August 2009 Meeting Summary

On August 30, 2009, the Southern California Chapter of the ION held a meeting, hosted by NavCom in Torrance, CA. 28 people were attendance to listen to a presentation by Slobodan Nedic. A short biography and abstract of the presentation follows, and the slides used during the meeting are attached.

Capsule Biography of Slobodan Nedic:
Slobodan Nedic is an independent consultant in communications and GPS technologies. He received the BS and MS degrees in EE from Belgrade University in 1974 and 1980, respectively. During the academic year 1981/82 he was a guest researcher at the Technische Hochschule in Darmstadt, Germany. There, he was investigating delay-spread and impulse noise resistance of time- and frequency-domain differential PSK in the context of OFDM. Most of his career was spent with the Michael Pupin Institute in Belgrade working on telephone and HF voice-band modem design and production.

He has been with NEC (NEC C&C Central Research Laboratory in Kawasaki, Japan and the NEC Research Laboratory in Princeton, NJ), working on R&D of DAB, cellular and H/ADSL systems. His latest full-time job was with the SiRF Technology Systems Group in Santa Ana, CA, where he worked on dual antenna indoor GPS reception, excision-based anti-jamming, and urban canyon multipath mitigation.

He has consulted for NEC, ASTRI, Airvana and Boeing on 4G system accessing formats, MIMO VDSL system, evaluation of WiMAX technology and GPS retransmission systems, respectively.

Abstract of Mr. Nedic’s Talk:
Slides: On GPS/GNSS Signal Multipath Modeling in Dynamic Environments
This presentation scrutinizes the traditionally used multi-path modeling, noting its failure to capture propagation mechanisms of importance for GPS receiver operations in dynamic environments. An enhanced multipath model is proposed that directly extends the LOS signal propagation model. The crucial point is that the total delay encountered in reception of a SV transmitted code is a sum of instantaneous physical delays and accumulated code delay due to the ‘code Doppler’. The result is that in some situations the correlation peak pertaining to a multipath signal may be measured before the LOS one. This situation is qualitatively and quantitatively evaluated for a simplified scenario of an aligned array of transmitter, reflector and receiver, with the latter two in relative motion. The lessons learned from an experiment conducted to provide the experimental proof for such an effect are provided, and the model is further applied to a set of processed IF samples to explain peculiarities of some urban environment measurements. A suggestion is made of the origin of partially unexplained multipath components obtained by high resolution measurements in data collected in aviation landing measurements