| 1. |
- António, Gonga, et al.
(författare)
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Multi-channel communication vs. adaptive routing for reliable communication in WSNs
- 2012
-
Ingår i: IPSN'12 - ACM/IEEE Proceedings of the 11th International Conference on Information Processing in Sensor Networks, (Beijing;16 - 20 April 2012). - New York, NY, USA : ACM. - 9781450312271 ; , s. 125-126
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Konferensbidrag (refereegranskat)abstract
- Interference and link dynamics constitute great concerns for stability and performance of protocols in WSNs. In this paper we evaluate the impact of channel hopping and adaptive routing on delay and reliability focusing on delay critical applications.
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| 2. |
- Antonioli, Roberto Pinto, et al.
(författare)
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Decentralized User Scheduling for Rate-Constrained Sum-Utility Maximization in the MIMO IBC
- 2020
-
Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 68:10, s. 6215-6229
-
Tidskriftsartikel (refereegranskat)abstract
- While the problems of sum-rate maximization and sum-power minimization subject to quality of service (QoS) constraints in the multiple input multiple output interference broadcast channel (MIMO IBC) have been widely studied, most of the proposed solutions have neglected the user scheduling aspect assuming that a feasible set of users has been previously selected. However, ensuring QoS for each user in the MIMO IBC involves the joint optimization of transmit/receive beamforming vectors, transmit powers, and user scheduling variables. To address the full problem, we propose a novel formulation of a rate-constrained sum-utility maximization problem which allows to either deactivate users or minimize the QoS degradation for some scheduled users in infeasible scenarios. Remarkably, this is achieved avoiding the complexity of traditional combinatorial formulations, but rather by introducing a novel expression of the QoS constraints that allows to solve the problem in a continuous domain. We propose centralized and decentralized solutions, where the decentralized solutions focus on practical design and low signaling overhead. The proposed solutions are then compared with benchmarking algorithms, where we show the effectiveness of the joint scheduling and transceiver design as well as the flexibility of the proposed solution performing advantageously in several MIMO IBC scenarios.
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| 3. |
- Antonioli, Roberto P., et al.
(författare)
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User Scheduling for Sum-Rate Maximization Under Minimum Rate Constraints for the MIMO IBC
- 2019
-
Ingår i: IEEE Wireless Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2162-2337 .- 2162-2345. ; 8:6, s. 1591-1595
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Tidskriftsartikel (refereegranskat)abstract
- While the problem of sum-rate maximization of the multiple-input-multiple-output interference broadcast channel (MIMO IBC) has been extensively studied, most of the proposed solutions do not ensure a minimum rate for each scheduled user. In practice, many services require a minimum rate from the underlying communication links. Therefore, in this letter, we consider a sum-rate maximization problem with per-link minimum rate constraints for the MIMO IBC. The key idea is scheduling a suitable subset of the communication links for simultaneous transmissions, such that a minimum rate for each scheduled link can be ensured. To this end, we pose the sum-rate maximization problem as a combinatorial optimization problem, in which we introduce binary variables to the classical transceiver design problem. We propose a centralized solution based on branch-and-bound and a low-complexity semi-distributed scheme, in which a centralized unit is responsible for scheduling decisions, while the transceiver computations are distributed. Simulations show that the proposed solutions handle the user scheduling effectively, while the proposed semi-distributed scheme performs closely to the centralized scheme.
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| 4. |
- Belleschi, Marco, et al.
(författare)
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Fast power control for cross-layer optimal resource allocation in DS-CDMA wireless networks
- 2009
-
Ingår i: 2009 IEEE International Conference on Communications. ; , s. 4341-4346
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel cross-layer design for joint power and end-to-end rate control optimization in DS-CDMA wireless networks, along with a detailed implementation and evaluation in the network simulator ns-2. Starting with a network utility maximization formulation of the problem, we derive distributed power control, transport rate and queue management schemes that jointly achieve the optimal network operation. Our solution has several attractive features compared to alternatives: it adheres to the natural time-scale separation between rapid power control updates and slower end-to-end rate adjustments, and uses simplified power control mechanisms with reduced signalling requirements. We argue that these features are critical for a successful real-world implementation. To validate these claims, we present a detailed implementation of a crosslayer adapted networking stack for DS-CSMA ad-hoc networks in ns-2. We describe several critical issues that arise in the implementation, but are typically neglected in the theoretical protocol design, and evaluate the alternatives in extensive simulations.
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| 5. |
- Demirel, Burak, et al.
(författare)
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Modular Co-Design of Controllers and Transmission Schedules in WirelessHART
- 2011
-
Ingår i: IEEE Conference on Decision and Control. ; , s. 5951-5958
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Konferensbidrag (refereegranskat)abstract
- We consider the joint design of transmissionschedules and controllers for networked control loops that useWirelessHART communication for sensor and actuator data. Byparameterizing the design problem in terms of the samplingrate of the control loop, the co-design problem separates intotwo well-defined subproblems which admit optimal solutions:transmission scheduling should be done to maximize the delayconstrained reliability while the control design should optimizeclosed-loop performance under packet loss. We illustrate howthese problems can be solved and demonstrate our co-designframework for the case of linear-quadratic contro
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| 6. |
- Demirel, Burak, et al.
