JPH03179849A - Exchange - Google Patents

Abstract

PURPOSE:To attain the effective utilization of frequency and to improve the reliability by sending only one packet signal to an outgoing line in response to the destination of the packet signal when plural same packet signals are inputted from plural input lines within a prescribed time. CONSTITUTION:When a packet is sent from a radio communication. terminal equipment 13 in a service area, all radio ports 12 receive the packet and plural same packets are sent to an exchange 11. The packets are latched in a buffer 15 in the exchange 11 through a demultiplexer 18 and since same latched packets exist in the buffer 15, it is detected by a same packet detector 16. Thus, only one of the same packets outputted from the buffer 15 is sent to the demultiplexer 18 by the changeover of a switch 17 and sent to an exchange in response to the destination of the packet. Thus, the frequency is utilized effectively and the reliability is improved.

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a switch used in a packet radio network that handles voice and data in an integrated manner, for example. (Prior Art) In recent years, studies have begun to consider campus wireless networks and small zone wireless networks that can accommodate the movement of terminals within a campus. For these networks, the following are essential: ■ Effective use of frequencies ■ Flexibility of the network and the signals that can be transmitted (multimedia support) ■ High reliability ■ Width of service area and flexibility with respect to its fluctuations. Incidentally, wireless services within premises have been provided to a limited extent to date. Examples include low-speed data transmission of about 4 to 8 Kbps between points called wireless modems, cordless phones that transmit FM analog voice, and message pagers that transmit messages in one direction at extremely low speeds. However, in the case of low-speed data transmission using a wireless modem, it can only be used point-to-point. ■When used for communication between computer terminals, etc., the line remains connected regardless of whether there is communication, so line usage efficiency and frequency usage efficiency are reduced. ■Since only low-speed data is used, it cannot be applied to workstations or engineering workstations that use a lot of image information and graphic information. ■Even if an attempt is made to increase the speed, fading and shadowing will be significant, making it impossible to achieve high reliability with the conventional method. ■It is not possible to handle audio, images, data, etc. in a unified manner. There are other problems. In addition, cordless phones, including those for business use, cannot be used for data transmission as they are because cordless phones use analog transmission and are line-controlled. ■Since radio waves are used, frequency-directed utilization technology is most important, and line switching using cordless phones is not suitable. ■Current cordless phones do not have any shadow intrusion measures, so there are many undetectable areas such as the shadows of premises fixtures. There are other problems. Furthermore, message pagers have many of the same drawbacks, and cannot meet the essential requirements described at the beginning. Considering the above points, a wireless network that satisfies at least the essential items explained at the beginning is a two-way wireless packet network that can packetize any media and handle it comprehensively and at high speed. However, such a network does not exist. Also,
The above-mentioned conventional wireless services fail to satisfy not only the essential item (■■) described at the beginning but also (■■). By the way, in order to improve the reliability of the wireless unit in small zone wireless networks etc. (this corresponds to the essential item ■ explained at the beginning),
The effectiveness of macroscopic diverging is demonstrated by a known example (■BEl?NII^RDT, R, C, :R1'
performance or macroscope
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onIEEE, Proc, GCOM 874g-
1) It is more obvious. In addition, these documents and the paper by the present inventors (Kanbara, Serizawa) (IEICE Technical Report RC389-12r Aloha Wireless Communication System with Slots Equipped with Multiple Base Stations) have introduced macroscopic diversity and multiple base stations. It has been stated that this has an extremely high effect on frequency utilization efficiency. In particular, IEICE technical report RC389-12 indicates that high throughput (high frequency utilization efficiency) can be obtained in wireless packet communication. However, this paper does not describe at all how to select one desired packet from a plurality of packets, nor does it disclose the same. On the other hand, as a packet selection method for macroscopic diversity, "^Radi. Access 5cheIlle I"or C by the present inventor
8MA/CD LAN, Proc, Icc'
8915,4° shows a method using bus contention, but this method was originally intended for C3MA/CD LANs, which are small-scale LANs, and is not suitable for large-scale networks that cover a wide area. . In addition, other traditional macroscopic diversity (
One method, for example, as shown in Figure 8, is to provide a diversity selection circuit 3 between port 1 and exchange 2, and to switch and combine between predetermined diversity techniques 4.4. . However, such a macroscopic diversity configuration does not provide flexibility with respect to changes in zone size, addition of wireless ports, and the like. That is,
In the method shown in the figure, since the correspondence between the zone configuration and the diversity selection technique is strictly determined, it is possible to reduce the size of the zone,
