Transmitter and receiver for a communication system, communication system and method for conveying information

Abstract

An embodiment of the present invention provides a transmitter (100) for a communication system comprising a modulation device (110) configured to generate a transmit signal (120) and to modulate information onto a plurality of sub-bands (120a, ..., 120d), at least two of the sub-bands (120a, ..., 120d) having different bandwidths.

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present invention relate to a communication system, transmitter and receiver for communicating information, for example in an automobile. [Background technology]

[0002] Communication systems are used in many applications, for example for communication between control devices, comfort devices and entertainment devices in automobiles. Electrical in-vehicle networks and / or communication systems in vehicles are currently being developed in the direction of zoning with respect to wiring. Several independent zones are connected to each other by a communication system. One factor of the trend towards zoning is the high complexity of customer-specific wiring harnesses. At the same time, several previously independent functions were often concentrated on high-performance integration platforms. The resulting zones or zone integration modules and between such integration platforms require high-performance backbone buses as part of the communication system that can carry large amounts of data and guarantee low latency, i.e. support several use cases simultaneously. If the number of zones remains small, for example less than five, switched Ethernet would in principle be suitable for this. This will be true as long as the zoning is based on a fine granularity of the power supply in the vehicle. For a larger zoning, for example in 10-25 zones, a switched system would be too complex and expensive. However, if the vehicle wire harness has to be manufactured in a fully automated manner, zoning in the direction of 20 to 25 zones is required.

[0003] EP 1 478 148 A1 describes a method for communication between radio stations of a wireless communication system using at least one frequency band which is divided into a number of sub-bands. The manner in which the at least one frequency band is divided into the sub-bands can be varied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent Application Publication No. 1478148 Summary of the Invention [Problem to be solved by the invention]

[0005] There is therefore a need to provide an improved communication system, for example for application in automobiles. This need is met by the transmitter, receiver, communication system and vehicle of the independent claims. [Means for solving the problem]

[0006] An embodiment of a transmitter for a communication system comprises a modulator configured to generate a transmit signal while modulating information on a plurality of sub-bands, at least two of the sub-bands having different bandwidths. Modulation on sub-bands of different widths can ensure that the transceiver electronics, in particular the analog-to-digital converter that digitizes the input signal, do not have to be oversized to transmit the required amount of information in each band while providing the backup power typically required in conventional applications.

[0007] An embodiment of a receiver for a communication system comprises a demodulation device configured to demodulate an input signal in a number of sub-bands of different bandwidths and to reconstruct information transmitted in one sub-band. The ability to demodulate an input signal by several sub-bands of different bandwidths allows the use of analog-to-digital converters in the receiver that have to operate with less power consumption compared to conventional solutions, which makes it, for example, more cost-effective.

[0008] An embodiment of a communication system for a vehicle comprises a data bus, an embodiment of a first transmitting device coupled to the data bus for transmitting information via the data bus, and an embodiment of a second transmitter coupled to the data bus for transmitting information via the data bus. The use of transmitters allows the communication system to be reliably and efficiently implemented in a daisy chain architecture.

[0009] An embodiment of a method for transmitting information that enables this includes modulating information onto a first subband and modulating further information onto a second subband, the first subband and the second subband having different bandwidths. [Brief description of the drawings]

[0010] These embodiments will now be described in more detail with reference to the accompanying drawings. [Figure 1] FIG. 2 is a schematic diagram of a transmitter. [Diagram 2] FIG. 2 is a schematic diagram of a receiver. [Diagram 3] FIG. 2 is a schematic diagram of a transceiver. [Figure 4] The figure shows the dependence of the transmittable bit rate on the bandwidth and the signal-to-noise ratio. [Diagram 5] FIG. 1 is a diagram of the structure of a communication system. [Figure 6] 1 is a schematic diagram of a communication system in a motor vehicle. [Figure 7] 1 is a flow chart of an embodiment of a method for receiving information. [Figure 8] 1 is a flow chart of an embodiment of a method for transmitting information. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Various embodiments will now be described more fully with reference to the accompanying drawings, in which several embodiments are shown and in which thickness dimensions of lines, layers and / or regions may be exaggerated for clarity.

