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ABSTRACT: 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.
Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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ABSTRACT: The paper is focused on evaluating the performances of a WiMAX system in a variety of service scenarios, with particular attention to video applications. 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 nomadic access are considered, for coverage ranges up to a few kilometers. The experiments results are presented in this paper.
Wireless Communications and Mobile Computing Conference, 2008. IWCMC '08. International; 09/2008
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ABSTRACT: 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.
IEEE Wireless Communications 07/2008; · 2.58 Impact Factor
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ABSTRACT: 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.
Networking and Services, 2008. ICNS 2008. Fourth International Conference on; 04/2008
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ABSTRACT: Detect and avoid procedures (DAA) improve Ultra-wideband (UWB) coexistence with existing narrowband/wideband victim systems operating in the same band, at the same time and area. In this paper we propose a DAA procedure that can be used to reduce the percentage of time the UWB interferes the victim devices which operate in accordance to a frequency division duplex (FDD) mode. A cooperative scenario is considered. Some UWB devices are integrated with the victim devices and can broadcast information on the status of the victim to other UWBs in the area. This information is used in the DAA to improve performance. The performance of the proposed DAA procedure are presented and discussed and their dependence on some key UWB transmission parameters, such as the bit rate and emitted power, are evidenced. It is shown that the DAA parameters can be selected so to arbitrarily reduce the average percentage of time the UWB interferes with the considered victim systems.
Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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ABSTRACT: In this paper we evaluate the impact of UWB transmissions on the performances of a WiMAX receiver, which employs orthogonal frequency-division multiplexing (OFDM) modulation and operates in a time division duplex (TDD) mode. To this aim, we compute the interference contribution caused by DS-UWB signals at the WiMAX receiver output, as well as the interference statistics, adopting a theoretical approach and simulations. We present a non-cooperative detect and avoid (DAA) procedure to mitigate the UWB interference to WiMAX. The results of the interference analysis are exploited to opportunely set the UWB transmission parameters in the DAA procedure, so that the targeted QoS is achieved for the WiMAX communications<sup>1</sup>.
Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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ABSTRACT: 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
Ultra-Wideband, The 2006 IEEE 2006 International Conference on; 10/2006
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ABSTRACT: The capacity of UWB enabled wireless personal area networks is analyzed in a dense multipath environment. The performances of UWB systems employing a direct-sequence multiple access scheme are evaluated in terms of link outage probability and average aggregate network throughput, considering a network topology based on a clustered structure, formed by a multitude of uncoordinated coexisting piconets. We study the dependence of the system performances on some critical design choices, such as the Rake receiver scheme, the mono-pulse characteristics of the transmitted UWB signals, the structure of the piconet frame, the traffic characteristics. Results are obtained by applying a semi-analytical estimate procedure, which accounts of the large and small scale fading phenomena for the UWB indoor propagation channel
Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on; 10/2006
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ABSTRACT: We assess the performances of multi-user UWB systems which employ direct-sequence and time-hopping access schemes, for transmissions of several Mbit/s in an operating environment characterized by dense multipath. The link outage probability and average aggregate network throughput are estimated, assuming a network topology based on a clustered structure, formed by a multitude of uncoordinated coexisting piconets. We investigate the impact on the system performances of some critical implementation choices, such as the UWB signal model, the traffic characteristics and the Rake receiver scheme, by employing a semi-analytical estimate procedure, which also accounts of the large and small scale fading phenomena for the UWB indoor propagation channel.
Wireless Communication Systems, 2006. ISWCS '06. 3rd International Symposium on; 10/2006
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ABSTRACT: 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.
Wireless Communication Systems, 2006. ISWCS '06. 3rd International Symposium on; 10/2006
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ABSTRACT: 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 25×25 points with 2 cm spacing, i.e., less than half of the minimum wavelength of the transmitted signal. A total of 625×16 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.
IEEE Transactions on Antennas and Propagation 05/2005; · 2.15 Impact Factor
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ABSTRACT: 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.
Personal, Indoor and Mobile Radio Communications, 2004. PIMRC 2004. 15th IEEE International Symposium on; 10/2004
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ABSTRACT: 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 × 25 points with 2 cm spacing. A total of 625 × 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.
Communications, 2004 IEEE International Conference on; 07/2004
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ABSTRACT: We derive a statistical model of the UWB indoor channel based on the experimental data collected in a modern office building. Measurements were made in different rooms throughout the floor and within each room the receiver antenna was moved over a square grid of 25 × 25 locations spaced 2 cm apart. The measurement technique was based on the use of a carrier at 4.78 GHz modulated by a train of short duration (0.4 ns) pulses shaped by a PN-sequence. Thus the probe signal covers the band 3.6 - 6 GHz. We coherently demodulate the received signals and cross-correlate their in-phase and q-phase components to an opportune PN-sequence template to extract the channel impulse responses from the recorded profiles. Then we post-process these "recovered" impulse responses by best-fit procedures to set up a statistical tapped delay line model of the UWB indoor channel. We model the path loss for LOS and NLOS conditions by distance power laws and the shadowing by log-normal distributions. The average power-delay profiles exhibit a clustered structure, which means that rays arrive at the receiver in groups, each having a given decay constant. We characterize the small-scale statistics by selecting the distribution that verifies with a 95%-confidence interval both the chi-square test and the Kolmogorov-Smirnov test applied to the experimental data. The gamma distribution verifies the abovementioned tests in most cases. The shape parameters of such gamma distributions spread in the range of 1 ÷ 3, and remain roughly constant around 2 with the excess delay.
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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ABSTRACT: The effects of adjacent channel interference (ACI) on WCDMA capacity are analyzed in the case of two operators allocated on adjacent radio channels or in the case of a single operator that uses two adjacent radio channels in a hierarchical cell structure. In contrast to existing literature, where ACI effects on system performance are generally evaluated by simulation, we propose a semi-analytical approach. The basic hypothesis is to model the ACI as a Gaussian random variable whose statistics, mean and variance, are obtained through simple and very fast simulation. Subsequently, the obtained statistics are used to calculate the outage probability using closed form equations. The advantage of this approach is that many different operating conditions can be analyzed with reduced computer calculation time as compared to the full Monte-Carlo method. Several performance results obtained by the application of the proposed approach are reported in the uplink case. Results are in very good agreement with those already presented in 3GPP reports.
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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ABSTRACT: 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 × 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.
Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st;