(författare)
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Modular Design of Jointly Optimal Controllers and Forwarding Policies for Wireless Control
- 2014
-
Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 59:12, s. 3252-3265
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the joint design of packet forwarding policies and controllers for wireless control loops where sensor measurements are sent to the controller over an unreliable and energy-constrained multi-hop wireless network. For fixed sampling rate of the sensor, the co-design problem separates into two well-defined and independent subproblems: transmission scheduling for maximizing the deadline-constrained reliability and optimal control under packet loss. We develop optimal and implementable solutions for these subproblems and show that the optimally co-designed system can be efficiently found. Numerical examples highlight the many trade-offs involved and demonstrate the power of our approach.
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| 7. |
- Fodor, Gabor, et al.
(författare)
-
Near optimum power control and precoding under fairness constraints in network MIMO systems
- 2009
-
Ingår i: International Journal of Digital Multimedia Broadcasting. - : Hindawi Limited. - 1687-7578 .- 1687-7586. ; 2010, s. 251719-
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of setting the uplink signal-to-noise-and- interference (SINR) target and allocating transmit powers for mobile stations in multicell spatial multiplexing wireless systems. Our aim is twofold: to evaluate the potential of such mechanisms in network multiple input multiple output (MIMO) systems, and to develop scalable numerical schemes that allow real-time near-optimal resource allocation across multiple sites. We formulate two versions of the SINR target and power allocation problem: one for maximizing the sum rate subject to power constraints, and one for minimizing the total power needed to meet a sum-rate target. To evaluate the potential of our approach, we perform a semianalytical study in Mathematica using the augmented Lagrangian penalty function method. We find that the gain of the joint optimum SINR setting and power allocation may be significant depending on the degree of fairness that we impose. We develop a numerical technique, based on successive convexification, for real-time optimization of SINR targets and transmit powers. We benchmark our procedure against the globally optimal solution and demonstrate consistently strong performance in realistic network MIMO scenarios. Finally, we study the impact of near optimal precoding in a multicell MIMO environment and find that precoding helps to reduce the sum transmit power while meeting a capacity target.
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| 8. |
- Fodor, Gabor, et al.
(författare)
-
Near Optimum Power Control Under Fairness Constraints in CoMP Systems
- 2009
-
Ingår i: GLOBECOM 2009 - 2009 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE. - 9781424441471 ; , s. 5274-5281
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of setting the uplink signal-to-noise-and-interference (SINR) target and allocating transmit powers for mobile stations in multicell spatial multiplexing wireless systems. Our aim is twofold: to evaluate the potential of such mechanisms in coordinated multipoint transmission (CoMP) systems, and to develop scalable numerical schemes that allow real-time near-optimal resource allocation across multiple sites. We formulate two versions of the SINR target and power allocation problem: one for maximizing the sum rate subject to power constraints, and one for minimizing the total power needed to meet a sum-rate target. To evaluate the potential of our approach, we perform a semi-analytical study in Mathematica using the augmented Lagrangian penalty function method. We find that the gain of the joint optimum SINR setting and power allocation may be significant depending on the degree of fairness that we impose. We develop a numerical technique, based on successive convexification, for real-time optimization of SINR targets and transmit powers. We benchmark our procedure against the globally optimal solution, and demonstrate consistently strong performance in realistic CoMP scenarios.
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| 9. |
- Fodor, Gabor, et al.
(författare)
-
On the impact of uplink power control in network MIMO systems with MMSE and SIC receivers
- 2010
-
Ingår i: 2010 IEEE International Symposium on 'A World of Wireless, Mobile and Multimedia Networks'. - 9781424472659
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Konferensbidrag (refereegranskat)abstract
- Network multiple input, multiple output (MIMO) systems are built around a broadband backbone network that allows for the fast communication of channel state information (CSI) as well as user data between different base stations. Previous works have shown that multicell channel adaptive (opportunistic) power control can minimize the sum power or maximize the sum rate when the backbone is used for the exchange of CSI in network MIMO systems. In this work we investigate the gains of multicell opportunistic power control under per user fairness constraints when both CSI and user data are shared between multiple sites. We find that multicell opportunistic power control working in concert with uplink joint signal detection is an efficient means both for the capacity and the power control problems that not only minimizes sum power or maximizes overall capacity, but is also able to provide arbitrary level of fairness.
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| 10. |
- Ghadimi, Euhanna, et al.
(författare)
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A metric for opportunistic routing in duty cycled wireless sensor networks
- 2012
-
Ingår i: Sensor, Mesh and Ad Hoc Communications and Networks (SECON), 2012 9th Annual IEEE Communications Society Conference on. - : IEEE. - 2155-5486 .- 2155-5494. - 9781467319058 ; , s. 335-343
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Konferensbidrag (refereegranskat)abstract
- Opportunistic routing is widely known to have substantially better performance than traditional unicast routing in wireless networks with lossy links. However, wireless sensor networks are heavily duty-cycled, i.e. they frequently enter deep sleep states to ensure long network life-time. This renders existing opportunistic routing schemes impractical, as they assume that nodes are always awake and can overhear other transmissions. In this paper, we introduce a novel opportunistic routing metric that takes duty cycling into account. By analytical performance modeling and simulations, we show that our routing scheme results in significantly reduced delay and improved energy efficiency compared to traditional unicast routing. The method is based on a new metric, EDC, that reflects the expected number of duty cycled wakeups that are required to successfully deliver a packet from source to destination. We devise distributed algorithms that find the EDC-optimal forwarding, i.e. the optimal subset of neighbors that each node should permit to forward its packets. We compare the performance of the new routing with ETX-optimal single path routing in both simulations and testbed-based experiments.
