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Embedded Systems and Signal Processing
| Digital Signal Processing Concepts for RFICs |
| Status | in progress |
| Advisor | Univ-Prof. Dr. Mario Huemer |
| Contact | Dipl.-Ing. Christian Lederer |
| E-Mail | |
| Description | Current transceivers for mobile communication devices supporting UMTS and/or HSPA are operating in full-duplex mode. That means that the transmitter and the receiver is operating at the same time, but at different frequency bands (Frequency Division Duplex).
Transmitter signals, which exhibit much more power compared to the receive signals, may leak into the receiver path because of non-linearities and/or out of band emissions. These leakage signals will be processed by the receiver path and so they will disturb the signal which should actually be received. Unfortunately, the amplitudes of the leakage signals can be much higher than the wanted signal, with the effect, that the wanted signal may be heavily distorted.
In case of homodyne receivers, which are most commonly used in modern mobile communication devices, severe problems are especially caused by second order intermodulation products. Because of second order nonlinearities in the transmitter and receiver chain and the finite isolation of the downconverting mixers, portions of the squared transmit signal will appear in the baseband. Since in homodyne receivers the RF passband signal is converted to the baseband directly, the leakage signal from the transmitter and the signal which should actually be received, cannot be separated using analog filters in the baseband.
Normally, excessive filtering (typically using Surface Acoustic Wave (SAW) filters) is already done in the RF band to avoid spurious signals after the downconverter. Such SAW filters are discrete devices that cannot be integrated into an IC, which increases the costs of the whole transceiver.
The idea is now to relax the requirements for analogue filtering by digital signal processing in the digital front end (DFE). As already stated in [1], it can be shown that adaptive filtering in the baseband can relax the requirements of the filters in the analog front end.
It can also be shown that the adaptive filtering after downconversion is less sensitive on the delay of the TX leakage signal than an analog adaptive filter in the RF passband is. Further investigations show that the residual error after adaptive filtering is nearly independent of the leakage power, which motivates for further investigations on adaptive filtering in the digital frontend.
References:
[1] Andreas Frotzscher and Gerhard Fettweis, “A Stochastic Gradient LMS
Algorithm for the Compensation of Tx Leakage on Zero-IF-Receivers”, In
IEEE Vehicular Technology Conference, May 2008
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| Track before Detect |
| Available | May 1, 2008 – April 30, 2011 |
| Status | in progress |
| Advisor | Univ-Prof. Dr. Mario Huemer |
| Contact | Dipl.-Ing. Andreas Weiss |
| E-Mail | |
| Description | Detection, Classification and Tracking are the three stages of processing in a Radar System. A target is detected first. In the second step classified and in the third step followed through consecutive scans resulting in the track (trajectory) of the target. Especially for small targets and/or in a noisy environment this approach is insufficient, because the continuous detection can not be guaranteed. If the detections stage fails the following steps Classification and Tracking can not be performed, too.
In cooperation with EADS (European Aerospace Defence and Space Company) new methods and algorithms are investigated which can handle the fact that the target is not always detected through time. The basic approach is to use the sporadic appearance of the target to create a trajectory, which can then be used to extract information about the target (velocity, direction, movement pattern etc.). Putting these mathematically challenging and computation-intensive methods to practice on state of the art hardware consisting of FPGA’s and microcontrollers is the second half of this project. Therefore this research project ranges from designing the algorithms to implementing them on hardware, leading to a hardware/software co-design process. The key challenge is to find the optimal balance between algorithmic complexity and hardware resources for different scenarios and targets. |
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| Power Management for DC-DC Converters |
| Available | January 1, 2008 - December 31, 2010 |
| Status | in progress |
| Advisor | Univ.-Prof. Dr. Mario Huemer |
| Contact | Dipl.Ing.(FH) Robert Priewasser, M.Sc. Matteo Agostinelli |
| E-Mail | |
| Description | The trend in recent hardware system designs, especially when they are battery driven (eg. notebooks, cellular phones or handhelds), is to operate the different components of the system (RF ciruits, baseband processor, etc. in case of a cellular phone) with different supply voltages, in order to achieve optimum performance and high power efficiency.
