GB2240009A - Transceiver pager - Google Patents

Abstract

A portable message pager with enhanced capability includes an alphanumeric keyboard 14, a modem (34), (Fig 2), an alphanumeric display 12 and a radio transmitter (36) and receiver (38) enabling the user to key in and transmit text messages to other similar message pagers, received messages being stored in a memory (32) and/or transferred to the display 12. Messages may be transmitted in packets each including data constituting a call sign for the intended destination, data identifying the sender, and error checking data. Transmission of a packet may be repeated until an acknowledgement signal is received. A port 24 is provided for connection to external apparatus, such as a printer or computer. The transceiver may be incorporated into a lap-top sized personal computer, but is preferably of a size that can be held in one hand. <IMAGE>

Description

TRANSCEIVER PAGER This invention relates to portable communication devices.

The original concept of the telephone service as a widely available communIcations network has now extended te portable telephones - used for voice transmission in the same way as conventional telephones - and to pagers and message pagers.

Both pagers and message pagers have the advantage of small size and easy portability. A simple pager can receive a signal and give an audible alarm to inform the user carrying the pager that he is being paged. A message pager has the capability to receive a message which is displaved on an LCD display. The message of course is data representing alphanumeric characters.

I have now appreciated that it would be desirable to provide a device which is portable and can be used like a pager but has an enhanced ability to receive messages and also an ability to transmit.

According to the present invention there is provided a portable transceiver having: an alphanumeric keyboard for data input; a radio transmitter and receiver; electronic memory for storage of data; an alphanumeric display for visible but impermanent display of data; digital electronic circuitry connected to each of the above, which circuitry includes a modem and serves to: i) transfer data which has been input at the keyboard to the radio transmitter via the modem, for transmission of said data ii) transfer data received by the radio receiver to the memory for storage and/or to the display.

In preferred forms of the invention, the transceiver is constructed with sufficiently small dimensions and weight that a user will be able to carry it around, much as conventional message pagers are carried at present. For this purpose the dimensions are likely to be less than 40cm x 15cm x locum, which itself would be rather a large size, and the dimensions are preferably less than 25cm x 10cm x 5cm. A size considerably smaller even than this can be envisaged, e.g. 12cm x 10cm x 2cm for a transceiver small enough to be carried in a jacket pocket.

The dimensions and shape may be such that the device can be held in one hand and operated with the other.

While such small size is preferred, an alternative possibility would be for the radio transmitter and receiver, with necessary connecting circuitry, to be included as part of a personal computer, for example of the so called lap-top size. This would not realise the advantage of very convenient portability which is preferred for this invention but it would constitute an addition to the capabilities of a portable personal computer.

The transceiver will generally have a self contained power supply. The preferred power supply is rechargeable batteries: these could be removable for recharging in a separate charger or alternatively the entire transceiver could be attached to a charger when not in use.

Single-use batteries might be employed instead of rechargeables.

The transceiver's display could be of any convenient type which is able to display alphanumeric characters. A liquid crystal display is strongly preferred because it can be made with small size and has a very low power requirement.

The circuitry of the transceiver will generally include a microprocessor operating to read the keyboard and transfer data to and from the modem, to and from the memory and to the display. The memory used for storage of data will generally be random access memory. It is desirable that received messages are automatically stored in memory even if they are also shown on the display.

It is envisaged that the keyboard will serve not only for the input of data to be transmitted as a message but will also serve to control the operation of the device generally.

A preferred feature is that the memory provided for the transceiver is of sufficient size, and the organization of the transceiver is such, that a plurality of messages can be received and stored in the memory.

Conveniently then the transceiver can be operated to recall each of the messages to the display to be read. It is also then preferred that the transceiver circuitry includes a port for connection by cable to an external device and the circuitry is able to transfer received messages from the memory via the said port to the external device. The purpose of this would be to enable the messages to be more permanently recorded, if desired, whilst also releasing the memory capacity of the transceiver. The external device might conceivably be a printer but is more likely to be a personal computer which may have its own printer. In this latter case, it will be possible for the messages to be transferred from the memory of the transceiver to the personal computer's screen and thereafter stored on magnetic disk, and/or printed out onto paper and/or discarded as the user might decide.

