Abstract:
PROBLEM TO BE SOLVED: To reduce power consumption of each of a plurality of transceiver stations constituting a spread spectrum communication system, especially a mobile subscriber station unit, as much as possible.SOLUTION: In a spectrum communication system which maintains an initial transmission power level of a second transceiver station in an inactive state, a first transceiver station despreads reception signals by using a selected chip code associated with a specific spread spectrum signal from the second transceiver station and measures a power level of the despread specific signal. The second transceiver station sometimes transmits the specific spread spectrum signal during the inactive state to a first transceiver, and the first transceiver station receives it, measures a noise power level in a communication channel, estimates a system transmission power level, compares the measured values with the estimated values, and transmits automatic power control (APC) signals to the second transceiver station on the basis of a comparison result. The second transceiver station adjusts the initial transmission power level in response to the APC signals.
Abstract:
A multiple access, spread-spectrum communication system processes a plurality of information signals received by a Radio Carrier Station (RCS) over telecommunication lines for simultaneous transmission over a radio frequency (RF) channel as a code-division-multiplexed (CDM) signal to a group of Subscriber Units (SUs). The RCS receives a call request signal that corresponds to a telecommunication line information signal, and a user identification signal that identifies a user to receive the call. The RCS includes a plurality of Code Division Multiple Access (CDMA) modems, one of which provides a global pilot code signal. The modems provide message code signals synchronized to the global pilot signal. Each modem combines an information signal with a message code signal to provide a CDM processed signal. The RCS includes a system channel controller coupled to receive a remote call. An RF transmitter is connected to all of the modems to combine the CDM processed signals with the global pilot code signal to generate a CDM signal. The RF transmitter also modulates a carrier signal with the CDM signal and transmits the modulated carrier signal through an RF communication channel to the SUs. Each SU includes a CDMA modem which is also synchronized to the global pilot signal. The CDMA modem despreads the CDM signal and provides a despread information signal to the user. The system includes a closed loop power control system for maintaining a minimum system transmit power level for the RCS and the SUs, and system capacity management for maintaining a maximum number of active SUs for improved system performance.
Abstract:
PROBLEM TO BE SOLVED: To reduce noise due to an interference signal in a direct sequence spread spectrum code division multiple access(CDMA) receiver. SOLUTION: In an interference eliminating device, the spread spectrum CDMA signal is inversely spread into plural inverse spread signals by using plural chip code signals from chip code signal generators 52, 62, 72 by correlation devices 54, 64, 74. A spread processing is performed for the plural inverse spread signals by using synchronous output of the plural chip code signal from delaying devices 53, 63, 73 by plural spread spectrum processing circuits 55, 65, 75. Each of N-1 pieces of the inverse spread signals to which the spread processing is performed is subtracted from the spread spectrum CDMA signals to recover a code channel using the i-th chip code signal and the subtracted signal is generated by this subtraction by a subtracting circuit 150. The subtracted signal is inversely spread by a channel correlation device 146.
Abstract:
A multiple access, spread-spectrum communication system processes a plurality of information signals received by a Radio Carrier Station (RCS) over telecommunication lines for simultaneous transmission over a radio frequency (RF) channel as a code-division-multiplexed (CDM) signal to a group of Subscriber Units (SUs). The RCS receives a call request signal that corresponds to a telecommunication line information signal, and a user identification signal that identifies a user to receive the call. The RCS includes a plurality of Code Division Multiple Access (CDMA) modems, one of which provides a global pilot code signal. The modems provide message code signals synchronized to the global pilot signal. Each modem combines an information signal with a message code signal to provide a CDM processed signal. The RCS includes a system channel controller coupled to receive a remote call. An RF transmitter is connected to all of the modems to combine the CDM processed signals with the global pilot code signal to generate a CDM signal. The RF transmitter also modulates a carrier signal with the CDM signal and transmits the modulated carrier signal through an RF communication channel to the SUs. Each SU includes a CDMA modem which is also synchronized to the global pilot signal. The CDMA modem despreads the CDM signal and provides a despread information signal to the user. The system includes a closed loop power control system for maintaining a minimum system transmit power level for the RCS and the SUs, and system capacity management for maintaining a maximum number of active SUs for improved system performance.
