The Experts below are selected from a list of 20103 Experts worldwide ranked by ideXlab platform

Gunther Auer - One of the best experts on this subject based on the ideXlab platform.

  • sum rate increase via variable Interference Protection
    IEEE Transactions on Mobile Computing, 2012
    Co-Authors: Sinan Sinanovic, Harald Haas, Harald Burchardt, Gunther Auer
    Abstract:

    The sum rate of spectrum-sharing in decentralized and self-organizing wireless networks is investigated in this paper. Such networks pose the following two fundamental challenges: 1) cochannel Interference and 2) the hidden node problem. For a slotted shared wireless medium, where resources are partitioned into time-frequency slots, time-multiplexed receiver initiated busy burst (BB) transmissions solve these problems by establishing an exclusion region around an active receiver by means of receiver feedback. The size of this exclusion region is controlled by an Interference threshold that determines whether a user is allowed to transmit on a specific time-frequency resource unit. We propose a novel approach for setting the Interference thresholds based on a heuristic derived for a two-link network. First, for two-links, the optimum threshold value is derived that maximizes the sum rate. Second, for multiple links, the new heuristic threshold that only relies on locally available information is derived. It is demonstrated via simulations that heuristic thresholding achieves superior sum rate compared to a fixed system-wide threshold. To complement simulation results, an analytical approach is developed to approximate the probability density function (pdf) of the sum of the interferers in BB setting with fixed threshold with a cumulant-based shifted log normal fitting method.

  • Uplink Interference Protection and scheduling for energy efficient OFDMA networks
    EURASIP Journal on Wireless Communications and Networking, 2012
    Co-Authors: Harald Burchardt, Gunther Auer, Zubin Bharucha, Harald Haas
    Abstract:

    One of the key challenges for future orthogonal frequency division multiple access-based networks is inter-cell Interference coordination. With full frequency reuse and small inter-site distances, coping with co-channel Interference (CCI) in such networks has become increasingly important. In this article, an uplink Interference Protection (ULIP) technique to combat CCI is introduced and investigated. The level of uplink Interference originating from neighbouring cells (affecting co-channel mobile stations (MSs) in the cell of interest) can be effectively controlled by reducing the transmit power of the interfering MSs. This is done based on the target signal-to-noise-plus-Interference ratio (SINR) and tolerable Interference of the vulnerable link. Bands are prioritised in order to differentiate those (vulnerable/victim) MSs that are to be protected from Interference and those (aggressor/interfering MSs) that are required to sacrifice transmission power to facilitate the Protection. Furthermore, MSs are scheduled such that those users with poorer transmission conditions receive the highest Interference Protection, thus balancing the areal SINR distribution and creating a fairer allocation of the available resources. In addition to Interference Protection, the individual power reductions also serve to decrease the total system uplink power, resulting in a greener system. It is shown through analytic derivation that the introduction of ULIP guarantees an increase in energy efficiency for all MSs, with the added benefit that gains in overall system throughput are also achievable. Extensive system level simulations validate these findings.

  • decentralized Interference coordination via autonomous component carrier assignment
    Global Communications Conference, 2011
    Co-Authors: Serkan Uygungelen, Zubin Bharucha, Gunther Auer
    Abstract:

    A distributed and dynamic resource reuse method applicable to randomly deployed, possibly dense wireless networks is presented in this paper. The main objective is to protect mobile users located near the cell boundary from detrimental downlink Interference originating from neighboring base stations (BSs) without compromising the system spectral efficiency. For this purpose, a novel autonomous resource assignment method that is particularly well suited for decentralized wireless networks is developed. The proposed method is designed such that the Interference Protection does not coincide with an intolerable reduction in the attainable spatial reuse of radio resources. System-level simulations reveal that cell-edge capacities are significantly boosted without a sharp decrease in average system throughput.

