8,303 research outputs found
Cooperative relaying in cellular networks for improving receiver diversity and cell radius
Title from PDF of title page, viewed on June 28, 2013Thesis advisor: Cory BeardVitaIncludes bibliographic references (pages 54-56)Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2013Wireless network sharing has been the principal idea in the recent developments of wireless communication systems not only for improvement in capacity, data rates and coverage area but when considering an emergency service model, establishing reliable communication is the foremost requirement. With the inception of cooperative relaying technology, a novel wireless relaying method of sharing the terminal node capabilities to forward the signal created a new paradigm to greatly improve the quality of the services and soon became the significant research area in 3G/4G cellular networks. The cooperative terminals (relays) exploit a larger form of space diversity to relay signals to destinations when placed in between source and destination to combat the effects of fading induced by multipath signal propagation. However, the position of the relay in between the source and destination plays a significant role in affecting the overall network performance. Our attempt in this thesis is to show how a cooperative relay can be used to provide improved coverage at the cell edge with certain reliability and also extend the cell radius by effectively positioning the relay. First, we investigate the famous 3-node relay assisted cellular system model and study the receiver diversity combining results by changing the relay positions with a relay forwarding the signal using the amplitude and forward protocol (AAF). The figure of merit of the considered 3-node system model is expressed in terms of Bit error rate (BER) and signal to noise ratio (SNR). The BER vs. SNR plots are computed for various linear receiver diversity combining techniques and are used to evaluate performance of the system. These results are also compared to the conventional cellular network performance with a single point-to-point link between source and destination. Second, we provide the problem formulation of the diversity results observed and solve to find the effective relay position with respect to the source and also compute the effective cell radius of the 3-node system model. To compute effective relay position, we use the Bernardin's coverage area probability relation with cell radius at the cell edge of the source where the relay is assumed to be placed with its probability of successfully forwarding the signal conditionally depending on its cell edge probability. We have obtained results of the two above problem formulations using MATLAB simulations. We have emulated the cooperative relaying technique in a cellular system to achieve 2nd order diversity when compared to the conventional cellular system. The BER vs. SNR plots for each of the combining techniques show the significant difference in the diversity results when the channel quality estimations are used compared to the other methods which don't. Signal to noise ratio combining (SNRC) and Estimated SNRC (ESNRC) perform 4≅5dB better than the other combining methods provided their SNR estimation is accurate. The highest diversity order (2nd) is achieved when the relay is placed close to the source and drops as the relay is moved towards the destination. Cell range extension results show that moving the relay to its optimal position between source and destination in a cell provides capabilities to extend the cell range to nearly 1.5 times the cell radius of the source and still performs within the acceptable coverage area probabilities.Introduction -- Literature survey -- Legacy cellular system model and problem description -- Relay system model for improved signal quality -- Relay system model for coverage extension -- Conclusion and future wor
Cooperative Transmission Protocols with High Spectral Efficiency and High Diversity Order Using Multiuser Detection and Network Coding
Cooperative transmission is an emerging communication technique that takes
advantages of the broadcast nature of wireless channels. However, due to low
spectral efficiency and the requirement of orthogonal channels, its potential
for use in future wireless networks is limited. In this paper, by making use of
multiuser detection (MUD) and network coding, cooperative transmission
protocols with high spectral efficiency, diversity order, and coding gain are
developed. Compared with the traditional cooperative transmission protocols
with single-user detection, in which the diversity gain is only for one source
user, the proposed MUD cooperative transmission protocols have the merits that
the improvement of one user's link can also benefit the other users. In
addition, using MUD at the relay provides an environment in which network
coding can be employed. The coding gain and high diversity order can be
obtained by fully utilizing the link between the relay and the destination.
From the analysis and simulation results, it is seen that the proposed
protocols achieve higher diversity gain, better asymptotic efficiency, and
lower bit error rate, compared to traditional MUD and to existing cooperative
transmission protocols.Comment: to appear, in the proceedings of IEEE International Conference on
Communications, Glasgow, Scotland, 24-28 June 200
Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks
Conventional cellular wireless networks were designed with the purpose of
providing high throughput for the user and high capacity for the service
provider, without any provisions of energy efficiency. As a result, these
networks have an enormous Carbon footprint. In this paper, we describe the
sources of the inefficiencies in such networks. First we present results of the
studies on how much Carbon footprint such networks generate. We also discuss
how much more mobile traffic is expected to increase so that this Carbon
footprint will even increase tremendously more. We then discuss specific
sources of inefficiency and potential sources of improvement at the physical
layer as well as at higher layers of the communication protocol hierarchy. In
particular, considering that most of the energy inefficiency in cellular
wireless networks is at the base stations, we discuss multi-tier networks and
point to the potential of exploiting mobility patterns in order to use base
station energy judiciously. We then investigate potential methods to reduce
this inefficiency and quantify their individual contributions. By a
consideration of the combination of all potential gains, we conclude that an
improvement in energy consumption in cellular wireless networks by two orders
of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843
Green Cellular Networks: A Survey, Some Research Issues and Challenges
Energy efficiency in cellular networks is a growing concern for cellular
operators to not only maintain profitability, but also to reduce the overall
environment effects. This emerging trend of achieving energy efficiency in
cellular networks is motivating the standardization authorities and network
operators to continuously explore future technologies in order to bring
improvements in the entire network infrastructure. In this article, we present
a brief survey of methods to improve the power efficiency of cellular networks,
explore some research issues and challenges and suggest some techniques to
enable an energy efficient or "green" cellular network. Since base stations
consume a maximum portion of the total energy used in a cellular system, we
will first provide a comprehensive survey on techniques to obtain energy
savings in base stations. Next, we discuss how heterogeneous network deployment
based on micro, pico and femto-cells can be used to achieve this goal. Since
cognitive radio and cooperative relaying are undisputed future technologies in
this regard, we propose a research vision to make these technologies more
energy efficient. Lastly, we explore some broader perspectives in realizing a
"green" cellular network technologyComment: 16 pages, 5 figures, 2 table
Dispensing with channel estimation: differentially modulated cooperative wireless communications
As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective
Performance Analysis of Micro Unmanned Airborne Communication Relays for Cellular Networks
This paper analyses the potential of utilising small unmanned-aerial-vehicles
(SUAV) as wireless relays for assisting cellular network performance. Whilst
high altitude wireless relays have been investigated over the past 2 decades,
the new class of low cost SUAVs offers new possibilities for addressing local
traffic imbalances and providing emergency coverage.We present field-test
results from an SUAV test-bed in both urban and rural environments. The results
show that trough-to-peak throughput improvements can be achieved for users in
poor coverage zones. Furthermore, the paper reinforces the experimental study
with large-scale network analysis using both stochastic geometry and multi-cell
simulation results.Comment: conferenc
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