JP2004007492A - Retransmission control system in data communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the re-collision of retransmitting data in the event of collision of transmitted data in a data communication over a shared media type network using indoor power lines or radio means, etc. <P>SOLUTION: If a transmitted packet is longer than a basic packet length of (n) slots, a system decides that data have collided. It takes an interval of (k) slots next to a slot at the end of the packet and transmits a basic packet by broadcasting for requesting the retransmitting with the next slot thereto set at a head. When a node sends a usual basic packet by itself, the system takes an interval of k slots next to its end. If there is a signal of (n) slots with the next slot thereto set at the head, it takes an interval of three or more slots from the end of its retransmit request packet, gives a sequence 1 to the next slot, and transmits the retransmitting packet with a head slot of a sequence corresponding to its own node address. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data communication using a spread spectrum communication system or an orthogonal frequency division modulation system, particularly, in a data communication of a shared media type network using an indoor power line or wireless, a data collision occurs and transmission data is generated on a receiving side. The present invention relates to a retransmission control method for controlling retransmission of data when restoration cannot be performed.
[0002]
[Prior art]
As a shared media type network, a CSMA / CD system represented by Ethernet is widely used (for example, see Patent Document 1). This method checks whether a data signal exists in a network prior to data transmission, and immediately starts data transmission when it does not exist. However, even with such a method, it is not possible to avoid collision based on data propagation delay.
[0003]
For this reason, it monitors whether the transmitted data does not collide with data transmitted from another node, stops the data transmission immediately upon detecting the collision, and issues a jam signal indicating the occurrence of the collision. Thereafter, the CSMA / CD system is a system in which transmission is retried after a certain period of time has elapsed.
[0004]
[Patent Document 1]
JP-A-6-276199
[Problems to be solved by the invention]
However, in the CSMA / CD method, the probability of occurrence of a collision again at the time of retry depends on how each node calculates the predetermined time. In addition, in the CSMA / CD system, when each node generates a random number P, retransmission starts after a lapse of 2P after the occurrence of a collision. However, if the generated random numbers match, collision occurs again. When a collision occurs, data transmission is delayed and the network may be congested.
[0006]
The present invention has been made in view of such circumstances, and in data communication of a shared media type network using an indoor power line or radio, when transmitted data has a collision, when the data is retransmitted, It is another object of the present invention to provide a retransmission control method capable of avoiding collision at the time of retransmission.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for dividing a transmission time of a basic packet, which is a basic unit of data communication, into n divisions (n = 1, 2, 2, 3) at the timing of each node in a data communication network using an indoor power line or wireless communication. ...) And a slot clock generating means for generating a slot clock for setting the division unit as a slot to be a unit of transmission time, and h slots (h = 5, 6,...) After transmission of the basic packet A means for taking a silence time between the next packet transmission with the above-mentioned fixed number of slots as a gap, a determining means for determining whether a transmitted packet is longer than n slots of the basic packet length, If the determination means determines that the length is longer than n slots, the next k slots (k = 1, 2,...; K <h) of the slot at the end of the packet are used. As a gap, a transmitting means for broadcasting a basic packet requesting retransmission with the next slot at the head, and when the node itself transmits a normal basic packet, the next k slot at its end is set as a gap, Detecting means for detecting whether or not there are n or more signals in the next slot at the head, and detecting a signal requesting retransmission or a mixed signal in which these packets collide with each other. Sometimes, the next slot after a gap of j slots (j = 3, 4,...; K <j <h) from the end of the packet for which retransmission is requested is designated as order 1 and its own node address. And a retransmission unit for transmitting a retransmission packet with a slot in an order corresponding to
[0008]
In the present invention, since it is assumed that a spread spectrum method or an orthogonal frequency modulation method is difficult to detect whether a collision has occurred, a basic packet is introduced as a unit of data communication. In addition, in order to measure the length of the basic packet and control the start of transmission of the next packet after the end of the packet, a slot obtained by dividing the basic packet into n (n = 1, 2,...) Introduce as a unit.
