My current research interests are in the wide area of wireless systems, and in particular:

  • Visible light communication systems
  • Mobile localization systems
  • Distributed spectrum monitoring systems
  • mm-wave Communication Systems
In the past, I have worked in the following topics:
  • Unmanned aerial vehicle networks
  • Cloud-based opportunistic communication
  • Wireless home networking
  • Impairments in the 802.11 transmission opportunities
  • MIMO communication

Visible Light Communication Systems

The research on visible light communication networks has been conducted by Dr. Giustiniano since the PostDoctoral at Disney Research, and it is currently one of his main research areas at IMDEA Networks Institute. Visible light communication (VLC) uses Light Emitting Diodes (LEDs) for communication. LEDs are used for various applications, including wearable devices, toys, vehicles, and displays. In addition, LEDs also have the capability to control the brightness at a frequency that is orders of magnitude higher than conventional light emitting devices. This property enables the use of LED-based light sources as communication transceivers by modulating the intensity of the emitted light to convey information through wireless communication. While most of the research on VLC has focused on point-to-point communication, at the time of this work there was very limited investigation of a network of LEDs, a scenario we can call VLC Networks, which imposes the investigation of new protocols that exploit the diverse channel of VLC with respect to the Radio-Frequency channel. In this work, we use the LED not only as transmitter of modulated light, but also for the reception of light (similarly to a photodiode), a scenario we refer as LED-to-LED communication. Each node of the network uses a half-duplex mode to switch between transmission and reception of the modulated light, according to the status of the node. In the project conducted at Disney Research, we introduce the communication and networking protocols of LED-to-LED communication networks. Our work address fundamental research challenges such as efficient carrier sense with collision detection (CD) medium access protocol and elimination of light flicker. We have built a prototype and demonstrated bi-directional data exchange in a network of up to four LEDs [1]. [1] has received the best paper award at IFIP Wireless Days '12.

The rapid proliferation of personal smart devices is driving the creation of innovative services. Mainstream research focuses on leveraging Radio Frequency (RF) communication, but using RF to implement data-intensive services has the drawback of exacerbating the spectrum crunch problem. The adoption of VLC networks technology would help significantly in this sense, as the visible light spectrum is much wider than the RF spectrum. Though there has been a great deal of interest in VLC in recent years, the lack of an open-source reference platform is hindering the progress of the research community. At IMDEA Networks Institute, Dr. Giustiniano and group are designing and implementing since 4 years an open-source software-defined VLC networking platform for fast prototyping of networking protocols that runs on a low-cost embedded board (with a total cost of approximately 50 dollars, including all the electronics necessary for communication networks). We interface the Light Emitting Diode (LED) and ancillary electronics to an embedded Linux networking platform and implement in a new driver of the Linux Operating System the necessary primitives at Physical (PHY) and Medium Access Control (MAC) for the communication, and we design, implement, and evaluate standard innovative access mechanisms [2,3,4]. The website of the project provides a short description of the objective of the initiative. Currently, the platform has contributors from European and US academic centers [5]. The activity in VLC networks has further resulted in the introduction of intra-frame bidirectional transmission approach for visible light communication networks using one “optical antenna” (that is, one LED) for transmission and reception. Our approach allows introduce full-duplex communication, similarly to RF communication, but in a much simpler way. This is thanks to the unique features of the LEDs and of the communication channel in visible light. Based on this concept, we present the design, analysis, implementation, and performance evaluation of the Carrier Sensing Multiple Access/Collision Detection&Hidden Avoidance (CSMA/CD-HA) MAC protocol. We implement the protocol customizing our OpenVLC platform, solve practical challenges, and show its superior ability to detect collisions and alleviate hidden nodes, thus boosting the system throughput [6].