By providing the transceiver with a port for transfer of messages by cable to a printer or to a personal computer, the transceiver acquires the ability to provide a paper record of messages received without the necessity of the user carrying the printer. While it is within the scope of the invention that the transceiver could include a printer, it is preferred that the transceiver should not include any printer.

A further preferred feature is that the transceiver should include means for giving an audible paging signal when a message is received, and it may be arranged that the pitch of this audible paging signal can be determined by the user. This would enable each user of a transceiver to determine his own paging signal(s), which would help an individual user to be able to recognise the signals from his own transceiver and ignore other paging signals which happen to be within earshot. This could for example be useful when a number of people present in a room are carrying transceivers or pagers.

In order to be able to receive messages in a manner convenient to the user, it is desirable that the transceiver is constructed and arranged so that it can be carried in a state (conveniently termed a "waiting" state) in which it is turned on and able to receive a radio transmission and store message data included in the transmission without requiring intervention by the user.

The transceiver may then give an audible paging signal and the user will be able to read the received message as soon as it is convenient to do so.

Preferably the organisation of the transceiver is such that it will automatically return to the waiting state after reception of a transmission, so as to be able to receive further messages while the earlier message(s) remains in its memory.

For the sake of convenience in carrying, it is desirable that the various parts of the apparatus, notably the transmitter and receiver, the keyboard, the display, the memory, the modem and the remainder of the circuitry and a power supply are all mounted on a common supporting structure so as to constitute a single item of apparatus.

This will generally mean that the various parts are enclosed within a common casing with the keyboard and display exposed on the surface of the casing. However, this casing may consist of a plurality of sections pivotally connected together, for instance a main casing with a pivotally attached flap carrying the keyboard or part of the keyboard.

Transceivers in accordance with this invention might be used to provide a private communications network for a single organisation, e.g. for the staff of a commercial company. In that event the number of transceivers able to send and receive messages to and from each other might be quite small and it might be acceptable that each transceiver would receive all the messages sent by any of the others. However, it is envisaged that transceivers in accordance with this invention would be used in a larger communications network, probably a generally accessible network to which anyone could subscribe. Then, in order that a message was only received and stored in memory by the particular transceiver intended to receive it, each transceiver could be assigned a unique call sign which would be a sequence of data, perhaps representing a multidigit number analogous to a telephone or telex number.The individual transceiver would then be arranged to detect reception of its call sign and respond to it by storing the message data contained in that transmission. Other call signs, and the messages accompanying those call signs, would be ignored.

More specifically, it is preferred that the data transmissions are effected in accordance with a protocol which requires the data constituting the transmitted message to be contained in one, or if necessary more than one, "packets" each of which has a predetermined maximum length and includes the call sign, i.e. data identifying the intended destination. Preferably the packet also includes data Identifying the origin of the packet and an error code generated by the originating transceiver's microprocessor in accordance with a predetermined algorithm.

Such a system enables checking that the message is received correctly at the intended destination. The transceiver to which the message is addressed identifies the packet as one intended for it because it contains the appropriate call sign for that transceiver. The packet is therefore taken into the memory of the receiving transceiver and it checks that the error code in the data as received is correctly calculated in accordance with the algorithm. If this is correct it is presumed that the message has been transmitted correctly. An acknowledgement message is then automatically sent back to the transceiver which originated the packet, to signal that the message has been correctly received. Transmission of the packet would be repeated automatically as many times as necessary, subject to a predetermined limit, until it had been acknowledged.While this method of error detection and correction is not infallible, it can give a high level of accuracy. Suitable algorithms for generating error detection codes are known and are used already in other systems which carry out electronic transmission of data.

It is preferred that the transceiver transmits data in a short "burst" with a data transfer rate of 512 baud or higher. This is very much faster than the rate at which a user could key data in. Consequently the amount of time for which the transceiver would actually be transmitting is very small.

