OFDM IQ Sample Compression for Fronthaul Capacity Limits
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Solution Overview
Problem
The high-speed transport requirements of fronthaul links in distributed base station systems, particularly for 5G networks, lead to increased costs and energy consumption due to the need for numerous high-speed links, which can bottleneck transmission capacity and jeopardize the feasibility of centralized radio access networks (C-RAN).
Innovation Solution
A method and apparatus that compress IQ samples by converting a second number of IQ samples into prediction errors using a predictive filter, allowing for reduced bit transmission over the fronthaul link while maintaining compliance with relevant radio standards, by transmitting un-coded or minimally coded IQ samples at the boundary between OFDM symbols and encoding prediction errors with fewer bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IQ samples are transmitted uncompressed over the fronthaul link, then transmission quality is maintained, but the data volume and transmission capacity requirements increase dramatically
Solution Approach 1:
The patent extracts and transmits only the essential information by converting IQ samples to prediction errors, removing the redundant predictive components that can be regenerated at the receiver side
Solution Approach 2:
The patent changes the representation parameter of IQ samples from direct amplitude values to prediction errors, transforming the data format to reduce the information that needs to be transmitted
2Quantity of substance
If data compression is applied to IQ samples, then the data volume is reduced, but transmission quality may be degraded
Solution Approach 1:
The patent uses feedback by transmitting prediction errors that allow the receiver to reconstruct the original IQ samples by adding the prediction errors to the predicted values, enabling quality recovery
Solution Approach 2:
The patent introduces prediction errors as an intermediary representation that bridges the original IQ samples and the compressed transmitted data, allowing lossless or near-lossless reconstruction
3Speed
If high-speed links are deployed to meet fronthaul requirements, then transmission capacity is increased, but cost and energy consumption increase dramatically
Solution Approach 1:
The patent changes the data representation from high-bit-rate IQ samples to lower-bit-rate prediction errors, reducing the transmission capacity requirement and associated energy consumption
Data Source
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AI summary
Described is a method performed by an encoder of a base station system (100) of a wireless communication network, for handling a bit stream for transmission over a transmission link (165) between a remote unit (160) and a base unit (170) of the base station system. The remote unit is arranged to transmit wireless signals to and receive from mobile stations (180). The bit stream comprises a first OFDM symbol and a second OFDM symbol, each OFDM symbol comprising a number of consecutive IQ samples. The method comprises, for a first number of the IQ samples situated at a boundary between the first and the second OFDM symbol, transmitting, over the transmission link to a decoder of the base station system, the first number of IQ samples having a representation spanning a first amplitude range. The method further comprises, for a second number of IQ samples of the second OFDM symbol, following the first number of IQ samples, converting, using a predictive filter, individual of the second number of IQ samples to IQ prediction errors, where the IQ prediction errors have a representation spanning a second amplitude range that is smaller than the first amplitude range, and transmitting the IQ prediction errors over the transmission link to the decoder.