PS-Poll Transmission Priority Mechanism for Wireless Networks
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Solution Overview
Problem
In the IEEE 802.11 power saving mode, the contention-based DCF leads to increased PS-Poll transmission failure probability and unfairness among terminals due to simultaneous transmissions, which existing techniques like Proxy CSMA, Station Grouping, and TIM Monitoring cannot completely avoid collisions and are complex to implement.
Innovation Solution
A method where terminals determine PS-Poll transmission priorities based on identifiers and transmit PS-Polls in a cyclic order, with the terminal with the highest priority selecting a backoff value and transmitting after an arbitrary timer expires, ensuring fair and collision-free PS-Poll transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If terminals transmit PS-Poll frames using contention-based DCF, then the transmission mechanism is simple, but the probability of PS-Poll collision increases as the number of contending terminals increases
Solution Approach 1:
The patent changes the transmission parameter from random backoff selection to deterministic transmission order based on AID values. Terminals transmit PS-Poll frames in ascending order of their AIDs, transforming the random contention parameter into an ordered sequence parameter, which eliminates collisions while maintaining simplicity.
Solution Approach 2:
The patent applies preliminary action by having terminals determine their transmission order based on AID values before actually transmitting PS-Poll frames. This pre-established order prevents collisions by ensuring that terminals transmit in a predetermined sequence rather than contending simultaneously.
2Ease of operation
If terminals transmit PS-Poll frames using random backoff, then the mechanism is easy to implement, but PS-Poll transmission fairness cannot be guaranteed for all competing terminals
Solution Approach 1:
The patent transforms the random backoff parameter into a deterministic parameter based on AID values. By using AID as the ordering parameter, the system guarantees fairness as each terminal has a predetermined transmission position in the sequence, eliminating the unfairness inherent in random backoff mechanisms.
Solution Approach 2:
The patent introduces asymmetry by assigning different transmission priorities to terminals based on their unique AID values. Instead of symmetric random access, each terminal has an asymmetric position in the transmission sequence, ensuring fair access while maintaining implementation simplicity.
3Reliability
If existing techniques like Proxy CSMA and Station Grouping are used, then PS-Poll collision can be reduced to some extent, but the implementation complexity increases significantly
Solution Approach 1:
The patent extracts the collision avoidance function from complex distributed mechanisms (Proxy CSMA, Station Grouping) and implements it through a simple centralized ordering rule based on AID values. This removes the need for complex terminal-side collision avoidance logic while maintaining effectiveness.
Solution Approach 2:
Instead of having terminals actively avoid collisions through complex sensing and backoff mechanisms, the patent inverts the approach by having terminals transmit in a predetermined order that naturally prevents collisions. The complexity is shifted from terminal-side collision avoidance to a simple ordering rule.
Data Source
AI summary
A method and an apparatus of transmitting power saving-poll (PS-Pall) for use in a wireless network are provided. The method includes a terminal in a wireless communication system determining PS-Poll transmission priorities of terminals based on identifiers of the terminals having downlink data to receive, monitoring to detect the PS-Polls of the terminals having downlink data to receive, and transmitting, when the PS-Poll of the terminal with a priority followed right by the priority of the terminal is received, the PS-Poll after expiry of an arbitrary backoff timer.