In addition to the transceivers, a suitable radio network will generally include at least one fixed receiver for receiving signals transmitted by the portable transceivers and at least one fixed transmitter for transmitting to the transceivers, with means for transferring signals received by the receiver(s) to the transmitter(s) for re-transmission at enhanced signal strength. More specifically, it is envisaged that a suitable radio network will have a plurality of fixed receivers and a voting system for selecting the receiver which is picking up the strongest or cleanest signal and passing that signal on for retransmission. If the operational area is of a sufficiently small size a single main transmitter will be adequate.If the operational area is larger, it becomes appropriate to sub-divide the operational area into individual cells each having its own transmitter and a plurality of fixed receivers and the voting system as referred to above. There would also be a control system monitoring the whereabouts of each transceiver and arranging that messages for that transceiver were transmitted to it from the appropriate fixed transmitter. A radio network of this character would be analogous to a cellular telephone system except that it would be handling data rather than voice signals.

If the data is transmitted in "bursts" in the manner referred to above, the total time for which any one transceiver is transmitting is very short and the available time can therefore be share between numerous transceivers.

Consequently it would be possible for a single transmission frequency to be used by a considerable number of transceivers. This enables good usage of a single radio frequency channel with fairly narrow band width. There is a possibility that two transceivers may both attempt to transmit bursts of data at the same time. To overcome this, each transceiver is arranged to receive from the transmission frequency and thereby test whether data is already in the process of transmission by some other transceiver before itself attempting to transmit. In the event that it discovers another transceiver is already in the process of transmission, the transceiver is arranged to wait for a short delay (typically in the order of milliseconds) before trying again. While this will reduce considerably the likelihood that two transceivers will both make transmissions simultaneously, (with the result that neither transmission is capable of being received in usable form), it does not wholly eliminate the possibility.

Consequently it is arranged that if a packet of data is transmitted and no acknowledgement signal is returned, there is a random delay before the transceiver makes a fresh attempt, again first checking that no other transceiver is already transmitting. Because this delay is random, one of the pair of transceivers which attempted to transmit at the same moment as the other will make its second attempt ahead of the other one, thereby compelling them to proceed in turn.

The fixed transmitter(s) might operate on the same frequency as the transceivers or on a separate frequency.

Embodiments of this invention will now be described by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a transceiver, Fig. 2 is a schematic diagram of the functional parts of a transceiver, and Fig. 3 illustrates the radio network for a small area.

Referring to Fig. 1, the transceiver has its parts accommodated in a case 10 which is of dimensions suitable to be held in the human hand. Exposed on the top surface of the case are a liquid crystal display 12 and a keyboard 14 with both numeral and alphabet keys. Alongside these keys are additional keys 16 used solely for control of the transceiver. A loudspeaker 44 for emitting paging signals is concealed behind a grill 18. A telescopic aerial 20 projects from the upper end of the transceiver. This would normally be retracted but could be extended to achieve a stronger signal if it was found that a transmission was not being received successfully. A small door 22 conceals a socket used for connection of a battery charger.

(Conventional single-use batteries might be used as an alternative to a built-in rechargeable battery). A coaxial socket 24 is used as a serial port for external connection.

In an alternative arrangement, not shown, the transceiver has a top flap overlying the top surface of the case and hinged to it at the left-hand side so that the top flap can be opened towards the left in exactly the same manner as opening the front cover of a book. With this transceiver the LCD display, numeral keys and keys for controlling operation of the transceiver are all on the front of the case concealed by the cover until this is opened. Alphabetic keys are provided as a key pad on the inside of the cover.

As shown in Fig. 2 the circuitry of the transceiver includes a logic section 30 which includes a microprocessor and is connected to RAM 32, the keyboard 14 and the LCD display 12 in accordance with conventional microcomputer architecture. The logic section is connected through a modem 34 to a radio transmitter 36. For transmission, data from the logic section is converted by the modem 34 into modulations of a carrier signal for radio transmission. The modem 34 is also connected to a radio receiver 38. Received signals are demodulated by the modem and passed as digital data to the logic section 30.

One possibility is that the receiver is connected to circuitry 40 for detecting the call sign of the particular transceiver. If the call sign is detected a signal is sent along a separate line to the logic section, possibly to an interrupt input of its microprocessor. It is only upon detection of the call sign that the logic section 30 proceeds to accept digital data from the modem 34. In that way messages intended for some other transceiver are effectively ignored.

As an alternative to dedicated circuitry 40, it would be possible for each received "burst" of data to be stored temporarily in RAM and examined by the logic section.

