Reservation-Based WLAN Protocol for Deterministic Video Transmission
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Solution Overview
Problem
Current IEEE 802.11 WLAN standards face challenges in providing reliable and deterministic delay for audio/video transmission due to insufficient support for broadcast and multicast transmissions, leading to collisions and lack of feedback mechanisms in wireless local area networks.
Innovation Solution
A reservation-based medium access scheme is implemented, where a TXOP information element is transmitted to reserve a transmit opportunity time interval, and protection frames are used to prevent collisions, along with block acknowledgements to ensure reliable transmission and deterministic delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If DCF protocol with CSMA/CA is used for medium access, then the network provides simple distributed access control, but transmission collisions occur frequently especially under high load conditions
Solution Approach 1:
The patent applies preliminary action by having stations perform carrier sense and back-off procedures before transmission. Each station waits for a random back-off period after detecting an idle medium, which prevents simultaneous transmissions and reduces collisions before they occur. This is implemented through the CSMA/CA protocol where stations decrement back-off counters only when the medium remains idle.
Solution Approach 2:
The patent implements feedback through the ACK mechanism where receiving stations send acknowledgement frames back to transmitting stations. This feedback loop allows the source station to verify successful transmission and request retransmission if needed, thereby improving reliability without fundamentally changing the distributed access approach.
2Reliability
If PCF protocol with centralized coordination is implemented, then transmission collisions are reduced through access coordination, but the system complexity increases and power saving mode integration becomes difficult
Solution Approach 1:
The patent uses preliminary carrier sense and back-off actions at the distributed level to achieve collision avoidance without requiring centralized polling. Stations independently perform these actions based on local medium status, eliminating the need for complex AP polling mechanisms while maintaining low collision rates.
Solution Approach 2:
The patent enables stations to self-regulate their transmission timing through distributed carrier sense and back-off procedures. Each station autonomously determines when to transmit based on medium idle periods and random back-off counters, eliminating the need for centralized coordination and reducing system complexity.
3Device complexity
If broadcast/multicast frames are transmitted without reservation, then the network maintains simple medium access, but intra-BSS and inter-BSS collisions occur during transmission
Solution Approach 1:
The patent applies preliminary carrier sense and back-off actions before broadcast/multicast transmission. The accessing station performs these procedures to ensure the medium is ready, and other stations follow similar procedures before attempting to transmit, thereby preventing collisions during broadcast/multicast operations without requiring complex reservation mechanisms.
4Ease of operation
If no feedback mechanism is provided for broadcast/multicast frames, then the network maintains simple operation, but reliable transmission cannot be ensured
Solution Approach 1:
The patent implements feedback by having receiving stations send ACK frames back to the transmitting station for broadcast/multicast frames. This allows the source station to verify successful delivery and trigger retransmission if needed, ensuring reliable transmission while adding only minimal operational complexity through the feedback mechanism.
Data Source
AI summary
A reliable and deterministic video communication protocol is provided. In one aspect, a method of transmitting data, audio or video frames in a basic service set having a plurality of stations in a wireless local area network transmits a transmit opportunity information element to reserve a transmit opportunity time interval. The method further transmits the data, audio or video frames to a number of the stations in the basic service set during the reserved transmit opportunity time interval. In another aspect, a method of transmitting data, audio or video frames in a basic service set having a plurality of stations in a wireless local area network first transmits protection frames to reserve a time interval, then transmits frames during the reserved time interval or during a non-reserved time interval. In yet another aspect, a method of transmitting data, audio or video frames in a basic service set having a plurality of stations in a wireless local area network utilizes acknowledgement frames from the plurality of stations to acknowledge the transmission. A wireless communication device is also provided.