Note: Descriptions are shown in the official language in which they were submitted.
WO9l/06190 2 0 6 5 2 7 ~ PCT/US90/05~13
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NATION-WIDE PAGING WITH LOCAL MODES
Field of the Invention
This invention relates in general to radio paging systems
and more particularly to a nation-wide paging system with
multiple local modes.
S Background of the Invention
Paging systems typically use a receiver that has at least
one unique selective call address associated therewith. This
receiver is commonly referred to as a selective call receiver
or pager. When a pager receives and decodes its address, the
pager typically alerts the user to the presence of incoming
information and operates to present this information. The
receiving, decoding, alerting, and presenting sequence as well
as other functional aspects associated with the pager are
commonly referred to as the pager's personality. A unique
operational personality is programmed in the pager by the
service provider before delivery, and generally cannot be
modified by the user or provider without returning the pager
to a service depot.
Wide area paging systems for the transmission and
reception of radio frequency information are well known to
those skilled in the art. In the United States, wide area
paging systems are licensed for operation on radio frequency
carriers that are restricted to a m~; mllm effective radiated
power output of 200 watts. This power limitation and the radio
frequency attenuation associated with the physical
characteristics of the surrounding environment, limits the
ground path propagation of radio frequency energy. A typical
paging signal that is transmitted from a ground based antenna
system will effectively cover an average metropolitan area of
approximately 400 square miles.
Alternative approaches have been tried to increase the
area of coverage for a wide area paging system. One method is
the use of multiple distributed transmission sites that
simulcast ~simultaneously broadcast) the information signal on
~i
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the same radio frequency carrier. Geographic coverage is
improved using this method, but due to a critical shortage of
available land-mobile channel assignments in the VHF (very
high frequency) band and governmental restrictions, a service
provider cannot implement this system on anything other than a
regional scale. Another method with more flexibility is used
in the recently approved 900 MHz nation wide paging services.
The nation wide paging concept uses a block of channels
specifically allocated for nation wide paging services. In
this system, the service provider supplies the user with a
pager that uses a common receive frequency for the areas in
which the person will be travelling. The user's pager will
- then be able to receive the correct radio frequency carrier
and address information, but because of the sheer volume of
information associated with a network of this kind, the
message may take an hour before broadcast to the user. If the
user happens to travel to a location where a different service
provider has a paging system on the user's assigned radio
frequency carrier, chances are that the user's pager will not
function.
The aforementioned scenarios are generally not acceptable
to a business user that needs their information as soon as
possible. A real time messaging system is required to
effectively relay information to a paging subscriber.
Thus, what is needed is an method that provides a
selective call receiver with dynamic personality and local
address configuration.
Summary of the Invention
Accordingly, it is an object of the present invention to
provide an improved selective call addressing method that
enables local mode paging in a nation wide paging network.
In carrying out the above and other objects of the
invention in one form, there is provided a method for
receiving a signal indicative of a location and operating a
selective call receiver in one of a plurality of predetermined
personalities which is selected in response to the received
slgnal .
WO91/06190 2 0 6 5 ~ 7 4 PCT/USg0iOssl3
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Brief Description of the Drawings
Fig. 1 is a system infrastructure diagram in accordance
with the preferred embodiment.
Fig. 2 is a diagram of prior art wide area selective call
signalling format.
Fig. 3 is a diagram of the improved wide area selective
call signalling format in accordance with the preferred
embodiment .
Fig. 4 is a block diagram of the selective call receiver
system in accordance with the preferred embodiment.
Fig. 5 is a flow diagram of the selective call receiver's
personality selection algorithm in accordance with the
preferred embodiment.
Detailed Description of the Invention
In addressing the problem of a nation-wide (wide area)
paging system from the service provider's point of view, the
most important criteria is the raw throughput available as a
function of the system loading (the number of users attempting
to access the system at any point in time as compared to the
number of messages pending transmission), baud rate (the
number of data units transmitted per second), and the
efficiency of the addressing scheme. Using a digital
selective call addressing scheme such as POCSAG (developed by
Great Britain's Post Office Code Advisory Group) or Golay
Sequential Code, the num~ber of selective call addresses
available in a digitally coded system is limited only by the
effective length of the addressing word.
