JPH0329338B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention is based on competition for a broadband frequency channel in a frequency division multiplexing network that transmits all types of information such as video, audio, voice, and data over a single transmission path. This relates to a method using band control signals.

<Background> With the advancement of the information society, even within Iesada,
In addition to home security systems with sensor networks for crime and disaster prevention, home telephones with functions such as intercoms, door phones, and parent-child telephones have been put into practical use, and it is expected that the so-called home information communication network will further develop in the future. It will be done. Home appliances that have traditionally been used at home,
By incorporating microcomputers, etc., it will become intelligent and will be incorporated into the home information and communications network along with new media devices such as CATV, teletext, and captains, and in the future, all of these devices will be integrated into the home computer. The idea is to save energy and labor by monitoring and controlling the system.

In this way, the home information communication network
It must handle various signals such as control signals, audio signals, and video signals, and the system must be easy to expand and change, be highly productive and economical, and be designed so as not to damage its appearance. Must be.

Currently, home transmission media include wireless media such as weak radio waves and infrared rays, and wired media such as coaxial cables, twisted pair wires, and optical fiber cables. However, when using a wired medium, it is unrealistic to run as many lines as there are devices in terms of scalability and appearance. is essential. Possible techniques for multiplex transmission include (i) frequency division multiplexing, (ii) time division multiplexing, and (iii) code division multiplexing.

At present, the frequency division multiplexing method (i) is considered to be the most practical in terms of economic efficiency for home use. Furthermore, the home public listening systems that are already in widespread use only distribute on-air TV broadcast waves from antennas to each room, and cannot be said to fully utilize the broadband transmission characteristics of coaxial cables. is the current situation. Therefore, if unused frequency bands are used for the transmission of digital signals, audio signals, etc., there is no need for wiring work, and it is superior in terms of system changes and expansion, as well as aesthetics. Multiplex transmission is an extremely reasonable concept.

Now, in a frequency division multiplexing network such as the one described above, it must be decided how to use frequency channels. In order to communicate between two modules, the frequency channels used must match, so if you want to communicate between arbitrary modules, each module must be configured to use all frequency channels. There must be.

That is, two modules that want to start communication search for an empty channel by some method, and after confirming that they will communicate on that channel, they start actual communication. Therefore,
Each module requires a way to find an empty channel and a configuration that allows it to vary the frequency channel it uses before communicating.

OBJECTS OF THE INVENTION The present invention provides a method for ensuring that two modules attempting to communicate can compete for a free channel. That is, when the calling module searches for an empty channel using a carrier detection circuit that searches the used frequency band, it sends a calling packet containing the channel information to the called module, and the called module receives it.
If your carrier detection circuit confirms that the channel is truly empty, it immediately returns an acknowledgment packet, and also ensures that no packets from other modules interrupt these two packets. This is a competition for channels.

<Examples> Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 4 shows how each module is connected to the network, and FIG. 5 shows an example of the configuration of the interface section of the module.

Reference numeral 10 in FIG. 4 denotes a transmission line constituting the network, which is called a bus, and is made up of, for example, one coaxial cable. Modules 11 to 14 are connected to the bus, and one module consists of a device 15 and an interface 16 to the bus.

FIG. 5 shows a detailed configuration of the interface 16, which mainly consists of a baseband section 20, a broadband section 21, and a control section 22, and is connected to the equipment 15 by a demodulation output line 36 and a modulation input line 37. The connection format with this device 15 is not unique;
This varies depending on the device, and the interface section may also vary slightly. The baseband section 20 consists of a baseband control section 23, a transmission section 24, and a reception section 25, and the control section 22 is comprised of data transmission lines (multiple) 3
0, a transmission start line 31, a transmission completion line 32, and a reception completion line 33. Broadband part 2
1 is a carrier detection section 26, a demodulation section 27, a modulation section 2
At the same time, the carrier detection output is input to the control section 22 through a line 35, and at the same time, the entire broadband section 21 is controlled by a signal on a control line (multiple lines) 34.

