GB2253503A

GB2253503A - Radio pager with data display device

Info

Publication number: GB2253503A
Application number: GB9125530A
Authority: GB
Inventors: Takayuki Asai
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1990-11-30
Filing date: 1991-11-29
Publication date: 1992-09-09
Anticipated expiration: 2011-11-29
Also published as: HK86797A; GB9125530D0; GB2253503B

Abstract

A radio pager adaptable to a radio paging system of the type adding a serial number to each message signal on a pager basis at a central station, so that each pager may detect the failed reception of any of a sequence of message signals sent from the central station at any intervals. For the detection of failed reception, the pager has, in addition to receiving means, demodulating means, decoding means, and display means customarily included in a pager, means for detecting the serial number, means for temporarily storing the detected serial number, means for storing a serial number received just before, and means for generating an alarm representative of failed reception when the difference between the outputs of the two storing means is greater than or equal to 2.

Description

RADIO PAGER WITH A DATA DISPLAY DEVICE BACKGROUND OF THE INVENTION (1) Field of the Invention The present invention relates to a radio pager with a data display device for receiving messages included ill call signals which are sent from a central station by a radio frequency (RF) carrier.

More particlarly, the present invention relates to a radio pager of the type described which is suitable for the reception of message signals each being accompanied by a serial number.

(2) Description of the Prior Art In a paging system using an RF signal, a radio pager receives an RF signal sent from a base station and having been mod!ated into a digital call signal including an address signal and a message signal. The pager demodulates the RF signal to produce the digital call signal and decodes the digital call signal to produce the address signal and message signal.If the address signal is coincident with an address stored in a memory built in thc- pager, the pager informs the user thereof the reception of a call by a loudspeaker and/or similar alertins means. i. e. by an alert tone and/or vibration and by message display means which shows a message thereon Recently, a radio pager of the tpe described is ptovided with a capability of receiving a message without an alert tone when the person carrying the pager presses a switch.Specifically, in a toneless receive mode, it is a common practice to store, every time a call signal meant for the pager is received, a message signal included in the call signal in a memory built in the pager, while showing Only the number of messages having been stored in Lhe memory on the display means. The user of the pager sees whether or not message signals have been received by looking at the display means and Operates a switch to see received message signals on the display means.

A radio pager of the type operable in such a toneless receive mode is disclosed in U. S. Pat. No. 4, 412, 217 (Oct. 25, 1983) "PACKER WITH VISIBLE DISPLAY INDICATING STATUS OF MEMORY". The pager disclosed in U.S. Pat. No. 4 412v 217 receives a call signal, stores a message signal included therein, displays the number of messages having been received and stored, and assigns numbers to the messages in order of reception to facilitate the selective display of messages.

The above-described type of conventional toneless message reception enhances the secrecy of calls or messages meant for the user of the pager to thereby broaden the applicable range of a pager.

On the other hand, if the user of the pager is in the Service area or is in a tunnel just when a call signal meant for the user is Sent from the central station, the pager cannot receive the call signal at all. In the case of the pager of the type producing an alert tone in response to every call, the failed reception is not critical since. it will urge the caller to call the pager again afterwards. However, the user of the pager with a toneless receive mode, i. e., with a memory for storing messages cannOt recognize the failed reception and is, therefore, apt to encounter a serious problem, depending on the content of the message.

To allow the user of the pager to surely recognize failed reception, a system in which a serial number is added to a message signal contained in each call signal on a subscriber(pager) basis is described in a recently filed unpublished pending Japanese Patent Application No.

03-23964/91 which is assigned to the same assignee as the present application.

In this type of system, the pager displays a serial number together a message associated therewith on display means thereof.

The user, therefore, can readily see failed reception by looking at the display means and be relieved by contacting a paging firm offering the paging system.

However, the conventional radio pagers including the pager taught ill U. S. patent No. 4, 412, 217 cannot satisfactorily coPe with the reception of a message signal with a serial number.

