Heavy Multipath Environment Research Articles

An Indoor Localization and Tracking System Using Successive Weighted RSS Projection

This letter proposes a novel successive weighted received signal strength (RSS) indoor localization and tracking system that projects previous time instance estimated mobile device (MD) position to provide projected RSS values. Such RSS projection increases the number of available RSS from Nm to Nm + N AP , where N AP is the total number of access points and Nm is the number of RSS values measured by MD, ranging from 0 to N AP . Our proposed system thus resolves the issues associated with insufficient or no RSS values received by MD. Inertial navigation system (INS) is merged with RSS localization system to provide a weighted fusion of projected and measured RSS values. The weighting factors are derived based on the INS and RSS localization accuracy where the former is initially accurate but deteriorates with time and the latter is time-independent but environment-dependent. The proposed system was tested in indoor environments and outperformed other existing localization systems such as RSS and INS fusion using extended Kalman filter and non-line-of-sight (NLOS) selection scheme, especially in heavy multipath environment, by 42% and 75%, respectively.

Wideband and Ultra Wideband Radio Propagation in Heavy Multipath Environments

The authors have focused on wideband, including ultra-wideband (UWB, 3.1 to 10.6GHz) radio propagation in various environments, such as a small space-craft and a passenger car, moreover on-body radio propagation measurements have been conducted. Many studies have been reported about indoor propagation for narrowband and wideband. However previous study has not been examined characteristics between 10-MHz and 1-GHz frequencies. In our previous study, UWB and narrowband propagation were measured in a UWB frequency band within closed/semi-closed spaces (e.g. a spacecraft, a passenger car, and a metal desk equipped with a metal partition). While narrowband propagation resulted in considerable spatial variations in propagation gain due to interferences caused by multipath environments, UWB yielded none. This implies that the UWB systems have an advantage over narrowband from a viewpoint of reducing fading margins. Thus, a use of UWB technology within spacecrafts has been proposed with a view to partially replacing wired interface buses with wireless connections. Adoption of wireless technologies within the spacecrafts could contribute to reduction in cable weight (and launching cost as a result), reduction in the cost of manufacture, more flexibility in layout of spacecraft subsystems, and reliable connections at rotary, moving, and sliding joints. Path gains and throughputs were also measured for various antenna settings and polarizations in the small spacecraft. Polarization configurations were found to produce almost no effect on average power delay profiles and substantially small effects on the throughputs. Furthermore, statistical channel models were proposed. Also UWB technologies have been considered for use in wireless body area networks (WBAN) because of their possible low power consumption and anti-multipath capabilities. A series of propagation measurements were carried out between on-body antennas in five different rooms. A new path loss and statistical models considering room volume had been proposed. In this paper, we evaluated propagation characteristics in heavy multipath environments, especially examined the channels at 10-MHz to 1-GHz frequencies.

Single reference mobile localisation in multipath environment

A wireless localisation scheme which requires just one reference device to estimate the mobile location is presented. The proposed scheme utilises the joint time-of-arrival and angle-of-arrival estimation of the line-of-sight path measured at both mobile and reference devices to construct areas of possible mobile devices (APMDs). The intersection of these APMDs will give an estimation of an MD location. Simulations in light and heavy multipath environments show that the performance of the proposed single reference localisation scheme dramatically improved the location accuracy as compared with the conventional localisation techniques that use four reference devices.

Sensing Driver Phone Use with Acoustic Ranging through Car Speakers

This work addresses the fundamental problem of distinguishing between a driver and passenger using a mobile phone, which is the critical input to enable numerous safety and interface enhancements. Our detection system leverages the existing car stereo infrastructure, in particular, the speakers and Bluetooth network. Our acoustic approach has the phone send a series of customized high frequency beeps via the car stereo. The beeps are spaced in time across the left, right, and if available, front and rear speakers. After sampling the beeps, we use a sequential change-point detection scheme to time their arrival, and then use a differential approach to estimate the phone's distance from the car's center. From these differences a passenger or driver classification can be made. To validate our approach, we experimented with two kinds of phones and in two different cars. We found that our customized beeps were imperceptible to most users, yet still playable and recordable in both cars. Our customized beeps were also robust to background sounds such as music and wind, and we found the signal processing did not require excessive computational resources. In spite of the cars' heavy multipath environment, our approach had a classification accuracy of over 90 percent, and around 95 percent with some calibrations. We also found, we have a low false positive rate, on the order of a few percent.