More recently, the publication “Passive Communication with Ambient Light” has been a runner-up to the Best Paper Award at ACM CoNEXT 2016, the 12th International Conference on emerging Networking EXperiments and Technologies, celebrated in December 2016, at Irvine, California (USA). We exploit uncontrolled light sources in our environments -such as any light bulbs in offices and roads or even the sun- as signal emitters. Data cannot be modulated using these uncontrolled light sources as in typical VLC systems. We instead propose that the environment itself modulates the ambient light signals. The paper further studies the research challenges of this new communication system and validate the systems with experimental studies, including evaluation in outdoor with cars moving up to 18 km/h [7].

Most of the studies in the area of VLC that focus on indoor positioning rely on two important assumptions: (i) lights are static, and (ii) the receiver has line-of-sight with multiple lights. These requirements limit the application of localization methods in scenarios where nodes have a single light and are mobile, such as motorbikes or swarms of robots. In general, this particular type of scenarios (single lights moving on a plane) lead to under-determined localization systems where no unique solution can be found. We follow a holistic approach that includes theory, simulations and experiments to overcome some of the limitations present in such type of scenarios. Our theoretical and simulation results show that if nodes are enhanced with sensors providing relative directions (such as compasses), we can derive dependencies in the system to obtain unique solutions. Our proof-of-concept implementation validates our model by showing that single lights can provide relative localization with high accuracy: an average error below 5 cm [8].

[1] Giustiniano, N. Tippenhauer, and S. Mangold, 'Low-Complexity Visible Light Networking with LED-to-LED Communication', IFIP Wireless Days, 2012, November, 2012, Best Paper Award.
[2] Q. Wang, D. Giustiniano, D. Puccinelli, 'OpenVLC: Software-Defined Visible Light Embedded Networks', ACM Visible Light Communication Systems Workshop, ACM Mobicom 2014, September 2014.
[3] Q. Wang, D. Giustiniano, D. Puccinelli, "An Open-Source Research Platform for Embedded Visible Light Networking", IEEE Wireless Communications Magazine, vol. 22, no. 2, pp. 94-100, 2015.
[4] Q. Wang, D. Giustiniano, D. Puccinelli, 'OpenVLC: Software-Defined Open Architecture for Visible Light Embedded Networks', Demo at ACM Visible Light Communication Systems Workshop, ACM Mobicom 2014, September 2014.
[6] Q. Wang, D. Giustiniano, "Communication Networks of Visible Light Emitting Diodes with Intra-Frame Bidirectional Transmission", ACM CoNEXT 2014. December 2014.
[7] Q. Wang. M. Zuniga, D Giustiniano' Passive Communication with Ambient Light', ACM CoNEXT 2016. December 2016. Best Paper Runner-up Award.
[8] A. Galisteo, Q. Wang, A. Deshpande, M. Zuniga, D. Giustiniano, 'Follow that Light: Leveraging LEDs for Relative Two-Dimensional Localization', ACM CoNEXT 2017. December 2017.

Mobile Localization Systems

Despite the increasing interest in the area of mobile indoor localization, the positioning capability of Wireless Local Area Network (WLAN)-based mobile devices does not meet the goal of high accuracy and fast time response, given the constraint of using a commodity smartphone as target device. The reason behind this lack of performance is in the ranging measurements, i.e. the distance estimation between two WLAN devices. At Disney Research, I worked on a solution called CAESAR, CArriEr Sense-bAsed Ranging, that combines Time-of-Flight (ToF) and signal-to-noise ratio measurements to calculate the distance between two stations. CAESAR measures the distance by estimating the MAC idle time in a data/ACK communication at a 44 MHz clock resolution and the ACK detection time based on the signal-to-noise ratio on a per-frame basis. CAESAR is a software-based solution that is entirely implemented at the transmitter and it does not require any protocol modifications. The experimental measurements confirm the accuracy of the solution and show the novel capability to track the distance to WLAN smartphones at pedestrian speeds [1]. The project on mobile indoor localization, and in particular on ToF echo techniques for ranging measurements has continued at ETH Zurich and now at IMDEA Networks Institute. Time-of-flight (ToF) echo techniques have been suggested for ranging mobile devices over WiFi radios. However, these techniques have yielded only moderate accuracy in indoor environments because WiFi ToF measurements suffer from extensive device-related noise which makes it challenging to differentiate between direct path from non-direct path signal components when estimating the ranges. Existing multipath mitigation techniques tend to fail at identifying the direct path when the device-related Gaussian noise is in the same order of magnitude, or larger than the multipath noise. In order to address this challenge, we propose a new method for filtering ranging measurements that is better suited for the inherent large noise as found in WiFi radios. Our technique combines statistical learning and robust statistics in a single filter. The filter is lightweight in the sense that it does not require specialized hardware, the intervention of the user, or cumbersome on-site manual calibration. This makes our method particularly suitable for indoor localization in large-scale deployments using existing legacy WiFi infrastructures. We evaluate our technique for indoor mobile tracking scenarios in multipath environments and, through extensive evaluations across four different testbeds covering areas up to 1000 m2, the filter is able to achieve a median 2-D positioning error between 2 and 3.4 m [2,3].

