Downlink Control Channel Signaling for Shortened TTI
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Solution Overview
Problem
In LTE communications systems, when the transmission time interval (TTI) is shortened from 1 ms to 0.5 ms, the control area of the second timeslot in a subframe cannot be reused for data transmission, leading to difficulties in determining the physical control channel and data channel for user equipment.
Innovation Solution
A method where a base station sends control area indication information, including frequency and time domain control indications, to user equipment using the physical control channel of the first timeslot, allowing the user equipment to determine the control area of the second timeslot and receive the physical control channel, thereby enabling data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If TTI is shortened from 1 ms to 0.5 ms, then transmission round-trip time and data transmission delay are reduced, but the control area of the second timeslot cannot be reused for data transmission, causing user equipment to be unable to determine the physical control channel and data channel
Solution Approach 1:
The base station sends control area indication information in advance using the physical control channel of the first timeslot, enabling user equipment to determine the control area of the second timeslot before data transmission occurs. This preliminary signaling resolves the ambiguity about where to find control channels in shortened TTIs.
Solution Approach 2:
Control area indication information acts as an intermediary message that bridges the gap between the first and second timeslots. It carries frequency and time domain control indications that enable user equipment to locate the physical control channel in the second timeslot without direct configuration.
2Reliability
If control area of the second timeslot is not reused for data transmission, then physical control channel can be transmitted, but it causes interference with the physical data channel of the 1-ms TTI on another frequency domain resource block
Solution Approach 1:
The control area indication information specifies exact frequency domain resource block locations for the control channel in the second timeslot. This localized resource allocation ensures that control channels are transmitted only in specific frequency regions, avoiding interference with data channels in other frequency regions while maintaining reliable control transmission.
Data Source
AI summary
The base station sends control area indication information of an (N+1)th timeslot to the user equipment by using a physical control channel of an Nth timeslot in a control area of the Nth timeslot, where the control area indication information includes frequency domain control indication information and time domain control indication information, the frequency domain control indication information is used to indicate a frequency domain resource block area occupied by a control area of the (N+1)th timeslot in the (N+1)th timeslot, and the time domain control indication information is used to indicate a time domain time unit area occupied by the control area of the (N+1)th timeslot in the (N+1)th timeslot; and the base station sends, in the control area of the (N+1)th timeslot, a physical control channel of the (N+1)th timeslot to the user equipment.