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| 11. |
- Ghadimi, Euhanna, et al.
(författare)
-
Hidden Terminal-Aware Contention Resolution With an Optimal Distribution
- 2011
-
Ingår i: Proceedings - 8th IEEE International Conference on Mobile Ad-hoc and Sensor Systems, MASS 2011. - 9780769544694 ; , s. 182-191
-
Konferensbidrag (refereegranskat)abstract
- Achieving low-power operation in wireless sensor networks with high data load or bursty traffic is challenging. The hidden terminal problem is aggravated with increased amounts of data in which traditional backoff-based contention resolution mechanisms fail or induce high latency and energy costs. We analyze and optimize Strawman, a receiver-initiated contention resolution mechanism that copes with hidden terminals. We propose new techniques to boost the performance of Strawman while keeping the resolution overhead small. We finally validate our improved mechanism via experiments.
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| 12. |
- Ghadimi, Euhanna, et al.
(författare)
-
Opportunistic routing in low duty-cycle wireless sensor networks
- 2014
-
Ingår i: ACM transactions on sensor networks. - : Association for Computing Machinery (ACM). - 1550-4867 .- 1550-4859. ; 10:4, s. 67-
-
Tidskriftsartikel (refereegranskat)abstract
- Opportunistic routing is widely known to have substantially better performance than unicast routing in wireless networks with lossy links. However, wireless sensor networks are usually duty cycled, that is, they frequently enter sleep states to ensure long network lifetime. This renders existing opportunistic routing schemes impractical, as they assume that nodes are always awake and can overhear other transmissions. In this article we introduce ORW, a practical opportunistic routing scheme for wireless sensor networks. ORW uses a novel opportunistic routing metric, EDC, that reflects the expected number of duty-cycled wakeups that are required to successfully deliver a packet from source to destination. We devise distributed algorithms that find the EDC-optimal forwarding and demonstrate using analytical performance models and simulations that EDC-based opportunistic routing results in significantly reduced delay and improved energy efficiency compared to traditional unicast routing. In addition, we evaluate the performance of ORW in both simulations and testbed-based experiments. Our results show that ORW reduces radio duty cycles on average by 50% (up to 90% on individual nodes) and delays by 30% to 90% when compared to the state-of-the-art.
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| 13. |
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| 14. |
- Koudouridis, Georgios, et al.
(författare)
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Multiple Connectivity and Spectrum Access Utilisation in Heterogeneous Small Cell Networks
- 2016
-
Ingår i: International Journal of Wireless Information Networks. - : Springer. - 1068-9605 .- 1572-8129. ; 23:1, s. 1-18
-
Tidskriftsartikel (refereegranskat)abstract
- In the context of heterogeneous and small cell networks, users will have the possibility to connect to multiple radio access (RA) carriers that will be available by a dense deployment of radio access infrastructure consisting of high-power and low-power access nodes. Determining which RAs a user should be associated with and select from, for its downlink transmissions, depends on the long-term and short-term data rates that these RAs may offer to the user. In this study the multi-RA allocation and utilisation is decomposed into a multi-RA to user association problem that assigns multiple RAs to users, and a multi-RA selection problem that determines which of the assigned RAs should be used at any time for the user transmissions. As a solution to the first problem, we propose a distributed dual-based spectrum access scheme (DSA) that considers multi-connectivity, whilst, the second problem is solved by means of a heuristic multi-RA selection scheme that utilise different multi-radio transmit diversity (MRTD) schemes while taking into account different inter-cell interference coordination (ICIC) schemes. Our two-step approach is evaluated by means of simulations which demonstrate cell-edge user throughput performance improvements that exceed 100% when the multi-connectivity dual-based spectrum access (MC-DSA) is employed. Further significant user rate and energy efficiency improvements up to 69% and 38% respectively can be achieved when MRTD is combined with ICIC.
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| 15. |
- Loretti, Simone, et al.
(författare)
-
Cross-layer optimization of multi-hop radio networks with multi-user detectors
- 2005
-
Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. ; , s. 2201-2206
-
Konferensbidrag (refereegranskat)abstract
- We present an efficient approach for crosslayer optimization of a class of wireless networks equipped with multi-user detectors. For a given network, the method provides the optimal operation of transport, routing and radio link layers as well as the optimal coordination across the layers. The algorithm combines a column generation procedure with an optimal greedy resource allocation scheme into a powerful numerical method for computing the performance limits for networks of significant sizes. The method is applied to a simple network scenario and performance benefits of multi-user detectors and cross-layer coordination over alternative schemes are investigated.
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| 16. |
- Park, Pan Gun, et al.