The system has also participated in indoor localization competitions, including the Microsoft Indoor Localization Competition in 2014 and 2016 [4]. Our system runs on commodity WiFi hardware and is the simplest solution available today to swiftly build a positioning system in a new indoor environment. Unless other systems, it does not require neither manual and costly offline pre-calibration nor any special hardware. Research has been also conducted in outdoor environments. In recent years, the rising demand for high-precision localization has challenged the use of Global Satellite Navigation System (GNSS) particularly in automotive applications. This is especially the case in urban scenarios where the most crucial GNSS disturbance is multipath. The work presented in [5] addressed the detection of multipath errors in pseudorange measurements for the special case of a moving receiver without the need for redundant observations or motion sensors. The proposed detection scheme is based on a combined observable that we call CMCD (Code-Minus-Carrier Deltarange). Simulations and experiments (test drive under heavy multipath conditions) confirm the soundness of the novel detector.

[1] D. Giustiniano, and S. Mangold, 'CAESAR: Carrier Sense-Based Ranging in Off-The-Shelf 802.11 Wireless LAN', ACM CoNEXT'11, December 2011.
[2] Andreas Marcaletti, Maurizio Rea, Domenico Giustiniano, Vincent Lenders, Aymen Fakhreddine, 'Filtering Noisy 802.11 Time-of-Flight Ranging Measurements', ACM CoNEXT 2014, December 2014.
[3] Maurizio Rea, Aymen Fakhreddine, Domenico Giustiniano, Vincent Lenders, 'Filtering Noisy 802.11 Time-of-Flight Ranging Measurements From Commoditized WiFi Radios', IEEE/ACM Transactions on Networking, PP (99). pp. 1-14. ISSN 1063-6692, May 2017.
[4] Dimitrios Lymberopoulos, Domenico Giustiniano, Vincent Lenders, Maurizio Rea, Andreas Marcaletti, - et al. (Microsoft Indoor localization Competition 2014), 'A Realistic Evaluation and Comparison of Indoor Location Technologies: Experiences and Lessons Learned', IEEE/ACM IPSN 2015, April 2015.
[5] Anton Beitler, Andreas Tollkuhn, Domenico Giustiniano, Bernhard Plattner, 'CMCD: Multipath Detection for Mobile GNSS Receivers', ITM 2015, January 2015.

Unmanned Aerial Vehicle Networks

Several research challenges and opportunities for micro unmanned aerial vehicles (UAVs) have been analyzed in [1] for two heterogeneous commodity airframe types (airplanes and copters). In the work, we have shown that providing wireless connectivity in this context is challenged by highly mobile and heterogeneous nodes, light-weight antenna design, body blockage, constrained embedded resources and limited battery power. Yet, the movement and location of micro unmanned aerial vehicles are known and may be controlled and steered to establish wireless links with best communication opportunities in time and space. Networking protocols can then exploit this novel dimension to answer to the challenges imposed by aerial wireless communication among unmanned aerial vehicles [1].