[0012] FIG. 1 shows a schematic diagram of an embodiment of a transmitter 100 for a communication system.

[0013] The transmitter is connected to a data bus 150 and includes a modulator 110 configured to generate a transmission signal and modulate information on a number of sub-bands 120a, 120b, 120c, and 120d, at least two of which have different bandwidths. The modulation can be performed using any modulation method and scheme. Each sub-band in turn has a number of sub-carriers, for example 256, 512, or 1024. In the example, four sub-bands 120a, 120b, 120c, and 120d are shown, but additional embodiments may use more or less sub-bands. In another approach, in an Orthogonal Frequency Division Multiplex (OFDM) system using several sub-bands, sub-bands of the same bandwidth are used, which are separated at the receiver side by an inverse Fourier transform before the transmitted information and / or bits are demodulated. Compared to such conventional methods, modulation on sub-bands of different bandwidths ensures that the required amount of information can always be transmitted in each band, while at the same time the transceiver electronics, in particular the analog-to-digital converter for digitizing the input signal, do not have to be oversized to accommodate the backup power typically required in conventional applications. This is especially necessary if the transmit power per sub-band is not dynamically adjusted. If this remains constant over time, the implementation is much less complex and cheaper. Furthermore, the communication overhead for conveying the receive power from the receiver to the transmitter, which would otherwise be necessary, is eliminated.

[0014] The advantage of sub-bands of different bandwidths becomes clear when one looks at the receiver as shown diagrammatically in Figure 2, and at the overall system, i.e., a communication system having several transmitters and receivers daisy-chained together via a data bus as shown diagrammatically in Figure 5. It should be noted that although the transmitters and receivers are initially shown separately in Figures 1 and 2 to provide a good separation between the transmit and receive aspects, in many practical implementations a single device and / or one of the nodes 520a,...,520d shown in Figure 6 can both transmit and receive on the data bus 510, i.e., includes a transceiver as shown diagrammatically in Figure 3.

[0015] According to some embodiments, with multiple transceivers simultaneously transmitting on different sub-bands, only one of the transceivers of one of the nodes 520a-520d may transmit at a time on one sub-band or on multiple sub-bands over the communications medium and / or data bus 510. According to further embodiments, different transceivers may also transmit simultaneously on the same sub-band using different sub-carriers.

[0016] Fig. 2 shows a schematic diagram of a receiver. Matching the transmitter 100 of Fig. 1, the receiver 200 includes a demodulator 210 for demodulating an input signal 220 by a number of sub-bands 220a, ..., 220d of different bandwidths and reconstructing the information transmitted in one sub-band. In a communication system, the transmitters and receivers in different nodes are connected to each other via a data bus of variable length. Furthermore, between two communication nodes there may be further nodes in a daisy-chain configuration. The additional nodes arranged between two communication nodes cause additional insertion losses as well. Thus, the receiver does not receive the power emitted by the transmitter, but the power is reduced depending on the length of the data bus between the transmitting transmitter and the receiving receiver and the number of nodes in between. The thus reduced received power per sub-band 220a, ..., 220d is shown diagrammatically in Fig. 2 for a received signal 220. Fig. 2 shows the power normalized to frequency on the X-axis and in dBm / Hz on the Y-axis. Figure 2 shows the general attenuation behavior of signals on a conductor, in particular, high frequency signals are attenuated more than low frequency signals. As a result, the signal power reaching the receiver is lower for subbands with higher center frequencies than for subbands with lower center frequencies, if the transmission power is the same for all subbands.

[0017] Fig. 3 shows transceiver 250 connected to data bus 150 merely for the sake of completeness. Transceiver 250 has the capabilities of transmitter 100 and receiver 200 of Figs. 1 and 2, such that the transceiver is able to transmit data to data bus 150 as well as read data from the data bus.

[0018] Figure 4 shows a diagram of the dependence of the transmittable bit rate on the subband bandwidth and the signal-to-noise ratio. The ADC digitizing the input signal in the receiver must be dimensioned to digitize all of the received power in all applications and configurations of the communication system. The selected modulation format determines the minimum resolution of the ADC, along with the expected maximum power, the number of quantization steps and the dynamic range of the ADC. The input signal to be digitized is a baseband signal. The more quantization steps the ADC has, the more semiconductor space it requires, the more expensive the ADC will be, and potentially the slower it will be. The power components to be considered when designing an ADC in a receiver to digitize an input signal over a wide band are illustrated diagrammatically in Figure 3.

