JPH03104496A - Telemeter system - Google Patents

Abstract

PURPOSE:To expand the movable range of a data transmission station by packetizing transmission sample data by each data transmission station, and transmitting a packet with the timing of probability set in advance after including an ID number proper to each data transmission station and the sequential number of transmission data in the packet. CONSTITUTION:The nt data transmission stations TXSi are prepared, and they transmit the packet with a timing at random mutually. As a result, packet transmission from two or more stations are necessarily generated simultaneously. It is called as packet collision. Then, the probability to dissipate the sample data due to nd times of collision of the packet including the sample data can be reduced by transmitting the same sample data as the packet for nd times. Therefore, it is possible to heighten possibility to receive the packet with a nearer data reception station without dissipating the packets simultaneously even when the packet collision occurs by providing plural data reception stations.

Description

[Detailed Description of the Invention] The present invention relates to a telemeter system, and more specifically, to a telemeter system in communication.
onMultiple Access), and is also applied to (medical) electrocardiogram monitors, heart rate monitors, blood pressure monitors, body temperature monitors, respiratory rate monitors, and exercise amount (body movement) monitors.

Documents describing the prior art related to the present invention include the following.

■Tobagi, F. A. , rMultiaccess
Link Control. Jin rcomput
ar Network Architectures
andProtocols. J (Edited by
Green, P. E. , Jr. ,PlenumPres
s, New York, 1982, ppl45-1
89. J This document is based on Randoa+ Access T
echniques, and the present invention belongs to the Pure ALOHA method in this document.

■Kleinrock, L. & Tobagi, F.
．． A. rPacket Switching in R
adio Channels: Part I-C
arrier Sense Multiple-Acc
ass Modes and their through
hput-Delay Characteristic
s. (IEEE Trans. on Commun
．． , vol. COM-23, No. 12, Dec
．． 1975. pp1400-1416. ) The document is A
LOHA and primarily CSMA (CarrierS
ense Multiple Access) Thr
The output-delay characteristics are analyzed.

■Abramson. N. ,rThe ALOHA
System-Anotheraltern
active for computer community
cations. J (in1970 Fall Jo
int Comput. Conf. , AFIPS
Conf. Proc. , vol. 37. Montval
e, N. J. :AFIPS Press, 1970, p.
p. 281-285. ) This document explains the ALOHA method, and especially (Offered) Channel Traff.
ic and ChannelUtilization (T
hroughput) has been analyzed. ■ Hiroji Nishino, "Survey on local area networks (LAN)" (Japan Electronic Industry Promotion Association, 58-A-203, March 1980, pp47-48.) In the document The following is stated. In other words, historically. It was developed at the University of Hawaii in 1970. The Pure ALOHA protocol is
It was first used as an access method for the ingle hop ALOHA system.

The ALOHA network uses a packet switching method using wireless lines, and can be said to be the simplest type of network. Pu
With re ALOHA, data can be transmitted whenever it is desired, and the terminal that has transmitted the data receives an acknowledgment signal (Acknowledgement) from the other terminal within a predetermined appropriate timeout period and completes the data transmission phase. .

On the other hand, if a collision occurs, it is necessary to control it. In order to avoid continuous collisions, the time delay for retransmission is randomly assigned to each terminal for each L7.

As can be seen from the above documents, random access schemes such as the ALOI{A network are suitable for computer communication. In such communications, much of the data traffic is bursty. That is, each terminal is required to generate a data message to be transmitted/received with a very high degree of randomness in both the time of generation and the amount thereof, and also to have a small relative delay time.

Therefore, for data traffic such as telemetry data that occurs regularly, the conventional ALOHA
method is not suitable.

In addition, in the ALOHA method, packet collisions cannot be avoided in principle (probabilistic), so as a countermeasure in the event of a collision, a response signal (Acknovledgesment) is sent.
A procedure is needed to retransmit the same packet when the packet is not returned from the receiving station. That is, the data transmitting station also receives this response signal (Acknowledge-me).
A control receiver is required to receive the nt).

As mentioned earlier, it is desirable to avoid installing a control receiver in a simple data transmission station. Furthermore, the retransmission procedure is complex, and it is well known that deadlocks occur unless all possible transmission errors are considered. In simple data transmissions, such as telemetry, the use of hardware and software for such complex retransmission procedures is extremely inappropriate due to equipment size and cost.

For example, in a hospital with a large number of seriously ill patients, if the electrocardiograms or heart rates of many patients were to be constantly monitored at the same time, one electrocardiogram or heart rate monitoring device would be required for each patient. Another disadvantage is that the patient being monitored cannot move beyond the length of the cable (electric wire) connecting the probe attached to the patient and the device, and even if he or she can, it is difficult to move. Although wireless alternatives to cables do not have these drawbacks, the method of assigning a separate radio frequency to each patient (FDMA) requires a (non-B) receiver for each patient; The entire system has to be large and expensive; in reality, only small-scale systems have been put into practical use.

