Bidirectional radio data transmission method

Abstract

Bidirectional radio data transmission method for transmitting measured value data telegrams from meter transmitters via uplink radio connections to a concentrator receiver and with downlink radio connections from a concentrator transmitter to meter receiver, characterized in that at the concentrator, information about the quality of an uplink radio connection in comparison to at least one other uplink radio connection is determined in a program-controlled manner and at least one parameter of at least one of the uplink radio connections is influenced via the downlink radio connection in such a way that its quality is reduced towards the quality of a poorer but still functional uplink radio connection.

Description

[0001] The invention relates to a method for bidirectional radio communication, as known from DE 10 2010 005 587 A1, for transmitting consumption measurement or energy management data between a terminal device and a central device designed, in particular, as a data collector. Data traffic between the devices occurs in two different frequency bands, which are approved by the regulatory authority for different maximum transmission powers; Energy management data is transmitted from the data collector to the terminal device at the higher transmission power, with a frequency deviation adapted to the frequency bandwidth of the assigned frequency band.For the terminal device operating with limited energy resources, the distance that can be bridged for the measurement data transmission to the data collector with its low transmission power can be increased by using a directional antenna, while this distance to the terminal device can be easily bridged by the data collector, which has a more energy-efficient position, with its higher transmission power.

[0002] The system described in EP 2 360 484 A2 also comprises an arrangement of a plurality of distributed terminal devices for recording the consumption of electricity, fluids (such as gas or water), or heat quantities, which are referred to simply as meters below. Each of these is equipped with a transmitter to transmit its individualized, digitized measured values ​​as so-called telegrams via short-range radio via an uplink radio connection to a remotely operated data collector, referred to as a concentrator (RDC, radio data concentrator), which serves as the central receiving device for several meters. Such measured value transmissions are usually unsynchronized, with identical performance data and constant lengths of the repeatedly repeated telegrams.In particular for consumption billing purposes, the measured values ​​temporarily stored in the concentrator and possibly re-encoded are periodically read out by a service employee - if the concentrator is not in contact with a mass storage device, particularly at a utility company, for quasi-continuous data transmission via a wide-area communication connection, such as a mobile network, WLAN or Ethernet.

[0003] Such a system is designed for bidirectional data transmission using transceivers at the meters and the concentrator, allowing data transmission via radio links not only from the meter transmitters to the concentrator receivers (uplinks), but also from a concentrator transmitter to meter receivers (downlinks). The downlink radio links can be used, among other things, to change the tariffs of energy consumers assigned to the meters.

[0004] From WO 2007 / 139 842 A2, a transmission network of meters communicating with each other and with spatially distributed concentrators for data acquisition and forwarding via an RF wide-area network is known, in which received signal strengths are recorded at the individual successive nodes via which the information is transmitted and then transmitted signal strengths are optimized.

[0005] WO 2015 / 096 916 A1 points out that even under future mobile communications standards, not only will the rapidly increasing connection demand have to be met, but communication with infrastructures integrated into the communications network will also occasionally be necessary, for example, for the transmission of data from intelligent energy metering devices or individual medical devices. According to this publication, a mechanism is provided for the mobile communications network that, when simultaneously pending communication requests occur, awards the contract to the one that best promises to meet the optimal transmission conditions specified based on current interface measurements. According to an undated internet publication, UMTS Overview / UMTS Power Control, various modalities for controlling uplink and downlink transmission power are already available in the traditional mobile communications standard.The withdrawn Wikipedia article “Link Adaption” from August 13, 2015, deals with the bit rate in the UMTS mobile communications standard, which depends on the transmission conditions.

[0006] This case specifically concerns the quality of uplink radio connections in the sense of the measurement data transmission from meters to a concentrator. The quality is assessed, for example, by the reception level and / or the signal-to-noise ratio in the received signal and depends on various constant and variable factors. These include, on the one hand, different building-related attenuation depending on the shielding conditions and distances between the individual meter installation locations and the concentrator installation location; and, on the other hand, there are, for example, uplink radio connections with higher and lower levels that currently overlap each other in the reception channel at the receiving location. Therefore, it is quite possible that analysable measurement value telegrams can be received via various radio connections only rarely, and in extreme cases practically not at all.

