Filippo Meucci

Multi-operator resource sharing scenario in the context of IMT-Advanced systems

This paper investigates and proposes a framework for the efficient integration of functionalities for dynamic spectrum use (e.g., spectrum aggregation) and cooperative radio resource management (RRM) in the scope of IMT-Advanced (IMT-A) candidate systems. The envisaged technical solution is based on a joint centralized and distributed approach for both intra-and inter-operator scenarios. Spectrum assignment decisions benefit from a distributed approach that can be realized by the pooling of resources at higher layers together. The paper investigates the possible interworking between the two techniques for the benefits of achieving higher performance and capacity gains. Based on the proposed framework, operators will be able to demand portions of the spectrum for a certain time period and coordinate this action with the actual network loads. The framework is described in terms of functionalities, physical entities, and mutual interactions. The proposed integrated framework can reduce the CAPEX and OPEX during the deployment of IMT-A systems.

An Adaptive Cross-Layer Strategy for QoS-Guaranteed Links in 4G Networks

This paper focuses on the problem of ensuring quality of service (QoS) to 4G network users. An adaptive cross-layer (ACL) strategy, that jointly optimizes the parameters of physical (PHY) and medium access control (MAC) layers using queueing theory, is proposed and applied to mobile user communications in an OFDM-based wireless network. PHY and MAC layers are referring to IEEE 802.16 standard, supporting, respectively, different modulations and the automatic repeat request (ARQ) protocol. PHY and MAC layer parameters are here optimally combined by ACL strategy to meet the QoS requirements. The main contribution of the paper is the evaluation of the impact of mobility on ACL strategy performance, by using an accurate channel model that accounts for shadowing effects. The simulation results show that the ACL strategy outperforms non-adaptive or single-layer strategies, in terms of bandwidth savings. Also, ACL strategy is able to guarantee the requested QoS in the different mobility scenarios with different degrees of performance.

Secure Physical Layer using Dynamic Permutations in Cognitive OFDMA Systems

This paper proposes a novel lightweight mechanism for a secure physical (PHY) layer in cognitive radio network (CRN) using orthogonal frequency division multiplexing (OFDM). Users data symbols are mapped over the physical subcarriers with a permutation formula. The PHY layer is secured with a random and dynamic subcarrier permutation which is based on a single pre-shared information and depends on dynamic spectrum access (DSA). The dynamic subcarrier permutation is varying over time, geographical location and environment status, resulting in a very robust protection that ensures confidentiality. The method is shown to be effective also for existing non-cognitive systems. The proposed mechanism is effective against eavesdropping even if the eavesdropper adopts a long-time patterns analysis, thus protecting cryptography techniques of higher layers. The correlation properties of the permutations are analyzed for several DSA patterns. Simulations are performed according to the parameters of the IEEE 802.16e system model. The securing mechanism proposed provides intrinsic PHY layer security and it can be easily implemented in the current IEEE 802.16 standard applying almost negligible modifications.

Cogito test-bed - wireless research evolved

With each ensuing generation, radio networks are envisioned to support more advanced and differentiated services, enabling new user applications, translating therefore on the need for more bandwidth.

Adaptive selection of MIMO schemes in IEEE 802.16e

In this paper, a selection of different multiantenna (MIMO) systems will be presented. The adopted MIMO configurations with four and two transmit antennas and two receive antennas are selected according to the IEEE 802.16e standard: diversity scheme, hybrid diversity scheme and spatial multiplexing. Computer results present an adaptive selection strategy among the considered MIMO schemes along with their performance.

Cross-Layer Modeling of Dynamic Service Addition Performance in IEEE 802.16 Networks

The IEEE 802.16 standard enables high transmission rates and supports mobility and quality of service (QoS) in cellular networks. To achieve such objectives, multicarrier transmission based on orthogonal frequency-division multiplexing (OFDM) is used and is combined with a connection-oriented approach at the medium access control (MAC) layer. Such connections, or service flows, are dynamically established using a three-way handshake protocol called the Dynamic Service Addition (DSA) protocol. This paper proposes an analytical model to analyze the performance of the DSA protocol in terms of signaling blocking, admission control blocking, and latency in an IEEE 802.16 network. The analytical model based on queueing theory is combined with the quality estimation of the OFDM-based physical layer, using a cross-layer approach. Two mobile radio channels have been considered to validate the analytical model: a block flat-fading channel and a time-varying frequency-selective fading channel in the presence of mobility at different speeds. The analytical model closely matches the results obtained by computer simulations for both types of radio channels. The impact of mobility on the DSA performance is assessed under various settings of DSA parameters and mobile station (MS) speeds. The results highlight the different impacts of DSA parameters on the various performance metrics. Such an evaluation is fundamental for optimally selecting the DSA parameters while taking into account the channel quality. In addition, this paper shows the need for the management of the service flows activated without knowledge of the involved MS, particularly in the case of high error rates.

