Sub-subchannel Control for Reduced Latency in LTE Networks
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Solution Overview
Problem
Current LTE systems face challenges in reducing packet data latency, particularly due to the limitations of existing control channels that transmit control information only once per 1ms subframe, leading to inefficiencies in resource sharing and increased overhead, which hinders further latency reduction and HARQ Round Trip Time (RTT) optimization.
Innovation Solution
The method involves providing separate control information for frequency and time resources within a subframe, enabling scheduling decisions within a subframe and allowing for dynamic sharing of resources between wireless terminals using 1ms subframes and shorter sub-subframes, thereby reducing frame alignment delay and HARQ RTT, and reducing overhead for downlink control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If control information is transmitted only once per 1ms subframe, then system complexity is reduced, but packet data latency increases and resource sharing efficiency deteriorates
Solution Approach 1:
The patent segments control information transmission by introducing multiple control channels (PDCCH and EPDCCH) that can operate independently within a subframe. The EPDCCH is further divided into multiple physical resource blocks, allowing granular control and reducing latency by enabling earlier scheduling decisions without overwhelming system complexity
Solution Approach 2:
The patent implements preliminary action by transmitting control information earlier in the subframe through the EPDCCH. The EPDCCH can be positioned in earlier OFDM symbols, allowing the network to make scheduling decisions before the full 1ms subframe elapses, thereby reducing packet data latency and HARQ RTT
2Productivity
If separate control information is provided for frequency and time resources, then resource sharing efficiency improves, but downlink control information overhead increases
Solution Approach 1:
The patent implements multi-functionality by designing the EPDCCH to serve multiple purposes: it can schedule both PDSCH and PUSCH transmissions, support both localized and distributed resource allocation, and accommodate different subframe structures (1ms and shorter). This universal control mechanism improves resource sharing efficiency without proportionally increasing overhead
Solution Approach 2:
The patent transitions from traditional time-domain only control to a two-dimensional control structure by introducing frequency-domain resource allocation in the EPDCCH. Control information is now provided across both time (OFDM symbols) and frequency (resource blocks) dimensions, enabling more efficient resource sharing through spatial multiplexing and reducing the need for redundant control signals
3Loss of time
If 1ms subframes are used for all wireless terminals, then system simplicity is maintained, but latency reduction and HARQ RTT optimization are limited
Solution Approach 1:
The patent introduces dynamics by enabling flexible subframe structures that can adapt to different service requirements. The system can dynamically switch between 1ms subframes and shorter subframes (e.g., half-subframes) based on traffic conditions and QoS requirements. The EPDCCH can schedule transmissions in these variable-length subframes, allowing the system to optimize HARQ RTT for latency-sensitive traffic while maintaining compatibility with legacy terminals
Solution Approach 2:
The patent implements parameter changes by modifying subframe duration as a configurable parameter. The system can adjust the number of OFDM symbols in a subframe (e.g., 14 symbols for 1ms, 7 symbols for half-subframe) and the number of resource blocks allocated to EPDCCH. These parameter adjustments enable the system to reduce HARQ RTT by allowing earlier scheduling and transmission opportunities without fundamentally changing the system architecture
Data Source
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AI summary
Methods may be provided to operate a network node of a radio access network. Such methods may include transmitting first control information to a wireless terminal, and the first control information may define a frequency resource available for data communication with the wireless terminal over a subframe. After transmitting the first control information, second control information may be transmitted to the wireless terminal. The second control information may define a time resource for a sub-subframe of the subframe. Communication of data may be provided between the network node and the wireless terminal during the sub-subframe of the subframe defined by the frequency resource of the first control information and the time resource of the second control information. Related network nodes and wireless terminals are also discussed.