Recent effort related to cognitive radio systems has lead to an in-depth analysis of context info... more Recent effort related to cognitive radio systems has lead to an in-depth analysis of context information management and exploitation based on a cognitive control channel for enhancement of management needed for, say, suitable link selection in a heterogeneous radio framework, dynamic radio resource management, and distributed sensing. Concerning the actual implementation of such a CCC, the focus was recently moved toward an in-band solution, where the information is transported building on existing radio access technologies. In this scope, this article illustrates relevant technical scenarios in which CCCs can be exploited and outlines a set of derived system requirements. The article provides an overview of various possible RAT independent and dependent implementation options, such as Diameter, distributed agents, 3GPP radio resource control (RRC) mechanisms, IEEE 802.21, IEEE 802.11, WiMedia UWB, and Bluetooth. The advantages and drawbacks of the various options are discussed.
This paper presents a novel end-to-end Quality of Service (QoS) architecture for wireless network... more This paper presents a novel end-to-end Quality of Service (QoS) architecture for wireless networks. The focus is placed in the coordination of QoS management between Common Radio Resource Management (CRRM), for heterogeneous radio access technologies, and the QoS enabled IP-based network segments. A functional reference QoS framework is introduced and the envisaged QoS management functions are described. The innovations proposed in the presented QoS framework arise mainly from the study of cross effects between the radio and fixed transport resources management. The proposed QoS framework has been designed considering the current 3GPP R6 networks as well as their long-term evolution (LTE) scenario. Some illustrative results for a coordinated admission control algorithm are given as a proof of concept, to show the advantages of CRRM and IP QoS management coordination.
Handling mobility at the transport layer is a promising approach to achieve seamless handover in ... more Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of Concurrent Multipath Transfer (CMT) to distribute data among two end-to-end paths of a mSCTP association during handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of such a sender-introduced reordering and its congestion control implications in a handover scenario. The proposed mSCTP-CMT handover scheme is benchmarked with a pure mSCTP handover scheme. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also the most important constraint of such a design: receiver buffer (rbuf) size. Rbuf size proves to be the major limiting factor shrinking significantly possible mSCTP-CMT application scope, yet not excluding definitively the proposed idea.
Cellular packet systems such as GPRS rely on cell update (CU)/routing area update (RAU) mechanism... more Cellular packet systems such as GPRS rely on cell update (CU)/routing area update (RAU) mechanisms to provide continuous connectivity within the service area. This paper is aimed to evaluate the impact that these mechanisms have on system performance. We show that the CU/RAU procedure could cause the loss of user data packets that, in case of reliable data services, can increase the amount of retransmission signaling to cope with such packet losses. In any case, it should be useful to characterize the amount of user data traffic affected in order to take into account this effect when QoS criteria are pursued
This paper describes the motivation, methodology and implementation approach of the testbed that ... more This paper describes the motivation, methodology and implementation approach of the testbed that has been developed in the framework of the EVEREST project. Such testbed is used for demonstrating some of the main concepts addressed within the project, concerning both: common radio resource management strategies and end-to-end QoS architectures and mechanisms for B3G systems based on the UMTS architecture. The complexity of the interaction between B3G systems and the user applications, while dealing with the QoS concept, pushes to develop this kind of emulation platforms, where algorithms and applications can/must be tested in realistic conditions, not achievable by means of off-line simulations
The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport ... more The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport layer protocol for IP networks that has been introduced as a complement to the well-established TCP and UDP transport protocols. Although initially conceived for the transport of PSTN signaling messages over IP networks, the introduction of key features in SCTP, such as multihoming and multistreaming, has spurred considerable research interest surrounding SCTP and its applicability to different networking scenarios. This article aims to provide a detailed survey of one of these new features-multihoming-which, as it is shown, is the subject of evaluation in more than half of all published SCTP-related articles. To this end, the article first summarizes and organizes SCTP-related research conducted so far by developing a four-dimensional taxonomy reflecting the (1) protocol feature examined, (2) application area, (3) network environment, and (4) study approach. Over 430 SCTP-related publications have been analyzed and classified according to the proposed taxonomy. As a result, a clear perspective on this research area in the decade since the first protocol standardization in 2000 is given, covering both current and future research trends. On continuation, a detailed survey of the SCTP multihoming feature is provided, examining possible applications of multihoming, such as robustness, handover support, and loadsharing.