Identity Theft Detection Based on Neural Network Non-Linearity Identification in OFDM System

Confidentiality of the communication is extremely important in wireless networks due to the broadcast nature of the radio channel. The secrecy of the communication can be achieved via secure PHY layers or by using crypto techniques which need a pre-shared secret between the sender and the legal receiver. A technique has been proposed in literature to avoid preshared secrets based on the noise-pattern of the radio channel. However, when the channel frequency selectivity is low or the eavesdropper is located near to the victim, the key exchange may fail to achieve security. The eavesdropper can gain access to the secure communication and steal the identity of one of the two communicating nodes. In this paper, a technique for identity theft detection is proposed: the receiving node can detect unintended change of senders identity. A Feed-Foward Neural Network is used to identify the non-linearities of the OFDM radio transceiver which are unique and characteristic of the transmitting and receiving devices. The simulation results show that the NN correctly detects the non linearities coefficients for pedestrian and high mobility terminals in the presence of severe fading and noise, providing a strong mean for radio signal identification to detect broken security.

Performance of Dynamic Service Addition in mobile WiMAX networks

In WiMAX mobile networks (IEEE 802.16e–802.16m), connections, also referred to as service flows, can be dynamically activated between the base station and the mobile stations, by using a three-way handshake protocol referred to as Dynamic Service Addition (DSA). However, degraded channel quality and unreliable message retransmissions may lead to a delayed or even unsuccessful activation of a service flow. In this paper, a thorough analysis of DSA protocol performance is carried out under a variety of scenarios. Blocking probability, admission control probability, and latency of DSA protocol are evaluated, by means of simulations, for different conditions of mobility and parameters of PHY and MAC layers. Results show the negative impact of a long channel coherence time caused by low mobility and of the loss of channel reciprocity. Results offer indications on how to compensate such effects.

IEEE 802.16: Enhanced Modes of Operation and Integration with Wired MANs

The evolution of wireless technologies allows users to be always connected to IP-based services through IP-based devices. Moreover the bandwidth available to wireless connected users is becoming comparable to the one provided by copper-based access technologies (e.g., xDSL). Worldwide Interoperability for Microwave Access (WiMax) is one of the wireless technologies that potentially allows users to utilize an access capacity in the order of tens of Mb/s. So far, WiMax (i.e., IEEE 802.16) has been exploited and investigated mainly in the Point-to-MultiPoint (PMP) mode, while IEEE 802.16 enhanced-modes of operation are still at their early research stages. Furthermore, how to integrate Wireless Metropolitan Area Networks (WMANs) based on IEEE 802.16 and wired/optical MAN to guarantee seamless Quality of Service (QoS) across the two transport domains still remains an open issue. This chapter addresses the IEEE 802.16 enhanced-modes of operation and the wireless/wired Metropolitan Area Network (MAN) integration. The focus is on advanced physical layer technologies for wireless transmission such as Multiple Input Multiple Output (MIMO) antennas and Adaptive Modulation and Coding (AMC), the optional IEEE 802.16 Mesh mode of operation, and the integration of wireless and wired/optical MANs. Current status and issues are presented and solutions are proposed.

Cost/revenue performance in an IMT-Advanced scenario with Spectrum Aggregation over non-contiguous frequency bands

This paper determines the cost/revenue performance of a mobile communication system in an IMT-Advanced scenario with integrated Common Radio Resource Management (iCRRM). The iCRRM performs classic CRRM functionalities jointly with Spectrum Aggregation (SA), being able to switch users between non-contiguous frequency bands. The SA scheduling is obtained with an optimized General Multi-Band Scheduling (GMBS) algorithm with the aim of cell throughput maximization. In particular, we investigate the dependence of the throughput on the cell coverage distance for the allocation of users over the 2 and 5 GHz bands for a single operator scenario under a constant average Signal to Interference-plus-Noise Ratio (SINR), for the same type of Radio Access Technology and both frequency bands. The operator has the availability of a non-shared 2 GHz band and has access to part (or all) of a shared frequency band at 5 GHz. An almost constant gain near 30 % was obtained with the proposed optimal solution compared to a system where users are first allocated in one of the two bands and later not able to handover between the bands. It is shown that the profit in percentage terms decreases as the cell radius increases. These results allow for evaluating the impact of the revenue from the channel in the total revenue and in the profit, defined as the difference between revenues and costs, in percentage. Maximum profits of about 1270, 585 and 240 % have been obtained for prices of 0.10, 0.05 and 0.025 €/MByte, respectively, when iCRRM is employed, while profits of 990, 440, and 170 % have been reached with no iCRRM, i.e., simple CRRM. Finally, an energy efficiency strategy is proposed and analyzed, showing that there is significant transmission power saving potential through the opportunistic reallocation scheme.