Code division multiple access (CDMA) communication system
DCFirst Claim
1. A multiple access, spread-spectrum communication system for processing a plurality of telecommunication information signals received simultaneously for simultaneous transmission over a radio frequency (RF) channel as a code-division-multiplexed (CDM) signal, the system comprising:
- means for receiving a call request signal corresponding to a telecommunication line information signal, and a user identification signal identifying a user to which the call request and information signal are addressed;
a plurality of modem processing means, one of the plurality of modem processing means providing a global pilot code signal, and each of the modem processing means providing a respective message code signal and combining one of the plurality of information signals with the respective message code signal to provide a spread-spectrum processed message signal, the plurality of message code signals of the plurality of modem processing means being synchronized to the global pilot code signal;
assignment means responsive to a channel assignment signal for coupling the information signals received on the telecommunication lines to respective indicated ones of the plurality of modem means;
a system channel controller, coupled to a remote call-processing means and responsive to the user identification signal, for providing the channel assignment signal; and
an RF transmitter means, connected to each of the plurality of modem processing means, for combining the plurality of spread-spectrum processed message signals with the global pilot code signal to generate a CDM signal;
for modulating a carrier signal with the CDM signal and for transmitting the modulated carrier signal through an RF communication channel.
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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 is 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.
266 Citations
9 Claims
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1. A multiple access, spread-spectrum communication system for processing a plurality of telecommunication information signals received simultaneously for simultaneous transmission over a radio frequency (RF) channel as a code-division-multiplexed (CDM) signal, the system comprising:
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means for receiving a call request signal corresponding to a telecommunication line information signal, and a user identification signal identifying a user to which the call request and information signal are addressed; a plurality of modem processing means, one of the plurality of modem processing means providing a global pilot code signal, and each of the modem processing means providing a respective message code signal and combining one of the plurality of information signals with the respective message code signal to provide a spread-spectrum processed message signal, the plurality of message code signals of the plurality of modem processing means being synchronized to the global pilot code signal; assignment means responsive to a channel assignment signal for coupling the information signals received on the telecommunication lines to respective indicated ones of the plurality of modem means; a system channel controller, coupled to a remote call-processing means and responsive to the user identification signal, for providing the channel assignment signal; and an RF transmitter means, connected to each of the plurality of modem processing means, for combining the plurality of spread-spectrum processed message signals with the global pilot code signal to generate a CDM signal;
for modulating a carrier signal with the CDM signal and for transmitting the modulated carrier signal through an RF communication channel. - View Dependent Claims (2, 3, 4, 9)
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5. A subscriber unit for a multiple access, spread-spectrum communication system that receives and processes a code-division multiplexed (CDM) signal which modulates a carrier signal in a radio frequency (RF) channel to reconstruct a transmitted information signal assigned to a subscriber comprising:
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receiving means for receiving the modulated carrier signal from the RF channel and for demodulating the CDM signal from the carrier signal; a subscriber unit controller; modem processing means comprising; a) global pilot code acquisition means comprising a global pilot code generation means for providing a global pilot code signal;
a plurality of global pilot code-phase delayed correlation means for correlating the global pilot code signal with the CDM signal to produce a despread global pilot code signal, the code phase of the global pilot signal being changed responsive to an acquisition signal; and
means for determining whether the despread global pilot signal is present to produce an acquisition signal;b) a plurality of message code generators which produce a plurality of message code signals synchronized to the global pilot code signal; and c) global pilot code tracking means for producing an error signal responsive to the acquisition signal; d) means for adjusting the global pilot code signal in phase, responsive to the error signal in a sense to produce the acquisition signal which corresponds to an increased level of the despread global pilot signal; and e) a plurality of message signal acquisition means for providing a plurality of despread receive message signals, each acquisition means including a plurality of message signal correlators, each message signal correlator correlating a respective one of the message code signals with the CDM signal to produce a respective despread receive message signal. - View Dependent Claims (6, 7, 8)
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Specification