MIMO Channel Estimation Using Orthogonal Code Multiplexing
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Solution Overview
Problem
Current massive MIMO communication systems face challenges in efficient channel estimation, increased overhead due to pilot transmission, and pilot contamination, which affect frequency utilization efficiency and throughput, especially when terminals are in close proximity or moving.
Innovation Solution
The method involves using orthogonal codes to spread pilot signals in both pilot transmission headers and data slots, allowing for channel estimation during data reception and updating channel information, while preventing pilot contamination by separating signals from different cells and terminals using distinct orthogonal codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pilot signals are transmitted from terminals in separate non-overlapping time-frequency slots to avoid interference, then channel estimation accuracy is improved, but frequency utilization efficiency deteriorates due to increased overhead and pilot period
Solution Approach 1:
The patent merges pilot signal transmission with data transmission by allowing terminals to transmit both pilots and data simultaneously in the same time-frequency resources. The base station separates these signals using code division multiplexing, where different orthogonal codes are assigned to pilots and data, enabling both functions to coexist without interference while maximizing resource utilization
Solution Approach 2:
The patent makes uplink data slots serve multiple functions: they carry both user data and pilot signals for channel estimation. By assigning different orthogonal codes to different signal types within the same slot, the system achieves multi-functionality without requiring separate dedicated pilot resources, thereby improving frequency utilization efficiency
2Measurement precision
If more pilot signals are transmitted to improve channel estimation accuracy for moving terminals or those in close proximity, then channel estimation accuracy is improved, but overhead increases and frequency utilization efficiency deteriorates
Solution Approach 1:
The patent combines pilot transmission with data transmission in the same time-frequency resources. Terminals transmit pilots and data simultaneously using different orthogonal codes, eliminating the need for separate pilot slots and reducing pilot overhead while maintaining accurate channel estimation for moving terminals or those in close proximity
3Reliability
If orthogonal codes are used to spread pilot signals in both pilot transmission headers and data slots, then pilot contamination is prevented and channel separation is improved, but system complexity increases
Solution Approach 1:
The patent introduces orthogonal codes as an intermediary mechanism to separate different signal types and terminals. By assigning distinct orthogonal codes to pilots and data, and to different terminals, the base station can effectively distinguish and separate signals without requiring complex spatial or temporal separation schemes, managing system complexity through code-domain multiplexing
Data Source
AI summary
A MIMO communication method of performing MIMO communication between a base station having a plurality of antennas and each of a plurality of terminals covered by the base station using uplink data slots and downlink data slots that are alternately placed on a time axis. The method includes, in the base station, despreading a received signal that is transmitted from each of the plurality of terminals demodulating the transmission data transmitted from a respective terminal on the basis of the value of the estimated channel; decoding a received signal included in the uplink data slots, estimating a current channel between each of all antennas of the base station and the respective terminal; and comparing the stored value of the estimated channel with a value of the estimated current channel and updating the stored value of the estimated channel to the value of the estimated current channel.