To comply with the evolving wireless standards,base stations must provide greater data rates over the serialdata link between base station processor and RF unit. Thislink is especially important in distributed antenna systemsand cooperating base stations settings. This paper explores thecompression of baseband signal samples prior to transfer over theabove-mentioned link. We study lossy and lossless compressionof baseband signals and analyze the cost and gain of eachapproach. Sample quantizing is proposed as a lossy compressionscheme and it is shown to be effective by experiments. WithQPSK modulation, sample quantizing achieves a compressionratio of 4:1 and 3.5:1 in downlink and uplink, respectively. Thecorresponding compression ratios are 2.3:1 and 2:1 for 16-QAM.In addition, lossless compression algorithms including arithmeticcoding, Elias-gamma coding, and unused significant bit removal,and also a recently proposed baseband signal compression schemeare evaluated. The best compression ratio achieved for losslesscompression is 1.5:1 in downlink. Our over-the-air experimentssuggest that compression of baseband signal samples is a feasibleand promising solution for increasing the effective bit rates of thelink to/from remote RF units without requiring much complexityand cost to the base station.
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