[0009]
The collision is detected by checking whether or not the length of the received packet is exactly n times the slot length. If the length is longer than that, it is determined that a collision has occurred. When a collision is detected, the slot next to the collision detection is used as a gap, and a packet for a retransmission request is transmitted from the next slot. The collision detection packet may also collide, but if it is assumed that only a retransmission request packet can be transmitted in one slot after one packet ends, the collision is caused by the packet being transmitted there. It turns out that it has happened. Then, the next slot after the gap of two slots next to the end of the retransmission request packet is set to order 1, and the slot in the order corresponding to the node address is a slot that can be retransmitted by the own node, thereby performing retransmission. Collision can be prevented.
[0010]
In the present invention, instead of the retransmission unit, when the transmission unit detects a packet requesting retransmission or a signal in which they collide with each other and coexist, the j slot (j = j = j) from the end of the packet requesting retransmission. 2, 3,...; The next slot having a gap of k <j <h) is set to order 1, and a predetermined order m (m = 1, 2,. In addition, the node in the order m may have a means for transmitting the retransmission packet with the slot in the order 2m-1 at the top.
[0011]
Similarly, instead of the retransmission packet transmitting means described above, when the transmitting means detects a packet requesting retransmission or a signal in which the packets collide with each other and are mixed, the j slot (from the end of the packet requesting retransmission) .. j = 2, 3,...; the next slot having a gap of k <j <h) is designated as order 1, and a predetermined order m (m = 1, 2,. ), The node in the order m may have means for transmitting the retransmission packet with the slot in the order {(n + 3) m− (n + 2)} at the top.
[0012]
Each functional unit (means) constituting the data retransmission control method of the present invention is provided, for example, at each node connected to a communication network.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
First, an outline of an embodiment of the present invention will be described for each item.
[0014]
[Basic packet transmission]
In the present embodiment, the basic data transmission unit of the data communication system is an 8-byte (64-bit) packet, which is referred to as a basic packet. Since the data transmission speed is 2 Mbps, the basic packet is 32 μsec long.
[0015]
In each node, the time corresponding to half the length of the basic packet, that is, the time corresponding to the transmission of 4 bytes is called a slot, and this is used as the basic time unit of data transmission. Therefore, the basic packet is transmitted using two slots. This division into slots is performed independently by each node, and phase adjustment between nodes is not performed.
[0016]
The transmission of the basic packet is performed without taking measures for avoiding collision. First, it is confirmed that no other signal exists in the shared medium, and transmission is started from the head of its own slot. This helps to prevent collisions since the beginning of this slot is slightly offset between nodes. The reason will be described with reference to FIG.
[0017]
In FIG. 1, when the node A sends out the basic packet 11, a signal is transmitted with a propagation delay indicated by 12, and the signal transmitted by the node A reaches the node B slightly before the time point 13 at the head of the slot. Node B does not send out data in slots starting at 13. That is, it is useful for collision avoidance.
[0018]
However, the signal from the node A reaches the node C with the propagation delay indicated by 12 slightly later than the head 14 of the slot of the node C, so that the node C sends out the basic packet 15. Therefore, the packet of the node A and the packet of the node C collide. However, the end of the packet of the node A arrives at a point 17 slightly later than the end 16 of the packet of the node C. The node transmitting the packet monitors the signal on the slot, and the node C terminates the packet transmitted by itself. Even notice that there is a signal in the next slot. This indicates that a collision has occurred.
[0019]
In the present embodiment, as shown in FIG. 2A, when a basic packet is sent out or detected, it is ruled that three slots after the end of the basic packet are set to a silence time during which no data is transmitted. To Further, when the end of the basic packet is at a time other than the break of its own slot, the three slots following that slot are set to the silence time. As a result, it can be determined whether or not the basic packet transmitted by itself has collided.
[0020]
Upon detecting the collision, the node C issues a NAK (unreceivable) command in the gap of one slot shown in FIG. Although small in probability, the basic packet from node A and the basic packet from node C may completely overlap in node C in two slots. At that time, the node C cannot detect the collision.
