Control of Redundant Submarine Robot Arms under Holonomic Constraints
E. Olgun-Daz, Vicente Parra‐Vega, D. Navarro-Alarc · InTech eBooks · 2008
In centralized MIMO systems, the presence of phase noise is an important limiting factor for a broadband system, i.e., a MIMO-OFDM system's performance, and depends on the quality and the operating conditions of the system's RF hardware.In conventional mobile radio systems around a carrier frequency of 2GHz, the phase noise constitutes typically no severe limitation, however, when the carrier frequency goes up to a higher frequency, such as 15GHz, its effects were less negligible and hence had to be investigated in more depth.In distributed MIMO systems, system performance are limited by independent PN at local oscillators of N t transmit antennas and N r receive antennas.Some MIMO techniques, such as precoding, will suffer from independent PN as the orthogonality among sub-data-streams is destroyed.This involves with both narrowband and broadband MIMO systems.This chapter will deal with the phase noise in centralized and decentralized (distributed) MIMO systems.The organization of this chapter is as follows.Section 2 presents an overview of the phase noise effect and modeling of phase noise.PN can be modeled as a sampled Wiener Process for a free-running oscillator, and an Ornstein-Uhlenbeck Process (a Gaussian process with zero-mean and bounded variance) for a phase-locked loop (PLL) frequency synthesizer.In the following sections, we will consider effects of either/both of these two types of phase noise.Section 3 addresses the influence of independent PN in centralized and distributed MIMO systems.We concentrate on narrowband systems applying linear precoding.In such a scenario, independent PN gives rise to SNR loss at the receiver and induces interference among sub-streams, and hence degrades the system performance.Then we discuss the feasible synchronization schemes for frequency and phase synchronization.Simulation results are then given in Section 4 and finally Section 5 discusses the future research directions and concludes the chapter.337 Analysis and Mitigation of Phase Noise in Centralized/De-centralized MIMO Systems www.intechopen.com