  • graph based dynamic frequency reuse in femtocell networks
    Vehicular Technology Conference, 2011
    Co-Authors: Serkan Uygungelen, Gunther Auer, Zubin Bharucha
    Abstract:

    We address Interference avoidance by resource partitioning in densely deployed femtocell networks. The main objective is to protect user equipments (UEs) that are located near the cell boundary of two or more femtocells from detrimental downlink Interference. The available frequency bands are divided into subbands that are distributed among femtocells in a way that directly adjacent cells do not occupy the same subbands. For this purpose, a novel centrally controlled resource partitioning method is developed based on graph coloring that assigns subbands in terms of resource efficiency. The proposed algorithm strikes a balance between Interference Protection and spatial frequency reuse of subbands, and is well suited for randomly deployed wireless networks. System-level simulations reveal that cell edge capacities are significantly boosted without causing a degradation in average system throughput.

  • Uplink Interference Protection and fair scheduling for power efficient OFDMA networks
    2011 8th International Workshop on Multi-Carrier Systems & Solutions, 2011
    Co-Authors: Harald Burchardt, Zubin Bharucha, Harald Haas, Gunther Auer
    Abstract:

    In this paper a new method for uplink inter-cell Interference coordination (ICIC) in a full frequency reuse system is proposed. The technique is named uplink Interference Protection (ULIP). ULIP exploits existing reference signals transmitted by all base stations (BSs). The fact that path loss and lognormal shadowing can be considered reciprocal in such frequency-division duplex (FDD) systems is exploited. Therefore, no additional signalling is required for a new mobile station (MS) to estimate the level of inter-cell Interference it would cause to ongoing uplink transmissions in neighbouring cells. Using the acquired knowledge, MSs can adjust their transmit power to ensure that existing links are not forced into outage. A scheduling scheme is suggested in which a fair allocation of priority resource blocks (RBs), based on user signal-to-Interference-plus-noise ratios (SINRs), enhances both cell-edge throughput and user throughput fairness. Through this, also significant system throughput gains are generated. Finally, it is demonstrated that as a side effect of the Interference reductions, considerable energy savings can be achieved.

Harald Haas - One of the best experts on this subject based on the ideXlab platform.

  • sum rate increase via variable Interference Protection
    IEEE Transactions on Mobile Computing, 2012
    Co-Authors: Sinan Sinanovic, Harald Haas, Harald Burchardt, Gunther Auer
    Abstract:

    The sum rate of spectrum-sharing in decentralized and self-organizing wireless networks is investigated in this paper. Such networks pose the following two fundamental challenges: 1) cochannel Interference and 2) the hidden node problem. For a slotted shared wireless medium, where resources are partitioned into time-frequency slots, time-multiplexed receiver initiated busy burst (BB) transmissions solve these problems by establishing an exclusion region around an active receiver by means of receiver feedback. The size of this exclusion region is controlled by an Interference threshold that determines whether a user is allowed to transmit on a specific time-frequency resource unit. We propose a novel approach for setting the Interference thresholds based on a heuristic derived for a two-link network. First, for two-links, the optimum threshold value is derived that maximizes the sum rate. Second, for multiple links, the new heuristic threshold that only relies on locally available information is derived. It is demonstrated via simulations that heuristic thresholding achieves superior sum rate compared to a fixed system-wide threshold. To complement simulation results, an analytical approach is developed to approximate the probability density function (pdf) of the sum of the interferers in BB setting with fixed threshold with a cumulant-based shifted log normal fitting method.

  • Uplink Interference Protection and scheduling for energy efficient OFDMA networks
    EURASIP Journal on Wireless Communications and Networking, 2012
    Co-Authors: Harald Burchardt, Gunther Auer, Zubin Bharucha, Harald Haas
    Abstract:

    One of the key challenges for future orthogonal frequency division multiple access-based networks is inter-cell Interference coordination. With full frequency reuse and small inter-site distances, coping with co-channel Interference (CCI) in such networks has become increasingly important. In this article, an uplink Interference Protection (ULIP) technique to combat CCI is introduced and investigated. The level of uplink Interference originating from neighbouring cells (affecting co-channel mobile stations (MSs) in the cell of interest) can be effectively controlled by reducing the transmit power of the interfering MSs. This is done based on the target signal-to-noise-plus-Interference ratio (SINR) and tolerable Interference of the vulnerable link. Bands are prioritised in order to differentiate those (vulnerable/victim) MSs that are to be protected from Interference and those (aggressor/interfering MSs) that are required to sacrifice transmission power to facilitate the Protection. Furthermore, MSs are scheduled such that those users with poorer transmission conditions receive the highest Interference Protection, thus balancing the areal SINR distribution and creating a fairer allocation of the available resources. In addition to Interference Protection, the individual power reductions also serve to decrease the total system uplink power, resulting in a greener system. It is shown through analytic derivation that the introduction of ULIP guarantees an increase in energy efficiency for all MSs, with the added benefit that gains in overall system throughput are also achievable. Extensive system level simulations validate these findings.