As long as the monitoring is concentrated in this way, by using the TDMA method, the wireless receiver on the monitor side (hereinafter referred to as the data receiving station) can be used with one unit, making the overall system smaller and cheaper. It seems possible. However, in normal TDMA, even the device on the data sending side requires a receiver to control the sending timing. In the field of telemetry, as in this example, the data transmitting station (the entire device including the wireless receiver) does not originally need to receive data, and adding a receiver for control would unnecessarily increase the complexity of the device. This results in larger, larger, and higher prices. Generally, a wireless transmitter with weak or low power output is a much simpler device than a receiver, so it is important to avoid placing a control receiver at the data transmitting station.

The present invention was made in view of the above-mentioned circumstances.
There is only one (none, l) receiver at the data receiving station,
It is possible to receive telemetering data from a large number of data transmitting stations that do not have control receivers, and only one
By providing multiple data receiving stations with multiple (wireless) receivers, the movable range of the data transmitting station can be greatly expanded.
Moreover, it was developed with the aim of providing a telemetry system that greatly increases the total number of data transmitting stations.

In order to achieve the above object, the present invention has (1) two or more data transmitting stations and one data receiving station, and each data transmitting station receives previously transmitted sample data. The transmitted sample data is packetized in a form that includes a part of
a), transmitting the packet at mutually independent random timing, and receiving the packet at the data receiving station;
Data is restored in chronological order for each data transmitting station from the ID number and sequence number in the packet, and if there is sample data that cannot be restored in chronological order, the sample data at that time is discarded or restored before and after. (2) Or, there are two or more data transmitting stations, two or more data receiving stations, and one data collecting station, and each data transmitting station uses previously transmitted samples. Transmission sample data is packetized in a form that includes a part of the data, and the packet includes an ID number unique to each data transmission station and a sequence number of transmission data, and each data transmission station receives a predetermined probability (a ), and the data receiving station receives the packet and restores the data in time series for each data transmitting station from the ID number and sequence number in the packet. , If there is sample data that cannot be restored in time series, a flag is set to indicate that the sample data at that sample point cannot be restored, and these sample data are sent to the data collection station, and the data collection station Restoring the sample data by comparing the sample data transmitted from each data receiving station for each data transmitting station in chronological order and selecting any of the sample data without the above-mentioned flannel at each sample time. , (3) Furthermore, the data collection station interpolates the unrecoverable sample data of each data reception station from adjacent error-free data; (4) Furthermore, the data collection station The number of data transmitting stations within the receiving range of the station is nt・tp/tt≦
1/2 (here a = t p / t L), (5) Furthermore, the sampling interval of sample data at the data transmitting station is ts, and the number of repetitions of transmission of the same packet is np. (np is a positive integer), and the number of sample data in the packet is n (na is a positive integer), that is, when ts:ilp'' tt, nP'' ni≧2, and further, (6) The method of each transmitter and each receiver is a frequency spreading method, and the same spreading code is used at all data transmitting stations; (7)!
9. A data transmitting station where urgent sample data has been generated is characterized in that it transmits a packet containing urgent sample data with a probability greater than a predetermined probability (a). Hereinafter, the present invention will be explained based on examples.

Offered Channel Traffic is G (here, 0≦G), Throughput tI:
S, in Pure ALOHA, S(G)=G-e-26(1). The maximum value Smax of S is when G=1/2, Smax=S(1/2)=1/2e40.18
(2).

Here, the probability P that a packet is transmitted without being damaged (without causing a collision) is p (G) = S / G = e-26 (3)6 Therefore, the probability that a packet is transmitted without being damaged (without causing a collision) is p (G) = S / G = e-26 (3). ) The probability r is r(G)=1-p=1-e-2G (4). These relationships are detailed in the above-mentioned document (■) and the older document (■).

Here, if O≦G〈〈1, then r (G)=1
− (1+ (-2G)+ (-2G)” / 2!+
(-2G)' /3! + − − )=2G −
2G2+ 4G3/3-...Yo2G
(5) is obtained. This means that even if G becomes somewhat small, the packet damage probability r will not become sufficiently small. For this, A
In the LOHA method, a terminal that has sent data receives an acknowledgment signal from the other terminal within a predetermined appropriate timeout period, completes the data transmission phase, and receives the response signal within the timeout period. If not, the problem is resolved by retransmitting the previous packet. Furthermore, in order to avoid continuous collisions, retransmission time delays are randomly assigned to each terminal. Although it is theoretically possible to reduce transmission errors to zero with this method, the transmission delay may become abnormally large, making it unsuitable for the field of telemetry, which requires real-time performance.

In the present invention, a type of time diversity is employed instead of employing complicated response signal return and retransmission procedures. Although it is not possible to eliminate errors, it is possible to sufficiently reduce the error probability and maintain real-time performance. Taking a heart rate monitor as an example, real-time performance within a delay time of about 10 seconds is absolutely necessary, but it is not necessarily necessary that all sampled data (Sampled Data) be completely received.

