Preamble Group Selection for Random Access Resource Allocation
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Solution Overview
Problem
In LTE wireless networks, non-synchronous random access transmissions by user equipment (UE) face challenges in efficiently allocating uplink resources and minimizing interference, particularly in scenarios where UEs are not time synchronized, leading to suboptimal resource allocation and potential power exceedance issues.
Innovation Solution
The implementation of a method that allows User Equipment (UE) to select between two message size groups for random access transmissions based on pathloss measurements and radio conditions, using complex amplitude zero autocorrelation (CAZAC) sequences for preamble signals, and broadcasting threshold values to optimize power control and resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-synchronous random access transmission is used by UE, then the UE can perform random access without time synchronization, but the resource allocation becomes suboptimal and interference increases
Solution Approach 1:
The preamble space is segmented into multiple groups (first group and second group) based on message size requirements. UEs select from appropriate groups based on their data buffer status, enabling differentiated resource allocation that optimizes both random access capability and resource efficiency simultaneously
Solution Approach 2:
Different preamble groups are assigned different properties (message size indications) to match different UE requirements. This local differentiation allows UEs with small messages to use group A and UEs with large messages to use group B, improving overall resource allocation efficiency while maintaining ease of operation
2Extent of automation
If UE transmits random access preamble without proper power control, then the transmission can be initiated autonomously, but the transmit power may exceed maximum allowed levels
Solution Approach 1:
The network provides pathloss reference information and message size group indications to UEs before random access transmission. UEs use this preliminary information to calculate appropriate transmit power levels, ensuring autonomous initiation while preventing power exceedance
Solution Approach 2:
The system uses pathloss measurements and message size group selections as feedback mechanisms. UEs adjust their transmit power based on pathloss references and the selected preamble group, creating a feedback loop that maintains automated operation within power constraints
3Productivity
If the network provides detailed resource allocation information, then resource allocation efficiency improves, but the signaling overhead increases
Solution Approach 1:
The pathloss reference information serves multiple functions: it enables power control, supports message size group selection, and provides timing reference. This multi-functionality improves resource allocation efficiency without requiring separate dedicated signaling for each function, thus limiting overhead increase
Data Source
AI summary
A transport block size (TBS) of a first uplink message (RACH Msg3) transmitted on a Physical Uplink Shared Channel (PUSCH) during a random access procedure in a User Equipment (UE) accessing a radio access network may be determined by receiving a pathloss threshold parameter. A downlink pathloss value indicative of radio link conditions between the UE and a base station (eNB) serving the UE is then determined. A smaller value of TBS is selected from a set of TBS values if the determined pathloss value is greater than an operating power level of the UE minus the pathloss threshold parameter. A larger value of TBS is selected if the pathloss value is less than the operating power level of the UE minus the pathloss threshold parameter and the TBS required to transmit the RACH Msg3 exceeds the smaller TBS value.