Implicit Link Adaptation via Transmit Duration Signaling
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Solution Overview
Problem
Wireless communication networks, such as IEEE 802.11, lack an explicit signaling mechanism for link adaptation, leading to inefficient and unreliable data transfer due to the absence of a standardized method for exchanging link adaptation messages between communicating stations.
Innovation Solution
An implicit signaling mechanism based on the transfer of transmit duration information is introduced, where a designated originating node sends a message indicating a current transmit duration, allowing the receiving node to select a desired data link rate and update the transmit duration, which is then signaled back to the originating node for link rate adjustment, without requiring changes to existing communication standards or introducing additional overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If implicit signaling based on transmit duration information is used, then link adaptation efficiency is improved, but complexity of the signaling mechanism increases
Solution Approach 1:
The patent uses the transmit duration field as an intermediary to convey link adaptation information. Instead of introducing a new explicit signaling mechanism, the invention repurposes the existing transmit duration field in RTS/CTS messages to implicitly signal the desired link rate. The receiving station encodes its preferred rate in the transmit duration value, and the transmitting station decodes this information to adjust its modulation and coding scheme, thus achieving link adaptation through an intermediary parameter.
Solution Approach 2:
The invention changes the interpretation and usage of the transmit duration parameter from its conventional meaning (time required to transmit a frame) to also serve as a carrier for link adaptation information. By modifying how this parameter is set and interpreted by the communicating stations, the system achieves dual functionality: maintaining collision avoidance timing information while simultaneously conveying preferred link rate information for adaptation.
2Adaptability or versatility
If new frame formats are introduced for link adaptation signaling, then link adaptation capability is improved, but compatibility with legacy stations deteriorates
Solution Approach 1:
The patent makes the existing transmit duration field multi-functional by having it serve both its original purpose (indicating transmission time for collision avoidance) and a new purpose (conveying link adaptation information). This universal usage allows link adaptation capability to be added without creating separate new frame formats, thereby maintaining full compatibility with legacy stations that continue to interpret the field in its traditional sense while advanced stations can exploit the extended functionality.
Solution Approach 2:
The existing RTS/CTS frame structure and transmit duration field are made to serve the additional function of link adaptation signaling without requiring external modifications or new protocols. The mechanism uses the stations' own existing message exchanges to carry the adaptation information, allowing the system to self-configure for link adaptation using resources already allocated for collision avoidance functionality.
3Productivity
If explicit link adaptation signaling is implemented, then data transfer rate optimization is improved, but overhead in communication increases
Solution Approach 1:
The patent merges the link adaptation signaling function with the existing RTS/CTS collision avoidance mechanism. The transmit duration information that is already being exchanged for medium access control purposes is combined with link adaptation feedback, allowing both functions to be achieved in a single signaling exchange. This merging eliminates the need for separate explicit link adaptation messages, thereby optimizing data transfer rates without increasing communication overhead.
Data Source
AI summary
Briefly, the invention concerns the issue of supporting link adaptation in a wireless network, and basically involves implicit signaling for link adaptation based on transfer of transmit duration information. More particularly, a designated originating node sends (S1) a first message, including an indication of a current transmit duration for transfer of a predetermined amount of information, to at least a designated receiving node. The current transmit duration corresponds to a currently assumed data link rate. The designated receiving node selects (S2) a desired data link rate for subsequent communication from the originating node, and then determines (S3) an updated transmit duration according to the selected data link rate. The receiving node sends (S4) a second message, including an indication of the updated transmit duration, to at least the designated originating node, and the originating node then determines (S5) an updated data link rate in response to the updated transmit duration. In particular, the transmit duration information may preferably be transferred in the existing duration field in the frames of contention-based network protocols with support for virtual carrier sensing.