  • Uplink Interference Protection and fair scheduling for power efficient OFDMA networks
    2011 8th International Workshop on Multi-Carrier Systems & Solutions, 2011
    Co-Authors: Harald Burchardt, Zubin Bharucha, Harald Haas, Gunther Auer
    Abstract:

    In this paper a new method for uplink inter-cell Interference coordination (ICIC) in a full frequency reuse system is proposed. The technique is named uplink Interference Protection (ULIP). ULIP exploits existing reference signals transmitted by all base stations (BSs). The fact that path loss and lognormal shadowing can be considered reciprocal in such frequency-division duplex (FDD) systems is exploited. Therefore, no additional signalling is required for a new mobile station (MS) to estimate the level of inter-cell Interference it would cause to ongoing uplink transmissions in neighbouring cells. Using the acquired knowledge, MSs can adjust their transmit power to ensure that existing links are not forced into outage. A scheduling scheme is suggested in which a fair allocation of priority resource blocks (RBs), based on user signal-to-Interference-plus-noise ratios (SINRs), enhances both cell-edge throughput and user throughput fairness. Through this, also significant system throughput gains are generated. Finally, it is demonstrated that as a side effect of the Interference reductions, considerable energy savings can be achieved.

  • Interference Protection versus spatial reuse in wireless networks
    Wireless Communications and Networking Conference, 2009
    Co-Authors: Harald Burchardt, Gunther Auer, Sinan Sinanovic, Peter Omiyi, Harald Haas
    Abstract:

    In this paper the capacity of decentralized wireless networks is addressed. An exclusion region is introduced that protects active receivers from destructive Interference of nearby transmitters. An exclusion range imposes an upper bound on the Interference that a transmitter may cause to receivers of competing links. While an exclusion region avoids excessive Interference and thus improves capacity per link, the spatial reuse in terms of concurrently served links is compromised. The resulting trade-off is elaborated by computer simulations, so to optimize the exclusion range as a function of the user density and maximum transmit power. We demonstrate that by an appropriately specified exclusion range, the network capacity is substantially enhanced. In this context, it has been found that the exclusion range that maximizes the system capacity does not vary greatly when changing the a priori user density. In addition, the trade-off between maximizing the system capacity and maintaining fairness is investigated.

E.s. Sousa - One of the best experts on this subject based on the ideXlab platform.

  • optimization of spectrum sensing for opportunistic spectrum access in cognitive radio networks
    Consumer Communications and Networking Conference, 2007
    Co-Authors: Amir Ghasemi, E.s. Sousa
    Abstract:

    Motivated by the low utilization of the licensed spectrum across many frequency bands, sensing-based oppor- tunistic spectrum access has recently emerged as an alternative to the outdated exclusive spectrum access policy. Under this new paradigm, a secondary (unlicensed) user monitors a primary (licensed) frequency band for a given time and opportunistically transmits if it does not detect any ongoing licensed operations. Evidently, selection of the sensing parameters involves balanc- ing a tradeoff between the speed and the quality with which the secondary user senses the licensed band. With the average throughput as the performance criterion, we obtain the sensing parameters so as to optimize the performance of the secondary user while providing the primary user with its desired level of Interference Protection. I. INTRODUCTION As evidenced by recent measurements, many frequency bands across the licensed spectrum are significantly under- utilized (1), (2). This finding suggests that the spectrum scarcity, as perceived today, is largely due to the inefficient fixed frequency allocations rather than the physical shortage of the spectrum and has led the regulatory bodies to consider the opportunistic access to the temporally/spatially unused licensed bands (a.k.a. the white spaces) as a means to improve the efficiency of spectrum usage. In the absence of cooperation or signalling between the primary licensee and the secondary users, spectrum availability for the opportunistic access may be determined by direct spectrum sensing where the secondary user monitors a licensed band for a given "sensing time" and opportunistically transmits if it does not detect any ongoing licensed operations. This approach is particularly appealing due to its low deployment cost and its compatibility with legacy primary users and is being considered for inclusion in the upcoming IEEE 802.22 standard for opportunistic access to the TV spectrum (3). Due to their ability to autonomously detect and to react to the changes in the spectrum usage, secondary users equipped with the spectrum sensing capability may be considered as a primitive form of the cognitive radio (4). Design of any sensing scheme involves balancing a tradeoff between the quality and the speed of sensing through an appropriate selection of the sensing time. As we shall illustrate, in the context of spectrum sensing, sensing time may be fine- tuned to enhance the secondary users' perceived quality-of- service (QoS) as long as the regulatory constraint for the Protection of the primary users against harmful Interference is satisfied. In particular, we will obtain the optimum sensing times at different stages of the spectrum sensing to maximize the average throughput of the secondary user. In this paper, simple energy detection (a.k.a. radiometry) (5) is chosen as the underlying detection scheme. In general, when some information about the structure of the primary signal is available, ad hoc feature-detectors offer a better performance (6). We note, however, that the methodology employed in this paper may be applied to optimize different spectrum sensors once the sensing quality is characterized in terms of the sensing time. The remainder of this paper is organized as follows. The regulatory constraints on spectrum sensing are described in the following section. Section 3 provides an overview of the energy-based spectrum sensing. The optimum sensing times for different stages of the spectrum sensing are derived in Section 4. Finally, this paper is concluded in Section 5.

  • collaborative spectrum sensing for opportunistic access in fading environments
    First IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks 2005. DySPAN 2005., 2005
    Co-Authors: Amir Ghasemi, E.s. Sousa
    Abstract:

    Traditionally, frequency spectrum is licensed to users by government agencies in a fixed manner where licensee has exclusive right to access the allocated band. This policy has been de jure practice to protect systems from mutual Interference for many years. However, with increasing demand for the spectrum and scarcity of vacant bands, a spectrum policy reform seems inevitable. Meanwhile, recent measurements suggest the possibility of sharing spectrum among different parties subject to Interference-Protection constraints. In this paper we study spectrum-sharing between a primary licensee and a group of secondary users. In order to enable access to unused licensed spectrum, a secondary user has to monitor licensed bands and opportunistically transmit whenever no primary signal is detected. However, detection is compromised when a user experiences shadowing or fading effects. In such cases, user cannot distinguish between an unused band and a deep fade. Collaborative spectrum sensing is proposed and studied in this paper as a means to combat such effects. Our analysis and simulation results suggest that collaboration may improve sensing performance significantly

Harald Burchardt - One of the best experts on this subject based on the ideXlab platform.

  • sum rate increase via variable Interference Protection
    IEEE Transactions on Mobile Computing, 2012
    Co-Authors: Sinan Sinanovic, Harald Haas, Harald Burchardt, Gunther Auer
    Abstract:

    The sum rate of spectrum-sharing in decentralized and self-organizing wireless networks is investigated in this paper. Such networks pose the following two fundamental challenges: 1) cochannel Interference and 2) the hidden node problem. For a slotted shared wireless medium, where resources are partitioned into time-frequency slots, time-multiplexed receiver initiated busy burst (BB) transmissions solve these problems by establishing an exclusion region around an active receiver by means of receiver feedback. The size of this exclusion region is controlled by an Interference threshold that determines whether a user is allowed to transmit on a specific time-frequency resource unit. We propose a novel approach for setting the Interference thresholds based on a heuristic derived for a two-link network. First, for two-links, the optimum threshold value is derived that maximizes the sum rate. Second, for multiple links, the new heuristic threshold that only relies on locally available information is derived. It is demonstrated via simulations that heuristic thresholding achieves superior sum rate compared to a fixed system-wide threshold. To complement simulation results, an analytical approach is developed to approximate the probability density function (pdf) of the sum of the interferers in BB setting with fixed threshold with a cumulant-based shifted log normal fitting method.