(författare)
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A generalized Markov chain model for effective analysis of slotted IEEE 802.15.4
- 2009
-
Ingår i: 2009 IEEE 6th International Conference on Mobile Adhoc and Sensor Systems. - 9781424451135 ; , s. 130-139
-
Konferensbidrag (refereegranskat)abstract
- A generalized analysis of the IEEE 802.15.4 medium access control (MAC) protocol in terms of reliability, delay and energy consumption is presented. The IEEE 802.15.4 exponential backoff process is modeled through a Markov chain taking into account retry limits, acknowledgements, and unsaturated traffic. Simple and effective approximations of the reliability, delay and energy consumption under low traffic regime are proposed. It is demonstrated that the delay distribution of IEEE 802.15.4 depends mainly on MAC parameters and collision probability. In addition, the impact of MAC parameters on the performance metrics is analyzed. The analysis is more general and gives more accurate results than existing methods in the literature. Monte Carlo simulations confirm that the proposed approximations offer a satisfactory accuracy.
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| 17. |
- Pesonen, Joonas, et al.
(författare)
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Methodology and tools for controller-networking codesign in WirelessHART
- 2009
-
Ingår i: ETFA 2009 - 2009 IEEE Conference on Emerging Technologies and Factory Automation. - : IEEE conference proceedings. - 9781424427284
-
Konferensbidrag (refereegranskat)abstract
- This paper describes a methodology for controller and communication scheduling co-design in control systems operating over wirelessHART networks. Data collection and dissemination operations are identified and scheduled to minimize the nominal communication latency. Techniques for improving the reliability of the network when link transmissions are unreliable are discussed, and a Markov-chain model for computing the latency distribution of data collection operations for a given schedule is proposed. The resulting latency models allow to represent the networked control loop as a jump-linear system, whose performance can be analyzed using techniques from stochastic control. We demonstrate how this framework can be used to co-design a networked LQG controller for a five-by-five MIMO control loop.
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| 18. |
- Soldati, Pablo, et al.
(författare)
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A low-signalling scheme for distributed resource allocation in multi-cellular OFDMA systems
- 2008
-
Ingår i: GLOBECOM 2008 - 2008 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE. - 9781424423248 ; , s. 3718-3723
-
Konferensbidrag (refereegranskat)abstract
- This paper considers distributed protocol design for joint sub-carrier, transmission scheduling and power management in uplink/downlink multi-cellular OFDMA wireless networks. The optimal solution to this problem is hard to achieve, both in theory and in practice. We propose a fully decentralized resource allocation scheme combining decomposition methods for convex optimization with a strategic non-cooperative game formulation of the power and sub-carrier allocation subproblem. Although the final protocols are suboptimal, they drastically reduce computation time while maintaining the overall system performance close to the optimal, exhibiting strong robustness to multiple access interference. We validate the theoretical framework and quantify the performance with numerical examples.
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| 19. |
- Soldati, Pablo, et al.
(författare)
-
A mathematical programming approach to deadline-constrained transmission scheduling in wireless HART networks
- 2008
-
Konferensbidrag (refereegranskat)abstract
- This paper considers transmission scheduling of deadline-constrained data in a wirelessHART network. We develop a thematical programming formulation and discuss efficient scheduling heuristics. We use the framework to schedule transmissions in a non-trivial network, and show how our results can be used to study design trade-offs such the use of multiple channels and multiple access points.
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| 20. |
- Soldati, Pablo
(författare)
-
Cross-layer optimization of wireless multi-hop networks
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The interest in wireless communications has grown constantly for the past decades, leading to an enormous number of applications and services embraced by billions of users. In order to meet the increasing demand for mobile Internet access, several high data-rate radio networking technologies have been proposed to offer wide area high-speed wireless communications, eventually replacing fixed (wired) networks for many applications.This thesis considers cross-layer optimization of multi-hop radio networks where the system performance can be improved if the traditionally separated network layers are jointly optimized. The networks we consider have links with variable transmission rates, influenced by the allocation of transmission opportunities and channels, modulation and coding schemes and transmit powers. First, we formulate the optimal network operation as the solution to a network utility maximization problem and review decomposition methods from mathematical programming that allow translating a centralized network optimization problem into distributed mechanisms and protocols. Second, particular focus is given to networks employing spatial-reuse TDMA, where we develop detailed distributed solutions for joint end-to-end communication rate selection, multiple time-slot transmission scheduling and power allocation which achieve the optimal network utility. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence and demonstrate how it suggests a distributed solution based on flow control optimization and incremental updates of the transmission schedule. We develop a two-step procedure for distributed maximization of computing the schedule updates (maximizing congestion-weighted throughput) and suggest two schemes for distributed channel reservation and power control under realistic interference models. Third, investigate the advantages of employing multi-user detectors within a CDMA/TDMA framework. We demonstrate how column generation techniques can be combined with resource allocation schemes for the multi-access channel into a very efficient computational method. Fourth, we investigate the benefits and challenges of using the emerging OFDMA modulation scheme within our framework. Specifically, we consider the problem of assigning sub-carriers to wireless links in multi-hop mesh networks. Since the underlying mathematical programming problem is computationally hard, we develop a specialized algorithm that computes optimal near-optimal solutions in a reasonable time and suggest a heuristic for improving computation at the price of relatively modest performance losses.
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| 21. |
- Soldati, Pablo, et al.
