Sprinklers: A Randomized Variable-Size Striping Approach to Reordering-Free Load-Balanced Switching

Internet traffic continues to grow exponentially, calling for switches that can scale well in both size and speed. While load-balanced switches can achieve such scalability, they suffer from a fundamental packet reordering problem. Existing proposals either suffer from poor worst-case packet delays or require sophisticated matching mechanisms. In this paper, we propose a new family of stable load-balanced switches called "Sprinklers" that has comparable implementation cost and performance as the baseline load-balanced switch, but yet can guarantee packet ordering. The main idea is to force all packets within the same virtual output queue (VOQ) to traverse the same "fat path" through the switch, so that packet reordering cannot occur. At the core of Sprinklers are two key innovations: a randomized way to determine the "fat path" for each VOQ, and a way to determine its "fatness" roughly in proportion to the rate of the VOQ. These innovations enable Sprinklers to achieve near-perfect load-balancing under arbitrary admissible traffic. Proving this property rigorously using novel worst-case large deviation techniques is another key contribution of this work

Planck-LFI radiometers tuning

"This paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst" This paper describes the Planck Low Frequency Instrument tuning activities performed through the ground test campaigns, from Unit to Satellite Levels. Tuning is key to achieve the best possible instrument performance and tuning parameters strongly depend on thermal and electrical conditions. For this reason tuning has been repeated several times during ground tests and it has been repeated in flight before starting nominal operations. The paper discusses the tuning philosophy, the activities and the obtained results, highlighting developments and changes occurred during test campaigns. The paper concludes with an overview of tuning performed during the satellite cryogenic test campaign (Summer 2008) and of the plans for the just started in-flight calibration.Comment: This is an author-created, un-copyedited version of an article accepted for publication in JINST. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at http://dx.doi.org/10.1088/1748-0221/4/12/T12013

Offset balancing in pseudo-correlation radiometers for CMB measurements

Radiometeric CMB measurements need to be highly stable and this stability is best obtained with differential receivers. The residual 1/f noise in the differential output is strongly dependent on the radiometer input offset which can be cancelled using various balancing strategies. In this paper we discuss a software method implemented in the Planck-LFI pseudo-correlation receivers which uses a tunable "gain modulation factor, r, in the sky-load difference. Numerical simulations and experimental data show how proper tuning of the parameter r ensures a very stable differential output with knee frequencies of the order of few mHz. Various approaches to calculate r using the radiometer total power data are discussed with some examples relevant to Planck-LFI. Although the paper focuses on pseudo-correlation receivers and the examples are relative to Planck-LFI, the proposed method and its analysis is general and can be applied to a large class of differential radiometric receivers.Comment: 12 pages, 8 figures, accepted for publication in A&A (updated version with few editorial changes

Intrinsically Mode Reconfigurable Load Modulation Balanced Amplifier Leveraging Transistor\u27s Analog-Digital Duality

The communication schemes have rapidly changed the face of the human means of communication. The evolution from one generation to another has triggered many challenges on the design methodologies of RF designers. As the evolution ensued, the spectrally efficient modulation schemes have resulted in the substantial rise of PAPR, the peak-to-average power ratio. To enable the efficient amplification of the high PAPR signals, this thesis explores the areas of Load modulated Balanced amplifiers that can be inherently reconfigured to achieve a better efficiency than the conventional RF power amplifiers that see a significant drop in the efficiency as the signal is backed-off from the maximum power level. In the communication environment, the load mismatch to the power amplifier does result in the degraded efficiency profile which is detrimental to the performance of the communication system. Hence, the power amplifier stage needs to be mismatch resilient. A three mode reconfigurable balanced power amplifier that can tolerate the mismatch due to the antenna array in massive MIMO is presented. The transistor\u27s analog-digital duality is exploited for deploying it as an amplifier and a switch in the designed amplifier stage to enable the reconfiguration between the respective modes of operation. In addition, the output matching topology is designed to be symmetric for the corresponding amplifier stages with an input branch-line quadrature coupler and a unique harmonic tuning methodology that is used to effectively achieve a higher order load modulation in one of the modes, HLMBA. The other two modes of the PA stage are mismatch resilient and their performance is also observed to be efficient with switch settings dedicated to offer mismatch resilience at varied terminations