404 research outputs found
ORLA/OLAA: Orthogonal Coexistence of LAA and WiFi in Unlicensed Spectrum
Future mobile networks will exploit unlicensed
spectrum to boost capacity and meet growing user demands
cost-effectively. The 3rd Generation Partnership Project (3GPP)
has recently defined a License Assisted Access (LAA) scheme
to enable global Unlicensed LTE (U-LTE) deployment, aiming
at 1) ensuring fair coexistence with incumbent WiFi networks,
i.e., impacting on their performance no more than another
WiFi device; and 2) achieving superior airtime efficiency as
compared with WiFi. We show the standardized LAA fails to
simultaneously fulfill these objectives, and design an alternative
orthogonal (collision-free) listen-before-talk coexistence paradigm
that provides a substantial improvement in performance, yet
imposes no penalty on existing WiFi networks. We derive two
optimal transmission policies, ORLA and OLAA, that maximize
LAA throughput in both asynchronous and synchronous (i.e.,
with alignment to licensed anchor frame boundaries) modes of
operation, respectively. We present a comprehensive evaluation
through which we demonstrate that, when aggregating packets,
IEEE 802.11ac WiFi can be more efficient than LAA, whereas
our proposals attains 100% higher throughput, without harming
WiFi. We further show that long U-LTE frames incur up to
92% throughput losses on WiFi when using 3GPP LAA, whilst
ORLA/OLAA sustain >200% gains at no cost, even in the
presence of non-saturated WiFi and/or in multi-rate scenarios.This work was supported in part by the EC H2020 5G-Transformer Project under Grant 761536
ORLA/OLAA: Orthogonal Coexistence of LAA and WiFi in Unlicensed Spectrum
Future mobile networks will exploit unlicensed spectrum to boost capacity and
meet growing user demands cost-effectively. The 3GPP has recently defined a
Licensed-Assisted Access (LAA) scheme to enable global Unlicensed LTE (U-LTE)
deployment, aiming at () ensuring fair coexistence with incumbent WiFi
networks, i.e., impacting on their performance no more than another WiFi
device, and () achieving superior airtime efficiency as compared to WiFi.
In this paper we show the standardized LAA fails to simultaneously fulfill
these objectives, and design an alternative orthogonal (collision-free)
listen-before-talk coexistence paradigm that provides a substantial improvement
in performance, yet imposes no penalty on existing WiFi networks. We derive two
LAA optimal transmission policies, ORLA and OLAA, that maximize LAA throughput
in both asynchronous and synchronous (i.e., with alignment to licensed anchor
frame boundaries) modes of operation, respectively. We present a comprehensive
performance evaluation through which we demonstrate that, when aggregating
packets, IEEE 802.11ac WiFi can be more efficient than 3GPP LAA, whereas our
proposals can attain 100% higher throughput, without harming WiFi. We further
show that long U-LTE frames incur up to 92% throughput losses on WiFi when
using 3GPP LAA, whilst ORLA/OLAA sustain 200% gains at no cost, even in the
presence of non-saturated WiFi and/or in multi-rate scenarios.Comment: 14 pages, 7 figures, submitted to IEEE/ACM Transactions on Networkin
Enabling Ultra-Reliable and Low-Latency Communications through Unlicensed Spectrum
© 2018 IEEE. In this article, we aim to address the question of how to exploit the unlicensed spectrum to achieve URLLC. Potential URLLC PHY mechanisms are reviewed and then compared via simulations to demonstrate their potential benefits to URLLC. Although a number of important PHY techniques help with URLLC, the PHY layer exhibits an intrinsic trade-off between latency and reliability, posed by limited and unstable wireless channels. We then explore MAC mechanisms and discuss multi-channel strategies for achieving low-latency LTE unlicensed band access. We demonstrate, via simulations, that the periods without access to the unlicensed band can be substantially reduced by maintaining channel access processes on multiple unlicensed channels, choosing the channels intelligently, and implementing RTS/CTS
Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives
© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements
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Spectrum utilization using game theory
This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.Spectrum utilization is the most recent communications issue which takes great deal of attention from communication researchers where most of the efforts have been dedicated for spectral efficient utilization. Spectrum sharing is one of the solutions considered in the problem of lack of available frequency for new communication services which are unlicensed. In this work we propose an optimal method for spectrum utilization to increase spectral efficiency. It considers the problem of spectrum holes found in Primary User's (PU) band and detected using one of the spectral sensing methods. The solution is formulated with the help of Game theory approach in such a way that the primary user who has unoccupied frequency can share it with a group of secondary users (SU) in a competitive way. One of the SUs will be a secondary primary user (SPU), share available frequency from PU then offer his sharing to serve other SUs in different rate of sharing. Each user in the group of secondary users has a chance to be secondary primary user depending on reputation of each SU. Enhancing reputation is the only way for any SU to assure a share in the spectrum where it considered the factor of increasing or decreasing rate of sharing as well as factor of being SPU or an ordinary SU. A theoretical non-cooperative game model is introduced in a comparison with a proposed non-dynamic technique which depends on number of subscribers who occupy frequency in each time period. Multi-users compete on sharing the frequency from one of the users who offers sharing at a time when he has low number of subscribers that occupy his band. It is found that non-dynamic sharing results in inefficient spectrum utilization which is one of the reasons of spectrum scarcity where this resource is allocated in fixed way. Spectrum sharing using game theory solves this problem by its ability to make users compete to gain highest rate of spectrum allocation according to the real requirement of each user at each time interval. The problem of urgent case is also discussed when the primary user comes back to using his band which is the specific band of sharing with the secondary users group. SPU makes it easy to unload the required band from multi-users because PU does not need to request his band from each SU in the group