Unmanned aerial vehicles can collect high resolution images of the supervised images with their embedded camera. Delivering these high resolution images in rescue operations is a time-critical operation. To help resolving this problem, we have studied how UAVs can take advantage of their controlled mobility to derive the optimum strategy for data transmission. Driven by real-world aerial experiments with both airplanes and quadrocopters equipped with 802.11n technology, we show that the UAV should not necessarily transmit as soon as a wireless link is established. Instead, it should wait until it reaches a suitable distance to the receiving UAV, only to transmit when the time to move to the new location and transmit is minimal. We then applied the principle of delayed gratification, where the UAV attempts to solve the tradeoff between postponing until it reaches this minimum and the impatience to deliver as much data as soon as possible, before any physical damage on-the-fly may occur. Our empirical-driven simulations demonstrated that the optimal distance of transmission greatly depends on the interplay of actual throughput, data size, UAV cruise speed, and failure rate, and that state-of-the-art UAVs can already benefit from our approach [2,3]. The work has been done as part of the SWARMIX project, laying the foundations for the design, implementation, and adaptive control of heterogeneous multi-agent systems that are composed of humans, animals, and robots, working in cooperation to solve distributed tasks that require a wide diversity of sensory-motor and cognitive skills.


[1] M. Asadpour, B. Van den Bergh, D. Giustiniano, K. A. Hummel, S. Pollin, B. Plattner, 'Micro Unmanned Aerial Vehicle Networks: An Experimental Analysis of Challenges and Opportunities', IEEE Communication Magazine, July 2014.
[2] M. Asadpour, D. Giustiniano, K. A. Hummel, S. Heimlicher, S. Egli, 'Now or Later ? Delaying Data Transfer in Time-Critical Aerial Communication', ACM Conext 2013, Santa Barbara, USA, December 2013.
[3] M. Asadpour, K. A. Hummel, D. Giustiniano, S. Draskovic, 'Route or Carry: Motion-driven Packet Forwarding in Micro Aerial Vehicle Networks', IEEE Transactions on Mobile Computing, May 2016

Collaborative Wideband Spectrum Sensing

Although the frequency allocation of electromagnetic (EM) spectrum is well-organized, there is little knowledge of its actual usage in different geographical places and times. While traditional methods to monitor the spectrum usage rely on expensive and specialized hardware of governmental agencies, an attractive emerging alternative consists on building a networked and distributed infrastructure using spectrum analyzers connected over the public Internet. However, despite this strict allocation scheme of the spectrum, the actual usage of the spectrum at different geographical places and times is often unknown. This problem is due to the fact that today's spectrum measurements are primarily performed by governmental agencies which drive around using expensive and bulky specialized hardware. This monitoring approach does not scale well and is not able to cover the pervasive deployment of wireless networks as well as the increasing range of spectrum frequencies being used. Recent suggestions to enable wide-scale and real-time spectrum monitoring have therefore been to build a networked and distributed infrastructure using remote spectrum analyzers, or leverage the masses and to crowdsource the measurement stations by trading-off radio device sensitivity with cooperation. Our work [1] is aligned with these ideas of exploiting the crowd for scalable monitoring of the spectrum's actual usage at different frequencies, locations and times. However, in contrast to previous works, we envision a monitoring system that builds upon low-cost hardware and in [1] we study the design challenges at system level such that a large number of nodes can be distributed to collaboratively enlarge the system's overall coverage. The collaboration would allow individual sensing nodes working together in a coordinated fashion towards a common goal of monitoring the spectrum over the defined area of coverage. For this, the individual nodes would report their spectrum sensing results to a fusion center that stores and assembles the collected data.

A detail map of the actual EM spectrum usage created by crowdsourcing would democratize the access and knowledge of the radio spectrum leading to the emergence of new desirable services for a wide range of different applications [2]. Cognitive radio could use the data as a baseline to optimizing their efforts to dynamically accessing the spectrum. The spectrum sensed might also be used to identify regions with high/low levels of electro smog, which it could be an inventive for users to participate in this crowdsourcing system.

