Random Access Response Resource Mapping for Reduced Bandwidth Devices
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Solution Overview
Problem
Current random access procedures in LTE networks face challenges with reduced bandwidth devices, such as MTC UEs, where limited bandwidth restricts the capacity of the Random Access Channel (RACH) and makes it difficult for UEs to receive scheduling information for Random Access Response (RAR) messages, leading to reduced RACH capacity and inability to receive entire system bandwidth for physical control channels.
Innovation Solution
A predefined mapping is established between random access preamble indices and random access response resources, allowing each preamble index to map to different response resources in each subframe, enabling UEs to determine the correct resource for RAR messages even with reduced bandwidth, and potentially allowing multiple preamble indices to map to the same resource, with the option to change center frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If reduced bandwidth is used for MTC UEs, then device cost and power consumption are reduced, but RACH capacity is limited and UEs cannot receive scheduling information for RAR messages
Solution Approach 1:
The patent segments the RAR reception process by dividing the system bandwidth into multiple bandwidth parts. Each MTC UE is assigned a specific bandwidth part for receiving RAR messages, while other bandwidth parts remain available for eMBB traffic. This segmentation allows reduced bandwidth devices to operate effectively without compromising overall system capacity.
Solution Approach 2:
The patent introduces a new dimension for resource allocation by enabling UEs to change center frequency dynamically. Instead of being confined to a fixed narrow bandwidth, UEs can shift their reception frequency to access different bandwidth parts, effectively transforming a one-dimensional bandwidth limitation into a multi-dimensional resource space.
2Loss of information
If entire system bandwidth is received for physical control channels, then complete scheduling information is available, but power consumption and device complexity increase
Solution Approach 1:
The patent applies local quality by providing different bandwidth configurations to different UE types. MTC UEs receive only the necessary bandwidth part containing their scheduling information, while eMBB UEs utilize the full system bandwidth. This localized resource allocation ensures each UE type receives appropriate information without unnecessary power consumption.
3Reliability
If RAR messages are transmitted on dedicated resources, then reduced bandwidth UEs can receive them efficiently, but overall resource utilization decreases
Solution Approach 1:
The patent introduces dynamic resource allocation where bandwidth parts assigned for RAR reception can be flexibly configured and changed based on system conditions and UE requirements. This dynamic approach allows the system to optimize resource utilization over time while ensuring reliable RAR reception when needed.
Solution Approach 2:
The patent creates multi-functional bandwidth parts that can serve both as RAR reception resources for MTC UEs and as data transmission resources for eMBB UEs at different times. This universal resource pool increases overall system productivity while maintaining reliable RAR delivery through dedicated time slots.
Data Source
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AI summary
Systems and methods relating to transmission and reception of a Random Access Response (RAR) message to a wireless device (e.g., a User Equipment (UE)) in a manner that is particularly well-suited for, but not limited to, reduced bandwidth devices, such as Machine Type Communication (MTC) devices, are disclosed, tn some embodiments, a method of operation of a wireless device to perform random access to a cellular communications network comprises transmitting a random access preamble on a physical random access channel and determining, from a random access preamble index of the random access preamble, one of a random access response resource and a channel to monitor for a transmission of an indication of the random access response resource. The method further comprises receiving a random access response on the random access response resource.