Over-the-Air Test Channel Emulation with Unequal Probe Counts
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Solution Overview
Problem
Existing over-the-air testing systems in anechoic chambers face challenges in simulating both uplink and downlink channels when there are different numbers of uplink and downlink probes, leading to incomplete emulation of fading effects, especially when fewer uplink probes are used.
Innovation Solution
The system divides primary impulse responses from more numerous downlink probes into subsets to define secondary impulse responses for uplink probes, setting a correlation between the primary and secondary channel models to ensure accurate emulation of over-the-air channels, even with unequal numbers of probes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fewer uplink probes are used in the anechoic chamber, then device complexity and cost are reduced, but the ability to accurately emulate uplink fading channels is degraded
Solution Approach 1:
The patent creates virtual uplink impulse responses by copying and processing downlink impulse responses. The virtual uplink channel is synthesized using the downlink channel measurements, allowing accurate uplink fading emulation without requiring physical uplink probes. This is achieved through the relationship h_UL[n] = h_DL[-n]* where * denotes complex conjugation, enabling the system to copy the downlink channel characteristics to represent the uplink channel.
Solution Approach 2:
The patent introduces an intermediary mathematical relationship between downlink and uplink channels. Instead of directly measuring uplink channels with physical probes, the system uses downlink impulse responses as an intermediary to derive uplink impulse responses. This intermediary approach allows the system to infer uplink fading characteristics from downlink measurements, bypassing the need for additional uplink probes.
2Adaptability or versatility
If different numbers of uplink and downlink probes are used, then system configuration flexibility is improved, but the correlation between primary and secondary channel models becomes difficult to maintain
Solution Approach 1:
The patent changes the parameters of the channel model by introducing a correlation coefficient ρ that can take different values based on the probe configuration. When the number of uplink and downlink probes differ, the system adjusts the correlation parameter to maintain accurate channel emulation. This allows the system to adapt to different probe configurations while preserving the essential correlation between uplink and downlink channel models.
Solution Approach 2:
The patent segments the channel emulation problem into two independent parts: downlink channel measurement and uplink channel synthesis. By separating the downlink and uplink channel models and establishing a mathematical relationship between them, the system can independently configure the number of downlink and uplink probes while maintaining overall channel correlation through the synthesized virtual uplink responses.
3Device complexity
If a single uplink probe is used without fading emulator, then system complexity is reduced, but uplink fading emulation capability is lost
Solution Approach 1:
The patent replaces the mechanical fading emulator hardware with a software-based mathematical transformation. Instead of using a physical fading emulator device to generate uplink fading, the system uses signal processing to synthesize faded uplink signals from downlink measurements. The fading effect is created through mathematical operations on the impulse responses rather than through dedicated hardware, eliminating the need for a separate uplink fading emulator.
Solution Approach 2:
The patent makes the downlink fading emulator serve a dual function by using it to generate both downlink faded signals and to synthesize uplink faded signals. The same fading emulator hardware is used universally for both uplink and downlink channel emulation through mathematical transformation, eliminating the need for separate uplink and downlink fading emulators and reducing overall system complexity.
Data Source
AI summary
A system for emulating an over-the-air channel for communicating with a device under test is provided. The system comprises an anechoic chamber having NA primary probes and NB secondary probes where NA>NB. The system also comprises a dividing module for dividing NA primary impulse responses {μn<sub2>A</sub2>} into NB subsets; and a defining module for defining NB secondary impulse responses {vn<sub2>B</sub2>} in terms of the primary impulse responses {μn<sub2>A</sub2>} and a set of NB complex sequences {λn<sub2>B</sub2>}. In the system, either the primary probes are downlink probes, the primary impulse responses are downlink impulse responses, the secondary probes are uplink probes and the secondary impulse responses are uplink impulse responses, or the primary probes are uplink probes, the primary impulse responses are uplink impulse responses, the secondary probes are downlink probes and the secondary impulse responses are downlink impulse responses.