GSM/EDGE RLC/MAC Window Size Adjustment for Latency Reduction
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Solution Overview
Problem
Current GSM/EDGE networks face significant latency issues in delivering RLC/MAC radio blocks to higher protocol layers, particularly in non-persistent mode, which affects delay-sensitive services like VoIP, due to the minimum window size causing intrinsic delays and discarding of packets outside the receive window.
Innovation Solution
The method involves setting a smaller transmit/receive window size for RLC/MAC radio blocks within a range of predetermined values, including notification messages to adjust window sizes dynamically, allowing for retransmissions and in-sequence delivery of correctly received blocks, reducing latency and packet loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a minimum window size of 64 RLC/MAC radio blocks is used in non-persistent mode, then reliable packet reception is ensured, but intrinsic latency of 1,280 ms is introduced
Solution Approach 1:
The patent applies dynamics by making the window size adjustable rather than fixed. The network can dynamically select from multiple predetermined window size values (e.g., 16, 32, 64, 128 blocks) based on traffic conditions and service requirements. This allows the system to adapt between reliability and latency trade-offs in real-time, resolving the contradiction between minimum window size constraints and latency reduction needs.
Solution Approach 2:
The patent changes the parameter of window size from a fixed minimum value to a variable parameter with multiple possible values. By allowing the window size to be configured based on service type and network conditions, the system can optimize the balance between packet reception reliability and transmission latency, directly addressing the technical contradiction presented in the background.
2Reliability
If a larger receive window size is used, then packet loss is reduced, but latency increases
Solution Approach 1:
The system dynamically adjusts the receive window size based on current network conditions and service requirements. For delay-sensitive services like VoIP, smaller window sizes can be selected to reduce latency, while for reliability-critical services, larger window sizes can be used to minimize packet loss. This dynamic adaptation resolves the contradiction between packet delivery success rate and delivery delay.
3Device complexity
If standard window sizes are used for all services, then protocol simplicity is maintained, but performance optimization for delay-sensitive services is lost
Solution Approach 1:
The patent segments the service types into different categories (e.g., delay-sensitive vs. non-delay-sensitive services) and applies different window size configurations to each segment. This allows the system to maintain protocol simplicity through standardized configurations while achieving performance optimization for specific service types, resolving the contradiction between protocol complexity and service performance efficiency.
Data Source
AI summary
A transmitting peer transmits radio blocks over a radio interface from within a transmit window. A receiving peer receives the radio blocks within a receive window, and in case of a not correctly received radio block, sending back a NACK (Not Acknowledged) signaling message to inform the transmitting peer of reception failure. Upon reception of the NACK signaling message, the transmitting peer retransmits, until expiration of the transmit window, the not correctly received RLC/MAC radio block. The radio blocks are re-assembling in sequence at the receiving peer. Each radio block is considered as being permanently lost if not correctly received within the receive window. All correctly received radio blocks are delivered to a higher protocol layer. The network transmits a notification message to both the transmitting peer and the receiving peer to select a size of the transmit and receive windows inside a range of predetermined values including values less than 64 radio blocks.