 |
Claims  |
|
|
We claim:
1. A paging terminal for delivering messages to a plurality of portable communication units, wherein each portable communication unit has a transmitter for transmitting an acknowledge
back signal and operates within a radio communication system, wherein the radio communication system comprises a plurality of communication cells and the paging terminal, and wherein each of the communication cells comprises one or more transmitters for
transmitting information signals intended for reception by a portable communication unit and one or more fixed receivers coupled to the paging terminal for receiving an acknowledge back signal from said portable communication unit which is communicated
to the paging terminal, the paging terminal comprising:
transmitter controller means coupled to the one or more transmitters for transmitting a first information signal which comprises a color code word which identifies a subset of the plurality of communication cells for which radio coverage does not
overlap;
receiving controller means, coupled to the one or more fixed receivers, said receiving controller means for buffering said acknowledge back signal received at one of the one or more fixed receivers from said portable communication unit, and
communicated to the receiving controller means, said acknowledge back signal comprising a reported color code value determined from said color code word transmitted in said first information signal;
assignment means coupled to said receiver controller means for analyzing said acknowledge back signal for an identification of said one of the fixed receivers and determining a cell location of said portable communication unit from said reported
color code value and the identification of said one of the fixed receivers, said assignment means comprising:
a subscriber data base, for storing said cell location in association with said portable communication unit; and
re-use means, coupled to said subscriber data base and to said transmitter controller means, for controlling transmissions of the information signals such that the same or differing information signals intended for portable communication units in
differing cells with cell locations in said subscriber data base with the same color code are transmitted simultaneously.
2. The paging terminal according to claim 1, further comprising:
set-up means coupled to said assignment means for assigning a non-valid cell location to said portable communication unit in said subscriber data base when no acknowledge back signal has been received from said portable communication unit, and
wherein said re-use means further controls the transmissions of the information signals such that a second information signal intended for said portable communication unit is selected and transmitted simultaneously from all transmitters within a
first subset of cells having a first color code when a non-valid cell location is assigned to said portable communication unit in said subscriber data base.
3. The paging terminal according to claim 2 wherein said re-use means further controls the transmissions of the information signals to transmit simultaneously from all transmitters within a second subset of cells having a second color code the
second information signal when no acknowledge back signal is received in response to the transmission of the second information signal from the first subset of cells having the first color code.
4. The paging terminal according to claim 2, wherein the paging terminal is for use in a simulcast communication system, and wherein said re-use means further controls the transmissions of the information signals such that a second information
signal intended for said portable communication unit is selected and transmitted simultaneously from all transmitters when a non-valid cell location is assigned to said portable communication unit in said subscriber data base.
5. A portable communication unit having a radio frequency (RF) receiver and an RF transmitter for transmitting an acknowledge back signal, and operating within a radio communication system comprising a plurality of communication cells and a
paging terminal, and wherein each of the communication cells comprises one or more transmitters for transmitting an information signal intended for reception by said the portable communication unit, said portable communication unit comprising:
demodulator means coupled to the RF receiver for demodulating said information signal, wherein said information signal includes a color code word which identifies a subset of the plurality of communication cells for which radio coverage does not
overlap, and further includes one or more induced errors;
sync correlator means coupled to said demodulator means for decoding one of a predetermined set of color code words of an error correcting code set from said information signal;
reporter means coupled to said sync correlator means and said RF transmitter for generating said acknowledge back signal which includes a reported color code value determined from said one of said predetermined set of color code words and
wherein said information signal comprises a bit synchronization code and an information message, and said color code word is within a first portion of the bit synchronization code, and wherein said sync correlation means comprises:
color code word pattern generator means for generating said predetermined set of color code words; and
color code decoder means coupled to said color code word pattern generator means and to said sync correlator means for matching said first portion of the bit synchronization code to a color code word of said predetermined set of color code words
to determine a number of bits which mismatch and assigning, as said reported color code value, one of a plurality of pre-determined valid color code values associated one for one with the color code words of said predetermined set of color code words
when the number of bits which mismatch is less than a predetermined number.
6. The portable communication unit according to claim 5, wherein said color code decoder means further assigns, as said reported color code value, a non-valid color code value other than all of said predetermined valid color code values, thereby
indicating that a valid color code word could not be decoded, when the number of bits which mismatch is equal to or greater than the predetermined number of bits.