When expanding, dispersing, etc., the diversity selection circuit 3 must be re-constructed from the fundamental point. (Problems to be Solved by the Invention) As described above, conventional networks 1. With the construction method (1), it was not possible to construct a small zone wireless system or a local wireless network that satisfied the conditions of the essential items (2) to (3) explained at the beginning. Therefore, the purpose of the present invention is to: -Effective use of frequencies -Flexibility for networks and signals that can be transmitted (multimedia compatible) -High reliability -Capable of constructing a network that satisfies the breadth of the service area and its flexibility against fluctuations. It provides an exchange.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides an exchange that sends out packet-like signals input from a plurality of input lines to one of a plurality of output lines according to the destination of each packet-like signal. When a plurality of identical packet-like signals are input from the input line within a predetermined time, only one packet-like signal among these packet-like signals is sent to the output line according to the destination of this packet-like signal. be. A second aspect of the invention is an exchange that sends out packet-like signals input from a plurality of input lines to one of a plurality of output lines according to the destination of each packet-like signal, in which a plurality of identical signals are sent from the plurality of input lines. When a packet-like signal is input within a predetermined time, only one packet-like signal predicted to have the least transmission error among these packet-like signals is sent to the output line corresponding to the destination of this packet-like signal. It is something to do. The third invention is 1. In the exchange according to claim 2, after only one packet signal among the plurality of identical packet signals is sent to an output line corresponding to the destination of the packet signal, the destination side of the packet signal When a packet signal is input to the side that has issued multiple identical packets, the output line connected to or closest to the input line to which one packet signal among the plurality of identical packet signals is input. A packet-like signal is sent from the destination side. (Function) In the present invention, when multiple identical packets are sent to an exchange, only one packet is sent to the exchange corresponding to the destination, so multiple wireless ports can be provided in the same service area. be able to. Therefore, effective frequency utilization and reliability improvement can be achieved by the macroscopic effect. Additionally, since multiple wireless ports can exist within the same service area, even if the wireless zone location is changed or macroscopic diversity technology is added, there is no need to change the exchange or its peripheral circuits. , it is possible to realize macroscopic diversity. That is, it is extremely flexible with respect to changing wireless zones, expanding or contracting service areas, etc. Furthermore, by actively performing macroscopic diversity using such exchanges, no changes will be made even when using extremely large numbers of diversity of 4 or more for use under extremely poor conditions or high traffic conditions. It can be used without Therefore, it is possible to construct a network that satisfies (1) effective use of frequencies, (2) flexibility in terms of the network and the signals that can be transmitted (multimedia support), (2) high reliability, and (2) flexibility in dealing with the wideness of the service area and its fluctuations. (Example) Hereinafter, details of an example of the present invention will be described based on the drawings. FIG. 1 is a diagram showing an embodiment in which a switching device according to the present invention is applied to a wireless communication system. In the figure, reference numeral 11 indicates an exchange according to the present invention. Each exchange 11 is connected to each other, and each exchange 11
A wireless port 12 is connected to the , and packet-like signals (hereinafter simply referred to as packets) are exchanged. The wireless port 12 has a wireless communication function, forms a wireless line with various wireless communication terminals 13, and exchanges packets. Specifically, between the wireless communication terminal 13 and the wireless port 12, all information such as audio, images, and data is divided into packets of a standardized size, and the packets are divided into packets using the slotted Aloha method, C8MA method, etc. is sent and received. FIG. 2 is a diagram schematically showing the configuration of the above-mentioned exchange 11, which employs a common buffer system. In the figure, 14 indicates a multiplexer that arranges packets sent from each wireless port 12 on one signal line. The packets arranged on this signal line are sequentially input to the buffer 15. Then, the packet output from the buffer 15 passes through the switch 17 and is sent to the demultiplexer 18. The demultiplexer 18 selects one output line from a plurality of output lines connected to other exchanges according to the destination of the packet, and sends the packet to that output line. Here, the buffer 15 is connected to an identical packet detection device 16 that detects identical packets from among the packets latched in the buffer 15. Then, when the same packet detection device 16 detects the same packet,
The switching of the switch 17 is controlled so that only one packet out of these packets is sent to the demultiplexer 18. Next, the operation of the communication system configured as described above will be explained. It is assumed that a plurality of wireless ports 12 exist within the same service area indicated by the broken line in the figure. When a packet is transmitted from the wireless communication terminal 13 within this service area, all the wireless ports 12 existing within this service area receive the packet, and multiple identical packets are sent to the exchange 11. Ru. In the exchange 11, these packets are sent to the demultiplexer 1.
