JP3961696B2 - Network system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a network system that enables communication between nodes having different transmission rates through a single transmission line.
[0002]
[Prior art]
Conventionally, when a plurality of home appliances are connected via a network, the transmission rate is determined by the control content of each home appliance, the amount of information required, the time for communication stations, and the required response time.
[0003]
FIG. 15 shows a schematic configuration of a conventional network system. The host node 13 is connected to the high speed bit rate nodes 16 and 17 through the high speed data line 11, and is further connected to the low speed bit rate nodes 15 and 18 through the gateway 14 through the low speed data line 12.
[0004]
For example, in an AV (Audio Visual) device, data with a large amount of information such as images and sounds needs to be communicated in real time, and the data is sent at a high transmission rate such as 100 Mbps, 200 Mbps, or 400 Mbps, and further advances in the direction of higher speed. It is out.
[0005]
On the other hand, in white goods such as air conditioners, microwave ovens, lighting, etc., control data is mainly transmitted and received as little as several tens of kilobytes, and it is not necessary to communicate in real time. For this reason, a transmission rate of 9.6 Kbps at present and about 100 Kbps in the future are sufficient.
[0006]
In such communication with different data to be handled, the protocol is different and the transmission rate is greatly different. Therefore, a method is used in which transmission is performed separately in two systems and finally connected by a gateway. For example, the AV system uses a protocol including an isochronous transfer type such as IEEE 1394, and the white goods home appliance system uses an asynchronous data transfer type (asynchronous trnsfer) protocol such as HBS or LONWORKS, and its physical specifications are also different. Thus, two transmission lines with different transceivers coexist. If the transmission medium is wired, two lines of wiring are laid in the home, and if it is wireless, radio waves of two different frequencies are used.
[0007]
[Problems to be solved by the invention]
However, the installation work becomes expensive due to the wiring of the two systems, and in the case of wireless, valuable frequency resources are consumed by using radio waves of two different frequencies. In any case, a transceiver having two modulators / demodulators with different transmission rates is required, which is an obstacle to standardization and cost reduction in each node of a high-speed network and a low-speed network.
[0008]
In order to solve the above problems, an object of the present invention is to provide a network system capable of communicating on the same transmission path even at different transmission rates.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, a network system according to the present invention is a network system in which nodes having different data communication speeds are connected by a communication medium. Each node includes carrier detection means for performing carrier sense prior to communication, and a packet. the cycle of the communication time is divided into a plurality of time-series communication range of different bit rates, comprising a communication area allocation means for allocating the transmission packet to the communication area of the bit rate assigned thereto therein, the communication area allocation means If no carrier is detected within a preset time, packet transmission is started, and if a carrier is detected within a preset time, a high-speed data packet and a low-speed data packet are determined according to the preamble bit period of the baseband signal. , Measure the time from the beginning of the packet, and send And determining the timing.
[0010]
With the above configuration, communication can be performed on the same transmission path even at different transmission rates.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1A shows a schematic configuration of a network system of the present invention in FIG. 1A, and FIG. 1B shows a packet sequence according to the communication method of the present invention.
[0013]
The host node 2 is connected to the high-speed bit rate nodes 4 and 5 and the low-speed bit rate nodes 3 and 6 through the data line 1. The data line 1 is wired, radio waves, light, or the like, and high-speed packets and low-speed packets are mixed and transmitted. The high-speed bit rate node 4 is a DVD (Digital Video Disc), and the high-speed bit rate node 5 is an HDTV (High Density Television), both of which transmit and receive packets at 100 Mbps. The low-speed bit rate node 3 is an air conditioner, and the low-speed bit rate node 6 is a microwave oven, both of which transmit and receive packets at 100 Kbps.
