The commonly used direct-conversion Radio Frequency (RF) chips exhibit an additive 1/f baseband noise around the DC. The 1/f noise level increases as the transistors inside the RF chip become ever smaller. This type of noise mainly affects the low frequencies and can be very significant for small frequency allocations around the DC in Orthogonal Frequency-Division Multiple Access (OFDMA) systems. In this article we present the effects of such 1/f baseband noise on small frequency allocations for a Long Term Evolution (LTE) User Equipment (UE). We proceed to estimate the 1/f baseband noise. Suppression of the 1/f baseband noise is achieved by subtracting the estimated 1/f baseband noise from the received signal. We show that considerable processing gain is achieved when the 1/f baseband noise suppression is applied.

The performance of discrete-time Decision Directed (DD) and Non-Data Aided (NDA) first-order Phase Looked Loops (PLL) for a QPSK modulated signal is evaluated under the disturbance of thermal noise and 1/f2phase noise. A well known continuous-time model is presented that closely approximates the loop¿s behavior. Using the continuous time model, Fokker-Planck techniques are applied to compute the Mean Time to Lose Lock (MTLL) for both PLLs. We optimize the loop filter using the MTLL as the optimization criterion. On the basis of the optimal MTLL, we determine the regions where one PLL outperforms the other. Monte-Carlo simulation results are presented to validate the analytic analysis. For the setting under study, the NDA PLL outperforms the DD PLL for SNR below 4.5dB regardless of the phase noise level. Applicability of the results for a second-order PLL is discussed.