8 is latched into a buffer 15 that passes through it. At this time, since there are identical packets latched in the buffer 15, the same packet detection device 1
This is detected by 6. Therefore, buffer 15
These same packets output from switch 17
Due to the switching, only one packet is sent to the demultiplexer 18. This packet is then sent by the demultiplexer 18 to an exchange corresponding to the destination of the packet. In this way, in this embodiment, when multiple identical packets are sent to an exchange, only one packet is sent to the exchange corresponding to the destination, and the remaining packets are discarded, so they can be sent to the same service area. Multiple wireless ports within 1
2 can exist. Therefore, effective frequency utilization and reliability improvement can be achieved by the macroscopic effect. In addition, multiple wireless ports 12 within the same service area
Even if there is a change in the radio zone arrangement or the addition of macroscopic diversity techniques, macroscopic diversity can be realized without changing the exchange 11 or its peripheral circuits. I can do it. That is, it is extremely flexible with respect to changing wireless zones, expanding or contracting service areas, etc. Furthermore, by actively performing macroscopic diversity using such an exchange 11, even when using diversity with an extremely large number of techniques of 4 or more for use under extremely poor conditions or high traffic conditions, It can be used without any modification. Therefore, by using the switching equipment of this embodiment, it is possible to improve the flexibility (multiple (media compatible) ■ High reliability ■ Able to satisfy wide service area and flexibility for its fluctuations. Next, an embodiment in which the present invention is applied to an output buffer type exchange will be described. Fig. 3 shows this exchange. 2 is a diagram schematically showing the configuration of the switch. In the switch shown in the diagram, each packet output from the switching element 22 is sent to a buffer 23 according to the destination.
is output to. The same packet detection device 24 is connected to each buffer 23 . When the same packet detection device 24 detects that the same packet exists in the buffer 23, a switch 25 provided on the output side of each buffer 23 detects that the same packet exists in the buffer 23.
Packets are selected and discarded in the same manner as in the first embodiment. Next, an embodiment in which the present invention is applied to a distributed buffer type exchange will be described. FIG. 4 is a diagram schematically showing the configuration of this exchange. In the exchange shown in the figure, packets output from each buffer 26 are input to a switching element 27. Two identical packet detection/discard circuits are connected to each switching circuit 28 provided in the switching element 27, and packets are selected and discarded. It should be noted that the present invention is applicable not only to the above-mentioned types of exchanges, but also to various types of exchanges such as the Banyan switch, the input buffer type, the common buffer type, etc. It is also possible to introduce it into a packet switch that performs software processing. However, especially in the case of the output buffer 7 system shown in FIG. 2, the configuration is particularly easy because the same packets are collected in the same buffer. That is, since all the same packets input from the accumulated input terminals are collected in the same output buffer, there is no need to compare packets between different buffers. Next, another embodiment of the present invention will be described. In this embodiment, first, a wireless boat is constructed as shown in FIG. In the figure, 30 is an antenna, and this antenna 3
The RFi signal received from 0 is multiplied by the output of the local oscillator 31 and the multiplier 32, converted into a baseband signal, and input to the demodulator 33. A reliability data detection circuit 34 is connected to this demodulator 33 . This reliability data detection circuit 34 determines the reception power at the time of reception, the reception power of the received packet, S! The likelihood function (11ke-l1ho
This detects packet reliability data such as od ('unction). Then, the Ri-added reliability data is added to the corresponding packet in the reliability data adding circuit 35 and sent to the exchange side. On the other hand, the exchange has a configuration as shown in FIG. That is, the buffer 36 includes a FIFO 36a and a delay device 36b.
The same packet detection circuit 38, which is made up of a combination of comparators 37, determines whether or not the packets in the delay device 36a are the same. If the same packets are detected, the packet discard control circuit 39 compares the reliability data of these same packets and switches the switch 40 so that the packet with the best reliability data is sent to the demultiplexer. control. Thereafter, the packet output from the switch 40 is sent to the demultiplexer side via a reliability data removal circuit 41 that removes unnecessary reliability data. As described above, in this embodiment, when identical packets/sotos exist, the highly reliable packets/sotos are left and the less reliable packets are discarded, so that even higher reliability can be obtained. Furthermore, after this unique and highly reliable packet is sent to the other party, the other party will not send a reply to the wireless communication terminal that sent this message. If so, the switch may select the input line on which the only reliable packet was sent and send the responding packet back. That is, the input line through which the only highly reliable packet was transmitted is naturally also highly reliable for the opposite route. Next, another embodiment of the present invention will be described. First, when each wireless port receives a packet, highly reliable packets are delayed immediately after receiving them, and unreliable packets are delayed by a time that decreases depending on their reliability. After that, the destination sends the packet to the switch. In the exchange, as shown in FIG.
