Annalisa Durantini

Time domain propagation measurements of the UWB indoor channel using PN-sequence in the FCC-compliant band 3.6-6 GHz

We have performed a propagation measurement campaign at the University of Rome Tor Vergata, Rome, Italy. We have sounded the channel by a probing signal at a carrier frequency of 4.78 GHz modulated by a train of pulses having a duration of 0.4 ns shaped by a pseudonoise (PN) sequence. The measurement band falls (3.6-6 GHz) in the frequency range allowed by the FCC ruling for ultrawide-band (UWB) operations. To characterize the channel behavior over the large and the small scale, the transmitter is moved in six different positions on the floor, while the receiver is moved in 625 different locations within each room. The receiver locations are arranged in a square grid of 25/spl times/25 points with 2 cm spacing, i.e., less than half of the minimum wavelength of the transmitted signal. A total of 625/spl times/16 impulse responses are recorded in nonline-of-sight (NLOS) conditions, 625 in line-of-sight (LOS) conditions within the rooms and 11 LOS measurements are made in the corridor at incremental spacing of 1 m. We describe the measurement technique as well as the procedure by which we process the experimental data to extract the amplitude, phase and delay associated to each component of the multipath profiles. We also derive path-loss and shadowing models for the UWB indoor channel in both LOS and NLOS conditions. Finally, we present an accurate analysis of the time dispersion of the UWB channel.

Performance Evaluation of Detect and Avoid Procedures for Improving UWB Coexistence with UMTS and WiMAX systems

Detect and avoid procedures (DAA) aim at improving ultra-wideband (UWB) coexistence with existing narrowband-wideband systems operating at the same time and in the same area. We assess the interference caused by UWB devices implementing DAA on UMTS, as well as on WiMAX systems, by estimating the time percentage where UWBs interferer with these systems. Both UMTS and WiMAX are supposed to provide primary services with respect to UWB. As a consequence, UWB is not allowed to influence their operations, i.e. no cooperation is assumed between UWB and UMTS, WiMAX devices. In this paper we present and discuss the performances of two DAA techniques, analyzing their dependence on some key UWB transmission parameters, such as the bit rate and emitted power. The proposed DAA procedures are simple to be implemented and their parameters can be selected so to arbitrarily reduce the average percentage of time the UWB interferes with the two considered victim systems

UWB propagation measurements by PN-sequence channel sounding

An extensive measurement campaign is carried out in a modern office building. The channel is sounded by a carrier at 4.78 GHz modulated by a train of pulses, each having a duration of 0.4 ns, shaped by a pseudo noise (PN) sequence, covering the band 3.6-6 GHz. The transmitter is moved in six different positions on the floor, while the receiver is moved within each room by a digitally controlled positioner in 625 different locations arranged in a square grid of 25 /spl times/ 25 points with 2 cm spacing. A total of 625 /spl times/ 16 profiles in nonline-of-sight (NLOS) and 625 in line-of-sight (LOS) conditions are recorded within the rooms. LOS measurements are made in the corridor in 11 locations at incremental spacing of 1 m. We describe the measurement technique as well as the procedure by which we process the experimental data to extract the amplitude, phase and delay associated to each path of the channel impulse responses. Finally, we derive LOS and NLOS path-loss models.

The role of path loss on the selection of the operating bands of UWB systems

We performed a propagation experiment in a modern office building in Rome, Italy. The propagation measurements are based on the use of a vector network analyzer (VNA) over the band 2-12 GHz, with a frequency resolution of 5 MHz. We propose a novel analysis of the dependence of path loss laws on the carrier frequency and bandwidth. Our experimental results show that the path loss exponent strongly depends on the carrier frequency. The path loss exponents increase with the increasing carrier frequency for the line-of-sight (LOS) scenarios, while exhibit an opposite behavior for the non-line-of-sight (NLOS) data. We explain this behavior by the frequency dependence of the reflection coefficient of the walls surrounding the transmitter. Indeed, the lowest frequencies (2-5 GHz) are reflected, while the highest frequencies (up to 12 GHz) pass through the walls.

A multi-wall path loss model for indoor UWB propagation

The paper presents a propagation experiment performed in a modern office/laboratory building to investigate the UWB indoor channel behavior over the band 3.6-6 GHz. We accomplished measurements employing a correlative channel sounding technique. PN-sequence modulation is applied to a train of 0.4ns pulses and a pair of direct sequence UWB transmitter and a correlation receiver is used. We collected data under extremely heterogeneous propagation conditions. LOS measurements are carried out along the corridor and in the office environment, while a total of 10 /spl times/ 118 measurements are collected in NLOS scenarios, within office rooms, for a coverage range up to about 18 m. We describe the exploited measurement technique as well as the data processing approach. Finally. a multi-wall path loss model is recommended, instead of the classical single-slope model, to fairly evaluate the power decay with the link distance, separately taking into account the losses due to architectural obstacles intercepted by the direct paths of the propagating signals.

