DSpace Collection:

A solution framework to provide management services for wireless communications in the digital home

Mon, 13 May 2013 14:15:57 GMT

Title: A solution framework to provide management services for wireless communications in the digital home Authors: Ferrús Ferré, Ramón Antonio; Sallent Roig, José Oriol; Pérez Romero, Jordi; Agustí Comes, Ramon Abstract: The future digital home (DH) is envisioned as a place where a plethora of diverse personal and machine-to-machine communications will coexist to support different applications in areas such as information and entertainment, home automation, home health care and home security and management. Wireless technologies are usually the preferred solution to cope with DH communications for their ease of installation and use. However, expected capacity demand and the lack of coordination between an increasing number of diverse wireless devices in use within the DH is seriously challenging the performance and usability of wireless technologies. This article outlines a novel technical solution intended to enhance capacity and quality of DH wireless communications. The proposed solution establishes a radio-independent coexistence framework where key operational radio settings of DH devices are coordinately determined, and new spectrum sources other than traditional ISM bands can be exploited for DH communications. The addressed solution enables a business player to offer management services for DH wireless communications so that ordinary users can be relieved of complex management tasks likely to arise within the DH. The article discusses how potential management service providers could benefit from the proposed solution. Besides, the functional architecture of the proposed solution together with the set of procedures necessary for the management of the DH wireless communications are outlined. A realistic indoor scenario is presented as an illustrative use case to show how proper decision making logic in managing the DH could improve the efficiency by selecting the most suitable spectrum for in-house wireless communications. Finally, the main implementation issues are identified and discussed in order to outline a feasible roadmap.

Processing-to-amplifier power ratio for energy efficient communications

Thu, 20 Dec 2012 14:13:30 GMT

Title: Processing-to-amplifier power ratio for energy efficient communications Authors: Gómez Miguelez, Ismael; Marojevic, Vuk; Gelonch Bosch, Antonio José Abstract: The energy consumption of modern communications systems is dominated by the signal processing and shaping circuitry. Assuming a rate-independent processing power consumption, the energy per bit spent for signal processing can be effectively reduced by increasing the transmission power. The optimal relation between processing and transmission power for energy efficient communications is derived. This relation is called processing-to-amplifier power ratio (PrAPR).

Cognitive resource management: for all wireless access layers

Wed, 19 Dec 2012 19:31:54 GMT

Title: Cognitive resource management: for all wireless access layers Authors: Marojevic, Vuk; Gómez Miguelez, Ismael; Gelonch Bosch, Antonio José

Channel assignment algorithms for OSA-Enabled WLANs exploiting prioritization and spectrum heterogeneity

Wed, 17 Oct 2012 10:45:18 GMT

Title: Channel assignment algorithms for OSA-Enabled WLANs exploiting prioritization and spectrum heterogeneity Authors: Novillo Parales, Francisco Vicente; Ferrús Ferré, Ramón Antonio Abstract: Allowing WLANs to exploit opportunistic spectrum access (OSA) is a promising approach to alleviate spectrum congestion problems in overcrowded unlicensed ISM bands, especially in highly dense WLAN deployments. In this context, novel channel assignment mechanisms jointly considering available channels in both unlicensed ISM and OSA-enabled licensed bands are needed. Unlike classical schemes proposed for legacy WLANs, channel assignment mechanisms for OSA-enabled WLAN should face two distinguishing issues: channel prioritization and spectrum heterogeneity. The first refers to the fact that additional prioritization criteria other than interference conditions should be considered when choosing between ISM or licensed band channels. The second refers to the fact that channel availability might not be the same for all WLAN Access Points because of primary users' activity in the OSA-enabled bands. This paper firstly formulates the channel assignment problem for OSA-enabled WLANs as a Binary Linear Programming (BLP) problem. The resulting BLP problem is optimally solved by means of branch and bound algorithms and used as a benchmark to develop more computationally efficient heuristics. Upon such a basis, a novel channel assignment algorithm based on weighted graph coloring heuristics and able to exploit both channel prioritization and spectrum heterogeneity is proposed. The algorithm is evaluated under different conditions of AP density and primary band availability.