7. A method of delivering messages to a plurality of portable communication units, wherein each of said plurality of portable communication units has a receiver for receiving information signals and a transmitter for transmitting acknowledge
back signals and operates within a radio communication system comprising a plurality of communication cells and a paging terminal having a subscriber data base within which cell locations are associated one to one with each of the plurality of portable
communication units, wherein each of the communication cells comprises one or more transmitters coupled to the paging terminal for transmitting said information signals intended for reception by said plurality of portable communication units, and wherein
each of the communication cells further comprises one or more fixed receivers coupled to the paging terminal for receiving the acknowledge back signals and communicating the acknowledge back signals to the paging terminal, said method comprising the
steps of:
transmitting, to a portable communication unit from one of the plurality of communication cell transmitters, an information signal which includes a predetermined color code word which identifies a subset of the plurality of communication cells
for which radio coverage does not overlap;
receiving at a fixed receiver an acknowledge back signal transmitted from said portable communication unit in response to said information signal received by said portable communication unit, said acknowledge back signal comprising a reported
color code value determined from said predetermined color code word;
communicating said acknowledge back signal from the fixed receiver to the paging terminal; and
analyzing said reported color code value in the paging terminal to determine a cell location of the portable communication unit,
assigning to said portable communication unit within the subscriber data base of the paging terminal, said cell location which is identified in said analyzing step;
identifying a plurality of differing information signals intended for portable communication units in cells having cell locations not necessarily the same and having a common color code assigned within said subscriber data base; and
simultaneously transmitting said plurality of differing information signals from the transmitters of cells having cell locations identified in said identifying step.
8. A method of locating a portable communication unit having a receiver for receiving an information signal and a transmitter for transmitting an acknowledge back signal, said portable communication unit operating within a radio communication
system comprising a plurality of communication cells and a paging terminal, wherein each of the communication cells comprises one or more transmitters coupled to the paging terminal for transmitting said information signal, and wherein each of the
communication cells further comprises one or more fixed receivers coupled to the paging terminal for receiving the acknowledge back signal and communicating the acknowledge back signal to the paging terminal, wherein said information signal comprises a
bit synchronization code and an information message, the method comprising the steps of:
transmitting, to said portable communication unit from one of the plurality of communication cell transmitters, said information signal which includes a color code word within a first portion of the bit synchronization code, wherein said color
code word identifies a subset of the plurality of communication cells for which radio coverage does not overlap;
receiving said information signal and one or more induced errors at said portable communication unit;
decoding, in said portable communication unit, said color code word from said information signal and the one or more induced errors, said step of decoding further comprising the steps of:
matching said first portion of the bit synchronization code containing said color code word to one color code word of a set of predetermined color code words to determine a number of bits which mismatch; and
assigning, as a reported color code value, one of a plurality of predetermined valid color code values associated one for one with said set of predetermined color code words when the number of bits which mismatch is less than a predetermined
number of bits in said matching step;
transmitting from said portable communication unit said acknowledge back signal including said reported color code value determined from said color code word;
receiving at a fixed receiver said acknowledge back signal;
communicating said acknowledge back signal from the fixed receiver to the paging terminal; and
analyzing, in the paging terminal, said reported color code value to determine a cell location of the portable communication unit.
9. The method according to claim 8 wherein said step of assigning further comprises assigning, as said reported color code value, a non-valid color code value different than all of said predetermined valid color code values, indicating that a
valid color code word could not be decoded, when said matching step results in a mismatch equal to or greater than the predetermined number of bits.
10. In a portable communication unit having a receiver for receiving information signals and a transmitter for transmitting acknowledge back signals, and operating within a radio communication system comprising a plurality of communication cells
and a paging terminal, wherein each of the communication cells comprises one or more transmitters for transmitting an information signal intended for reception by said portable communication unit, a method of identifying a subset of the plurality of
communication cells for which radio coverage does not overlap, wherein said information signal includes a color code word which identifies said subset, and wherein said information signal comprises a bit synchronization code and an information message,
and said color code word is within a first portion of the bit synchronization code, the method comprising the steps of:
receiving at said portable communication unit said information signal and one or more induced errors;
decoding said color code word from said information signal and the one or more induced errors, said step of decoding further comprising the steps of:
matching said first portion of the bit synchronization code to one color code word of a predetermined set of color code words to determine a number of bits which mismatch; and
assigning, as a reported color code value, one of a plurality of pre-determined valid color code values associated one for one with the color code words of said predetermined color code words when the number of bits which mismatch is less than a
predetermined number; and
transmitting from said portable communication unit, for communication to said paging terminal, an acknowledge back signal comprising said reported color code value determined from said color code word decoded in said decoding step.
