K.C.H. Blom

Underwater localization by combining Time-of-Flight and Direction-of-Arrival

In this paper we present a combined Time-of-Flight (ToF) and Direction-of-Arrival (DoA) localization approach suitable for shallow underwater monitoring applications such as harbor monitoring. Our localization approach combines one-way ranging and DoA estimation to calculate both position and time-synchronization of the blind-node. We will show that using this localization approach, we are able to reduce the number of reference nodes required to perform localization. By combining ToF and DoA, our approach is also capable of tracking and positioning of sound sources under water. We evaluate our approach through both simulation and underwater experiments in a ten meter deep dive-center (which has many similarities with our target application in terms of depth and reflection). Measurements taken at the dive-center show that this environment is highly reflective and resembles a shallow water harbor environment. Positioning results using the measured Time-of-Arrival (ToA) and DoA indicate that the DoA approach outperforms the ToF approach in our setup. Investigation of the DoA and ToF measurement error distributions, however, indicate the ToF-based localization approach has a higher precision. Shown is that both ToF and DoA and the combined approach achieve sub-meter positional accuracy in the test environment. Using the error distributions derived from the measurement in the dive-center, we run simulations of the same setup. Results from the simulation indicate ToF is more accurate than DoA positioning. Also in simulation all approaches achieve sub-meter accuracy.

DVB-S Signal Tracking Techniques for Mobile Phased Arrays

A system that uses adaptive beamforming techniques for mobile DVB-S reception is proposed in this paper. The purpose is to enable DVB-S reception in moving vehicles. Phased arrays are able to electronically track the desired signal during dynamic behaviour of the vehicle the array is mounted on. The proposed system uses blind beamforming to adapt the array steering vector to changing signal (conditions and) directions. Movement of the vehicle, the phased array is mounted on, leads to modulus and phase deviations at the beamformer output. An extended version of the CMA algorithm is used to adapt the steering vector weights to compensate for those deviations. For simulation of the proposed system a model of vehicle dynamics is used to generate realistic antenna data. Simulation of the proposed system based on this antenna data shows appropriate corrections for modulus and phase deviations.

Adaptive Beamforming Using the Reconfigurable MONTIUM TP

Until a decade ago, the concept of phased array beam forming was mainly implemented with mechanical or analog solutions. Today, digital hardware has become powerful enough to perform the massive number of operations required for real-time digital beam forming. While more and more applications are using beam forming to improve the communication channel utilization both in space and frequency, many dedicated digital architectures are proposed for the processing. By using a reconfigurable architecture, the same hardware platform can be reused for different applications with different processing needs. In this paper, we present a reconfigurable Multi-processor System-on-Chip based solution for phased array processing that supports advanced tracking mechanisms to continuously receive signals with a mobile receiver. An adaptive beam former for DVB-S satellite reception is presented, that uses a Constant Modulus Algorithm to track satellites. The processing of a receiver with 64 antennas and 3 beams is mapped on a reconfigurable processor named Montium TP. The total implementation of such a receiver requires about 570 clock cycles on a single Montium TP, but can also be partitioned over multiple Montium TPs to support larger phased arrays.

Nonminimum-phase channel equalization using all-pass CMA

A nonminimum-phase channel can always be decomposed into a minimum-phase part and an all-pass part. In our approach, called all-pass CMA, the dimensionality of the CMA algorithm has been reduced to improve blind equalization of a nonminimum-phase channels all-pass part. The dimensionality reduction has been performed by parameterizing the CMA cost function in terms of the nonminimum-phase zero location of the all-pass part to be compensated. Currently, all-pass CMA can only compensate a single nonminimum-phase zero. However, compared to CMA, it typically provides a faster and more accurate compensation of this zero.

Low-cost multi-channel underwater acoustic signal processing testbed

Current systems for multi-channel underwater signal processing suffer from a tied relation between the hardware and physical layer software or require a large amount of engineering work. To provide a low-cost, small form factor and flexible solution, this work presents a multi-channel testbed consisting of an off-the-shelf FPGA board and a simple expansion board. Nonetheless, the proposed testbed provides the flexibility and processing power to evaluate novel multi-channel physical layer algorithms.

Mobile satellite reception with a virtual satellite dish based on a reconfigurable multi-processor architecture

Traditionally, mechanically steered dishes or analog phased array beamforming systems have been used for radio frequency receivers, where strong directivity and high performance were much more important than low-cost requirements. Real-time controlled digital phased array beamforming could not be realized due to the high computational requirements and the implementation costs. Today, digital hardware has become powerful enough to perform the massive number of operations required for real-time digital beamforming. With the continuously decreasing price per transistor, high performance signal processing has become available by using multi-processor architectures. More and more applications are using beamforming to improve the spatial utilization of communication channels, resulting in many dedicated digital architectures for specific applications. By using a reconfigurable architecture, a single hardware platform can be used for different applications with different processing needs. In this article, we show how a reconfigurable multi-processor system-on-chip based architecture can be used for phased array processing, including an advanced tracking mechanism to continuously receive signals with a mobile satellite receiver. An adaptive beamformer for DVB-S satellite reception is presented that uses an Extended Constant Modulus Algorithm to track satellites. The receiver consists of 8 antennas and is mapped on three reconfigurable Montium TP processors. With a scenario based on a phased array antenna mounted on the roof of a car, we show that the adaptive steering algorithm is robust in dynamic scenarios and correctly demodulates the received signal.