Coverage Enhancing Device Delay for OFDM Orthogonality
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Solution Overview
Problem
The existing communication systems using coverage enhancing devices (CEDs) face challenges in maintaining orthogonality among subcarriers of OFDM symbols due to differing propagation path lengths, leading to signal interference and reduced transmission performance.
Innovation Solution
A method is introduced where a communication node provides a message indicative of a delay to be applied by the CED, ensuring that signal portions from different propagation paths align at the receiver, preserving orthogonality among subcarriers by adjusting the delay to keep the combined propagation time within the cyclic prefix duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If OFDM symbols are transmitted via multiple propagation paths involving CEDs, then coverage area is extended, but orthogonality among subcarriers is lost due to differing propagation path lengths
Solution Approach 1:
The patent applies parameter changes by adjusting the delay of incident signals reflected by the CED. The CED is configured to apply a specific delay parameter to the reflected signal, which compensates for the propagation path length difference between direct and reflected paths. This delay adjustment ensures that the channel impulse response remains within the cyclic prefix duration, thereby preserving subcarrier orthogonality while maintaining coverage extension benefits
Solution Approach 2:
The patent introduces an intermediary mechanism where the CED acts as a mediator between the transmitting and receiving nodes. The CED receives incident signals, applies a controlled delay, and reflects the delayed signals toward the receiver. This intermediary delay application allows the system to manage multipath propagation effects while maintaining orthogonality, enabling reliable communication over extended coverage areas
2Area of stationary object
If signals are transmitted via reflected paths through CEDs, then transmission coverage is improved, but signal alignment at the receiver deteriorates due to propagation time differences
Solution Approach 1:
The patent implements preliminary action by pre-configuring the CED with a specific delay value before signal transmission. The delay parameter is determined based on the expected propagation path differences, and the CED is prepared to apply this delay to incident signals. This preliminary setup ensures that reflected signals are properly aligned with direct signals at the receiver, maintaining signal integrity across extended coverage areas
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves transmission performance by maintaining orthogonality among subcarriers, allowing for effective demodulation and reducing the need for complex demodulation algorithms, thereby enhancing the overall communication efficiency.
Implementation Method 1
An RRD can be implemented by an array of antennas that can reflect incident electromagnetic waves/signals
Implementation Method 2
the antennas can impose a variable phase shift and typically provide no signal amplification
Data Source
AI summary
According to a first aspect, examples provide a method of operating a first communication node (CN) wherein the first CN is configurable for transmitting, to a second CN on a radio channel, orthogonal frequency-division multiplexing (OFDM) symbols via a first propagation path and a second propagation path, wherein each OFDM symbol comprises a prefix, in particular a cyclic prefix, wherein transmitting the OFDM symbols via the first propagation path comprises transmitting the OFDM symbols to the second CN via a coverage enhancing device, wherein the method comprises providing, to the CED, a message indicative of a delay which is to be applied, by the CED, to incident signals, wherein the first CN selects the delay which is to be applied, by the CED, to the incident signals, to result in an arrival, at the second CN, of a first signal portion transmitted via the first propagation path of a first OFDM symbol being aligned with an arrival, at the second CN, of a second signal portion transmitted via the second propagation path of a second OFDM symbol. Further, a method of operating a second CN as well as a first CN and a second CN are provided.