DE10116286A1 - Operating system with nodes and base station in accordance with TDMA involves setting d.c. component or phase rotation for preceding block for given time slice at start of time slice - Google Patents

Abstract

The method involves transmitting cyclic TDMA data transmission blocks and composing each block from successive time slices (TS.1-TS.n), each associated with a defined node. The d.c. component or phase rotation set for the preceding block for a given time slice is adopted and set as a pre-set value for signal detection in the base station receiver at the start of each time slice.

Description

The invention relates to a method for operating a system with several Node and a base station according to TDMA, wherein cyclic TDMA data about blocks are transmitted and each TDMA frame out successively composed successive time slots, each time slot is assigned to a specific node.

The invention can be used, for example, in a system with a large number of wireless sensors sensors and / or actuators (nodes) and a base station are used, which in a machine or system, for example industrial robots, production machines or Manufacturing machine is installed. Proximity scarf can be used as sensors or actuators ter / proximity sensors, temperature sensors, pressure sensors, ammeters sensors or voltage measuring sensors or micromechanical, piezoelectric, electro chemical, magnetostrictive, electrostatic or electromagnetic actuators ver be applied.

In DE 199 26 799 A1, a system for a machine having a plurality of wireless proximity sensors, in particular a production machine, is proposed, wherein

• - Each proximity sensor at least one for energy consumption from a medium fre quent magnetic field has suitable secondary winding,
• - At least one primary winding fed by a medium-frequency oscillator for the wireless supply of proximity sensors with electrical energy see is
• - And wherein each proximity sensor is equipped with a transmitter, which radio signals containing interesting sensor information to a central, with outputs a base station connected to a process computer of the machine.

Compared to conventional solutions, this wireless system is also eliminated Wire / cable connection for electrical power supply and for communication relatively high due to planning, material, installation, documentation and maintenance Cost factor of the wire / cable connections. Failures due to Ka broken or bad, for example corroded contacts occur.

DE 199 26 562 A1 describes a method and an arrangement for wireless Supply of a large number of actuators with electrical energy, one actuator and one primary development and a system for a large number of actuators Schine proposed, the proposed technology with respect to Energiever Supply and communication similar to that for DE 199 26 799 A1 given technology.

The TDMA technology (Time Divisi on multiple access) in which the information from / to the actuators or sen sensors (nodes) is transmitted in the form of cyclic TDMA frames, each sensor / actuator has a specific time slot within a data transfer supply block is assigned.

If for modulation (frequency modulation FM) of, for example, radio transmitters of the signals emitted and for demodulation of, for example, the Radio receivers of the base station received signals not exactly the same Oscillator frequencies are used, but due to oscillator tolerance If frequency differences are set here, this translates to frequency-modulated ones  Signals into an unwanted DC component in the signal after the demo dulator (DC component not equal to zero) in the radio receiver. The data is from the Sign of this signal is detected. If there is a DC component, the result is Detection errors. In order to avoid such detection errors, it is necessary to to compensate for the DC component that occurs. To do this, the DC component must be determined and to be taken into account in the detection, d. H. the detection threshold is neutral Shift value zero to the value of the DC component.

The same problem arises if instead of frequency modulation, coherent digital Mo dulation / demodulation such as PSK (phase shift keying) or QAM (quadrature amplitude Modulation) is used. Here a frequency offset leads to a residual phase rotation hung, which is to be compensated by means of a corresponding counter-phase rotation.

The invention has for its object to provide a method for operating a system to specify several nodes and a base station in accordance with TDMA, which also applies to not exactly the same oscillator frequencies used for modulation and demodulation zen the radio transmitter and the radio receiver an error-free detection of the data of the received signal.

This task is fiction, in connection with the features of the preamble solved according to that in the receiver of the base station at the beginning of each time slot of the previous TDMA frame for this time slot for the signal detection set direct current component or the phase shift is adopted as the preset value and preset.

The advantages that can be achieved with the invention are, in particular, that the pre The proposed measure is a quick synchronization between radio transmitter and radio enables receiver, improves reception and in particular allows a use shortened preamble. By shortening the preamble increases with same total duration of a time slot advantageous for the transmission of the actual Chen duration available (or the corresponding number bits that can be made available for message transmission).  

Further advantages are evident from the description below.

Advantageous embodiments of the invention are characterized in the subclaims net.

The invention is described below with reference to the embodiment shown in the drawing Examples explained. Show it:

Fig. 1 is a cyclic TDMA data transmission block,

Fig. 2 is a time slot of a TDMA data transmission block,

Fig. 3 shows a system with a variety of sensors and / or actuators and a base station.

In Fig. 3, a system with a plurality of nodes, preferably sensors and / or actuators (nodes) and a base station is shown. It is a multitude of sensors and / or actuators S.1, S.2, S.3. , .Sn (n = any integer positive number) are provided, which are installed, for example, within a system or attached to a machine, in particular a production machine. It is always from sensors / actuators p.1 below. , .Sn, where the individual component can be either a sensor or an actuator. In general, the sensors have a sensor head which detects the sensor environment with a downstream signal evaluation, and the actuators have an actuator unit (for example a compressed air valve or a contactor) and a control unit therefor.