This type of telemetry data has a kind of continuity, and the lack of a small amount of sample data along the way is often not a problem. Also, such missing sample data can be interpolated from previous and subsequent complete sample data.

Figures 1, 2, and 3 are explanatory diagrams for explaining an embodiment of the telemeter system according to the present invention. FIG. 3 is a conceptual diagram of the data receiving station, and is a diagram showing the structure of a packet transmitted from the data transmitting station. In the figure, 1 is a clock signal generator, 2 is a frequency divider, 3 is a sensor, 4 is a sampler, 5 is a packet information assembler, 6 is a FIFO buffer, 7 is a packet assembler, 8 is a random number generator, and 9 is a Comparator, 10
is a transmitter, 11 is an antenna, TXSi (1≦i≦nt
) is a data transmitting station, and RXS is a data receiving station.

An example of an electrocardiogram monitor or an electromyogram monitor will be explained below. The sensor 3 shown in Figure 1 consists of electrodes for inputting electrocardiograms or electrocardiograms, an amplifier circuit, and a low-pass filter. Here, it is assumed that frequencies above 50 Hz are completely removed. Sampler 4 consists of a sample and hold and an A/D converter.

The sampling frequency here is f. is f. = 100Hz (100S
ample/See) (6) That is, the sampling period t, is tB=10mSec
(7). Also, the conversion accuracy of the A/D converter is 8b.
Let it be. 3rd by packet information assembler 5? The contents from ID to SX-< are packetized.

In Figure 3. The ID is a number unique to the data transmitting station and is 8.
It shall be expressed in bits. Further, No is a number (here k) indicating the k-th sample data. The number of bits for expressing NO will be described later. SX,
Sx-4 is n sample data (here n==5), and each of them is currently
t, time past......, 4t. This is sample data from the past. As long as data is sampled continuously, k can take on an infinitely large value, but as a general method, k
The value of can be restricted from O to j-1. , j is usually a power of 2, which is easy to calculate (only the lower 1 og a j bits need to be added). Here j
= 2 I1. That is, it is assumed that NO is 8 bits.

C R C (Cyclic Redundancy)
Check) is generally well known and is used to check whether there are any errors in the information (from ID to Sκ1) in the transmitted packet. Here C
Let RC be 16 bits. Preambles are for establishing the bit period in the receiver, and are, for example, 101010...10. Sync establishes the frame period in the receiver,
Here, any bit pattern that can be clearly distinguished from Preamble is sufficient, for example. It is 11001100. Note that in the embodiment of the present invention, since the packet length is fixed (constant), the same bit 1 to Sync pattern may appear in the packet information. In normal communication with variable packet length, data transparency (Transparency) is required.
In order to realize y), a special escape sequence is used or an O bit is inserted like HDLC. Furthermore, since the packet length is fixed, the bit pattern indicating the end of the CRC is not needed. Posta
Although mble is not necessarily essential, it is inserted here to protect the last part of the CRC. Although the bit pattern is not particularly limited, it is assumed to be 0000 here. Preamble, Sync, Postam above
The number of bits of ble is 16, 8, and 4, respectively.
Prean+ble. Sync, ID. No. S
x. Sx-t, SX-X, SX-S, SX-4, C
R.C. Each Postamble is 16, 8, 8, 8
,8,8,8,8,8,16,4 bits, so
The entire packet is 100 bits. Among these, the packet information from ID to SK-4 is (7×8=)56 bits.

The 56-bit packet information assembled into a packet by the packet information assembler 5 is sent to the FIF○ buffer 6. The output from the FIFO buffer 6 (56-bit packet information) is preambled by the packet assembler 7.
Sync. CRC. A Postamble is added to form a complete 100-bit packet as shown in FIG. 3, which is modulated by the transmitter 10 and transmitted as a radio wave from the antenna 11. This transmitter 10 is F S
K (FREQUENCY ShiftKeyin
g), and the transmission speed fb is fb=lMb sp (8
). Therefore. A complete packet of 100 bits is tp=100/fb
(9) Transmission ends in 100μ Sec. Here, tP is particularly referred to as the packet length.

Since a packet is generated every time t, the proportion a of the transmission time occupied by packets of this transmitting station is a = tp/ts
(10) = 1 0 0 μSec. / 1
0 m See. =0.01.

The clock (CLOCK) in Figure 1 is the frequency m'f
s, that is, the clock signal generator 1 with a period t,/m, the frequency divider 2 divides the output frequency of the clock (CLOCK) into 1/m, and divides the output frequency of the clock (CLOCK) into a frequency f. That is, the period t. Outputs the signal. The sampler 4 and the packet information assembler 5 each sample the output of the sensor 3 at the timing of the output of the frequency divider 2 (for example, at the rising edge of the output signal), perform A/D conversion, and packetize the sample data. .

