U.S. Philips Corporation

Advantra International N.v.

Anthony K Sharpe

Andrew D McPherson

Peter J Mabey

Richard C Burbidge

Andrew T Yule

A method of transmitting messages in a communication system including a primary station and at least one secondary station, the secondary station being identifiable by an address code word, the primary station transmitting messages signals in the format of the address code word of an addressed secondary station concatenated with a plurality of message code words, wherein the primary station indicates the provision of an optional facility which it can provide to a secondary station by transmitting indicia representative of the facility in a field contained in at least one of the message code words concatenated with the secondary station's address code word.

Method of, and communication system for, sending messages

A message transmission system, such as a paging system, provides message compression through the use of corresponding memories or memory areas in a primary station and a secondary station storing identically the most frequently used n items of numeric only or alpha-numeric data. The contents of the memories are updated dynamically to reflect changes in the most frequently used items by the primary station examining messages to be sent to a particular secondary station to see if an item is being used more frequently than one of those stored, in which case the primary station initiates a reprogramming message which is sent to the secondary station. In response to receipt of the reprogramming message, the particular secondary station updates its memory and acknowledges to the primary station that it has done so, and upon receipt of the acknowledgement, the primary station correspondingly updates its memory. The message compression technique may also be applied to frequently used phrases and also to complex graphical data which it is more efficient to store in the primary and secondary stations and to transmit a memory location indicator.

Message transmission system, a method of operating the message

A display system comprises a display apparatus such as an electronic notice board, TV set or computer monitor. Radio messages are received by a point-to-point receiving apparatus, such as a wide area digital pager, adjustably mounted relative to the display apparatus. The receiving apparatus generates non-electrical signals which are transmitted to the display apparatus, the display apparatus displaying said signals. The receiving apparatus is adjusted to minimize the error rate in the signal received by said apparatus.

Displaying data transmitted by radio

A selective call system including a base station having a transmitter for transmitting digital paging signals in the form of batches, each batch including a synchronization code word and concatenated message signals. While the bit rate of the message signals within each batch is the same, the synchronization code word of a particular batch contains information indicating the bit rate of the message signals in its batch.

Selective call system with bit rate embedded in synchronization code word

A selective call system comprises at least one base station which transmits address code words at a predetermined data rate. High rate telescript information having a length of more than 500 characters, for example, an E-mail message, is transmitted at a data rate greater than that used for sending address code words. In the event of the system comprising a simulcast system, intersymbol interference (ISI) may occur and in order to reduce the effects of ISI on the decoding the telescript information while avoiding an unnecessarily large drain on a secondary station's batteries, the telescript information as received for a specific secondary station is stored and subsequently equalized in non-real time. The secondary station can comprise a mobile terminal unit and may include a transmitter for transmitting acknowledgement or other response signals, for example, such as spread spectrum signals. The acknowledgement signals may be used for locating the mobile terminal unit.

Selective call system and a secondary station for use therein

A method of, and system for, communicating messages in an environment which is subject to fading, in which data to be transmitted is encoded and formatted, a checksum is determined for said encoded and formatted data and in which the checksum is added to an address code word which is concatenated with the encoded and formatted message code words to form a message. A receiver is energized for receiving transmissions in its predetermined frame. In response to recognizing its address code word the concatenated code words are decoded and stored. As each code word is stored, substantially simultaneously a checksum is computed for the message assembled so far and is compared to the checksum in the address code word, if and when they are equal it is concluded that a complete message has been received and further analysis of the stored message is terminated. In a variant of the present invention each message is transmitted at least twice and a final version of the message is assembled code word by code word by comparing the corresponding code words in the respective transmissions and selecting the better (or best) version. As the final version is being assembled the checksum is computed and compared to determine the end of the message. In a further variant the detection of an address or idle code word following a message code word is treated as the beginning of a new message and the computed checksum is used when an undecodable code word is received.