[0021]
However, the phase of the basic packet from the node A and the phase of the basic packet from the node C are shifted from one another in any of the nodes in the network, and the basic packet is received out of two slots, so that a collision can be detected. At that time, the node that has detected the collision broadcasts a NAK command in one slot gap. Nodes A and C that hear this retransmit the basic packet.
[0022]
[Gap after packet end]
Next, the gap after receiving one normal basic packet will be described with reference to FIG.
[0023]
First, since the slot does not adjust the phase between nodes, the received basic packet 21 does not coincide with the end and end of its own slot. Therefore, the slot in which the end of the received basic packet 21 is located is ignored, and a gap is made from the next slot. That is, a case where only the slot of reference numeral 22 is a gap is referred to as a one-slot gap, a case where two slots of reference numeral 23 is a gap, and a case where three slots of reference numeral 24 are a gap. I do. Normal packets have at least a 5-slot gap and transmit in the next slot.
[0024]
Then, as shown in FIG. 2A, the normal packet 25 is transmitted with a 5-slot gap, that is, a silence time of 5 slots or more. By doing so, a node that detects a collision with respect to basic command transmission broadcasts a NAK command in a one-slot gap. Because collisions are likely to be detected at many nodes, NAK commands are also likely to collide. However, since only a NAK command can be transmitted in one slot gap, the presence of the command here means that a collision has occurred. A retransmission packet when a collision occurs is basically transmitted in a three-slot gap.
[0025]
FIG. 2B shows the reason why the slot gap of the retransmission packet in order 1 is set to 3. When the phases of the nodes A and B adjacent to each other match, the packet end R from another node is received separately on the opposite side of the slot boundary M when it is near the slot boundary M. Then, the count of the slot gap is shifted by almost one slot. Then, since the leading end S of the packet in the one-slot gap of the node B reaches the node A after the two-slot gap, if there is a packet in the two-slot gap, the node A transmits it (T). Would. In order to prevent this, it is necessary to provide a guard slot of one slot also in the slot gap, to provide a three-slot gap after the one-slot gap, and a five-slot gap next to the one-slot gap.
[0026]
[Configuration of Basic Packet]
FIG. 3 shows the configuration of an 8-byte basic packet. In the basic packet of FIG. 3, 8 bits are assigned to the destination address and the transmission address, and when the destination address is all 1, it means that all the addresses are to be received, which is called a broadcast. The next 8 bits specify the command. The NAK command requesting retransmission is one of them. The next 8 bits are used for control, and if 1 is set in the first bit, it means that the packet is a retransmission packet. Note that the auxiliary addresses and data 0 and 1 are not directly related to the present invention. The last 8 bits are redundant bits for error correction, which correct a transmission error occurring in the basic packet, so that retransmission due to an error does not occur in the basic packet.
[0027]
[Data retransmission control]
First, in the present embodiment, the rule is that if a collision occurs, no other packet is transmitted until a retransmission packet is transmitted.
[0028]
At the time of retransmission, the node of address 1 transmits a retransmission packet with a 3-slot gap, address 2 with a 5-slot gap, and address m with a (2m + 1) -slot gap. At this time, if a packet signal exists before the retransmission start slot, it is assumed that the slot (the number of packet slots + 3) does not exist, and the gap of (2m + 1) slots is counted. In this way, collision of retransmission packets can be prevented.
[0029]
Next, more specific embodiments of the present invention will be described.
[0030]
FIG. 4 is a block diagram showing the configuration of the embodiment of the present invention. In this embodiment, the basic packet is 8 bytes, and the slot length is half the basic packet length (4 bytes). The retransmission request packet is transmitted in a one-slot gap, and the retransmission packet counts the next slot in a three-slot gap as order 1. Further, it is assumed that a normal packet is transmitted in a gap of three slots or more. Each configuration (functional unit) shown in FIG. 4 is provided in each node connected to the network.