PEER-TO-PEER LOCALIZATION IN URBAN AND INDOOR ENVIRONMENTS

This paper presents a novel peer-to-peer or mobile- to-mobile localization scheme for general indoor and outdoor environments. In this scheme, two mobile nodes at arbitrary locations are able to locate each other without the need of Line-of-Sight (LOS) path between the two mobile device, and without the need for any reference devices such as GPS or land base beacons. Existing peer- to-peer localization techniques make use of Time of Arrival (TOA) and Angle of Arrival (AOA) of LOS and single bounce scattering paths to derive line of possible mobile device positions (LPMDs). The intersections of LPMDs are then used to estimate the unknown mobile device position | referred to as the Line Segment Intersection. However, in a heavy multipath environment with many multiple- bounce scattering paths, existing techniques require weighting factors and threshold values which are speciflcally chosen for that particular environment in order to select the LPMDs that correspond to LOS and single-bounce scattering paths for localization. Large localization error will occur if multiple-bounce scattering paths' LPMDs are mistakenly used for intersections. In addition, existing techniques also do not work well in a multipath environment with high level of TOA and AOA noises especially when the angles between LPMDs are small. The accuracy of the Line Segment Intersection also deteriorates as the distance traveled by multipath signals become comparable to each other. This renders the weighting and threshold values inefiective. This paper presents a novel Gaussian weighting process to remove the abovementioned limitations. The Gaussian weighting process also dramatically improves the accuracy of the localization. Experimental coupled with simulation results show that our proposed localization scheme outperforms existing Peer-to-peer localization technique by a signiflcant margin of up to 83% and 54%

Studies on an Iterative Frequency Domain Channel Estimation Technique for MIMO-UWB Communications

MIMO (Multiple-Input Multiple-Output) technologies have attracted much interest for high-rate and high-capacity wireless communications. MIMO technologies under frequency-selective fading environments (wideband MIMO technologies) have also been studied. A wideband MIMO system is affected by ISI (Inter Symbol Interference) and CCI (Co-Channel Interference). Hence, we need a MIMO signal detection technique that simultaneously suppresses ISI and CCI. The OFDM system and SC-FDE (Single Carrier-Frequency Domain Equalization) techniques are often used for suppressing ISI. By employing these techniques with the ZF (Zero Forcing) or the MMSE (Minimum Mean Square Error) spatial filtering technique, we can cancel both ISI and CCI. To use ZF or MMSE, we need channel state information for calculating the receive weights. Although an LS (Least Square) channel estimation technique has been proposed for MIMO-OFDM systems, it needs a large estimation matrix at the receiver side to obtain sufficient estimation performance in heavy multipath environments. However, the use of a large matrix increases computational complexity and the circuit size. We use frequency domain channel estimation to solve these problems and propose an iterative method for achieving better estimation performance. In this paper, we assume the use of a MIMO-UWB system that employs a UWB-IR (Ultra-Wideband Impulse Radio) scheme with the FDE technique as the wideband wireless transmission scheme for heavy multipath environments, and we evaluate the iterative frequency domain channel estimation through computer simulations and computational complexity calculations.

Performance of the Proposed Galileo CBOC Modulation in Heavy Multipath Environment

In the framework of the modernization plans of Global Navigation Satellite Systems (GNSS) a new Multiplexed Binary Offset Carrier (MBOC) modulation has been proposed as a possible Signal-In-Space (SIS) with improved performance with respect to the robustness against external sources of degradation. Discussion around such signal format are still on-going at the time of writing, anyway it is the most probable candidate signal that will be adopted by both GPS L1C and the Galileo E1 Open Service (OS) signals [( http://ec.europa.eu/dgs/energy_transport/galileo/documents/doc/2004_06_21_summit_2004_en.pdf , 2004)] as modernization of the present BOC(1,1). In the context of the integration between wireless communication and satellite navigation, one of the major problems is that usually the GNSS receiver has to work in a critical environment characterized by a heavy presence of multipath or interference sources. Some examples are urban canyons or light indoor spaces. These are also typical situations for the usage of personal communications systems. The new MBOC modulation have been studied with the specific goal to create a signal more robust with respect to multipath, bringing the high performance of Galileo in situations in which the present BOC(1,1) shows limitations. In this sense, future Location Based Services (LBS) provided on the basis of the GNSS OS will benefits from this intrinsic robustness of the signal. Throughout the paper a review of the MBOC structure will be presented, specifying that in the Galileo framework such a structure has been proposed in a version named Composite BOC (CBOC). In particular, the paper presents the simulation of the CBOC behavior in presence of multipath showing the extreme improvement with respect to other BOC solutions.

Rake Performance for UWB-IR System with SISO and MISO

In this letter, we compare a Multiple-Input Single-Output (MISO)-Ultra WideBand (UWB)- Impulse Radio (IR) system and a Single-Input Single-Output (SISO)-UWB-IR system at high transmission rates. We evaluate the Bit Error Rate (BER) of the two systems with some RAKE receivers under heavy multipath environments. From the results of our computer simulation, we show that the SISO-UWB-IR system with Minimum Mean Square Error (MMSE)-RAKE receiver is a good candidate to achieve high transmission rates.