On the other hand, the clock (CLOCK) also outputs a clock signal with a period of t, /m to the random number generator 8. The random number generator 8 generates a random number at every timing of a signal from the clock (CLOCK) (for example, every time the signal rises).
Assume that uniformly distributed random numbers from O to l are generated. The comparator 9 compares the random number generated from the random number generator 8 with a predetermined threshold 1 7 m, generates an output pulse when the random number is smaller than 1 / m, and sends the packet to the transmitter IO. Order transmission. The period of the output pulse of this comparator 9 is random, and the average period is m times that of the input signal, so the transmitter 10 has an average period of t. Send packets at random timing.

Note that when the transmitter 10 attempts to transmit a packet at the timing of the output pulse of the comparator 9, if complete packet information is not yet prepared in the FIF○ buffer,
We have decided to cancel the transmission. This situation often occurs immediately after turning on the power and starting operation, but if it happens several times. This will no longer occur since enough packet information has accumulated in the FIFO buffer.

In this example, t+=ts (11
). That is, each time data from the sensor is sampled, one packet is sent.

However, the packets are sent at random timing. Since the contents of the packet are as shown in FIG. 3, in this example, the same sample data is transmitted n times (here, 5 times) in separate packets.

Note that Equation (10) is a special case where Equation (11) holds true, and generally, the proportion a of the transmission time occupied by packets is expressed by the following equation (lla).

a = tp/tr
(10a.) FIG. 4 is a block diagram of a data receiving station, in which 21 is an antenna, 22 is a receiver, 23 is a bit synchronizer, 24 is a packet disassembler, and 25 is a microprocessor. Radio waves received by the antenna 21 are demodulated by the receiver 22. Here we use FSK Demodulator
It is. The received signal demodulated by receiver 'a 23 is input to a bit synchronizer 23 and a packet decomposer 24.

The bit synchronizer 23 extracts the timing at which the received signal should be sampled from the 1.0 pattern transition of the received signal.

In this regard, for example, the series of patents: 1,331,5
55, 1,347,926, 1,347,927, 1,
No. 347,928, No. 1,347,938, "Timing Information Reproduction Method". The bit synchronization signal extracted by the bit synchronizer 23 is output to the packet decomposer 24.

The packet decomposer 24 samples the received signal at the timing indicated by the bit synchronization signal, and
c bit pattern is detected, frame synchronization is performed, and ID
It decomposes the information into packet information from SK-4 to SK-4, and performs error detection using CRC. This packet information and the error detection result based on CRC are passed to the microprocessor 25. In the example using the HDLC format, this packet decomposer 24 is a MOTOROLA Advanced D
ata-Link Controller (MC685
4), which has a function equivalent to this LSI. The microprocessor 25 uses the current packet information (ID to SE-4) only when the packet decomposer 24 indicates that there are no CRC errors. If an error is indicated, the packet information is discarded.
The microprocessor 25 has a number and a buffer for each ID number in its memory, and sample data is placed in this buffer. FIG. 6 shows how the microprocessor 25 restores sample data in time series. No is a pointer in memory indicating the location of the last restored sample data. Here, since No is 8 bits, the buffer is 28 words and is realized in the form of a ring buffer. FIG. 6 shows the structure of this ring buffer. RD is a pointer for reading sample data restored in time series from this buffer. The microprocessor reads the sample data at the location indicated by this RD as necessary,
The sample data can be displayed, recorded on a magnetic disk, etc., monitored, or outputted to other devices.

The microprocessor 25 sends normal packet information (determined to be free of errors by CRC) to the packet decomposer 2.
4, sample data S in the packet information
K-4, Sx-a. Sx-x, SX-t, Sx and No
(this value is k) is the buffer in the memory of the microprocessor 25 corresponding to the ID number of the packet information and N
Copy to o. At this time, NO is copied last.

Also, an index k indicating time information of sample data
-i (i=o, 1, 2, 3.4) is the index k- indicating the location (address) of the sample data in the buffer.
Make it correspond to i.

As already mentioned, since NO is an 8-bit unsigned integer, ki is also an 8-bit unsigned integer, and modulo 256 is taken. For example, if No. in the packet information is k=2, then k-4, k-
3, k-2, k-1, k(n+odulo 25
6) are 254, 255, 0, and 1, respectively. It becomes 2, S! 54 9 S2&S + s, IS1,S
2 is stored in the buffer as shown in FIG.

The microprocessor 25 does not perform a read operation on the buffer when the number of sample data between RD and No. is 5 or less. 6 or more, the sample data at the location indicated by RD can be read, and when this is read, the data at that location is rewritten to invalid data after reading.

This invalid data uses numerical values other than the values that normal sample data can take. For example, since the sample data at the data transmitting station was 8 bits, normal sample data ranges from -128 to +127 (expressed as an integer value). Therefore, for example, a value such as +128 is used as invalid data. This means that each word in Bathofa is 9.
This indicates that a bit or more is sufficient. Further, the lower bit of each word can be regarded as sample data, and the upper bit can be regarded as a flag indicating whether the sample data is valid or invalid. Setting l in the upper one bit corresponds to setting a flag when the sample data cannot be restored in claim 2.