Interworking mechanisms are of prime importance to achieve ubiquitous access and seamless mobilit... more Interworking mechanisms are of prime importance to achieve ubiquitous access and seamless mobility in heterogeneous wireless networks. In this article we develop a comprehensive framework to categorize interworking solutions by defining a generic set of interworking levels and its related key interworking mechanisms. The proposed framework is used to analyze some of the most relevant interworking solutions being considered in different standardization bodies. More specifically, I-WLAN and GAN approaches for WLAN and cellular integration, solutions for WiMAX and 3GPP LTE/SAE interworking, and the forthcoming IEEE 802.21 standard are discussed from the common point of view provided by the elaborated framework.
Eurasip Journal on Advances in Signal Processing, 2005
Future radio transceivers supporting the software radio concept will provide increased features f... more Future radio transceivers supporting the software radio concept will provide increased features for radio access networks. However, the reconfiguration of radio equipment requires the existence of an architecture, a common framework, which allows the flexible management of software running on radio processors. Such a framework must take into account the heterogeneity of hardware devices and platforms for radio applications. Since the flexibility has a cost in terms of added overhead, a conceptually simple but efficient structure that allows powerful mechanisms to develop and deploy software radio applications is required. This paper describes our approach, the reasons that motivated it, and some implementation issues. The proposed framework is essentially based on four items: an abstraction layer which hides any platform-dependent issue, a simple time-driven software structure, a delimited interface format for software blocks which does not actually constrain communication, and a global time-reference mechanism to guarantee real-time behaviour.
Handling mobility at the transport layer is a promising approach to achieve seamless handover in ... more Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of Concurrent Multipath Transfer (CMT) to distribute data among two end-to-end paths of a mSCTP association during handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of such a sender-introduced reordering and its congestion control implications in a handover scenario. The proposed mSCTP-CMT handover scheme is benchmarked with a pure mSCTP handover scheme. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also the most important constraint of such a design: receiver buffer (rbuf) size. Rbuf size proves to be the major limiting factor shrinking significantly possible mSCTP-CMT application scope, yet not excluding definitively the proposed idea.
... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson ... more ... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson 3 Affiliation: 1 Department of Signal Theory and Communications, Universitat Politècnica de Catalunya (UPC), 08034, Barcelona, Spain 2 King's College London, Centre for ...
... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson ... more ... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson 3 Affiliation: 1 Department of Signal Theory and Communications, Universitat Politècnica de Catalunya (UPC), 08034, Barcelona, Spain 2 King's College London, Centre for ...
Eurasip Journal on Advances in Signal Processing, 2005
Future radio transceivers supporting the software radio concept will provide increased features f... more Future radio transceivers supporting the software radio concept will provide increased features for radio access networks. However, the reconfiguration of radio equipment requires the existence of an architecture, a common framework, which allows the flexible management of software running on radio processors. Such a framework must take into account the heterogeneity of hardware devices and platforms for radio applications. Since the flexibility has a cost in terms of added overhead, a conceptually simple but efficient structure that allows powerful mechanisms to develop and deploy software radio applications is required. This paper describes our approach, the reasons that motivated it, and some implementation issues. The proposed framework is essentially based on four items: an abstraction layer which hides any platform-dependent issue, a simple time-driven software structure, a delimited interface format for software blocks which does not actually constrain communication, and a global time-reference mechanism to guarantee real-time behaviour.
Software Radio applications require a framework to develop and deploy applications, especially th... more Software Radio applications require a framework to develop and deploy applications, especially those related to radio infrastructure. It is interesting that a given application may be executed on any software radio. But, since the hardware platforms used in this context will have multiple architectures and devices, a software layer to make applications independent from hardware is mandatory. Ad-hoc software for a given hardware platform may produce the best software performance. Conversely, when software is not targeted to any concrete platform the lost of performance may be excessive and the overhead introduced by any platform-dependent library could become intolerable. In this paper the resource utilization of a software radio application using a simple hardware abstraction layer is studied and compared to an ad-hoc implementation to make an assessment of the introduced overhead. The particularity of the hardware abstraction layer is that it runs on a platform which only processors are FPGA devices. Abstract P-HAL P-HAL P-HAL P-HAL Platform 2, DSP Application Platform 1, GPP Platform 3, FPGA Abstract P-HAL
The paper analyses the performance of a novel MAC-PHY scheme for wireless local area networks (WL... more The paper analyses the performance of a novel MAC-PHY scheme for wireless local area networks (WLAN) that makes use of distributed queues and cross-layer concepts to improve radio channel utilisation. Analytical values for the maximum throughput performance are derived as a function of different scenario parameters. The obtained results show that the proposed scheme outperforms throughput bounds achieved when using a legacy 802.11 MAC protocol. The usage of distributed queues and cross-layer information eliminates back-off periods and collisions in data packet transmissions, makes performance to be independent of the number of stations transmitting in the system and provides stability for high load conditions. Furthermore, the cross-layer concept allows the MAC layer to improve its decisions by means of physical layer information knowledge.