[0019] In another embodiment, when using a carrier signal, if the data bus medium is capable of carrying higher frequencies, the input signal can also be a baseband signal downmixed from the carrier signal.

[0020] For the following considerations, the channel characteristics (especially the channel attenuation) are essentially taken into account for the design of the system. Therefore, the noise components of the process noise 310, which are essentially due to the design of the hardware, the cable and PCB design, and the background noise, which can be understood in the sense of the ambient noise inside the vehicle, are not discussed in detail. Therefore, for the design of the system, the components of the channel attenuation 320 and the bit rate and / or amount of information transmitted per subband 330 should be taken into account. The latter is explained by the Shannon-Hartley theorem shown in Fig. 3. This theorem explains the number of transmittable bits as a function of the bandwidth B of the subband and the signal-to-noise ratio S / N. If the bandwidth B is set to 1 Hz, the result normalized to the frequency, i.e. the number of bits that can be transmitted per bandwidth, is illustrated. The maximum possible length of the data bus and the maximum possible number of nodes define the maximum channel attenuation and are included in the equation via the reduced signal power and the signal-to-noise ratio.

[0021] For example, when transmitted at a bit rate of 10 bits / Hz, the equation results in a required S / N of only 30 dB.

[0022] As in conventional systems, and in contrast to FIG. 2, if all subbands were given the same bandwidth, either the ADC would have to be oversized or bit rate would be wasted since the channel attenuation depends on the distance between the communicating nodes, especially on the frequency. First, assuming the normal behavior of the channel attenuation increasing with frequency, the S / N decreases with increasing frequency. If one wants to transmit the same amount of information per subband, the ADC would have to be designed to be able to digitize the input signal of the highest frequency subband with the required resolution. This means that the ADC would have to be oversized for the lower frequency subbands in order to be able to handle the higher received power without clipping. If this was not desired, bit rate would be wasted.

[0023] For example, if one realistically assumes a linearly decreasing channel attenuation (e.g., 0.1-0.5 dB / m) between a frequency f1 of 100 kHz and a frequency f2 of 300 MHz, a constant required bit rate per subband, and a communication system structure with four subbands 220a,...,220d, would result in the situation shown in Figure 4. Furthermore, one can realistically assume that the insertion loss per node is 1.5 dB and is constant with frequency.

[0024] The worst possible S / N value should be used to calculate the bandwidth of each subband 220a, ..., 220d. Due to the attenuation increasing monotonically with frequency, there is a value marked with an X at the upper end of each of the subbands 220a, ..., 220d. This results in the width of each subband for the required bit rate, or the bit rate per subband for a particular bandwidth. If, for example, the same bit rate per subband is required, this results in the effective range (width of the subband times the attenuation at the critical point) covered by each subband 520a, ..., 520d being the same. Of course, if different transmission bandwidths and / or bit rates are required for each subband, e.g. if the ADC used has to be of effective size, different bandwidths can also be generated for those subbands.

[0025] FIG. 6 shows a schematic diagram of a communication system in a car 500 as one possible application of the concepts described herein. The communication system comprises a wired data bus 510 to which several nodes 520a, ..., 520d are coupled. The nodes 520a, ..., 520d are arranged in series in the data bus 510 in a daisy-chain configuration. Each of the nodes 520a, ..., 520d includes a transmitter and / or a receiver, in particular where the individual nodes interconnect different zones of a zoned architecture in the car 500. The data bus 510 is a passive wired data bus 510, and thus is a good and stable transport medium, as compared to, for example, a cordless system. For example, a data bus according to an embodiment of the invention may use one or more pairs of unshielded twisted pair (UTP), shielded UTP, or shielded twisted pair (STP). Similarly, one or more coaxial cables or optical fibers may be used. In a passive daisy-chain configuration, the individual nodes 520a,...,520d do not actively amplify the signal, i.e. the electronic devices are connected to the data bus interior, for example via the shortest possible stub wires. In the passive version, two connections within the node are connected to each other and / or a connection is closed through between two possible connections for the external connection of the node to the data bus.

