Research On Causes And Solutions Of Adjacent Carrier Interference In CDMA2000EVDO Rev B

Multicarrier EVDO system, which is cdma2000EVDO Rev B, was launched by3GPP2in May2006as the first phase of EVDO evolution roadmap, the most compelling feature ofwhich is allowing the access terminal to use the multi-carrier to communicate with radioaccess network(RAN). The multicarrier EVDO system offers higher peak date rates andsystem throughput in both the downlink and uplink by aggregating multi EVDO Rev Acarriers. The most common configuration is an aggregation of three carriers within a5MHzchannel considering the complexity of the access terminal.All carriers in the same sector are using the same PN sequence for modulation under thetraditional CDMA configuration and no adjacent carrier interference (ACI) occurs. But in themulti-carrier deployment of EVDO Rev B system serious adjacent carrier interference occurswhen all carriers are using the same PN sequence. Especially when the carrier frequencyspacing is F=1.23MHZ，the pilot aliasing phenomenon happens. It would distort the channelestimation which would degrade demodulation performance.This paper mainly focuses on ACI in the EVDO Rev B network, and proposes a solutionwith optimized baseband filter. The main work and achievements are:(1) The CDMA2000EVDO Rev A technical characteristics are described in detail, andthe improvement of EVDO Rev B compared to EVDO Rev A is expounded with focus on keytechnology of EVDO Rev B.(2) The frequency distribution of EVDO Rev B is analyzed in detail, then the structure offorward channel in EVDO Rev B is described with a detailed analysis on the operatingprinciple, function of each channel as well as the structure of TS; the structure of backwardchannel is also analyzed. Finally, Turbo code was studied.(3) By analyzing the mathematics model of the transmission signal, two reasons of ACIare obtained: spectrum leakage and sampling aliasing; then a few key factors that affect DOperformance are studied: carrier spacing, carrier deployment, transmission filter, frequencyoffset and time offset. (4) Finally, A solution to the ACI is proposed by introducing a filter with more steeperroll-off. The simulation shows that this kind of filter with high attenuation in stop-band caneffectively reduce the value of the ACI in the guarantee of good system performance.