TV White Spaces: A Pragmatic Approach
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Cognitive MAC protocols for mobile Ad-Hoc networks
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The term of Cognitive Radio (CR) used to indicate that spectrum radio could be accessed dynamically and opportunistically by unlicensed users. In CR Networks, Interference between nodes, hidden terminal problem, and spectrum sensing errors are big issues to be widely discussed in the research field nowadays. To improve the performance of such kind of networks, this thesis proposes Cognitive Medium Access Control (MAC) protocols for Mobile Ad-Hoc Networks (MANETs). From the concept of CR, this thesis has been able to develop a cognitive MAC framework in which a cognitive process consisting of cognitive elements is considered, which can make efficient decisions to optimise the CR network. In this context, three different scenarios to maximize the secondary user's throughput have been proposed. We found that the throughput improvement depends on the transition probabilities. However, considering the past information state of the spectrum can dramatically increases the secondary user's throughput by up to 40%. Moreover, by increasing the number of channels, the throughput of the network can be improved about 25%. Furthermore, to study the impact of Physical (PHY) Layer errors on cognitive MAC layer in MANETs, in this thesis, a Sensing Error-Aware MAC protocols for MANETs has been proposed. The developed model has been able to improve the MAC layer performance under the challenge of sensing errors. In this context, the proposed model examined two sensing error probabilities: the false alarm probability and the missed detection probability. The simulation results have shown that both probabilities could be adapted to maintain the false alarm probability at certain values to achieve good results. Finally, in this thesis, a cooperative sensing scheme with interference mitigation for Cognitive Wireless Mesh Networks (CogMesh) has been proposed. Moreover, a prioritybased traffic scenario to analyze the problem of packet delay and a novel technique for dynamic channel allocation in CogMesh is presented. Considering each channel in the system as a sub-server, the average delay of the users' packets is reduced and the cooperative sensing scenario dramatically increases the network throughput 50% more as the number of arrival rate is increased
Belaidžio ryšio tinklų terpės prieigos valdymo tyrimas
Over the years, consumer requirements for Quality of Service (QoS) has been growing exponentially. Recently, the ratification process of newly IEEE 802.11ad amendment to IEEE 802.11 was finished. The IEEE 802.11ad is the newly con-sumer wireless communication approach, which will gain high spot on the 5G evolution. Major players in wireless market, such as Qualcomm already are inte-grating solutions from unlicensed band, like IEEE 802.11ac, IEEE 802.11ad into their architecture of LTE PRO (the next evolutionary step for 5G networking) (Qualcomm 2013; Parker et al. 2015). As the demand is growing both in enter-prise wireless networking and home consumer markets. Consumers started to no-tice the performance degradation due to overcrowded unlicensed bands. The un-licensed bands such as 2.4 GHz, 5 GHz are widely used for up-to-date IEEE 802.11n/ac technologies with upcoming IEEE 802.11ax. However, overusage of the available frequency leads to severe interference issue and consequences in to-tal system performance degradation, currently existing wireless medium access method can not sustain the increasing intereference and thus wireless needs a new methods of wireless medium access. The main focal point of this dissertation is to improve wireless performance in dense wireless networks. In dissertation both the conceptual and multi-band wireless medium access methods are considered both from theoretical point of view and experimental usage.
The introduction chapter presents the investigated problem and it’s objects of research as well as importance of dissertation and it’s scientific novelty in the unlicensed wireless field.
Chapter 1 revises used literature. Existing and up-to-date state-of-the-art so-lution are reviewed, evaluated and key point advantages and disadvantages are analyzed. Conclusions are drawn at the end of the chapter.
Chapter 2 describes theoretical analysis of wireless medium access protocols and the new wireless medium access method. During analysis theoretical simula-tions are performed. Conclusions are drawn at the end of the chapter.
Chapter 3 is focused on the experimental components evaluation for multi-band system, which would be in line with theoretical concept investigations. The experimental results, showed that components of multi-band system can gain sig-nificant performance increase when compared to the existing IEEE 802.11n/ac wireless systems.
General conclusions are drawn after analysis of measurement results
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