... Then, chunks from different streams can be concatenated inside one packet. ... As it was ment... more ... Then, chunks from different streams can be concatenated inside one packet. ... As it was mentioned before, earlier works on the mobility management in the heterogeneous networks proposed solutions either in the network layer, as in case of Mobile IP or in the application ...
The division in several layers of the implementation of systems is a solution adopted to avoid co... more The division in several layers of the implementation of systems is a solution adopted to avoid complexity, provide flexibility and improve portability and code reusability through different hardware. Middleware (intermediate layer between two other layers) implementations are based on the use of increasingly high-level languages and application programming interfaces (API). The field programmable gate arrays (FPGA) world can also apply this approach to produce building blocks independent from hardware platforms and devices. This paper presents details of the implementation of a middleware, called platform and hardware abstraction layer (P-HAL) when applied to FPGA devices. It was specially designed for radio applications and allows designing specific functions independently of the hardware context where they are applied, thus providing flexibility to the so-called software radios employing FPGA devices.
This paper describes the implementation and the achieved capabilities of a real-time UMTS demonst... more This paper describes the implementation and the achieved capabilities of a real-time UMTS demonstrator developed within the framework of the IST ARROWS (advanced radio resource management on wireless services) project. Among the main goals of the ARROWS demonstrator are the evaluation of radio resource management (RRM) strategies in a UMTS network and the analysis of the impact that these strategies have on the end-to-end behaviour of multimedia applications with quality of service (QoS) requirements. The demonstrator platform is built over a network of personal computers and copes with the real-time restrictions imposed by the emulation of UMTS transport bearers. After providing a brief description of the developed HW/SW platform, the different approaches taken to emulate the main functions included in the test-bed are described, together with some of the achieved capabilities in terms of implemented RRM algorithms, supported scenarios, lower layer emulation and included services and applications with QoS requirements.
This paper analyses the possibility to exploit opportunistic spectrum access (OSA) for short-rang... more This paper analyses the possibility to exploit opportunistic spectrum access (OSA) for short-range radio communication systems within indoor locations in dense urban areas. In particular, considering the service area of a primary system devoted to providing outdoor coverage in a dense urban scenario, the percentage of indoor locations where the secondary users can reuse the primary frequency band without disturbing the primary system or being disturbed is estimated. The analysis considers heterogeneous path loss models for the primary and secondary systems encompassing the characterization of outdoor, indoor and building penetration losses. Obtained results quantify how aspects like the location of the primary network elements and the considered interference margins to protect primary transmissions impact on the spatial availability of the primary band within the interior of the buildings.
Software Radio applications require a framework to develop and deploy applications, especially th... more Software Radio applications require a framework to develop and deploy applications, especially those related to radio infrastructure. It is interesting that a given application may be executed on any software radio. But, since the hardware platforms used in this context will have multiple architectures and devices, a software layer to make applications independent from hardware is mandatory. Ad-hoc software for a given hardware platform may produce the best software performance. Conversely, when software is not targeted to any concrete platform the lost of performance may be excessive and the overhead introduced by any platform-dependent library could become intolerable. In this paper the resource utilization of a software radio application using a simple hardware abstraction layer is studied and compared to an ad-hoc implementation to make an assessment of the introduced overhead. The particularity of the hardware abstraction layer is that it runs on a platform which only processors are FPGA devices. Abstract P-HAL P-HAL P-HAL P-HAL Platform 2, DSP Application Platform 1, GPP Platform 3, FPGA Abstract P-HAL
Recent effort related to cognitive radio systems has lead to an in-depth analysis of context info... more Recent effort related to cognitive radio systems has lead to an in-depth analysis of context information management and exploitation based on a cognitive control channel for enhancement of management needed for, say, suitable link selection in a heterogeneous radio framework, dynamic radio resource management, and distributed sensing. Concerning the actual implementation of such a CCC, the focus was recently moved toward an in-band solution, where the information is transported building on existing radio access technologies. In this scope, this article illustrates relevant technical scenarios in which CCCs can be exploited and outlines a set of derived system requirements. The article provides an overview of various possible RAT independent and dependent implementation options, such as Diameter, distributed agents, 3GPP radio resource control (RRC) mechanisms, IEEE 802.21, IEEE 802.11, WiMedia UWB, and Bluetooth. The advantages and drawbacks of the various options are discussed.
