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Claims  |
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I claim:
1. A method of connecting a telecommunication network to a
telecommunication system, the telecommunication system including:
a plurality of telecommunication facilities for distributing forward
message and signaling data from the telecommunication network to
telecommunication system users and for directing reverse message and
signaling data from telecommunication system users to the
telecommunication network;
a control means for switching message and signaling data between the
telecommunication network and the plurality of telecommunication
facilities;
a plurality of independent, not necessarily uniform, general processors to
run respective modem programs for receiving and transferring forward
message and signaling data and for receiving and transferring reverse
message and signaling data; and
a plurality of modem apparatuses for modulating forward message and
signaling data for distribution to telecommunication system users and for
demodulating reverse message and signaling data for provision to the
telecommunication network;
wherein, each telecommunication facility includes:
one or more general processors, each general processor of the one or more
general processors coupled to the control means;
one or more modem apparatuses; and
one or more interfaces, each interface connecting a respective general
processor of the one or more general processors with a respective modem
apparatus of the one or more modem apparatuses and including signal
connections and control functions that are specific to the respective
general processor of the one or more general processors;
the method including the steps of:
running a modem program in a general processor to receive and transfer
forward message and signaling data and to receive and transfer reverse
message and signaling data;
issuing messages from the modem program to the control means to provide
reverse message and signaling data;
receiving messages from the control means that include forward message and
signaling data;
formatting the forward message and signaling data; and
the respective modem program calling interface control functions to provide
forward message and signaling data to, and receive reverse message and
signaling data from, signal connections of a respective interface that
connects the general processor with the modem apparatus.
2. The method of claim 1, wherein the modem program includes:
pilot channel means for generating a pilot code sequence;
synchronization channel means for generating a repeating synchronization
message;
paging channel means for receiving forward signaling data from the control
means;
traffic channel means for receiving forward message data from the control
means; and
driver means for coupling the pilot channel means, synchronization channel
means, paging channel means, and traffic channel means to the respective
interface;
the step of running a modem program including:
operating one or more of the pilot channel means, the synchronization
channel means, and the paging channel means; or
operating the traffic channel means; and
coupling the pilot code sequence, the synchronization message, and forward
signaling data, or forward message data to the respective interface.
3. The method of claim 1, wherein the modem program includes:
access channel means for receiving reverse signaling data from the
respective interface;
traffic channel means for receiving reverse message data from the
respective interface; and
driver means for coupling the access channel means and the traffic channel
means to the respective interface;
the step of running a modem program including:
operating the access channel means; or
operating the traffic channel means; and
coupling reverse signaling data to the access channel means or coupling
reverse message data to the traffic channel means.
4. The method of claim 2, wherein the modem program further includes:
access channel means for receiving reverse signaling data from the
respective interface;
and, wherein:
the traffic channel means is further for receiving reverse message data
from the respective interface; and
the driver means is further for coupling reverse signaling data from the
respective interface to the access channel means and for coupling reverse
message data from the respective interface to the traffic channel means;
the step of running a modem program including:
operating the pilot channel means and synchronization channel means; and
coupling the pilot code sequence and the synchronization message to the
respective interface.
5. The method of claim 2, wherein the modem program further includes:
access channel means for receiving reverse signalling data from the
respective interface;
and, wherein:
the traffic channel means is further for receiving reverse message data
from the respective interface; and,
the driver means is further for coupling reverse signalling data from the
respective interface to the access channel means and for coupling reverse
message data from the respective interface to the traffic channel means;
the step of running a modem program including:
operating the pilot channel means and paging channel means; and
coupling the pilot code sequence and forward signalling data to the
respective interface.
6. The method of claim 2, wherein the modem program further includes:
access channel means for receiving reverse signalling data from the
respective interface;
and, wherein:
the traffic channel means is further for receiving reverse message data
from the respective interface; and
the driver means is further for coupling reverse signalling data from the
respective interface to the access channel means and for coupling reverse
message data from the respective interface to the traffic channel means;
the step of running a modem program including:
operating the access channel means and coupling reverse signalling data
from the respective interface to the access channel means.
7. The method of claim 2, wherein the modem program further includes:
access channel means for receiving reverse signalling data from the
respective interface;
and, wherein:
the traffic channel means is further for receiving reverse data message
from the respective interface; and
the driver means is further for coupling reverse signalling data from the
respective interface to the access channel means and for coupling reverse
message data from the respective interface to the traffic channel means;
the step of running the modem program including:
operating the traffic channel means;
coupling forward message data from the traffic channel to the respective
interface; and
of coupling reverse message data from the respective interface to the
traffic channel means.