Abstract:
The present invention claims a multiple access spread-spectrum communication system for dynamically changing a transmission rate of an information signal received from a remote processing unit (RPU) over a telecommunication line and transmitted to a subscriber through a first spread-spectrum message channel of a plurality of spread spectrum message channels, the system comprising a) a base station, connected to the RPU, which identifies an information signal rate of the respective information signal and provides a modify signal responsive to the information signal rate; comprising: a system channel controller which assigns the information signal and the modify signal to respectively different ones of the plurality of spread-spectrum message channels; first information channel mode modification means connected to the system channel controller and responsive to the modify signal for switching the respective information signal from the first spread-spectrum message channel supporting a first information channel rate to one other pre-determined spread-spectrum message channel, the one other pre-determined spread-spectrum message channel having a different information channel rate supporting the identified information signal rate; and b) a subscriber unit comprising: a first despreading means for recovering the respective information signal and modify signal from the first spread spectrum message channel; second information channel mode modification means responsive to the modify signal for reassigning the first despreading means to a second despreading means which supports the different information channel rate, the second despreading means corresponding to the second spread spectrum message channel.
Abstract:
PROBLEM TO BE SOLVED: To provide a subscriber station unit for a large capacity multiple access spread spectrum communication system, which forms a plurality of concurrent user bearer channels through a prescribed radio frequency, to enable dynamic allocation of a bearer channel speed, while preventing multipath interference. SOLUTION: The subscriber station unit for the multiple access spread spectrum communication system includes a receiving means, a subscriber station unit controller, and a modem-processing means provided with a global pilot code acquiring means, a plurality of message code generators, a global pilot code tracking means, a phase-adjusting means and a plurality of message- acquiring means. COPYRIGHT: (C)2003,JPO
Abstract:
PROBLEM TO BE SOLVED: To provide a high-speed capture device by which the spread code phase of a spread spectrum communication system is rapidly synchronized with a transmission code signal provided with a transmission I code signal including a first spread code sequence and a transmission Q code signal includ ing a second spread code sequence. SOLUTION: The high-speed capture device includes: a receiving means for receiving the transmission code signal, and separating the transmission I code signal from the transmission Q code signal; a correlation means provided with an I code signal correlator and a Q code signal correlator; a local code sequence generator; and a controller which is connected to the I code signal correlator, the Q code signal correlator, and the local code sequence generator, so as to decide, achieve and keep a code sequence lock. COPYRIGHT: (C)2003,JPO
Abstract:
PROBLEM TO BE SOLVED: To provide a method for managing capacity in a spread spectrum communication system including a base station and a plurality of subscriber stations. SOLUTION: The base station includes the processes for: measuring the transmission power levels of a connection channel and a plurality of message channels; comparing the transmission power levels with a first prescribed power value to generate a power comparison result value; and setting a traffic connection value in the first prescribed value to interrupt the transmission of an allocated channel and the message channels of each of the subscriber stations when the transmission power level is consequently equal to or more than the prescribed power value. Each of the subscriber stations includes the processes for: allocating a transmission power level to measure a channel and a message channel; comparing the transmission power level with a second prescribed value; and displaying a maximum power state in the base station when one transmission power level is equal to or more than the second prescribed value. The base station further includes a process for interrupting the transmission of the allocated channel and message channel of each of the subscriber stations in response to the maximum power state. COPYRIGHT: (C)2003,JPO
Abstract:
PROBLEM TO BE SOLVED: To provide a method of efficiently utilizing an ISDN radio link capacity of a spread spectrum communication system, including first and second spread spectrum transceivers. SOLUTION: The method comprises a process for delaying a digital data signal by a first spread spectrum transceiver to form a delayed digital data signal, a process for monitoring the digital data signal to detect a predetermined flag pattern, a process for transmitting the delayed digital data signal to a second spread spectrum transceiver as a spread spectrum signal, a process for interrupting transmission of the delayed digital data signal when the predetermined flag pattern exists, a process for detecting absence of the delayed digital data signal by the second spread spectrum transceiver, and a process for inserting the predetermined flag pattern into the transmitted digital data signal. COPYRIGHT: (C)2003,JPO
Abstract:
A spread-spectrum CDMA interference canceler for reducing interference in a DS/CDMA receiver having N chip-code channels. The interference canceler includes a plurality of correlators (54, 64, 74), a plurality of spread-spectrum-processing circuits (55, 65, 75), subtracting circuits (150), and channel correlators (146). Using a plurality of chip-code signals generated from chip codeword signal generators (52, 62, 72), the correlators (54, 64, 74) despreads the spread-spectrum CDMA signal as a plurality of despread signals. The plurality of spread-spectrum-processing circuits (55, 65, 75) uses a timed version of the plurality of chip-code signals generated from the delay devices (53, 63, 73), for spread-spectrum processing the plurality of despread signals. For recovering a code channel using an ith chip-code-signal, the subtracting circuits (150) subtracts from the spread-spectrum CDMA signal, each of the N-1 spread-spectrum-processed-despread signals thereby generating a subtracted signal. The channel-correlator (146) despreads the subtracted signal.