In a nation-wide system, it is desirable for the number
of available addresses to be around one billion. This can be
represented by a digital address code word that has a m; ni m~lm
of 30 address bits (230 z 1 billion). When parity is added, a
nation-wide address can occupy two 32,21 code words. The
notation 32,21 denotes a 32 bit code word comprising 21
information bits and 11 parity bits for error detection and
correction. Using conventional techniques, the increase in
transmitted address bits to address one billion pagers will
0852'~4 ~`~ PCT/US90/05~13
cause a nation-wide paging system to "bog down." To improve
throughput of a wide area signalling system, a user's
selective call receiver (pager) can be registered as a local
user in a participating area of a wide area paging system.
This gives a user the advantages associated with a local
paging system such as low-latency messaging using a single
32,21 code word address. By using the local mode with a
single 32,21 code word address, the service provider will
effectively double the addressing throughput and significantly
improve the overall system efficiency.
Referring to Fig. 1, the preferred embodiment of a wide
area selective call signalling system comprises networked base
stations that are accessed via data entry devices (eg.
computers, telephones). Each base has its own selective call
signalling encoder and transmitter. The transmitters may have
more than one frequency (denoted on Fig. 1 by F1, F2, F3, F4)
depending on the channel loading in a particular area. As
shown in Fig. 1, the New York area 101 uses three frequencies,
F1, F2, and F4. If the user requires a pager that will
function in all three areas 101, 102, 103, but the user rarely
travels to Miami 102, the user's pager would be registered as
being "primary" (me~ning the user is most likely to be in this
area) in New York 101 on frequency F4 and Chicago 103 on
frequency F1. Local addresses are assigned to the pager for
each registered service area. These assigned addresses need
not be unique in different service areas. In this
configuration, the user can travel to any of the three areas
101, 102, 103, and receive pages.
When the user travels to New York 101 or Chicago 103, the
user's pager will respond to the local area address assigned
in the respective areas. This local area address is
automatically selected by the user's selective call receiver
when the New York 101 or Chicago 103 area location ID is
recognized. In Chicago, 103, the pager scans receive
frequencies until it receives and decodes the location ID
transmitted on frequency F4 (for example) then automatically
switches to the predetermined receive frequency F1 and loads
the predetermined local area address for Chicago 103. When
the pager no longer receives the transmitter signal, the user
WO9l/06190 PCT/US90/05513
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has left Chicago 103 and the receive frequency automatically
reverts to its nation-wide frequency sc~nning mode. If the
user has planned a trip to Miami 102 and would like the pager
to be operational in the Miami 102 area, the user would call
the service provider and request that the Miami 102 system
broadcast messages directed to the user on the pager's nation-
wide address. The Miami 102 system would then broadcast
messages directed to the user on the pager on all available
frequencies using the nation-wide address of the pager. Thus,
the pager may receive messages in Miami 102. While causing
the system in Miami 102 to "bog down" by sending messages with
longer nation-wide addressing on a plurality of frequencies.
Note the same messages are transmitted in New York 101 and
Chicago 103 on a single frequency with a shorter local address
thereby relieving "bog down" in these areas.
Referring to Fig. 2, a selective call signalling format
comprises an address field 201 and message field 202. The
address field comprises pager addresses of one word 203 and
two words 204. In this diagram, the single word pager address
203 and dual word pager address 204 have corresponding
information in message A 205 and message B 206, respectively.
Referring to Fig. 3, the preferred embodiment of the
improved wide area selective call signalling format comprises
a location identifier 301, address field 302, and message
field 303. The address field comprises pager addresses of one
word 304 and two words 305. In this diagram, the single word
pager address 304 and dual word pager address 305 have
corresponding information in message A 306 and message B 307,
respectively. Interleaving, as used in selective call
signalling protocols, is defined as the orderly insertion of a
predetermined information word (for example an address or pre-
address data word) within in a data stream. In the case of a
location identifier, it is broadcast in a time window that has
m;nimllm and m~im~lm spacings specified between transmissions
in order for the pager to properly recognize the location
identifier. In the preferred embodiment of the present
invention, the improved wide area selective call signalling
format transmission is interleaved at a predetermined interval
with the selective call signalling format shown in Fig. 2 to
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provide transmission of the location identifier 301 for
reception by active paging receivers. Alternatively, the
location identifier 301 may be transmitted in a stand-alone
fashion (me~n;ng there is no connection with the actual
addressing-messaging data block shown in Fig. 2) while
maintaining an acceptable interleave interval for detection by
active paging receivers.