Specifically, Since the serial number is merely appears on the display means as part of a received message signal, the user of the pager cannot recognize failed reception unless the user memorizes the serial number at all times. This not only aggravates the burden to the user but also prevents the user from Surely recognising failed reception.

A feature of an embodiment to be described is the provision of - a radio pager with a data display device which allows the user of the pager to recognize failed reception with ease.

A radio pager with a data display device has, in an embodiment to be described, means for separating from a received message signal a serial number particular to the pager and inserted in the message signal at a central station to implement the detection of failed reception, means for storing the separated serial number, means for calculating a difference between the output of the storing means and the output of discriminating means which is associated with a message signal received just before the above mentioned message signal, and means response to the output of the calculating means for producing an alarm when the difference is greater than or equal to 2.

The pager is capable of displaying at least two of the serial numbers of consecutive message signals on display means thereof, as needed.

Since the pager of this embodiment automatically dctects failed reception and produces an alarm, the user of the pager can surely recognize the failed reception. Displaying at least two serial numbers on the display means further promotes the accurate recognition of failed reception.

Embodiments of the invention will now be described, by way of example with reference to the accompanying drawings, in which: FIG. l is a block diagram schematically showing a radio pager embodying the present invention; FIXES. 2 (a) -2 (d) show signal formats of a digital call signal; FIG. 3 is a flowchart demonstrating a specific signal processing sequence up to the detection of failed reception and alarm generation particular to the embodiment; FIG. 4 shows a specific waveform of a paging alert signal included in the embodiment; FIG. S shows a specific waveform of a failed reception alert signal also included in the embodiment; FZG 6 shows a specific picture appearing oil message display means of the embodiment when reception fails; and FIG. 7 shows a specific Picture appearing on the message display when reception does not fail.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawings, a radio pager embodying the present invention is shown and includes an antenna Ii. An RF signal sent from a central station, not shown, comes in the pager through the antenna 11. A receiver/demodulator 12 densodulates the RF signal to produce a digital call signal Sa. A decoder 14 decodes the call Sa and determines whether or not an address signal included in the signal Sa is identical with an address stored in an address memory 13 which is built in the pager, i. e., whether or not the paging signal is meant for this pager. The output of the decoder 14 is applied to a microprocessor (CPU) 20.

The CPU 20 has, although not shown in the figure, a program memory storing sequences of instructions to execute, i. e.

programs, a program counter for designating the read address of the memory, an instruction decoder for decoding an instruction read out of the memory and delivering control signals matching the decoded instruction to the inside and the outside of the CPU 20, an arithmetic and logical unit for performing arithmetic and logical operations via an accumulator, a system clock generator for generating a system clock, and a data bus. The CPU 20 operates on the basis of the Program read out of the program memory. When the received address signal and the address assigned to the pager and stored in the address memory 13 match as determined by the decoder 14, the CPU 20 commands a paging alert oscillator 18 to generate a paging alert signal. As a result.

the paging alert oscillator 18 generates a paging alert signal PA.

When means and a procedure which will be described detect the failure of the reception, the CPU 20 commands a failed reception alert oscillator 1 7 to generate a failed reception alert signal FA.

The signal PA or FA is fed to z loudspeaker 19 via an amplifier 18 with the result that an audible alert tone is produced via the loudspeaker 19.

When the received address signal and the address of the address memory 13 match as stated above, a message signal fed from the decoder 14 to the CPU 20 is stored in a message memory 21. Implemented as a RAM (Random Access memory), the message memory 21 stores the received message together with a serial number included in the digital call Sa. A register 22 stores the serial number of a message signal received just before the above-stated received message signal, while a buffer 23 temporarily stores the serial number of the message signal having just been received. These received messages and their associated serial numbers are displayed on a message display 31 via a display controller 30. The message display 31 is constituted by a liquid crystal display.A data display radio pager with a miroprocessor is conventional and described in, for example, previously stated U. S. Pat, No. 4, 412, 217. The following description will, therefore, concentrate only on the part of such a pager that relates to the purport of the present invention.