(författare)
-
Deadline-constrained transmission scheduling and data evacuation in wireless HART networks
- 2009
-
Ingår i: Proceedings of ECC. - : IEEE. - 9783952417393 ; , s. 4320-4325
-
Konferensbidrag (refereegranskat)abstract
- Real-time data delivery is a critical issue in wirelessHART networks. This paper develops a novel mathematical programming framework for joint routing and link scheduling of deadline-constrained traffic in wirelessHART networks. The general framework explores dynamic network flows on a time-expanded graph model and can provide flexible solutions for a variety of real-time data delivery problems. Data evacuation, an important communication paradigm in wirelessHART networks, is a special case of this general framework. We establish the lower bound on evacuation time for line, multi-line and binary tree networks. Moreover, we design a novel scheduling algorithm for data evacuation in binary tree networks, and prove that this scheduling algorithm can always achieve the lower bound on evacuation time. We evaluate our scheduling algorithm through numerical simulations, and results show that our algorithm can always minimize the evacuation time with the least number of channels.
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| 22. |
- Soldati, Pablo, et al.
(författare)
-
Distributed optimization of end-to-end rates and radio resources in WiMax single-carrier networks
- 2006
-
Ingår i: GLOBECOM - IEEE Global Telecommunications Conference. - 9781424403561
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of joint end-to-end band-width allocation and radio resource management in WiMax single-carrier wireless networks. The design problem is posed as a utility maximization problem subject to link rate constraints which involve transmission scheduling and power allocation. Inspired by a centralized algorithm for solving the associated optimization problem, we proceed systematically in our development of distributed resource allocation mechanisms. Contrary to the centralized algorithm, the proposed solution is distributed and of low computational complexity, generates schedules of finite length and with fixed time-slot durations, and acts on local neighborhood information only. Although the final scheme is suboptimal, we isolate and quantify the performance losses incurred and demonstrate strong performance in examples.
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| 23. |
- Soldati, Pablo, et al.
(författare)
-
Distributed Spectrum Access in Dense 5G Networks
- 2015
-
Konferensbidrag (refereegranskat)abstract
- The next generation of radio access networks is expected to offer users flexible radio access to a wide range of frequency bands and radio access technologies (RATs) in dense deployments. In this context, we investigate novel lightweight algorithms for spectrum access in ultra-dense networks. We pose the problem as a network utility maximization and apply Lagrange duality to devise distributed algorithms for users to jointly select access nodes and spectrum bands. Leveraging our theoretical framework, we further propose a heuristic scheme for spectrum access based on the expected long-term user data rate per RAT, hence on a measure of the RATs’ traffic load. Numerical examples show that our schemes achieve significant throughput gains on top of the gains achievable by network densification.
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| 24. |
- Soldati, Pablo, et al.
(författare)
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Network-wide resource optimization of wireless OFDMA mesh networks with multiple radios
- 2007
-
Ingår i: 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS. - 9781424403523 ; , s. 4979-4984
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of joint end-to-end rate optimization and radio resource management in wireless OFDMA-based mesh networks. Radio units equipped with multiple radio interfaces are combined with the OFDMA medium access scheme to make up for the classical limitations of single-carrier wireless networks. We pose the problem as a utility maximization problem subject to link-rate constraints, power control and transmission scheduling in terms of time slots, channels and radio interfaces. The optimal solution to this problem is in general hard to achieve, both in theory and in practice. We propose an alternative solution approach that drastically reduces the computation time, and suggest a heuristic scheme that attempts to reduce the computation time even further while maintaining the overall system performance close to the optimal. For each scheme we validate the theoretical framework and quantify the performance with numerical examples.
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| 25. |
- Soldati, Pablo, 1978-
(författare)
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On Cross-Layer Design and Resource Scheduling in Wireless Networks
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless technology has revolutionized the world of communications, enabling ubiquitous connectivity and leading every year to several new applications and services embraced by billions of users. To meet the increasing demand for high data-rate wireless services, standardization bodies and vendors released a new generation of standard-based devices capable to offer wide area high-speed and high-quality wireless coverage. More recently, wireless sensor networks (WSNs) have captured the attention of the industry society to migrate substantial parts of the traditionally wired industrial infrastructure to wireless technologies. Despite the increasing appetite for wireless services, the basic physical resource of these systems, the bandwidth, is limited. Therefore, the design of efficient network control mechanisms for optimizing the capabilities of complex networks is becoming an increasingly critical aspect in networking. In this thesis, we explore the application of optimization techniques to resource allocation in wireless systems. We formulate the optimal network operation as the solution to a network utility maximization problem, which highlights how system performance can be improved if the traditionally separated network layers are jointly optimized. The advantage of such cross-layer optimization is twofold: firstly, joint optimization across layers reveals the true performance limits that can be achieved by practical protocols, and is hence useful for network design or performance analysis; secondly, distributed optimization techniques can be used to systematically engineer protocols and signalling schemes that ensure the globally optimal system operation. Within this framework, we consider several challenging problems. The first one considers the design of jointly optimal power and end-to-end rate allocation schemes in multi-hop wireless networks that adhere to the natural time-scales of transport and physical layer mechanisms and impose limited signalling overhead. To validate the theoretical development, we present a detailed implementation of a cross-layer networking stack for DS-CDMA ad-hoc networks in the network simulator ns-2. This implementation exercise reveals several critical issues that arise in practice, but are typically neglected in the theoretical protocol design. Second, we consider networks employing resource scheduling at the data link layer, and we develop detailed distributed solutions for joint end-to-end communication rate selection, multiple time-slot transmission scheduling and power allocation that achieve the optimal network utility. We show with examples how the mathematical framework can be applied to optimize the resource allocation in spatial-reuse time division multiple access (S-TDMA) networks and orthogonal frequency division multiple access (OFDMA) networks. We then make a slight shift in focus, and consider off-line cross-layer optimization to investigate the benefits of various routing strategies in multi-hop networks, and apply these results to a techno-economical feasibility study of cellular relaying networks. Finally, we consider the design of efficient resource scheduling schemes for deadline-constrained real-time traffic in wireless sensor networks. Specifically, we develop theory and algorithms for time- and channel-optimal scheduling of networks operating according to the recent Wireless HART standard.
