Data transmission method between at least two transmitting units and at least one receiving unit on at least one transmission channel

The invention relates to a method for transmitting of data between at least two transmitting units and at least one receiver unit to at least one Data transmission channel according to the preamble of claim 1.

Such a process is for example in wireless telephones used. It has the advantage that the transmission capacity the data transmission channel accessed can be. The assignment of time slots to the individual Transmitter units can be static or dynamic. A prerequisite of the method that in the Data transmission channel no further users are, what not prescribed to the allocation of time slices and the keep communication protocols. Since the Management of various of the sending units skillful data streams associated with considerable effort is, are not such data transmission channels free of charge.

As far as the public free frequency ranges are provided, these are for a frequency band, the well of time users as hams or wireless headphones and the like is are. Such data transmission channels, however, are for no data transmission purposes usable. There are also Frequency bands are available, in which at least time users are excluded and where for each sub-band only a certain maximum duty cycle (usage percentage) is permitted for each participant. On Such a frequency band is in Europe between 868 and 870 MHz. Depending on the sub-band of the duty cycle is 0.1%, 1% or 10% limits, where the averaging time is one hour concerns.

In addition to the limitation of the duty cycle there are no further technical limitations on the use of this Frequency band, so that it must be expected that different users to arbitrarily different Times transmit data in different data formats.

Such purely coincidental used to transfer data Data transmission channels have the disadvantage that their average passenger load may be only slight. In bidirectional Data transmission not only each failed Test the data transfer itself but also each failed attempt of feedback, that the data was received correctly, to the fact that the Data transmission is started again. In only unidirectional Data transmission to the data multiple times are transmitted, for example five times specified in stochastically Intervals. It does so to a large number of failed communication attempts, the the transmission capacity of the channel is further reduced, so that the channel ultimately collapses. Starting from 15% utilization can stochastically genützte data transmission channels become unstable; in the middle is the stable net utility under 20%.

When working with collision detection, the transmission capacity is a data transmission channel also reduced because the switching of a transmitting / receiving unit relatively between sending and receiving much time. By this switching the data transmission channel an additional burden. Also it may be that the data transmission channel again is busy, switched to transmit mode becomes. Finally, one must also take into account that on the data transmission channel also weak jammers are (for radio data transmission channels as further remote transmitter units), the monitoring of the channel at be taken into account for collisions, in the but do not interfere with practice sending procedure relevant would.

Standing in a frequency band a plurality of data transmission channels available, so you can reduce the Error rate in the data transfer for the data transmission simultaneously use multiple channels, between those with a comparison with the cycle time of the Data transmission (bit time) switched small Switchover becomes. It is thus one bit at the receiver end reconstruct, if only a portion thereof over a the channels has been received correctly. The failure to a channel then acts according to the type of white noise from which is averaged out over a bit of time. For this procedure to be performed can, you need a high computing capacity. Also is the establishment of a connection slow because transmission unit and receiving unit down to a fraction of a bit time must be synchronized. The latter can be in already established connections realized easily because the data stream be shared also for synchronization can. But if one has between different data transfer cycles long communication breaks or must the compound to be rebuilt, so it takes a long time, until a sufficiently good synchronization of transmitter unit and receiving unit is obtained. This is especially in battery-powered receiver units (And transmission units) disadvantageous because the synchronization the battery is charged without regard the data transfer to be of benefit. This Problem is when transmitting units despite their high power consumption less severe, as in typical applications as the wireless reading of consumption meters, at the Building monitoring, etc., the transmission frequency is small. However, a receiving unit must constantly for potential Data transfer to be ready and sensitive receiver units have at the interest here high Frequencies already in pure receptivity no data reception a significant power requirement. the could encounter in that the receiving unit is characterized only at certain prearranged data transmission time points activated and before a transmission telegram of Transmission unit is a header which no user data contains and whose duration is greater than the time-out of the Receiving unit. Such methods, however, can in Anyone not use tapes for it - apart the maximum duty cycle - no rules are.

The present invention is based on the object, the quality of data transmission between a plurality of transmit units and a receiver unit on an Everyman data transmission path to improve.

This object is achieved by a method with the features specified in claim 1.

The inventive method combines the high effective Channel usage of slot method (time slice and / or frequency slice), and their particular suitability for battery powered clocked receiver units with the noise immunity of statistical methods both against periodic and against random Disorders. This advantage is obtained without high Demands on computing power, bandwidth, and high time synchrony of receiver unit and transmitter unit have to be met.

