Ultra-wideband Interference Research Articles

A stochastic geometry approach to coexistence in heterogeneous wireless networks

With the increasing proliferation of different communication devices sharing the same spectrum, it is critical to understand the impact of interference in heterogeneous wireless networks. In this paper, we put forth a mathematical model for coexistence in networks composed of both narrowband (NB) and ultrawideband (UWB) wireless nodes, based on fundamental tools from stochastic geometry. Our model considers that the interferers are spatially scattered according to a Poisson field, and are operating asynchronously in a wireless environment. We first determine the statistical distribution of the aggregate interference for both cases of NB and UWB emitters. We then provide error probability expressions for two dual configurations: 1) a NB victim link subject to the aggregate UWB interference, and 2) a UWB victim link subject to the aggregate NB interference. The results show that while the impact of a single interferer on a link is often negligible due to restrictions on the transmitted power, the aggregate effect of multiple interferers may cause significant degradation. Therefore, aggregate interference must be considered to ensure coexistence in heterogeneous networks. The proposed analytical framework shows good agreement with physical-level simulations of the system.

Ultra wideband technologies coexistence in Nakagami- m fading channels

The wide spectrum of ultra wideband (UWB) communications makes it inevitable to consider strategies for avoiding and mitigating interference from narrowband wireless systems such as GPS, UMTS, and WLAN, or other UWB wireless technologies. In this paper, we provide a performance analysis of multiband orthogonal frequency division multiplexing (MB-OFDM) UWB in the presence of binary phase-shift keying time-hopping (BPSK-TH) UWB or BPSK-DS UWB interfering transmissions under Nakagami-m fading. In the bit-error rate (BER) analysis, several UWB interferers are considered to affect the MB-OFDM signal. A Gaussian approximation is considered for the UWB interferers and used in the analysis of the BER performance of the MB-OFDM UWB system. The Nakagami-m distribution is applied to characterise the amplitude of the fading channels for both the reference signal and the interference signals. Furthermore, a waveforming technique is considered for mitigating the effect of interference and its efficiency is illustrated in terms of BER improvement. Numerical and simulation results are provided and compared for different coexistence scenarios.

Ultra-wideband detect and avoid procedure for WiMAX victims

Detect and avoid (DAA) procedures aim at improving ultra-wideband (UWB) coexistence with existing narrowband/wideband licenced/unlicenced victim terminals operating in the same band at the same time and area. The authors propose a DAA procedure that can be used to reduce the percentage of time the UWB interferes with victims operating in a time division duplexing (TDD) mode. The authors consider a system scenario where a TDD terminal has a primary role and UWB devices create a secondary network on a local area basis. A DAA procedure is implemented only in the UWB devices that adapt their transmissions in order to avoid or reduce interference on primary device(s) in the same area. The performance of the proposed DAA procedure is presented and discussed and its dependence on some key UWB transmission parameters, bit rate and the emitted power is evidenced. It is shown that the DAA timeout parameters can be tuned so as to arbitrarily reduce the average percentage of time the UWB interferes with the considered victim systems even well below the limits imposed by regulatory bodies. It is shown that interference reduction is obtained at the expense of reduced performance of the UWB transmission. The proper selection of DAA timeouts for a desired percentage of UWB interference and UWB link efficiency is discussed.

Analysis on IR/TR-UWB Interference against Narrowband Systems

This paper presents the analysis of in-band interference caused by pulse-based ultra-wideband (UWB) systems. The analysis contains both plain Impulse Radio UWB (IR-UWB) and Transmitted Reference UWB (TR-UWB) systems as a source of interference. The supposed victim is a narrowband BPSK system with a band-pass filter. The effect of pulse-based UWB systems is analyzed in terms of bit error rate. The analysis is given in terms of the specific combinations of pulse repetition frequency and center frequency of the narrowband bandpass filter. In those situations, the UWB interference cannot be modeled as a Gaussian noise. It also manifests situations in which the victim is under the severest or the slightest interference from TR-UWB. According to its result, the analysis is validated via simulation.