  • Uplink Interference Protection and scheduling for energy efficient OFDMA networks
    EURASIP Journal on Wireless Communications and Networking, 2012
    Co-Authors: Harald Burchardt, Gunther Auer, Zubin Bharucha, Harald Haas
    Abstract:

    One of the key challenges for future orthogonal frequency division multiple access-based networks is inter-cell Interference coordination. With full frequency reuse and small inter-site distances, coping with co-channel Interference (CCI) in such networks has become increasingly important. In this article, an uplink Interference Protection (ULIP) technique to combat CCI is introduced and investigated. The level of uplink Interference originating from neighbouring cells (affecting co-channel mobile stations (MSs) in the cell of interest) can be effectively controlled by reducing the transmit power of the interfering MSs. This is done based on the target signal-to-noise-plus-Interference ratio (SINR) and tolerable Interference of the vulnerable link. Bands are prioritised in order to differentiate those (vulnerable/victim) MSs that are to be protected from Interference and those (aggressor/interfering MSs) that are required to sacrifice transmission power to facilitate the Protection. Furthermore, MSs are scheduled such that those users with poorer transmission conditions receive the highest Interference Protection, thus balancing the areal SINR distribution and creating a fairer allocation of the available resources. In addition to Interference Protection, the individual power reductions also serve to decrease the total system uplink power, resulting in a greener system. It is shown through analytic derivation that the introduction of ULIP guarantees an increase in energy efficiency for all MSs, with the added benefit that gains in overall system throughput are also achievable. Extensive system level simulations validate these findings.

  • Uplink Interference Protection and fair scheduling for power efficient OFDMA networks
    2011 8th International Workshop on Multi-Carrier Systems & Solutions, 2011
    Co-Authors: Harald Burchardt, Zubin Bharucha, Harald Haas, Gunther Auer
    Abstract:

    In this paper a new method for uplink inter-cell Interference coordination (ICIC) in a full frequency reuse system is proposed. The technique is named uplink Interference Protection (ULIP). ULIP exploits existing reference signals transmitted by all base stations (BSs). The fact that path loss and lognormal shadowing can be considered reciprocal in such frequency-division duplex (FDD) systems is exploited. Therefore, no additional signalling is required for a new mobile station (MS) to estimate the level of inter-cell Interference it would cause to ongoing uplink transmissions in neighbouring cells. Using the acquired knowledge, MSs can adjust their transmit power to ensure that existing links are not forced into outage. A scheduling scheme is suggested in which a fair allocation of priority resource blocks (RBs), based on user signal-to-Interference-plus-noise ratios (SINRs), enhances both cell-edge throughput and user throughput fairness. Through this, also significant system throughput gains are generated. Finally, it is demonstrated that as a side effect of the Interference reductions, considerable energy savings can be achieved.

  • Interference Protection versus spatial reuse in wireless networks
    Wireless Communications and Networking Conference, 2009
    Co-Authors: Harald Burchardt, Gunther Auer, Sinan Sinanovic, Peter Omiyi, Harald Haas
    Abstract:

    In this paper the capacity of decentralized wireless networks is addressed. An exclusion region is introduced that protects active receivers from destructive Interference of nearby transmitters. An exclusion range imposes an upper bound on the Interference that a transmitter may cause to receivers of competing links. While an exclusion region avoids excessive Interference and thus improves capacity per link, the spatial reuse in terms of concurrently served links is compromised. The resulting trade-off is elaborated by computer simulations, so to optimize the exclusion range as a function of the user density and maximum transmit power. We demonstrate that by an appropriately specified exclusion range, the network capacity is substantially enhanced. In this context, it has been found that the exclusion range that maximizes the system capacity does not vary greatly when changing the a priori user density. In addition, the trade-off between maximizing the system capacity and maintaining fairness is investigated.

Jon M Peha - One of the best experts on this subject based on the ideXlab platform.