[0031]
In this embodiment, first, the clock generated by the basic clock generator 101 is sent to the 1 / 256-slot clock generator 102 to create a 1 / 256-slot clock having a slot length. Then, 256 clocks are sent and a slot clock is generated.
[0032]
On the other hand, the basic packet from the network is received by the basic packet receiving unit 104, and the received signal detecting unit 105 detects a signal from the beginning to the end of the received basic packet signal as a received signal period. The detection signal is passed to an AND circuit (logical product) 106. The AND circuit 106 calculates the logical product of the signal from the received signal detecting unit 105 and the 1/256 slot clock from the 1/256 slot clock generating unit 102, so that the 1/256 slot clock has the received signal. The detection signal from reception signal detection section 105 is sent to basic packet length counting section 107 for a period corresponding to the period.
[0033]
The length of the transmitted signal, that is, the length of the basic packet is counted by the basic packet length counting unit 107. The count value exactly matches the basic packet length is twice 256, that is, 512 counts. However, when the count is over, it means that a collision has occurred, and the collision detection unit 108 is notified of the occurrence of the collision. Inform.
[0034]
When the basic packet length matches 512 in the basic packet length counting section 107, the fact is notified to the content analyzing section 115, and the leading end detecting section 117 detects the leading end of the packet. Further, when a collision is detected by the collision detection unit 108, the fact is notified to the retransmission request packet generation unit 112, and information on the collision is supplied to the slot interval control unit 111.
[0035]
On the other hand, when requested to transmit a basic packet from the upper layer, the basic packet generator 109 generates a basic packet in accordance with the 5-slot gap information from the slot interval controller 111, and the basic packet transmitter 110 A slot clock corresponding to the leading end of the slot is received from the generator 103, and slot synchronization is performed.
[0036]
In the case of a normal packet, the basic packet transmitting section 110 starts transmission from the next slot with a gap of 5 slots from the end of the previous packet. When the transmitted packets collide with each other, the basic packet receiving unit 104, the received signal detecting unit 105, the AND circuit 106, the basic packet length counting unit 107, and the collision detecting unit 108 detect a collision by themselves. Generate a retransmission request packet.
[0037]
In addition, a retransmission request packet may be generated somewhere at one slot interval even if the collision detection device does not detect the collision. In this case, the basic packet received by the basic packet receiving unit 104 is analyzed by the content analyzing unit 115. If the analyzed content is analyzed by the gap information from the slot interval control unit 111 as a retransmission request, the determining unit At 116, it is confirmed that the request is a retransmission request for its own transmission.
[0038]
When the retransmission request for the own transmission becomes clear in this way, a retransmission packet is generated in retransmission packet generating section 114. However, the retransmission start timing of the transmission right slot detection unit 113 is obtained from the slot interval control unit 111 from the end of the collision signal with information on the three-slot gap, the next slot is in order, and the size of the own address is in order. This is generated by counting the slot clocks sent from the slot clock generation unit 103 up to.
[0039]
Next, upon receiving the collision detection information from the collision detection unit 108, the retransmission request packet generation unit 112 generates a retransmission request packet in one slot gap transmitted from the slot interval control unit 111 and transmits it to the basic packet transmission unit 110. Ask for.
[0040]
The basic packet length counting unit 107 counts the received basic packet length, and when the count value matches 512, supplies it to the content analysis unit 115 to inform that the collision of the received packet has not been detected. If the result of the analysis is for your own address, inform the higher rank.
[0041]
When there is a signal in one slot interval in the content analysis unit 115, the fact is transmitted to the determination unit 116. The retransmission request packet generated by the retransmission request packet generation unit 112 is also supplied to the determination unit 116, and when the self-origination collides, the retransmission packet generation unit 114 is activated as described above.
[0042]
The slot interval control unit 111 refers to the termination information of the packet received from the front end termination detection unit 117 and, based on the slot clock of the slot clock generation unit 103, generates one slot, three slots, five slots, and more gap signals. And request it where needed. When there is a basic packet transmission request from the upper level, the basic packet generation unit 109 generates the basic packet, obtains 5-slot information from the slot interval control unit 111, and requests the basic packet transmission unit 110 to transmit.
