| 摘要 |
A frequency-hopping packet communication system without a master clock or master control unit is based on use of a receiver's frequency hopping timing and identification to control communication. A frequency-hopping band plan, involving the number of channels and the pseudo-random pattern of frequency change and nominal timing of changes, is universally known to each node in the network. Frequency-hopping is implemented by the division of communication slots and the accumulation of slots into epochs, wherein each epoch equals the total number of available slots (number of channels times the number of time frames per channel). A transmitting node tracks the preestablished frequency-hopping pattern for its target receiver based on previously-acquired information. The transmission node identifies a receiver node and a current frequency channel of such receiver node. The transmission node then checks the frequency channel to determine if available (e.g., not in use and within an acceptable noise margin). If unavailable, the transmission node delays transmission to the identified node to a later slot. During the delay, the transmission node identifies another receiver node and a corresponding current frequency channel. The steps of identifying a receiver node and checking the corresponding current frequency channel are repeated until a node having an available frequency channel is identified. The transmission node then sends a packet to the selected receiver node at a frequency and for a duration defined according to the current slot. Such transmission node tracks the changing frequency of the selected receiver node to maintain frequency synchronization. |