8. The method of claim 1, wherein the modem program includes:
traffic channel means for receiving forward message data from the control
means and for receiving reverse message data from the respective
interface; and
driver means for coupling the traffic channel means to the respective
interface;
the step of running a modem program including:
operating the traffic channel means;
coupling forward message data from the traffic channel means to the
respective interface; and
coupling reverse message data from the respective interface to the traffic
channel means.
9. The method of claim 1, wherein the modem program includes:
pilot channel means for generating a pilot sequence; and
driver means for coupling the pilot channel means to the respective
interface;
the step of running a modem program including:
operating the pilot channel means; and
coupling the pilot code sequence to the respective interface.
10. A telecommunications interface system, to connect:
a telecommunication network; with
a telecommunication system for distributing forward message and signaling
data from the telecommunication network to telecommunication system users
and for directing reverse message and signaling data from
telecommunication system users to the telecommunication network;
the telecommunications interface system comprising:
a control means connected to the telecommunication network and to the
telecommunication system for switching message and signaling data
therebetween; and
a plurality of telecommunication facilities connected to the control means,
each telecommunication facility including:
one or more independent but not necessarily uniform general processors to
run respective modem programs for receiving forward message and signaling
data and for receiving reverse message and signaling data;
one or more modem apparatuses for modulating forward message and signaling
data for distribution to the telecommunication system users and for
demodulating reverse message and signaling data for provision to the
telecommunication network;
one or more interfaces, each interface connecting a respective general
processor of the one or more general processors with a respective modem
apparatus of the one or more modem apparatuses and including signal
connections and control functions that are specific to the respective
general processor; and
each modem program executing in a general processor of the one or more
general processors to receive forward message and signaling data and to
receive reverse message and signaling data by:
issuing messages to the control means that include reverse message and
signaling data;
receiving messages from the control means that include forward message and
signaling data;
executing in its own process space the control functions of an interface to
provide forward message and signaling data to the signal connections of
the interface and to receive the demodulated reverse message and signaling
data from the signal connections of the interface.
11. The telecommunications interface system of claim 10, wherein each modem
program includes:
pilot channel means for generating a pilot code sequence;
synchronization channel means for generating a repeating synchronization
message;
paging channel means for receiving forward signalling data from the control
means;
traffic channel means for receiving forward message data from the control
means; and
driver means for coupling the pilot channel means, synchronization channel
means, paging channel means, and traffic channel means to the interface.
12. The telecommunications interface system of claim 11, wherein the modem
program concurrently operates the pilot channel means and the
synchronization channel means, whereby the pilot code sequence and the
synchronization message are coupled to the interface.
13. The telecommunications interface system of claim 11, wherein the modem
program operates the pilot channel means and the paging channel means,
whereby the pilot code sequence and forward signalling data are coupled to
the interface.
14. The telecommunications interface system of claim 10, wherein the modem
program includes:
access channel means for receiving reverse signalling data from the
interface;
traffic channel means for receiving reverse message data from the
interface; and
driver means for coupling the access channel means or the traffic channel
means to the interface;
whereby reverse signalling data is coupled to the access channel means or
reverse message data is coupled to the traffic channel means.
15. The telecommunications interface system of claim 10, wherein the modem
program means includes:
traffic channel means for receiving forward message data from the control
means and for receiving reverse message data from the interface; and
driver means for coupling the traffic channel means to the interface;
whereby forward signalling data is coupled from the traffic channel means
to the interface and reverse message data is coupled from the interface to
the traffic channel means.
16. The telecommunications interface system of claim 10, wherein the modem
program includes:
pilot channel means for generating a pilot code sequence; and
driver means for coupling the pilot channel means to the interface.
17. The telecommunications interface system of claim 10, wherein the modem
program includes:
synchronization channel means for generating a repeating synchronization
message; and
driver means for coupling the synchronization channel means to the
interface.
18. The telecommunications interface system of claim 10, wherein the modem
program includes:
paging channel means for receiving signalling data from the control means;
and
driver means for coupling the paging channel means to the interface.
19. The telecommunications interface system of claim 10, wherein the modem
program includes:
access channel means for receiving a reverse signalling data from the
interface; and
driver means for coupling the access channel means to the interface.
