LPP Reliable Transport via Implicit Acknowledgement
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Solution Overview
Problem
The LTE Positioning Protocol (LPP) experiences reliability issues due to senders becoming stuck in a wait-for-acknowledgement state when non-piggybacked acknowledgments are lost, leading to unnecessary retransmissions and latency in location-based services, especially in latency-tolerant applications like E-911 emergency services.
Innovation Solution
Implementing a mechanism where mobile devices and location servers can accept a substitute/implicit acknowledgement, such as an LPP Provide Assistance Data or Error message, to exit the wait-for-acknowledgement state, allowing for continued uplink signaling and reducing unnecessary retransmissions by matching transaction IDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sender waits for a non-piggybacked acknowledgement before sending the next message, then message delivery reliability is improved, but system latency increases and productivity decreases
Solution Approach 1:
The receiver sends the acknowledgement message in advance before the timeout period expires, allowing the sender to proceed with subsequent messages without waiting for the full timeout duration. This preliminary action reduces system latency while maintaining reliable message delivery.
Solution Approach 2:
The system dynamically adjusts the wait time for acknowledgements by implementing a configurable timeout period that can be optimized based on network conditions and service requirements, balancing reliability and latency for different operating scenarios.
2Reliability
If the sender retransmits unacknowledged messages multiple times, then message delivery reliability is improved, but signaling load increases and network resources are wasted
Solution Approach 1:
The system implements a feedback mechanism where the receiver proactively sends acknowledgements to inform the sender about successful message reception. This feedback prevents unnecessary retransmissions by providing timely confirmation, thereby reducing network signaling load and energy consumption.
Solution Approach 2:
The receiver autonomously manages the acknowledgement process by automatically sending confirmation messages when data is successfully received, eliminating the need for the sender to continuously retransmit and wait for confirmation, thus reducing overall network traffic.
3Stability of the object's composition
If the sender enters a wait-for-acknowledgement state, then message ordering is maintained, but device complexity increases and ease of operation decreases
Solution Approach 1:
Instead of requiring the sender to wait for acknowledgements before sending any subsequent messages, the system allows partial progression by enabling the sender to transmit messages within the timeout period while maintaining ordering through sequence numbers and timeout-based flow control.
Data Source
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AI summary
Techniques disclosed herein provide for enhanced LTE Positioning Protocol (LPP) Reliable Transport where the receiver of an LPP message sends a non-piggybacked acknowledgement. An example method for executing on a mobile device a protocol session with a location server includes sending a first protocol session message associated with a first protocol session to the location server, entering a wait-for-acknowledgement state in which uplink transmissions from the mobile device to the location server are suspended while waiting for an acknowledgement from the location server in response to the first protocol session message, receiving a second protocol session message associated with a second protocol session which is not an acknowledgement to the first protocol session message but includes information requested in the first protocol session message; exiting the wait-for-acknowledgement state responsive to receiving the second protocol session message; and performing an action using the information received in the second protocol session message.