11. The method according to claim 10 wherein said step of assigning further comprises assigning, as said reported color code value, a non-valid color code value different than all of said predetermined valid color code values, thereby indicating
that a valid color code word could not be decoded, when said matching step results in a mismatch equal to or greater than the predetermined number of bits. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
FIELD OF THE INVENTION
This invention relates in general to radio communication systems and more specifically to methods and apparatus for identifying transmitters for re-use transmission in a two-way radio communication system.
BACKGROUND OF THE INVENTION
Radio communication systems that utilize simulcast transmissions are in wide use today. A typical example is a radio paging system. Simulcast transmissions, in which a single information signal is simultaneously transmitted from a plurality of
geographically disperse transmitters to provide radio coverage over a wide geographic area, are employed in most wide area radio paging systems.
Whenever the number of users of a simulcast radio communication system increases within a given geographic coverage area, communication traffic can eventually reach the capacity limits of the system, and steps must be taken to increase the
traffic capacity of the system before additional geographic coverage areas and users can be accommodated. One step that is often taken is to add another radio channel to the system. That step, is at best expensive, and may be impossible in some
locations where all available channels are occupied.
Conventional radio paging systems, including acknowledge-back communication systems, have utilized simulcast fixed-to-portable radio transmissions that operate ubiquitously, i.e., simulcasting substantially every fixed-to-portable communication
from substantially every fixed transmitter in the system. If, however, there could be found a way of locating portable communication units as they move about the system, then the number of base transmitters and receivers utilized for communications with
any one individual portable communication unit could be isolated only to those fixed transmitters and receivers near each portable communication unit. This isolation would allow simultaneous reuse of base transmitters, receivers, and communication
spectrum for additional communication with other portable communication units in other parts of the geographic coverage area of the system on the same radio channel.
Thus, what is needed is a method and apparatus for increasing the capacity limits of a simulcast radio communication system in a manner that does not require an additional radio channel.
SUMMARY OF THE INVENTION
Accordingly, in a first aspect of the preferred embodiment of the present invention, a method of locating a portable communication unit having a transmitter for transmitting acknowledge back signals comprises the steps of transmitting an
information signal, receiving an acknowledge back signal including a reported color code word, and analyzing the color code word. The portable communication unit operates within a radio communication system comprising a plurality of communication cells
and a paging terminal, wherein the communication cells comprise one or more transmitters for transmitting information signals intended for reception by the portable communication unit. The transmitting step consists of transmitting, to the portable
communication unit from the communication cell transmitters, an information signal which comprises one of a plurality of predetermined color code words which identify subsets of the plurality of communication cells for which radio coverage does not
overlap. The receiving step consists of receiving an acknowledge back signal from the portable communication unit comprising a reported color code value determined from the color code word transmitted in the information signal. The analyzing step
consists of analyzing the reported color code value to determine a cell location of the portable communication unit.
In a second aspect of the preferred embodiment of the present invention, a method in a portable communication unit, of identifying one of the subsets of a plurality of communication cells for which radio coverage does not overlap, comprises the
steps of receiving the information signal, decoding a predetermined color code word, and transmitting an acknowledgment. The portable communication unit has a transmitter for transmitting acknowledge back signals, and operates within a radio
communication system comprising a plurality of communication cells and a paging terminal, and the communication cells comprise one or more transmitters for transmitting an information signal intended for reception by the portable communication unit. The
step of receiving the information signal consists of receiving at the portable communication unit the transmitted information signal comprising one of a plurality of predetermined color code words which identify subsets of the plurality of communication
cells for which radio coverage does not overlap, wherein the information signal as received includes induced errors. The step of decoding a predetermined color code word consists of decoding from the information signal including errors, received in said
receiving step, the predetermined color code word transmitted in the information signal. The step of transmitting an acknowledgment consists of transmitting from the portable communication unit an acknowledge back signal comprising a reported color code
value for the color code word decoded in said decoding step.