Not only individual users has increased by Security of data transmission gain time, also other users can benefit from the invention Process through the lower channel loading hereby obtained for reduction of failed attempts.

Typical applications for the novel process include groups of typically 10 to 100 Sending units to a maximum of about 1,000 transmission units, the need to communicate with a receiver unit. Transmitter units can eg alarm generator or utility meter and radio-controlled radiator valves or other be consumers of an apartment or house.

Advantageous developments of the invention are in the dependent claims indicated.

With the development of the invention according to claim 2 is achieved, that a first group of transmit units specifically only with a first receiving unit and a second set of transmission units only targeted at a collaborate second receiving unit, although the radio cells in which the various Transmitter units are overlapping. can in practice to such overlaps often not prevent. Technically radio must be ensured on the one hand, that belonging to a group communication partner another directly, optionally indirectly through an intermediary reachable. The same applies to a another group. In practice, however, the groups are spatially adjacent, that they are not purely by radio can (think decouple only to supply meter different Flats of a house where a make apartment belonging utility meter a group or intended to alarm systems of different apartments a house or different houses). The in Claim procedure indicated 2 ensures a smooth data transmission Decoupling of adjacent radio technology Groups of communication partners.

With the development of the invention according to claim 3 it is ensured that the duty cycle of the request used Everyman channel is maintained.

The development of the invention according to claim 4, be advantageous, if the individual transmission units must be each larger amounts of data. One can Then for example in a first succession Abtragezyklus the safety of the transmission units to transfer the transferring data and only later in a second or further data packet the less important Data transfer.

In the method shown in Figure 5, the Time window for the individual transmission units by internal Precision watches and any associated window comparators specified. This means that such a The method also can apply unidirectional, at least settle over extended periods unidirectional can.

The development of the method according to claim 6 Allowed is to use precision internal clocks which in the different transmission units is not highly accurate match. The locations of the precision clocks can each appropriate after the manufacturing variations carried out number of polling cycles, with less accurate Precision watches to the beginning or end of a polling cycle respectively.

It is in accordance with the development of the invention Claim 7 ensures that only in each case by a control signal the internal precision watches a predetermined Group are provided by transmitter units, but not those further transmission units that contained a overlapping radio cell are located.

allowed the development of the invention according to claim 8 the stochastic variation of at least one transmission parameter using simple means. Random access to cheap by Random functions contained in many high-level programming languages are formed.

The development of the invention according to claim 9 again in view of a good data transmission even Decoupling of data transfers advantageous that Transmission units of different groups of transmit units concern that in overlapping radio cells . are

allowed the development of the invention according to claim 10 the stochastic laying a polling cycle under low circuit moderate effort in the in great Number to be provided transmission units.

allowed the development of the invention according to claim 11 to relocate the polling cycles stochastically, Although the transmitting units not receiving data are designed.

In a method according to claim 12, the phase position is the polling cycle to absolute time with every scan cycle stochastically changed. To find each query under new conditions with respect to the channel otherwise lying noise instead of what the probability a correct data transmission in the next cycle elevated.

The development of the invention according to claim 13 in terms of low power consumption of battery-powered Transmission units of advantage.

It allows the development of the invention according to claim 14, transmitter units, which are also to receive data are formed, together control commands to to transfer. This can be not only to commands act to preset internal precision watches, but also commands which time slot allocation the Change for sending units or transmitter units for a predetermined time completely totschaltet (eg sensors a monitoring system during office working hours).

In a method according to claim 15 is the Transmission of the control commands only a small fraction the capacity of the data transmission channel is required.

A method according to claim 16 makes it possible that the Receiving unit via the respective operating state the different transmission units is informed, for example, on occurring there errors as exhaustion of a long-life battery.

Hereinafter, the invention by means of embodiments explained in more detail with reference to the drawing.

Therein:

<dl tsize="9"><dt>Figure 1:</dt><dd>a schematic view of a residential complex and a system for transferring the article of flowmeters, at different Ask different apartments of different Houses of the complex attached, to a central office;</dd><dt>Figure 2:</dt><dd>a block diagram of a transmission unit of the shown in Figure 1 data transmission system;</dd><dt>figure 3</dt><dd>Is a block diagram of a receiving unit the Datenübertragunsanlage shown in Figure 1;</dd><dt>Figure 4:</dt><dd>a view similar to Figure 2, in which However, given a modified transmission unit is;</dd><dt>Figure 5:</dt><dd>a view similar to Figure 3, in which However, a modified receiving unit is reproduced, to the transmitter unit fits of Figure 4;</dd><dt>Figure 6:</dt><dd>similar to Figure 2 Block diagram another modified transmission unit, the not cooperating with the data transmission channel comprising receiving part; and</dd><dt>Figure 7:</dt><dd>a timing chart in which the interleave of time slice packets within which different sets of flowmeters send, is displayed.</dd></dl>

In Figure 1, with 10 of a building complex called, which houses four 12, 14, 16, 18.

