Ultra Wideband Noise Channel Measurement using a Vector Network Analyzer

In this paper, we analyze the measurement of ultra wideband (UWB) noise channels in different indoor environments. All measurements are done using a vector network analyzer (VNA) which allows us to measure the noise channel transfer functions. We find that the noise power of the system is decreased by increasing the intermediate frequency (IF) bandwidth which leads to an increase in time taken to perform measurements of the channels. Also, we measure the environmental noise power and find that it is slightly affected by fluorescent light sources inside the measurement environments. In addition, we find that the environmental noise is decreased when enclosed in a Faraday cage (steel shed), within an intense multipath measurement environment. As secondary application, we show how a frequency detection device can be used to re-adjust a maladjusted frequency selection on a remote controller for a garage door, in presence of environmental noise power

Measurement of Ultra Wideband Channel Sounding Using a Vector Network Analyzer

In this paper, we analyze the measurement of ultra wideband (UWB) noise channels in different indoor environments. All measurements are done using a vector network analyzer (VNA) which allows us to measure the noise channel transfer functions. We find that the noise power of the system is decreased by increasing the intermediate frequency (IF) bandwidth which leads to an increase in time taken to perform measurements of the channels. Also, we measure the environmental noise power and find that it is slightly affected by fluorescent light sources inside the measurement environments. In addition, we find that the environmental noise is decreased when enclosed in a Faraday cage (steel shed), within an intense multipath measurement environment. We found that, the Environmental noise decreases slightly by using the LPDA antenna compared to using the Teardrop and Horn antennas. Our results show that the Horn antenna is less suitable for UWB channel measurements compared to the LPDA directional antennas because of lower S11 (Return Loss) values. While foromnidirectional antennas, the Teardrop antenna is much more suitable than the monocone antennas for UWB measurements (due to lower S11 values) and decreases the Environmental noise power. As secondary application, we show how a frequency detection device can be used to re-adjust a maladjusted frequency selection on a remote controller for a garage door, in presence of environmental noise power

In-vehicle channel sounding in the 5.8-GHz band

The article reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard. Experiments for both intra-vehicle and out-of-vehicle environments were carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best described through a two-term exponential decay model, in contrast to the linear models which are suitable for popular ultra-wideband (UWB) systems operating in the 3- to 11-GHz band. The small-scale variations (SSVs) are separated from the PDP by subtracting the LSV and characterized utilizing logistic, generalized extreme value (GEV), and normal distributions. Two sample Kolmogorov-Smirnov (K-S) tests validated that the logistic distribution is optimal for in-car, whereas the GEV distribution serves better for out-of-car measurements. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR), i.e., tap gains at different delays. Next, the CIR information is fed to an 802.11p simulation testbed to evaluate the bit error rate (BER) performance, following a Rician model. The BER results strongly vouch for the suitability of the protocol for in-car as well as out-of-car wireless applications in stationary environments.The article reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard. Experiments for both intra-vehicle and out-of-vehicle environments were carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best described through a two-term exponential decay model, in contrast to the linear models which are suitable for popular ultra-wideband (UWB) systems operating in the 3- to 11-GHz band. The small-scale variations (SSVs) are separated from the PDP by subtracting the LSV and characterized utilizing logistic, generalized extreme value (GEV), and normal distributions. Two sample Kolmogorov-Smirnov (K-S) tests validated that the logistic distribution is optimal for in-car, whereas the GEV distribution serves better for out-of-car measurements. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR), i.e., tap gains at different delays. Next, the CIR information is fed to an 802.11p simulation testbed to evaluate the bit error rate (BER) performance, following a Rician model. The BER results strongly vouch for the suitability of the protocol for in-car as well as out-of-car wireless applications in stationary environments