In a third aspect of the preferred embodiment of the present invention, a system comprises a transmitter controller, a receiving controller, and an assignment means. The system is for locating a portable communication unit which has a
transmitter for transmitting acknowledge back signals and operates within a radio communication system, wherein the radio communication system comprises a plurality of communication cells and a paging terminal, and wherein the communication cells
comprise one or more transmitters for transmitting information signals intended for reception by the portable communication unit and one or more fixed receivers for receiving an acknowledge back signal from the portable communication unit and forwarding
the acknowledge back signal to the paging terminal. The transmitter controller means is coupled to the one or more transmitters for transmitting an information signal which comprises one of a plurality of predetermined color code words which identify
subsets of the plurality of communication cells for which radio coverage does not overlap. The receiving controller means is coupled to the fixed receivers for receiving the acknowledge back signal from the portable communication unit comprising a
reported color code value determined from the color code word transmitted in the information signal. The assignment means is coupled to the receiver controller means for analyzing the acknowledge back signal for reported color code values and fixed
receiver identification to determine a cell location of the portable communication unit.
In a fourth aspect of the preferred embodiment of the present invention, a portable communication unit comprises a demodulator means, a sync correlator means, and a reporter means. The portable communciation unit has a radio frequency (RF)
receiver and an RF transmitter for transmitting acknowledge back signals, and operates within a radio communication system comprising a plurality of communication cells and a paging terminal, wherein the communication cells comprise one or more
transmitters for transmitting an information signal intended for reception by the portable communication unit. The demodulator means is coupled to the RF receiver for demodulating the information signal comprising one of a plurality of predetermined
color code words which identify subsets of the plurality of communication cells for which radio coverage does not overlap, and wherein the information signal as received includes induced errors. The sync correlator means is coupled to the demodulator
means for decoding from the received information signal the color code word transmitted within the information signal. The reporter means is coupled to the decoder means for generating an acknowledge back signal which reports the decoded color code
value.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an electrical block diagram of a radio communication system in accordance with the preferred embodiment of the present invention.
FIG. 2 is a pictorial diagram depicting communication cells of the radio communication system in accordance with the preferred embodiment of the present invention.
FIG. 3 is an electrical block diagram of a terminal and transmitter for processing and transmitting message information in accordance with the preferred embodiment of the present invention.
FIG. 4 is a pictorial diagram depicting a portion of the communication cells of the radio communication system in accordance with the preferred embodiment of the present invention.
FIGS. 5-7 are timing diagrams illustrating the transmission format of the signaling protocol utilized in accordance with the preferred embodiment of the present invention.
FIGS. 8 and 9 are timing diagrams illustrating the synchronization signals utilized in accordance with the preferred embodiment of the present invention.
FIG. 10 is an electrical block diagram of a portable communication unit in accordance with the preferred embodiment of the present invention.
FIG. 11 is an electrical block diagram of a synchronization correlator utilized in the portable communication unit of FIG. 10.
FIG. 12 is an electrical block diagram of a fixed receiver in a fixed communication unit in accordance with the preferred embodiment of the present invention.
FIG. 13 is a flow chart illustrating the synchronization correlation sequence in accordance with the preferred embodiment of the present invention.
FIG. 14 is a flow chart illustrating the method of locating portable communication units and simultaneously re-using communication cell transmission resources in accordance with the preferred embodiment of the present invention.
DETAILED
DESCRIPTION OF THE INVENTION
A method and apparatus for identifying communication cells within an acknowledge-back radio communication system is described herein below, in accordance with the preferred embodiment of the present invention. The method and apparatus can be
utilized for locating portable communication units to achieve the advantages of transmitter, receiver, and spectrum reuse.