[0014]
Each node can transmit and receive a packet at a cycle time T. The cycle time T is divided into a high-speed packet area and a low-speed packet area, and the high-speed bit rate nodes 4 and 5 and the low-speed bit rate node 3 connected by the data line 1. , 6 can communicate only in the packet area assigned to each. If the low-speed packet is within the allocation time t and the high-speed packet is within the time (T−t), the high-speed and low-speed packets can be mixed and transmitted within the cycle time T. It is also possible to divide into three or more different bit rate packet communication areas.
[0015]
FIG. 2 shows a first configuration example of nodes constituting the network system of the present invention. The first to seventh layers 101 of the OSI (Open Systems Interconnection) model exchange baseband packets with a part 102 of the OSI1 layer, and further exchange data packets with other nodes via the transceiver 103. The memory 104 stores a bit rate value, a T value, a t value, and a communication area allocation value (communication available area).
[0016]
In part 102 of the OSI 1 layer, the baseband packet received from the OSI 1-7 layer 101 is temporarily stored in the packet buffer 102a, and a bit period is generated from the bit period generator 102b in accordance with the bit rate designation from the OSI 1-7 layer 101. Then, the data in the packet buffer 102 a is output to the transceiver 103, modulated by the modulator 103 a, and sent to the data line 1.
[0017]
The packet signal from the data line 1 is demodulated by the demodulator 103b, the bit rate is discriminated by the bit rate discriminator 102d, and the packet having the bit rate value assigned to it by the memory 104 is the packet transmission discriminator. It is selected at 102d, stored in the packet buffer 102c, and sent to the OSI 1-7 layer 101.
[0018]
Next, a method for determining the transmission timing of each node will be described. As shown in FIG. 3, the transmission node monitors the T-time carrier, and if no carrier is detected during that time, the transmission node starts packet transmission at a predetermined bit rate after the monitoring is completed. At this time, each node has a time slot (time width ts), determines a random value n after the end of monitoring, and starts packet transmission from the nth time slot n. However, n * ts (* represents multiplication. The same applies hereinafter) is selected to be sufficiently small with respect to T. By this carrier monitoring before transmission, packet collision due to simultaneous transmission of a plurality of nodes can be avoided.
[0019]
When a carrier is detected during carrier monitoring for T time, the preamble time of the detected packet is determined. After demodulating the received signal into a baseband signal by the demodulator 103b, the cycle of the preamble pulse added to the head of the packet is measured by the bit rate discriminator 102d to determine whether it is a high-speed packet or a low-speed packet. At the same time, the first appearance time of the preamble pulse is detected.
When a plurality of high-speed or low-speed packets are detected, the detection time of each initial preamble is determined as the start time of the high-speed packet area or the low-speed packet area within the cycle time. If at least one packet is detected during the cycle time T, the transmission timing of each node in the next cycle is uniquely determined by the bit rate determination result, the preamble start time, and the t value.
[0020]
For example, as shown in FIG. 4, when only a high-speed packet is first detected, the high-speed bit rate node has a transmission right after a time T has elapsed from the head preamble. The low-speed bit rate node has a transmission right after (2T−t). After acquiring the timing information of the high-speed packet area or the low-speed packet area, each node determines the transmission start time by carrier sense. Note that the bit rate is determined by comparing with the bit rate value of itself or other nodes stored in advance in the memory of each node.
[0021]
The physical layer (OSI1 layer) of the communication processing unit of each node is provided with a bit rate period signal generator (bit period generator 102b in FIG. 1), and this period is determined by the packet communication area assigned to each node. Corresponds to the bit rate period. Normally, each node has a fixed bit rate period, but the host node 2 (centralized control device) has a bit rate period signal generator that can be switched according to the bit rate period of each of high speed and low speed, Switch accordingly.
[0022]
The received packet is stored in the packet buffer memory corresponding to the bit rate value, and passed to the OSI upper layer.
