites with a receiver for receiving communication links from the ground station and a transmitter for transmitting communication links to user terminals; (b) in response to a request for service, determining if a highest elevation angle satellite can be assigned a new communications link; (c) if yes, assigning a new communication link to the highest elevation angle satellite; (d) if no, determining if a second highest elevation angle satellite can be assigned a new communications link; and (e) if yes, assigning a new communication link to the second highest elevation angle satellite. A number of different criteria can be employed in determining if a satellite can be assigned a new communication link, including: determining if the associated satellite has already been assigned a predetermined maximum number of communication links; and determining if the associated satellite, or a particular beam, is transmitting at or near to a power level that corresponds to a maximum peak flux density at the surface of the earth. Each of the steps of assigning is preferably accomplished such that the communication link is simultaneously established through at least two of the satellites to provide for diversity reception at a user's terminal (13).
摘要:
A communication system (10), and a method executed by same, for allocating communications traffic through a plurality of satellites (12) of a constellation of low earth orbit satellites. Each of the plurality of satellites is oriented, at any given time when in view of a ground station (18), at a particular elevation angle. The method comprises the steps of: (a) providing each of the plurality of satellites with a receiver for receiving communication links from the ground station and a transmitter for transmitting communication links to user terminals; (b) in response to a request for service, determining if a highest elevation angle satellite can be assigned a new communications link; (c) if yes, assigning a new communication link to the highest elevation angle satellite; (d) if no, determining if a second highest elevation angle satellite can be assigned a new communications link; and (e) if yes, assigning a new communication link to the second highest elevation angle satellite. A number of different criteria can be employed in determining if a satellite can be assigned a new communication link, including: determining if the associated satellite has already been assigned a predetermined maximum number of communication links; and determining if the associated satellite, or a particular beam, is transmitting at or near to a power level that corresponds to a maximum peak flux density at the surface of the earth. Each of the steps of assigning is preferably accomplished such that the communication link is simultaneously established through at least two of the satellites to provide for diversity reception at a user's terminal (13).
摘要:
The signal acquisition process of the present invention enables a radio to rapidly acquire a pilot signal from a satellite after the radio has been out of contact with the satellite for a length of time. The radio first acquires a satellite pilot signal and determines its position in relation to the earth. If the radio is now shut off or loses track of the pilot signal for some other reason, the radio keeps track of the length of time that it has been out of contact with the satellite. This length of time enables the radio to estimate the extent of possible position changes and, therefore, which satellites might be in view and their relative positions to the radio. This allows the radio to make assumptions about variables such as the Doppler shift of the signal that reduces the uncertainty inherent in the acquisition process and the size of the window that must be searched.
摘要:
The various embodiments provide systems, devices, and methods which include an acoustic tag configured to transmit an acoustic signal through a contact medium that may be received by an acoustic modem, with the acoustic signal configured to transmit information. By modulating sound traveling through an acoustic connection between the fluid container and a pump, meter or valve, information such as an identifier of the fluid or container may be transmitted without risk of confusion with other fluid containers in the vicinity. In a medical embodiment, IV fluid and the IV drip tube provide a fluid and plastic acoustic connection to an IV pumping or metering device and an IV bag through which sound may be transmitted. The transmission of identification information through this physical connection may insure that the pumping or metering device only communicates with the IV bag coupled to the pump. Acoustic tags may be active or passive.
摘要:
A server-assisted approach for synchronizing timebases (120 and 140) in a client-server system utilizes global positioning system (GPS) receivers (136 and 110) at both the client and server. In a typical implementation, the GPS receiver (136) associated with the client system receives fragmentary or incomplete data from satellites that are part of the GPS. Thus, the client GPS receiver (136) is capable of receiving only fragmentary information and cannot derive accurate time signals therefrom. The server system (102) is associated with a GPS receiver (110) capable of generating accurate time and position data based on signals from GPS satellites (114). The fragmentary information from the client GPS receiver (136) is transmitted to the server (126) along with time information indicating the time at which the client captured the fragmentary GPS data. The server (126) analyzes the fragmentary GPS data with respect to the complete GPS data available from the GPS receiver (110) associated with the server. The server (126) accurately determines the actual time at which the fragmentary GPS data was captured and transmits timing signals to the client (146). The timing signals are used to correct the client timebase (140) thus synchronizing the client and server timebases (140 and 120).
摘要:
Method and apparatus for tracking the frequency and phase of signals in spread spectrum communication systems that makes more efficient use of available carrier frequency and phase information by utilizing a substantial portion or all of the energy occupying the frequency spectrum of a received carrier signal, including energy from communication signals intended for other system users. Multiple spread spectrum communication signals are input in parallel to data receivers where they are despread using preselected despreading codes at an adjustable phase angle and decoded over multiple orthogonal codes active within the communication system. Multiple decoded signals are then combined to form a single phase detection signal which is used by at least one tracking loop to track frequency and phase of the carrier signal for the received communication signals. The tracking loop generates a timing signal which is used to adjust the phase angle used during despreading. In further embodiments, the communication signals are despread using appropriate PN codes and separated into in-phase (I) and quadrature channels (Q) where data symbols are processed by fast Hadamard transformers to generate corresponding data bits. The data is formed into pairwise products between the channels and summed over multiple or all active subscriber orthogonal codes. This sum indicates a degree to which the estimated phase differs from the actual phase of received communication signals and is used to adjust the phase of application for the PN codes.