Emerging media overlay networks for wireless applications aim at delivering Variable-Bit-Rate (VBR) encoded media contents to nomadic end-users by exploiting the (fading-impaired and time-varying) access capacity offered by the "last-hop" wireless channel. In this application scenario, a still open question concerns the design of control policies maximizing the average throughput over the wireless last-hop, under constraints on the maximum connection bandwidth allowed at the Application (APP) layer, the queue-capacity available at the data-link (DL) layer, and the average and peak transmit energies sustained by the Physical (PHY) layer. The main feature of the approach we follow relies on the maximization (on a per-slot basis) of the throughput averaged over the fading statistics and conditioned on the queue-state. The resulting optimal controller is rate-based and operates in a cross-layer fashion that involves the APP, DL and PHY layers of the underlying protocol stack. This means that the proposed controller dynamically allocates connection bandwidth at the APP Layer, throughput at the DL layer and transmit energy at the PHY layer by basing on both current queue and channel states. The carried out numerical tests give insights about the connection bandwidth-vs.-queue delay tradeoff attained by optimal controller.

Wireless mesh networks (WMNs) are envisioned for extending the coverage of WLANs by interconnecting the underlying access points (APs) via high-capacity wireless backbones. Since the ultimate goal of a WMN is to provide Internet connectivity to residential clients, WMN traffic is mainly routed over the backbone either toward the Internet gateways (IGWs) or from the IGWs to the APs. In principle, the transport capacity of a WMN can further be upgraded by equipping the underlying backbone routers with multiantenna (MA) radio modules. Motivated by the above consideration, in this paper, we focus on the optimized node selection (e.g., path-routing) over MA mesh backbones when the target is to maximize the end-to-end routed information rate subject to a constraint on the total power available for the relays. Under the assumption of Rayleigh-distributed block fading, we assume that point-to-point capacity-achieving space-time codes (STCs) are used for the single-hop link. At first, we tackle the routing problem when neither interference mitigation (IM) nor transmit beamforming (TB) is performed at the relay nodes, and then, we extend the analysis to the cases when IM and/or TB are also carried out. The effects of channel-state-information (CSI) possibly available at the relay nodes are also investigated. So doing, we are able to gain insight about the combined effect of spatial multiplexing and IM capabilities of the overall MA architecture on both end-to-end capacity and access medium performance of the considered WMN.

Main goal of this work is to give insight on the possible performance improvement arising in the wireless local and/or ad-hoc access from the synergic cooperation of two emerging paradigms, e.g., multi-antenna and cognitive radios. As application scenario, we consider both the faded uplink of a WLAN working in infrastructure-mode, where noncooperative Multi-Antenna cognitive radios attempt to join to a (possibly multi-antenna) access point (AP) and an ad-hoc scenario where each node can communicate with each free node. The target can be twofold and two different approaches are considered. The first is the competitive maximization of own access throughput in the presence of multiple-access Interference (MAI) induced by the other accessing terminals, the second one is the BER minimization. Being the radios cognitive, they are capable to autonomously learn the ambient-context and, then, self-configure their access strategy via suitable power-allocation that is time-frequency-code-space signal-shaping. Furthermore, a generalized approach is developed that allows the node to access with a (possibly hybrid) scheme to the medium by combining different x-DMA strategies under QoS-guaranteed access policy.

In this contribution, the problem of the synchronization for ultra wideband impulse radio (UWB-IR) systems, through the adoption of a multi-antenna platform working on multipath faded channels, is afforded. In this regard, we propose a novel UWB-IR synchronizer devoted to jointly estimate (according to the maximum likelihood (ML) criterium) the arrival times and their (Poisson distributed) number, composing a typical UWB-IR multipath faded channel. Such estimate is effected without any knowledge on the value of the channel paths (noncoherent ML synchronizer). The architecture of such synchronizer is based on a single-input multiple-output (SIMO) platform, instead of a multiple-input multiple-output MIMO one, according to a previous result in the literature. Related performance of this joint ML estimation is expressed in closed via the Cramer-Rao bound (CRB) and is tested by simulations, under acquisition and tracking conditions.

In this contribution we develop a multiple-input multiple-output (MIMO) impulse radio ultra wide band (IR-UWB) transceiver for orthogonal signalling over (baseband) muhipath faded MIMO channels. The proposed maximum-likelihood receiver results to be "partially coherent", since it is optimized to work without any information about channel coefficients, and it is based on the knowledge of the arrivals' times of the transmitted signals' replicas. The behavior of the proposed transceiver has been evaluated via three suitable versions of the Union-Chernoff Bound related to several indoor and outdoor propagation scenarios, and these limits are considered to introduce a novel family of unitary orthogonal space-time block codes (e.g., the space-time OPPM (STOPPM) codes), that are able to attain maximum diversity and coding gains.

The emerging proxy-based wireless content delivery networks (CDNs) should to be designed to download huge-size files over fading-affected channels. However, from a radio resource management point of view, several basic problems still need to be solved for such wireless delivery systems to operate efficiently. Specifically, due to the fading nature of the downlink channel, a still open basic problem is how to design optimal energy-allocation (for example, scheduling) policies that minimize the requested download time when constraints on the total available energy and peak energy are simultaneously active. In this contribution, this problem is solved for application scenarios where the downlink channel is slotted and continuous-state, the carried out traffic is elastic, and the resulting conveyed throughput is measured by any desired increasing concave rate function. Specifically, the optimal energy-allocation policy minimizing the download time is computed in closed form, and its performance is compared against that of a basic on-off heuristic energy scheduler on some Rayleigh-faded multi-antenna delivery systems of practical interest. The carried out performance comparisons point out that the presented optimal policy typically may outperform the heuristic one up to two orders of magnitude, especially when the delivery system is strongly energy limited.

