5 research outputs found
Multi-antenna Enabled Cluster-based Cooperation in Wireless Powered Communication Networks
In this paper, we consider a wireless powered communication network (WPCN)
consisting of a multi-antenna hybrid access point (HAP) that transfers wireless
energy to and receives sensing data from a cluster of low-power wireless
devices (WDs). To enhance the throughput performance of some far-away WDs, we
allow one of the WDs to act as the cluster head (CH) that helps forward the
messages of the other cluster members (CMs). However, the performance of the
proposed cluster-based cooperation is fundamentally limited by the high energy
consumption of the CH, who needs to transmit all the WDs' messages including
its own. To tackle this issue, we exploit the capability of multi-antenna
energy beamforming (EB) at the HAP, which can focus more transferred power to
the CH to balance its energy consumption in assisting the other WDs.
Specifically, we first derive the throughput performance of each individual WD
under the proposed scheme. Then, we jointly optimize the EB design, the
transmit time allocation among the HAP and the WDs, and the transmit power
allocation of the CH to maximize the minimum data rate achievable among all the
WDs (the max-min throughput) for improved throughput fairness among the WDs. An
efficient optimal algorithm is proposed to solve the joint optimization
problem. Moreover, we simulate under practical network setups and show that the
proposed multi-antenna enabled cluster-based cooperation can effectively
improve the throughput fairness of WPCN.Comment: This paper has been accepted for publication by IEEE ACCESS journal
in July 201
Reusing Wireless Power Transfer for Backscatter-assisted Cooperation in WPCN
This paper studies a novel user cooperation method in a wireless powered
communication network (WPCN), where a pair of closely located devices first
harvest wireless energy from an energy node (EN) and then use the harvested
energy to transmit information to an access point (AP). In particular, we
consider the two energy-harvesting users exchanging their messages and then
transmitting cooperatively to the AP using space-time block codes.
Interestingly, we exploit the short distance between the two users and allow
the information exchange to be achieved by energy-conserving backscatter
technique. Meanwhile the considered backscatter-assisted method can effectively
reuse wireless power transfer for simultaneous information exchange during the
energy harvesting phase. Specifically, we maximize the common throughput
through optimizing the time allocation on energy and information transmission.
Simulation results show that the proposed user cooperation scheme can
effectively improve the throughput fairness compared to some representative
benchmark methods.Comment: The paper has been accepted for publication in MLICOM 201
Optimizing Throughput Fairness of Cluster-based Cooperation in Underlay Cognitive WPCNs
In this paper, we consider a secondary wireless powered communication network
(WPCN) underlaid to a primary point-to-point communication link. The WPCN
consists of a multi-antenna hybrid access point (HAP) that transfers wireless
energy to a cluster of low-power wireless devices (WDs) and receives sensing
data from them. To tackle the inherent severe user unfairness problem in WPCN,
we consider a cluster-based cooperation where a WD acts as the cluster head
that relays the information of the other WDs. Besides, we apply energy
beamforming technique to balance the dissimilar energy consumptions of the WDs
to further improve the fairness. However, the use of energy beamforming and
cluster-based cooperation may introduce more severe interference to the primary
system than the WDs transmit independently. To guarantee the performance of
primary system, we consider an interference-temperature constraint to the
primary system and derive the throughput performance of each WD under the peak
interference-temperature constraint. To achieve maximum throughput fairness, we
jointly optimize the energy beamforming design, the transmit time allocation
among the HAP and the WDs, and the transmit power allocation of each WD to
maximize the minimum data rate achievable among the WDs (the max-min
throughput). We show that the non-convex joint optimization problem can be
transformed to a convex one and then be efficiently solved using off-the-shelf
convex algorithms. Moreover, we simulate under practical network setups and
show that the proposed method can effectively improve the throughput fairness
of the secondary WPCN, meanwhile guaranteeing the communication quality of the
primary network.Comment: The paper has been submitted for potential journal publication. arXiv
admin note: text overlap with arXiv:1707.0320
Collaborative Computation Offloading in Wireless Powered Mobile-Edge Computing Systems
This paper studies a novel user cooperation model in a wireless powered
mobile edge computing system where two wireless users harvest wireless power
transferred by one energy node and can offload part of their computation tasks
to an edge server (ES) for remote execution. In particular, we consider that
the direct communication link between one user to the ES is blocked, such that
the other user acts as a relay to forward its offloading data to the server.
Meanwhile, instead of forwarding all the received task data, we also allow the
helping user to compute part of the received task locally to reduce the
potentially high energy and time cost on task offloading to the ES. Our aim is
to maximize the amount of data that can be processed within a given time frame
of the two users by jointly optimizing the amount of task data computed at each
device (users and ES), the system time allocation, the transmit power and CPU
frequency of the users. We propose an efficient method to find the optimal
solution and show that the proposed user cooperation can effectively enhance
the computation performance of the system compared to other representative
benchmark methods under different scenarios.Comment: The paper is accepted for publication by IEEE GLOBECOM 2019, at
Waikoloa, HI, USA, in Dec. 201
Reusing Wireless Power Transfer for Backscatter-assisted Relaying in WPCNs
User cooperation is an effective technique to tackle the severe near-far user
unfairness problem in wireless powered communication networks (WPCNs). In this
paper, we consider a WPCN where two collaborating wireless devices (WDs) first
harvest wireless energy from a hybrid access point (HAP) and then transmit
their information to the HAP. The WD with the stronger WD-to-HAP channel helps
relay the message of the other weaker user. In particular, we exploit the use
of ambient backscatter communication during the wireless energy transfer phase,
where the weaker user backscatters the received energy signal to transmit its
information to the relay user in a passive manner. By doing so, the relay user
can reuse the energy signal for simultaneous energy harvesting and information
decoding (e.g., using an energy detector). Compared to active information
transmission in conventional WPCNs, the proposed method effectively saves the
energy and time consumed by the weaker user on information transmission during
cooperation. With the proposed backscatter-assisted relaying scheme, we jointly
optimize the time and power allocations on wireless energy and information
transmissions to maximize the common throughput. Specifically, we derive the
semi-closed-form expressions of the optimal solution and propose a
low-complexity optimal algorithm to solve the joint optimization problem. By
comparing with some representative benchmark methods, we simulate under
extensive network setups and demonstrate that the proposed cooperation method
effectively improves the throughput performance in WPCNs.Comment: This paper has been submitted for potential journal publicatio