Paola Pulini

Forward Link Performance Analysis for the Future IEEE 802.16-Based Airport Data Link

In this paper, an analysis of the performance of the OFDM version of the IEEE 802.16e standard is provided in a realistic airport scenario. We implemented a novel stochastic airport channel model describing the main wireless propagation phenomena related to the airport environment. Multi-path and Doppler effects with the potentially resulting inter-symbol interference and inter-carrier interference have been taken into account, respectively. System performance is evaluated for the forward link case in the apron, parking, taxi and runway scenarios, showing strengths and lacks of the system characteristics. For the most critical scenario (i.e., the parking one), an investigation of the reduction of the pilot sub-carriers spacing and on the introduction of antenna diversity is proposed, showing large performance gains.

Unequal Diversity LDPC Codes for Relay Channels

A novel protograph-based construction of low-density parity-check (LDPC) codes for the relay channel is proposed, which provides an enhanced unequal error protection property named unequal diversity. The focus is on quasi-static fading channels and on the high-code-rate (R>1/2) regimes, for which (according to the Singleton bound) no full diversity can be achieved. In the proposed construction, some nodes (and the corresponding codeword fragment) associated with the code graph enjoy the diversity provided by the relay, whereas the remaining nodes do not experience any diversity. The proposed approach can be thus tailored to transmit information blocks with different priority levels. An extrinsic information transfer (EXIT) analysis is developed, which allows an accurate performance prediction over the considered channel model, and more in general over block-fading channels.

On-Line Construction of Irregular Repeat Accumulate Codes for Packet Erasure Channels

In many applications erasure correcting codes are used to recover packet losses at high protocol stack layers. The objects (e.g. files) to be transmitted often have variable sizes, resulting in a variable number of packets to be encoded by the packet-level encoder. In this paper, algorithms for the (on-line) flexible design of parity-check matrices for irregular-repeat-accumulate codes are investigated. The proposed algorithms allow designing in fast manner parity-check matrices that are suitable for low-complexity maximum-likelihood decoding. The code ensembles generated by the algorithms are analyzed via extrinsic information transfer charts. Numerical results show how the designed codes can attain codeword error rates as low as 10-5 without appreciable losses w.r.t. the performance of idealized maximum-distance separable codes. Finally, we apply the proposed codes to the upcoming aeronautical communication standard, showing large performance improvements and proving the efficiency and the flexibility of the developed method.

Sandra flight trials - Concept, validation, and results

A new integrated aircraft communications system combining legacy and future technologies has been designed, developed and validated under real environment conditions within the framework of the EU FP7 SANDRA project. With IPv6 as unification point, this system integrates all the aeronautical service domains within a common IP-based aeronautical network as well as with legacy and non-legacy radio technologies. This paper presents the flight trial outcomes of the SANDRA system that occurred in the vicinity of the German Aerospace Center (DLR) in Oberpfaffenhofen, Germany in June 2013. The presented results will emphasize the flexibility and scalability of the SANDRA network and demonstrate the seamless service coverage of the SANDRA architecture across different airspace domains.

Protograph EXIT analysis over block fading channels with application to relays

An accurate extrinsic information transfer (EXIT) analysis is developed for protograph low-density parity-check (LDPC) codes over the block fading channel (BFC). The analysis is thus exploited for analyzing the behavior of distributed protograph LDPC ensembles over block fading relay channels. A novel protograph-based construction of low-density parity-check (LDPC) codes for the relay channel is proposed, which provides an enhanced unequal error protection (named unequal diversity, UD) property. The focus is on quasi-static fading channels and on the high-code-rate (R >; 1/2) regimes, for which (according to the Singleton bound) no full diversity can be achieved. In the proposed construction, some nodes (and the corresponding codeword fragments) associated with the code graph enjoy the diversity provided by the relay, whereas the remaining nodes do not experience any diversity. The proposed approach can be thus tailored to transmit information blocks with different priority levels.

Flexible On-Line Construction of IRA Codes for Packet Erasure Correction with Application to Aeronautical Communications

In many applications erasure correcting codes are used to recover packet losses at high protocol stack layers. The objects (e.g. files) to be transmitted often have variable sizes, resulting in a variable number of packet to be encoded by the packet-level encoder. In this paper, algorithms for the (on-line) flexible design of parity-check matrices for irregular-repeat-accumulate codes are investigated. The proposed algorithms allow designing in fast manner parity-check matrices that are suitable for low-complexity maximum-likelihood decoding. The code ensembles generated by the proposed algorithms are analyzed via extrinsic information transfer charts. Numerical results show how the designed codes can attain codeword error rates as low as 10^{-5} without appreciable losses w.r.t. the performance of idealized maximum-distance separable codes. The application of the proposed techniques to the upcoming aeronautical communication standard is investigated, proving the efficiency and the flexibility of the approach.

Improving the performance of AeroMACS by cooperative communications

Cooperative communications have gained in the past years an increasing attention, showing promising outcomes on the performance of the systems. The future airport surface communication system represents a potential candidate for the exploitation of these techniques. Focusing on the airport context, we analyze low complexity single-relay cooperative methods. Moreover, we implement a simple amplify and forward scheme showing its performance in the airport communication context.

Simplified airport surface channel model based on the WSSUS assumption

The paper proposes a channel model for an airport data link in taxi line-of-sight and parking non-line-of-sight scenarios. It is realized as a tapped-delay-line fulfilling WSSUS assumption within a data frame. Proposed channel parameters are derived from the measurement results and from the characteristic of the channel spreading function during an aircraft movement.

AeroMACS evolution - analysis during landing, takeoff, and approach phases

The Aeronautical Mobile Airport Communications System (AeroMACS) has been developed for future high-rate, secure, and safety enhancing airport communications in the C-band. Although initially designed for ground applications, the relatively large radio coverage area of AeroMACS suggests its potential extension to new operative scenarios wherein a data link is established between the control tower and the aircraft even when the latter is not in contact with the airport surface. An examination is needed for these new applications concerning channel properties, synchronization aspects, and general performance behaviors. In this paper, the possibility of using AeroMACS during the approach, landing, and takeoff phases of an aircraft flight is investigated. After deriving the channel parameters for the new application scenarios, the synchronization and channel estimation algorithms are presented and the overall error rate performance is assessed by means of computer simulations. Our results indicate that AeroMACS is able to cope with the new operational phases and its use can be extended beyond airport surface applications.

WIMAX Performance in the Airport Environment

In this paper, the multicarrier physical layers of WiMAX are evaluated in the context of airport data links. The orthogonal frequency-division multiplexing (OFDM) and orthogonal frequency-division multiple-access (OFDMA) cases are applied to the forward link (FL) and reverse link (RL), respectively. The performance of the so called parking and taxi scenarios is presented for airport communications in C-band. Numerical results show that the proposed scheme brings good performance for both the FL and the RL. For the OFDMA case a structure changing called double-tile is also proposed to improve the system performance.