[0026] For completeness, the essential steps of the method as carried out in the transmitter or receiver mentioned above will now be briefly described again with reference to FIGS.

[0027] First, the method of receiving information optionally includes receiving a transport signal from a data bus as an input signal for an ADC (step 610). The input signal is digitized by the ADC (step 620). The method further includes demodulating at least two subbands of different bandwidths within the input signal to reconstruct information (e.g., data bits) transmitted in each subband (step 630).

[0028] The method for transmitting information includes modulating information onto a first subband (step 710) and modulating information (e.g., data bits) onto a second subband (step 720), the first subband and the second subband having different bandwidths. The method further includes transmitting a transmission signal comprising the first subband and the second subband (step 730). The transmission signal may be, for example, a signal made up of the subbands itself, or the signal may be a signal generated by mixing a signal of the subbands into a transport signal.

[0029] In summary, the above-described embodiments of the present invention enable OFDMA (Orthogonal Frequency Division Multiplex with additional separation of sub-bands) as a physical layer for example Ethernet, with broadband connection of all nodes via passive daisy chain. In particular, this allows the Analog to Digital Converter (ADC) to be designed taking into account the required bit rate, channel attenuation (daisy chain) and bandwidth of the sub-bands (Hz or number of sub-carriers).

[0030] Although in the above, embodiments of the invention have been motivated essentially by applications in automobiles, further embodiments may be used in any other applications where robust and flexible data communication is required. Criteria other than the mere attenuation of the channel itself may be used to design the communication system and to determine the bandwidth of the sub-bands. For example, the spectral transmission power may be limited in some applications, e.g., the G.HN standard for data transmission over coaxial cables and over telephone lines (ITU-T G.9660). Such spectral masks can be easily taken into account in the design of the communication system according to the above considerations. [Explanation of symbols]

[0031] 100 Transmitter 110 Modulation Device 120 Transmitting Signal 120a, …, 120d sub-bands 150 Data Bus 200 Receiver 210 Demodulator 220 Input Signal 220a, …, 220d subbands 250 Transceiver 310 Process Noise 320 Channel Attenuation 330 Power required for information transmission 350 dimensioning range 500 Automobiles 510 Data Bus Nodes 520a, ..., 520d 610 Receive 620 Digitize 630 Recover 710 Modulation 720 Modulation 730 Send

Claims

1. A transmitter for a communication system, comprising: a modulator configured to generate a transmission signal and to modulate information onto a plurality of sub-bands, at least two of the sub-bands having different bandwidths.

2. The transmitter of claim 1 , wherein the bandwidths of the multiple subbands increase monotonically with a center frequency of the subband.

3. 3. A modulator as claimed in claim 1 or 2, wherein the amount of information modulated on each subband is the same.

4. 4. The transmitter of claim 1, further comprising an output for the transmission signal, the output being configured to be coupled to a wired medium.

5. a demodulation device configured to demodulate an input signal by a number of subbands of different bandwidths and to reconstruct information transmitted in one subband such that the amount of said information in each subband (120a, ..., 120d) is identical; A receiver for a communication system comprising:

6. 6. The receiver of claim 5, further comprising an analog-to-digital converter configured to digitize a received signal and provide it as a digital input signal to the demodulator.

7. 1. A communication system for a vehicle, comprising: A data bus; a first node comprising a first transmitter according to any one of claims 1 to 4, coupled to a data bus for transmitting information via said data bus; at least one second node comprising a second transmitter according to any one of claims 1 to 4, coupled to the data bus for transmitting information via said data bus; A communication system comprising:

8. 8. The communication system of claim 7, wherein the first node and the second node are coupled to the data bus in a daisy-chain configuration.

9. A motor vehicle comprising a communication system according to claim 7 or 8.

10. 1. A method for transmitting information, comprising: modulating information onto a first subband; modulating information into a second subband, wherein the first subband and the second subband have different bandwidths; transmitting a transmission signal comprising the first subband and the second subband; The method includes:

Images