STA PS-Poll Retransmission in Wireless LAN Beacon Intervals
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Solution Overview
Problem
In wireless local area networks, especially in scenarios with a large number of STAs, existing methods fail to handle situations where STAs cannot successfully receive or transmit data within designated time periods, leading to energy inefficiency and data loss due to collisions and retransmissions, particularly in intelligent meter reading scenarios with up to 6000 STAs.
Innovation Solution
A method and device that allow STAs to retransmit PS-Polls and uplink data in reserved time periods after initial unsuccessful attempts, enabling them to acquire or transmit data correctly by reselecting time slots within the current or subsequent beacon intervals, thereby reducing data loss and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If STAs use time-slot division with CSMA/CA for PS-Poll competition, then collision probability of PS-Polls is reduced, but data loss occurs when PS-Poll or ACK is lost within the time slot
Solution Approach 1:
The patent pre-divides the beacon interval into multiple time slots and assigns specific time slots for PS-Poll transmission and other data transmissions. This preliminary arrangement prevents collisions between different types of traffic and ensures that STAs know exactly when to transmit or receive, improving reliability without requiring excessive retransmissions.
Solution Approach 2:
The patent implements a feedback mechanism where the AP sends ACK frames to confirm successful receipt of PS-Polls, and STAs can request retransmission if data is lost. This feedback system ensures reliable data delivery while minimizing energy waste through targeted retransmissions only when necessary.
2Reliability
If STAs are awakened periodically to receive beacons and compete for PS-Polls, then downlink data can be acquired, but energy consumption increases due to competition and waiting
Solution Approach 1:
The patent uses periodic beacon intervals with pre-assigned time slots for different transmissions. STAs wake up periodically to receive beacons and then transmit or receive data in their assigned time slots without continuous competition, reducing energy consumption while maintaining reliable data transmission.
Solution Approach 2:
The patent segments the beacon interval into multiple time slots with different functions (PS-Poll competition, downlink data transmission, uplink data transmission). This segmentation allows STAs to sleep during non-critical periods and only wake for essential operations, reducing overall energy consumption while ensuring data reliability.
3Reliability
If PS-Polls are scattered and transmitted separately from downlink data, then conflict probability is reduced, but handling mechanism is unavailable when data cannot be received within divided time period
Solution Approach 1:
The patent divides the beacon interval into distinct time slots for PS-Poll transmission, downlink data transmission, and uplink data transmission. This segmentation separates different traffic types to eliminate conflicts while providing clear rules for STA behavior in each slot, managing complexity through structured organization.
Solution Approach 2:
The patent incorporates feedback mechanisms within each time slot type, allowing STAs to receive ACKs for successful transmissions and request retransmissions when data is lost. This feedback system maintains reliability across the segmented structure without requiring complex centralized control.
4Productivity
If uplink data transmission is based on time-slot division, then channel access is organized, but retransmission handling is unavailable when transmission is unsuccessful
Solution Approach 1:
The patent allocates periodic uplink time slots within beacon intervals for STAs to transmit data. If transmission fails, the structured periodic nature of the time slots provides natural opportunities for retransmission in subsequent cycles, maintaining both efficiency and reliability.
Solution Approach 2:
The patent implements feedback mechanisms where the AP acknowledges successful uplink transmissions and triggers retransmissions when data is lost. This feedback system ensures reliable uplink data transmission while maintaining the efficiency benefits of time-slot organized access.
Data Source
AI summary
The present invention provides a method and device for acquiring and transmitting data by an STA in a wireless local area network. The method includes: transmitting, by the STA, a PS-Poll, and receiving downlink data returned by the AP upon receipt of the PS-Poll, in a reserved time period within a current beacon interval according to a TIM contained in a beacon, after learning that the AP has the downlink data of the STA according to the received beacon, wherein the reserved time period is a period of time interval within the beacon interval; retransmitting, by the STA, the PS-Poll after the reserved time period to acquire the downlink data, if the STA can not successfully receive the downlink data within the reserved time period. Through the above solution, a mechanism is provided to address a situation that unsuccessful receiving/transmission of data can not be handled.