FIG. 2 (a) shows a specific format of the digital call signal Sa. In the figure, the signal format is implemented as a so-called POCSAG (Post Office Code Standardization Advisory Group) standard format (see CCIR Rec. 584). As shown, the signal Sa has a preamble signal P in which "1" and "0" repetitively appear over 576 bits, and a plurality of batches each being made up of seventeen codewords (which have thirty-two bits each). In each batch, the codewords other than the single leading codeword for synchronization (SC) each forms a single frame together with the codeword next thereto, whereby eight frames are formed in total.

The address signal A is constituted by a single codeword and inserted in predetermined one of the eight frames. The address signal A is followed br a message signal M in the form of a particular number of message codewords MO-Mn matching the size of a message to be transmitted. An idle code I is inserted in the time slots other than the time slots assigned to the signals A and M.

A single paging signal Sa may included a plurality of combinations of such address signal A and message signal M.

Then, to distinguish the signals A and M from each other, the most significant bit (MSB) of a 32-bit codeword constituting each of the signals A and M is used as a flag bit. When the flag bit is "O", it indicates that the associated codeword is an address signal A; when it is "1" it indicates that the associated codeword is one of the message codewords MO-Mn (FIGS. 2 (b), 2 (c) and 2 (d)).

Elevell check bits re. A added to each of the codewords of the signals A and M for error correcting purpose (FIGS. 2 (b), 2 (c) and 2 (d).

In the digital paging signal Sa to which the pager of the invention is applicable, among the twenty message bits of the leading message cordeword MO of the message signal M which is adapted for the POCSAG system, the second bit to the fifth bit are assigned to data bits 201 corresponding to a serial number to be inserted at the central station, and the sixth bit to the twentyfirst bit are assigned to message data bits 202 meant for the pager (FIG 2 (c)). Regarding the succeeding message codewords M1-Mn, the serial number is not necessary and, therefore, all the data bits 201 form part of the message data bits 202 1FI6 2(d)).

A reference will also be made to FIG. 3 for dcscribing a specific signal processing procedure up to the detection of failed reception. The digital call signal Sa produced by the receiverfdelnodulator 12 from an RF signal coming in through the antenna 11 is applied to the decoder 14 (step 501). Assume that an address determined by an address code included in the address signal A of the signal Sa and by the frame position of the address code matches the address stored in the address memory 13, as determined by the decoder 14 (502). Then, the decoder 14 renders the CPU 20 Operative and transfers a message signal M subsequent to the address signal A to the CPU 20 (503).

Started by the decoder 14, the CPU 20 sends a command to the paging alert oscillator 16 to cause the latter to generate the paging alert signal PA. As shown in FIC. 4, the paging alert signal PA are constituted by pulses having a period of 1 second and a duty factor of 75 Percent. The signal PA is amplified by the amplifier 18 and then drives the loudspeaker 19 with the result that an alert tone is produced to inform the user of the pager of the reception of a call.

The CPU 20 stores in the buffer 23 the second bit to the fifth bit of the message codeword MO which is representative of the serial number of the message signal M (504). At the same time, the CPU 20 stores in the message memory 21 the message portions of the codewords Mo-Mn except for the flag bits and check bits, i.e., the second bit to tbe twenty-first bit (data bits 201 and 202) of each codeword.Since the register 22 stores the serial number of a message signal received just before the above-stated message s.gnal M, the existing content of the register 22 is subtracted from the content of the buffer 23 (505) If the resulting difference is greater than or equal to 2 (YES, 506), the CPU 2 3 sends a start command to the failed reception alert oscillator 17 (507). In response, the alert oscillator 17 generates the alert signal FA. The signal FA is amplified by the amplifier 18 and then drives the loudspeaker 19. As shown in FIG. 5, the signal FA is implemented as pulses having a period of 20 milliseconds and a duty factor of 50 percent to be distinguished from the previously mentioned paging alert signal PA. If the difference determined in the step 506 is 1 (N0, 508), the CPU 20 does not send a start command to the alert oscillator 17. In any case, on completing the procedure up to the step 501, the CPU 20 transfers the content of the buffer 23 to the register 22 to prepare for the decision on the failed reception of the next message signal (508).