After rewriting invalid data, increase the value of RD by l (
However, modulo256 addition). Note that the initial value of the buffer is all words, invalid data (+i28), and in its initial state, NO=RD=O. 'In FIG. 6, invalid data is indicated by an X. Regarding the current ID, R
Assume that D=k. At this time. NO is k, k+1,
k+2, k+3, k+4, (modulo 256
), the kth (O or
gin indexing) can be read out, and after reading out, the contents of the k-th buffer are rewritten to invalid data X. Then R D 4-k
+ 1 (modulo 256), i.e. RD is 1
only increases.

Regarding a current ID, when a packet with that ID number is received normally, as mentioned earlier, the value of No in the packet information is set to k, and the sample data S X-4 in the packet information is SX-3. S X-X, Sx-+
．． Sx is copied to the buffer in the microprocessor's memory corresponding to the ID number of the packet information, and NO and RD in the microprocessor's memory are handled as follows. If No=RD (=O), this indicates that the buffer is in its initial state (with respect to its ID), so set the value of RD to the index of the oldest sample data. That is, NO=k and RD=k-4 are set. If the program in the microprocessor can access No and RD simultaneously by multitasking, No and RD must be set at the same time.

At least while rewriting the No and RD values,
This NO and RD should be made inaccessible by other tasks. A simple technique often used in microprocessors is to disable interrupts only while rewriting No. and RD. On the other hand, NO≠RD
If , the buffer is not in its initial state. Buffered some normal sample data in the past. in this case,
Sample data in packet information S X-4, SK-3
, sx-z. Copy sx-t, Sx and No (this value is k) to the buffer and No in the microprocessor memory corresponding to the ID number of the packet information. As a result, No (=k) in the memory of the microprocessor
The relationship between the values of and RD is RD=k, k+l, k+2, k
◆If none of 3 occurs, it is normal and no further operation will be performed, but which one? If this happens, it is abnormal. This abnormality occurs when a packet with the current ID number is not received normally for a long time, or when a read operation to the buffer becomes abnormally slow. When this abnormality is discovered, the processor notifies other programs or external devices that an abnormality has occurred regarding this ID number.

At this time, the processor processes k-4, k-3, k-2,
The buffers other than k-1 and k are set to the initial state, and the RD in the memory is set to k-4.

The No. numbers of the past 4 packets that were successfully received for the current ID packet are 245, 248, 245, 248,
252. Suppose it was 2. The contents of the buffer then become as shown in FIG. With N O = 245 packets, sample data S■. ~S2. , was written. Packets with NO=246 and 247 are lost due to collision, and the corresponding latest sample data S24 and S247
is still invalid at that point. However, NO=248
Sample data S 244-
524G-Sz47 becomes valid when 5248 is written. Then N O = 249, 250, 251
Although packets were lost consecutively, N O = 252
At the stage when is received normally, S24 to SZS2 become valid. Furthermore, after that, N O = 253,
254, 255, 0, ■ When NO=2 is successfully received after (5) consecutive packets are lost, NO=2
FIG. 6 shows a case in which packets 51154 to S2 became valid, but 5253 did not become valid (could not be restored).

When sample data is read and the data is invalid, interpolation can be performed using valid data before and after it. For example, interpolation is performed using the average value of the two data immediately before and after (primary interpolation). If n+1 valid data are used, nth-order interpolation can be performed. If the sample data has periodicity, an interpolation method suitable for the periodicity can be used. These interpolation operations read data from this buffer and then
As shown in FIG. 2, there are n data transmitting stations TXS i as shown in FIG. 1, which are executed by another program in the microprocessor, and these transmit packets at mutually independent random timings. Naturally, packet transmission may be performed simultaneously by two or more stations (at least a portion of the packets overlap each other). This is called a packet collision. The probability r (G) of packet collision occurring is expressed by equation (4).

Click here for Offered Channel Traffi
Since the ratio of the transmission time occupied by the packets of each data transmitting station is the average a, c
It can be expressed as (12).

Packet length t,=100μSee. , average packet transmission interval t 1 = 10 mSec. , if the number of data transmitting stations nc=5o. a=tp/tt=0.1,
G=0.5. The probability r (G) of packet collision occurring at this time is r (G) = r (n . ・a) = r (50X
O. Ol) = r (0.5)-2・0.5
-1 =1-e=1-e =0.63212
(13), and it can be seen that most packets are damaged by collisions. In the present invention, by transmitting the same sample data as a packet nd times (here, 5 times), the probability that the packet containing the sample data will collide n times (all packets) and the sample data will be lost is calculated. r (G). G=0.5.
If n, = 5, then r (0.5)S = 0.63212'
= 0.10 (14).