In House 12 is a variety of measurement units 20-1, 20-2, ..., 20-i are provided corresponding respectively to the consumption measure on a consumer good (water, heat, electricity, etc.) and wirelessly Add to a management unit 22 of the house.

Similarly, in the houses 14, 16, 18 measuring units 24-i, 26-i and 28-i arranged the various the Measured values ​​to management units 30, 32, 34 to pass.

The invention is exemplified with reference to units of measurement described, it should be understood that in the same manner also mere sensors in terms of data with a management unit may couple, for example, fire alarms, surveillance sensors, Brightness sensor etc.

The various management units 22, 30, 32, 34 in turn are via radio channels with a central Management unit 36, the further away from themselves Building complex 10 Located in the premises of a is on building management specialist company.

For reasons of cost for the radio transmission between the measuring units and the management units as well as between the management units and the central management unit an everyman radio channel used. In this are also noise from other channel users what an example of a radio-controlled garage with drive an attached garage receiving unit 38 and one mounted in a vehicle transmission unit 42 reproduced.

It is seen that the measuring units 20-i, 24-i, 26-i and 28-i total today are so close that the radio cells the transmitting units to adjacent houses include overlap.

Hereinafter, with reference to the figures 2 and 3. how to ensure that the to a house belonging Management Units only those further process data provided by the same House located measuring units derived, but not responsive to data from a measuring units from neighboring house date. The described below Training of measuring units and management units is at the same time prevents the Data transmission channels lying interference of third parties the efficiency of data transfer reduces appreciably.

As in Figure 2 can be seen, there is a measuring unit 20-i from a sensor or transducer 44 and a total with 46 designated transmitting unit.

The sensor is connected to an input-side format converter 48 of the transmitting unit 46. This digitized optionally, the output signal of the transducer 44, if the latter provides an analog output signal, and converts it into a serial bit stream. These Bit sequence is depending on the type of modulation used (For example, amplitude or frequency modulation) in a corresponding reacted modulator control signal, which is applied to a modulator 50th contains latter at its second input via a controllable switch 52 alternately from a first high-frequency generator 54 or from a second RF generator 56 a carrier signal HF1 or HF2. The working frequencies of RF generators 54 and 56 are both in Every man band 868-870 MHz.

The switch 52 is controlled by a clock output C 'of a clock circuit 60 fro driven which provides clock pulses, the double bit frequency (frequency that the transfer individual bits). The bit rate is serves at an output C of the clock circuit 60 and ready for clocking all the serial data transmission concerned Circuits.

The bit is also the common time frame for Transmitting units and receiving units; same multiples are used to specify the position and length of time slices. Time slices are those successive time periods, in each of which a data transmitting unit to may make the receiving unit or other work can do that in coordination with the other transmission units or the receiving unit of the associated Management unit. must be effected, in particular the Synchroniserung of different remote sensor units on a common time standard. A polling cycle is the duration all time slices, so the time between sending a first transmission unit and a nmächsten Send this first transmission unit elapses.

By means of the switch 52 that is on the modulator 50 given signal alternatingly a high frequency voltage HF1 and HF2 modulated a high frequency voltage.

The resulting at the output of the modulator 50 modulated Signal passes through a transmit / receive switch 62 an antenna 64th

The above-mentioned clock circuit 60 does not include a separately shown freewheeling clock, for example, a stabilized quartz good accuracy, the frequency divider through not reported separately, with the Clock output terminals C and C ', respectively, and a further frequency divider also not visible counter, the state of internal time in bit clocks corresponds, with a time-output terminal T of the clock circuit 60 connected is. Typically, the clock frequency is eg set to 10 kHz, so that per minute 60 000 Clock pulses has. If the query cycle, a minute, can be awarded in 1000 time slices, each 600 are bit clocks long.