[0043]
The retransmission control is performed as described above. Among the respective processes, the details of the process in the basic packet transmitting unit 110 will be described below with reference to FIG.
[0044]
In FIG. 5, the generated basic packet received by the basic packet transmission unit 110 is put into a basic packet transmission preparation unit 201, and the determination unit 202 refers to the signal in the network received by the basic packet reception unit 104 in FIG. After confirming that there is no signal in the network, the basic packet is transmitted from the packet transmitting unit 203 in synchronization with the slot clock.
[0045]
On the other hand, if there is a signal in the network as a result of the determination by the determination unit 202 and the signal is a retransmission request, it means that a retransmission request has already been issued from another node, so the retransmission request is stopped, and In the case of a command, the system waits until there is no signal in the network, counts the slot gap, and returns to the judging unit 202 if the timing comes (judging unit 204).
[0046]
Here, in the above embodiment, the gaps of one slot, three slots, and five slots are 1, 3, and 5, respectively, but the present invention is not limited to this.
[0047]
In the present invention, the point is that the retransmission request command is issued as quickly as possible, and in a slot determined to be able to recognize a collision, and the retransmission packet is issued in a slot gap longer than the retransmission request. The priority is increased by making the slot gap smaller than other packets. It is also included in the present invention to make a rule that other nodes do not normally output packets until a retransmission packet is output. In this case, the five-slot gap control is unnecessary, and instead, the basic packet generator 109 shown in FIG. You will get a signal.
[0048]
Furthermore, the slot does not need to be half the length of the basic packet, and may be 1/4 or 1/8 or the same length.
[0049]
There is no particular limitation on the count of the gap for the retransmission packet. When the size of the address is m, (2m + 1) is set as the gap. However, also in this case, the smallest address that actually exists is set to order 1, only the used addresses are counted as 2, 3, 4,..., The order m is set, and the (2m + 1) slot is set as a gap. This can reduce waste.
[0050]
Here, there is a possibility that retransmission packets may collide even if the above retransmission control is performed. For example, when the order of the node S and the node T that cannot directly communicate with each other is that the node S is p and the node T is (p + 1), the node S starts transmission of a retransmission packet in a (2p + 1) slot gap. , The node T does not hear it, and starts retransmission in the (2p + 3) slot gap.
[0051]
For the node U that can directly communicate with both the node S and the node T, the collision between the latter half of the packet of the node S and the packet of the node T is recognized, and a retransmission request is issued. In this case, re-sending is performed. In such a case, when 1 is set in the second bit of the control unit in FIG. 3, it is determined that retransmission is performed. Here, 1 is set and the slot gap is set to (5m-3) slot. Thus, in the re-retransmission, a space of three slots is provided after the basic packet of two slots, so that re-retransmission does not collide. Further, any node can see a gap of two or more slots between packets, so that it is not mistaken for a retransmission request.
[0052]
The above description has been made with re-retransmission. However, if the (5m-2) slot gap is directly applied to retransmission, collision in retransmission can be completely avoided. Such a method is also included in the present invention. Specifically, when the 1-slot gap, the 3-slot gap, and the 5-slot gap are generalized to be k, j, and h slots (k <j <h), respectively, 5m−2 is 5 (m− 1) It becomes + j.
[0053]
Also, in this example, the description has been made of a packet having two slots. However, the present invention is not limited to this. For an n-slot packet, 5m−2 becomes {(n + 3) m−n}. When m = 1, there is a three-slot gap. Even if the gap is j-slot, if the next slot is sequence 1, the node in sequence m will start with the slot in sequence {(n + 3) m- (n + 2)}. It will be a slot. In this case, the expression can be made independent of the slot gap.
