791 research outputs found
Power Control for D2D Underlay in Multi-cell Massive MIMO Networks
This paper proposes a new power control and pilot allocation scheme for
device-to-device (D2D) communication underlaying a multi-cell massive MIMO
system. In this scheme, the cellular users in each cell get orthogonal pilots
which are reused with reuse factor one across cells, while the D2D pairs share
another set of orthogonal pilots. We derive a closed-form capacity lower bound
for the cellular users with different receive processing schemes. In addition,
we derive a capacity lower bound for the D2D receivers and a closed-form
approximation of it. Then we provide a power control algorithm that maximizes
the minimum spectral efficiency (SE) of the users in the network. Finally, we
provide a numerical evaluation where we compare our proposed power control
algorithm with the maximum transmit power case and the case of conventional
multi-cell massive MIMO without D2D communication. Based on the provided
results, we conclude that our proposed scheme increases the sum spectral
efficiency of multi-cell massive MIMO networks.Comment: 6 Pages, 3 Figures, WSA 201
Energy Efficiency and Sum Rate Tradeoffs for Massive MIMO Systems with Underlaid Device-to-Device Communications
In this paper, we investigate the coexistence of two technologies that have
been put forward for the fifth generation (5G) of cellular networks, namely,
network-assisted device-to-device (D2D) communications and massive MIMO
(multiple-input multiple-output). Potential benefits of both technologies are
known individually, but the tradeoffs resulting from their coexistence have not
been adequately addressed. To this end, we assume that D2D users reuse the
downlink resources of cellular networks in an underlay fashion. In addition,
multiple antennas at the BS are used in order to obtain precoding gains and
simultaneously support multiple cellular users using multiuser or massive MIMO
technique. Two metrics are considered, namely the average sum rate (ASR) and
energy efficiency (EE). We derive tractable and directly computable expressions
and study the tradeoffs between the ASR and EE as functions of the number of BS
antennas, the number of cellular users and the density of D2D users within a
given coverage area. Our results show that both the ASR and EE behave
differently in scenarios with low and high density of D2D users, and that
coexistence of underlay D2D communications and massive MIMO is mainly
beneficial in low densities of D2D users.Comment: 30 pages, 10 figures, Submitte
Energy Efficiency in MIMO Underlay and Overlay Device-to-Device Communications and Cognitive Radio Systems
This paper addresses the problem of resource allocation for systems in which
a primary and a secondary link share the available spectrum by an underlay or
overlay approach. After observing that such a scenario models both cognitive
radio and D2D communications, we formulate the problem as the maximization of
the secondary energy efficiency subject to a minimum rate requirement for the
primary user. This leads to challenging non-convex, fractional problems. In the
underlay scenario, we obtain the global solution by means of a suitable
reformulation. In the overlay scenario, two algorithms are proposed. The first
one yields a resource allocation fulfilling the first-order optimality
conditions of the resource allocation problem, by solving a sequence of easier
fractional problems. The second one enjoys a weaker optimality claim, but an
even lower computational complexity. Numerical results demonstrate the merits
of the proposed algorithms both in terms of energy-efficient performance and
complexity, also showing that the two proposed algorithms for the overlay
scenario perform very similarly, despite the different complexity.Comment: to appear in IEEE Transactions on Signal Processin
Energy Efficiency and Sum Rate when Massive MIMO meets Device-to-Device Communication
This paper considers a scenario of short-range communication, known as
device-to-device (D2D) communication, where D2D users reuse the downlink
resources of a cellular network to transmit directly to their corresponding
receivers. In addition, multiple antennas at the base station (BS) are used in
order to simultaneously support multiple cellular users using multiuser or
massive MIMO. The network model considers a fixed number of cellular users and
that D2D users are distributed according to a homogeneous Poisson point process
(PPP). Two metrics are studied, namely, average sum rate (ASR) and energy
efficiency (EE). We derive tractable expressions and study the tradeoffs
between the ASR and EE as functions of the number of BS antennas and density of
D2D users for a given coverage area.Comment: 6 pages, 7 figures, to be presented at the IEEE International
Conference on Communications (ICC) Workshop on Device-to-Device Communication
for Cellular and Wireless Networks, London, UK, June 201
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