Riccardo Veronesi

Multi-radio resource management for communication networks beyond 3G

In ‘Beyond 3G’ wireless networking scenarios, characterized by the cooperation of multiple access networks comprising different radio access technologies, Multi-Radio Resource Management (MRRM) mec ...

Power-shaped advanced resource assignment (PSARA) for fixed broadband wireless access systems

We propose and investigate a new resource allocation technique for the downlink of time-division multiple access (TDMA)-based fixed broadband wireless access systems (FBWA) with full frequency reuse. This technique, named power-shaped advanced resource assignment exploits an appropriate set of power profiles which limit (or shape) the power transmitted in each slot of the frame and are suitably reused among the cells, in order to efficiently distribute the intercell and intersector interference inside the frame and to make it partially predictable. In systems where base stations assign radio resources in an uncoordinated fashion, this allows the allocation algorithm to assign time slots to users on the basis of the power required to fulfill a predefined carrier-to-interference ratio, since worst case interference can be suitably estimated; moreover, different degrees of protection against interference are provided across the slots to efficiently accommodate users with different location-dependent channel conditions. Simulation results for a typical cellular FBWA system show that this technique significantly improves the capacity with respect to other techniques recently proposed, e.g., the enhanced staggered resource assignment, even when they use power control. Moreover, an analytical framework useful to understand the concept of power shaping and to discuss some guidelines for the design of power profiles is provided.

Multi-radio resource management for ambient networks

The ambient networks concept targets forthcoming dynamic communication environments, characterized by the presence of a multitude of different wireless devices, radio access technologies, network operators and business actors, which can form instant inter-network agreements with each other. Multi-radio resource management (MRRM) mechanisms, coordinating several radio accesses, fulfill a key role for providing wireless services with improved resource efficiency, coverage and service quality. This paper presents an MRRM concept for Ambient Networks, describes the principal MRRM functions and discusses design criteria

Distributed dynamic resource allocation for multicell SDMA packet access net

This paper addresses the issues of distributed dynamic resource allocation (DRA) in the downlink of a SDMA broadband wireless packet network with multiple access points and adaptive antennas. Packet access and downlink beamforming make the intercell interference hard to predict, and how to handle it in order to efficiently perform slot and power allocation is still an open issue. We propose here new DRA strategies for efficient allocation in a distributed environment, which jointly consider spatial compatibility of users and an intercell interference estimation based on a fraction of the worst case interference measurements. The latter is independent of the actual allocation. We consider a low mobility TDD system with synchronized base stations and we assume perfect channel knowledge. The algorithms which are introduced and compared are the distributed max-min fit (DMMF) and the distributed reverse fit (DRF), which are based on the max-min fit criterion, the DMMF combined with the novel concept of nulls preallocation, where each AP reserves some beamforming nulls for the most interfered users of neighboring cells, and the power shaping technique (PS-DRA for SDMA), which efficiently exploits static power preallocation on time slots. The numerical results show that our techniques are able to significantly reduce the gap between a greedy centralized strategy that fully coordinates all the access ports and the baseline case of random distributed allocation, previously proposed for packet access. However, distributed power control in a packet switched environment with downlink beamforming still remains a hard task: nevertheless, PS-DRA is an efficient solution for joint slot-power allocation

Energy efficient forwarding strategies for wireless sensor networks in presence of fading and power control

In this paper we propose energy efficient forwarding techniques in a fading environment which exploit channel knowledge by means of nodes cooperation. Unlike forwarding strategies based on geographic information only, channel knowledge allows to take advantage from diversity by means of selection of the best node to forward the packet, and also to achieve higher energy savings thanks to power control. We also consider the case of multi-route diversity where redundancy packets are sent over different paths. We propose several adaptive strategies which explicitly address the energy issues and we compare them in terms of total consumed energy, mean packet error probability and delay. As a reference case we consider a forwarding strategy based on pure geographic routing (without channel knowledge). The results show that a considerable improvement can be obtained with respect to the pure geographic forwarding. Our algorithms are also in the direction of a cross layer view, since routing decisions are taken adaptively through physical layer information

Distributed dynamic resource allocation with power shaping for multicell SDMA packet access networks

We consider distributed dynamic slot and power allocation for the downlink of a TD/SDMA broadband wireless packet network with multiple access ports and adaptive antennas. The still open issue for packet multicell SDMA is how to manage the intercell interference, which is very difficult to predict in an uncoordinated environment, due to packet access and downlink beamforming. For this reason, doing distributed allocation efficiently as well as improving the performance by means of power control results in a very hard task. We propose a greedy SDMA algorithm exploiting the power shaping technique, which is based on a static preallocation of the transmit power to each slot of the frame. This permits to obtain a partial predictability of intercell interference, allowing different levels of estimated intercell interference and available power for each slot. We show that our greedy SDMA algorithm with power shaping increases system capacity with respect to the same algorithm without power shaping and reduces the performance gap with respect to a greedy centralized strategy, thus limiting the need of coordination among cells. Both centralized and distributed algorithms are compared, as reference, to the baseline case of random allocation, previously proposed for packet access.