Most of the sample data will be received at the receiving station overnight without being lost. Data loss probability r (G)
The required value can be obtained by setting G and n. In the case of telemetry data as in the embodiment of the present invention,
Most of the data has strong temporal continuity and periodic correlation, and if some sample data is lost, it can be estimated and interpolated from previous and subsequent normal sample data using a generally well-known method. The packet information includes the sample data sequence number N.
o is included, so the data receiving station can determine which sample data is lost and which sample data is normal. Generally, in order to reduce the probability of data loss r (G), it is sufficient to reduce G. On the other hand, the number of packets without collision (per unit time) (ie, TroughputS) is maximized when G=0.5. Therefore, G is 0
．． Should be selected below 5. In order to increase S, that is, the number of data transmitting stations n, G should be set to 0.5 as much as possible.
It is a question to be decided depending on the application whether G should be brought closer to 0.5 or G should be made much smaller than 0.5 in order to reduce the probability of data loss r (G). In any case, G=n.・tp/t,≦1/2 (1
5).

In reality, the data loss probability is usually smaller than the value in equation (14).

In wireless communication, two (
This is because when the signal radio waves (above) are received at the same time, there is a capture effect in which the one with a higher signal level suppresses and overcomes the one with a lower signal level. In other words, even if a packet collision occurs,
At the data receiving station without any one packet being destroyed (
This is because a phenomenon occurs in which the packet is received normally. This capture effect is noticeable, for example, in frequency modulation (FM) systems. From the perspective of the capture effect, packets from a data transmitting station close to a data receiving station are particularly likely to win when a collision occurs, and packets from a far data transmitting station are likely to lose. Incidentally, the propagation loss (fIs force value) of radio waves is typically proportional to the fourth power of the distance (on a flat ground).

Therefore, as shown in Figure 5, by providing multiple data receiving stations. Bucket 1 - Even when a collision occurs, the possibility that both packets will not be lost at the same time and will be received by one of the nearest data receiving stations is dramatically increased. In this method, by arranging a plurality of data receivers as widely as possible and far from each other, the probability of data loss as a whole can be drastically reduced.

In applications such as electrocardiogram monitors and electrocardiogram monitors,
In a hospital, most of the patients are in the hospital room, and in a sports training center, most of the trainees spend a lot of time on various practice equipment and practice areas. Therefore, it is easy to set the reception range of each of the five data reception stations in advance, and the number of data transmission stations n, which fall within this reception range, can be set so that G≦0.5 (formula ( 12)). This means that when the number of data receiving stations is 01, the total number of data transmitting stations n, J
is approximately nt = n,'fi, (
16). In reality, the receiving ranges of data receiving stations adjacent to the WJ need to overlap with each other, so n,' is smaller than n,·n, but the general tendency is as shown in equation (16). That is, installing a plurality of data receiving stations not only helps reduce the probability of data loss, but also can be used as a means to increase the total number of data transmitting stations.

Furthermore, −a is site diversity (SitθD1ν
At the same time, an effect well known as ersity is exhibited. In other words, even if the radio wave propagation characteristics to some data receiving station are deteriorated due to a phenomenon such as multipath or due to an obstacle, what is the difference? There is a high probability that data can be received well at the data receiving station.

Furthermore, even if a person moves with this data transmitting station, there is a possibility that the data can be received somewhere, making it possible to significantly expand the range of movement.

In the embodiment shown in FIG. 5, data reception ("6 stations RSX■ and RS
In each of X2, the lost sample data is not interpolated, but the sample data from each data transmitting station restored in time series is transmitted to a computer (not shown) (by communication means such as a LAN), With this computer, it is possible to obtain a sample data time series with fewer defects of the sample data of each data sending station {jr} from the sample data from the two data receiving stations. Of course, from such a sample data time series with fewer defects,
It is easy to see that it is effective to compensate for slight defects.

Incidentally, it is naturally possible to use a form in which the data reception station has the function of a data collection station. This is because a computer such as a microprocessor is usually used as a data receiving station, and it is easy to double it as a data collecting station.

Also, by providing multiple data receiving stations as in this example,
The range of movement of data transmitting stations can be greatly expanded. This is because the data only needs to be received by any data receiving station. This requires a complicated procedure in conventional techniques. In the prior art, it was necessary to allocate different radio frequencies for use in adjacent zones to each data receiving station. Therefore, when moving from one zone to the next, a frequency switching operation was required. For this purpose, it is necessary to exchange control signals for frequency switching between the data transmitting station and the data receiving station, and the data transmitting station needs to be equipped with a wireless receiver, which increases the complexity of the equipment.
This results in larger size and higher prices. According to the invention,
A moving data transmitting station can use exactly the same frequency no matter what zone it is in, and no control is required when moving between zones.

