Unifying slot assignment protocol multiple access system

Details Unifying slot assignment protocol multiple access system Unifying slot assignment protocol multiple access system

1999-04-30

2001-12-18

Olms, Douglas (Department: 2661)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S350000, C370S436000, C370S442000

Reexamination Certificate

active

06331973

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for managing communication resources between nodes of a network, and more particularly to a dynamic distributed multi-channel Time Division Multiple Access (TDMA) slot assignment method.
BACKGROUND OF THE INVENTION
Mobile multi-hop broadcast packet radio networks are known for their rapid and convenient deployment, self organization, mobility, and survivability. In this type of network as illustrated in
FIG. 1
, a transmission from one node, for example node
1
, is broadcast to all nodes in its “neighborhood”. Ultra-high frequency (UHF) systems generally have a neighborhood defined by nodes within line of sight of the transmitting node (these nodes being termed within one “hop” of the transmitting node). For example, in
FIG. 1
nodes
1
,
3
,
4
,
5
,
6
,
7
, and
8
make up one neighborhood. For data transmitted from node
1
to propagate multiple hops, the data must be relayed by one or more of node
1
's neighbors. For example, node “a” (likewise nodes b, c, and g) is two hops away from the node
1
transmitter. The data will be relayed in this manner until it has arrived at all intended destination nodes.
Since there are generally limitations on the number of simultaneous transmissions that a receiver can successfully process (typically one), collisions can be avoided by the assignment of time slots in which individual nodes can transmit. There are many approaches to deciding which nodes are assigned which slots, and the approach is generally driven by the network applications, such as, broadcast, multicast, unicast, datagrams, virtual circuits, etc. Because the problem of optimally assigning slots in this environment is mathematically intractable, a heuristic approach is taken to design an integrated protocol that both chooses the number of slots to assign to each neighboring node and coordinates their activation in the network.
Tactical military and commercial applications require self-organizing, wireless networks that can operate in dynamic environments and provide peer-to-peer, multi-hop, multi-media communications. Key to this technology is the ability of neighboring nodes to transmit without interference. Neighboring nodes transmit without interference by choosing time slots and channels that do not cause collisions at the intended unicast or multicast receivers. This functionality is provided by the Unifying Slot Assignment Protocol (USAP) which is the subject of U.S. Pat. No. 5,719,868 the disclosure of which is herein incorporated by reference. The function of USAP is to monitor the RF environment and allocate the channel resources on demand and automatically detect and resolve contention resulting from changes in connectivity.
Wireless channel access schemes traditionally come in two flavors: contention and reservation. Contention has been the favorite for ad hoc broadcast networks because its lack of structure lends itself well to the mobile environment. Also, low access delays make it suitable for both tactical voice, where push-to-talk is the norm, and bursty data. However, when the network is heavily loaded contention is inefficient. At that point a structured access like reservation Time Division Multiple Access (TDMA) can achieve much higher efficiencies.
Another division in this field is the difference between broadcast and unicast. Broadcast techniques, in which a node transmits to all of its neighbors, and unicast techniques, in which a node transmits to only one of its neighbors, both have their own unique advantages dependent upon the application. Traditional wireless systems, however, are not capable of utilizing both broadcast and unicast schemes.
Ideally, a wireless channel access system would support both reserved circuits and datagrams in whatever combination is required. Conventional wireless channel access systems however are not capable of supporting both reserved circuits and datagrams.
Conventional wireless communication systems are capable of handling only one or a small number of data types, including low latency voice, delay tolerant data, bursty transactions, high throughput streams, error sensitive data, and error tolerant video. However, conventional systems are not capable of handling the full range of data types.
Conventional wireless communications systems are typically capable of establishing and maintain only one type of virtual circuits, including either the establishment and maintenance of hard circuits or the establishment and maintenance of permanent datagrams service that can allocate soft circuits in response to traffic surges. Furthermore, conventional wireless communication systems are not able to supply selective hop-by-hop reliability to both types of traffic to overcome the effects of collisions and errors induced by the channel.
Thus, there is a need and desire for a channel access scheme to use TDMA in contention and reservation modes of operation to accommodate changing traffic patterns. Further, there is a need and desire for a wireless communication scheme capable of using both broadcast and unicast techniques dependent upon the state of the communication environments. Further still, there is a need and desire for a wireless communication system that is able to handle a full range of data types including low latency voice, delay tolerant data, bursty transactions, high throughput streams, air sensitive data, and air tolerant video. Further still, there is a need and desire for a channel access system that is capable of providing both reserve circuits and datagram service. Further still, there is a need and desire for a wireless communication system that is able to handle the full range of data types while optimizing for densities ranging from fully connected to sparse and because of its reliance only on local information is able to scale to large network sizes.
SUMMARY OF THE INVENTION
The present invention relates to a method for automatically managing the communication channel resources between two nodes having neighboring nodes in a network of transceiver nodes. Each node communicates during specific time slots and uses multiple frequencies on a time multiplex basis. The method includes storing a table of possible communication time slots and frequencies between nodes in the network at each node. The method further includes announcing and transmitting from a first node during a specific time slot, a specific transmit slot and frequency and the identification of a second node to all neighboring nodes of the first node including a first set of neighboring nodes. Further still, the method includes transmitting from the first node a control packet containing the set of transmit slot and frequency pairs on which the first node is transmitting, the set of transmit slot and frequency pairs on which the first node is receiving, and the set of transmit slot and frequency pairs on which the first set of neighboring nodes are transmitting on. Further still, the method includes identifying in the tables of each of the nodes of the first set of neighboring nodes the announced selected transmit slot and frequency used to establish substantially contention free communication on the selected transmit slot and frequency between the first and second nodes, and adapting to the transceiver node network topology and available channel resources by utilizing a set of predetermined heuristics.
The present invention further relates to a communication network. The communication network includes a network of transceiver nodes, each node having neighbors, utilizing a time division multiple access structure, the time division multiple access structure having broadcast slots. The time division multiple access structure includes a slot assignment protocol that chooses the number of slots to assign to each neighboring node and coordinates the activation of the slots for the neighboring nodes, and at least one adaptive slot handling heuristic that controls the assignment of slots.
The present invention still further relates to a method for automatically managing the c

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