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| 26. |
- Soldati, Pablo, et al.
(författare)
-
On pilot dimensioning in multicell single input multiple output systems
- 2011
-
Ingår i: 2011 IEEE GLOBECOM Workshops, GC Wkshps 2011. - : IEEE. - 9781467300407 ; , s. 1382-1387
-
Konferensbidrag (refereegranskat)abstract
- Resource management schemes in multicell orthogonal frequency division multiplexing (OFDM) networks typically assume perfect channel knowledge at the transmitter or employ a statistical channel estimation error. In this paper we propose a model that explicitly captures the inherent tradeoff between the power allocated to transmitting data and pilot signals in multicell single input multiple output (SIMO) systems. We first study the asymptotic behavior of the required data power to reach a predefined signal-to-noise ratio (SNR) target as a function of the employed pilot power in a single OFDM cell, then develop a distributed multicell algorithm that strives to minimize the multi-cell sum data power with respect to a predefined signal-to-interference-and-noise-ratio (SINR) target vector. The results provide new insights in dimensioning the pilot and data transmit power levels and serve as a basis for developing distributed power control schemes in multicell systems.
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| 27. |
- Soldati, Pablo, et al.
(författare)
-
Optimal Routing and Scheduling of Deadline-Constrained Traffic Over Lossy Networks
- 2010
-
Ingår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010. - 9781424456383
-
Konferensbidrag (refereegranskat)abstract
- The traditionally wired automation infrastructure is quickly migrating to more flexible and scalable wireless solutions. To cope with the stringent requirements of process automation in terms of latency and reliability, the network resources must be optimized to ensure timely and reliable communication. This paper considers the joint routing and transmission scheduling problem for reliable real-time communication over lossy networks. Specifically, we impose a strict latency bound for packet delivery from source to destination, and devise optimal transmission scheduling policies that maximize the success probability of delivering the packet within the specified deadline. A solution to this problem allows to characterize the set of achievable latencies and packet reliability for a given network. We offer a complete understanding of the problem when erasure events on links are independent and follow a Bernoulli process. We consider both static and dynamic resource allocation policies, and compare them in numerical examples.
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| 28. |
- Soldati, Pablo, et al.
(författare)
-
Proportionally fair allocation of end-to-end bandwidth in STDMA wireless networks
- 2006
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Ingår i: Proceedings of the International Symposium on Mobile Ad Hoc Networking and Computing. - New York, NY, USA : ACM. - 9781595933683 ; , s. 286-297
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of designing distributed mechanisms for joint congestion control and resource allocation in spatial-reuse TDMA wireless networks. The design problem is posed as a utility maximization subject to link rate constraints that involve both power allocation and transmission scheduling over multiple time-slots. Starting from the performance limits of a centralized optimization based on global network information, we proceed systematically in the development of distributed and transparent protocols. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence for the utility maximization problem and demonstrate how it suggests a distributed solution based on flow control optimization and incremental updates of the transmission schedule. We develop a two-step procedure for finding the schedule updates and suggest two schemes for distributed channel reservation and power control under realistic interference models. Although the final protocols are suboptimal, we isolate and quantify the performance losses incurred by each simplification and demonstrate strong performance in examples.
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| 29. |
- Soldati, Pablo, et al.
(författare)
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Reducing signaling and respecting time-scales in cross-layer protocols design for wireless networks
- 2009
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Ingår i: GLOBECOM 2009 - 2009 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE. - 9781424441471 ; , s. 3984-3991
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Konferensbidrag (refereegranskat)abstract
- Current proposals for joint power and rate allocation protocols in ad hoc networks require a large signaling overhead, and do not adhere to the natural time-scales of transport and power control mechanisms. We present a solution that overcomes these issues. We pose the protocol design as a network utility maximization problem and adopt primal decomposition techniques to devise a novel distributed cross-layer design for transport and physical layer that achieves the optimal network operation. Our solution has several attractive features compared to alternatives: it adheres to the natural time-scale separation between rapid power control updates and slower end-to-end rate adjustments; it allows simplified power control mechanisms with reduced signalling requirements, and distributed slow rate cross-layer signalling mechanisms; and it maintains feasibility at each iteration. We validate the theoretical framework and compare the solution alternatives with numerical examples.
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| 30. |
- Timus, Bogdan, et al.
