Vladimir Kravtsov

Multi-user MIMO and adaptive frequency reuse for next-generation mobile broadband networks

In order to meet the constantly increasing demand for ubiquitous, mobile access to the internet, next-generation mobile broadband communications systems based on OFDMA, such as IEEE 802.16m, require a significant performance increase over previous generation systems, such as IEEE 802.16e-2005, particularly in cell-edge and average spectral efficiency [2]. In this paper, we address the downlink adaptive frequency reuse (AFR) and multi-user MIMO (MU-MIMO) techniques which are considered to be the most promising candidates for meeting the requirements on cell-edge and average spectral efficiency of next-generation mobile broadband systems.

A 32dBm power amplifier for WiMAX applications in 90nm CMOS

A compact 90nm CMOS power amplifier with integrated transformer/BALUN matching network, for 2.32.7GHz WiMAX (802.16e) band applications, is demonstrated. The PA gain and saturated power are +18dB and +32dBm, respectively, working from a 3.3V supply, with a peak power added efficiency (PAE) of 48%. A memory-less Digital Pre Distortion (DPD) technique is used to enhance the PA linearity. The measured EVM for a 64-QAM OFDM signal is improved from −24dB to −30dB at +25dBm output power. Compliance with the 802.16e standard 10MHz WiMAX mask and FCC regulations is demonstrated at +25dBm of output power with power efficiency of ~25%, and with a measured second harmonic level of −31[dBm/MHz].