First, an overview of the baseband protocol will be explained.

The baseband line competition method is CSMA/CD
It is a type. In other words, the module attempting to transmit first checks whether the bus is idle (there are no transmission signals from other modules on the bus) before transmitting a signal onto the bus, and then checks to see if there are any abnormalities in the transmitted signal ( Continuously check to see if there are any collisions with other modules' transmission signals. If there is an abnormality, it will stop its own transmission and attempt to retransmit after a certain variable amount of time. Also, if the bus is busy in advance (there are transmission signals from other modules on the bus), the module waits until the bus becomes idle (its transmission is completed) and starts its own transmission after a certain period of time.

FIG. 6 shows the timing when two signal packets are transmitted successively.

In the figure, 40 is a signal packet of a certain module,
41 is a signal packet of another module which is about to start transmission during the _T2 period. Here, it is shown that the next packet 41 cannot be sent until at least a period _T1 has elapsed since the previous packet 40 was completed. Furthermore, even after T ₁ period, αT ₀ (an integer of α0) depends on the type of module and the type of signal.
Only later can packet 41 be sent out.

If two or more modules try to start transmitting within period _T2 , those packets will start transmitting almost simultaneously after time _t0 , so what is the α of both packets at that time? The question is: If α is different, the packet with the smaller α will be sent out first, and the packet with the larger α will have to wait for transmission again. A collision occurs when α is the same. That is, α is a factor that determines the priority of packets in bus contention, and the smaller α is, the higher the priority is. _T1 is a period provided to complete packet separation.

The detailed timing and protocols mentioned above are explained in the 5th section.
Since everything is managed by the baseband control section 23 in the figure, the control section 22 cannot be directly involved and only knows through the control lines 30 to 33. The data transmission line 30 is a line through which transmission data is sent from the control section 22 to the baseband control section 23 at the time of transmission, and conversely receives received data at the time of reception. The transmission start line 31 is a control line for starting transmission to the baseband section 20, and the transmission completion line 32
is a control line indicating that transmission has been completed normally, and reception completion line 33 is a control line indicating that data addressed to itself has been successfully received and completed.

In Figure 7, module 11 becomes module 12,
A time chart on the bus when the module 13 transmits data to the module 14 with a slight delay and the operation of the control lines 31 to 33 of each module are shown.

42 is a transmission packet from module 11 to module 12, and 43 is a transmission packet from module 13 to module 14. At time _t4 , the control section 22 of the module 11 tries to start transmission and sends a transmission start signal 31 (using the same code as the control line,
(The same applies hereafter), the baseband control unit 23 can immediately output the transmission packet 42 since the bus is idle. Module 13 at time t ₅
The control unit 22 of the module 1 issues a transmission start signal 31 in an attempt to transmit data to the module 14, but the module 1
Since the bus is busy, the baseband control unit 23 of No. 3 waits for transmission.

When the packet 42 is completed at time t ₆ , the baseband control section 23 of the module 11 issues a transmission completion signal 32 , and the baseband control section 23 of the module 12 issues a reception completion signal 33 . T ₁ + from t ₆
At time t ₇ , delayed by αT ₀ , the transmission request of module 13 that occurred at t ₅ becomes packet 43 and is transmitted to module 14, and at t ₈ , the transmission request of module 13 is sent to module 14.
Then, the transmission completion signal 32 is output, and the module 14 outputs the reception completion signal 3.

What should be noted here is the timing of the transmission packet 43 of the module 13. If the bus is idle and there are no collisions, as in module 11, and the transmission packet 42 is output immediately, the time width of the transmission start signal 31 and transmission completion signal 32 can be easily determined from the time width of the transmission packet 42 that the module 13 outputs. If the transmission packet 43 is delayed due to the bus not being idle or due to a collision, the completion of transmission will naturally be delayed and the time cannot be predicted from the control section 22's perspective. In other words, even if it issues the transmission start signal 31, the controller 22 has no idea how many packets from other modules have appeared on the bus during that time.