Channel characteristics for intra-vehicle wireless communications

Vehicles are continuously being improved to enhance the driving experience by integrating new technologies. Recent luxury vehicles may have over 70 Electronic Control Units (ECU) and 2200 cables. It is estimated that the number of ECUs and connections between ECUs and sensors will continuously increase to meet growing network requirements. The wire harness is the third most expensive component in a vehicle, reducing the number of cables through wireless communications would consequently result in space, cost, and fuel savings. However, the behaviour of the intra-vehicle channel and suitable wireless network technologies for an intra-vehicle network have not been fully addressed. In this research, the intra-vehicle narrowband loss performance in non-line-of-sight and line-of-sight condition was investigated and compared through real field tests. The results indicate that fading behaviour is primarily caused by small-scale rather than large-scale fading. An empirical-based path loss model is proposed with its parameters extracted from the real field test measurements. Further analysis of the small-scale fading through Rician K-factor reveals the dependence of the K-factor with distance and locations. These investigations suggest that for a narrowband system whereby the bandwidth of the transmitted signal is lower than the coherence bandwidth; the channel can be modelled using Rician fading. Furthermore, the wideband and ultra-wideband channel was characteristics through a real field tests. The results demonstrate that the multipath fading of intra-vehicle channel is much worse than other type of environments such as factory workshops and hospitals. Finally, the time-varying characteristics of the intra-vehicle channel, tested under various scenarios, suggest that the channel's coherence time is primarily impacted by passenger motion in the vehicle. Considering both the channel loss and time-varying characteristics, the performance trade-off's of the cooperative communication system against retransmission was evaluated

Predicted MIMO performance in intra-vehicle channels

Journal ArticleWireless sensor networks inside vehicles face particularly harsh multipath and shadowing constraints. The closed or semi-closed metallic structure functions much like a reverberation chamber, but with some regions shielded from other regions. Vehicles (particularly aircraft) often have extremely high electromagnetic interference across reverberates within the shell of the vehicle, creating a strong multipath noise environment. This poses unique challenges and unique opportunities

Characterization of vehicle penetration loss at wireless communication frequencies

Automotive window films are widely used for heat rejection, protection from ultraviolet radiations and glare control purposes. For an increased performance, these films are usually metallized since metals effectively reflect the impinging electromagnetic radiations. The expend of metallization in these films may affect the communication of radio signals into vehicles. In this perspective, the provision of reliable in-vehicle coverage is a major goal of both wireless network providers and automotive industry. In order to quantify the effects of automotive window films on communication signals inside a vehicle, this research study was undertaken with industrial cooperation. The thesis presents the characterization of Vehicle Penetration Loss (VPL) at major wireless communication frequencies based on empirical and numerical evaluation and by exploiting different window coatings including a commercially available automotive window film and Aluminium metal foil. The research involves ultra-wideband (UWB) car measurement campaign for the frequency range of 0.6-6.0 GHz in an indoor industrial environment at an isolated storage facility in Helsinki utilizing a regular sized hatchback car. Several realistic measurement scenarios were considered to obtain large measurement sets. The measurement data was post-processed using fine algorithms to exploit various channel characteristics to gain sufficient understanding of associated propagation phenomenon. Window films were also exclusively measured in a specialized environment to accurately assess the associated penetration loss. Apart from measurements, numerical analysis based on Finite-difference time-domain (FDTD) method for the assessment of VPL was carried out at discrete frequencies, 900 MHz and 1.2 GHz. The numerical approach can serve as a future alternate to measurements provided that adequate computational resources are available. The results infer that the use of metallized automotive films can severely affect the communication of radio signals into vehicles