[0007] Avoiding such effects is the technical problem underlying the present invention; namely, in particular, taking into account that, on the one hand, according to current standards, the meters, including their transmitters and receivers (transceivers), are equipped with non-replaceable energy sources (primary batteries) that are usually intended to ensure ten years of uninterrupted operation, which already places strict limits on a mere increase in the transmission power of transmitters with weak reception; and that, on the other hand, according to the relevant standards, when using the so-called ISM bands for short-range data radio, usage limitations must be observed with regard to levels, frequency bandwidth, and relative duty cycle in the individual channels.

[0008] This problem is solved according to the features specified in patent claim 1. According to this, the uplink transmission parameters of the currently better-received transmitters are varied, primarily radio-controlled from the concentrator, until, based on statistical evaluation, they are approximately leveled to the reception conditions of those transmitters that still provide sufficient reception field strength for reliable measurement value transmission.

[0009] Because relatively strong reception field strengths from uplink transmitters no longer dominate weaker reception field strengths, all transmitters transmitting their measured values ​​according to the random access principle are received by the concentrator with approximately the same level of quality; that is, from the receiver's perspective, a weak reception field strength is not temporarily or even permanently suppressed by a strong one superimposing it.

[0010] For this purpose, the concentrator is set up to influence the downlink by means of control signals on the various meter transmitters in accordance with automatic evaluations of quality criteria of the measured value telegrams received from those uplink.

[0011] Such evaluations can provide common statistical assessment methods implemented in the concentrator, such as signal-to-noise ratio values ​​(e.g. CQI channel quality indicator or PER packed error rate) as quality criteria.

[0012] However, a quality assessment can also result from simply counting how many times usable measurement values ​​are received uplink from a specific transmitter, compared to a currently or default selected uplink reference transmitter, whose measurement values, in contrast, are received less reliably. Then, for the transmitter with better reception, the number of telegram repetitions in the transmission interval can be remotely controlled by the concentrator, reduced to a fixed value or, depending on that ratio, by a percentage. As a result, the poorly received measurement values ​​are less frequently overlaid by the stronger reception field strengths of this dominant uplink transmitter, and thus ultimately received more reliably. At the same time, the reduced sequence (duty cycle) of telegram transmissions from the uplink transmitter with better reception reduces the channel load.

[0013] Additionally or instead, according to a further development of the inventive solution, the transmission power of the uplink transmitter with good reception can be reduced, in extreme cases to such an extent that it cannot receive usable measurement data telegrams any better than a transmitter with poor reception—or even just barely. The collision of the telegrams, which are then constantly approximately equally well received, can be managed on the receiving side using known signal processing and evaluation methods, so that ultimately all uplink transmitters deliver usable measurement data. Reducing the radio channel load here is based on reducing unnecessarily high transmission levels.

[0014] Instead of or in addition to the two aforementioned options, the measured values ​​from the uplink transmitters, which are easily received by the concentrator, can still be transmitted at an increased data rate. Due to the higher data rate, the bit pulse durations are shortened, and while the data content remains the same, the effective telegram durations. The reception quality of the telegrams at the concentrator and the aforementioned criteria are used as the basis for increasing the data rate. If these comparatively short telegrams with an increased data rate overlap the comparatively long telegrams with a normal transmission rate during radio transmission, the data from both telegrams can be reconstructed and received correctly using error correction methods. The data rate is set in such a way that all of the telegrams involved can be reconstructed at the receiver during this overlap.This measure increases the data throughput in the system and thus the number of usable measurement telegrams. Furthermore, the shorter telegrams reduce the channel load and energy consumption of these uplink transmitters.

[0015] In addition to increasing reception reliability, resulting in faster processing of communication connections, each of the measures outlined above leads to a reduction in the channel load on the uplink channel; and at the same time, the energy source of the uplink transmitter is protected, whose specified service life is therefore more reliably achieved.

