JP3110137B2 - Communication method in home wireless communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication method in a home communication system in which a plurality of devices having transmission terminals are mixed.

[0002]

2. Description of the Related Art In a wireless home control system in which a security transmission terminal and a control reception terminal coexist, security information transmitted by radio transmission by a security transmission terminal is received by an adapter in a room and is transmitted to a main control device through a home bus. To be transmitted. Further, the control information sent from the main controller to the home bus is converted into radio waves by an adapter in the room, is released on the radio waves, and is received by the control receiving terminal. Alternatively, there is also a system in which the main controller receives signals without using a home bus.

In such a system, when security signals having security information are continuously transmitted from two transmitting terminals, transmission of security information cannot be performed due to collision of packets, and the function of the system is lost. Become. In addition, important devices that require a reply among the transmitting terminals are mixed in the system with a bidirectional communication function, but cannot be mixed when there are terminals that continuously transmit.

[0004] Regarding such a home communication network, there is a paper published under the name of "HPRS" by the home packet radio system research committee of the Radio Technology Association of Japan.
In this paper, the urgency of the equipment constituting the home packet radio system is classified into three levels as shown in the table below. FIG. 4 shows a packet format in a conventional home packet radio system.

[0005]

[Problems to be solved by the invention]

Since the retransmission of the device belonging to the level 1 is performed at a fixed time interval of 2 to 4 seconds, if two transmitting terminals transmit simultaneously, if the retransmission time interval is the same, the retransmission is performed several times. Even if repeated, both packets will collide, and even if the retransmission time interval is made variable,
If it is between seconds, the minimum waiting time of 2 seconds is wasted time. The same occurs when devices belonging to level 1 and devices belonging to level 2 transmit at the same time. Also,
If the error rate of the line of the device belonging to level 3 is high, the opportunity (probability) of communication is extremely reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and it is possible to reliably transmit information of a device having the highest urgency level, and to transmit information of other level devices within a design range. It is an object of the present invention to provide a communication method in a reliable home wireless communication network which can be realized at a loss.

[0007]

To achieve the above object, according to the present invention, in a home communication system in which a plurality of devices having transmission terminals are mixed, the devices are arranged in descending order of urgency. The devices belonging to level 1 are classified into four levels of urgency, and the devices belonging to level 1 are devices having a receiver and requesting the return of the confirmation signal, and repeat retransmission until the confirmation signal is received. The device repeats retransmission at least as many times as the packet collision probability becomes a predetermined probability, the device of level 3 has a limited number of retransmissions, each retransmission is a retransmission at a random time interval, and the device belonging to level 4 does not retransmit. did.

[0008] A second aspect of the present invention is characterized in that devices of any level are mixed in the network.

According to a third aspect of the present invention, error detection of a packet is performed using an error detection code.

According to the fourth aspect, the predetermined collision probability P of level 2
The retransmission count m is (Where n is the randomization rate, x is the number of devices belonging to level 2, y is the number of devices that transmit simultaneously).

According to claim 5, the number of retransmissions m of level 3 is:
Assuming that the probability that the first packets transmitted by the two transmitting terminals collide is Po, the collision probability P in the following equation is The number of retransmissions is equal to or less than a predetermined probability.

[0012]

According to the present invention, devices with high urgency are classified into two levels, one that requires a transmission / reception terminal to request an acknowledgment signal and one that does not have a reception terminal, and does not have a reception terminal. Those are unlimited continuous retransmissions, and sensors and remote controllers that do not require urgency limit the number of retransmissions but make retransmissions, and the retransmission time interval is random, so at each level, and even between levels, Compared with the related art, the probability of communication can be increased, and the reliability can be greatly improved.

[0013]

An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the urgency of the equipment constituting the home packet radio system is classified into four levels as shown in the table below.

[0015] For devices belonging to level 1, as shown in FIG.
Since retransmission is repeated until a confirmation signal is received from the device, transmission can be performed reliably. This is a so-called AGR method. In FIG. 1, t is the length of one packet + margin, and n is the randomization rate. The device belonging to the random time interval retransmission, level 2, repeats the retransmission indefinitely as shown in FIG.

The probability P of x devices belonging to level 2 in the system, of which y devices transmit simultaneously and cannot receive a signal due to collision after transmitting m + 1 times, is Since the first collision always occurs, the probability of non-reception is 1, 2
The first transmission is performed after a time interval of t to nt, and thus becomes 1 / n. However, since packets do not always completely overlap and collide, there is a possibility of collision with two packets before and after. Becomes Furthermore, the third time becomes 2 / n square, and after m + 1 times transmission, it becomes 2 / n m. If the number of terminals in the system is _x , the combination becomes xC _y times.

From the above equation (1), conversely, the value of m at which the probability is P is: From this equation, the value of m can be assumed, so that devices belonging to level 2 do not necessarily have to have an unlimited number of transmissions. However, it is conceivable that the state of the line is bad. Therefore, the transmission may be paused after a certain period of time T1> t, and the transmission may be resumed after a certain period of time T2> t.