Distributed dynamic resource allocation for multicell SDMA packet access networks

This paper addresses the issues of distributed dynamic resource allocation (DRA) in the downlink of a SDMA broadband wireless packet network with multiple access points and adaptive antennas. Packet access and downlink beamforming make the intercell interference hard to predict, and how to handle it in order to efficiently perform slot and power allocation is still an open issue. We propose here new DRA strategies for efficient allocation in a distributed environment, which jointly consider spatial compatibility of users and an intercell interference estimation based on a fraction of the worst case interference measurements. The latter is independent of the actual allocation. We consider a low mobility TDD system with synchronized base stations and we assume perfect channel knowledge. The algorithms which are introduced and compared are the distributed max-min fit (DMMF) and the distributed reverse fit (DRF), which are based on the max-min fit criterion, the DMMF combined with the novel concept of nulls preallocation, where each AP reserves some beamforming nulls for the most interfered users of neighboring cells, and the power shaping technique (PS-DRA for SDMA), which efficiently exploits static power preallocation on time slots. The numerical results show that our techniques are able to significantly reduce the gap between a greedy centralized strategy that fully coordinates all the access ports and the baseline case of random distributed allocation, previously proposed for packet access. However, distributed power control in a packet switched environment with downlink beamforming still remains a hard task: nevertheless, PS-DRA is an efficient solution for joint slot-power allocation

Resource allocation with power-shaping in TDMA-based mobile radio systems

We apply dynamic slot allocation with power-shaping to TDMA-based (pure or hybrid) mobile radio systems. We show that this technique, originally proposed by the Authors for fixed broadband wireless access systems, where interference is mitigated by the use of highly directional antennas, is able to increase the capacity even in full frequency reuse cellular systems with omnidirectional antennas. By using a set of power profiles, suitably defined here for hexagonal cells with three sectors, that limit (or shape) the power transmitted in each slot of the frame, this allocation technique partially organizes the intercell and intersector interference in the available slots and makes it partially predictable. This allows an efficient use of radio resources, when the base stations assign radio resources in an uncoordinated fashion without the need of centralized strategies requiring heavy signaling load.

DCA with power-shaping (PS-DCA) in TDMA and TD/CDMA cellular systems with centralized and distributed control

In this paper we investigate a new dynamic resource allocation technique for TDMA and TD/CDMA cellular radio systems with full frequency reuse. Unlike traditional allocation strategies, that first allocate the time slots and then perform power control, the proposed technique first assigns in advance (static allocation) a maximum power level to each channel and then dynamically performs channel allocation and fine power control. This is done by exploiting a set of suitably reused power profiles that partially organize the intercell and intersector interference in the available slots and make it partially predictable. We show that this technique, originally proposed by the Authors for fixed broadband wireless access systems, where interference is mitigated by the use of highly directional antennas, is able to increase the capacity of systems with and without centralized or partially centralized resource management control. Moreover, it is also able to fill the efficiency gap between centralized and not centralized strategies. In our investigation a greedy algorithm for resource allocation suitable for both centralized and not centralized management is also proposed.

On the impact of interference on data protocol performance in multicellular wireless packet networks with MIMO links

We study here the performance of the data transmission protocol in a multicell SDMA/TDMA MIMO system running a distributed throughput-driven slot allocation algorithm, as a function of reuse distance, propagation exponent, and network load. Multiple antenna elements are used at both transmitter and receiver side, and perfect channel state information (CSI) is available at the receiver only. A simplified scenario with two access points is considered. We find that the capacity of the network is heavily affected by the presence of interference and we show that the joint use of an estimation of interference covariance matrix and adaptive stream-limited antenna selection prevents capacity degradation when the offered load increases. The results show that the adaptive stream-limited antenna selection introduces a considerable performance improvement over the traditional approach of frequency reuse.