20. A telecommunications interface system, to connect:
a telecommunication network; with
a telecommunication system for distributing forward message and signalling
data from the telecommunication network in forward channels to
telecommunication users and for directing reverse message and signalling
data in reverse channels from telecommunication system users to the
telecommunication network;
the telecommunications interface system comprising:
a control means connected to the telecommunication network and to the
telecommunication system for switching message and signalling data
therebetween, and for providing channel commands representing forward and
reverse channels;
a plurality of telecommunication facilities connected to the control means,
each telecommunication facility including:
one or more independent but not necessarily uniform general processors to
run respective modem programs;
one or more modem apparatuses for modulating forward message and signalling
data for distribution to the telecommunication system users in forward
channels and for demodulating reverse message and signalling data in
reverse channels for provision to the telecommunication network;
one or more interfaces, each interface connecting a respective general
processor of the one or more general processors with the respective modem
apparatus of the one or more modem apparatuses and including signal
connections and control functions that are specific to the respective
general processors; and
each modem program for executing in a general processor of the one or more
general processors to receive channel commands from the control means to
establish forward channels and reverse channels in response to the channel
commands by:
providing the channel configuration information to a respective modem
apparatus coupled by a respective interface to the general processor of
the one or more general processors in which the modem program executes.
21. The telecommunications interface system of claim 20, wherein each modem
program includes:
pilot channel means for generating pilot channel configuration information;
synchronization channel means for generating synchronization channel
configuration information;
paging channel means for generating paging channel configuration
information;
traffic channel means for generating traffic channel configuration
information; and
driver means for coupling the pilot channel means, synchronization channel
means, paging channel means, and traffic channel means to the interface.
22. The telecommunications interface system of claim 21 wherein the modem
program concurrently operates the pilot channel means and the
synchronization channel means, whereby the pilot channel configuration
information and the synchronization channel configuration information are
coupled to the interface.
23. The telecommunications interface system of claim 21, wherein the modem
program operates the pilot channel means and the paging channel means,
whereby the pilot channel configuration information and the paging channel
configuration information are coupled to the interface.
24. The telecommunications interface system of claim 20, wherein the modem
program includes:
access channel means for generating access channel configuration
information;
traffic channel means for generating traffic channel configuration
information;
driving means for coupling the access channel means or the traffic channel
means to the interface; and
whereby, access channel configuration information or traffic channel
configuration information is coupled to the interface.
25. The telecommunications interface system of claim 20, wherein the modem
program includes:
traffic channel means for generating traffic channel configuration
information;
driver means for coupling the traffic channel configuration information to
the interface; and
whereby traffic channel configuration information is coupled from the
traffic channel means to the interface.
26. The telecommunications interface system of claim 20, wherein the modem
program includes:
pilot channel means for generating pilot channel configuration information;
and
driver means for coupling the pilot channel configuration information to
the interface.
27. The telecommunications interface system of claim 20, wherein the modem
program includes:
synchronization channel means for generating synchronization channel
configuration information; and
driver means for coupling the synchronization channel configuration
information to the interface.
28. The telecommunications interface system of claim 20, wherein the modem
program includes:
paging channel means for generating paging channel configuration
information; and
driver means for coupling the paging channel configuration information to
the interface.
29. The telecommunications interface system of claim 20, wherein the modem
program includes:
access channel means for generating access channel configuration
information; and
driver means for coupling the access channel configuration information to
the interface.
30. A method of connecting a telecommunication network to a
telecommunication system, the telecommunication system including:
a plurality of telecommunication facilities for distributing forward
message and signalling data from the telecommunication network in forward
channels to telecommunication user and for directing reverse message and
signalling data in reverse channels from telecommunication system users to
the telecommunication network;
control means for switching message and signalling data between the
telecommunication network and the plurality of telecommunication
facilities and for providing channel commands representing forward and
reverse channels;
a plurality of independent, not necessarily uniformed, general processors
to run respective modem programs; and
a plurality of modem apparatuses responsive to channel configuration
information for modulating forward message and signalling data for
distribution to the telecommunication system users in forward channels and
for demodulating reverse message and signalling data in reverse channels
for provision to the telecommunication network;
wherein, each telecommunication facility includes:
one or more general processors, each general processor of the one or more
general processors coupled to the control means;
one or more modem apparatuses; and
one or more interfaces, each interface connecting a respective general
processor of the one or more general processors with a respective modem
apparatus of the one or more modem apparatuses and including signal
connections and control functions that are specific to the respective
general processor of the one or more general processors;
the method including the steps of:
running a modem program in a general processor to receive channel commands
representing forward and reverse channels;
providing the channel configuration information to a respective modem
apparatus coupled by a respective interface to the general processor of
the one or more general processors in which the modem program executes.
