Adjacent channel interference resistance of a multi-Gbps millimeter-wave WPAN system

Abstract

This paper investigates the adjacent channel interference (ACI) resistance of a multi-Gbps single carrier wireless personal area network (WPAN) operating in the 60 GHz millimeter-wave band. The significance of performance degradation due to ACI is investigated corresponding to varying factors such as types of modulation and radio frequency (RF) hardware impairments. The level of modulation scheme is found to change the system resistance against ACI considerably. RF hardware impairments such as power amplifier (PA) non-linearity and phase-locked loop (PLL) phase noise are also major factors affecting ACI generation. The tolerable ACI for WPAN system design is defined as the ACI that causes 0.5 dB degradation in required signal to noise ratio (SNR) at bit error rate (BER)=10-6. It is found that for a system employing pi/2 binary phase shift keying (BPSK) with PA output backoff (OBO)=3 dB, ACI=13.5 dB causes 0.5 dB BER degradation. For systems employing quadrature phase shift keying (QPSK) modulation, the tolerable ACI with PA OBO=3 dB and 5 dB are observed at 9 dB and 15 dB, respectively. For modulation schemes with higher levels such as the 16-quadrature amplitude modulation (QAM) system with PA OBO=3 dB and 5 dB, the tolerable ACI of 1 dB and 5 dB are observed. Next, the maximum ACI resistance is defined as the tolerable ACI by the system before the BER performance degrades and saturates towards 0.5. The performance of pi/2-BPSK system with PA OBO=3 dB has maximum resistance against ACI up to 25 dB before the BER saturates towards 0.5. Similar performance can be observed in QPSK system, but with PA OBO increased to 5 dB. Systems with 16-QAM are found to saturate to BER=0.5 beyond ACI=10 dB. Additionally, the presence of PLL phase noise is found to severely compromise the system performance particularly those with higher modulation levels. ACI as low as 0 dB is found to cause error floor to 16-QAM systems.