Uplink Channel Estimation via Request Channel
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in estimating uplink channel responses for UEs, leading to excessive consumption of uplink resources during MIMO transmission, which hampers performance and reliability.
Innovation Solution
A UE sends a request for uplink resources on a request channel (REQCH) from multiple antennas, either simultaneously or in a time-switched manner, using both data and pilot subcarriers distributed across the system bandwidth, allowing the Node B to estimate channel gains and derive channel estimates for each antenna without dedicating additional resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated pilot resources are allocated for uplink channel estimation, then channel estimation precision is improved, but uplink resource consumption increases
Solution Approach 1:
The REQCH message serves dual purposes: (1) as a signaling channel for uplink resource requests, and (2) as a pilot channel for channel estimation. By making the REQCH multi-functional, the system obtains channel estimates without allocating separate dedicated pilot resources, thus resolving the contradiction between estimation precision and resource consumption
Solution Approach 2:
The REQCH transmission itself provides the channel estimation function. The uplink resources requested by UEs for sending resource requests automatically serve as the pilot signals needed for channel estimation, eliminating the need for additional dedicated pilot resources and achieving self-sufficiency in channel estimation
2Reliability
If uplink resources are increased for channel estimation, then MIMO transmission performance is improved, but resource overhead increases
Solution Approach 1:
The REQCH is designed to simultaneously fulfill signaling and pilot functions. The same time-frequency resources used for uplink resource requests are also used for channel estimation, enabling MIMO transmission performance improvement without increasing overall resource overhead
Solution Approach 2:
The patent merges the signaling channel (REQCH) and pilot channel into a single unified structure. By combining these two previously separate functions into one channel, the system achieves efficient channel estimation for MIMO while avoiding duplicate resource allocation
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
Techniques for efficiently deriving uplink channel estimates without consuming much additional uplink resources are described. A user equipment (UE) may send a request for uplink resources on a request channel (REQCH) whenever the UE desires to transmit data on the uplink. The UE may send the REQCH on a set of subcarriers and from multiple antennas, e.g., send REQCH data on data subcarriers and pilot on pilot subcarriers. A Node B may receive the request, estimate the complex channel gains for the pilot subcarriers based on received pilot symbols, and coherently demodulate received data symbols based on the channel gain estimates. The Node B may estimate the complex channel gains for the data subcarriers based on demodulated data symbols and derive a channel estimate for each UE antenna based on the channel gain estimates for the pilot and data subcarriers. The Node B may use the channel estimates for MIMO scheduling, subband scheduling, and rate selection.