Method of and system for communicating messages

Selective call systems such as the CCIR Radiopaging Code No. 1 (or POCSAG) have a signal format of successive data batches, each batch having a synchronization codeword followed by a 8 data frames. Each pager is assigned to a frame in every batch, resulting in a battery power conservation duty cycle of 1:8. The invention enables any number of the pagers to operate in accordance with a preselected longer duty cycle. Every N (N&gt;2) successive batches constitute a superbatch, and a pager is assigned to only one or certain ones of the frames thereof. To provide superbatch synchronization a predetermined codeword (PCW) is transmitted in one frame of one batch, preferably the first, of the entire superbatch. A pager energizes its receiving section to receive the PCW codeword, based thereon synchronizes to the batch and super batch, then de-energizes its receiving section for a predetermined interval T1 until reception of the its assigned frame, after which it de-energizes again for another predetermined interval T2 until the PCW codeword of the next succeeding superbatch is received. If N=16, a battery power conservation duty cycle of 1:128 can be achieved. Since the PCW codeword is only transmitted once in every N batches, it does not significantly effect the standard signal format and so the system is transparent to pagers which are to operate at the conventional 1:8 duty cycle. Also, since the synchronization codewords are not effected, rapid recovery of synchronization is retained following deep fade or loss of the transmitted carrier.

Paging or other selective call system with battery power conservation

A communications receiver such as a radiopager derives information which is necessary for operation thereof from a discardable read-only data card which is inserted therein. Such information may include a radio identity code (RIS) for relating the receiver to a particular user, and prepaid credit units which are cancelled by the receiver based on the number of received messages or time intervals of operation thereof. The information may also include a particular frequency and data rate for adapting the receiver to operate on a paging system used in a particular country. Once the information on the data card has been read-out and stored in a non-volatile store, the card can be removed and either discarded or recharged with new credit units upon payment of a fee at an authorized station. The receiver may be adapted for use in a different country simply by inserting a data card relating to that country, paying for usage of the receiver as the user goes from country to country.

Radio paging receiver wherein programming information is readout from a

In a radio paging system each pager includes a timer having a clock to provide date and time stamping of received messages. To set the time of the pager clock, the system base station transmits time message signals at regular intervals but which are of variable accuracy due to delays in signal formatting and propagation. The invention provides a pager wherein a control unit sets the timer clock in accordance with the time indicated by a transmitted time message signal which is determined to be the most accurate, such signal being selected as a time reference signal. The most accurate signal is determined by comparing the differences in indicated times of transmission and reception of an already selected current time reference signal with those of a presently received time message signal. If the presently received time message signal is the more accurate, it is substituted as a new time reference signal in place of the current time reference signal.

Communications system and receiver for use therein which indicates time

A pager decoding system which is suitable for use with signal formats, such as POCSAG, in which code words are sent in batches, each batch containing a synchronization code word and (n-1) address/message code words, n being the number of code words in a batch, each code word comprising m bits. The pager is able to detect or regain synchronization code word when the carrier signal is lost due to fading. When synchronization is lost input data received by the pager is combed through by switching-on the pager for a duration of m bits at intervals corresponding to (n+1) code words. The data received is stored in a shift register having m stages and in which a synchronization code word can be assembled within two batch periods. Once the synchronization code word has been detected the pager can be switched to a normal data receive mode. In another fade recovery mode the (m-1)th, mth, and (m+1)th bit positions every nth code word are searched to see if a preamble or synchronization code word is present. If none is detected after a predetermined number of batches has been searched then the pager assumes the loss of synchronization mode described above.

Pager decoding system

In digitally encoded data transmission systems such as paging systems using a code word format, such as POCSAG, each code word includes a number of bits collectively termed the cyclic redundancy check bits. In a paging receiver the cyclic redundancy check bits are used to determine if there are errors in the received message code words. If an error is detected then one bit random error correction is generally applied because it has a more acceptable falsing rate compared to say two bit random error correction or four bit burst error correction. However a less acceptable falsing rate correction technique, such as four bit burst error correction, can be given if additional protection against falsing is provided. The additional protection comprises error detection check bits which are included in the entire message transmitted by the base station. At the receiver any errors in the message code words are subjected to four bit burst error correction and thereafter the entire 'corrected' message is subjected to a further check using the error detection check bits. Whether or not error detection check bits have been included in the message is indicated by preconditioning the message, for example by using predetermined ones of the plurality of addresses allocated to each pager for different purposes. If error detection check bits have not been included a more acceptable falsing rate correction technique is applied.

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Cambridge, United Kingdom

Anthony K Sharpe