1,302 research outputs found
Design of Cooperative Non-Orthogonal Multicast Cognitive Multiple Access for 5G Systems:User Scheduling and Performance Analysis
Non-orthogonal multiple access (NOMA) is emerging as a promising, yet challenging, multiple access technology to improve spectrum utilization for the fifth generation (5G) wireless networks. In this paper, the application of NOMA to multicast cognitive radio networks (termed as MCR-NOMA) is investigated. A dynamic cooperative MCR-NOMA scheme is proposed, where the multicast secondary users serve as relays to improve the performance of both primary and secondary networks. Based on the available channel state information (CSI), three different secondary user scheduling strategies for the cooperative MCR-NOMA scheme are presented. To evaluate the system performance, we derive the closed-form expressions of the outage probability and diversity order for both networks. Furthermore, we introduce a new metric, referred to as mutual outage probability to characterize the cooperation benefit compared to non cooperative MCR-NOMA scheme. Simulation results demonstrate significant performance gains are obtained for both networks, thanks to the use of our proposed cooperative MCR-NOMA scheme. It is also demonstrated that higher spatial diversity order can be achieved by opportunistically utilizing the CSI available for the secondary user scheduling
A Simple Cooperative Diversity Method Based on Network Path Selection
Cooperative diversity has been recently proposed as a way to form virtual
antenna arrays that provide dramatic gains in slow fading wireless
environments. However most of the proposed solutions require distributed
space-time coding algorithms, the careful design of which is left for future
investigation if there is more than one cooperative relay. We propose a novel
scheme, that alleviates these problems and provides diversity gains on the
order of the number of relays in the network. Our scheme first selects the best
relay from a set of M available relays and then uses this best relay for
cooperation between the source and the destination. We develop and analyze a
distributed method to select the best relay that requires no topology
information and is based on local measurements of the instantaneous channel
conditions. This method also requires no explicit communication among the
relays. The success (or failure) to select the best available path depends on
the statistics of the wireless channel, and a methodology to evaluate
performance for any kind of wireless channel statistics, is provided.
Information theoretic analysis of outage probability shows that our scheme
achieves the same diversity-multiplexing tradeoff as achieved by more complex
protocols, where coordination and distributed space-time coding for M nodes is
required, such as those proposed in [7]. The simplicity of the technique,
allows for immediate implementation in existing radio hardware and its adoption
could provide for improved flexibility, reliability and efficiency in future 4G
wireless systems.Comment: To appear, IEEE JSAC, special issue on 4
Design of Cooperative Non-Orthogonal Multicast Cognitive Multiple Access for 5G Systems:User Scheduling and Performance Analysis
Non-orthogonal multiple access (NOMA) is emerging as a promising, yet challenging, multiple access technology to improve spectrum utilization for the fifth generation (5G) wireless networks. In this paper, the application of NOMA to multicast cognitive radio networks (termed as MCR-NOMA) is investigated. A dynamic cooperative MCR-NOMA scheme is proposed, where the multicast secondary users serve as relays to improve the performance of both primary and secondary networks. Based on the available channel state information (CSI), three different secondary user scheduling strategies for the cooperative MCR-NOMA scheme are presented. To evaluate the system performance, we derive the closed-form expressions of the outage probability and diversity order for both networks. Furthermore, we introduce a new metric, referred to as mutual outage probability to characterize the cooperation benefit compared to non cooperative MCR-NOMA scheme. Simulation results demonstrate significant performance gains are obtained for both networks, thanks to the use of our proposed cooperative MCR-NOMA scheme. It is also demonstrated that higher spatial diversity order can be achieved by opportunistically utilizing the CSI available for the secondary user scheduling
Towards the Optimal Amplify-and-Forward Cooperative Diversity Scheme
In a slow fading channel, how to find a cooperative diversity scheme that
achieves the transmit diversity bound is still an open problem. In fact, all
previously proposed amplify-and-forward (AF) and decode-and-forward (DF)
schemes do not improve with the number of relays in terms of the diversity
multiplexing tradeoff (DMT) for multiplexing gains r higher than 0.5. In this
work, we study the class of slotted amplify-and-forward (SAF) schemes. We first
establish an upper bound on the DMT for any SAF scheme with an arbitrary number
of relays N and number of slots M. Then, we propose a sequential SAF scheme
that can exploit the potential diversity gain in the high multiplexing gain
regime. More precisely, in certain conditions, the sequential SAF scheme
achieves the proposed DMT upper bound which tends to the transmit diversity
bound when M goes to infinity. In particular, for the two-relay case, the
three-slot sequential SAF scheme achieves the proposed upper bound and
outperforms the two-relay non-orthorgonal amplify-and-forward (NAF) scheme of
Azarian et al. for multiplexing gains r < 2/3. Numerical results reveal a
significant gain of our scheme over the previously proposed AF schemes,
especially in high spectral efficiency and large network size regime.Comment: 30 pages, 11 figures, submitted to IEEE trans. IT, revised versio
Improving Third-Party Relaying for LTE-A: A Realistic Simulation Approach
In this article we propose solutions to diverse conflicts that result from
the deployment of the (still immature) relay node (RN) technology in LTE-A
networks. These conflicts and their possible solutions have been observed by
implementing standard-compliant relay functionalities on the Vienna simulator.
As an original experimental approach, we model realistic RN operation, taking
into account that transmitters are not active all the time due to half-duplex
RN operation. We have rearranged existing elements in the simulator in a manner
that emulates RN behavior, rather than implementing a standalone brand-new
component for the simulator. We also study analytically some of the issues
observed in the interaction between the network and the RNs, to draw
conclusions beyond simulation observation.
The main observations of this paper are that: ) Additional time-varying
interference management steps are needed, because the LTE-A standard employs a
fixed time division between eNB-RN and RN-UE transmissions (typical relay
capacity or throughput research models balance them optimally, which is
unrealistic nowadays); ) There is a trade-off between the time-division
constraints of relaying and multi-user diversity; the stricter the constraints
on relay scheduling are, the less flexibility schedulers have to exploit
channel variation; and ) Thee standard contains a variety of parameters
for relaying configuration, but not all cases of interest are covered.Comment: 17 one-column pages, 9 figures, accepted for publication in IEEE ICC
2014 MW
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