If the burst was found to contain the call sign for that particular transceiver, the burst would be manipulated further, if not the logic section would take no further action so that subsequently the burst was overwritten by the next received burst.

As shown at 42 the logic section also controls the connection of the aerial to either the transmitter or the receiver. If it is necessary to transmit or receive on more than one frequency, the logic section is also connected (as shown chain dotted at 48) to the transmitter and/or receiver to control their frequency.

The circuitry of the transceiver includes a real time clock 46 connected to the logic section 30. The logic section 30 can make use of the real time clock for recording the time of receipt of a received message, for automatically switching the transceiver into an "off" state at programmed times and thirdly for enabling the transceiver to act as an alarm clock. The "off" state just mentioned would probably not be a true off state in which all the circuitry was disconnected from the power supply but rather it would be a state in which the transceiver remained under power, but would not receive or acknowledge any incoming messages.

On receipt of a burst which is intended for the transceiver, the logic section checks that the error detection code calculated from the data as received is correct. If it is, a raturn sIgnal is automatically transmitted to the originating transceiver to confirm that the burst has been received correctly.

Operation of the portable data transceiver is simple. When the user wishes to send a message he pushes one of the control keys 16 which causes the transceiver to function as a transmitter. The user then keys in the call sign of the intended recipient followed by the message.

The data is manipulated by the logic section into the appropriate form for transmission in accordance with the data communication protocol of the communication network in which the transceiver is used. For the preferred protocol in which data is transmitted as "bursts" the data is manipulated by the logic section 30 so as to form bursts for transmission with each burst including call sign data identifying the intended destination, call sign data identifying the origin and also error detection data calculated by the logic section in accordance with a predetermined algorithm. To transmit each burst, the logic section first receives on the transmission channel to check that no other transceiver is currently transmitting, then the data for one "burst" is passed via the modem 34 to the transmitter 36.After the burst is acknowledged by the recipient transceiver, the next burst is transmitted in the same way. When every burst of data that makes up a single message has been transmitted and acknowledged by the recipient transceiver, a signal to that effect is shown on the LCD display.

The process of manipulating data for transmissIon into bursts, of giving acknowledgement of correctly received bursts and retransmitting any burst which is not acknowledged is automatic and not noticeable by the user.

A variation on the above arrangement would be that the user pushes a control key to indicate that he is about to type in a message for transmission, he then types in the message on the keyboard and it appears on the display as he types it, as a confirmation of correct typing. Once the message has been typed in and if appropriate any errors have been corrected, the user then pushes a second control key followed by the call sign of the intended recipient.

Thereupon the microprocessor effects transmission of the message which has already been keyed in.

The user normally carries the transceiver switched on, but in a passive state waiting to receive a transmission. When a transmission is received the call sign of the transceiver is recognised by the circuitry 40 and the remainder of the transmission is then handled by the modem and the microprocessor. The data constituting the message is recorded in RAM and the microprocessor generates an audible signal through the loudspeaker 44 to alert the user that a message has been received. The message is displayed on the LCD display. If the message is longer than can be shown complete on the display, keys of the transceiver provide for scrolling through the message.

Unless the user intervenes, e.g. to read the message or transmit a reply, the transceiver returns to its "waiting" state. If further transmissions are received the further messages are likewise stored in RAM. Later, individual messages can be called to the display if the user inputs appropriate commands.

The logic section 30 is also connected to the seriai port 24. This port can be connected to an external device by flexible cable, for transferring stored messages to the external device.

Fig. 3 illustrates the radio network. This has a fixed transmitter 50 serving the operational area. There is also a main receiver 52 which is at the same location as the main transmitter. In addition there are two further receivers 54,56 at other locations in the operational area.

Because these are at some distance from the main receiver they are referred to as "satellite" receivers. Signals received by any of the receivers are passed to a voting circuit 58. In the case of satellite receiver 56 the signals are transmitted to the voting circuit by land line, i.e. a fixed cable which may well be provided by a telephone company. In the case of the other satellite receiver 54 the signals are passed to the voting circuit via a fixed radio link. The number of satellite receivers provided and connected to the voting circuit should be sufficient that the entire operational area is covered without any "dead spots" from which reception is not possible.