To reset the clock circuit 60 is a demodulator 66 to the other output of the transmit / receive switch connected. This sets of a management unit obtained control signals back to parallel representation to and passes a given in these and from him separated synchronization command to a comparator 68th The comparator 68 receives a second input signal by a read only memory 70. This is a special Reset code stored, the one all measuring units House is common, while the reset signals of measuring units in different houses each other differ. If the comparator 68 determines that the input signal and output (synchronization command and Reset code) are the same, it outputs a reset signal the "R" terminal of the clock circuit 60. In this Way the clocks are circuits of all members of a group Measuring units by the associated receiver unit 38 set to the same initial value (eg "0"), and the internal time of the measuring units are then identical.

The demodulator further separated from the control signals a Phase command that indicates how much of the next Synchronization command offset from the point of time will be that simply by adding the duration one polling cycle to the beginning of the current duty cycle results. This phase command is in a buffer memory 69 stored.

The T-output of the watches circle 60 is set to a given the inputs of a window comparator 72nd Of the second input of the window is provided with a Memory cell of a read-only memory 74 is connected. This includes that of internal timing, in which the Start sending measured data by the measuring unit 20 should. A further input of the window comparator 72 is another memory cell of the ROM 74. and so is granted to internal time at which the transmission is to be completed by data. Of the Window comparator 72 generates always a positive Output when the internal time within the Airtime window shown above is.

The output of the window comparator 72 is connected to one Input of an OR gate 76 is connected. A second Input of the OR gate is connected to the output of a further Window comparator 78 is connected. This gets similarly as described above for the window comparator 72, from the read-only memory 74 two reference periods, to which a Synchronisierzeitscheibe for measuring unit to begin or end.

These reference times for each polling cycle re-read from the buffer memory 69, of this activated by the output of the comparator 68 becomes.

The output of the OR gate 76 is connected to the control input a switch 80, via which a battery 82 connected to the power consumers of the measuring unit is the only required when the measuring unit is to deliver data or must be synchronized. Those Blocks, the internal control for the Measuring unit 20 are provided, is a holding battery 84 provided. The supplied through it components (Watch circuit 60, OR gate 76 and window comparator 78) are marked with an "H".

The memories 74-i, the different to the Measurement units include 20-i, respectively with respect to the Meßzeitfenster programmed differently, so that the Meßzeitfenster not overlap. To this Manner, the measuring units associated with the transmitting units 46 to be transmitted sequentially to deliver the Data causes. The in consecutive time slots so via radio waves transmitted data of the individual Units can from the common management units due to their position in time the individual Measuring units are allocated so that the transferred Data no signals identifying need to include individual measurement units.

As can be seen from Figure 3, includes the measuring units 20-i corresponding management unit 22, a receiving unit 86 and an output connected to the output Computer 88. The latter has a mass storage device 90, for example, a hard disk. It can communicate with a control computer 92 are connected, the formed eg by a laptop can be. Further, the computer 88 operates at a Transmitting unit 94 together, be their structure is the same can as that of the transmitting unit 46th

At a reception side antenna 96 is a transmit / receive switch 98 is connected, by a comparator 100 is driven forth. This is replaced by a clock circuit 102 which is constructed similarly to the circuit 60 watches a first input signal and of a read-only memory 104 a second input signal. An adder circuit 106 is connected to the output of the ROM 104 and added to the contents in a another read only memory 108 number lying added that the duration the control time slice (synchronization and transmission Phase commands) corresponds. The output of the adding circuit 106 is connected to a further input of the window comparator 100 connected. The ROM 104 is read by a random 110 ago. This can eg operate so that, depending on he his Output, the contents of a memory Multiplier 111 and (if desired) of real time, giving it a RTC is received 112, generates a random number.

The contents of the multiplier-accumulator 111 is for all Receiving units of the entire data transmission system unique and can therefore also as a group identification code are considered, similar to the time slice, which a transmitting unit is assigned, as a measuring unit identification code can be considered. To this Way are the starting points of the polling cycles for different Groups of measuring units in different Way stochastically determined.

The fluctuation range of the random number is chosen so that he a desired temporal fluctuation range capable of synchronizing signal, by which Watches circular 60 of measuring units 20-i is reset, equivalent. The temporal variability of the position of Synchronizing signal is obtained by multiplying the maximum allowable duty cycle of each frequency band with the averaging time for the frequency band determined. In 0, 1% duty cycle band are obtained when an averaging duration one hour a fluctuation range of at least 3.6 seconds.

