Data-transmitting method and selective calling receiver

Method for transmitting data and selective call receiver

The present invention relates to a selective call system, and more specifically to the format of a transmission signal, and a method and receiver for receiving the transmission signal.

For selective call receivers commonly used on roads, the life of a battery used as a power source is a basic performance index. In particular, with the miniaturization of receivers in recent years, there has been an increasing need for smaller batteries. Therefore, how to extend the life of the battery has become a very important technical issue.

The battery life is determined by the two main parameters of the receiver's power consumption and the intermittent reception interval. Since a considerable part of the power consumption is consumed in the radio frequency system, so long as the receiving operation is performed, it is impossible to hope to greatly improve the power consumption. Therefore, a method of making the intermittent reception interval longer has been proposed to reduce the average power consumption. In order to make the intermittent reception interval longer, a synchronous system is being considered to replace the currently widely used asynchronous system (for example, the POCSAG system). An example of a synchronization system is ERMES (European Radio Telegraph System).

ERMES uses the following method: divide the number of frames into each time-division frame in advance and the base station transmits a call signal with the number of frames that a certain receiver should receive. Compared with the asynchronous system, this method makes the intermittent reception interval significantly longer.

The transmission signal of ERMES includes synchronization field, address field and message field. The message field further includes the message and the message header indicating the message flag. Since the message header indicates the address to which the message belongs, the transmission order of the message can be arbitrarily determined regardless of the address of the message. For example, the paging system disclosed in Japanese Patent Unexamined Publication No. 63-158924 (Publication Date: July 1, 1988) uses a method of making the receiving interval longer by specifying the number of frames that should be received.

However, the above-mentioned conventional selective call system requires a complicated system configuration. Furthermore, a lot of additional bits are needed in the transmission of the message signal, which leads to an increase in the additional signal of the message signal and will cause a decrease in the efficiency of message transmission. Therefore, even if a high-speed transmission system is adopted, it is impossible to obtain the expected increase in user capacity.

An object of the present invention is to provide a data communication method which can improve the transmission efficiency, obtain a larger capacity user and a user receiver with low power consumption.

Another object of the present invention is to provide a method for receiving a message signal with high reliability in simple steps.

Another object of the present invention is to provide a selective call data capable of receiving message signals with high reliability, simple structure and low power consumption.

The transmission signal format according to the present invention is as follows. Divide a specific time period into multiple frames. Each frame includes a synchronization field, an address field and a message field. The address field includes a plurality of addresses respectively corresponding to the user's receiver. The message field includes a plurality of messages respectively corresponding to addresses. The message consists of a message and a message header including the number of address transmission sequences corresponding to the message.

A base station transmits the transmission signal to multiple receivers. The receiver intermittently receives one frame of each transmission signal. When the receiver receives the frame, the receiver sequentially searches the address field as the ID (identifier) address of the receiver itself, and at the same time increases the received sequence count on each address. When the receiver finds the ID address, the receiver stores the sequence count received at that time. Next, the receiver searches for a message field as a message corresponding to the ID address by comparing the stored reception sequence count with the transmission sequence number included in the message. When the sending sequence number is consistent with the receiving sequence count, the message data sent to the receiver is detected from the message field.

Preferably, the address field is terminated by a predetermined word. When the receiver finds the predetermined word, the receiver stops looking up the address field and returns to the receiving step.

More specifically, the message header further includes: a first field including a message header indicator code, a second field including a transmission sequence number, a third field including a message type, and a fourth field including a message length. In this case, when the receiver compares the stored reception sequence count with the transmission sequence number contained in the message header, the receiver detects the message header from the message field. When the stored receiving sequence count is consistent with the sending sequence number, use the message type and message length to input the message sent to the receiver itself.

As described above, the communication method according to the present invention provides the relationship between the transmission order of each address of the address field in the first message frame and the number of address transmissions in the first message header of the message field. Therefore, even if a synchronous system is used, the message can be determined by a short message header.

In addition, the selective call receiver according to the present invention stores the received transmission sequence of its own address in the address field of the message frame. When the stored transmission sequence is consistent with the transmission sequence number of the message header, the receiver selects the message data after the message header as the message sent to the transmitter. Therefore, high reliability can be realized with a simple structure.

Fig. 1 is a schematic diagram describing the frame structure of a message signal according to an embodiment of the present invention; Fig. 2 is a schematic diagram describing an example of a message header in the message signal format of Fig. 1; Fig. 3 is a diagram describing the present embodiment A schematic diagram of the one-word format of the BCH (31,21) code used in;

Fig. 4 is a block diagram showing a base station in a selective call system according to an embodiment of the present invention; Fig. 5 is a block diagram showing a selective call receiver in an embodiment; Fig. 6 is a block diagram showing a selective call receiver in an embodiment of the present invention Flow chart of operation.