31. The method of claim 30, wherein the modem program includes:
pilot channel means for generating pilot channel configuration information;
synchronization channel means for generating synchronization channel
configuration information;
paging channel means for generating paging channels configuration
information;
traffic channel means for generating traffic channel configuration
information; and
driver means for coupling the pilot channel means, synchronization channel
means, paging channel means, and traffic channel means to the respective
interface;
the step of running a modem program including:
operating one or more of the pilot channel means, the synchronization
channel means, and the paging channel means; or
operating the traffic channel means; and
coupling the pilot channel configuration information, the synchronization
channel configuration information, and paging channel configuration
information; or
coupling traffic channel configuration information to the respective
interface.
32. The method of claim 30, wherein the modem program includes:
access channel means for generating access channel configuration
information;
traffic channel means for generating traffic channel configuration
information;
driver means for coupling the access channel means and the traffic channel
means to the respective interface;
the step of running a modem program including:
operating the access channel means; or
operating the traffic channel means; and
coupling access channel configuration information or traffic channel
configuration information to the respective interface.
33. The method of claim 30, wherein the modem program means includes:
traffic channel means for generating traffic channel configuration
information; and
driver means for coupling the traffic channel means to the respective
interface;
the step of running a modem program including:
operating the traffic channel means; and
coupling the traffic channel configuration information from the traffic
channel means to the respective interface.
34. The method of claim 30, wherein the modem program includes:
pilot channel means for generating pilot channel configuration information;
and
driver means for coupling the pilot channel means to the respective
interface;
the step of running a modem program including:
operating the pilot channel means; and
coupling the pilot channel configuration information to the respective
interface. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a spread spectrum telecommunications
system and, more particularly, to a channel element modem in a CDMA
cellular communication system.
2. Description of the Related Art
To serve a large number of telecommunication users over a limited
electro-magnetic spectrum, one of a variety of multiple access techniques
may be used. These techniques include, for example, time division multiple
access (TDMA), frequency division multiple access (FDMA), and code
division multiple access (CDMA). The CDMA technique has many advantages
over the other techniques, and an exemplary CDMA system is described in
U.S. Pat. No. 4,901,307 issued Feb. 13, 1990, assigned to the assignee of
this invention, and incorporated herein by reference.
In the CDMA cellular system described in the '307 patent, a large number of
mobile telephone system users, each having a transceiver, communicates
through satellite repeaters or terrestrial stations which are also
referred to as cells. Each cell includes a physical plant called a base
station. A cell covers a limited geographic area and routes calls carried
over cellular telephones to and from a telecommunication network such as a
public switched telephone network (PSTN). When a cellular telephone user
moves into the geographic area of a new cell, the routing of that user's
call may be eventually made through the new cell by a process called
"handing off".
A cellular telephone or, more specifically, a mobile unit, broadcasts a
signal that is received by a cell and then is routed to the PSTN and to
telephone lines or other mobile units. A cell broadcasts a cell signal
that is received by mobile units. The cell-to-mobile signal transmission
path is generally referred to as the "forward link" and the mobile-to-cell
transmission path is generally referred to as the "reverse link".
The CDMA technique permits a frequency spectrum to be effectively used
multiple times within a time interval, thus increasing system user
capacity. The CDMA technique described in the '307 patent makes use of
high-frequency pseudo-noise (PN) code modulation of individual calls, as
well as modulation by codes including orthogonal binary sequences, to
combine many calls and broadcast them as a single CDMA signal. In this
way, the CDMA technique permits discrimination between many calls that
occupy the same frequency band and provides increased spectral efficiency
as compared with other techniques.
A system and method for CDMA telephone system communications is described
in U.S. Pat. No. 5,103,459, issued Apr. 7, 1992 and in U.S. Pat. No.
