Dynamic Transport Block Size Control via Backhaul Packet Loss
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Solution Overview
Problem
IP packets can be lost during transmission from a UE to a remote entity due to backhaul congestion and other issues, leading to increased load on the air interface and retransmissions.
Innovation Solution
An access node dynamically controls the size of transport blocks based on the level of uplink packet loss on its backhaul interface, causing UEs to scale down the size of their transport blocks to reduce the load on the air interface during TCP retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If UEs transmit large transport blocks over the air interface, then data throughput is improved, but load on the air interface increases during retransmissions when packet loss occurs
Solution Approach 1:
The patent implements dynamic adjustment of transport block size based on real-time backhaul packet loss rate monitoring. The access node scales the TBS dynamically - using larger blocks when packet loss is low to maximize throughput, and scaling down when packet loss increases to reduce retransmission overhead. This dynamic adaptation resolves the contradiction by making the system flexible rather than static.
Solution Approach 2:
The system establishes a feedback loop where the access node monitors the backhaul packet loss rate and uses this information to control the TBS for air-interface transmissions. The packet loss rate measurement feeds back to the TBS scaling decision, creating a closed-loop control system that automatically adjusts to network conditions to balance throughput and retransmission load.
2Reliability
If transport block size is reduced to minimize retransmission overhead, then air interface load during retransmissions is reduced, but data throughput decreases
Solution Approach 1:
Rather than using a fixed reduced TBS, the system dynamically scales the TBS based on the monitored packet loss rate. When packet loss is low, the full TBS is used to maximize throughput. When packet loss increases, the TBS is scaled down proportionally to reduce retransmission overhead. This dynamic approach resolves the contradiction by adapting to actual network conditions.
Solution Approach 2:
The system changes the TBS parameter based on the packet loss rate condition. The access node calculates a scaled TBS that is a proportion of the original TBS, where the scaling factor is determined by the packet loss rate. This parameter change allows the system to optimize the balance between throughput and retransmission load according to real-time network state.
3Reliability
If TCP retransmissions are allowed to proceed normally, then data delivery reliability is maintained, but congestion on the air interface worsens due to repeated transmissions
Solution Approach 1:
The system takes preliminary action by scaling down the TBS before retransmissions occur, based on predictive monitoring of backhaul packet loss rate. By anticipating potential retransmission needs and pre-adjusting the TBS accordingly, the system prevents air interface congestion from worsening while still maintaining data delivery through TCP retransmission mechanisms.
Solution Approach 2:
The feedback mechanism monitors packet loss and adjusts TBS to control retransmission impact. When packet loss is detected, the system scales down TBS to reduce the burden of upcoming retransmissions on air interface capacity, while still allowing TCP retransmissions to proceed for reliability. This feedback-controlled approach balances reliability maintenance with congestion prevention.
Data Source
AI summary
A method and system to control transport block size (TBS) that a user equipment device (UE) served by an access node will use for uplink air-interface transmission from the UE to the access node, the TBS defining a quantity of data that the UE will provide in the uplink air-interface transmission. An example method includes (i) determining a rate of uplink backhaul packet loss of the backhaul interface and (ii) using the determined rate of uplink backhaul packet loss as a basis to control what TBS the UE will use for the uplink air-interface transmission.