[0023]
Each node has a protocol corresponding to the bit rate value 1: 1, and stores a bit rate value, a T value, a t value, and a communication area allocation value. Here, the communication area allocation value is a value in which values such as 0 and 1 are allocated to areas in order as shown in FIG. 5A, for example, when one cycle time is divided into packet areas for each bit rate. FIG. 5B shows memory data of the node 1 as an example. In this example, the node 1 has a transmission right in the second half of the cycle time because the transmission bit rate is 100 Kbps and the communication area allocation value is 1.
[0024]
In particular, when a plurality of packets are exchanged in each packet area, it is necessary to manage so that each designated area does not protrude. First, one maximum packet length is (T−t) for high speed and within time t for low speed. Especially for high speed use, the amount of data handled is large, and it is often impossible to send all the data in one packet, and the data is often transmitted over a plurality of cycle times. Here, the message generated in the application layer (OSI7 layer) is transferred from the OSI upper layer to the OSI lower layer, sequentially added with data, and finally stored in the transmission packet buffer 102a. The total number of bits constituting the packet stored in the transmission packet buffer 102a is determined by its occupied memory size. If this is m bytes, the packet transmission time Tp = (8 * m / transmission bit rate (bps)) seconds.
[0025]
FIG. 6 shows an example in which a plurality of low-speed nodes transmit packets in the low-speed packet area at time t. The B node can be obtained as an allowable time t _remain = t− (A end time−A start time) remaining from the packet transmission end time of the A node.
[0026]
A packet transmission algorithm for the second and subsequent cycle times will be described with reference to the flowchart of FIG. First, n = 2 is set (ST1), and a packet length Tp to be transmitted is calculated (ST2). Then, carrier sense is performed (ST3), and when completed (ST4), t _remain is calculated (ST5). Assuming that α = time slot width ts * maximum number of slots, if t _remain ≧ Tp + 2 * α (ST6), the B node transmits (ST7), and n = n + 1, that is, in the third packet 3 * α is added (ST8), and the process returns to step ST2. Otherwise, it does not transmit and waits for the next cycle time (ST9).
[0027]
Next, the case of transmitting to nodes having different bit rates will be described. FIG. 8 shows memory data of the node 3, which has two self-transmission bit rate values and self-communication area allocation values, and can communicate with nodes having different bit rates. For example, when a packet is transmitted to the node 5, it must be transmitted from the memory table with a communication area allocation value 0 at 100 Mbps.
[0028]
FIG. 9 shows a second configuration example of the nodes constituting the network system of the present invention. The application layer 201 exchanges data with the OSI 1 to 6 high-speed layer 202 or the OSI 1 to 6 low-speed layer 203, exchanges baseband packets with a part 204 of the OSI 1 layer, and further passes through other nodes via the transceiver 205. And exchange of modulated data packets. The memory 206 stores a bit rate value, a T value, a t value, and a communication area allocation value.
[0029]
In a part 204 of the OSI 1 layer, the baseband packet received from the OSI 1-6 high speed layer 202 or the OSI 1-6 low speed layer 203 is temporarily stored in the packet buffer 204a, and the OSI 1-6 high speed layer 202 or OSI 1-6 low speed A bit period is generated from the bit period generator 204 c in accordance with the bit rate designation from the layer 203 for use, the data in the packet buffer 204 a is output to the transceiver 205, modulated by the modulator 205 a, and transmitted to the data line 1.
[0030]
The packet signal from the data line 1 is demodulated by the demodulator 205b, the bit rate is discriminated by the bit rate discriminator 204f, and the packet having the bit rate value assigned to it by the memory 206 is the packet transmission discriminator. It is selected at 204e, stored in the packet buffer 204d, and sent to the OSI 1-6 high speed layer 202 or the OSI 1-6 low speed layer 203.
[0031]
The packet demodulated by the demodulator 205b is determined by the bit rate discriminator in the period of its preamble portion. In the single bit rate node, whether or not the packet is addressed to itself is determined based on this determination content. If they are different, the switch inside the packet passage determination unit 204e is opened with the determination signal flag so that it is not transmitted to the packet buffer 204d. In the case of a node capable of communicating at a high speed / low speed bit rate, after the bit rate is discriminated by the bit rate discriminator 204f, after the high speed or low speed layer is selected by the discrimination signal flag, the selected upper layer layer The packet is discarded after the destination address in the packet is compared with the self address.