This paper presents a novel end-to-end Quality of Service (QoS) architecture for wireless network... more This paper presents a novel end-to-end Quality of Service (QoS) architecture for wireless networks. The focus is placed in the coordination of QoS management between Common Radio Resource Management (CRRM), for heterogeneous radio access technologies, and the QoS enabled IP-based network segments. A functional reference QoS framework is introduced and the envisaged QoS management functions are described. The innovations proposed in the presented QoS framework arise mainly from the study of cross effects between the radio and fixed transport resources management. The proposed QoS framework has been designed considering the current 3GPP R6 networks as well as their long-term evolution (LTE) scenario. Some illustrative results for a coordinated admission control algorithm are given as a proof of concept, to show the advantages of CRRM and IP QoS management coordination.
Handling mobility at the transport layer is a promising approach to achieve seamless handover in ... more Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of Concurrent Multipath Transfer (CMT) to distribute data among two end-to-end paths of a mSCTP association during handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of such a sender-introduced reordering and its congestion control implications in a handover scenario. The proposed mSCTP-CMT handover scheme is benchmarked with a pure mSCTP handover scheme. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also the most important constraint of such a design: receiver buffer (rbuf) size. Rbuf size proves to be the major limiting factor shrinking significantly possible mSCTP-CMT application scope, yet not excluding definitively the proposed idea.
Cellular packet systems such as GPRS rely on cell update (CU)/routing area update (RAU) mechanism... more Cellular packet systems such as GPRS rely on cell update (CU)/routing area update (RAU) mechanisms to provide continuous connectivity within the service area. This paper is aimed to evaluate the impact that these mechanisms have on system performance. We show that the CU/RAU procedure could cause the loss of user data packets that, in case of reliable data services, can increase the amount of retransmission signaling to cope with such packet losses. In any case, it should be useful to characterize the amount of user data traffic affected in order to take into account this effect when QoS criteria are pursued
This paper describes the motivation, methodology and implementation approach of the testbed that ... more This paper describes the motivation, methodology and implementation approach of the testbed that has been developed in the framework of the EVEREST project. Such testbed is used for demonstrating some of the main concepts addressed within the project, concerning both: common radio resource management strategies and end-to-end QoS architectures and mechanisms for B3G systems based on the UMTS architecture. The complexity of the interaction between B3G systems and the user applications, while dealing with the QoS concept, pushes to develop this kind of emulation platforms, where algorithms and applications can/must be tested in realistic conditions, not achievable by means of off-line simulations
The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport ... more The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport layer protocol for IP networks that has been introduced as a complement to the well-established TCP and UDP transport protocols. Although initially conceived for the transport of PSTN signaling messages over IP networks, the introduction of key features in SCTP, such as multihoming and multistreaming, has spurred considerable research interest surrounding SCTP and its applicability to different networking scenarios. This article aims to provide a detailed survey of one of these new features-multihoming-which, as it is shown, is the subject of evaluation in more than half of all published SCTP-related articles. To this end, the article first summarizes and organizes SCTP-related research conducted so far by developing a four-dimensional taxonomy reflecting the (1) protocol feature examined, (2) application area, (3) network environment, and (4) study approach. Over 430 SCTP-related publications have been analyzed and classified according to the proposed taxonomy. As a result, a clear perspective on this research area in the decade since the first protocol standardization in 2000 is given, covering both current and future research trends. On continuation, a detailed survey of the SCTP multihoming feature is provided, examining possible applications of multihoming, such as robustness, handover support, and loadsharing.