The contents of the ROM 108 and the output signal the adding circuit 106 is thus the front given and rear end of the Synohronisier time slice.

controls the output of the window 100 the transmit / receive switch 98 in the transmit position. By the signal is further provided a synchronizing signal 114 activated, which then via the antenna 96 for the the associated group characteristic of measuring units Sync outputs, which then of the receiving units 20 is used for resetting the internal time becomes.

One other to the output of the transmit / receive switch 98 connected soft 116 is again through the C'-output the watch circle back and forth 102 and so are the incoming signal to a Demodulator 120 for frequency HF1 and a demodulator 122 for frequency HF2. The outputs of the two Modulators 120, 122 are applied to an OR gate 124, the thus a function similar to an integrator fulfilled. The output signal of the OR gate 124 comes to the carbon output of the watches circle 102 clocked format converter 126, the incoming the Bits again in a further for evaluation desired format converts, eg parallel representation. This signal is a port of the computer 88 given the same time as the internal time of the receiving unit 86 is acted upon by the clock circuit is issued 102nd From the internal time, the computer recognize and 88 beginning and end of a record assign it to a specific measurement unit. The data can then be stored on the mass storage 90th

An output port of the computer 88 is connected the transmitting unit 94, the same internal Construction as the transmitting unit 20 of FIG. 2 As is to the transmitting unit 94 of the computer 88 as a data source connected, whereas at the transmitter unit 20 of Figure 2 by the transducer 44 and the format converter 48 unit formed was. In this way, the management unit 22 in the same Way with the parent management unit 36 communicate, and the data transfer between these two units can equally be organized as the data transmission between the measuring units 20 and the management unit 22. Also, the hierarchical parent management unit 36, the internal time Reset the management unit 22, similar to the transmitting unit 94 concerned for the measuring units 20th

Thus can be used both at the level of the lower groups as well as at senior groups mixed by the time slice principle and the principle of stochastic Transmission times operating data transmission system build up.

Above has been with reference to Figures 2 and 3, the construction of a measuring unit 20 and a management unit 22 described. The houses 14, 16 and 18 associated Measuring units 24, 26, 28 and management units 30, 32, 34 have similar structure. The management unit 36 includes, as already explained, a receiving unit, which corresponds structurally to the receiving unit 86th

Insofar as the modified measurement unit shown in Figure 4 corresponding to that of Figure 2, are its components again provided with the same reference numerals. This need not be described again below also will.

The measuring unit of Figure 4 differs from that according to figure 2 primarily by the generation the reset signal for the clock circuit 60. To this end, the procedure is similar as in the receiving unit according to Figure 3 for fixing the Synchronisiersignalfensters The procedure is: a random number generator 130, of the structure and the random generation algorithm used the random number generator 110 fully corresponds, on an input back to its output signal, on another with the content of Multiplier-accumulator 131 to that of the group-specific Multiplier 111 corresponds to memory, and on the last Input with the absolute time output TM a RTC 132 applied. The output of the random generator 130 is connected to one input of an adding circuit 134 is connected, the second input coupled to the output RTC 132 is connected. The output of the adding circuit 134 and the output of the real-time clock 132 with the two inputs of a comparator 136, respectively. Its output signal is used to reset the clock circuit 60th

Figure 5 shows a modified management unit 22 in itself is self-sufficient and not with a parent Management unit cooperates. Their watches circle 102 automatically switches to Overflow.

In another variant of the invention, the real-time clocks can each be radio controlled clock modules at regular asked intervals over long wave to Standard Time are such that the synchronization of the various Real Time Clocks without load of the data transfer serving between units and management units can be carried out transmission channel.

In the embodiment according to further modified Figure 6 includes the read only memory 70, a plurality of pairs of memory cells, each initial time pretend and end time of a transmission window. Accordingly, a plurality of window comparators 72 provided.

In this embodiment, the measuring unit can be selected Measurement units within a query cycle (period between the resetting of clocks circles 102) respectively Add more data packets to the management unit or more extensive data packets to two Time slices distributed to the management unit transmit.

Data communication systems, such as those described above, may typically have the following properties: obtained when using commercially available circuits Watches to the typical required accuracy of Specifying the time slices with a length of 1 to 10 msec by synchronizing every 5 minutes. hereby the data transmission channel is loaded only slightly. At a polling cycle with a total duration of a Minute can be 1000 time slices to each 60 msec pretend. One can as a large number of measuring units Connect to a management unit. The postponement the commencement of polling cycles, which is also as pause statistical length between successive may view polling cycles, can in 3.6 seconds lie. Looking at a minimum break time of a Second before, so vary the distances between successive Query cycles between about 1 and 5 seconds.