Reduced cluster search ML decoding for QO-STBC M-QAM MIMO systems

Wed, 12 Sep 2012 10:52:45 GMT

Title: Reduced cluster search ML decoding for QO-STBC M-QAM MIMO systems Authors: Abrao, Taufik; Suzuki, Isaque; Angelico, Bruno A.; Ciriaco, Fernando; Jeszensky, Paul Jean E.; Casadevall Palacio, Fernando José Abstract: Since the maximum likelihood (ML) decoding for quasi-orthogonal space-time block codes (QO-STBC) with inner and outer codes multipleinputmultiple- output (MIMO) antenna systems results too complex when the modulation order index and the number of receive antennas increases, an efficient reduced complexity ML-based decoding scheme is proposed in this contribution, aiming to reach promising QO-STBC coded MIMO system throughput × complexity trade-off. Under high-order modulation indexes (16 ≤ M)-QAM, 4 × nR antennas, with nR ≥ 1, this work proposes a reduced cluster search ML decoder (RCS-ML) and compares the performancecomplexity with the ML decoding approach. Numerical results have indicated no degradation in performance and an increasing reduction in the complexity of RCS-ML decoder when the modulation order increases, been 12.5% of ML decoding complexity for 16-QAM, and <1% for 256-QAM.

Resource management for software-defined radio clouds

Mon, 10 Sep 2012 10:52:16 GMT

Title: Resource management for software-defined radio clouds Authors: Gómez Miguelez, Ismael; Marojevic, Vuk; Gelonch Bosch, Antonio José Abstract: Software-defined radio (SDR) clouds combine SDR concepts with cloud computing technology for designing and managing future base stations. They provide a scalable solution for the evolution of wireless communications. The authors focus on the resource management implications and propose a hierarchical approach for dynamically managing the real-time computing constraints of wireless communications systems that run on the SDR cloud.

Dynamic cooperator selection in cognitive radio networks

Thu, 12 Jul 2012 09:28:27 GMT

Title: Dynamic cooperator selection in cognitive radio networks Authors: Vucevic, Nemanja; Akyildiz, Ian F.; Pérez Romero, Jordi Abstract: The primary objective of cooperation in cognitive radio (CR) networks is to increase the spectrum access efficiency and improve the network performance. However, Byzantine adversaries or unintentional erroneous conduct in cooperation can lead to destructive behavior of CR users that can decrease their own and others’ performances. This work presents a dynamic solution for cooperation reliability in conditions with constraints typical for a CR network. Specifically, in CR networks, the information on the success of cooperation can be limited only to cases with interference; when malicious, cooperators can be completely non-correlated and can alter behavior; and the set of available cooperators can dynamically change in time. In order to face these challenges, each CR user autonomously decides with whom to cooperate by learning cooperators behavior with a reinforcement learning (RL) algorithm. This RL algorithm determines the suitability of the available cooperators, and selects the most appropriate ones to cooperate with the objective to increase the efficiency of spectrum access in CR networks. The simulation results demonstrate the learning capabilities of the proposed solution and especially its reliable behavior under highly unreliable conditions.

SDR receiver computational model for application in power control

Thu, 10 May 2012 17:27:50 GMT

Title: SDR receiver computational model for application in power control Authors: Gómez Miguelez, Ismael; Marojevic, Vuk; Gelonch Bosch, Antonio José Abstract: Software-defined radio (SDR) permits dynamic switches of the employed radio access technology (RAT), over-the-air (OTA) software updates, software and hardware reuse. This extended flexibility comes at the price of a higher computing complexity and, in particular, the energy consumption at the receiver. The analysis of the computational profile of signal processing algorithms is of great importance in SDR for understanding the implication on the energy consumption. Several signal processing algorithms show a different profile as a function of the signal quality perceived at the receiver antenna. Therefore, power control policies have an implication on the computational performance of SDR receivers. Understanding the behaviour of these algorithms allows trading transmitted power against receiver energy consumption. This paper presents a model for characterizing the computational profile of Turbo and LDPC decoders and demonstrates is applicability in existing power control strategies.