Referring to FIG. 1, an electrical block diagram of a radio communication system 100 in accordance with the preferred embodiment of the present invention comprises a paging terminal 102 one or more telephone inputs 110 for interfacing with the
Public Switched Telephone Network in a manner well known in the art. Preferably, the paging terminal 102 is similar to a model E09DAB0010 Metro-Page.RTM. paging terminal manufactured by Motorola, Inc. of Schaumburg, Ill., modified with special
firmware elements in accordance with the preferred embodiment of the present invention, as described herein below. It will be appreciated that other similar equipment may be used as well for the paging terminal 102.
The paging terminal 102 is coupled to a plurality of fixed communication units 101, preferably by a plurality of telephone lines 106. It will be appreciated that radio links can be used as well to couple the paging terminal 102 with the fixed
communication units 101. Each of the fixed communication units 101 provides radio coverage within one of a plurality of communication cells 500 (FIG. 2) of the radio communication system 100, as will be further defined herein below.
The fixed communication units 101 preferably each comprises one or more fixed receivers 103 positioned in geographically disperse locations within a communication cell, and a cell transmitter 104. The cell transmitter 104 and the plurality of
receivers 103 are coupled by radio links with a plurality of portable communication units 108, preferably radio pagers having acknowledge-back capability, for sending and receiving information to and from the portable communication units 108. Radio
pagers having such acknowledge-back capability are disclosed in U.S. Pat. Nos. 5,124,697 to Moore, entitled "Acknowledge Back Pager," 5,153,582 to Davis, entitled "Method and Apparatus for Acknowledging and Answering a Paging Signal," and 4,875,038 to
Siwiak et al., entitled "Frequency Division Multiplexed Acknowledge Back Paging System." Preferably, the cell transmitter 104 is similar to a model C73 PURC 5000.RTM. transmitter manufactured by Motorola, Inc. of Schaumburg, Ill. It will be
appreciated that other similar transmitters may be used as well for the cell transmitter 104. The plurality of receivers 103 and the portable communication units 108 will be described in further detail herein below. It will be appreciated that the
portable communication units 108 could also have capabilities of full two way (receive and transmit) digital messaging.
During initial setup of the radio communication system 100, the paging terminal 102 preferably defines and assigns identification codes hereinafter called color codes (CC's) for each of the communication cells 500, as well as unique transmitter
identification codes (TID's) for each transmitter 104 and unique fixed receiver identification codes (RID's) for each fixed receiver 103, in accordance with the preferred embodiment of the present invention. During subsequent operation of the radio
communication system 100, callers preferably place telephone calls to the central controller 102 through the telephone inputs 110 to request that specific ones of the portable communication units 108 be signaled, thereby forming a random group of
portable communication units 108 to be signaled. Preferably, the callers are using a suitable input device, e.g., a tone dialing telephone or an alphanumeric page entry device, so that a message, e.g., a call-back number, is entered as well. The paging
terminal 102 preferably formats and queues a plurality of selective call addresses and associated messages corresponding to the random group for subsequent transmission.
Next, the paging terminal 102 formats acknowledgment assignment information along with the queued selective call addresses and messages, the acknowledgment assignment information preferably comprising instructions for each member of the random
group, designating a time and a channel to be utilized for the acknowledgment signal. The paging terminal 102 then forwards the selective call addresses and associated messages and acknowledgment assignment information to the transmitters 104 of the
fixed communication units 101 in a manner well known in the art. One or more of the transmitters 104 transmits, or simulcasts (simultaneously transmits), in the case of more than one transmitter) the selective call addresses and associated information,
comprising the messages and acknowledgment assignment information, to the portable communication units 108 using the paging protocol described herein below, on a paging channel. In addition, the paging terminal 102 controls each of the transmitters 104
to periodically transmit the color code assigned to the communication cell 500 in which the cell transmitter 104 is located. Each assigned color code defines a non-interfering subset of the plurality of communication cells 500, as will be described
herein, below.
In response to the portable communication unit 108 receiving the signal containing the selective call address, message information, and acknowledgment assignment information, and finding that the selective call address matches a selective call
address programmed therein, the portable communication unit 108 further receives the associated information and transmits an acknowledgment signal at a designated time on a designated channel. The acknowledgment signal comprises at least a reported
value of the transmitter color identified from the last received transmission in accordance with the preferred embodiment of the present invention, and the RID, as will be further described herein below.