The project proposed in co-operation with Infineon Villach aims to investigate and also develop a PWM-based digital control logic for future DC-DC converters, with the goal to reduce the overall power consumption and optimize the system for load or line variations. The solution should be robust and insensitive to parameter-variations of external components. It might be necassary to investigate adaptable control logic, which autonomously can estimate the parameters of the external elements (tolerances of coils, capacitors, etc.). With a more accurate knowledge of the control path, the control process can be optimized. Furthermore, power savings can possibly be achieved by optimizing the transient effects when turning the circuit on and off, which is a common task in modern designs, where only active hardware blocks are powered on. The research results should be verified by simulations and by measurements on real prototype hardware on silicon. |
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| Near Field Communication |
| Status | in progress |
| Advisor | Univ.-Prof. Dr. Mario Huemer |
| Contact | Univ.-Ass. Dipl.-Ing. Thomas Schlechter |
| E-Mail | |
| Phone | +43 (0)463 2700 3663 |
| Description | Near Field Communication (NFC) is a new, short-range wireless connectivity technology that evolved from a combination of existing contactless identification and interconnection technologies. Products with built-in NFC will dramatically simplify the way consumer devices interact with one another.
NFC technology is currently mainly aimed at being used with mobile phones. Though, plenty of applications will be possible such as:
- Mobile ticketing in public transport - an extension of the existing contactless infrastructure.
- Mobile Payment - the mobile phone acts as a debit/ credit payment card.
- Smart poster - the mobile phone is used to read RFID tags on outdoor billboards in order to get info on the move.
- Bluetooth pairing - in the future pairing of Bluetooth 2.1 devices with NFC support will be as easy as bringing them close together and accepting the pairing. The process of activating Bluetooth on both sides, searching, waiting, pairing and authorization will be replaced by a simple "touch" of the mobile phones.
- Electronic passport (containing finger prints, photos, information for identification by the human iris, etc.)
The goal of this research area is to push the transmission rates up to several tens of Mbits/s.
Combining circuit design knowledge in the field of RFID with modern communication technology is a promising approach. |
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| UW‑OFDM |
| Status | in progress |
| Advisor | Univ.-Prof. Dr. Mario Huemer |
| Contact | Univ.-Ass. Dipl.-Ing. Alexander Onic |
| E-Mail | |
| Phone | +43 (0)463 2700 3662 |
| Description |
At this moment, Orthogonal Frequency Division Multiplexing (OFDM) is the dominating transmission practice in wireless as well as wired communication.
Currently the guard interval in OFDM transmission, which is needed to avoid intersymbol interferences, is filled with a cyclic prefix (CP). This depends on the transmitted message and is thus random.
A novel technique utilizes a deterministic predefined sequence, that is called Unique Word (UW). This offers many advantages over the use of a CP, that need to be developed and researched and developed thoroughly. |
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| RELAY - Cooperative Relaying in Wireless Networks |
| Status | in progress |
| Advisor | Univ.-Prof. Dr. Mario Huemer |
| Contact | Dipl.-Ing. (FH) Christian Hofbauer |
| E-Mail | |
| Description | Recently, the idea of cooperative relaying has gained significant interest in the research community. More in detail, cooperative relaying means that several devices cooperate in some fashion in order to transfer the data from the transmitter to the receiver.
This approach promises to enhance the performance in comparison to todays’ wireless communication systems in terms of coverage, link reliability and capacity, respectively. Moreover, this concept seems to make the advantages of classical Multi Input Multi Output systems, namely spatial diversity and increased data rate, also available for distributed systems like sensor networks. Such distributed systems are expected to play an important role in future wireless communication standards, as they do not require fixed and expensive infrastructure.
However, a cooperative approach like this does not only require the design of new communications protocols, but significantly affects physical layer related system aspects as well. Hence, intensive research is required to efficiently handle the classical tasks of wireless communications, like for instance channel estimation, channel equalization or modulation, also in a cooperative and distributed system. Furthermore, the robustness of the developed solutions with respect to synchronization related issues seems to be an important and challenging task.
The research methodology in this project will mainly include simulation-based studies and implementation on off-the-shelf hardware. |
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