Towards a more efficient spectrum usage: spectrum sensing and cognitive radio techniques

Tue, 17 Jan 2012 18:26:34 GMT

Title: Towards a more efficient spectrum usage: spectrum sensing and cognitive radio techniques Authors: Pérez Romero, Jordi; Noguet, Dominique; López Benítez, Miguel; Casadevall Palacio, Fernando José Abstract: The traditional approach of dealing with spectrum management in wireless communications has been through the definition on a license user granted exclusive exploitation rights for a specific frequency.

Control of the trade-off between resource efficiency and user fairness in wireless networks using utility-based adaptive resource allocation

Thu, 29 Dec 2011 15:40:49 GMT

Title: Control of the trade-off between resource efficiency and user fairness in wireless networks using utility-based adaptive resource allocation Authors: Rodrigues, Emanuel B.; Casadevall Palacio, Fernando José Abstract: This work addresses the fundamental problem of the trade-off between resource efficiency and user fairness in wireless networks that use opportunistic radio resource allocation. The concept of managing the trade-off by controlling the system fairness index is applied. In order to do that, two adaptive utility-based resource allocation frameworks consisting of subcarrier assignment and power allocation algorithms are proposed. These frameworks are named utility-based alpha-rule and beta-rule, and are suitable for non-real-time and real-time services, respectively. Not only can both frameworks be designed to work as wellknown classic policies found in the literature, but also as adaptive policies, which are able to meet a desired system fairness target. System level simulations show that the proposed frameworks are powerful tools to the network operator, since they can decide in which trade-off point of the efficiency-fairness plane they want to operate the system.

Common radio resource management algorithms for multimedia heterogeneous wireless networks

Thu, 27 Oct 2011 17:35:44 GMT

Title: Common radio resource management algorithms for multimedia heterogeneous wireless networks Authors: López Benítez, Miguel; Gozalvez, Javier Abstract: Heterogeneous wireless systems are envisaged as the integration and joint cooperative management of diverse radio access networks and technologies through which network providers can satisfy the wide variety of user/service demands in a more efficient manner by exploiting their varying characteristics and properties. To achieve this objective, a key tool is common radio resource management technique designed to jointly manage the radio resources from different radio access technologies. In this context, this work proposes and optimizes new common radio resource management techniques designed to efficiently distribute traffic among the available radio access technologies while providing adequate quality of service levels under heterogeneous traffic scenarios. The obtained results demonstrate the ability of the proposed solutions to provide high user/service satisfaction levels while adequately exploiting the overall system resources.

Empirical Time-Dimension Model of Spectrum Use Based on a Discrete-Time Markov Chain With Deterministic and Stochastic Duty Cycle Models

Thu, 27 Oct 2011 17:14:57 GMT

Title: Empirical Time-Dimension Model of Spectrum Use Based on a Discrete-Time Markov Chain With Deterministic and Stochastic Duty Cycle Models Authors: López Benítez, Miguel; Casadevall Palacio, Fernando José Abstract: The spectrum occupancy models widely used to date in dynamic spectrum access/cognitive radio (DSA/CR) research frequently rely on assumptions and oversimplifications that have not been validated with empirical measurement data. In this context, this paper presents an empirical time-dimension model of spectrum use that is appropriate for DSA/CR studies. Concretely, a two-state discrete-time Markov chain with novel deterministic and stochastic duty cycle models is proposed as an adequate mean to accurately describe spectrum occupancy in the time domain. The validity and accuracy of the proposed modeling approach is evaluated and corroborated with extensive empirical data from a multiband spectrum measurement campaign. The obtained results demonstrate that the proposed approach is able to accurately capture and reproduce the relevant statistical properties of spectrum use observed in real-world channels of various radio technologies. The importance of accurately modeling spectrum use in the design and evaluation of novel DSA/CR techniques is highlighted with a practical case study.