Interworking mechanisms are of prime importance to achieve ubiquitous access and seamless mobilit... more Interworking mechanisms are of prime importance to achieve ubiquitous access and seamless mobility in heterogeneous wireless networks. In this article we develop a comprehensive framework to categorize interworking solutions by defining a generic set of interworking levels and its related key interworking mechanisms. The proposed framework is used to analyze some of the most relevant interworking solutions being considered in different standardization bodies. More specifically, I-WLAN and GAN approaches for WLAN and cellular integration, solutions for WiMAX and 3GPP LTE/SAE interworking, and the forthcoming IEEE 802.21 standard are discussed from the common point of view provided by the elaborated framework.
Eurasip Journal on Advances in Signal Processing, 2005
Future radio transceivers supporting the software radio concept will provide increased features f... more Future radio transceivers supporting the software radio concept will provide increased features for radio access networks. However, the reconfiguration of radio equipment requires the existence of an architecture, a common framework, which allows the flexible management of software running on radio processors. Such a framework must take into account the heterogeneity of hardware devices and platforms for radio applications. Since the flexibility has a cost in terms of added overhead, a conceptually simple but efficient structure that allows powerful mechanisms to develop and deploy software radio applications is required. This paper describes our approach, the reasons that motivated it, and some implementation issues. The proposed framework is essentially based on four items: an abstraction layer which hides any platform-dependent issue, a simple time-driven software structure, a delimited interface format for software blocks which does not actually constrain communication, and a global time-reference mechanism to guarantee real-time behaviour.
Handling mobility at the transport layer is a promising approach to achieve seamless handover in ... more Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of Concurrent Multipath Transfer (CMT) to distribute data among two end-to-end paths of a mSCTP association during handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of such a sender-introduced reordering and its congestion control implications in a handover scenario. The proposed mSCTP-CMT handover scheme is benchmarked with a pure mSCTP handover scheme. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also the most important constraint of such a design: receiver buffer (rbuf) size. Rbuf size proves to be the major limiting factor shrinking significantly possible mSCTP-CMT application scope, yet not excluding definitively the proposed idea.
... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson ... more ... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson 3 Affiliation: 1 Department of Signal Theory and Communications, Universitat Politècnica de Catalunya (UPC), 08034, Barcelona, Spain 2 King's College London, Centre for ...
... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson ... more ... Ramon Agustí 1 Nima Nafisi 2 , Lin Wang 2 , Mischa Dohler 2 , Hamid Aghvami 2 Peter Karlsson 3 Affiliation: 1 Department of Signal Theory and Communications, Universitat Politècnica de Catalunya (UPC), 08034, Barcelona, Spain 2 King's College London, Centre for ...
Eurasip Journal on Advances in Signal Processing, 2005
Future radio transceivers supporting the software radio concept will provide increased features f... more Future radio transceivers supporting the software radio concept will provide increased features for radio access networks. However, the reconfiguration of radio equipment requires the existence of an architecture, a common framework, which allows the flexible management of software running on radio processors. Such a framework must take into account the heterogeneity of hardware devices and platforms for radio applications. Since the flexibility has a cost in terms of added overhead, a conceptually simple but efficient structure that allows powerful mechanisms to develop and deploy software radio applications is required. This paper describes our approach, the reasons that motivated it, and some implementation issues. The proposed framework is essentially based on four items: an abstraction layer which hides any platform-dependent issue, a simple time-driven software structure, a delimited interface format for software blocks which does not actually constrain communication, and a global time-reference mechanism to guarantee real-time behaviour.
Software Radio applications require a framework to develop and deploy applications, especially th... more Software Radio applications require a framework to develop and deploy applications, especially those related to radio infrastructure. It is interesting that a given application may be executed on any software radio. But, since the hardware platforms used in this context will have multiple architectures and devices, a software layer to make applications independent from hardware is mandatory. Ad-hoc software for a given hardware platform may produce the best software performance. Conversely, when software is not targeted to any concrete platform the lost of performance may be excessive and the overhead introduced by any platform-dependent library could become intolerable. In this paper the resource utilization of a software radio application using a simple hardware abstraction layer is studied and compared to an ad-hoc implementation to make an assessment of the introduced overhead. The particularity of the hardware abstraction layer is that it runs on a platform which only processors are FPGA devices. Abstract P-HAL P-HAL P-HAL P-HAL Platform 2, DSP Application Platform 1, GPP Platform 3, FPGA Abstract P-HAL
The paper analyses the performance of a novel MAC-PHY scheme for wireless local area networks (WL... more The paper analyses the performance of a novel MAC-PHY scheme for wireless local area networks (WLAN) that makes use of distributed queues and cross-layer concepts to improve radio channel utilisation. Analytical values for the maximum throughput performance are derived as a function of different scenario parameters. The obtained results show that the proposed scheme outperforms throughput bounds achieved when using a legacy 802.11 MAC protocol. The usage of distributed queues and cross-layer information eliminates back-off periods and collisions in data packet transmissions, makes performance to be independent of the number of stations transmitting in the system and provides stability for high load conditions. Furthermore, the cross-layer concept allows the MAC layer to improve its decisions by means of physical layer information knowledge.