In [3], we study the problem of recombining signals collaboratively from different sensors, using coarse synchronization provided by GPS disciplined oscillator and accurate signal reconstruction with a combination of signal processing in the backend and feedback loop to the sensors to decide what chunk of I/Q samples to send to the backend.

Solutions investigated in this area are then implemented in the Electrosense network [4], a non-for-profit association with Dr. Giustiniano as one of the founders. Low-cost sensors collect spectrum information which is sent to the Electrosense backend. Different algorithms are run on the collected information in the backend and the results of these algorithms are provided to the users as a service through an open API. In addition the users could develop their own applications from the spectrum information retrieved using the API. Currently, 50 sensors are deployed mainly around Europe, and a backend cluster based lambda architecture process the data and give it back to the users.

[1] Damian Pfammatter, Domenico Giustiniano, Vincent Lenders (April 2015), 'A Software-defined Sensor Architecture for Large-scale Wideband Spectrum Monitoring', In: ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN 2015), 13-16 April 2015, Seattle, USA
[2] Roberto Calvo Palomino, Damian Pfammatter, Domenico Giustiniano, Vincent Lenders (April 2015), 'Demonstration Abstract: A Low-cost Sensor Platform for Large-scale Wideband Spectrum Monitoring (Demo)', In: ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN 2015), 13-16 April 2015, Seattle, USA.
[3] R. Calvo-Palomino, D. Giustiniano, V. Lenders, and A. Fakhreddine, 'Crowdsourcing spectrum data decoding', IEEE International Conference on Computer Communications (INFOCOM), 2017.

mm-wave Communication Systems

The spectrum fragmentation below 6 GHz makes current wireless communication systems not suitable to support user data rates of Gb/s and above in a commercially viable manner. Such bandwidth shortage has motivated the exploration of vacant, unlicensed spectrum at higher frequencies, and in particular in the millimeter-wave (mmWave) frequency bands which the future fifth-generation (5G) wireless standard is expected to exploit. Traditional MIMO processing performed in sub-6 GHz systems is, at present, impractical at mmWaves because the high cost, power consumption, and complexity of mixed-signal hardware at such frequencies hinder the use of a dedicated RF chain for each antenna element. For this reason, most of the literature proposes analog/RF beamforming architectures which rely on networks of RF phase shifters to control the phase of the signal at each antenna element. Compared to fully-digital beamforming architectures which enable to precisely control both phase and amplitude of the transmitted/received signals, analog beamforming is sub-optimal because of the constant amplitude and the low phase resolution constraints affecting the RF phase shifters currently available at mmWaves. Hybrid analog-digital architectures aim at approaching the performance of fully-digital beamforming by dividing the precoding/combining operations between the analog and digital domains and adopting fewer RF chains compared to pure digital architectures. The availability of multiple RF chains allows hybrid analog-digital architectures to shape beam patterns very close to those attained by a fully-digital architecture, i.e., with limited overlap between adjacent beams and excellent flatness over the covered sectors. Despite the substantial research interest recently gained by hybrid beamforming for mmWave systems, most of the literature has until now proposed high complexity solutions relying on unrealistic hardware, e.g., assuming the availability of a considerable number of RF chains and RF phase shifters with large (or even infinite) number of quantization bits. Our research work in this field addresses relevant aspects of the initial access procedure at mmWave frequencies when hybrid analog-digital architectures are exploited at both the base station (BS) and mobile station (MS). As discussed in our publications [1], [2], the constant amplitude and low phase resolution constraints of RF phase shifters make analog beamforming architectures unable to (1) shape flat-top beams with limited overlap as required for a precise angular domain partitioning, (2) scan multiple spatial directions simultaneously, (3) achieve multiplexing gain by transmitting over multiple parallel data streams. On the contrary, splitting the beamforming operations between the analog and the digital domains and exploiting more than one RF chain, hybrid analog-digital architectures allow overcome such limitations.