One of the key points of the present invention is that by randomizing packet transmission, packet collision phenomena can be grasped probabilistically, and the loss of sample data when a packet collision occurs can be reduced by sending the same sample data multiple times. By doing so, the probability that the sample data will never be received normally can be reduced to a necessary value. In the method described above, nd sample data are stored in one packet in order to transmit the same sample data multiple times. If n, ≥ 2, and each time new sample data is generated, assemble the latest n sample data into a new bucket 1~ and send that bucket 1~ only once, then the same sample data can be sent n times. will be sent. If the same bucket 1- is transmitted nP times, the same sample data will be transmitted rlp·06 times. That is, np” nd≧2 (16
) is necessary in order to transmit the same sample data multiple times (twice or more). In the case of formula (16), n4
may be a positive integer (nd≧engineering). Also in this case.
The average transmission interval of packets is the sampling interval of sample data, and the number of repetitions of transmission of the same packet is n.
The value divided by P, that is, t c = t s/ np
(17a). This also means ts” np ' t t
(17b).

Earlier, we described a phenomenon called the capture effect, in which when a packet collision occurs, the packet with the higher reception 43u level is received without being destroyed. A similar phenomenon occurs when modulating and demodulating using the spread frequency method. In the frequency spreading method, even if multiple transmissions are performed at the same time within the same frequency band, if the spreading codes are different, or if the phases of the codes are different even if the spreading code is the same, mutually independent transmission will occur. Can communicate. This is well known as multiple access in frequency spreading. Another embodiment of the present invention uses a frequency spreading method in which all transmitters and all receivers use the same spreading code. The idea of using the same spreading code is the same as using the same channel (ie, the same carrier frequency) in FM modulation. That is, only one (wireless) receiver is required for (each) data receiving station. The only difference is how packet 1 survives when a packet collision occurs. FM
In a typical modulation method such as 1-1', the bucket 1~ with the higher received signal level survives (is normally received).
I was able to do that. In this case, the difference in received signal levels had to be sufficient to a certain extent. However, in the frequency spreading method, once synchronization is applied to the received signals of buckets 1 to 1, received signals other than those of buckets 1 to 1 are excluded by the process gain of frequency spreading. However, in this case, since the spreading codes are the same, if the phases of the spreading codes of the two received signals match, the received signals cannot be separated, but the probability of this is sufficiently small. Assume now that the spreading code is an M sequence with a period of 127. It is also assumed that a direct spread method is used for frequency spreading. Then, the two received signals can be received sufficiently separated if they are separated by two or more chips from each other (theoretically, it is sufficient if they are separated by one chip, but considering fluctuations in synchronization, one chip + α is required). Therefore, it can be said that the probability that interference will occur because the phases of the spreading codes of two received signals are not sufficiently apart is less than 2/127. Generally, the longer the period of the spreading code, the easier it is to increase the multiplicity and the easier it is to increase the process gain, but the shorter the period of the spreading code, the shorter the time required for synchronization. Also D D L (Delay Locked
Matched filters and SAWs that do not use synchronization mechanisms such as loops
When using a convolver, the shorter the period of the spreading code, the easier it is to manufacture.

The advantage of using the frequency spreading method is that survival is determined by which packet started to be transmitted first, rather than by the difference in reception f3 signal levels between two colliding packets. In other words, as with the FM modulation method, the one with the lower received signal level (i.e., the bucket 1- of the data transmitting station that is further away from the data receiving station) has a high possibility of not surviving in the event of an accident. There is a possibility that the data loss rate from the data transmitting station becomes abnormally high (as mentioned earlier, this can be solved by providing multiple data receiving stations, but Can not). On the other hand, in the frequency spread method, the receiving A signal level is not affected much (except when the signal level of a delayed packet is so strong that it cannot be suppressed by the process gain), so the signal level from each data transmitting station is It becomes possible to keep the data loss rate almost constant. That is, there is fairness in the probability of survival in the event of a collision. Of course, in cases where the signal levels are extremely different, it is effective to apply the method of providing a plurality of data receiving stations as described above.

It is said that the frequency spread method has a more complicated structure than the FM modulation method. This mainly concerns the receiver side, especially around the synchronization circuit, and the transmitter has a similar configuration (especially in the direct spread method). Regarding the receiver, if the period of the spreading code is short, it is quite fff.
rllll! Eight different techniques can be used and are only slightly more complex than FM modulation schemes. Especially matched filters and SAW
When a convolver is used, the FM modulation method and the complexity of its structure are not much different. Especially when the period of the spreading code is short, these matched filters and SAW convolvers are
Since it is not much different from the SAW filter used in the M modulation method, which has good cutoff characteristics and excellent phase characteristics, the manufacturing cost of the receiver is also not much different. In the present invention, data is continuously transmitted from the data transmitting station, and loss of sample data occurs stochastically. Normally, it is good to set the probability of loss to be sufficiently small in advance, but
In some emergency situations, it may be necessary to further reduce the probability of losing the urgent data. for example,
When you think of things like electrocardiograms, heart rate, or breathing rate monitors in medicine, in normal cases when the patient is normal, losing a small amount of sample data is not a problem at all. However, in an emergency situation, such as when the heart or breathing is about to stop (heart rate or breathing rate drops abnormally), it is necessary to reduce the loss of sample data as much as possible. In contrast, in the present invention, this is achieved by increasing the packet transmission probability a higher than the predetermined average packet transmission probability a in an emergency. As a specific example, the value of the number np of repeated transmissions of the same packet is temporarily increased to (n, degrees). As a result, the same sample data is transmitted more times, reducing the probability of losing the sample data. In fact, since the average transmission probability a of a packet from a particular data transmitting station increases temporarily, the Offered Channel
alTraffic G also increases, but only slightly. This is because one of the many data transmitting stations
This is because it is just a station. Therefore, the sample data loss probability is obtained when the number of transmission repetitions of the same packet changes from nP to nP'.

