Abstract-This paper describes the implementation and characterisation of a mobile ad-hoc network (MANET) of ultra-light intelligent flying robots. The flying nature of the network makes it suitable to collect or disseminate content in urban areas or challenging terrain, where line-of-sight connection between the Micro Air Vehicles (MAVs) allows for more efficient communication. Dynamic routing in the network enables the nodes to intelligently establish multi-hop routes to extend the communication range or to overcome obstacles. The presented MANET relies on the IEEE 802.11n WiFi standard for data communications and uses the OLSR routing protocol. Routing decisions based on dynamic link quality measurements allow the network to cope with the fast variability of the wireless channel and the high mobility of the MAVs. The implementation of such a system calls for the integration of advanced communication and control technologies in a very restrictive platform, be it in terms of weight, power consumption or availability of suitable off-the-shelf hardware. A detailed description of the system design is presented, and its performance is characterised based on in-flight network measurements. To the best of our knowledge, this is the first report of OLSR successfully tested in a MANET with such fast dynamics. We verify the trade-off between achievable throughput and the number of hops, and we report on the sensitivity of communication performance and routing behaviour to MAV orientation and flight path. Mitigation of such dependencies and improvements to the routing algorithm are discussed along with future research directions.

Future 4th Generation (4G) wireless multiuser communication systems will have to provide advanced multimedia services to an increasing number of users, making good use of the scarce spectrum resources. Thus, 4G system design should pursue both higher-transmission bit rates and higher spectral efficiencies. To achieve this goal, multiple antenna systems are called to play a crucial role. In this contribution we address the implementation in FPGAs of a multiple-input multiple-output (MIMO) decoder embedded in a prototype of a 4G mobile receiver. This MIMO decoder is part of a multicarrier code-division multiple-access (MC-CDMA) radio system, equipped with multiple antennas at both ends of the link, that is able to handle up to 32 users and provides raw transmission bit-rates up to 125 Mbps. The task of the MIMO decoder is to appropriately combine the signals simultaneously received on all antennas to construct an improved signal, free of interference, from which to estimate the transmitted symbols. A comprehensive explanation of the complete design process is provided, including architectural decisions, floating-point to fixed-point translation, and description of the validation procedure. We also report implementation results using FPGA devices of the Xilinx Virtex-4 family.

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In this paper we address the implementation in FPGAs of a Multiple-Input Multiple-Output (MIMO) decoder embedded in a prototype of a 4G mobile receiver. This MIMO decoder is part of a multi-carrier code-division multiple-access (MC-CDMA) radio system, equipped with multiple antennas at both ends of the link, that is able to handle up to 32 users and provides raw transmission bit-rates up to 125 Mbps.The task of the MIMO decoder is to appropriately combine the signals simultaneously received on all antennas to construct an improved signal, free from interference, from which to estimate the transmitted symbols. A comprehensive explanation of the complete design process is provided, including architectural decisions, floating-point to fixed-point translation and description of the validation procedure. Implementation results using FPGA devices of the Xilinx Virtex-4 family are also reported.