The future wireless network, such as Centralized Radio Access Network(C-RAN), will need to deliver data rate about 100 to 1000 times the current 4Gtechnology. For C-RAN based network architecture, there is a pressing need fortremendous enhancement of the effective data rate of the Common Public RadioInterface (CPRI). Compression of CPRI data is one of the potentialenhancements. In this paper, we introduce a vector quantization basedcompression algorithm for CPRI links, utilizing Lloyd algorithm. Methods tovectorize the I/Q samples and enhanced initialization of Lloyd algorithm forcodebook training are investigated for improved performance. Multi-stage vectorquantization and unequally protected multi-group quantization are considered toreduce codebook search complexity and codebook size. Simulation results showthat our solution can achieve compression of 4 times for uplink and 4.5 timesfor downlink, within 2% Error Vector Magnitude (EVM) distortion. Remarkably,vector quantization codebook proves to be quite robust against data modulationmismatch, fading, signal-to-noise ratio (SNR) and Doppler spread.
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