5,267,261, issued Nov. 30, 1993, both assigned to the assignee of the
present invention, and both incorporated herein by reference. These
patents both disclose base station architecture and operation. The
following co-pending U.S. Patent Applications, assigned to the assignee of
this application, describe modulator-demodulator (MODEM) architectures
that implement a complete CDMA base band modem that performs reverse link
demodulation and forward link modulation:
1. U.S. patent application Ser. No. 08/316,156, filed Sep. 30, 1994, for
"SERIAL LINKED INTERCONNECT FOR SUMMATION OF MULTIPLE WAVEFORMS ON A
COMMON CHANNEL", inventors K. Easton et al.;
2. U.S. patent application Ser. No. 08/316,177, filed Sep. 30, 1994, for
"MULTIPATH SEARCH PROCESSOR FOR A MULTIPLE ACCESS COMMUNICATION SYSTEM",
inventors K. Easton et al.;
3. U.S. patent application Ser. No. 08/372,632, filed Jan. 13, 1995, for
"CELL SITE DEMODULATOR ARCHITECTURE FOR A SPREAD SPECTRUM MULTIPLE ACCESS
COMMUNICATION SYSTEM", inventors K. Easton et al.; and
4. U.S. patent application Ser. No. 08/492,592, filed Jan. 20, 1995, for
"MOBILE DEMODULATOR ARCHITECTURE FOR A SPREAD SPECTRUM MULTIPLE ACCESS
COMMUNICATION SYSTEM", inventors K. Easton et al.
The main thrust for development of the physical modem architecture
described in detail in these co-pending applications has been to provide
reduction in component count and cost. Assuming implementation of a base
station modem architecture in a single application specific integrated
circuit (ASIC), there is a concurrent need for an accompanying processing
component that supports the physical implementation of modem functions in
ASIC.
At the heart of a CDMA system is a physical layer embracing a number of
forward and reverse CDMA channels. In this regard, a forward CDMA channel
is a channel from a base station to mobile stations and includes one or
more code channels. Code channels are subchannels of forward CDMA channels
that are assigned for specific purposes and distinguished by orthogonal
coding. A reverse CDMA channel is a code channel from a mobile station to
a base station. Preferably, a channel element in a CDMA base station is a
subsystem comprising hardware and software that supports one forward and
one reverse code channel. Each channel element of a plurality of channel
elements in a base station includes a modem ASIC, and a channel element
software program to implement control of the physical structure's channel
operations.
SUMMARY OF THE INVENTION
The invention resides in a layered channel software element which
supervises the operation of channel element physical resources in order to
fully implement a channel element. The layered channel software element
(hereinafter, "the layered element") executes on a channel processor.
Preferably, a layered element would provide an architecture and
platform-independent implementation of channel element physical resource
supervision. In this regard, the layered software element would be generic
and transportable between various combinations of network architectures
and channel element processors.
In the description which follows, a portion of the layered element is
presented as an architecture and platform-independent implementation that
controls the operation of the physical resources of a channel element.
Preferably, a layered element according to the invention acts on
instructions to provide high level physical layer services. Relatedly, the
layered element has the capability of supporting all required channel
element functionality.
Benefits and advantages of the present invention will become apparent from
the following description of the preferred embodiment when it is
considered with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The features, objects, and advantages of the present invention will become
more apparent from the detailed description set forth below when taken in
conjunction with the drawings in which like reference characters identify
correspondingly throughout and wherein:
FIG. 1 is a block diagram presenting a schematic overview of an exemplary
CDMA cellular telephone system in accordance with the present invention.
FIG. 2 is a functional block diagram illustrating forward and reverse CDMA
channels in a CDMA base station.
FIG. 3 is a block diagram illustrating the physical implementation of the
channel architecture illustrated in FIG. 2.
FIG. 4A is a block diagram showing a representative modulator section of a
CDMA modem ASIC.
FIG. 4B is a block diagram showing a representative demodulator section of
a CDMA modem ASIC.
FIG. 5 is a block diagram illustrating the structural and functional
partitioning of a layered element according to the invention.
FIGS. 6A and 6B are flow diagrams illustrating the exchange of commands and
responses in the layered element.
FIG. 7 is a schematic block diagram of a sync channel application.
FIG. 8 is a schematic block diagram illustrating a paging channel
application.
FIGS. 9A and 9B are, respectively, schematic block and flow diagrams
illustrating an access channel application.
FIG. 10 is a schematic block diagram illustrating a traffic channel
application.
FIG. 11 is a schematic block diagram illustrating a master timing module.
FIG. 12 is a schematic block diagram illustrating an encoder driver.
FIG. 13 is a schematic block diagram illustrating a decoder driver.
FIG. 14 is a schematic block diagram illustrating the demodulator driver.