In [1], [2], we formulate an optimization problem to approximate fully-digital, multi-beam, multi-beamwidth beam patterns by means of a hybrid analog-digital architecture requiring a number of RF chains much lower than the number of antenna elements and only 2-bit RF phase shifters. We propose and implement two algorithms for the synthesis of hybrid codebooks: (i) a variant of the classical OMP algorithm which exploits a dynamic dictionary learning (DDL) mechanism [1] and (ii) a greedy geometric approach based on a low-complexity, dictionary-free algorithm [2]. Both solutions allow to synthesize beam patterns with reduced sidelobe level, excellent flatness over the covered sector, and limited overlap with adjacent beams. In [1], we leverage our codebooks in the framework of a sequential adaptive beam training protocol to estimate the most promising angle-of-departure and angle-of-arrival of the mm-wave channel. In [2], instead, we propose a beam search strategy which effectively accelerates the link establishment by exploiting the ability of mm-wave devices to receive from multiple directions simultaneously. Compared to the literature, which proposes complex algorithms based on the use of RF phase shifters with very high (or even infinite) resolution, our approaches provide significantly better performance with lower complexity hardware.

[1] D. De Donno, J. Palacios, D. Giustiniano, and J. Widmer, 'Hybrid Analog-Digital Beam Training for mmWave Systems with Low-Resolution RF Phase Shifters', In: International Workshop on 5G RAN Design in co-location with IEEE ICC 2016, 23-27 May 2016 , Kuala Lumpur, Malaysia.
[2] J. Palacios, D. De Donno, D. Giustiniano, and J. Widmer, 'Speeding Up mmWave Beam Training through Low-Complexity Hybrid Transceives', In: The 27th Annual IEEE International Symposium on Personal Indoor and Mobile Radio Communications (IEEE PIMRC 2016), 4-7 September 2016, Valencia, Spain.

Wireless Home Networking

Extensive research in the area of wireless home networking has been conducted when I worked at Telefonica Research. The main objective of the activity was the analysis, implementation and validation of a system that can efficiently increase the speed of residential Internet Access, aggregating the speed of multiple ADSL/Cable via wireless connections [1]. A solution to such a problem is not trivial if we require a cost-effective and scalable solution that does not need modifications neither on the backbone network nor at the APs, and it can work even with a standard-compliant off-the-shelf single radio Wi-Fi chipset. The result of our investigation is a 2.5 layer solution, named ClubADSL, running only at the client side (user laptop) and transparently to the TCP/IP network operations. ClubADSL connects in time division to multiple APs (that can also be on different radio frequencies) for a short time, aggregates the bandwidth of several ADSLs and increases the speed respect to the standard scenario of connection to only one ADSL. The design of the system has involved:

  • the distributed and dynamic computation of the optimum percentage of time that each client (with its single radio) dedicates to each AP. The objective of the approach was to guarantee a fair bandwidth among the participating users, for any topology and application, solution based on a modification of the Kelly algorithm. The solution computes (locally and accurately) the metrics needed for the correct operations of the algorithm, so that no message passing and/or protocol over- head is requested at all [1].
  • several engineering tasks needed to be addressed to develop not only a prototype but a stable working solution. This phase required a complete re-thinking and optimization of the features of the Wi-Fi standard to allow a time-division access to each AP from the single-radio Wi-Fi chipset. This required in-depth driver modifications, with i) the introduction and the management of multiple virtual stations at the client, each one connected to one AP ii) an efficient usage of the standard power saving feature, that is re-used to switch among multiple APs and store data while connected to other APs iii) the optimization of the queue management at the driver level to quickly switch among APs (down to the msec resolution), while avoiding packet losses and delay in the radio-channel switching [2]. This last task was necessary to guarantee that Transmission Control Protocol (TCP) traffic is not affected by any queue delay caused by the time-division approach.
  • The design and the validation of a solution that can optimize the TCP performance in a network with ClubADSL/Themis clients. The main problem to solve was to devise an approach to alleviate any delay introduced on single TCP flows by the time division approach (necessary for the aggregation of ADSLs on orthogonal Wi-Fi channels). The algorithm run at the client side, i) split the percentage of connection to each AP in short slots and ii) dynamically estimated the length, the number and the allocation of the slots assigned to each AP in order to minimize the end-to-end delay of each TCP flow [3].