The sensors and / or actuators p.1. , .S.n each have a communication device device, which contains the required radio transmitter and / or radio receiver in order such a wireless communication between the base station BS and the Senso ren / actuators p.1. , To enable .S.n. The processed sen reaches a sensor sensor signal to a modulator / encoder with a downstream radio transmitter and antenna, where it is sent to the base station BS. In the case of an actuator, this comes from the base station  Control signal sent via an antenna, a radio receiver and a demodulator / decoder to the control unit.

The base station BS is expediently connected to a central computer (process computer, storage programmable controller) and has a communication direction 3 on which sensor signals of the sensors and signal signals relating to the current state of actuators (uplink, from the sensors / actuators to the base station) receives control signals for activation / deactivation of the actuators and Si signals for setting specific parameters of the actuators and sensors (downlink, from the base station to the sensors / actuators). The communication direction of the base station BS has an antenna to which a radio receiver and a radio transmitter are connected. The signals from the radio receiver become one Demodulator / decoder supplied and the radio transmitter is a modulator / encoder upstream.

Due to oscillator tolerances, the oscillator frequencies are the individual radio transmitter and radio receiver are not exactly the same, so that measures have to be taken to Prevent errors in signal detection (demodulation, "down-mixing").

In Fig. 1, a cyclic TDMA frame is shown, as used in the proposed system. Such a data transmission block or frame FR.1 is composed of n successive time slots TS.1, TD.2. , .TS.n together. Each time slot TS.1. , .TS.n is a specific sensor or actuator S.1. , .Sn assigned. For example, although the sensors generate their messages at random moments, the time slot TS.1 assigned to them occurs. , .TS.n customized transmission. To ensure that the TS.1. , Information contained in .TS.n is also assigned to the correct actuator, or to ensure that a sensor transmits the information to be transmitted to the base station during the correct time slot, each time slot contains TS.1. , .TS.n a typical synchronization word for exact synchronization between base station BS on the one hand and sensors / actuators S.1. , .Sn on the other hand.

A sequence of successive successions is used for continuous signal transmission Data frames or frames FR.1, FR.2, FR.3. , .FR.m (m = belie whole positive number).

In FIG. 2, a time slot of a TDMA data transmission block is shown. The time slot TS.1 is composed of the first part PR1 of the preamble, the second part PR2 of the preamble, the symbol sequence of the actual message (pay load) PL and a safety distance (guard time) GT. The first part PR1 of the preamble is used to determine the DC component. For example, eight bits are repeated as 0 1 0 1. , , transmitted in order to measure and calculate the DC component in this way, as already mentioned at the beginning. The second part PR2 of the preamble contains the information required for synchronization between radio receiver and radio transmitter and comprises, for example, seven bits.

The receiver of the base station BS can be assigned to each time slot Number unmistakably the respective radio transmitter, d. H. the relevant sen Determine sensor / actuator (node). The oscillator frequency of the rele in each time slot vanten radio transmitter does not change, at least not to a significant extent. The for the DC component responsible frequency difference of the oscillator frequencies of radio The transmitter and radio receiver also do not change, at least not in mean the scope. As a result, the radio receiver is advantageously able to start of each time slot that in the previous data transmission block or Frame for this time slot set DC component as a preset value take over and preset. This presetting is advantageously carried out very quickly. The first part PR1 of the preamble can be greatly shortened. The default DC component can depend on the greatly shortened first part PR1 of the pre Ambel of the current time slot corrected according to the current circumstances in order to set the optimal DC component. This correction is in in most cases very low in relation to the pre-setting.

Alternatively, an averaged direct current can also be used at the beginning of each time slot preset, which is the average of several DC components (for  this time slot) of the previous frames or frames is averaged and calculated.

In the above embodiment, frequency modulation FM with conventional FM discriminator demodulation, in which a Fre sequence offset leads to a DC offset. As already mentioned at the beginning, this is suitable proposed methods also for coherent digital modulation / demodulation, such as PSK and QAM, in which a frequency offset leads to a residual phase shift, which is to be compensated by a corresponding counter-phase rotation.

Here, too, it is possible to use an average phase shift (or Phase shift), which is the average of several phase shifts for previous time slot is determined and calculated. The far ren it is possible in the same way to select the preset phase shift to correct the current time slot according to the current circumstances ren in order to insert the optimal phase shift (or counter phase shift) in this way put.

Claims (3)

1. Method for operating a system with several nodes (S.1... Sn) and a base station (BS) according to TDMA (Time Division Multiple Access), whereby cyclical TDMA data blocks (FR.1.. .FR.m) are transmitted and each TDMA data frame is composed of successively successive time slots (TS.1.. .TS.n), each time slot (TS.1.. .TS.n) belonging to a specific node (S.1... Sn) is assigned, characterized in that in the receiver of the base station at the beginning of each time slot (TS.1... TS.n) the DC component set for the signal detection in the preceding TDMA data transmission block for this time slot or the phase shift is adopted as a preset value and preset. 2. The method according to claim 1, characterized in that in the recipient base station at the beginning of each time slot (TS.1... TS.n) an averaged DC component or an average phase shift is preset, wel cher / which as the mean of several DC components or phase shifts for frames or frames preceding this time slot are determined and is calculated. 3. The method according to claim 1 and / or 2, characterized in that the preset DC component or phase shift during the current Time slot is corrected in accordance with the current circumstances, in such a way to set the optimal direct current component or the optimal phase shift.