3, and each comparator 44 determines whether the packet is the same as each packet in the delay device 43. Then, the output of each comparator 44 is sent to the switching control side of the switch 46 via an OR circuit 45. Therefore, by switching the switch 46, the packet that arrives earliest from a plurality of identical packets is selected. In this way, in this embodiment, the probability that the most reliable packet among a plurality of identical packets will arrive at the bus sofa 42 of the exchange earliest is highest. However, this probability depends on Trabik. Therefore, highly reliable packets can be obtained by configuring the exchange to select the earliest packet from a plurality of identical packets and discard the second and subsequent packets as described above. Furthermore, since the switching equipment of this embodiment does not use a delay device as shown in Fig. 6, the time required for switching can be shortened, and it is extremely advantageous for transmitting signals such as voice that cannot tolerate large delays. It is. The above-described embodiments are based on the assumption that the exchange according to the present invention is applied to a wireless communication system, but the exchange according to the present invention can also be applied to a wired communication system. For example, the switch according to the present invention is used in a conventional public network. However, when the switch in the above-described embodiment sends multiple identical packets from the terminal side to another switch,
In this case, when the exchange sends multiple identical packets from another exchange to the terminal side, it sends only one packet to the terminal side. Do it like this. For example, when an emergency call occurs, the originating exchange that receives the call sends packets related to the call to multiple routes. The destination exchange uses the function according to the present invention to send only packets related to the first received call to the destination terminal. Therefore, in this case, it is possible to shorten the packet transmission time as much as possible. In other words, in conventional public networks, a route is selected by estimating the route with the shortest transmission time, but for example, if a certain point within this route becomes congested, etc. However, sometimes the route was not always the shortest. Therefore, by transmitting packets along multiple routes as described above, it is possible to always transmit packets using the shortest route. [Effects of the Invention] As explained above, according to the switching system of the present invention, ■ Effective use of frequencies ■ Flexibility for networks and signals that can be transmitted (multimedia compatible) ■ High reliability ■ Width of service area and its fluctuations It is possible to build a network that satisfies flexibility.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a diagram showing an embodiment of the switch according to the present invention applied to a wireless communication system, and FIG. 2 schematically shows the configuration of the switch shown in FIG. 1. Figure, Figure 3, Figure 4, Figure 6
5 and 7 are diagrams showing other examples of the switching equipment of the present invention, and FIG.
8 is a diagram showing the configuration of a wireless boat according to another embodiment of the present invention, and FIG. 8 is a diagram showing the configuration of a conventional wireless communication system. 11... Exchange, 12... Wireless port, 13...
Wireless communication terminal, 14... multiplexer, 15...
Buffer, 16... Same packet detection device, 17...
- Switch, 18... Demultiplexer.

Claims (3)

[Claims] (1) In an exchange that sends out packet-like signals input from a plurality of input lines to one of a plurality of output lines according to the destination of each packet-like signal, a plurality of identical packet-like signals are sent from the plurality of input lines. is input within a predetermined period of time, the switching equipment is characterized in that only one packet-like signal among these packet-like signals is sent to the output line according to the destination of this packet-like signal. (2) In an exchange that sends out packet-like signals input from a plurality of input lines to one of a plurality of output lines according to the destination of each packet-like signal, a plurality of identical packet-like signals are sent from the plurality of input lines. is input within a predetermined time, only one packet-like signal predicted to have the least transmission error among these packet-like signals is sent to the output line corresponding to the destination of this packet-like signal. An exchange machine that does. (3) In the exchange according to claim 2, after only one packet-like signal among a plurality of identical packet-like signals is sent to an output line corresponding to the destination of this packet-like signal, the destination of this packet-like signal is When a packet-like signal is input from the side to the side that has issued the plurality of identical packets, one of the plurality of identical packet-like signals
A switching system characterized in that a packet-like signal from the destination side is sent to an output line connected to or closest to an input line into which the packet-like signal is input.