[0032]
There are two functions specific to this node. First, there is a function of storing the transmission data length in the communication area for each communication bit rate. That is, the data is divided so as to be within the allowable length of the transmission data from the bit rate value of the transmission partner and the communication area time, a packet code is added, and the remaining data is packetized and transmitted at the next cycle time. The over buffer memory 204b is provided separately from the transmission packet buffer 204a, stores the portion exceeding the allowable value of the telegram data, and reads the stored value after the end of one cycle time.
[0033]
This function will be described with reference to the flowchart of FIG. The overbuffer memory 204b is initialized (ST11), data is read from the overbuffer memory 204b (ST12), and a transmission telegram is generated based on an event (such as input from an input device) (ST13). Then, the total data bit length of the generated telegram, the data from the over buffer memory 204b and the additional data (address, error correction code, etc.) is calculated (ST14). Here, as the allowable bit length of the data communication area = communication area time * communication rate (bps), the allowable bit length of the data communication area is read (ST15), and it is determined whether the transmission packet length <the allowable bit length (ST16). For example, the allowable overbit is stored in the overbuffer memory 204b (ST17). Then, the permissible data is stored in the transmission packet buffer 204a (ST18), and a packet number is added (ST19). If the transmission packet length is shorter than the allowable bit length in step ST16, it is stored in the transmission packet buffer 204a (ST20). Then, it is transmitted after carrier sense (ST21), waits until the next cycle time (ST22), and returns to step ST12.
[0034]
FIG. 11 shows an example in which data is divided into a plurality of packets and transmitted by the above algorithm.
[0035]
In the protocol interpretation mechanism, the same protocol communication layer is prepared for communication only between high-speed nodes and only between low-speed nodes. However, when transmitting from a high-speed node to a low-speed node or vice versa, it is necessary for the protocol to be correctly interpreted by the other party. For this reason, as the second function, the high speed layer 202 and the low speed layer 203 are prepared and selected according to the destination. In addition, when a packet with the divided packet number is received, a mechanism for interpreting the packet number and sequentially reassembling is required in the OSI layer, which is a known technique. Usually, it is sufficient to have either a high-speed layer or a low-speed layer.
[0036]
Next, a case where transmission is performed with variable T values and t values will be described. Depending on the application, for example, when many nodes want to access the low-speed packet side, there are cases where it is desired to increase the occupied time zone of the low-speed packet area. Conversely, there is a case where it is desired to widen the high-speed packet area. In such a case, the host node 2 included in both the high speed and the low speed broadcasts the T value and the t value together with the set command to all nodes, and rewrites the memory tables of other nodes.
[0037]
As shown in FIG. 12, a message such as a T value, a t value, and a set command is transmitted by the host node 2 in packets of two different bit rates in the broadcast mode. FIG. 13 shows an example of this message. A command designating T = 20 msec and t = 8 msec is inserted after the broadcast command and the set command. The node that has received this packet immediately rewrites the data in the memory, and then returns ACK (acknowledge) to the transmission source host node 2 at an arbitrary timing. The host node 2 retransmits the rewrite packet until ACK is returned to the node to which ACK does not return. In this way, the memory data of all the nodes is rewritten, and thereafter communication is started with new T values and t values.
[0038]
When the reset command is broadcast, default T and t values prepared in advance for each node are set. This rewriting procedure is the same as that of the set command.
[0039]
Next, functions of the modulator 205a and the demodulator 205b of the transceiver 205 will be described. The modulator 205a receives the bit string of the packet, modulates it, and outputs it. As the modulation method, ASK (Amplitude Shift Keing), FSK (Frequency Shift Keing), PSK (Phase Shift Keing), SS (Spread Spectrum), etc. are selected, but all nodes are the same including the demodulator. The system is standardized, and physical parameters such as output level, modulation frequency, and modulation degree are also set in common.
