Multicast Frame Transmission Using Directional Antennas and RTS-CTS Negotiation
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Solution Overview
Problem
Current multicast transmission in wireless local area networks (WLANs) faces challenges in ensuring reliable data delivery and expanding service coverage, particularly in VHT WLAN systems operating at 60 GHz, where narrow service coverage and lack of error recovery mechanisms lead to unreliable data transmission.
Innovation Solution
The method involves using a directional antenna for transmitting multicast frames, with a request to send (RTS) frame and clear to send (CTS) frame exchange to determine the antenna mode, and incorporating a retransmission indicator field in the multicast frame to manage retransmissions, ensuring that all stations receive the data correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a directional antenna is used for multicast frame transmission, then service coverage is expanded and transmission reliability is improved, but the complexity of determining antenna mode and managing retransmissions increases
Solution Approach 1:
The patent applies preliminary action by having the transmitting station send an RTS frame before the actual multicast frame to negotiate and determine the antenna mode in advance. This preliminary communication ensures that all receiving stations are prepared with the correct antenna configuration before data transmission begins, reducing complexity during the actual transmission process.
Solution Approach 2:
The patent implements feedback through the RTS-CTS frame exchange mechanism. The transmitting station receives feedback from receiving stations about their antenna mode capability and preference, and adjusts the transmission accordingly. This feedback loop ensures reliable communication while managing complexity through standardized protocols.
2Area of stationary object
If directional antenna transmission is used, then service coverage is expanded, but the need for RTS/CTS frame exchange increases protocol complexity
Solution Approach 1:
The RTS frame is sent as a preliminary action before the actual multicast transmission to establish the antenna mode and reserve the transmission channel. This preliminary step enables directional transmission to cover expanded areas while managing protocol complexity through a standardized preliminary exchange.
Solution Approach 2:
The RTS frame serves multiple functions: it reserves the transmission channel, determines the antenna mode, and coordinates the transmission timing. This multi-functionality reduces the need for separate protocol steps, thereby managing complexity while enabling expanded service coverage.
3Productivity
If multicast frames are transmitted without error recovery mechanisms, then transmission speed is maintained, but data delivery reliability deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a retransmission indicator field in the multicast frame that prepares receiving stations for potential retransmissions. This field allows stations to identify and handle retransmitted frames appropriately, cushioning against transmission errors without significantly impacting the overall transmission speed.
Solution Approach 2:
The retransmission indicator field provides feedback information to receiving stations about the transmission status, enabling them to manage retransmissions efficiently. This feedback mechanism maintains reliability by allowing stations to know when retransmission is needed while minimizing the impact on transmission speed.
4Area of stationary object
If directional antenna mode is used for multicast transmission, then service coverage is expanded, but the difficulty of detecting duplicate frames increases
Solution Approach 1:
The retransmission indicator field provides feedback information that helps receiving stations detect duplicate frames. By knowing whether a frame is a retransmission through this indicator, stations can easily identify duplicates even when directional antenna transmission is used, thereby reducing detection difficulty while maintaining expanded service coverage.
Data Source
AI summary
A method and apparatus of transmitting a multicast frame in a wireless communication system is provided. The method comprises transmitting a request to send (RTS) frame to stations (STAs) included in a multicast group by using an omni-directional antenna, and receiving a clear to send (CTS) frame transmitted by the STAs included in the multicast group in response to the RTS frame, and transmitting the multicast frame to the STAs included in the multicast group by using a directional antenna.