(författare)
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A Joint Routing-MAC Model for Cellular-Relaying Networks
- 2008
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Ingår i: 2008 IEEE 19TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS. - NEW YORK : IEEE. - 9781424426430 - 9781424426447 ; , s. 1214-1219
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Konferensbidrag (refereegranskat)abstract
- We present an iterative joint scheduling-routing algorithm for characterizing the long-term performance of a cellular-relaying network. The physical layer model is based on ideal rate adaptation, fixed transmission power, and average interference. At the MAC layer, time-shares of a common channel are allocated to links in a CSMA/CA-like fashion. At the transport layer, one or more parallel routes can transfer the data flow from a source to the destination, and the average end-user rates are adjusted so as to maximize a global utility function. The general problem of allocating time-shares and selecting link rates is nonconvex. We propose an iterative algorithm and a novel approximation for the physical layer so as to obtain a convex formulation at each iteration step. If only one route is available per source, the problem admits a convex equivalent formulation and the iterative algorithm converges to the global optimum. If more routes per source are available, the problem remains nonconvex. However we show in a simple tractable example that the joint formulation yields sum-log-utility values comparable to the results obtained through exhaustive search of all possible route combinations.
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| 31. |
- Timus, Bogdan, et al.
(författare)
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Cellular-Relaying Network Dimensioning with Cross-Layer Resource Allocation
- 2008
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Ingår i: 2008 IEEE 19TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS. - NEW YORK : IEEE. - 9781424426430 ; , s. 1236-1240
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Konferensbidrag (refereegranskat)abstract
- The enhancement of cellular networks with relaying technologies is expected to bring significant techno-economic benefits, but proper allocation of resources may be a challenging task. This paper addresses the question whether cross-layer optimization is essential for obtaining the expected relaying benefits. We present a network dimensioning approach based on joint routing and radio resource allocation. We consider a macro-cellular scenario with a max-min user-rate objective. If a single route per source is fixed, rates and time-shares can be optimally allocated to each link. In a simple macro-cellular propagation environment, the relays must cost at most 10-25% of a base station cost, if the network is deployed at once. The results are only slightly better when the routing is included in the joint resource allocation.
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| 32. |
- Timus, Bogdan, et al.
(författare)
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Cross-Layer Resource Allocation Model for Cellular-Relaying Network Performance Evaluation
- 2011
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 60:6, s. 2765-2776
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Tidskriftsartikel (refereegranskat)abstract
- The enhancement of cellular networks with relaying technologies is expected to bring significant technoeconomic benefits at the expense of more complex resource allocation. Suitable models for solving network dimensioning problems in cellular-relaying networks must handle radio resource allocation among hundreds of links and tackle interactions between networking layers. For this purpose, we propose a novel cross-layer resource allocation model based on average interference and ideal rate adaptation for the physical layer (PHY), time shares for the medium access layer, and fluid flows for the transport and network layers. We formulate a centralized social welfare maximization problem. When the routes are selected with an a priori algorithm, we show that the resource allocation problem admits an equivalent convex formulation. We show a numerical example for how to use the proposed framework for configuring the backhaul link in a practical relaying network. The overall problem of selecting routes and allocating time shares and link rates is nonconvex. We propose an iterative suboptimal algorithm to solve the problem based on a novel approximation of PHY. We state and prove several convergence properties of the algorithm and show that it typically outperforms routing based on signal-to-noise ratio only.
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| 33. |
- Timus, Bogdan, et al.
(författare)
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Implications of fairness criteria on the techno-economic viability of relaying networks
- 2009
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Ingår i: 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE. - 9781424425167 ; , s. 3050-3054
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Konferensbidrag (refereegranskat)abstract
- The introduction of relaying techniques into cellular networks is expected to reduce the total infrastructure cost, especially when coverage extension is sought. With the advent of networks such as LTE, guaranteeing high data-rate coverage may become a challenge even for incumbent operators which nowadays provide full coverage for voice service. However it is not straightforward that operators will be able (or want) to guarantee coverage for the high data-rates. In this paper we study how the techno-economic viability of the relaying solution depends on the type of service to be provided by the operator. We exemplify the trade off between coverage and system throughput with two fairness criteria: perfect fairness (coverage guarantee) and proportional fairness. We show that relays provide advantages when the operator is interested in providing bit-rate/QoS guarantees. When maximizing the system throughput or cell capacity, relays are of less value.
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| 34. |
- Zhang, Haibo, et al.
(författare)
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Optimal Link Scheduling and Channel Assignment for Convergecast in Linear Wireless HART Networks
- 2009
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Ingår i: 2009 7TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS. - NEW YORK : Institute of Electrical and Electronics Engineers (IEEE). - 9781424449194 ; , s. 82-89
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Konferensbidrag (refereegranskat)abstract
- Convergecast, in which data from a set of sources is routed toward one data sink, is a critical functionality for wireless networks deployed for industrial monitoring and control. We address the joint link scheduling and channel assignment problem for convergecast in networks operating according to the recent WirelessHART standard. For a linear network with N single-buffer devices, we demonstrate that the minimum time to complete convergecast is 2N - 1 time-slots, and that the minimum number of channels required for this operation is inverted right perpendicularN/2inverted left perpendicular. When the devices are allowed to buffer multiple packets, we prove that the optimal convergecast time remains the same while the number of required channels can be reduced to inverted right perpendicularN - root N-(N-1)/2inverted left perpendicular. For both cases, we present jointly time- and channel-optimal scheduling policies with complexity O(N-2). Numerical results demonstrate that our schemes are also efficient in terms of memory utilization.
