RRC Connected UE Uplink Synchronization Management
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Solution Overview
Problem
In LTE cellular networks, maintaining uplink synchronization for all User Equipment (UE) devices can lead to a higher probability of call failure when unsynchronized UEs attempt to start uplink data transmission, due to resynchronization and resource allocation challenges, limiting the number of UEs that can remain in the RRC Connected state.
Innovation Solution
A method and system that dynamically determine whether RRC connected user equipment devices should be kept uplink synchronized or allowed to become unsynchronized based on specific conditions within the cell, such as load thresholds, by adjusting the time alignment timer value and using inactivity timers to manage resource allocation and reduce synchronization requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all RRC connected UEs are kept uplink synchronized, then call reliability is improved, but the number of UEs that can remain in RRC Connected state is limited due to resource allocation constraints
Solution Approach 1:
The patent applies dynamics by making the time alignment timer value configurable and adjustable based on network conditions. The base station can dynamically set the timer to zero or non-zero values, and the UE adapts its synchronization behavior accordingly, transitioning between synchronized and unsynchronized states as needed to balance reliability and capacity.
Solution Approach 2:
The patent changes the parameter of the time alignment timer value from a fixed state to a variable state. By modifying this parameter (setting it to zero or non-zero), the system controls whether UEs maintain uplink synchronization, thereby adjusting the balance between call reliability and the number of connected UEs the network can support.
2Quantity of substance
If RRC connected UEs are allowed to become unsynchronized, then the number of UEs in RRC Connected state increases, but call failure probability increases during uplink data transmission
Solution Approach 1:
The system dynamically adjusts the synchronization state of UEs based on network load and conditions. When capacity is needed, UEs are allowed to become unsynchronized; when reliability is prioritized, the system can enforce synchronization by setting the time alignment timer appropriately, creating a flexible response to varying operational requirements.
Solution Approach 2:
By changing the time alignment timer parameter between zero and non-zero values, the system controls the degree of synchronization maintained by UEs. This parameter change enables the network to modulate between supporting more UEs in connected state versus maintaining higher call reliability, depending on current network conditions.
3Reliability
If the time alignment timer is set to zero, then UEs never lose uplink synchronization, but resource allocation demands increase during high load periods
Solution Approach 1:
Instead of maintaining full synchronization (time alignment timer set to zero) for all UEs at all times, the patent applies partial action by allowing some UEs to operate with relaxed synchronization requirements (non-zero timer values that allow expiration). This reduces the overall resource allocation burden on the network while maintaining sufficient synchronization for active transmissions.
Solution Approach 2:
The patent changes the time alignment timer parameter from a fixed zero value to a variable value that can be adjusted based on network load. This parameter change allows the system to reduce resource allocation demands during high load periods by permitting UEs to lose synchronization, while maintaining synchronization when resources are abundant.
Data Source
AI summary
Embodiments include methods of operating a user equipment (UE) in a serving cell provided by a base station in a cellular communications network. These embodiments include establishing a Radio Resource Control (RRC) connection with the base station, such that the UE is operating in an RRC Connected state according to a first value of a parameter (e.g., a time alignment timer value) affecting the UE's uplink synchronization with the serving cell. These embodiments also include initiating a reconfiguration of the RRC connection towards the base station and, in response to initiating the reconfiguration, receiving from the base station a second value of the parameter affecting the UE's uplink synchronization with the serving cell. These embodiments also include operating in an RRC Connected state according to the second value of the parameter. Other embodiments include UEs configured to perform operations corresponding to these methods.