It is to be noted that when the pager is used for the first time in a paging service network of the kind giving a serial number to a message signal, zero is initially stored in the register 22 as a serial number. The content of the register 22 is incremented by 1 every time the pager receives a message meant therefor. The CPU 20 is programmed such that after the content of the register 22 has reached 15, it is reset to zero on the reception of the next message signal.

The message codewords MO-Mn stored in the message memory 21 are displayed on the display 31 under the control of the CPU 20. Specifically, the four data bits 201 forming part of the codeword MO and representative of the serial number, the other data bits 202, and the data bits 202 of the other message codewords M1-Mn are shown on the display 31. Further, the content of the register 22, i. e., the serial number of the immediately preceding message also appears on the display 31 to allow the user of the pager to see the occurrence of failed reception and to see the message or messages having not received with ease.

FIGS. 6 and 7 each shows specific information appearing on the display 31. In FIG. 6, a condition just after the reception of a message signal having a serial number "6" is shown in which the serial number "1" of the message signal received immediately before also appears. By looking at such a picture on the display 31, the user sees that four consecutive messages numbered "2" to are are missing. In FIG. 7, the picture shows the user that the serial number of the message signal received just before the message signal numbered "7" is "8", i. e. , that no message signals are missing.

In the embodiment shown in FIG. 1, the register 22 is implemented by a nonvola C memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory). When a nonvolatile memory is not used, a memory with a back-up battery may be used to hold the stored data.

While the embodiment has been shown and described in relation to a digital call signal adaptable to the POCSAG standard system, it will be apparent that the present invention is practicabie even with any other paging system using a particular signal format.

In Summary. it will be seen that a radio pager has been described which automatically detects the failed reception of a message signal and produces an alarm, insuring the recognition of failed reception by the user of the pager. Further, the pager described displays the serial number of a message signal received just before the following message signal together with the serial number of the latter, facilitating the recognition of failed reception as well as missing message signals.

Although the invention has been described with reference to a specific embodiment, this description is not to be construed in a limiting sense. Variations and modifications of the disclosed embodiment, as well as other embodiments of the invention, may become apparent to persons skilled in the art upon reference to the description of the invention and may be made within the scope of the appended claims.

Claims

1. A radio pager with a data display device capable of receiving a sequence of message signals sent from a central station at anY time intervals, said radio pager comprising; means for receiving from said central station a radio frequency (RF) signal having been modulated by a digital call signal which includes an address signal and a message signal; demodulating means for demodulating said RF signal to produce said digital call signal; decoding means for decoding said call signal to produce said address signal and said message signal; alert generating means for selectively generating an alert in response to the output of said decoding means; display means for selectively displaying the output of said decoding means in a visible form;; serial number detecting means for detecting a serial number included in said message signal and indicative of an order of transmission from said base station, first storing means for temporarily storing the latest serial number outputted by said serial number detecting means; a second storing means for storing an immediately preceding serial number assigned to, among said sequence of message signals, a message signal received just before a message signal to which said latest serial number is assigned, at least until said message signal with said latest serial number has been received; means for subtracting the output of said second storing means from the output of said first storing means; and alarm. generating means for generating an alarm when the output of said subtracting means is greater than or equal to 2.

2. A radio pager as claimed in claim 1, wherein said latest serial number and said immediately preceding serial number are displayed together.

3. A radio pager as claimed in claim 1 or 2, wherein the output of said alert generating means and the output of said alarm generating means have signal configurations which are distinguishable from each other

4. A radio pager as claimed in claim 1 substantially as described herein with reference to any one of the accompanying drawings.