Early Uplink TBF Establishment for EGPRS Latency Reduction
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Solution Overview
Problem
The setup time of a TBF in (E)GPRS systems is several hundreds of milliseconds, which significantly impairs performance for delay-sensitive real-time applications like VoIP over cellular networks, as existing solutions like 'Phantom TBFs' add complexity and require multiple TBF support.
Innovation Solution
A method for early uplink TBF establishment where a mobile station requests and the network sets up an uplink TBF even before data is available, allowing transmission of dummy packets until actual data is ready, thus avoiding the need for re-establishing the TBF during data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a TBF is established using the conventional random access procedure, then the connection is reliably established, but the setup time is several hundreds of milliseconds which impairs performance for delay-sensitive applications
Solution Approach 1:
The mobile station initiates TBF establishment before actual data is available for transmission. The network allocates uplink resources and establishes the TBF in advance, so that when data becomes available, transmission can begin immediately without waiting for the conventional random access procedure. This preliminary action reduces the effective setup time experienced by the application.
2Loss of time
If early TBF establishment is implemented, then setup time is reduced to near zero, but the network must allocate resources and manage TBFs before data is available
Solution Approach 1:
The mobile station autonomously determines when to initiate TBF establishment based on its own data availability status. The mobile sends data directly on the allocated uplink TBF when ready, without requiring network coordination or special signaling. This self-service approach reduces network management complexity while maintaining the benefits of early establishment.
3Productivity
If the mobile transmits data immediately when available, then real-time performance is improved, but the TBF setup time of several hundreds of milliseconds cannot be avoided
Solution Approach 1:
The network performs the resource allocation and TBF setup actions in advance, before the mobile has data to transmit. This preliminary action separates the setup phase from the data transmission phase, allowing the mobile to begin transmitting immediately when data becomes available, thus achieving both fast transmission and reduced effective setup time.
Data Source
AI summary
A mobile station operating in EGPRS mode needs to the early establishment of an uplink TBF although has not data to send, at the only precautionary purpose of preventing an intolerable latency negatively affecting the subsequent delay-sensitive transmissions. To this aim, the mobile sends a Packet Channel Request message in one phase access mode including a new establishment cause called “Early TBF establishment.” The network establishes an uplink TBF indicating the requester and assigns a radio resource on one PDCH channel or more. Then the network schedules the transmission from the mobile station also when it does not have data to transmit other than dummy packets. This is performed through the USF flags in the usual manner. As soon as actual data become available for transmission, the mobile send them instead of dummy packets. In an alternative embodiment the mobile sends the Packet Channel Request message in two phase access mode. As soon as the Packet Uplink Assignment message is received by the mobile station, it sends a Packet resource Request message including an extended Uplink TBF information. The network behaves as in the previous case.