Next, how to use the broadband channel will be explained.

In principle, any signal can be handled by the broadband channel, including data signals other than those handled by the baseband, analog signals such as audio and video, and RF.
The simplest form is that each signal occupies one frequency channel during communication. At the same time, as the number of modules communicating increases, finding a new empty channel to communicate with is the most flexible and efficient way to use frequencies. Instead, each module is configured to be able to communicate on any frequency channel, and the channel to be used must always be determined prior to communication.

The present invention reliably performs channel contention between two modules attempting broadband transmission using the baseband control protocol described above.

FIG. 1 is a time chart explaining this method. A case is shown in which module 11 communicates with module 12 using channel n.

At time _t9 , module 11 searches for an empty channel and confirms that there is no carrier on channel n. Immediately after the control unit 22 recognizes this,
At t ₁₀ , the transmission start signal 13 is output to the baseband controller 23 . At that time, if there is no carrier on the baseband bus, the communication request packet 44 containing channel n information is sent to the module 12.
Send to. At time _t11 , a transmission completion signal 32 is output to the control line of the module 11, and a reception completion signal 33 is output to the control line of the module 12 to notify the control unit 22. The control unit 22 of the module 12 learns that the packet 44 is a communication request packet using channel n, confirms that there is no carrier for channel n at time _t12 , and transmits the packet at time t12.
At _t13 , an acknowledgment (ACK) packet 45 is sent to the module 11.

Here, by setting t ₁₃ −t ₁₁ =T ₁ and α=0, it is guaranteed that this acknowledge packet 45 is always output at timing t ₁₃ . That is, by setting all other packets to α1,
The timing of t ₁₃ is determined so that no collision will occur. And module 12 is almost t ₁₃
At the timing, a frequency division multiplexing (hereinafter simply abbreviated as FDM) carrier 50 is sent to channel n. Once a carrier appears on channel n, other modules cannot interrupt this channel unless this carrier disappears, so modules 11 and 12 are occupied and can use this channel n. .

If the module 12 checks channel n at time _t12 and there is a carrier, it will not return an acknowledgment (ACK) packet 45 at time _t13 .
At this time, a non-acknowledgement (NAK) packet (described later, Fig. 2, 49) is returned, and the module 11
learns that it is not possible to communicate using channel n.

Note that if the called module 12 itself is in a busy state, it will of course return a non-acknowledge (NAK) packet regardless of whether there is a carrier or not. The above is called module 12
This is a case where the user is an idol and there is a carrier when channel n is checked at time _t12 .

The question then becomes why a carrier appears at time t ₁₂ on channel n, which had no carrier at time t _9. This case is shown in FIG. 2.

In Figure 2, module 11 is connected to module 12.
If module 13 tries to start communication with module 14 almost simultaneously using channel n, module 13 checks channel n at time t ₁₅ and module 11 checks channel n at time t ₉ and determines that there is no carrier in either case. However, this is when the modules 11 and 13 output the transmitting signal 31 almost simultaneously. Assuming that the communication request packet 46 issued by the module 13 is given priority on the baseband, the modules 13 and 14 receive the packet at time _t18 in the same sequence as in FIG.
At time _t12 , when module 12 examines channel n, carrier 5 has already arrived.
0 appears.

That is, although no other packets will intervene between packets 44 and 45 in FIG. ₁ , as shown in FIG. Since there is a possibility that a packet of 1000 will interrupt and use channel n, it is necessary to check the carrier of channel n again at time _t12 .