FIG. 15 is a schematic block diagram illustrating the search engine.
FIG. 16 is a schematic block diagram illustrating a demodulation engine.
FIG. 17 is a schematic block diagram illustrating the interface between the
layered element and a CDMA modem ASIC.
FIG. 18 is a flow diagram illustrating the logic of a device interface
module shown in FIG. 17.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a CDMA cellular communication system, each base station has a plurality
of modulator-demodulator apparatuses (modems) for spread-spectrum
modulation and demodulation of message and signaling data. Each modem
includes a digital spread spectrum transmit modulator, at least one
digital spread spectrum data receiver, and a searcher receiver. Each modem
at a base station is assigned to a mobile unit as needed to facilitate
communications with the assigned unit. Consequently, many modems are
available for use at any base station, while other modems may be active in
communicating with respective mobile units.
In order to provide service to a plurality of mobile units, communications
from the standpoint of a base station are separated into discrete
channels. In this application, a set of channels transmitted from, and
received by, a base station on a given frequency is referred to
collectively as a CDMA channel. A forward CDMA channel is a channel from a
base station to mobile units. A forward CDMA channel comprises one or more
code channels that are transmitted on the CDMA frequency with reference to
a particular pilot signal. For example, code channels may include a pilot
channel, a synchronization (sync) channel, paging channels, and traffic
channels. The forward CDMA channel typically includes a pilot channel, one
sync channel, one or more paging channels, and one or more traffic
channels. In the preferred embodiment, the total number of code channels,
including the pilot channel, is no greater than 64. A CDMA channel from a
mobile unit to a base station is called a reverse CDMA channel. For any
base station, the reverse CDMA channel is the sum of all mobile unit
transmissions received by the base station on the CDMA frequency.
The pilot channel is used by a base station to transmit an unmodulated,
direct-sequence spread spectrum pilot signal that is spread by a
pseudo-random noise (PN) spreading code common typically, but not
necessary common to the PN spreading of the other transmitted signal. The
pilot signal continuously transmitted by the base station is used by
mobile units to obtain initial system timing, serve as a phase reference
for coherent modulation, and a signal strength reference for comparisons
between base station pilot signals to support hand off.
Preferably, the pilot signal transmitted by each base station has the same
PN spreading code, but a code phase offset different than the offsets of
all other base stations. Phase offset allows the pilot signals to be
distinguished one from another by mobile units, thereby providing a means
for the mobile units to differentiate between base stations.
Each base station also transmits a sync channel signal comprising a
modulated, encoded, interleaved, direct sequence, spread spectrum signal
used by mobile units to acquire additional synchronization, system time,
and overhead control information. Each base station sync channel consists
of a sync message with a fixed format, having a predetermined timing
relationship with the base station's pilot signal and a predetermined
channel code. The message includes system identification, network
identification, pilot PN sequence offset index, a public long PN code mask
for public use in paging and access channels, system time parameters, and
a paging channel data rate.
The set of forward channels transmitted by a base station also includes one
or more paging channels that carry paging channel signals. Paging channel
signals are modulated, interleaved, scrambled, direct sequence, spread
spectrum signals which contain control and overhead information. A paging
channel is used to communicate forward link signaling data to mobile
units. The public long PN code mask portion of the sync and paging
channels is used by a mobile unit to descramble the paging channel
scrambled signal. Like the sync channel signals, the paging channel
signals are spread and despread using the same short PN code and offset as
the pilot channel.
The base station forward channels include a plurality of traffic channels.
Each mobile unit is assigned to a unique traffic channel for receiving
message data intended for the mobile unit. Each traffic channel signal is
a modulated, interleaved, scrambled, direct sequence, spread spectrum
signal transmitted to a mobile unit on a respective traffic channel
signified by a long spreading code. Information received in the sync
channel message is used by a mobile unit to descramble traffic channel
signals.
Reverse CDMA channels include access channels that are used by mobile units
for communicating with a base station. An access channel is used for short
signaling message exchanges including reverse signaling data, responses to
pages, and registrations. A reverse CDMA traffic channel is used to
transmit reverse message data from a mobile unit to a base station.
An exemplary illustration of a CDMA cellular telephone system is
illustrated in FIG. 1. The CDMA cellular telephone system is indicated
generally by 8 and includes a system controller and switch 11 also
referred to as a mobile telephone switching office (MTSO), that includes
interface and processing circuitry for providing system control to the
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