Francesco Rossetto

On the design of practical asynchronous physical layer network coding

Decode-and-forward physical layer network coding is one of the most high-performing ideas for wireless network coding. However, all the present schemes work under rather ideal assumptions, such as synchronous reception of the colliding signals. This paper proposes a simple and practical system which removes many of the assumptions made in the past and also designs a soft-output demodulator for this type of network coding.

A geographic routing strategy for north Atlantic in-flight internet access via airborne mesh networking

The Airborne Internet is a vision of a large-scale multihop wireless mesh network consisting of commercial passenger aircraft connected via long-range highly directional air-to-air radio links. We propose a geographic load sharing strategy to fully exploit the total air-to-ground capacity available at any given time. When forwarding packets for a given destination, a node considers not one but a set of next-hop candidates and spreads traffic among them based on queue dynamics. In addition, load balancing is performed among Internet Gateways by using a congestion-aware handover strategy. Our simulations using realistic North Atlantic air traffic demonstrate the ability of such a load sharing mechanism to approach the maximum theoretical throughput in the network.

On the achievable rates for the return-link of multi-beam satellite systems using successive interference cancellation

This paper investigates the theoretically reachable rates in the return-link of multi-user multi-beam satellite systems. The return-link can actually be analyzed by means of multiple-input multiple-output signal processing techniques. While MIMO inspired multi-user detection for the return-link of satellite systems has been partly investigated in the past, a fundamental look at the achievable gains by these advanced signal processing techniques for satellite communications is missing. Depending on the number of colors used in the system, the available bandwidth per beam can be traded off against the level of co-channel interference. This paper explores the fundamental limits dictated by information theory to the communication rates on satellite multi-beam scenarios, and the impact of a realistic beam patterns on these data rates.

User scheduling for large multi-beam satellite MIMO systems

Very large size MIMO systems (hundreds of antennas) are practically relevant, for instance in the return link of satellite communications. Indeed, satellites routinelly have about one hundred beams and hundreds of terminals may be present in each beam. Scheduling can become very challenging in in this large-size scenario: an arbitrarily selected scheduling plan may result in users with low offered rates; on the other hand searching for the best scheduling plan is unfeasible due to the huge number of possible combinations. This work proposes a low complexity heuristic based on graph theory to find a scheduling plan that well balances the offered rates to the served users.

Routing in the Airborne Internet

The Airborne Internet is envisioned to be a large scale multihop wireless mesh network of civil aviation aircraft connected via long range highly directional air-to-air radio links. We propose a novel geographic load share routing metric to mitigate congestion in this network, taking into account the underlying link scheduling constraints with directional antennas. When forwarding packets for a given destination, a node considers not one but a set of next hop candidates, and spreads traffic among them based on queue dynamics. Our simulations show that introducing this flexibility in the routing function can greatly increase a nodes ability to satisfy its bandwidth demands during link scheduling, yielding significant performance improvements in terms of network throughput and average packet delay. The ability to exploit this flexibility depends on the spatial reuse of the underlying network. For the simulated scenario, an increase in network throughput of 200% on average is shown, compared to a state-of-the-art geographic routing algorithm.

A Robust Approach to Carrier Sense for MIMO Ad Hoc Networks

This paper proposes a method to improve the robustness of the carrier sense system for Opportunistic MAC (OMAC). This carrier sense method is specific for MIMO and the new version here illustrated is robust to noise and interference. Network simulations prove that this modified MIMO carrier sense correctly estimates whether a new communication would harm other ongoing transmissions for a wide range of system parameters.

A simple analytical model for Robust Header Compression in correlated wireless links

Robust Header Compression (ROHC) has been successfully included in some wireless standards in order to reduce the excessive IP overhead for small packets, for instance Voice over IP frames. So far, there is limited understanding on how the ROHC performance depends on the design parameters and the characteristics of the wireless channel. In this paper we propose an analytical model that provides simple expressions for the probability of losing synchronization as a function of the mentioned parameters, and also yields insightful relationships between the design variables and the desired system performance. The results are validated against sophisticated and realistic models of ROHC.

Design considerations for massively parallel channel estimation algorithms

Accurate channel estimation may require complex algorithms for effective results, especially in the case of a multiuser detector. The introduction of Graphic Processing Units (GPUs) has opened up new possibilities for the implementation of numerically intensive channel estimation algorithms. This paper studies the implementation on GPUs of channel estimation algorithms for channels affected by strong phase noise. While classic Maximum Likelihood estimation is still the most competitive in terms of throughput and memory bandwidth, Steepest Ascent algorithms show the largest speed improvement due to their structure, which is the most suitable for implementation on a parallel processor like the GPU.