Rapid acquisition spreading codes for spread-spectrum communications
First 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.
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Citations
14 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 (5, 6, 7)
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2. 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 (RP) 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 (3, 4, 8)
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9. A bearer channel modification system for a multiple access spread-spectrum communication system including a plurality of information signals each having several different channel rates which information signals are transmitted as a plurality of message code channels over an Radio Frequency (RF) channel as a Code Division Multiplexed (CDM) signal, the system comprising
means for providing a plurality of call type signals corresponding to the information signal rates for the information signals; - wherein each of the plurality of message code channels supports a predetermined information channel rate;
a transmitter including a first information channel mode modification means responsive to the call type signal for changing the combination of the information signal from a first one of the message code signals to a second one of the message code signals which second message code signal supports a different information channel rate than the first message code signal; and
a receiver including a second information channel mode modification means responsive to the call type signal for changing a received information signal from the first message code signal to the second message code signal to support the different information channel rate. - View Dependent Claims (10, 11)
- wherein each of the plurality of message code channels supports a predetermined information channel rate;
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12. A multiple access spread-spectrum communication system for dynamically changing the transmission rate of a plurality of information signals received simultaneously over telecommunication lines by a base station and transmitted to a subscriber through a plurality of spread-spectrum message channels, the system comprising
a) a base station, connected to a remote call-processor which provides a call type signal identifying an information signal rate of the respective information signal and a conversion method for the respective information signal; - comprising;
a system channel controller which assigns each of the information signals and call type signals to a respective spread-spectrum message channel;
first information channel mode modification means connected to the system channel controller and responsive to the call type signal for changing the combination of the respective information signal from one spread-spectrum message channel to another pre-determined spread-spectrum message channel which supports a different information channel rate; and
b) a subscriber unit comprising;
a plurality of despreading means, each of the despreading means for recovering a respective one of the information signals and a respective one of the call type signals from a respective one of the spread-spectrum message channels;
second information channel mode modification means responsive to the call type signal for reassigning the despreading means to another determined despreading means corresponding to a different spread spectrum channel wherein a different information signal rate is supported; and
a signal conversion means responsive to the call type signal for selectively converting the despread information signal into a digital data signal.
- comprising;
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13. A method for capacity management in a spread-spectrum communication system including a base station and a plurality of subscriber units (SUs), wherein the base station transmits to the SUs a plurality of spread-spectrum channels including an access channel having a traffic access value which is received by each SU, and a respective plurality of message channels;
- and wherein each SU transmits to the base station an assigned channel having a power alarm value and a SU message channel, the method comprising the steps of;
measuring, by the base station, a transmit power level of the access channel and the plurality of message channels;
comparing, by the base station, the transmit power level to a first predetermined power value to produce a power comparison output value;
blocking transmission of an assigned channel and a respective SU message channel, responsive to the power comparison output value, by setting the traffic access value to a first predetermined value when the transmit power level is equivalent to or greater than the predetermined value, wherein one SU of the plurality of SUs, responsive to the traffic access value, does not transmit the assigned channel and the SU message channel;
measuring, by each ones of the SUs, a transmit power level of the respective SU for the respective assigned channel and message channel;
comparing by each ones of the SUs the transmit power level of the respective SU to a second predetermined value; and
indicating a maximum power condition to the base station, by one SU, by setting the respective power alarm value to an alarm condition value when the transmit power level of the SU is equivalent to or greater than the second predetermined value; and
blocking transmission of the respective assigned channel and SU message channel of each ones of the SUs, by the base station responsive to the alarm condition value, by setting the traffic access value to the first predetermined value.
- and wherein each SU transmits to the base station an assigned channel having a power alarm value and a SU message channel, the method comprising the steps of;
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14. A method for conserving capacity of an ISDN wireless link of a spread-spectrum communication system including a first spread-spectrum transceiver and a second spread-spectrum transceiver, said first spread-spectrum transceiver receiving a digital data signal including a predetermined flag pattern corresponding to an idle period and transferring the digital data signal to said second transceiver as a spread spectrum signal, and said second spread-spectrum transceiver receiving the spread spectrum signal and delivering the digital data signal, the method comprising the steps of:
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delaying, by the first transceiver, the digital data signal to form a delayed digital data signal;
monitoring the digital data signal to detect the predetermined flag pattern;
transmitting the delayed digital data signal as the spread-spectrum signal to the second transceiver;
suspending transmission of the delayed digital data signal when the flag pattern is present;
detecting, by the second transceiver, the absence of the delayed digital data signal; and
inserting the predetermined flag pattern in the delivered digital data signal.
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Specification