Lorenzo Galati Giordano

Massive MIMO Unlicensed: A New Approach to Dynamic Spectrum Access

Nowadays, the demand for wireless mobile services is copious and will continue increasing in the near future. Mobile cellular operators are therefore looking at the unlicensed spectrum as an economical supplement to augment the capacity of their soon-to-be overloaded networks. The same unlicensed bands are luring Internet service providers, venue owners, and authorities into autonomously setting up and managing their high-performance private networks. In light of this exciting future, enhancing the coexistence between multiple unlicensed technologies becomes a pivotal issue. In this article, we present the fundamentals and the main challenges behind massive MIMO unlicensed, a new approach for technology coexistence in the unlicensed bands, that is envisioned to boost spectrum reuse for a plethora of use cases.

Resource Scheduling for Mixed Traffic Types with Scalable TTI in Dynamic TDD Systems

This paper analyses the performance benefits of a user-centric scheduling approach, exploiting the flexibility of both dynamic time division duplex (TDD) and a variable transmission time interval (TTI), where the downlink to uplink ratio and TTI duration can be adapted to the traffic load. The formulation of the joint optimisation problem takes into consideration the individual requirements of each single user in terms of sustainable latency and desired throughput, thus implementing a real user-centric scheduling approach. Moreover, the developed solution is evaluated in a scenario with mixed traffic types, mobile broadband (MBB) and mission critical communications (MCC), showing remarkable performance enhancement of the proposed scheme over baseline dynamic TDD schemes with a fixed TTI in terms of both achievable throughput of the MBB users and guaranteed latency for the MCC users.

Small LTE Base Stations Deployment in Vehicle-to-Road- Infrastructure Communications

Rational and efficient handling of vehicular traffic and people movement is already nowadays a huge challenge that increasingly needs to be supported by dedicated technologies. Scenarios like Smart Cities and Smart Roads are therefore among the most promising areas in which major technological breakthroughs are expected in the next two decades. The delivery of end user services in these scenarios surely call for an ensemble of different technologies to be displaced together; for successful deployment of such technologies and for positive and effective impact on daily life, one of the most important factors is certainly the efficient, fast and flexible distribution of information. The possibility to transmit a large quantity of data is of course necessary in these kind of scenarios, but is not to be separated from the possibility to have higher spectral efficiency and higher flexibility of spectrum configuration. Another key factor is the cost of the network infrastructure, which can easily become a showstopper even for the most promising service or technology. In fact in recent years, vehicle-to-vehicle (V2V) and vehicle-to-road-infrastructure (V2I) communications have attracted great interest for the potentially extended usage in traffic applications and emergency situations. While in the former case the communication system is realized by means of an ad-hoc network (denoted as VANET), in the latter vehicles, i.e. mobile terminals, exchange data packets each other and with the Internet by means of a base station (BS) situated close to the road side. So, in V2I the BS controls the network and manages the connections with and between the vehicles, simplifying the vehicle transceiver and improving performance, including the reliability of emergency communications.

Discrete-rate allocation schemes in multi-cell scenarios with power adaptation

Interference mitigation and adaptive multi-user resource allocation are among the most promising technological breakthroughs that should improve capacity of future broadband wireless communications. In a multi-cell scenario, where co-channel interference is the performance limiting factor, discrete-rate resource allocation algorithms, selecting those channels with best Signal-to-Interference and Noise-Ratio (SINR), can reduce the transmission power in each base station, acting indirectly on the co-channel interference levels. In this paper we investigate multi-cell systems in which power adaptation acts as a positive factor for the interference reduction. We are interested here in the convergence properties of the dynamic model of the system and in the role of the number and position of SINR thresholds of the discrete-rate profiles. We find that, in multi-cell scenarios, the application of power reduction makes the spectral efficiency of the system relatively insensitive to the number of discrete-rate profiles, once fixed the minimum and maximum SINR thresholds.

Two-dimensional radio resource allocation algorithms with contiguity constraint for IEEE 802.16e systems

Adaptive multi-user resource allocation is one of the key features towards high speed wireless network based on Orthogonal Frequency Division Multiplexing Access (OFDMA). According to IEEE 802.16e (WiMAX) standard radio, resource allocation problem has to be performed on a two-dimensional space (frequency and time) with the constraint that each transmitted burst should occupy a contiguous portion of the frame. The paper introduces two different strategies and it investigates the advantages, drawbacks and challenges of the radio resource allocation procedure in two dimensions.