The design of the radio communication system is such that the acknowledgment signal is received with substantial certainty by one or more of the fixed receivers 103. The reported color code value received at the one or more fixed receivers 103
from the portable communication unit 108 is forwarded along with the RID by the fixed receivers 103 to the paging terminal 102, along with the time slot and channel information.
The paging terminal then determines the best cell of the plurality of communication cells 500 by reference to a stored best cell table 254 (FIG. 3) which cross references all the communication cells 500 to all color codes and all fixed receivers
10. The paging terminal 102 preferably selects the determined best cell for further communications with the reporting portable communication unit 108, while terminating further transmissions from all other communication cells 500 in accordance with the
preferred embodiment of the present invention, thereby permitting all other non-interfering cells to be re-used simultaneously on a non-interfering basis for communications with other portable communication units 108.
It will be appreciated that the minimum number of cell transmitters 104 utilized for each of the communication cells 500 is one. Still, for system robustness, it is preferable that more than one transmitter 104 can be utilized in one or more of
the plurality of communication cells 500, for example, in certain geographic situations where two antenna sites are necessary to cover a contiguous cell area, and, for example, for redundancy purposes. When two or more transmitters 104 are used within
one of the communication cells 500, the transmitters 104 transmit the same color code.
FIG. 2 is a pictorial diagram depicting, for a nine cell example, the communications cells 500 of the radio system 100 in accordance with the preferred embodiment of the present invention. The approximate coverage peripheries of the
communication cells 500 are represented by a circular boundary 505. In each communication cell 500, one transmitter 104 and three receivers 103 are shown by way of example. Next to each transmitter, the TID and the color code (CC), which are assigned
at the time of initial system setup, are shown. Next to each fixed receiver 103, the RID is shown. At the time of assignment, the color codes are selected to provide the ability to distinguish the signals received by the portable communication unit 108
simultaneously from transmitters 104 located in different communication cells 500, and in the coverage overlap regions 510 of interfering cells. These regions are the areas where the capture effect, well known in the art of FM radio communications, does
not occur reliably from any one of the transmitters 104 as the signals are often of similar strength within the region. While in this example three color codes are sufficient to provide the capability to distinguish different communication cells, it
will be appreciated that other quantities of color codes can be used also.
It will be appreciated that the radio communication system can be either a simulcast communication system, wherein the timing of transmissions is adjusted so that signals received in the overlap areas are simultaneous to within a small part of an
information symbol, thereby increasing the probability of receiving a message when two of the same signals of similar strength are received from two or more transmitters, or a conventional system wherein such timing refinements are not necessarily
undertaken.
It will be appreciated that the use of circles as the cell coverage periphery is a simplification of the actual coverage peripheries found in typical systems, which does not substantially affect the conclusions of this system description.
FIG. 3 is an electrical block diagram of the paging terminal 102 and transmitter 104 utilized for processing and controlling the transmission of the message information in accordance with the preferred embodiment of the present invention. An
assignment element 260 is used at the time of system initialization for setting up the RID's, the TID's, the subscriber data base 208, the cell color codes, and the best cell table 254, described further herein, below. Short messages, such as tone-only
and numeric messages which can be readily entered using a Touch-Tone telephone are coupled to the paging terminal 102 from the telephone input connection 110 through a telephone interface 202 in a manner well known in the art. Longer messages, such as
alphanumeric messages which require the use of a data entry device are coupled to the paging terminal 102 from the public switched telephone network input/output connection 110 through a modem 206 using any of a number of well known modem transmission
protocols. When a call to place a message is received, a controller 204 handles the processing of the message. The controller 204 is preferably a microcomputer, such as an MC68000 or equivalent, which is manufactured by Motorola Inc., of Schaumburg,
Ill., and which runs various pre-programmed routines for controlling such terminal operations as voice prompts to direct the caller to enter the message, or the handshaking protocol to enable reception of messages from a data entry device. When a call
is received, the controller 204 references information stored in the subscriber data base 208 to determine how the message being received is to be processed. The subscriber data base 208 includes, but is not limited to such information as addresses
assigned to the portable communication unit 108, message type associated with the address, and information related to the status of the portable communication unit 108, such as active or inactive for failure to pay the bill. A data entry terminal 240 is
provided which couples to the controller 204, and which is used for such purposes as entry, updating and deleting of information stored in the subscriber data base 208, for monitoring system performance, and for obtaining such information as billing
information.
