Random Access on Unlicensed Carrier via Licensed Mediator
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, the random access procedure on unlicensed carriers faces challenges due to resource contention, leading to potential failures in transmitting or receiving random access preambles and responses, which hinders efficient access initiation and response mechanisms.
Innovation Solution
A method and apparatus for user equipment (UE) to perform a random access procedure on an unlicensed carrier by transmitting a random access preamble and receiving a response, including an index of a second cell, where the first cell is on a licensed carrier and the second cell is on an unlicensed carrier, enabling efficient random access procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If random access procedure is performed on unlicensed carrier, then service capacity and frequency band utilization are improved, but resource contention and transmission reliability deteriorate
Solution Approach 1:
The patent introduces a licensed carrier as an intermediary channel for random access procedures. The UE transmits random access preambles on the licensed carrier (which has guaranteed resources) rather than directly on the unlicensed carrier, while still establishing access to cells on unlicensed carriers. This mediator approach allows the system to benefit from unlicensed spectrum capacity while avoiding its contention-based reliability issues.
2Speed
If random access preamble transmission on unlicensed carrier is attempted, then access speed is improved, but transmission success rate deteriorates due to resource contention
Solution Approach 1:
The patent segments the random access procedure into two distinct phases: (1) preamble transmission phase on the licensed carrier with guaranteed resources, and (2) data transmission phase on the unlicensed carrier. This segmentation allows the critical access initiation step to occur on a reliable channel while still enabling eventual access to unlicensed carrier resources, thus maintaining both speed and success rate.
3Adaptability or versatility
If unlicensed spectrum is used for data transmission, then frequency band utilization is improved, but coexistence with other technologies becomes more difficult
Solution Approach 1:
The licensed carrier serves as a mediator that simplifies coexistence management. By handling random access procedures on the licensed carrier, the system avoids direct contention with Wi-Fi and other unlicensed technologies during the critical access phase. The unlicensed carrier can then be used for data transmission with reduced interference from random access activities of other systems.
Data Source
AI summary
A method and apparatus for performing a random access procedure at a cell on an unlicensed carrier in a wireless communication system is provided. A user equipment (UE) transmits a random access preamble, and receives a random access response including an index of a second cell. A first cell is a first serving cell on a licensed carrier, and the second cell is a second serving cell on the unlicensed carrier.