Common Bandwidth and Power Scheme for sTTI DMRS
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Solution Overview
Problem
The reduction of transmission time intervals (TTIs) in LTE systems leads to increased overhead due to the need for reference symbols, which can result in prohibitive system throughput due to at least 50% payload transmission overhead, especially in the uplink direction.
Innovation Solution
Implementing a common bandwidth and power scheme for successive TTIs sharing a common reference signal, where the wireless device sets the bandwidth or power to a common value to ensure efficient resource allocation and minimize overhead, such as using the same output power for data channels sharing a demodulation reference signal (DMRS).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If transmission time intervals are shortened to reduce latency, then packet data latency is improved, but overhead due to reference symbols increases to at least 50% payload transmission overhead
Solution Approach 1:
The patent merges reference signals from multiple successive TTIs into a single common reference signal that is shared across these TTIs. This consolidation reduces the number of reference symbols that need to be transmitted, thereby reducing overhead while maintaining the ability to support shortened TTI durations for low latency communication.
Solution Approach 2:
The common reference signal serves multiple TTIs simultaneously, making it a universal resource that fulfills the reference signal requirement for multiple transmission intervals. This multi-functional approach allows the system to support shortened TTIs without proportionally increasing reference signal overhead.
2Adaptability or versatility
If different bandwidths are allocated to successive TTIs, then resource allocation flexibility is improved, but RF implementation impact and phase discontinuity issues increase
Solution Approach 1:
The patent applies different bandwidth allocations to different logical channels or data types within the same TTI structure, while maintaining a common reference signal bandwidth. This localized differentiation allows resource allocation flexibility for specific data requirements without causing RF implementation issues that would arise from changing the overall signal bandwidth between TTIs.
Solution Approach 2:
The patent segments the resource allocation into two independent dimensions: the data channel bandwidth can vary flexibly according to traffic requirements, while the reference signal bandwidth remains fixed and common across successive TTIs. This segmentation allows flexibility where needed while maintaining RF stability where required.
3Adaptability or versatility
If different output powers are used for successive TTIs, then power control flexibility is improved, but phase discontinuity issues and demodulation performance degrade
Solution Approach 1:
The patent enables different output powers to be applied to different data channels or logical channels within the transmission framework, while maintaining consistent power levels for the common reference signal across successive TTIs. This localized power control flexibility allows adaptation to different channel conditions without causing phase discontinuity in the reference signal, thereby preserving demodulation performance.
4Measurement precision
If more reference symbols are added to shortened TTIs, then demodulation accuracy is improved, but overhead increases to prohibitive levels
Solution Approach 1:
The patent combines reference signal resources from multiple successive TTIs into a single common reference signal structure. This merging maintains sufficient reference signal density for accurate demodulation while reducing the total number of reference symbols required, thereby improving payload transmission efficiency without sacrificing demodulation accuracy.
Solution Approach 2:
The common reference signal provides continuous reference information across multiple successive TTIs, ensuring that demodulation accuracy is maintained throughout the shortened TTI sequence. This continuous reference availability allows accurate demodulation without requiring separate reference symbols in each TTI, thus avoiding prohibitive overhead.
Data Source
AI summary
According to one aspect, a method includes selecting at least one of a common bandwidth scheme and a common power scheme. If the selected at least one scheme includes a common bandwidth scheme, a common bandwidth to be used by the wireless device for transmission of two data channels in two successive short transmission time intervals, sTTIs, that share a common demodulation reference signal, DMRS, is determined. An indication of the common bandwidth to the wireless device to enable the wireless device to set the bandwidth of the two data channels to a common bandwidth value is sent. If the selected at least one scheme includes a common power scheme, then a common power control command to control an output power to be set by the wireless device for two data channels in two successive sTTI, that share a common DMRS is determined.