Transmission Techniques
Inverse Symbol Error Probability for Diversity Reception: derived new upper and lower bounds on the inverse symbol error probability (SEP) for multi-channel reception with MRC that are tight for all signal-to-noise ratios and invertible. The bounds enable the derivation of the symbol error outage (SEO), the SEP-based outage probability, in a shadowing environment and are useful for the design of digital radio systems with diversity reception. Related papers: [J5][J9][C15][C16][C19]. In particular, bounds derived in [J9] are referenced in M.K. Simon, M.-S. Alouini, Digital Communication over Fading Channels, Wiley-Interscience, II edition.
Slow Adaptive Modulation: evaluated the performance, in terms of exact bit error probability (BEP), bit error outage (BEO), the BEP based outage probability, and normalized throughput (NT) for slow adaptive M-QAM with multi-channel reception in fading channels. The proposed slow adaptive modulation (SAM) technique adapts the constellation size to the slow variation of the channel, such as shadowing, and is applicable to different modulation schemes. The proposed SAM technique, even if is more practical than adaptive modulation techniques requiring the adaptation following fast fading variations, provide very good performance in terms of both BEO and NT. Related papers: [C23][C25][C30][J12].
Frequency Hopping Mobile Radio Systems: derived a semi-analytical procedure for outage evaluation of mobile radio systems adopting slow frequency hopping in a complete scenario composed by co-channel interference (different tiers of interfering cells, cluster size and sectorization are considered), thermal noise, fast fading, shadowing, path-loss, power control (ideal and non-ideal), antenna diversity, and different coding techniques. As example result, the outage versus spectral efficiency for different cluster-size and system parameters is obtained for a given requirement on the QoS. Related papers: [J1][C1][C2][COST1][COST2][TR1].
Power Control Techniques: analyzed power control algorithm that adapts the transmitted power to slow channel variations such us shadowing. Complete and partial compensation of slow processes are taken into account and how they affect both outage and the usage of terminal battery is analytically evaluated. As example results it is shown that partial compensation power control techniques extend battery life and reduce health-risks at the same level of performance. Related papers: [J2][C3][C4][COST3][TR3].
CDMA systems in the presence of Non-Linear Effects: characterized non-linear effects due to high power amplifier (HPA such as, e.g., SSP, TWT, ideal limiter) and evaluated the impairment on the performance of code division multiple access (CDMA) systems. By using the extension of Bussgang's theorem, non-linearities are considered as thermal noise with parameters derived by AM/AM and AM/PM characteristics of the HPA. Derived the bit error probability for both synchronous and asynchronous CDMA systems and the total degradation (TD). The TD provides information about the penalty due to non-linearities in both the SNR and the output back-off (OBO) for a given QoS. As example result, the best working point of the HPA is obtained for different HPA characteristics. Related papers: [J3][C6][C10][TR4].
Coding techniques on MIMO faded channels: evaluated the performance of different coding techniques in block fading channel (BFC) with single reception; proposed and analyzed pragmatic space-time codes in MIMO faded channels. With regard to convolutional codes in BFC, polynomial generators are designed for different channel conditions and interleaving strategies. For STC, we propose a pragmatic architecture that reduce the complexity of encoder and decoder for a given QoS. Proposed a design criteria for pragmatic STC with different channel correlation level and interleaving strategies. Analytical upper-bounds on the codeword error probability. Related papers: [J11][C2][C7][C8][C13][C14][C17][C21][C22][TR2].
Partial combining for MC-CDMA systems: evaluated the performance of MC-CDMA systems (spreading in frequency domain) with different combining techniques and proposed a partial combining technique on different subcarriers signals. The proposed technique has the same complexity of known MRC, EGC, ORC and depends on a parameter that is analytically optimezed depending on slow processes such as the number of active users, the number of sub-carriers and the mean SNR averaged over fast fading. Analytical and simulative results are in a very good agreement. Related papers: [C23][C25].
Channel estimation for TD-CDMA modile radio systems: midamble-based channel estimation techniques have been considered. The optimal energy partition between midamble and data has been analytically carried out to minimize the error probability. Optimum partition and equal amplitude techniques have been compared through the analytical methodology and simulations. Related papers: [J4][C9].
MAC-layer performance and networks coexistence
Performance and Coexistence Issue between WLAN and WPAN: addressed the performance evaluation and the coexistence of IEEE802.11b and Bluetooth in a heterogeneous environment by means of an integrated analytical approach. The methodology proposed carefully takes both physical (i.e., thermal noise, propagation, interference, modulation formats and coding techniques) and medium access control (frequency hopping, packet structure, traffic loads) aspects into account. This model can also be implemented when developing network simulators, thus avoiding extensive bit level simulations. As example results, the mean packet error probability as a function of the relative distance between the two systems for different conditions and the coexistence domain are evaluated. Related papers: [J8][C18][C20][C26].
Wireless Sensor Network for environmental monitoring: a network of randomly positioned wireles sensors is deploied to sense a spatial process. The sensors sense the process and transmit the sample to a supervisor (i.e., monitor, collector) through proper communications protocols and distributed processing. An analytical methodology has been derive to evaluate the estimation error and the energy efficiency of the WSN as a function of nodes and protocols parameters (PHY and MAC related to) to obtain the trade-off between estimation and network life-time both in the presence and in the absence of distributed signal processing. The connectivity among nodes is carefully taken into account in the presence of path-loss and shadowing, and evaluating the probability of isolated nodes depending (communications failed due to connectivity or MAC issues). Related papers: [C24][C27][C29][C31].
Experimental research activities
Network of Laboratories and Telemeasurement for the characterization of TLC systems: -->LINK experimental activity of measurement and telemeasurement of communications systems through heterogeneous communication networks (bit error rate, spectra, eyes diagram, constellation, etc) with remote configuration of both instrumentation and DSP-based circuits, together with interconnections (with a programmable RF connection matrix). Involved in projects (e.g., ASI-CNIT, Teledoc2, VICom, SUMMIT, CRIMSON) for the realization of a cooperative distributed platform for sharing instruments and circuits within a network of laboratories. Proposed low complexity algorithm for acquisition, tracking and frequency offset recovery in DSP realization of high loaded CDMA satellite modem. At the user side a 3D immersive access is developed. Concerning the architecture, the cooperation among distributed laboratories is exploited studying also the impact of communication network to the measurement quality. Related papers: [J6][J10][C11][C28].
Indoor localization through wireless sensor network: within the Project VICom a network of commercial wireless sensors has been realized to support indoor localization. The study considers different layers, such as interconnectivity issues among nodes, localization algorithms and localization applications for the virtual guiding of users. Activities are done in all these aspects. At the application level a full interoperability with a multiuser outdoor localization component realized with the integrated GPS-UMTS technology is given. Indoor localization algorithms based on RSSI measurement are considered. Measurement campains and comparisons with Ray-tracing results.
Satellite station management: in the period 1999-2002 he collaborates in the management and the characterization of the ITALSAT F2 CNIT satellite network at the UoR of Bologna. The link was in Ka-band (30GHz up - 20GHz dw). On the heterogeneous netowrk composed by satellite and wireless/wired terrestrial links multimedia services (e.g., videoconference in projects ASI-CNIT and Teledoc) have been tested and experimented. Related papers: [J7][C5][C12][COST4].