On the Impact of Ultra-Wideband (UWB) on Macrocell Downlink of UMTS and CDMA-450 Systems

Results of the analytical analysis to assess the effect of the ultra-wideband (UWB) emissions on the [universal mobile telecommunication system (UMTS) and code division multiple access systems (CDMA-450)] are presented. The (UMTS and CDMA- 450 systems) normalized range and normalized capacity degradation are evaluated. A free-space propagation model is used to calculate the UWB signal power that interferes with both mobile systems. It is shown that, for the case of a single UWB transmitter, the UMTS can easily tolerate UWB interference when the UWB equivalent isotropically radiated power (EIRP) is -92.5 dBm/MHz or less for a distance between the UWB transmitter and the UMTS mobile of 1 m or higher. Also, it is shown that, for the case of multi-UWB transmitters, the UMTS can easily tolerate the UWB interference when the UWB EIRP is -94.5 dBm/MHz. For the single UWB transmitter case, the CDMA-450 downlink can tolerate UWB interference when the UWB power density is in the order of -106 dBm/MHz. For the case of multi-UWB transmitters, the power density that can be tolerated by the downlink of the CDMA- 450 system is in the order of -108 dBm/MHz.

Analysis of Narrowband Communication Systems Impaired by MB-OFDM UWB Interference

In this paper, we investigate the effect of multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) interference on narrowband (NB) receivers. For this purpose, we first derive the exact moment generating function of MB-OFDM UWB interference. Based on this result, we develop analytical expressions for the amplitude probability distribution (APD) and the bit error rate (BER) of a binary phase-shift keying NB receiver. These expressions can be efficiently numerically evaluated and the presented analysis is general enough to encompass non-fading and various fading NB channels. We show that for NB signals with, respectively, much smaller and much larger bandwidths than the MB-OFDM sub-carrier spacing a Gaussian approximation (GA) and an impulsive GA (IGA) of the MB-OFDM UWB interference lead to accurate performance predictions. However, for most NB channel models and signal bandwidths the exact BER analysis has to be used to obtain meaningful results. An exception is the Rayleigh fading NB channel where both GA and IGA yield tight approximations of the exact BER regardless of the NB signal bandwidth.

초광대역 시스템에 의한 WiMAX로의 간섭 및 송신 전력 제어 간섭 저감 방법 해석 연구

This paper presents the analysis of the potential ultra-wideband(UWB) interference to WiMAX at 3.5 GHz bands and the mitigation method using transmit power control(TPC) of UWB system. UWB interference effect is evaluated with WiMax`s outage probability over UWB density when multiple UWB systems and single WiMAX receiver distribute in unit area of 1, When UWB distribution density is 20 and the dynamic range of TPC is 30 dB, UWB interference effect with TPC is decreased by 42 % rather than that without mitigation scheme. Finally, we describe that the proposed TPC is an effective method to mitigate UWB interference to WiMAX.

Analysis of UWB Interference to MPSK Narrowband Receivers

This paper studies the in-band interference of time-hopping spread spectrum (TH-SS) ultra-wideband (UWB) signals to narrowband receivers. Based on the analysis of general power spectral density (PSD) of TH-SS UWB signal, the interference of UWB signal is partitioned into two parts: (1) additive white Gaussian noise interference, and (2) jamming tone interference. Following this framework, a novel analytical symbol error rate (SER) evaluation method for binary phase-shift keying (BPSK) and M-ary phase-shift keying (MPSK) signals subject to UWB interferences is proposed and corresponding simulation results are demonstrated. It is shown that as the number of in-band jamming tones increases, the UWB interference effect tends to be closer to the effect of the equivalent Gaussian noise. When there is only one UWB tone interferer within the narrowband receiver bandwidth, and when the signal-to-interference-and-noise ratio is higher than a certain value, the narrowband symbol error rate decreases as the relative tone power portion in the overall interference and noise power increases.