  • The validation has been carried out deploying small controlled test beds and a realistic deployment at Telefonica Lab, with 10 Telefonica ADSLs placed over 3 floor of the building, 10 APs and 10 ClubADSL stations, and testing real applications. To deploy the testbed was a huge effort of work and coordination with the members of the team. A demo of the project is also available on Youtube (prepared with E. Goma and A. Lopez) [4].


    High attention has been achieved in the Spanish news and blogs [5-8], after a short description of the project added into the Telefonica R&D webpage (and so with no official press release yet). Finally the team (myself, E.Goma and A. Lopez) has been awarded by Telefonica R&D in the beginning of 2010 for the best project of 2010 of all the R&D groups (including the centers in Barcelona, Madrid, Valladolid, Granada, Sao Paulo, Huesca, Mexico City) for its innovation and impact versus the coorporation and the users.

    The collaboration with Telefonica Research Barcelona has continued beyond the PostDoc, as demonstrated by some more recent work, SmartAP [9]. In this work, we investigated solutions to move the logic of ClubADSL/Themis from the mobile device to the AP. The main advantage is that APs are own by the network provider, and thus they could be easily upgraded. The work investigated approaches to adapt ClubADSL/Themis to the new context, that was seen necessary for the commercial success of the project (in 2008-2010, we were only at the beginning of the smartphone and tablet proliferation, and it was then seen more obvious to devise a solution running on a laptop or desktop machine). While some loss of performance has been measured, the cost-saving was undoubtedly appealing for the final deployment. The work is currently the subject of commercialization at Telefonica [10].

    [1] D. Giustiniano, E. Goma, A. Lopez, J. Morillo, I. Dangerfield, P. Rodriguez, 'Fair WLAN Backhaul Aggregation', Mobicom 2010, September 2010.
    [2] D. Giustiniano, E. Goma, A. Lopez, P. Rodriguez, 'WiSwitcher: An Efficient Client for Managing Multiple APs', Presto Workshop, Sigcomm 2009, August 2009.
    [3] D. Giustiniano, E. Goma, A. Lopez and G. Athanasiou, 'Optimizing TCP Performance in Multi-AP Resi- dential Broadband Connections via Mini-Slot Access', Hindawi International Journal of Computer Networks and Communications, March 2013. [4], Demo of ClubADSL project on Youtube, in collaboration with E. Goma and A. Lopez.
    [5], Martin Varsasky blog, founder of Jazztel, FON,
    [9] E. Goma, D. Giustiniano, ``SmartAP: Practical WLAN Backhaul Aggregation'', IFIP Wireless Days 2013, Valencia, November 2013.

    Impairments in the 802.11 Transmission Opportunities

    The work of the PhD thesis has focused on the experimental assessment of the channel quality at MAC and PHY layer and the mitigation of the channel impairments in 802.11 networks. Particularly, the first part of the thesis analyzed to what large extent measurement results may depend on proprietary undocumented algorithms implemented in the vendor specific card/driver employed. This work has been carried out within a joint collaboration between the University of Rome and the University of Palermo.
    The work mainly focused on the experimental study of IEEE 802.11b/g outdoor links based on the widely used Atheros/MadWiFi chipset/driver pair. It shows that significant and unexpected performance degradation can occur as a consequence of two Atheros’ proprietary algorithms: Transmit Antenna Diversity and Ambient Noise Immunity. The analysis has required an extensive experimental campaign over the roofs of two independent university campuses (Rome Tor Vergata and Palermo). The different interference pattern of the two campuses helped to understand the problems behind the unexpected performance degradation.

