Loss-less Roaming Wireless Bridging for VoIP Packet Delivery
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Solution Overview
Problem
Wireless VoIP communication experiences packet loss during roaming between access points, leading to transmission interruptions and degraded voice quality due to high latency and inefficient handoff processes in wireless switch architectures.
Innovation Solution
A method and system for loss-less roaming that involves retransmitting voice packets from the initial access point to a mobile unit a predetermined number of times before forwarding them to a neighboring access point if acknowledgement is not received, ensuring seamless VoIP communication by minimizing packet exchange and utilizing IEEE 802.11r for fast handoffs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If voice packets are transmitted directly from the first access point to the mobile unit during roaming, then transmission speed is improved, but packet loss occurs when the mobile unit moves out of range before acknowledgement is received
Solution Approach 1:
The system performs preliminary retransmission actions at the first access point before the mobile unit fully roams to the second access point. By retransmitting packets a predetermined number of times and monitoring for acknowledgments, the system proactively ensures packet delivery during the transition period, preventing packet loss that would occur with direct transmission only.
Solution Approach 2:
The first access point acts as an intermediary between the voice packet source and the mobile unit during roaming. It receives voice packets, attempts delivery to the mobile unit, and if unsuccessful, forwards them to the second access point. This intermediary role ensures reliable packet delivery by providing multiple delivery paths during the roaming transition.
2Reliability
If the system retransmits voice packets multiple times before forwarding to the second access point, then packet loss is reduced, but transmission latency increases
Solution Approach 1:
The system performs a predetermined number of retransmission attempts (partial action) rather than unlimited retransmissions (excessive action). This limited retransmission approach provides sufficient reliability improvement while avoiding excessive latency that would result from continuous retransmission attempts, finding an optimal balance between the two competing requirements.
Solution Approach 2:
The retransmission process occurs in periodic intervals rather than continuously. The system attempts delivery, waits for acknowledgment, and if unsuccessful, retransmits after a predetermined interval. This periodic approach reduces continuous latency accumulation while maintaining reliability through multiple structured attempts before forwarding to the second access point.
3Speed
If the system forwards packets to the second access point immediately when acknowledgement is not received, then transmission speed is maintained, but packet loss occurs during the handoff transition
Solution Approach 1:
The system performs preliminary retransmission actions at the first access point before the mobile unit fully roams to the second access point. By retransmitting packets a predetermined number of times and monitoring for acknowledgments, the system proactively ensures packet delivery during the transition period, preventing packet loss that would occur with direct transmission only.
Solution Approach 2:
The system uses acknowledgment feedback from the mobile unit to determine whether to retransmit or forward packets. When an acknowledgment is received, the system knows the packet was successfully delivered. When no acknowledgment is received after predetermined retransmission attempts, the system forwards the packet to the second access point. This feedback mechanism optimizes the balance between speed and packet loss prevention.
Data Source
AI summary
Described is a method for transmitting a voice packet from a first access point (“AP”) to a mobile unit (“MU”), forwarding the voice packet from the first AP to a second AP when acknowledgement of receipt of the voice packet is not received by the first AP and transmitting the voice packet from the second AP to the MU. Also, a system having a first access point (“AP”) transmitting a voice packet to a mobile unit (“MU”) and forwarding the voice packet when acknowledgement of receipt of the voice packet from the MU is not received by the first AP and a second AP receiving the forwarded voice packet from the first AP and transmitting the voice packet to the MU.