One frame of the message transmission signal is determined by dividing a specific time period into multiple frames. For example, if one minute is divided into 120 equal parts, the time period of one frame is 0.5 seconds. When using the transmission speed of 9600bps and the word format of the BCH (31, 21) code, a frame with a period of 0.5 seconds is composed of 150 words. The word format will be shown in Figure 4. In this case, the selective call receiver performs the receiving operation only during one frame of 120 frames. Which frame to receive depends on the occasion of use.

The signal frame format is shown in Figure 1. A frame composed of 150 words includes a synchronization (SYNC) field, an address field and a message field. The synchronization field further includes a bit synchronization signal, a frame synchronization signal and a frame information signal, and each signal has a word length. The selective call receiver corrects bit errors by using the bit synchronization signal of the synchronization field and establishes word synchronization by using the frame synchronization signal. The frame information signal of the synchronization field includes a frame number signal (8 bits), a time information signal (5 bits), and another frame information signal (8 bits), and these signals are not shown in the figure. If one frame is preset in a predetermined time period and the frame #0 is the same as the table one time instant, the receiver obtains time information by receiving the frame. In addition, the receiver can also monitor the time information signal (5 bits) of the frame information signal to achieve certain functions such as displaying the time of day and the time of receiving a message.

As shown in Figure 1, the address field is a group of addresses (here there are 5 addresses A1-A5), and each address has a word length. In the case of the BCH (31, 21) code, since a word has a 21-bit information field, approximately two million users can be visited. The address field is ended by the address end word P. When the receiver detects the address end word P, the receiver judges whether there is its own address in the received frame, and ends the address search. It should be noted that the address transmission order in the address field is determined in advance by the base station.

The message field is a group of sub-messages (here there are 5 sub-messages M1-M5), each sub-message has a variable length and includes a message header MH and a message. The message header MH further includes a message header indication signal F (1 bit), an address transmission number signal A (5 bits), a message type signal T (2 bits) and a message length signal N (7 bits), totaling 15 Bit. The remaining bits of a word except the message header MH are used as messages. Therefore, this embodiment can define a message using 15 additional bits, thereby greatly improving the message transmission efficiency compared with the conventional system.

The message header indication signal F is a binary bit that distinguishes the message header MH from the message code word according to the value 0 or 1. For example, the value 1 represents the message header MH and the value 0 represents the message codeword. Therefore, the receiver can find the message header MH only by checking the first bit of each word.

The address transmission number signal A indicates the transmission sequence of each address (A1-A5) in the address field. For example, the message header MH corresponding to the first address A1 that is transmitted first has the address transmission number A='1'. The message header MH corresponding to the fifth address A5 has the address transmission number A='5'. As will be described below, the receiver looks for the address field as its own address. When the receiver detects its own address, the receiver stores the number of addresses detected, that is, the address transmission sequence. Next, while the receiver searches the message fields, the receiver searches for messages with the address transmission number A consistent with the stored address number.

The message type signal T indicates the message type transmitted immediately after the message header MH. For example, the two-bit message type signal T is defined as shown in Table 1.

Table 1

In this embodiment, four types of messages can be identified at most and the fourth message type with T='11' is reserved. Defined in another way, for example, binary data can be transmitted.

The message length signal N indicates the length of the message or the number of code words of the message. Since the message length signal N has a length of 7 bits, it can specify a message length of up to 128 words. When the receiver receives the message, the receiver counts the number of words in the message and compares the count value with the message length signal N at the same time. When the count value reaches the message length N, the receiver judges the end of the message sent to itself. Since the message length signal N indicates the message length, a more accurate message display can be obtained. Therefore, compared with the case where the message display range is determined only by the message header indicator signal F, the reliability is higher.

Figure 2 shows an example of the message header MH.

Since the first bit of the bit string '100101100001110' is '1', this word includes the message header. The address transmission number A is '00101', so the message is the fifth sub-message M5 corresponding to the address A5. Since the message type T is '10', the message type is word end. Finally, since the message length signal N is '0001110', the message consists of 40 characters.

It should be noted that the word used in this embodiment is a BCH code, such as the 32-bit BCH (31, 21) code used in the POCSAG system. The word format of the BCH (31, 21) code is shown in Figure 3. A word includes a 21-bit signal bit field, a 10-bit parity bit field, and an even parity bit.