    Furthermore, experiments in controlled environment and with a customized 802.11 MAC FPGA platform were used to validate these findings. These results appear quite critical in sight of the fact that part of the WLAN research community is often unaware of the existence of these proprietary mechanisms and can lead to biased experimental trials and/or to erroneous interpretation of experimental results [1-4].
    The second part of the thesis proposed a powerful MAC/PHY cross layer approach to measuring and understanding the caused of missed 802.11 transmission opportunities in WLAN networks on a per link basis. This work has been carried out within a joint collaboration between the Hamilton Institute (Ireland) and Intel Research Lab (Pittsburgh). The estimator can operate at a single 802.11 station and it is able to i) classify losses caused by noise, collisions and hidden nodes, and ii) distinguish between these losses and the unfairness caused by both exposed nodes and channel capture. The estimator provides quantitative measures of the different causes of lost transmission opportunities, requiring only local measures at the 802.11 transmitter and no modification to the 802.11 protocol or in other stations.
    The approach is suited to implementation on commodity hardware and the prototype implementation has been validated via customized experimental tests. The estimator can be applied not only run-time at a node to optimize and select the PHY rate, operative radio frequency, carrier sense level and transmission power so that the missed transmission opportunities are minimized, but also offline to verify the presence/absence of impairments in the deployment. This is a fundamental issue for network operators while troubleshooting, and for researchers when establishing the realism and status of testbeds [5,6].
    Within the PhD thesis, most of the quantitative analysis required implementations on commodity hardware and deployments of wireless networks of up to 16 nodes. This needed an accurate investigation of two brands of WLAN chipsets, particularly the Atheros and Intel ones, and their driver/firmware, respectively Atheros MADWiFi and Intel IPW2200, and the writing of several scripts for executing the tests and processing the collected data.

    [1] I.Tinnirello, D. Giustiniano, L. Scalia G. Bianchi, 'On the side effects of proprietary solutions for fading and interference mitigation in IEEE 802.11b/g outdoor links', Elsevier Computer Network Journal, February 2009.
    [2] D. Giustiniano, G. Bianchi, L. Scalia, I. Tinnirello, 'An Explanation for Unexpected 802.11 Outdoor Link Level Measurements Results', INFOCOM Mini Symposiums 2008, April 2008.
    [3] L. Scalia, I. Tinnirello, D. Giustiniano, 'Side Effects of Ambient Noise Immunity Techniques on Outdoor IEEE 802.11 Deployments', Globecom 2008, December 2008.
    [4] D. Giustiniano, I. Tinnirello, L. Scalia, A. Levanti, 'Revealing Transmit Diversity Mechanisms and their Side Effects in Commercial IEEE 802.11 Cards', QoSIP 2008, Venice, Italy, February 2008.
    [5] D. Giustiniano, D. Malone, D. Leith and D. Papagiannaki, 'Experimental Assessment of 802.11 MAC Layer Channel Estimators', IEEE Communications Letters, December 2007.
    [6] D. Giustiniano, D. Malone, D. J. Leith, and D. Papagiannaki, 'Measuring transmission opportunities in 802.11 links', accepted to IEEE Transaction of Networking, April 2010.

    MIMO communication

    Digital transmission was the main focus of my research during my master thesis (carried out at the University of Ulm, Germany) and before the PhD studies (in one year of research collaboration at the University of Palermo). I worked in the area of space time codes, proposing and evaluating via Matlab simulations an algebraic code characterized by an efficient decoding scheme, and that is able to exploit almost all the spatial diversity of the system without expensive maximum likelihood equalizations [1] and presenting and studying an equalizer for HSDPA, able to provide spatial and frequency diversity at the receiver over frequency selective fading channels [2].

    [1] D. Giustiniano, P. Lusina, G. Garbo, 'Diagonal space time Hadamard codes with erasure decoding algorithm', WCNC 2005, New Orleans, LA, USA, March 2005.
    [2] D. Giustiniano, S. Mangione, G. Garbo, G. Avellone, 'LMMSE equalizer for HSDPA in full rate STTD schemes', VTC 2005 Spring, Stockholm, Sweden, May June 2005.