In this contribution Time-Hopping (TH) codes are developed based upon the theory of congruences. These codes can be used for coherent multiuser asynchronous spread spectrum communication systems. They represent a compromise between Costas codes, which have nearly ideal auto-ambiguity properties, and congruential codes presenting nearly ideal cross-properties. The presented code applied not in ranging applications but communications system presents good performance in terms of Bit Error Rate (BER) for UltraWide Band Impulse Radio (UWB-IR) systems. Examples of typical auto- and cross-ambiguity functions are given to illustrate the performance of the presented codes jointly with BER evaluation.

This contribution analyzes the problem of multi-user interference suppression via estimation and subtraction. In particular it is shown that spatial diversity helps the suppression capability of a Base Station and this has an important impact on performance. By fact, we show that the best solution does not consist in transmit at maximum energy level but, in order to allow interference estimation and cancellation, a trade off has to be solved. So, interference suppression can give arise to performance improvements both for achieved throughput (that can be "enhanced") and for error probability (that can be reduced).

In this contribution, the problem of download time minimization, by considering channel state, is solved for application scenario where the downlink channel is slotted and continuous-state, while the resulting conveyed throughput is measured by any desired increasing concave rate-function. Specifically, the optimal energy-allocation policy minimizing the download-time is found and its performance is compared against that of a basic on-off type heuristic scheduler for some Rayleigh-faded multi-antenna downloading systems of practical interest

The paper focuses on competitively optimal power-control and signal-shaping for "ad-hoc" networks composed of multiple-antenna noncooperative transmit/receive terminals affected by spatially colored multi-access interference (MAI). The target is the competitive maximization of the information throughput of each link active over the network. For this purpose, the MAI-impaired network is modeled as a noncooperative strategic game, and sufficient conditions for the existence and uniqueness of the Nash equilibrium are provided. Specifically, the main contribution of the paper may be so summarized. First, we develop fully. distributed and scalable power-control and signal-shaping algorithms allowing the implementation of asynchronous space-division multiple access strategies (SDMACSs) able to guarantee the competitive maximization of the users' throughput under both best effort and contracted QoS access policies. Second, we give evidence that the developed SDMACSs outperform (in terms of aggregate throughput) the conventional centralized ones (such as TDMA/FDMA/CDMA), especially in operating scenarios affected by strong MAI.

The paper focuses on competitively optimal power-control and signal-shaping for "ad-hoc" networks composed of multiple-antenna noncooperative transmit/receive terminals affected by spatially colored multi-access interference (MAI). The target is the competitive maximization of the information throughput (measured in bits/slot) sustained by each link active over the network. For this purpose, the MAI-impaired network is modeled as a noncooperative strategic game, and sufficient conditions for the existence and uniqueness of the Nash equilibrium are provided. We develop fully distributed and scalable power-control and signal-shaping algorithms allowing the implementation of asynchronous space-division multiple access strategies (SDMACSs) able to guarantee the competitive maximization of the users' throughput under both best effort and contracted QoS access policies. We give evidence that the developed SDMACSs outperform (in terms of aggregate throughput) the conventional centralized ones (such as TDMA/FDMA/CDMA), especially in operating scenarios affected by strong MAI. We study the convergence property of the presented SDMACSs and show that, when the throughput set requested by the users is not achievable by the network, then the developed SDMACSs are able to move the working point of the system to the nearest one sustainable by the network. By exploiting the distributed feature of the presented SDMACSs, we propose two connection admission procedures (CAPs) able to optimize (in a competitive sense) the tradeoff between aggregate networking throughput and connection requirements advanced by the users.

This contribution considers the power control and signal-shaping problem for ad-hoc networks composed by multi-antenna non-cooperative terminals affected by spatially colored multiple-access interference (MAI). The multi-antenna interference channel is modeled as a non cooperative and strategic game. Furthermore iterative power control and signal shaping algorithms are presented to efficiently achieve the Nash equilibrium under best effort and "contracted QoS" policies.

This paper focuses on the competitively optimal power-control and signal-shaping for "ad-hoc" networks composed by multiple-antenna noncooperative transmit/receive terminals affected by spatially colored multiple-access interference (MAI). For this purpose, the MAI-impaired network is modeled as a noncooperative strategic game, and sufficient conditions for the existence and uniqueness of the Nash equilibrium are provided. Connection admission procedures are presented with related performance.

In the last years a lot of attention has been paid to multiantenna systems with space-time coding (STC) and to ultra wide band (UWB). In this paper we aim to propose a transceiver scheme in order to evaluate if these two technologies can be considered adequate candidates for next generation WLANs. Merging ultra wide band signals with multiple antenna schemes allows us to achieve very high bit rate and error probability matched to QoS requested by 4GWLANs at low SNR. This contribution presents a simple way to combine ultra wide band and multiple antenna schemes so to improve performance and coverage with respect to the conventional UWB approach in order to promote this approach application scenarios by considering a base band channel model and selective are considered.