[0054]
【The invention's effect】
As described above, according to the present invention, when a transmitted packet is longer than n slots of the basic packet length, it is determined that a data collision has occurred, and the k-th slot next to the slot at the end of the packet has a gap. Then, the basic packet requesting retransmission is transmitted by broadcast with the next slot at the head, and when the node itself transmits a normal basic packet, the next k slot at the end is set as a gap, and the next If there are n or more signals at the beginning of the slot, the next slot after leaving a gap of 3 or more slots from the end of the retransmission request packet is designated as order 1, and its own node address is Since retransmission packets are transmitted with the slot in the corresponding order at the top, shared media type networks using indoor power lines or wireless In data communication click, it is possible to avoid a collision when data is retransmitted.
[Brief description of the drawings]
FIG. 1 is a diagram showing a slot and a basic packet transmission method applied to the present invention.
FIG. 2 is an explanatory diagram of a gap after receiving a basic packet.
FIG. 3 is a diagram showing a configuration of a basic packet.
FIG. 4 is a block diagram illustrating a configuration of an embodiment of the present invention.
FIG. 5 is a block diagram illustrating a configuration of a basic packet transmitting unit in FIG. 4;
[Explanation of symbols]
A, B, C Node 101 Basic clock generator 102 1/256 slot clock generator 103 Slot clock generator 104 Basic packet receiver 105 Received signal detector 106 AND circuit (logical product)
107 Basic packet length counting unit 108 Collision detection unit 109 Basic packet generation unit 110 Basic packet transmission unit 111 Slot interval control unit 112 Retransmission request packet generation unit 113 Transmission right slot detection unit 114 Retransmission packet generation unit 115 Content analysis unit 116 Judgment unit 117 Tip end detector

Claims (3)

In a data communication network using an indoor power line or wireless communication, the transmission time of a basic packet, which is a basic unit of data communication, is divided by n (n = 1, 2,...) At the timing of each node, and the division unit is defined as a slot. Slot clock generating means for generating a slot clock for use as a unit of transmission time,
Means for setting a fixed number of slots equal to or greater than h slots (h = 5, 6,...) After transmission of the basic packet as a gap and taking a silence time between transmission of the next packet;
Determining means for determining whether or not the transmitted packet is longer than n slots of the basic packet length;
When the determination means determines that the slot is longer than n slots, the next k slots (k = 1, 2,...; K <h) of the slot at the end of the packet are set as gaps, and the next slot is set as the next slot. Transmitting means for transmitting a basic packet requesting retransmission at the beginning by broadcasting;
Detecting means for detecting whether or not there are n or more slots when the node itself transmits a normal basic packet, with the next k slots at the end as gaps and the next slot at the head, ,
When the detecting means detects a packet requesting retransmission or a mixed signal colliding with each other, j slots (j = 3, 4,...; K <j) from the end of the packet requesting retransmission. <H) a retransmitting means for transmitting the retransmission packet with the next slot after the gap is taken as order 1 and the slot in the order corresponding to its own node address at the top,
A retransmission control method in data communication, comprising: In the retransmission control method in data communication according to claim 1, in place of the retransmission unit,
When the transmitting means detects a packet requesting retransmission or a mixed signal colliding with each other, j slots (j = 2, 3,...; K <j <) from the end of the packet requesting retransmission. h), the next slot having a gap is designated as order 1, and a predetermined order m (m = 1, 2,...) is assigned to addresses existing in the network in advance. A retransmission control method in data communication, comprising means for transmitting a retransmission packet with a slot at the head. In the retransmission control method in data communication according to claim 1, in place of the retransmission packet transmitting means,
When the transmitting means detects a packet requesting retransmission or a mixed signal colliding with each other, j slots (j = 2, 3,... K <j <h) from the end of the packet requesting retransmission. )), The next slot having a gap is designated as order 1, addresses existing in the network are given a fixed order m (m = 1, 2,...) In advance, and a node in order m is assigned an order ｛(n + 3) m A retransmission control method in data communication, comprising means for transmitting a retransmission packet with the (n + 2)} slot at the top.

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