605 research outputs found
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
Cooperative Relaying In Power Line Environment: A Survey and Tutorial
Exchange of information is essential in any society and the demand for faster, cheaper, and secure
communications is increasing every day. With other hi-tech initiatives like IPv6 and Internet-of-Things (IOT) already
in the horizon, demand for broadband is set to escalate beyond its current level. Inherently laden in the challenges
posed by this technology are fresh opportunities in terms of penetration of data services into rural communities and
development of innovative strategies for more efficient use of the grid. Though still in its developmental phase/stage,
Power Line Communication (PLC) has grown beyond theoretical fantasy to become a reality. The proofs are the
readily available PLC systems that can be purchased off the shelfto achieve in-house networking and the much talked
about, smart metering technology; generally regarded as the “new bride” in utilities industry. One of the biggest gains
of PLC is its use of existing electrical cables, thereby eliminating cost of installation and maintenance of data cables.
However, given that the power infrastructure was traditionally built to deliver electricity, data signals do suffer various
forms of distortions and impairments as they transit it. This paper presents a tutorial on the deployed wireless system
technique which is to be adapted to PLC scenario for the purpose of managing the available source energy for
achieving reliable communication system. One of these techniques is the cooperative diversity. Its application and
deployment in power line environment is explored. The improvement achieved through cooperative diversity in some
PLC systems were presented along with the associated limitations. Finally, future areas of research which will further
improve the reliability of PLC systems and reduce its power consumption during transmission is shown
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
Multi-Source Cooperative Communication with Opportunistic Interference Cancelling Relays
In this paper we present a multi-user cooperative protocol for wireless
networks. Two sources transmit simultaneously their information blocks and
relays employ opportunistically successive interference cancellation (SIC) in
an effort to decode them. An adaptive decode/amplify-and-forward scheme is
applied at the relays to the decoded blocks or their sufficient statistic if
decoding fails. The main feature of the protocol is that SIC is exploited in a
network since more opportunities arise for each block to be decoded as the
number of used relays NRU is increased. This feature leads to benefits in terms
of diversity and multiplexing gains that are proven with the help of an
analytical outage model and a diversity-multiplexing tradeoff (DMT) analysis.
The performance improvements are achieved without any network synchronization
and coordination. In the final part of this work the closed-form outage
probability model is used by a novel approach for offline pre-selection of the
NRU relays, that have the best SIC performance, from a larger number of NR
nodes. The analytical results are corroborated with extensive simulations,
while the protocol is compared with orthogonal and multi-user protocols
reported in the literature.Comment: in IEEE Transactions on Communications, 201
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