1,261 research outputs found
On the Capacity Region of Multi-Antenna Gaussian Broadcast Channels with Estimation Error
In this paper we consider the effect of channel estimation error on the capacity region of MIMO Gaussian broadcast channels. It is assumed that the receivers and the transmitter have (the same) estimates of the channel coefficients (i.e., the feedback channel is noiseless). We obtain an achievable rate region based on the dirty paper coding scheme. We show that this region is given by the capacity region of a dual multi-access channel with a noise covariance that depends on the transmit power. We explore this duality to give the asymptotic behavior of the sum-rate for a system with a large number of user, i.e., n rarr infin. It is shown that as long as the estimation error is of fixed (w.r.t n) variance, the sum-capacity is of order M log log n, where M is the number of antennas deployed at the transmitter. We further obtain the sum-rate loss due to the estimation error. Finally, we consider a training-based scheme for block fading MISO Gaussian broadcast channels. We find the optimum length of the training interval as well as the optimum power used for training in order to maximize the achievable sum-rate
Cooperative Feedback for MIMO Interference Channels
Multi-antenna precoding effectively mitigates the interference in wireless
networks. However, the precoding efficiency can be significantly degraded by
the overhead due to the required feedback of channel state information (CSI).
This paper addresses such an issue by proposing a systematic method of
designing precoders for the two-user multiple-input-multiple-output (MIMO)
interference channels based on finite-rate CSI feedback from receivers to their
interferers, called cooperative feedback. Specifically, each precoder is
decomposed into inner and outer precoders for nulling interference and
improving the data link array gain, respectively. The inner precoders are
further designed to suppress residual interference resulting from finite-rate
cooperative feedback. To regulate residual interference due to precoder
quantization, additional scalar cooperative feedback signals are designed to
control transmitters' power using different criteria including applying
interference margins, maximizing sum throughput, and minimizing outage
probability. Simulation shows that such additional feedback effectively
alleviates performance degradation due to quantized precoder feedback.Comment: 5 pages; submitted to IEEE ICC 201
Cooperative Transmission for a Vector Gaussian Parallel Relay Network
In this paper, we consider a parallel relay network where two relays
cooperatively help a source transmit to a destination. We assume the source and
the destination nodes are equipped with multiple antennas. Three basic schemes
and their achievable rates are studied: Decode-and-Forward (DF),
Amplify-and-Forward (AF), and Compress-and-Forward (CF). For the DF scheme, the
source transmits two private signals, one for each relay, where dirty paper
coding (DPC) is used between the two private streams, and a common signal for
both relays. The relays make efficient use of the common information to
introduce a proper amount of correlation in the transmission to the
destination. We show that the DF scheme achieves the capacity under certain
conditions. We also show that the CF scheme is asymptotically optimal in the
high relay power limit, regardless of channel ranks. It turns out that the AF
scheme also achieves the asymptotic optimality but only when the
relays-to-destination channel is full rank. The relative advantages of the
three schemes are discussed with numerical results.Comment: 35 pages, 10 figures, submitted to IEEE Transactions on Information
Theor
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
Cooperative Precoding with Limited Feedback for MIMO Interference Channels
Multi-antenna precoding effectively mitigates the interference in wireless
networks. However, the resultant performance gains can be significantly
compromised in practice if the precoder design fails to account for the
inaccuracy in the channel state information (CSI) feedback. This paper
addresses this issue by considering finite-rate CSI feedback from receivers to
their interfering transmitters in the two-user multiple-input-multiple-output
(MIMO) interference channel, called cooperative feedback, and proposing a
systematic method for designing transceivers comprising linear precoders and
equalizers. Specifically, each precoder/equalizer is decomposed into inner and
outer components for nulling the cross-link interference and achieving array
gain, respectively. The inner precoders/equalizers are further optimized to
suppress the residual interference resulting from finite-rate cooperative
feedback. Further- more, the residual interference is regulated by additional
scalar cooperative feedback signals that are designed to control transmission
power using different criteria including fixed interference margin and maximum
sum throughput. Finally, the required number of cooperative precoder feedback
bits is derived for limiting the throughput loss due to precoder quantization.Comment: 23 pages; 5 figures; this work was presented in part at Asilomar 2011
and will appear in IEEE Trans. on Wireless Com
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