462 research outputs found
Portability, compatibility and reuse of MAC protocols across different IoT radio platforms
To cope with the diversity of Internet of Things (loT) requirements, a large number of Medium Access Control (MAC) protocols have been proposed in scientific literature, many of which are designed for specific application domains. However, for most of these MAC protocols, no multi-platform software implementation is available. In fact, the path from conceptual MAC protocol proposed in theoretical papers, towards an actual working implementation is rife with pitfalls. (i) A first problem is the timing bugs, frequently encountered in MAC implementations. (ii) Furthermore, once implemented, many MAC protocols are strongly optimized for specific hardware, thereby limiting the potential of software reuse or modifications. (iii) Finally, in real-life conditions, the performance of the MAC protocol varies strongly depending on the actual underlying radio chip. As a result, the same MAC protocol implementation acts differently per platform, resulting in unpredictable/asymmetrical behavior when multiple platforms are combined in the same network. This paper describes in detail the challenges related to multi-platform MAC development, and experimentally quantifies how the above issues impact the MAC protocol performance when running MAC protocols on multiple radio chips. Finally, an overall methodology is proposed to avoid the previously mentioned cross-platform compatibility issues. (C) 2018 Elsevier B.V. All rights reserved
Airborne Directional Networking: Topology Control Protocol Design
This research identifies and evaluates the impact of several architectural design choices in relation to airborne networking in contested environments related to autonomous topology control. Using simulation, we evaluate topology reconfiguration effectiveness using classical performance metrics for different point-to-point communication architectures. Our attention is focused on the design choices which have the greatest impact on reliability, scalability, and performance. In this work, we discuss the impact of several practical considerations of airborne networking in contested environments related to autonomous topology control modeling. Using simulation, we derive multiple classical performance metrics to evaluate topology reconfiguration effectiveness for different point-to-point communication architecture attributes for the purpose of qualifying protocol design elements
On the performance of STDMA Link Scheduling and Switched Beamforming Antennas in Wireless Mesh Networks
Projecte final de carrera realitzat en col.laboració amb King's College LondonWireless Mesh Networks (WMNs) aim to revolutionize Internet connectivity due to
its high throughput, cost-e ectiveness and ease deployment by providing last mile
connectivity and/or backhaul support to di erent cellular networks. In order not to
jeopardize their successful deployment, several key issues must be investigated and
overcome to fully realize its potential. For WMNs that utilize Spatial Reuse TDMA
as the medium access control, link scheduling still requires further enhancements.
The rst main contribution of this thesis is a fast randomized parallel link swap
based packing (RSP) algorithm for timeslot allocation in a spatial time division multiple
access (STDMA) wireless mesh network. The proposed randomized algorithm
extends several greedy scheduling algorithms that utilize the physical interference
model by applying a local search that leads to a substantial improvement in the
spatial timeslot reuse. Numerical simulations reveal that compared to previously
scheduling schemes the proposed randomized algorithm can achieve a performance
gain of up to 11%. A signi cant bene t of the proposed scheme is that the computations
can be parallelized and therefore can e ciently utilize commoditized and
emerging multi-core and/or multi-CPU processors.
Furthermore, the use of selectable multi-beam directional antennas in WMNs,
such as beam switched phase array antennas, can assist to signi cantly enhance
the overall reuse of timeslots by reducing interference levels across the network and
thereby increasing the spectral e ciency of the system. To perform though a switch
on the antenna beam it may require up to 0.25 ms in practical deployed networks,
while at the same time very frequent beam switchings can a ect frame acquisition
and overall reliability of the deployed mesh network.
The second key contribution of this thesis is a set of algorithms that minimize the
overall number of required beam switchings in the mesh network without penalizing
the spatial reuse of timeslots, i.e., keeping the same overall frame length in the
network. Numerical investigations reveal that the proposed set of algorithms can
reduce the number of beam switchings by almost 90% without a ecting the frame
length of the network
Managing Shared Access to a Spectrum Commons
The open access, unlicensed or spectrum commons approach to managing shared access to RF spectrum offers many attractive benefits, especially when implemented in conjunction with and as a complement to a regime of marketbased, flexible use, tradable licensed spectrum ([Benkler02], [Lehr04], [Werbach03]). However, as a number of critics have pointed out, implementing the unlicensed model poses difficult challenges that have not been well-addressed yet by commons advocates ([Benjam03], [Faulhab05], [Goodman04], [Hazlett01]). A successful spectrum commons will not be unregulated, but it also need not be command & control by another name. This paper seeks to address some of the implementation challenges associated with managing a spectrum commons. We focus on the minimal set of features that we believe a suitable management protocol, etiquette, or framework for a spectrum commons will need to incorporate. This includes: (1) No transmit only devices; (2) Power restrictions; (3) Common channel signaling; (4) Mechanism for handling congestion and allocating resources among users/uses in times of congestion; (5) Mechanism to support enforcement (e.g., established procedures to verify protocol is in conformance); (6) Mechanism to support reversibility of policy; and (7) Protection for privacy and security. We explain why each is necessary, examine their implications for current policy, and suggest ways in which they might be implemented. We present a framework that suggests a set of design principles for the protocols that will govern a successful commons management regime. Our design rules lead us to conclude that the appropriate Protocols for a Commons will need to be more liquid ([Reed05]) than in the past: (1) Marketbased instead of C&C; (2) Decentralized/distributed; and, (3) Adaptive and flexible (Anonymous, distributed, decentralized, and locally responsive)
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