[0016] An additional, useful effect of the transmission optimizations can be argued to be that the resulting reduced average transmission levels reduce the electromagnetic pollution of the environment.

[0017] According to the invention, beyond the uplink interventions, it is also possible to influence the downlink radio connections for transmitting control signals from the concentrator to the meter transmitters. For this purpose, it is assumed, in a manner known per se, that the uplink and downlink data traffic takes place on different radio channels; with the exception of the duty cycles, transmission powers of different maximum strengths are permitted over the individual radio channels available for such services in the so-called ISM bands.

[0018] At the meter-side receivers, the current transmission quality of the concentrator control signal received downlink is assessed, again using standard methods such as CQI, RSSI, or PER, and fed back to the concentrator's transceiver. This determines which of the above options for uplink measurement transmission will currently optimize data throughput. Furthermore, depending on the current conditions, the downlink transmission power can be reduced or increased by switching to a channel with adjusted permissibility. The respective meter-side receiver receives the message from the concentrator, i.e., the instruction to which channel it should switch for future downlink reception of any control signals from the concentrator.

[0019] In order to more reliably receive measured value data telegrams from meter transmitters to a concentrator via uplink radio connections in a bidirectional data transmission radio system, the invention intelligently reduces the quality of uplink radio connections that are easier to receive in order to increase the overall reliability of a system with many meters and concentrators. To this end, the concentrator uses control signals via downlink radio connections to influence parameters such as transmission power or telegram management for the operation of uplink transmitters. Uplink quality criteria that can be automatically obtained by the concentrator include, in particular, absolute or relative levels, noise, and the relative number of receivable data telegrams.

Claims

[1] Bidirectional radio data transmission method for transmitting measured value data telegrams from meter transmitters via uplink radio connections to a concentrator receiver and with downlink radio connections from a concentrator transmitter to the meter receiver, characterized by that at the concentrator, information about the quality of an uplink radio connection in comparison to at least one other uplink radio connection is determined in a program-controlled manner and at least one parameter of at least one of the uplink radio connections is influenced via the downlink radio connection in such a way that its quality is reduced towards the quality of a poorer but still functional uplink radio connection. [2] Method according to claim 1, characterized by that one parameter is the transmission power. [3] Method according to one of the preceding claims, characterized by that one parameter is the number of telegram repetitions. [4] Method according to one of the preceding claims, characterized by that one parameter is the telegram length. [5] Method according to one of the preceding claims, characterized by that reception levels are quality criteria. [6] Method according to one of the preceding claims, characterized by that signal-to-noise ratios are quality criteria. [7] Method according to one of the preceding claims, characterized by that numbers of usable measured values ​​received are quality criteria. [8] Method according to one of the preceding claims, characterized by that transmission parameters are varied in relation to quality criteria. [9] Method according to one of the preceding claims, characterized by that one of two telegrams belonging to a foreign system is treated as an interference signal. [10] Method according to one of the preceding claims, characterized bythat error correction procedures are used when telegrams are superimposed at the receiving end. [11] Method according to claim 10, characterized by that the reception of a comparatively short telegram is not disturbed by at least one overlay with a comparatively longer telegram due to error correction. [12] Method according to claim 10, characterized by that the error correction as well as the entire physical layer supports a negative signal-to-noise ratio, so that data from telegrams received with a negative signal-to-noise ratio can be transmitted without errors. [13] Method according to claim 10, characterized by that the error correction and the entire physical layer support a positive signal-to-noise ratio. [14] Method according to claim 12, characterized bythat when two telegrams are superimposed, their level difference is controlled via a power control so that the level difference is smaller than the negated signal-to-noise ratio of the physical layer in order to receive both telegrams. [15] Method according to claim 13, characterized by that when two telegrams are superimposed, the level difference is controlled via power control so that it is greater than the signal-to-noise ratio of the physical layer in order to receive at least one of the two telegrams.