... Then, chunks from different streams can be concatenated inside one packet. ... As it was ment... more ... Then, chunks from different streams can be concatenated inside one packet. ... As it was mentioned before, earlier works on the mobility management in the heterogeneous networks proposed solutions either in the network layer, as in case of Mobile IP or in the application ...
The division in several layers of the implementation of systems is a solution adopted to avoid co... more The division in several layers of the implementation of systems is a solution adopted to avoid complexity, provide flexibility and improve portability and code reusability through different hardware. Middleware (intermediate layer between two other layers) implementations are based on the use of increasingly high-level languages and application programming interfaces (API). The field programmable gate arrays (FPGA) world can also apply this approach to produce building blocks independent from hardware platforms and devices. This paper presents details of the implementation of a middleware, called platform and hardware abstraction layer (P-HAL) when applied to FPGA devices. It was specially designed for radio applications and allows designing specific functions independently of the hardware context where they are applied, thus providing flexibility to the so-called software radios employing FPGA devices.
This paper describes the implementation and the achieved capabilities of a real-time UMTS demonst... more This paper describes the implementation and the achieved capabilities of a real-time UMTS demonstrator developed within the framework of the IST ARROWS (advanced radio resource management on wireless services) project. Among the main goals of the ARROWS demonstrator are the evaluation of radio resource management (RRM) strategies in a UMTS network and the analysis of the impact that these strategies have on the end-to-end behaviour of multimedia applications with quality of service (QoS) requirements. The demonstrator platform is built over a network of personal computers and copes with the real-time restrictions imposed by the emulation of UMTS transport bearers. After providing a brief description of the developed HW/SW platform, the different approaches taken to emulate the main functions included in the test-bed are described, together with some of the achieved capabilities in terms of implemented RRM algorithms, supported scenarios, lower layer emulation and included services and applications with QoS requirements.
This paper analyses the possibility to exploit opportunistic spectrum access (OSA) for short-rang... more This paper analyses the possibility to exploit opportunistic spectrum access (OSA) for short-range radio communication systems within indoor locations in dense urban areas. In particular, considering the service area of a primary system devoted to providing outdoor coverage in a dense urban scenario, the percentage of indoor locations where the secondary users can reuse the primary frequency band without disturbing the primary system or being disturbed is estimated. The analysis considers heterogeneous path loss models for the primary and secondary systems encompassing the characterization of outdoor, indoor and building penetration losses. Obtained results quantify how aspects like the location of the primary network elements and the considered interference margins to protect primary transmissions impact on the spatial availability of the primary band within the interior of the buildings.
Software Radio applications require a framework to develop and deploy applications, especially th... more Software Radio applications require a framework to develop and deploy applications, especially those related to radio infrastructure. It is interesting that a given application may be executed on any software radio. But, since the hardware platforms used in this context will have multiple architectures and devices, a software layer to make applications independent from hardware is mandatory. Ad-hoc software for a given hardware platform may produce the best software performance. Conversely, when software is not targeted to any concrete platform the lost of performance may be excessive and the overhead introduced by any platform-dependent library could become intolerable. In this paper the resource utilization of a software radio application using a simple hardware abstraction layer is studied and compared to an ad-hoc implementation to make an assessment of the introduced overhead. The particularity of the hardware abstraction layer is that it runs on a platform which only processors are FPGA devices. Abstract P-HAL P-HAL P-HAL P-HAL Platform 2, DSP Application Platform 1, GPP Platform 3, FPGA Abstract P-HAL
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Papers by Ramon Ferrús