Reduction of UWB interference at NB systems based on a generalized pulse waveform

This work proposes a pulse waveform to reduce UWB interference at narrowband (NB) systems. The pulse waveform is represented as a generalized form of Gaussian pulse family which can be used in ultra wideband (UWB) impulse radio systems. It is obtained by combining two higher order derivatives of Gaussian pulses. The pulse waveform reduces UWB interference power at NB systems by introducing spectral notches at the center frequency of NB systems.

Co-existence measurements between UMTS and UWB systems

The paper presents results of a co-existence measurement study between multiple ultra wideband (UWB) transmitters and a Universal Mobile Telecommunications System (UMTS) mobile phone. Two environments were explored: an anechoic chamber with one operating UMTS link and a true operational UMTS network. A large number of FCC compatible UWB transmitters were used to generate interference for an active UMTS connection. In an anechoic chamber, only the voice service was studied between a radio communication analyser (used as a base station) and a mobile terminal. In the true commercial UMTS network case, both the voice and data services were investigated in a shelter having a low UMTS signal level. The results clearly show that UMTS and high pulse repetition rate UWB devices can co-exist at link level when a moderate number of simultaneously active UWB devices operate in close proximity of the UMTS 'victim' receiver. The results also show that the activity factor of the UWB transmitter disproportionately impacts the effective interference. When using low activity factors, even with high pulse repetition rates and very large numbers of UWB devices, it is difficult to detect UMTS link performance degradation. As the activity factors grow beyond 5%, the impact of the UWB interference becomes visible. However, this study covers only one active UMTS link in both environments but does not report on the UWB impact on the UMTS radio access network.

Spectral Analysis of UWB Multiple Access Schemes Using Random Scrambling

With the new release of the Federal Communication Commission on matters of regulation of marketing and operation of ultra-wideband (UWB) devices, an analytical framework to enable tractable analysis of the spectrum shape of these signals is needed. We extend the framework introduced by W. A. Gardner to the case of UWB signals. We introduce a generalized UWB signal model that can be specialized to represent the traditional time-hopping (TH) technique as well as the alternative multiple access technique that we indicate as delay coded sequence (DCS). The DCS technique resembles the traditional direct sequence spread spectrum techniques, but it is not based on pulse polarity inversion. The considered matrix signal formulation allows us to easily evaluate the spectral characteristics of UWB signals under many different operating conditions: continuous or discontinuous transmissions, random or periodic scrambling operations, with or without jitter. We evaluate the spectrum of the general UWB signal under the random scrambling assumption, then we specialize it to the TH and DCS cases and discuss the variability of the spectra to some critical design parameters. We obtain an asymptotic expression of the general UWB spectrum that we use to evaluate the UWB interference power at the output of a generic receiver.

Ultra-Wideband Signal Impact on the Performances of IEEE 802.11b and Bluetooth Networks

This paper presents the results of a coexistence study investigating the impact of ultra-wideband (UWB) interference on IEEE 802.11b and Bluetooth networks. The results are based on the experimental test measurements made at the University of Oulu, Finland. Simple high-power UWB transmitters are used to interfere with victim networks. Preliminary results show that only under extreme interference conditions with thousands of equivalent Federal Communications Commission– (FCC)-compliant devices in close proximity, will the IEEE 802.11b and Bluetooth networks experience significant performance degradation. The impact of the UWB interference on the IEEE 802.11b network was insignificant if the distance to UWB transmitters was greater than 40 cm. The impact on Bluetooth was even less noticeable. In our study, several high-power UWB transmitters that greatly exceed the FCC radiation regulations have been used, and the measurement settings presents the worst case scenario because of the very short distance between the interferers and the victim system. Effectively our study approximates the use of thousands of FCC-complaint UWB devices in the same space.