The loss probability r,, r3' of each sample data is r5=
r (G)nP''' and, + = r (G)''''゜, where 0< r (G)<l, n d≧l
．． Since n p> n 1) 0, rs>rs.

now. G=0.5, n,=5, np=1. If n,' = 3, rs ``0.63212''゜5 = 0・1 (
14' ) r s' ”0.63212 3゜5 = 0.001
(18) is obtained.

Note that it is extremely easy to transmit the same packet multiple times as shown in FIG. Multiply the evening lock frequency to the random number generator by nP or n1, and the transmitter uses the same output of the packet assembler np or n,' times, and then
The packet assembler may extract packet information from FIF○.

Process - Results As is clear from the above explanation, the present invention is based on A.
It belongs to the LOIIA method, but by improving it, telemetry data can be efficiently and extremely easily stored even when data traffic occurs regularly, that is, it is not bursty and there is no randomness. It is useful for downsizing and lowering the cost of devices.

In addition, only one (wireless) receiver at the data receiving station can receive telemetering data from a large number of data transmitting stations that do not have control receivers, and only one (wireless) ) By installing multiple data receivers with receivers, the movement range of the data receiving station can be greatly expanded,
In addition, the total number of data transmitting stations is significantly increased.

[Brief explanation of drawings]

Fig. 2 is a block diagram of a data transmitting station used in the telemeter system according to the present invention, Fig. 2 is a conceptual diagram of a data transmitting station and a data receiving station, and Fig. 3 is a diagram showing the structure of a packet transmitted from the data transmitting station. 4 is a diagram showing the configuration of a data receiving station, FIG. 5 is a diagram showing a case where a plurality of data receiving stations are provided, and FIG. 6 is a diagram showing buffer contents. Engineering: Clock signal generator, 2: Frequency divider. 3...
・Sensor, 4... Sampler, 5... Packet information assembler, 6... FIF○ buffer, 7... Packet assembler, 8... Random number generator, ↓1... Antenna. 9... Comparator, 10... Transmitter,

Claims (1)

[Claims] There are one or more data transmitting stations and one data receiving station, and each data transmitting station sends transmitted sample data into packets including a part of previously transmitted sample data. turned into
The packet includes an ID number unique to each data transmitting station and a sequence number of transmitted data, and each data transmitting station transmits the packet at mutually independent random timing with a predetermined probability (a). However, the data receiving station receives the packet and restores the data in chronological order for each data transmitting station from the ID number and sequence number in the packet, and if there is sample data that cannot be restored in chronological order, it A telemetry method characterized by discarding time sample data or interpolating from previous and subsequent restored sample data. 2. There are two or more data transmitting stations, two or more data receiving stations, and one data collecting station, and each data transmitting station collects transmitted sample data, including part of previously transmitted sample data. The packets include an ID number unique to each data transmitting station and a sequence number of the transmitted data, and each data transmitting station transmits data at mutually independent random timing with a predetermined probability (a). The packet is transmitted, and the data receiving station receives the packet and restores the data in chronological order for each data transmitting station from the ID number and sequence number in the packet, and if there is sample data that cannot be restored in chronological order. If so, it sets a flag indicating that the sample data at that sample point cannot be restored, and sends these sample data to the data collection station. A telemeter method characterized in that the sample data is restored by comparing the received sample data in chronological order and selecting the sample data for which any of the above flags is not set at each sample time. 3. The telemeter system according to claim 2, wherein the data collection station interpolates sample data that could not be restored from each data receiving station from adjacent error-free data. 4. When the number of data transmitting stations within the reception range of one data receiving station is n_t, the packet length is t_p, and the average packet transmission interval at each data transmitting station is t_i, then n_t・t_p/t_i≦1/ 3. The telemeter system according to claim 1, wherein: 2a=t_p/t_i. 5. When the sampling interval of sample data at the data transmitting station is t_s, the number of transmission repetitions of the same packet is n_p (n_p is a positive integer), and the number of sample data in the packet is n_d (n_d is a positive integer), 3. The telemeter system according to claim 1, wherein when t_s=n_p·t_i, n_p·n_d≧2. 6. The telemeter system according to claim 1 or 2, wherein the method of each transmitter and each receiver is a frequency spread method, and the same spreading code is used at all data transmitting stations. 7. According to claim 1 or 2, the data transmitting station where the urgent sample data has been generated transmits the packet containing the urgent sample data with a probability greater than a predetermined probability (a). Telemeter method.