Sounding Reference Signal Transmission Period Configuration for Uplink Overhead Reduction
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Solution Overview
Problem
In the LTE-A system, the use of multiple antennas for transmitting SRS increases uplink SRS resource overhead, reducing system efficiency and limiting the number of UEs that can be accommodated due to increased resource requirements.
Innovation Solution
The eNB configures distinct SRS transmission periods for each antenna of the UE, allowing the UE to transmit SRS using corresponding periods, which can be the same or different, to optimize resource usage and reduce overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple antennas are used for transmitting SRS in LTE-A system, then the uplink channel capacity and system performance are improved, but the uplink SRS resource overhead increases significantly
Solution Approach 1:
The patent combines SRS resources across multiple antennas by allowing UEs to share the same time-frequency resources for SRS transmission. Multiple UEs are configured to transmit SRS on the same resource using different cyclic shifts of the same root sequence, thereby merging resource usage and reducing overall SRS overhead in the system.
Solution Approach 2:
The patent makes a single SRS resource serve multiple functions by enabling multiple UEs to utilize the same time-frequency resource for channel sounding. The resource is universally shared across multiple UEs through code division multiplexing using cyclic shifts, allowing one resource to support multiple antennas and UEs simultaneously.
2Measurement precision
If distinct SRS resources are allocated for each antenna, then accurate channel estimation is achieved, but the number of available UEs that can be accommodated is reduced
Solution Approach 1:
The patent merges channel estimation functionality across multiple antennas by using the same root sequence with different cyclic shifts for different antennas. This allows accurate channel estimation for each antenna while sharing the underlying SRS resource, thereby supporting more UEs within the same resource constraints.
Solution Approach 2:
The patent changes the cyclic shift parameter of the SRS sequence to differentiate between multiple antennas and UEs using the same resource. By varying the cyclic shift parameter rather than allocating entirely separate resources, the system maintains measurement precision while accommodating more users.
3Adaptability or versatility
If the same root sequence is used with different cyclic shifts for multiple UEs, then Code Division Multiple Access is achieved, but the number of available code resources is limited to eight
Solution Approach 1:
The patent extends the code resource space by introducing an additional dimension - the antenna port dimension. Instead of only using cyclic shifts within a single antenna context, the system uses cyclic shifts across multiple antenna ports, effectively multiplying the available code resources by the number of antennas configured for SRS transmission.
Data Source
AI summary
An eNB, user equipment, system and method for transmitting sounding reference signals by using multiple antennas are disclosed in the present invention, which can reduce overhead of uplink sounding reference signals. The method includes: if an Advanced Long Term Evolution (LTE-A) system has uplink multiple antennas, an eNB configures respectively transmission periods of Sounding Reference Signals (SRSs) which are transmitted over each antenna for a User Equipment (UE); according to the configuration by the eNB, the UE transmits an uplink SRS over each antenna with the corresponding SRS transmission period. The present invention can reduce the uplink SRS overhead in the system remarkably if there are multiple antennas.