Reliable Broadcast Multicast Transmission in Wireless LAN
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Solution Overview
Problem
Current wireless communication systems face challenges in ensuring reliable and high-throughput multicast/broadcast traffic, particularly for streaming media, due to infrequent and unreliable broadcast/multicast frames in wireless networks.
Innovation Solution
Implementing a method that marks each frame as reliable, uses collision avoidance message exchanges before transmission, adjusts transmission rates based on feedback from stations, and schedules RBM bursts at optimal times, including the use of RTS/CTS sequences and higher physical layer rates, with feedback mechanisms for packet error rate, received signal strength, and modulation coding schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If broadcast/multicast frames are transmitted at basic rate to ensure all stations can receive, then coverage and compatibility are improved, but transmission throughput and efficiency deteriorate
Solution Approach 1:
The patent segments broadcast/multicast traffic into two categories: traditional control traffic (sent at basic rate for compatibility) and reliable broadcast/multicast (RBM) traffic (sent at higher rates for efficiency). This segmentation allows different transmission strategies for different traffic types, resolving the contradiction between coverage and throughput.
Solution Approach 2:
The patent implements dynamic transmission rates by allowing stations to negotiate and report their capabilities, with the access point adjusting RBM transmission rates based on station feedback. This dynamic approach enables higher throughput for capable stations while maintaining basic rate compatibility for all stations.
2Device complexity
If traditional broadcast/multicast is used without acknowledgment, then system complexity is reduced, but transmission reliability deteriorates
Solution Approach 1:
The patent introduces feedback mechanisms where receiving stations send acknowledgments for RBM frames, and transmitting stations retransmit if acknowledgments are not received. This feedback loop significantly improves reliability while maintaining manageable system complexity through selective application to RBM traffic only.
Solution Approach 2:
The patent applies different reliability mechanisms to different traffic types: traditional BM traffic maintains simple no-acknowledgment operation, while RBM traffic implements full acknowledgment and retransmission. This local quality differentiation resolves the contradiction by applying complexity only where needed for reliability.
3Reliability
If collision avoidance protocols are implemented before RBM transmission, then transmission reliability is improved, but transmission delay increases
Solution Approach 1:
The patent implements preliminary collision avoidance actions (RTS/CTS exchanges) before RBM transmission bursts. These preliminary actions reserve the medium and prevent collisions, ensuring reliable transmission of the subsequent data burst while minimizing overall delay through efficient medium reservation.
Data Source
AI summary
Broadcast and multicast (BM) systems have not been reliable in the wireless local area networks. Higher bandwidth and more reliable BM transmissions are necessitated by video and audio applications. A class of BM reliable frames is transmitted at a higher rate. The access point performs some rudimentary collision avoidance to enhance reliability, and individual stations are given the ability to send feedback to the access point regarding the quality of the transmission.