ALOE: an open-source SDR execution environment with cognitive computing resource management capabilities

Tue, 18 Oct 2011 12:17:43 GMT

Title: ALOE: an open-source SDR execution environment with cognitive computing resource management capabilities Authors: Gómez Miguelez, Ismael; Marojevic, Vuk; Gelonch Bosch, Antonio José Abstract: Future radio transceivers will offer more functionalities and system features for potentiating flexible and reconfigurable radio access networks. Since flexibility in this case comes at a price of computing resource overhead, we propose a conceptually simple though powerful framework for digital signal processing applications. The abstraction layer and operating environment (ALOE) is an open source execution environment for software-defined radios. It is essentially based on a hardware abstraction layer, a lightweight and time-driven software architecture, and a simple interface format. ALOE accounts for heterogeneous multiprocessor platforms. Its cognitive computing resource management capabilities enable flexible and dynamic management of SDR platforms and applications for distributed realtime execution of applications and dynamic reconfiguration of platforms.

A roadmap from UMTS optimization to LTE self-optimization

Thu, 29 Sep 2011 18:41:57 GMT

Title: A roadmap from UMTS optimization to LTE self-optimization Authors: Sallent Roig, José Oriol; Pérez Romero, Jordi; Sánchez González, Juan; Agustí Comes, Ramon; Díaz Guerra, Miguel Angel; Henche, David; Paul, Daniel Abstract: Self-Organizing Networks (SON) are currently being introduced by the 3rd Generation Partnership Project (3GPP) as part of the Long Term Evolution (LTE) system as a key driver for improving the operation of wireless networks. Given that many challenges have been identified when moving from the SON concept to practical implementation, this article claims the suitability to gain insight into the problem by taking advantage of optimization mechanisms in live Universal Mobile Telecommunications System (UMTS) networks. From that perspective, this article outlines a roadmap from actual manual optimization toward the inclusion of SON concepts in future networks. In particular, an optimization framework is developed considering different stages that include the collection of inputs from different sources (network counters, measurement reports, drive tests), the tuning parameters to achieve optimization, and the optimization procedure itself. Even though the proposed framework is presented and evaluated for convenience in a UMTS context, it is rather generic and technology-agnostic and, therefore, it can be formulated as an initial reference for LTE self-optimization use cases. The proposed framework is applied to a practical coverage optimization use case supported by data extracted from a real UMTS network in a European city, illustrating the capability to automatically identify a cell with sub-optimal coverage and to provide a solution to the problem. The extension of the case study to LTE is also analyzed. Finally, as a result of the lessons learned, the article makes a projection to the LTE context by identifying the key points to be solved for the materialization of a self-optimization procedure.

Performance evaluation of radio access selection strategies in constrained multi-access/multi-service wireless networks

Wed, 14 Sep 2011 11:46:06 GMT

Title: Performance evaluation of radio access selection strategies in constrained multi-access/multi-service wireless networks Authors: Gelabert Doran, Xavier Bernardi; Sallent Roig, José Oriol; Pérez Romero, Jordi; Agustí Comes, Ramon Abstract: The benefits of jointly managing the combined set of radio resources offered by heterogeneous networks consisting of several radio access technologies (RATs) have been profusely studied and assessed in recent years. This notion has been coined as common radio resource management (CRRM). Nevertheless, most of the existing work assumes scenarios where all RATs are accessible (provided the RAT is not at full capacity) to those users demanding a particular service. If this is so, the obtained benefits become rather optimistic given that we neglect the fact that the deployed RATs may have different coverage overlapping conditions among them and that users may not have terminals that support all RATs (i.e. multimode terminals). In this paper we extend a previously developed Markov framework in order to capture the effect of having different coverage overlapping conditions along with the capability of certain terminals to support all or a subset of available RATs. Probabilistic models are obtained for the characterization of a wide range of coverage and terminal heterogeneity scenarios. Extensive performance evaluation is carried out in order to identify those parameters influencing the suitability of a particular initial RAT selection strategy, that is, to choose the most suitable RAT at call/session initiation among those accessible. Results indicate that suitable RAT selection is tightly dependent on: the ratio between the different offered traffic loads (or service-mix), the contention (if any) for radio resources by different services in particular RATs, and the identification of access-constrained RATs due to lack of coverage and/or terminal capability. In this paper we provide specific guidelines and rules concerning resource allocation for the utmost utilization of radio resources, in terms of Erlang capacity, and enhanced perceived quality by the users, in terms of achievable throughput.