PDU Ordering Unit for Multi-Channel Wireless Terminals
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Solution Overview
Problem
In multi-FA personal subscriber terminals accessing multiple frequency channels, TCP/IP packet transmission efficiency is reduced due to out-of-order packet reception and retransmissions caused by HARQ error control in wireless communication systems.
Innovation Solution
A method and terminal that simultaneously access two frequency channels, reordering protocol data units (PDUs) to ensure sequential transmission and reception, minimizing errors and retransmissions by aligning PDUs according to sequence numbers and using a PDU ordering unit to manage packet flow between physical and MAC layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple frequency channels are accessed simultaneously for data transmission, then data transmission rate is improved, but packet transmission errors increase due to out-of-order reception
Solution Approach 1:
The patent introduces a PDU ordering unit that pre-processes and reorders protocol data units before they are delivered to the TCP/IP layer. This preliminary action ensures that packets are arranged in correct sequence numbers, preventing out-of-order delivery issues that would otherwise require retransmissions and degrade reliability.
Solution Approach 2:
The PDU ordering unit acts as an intermediary component between the multiple frequency channel access mechanism and the TCP/IP protocol stack. It mediates the conflict by receiving PDUs from different channels, reordering them based on sequence numbers, and delivering them in the correct order to higher layers, thus maintaining reliability while allowing parallel channel access.
2Reliability
If HARQ error control is used for wireless transmission, then error correction capability is improved, but transmission efficiency decreases due to retransmissions
Solution Approach 1:
The system performs preliminary error correction using HARQ at the physical layer before packets are transmitted over multiple frequency channels. By correcting errors early and ensuring packet integrity, the need for TCP-level retransmissions is reduced, thereby improving overall transmission efficiency while maintaining error correction capability.
Solution Approach 2:
The patent segments the error control function into two parts: HARQ at the physical layer for initial error correction, and PDU ordering at the MAC layer for sequence management. This segmentation allows each layer to focus on its specific function, reducing redundant retransmissions and improving efficiency.
3Productivity
If TCP cumulative ACK mechanism is used, then retransmission overhead is reduced, but data integrity cannot be ensured when packets arrive out of order
Solution Approach 1:
The PDU ordering unit serves as an intermediary that ensures data integrity by reordering packets before they reach the TCP cumulative ACK mechanism. This allows the cumulative ACK to work efficiently without causing data integrity issues, as the ordering is guaranteed at the PDU layer below.
Solution Approach 2:
The system performs preliminary ordering of PDUs based on sequence numbers before TCP processing. This preliminary action ensures that even though TCP uses cumulative ACK which assumes in-order delivery, the actual packets are already in the correct order, maintaining data integrity while allowing efficient ACK processing.
Data Source
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AI summary
A multi-FA personal subscriber station and a method of ordering protocol data units thereof having advantages of simultaneously accessing two frequency channels to transmit and receive data and appropriately ordering protocol data units transmitted through each frequency channel, thereby minimizing errors in TCP/IP packet transmission, are disclosed. According to the multi- FA personal subscriber terminal and the method of ordering protocol data units thereof according to exemplary embodiments of the present invention, two frequency channels are simultaneously accessed to transmit and receive data and protocol data units transmitted through each of the frequency channels are ordered, thereby minimizing errors in TCP/IP packet transmission.