Referring to Fig. 4, the block diagram shows the
preferred embodiment of a battery 401 powered selective call
receiver (pager) which implements the present invention. The
transmitted signal is coupled via an antenna 402 to the
receiver 403 for recovery of the modulated data. The
recovered data is coupled to the controller 404 and decoder
406. The controller 404 manages the operation of the pager's
receiver 403, decoder 406, user controls 405, alert 408
presentation means, and dispiay 409 presentation means.
When the pager is activated by the user, the controller
404 commands the decoder 406 to read the default wide area
information from the code plug 407. The pager then configures
its operational characteristics according to the data read
from the code plug 407 associated with the wide area mode.
When a signal is decoded by the decoder 406 that contains a
valid address for the wide area mode, the decoder notifies the
controller to take the appropriate actions to alert the user
and present the received information.
In the case where the user is in an area that uses one of
the location ID's programmed in the code plug 407, the pager
will configure its operational characteristics accordingly and
search for the address associated with the active location ID.
Each location ID as well as the wide area default
structure has a personality associated with it. These
"personalities" are programmed by the service provider and
comprise a selective call address, receive frequency, protocol
mode, presentation mode, and operation mode. The code plug
407 is shown having 4 personallties. Three of the
personalities are dependant upon the pager being in one of
three predetermined areas and the fourth personality being
dependant on the pager being in an area other than the three
predetermined areas. Using the location ID as the determiner,
WO91/061~ PCT/US90/05513
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the pager can alter its complete mode of operation when
travelling from one area to another. This feature can be very
useful if, for example, a user desires a fully functional
alphanumeric pager in the area where their home office and
local paging service provider has alphanumeric input
capability, and a low latency tone-only numeric pager in a
rural area where the paging service provider may only have
tone-only numeric capability.
Dynamic re-configuration of the pager by selecting
different personalities has many advantages. In the previous
example, the user had two personalities corresponding to two
different areas. The first personality having alphanumeric
capability, uses a local address (an address option that
lowers the service provider's system overhead), local area
frequency F2 (a frequency dedicated for local area
addressing), high speed coding (a protocol mode option for
faster information delivery), extended frame data interleaving
(a protocol mode option for improved battery life),
alphanumeric display (a presentation mode option allowing the
display of both numeric and alpha characters), and silent
alert capability (an operation mode option enabling a
mechanical vibrator when alerted). The second personality
having tone-only capability, is set-up as the default wide
area personality. The second personality uses a two word wide
area address (an address option), wide area frequency Fl (a
shared frequency dedicated for wide area addressing and
location identification), normal speed coding (a protocol mode
option), normal frame data interleaving (a protocol mode
option for normal battery life), numeric display (a
presentation mode option allowing the display of numeric
characters), and audible alert capability (an operation mode
option enabling an acoustic transducer when alerted).
The protocol mode selected within a personality functions
to control parameters associated with the selective call
coding format such as the baud rate (number of information
bits per second) and receiver battery saver rate (the on/off
strobing of circuitry within the pager to extend battery
life).
WO91/06190 ~ PCT/US90/05513
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The presentation mode selected within a personality
functions to control parameters associated with the pager's
information presentation means. Examples of selections
available for information presentation are numeric,
alphanumeric, or graphic modes.
The operation mode selected within a personality
functions to control parameters associated with the pager's
messaging capability and alerting functions. Messaging modes
can include tone-only, tone numeric, tone & voice, tone &
voice numeric, or alphanumeric to name a few. Alerting modes
commonly used include audible tone alert and sensible
vibrating alert as well as a selection between various alert
tones, patterns, or melodies.
Referring to Fig. 5, when the pager is activated 501 it
loads the default personality that corresponds to the wide
area paging mode 502. When the pager is in the wide area
paging mode, it continuously searches each channel (frequency)
for received data indicative of a protocol for which the pager
receives messages. The data may be in the form of a baud rate
or a predetermined synchronization signal. Upon finding such
a channel, it searches for its corresponding wide area
selective call address and any local area identifier that is
broadcast. If a valid local area identifier is detected 503,
the pager then selects the appropriate local parameters that
correspond with the detected local area identifier. The
selected local area personality is enabled by selecting the
local paging address 504, local receive frequency 505, local
protocol mode 506, local presentation mode 507, and local
operation mode 508. When personality configuration is
complete, the pager changes from the wide area mode to the
local mode 509. If the signal transmitted from the paging
base station is lost 510 for a predetermined period of time,
the pager will revert to the wide area paging mode 502.