Above it was stated that the random different for different groups of measuring units.

This can be seen with the use of random number generators of some realize high-level languages ​​in the following manner: This Random generators operate mostly depending of a Synchronisierwert and a multiplication constant. By multiplying the initial number to the Multiplier and cutting out some places in rear third of the much-digit earnings generated one a first random number. From this we obtain by further multiplication and Cutting a string another in the rear part of the result Random number, etc. The random numbers are therefore being statistically spread, starting from the same initial value and the same multiplication constant is obtained but still the same sequence of random numbers. The Random numbers are thus determined.

By making the initial value and / or the multiplication constant modifies, can another random number generator produce, the first to be uncorrelated Random number generator is, etc ..

In this way it is ensured that even more Groups of measuring units, which are distinguished by different Group Codes (equivalent Synchronisiersignalcode) different, with different random number sequences work. So that they can then only accidentally collide, if they are in the same radio cell.

If one uses such uncorrelated random number generators, is obtained at an average over time about 10% occupied radio channel at the first attempt with 90% Probability correct data transmission, with two experiments a probability of correct Data transmission of 99%, etc.

Any desired foreign interferers with random channel assignment and also foreign interferers with periodic or other deterministic Channel allocation in this way to stochastic interferers with a known distribution function.

As stated, the next random number must be different than for multiplexing more than once within a Bit time but only once every cycle, So be calculated per time slot block, as each Minute.

Using the data transmission systems described above counts the synchronization request only Section msec instead of microseconds.

Next is the data transmission systems described above, advantageous in that even if only temporarily active Receiving units, the receiving units their readiness to receive according to them within their Group assigned receive time slices pseudo statistically Move associated. Nevertheless, they reach a transmission unit her group always in a time / frequency window, which a rigid position relative to the stochastic including commencement of the polling cycle.

In the above, the invention has been with reference to embodiments discussed in which two frequency subchannels used within the respective frequency band Everyman has been. It is understood that the invention use both for data transmission systems can that work in only one frequency subchannel. Also you can instead switch between two Frequency subchannels also different between two Modulation method switch (eg between Amplitude modulation and frequency modulation). In turn alternatively you can influence other radio transmission Parameter switch. Switching was above described so that it (at two frequency sub-channels) each twice a bit time (clock at the output "C" of the clock circuit 60) is carried out.

It is understood that also a larger number of one switch the data transmission parameters defined can. is always by the stochastic for a group specific installation of polling cycle (and thus the individual time slices) to ensure that a reliable data transfer receives, even if in the same radio cell outside the group belonging more Transmitter units located. Also obtained as a uniform Use of a frequency channel or multiple frequency subchannels. The constant change between a Plurality of frequency subchannels is also the disturbing Influence of induced by multiple reflections interference cancellation reduced, since at these frequency changes (And thus appropriate changes the wavelength) each change somewhat, whereby at least the most disturbing case of total interference cancellation can be avoided.

In Figure 7 is over time (arbitrary units) applied, in which time the areas Flowmeters 20-i, 24-i, 26-i and 28-i send which management units to 22, 30, 32 and 34 associated.

The various management units give each statistically distributed time slice packets 138-k, 140-k, 142-k and 144-k before. Each time slice packets consists of a sequence of individual equidistant Time slices 146-l, as for a time slice package 138-3 shown. Within each of these time slices 146-l sends the assigned Flowmeters 20-l, as above described in detail, each of the time slices 146-l in turn a predetermined number of Bit clocks comprises, as also already explained.

It is seen that there are time periods in which belonging to different groups time slice packets overlap, resulting in transmission errors. Such a time is, eg, t = 0.25 for the management units 22 and 30 and at t = 2.05 But for the management units 30 and 32. It can be seen, that already within two units of time every time slice packets could be transferred once undisturbed.

In the bottom part of Figure 7 in order to Factor 100 compressed scale of the data exchange between the central management unit 36 ​​and the Group-management units 22, 30, 32 and 34 are reproduced. This is carried out at longer intervals, because the central management unit 36 ​​only on longer term Changes in Flowmeters Scores informed to be needed. The organization and management the data exchange is but similar between Group-management units 22, 30, 32, 34 and the measuring units 20-i, 24-i, 26-i and 28-i.