Intra- and Out-of-Vehicle Channel Measurements and Modeling

Disertační práce je zaměřena na měření a modelování kanálu uvnitř a vně vozidla pro komunikaci a lokalizaci. Pro účely vytvoření integrovaného inteligentního dopravního systému ITS (Intelligent transportation system) je důležitý odhad vlastnosti kanálů pro vnitřní a venkovní scénáře. Za tímto účelem je vhodné provést řadu činností, které jsou obsahem disertační práce: Simulace fyzické vrstvy 802.11p, její srovnávání s 802.11a, měření kanálu pro různé scénáře pro 802.11p a pro širokopásmový systém (UWB), vytvoření modelů kanálů pro 802.11p a UWB a výzkum vlastností lokalizace založené na měření v pásmu UWB. Výzkum komunikace vozidla s okolím založená na IEEE 802.11p standardu. Jedním z cílů disertační práce je ukázat rozdíly mezi standardy fyzické vrstvy IEEE 802.11a a IEEE 802.11p prostřednictvím simulace s použitím modelu kanálu HIPERPLAN/2. V práci je uvedena simulace přenosu signálu 802.11p kanálem ITU-R M.1225 s odlišným zpožděním a středním výkonem (pro chodce a vozidla). Vliv kanálu na signál je analyzován za použití simulace v prostředí MATLABu pomocí vyhodnocení chybovosti. Určení vlastností kanálů v kmitočtovém pásmu 5,8 GHz pro standard IEEE 802.11p a UWB. Experimenty byly prováděny pro vnitřní a vnější prostředí vozidla. Bylo zjištěno, že pro protokol 802.11p může být trend (dlouhodobý vývoj) profilu PDP (power delay profile) nejlépe aproximován pomocí modelu obsahujícího dvě klesající exponenciální funkce, na rozdíl od Saleh-Valenzuelova (S-V) modelu, který je více vhodný pro UWB systémy pracující v pásmu 3 až 11 GHz. Vytvoření odpovídající impulzní odezvy (CIR) s využitím trendu PDP. Informace o CIR byla použita pro simulaci 802.11p za účelem vyhodnocení chybovosti při použití Ricianova modelu. Výsledky odhadu BER ukazují vhodnost protokolu pro vnitřní a vnější prostředí bezdrátových aplikací. Výsledky simulací dále ukazují, že se chybovost zásadně nemění a proto je možné určit střední křivku BER pro celou sadu změřených dat. Určení vlivu malé změny polohy antény na vlastnosti kanálu. Práce ukazuje náhodnost parametrů UWB kanálu pro malé změny polohy antény okolo vozidla, zaparkovaného v podzemní garáži. Ztráty šířením jsou monotónně rostoucí se vzdáleností, avšak náhodně se mění v závislosti na úhlu a výšce antén, a proto je vyhodnocení vzdálenosti pomocí síly signálu pro tyto scénáře nevhodné. Na druhé straně může být pro spolehlivé určení vzdálenosti bez ohledu na úhel nebo výšku antény použita doba příchodu prvního svazku. Ověření vlivu změn konfigurace kanálu na parametry S-V modelu. Práce demonstruje závislost parametrů Saleh-Valenzuela modelu v na vzdálenosti a výšce antén, avšak ukazuje, že jejich průměrné hodnoty jsou blízké IEEE 802.15.3 standardu. Ověření možnosti lokalizace pomocí metody TOA (time of arrival). Vzdálenost mezi anténami byla určena z profilu PDP s využitím lineární závislosti vzdálenosti na zpoždění. Souřadnice vysílací antény byly nalezeny pomocí dvou přijímacích antén pomocí 2-D lokalizační techniky TOA. Porovnání vypočtených souřadnic s původními vykazuje chybu menší než 6%, což ukazuje vhodnost navrženého přístupu pro lokalizaci vozidel.The dissertation is focused on channel measurements and modeling for vehicle-to-X communication and on localization. In order to realize an integrated intelligent transportation system (ITS), it is important to estimate channel features for intra-vehicle and out-of-vehicle scenarios. For this propose the following activities are carried out: simulation of the 802.11p PHY; comparison with 802.11a; channel measurements for different scenarios based on the 802.11p and ultra-wideband (UWB); creating channel models for 802.11p and UWB; UWB measurements to assess performance of localization. The vehicle-to-X communication is supposed on the IEEE 802.11p standard. The dissertation presents the differences between IEEE 802.11a and IEEE 802.11p physical layer standards through the simulation results of the transmission over a HIPERPLAN/2 channel. Further, the simulation of the 802.11p signal transmission over ITU-R M.1225 channel, which includes pedestrian and vehicle models with different relative delays and average power, is presented. The influence of the channel on the signal is analyzed using MATLAB simulation in terms of bit error rate (BER). The dissertation reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard and for UWB (3-11 GHz). Experiments for both intra-vehicle and out-of-vehicle environments are carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best approximated through a two-term exponential decay model for the 802.11p protocol, in contrast to the Saleh-Valenzuela (S-V) model which is suitable for UWB systems. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR). Next, the CIR is used in 802.11p simulation to evaluate the BER performance, following a Rician model. The results of the BER simulation shows the suitability of the protocol for in-car as well as out-of-car wireless applications. The simulation for out-of-car parameters indicate that the error performances do not vary much and it is possible to determine an average BER curve for the whole set of data. The randomness in UWB channel for small positional variations around a car, parked in an underground garage, is reported. The path loss (PL) is found to be monotonically increasing with distance but varies randomly with angle and height and thereby renders signal strength based ranging inaccurate for such scenarios. On the other hand, arrival time of the first ray can be used for reliable estimation of distance, independent on transmitter angle or height. The number of clusters in the PDP is reduced with distance but the nature of the profile remains fairly consistent with angle. The S-V model parameters also vary with distance and height but their average values are close to the IEEE 802.15.3 recommended channel model. For localization applications the distance between the antennas is calculated exploiting the linear dependence of distance on delay from PDP. The coordinates of a transmitting antenna are found with the help of two receiving antennas following a two-dimensional (2-D) time-of-arrival (TOA) based localization technique. A comparison of the calculated coordinates with the original ones exhibits an error of less than 6% which supports the suitability of the proposed approach for localization of the cars.