Variable-Length Sequence Numbers in ARQ Systems
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Solution Overview
Problem
In next-generation mobile communication systems like LTE, the overhead caused by 12 to 16-bit sequence numbers for ARQ is excessive, especially in poor channel conditions, necessitating a method to efficiently use sequence numbers for packet transmission and retransmission.
Innovation Solution
A method and apparatus that use a variable-length sequence number, where a short sequence number is used for initial transmission and a full sequence number for retransmission, with a flag to distinguish between the two, reducing confusion and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full sequence number (12-16 bits) is used for ARQ packet transmission, then packet identification reliability is improved, but transmission overhead increases significantly
Solution Approach 1:
The patent applies dynamics by making the sequence number length variable rather than fixed. The system dynamically adjusts the sequence number length based on transmission context: using shorter sequence numbers for initial transmissions and longer sequence numbers for retransmissions. This dynamic adaptation resolves the contradiction by optimizing the balance between identification reliability and overhead for different transmission scenarios.
Solution Approach 2:
The patent changes the parameter of sequence number length from a fixed value (12-16 bits) to a variable parameter that can take different lengths (e.g., 5 bits for initial transmission, 15 bits for retransmission). This parameter change allows the system to use minimal overhead when possible while ensuring sufficient identification capability when needed, directly resolving the contradiction between reliability and overhead.
2Quantity of substance
If a short sequence number is used for initial transmission, then transmission overhead is reduced, but packet identification accuracy may be compromised
Solution Approach 1:
The system dynamically selects sequence number length based on transmission type. For initial transmissions, shorter sequence numbers are used to minimize overhead. For retransmissions, the system switches to longer sequence numbers to ensure accurate packet identification and avoid confusion between different transmission instances. This dynamic selection resolves the contradiction by adapting to the specific transmission context.
Solution Approach 2:
The patent segments the sequence number usage into different phases: initial transmission phase using short sequence numbers and retransmission phase using long sequence numbers. This segmentation allows each phase to use the appropriate sequence number length, optimizing overhead for initial transmissions while ensuring identification accuracy for retransmissions.
3Productivity
If a variable-length sequence number is used, then transmission efficiency is improved, but system complexity increases due to flag management
Solution Approach 1:
The patent introduces a flag field as an intermediary element that indicates whether a packet is an initial transmission or retransmission. This flag acts as a mediator that enables the receiver to correctly interpret variable-length sequence numbers. The flag management adds minimal complexity compared to the gains in transmission efficiency from using optimized sequence number lengths.
Solution Approach 2:
The system changes the parameter of sequence number length based on the transmission type indicated by the flag. This parameter change enables efficient use of transmission resources by using shorter sequence numbers when appropriate, while the complexity increase is limited to simple flag checking and sequence number length selection logic.
Data Source
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AI summary
A method and apparatus for transmitting a packet in a mobile communication system. A transmitting side allocates a short sequence number for an initial transmission packet using some bits among bits of a predetermined length for expressing a sequence number of the packet, and sets a first flag indicating use of the short sequence number. The transmitting side inserts the short sequence number and the first flag into the packet, and transmits the packet to a receiving side.