Grouped DTIM Scheduling for WLAN Buffer Collision Reduction
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Solution Overview
Problem
In wireless local area networks (WLANs), the power save mode leads to collisions among multiple stations accessing the channel to retrieve buffered data, as the traffic indication map (TIM) is not efficiently managed, resulting in increased power consumption and network performance issues.
Innovation Solution
The solution involves grouping stations based on service and traffic characteristics, assigning different wake-up intervals, and using a delivery traffic indication map (DTIM) with a group ID, counter, and offset to manage the transmission schedule, allowing stations to wake up at different times and reducing collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple STAs wake up at the same time to check buffered data, then they can all access the channel to retrieve their data, but collisions occur between STAs during channel access
Solution Approach 1:
The patent segments the single TIM structure into multiple group DTIM structures, each serving a specific group of STAs. By dividing the 2007 STAs into multiple groups (e.g., Group 0, Group 1, etc.), each group has its own DTIM transmission schedule, which distributes channel access attempts across different time slots and reduces collision probability.
Solution Approach 2:
The patent implements periodic group DTIM transmissions with different intervals for different groups. Each group wakes up at periodic intervals determined by their group DTIM transmission schedule, staggering their channel access attempts. For example, Group 0 may wake up every 100ms while Group 1 wakes up every 200ms, creating a periodic pattern that avoids simultaneous access.
2Quantity of substance
If the TIM includes bits for many STAs (e.g., 2008 bits for 2007 STAs), then all STAs can be monitored, but the TIM becomes large and managing buffered data for hundreds of STAs causes collisions
Solution Approach 1:
The patent divides the large TIM structure into multiple smaller group DTIM structures. Instead of one TIM covering all 2007 STAs, the system creates multiple group DTIMs, each covering a subset of STAs. This segmentation reduces the number of STAs that need to be monitored simultaneously in each DTIM, thereby reducing collision probability while maintaining coverage of all STAs.
Solution Approach 2:
The patent introduces a new dimension of group identification (group ID) to organize STAs. By adding the group dimension, the system transitions from a flat TIM structure to a hierarchical structure where STAs are first divided into groups, then managed within each group. This dimensional change enables more efficient management of large numbers of STAs.
3Loss of time
If STAs wake up frequently to check for buffered data, then they can retrieve data quickly, but power consumption increases
Solution Approach 1:
The patent implements periodic wake-up schedules for different STA groups, where each group wakes up at predetermined intervals to check for group DTIM transmissions. This periodic action allows STAs to remain in sleep mode for extended periods, reducing power consumption, while still enabling timely data retrieval when data is available. The periodic wake-up pattern balances energy savings with data access responsiveness.
Solution Approach 2:
The patent enables dynamic adjustment of wake-up intervals for different groups based on their data reception patterns. Groups with frequent data arrivals can have shorter wake-up intervals, while groups with infrequent data can have longer intervals, optimizing the balance between power consumption and data retrieval time dynamically.
4Device complexity
If a single TIM is used for all STAs, then the structure is simple, but managing buffered data for large numbers of STAs (e.g., 6000 sensor nodes) causes collisions and inefficiency
Solution Approach 1:
The patent segments the monolithic TIM structure into multiple group DTIM structures, each managing a subset of STAs. This segmentation improves network performance by reducing collisions and enabling more efficient buffered data management, while the modular group-based structure maintains manageable complexity through standardized group formation and DTIM transmission procedures.
Data Source
AI summary
Disclosed is a technology that enables an access point, configured to manage a network, to control a transmission schedule of buffered data and enables a terminal to obtain information associated with the transmission schedule in a wireless local area network (WLAN) environment. An apparatus for controlling a transmission schedule of buffered data in a WLAN according to an embodiment may group terminals based on at least one of a service characteristic and a traffic characteristic of each of the terminals, assign group information to each of the grouped groups to wake up in a different time, and transmit at least one of delivery traffic indication map (DTIM) information and the buffered data based on the assigned group information.