A Simple and Efficient IQ Data Compression Method Based on Latency, EVM, and Compression Ratio Analysis

Jewon Lee,Joon-Young Jung,Eunhee Hyun

doi:10.1109/access.2019.2936218

Jewon Lee, Joon-Young Jung + Show 1 more

Open Access

https://doi.org/10.1109/access.2019.2936218

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Abstract

Latency, error vector magnitude (EVM) and compression ratio (CR) are performance evaluation factors of IQ data compression. The purposes of IQ data compression are to minimize the latency, EVM and to maximize the CR. However, there is a tradeoff between them. In this paper, based on the evaluation factors, we analyze existing IQ data compression schemes and propose a simple and efficient method from the analyzed results. The proposed method is composed of partial cyclic prefix and cyclic suffix insertion, $K/L$ decimation, low-order bits removal, and partial Huffman code. It presents the techniques to minimize the EVM caused by $K/L$ decimation and to optimize the number of removable low bits and available Huffman encoding bits based on the average signal power and desired EVM. The proposed method can achieve the CR of 4 times or more in about 2% EVM for the LTE downlink and uplink. The simulation results show that the proposed method is applicable to SIMO and MIMO environments.

Highlights

In the cloud radio access network (C-RAN), in which eCPRI radio equipment control and eCPRI radio equipment are separated, the eCPRI provides an interface between eREC and eRE in order to transmit user data, control and management signal, and synchronization signal [1]
From analysis of the existing compression algorithms, in K /L decimation which is the method reducing the samples of the original data, we discovered that error vector magnitude (EVM) is not reduced because of the aliasing and inter-symbol interference (ISI)
It is assumed that EVM can be calculated in the frequency domain with the input of IQ data compression and the output of IQ data decompression for the downlink and uplink

Summary

INTRODUCTION

In the cloud radio access network (C-RAN), in which eCPRI radio equipment control (eREC) and eCPRI radio equipment (eRE) are separated, the eCPRI provides an interface between eREC and eRE in order to transmit user data, control and management signal, and synchronization signal [1]. The aim of IQ data compression was the compression ratio (CR) of 2 times It can be achieved by performing 3/4 decimation and 5 lower bits removal when the sample is represented by 15 bits in eCPRI. The authors of [24], [25] have proposed a compression method which is consisted of cyclic prefix (CP) removal, K /L decimation, BS, vector quantization (VQ), and Huffman code It can achieve the CR of 4 times or more within about 2% EVM. The proposed method can reduce the EVM in K /L decimation and present a simple and efficient solution to the bit-level data compression based on the power and pdf of the signal.

ANALYSIS OF EXISTING IQ DATA COMPRESSION METHODS

LATENCY

ERROR VECTOR MAGNITUDE EVM is defined as

SIMULATION RESULTS

CONCLUSION