750 research outputs found
WiFi and LTE Coexistence in the Unlicensed Spectrum
Today, smart-phones have revolutionized wireless communication industry towards an era of mobile data. To cater for the ever increasing data traffic demand, it is of utmost importance to have more spectrum resources whereby sharing under-utilized spectrum bands is an effective solution. In particular, the 4G broadband Long Term Evolution (LTE) technology and its foreseen 5G successor will benefit immensely if their operation can be extended to the under-utilized unlicensed spectrum. In this thesis, first we analyze WiFi 802.11n and LTE coexistence performance in the unlicensed spectrum considering multi-layer cell layouts through system level simulations. We consider a time division duplexing (TDD)-LTE system with an FTP traffic model for performance evaluation. Simulation results show that WiFi performance is more vulnerable to LTE interference, while LTE performance is degraded only slightly. Based on the initial findings, we propose a Q-Learning based dynamic duty cycle selection technique for configuring LTE transmission gaps, so that a satisfactory throughput is maintained both for LTE and WiFi systems. Simulation results show that the proposed approach can enhance the overall capacity performance by 19% and WiFi capacity performance by 77%, hence enabling effective coexistence of LTE and WiFi systems in the unlicensed band
Survey of Spectrum Sharing for Inter-Technology Coexistence
Increasing capacity demands in emerging wireless technologies are expected to
be met by network densification and spectrum bands open to multiple
technologies. These will, in turn, increase the level of interference and also
result in more complex inter-technology interactions, which will need to be
managed through spectrum sharing mechanisms. Consequently, novel spectrum
sharing mechanisms should be designed to allow spectrum access for multiple
technologies, while efficiently utilizing the spectrum resources overall.
Importantly, it is not trivial to design such efficient mechanisms, not only
due to technical aspects, but also due to regulatory and business model
constraints. In this survey we address spectrum sharing mechanisms for wireless
inter-technology coexistence by means of a technology circle that incorporates
in a unified, system-level view the technical and non-technical aspects. We
thus systematically explore the spectrum sharing design space consisting of
parameters at different layers. Using this framework, we present a literature
review on inter-technology coexistence with a focus on wireless technologies
with equal spectrum access rights, i.e. (i) primary/primary, (ii)
secondary/secondary, and (iii) technologies operating in a spectrum commons.
Moreover, we reflect on our literature review to identify possible spectrum
sharing design solutions and performance evaluation approaches useful for
future coexistence cases. Finally, we discuss spectrum sharing design
challenges and suggest future research directions
LTE Spectrum Sharing Research Testbed: Integrated Hardware, Software, Network and Data
This paper presents Virginia Tech's wireless testbed supporting research on
long-term evolution (LTE) signaling and radio frequency (RF) spectrum
coexistence. LTE is continuously refined and new features released. As the
communications contexts for LTE expand, new research problems arise and include
operation in harsh RF signaling environments and coexistence with other radios.
Our testbed provides an integrated research tool for investigating these and
other research problems; it allows analyzing the severity of the problem,
designing and rapidly prototyping solutions, and assessing them with
standard-compliant equipment and test procedures. The modular testbed
integrates general-purpose software-defined radio hardware, LTE-specific test
equipment, RF components, free open-source and commercial LTE software, a
configurable RF network and recorded radar waveform samples. It supports RF
channel emulated and over-the-air radiated modes. The testbed can be remotely
accessed and configured. An RF switching network allows for designing many
different experiments that can involve a variety of real and virtual radios
with support for multiple-input multiple-output (MIMO) antenna operation. We
present the testbed, the research it has enabled and some valuable lessons that
we learned and that may help designing, developing, and operating future
wireless testbeds.Comment: In Proceeding of the 10th ACM International Workshop on Wireless
Network Testbeds, Experimental Evaluation & Characterization (WiNTECH),
Snowbird, Utah, October 201
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