  • location privacy from dummy devices in database coordinated spectrum sharing
    IEEE International Symposium on Dynamic Spectrum Access Networks, 2017
    Co-Authors: Nirajan Rajkarnikar, Jon M Peha, Ana Aguiar
    Abstract:

    One way to make more spectrum available is through white space sharing, where secondary spectrum users are allowed to transmit from any location except inside exclusion zones (EZs) that are drawn around primary spectrum users (PUs). However, EZ boundaries reveal the locations of PUs, and for some devices, location privacy is extremely important. Location privacy can be improved by increasing the area blocked inside EZs, but this decreases spectrum utilization efficiency. This paper derives a Pareto optimal strategy that builds on two such approaches: generating dummy PUs and creating EZs around them, and making EZs larger than needed for Interference Protection alone. We find that in many circumstances, including cases where an attacker threatens a jamming attack, the optimal strategy is to maximize the number of dummy PUs while making EZs as small as possible. In the remaining circumstances, the optimal strategy is to generate no dummy EZs. We derive the Pareto optimal results achieved by using whichever of these strategies is best for given circumstances, and show that the results are far superior to those achieved with some previously proposed algorithms. Moreover, with our approach, even a small increase in the amount of area blocked from secondary use can greatly improve location privacy for PUs, although as more and more area is blocked, there are diminishing returns.

  • sharing spectrum through spectrum policy reform and cognitive radio
    Proceedings of the IEEE, 2009
    Co-Authors: Jon M Peha
    Abstract:

    Traditionally, Interference Protection is guaranteed through a policy of spectrum licensing, whereby wireless systems get exclusive access to spectrum. This is an effective way to prevent Interference, but it leads to highly inefficient use of spectrum. Cognitive radio along with software radio, spectrum sensors, mesh networks, and other emerging technologies can facilitate new forms of spectrum sharing that greatly improve spectral efficiency and alleviate scarcity, if policies are in place that support these forms of sharing. On the other hand, new technology that is inconsistent with spectrum policy will have little impact. This paper discusses policies that can enable or facilitate use of many spectrum-sharing arrangements, where the arrangements are categorized as being based on coexistence or cooperation and as sharing among equals or primary-secondary sharing. A shared spectrum band may be managed directly by the regulator, or this responsibility may be delegated in large part to a license-holder. The type of sharing arrangement and the entity that manages it have a great impact on which technical approaches are viable and effective. The most efficient and cost-effective form of spectrum sharing will depend on the type of systems involved, where systems under current consideration are as diverse as television broadcasters, cellular carriers, public safety systems, point-to-point links, and personal and local-area networks. In addition, while cognitive radio offers policy-makers the opportunity to improve spectral efficiency, cognitive radio also provides new challenges for policy enforcement. A responsible regulator will not allow a device into the marketplace that might harm other systems. Thus, designers must seek innovative ways to assure regulators that new devices will comply with policy requirements and will not cause harmful Interference.

  • sharing spectrum through spectrum policy reform and cognitive radio policy management by regulators and license holders is important for implementing the best means for dynamically sharing the limited and precious communications spectrum
    2009
    Co-Authors: Jon M Peha
    Abstract:

    Traditionally, Interference Protection is guaran- teed through a policy of spectrum licensing, whereby wireless systems get exclusive access to spectrum. This is an effective way to prevent Interference, but it leads to highly inefficient use of spectrum. Cognitive radio along with software radio, spectrum sensors, mesh networks, and other emerging tech- nologies can facilitate new forms of spectrum sharing that greatly improve spectral efficiency and alleviate scarcity, if policies are in place that support these forms of sharing. On the other hand, new technology that is inconsistent with spectrum policy will have little impact. This paper discusses policies that can enable or facilitate use of many spectrum-sharing arrange- ments, where the arrangements are categorized as being based on coexistence or cooperation and as sharing among equals or primary-secondary sharing. A shared spectrum band may be managed directly by the regulator, or this responsibility may be delegated in large part to a license-holder. The type of sharing arrangement and the entity that manages it have a great impact on which technical approaches are viable and effective. The most efficient and cost-effective form of spectrum sharing will depend on the type of systems involved, where systems under current consideration are as diverse as television broadcasters, cellular carriers, public safety systems, point-to-point links, and personal and local-area networks. In addition, while cognitive radio offers policy-makers the opportunity to improve spectral efficiency, cognitive radio also provides new challenges for policy enforcement. A responsible regulator will not allow a device into the marketplace that might harm other systems. Thus, designers must seek innovative ways to assure regulators that new devices will comply with policy require- ments and will not cause harmful Interference.