1,275 research outputs found
On the Outage Probability of the Full-Duplex Interference-Limited Relay Channel
In this paper, we study the performance, in terms of the asymptotic error
probability, of a user which communicates with a destination with the aid of a
full-duplex in-band relay. We consider that the network is
interference-limited, and interfering users are distributed as a Poisson point
process. In this case, the asymptotic error probability is upper bounded by the
outage probability (OP). We investigate the outage behavior for well-known
cooperative schemes, namely, decode-and-forward (DF) and compress-and-forward
(CF) considering fading and path loss. For DF we determine the exact OP and
develop upper bounds which are tight in typical operating conditions. Also, we
find the correlation coefficient between source and relay signals which
minimizes the OP when the density of interferers is small. For CF, the
achievable rates are determined by the spatial correlation of the
interferences, and a straightforward analysis isn't possible. To handle this
issue, we show the rate with correlated noises is at most one bit worse than
with uncorrelated noises, and thus find an upper bound on the performance of
CF. These results are useful to evaluate the performance and to optimize
relaying schemes in the context of full-duplex wireless networks.Comment: 30 pages, 4 figures. Final version. To appear in IEEE JSAC Special
Issue on Full-duplex Wireless Communications and Networks, 201
Massive MIMO Multicasting in Noncooperative Cellular Networks
We study the massive multiple-input multiple-output (MIMO) multicast
transmission in cellular networks where each base station (BS) is equipped with
a large-scale antenna array and transmits a common message using a single
beamformer to multiple mobile users. We first show that when each BS knows the
perfect channel state information (CSI) of its own served users, the
asymptotically optimal beamformer at each BS is a linear combination of the
channel vectors of its multicast users. Moreover, the optimal combining
coefficients are obtained in closed form. Then we consider the imperfect CSI
scenario where the CSI is obtained through uplink channel estimation in
timedivision duplex systems. We propose a new pilot scheme that estimates the
composite channel which is a linear combination of the individual channels of
multicast users in each cell. This scheme is able to completely eliminate pilot
contamination. The pilot power control for optimizing the multicast beamformer
at each BS is also derived. Numerical results show that the asymptotic
performance of the proposed scheme is close to the ideal case with perfect CSI.
Simulation also verifies the effectiveness of the proposed scheme with finite
number of antennas at each BS.Comment: to appear in IEEE JSAC Special Issue on 5G Wireless Communication
System
All-Digital Self-interference Cancellation Technique for Full-duplex Systems
Full-duplex systems are expected to double the spectral efficiency compared
to conventional half-duplex systems if the self-interference signal can be
significantly mitigated. Digital cancellation is one of the lowest complexity
self-interference cancellation techniques in full-duplex systems. However, its
mitigation capability is very limited, mainly due to transmitter and receiver
circuit's impairments. In this paper, we propose a novel digital
self-interference cancellation technique for full-duplex systems. The proposed
technique is shown to significantly mitigate the self-interference signal as
well as the associated transmitter and receiver impairments. In the proposed
technique, an auxiliary receiver chain is used to obtain a digital-domain copy
of the transmitted Radio Frequency (RF) self-interference signal. The
self-interference copy is then used in the digital-domain to cancel out both
the self-interference signal and the associated impairments. Furthermore, to
alleviate the receiver phase noise effect, a common oscillator is shared
between the auxiliary and ordinary receiver chains. A thorough analytical and
numerical analysis for the effect of the transmitter and receiver impairments
on the cancellation capability of the proposed technique is presented. Finally,
the overall performance is numerically investigated showing that using the
proposed technique, the self-interference signal could be mitigated to ~3dB
higher than the receiver noise floor, which results in up to 76% rate
improvement compared to conventional half-duplex systems at 20dBm transmit
power values.Comment: Submitted to IEEE Transactions on Wireless Communication
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