A performance comparison of in-band full duplex and dynamic TDD for 5G indoor wireless networks
Al-Saadeh and Sung EURASIP Journal on Wireless Communications and
Networking
A performance comparison of in-band full duplex and dynamic TDD for 5G indoor wireless networks
Osama Al-Saadeh 0
Ki Won Sung 0
0 Communication Systems Department, KTH Royal Institute of Technology , Stockholm , Sweden
In-band full duplex has emerged as a solution for high data rate and low access delay for 5G wireless networks after its feasibility has been demonstrated. However, the impact of the in-band full duplex on the system-level performance of multi-cell wireless networks has not been investigated thoroughly. In this paper, we conduct an extensive simulation study to investigate the performance of in-band full duplex for indoor 5G small cell wireless networks. Particularly, we compare the in-band full duplex with static and dynamic time division duplexing schemes which require much less hardware complexity. We examine the effects of beamforming and interference cancellation under various traffic demands and asymmetry situations in the performance comparison. Our objective is to identify under which condition and with which technology support the in-band full duplex becomes advantageous over the simpler duplexing schemes. Numerical results indicate that for highly utilized wireless networks, in-band full duplex should be combined with interference cancellation and beamforming in order to achieve a performance gain over traditional duplexing schemes. Only then in-band full duplex is considered to be advantageous at any number of active mobile stations in the network and any downlink to uplink traffic proportion. Our results also suggest that in order to achieve a performance gain with the in-band full duplex in both links, the transmit power of the access points and the mobile stations should be comparable.
Wireless networks; In-band full duplex; Static time division duplexing; Dynamic time division duplexing; Interference mitigation techniques; Small cell; 5G; mmWave bands; Beamforming; Interference cancellation
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time division duplex (TDD). Both FDD and TDD have
the disadvantage of wasting time and frequency resources
[5]. However, recent advances in signal processing have
made it possible to reduce the effect of SI, allowing IBFD
wireless communications [6, 7]. The authors of [6]
demonstrated that it is possible to reduce the SI using analog
and digital interference cancellation techniques by more
than 78 dB with antenna separations of 20 and 40 cm. In
[7], a 110 dB of SI cancellation was achieved in a dense
indoor office environment with 80 MHz bandwidth. The
analog cancellation circuit in [7] has the dimensions of
(10cm × 10cm). Both [6] and [7] suggest that it would be
difficult to implement the IBFD in user equipments due to
the limited device sizes, whereas it is not a limiting factor
for access points (APs).
The IBFD can bring benefits to the wireless systems
in various angles. For example, the IBFD can provide a
better way to detect collisions in contention-based access
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protocols [8]. Also, in [9], it is reported that IBFD can
improve the secrecy of relay networks significantly. In this
study, we focus on the improvement of user data rate in
a capacity-demanding indoor environment. In an ideal
situation, a wireless system that operates in IBFD only
requires half the frequency and time resources required
to operate in FDD and TDD or double the data rate with
the same amount of resources. In practice, however, IBFD
might not lead to the performance improvement because
it induces higher interference compared to its half duplex
alternatives. It can be particularly the case for a network
of high utilization. Thus, system-level performance of full
duplex is of profound interest for the design of 5G wireless
networks.
Several investigations have been conducted on the
performance of IBFD-enabled systems. In [10], the
performance of IBFD in a dense small cell network was evaluated
and compared against the conventional half duplex
transmission. It is argued in [10] that IBFD provides 30–40%
mean throughput gain over the half duplex for indoor
scenarios. The 100% throughput gain is only noticed when
the cells are isolated by extremely high wall loss figures.
In [11], it was demonstrated that IBFD cannot double
the throughput of half duplex transmission with ALOHA
medium access control (MAC) protocol. Even with the
perfect SI cancellation, the actual throughput gain ranges
from 0–33% for the path loss exponent range [2, 4]. The
authors of [11] arrived to the conclusion that there is a
strong need fo (...truncated)