Target Wake Time Multicast Logic for Latency Reduction
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Solution Overview
Problem
Current wireless local area network (WLAN) standards, such as 802.11, face latency and priority inversion issues when handling multicast traffic in a basic service set (BSS), as all clients in a doze power save state must wait for a scheduled Delivery Traffic Indication Message (DTIM) time, leading to increased latency and priority inversion.
Innovation Solution
Implementing Target Wake Time (TWT) for multicast transmission logic, which identifies qualified IP multicast groups, negotiates a coincident overlap window for clients' wake times, and transmits multicast traffic during this window instead of the DTIM period, allowing for reduced latency and priority inversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If all clients in doze power save state wait for scheduled DTIM time to receive multicast traffic, then power save state is maintained, but latency increases and priority inversion occurs
Solution Approach 1:
The patent segments clients into different groups based on their multicast traffic requirements. Clients receiving time-sensitive multicast traffic are placed in a separate group from those that can tolerate longer delays. This segmentation allows the system to negotiate different TWT parameters for different client groups, reducing latency for urgent traffic while maintaining power save mode for all clients.
Solution Approach 2:
The patent implements dynamic TWT negotiation where the AP and clients can adjust their wake time schedules based on actual traffic conditions. The system dynamically creates coincident overlap windows when multicast traffic is detected, allowing clients to wake up at optimized times rather than fixed DTIM intervals. This dynamic adjustment reduces latency and priority inversion while maintaining power efficiency.
2Use of energy by moving object
If multicast traffic is held until DTIM time for clients in doze state, then power consumption is reduced, but priority inversion and latency increase
Solution Approach 1:
The patent performs preliminary action by negotiating TWT schedules in advance based on predicted multicast traffic patterns. The AP and clients establish coincident overlap windows before multicast traffic arrives, so that when time-sensitive multicast traffic needs to be delivered, clients are already scheduled to wake up at the appropriate time. This eliminates the need to hold all multicast traffic until DTIM time, maintaining both power efficiency and traffic priority.
Solution Approach 2:
The patent changes the timing parameters of client wake-ups from fixed DTIM intervals to negotiated TWT schedules. By adjusting the TWT parameters dynamically based on multicast traffic requirements, the system can reduce latency for high-priority traffic while maintaining extended doze periods for power savings. The coincident overlap window parameter is specifically tuned to match multicast traffic arrival times.
3Productivity
If all clients wake up at the same time after beacon for medium access, then simple power management is maintained, but contention increases and efficiency decreases
Solution Approach 1:
The patent implements periodic TWT schedules where clients wake up at staggered, predetermined intervals rather than all at once. The coincident overlap windows are negotiated periodically based on multicast traffic patterns, creating a rhythmic wake-up schedule that reduces contention. This periodic structure maintains simplicity while improving medium access efficiency by distributing client wake-ups over time.
Data Source
AI summary
Presented herein are methodologies for handling multicast traffic that is transmitted to mobile devices in a given basic service set (BSS). The methodology includes detecting membership of clients in an Internet Protocol (IP) multicast group in a basic service set of a wireless network; determining whether the IP multicast group and its associated multicast traffic meet predetermined criteria; when the IP multicast group and its associated multicast traffic meet the predetermined criteria, negotiating with each client in the IP multicast group to have a target wake time (TWT) that includes, at least, a coincident overlap window of sufficient duration to transmit the multicast traffic associated with the IP multicast group; and transmitting the multicast traffic associated with the IP multicast group during the coincident overlap window, wherein the coincident overlap window is different from a delivery traffic indication message (DTIM) service period.