The subscriber data base 208 also comprises such information as a transmission frame assignment, a transmission phase assignment, the acknowledgment assignment, and the time and cell identification of the last cell location of the portable
communication unit 108, as will be described in further detail below. The received message is stored in an active page file 210 which stores the messages in queues according to the transmission phase assigned to the portable communication units 108. In
the preferred embodiment of the present invention, four phase queues are provided in the active page file 210 for messages to be simulcast on transmitters 104, as well as four additional phase queues for each cell, for messages which are to be
individually transmitted within a communication cell 500. The active page file 210 is preferably a dual port, first in first out random access memory, although it will be appreciated that other random access memory devices, such as hard disk drives, can
be utilized as well. Periodically the message information stored in each of the phase queues is recovered from the active page file 210 under control of controller 204 using timing information such as provided by a real time clock 214, or other suitable
timing source. The recovered message information from each phase queue is sorted by frame number and is then organized by address, message information, and any other information required for transmission, and then batched into frames based upon message
size and cell identification, for the phase queues associated with individual cells, by frame batching controller 212. The batched frame information for each phase queue is coupled to frame message buffers 216 which temporarily store the batched frame
information until a time for further processing and transmission. Frames are batched in numeric sequence, so that while a current frame is being transmitted, the next frame to be transmitted is in the frame message buffer 216, and the next frame
thereafter is being retrieved and batched. The controller 204 identifies phase queues that are associated with individual, non-overlapping cells for simultaneous transmission. At the appropriate time, the batched frame information stored in the frame
message buffer 216 is transferred to a frame encoder 218, again maintaining the phase queue relationship. The frame encoder 218 encodes the address and message information into address and message code words required for transmission, as will be
described below. The encoded address and message code words are ordered into blocks and then coupled to a frame message interleaver 220 which interleaves preferably eight code words at a time for transmission in a manner well known in the art. The
interleaved code words from each frame message interleaver 220 are then serially transferred to a phase multiplexer 221, which multiplexes the message information on a bit by bit basis into a serial data stream by transmission phase. The controller 204
next enables a frame sync generator 222 which generates a synchronization code which is transmitted at the start of each frame transmission. The synchronization code is multiplexed with address and message information under the control of controller 204
by a serial data splicer 224, and generates therefrom a message stream which is properly formatted for transmission. The message stream is next coupled to a transmitter controller 226, which under the control of controller 204 transmits the message
stream over a transmitter distribution channel 228. The transmitter distribution channel 228 may be any of a number of well known distribution channel types, such as wire line, a radio frequency (RF) or microwave distribution channel, or a satellite
distribution link. The distributed message stream is transferred to one or more transmitter stations 104, depending upon the size of the communication system. The message stream is first transferred into a dual port buffer 230 which temporarily stores
the message stream prior to transmission and modifies the synchronization portion of the message stream, as further described herein, below, to include the color code assigned to the cell in which the transmitter 104 is located. At an appropriate time
determined by timing and control circuit 232, the message stream is recovered from the dual port buffer 230 and coupled to the input of preferably a 4-level frequency shift keyed (FSK) modulator 234. The modulated message stream is then coupled to the
transmitter RF stage 236 for transmission via antenna 238. It will be appreciated that the modification of the synchronization portion of the message to include the color code unique to the transmitter 104 could equally be done in the timing and control
circuit 232 of the transmitter 104.
When the portable communication unit 108 receives a paging transmission, the portable communication unit 108 responds with an acknowledgment as described above. The decoded color code received in the acknowledgment from the portable
communication unit 108 by the one or more fixed receivers 103 is forwarded along with the receiver identification through a receiver distribution channel 250 from the fixed receivers 103 to a receiver controller 252 in the paging terminal 102, along with
time slot and channel information. The receiver controller 252 buffers the information for reception and decoding by the controller 204. Within the controller 204, an assignment element 256 uses the time slot and channel information to identify the
portable communication unit 108, and uses the decoded color code, the fixed receiver 103 identification, and the best cell table 254 to determine the cell site location of the portable communication unit 108. The cell location for the portable
communication unit 108 is t | | |
