Method for frequency sharing in frequency hopping communications network
First Claim
1. In a packet communication network having a plurality of communication nodes, each node having a terminal node controller which includes processing means and memory means, a method for frequency sharing within said network comprising the steps of:
- at each node, changing, according to a known pattern, a slot for transmission and reception of signals to a current slot, a slot being a frequency channel during a preselected time period, a current slot being the frequency channel for a current time period, said known pattern being known to each other node in said network, said step of changing at one node being independent of the changing for each other node;
at a source node, identifying a first receiver node and the frequency channel of the current slot of said first receiver node;
checking the frequency channel of said first receiver node to determine if available for a transmission;
when said frequency channel of said first receiver node is unavailable, repeating the steps of identifying and checking until an available frequency channel is found, the receiver node which has an available frequency channel being a selected receiver node; and
transmitting an information packet from said source node to the selected receiver node during the current slot of said selected receiver node, the source node tracking the changing frequency of the selected receiver node.
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Accused Products
Abstract
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.
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Citations
5 Claims
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1. In a packet communication network having a plurality of communication nodes, each node having a terminal node controller which includes processing means and memory means, a method for frequency sharing within said network comprising the steps of:
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at each node, changing, according to a known pattern, a slot for transmission and reception of signals to a current slot, a slot being a frequency channel during a preselected time period, a current slot being the frequency channel for a current time period, said known pattern being known to each other node in said network, said step of changing at one node being independent of the changing for each other node; at a source node, identifying a first receiver node and the frequency channel of the current slot of said first receiver node; checking the frequency channel of said first receiver node to determine if available for a transmission; when said frequency channel of said first receiver node is unavailable, repeating the steps of identifying and checking until an available frequency channel is found, the receiver node which has an available frequency channel being a selected receiver node; and transmitting an information packet from said source node to the selected receiver node during the current slot of said selected receiver node, the source node tracking the changing frequency of the selected receiver node. - View Dependent Claims (2)
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3. In a packet communication network having a plurality of communication nodes, each node having a terminal node controller which includes processing means and memory means and employing a clock, a method for maintaining frequency and time synchronization within said network comprising the steps of:
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generating at each node an age value by means of the clock of said node, said age value being representative of the age of said node; at each node, supplying a representation of the age value to any other node as part of transmission of a packet; at each node, collecting said representation of the age value for other nodes within said network; at each node, changing, according to a known pattern, a slot for transmission and reception of signals to a current slot, a slot being a frequency channel during a preselected time period, a current slot being the frequency channel for a current time period, said known pattern being known to each other node in said network, said step of changing at one node being independent of the changing for each other node; at a source node, identifying a receiver node and frequency channel of the current slot of said receiver node which is available to receive a packet of information; and transmitting said information packet from said source node to said identified receiver node on the frequency channel defined by the current slot of said identified receiver node during said current slot of said identified receiver node, the source node tracking the changing frequency of the identified receiver node. - View Dependent Claims (4, 5)
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Specification