The base station is shown in Figure 4, and several telephone lines are connected to the conversion system 1 of the central base station. The number of calls and the messages received from the telephone of the calling user are transferred to the message processing unit 2 through the conversion system 1. The message processing unit 2 generates the message data necessary for the selective call and transfers the generated message data to the protocol encoding processor 3. The protocol encoding processor 3 uses the address transmission count memory 4 to generate a transmission signal having a frame format as shown in FIGS. 1-3. This transmits the transmission signal from the transmitter 5 to the remote call receiver.

Selective call receiver FIG. 5 is a block diagram showing an embodiment of a selective call receiver according to the present invention. A battery-powered receiver has a receiving circuit composed of a built-in antenna 10, a radio frequency receiver 11, and a demodulator 12. After receiving the demodulated signal from the demodulator 12, the decoder 13 decodes the received demodulated signal into received data.

When inputting and receiving data from the decoder 13 to the processor 14, the processor 14 uses the ID address storage 15, the address count storage 16 and the message storage 17 for receiving control according to the instructions input by the user through the keyboard. This will be described in detail below description. The ID address memory 15 stores the receiver's own address or predetermined ID (identification) number.

Under the control of the processor 14, the received message and other required data are displayed on the display 19 through the display driver, and the call indicator 20 is operated through the driver when an incoming call is received. There is a battery 21 in the receiver, and under the control of the processor 14, the power controller 22 provides the power of the battery 21 to the receiver circuit, such as the radio frequency receiver 11 and the demodulator 12. For example, power is supplied to these circuits intermittently during intermittent reception.

Receiving Operation FIG. 6 shows the receiving operation of the selective call receiver shown in FIG. 5. The demodulator 12 uses the synchronization field of the signal frame shown in FIG. 1 to establish synchronization. After the synchronization of the demodulator 12 has been established, the demodulated signal is passed from the demodulator 12 to the decoder 13, and the decoder 13 decodes the demodulated signal into received data.

The processor 14 uses the following procedure to find the address field (A1-A5) of the frame corresponding to its own address. First, when receiving the first address A1 (S101), the processor 14 increments the count of the address counter (S102), and then determines whether the first address A1 is consistent with the ID address stored in the ID address memory 15 (S103). If the first address A1 is not consistent with the ID address (No in S103), it is further determined whether the first address A1 is consistent with the address end word P (S104). If the first address A1 does not match the address end word P, the processor 14 inputs the subsequent second address A2 (S101) and increments the count of the address counter (S102). Repeat this address search step until the ID address is detected.

Assume that the ID address is found in the third address A3. Each time the first address A1 is input and then the second address A2 is input, the processor 14 increments the address counter, but skips these addresses. When the third address A3 is input, the processor 14 increases the address count to the count '3' (S102), and then detects the ID address (Yes in S103). When the ID address is detected, the address count "3" at this time is stored in the address count memory 16 (S105).

Then, the message search is started (S106). The processor 14 distinguishes the message header MH by looking for the message header indication signal F from the bit string received by the decoder 13. After extracting the 5-bit address transfer number A from the message header MH (S107), the processor 14 determines whether the address transfer number A matches the address count stored in the address count memory 16 (S108). If they do not match, input the following message header MH (S106) and check the address transmission number A in the same way (S107 and S108). If the address transmission number A is consistent with the address count stored in the address count memory 16 (Yes in S108), the message following the message header MH is stored in the memory 17 to which the message is sent (S109). Then, the receiving operation is ended (S110).

Assuming that the ID address is found at the third address A3, the number of address transmissions of messages M1 and M2 is inconsistent with the address count stored in the address count memory 16, while the number of address transmissions of message M3 is consistent with the address stored in the address count memory 16. The counts are consistent. Therefore, the message of the message M3 is stored in the message memory 17 according to the message type T and the message length signal N of the message header MH of the message M3. The processor 14 informs the user of the incoming call with the call indicator 20 and reads the message from the message memory 17 to display the message and other necessary data on the display 19.

Comparison The following compares the above-mentioned selective call system with other systems in the direction of message efficiency. In order to transmit a 40-character letter message, a total of 16 words including a word address and a 15-word message are required according to the embodiment of the present invention. On the other hand, the POCSAG system requires 15 words in order to transmit the same message. Therefore, compared with the POCSAG system, the overhead of the message signal has increased by about 7%.

Since the word structure of this embodiment is different from that of the ERMES system, it is simple and useless. However, the ERMES system requires 20 words in order to transmit the same message. Therefore, this embodiment improves the transmission efficiency by about 20%. Especially in the case of relatively short messages, such as digital messages, the transmission efficiency has been significantly improved. For example, when a 10-character message is transmitted, the ERMES system requires 7 words while this embodiment only requires 4 words.