Frequency Hopping Retuning for MTC Devices
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Solution Overview
Problem
In wireless communication systems, machine type communication (MTC) devices face challenges with frequency retuning, which introduces delays and increases network overhead, especially for devices with limited transmitting and receiving capabilities, as they need to adjust to different frequency bands, leading to inefficiencies in spectral usage and increased retuning times.
Innovation Solution
The method involves transmitting messages in one frequency band, retuning to another band during a designated portion of the transmission time interval (TTI), and continuing transmission in the new band, with the duration of the retuning period optimized based on the longest retuning time among devices or specific retuning capabilities, and incorporating techniques like rate-matching and puncturing to accommodate retuning delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MTC devices perform frequency retuning to support frequency hopping, then frequency diversity and interference avoidance are achieved, but transmission delays increase and spectral efficiency deteriorates
Solution Approach 1:
The base station performs preliminary actions by refraining from transmitting during the retuning period before the UE can retune its receiver. This anticipatory approach ensures that when the UE completes retuning, the transmission resources are already aligned, eliminating the need for the UE to miss transmission opportunities and reducing effective retuning delay
Solution Approach 2:
The system dynamically adjusts the transmission timing based on the UE's retuning capability. The base station adapts its transmission schedule to accommodate the retuning period, creating a dynamic coordination mechanism that optimizes both frequency hopping benefits and transmission efficiency
2Reliability
If MTC devices with limited capabilities perform wideband operation, then frequency hopping support is improved, but device complexity and power consumption increase
Solution Approach 1:
The system segments the frequency hopping operation into manageable parts: the base station handles the wideband frequency changes and timing coordination, while the UE performs simpler narrowband retuning to specific frequency bands. This segmentation allows limited-capability UEs to support frequency hopping without requiring full wideband operation capability
Solution Approach 2:
The base station acts as an intermediary that manages the frequency hopping coordination. It determines retuning delays, refrains from transmission during retuning periods, and aligns its transmissions with the UE's retuning capability, thereby enabling frequency hopping support without requiring the UE to have complex wideband operation capabilities
3Loss of time
If the base station refrains from transmitting during retuning periods, then retuning delays are accommodated, but spectral efficiency and network overhead deteriorate
Solution Approach 1:
The system implements periodic frequency hopping with structured retuning intervals. By organizing transmissions into periodic patterns that account for retuning delays, the system optimizes the balance between accommodating UE retuning and maintaining spectral efficiency, ensuring that transmission resources are efficiently utilized while supporting frequency hopping
Solution Approach 2:
The base station dynamically adjusts transmission parameters such as timing offsets and frequency band selections based on the UE's retuning capability. By changing these parameters adaptively, the system minimizes the impact of retuning delays on spectral efficiency while ensuring reliable frequency hopping operation
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. User equipment (UE) and base stations may support frequency hopping with fast retuning for enhanced machine type communication (eMTC). For example, a UE may need to retune portions of its receive or transmit chain to support operation on various frequency bands, and it may perform the retune within a few symbols. Both base station and UE may anticipate or account for the retuning delay and communicate accordingly. A base station may refrain from transmitting for a certain period of time, for example. A base station may also account for frequency hopping delays for uplink communications. Systems may employ other techniques to support eMTC. For example, UEs may leverage reference signal patterns in certain control channels for demodulation. In some cases, base stations may alter control channel transmissions to account for various types of UEs with in the system.