| 摘要 |
Method of controlling the access of devices to the communication media in distributed networks of CSMA (Carrier Sense Multiple Access) type is characterized by that each time before the packet transmission attempt, if the communication medium is detected to be idle, the prespecified fixed time interval equal to the minimum interpacket space is timed out during which the random numbers of time slots defining the order of media access are selected from the fixed number of slots of equal width using the pseudorandom number generator in every node where the probability of a selection of a particular slot is geometric with a characteristic parameter defined as the ratio of the probability of a selection of a given slot to the probability of a selection of the next slot, which changes from zero to one as a discrete function of the state of the node's counter, and after that the time interval of random delay corresponding to the selected random is assigned. After the minimum interpacket space the phase of known sequential priority access is started and subsequently, the random delay assigned previously is timed out and at the same time the state of the communication medium is sensed again, and if the communication medium is still sensed idle, it is made available to the node with the lowest number of the slot randomly selected. After completing a given packet reception, the states of the counters in all the nodes in a given network segment are increased by the increment defining the number of expected packets that will be generated in a result of the reception of the transmitted packet reduced by one, and next, the cycle is repeated. During the data packet transmission the collisions are detected optionally in the communication medium by the collision detectors, and next, the states of the counters are changed in the nodes with the use of the corresponding control signals obtained from the collision detectors, and in case the communication medium is detected to be idle after the time equal to the sum of the minimum interpacket space and the time delay defined by the prespecified fixed maximum number of slots, the states of the counters in all the nodes in a given network segment are decreased by one with the use of the control signals obtained from the communication medium state detectors. |
