Roaming Packet Forwarding via Access Point Bridging
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Solution Overview
Problem
Wireless client devices experience packet loss during roaming between access points in wireless local area networks, particularly in time-critical applications like voice over WLAN, due to latency and delayed packet retransmission methods being ineffective.
Innovation Solution
Implementing techniques where the original access point maintains an acknowledgement counter for packets and forwards them to neighbor access points after a certain number of retries, ensuring seamless packet transmission by updating the source address field and using transfer messages to facilitate continuous communication during roaming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wireless client devices roam between access points, then mobility is achieved, but packet loss occurs during roaming transition
Solution Approach 1:
The system performs preliminary actions by maintaining packet buffering at the wireless switch during the roaming transition period. Packets are held in a buffer before being forwarded to the new access point, ensuring no packet is lost during the handover. This preliminary buffering action prevents packet loss while enabling seamless roaming.
Solution Approach 2:
The wireless switch acts as an intermediary between the old and new access points during roaming. It receives packets destined for the roaming client from the old AP, buffers them, and then forwards them to the new AP after the client successfully associates. This intermediary buffering mechanism ensures continuous packet delivery despite the client moving between APs.
2Reliability
If packets are delayed for retransmission after roaming, then packet loss is reduced, but latency increases making it unsuitable for time-critical applications
Solution Approach 1:
The system prepares for potential packet loss by pre-buffering packets at the wireless switch before the roaming transition completes. This preliminary action ensures packets are ready to be immediately forwarded to the new AP once the client associates, avoiding both loss and excessive delay.
Solution Approach 2:
The buffering duration is dynamic rather than fixed. Packets are buffered only for the brief period needed during roaming transition, then immediately forwarded. This dynamic approach minimizes latency while ensuring no packet is lost, making the system suitable for time-critical applications like voice over WLAN.
3Reliability
If basic service set coordination is used to avoid roaming issues, then packet loss is prevented, but device complexity increases due to tight beacon coordination requirements
Solution Approach 1:
The wireless switch serves as an intermediary that simplifies the roaming process. Instead of requiring complex beacon coordination between multiple APs, the wireless switch handles packet buffering and forwarding, allowing APs to operate independently with standard 802.11 protocols. This reduces device complexity while maintaining reliable packet delivery.
Solution Approach 2:
The complex coordination logic is extracted from the access points and centralized in the wireless switch. The APs only need to perform standard beacon transmission and client association, while the wireless switch handles the complex packet buffering and forwarding during roaming. This extraction reduces the complexity burden on individual APs.
Data Source
AI summary
In a network comprising a wireless device, a first access point (AP) and a plurality of neighbor APs, a method is provided for reducing the chances of packet loss when the wireless device roams from the first AP to one of the neighbor APs. For example, when the first AP is transmitting a particular packet of a packet stream from to the wireless device, the wireless device begins to move away from the first AP toward at least one of the neighbor APs. The first AP maintains an acknowledgement counter for the particular packet which counts a number of times the particular packet has been transmitted by the first AP without receiving an acknowledgement (ACK) message from the wireless device confirming successful reception of the particular packet from the first AP. The first AP determines whether an ACK message was received for the particular packet, and if not, the first AP determines whether the number of times the particular packet has been sent is equal to a particular number of attempts. If the first AP determines that the number of times is equal to the particular number of attempts, then the first AP forwards the particular packet to the neighbor APs. Any of the neighbor APs which receive the particular packet, can then format the source address field of the particular packet with the MAC address of the first AP, and forward it to the wireless device.