Hanns-Ulrich Dehner

A Simple and Fast Detect and Avoid Algorithm for Non-Coherent Multiband Impulse Radio UWB

In this paper we present a simple and fast detect and avoid (DAA) algorithm for non-coherent multiband impulse radio UWB. By independent par- allelized interception of all subbands, this algorithm shows a very robust and reliable behavior in the de- tection of narrowband interference such as the IEEE 802.11a wireless LAN (WLAN) standard (1). Thereby, narrowband interference detection is possible during an initialization mode but also during data transmission. The detection is based on a static threshold which guarantees a maximum bit error rate in each subband. If a narrowband interferer is present the transmission is avoided on the corresponding subband and a receiver known initialization sequence is transmitted. Due to the fact that there is a loss in data rate, this approach retains the possibility of using all subbands when no interferer is present. radio UWB system including its capability for narrowband interference mitigation is necessary. This paper presents a simple and novel narrowband interference mitigation technique for non-coherent multi- band impulse radio UWB. The proposed detect and avoid algorithm is based on an extended initial channel estima- tion as well as a recursive channel estimation which is described in (7). Thereby, the estimated values are used to detect a narrowband interferer within the initialization or the data transmission phase. The detection algorithm is very fast and an active narrowband interferer can be detected in less than 250 ns. The disturbed subband will be deactivated and remains off until a new channel estimation is initialized. The accuracy in the frequency domain of the detect and avoid algorithm depends on several system parameters, especially on the number of subbands. This paper is organized as follows: Section II introduces the system model including the non-coherent energy de- tection scheme. In section III we illustrate the impact of a specific narrowband interference source to a multiband impulse radio UWB system. Section IV shows the appli- cation of a static mitigation approach as well as a simple and robust detect and avoid algorithm. Finally, simulation results as well as conclusions are given.

The Teager-Kaiser Energy Operator in Presence of Multiple Narrowband Interference

As the analog front-end of an energy detector is highly susceptible to narrowband interference a modified energy detection scheme based on the Teager-Kaiser operator and high-pass filtering is considered. This letter analyzes the Teager-Kaiser operator output for an arbitrary number of narrowband band-pass signals having different amplitudes, center frequencies and bandwidths. The analysis reveals that additional cross components occur at the operators output in case of multiple narrowband interference. Hence, a simple narrowband interference suppression with Teager-Kaiser operator and high-pass filtering can be insufficient.

A low complex and efficient coexistence approach for non-coherent multiband impulse radio UWB

When bringing a high data rate multiband impulse radio UWB system to the market it has to coexist with other already existing UWB technologies such as multiband OFDM UWB [1]. This paper analyzes the interference impact of a multiband OFDM UWB system on a non-coherent multiband impulse radio UWB system. It is shown that the impact can be so dominant that communication within the impulse based multiband UWB system gets worse. For this reason a static as well as a dynamic coexistence approach are considered. The dynamic approach uses an efficient, robust and easy to realize “pixel” based interference detection algorithm in conjunction with an adapted bandplan array. In comparison to the static approach, the dynamic coexistence approach allows higher data rates during data transmission phases without significant losses in bit error rate performance.

Narrow-Band Interference Robustness for Energy Detection in OOK/PPM

This paper investigates robustness of a non-coherent multi-band impulse radio ultra-wideband communication system with respect to narrow-band interference. A statistical analysis of interference at the energy detector output gives insight into its impact and system dependency. Furthermore, the potential of interference mitigation is shown and verified with respect to the processing gain.

On the modified Teager-Kaiser energy operator regarding narrowband interference

This paper analyzes a modified Teager-Kaiser energy operator under narrowband interference within a subband of a multiband impulse radio UWB system. It is shown that a simple weighting of the Teager-Kaiser operator results in a significant frequency dependent energy distribution of the received signal. Hence, the modified Teager-Kaiser operator is not only a DC shifter. In comparison to the traditional Teager-Kaiser operator, a considerable increase of the amplitude spectrum around twice the subbands carrier frequency occurs at its output, which can improve the detection performance in absence or in presence of narrowband interference.

Narrow- and Broadband Interference Robustness for OOK/BPPM Based Energy Detection

An analysis of narrow- and broadband interference robustness within an On-Off Keying/Binary Pulse Position Modulation based noncoherent multiband impulse radio ultra-wideband communication system is presented. Using the energy detectors processing gain closed-form expressions of the noise and interference related second order moment statistics at the output of an energy detection receiver are derived. This allows separate statements on the relative modulation specific processing gain with respect to various interference parameters.

Treatment of temporary narrowband interference in non-coherent multiband impulse radio UWB

This paper considers low complex interference handling with regard to temporary narrowband interference occurrence within a non-coherent On-Off Keying based multiband impulse radio UWB system. The approach allows a precise and reliable sub-band specific on-line detection of narrowband interferences presence or absence within a packets data phase. Due to the systems instability after detection of interference absence, a decision threshold replacement is applied to correctly demodulate the data packets remaining possibly not interfered data bits. Hence, an increased flexibility with respect to efficient interference handling as well as a significant performance gain can be achieved.

Iterative coexistence approaches for non-coherent multi-band impulse radio UWB

This paper presents two easy to realize iterative coexistence approaches for non-coherent multi-band impulse radio ultra wide band systems with respect to multiple interference. Thereby, the global coexistence approach presented in [1] is extended to an iterative detection of possible interfered time-frequency gaps by means of an adaptive two-dimensional band plan. The proposed coexistence approaches can be applied for various periodic or constant operating broad-or narrow-band interfering signals. The iterative coexistence approaches outperform the global coexistence approach and hence contribute to more reliable interference detection under realistic dynamic interference scenarios.

MIRA – Physical Layer Optimisation for the Multiband Impulse Radio UWB Architecture

Future wireless communication systems have to be realised in a simple and energy efficient manner while guaranteeing sufficient performance. Furthermore, the available frequency resources have to be used flexibly and efficiently. In this context two different approaches have been considered in recent years: On one hand OFDM-based overlay systems in which a primary user dynamically allocates unused frequencies to one or more secondary users [57] and on the other hand unlicensed, easy-to-realise and low-cost ultra-wideband (UWB) systems. This underlying technology operates with an extremely low transmission power over a wide frequency range and does not interfere with existing licensed systems [15].

High data rate coexistence-based channel coding for noncoherent Multiband Impulse Radio UWB

This paper investigates the performance of high data rate coexistence-based channel coding within a noncoherent Multiband Impulse Radio UWB system. It is shown that in the presence of interference the combination of adaptive image-based thresholding and channel coding can lead to a significant performance gain in comparison to thresholding-only. For thresholding two low complex methods, the Otsu algorithm as well as the nonlinear Teager-Kaiser filtering operation, are considered.