NLOS Backhaul Downlink Scheduling With DFT-Spread SC-FDMA
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Solution Overview
Problem
The increasing cell density in radio access networks leads to non-line-of-sight (NLOS) wireless backhaul channels, which require efficient communication mechanisms to manage higher traffic loads and maintain low latency, error rates, and steadier operations compared to mobile access channels.
Innovation Solution
A method and apparatus for NLOS wireless backhaul communication using a radio frame with adjustable link directionality, employing single carrier block transmission with Discrete Fourier Transform (DFT) spreading for frequency diversity, and combining SC-FDMA with OFDM through sub-carrier mapping, along with Reed-Solomon and Turbo encoding for error correction, to balance traffic load and ensure low latency and error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cell density is increased to meet growing demand for voice and data services, then service capacity is improved, but wireless backhaul communication reliability deteriorates due to NLOS conditions
Solution Approach 1:
The patent changes the fundamental transmission parameter from single carrier to multi-carrier OFDM to adapt to NLOS conditions. By using multiple orthogonal sub-carriers, the system can achieve frequency diversity and maintain reliable communication when cell density increases and LOS paths become unavailable.
Solution Approach 2:
The patent introduces frequency domain multiplexing as an additional dimension for resource allocation. By distributing data across multiple frequency sub-carriers rather than relying on a single carrier, the system achieves spatial-frequency diversity that improves reliability in dense NLOS deployments.
2Device complexity
If P2P LOS wireless backhaul mechanisms are used, then transmission simplicity is maintained, but adaptability to dense small cell environments deteriorates
Solution Approach 1:
The patent creates a universal backhaul transmission mechanism that functions in both LOS and NLOS conditions. The OFDM-based system with configurable cyclic prefix can adapt to different propagation environments, making it versatile for dense small cell deployments while maintaining manageable complexity through standardized processing.
3Device complexity
If single carrier waveforms are used for transmission, then time-domain equalization is simplified, but frequency diversity and error rate performance deteriorate in NLOS channels
Solution Approach 1:
The patent transitions from time-domain single carrier equalization to frequency-domain multi-carrier transmission. By using OFDM, the system achieves frequency diversity through multiple sub-carriers, improving error rate performance in NLOS channels while the cyclic prefix handles time-domain dispersion simplistically.
Data Source
AI summary
A method for communicating over a wireless backhaul channel comprising generating a radio frame comprising a plurality of time slots, wherein each time slot comprises a plurality of symbols in time and a plurality of sub-carriers in a system bandwidth, broadcasting a broadcast channel signal comprising a transmission schedule to a plurality of remote units in a number of consecutive sub-carriers centered about a direct current (DC) sub-carrier in at least one of the time slots in the radio frame regardless of the system bandwidth, and transmitting a downlink (DL) control channel signal and a DL data channel signal to a first of the remote units, wherein the DL data channel signal is transmitted by employing a single carrier block transmission scheme comprising a Discrete Fourier Transform (DFT) spreading for frequency diversity.