Wireless Transmitting Device Preamble Reduction for HARQ Retransmissions
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Solution Overview
Problem
In wireless communication networks, particularly under IEEE 802.11 standards, the overhead due to preambles is significant for small payloads, such as retransmissions in Hybrid Automatic Repeat Request (HARQ) schemes, leading to inefficient use of transmission opportunities (TXOPs) since the preamble size remains unchanged even for shorter retransmissions.
Innovation Solution
Implementing a method where a wireless transmitting device uses a shorter or no preamble for subsequent transmissions within a TXOP, allowing for more efficient data transmission by reducing the overhead, especially for retransmissions, which often have smaller sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full preamble is used for every transmission within a TXOP, then transmission reliability is maintained through complete channel estimation and synchronization, but transmission efficiency deteriorates due to significant overhead for small payloads like retransmissions
Solution Approach 1:
The patent applies local quality by differentiating preamble requirements based on transmission context: initial transmissions receive full preambles for complete channel estimation and synchronization, while subsequent transmissions within the same TXOP use shortened preambles or no preambles since the channel conditions are already established. This localized adaptation of preamble length to specific transmission needs resolves the contradiction between maintaining reliability and improving efficiency.
Solution Approach 2:
The patent implements dynamics by making preamble length variable rather than fixed. The transmitting device dynamically adjusts preamble presence and length based on transmission sequence position (initial vs. subsequent), payload size, and channel conditions. This dynamic adaptation allows the system to optimize between reliability and efficiency in real-time according to actual transmission requirements.
2Measurement precision
If retransmissions include complete preambles, then decoding accuracy is ensured, but TXOP utilization deteriorates as retransmissions consume disproportionate time relative to their smaller payload sizes
Solution Approach 1:
The patent applies preliminary action by performing complete channel estimation and synchronization during the initial transmission's full preamble phase. This preliminary work establishes the channel characteristics that can be reused for subsequent retransmissions, allowing those retransmissions to use shortened or omitted preambles without sacrificing decoding accuracy. The preliminary action during the first transmission enables time savings in subsequent transmissions.
Solution Approach 2:
The patent implements discarding and recovering by selectively discarding redundant preamble elements in subsequent transmissions within the same TXOP. Since channel conditions are already characterized from the initial transmission, the system can discard repetitive preamble components while recovering the essential decoding information through the established channel model, thereby reducing overhead without compromising accuracy.
3Productivity
If preambles are shortened or omitted for subsequent transmissions, then overhead is reduced and TXOP efficiency improves, but transmission robustness may deteriorate if channel conditions change
Solution Approach 1:
The patent applies universality by designing the shortened preamble structure to retain essential functions despite reduced length. The shortened preambles maintain critical synchronization and basic channel information while omitting redundant elements. This multi-functional approach allows the condensed preamble to serve multiple purposes (synchronization, basic channel estimation, transmission signaling) without requiring full-length structure, thus maintaining robustness while improving efficiency.
Solution Approach 2:
The patent implements continuity of useful action by maintaining the established channel context throughout the TXOP without requiring complete re-estimation for each transmission. The shortened preambles preserve the continuous channel model from the initial transmission, allowing the system to maintain robustness through ongoing use of the established channel characteristics while minimizing redundant overhead in each subsequent transmission.
Data Source
AI summary
A method is performed by a wireless transmitting device for a communication network. The communication network implements a standard in which transmitting devices contend for access to a wireless transmission medium, a transmitting device being permitted to transmit using the wireless transmission medium for a window of time upon winning contention. The method includes: initiating a first, initial transmission to one or more wireless receiving devices in the window of time, the first transmission including a first preamble; and, subsequent to the first transmission, initiating a second transmission to one or more wireless receiving devices in the window of time, the second transmission including a second preamble which is shorter than the first preamble, or including no preamble.