[0040]
The demodulator 205b demodulates the modulated signal. However, since the modulation method is unified among all nodes, the modulated signal output from all nodes in this network system is demodulated into a baseband signal at the receiving node. can do.
[0041]
In order to determine the bit rate by measuring the period with the baseband signal, the baseband system code always uses a code that produces a pulse in both logical 1 and 0 periods.
[0042]
FIG. 14 shows a code waveform of a baseband system, (a) shows a waveform of code A, and (b) shows a waveform of code B. Both the code A and the code B can determine the bit rate by measuring the period. Each node only needs to be able to determine this bit rate, and there is no need to interpret different protocols. In particular, when the baseband transmission method is used with the communication medium as a wire, a pulse appears on the same signal line. Therefore, the pulse period can be measured by matching the signal level between the high-speed and low-speed nodes.
[0043]
【The invention's effect】
As described above, the network system of the present invention, with a cycle time of a packet communication is divided into a plurality of time-series communication range of different bit rates, assigned to transmission packet to the communication area of the bit rate allocated to the self therein If a carrier is not detected within a preset time, packet transmission is started, and if a carrier is detected within a preset time, a high-speed data packet and a low-speed data packet are determined according to the preamble bit period of the baseband signal. Node , which measures the time from the beginning of the packet and determines the transmission timing, so that nodes that can communicate on the same transmission path even at different transmission rates while avoiding packet collisions due to simultaneous communication of multiple nodes Standardization becomes easier, and the cost of the system is reduced. It can be achieved.
[Brief description of the drawings]
FIG. 1A is a schematic configuration diagram of a network system of the present invention, and FIG. 1B is a diagram showing a packet sequence according to a communication method of the present invention.
FIG. 2 is a diagram showing a first configuration example of a node constituting the network system of the present invention.
FIG. 3 is an explanatory diagram of a transmission timing determination method. FIG. 4 is a diagram illustrating a signal example of a high-speed / low-speed packet.
FIG. 5A shows an example in which values are assigned to communication areas, and FIG. 5B is a diagram showing an example of memory data of a node 1;
FIG. 6 shows an example in which a plurality of low-speed nodes transmit packets in a low-speed packet area.
FIG. 7 is a flowchart illustrating a packet transmission algorithm.
FIG. 8 is a diagram illustrating an example of memory data of a node 3;
FIG. 9 is a diagram showing a second configuration example of the nodes constituting the network system of the present invention.
FIG. 10 is a flowchart for explaining a function of storing a transmission data length in a communication area for each communication bit rate.
FIG. 11 is a diagram illustrating an example in which data is divided into a plurality of packets and transmitted.
FIG. 12 is a diagram illustrating an example of a message transmitted by a host node.
FIG. 13 is a diagram illustrating an example of a telegram message.
14A and 14B show a code waveform of a baseband system, where FIG. 14A shows a waveform of code A, and FIG. 14B shows a waveform of code B;
FIG. 15 is a diagram showing a schematic configuration of a conventional network system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Data line, 2 ... Host node, 3 ... Low speed bit rate node, 4 ... High speed bit rate node, 5 ... High speed bit rate node, 6 ... Low speed bit rate node

Claims (1)

In a network system in which nodes having different data communication speeds are connected by a communication medium, each of the nodes includes carrier detection means for performing carrier sense prior to communication, and a plurality of time-series communication areas having different bit rates for packet communication cycle times. If the divided, comprises a communication region allocation means for allocating the transmission packet to the communication area of the bit rate assigned thereto therein, the communication area allocation unit does not detect the carrier within a predetermined time, When packet transmission is started and a carrier is detected within a preset time, the high-speed data packet and the low-speed data packet are determined by the preamble bit period of the baseband signal, and the time from the beginning of the packet is measured, network system and determining the transmission timing

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