Page 26 - ITU KALEIDOSCOPE, ATLANTA 2019

2019 ITU Kaleidoscope Academic Conference

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ergodic capacity of FD-NOMA can be given as [7].
16
M N n+1 t+1
( )
X X X X 1
C ≈ π log e e ¯ γ i,j ×
14 2
i=1 j=1 k=1 s=1 (2)
System capacity (Bit/s/Hz) 10 8 where M, N denote the transmitter number and
1
12
)
p
b k a s e
,
(−b k b s ¯γ i,j
a k
respectively.
receiver number,
We denote α i,k
as the FD self-interference from transmitter i to
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receiver j.
ρα i,j Moreover, ¯γ i,j can be given by ¯γ i,j =
, with α i,j , ρ, η, α i,k the NOMA
4 ρ( P N α i,l +ηα i,k )+1
l=i+1
power coefficient, signal to noise ratio (SNR), FD
2 coefficient and its corresponding FD self-interference.
With regard to a k , b k , a s , b s , we have a k = θ k −θ k−1 , b k =
0 π
5 10 15 20 25 cot θ k−1 −cot θ k , a s = θ s −θ s−1 , b s = cot θ s−1 −cot θ s , and 0 ≤
π π π
SNR (dB) π π
θ 1 < ...θ k < ... , 0 ≤ θ 1 < ...θ s < ... . On the contrary,
2 2
Figure 6 – System capacity comparison between the half-duplex (HD) based NOMA capacity expression
HD-OMA, HD-NOMA, FD-OMA, and FD-NOMA. can be obtained while removing the FD self-interference
part. In literature, capacity expressions for HD-OMA
and successive interference cancellation (SIC) for and FD-OMA have been investigated a lot, we omitted
simultaneously encoding and decoding multiple user’s the derivations here.
information[7]. In NOMA studies, we generally assumed In this comparison, we paired 3 users of the NOMA
that SIC can perfectly eliminate the interference from scheme with normalized channel noise. The allocated
other users within the same resource block that are NOMA powers are [4, 2, 1]. We average the allocated
with inferior channel conditions. This is an ideal power for the OMA scheme, i.e., the power allocation
assumption, which is almost impossible. Moreover, SIC for OMA user is 4+2+1 = 3.5. The comparison
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is a time-consuming and of great complexity method, results are given as in Fig. 6. We can find that
which might even be beyond the processing ability of combining the FD and NOMA always has better
current electronic devices. In future studies, some novel capacity performance compared to the half duplex (HD)
encoding methods besides SIC might be needed. and OMA schemes. However, due to self-interference,
the merit of FD-NOMA is reduced.
Compared to massive MIMO and NOMA, FD enables
synchronous transmission and reception. FD offers 4.2 Redesigning the networking architecture
even lower latency and better capacity performance technologies
[7]. The weakness of FD lies in the self-interference
[14] generated by its own transmitter. In order to The current driving force of wireless evolution is
deal with this problem, we may employ interference from the data-centric with the aim to connect more
cancellation devices at the receiver side. This is devices and provide even faster transmission speeds
not a simple job because digital-domain cancellation for the devices. As we know, massive connected
can be successfully implemented only when up to its devices and their faster transmission speeds bring in
effective dynamic range of the analog-to-digital (ADC) traffic overload, especially to wireless networks such
(suppose the FD terminal uses a B-bit ADC, the as base stations (BS). Nevertheless, users do not
range is about 6.02(ENOB − 2) dB [15]. Additionally, care about how and where the data comes from
this cancellation implementation generally has multiple but only the quality of service (QoS) and quality
stages. Due to the consumed processing time of of experience (QoE) of its service. In order to
these multiple stages, latency is increased. In future, solve this problem while catering to the driving
self-interference cancellation algorithms and some fast force’s shift from data-centric to information-centric,
processing devices can be some good topics for the FD the information-centric networking (ICN) and edge
studies. Besides, combining these 5G NR technologies computing technologies receive increasing attention [16,
can further improve performance, which is another 17, 18, 19].
interesting topic for future studies. In Fig. 7, we compare the network throughput
between the edge computing-assisted ICN and
We compare the capacity performance between conventional network TCP technologies while
half duplex-NOMA (HD-NOMA), FD-NOMA, increasing the subscriber numbers with per subscriber’s
HD-orthogonal multiple access (HD-OMA) and transmission rate 10 MBit/s. As depicted by this
FD-OMA by considering the Relay channel model. figure, with subscriber numbers growing, curves
According to previous work, the achievable system of edge computing-assisted ICN remain constant

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