7 research outputs found
Analytical characterisation of the terahertz in-vivo nano-network in the presence of interference based on TS-OOK communication scheme
The envisioned dense nano-network inside the human body at terahertz (THz) frequency suffers a communication performance degradation among nano-devices. The reason for this performance limitation is not only the path loss and molecular absorption noise, but also the presence of multi-user interference and the interference caused by utilising any communication scheme, such as time spread ON—OFF keying (TS-OOK). In this paper, an interference model utilising TS-OOK as a communication scheme of the THz communication channel inside the human body has been developed and the probability distribution of signal-to-interference-plus-noise ratio (SINR) for THz communication within different human tissues, such as blood, skin, and fat, has been analyzed and presented. In addition, this paper evaluates the performance degradation by investigating the mean values of SINR under different node densities in the area and the probabilities of transmitting pulses. It results in the conclusion that the interference restrains the achievable communication distance to approximate 1 mm, and more specific range depends on the particular transmission circumstance. Results presented in this paper also show that by controlling the pulse transmission probability and node density, the system performance can be ameliorated. In particular, SINR of in vivo THz communication between the deterministic targeted transmitter and the receiver with random interfering nodes in the medium improves about 10 dB, when the node density decreases one order. The SINR increases approximate 5 and 2 dB, when the pulse transmitting probability drops from 0.5 to 0.1 and 0.9 to 0.5
UxNB-Enabled Cell-Free Massive MIMO with HAPS-Assisted Sub-THz Backhauling
In this paper, we propose a cell-free scheme for unmanned aerial vehicle
(UAV) base stations (BSs) to manage the severe intercell interference between
terrestrial users and UAV-BSs of neighboring cells. Since the cell-free scheme
requires enormous bandwidth for backhauling, we propose to use the
sub-terahertz (sub-THz) band for the backhaul links between UAV-BSs and central
processing unit (CPU). Also, because the sub-THz band requires a reliable
line-of-sight link, we propose to use a high altitude platform station (HAPS)
as a CPU. At the first time-slot of the proposed scheme, users send their
messages to UAVs at the sub-6 GHz band. The UAVs then apply match-filtering and
power allocation. At the second time-slot, at each UAV, orthogonal resource
blocks are allocated for each user at the sub-THz band, and the signals are
sent to the HAPS after analog beamforming. In the HAPS receiver, after analog
beamforming, the message of each user is decoded. We formulate an optimization
problem that maximizes the minimum signal-to-interference-plus-noise ratio of
users by finding the optimum allocated power as well as the optimum locations
of UAVs. Simulation results demonstrate the superiority of the proposed scheme
compared with aerial cellular and terrestrial cell-free baseline schemes.Comment: 32 pages, 13 figure
Can Terahertz Provide High-Rate Reliable Low Latency Communications for Wireless VR?
Wireless virtual reality (VR) imposes new visual and haptic requirements that
are directly linked to the quality-of-experience (QoE) of VR users. These QoE
requirements can only be met by wireless connectivity that offers high-rate and
high-reliability low latency communications (HRLLC), unlike the low rates
usually considered in vanilla ultra-reliable low latency communication
scenarios. The high rates for VR over short distances can only be supported by
an enormous bandwidth, which is available in terahertz (THz) frequency bands.
Guaranteeing HRLLC requires dealing with the uncertainty that is specific to
the THz channel. To explore the potential of THz for meeting HRLLC
requirements, a quantification of the risk for an unreliable VR performance is
conducted through a novel and rigorous characterization of the tail of the
end-to-end (E2E) delay. Then, a thorough analysis of the tail-value-atrisk
(TVaR) is performed to concretely characterize the behavior of extreme wireless
events crucial to the real-time VR experience. System reliability for scenarios
with guaranteed line-of-sight (LoS) is then derived as a function of THz
network parameters after deriving a novel expression for the probability
distribution function of the THz transmission delay. Numerical results show
that abundant bandwidth and low molecular absorption are necessary to improve
the reliability. However, their effect remains secondary compared to the
availability of LoS, which significantly affects the THz HRLLC performance. In
particular, for scenarios with guaranteed LoS, a reliability of 99.999% (with
an E2E delay threshold of 20 ms) for a bandwidth of 15 GHz along with data
rates of 18.3 Gbps can be achieved by the THz network (operating at a frequency
of 1 THz), compared to a reliability of 96% for twice the bandwidth, when
blockages are considered.Comment: arXiv admin note: text overlap with arXiv:1905.0765