1,423 research outputs found
Full-Duplex Radio for Uplink/Downlink Transmission with Spatial Randomness
We consider a wireless system with a full-duplex (FD) access point (AP) that
transmits to a scheduled user in the downlink (DL) channel, while receiving
data from an user in the uplink (UL) channel at the same time on the same
frequency. In this system, loopback interference (LI) at the AP and inter user
interference between the uplink (UL) user and downlink (DL) user can cause
performance degradation. In order to characterize the effects of LI and inter
user interference, we derive closed-form expressions for the outage probability
and achievable sum rate of the system. In addition an asymptotic analysis that
reveals insights into the system behavior and performance degradation is
presented. Our results indicate that under certain conditions, FD transmissions
yield performance gains over half-duplex (HD) mode of operation.Comment: Accepted for the IEEE International Conference on Communications (ICC
2015
Simultaneous Transmission and Reception: Algorithm, Design and System Level Performance
Full Duplex or Simultaneous transmission and reception (STR) in the same
frequency at the same time can potentially double the physical layer capacity.
However, high power transmit signal will appear at receive chain as echoes with
powers much higher than the desired received signal. Therefore, in order to
achieve the potential gain, it is imperative to cancel these echoes. As these
high power echoes can saturate low noise amplifier (LNA) and also digital
domain echo cancellation requires unrealistically high resolution
analog-to-digital converter (ADC), the echoes should be cancelled or suppressed
sufficiently before LNA. In this paper we present a closed-loop echo
cancellation technique which can be implemented purely in analogue domain. The
advantages of our method are multiple-fold: it is robust to phase noise, does
not require additional set of antennas, can be applied to wideband signals and
the performance is irrelevant to radio frequency (RF) impairments in transmit
chain. Next, we study a few protocols for STR systems in carrier sense multiple
access (CSMA) network and investigate MAC level throughput with realistic
assumptions in both single cell and multiple cells. We show that STR can reduce
hidden node problem in CSMA network and produce gains of up to 279% in maximum
throughput in such networks. Finally, we investigate the application of STR in
cellular systems and study two new unique interferences introduced to the
system due to STR, namely BS-BS interference and UE-UE interference. We show
that these two new interferences will hugely degrade system performance if not
treated appropriately. We propose novel methods to reduce both interferences
and investigate the performances in system level.Comment: 20 pages. This manuscript will appear in the IEEE Transactions on
Wireless Communication
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