Enhanced RTS CTS Protocol for 802.11ac Multi-Channel Access
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Solution Overview
Problem
The legacy RTS/CTS signaling protocol in WLAN systems is inefficient in the new IEEE 802.11ac standard, as it restricts the use of the entire 80 or 160 MHz bandwidth, leading to wasted transmission capacity due to unsynchronized channel access and interference from hidden terminals.
Innovation Solution
The proposed solution involves an enhanced RTS/CTS protocol where the access node sends a CTS on secondary channels that are determined to be free from interference, synchronizing the NAV protection duration across all channels, allowing devices to transmit on assigned channels based on an unsolicited CTS frame, even if they did not send a reservation request on those channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the legacy RTS/CTS signaling protocol is used in IEEE 802.11ac systems, then channel access protection against hidden terminals is provided, but transmission capacity is wasted due to restriction of the entire 80 or 160 MHz bandwidth
Solution Approach 1:
The patent segments the 80 or 160 MHz bandwidth into multiple 20 MHz or 40 MHz channels, allowing different stations to transmit simultaneously on different channels. This segmentation enables parallel transmissions while maintaining protection against hidden terminal interference through channel-specific RTS/CTS signaling.
Solution Approach 2:
The patent introduces a new dimension to the RTS/CTS protocol by enabling the access point to send CTS frames to multiple stations simultaneously across different channels. This dimensional expansion from single-channel to multi-channel operation allows the system to maintain reliability while increasing overall transmission capacity.
2Productivity
If RTS/CTS signaling is extended to multiple channels, then more devices can transmit simultaneously, but channel access coordination becomes more complex
Solution Approach 1:
The patent creates a universal channel access mechanism where the access point manages multiple channels using an extended RTS/CTS protocol. The access point serves multiple stations across multiple channels simultaneously, providing multi-functionality that simplifies coordination compared to independent channel management.
Solution Approach 2:
The access point acts as an intermediary that coordinates channel access for multiple stations. By centralizing control at the access point and using it to send CTS frames to multiple stations, the system simplifies the coordination complexity that would otherwise exist between multiple peer stations.
3Reliability
If legacy devices transmit in 20 or 40 MHz bands using RTS/CTS, then they protect their transmissions, but other devices cannot use the entire 80 or 160 MHz spectrum
Solution Approach 1:
The patent segments the spectrum into multiple channels and allows legacy devices to operate on their assigned channels while non-legacy devices simultaneously use other channels. This segmentation enables spectrum utilization to expand to the entire 80 or 160 MHz band rather than being restricted to individual 20 or 40 MHz portions.
Solution Approach 2:
The patent applies different transmission characteristics to different channels based on local conditions. Legacy devices maintain their protected transmissions on their assigned channels, while other devices can transmit on different channels without interference, optimizing spectrum utilization according to local device capabilities and channel conditions.
Data Source
AI summary
In one embodiment, in absence of transmitting from an apparatus a reservation request frame, the apparatus receives a reservation response frame on an assigned channel. The reservation response frame indicates a duration of a frame transmission. In response to receiving the reservation response frame, the apparatus transmits a frame on the assigned channel during the frame transmission. In another embodiment, in response to receiving a reservation request frame on a first channel at an apparatus, the apparatus transmits a reservation response frame on the first channel and on at least one second channel. The reservation request frame indicates a duration of a frame transmission. The reservation response frame indicates the duration of the frame transmission. After transmitting the reservation response frame, this apparatus receives during the frame transmission a first frame on the primary channel and a second frame on the at least one secondary channel.