High Processing Gain Header for Wireless Collision Avoidance
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Solution Overview
Problem
In wireless communication networks, particularly ad-hoc networks, existing medium access control methods fail to effectively avoid packet collisions due to hidden nodes, exposed nodes, and shadowing issues, leading to inefficient bandwidth utilization and increased overhead.
Innovation Solution
The system and method involve prepending a high processing gain header to packets, allowing distant nodes to decode the header and avoid collisions, while selecting data rates based on interference estimation to maximize channel utilization and minimize destructive interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional medium access control methods are used, then nodes can transmit packets, but packet collisions occur due to hidden nodes and exposed nodes
Solution Approach 1:
The packet is segmented into two parts with different processing gains: a header with high processing gain (first processing gain) that can be decoded by distant nodes to prevent collisions, and a payload with lower processing gain (second processing gain) that only the recipient node decodes. This segmentation allows distant nodes to detect ongoing transmissions and avoid collisions while maintaining efficient bandwidth utilization.
Solution Approach 2:
Different parts of the packet are assigned different processing gains based on their specific functions. The header requires high processing gain for wide detectability to prevent collisions, while the payload uses lower processing gain for efficient transmission to the recipient. This local quality differentiation resolves the contradiction between reliability and productivity.
2Reliability
If high processing gain is used for entire packet, then collisions are avoided, but overhead increases and bandwidth utilization decreases
Solution Approach 1:
The packet is divided into header and payload with different processing gains. Only the header uses high processing gain to provide collision avoidance information to distant nodes, while the payload uses lower processing gain to minimize transmission time and overhead. This segmentation eliminates the need to apply high processing gain to the entire packet.
Solution Approach 2:
High processing gain is applied partially only to the header portion of the packet rather than the entire packet. This partial application provides sufficient collision avoidance capability while minimizing the overhead and time loss associated with high processing gain transmission.
3Reliability
If all nodes decode every packet, then no collisions occur, but processing complexity and energy consumption increase
Solution Approach 1:
The packet structure is segmented into header and payload with different processing gains. Nodes can decode the high processing gain header to determine if transmission is ongoing and avoid collisions, without needing to decode the lower processing gain payload. This selective decoding reduces energy consumption while maintaining collision-free transmission.
Solution Approach 2:
Nodes perform partial decoding by only decoding the header portion of packets with high processing gain to detect ongoing transmissions. Full payload decoding is performed only by the intended recipient node, reducing overall processing complexity and energy consumption across the network.
4Productivity
If data rate is increased to maximize channel utilization, then throughput improves, but interference from hidden nodes increases
Solution Approach 1:
The high processing gain header is transmitted preliminarily before the payload at a lower data rate. This preliminary transmission allows distant hidden nodes to decode the header and detect ongoing transmissions before the higher data rate payload transmission begins, enabling them to avoid interference while maintaining high channel utilization.
Solution Approach 2:
The system changes the processing gain parameter differentially across packet segments. The header uses high processing gain transmitted at lower data rate for wide detectability, while the payload uses lower processing gain allowing higher data rate transmission. This parameter change enables high channel utilization while preventing interference from hidden nodes.
Data Source
AI summary
A system and method for avoiding collisions between packets transmitted in a wireless network (100). A first node (102, 106 or 107) in the wireless network (100) can transmit a packet to a second node (102, 106 or 107) in the wireless network (100), such that packet includes a header that is transmitted with a higher processing gain than the data, therefore, may be received and processed by a third node (102, 106 or 107. This allows the third node (102, 106 or 107) to detect the transmission of a packet by the first node (102, 106 or 107), which can cause the third node (102, 106 or 107) to avoid transmission of a packet during the transmission by the first node (102, 106 or 107) to avoid collision between the packets. The system and method further enables the nodes (102, 106 or 107) to determine whether they can transmit to another node (102, 106 or 107) based on estimates of interference conditions that can be experienced due to the presence of other nodes (102, 106 or 107).