Collision Avoidance Protocol Data Units in 4G ALE Networks
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Solution Overview
Problem
Automatic Link Establishment (ALE) networks face interference issues due to the 'hidden node' problem, where a third node unaware of an ongoing linked call initiates its own call, affecting the bit error rate (BER) performance of the original call, despite existing channel sensing and listen-before-transmit/responding protocols.
Innovation Solution
Participating nodes in the ALE network transmit collision avoidance protocol data units (CA PDUs) during a dwell time, including a unique identifier, priority level, and sub-channel vectors for transmission and reception channels, to inform other nodes of an ongoing linked call, preventing interference. This ensures that proximate nodes can avoid initiating calls that may interfere with the linked call.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel sensing and listen-before-transmit/responding protocols are implemented, then interference with ongoing active communications links is avoided, but hidden node problem persists where third nodes unaware of linked calls create interference
Solution Approach 1:
The patent applies preliminary action by transmitting collision avoidance PDUs during the dwell time period before actual data transmission begins. This early notification allows third nodes to become aware of the upcoming linked call and adjust their behavior accordingly, preventing the hidden node problem before it occurs. The collision avoidance information is sent in advance during the channel establishment phase, enabling proactive interference prevention rather than reactive measures.
2Reliability
If collision avoidance PDUs are transmitted during dwell time, then hidden node interference is prevented, but network communication overhead increases
Solution Approach 1:
The patent implements partial action by transmitting collision avoidance PDUs selectively during the dwell time period rather than continuously. The collision avoidance information is sent for a limited duration sufficient to notify third nodes, without requiring continuous transmission throughout the entire linked call. This approach provides adequate notification to prevent hidden node interference while minimizing the total amount of overhead communication.
3Reliability
If transmission power is increased to expand collision avoidance range, then more nodes are notified of linked calls, but energy consumption increases
Solution Approach 1:
The patent applies dynamics by adjusting transmission power adaptively based on the specific requirements of each collision avoidance PDU transmission. Rather than using a fixed high power level continuously, the system dynamically modulates transmission power during the dwell time period to achieve sufficient notification range while conserving energy. The power level is optimized to reach the necessary notification distance without excessive energy consumption.
Data Source
AI summary
A system and method for collision avoidance within nodes of an Automatic Link Exchange (ALE) network establishes a handshake between transmitting and receiving nodes for a linked call over an assigned frequency band. The transmitting and receiving nodes mutually determine transmission and reception sub-channel vectors within the assigned frequency band, e.g., for calling and response. Before the linked call commences, and when other scanning stations of the ALE network dwell on the assigned frequency band, the transmitting and receiving nodes transmit collision avoidance protocol data units (PDU) identifying the nodes, the transmission and reception sub-channel vectors, and the duration of the linked call such that scanning nodes may prevent interference with the linked call by avoiding transmission over the identified sub-channels.