Further, assuming a collision probability P,
It can be seen that the reception can be reliably performed after the time of m · nt · t.

Since the transmission time of a device belonging to level 3 is shorter than that of a device belonging to level 2, it is sufficient to assume that at most two terminals collide as an actual use state. In a state where it is necessary to consider the probability of collision of three or more terminals, it is considered that the traffic density is too high when actually used.

Let Po be the probability that the first packets transmitted from the two terminals collide. From FIG. 3, as in the case of level 2, the probability that the second packet will collide is 2 / n, and the probability that all packets will collide until the m-th time is (2 / n) m-1. Therefore, the collision probability P after retransmission is, under the condition that Po is sufficiently small, Becomes At this time, Po is based on the Erlang B formula of the well-known trafficking theory, Here, N = the number of terminals, λ = 1 the occurrence probability of a terminal, λ = 1 a device with a different hold time level of a packet, for example, level 2
If the number of retransmissions n is the same, the collision between the packet from the device and the packet from the device at the level 3 is maintained as designed.

For packet collisions when there are three or more terminals, level 2 devices can assume a collision probability by selecting the value of y to be 3. In addition, for a device of level 3, the collision probability increases as compared with the case where the number of terminals is 2, but is improved as compared with a case where the retransmission time interval is not randomized. In practice, the probability that buckets from three or more terminals will collide is sufficiently lower than the probability that two terminals will collide, and is only slightly worse than the probability described in equation (3).

Next, assuming an actual system, in the above equation (1), if x = 10 units, y = 3 units, n = 6, and P = 10 ^-6 is requested, That is, if retransmission is repeated 18 times or more, a collision probability of 10 ^-6 can be secured. Assuming that t = 0/1 second, since n = 6, the maximum transmission time is n · t × 18.
+ T = 6 × 0.1 × 18 + 0.1 = 10.9 seconds, that is, only 11 seconds need be transmitted.

In the equation (3), n = 6 and m = 3
And assuming Po = 10 ^-2 traffic, Thus, an improvement of about one digit can be achieved. Here, if m is increased, the improvement can be further improved, but since the above-mentioned condition that the traffic density is sufficiently low is not satisfied,
It is difficult to obtain the improvement as calculated. The transmission time at this time is
Assuming that t = 0.1 second, (m-1) .nt + t = (3-
1) × 0.1 + 0. . 1 = 1.3 seconds, which is a sufficient improvement over the transmission time.

It is desirable that the error rate of the packet be improved by an error correction code when the error rate of the line is high. In the above design, error correction is performed not by retransmission but by code.

[0025]

As described above, according to the present invention, devices with high urgency are classified into two levels, one having a transmitting / receiving terminal and requesting an acknowledgment signal, and the other having no receiving terminal. Those that do not have a receiving terminal are unlimited continuous retransmissions, and sensors and remote controllers that do not require urgency limit the number of retransmissions so as to retransmit, and the retransmission time interval is random, so at each level, In addition, the level of communication can be increased between the levels as compared with the conventional case, and the reliability can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of transmitting a device belonging to level 1 in an embodiment of the present invention.

FIG. 2 is a diagram for explaining a transmission method of a device belonging to level 2 in the embodiment.

FIG. 3 is a diagram for explaining a method of transmitting a device belonging to level 3 in the embodiment.

FIG. 4 is a diagram showing a packet format in a conventional home packet radio system.

Claims (5)

(57) [Claims] In a home communication system in which a plurality of devices having transmission terminals coexist, the devices are classified into four levels of urgency from 1 to 4 in descending order of urgency.
Are devices that have a receiving terminal and request the return of an acknowledgment signal, and repeat retransmission until the acknowledgment signal is received. Level 2 devices require urgency but do not have a receiving terminal. The retransmission is repeated at least as many times as the packet collision probability becomes a predetermined probability, the level 3 device is limited in the number of retransmissions, each retransmission is a retransmission at a random time interval, and the device belonging to level 4 is not retransmitted. Communication method in a home wireless communication network. 2. The communication method in a home wireless communication network according to claim 1, wherein devices of any level are mixed in the network. 3. The communication method in a home wireless communication network according to claim 1, wherein error detection of the packet is performed using an error detection code. 4. The number of retransmissions m that results in a predetermined collision probability P of level 2 is represented by the following equation: 4. The home wireless communication network according to claim 1, wherein the estimation is made from (n: randomization rate, x: number of devices belonging to level 2, y: number of devices transmitting at the same time). Communication method. 5. The number of retransmissions m at level 3 is defined as Po, where the probability of collision of the first packets transmitted by the two transmitting terminals is Po, and 4. The communication method in a home wireless communication network according to claim 1, wherein (n; randomization rate) is the number of retransmissions equal to or less than a predetermined probability.