3 research outputs found
Wireless Powered Communications: Performance Analysis and Optimization
This paper investigates the average throughput of a wireless powered
communications system, where an energy constrained source, powered by a
dedicated power beacon (PB), communicates with a destination. It is assumed
that the PB is capable of performing channel estimation, digital beamforming,
and spectrum sensing as a communication device. Considering a time splitting
approach, the source first harvests energy from the PB equipped with multiple
antennas, and then transmits information to the destination. Assuming
Nakagami-m fading channels, analytical expressions for the average throughput
are derived for two different transmission modes, namely, delay tolerant and
delay intolerant. In addition, closed-form solutions for the optimal time
split, which maximize the average throughput are obtained in some special
cases, i.e., high transmit power regime and large number of antennas. Finally,
the impact of co-channel interference is studied. Numerical and simulation
results have shown that increasing the number of transmit antennas at the PB is
an effective tool to improve the average throughput and the interference can be
potentially exploited to enhance the average throughput, since it can be
utilized as an extra source of energy. Also, the impact of fading severity
level of the energy transfer link on the average throughput is not significant,
especially if the number of PB antennas is large. Finally, it is observed that
the source position has a great impact on the average throughput.Comment: accepted to appear in IEEE Transactions on Communication
Energy-Efficient Resource Allocation for Wireless Powered Communication Networks
This paper considers a wireless powered communication network (WPCN), where
multiple users harvest energy from a dedicated power station and then
communicate with an information receiving station. Our goal is to investigate
the maximum achievable energy efficiency (EE) of the network via joint time
allocation and power control while taking into account the initial battery
energy of each user. We first study the EE maximization problem in the WPCN
without any system throughput requirement. We show that the EE maximization
problem for the WPCN can be cast into EE maximization problems for two
simplified networks via exploiting its special structure. For each problem, we
derive the optimal solution and provide the corresponding physical
interpretation, despite the non-convexity of the problems. Subsequently, we
study the EE maximization problem under a minimum system throughput constraint.
Exploiting fractional programming theory, we transform the resulting non-convex
problem into a standard convex optimization problem. This allows us to
characterize the optimal solution structure of joint time allocation and power
control and to derive an efficient iterative algorithm for obtaining the
optimal solution. Simulation results verify our theoretical findings and
demonstrate the effectiveness of the proposed joint time and power
optimization.Comment: Transactions on Wireless Communication
Fundamental Green Tradeoffs: Progresses, Challenges, and Impacts on 5G Networks
With years of tremendous traffic and energy consumption growth, green radio
has been valued not only for theoretical research interests but also for the
operational expenditure reduction and the sustainable development of wireless
communications. Fundamental green tradeoffs, served as an important framework
for analysis, include four basic relationships: spectrum efficiency (SE) versus
energy efficiency (EE), deployment efficiency (DE) versus energy efficiency
(EE), delay (DL) versus power (PW), and bandwidth (BW) versus power (PW). In
this paper, we first provide a comprehensive overview on the extensive on-going
research efforts and categorize them based on the fundamental green tradeoffs.
We will then focus on research progresses of 4G and 5G communications, such as
orthogonal frequency division multiplexing (OFDM) and non-orthogonal
aggregation (NOA), multiple input multiple output (MIMO), and heterogeneous
networks (HetNets). We will also discuss potential challenges and impacts of
fundamental green tradeoffs, to shed some light on the energy efficient
research and design for future wireless networks.Comment: revised from IEEE Communications Surveys & Tutorial