On the other hand, as long as there is a check at time t ₁₂ , a check at time t ₉ seems unnecessary, but module 12
The time from receiving the communication request packet 44 (time t ₁₁ ) to interpreting the packet and issuing an acknowledgment (ACK) packet 45 or non-acknowledge (NAK) packet 49 (time t ₁₃ ) is T ₁ . Since t is simply a time for distinguishing between packets, making it too large is undesirable as it lowers baseband utilization efficiency, and carrier detection at time _t12 needs to be performed in a short time. Therefore, during this time, it is difficult to search for an empty channel and perform carrier detection (which takes time as the number of channels increases as the frequency is scanned) to determine the channel to be used. This is to check whether there is a carrier or not.

In FIG. 3, module 11 issues a communication request to module 12, and module 12 sends a communication request to channel n.
An example is shown in which a carrier is sent to the module, but in this case only unidirectional communication from module 12 to module 11 is possible. Considering two-way communication such as a telephone call, not only one channel but two communication channels are required, and a method for competing for channels in such a case is shown in FIG.

Channel n means channel n _L and channel
Specifies that it must be used in pairs of n _{and U.} During unidirectional communication, only one channel is used; the other channel is actually free, but other modules are not allowed to use it. Therefore, detection of the presence or absence of a carrier is performed on the channel that is also used for unidirectional communication (n _L in Figure 3).
The module 12 detects the absence of a carrier on channel _nL at time _t12 , and at time _t13 outputs an acknowledge (ACK) packet 45 and at the same time outputs a carrier 50 on _nL . The module 11 that received the acknowledgment (ACK) packet 45 at time _t14 ,
Sends own carrier on channel n _U as 51. Other modules are then channel
Looking at the carrier on n _L , we know that these channels n _L and n _U cannot be used. module 11 to 1
Transmission to module 2 takes place using carrier 51 on channel _nU , and transmission from module 12 to module 11 takes place using carrier 50 on channel _nL .

<Effects of the Invention> As described above, the present invention reliably controls broadband channel contention in the baseband in a network that handles baseband control signals and various broadband signals, and does not require any special protocol for broadband signals. The present invention provides a system that allows efficient use of frequency channels without having to use a single bus, and is extremely useful for transmitting audio, music, video, RF signals, etc. on one bus.

[Brief explanation of the drawing]

FIG. 1 is a timing diagram at the time of channel contention showing an embodiment of the present invention, and FIG. 2 is a timing diagram at the time of channel contention in a situation different from that in FIG. 1.
Fig. 3 is a timing diagram during channel contention in two-way communication, Fig. 4 is a system diagram showing an example of a network configuration, Fig. 5 is a block diagram showing a detailed example of the interface part in Fig. 4, and Fig. 6 The figure is a timing diagram showing a basic example of transmission and reception of baseband packets, and FIG. 7 is a timing diagram showing a specific example of the same control. 10...Network bus, 11-14...Module, 15...Device, 16...Interface, 20...Baseband section, 21...Broadband section, 22...Control section, 26...Carrier detection section , 31... Transmission start signal (line), 32... Transmission completion signal (line), 33... Reception completion signal (line),
44, 46... Communication request packet, 45, 47...
...Acknowledge (ACK) packet, 49...Non-acknowledge (NAK) packet, 50, 51
...broadband carrier.

Claims (1)

[Claims] 1. In frequency division multiplexing transmission including baseband, occupation of a broadband frequency channel,
In a network in which opening is controlled by baseband packets, the transmitting station searches for an empty channel by varying the reception frequency for carrier detection, sends out a communication request packet containing the found channel information, and the receiving station performs the communication. When a request packet is received,
The transmitter itself re-detects whether one channel specified in the information in the packet is empty, and based on the re-detection result, sends an acknowledge (ACK) packet or non-acknowledge packet to the transmitting station in preference to other packets. (NAK) packet and redetection of the specified one channel is performed within a limited period between receiving the communication request packet and returning the acknowledge (ACK) packet or non-acknowledge (NAK) packet. Broadband channel competition method.