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| 35. |
- Zhang, Haibo, et al.
(författare)
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Performance Bounds and Latency-Optimal Scheduling for Convergecast in WirelessHART Networks
- 2013
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 12:6, s. 2688-2696
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Tidskriftsartikel (refereegranskat)abstract
- Convergecast, in which data from a set of source devices is delivered to a single data sink, is a critical functionality in networks deployed for industrial monitoring and control. We address the latency-optimal link scheduling problem for convergecast in networks operating according to the recent WirelessHART standard. When there is no restriction on the number of channels, we present a latency-optimal scheduling policy in which each routing node is required to buffer at most one packet at any point in time. For networks with a limited number of channels, we first establish a lower bound on the number of channels for latency-optimal convergecast and a lower bound on latency for convergecast using a fixed number of channels, and then present a heuristic scheme for channel-constrained latency-optimal convergecast scheduling. Simulation results confirm that, at much modest computational cost, our heuristic scheme can construct convergecast schedules with latency close to that of the optimal schedules.
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| 36. |
- Zhang, Haibo, et al.
(författare)
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Rapid convergecast on commodity hardware : Performance limits and optimal policies
- 2010
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Ingår i: SECON 2010 - 2010 7th Annual IEEE Communications Society Conference on Sensor. - 9781424471515
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Konferensbidrag (refereegranskat)abstract
- The increased industrial interest in wireless sensor networks demands a shift from optimizing protocols for reporting sporadic events, to solutions for high-rate data collection and dissemination. We study time-optimal convergecast under the communication constraints of commodity sensor network platforms. We propose a novel convergecast model in which packet copying between the microcontroller and the radio transceiver is separated from packet transmission, thereby improving channel utilization and system throughput. Based on this model, we establish the tight lower bound on the number of time slots for convergecast in networks with tree routing topology, and present both centralized and distributed algorithms for computing time-optimal convergecast schedules. Our scheme is memory-efficient as each node buffers at most one packet at any time. We evaluate our scheme in simulation and on real hardware, and show that our scheme can achieve a throughput of 203 kbit/s (86.4% of the theoretical upper bound): up to 86.24 % improvement compared with traditional TDMA-based convergecast. With an optimal routing tree and the maximum MAC layer payload, convergecast in a network with 20 sensor nodes can be completed in only 100ms.
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| 37. |
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| 38. |
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| 39. |
- Zhang, Haibo, et al.
(författare)
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Time-optimal convergecast with separated packet copying : Scheduling policies and performance
- 2015
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 54:2, s. 793-803
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Tidskriftsartikel (refereegranskat)abstract
- Convergecast, in which packets originating from multiple sources are reported to a single sink, is a fundamental primitive for data collection in wireless sensor networks. This paper investigates the time-optimal link-scheduling problem for time-division multiple-access (TDMA)-based convergecast, aiming to minimize the amount of time required to complete convergecast. We observe that packet copying between the microcontroller and the radio transceiver in existing sensor platforms has a big impact on the packet forwarding delay, and we propose a novel model for convergecast in which packet copying is separated from packet transmission and reception. We establish tight lower bounds on the number of time slots required for convergecast in networks with line and tree routing topologies, and we present both centralized and distributed algorithms for constructing the time-optimal convergecast schedules. We evaluate our scheme in both simulations and experiments on hardware. The results show that our scheme can achieve a system throughput (defined as the number of data bits received by the sink per second) of 202.8 kb/s, which is 86.31% of the theoretical bound. In comparison with the traditional TDMA-based convergecast schemes, our scheme can achieve up to a 86.22% improvement on system throughput.
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| 40. |
- Zou, Zhenhua, et al.
(författare)
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Delay-constrained maximum reliability routing over lossy links
- 2010
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - : IEEE. - 9781424477456 ; , s. 973-978
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Konferensbidrag (refereegranskat)abstract
- This paper studies the problem of joint routing and transmission scheduling for reliable real-time communication over lossy networks. We impose a strict latency bound on the packet delivery from source to destination and develop transmission scheduling policies that maximize the probability that the packet is delivered within the specified deadline. A solution to this problem allows to characterize the set of achievable latencies and packet loss probabilities for a given network. We develop dynamic programming-based solutions for deadline-constrained maximum reliability routing under Bernoulli and Gilbert-Elliot packet loss models. Particular instances of the problem that admit numerically efficient solutions are discussed and our results are demonstrated on several examples.
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| 41. |
- Zou, Zhenhua, et al.
(författare)
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Energy-efficient deadline-constrained maximum reliability forwarding in lossy networks
- 2012
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 11:10, s. 3474-3483
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the problem of optimal forwarding for reliable and energy-efficient real-time communication over multi-hop wireless lossy networks. We impose a strict per-packet latency bound and develop forwarding policies that maximize the probability that the packet is delivered within the specified deadline minus a transmission energy cost. A solution to this problem allows to characterize the set of achievable latency-reliability pairs and to trace out the Pareto frontier between achievable deadline-constrained reliability and transmission energy cost. We develop dynamic programming-based solutions under a finite-state Markov channel model. Particular instances with Bernoulli and Gilbert-Elliot loss models that admit numerically efficient solutions are discussed and our results are demonstrated on several examples.
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