Integration of Broadband Wireless Technologies and PMR Systems for Professional Communications

The paper contributes to the evolution of Public Safety and Disaster Relief (PSDR) communications by specifying a solution for interoperability and integration among Professional Mobile Radio systems (TETRA and Simulcast), public systems (GSM/GPRS/UMTS), and broadband wireless technologies, such as WiMAX. A policy for PSDR services scheduling and fundamental guidelines for mapping the quality of service over heterogeneous networks are presented. Hence, the paper outlines the key issues to be debated by a regulatory authority. Operation of the devised PSDR mobile integration solution is tested to ensure complete connectivity among users adopting different communication standards, as well as to enable distributed services provisioning guaranteeing always best connection to bandwidth demanding applications provided by an IP-based core network. Finally, the employment of the envisaged integration platform is detailed in Mobile Ad-Hoc and Wireless Sensor Networks.

Test of 2.5 GHz WiMAX performances for business and SOHO in a multi-service environment

The paper is focused on evaluating the performances of a WiMAX system in a variety of single and multiple play scenarios for SOHO and Business customers. To this aim several experiments are carried out over a 2.5 GHz WiMAX test-bed deployed at the radiocommunication laboratories of the University of Rome Tor Vergata. Throughput and link quality are tested in uplink and downlink in correspondence of different system configuration profiles and WiMAX service classes. Fixed and portable access are considered, for coverage ranges up to a few kilometers.

Measurements, modeling and simulations of the UWB propagation channel based on direct-sequence channel sounding

The paper presents the statistical model for the ultra-wideband (UWB) indoor channel having a bandwidth of 2.4 GHz and a central frequency of 4.78 GHz. The model is based on propagation experiments performed in different rooms on a floor of an office-laboratory building. Within each room the receiver antenna is automatically moved over a square grid of 25 × 25 locations spaced 2 cm apart. A correlative channel sounding technique is employed; actually the carrier is modulated by a train of short duration (0.4 ns) pulses shaped by a PN-sequence. After coherently demodulating the detected signals and removing the PN-sequence modulation, we post-process the extracted channel impulse responses by best-fit procedures to set up a statistical tapped delay line model (STDL) of the UWB indoor channel. We characterize the path loss for line-of-sight (LOS) and non-line-of-sight (NLOS) conditions by distance-power laws and the shadowing by lognormal distributions. A clustered structure is observed in the average power-delay profiles; rays arrive at the receiver in groups, exponentially decaying with different decay constants. The small-scale effects are modeled by the Gamma distribution since it verifies with a 95%-confidence interval both the Chi-Square test and the Kolmogorov–Smirnov test applied to the experimental data. The shape parameters of such Gamma distributions are truncated Gaussian variables spreading in the range from 1 to 3. An implementation of the derived STDL model is finally proposed and a comparison between the simulated and the measured statistics is performed proving the validity of our approach. Copyright

Performance comparison of vertical handover strategies for psdr heterogeneous networks

In this article we suggest a vertical handover (VHO) solution able to optimize mobility management over heterogeneous networks in terms of handoff delay and signaling load. The presented strategy discriminates the best mobility protocol to be used based on a scheduling policy. It is specifically designed for an integrated network architecture to provide PSDR organizations using TETRA and TETRA2 systems with the capability to exploit WiFi and WiMAX broadband access technologies in order to enjoy advanced services. The article presents the operational scenarios where integration between TETRA and WiFi/WiMAX is needed and the main resulting benefits. Performances of the suggested VHO management scheme are described and evaluated against other protocol solutions.

Detect and Avoid Procedure for UWB Interference Mitigation on Narrowband Systems

Detect and avoid procedures (DAA) are helpful to solve coexistence issues between ultra-wideband (UWB) devices and existing narrowband system operating in the same area and at the same time. We consider a system scenario where a narrowband UMTS terminal is considered to be primary and UWB devices create a secondary network on a local area basis. DAA procedures are only implemented in the UWB devices that coordinate their transmissions in order to reduce and/or to avoid interference to primary device(s) in the same area. UWB cannot alter the operations of the primary device in any way. We present and analyze the performance of an effective DAA procedure to be implemented in the UWB device(s) whose parameters can be tuned in order to reduce the percentage of time the UWB interferes the UMTS device. It is shown that interference reduction is obtained at the expense of a reduced performance of the UWB devices.