When a transceiver in the operational area transmits, its transmission will be received by one or probably more than one of the various receivers. The sIgnals picked up by the various receivers will be cf different quality and the voting circuit 58 takes the received signal of best quality and passes it on through a modem 60 to a central computer 62 controlling operation of the network. Provided that the received signal meets the requirements of the data communication protocol for the network it is retransmitted from the main transmitter for reception by the intended recipient.

Messages for transmission may also be keyed in through one or more data entry terminals (not shown) connected to the controlling computer. This would enable a message for the user of the transceiver to be communicated verbally, for example by telephone, to an operator who would key the message in for transmission.

If the operational area was larger, it would be sub-divided into cells each having a transmitter and one or more receivers. Each cell would have its own frequency and the controlling computer of each cell would be connected by land line or a fixed radio communication link to a central computer for the entire system. The logic section of each individual transceiver would be arranged to control the frequency of the radio in its transceiver and to adjust that frequency to correspond with the operating frequency of the cell in which the transceiver happened to be. The central computer for. the system would maintain a record of the cell in which each transceiver was currently operating. When a message is sent from a transceiver in one cell and intended for a transceiver in another cell, the message would be passed to the central computer which would pass it on to te cell containing the transceiver of the intended recipient.

If a cell is small enough, it may have only one receiver. Alternatively a cell may have several receivers connected to a voting circuit, as in the arrangement shown in Figure 3.

Claims (15)

CLAIMS:

1. A portable transceiver having: an alphanumeric keyboard for data input; a radio transmitter and receiver; electronic memory for storage of data; an alphanumeric display for visible but impermanent display of data; digital electronic circuitry connected to each of the above, which circuitry includes a modem and is arranged to: i) transfer data which has been input at the keyboard to the radio transmitter via the modem, for transmission of said data ii) transfer data received by the radio receiver to the memory for storage and/or to the display.

2. A portable transceiver according to claim 1 wherein the transceiver has a case which is shaped and dimensioned to be held in a human hand with the keyboard exposed for use.

3. A portable transceiver according to any one of the preceding claims wherein the dimensions of the transceiver are less than 40cm x 15cm x locum, preferably less than 25cm x 10cm x 5cm.

4. A portable transceiver according to any one of the preceding claims wherein the electronic circuitry includes means to recognise a received data sequence constituting a call sign for the individual transceiver, and is arranged, reception of said sequence, to retain received data in said memory, but to ignore any received transmissions not including said sequence.

5. A portable transceiver according to any one of the preceding claims constructed and arranged to be carried in a state in which the transceiver is able to receive a radio transmission and store data included in the transmission without intervention by the user.

6. A portable transceiver according to any one of the preceding claims wherein the transmitter and receiver, the keyboard, the display, the memory, the modem and the remainder of the said circuitry are mounted on a common supporting structure so as to constitute a single item of apparatus.

7. A portable transceiver according to any one of the preceding claims wherein said memory is of sufficient size to store a plurality of messages received in respective transmissions and said circuitry is operable to display individual messages on said display.

8. A portable transceiver according to any one of the preceding claims wherein the data processing circuitry includes a microprocessor.

9. A portable transceiver according to any one of the preceding claims wherein the transceiver includes means far giving an audible signal on receipt of a radio transmission to it.

10. A portable transceiver according to any one of the preceding claims wherein the transceiver has a self contained power supply, preferably rechargeable batteries.

11. A portable transceiver according to any one of the preceding claims wherein the transceiver includes a data port for cable connection to other electronic equipment.

12. A portable transceiver according to any one of the preceding claims wherein the alphanumeric display is an LCD display.

13. A portable transceiver according to any one of the preceding claims constructed and arranged to manipulate data intended for transmission into packets which each contain a data sequence constituting a call sign for the intended destination, a data sequence identifying the originating transceiver and calculated error checking data.

14. A portable transceiver substantially as herein described.

15. A communications system comprising a plurality of portable transceivers according to any one of the preceding claims together with at least one fixed receiver, at least one fixed transmitter, and equipment arranged to retransmit from the fixed transmitter signals received by the fixed receiver from any of the transceivers.