Distributed Medium Access Control With Neighbor-Aware Slot Scheduling
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Solution Overview
Problem
Existing medium access control protocols for ad hoc wireless networks suffer from inefficiencies such as increased overhead, latency, and reduced throughput due to the hidden and exposed node problems, leading to suboptimal utilization of the available spectrum.
Innovation Solution
A distributed medium access control device and method that maintains a scheduling table of slot usage, collects information from neighbor nodes, and allocates slots efficiently to avoid collisions and maximize spectrum use, without requiring central control or knowledge of network topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centralized control model is used for dynamic TDMA scheduling, then scheduling decisions can be made centrally, but the system requires a huge amount of control messages and does not scale well
Solution Approach 1:
The patent segments the centralized scheduling function into distributed decision-making at individual nodes. Each node maintains its own scheduling table and makes local scheduling decisions based on neighbor information, eliminating the need for a central controller and reducing control message overhead while maintaining reliable scheduling through local consistency.
Solution Approach 2:
Nodes perform self-service by autonomously maintaining scheduling tables and making scheduling decisions based on information from neighbor nodes. The system eliminates dependency on central control by enabling each node to independently manage its own slot allocation and avoid collisions through local scheduling logic.
2Reliability
If reservation slots are required for each data slot, then collisions can be avoided, but the protocol becomes sequential and control packet overhead becomes huge
Solution Approach 1:
The patent implements preliminary action by having nodes pre-maintain scheduling tables that record slot usage information from neighbor nodes before actual data transmission occurs. This allows nodes to proactively identify available slots and avoid collisions without requiring sequential reservation procedures, reducing both time loss and control overhead.
Solution Approach 2:
The scheduling tables are continuously updated with slot usage information from neighbor nodes, enabling continuous availability of scheduling information. This eliminates the need for repeated sequential reservation queries and allows nodes to make scheduling decisions based on up-to-date information without time loss.
3Reliability
If timeslots are considered unavailable when a neighbour node is transmitting, then collisions are avoided, but spectrum utilization is reduced due to the exposed node problem
Solution Approach 1:
The patent applies local quality by differentiating between slots used by direct neighbors versus slots where the neighbor's receiver is out of range. The scheduling table records whether a neighbor node uses a slot for transmission only, reception only, or both, allowing node A to selectively avoid collisions while permitting transmissions when spatial reuse is safe, thus optimizing spectrum utilization locally.
Solution Approach 2:
Instead of conservatively marking all neighbor-transmitted slots as unavailable, the patent inverts the approach by marking only those slots as unavailable when the neighbor's receiver is within range of the transmitting node. This allows spectrum utilization in cases where the exposed node problem does not apply, resolving the contradiction between collision avoidance and spectrum utilization.
4Reliability
If reservation information is transmitted to nodes two hops away, then collision avoidance is improved, but control packet overhead increases
Solution Approach 1:
The patent extracts the essential scheduling information by having neighbor nodes directly share their slot usage status (transmission only, reception only, or both) with adjacent nodes. This localized information exchange eliminates the need to propagate reservation information two hops away, reducing control packet overhead while maintaining sufficient collision avoidance capability through direct neighbor awareness.
Data Source
AI summary
A device for medium access control in a node of a wireless communication network with shared medium, including: a registration module, configured to maintain in a scheduling table the use of slots, including timeslots and/or frequency channels; an information exchange module, configured to collect slot usage information indicative for the use of slots by neighbor nodes in the range of the node, this slot usage information specifying use of a slot for transmission by a neighbor node and/or use of a slot for receipt by a neighbor node; a slot allocation module, configured to allocate a slot for communication with a neighbor node by consulting the scheduling table in a slot allocation procedure with a neighbor node, resulting in an allocated slot.