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 i 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.
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:
An automatic power control (APC) system for a spread-spectrum communications system includes an automatic forward power control (AFPC) system, and an automatic reverse power control (ARPC) system. In the AFPC, each subscriber unit (SU) measures a forward signal-to-noise ratio of a respective forward channel information signal to generate a respective forward channel error signal which includes a measure of the uncorrelated noise in the channel and a measure of the error between the respective forward signal-to-noise ration and a pre determined signal-to-noise value. A control signal generated from the respective forward channel error signal is transmitted as part of a respective reverse channel information signal. A base unit includes AFPC receivers which receive respective reverse channel information signals and extract the forward channel error signals therefrom to adjust the power levels of the respective forward spread-spectrum signals. In the ARPC system, each base measures a reverse signal-to-noise ratio of each of the respective reverse channel information signals and generates a respective reverse channel error signal which includes a measure of the uncorrelated noise in the channel and a measure of the error between the respective reverse signal-to-noise ratio and a pre determined signal-to-noise value. The base unit transmits a control signal generated from the respective reverse channel error signal as a part of a respective forward channel information signal. Each SU includes an ARPC receiver which receives the forward channel information signal and extracts the respective reverse error signal to adjust the reverse transmit power level of the respective reverse spread-spectrum signal.
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:
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:
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:
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:
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.