944 research outputs found
Throughput Scaling of Wireless Networks With Random Connections
This work studies the throughput scaling laws of ad hoc wireless networks in
the limit of a large number of nodes. A random connections model is assumed in
which the channel connections between the nodes are drawn independently from a
common distribution. Transmitting nodes are subject to an on-off strategy, and
receiving nodes employ conventional single-user decoding. The following results
are proven:
1) For a class of connection models with finite mean and variance, the
throughput scaling is upper-bounded by for single-hop schemes, and
for two-hop (and multihop) schemes.
2) The throughput scaling is achievable for a specific
connection model by a two-hop opportunistic relaying scheme, which employs
full, but only local channel state information (CSI) at the receivers, and
partial CSI at the transmitters.
3) By relaxing the constraints of finite mean and variance of the connection
model, linear throughput scaling is achievable with Pareto-type
fading models.Comment: 13 pages, 4 figures, To appear in IEEE Transactions on Information
Theor
Signal Alignment: Enabling Physical Layer Network Coding for MIMO Networking
published_or_final_versio
Interference-Aware Scheduling for Connectivity in MIMO Ad Hoc Multicast Networks
We consider a multicast scenario involving an ad hoc network of co-channel
MIMO nodes in which a source node attempts to share a streaming message with
all nodes in the network via some pre-defined multi-hop routing tree. The
message is assumed to be broken down into packets, and the transmission is
conducted over multiple frames. Each frame is divided into time slots, and each
link in the routing tree is assigned one time slot in which to transmit its
current packet. We present an algorithm for determining the number of time
slots and the scheduling of the links in these time slots in order to optimize
the connectivity of the network, which we define to be the probability that all
links can achieve the required throughput. In addition to time multiplexing,
the MIMO nodes also employ beamforming to manage interference when links are
simultaneously active, and the beamformers are designed with the maximum
connectivity metric in mind. The effects of outdated channel state information
(CSI) are taken into account in both the scheduling and the beamforming
designs. We also derive bounds on the network connectivity and sum transmit
power in order to illustrate the impact of interference on network performance.
Our simulation results demonstrate that the choice of the number of time slots
is critical in optimizing network performance, and illustrate the significant
advantage provided by multiple antennas in improving network connectivity.Comment: 34 pages, 12 figures, accepted by IEEE Transactions on Vehicular
Technology, Dec. 201
CSI Feedback Reduction for MIMO Interference Alignment
Interference alignment (IA) is a linear precoding strategy that can achieve
optimal capacity scaling at high SNR in interference networks. Most of the
existing IA designs require full channel state information (CSI) at the
transmitters, which induces a huge CSI signaling cost. Hence it is desirable to
improve the feedback efficiency for IA and in this paper, we propose a novel IA
scheme with a significantly reduced CSI feedback. To quantify the CSI feedback
cost, we introduce a novel metric, namely the feedback dimension. This metric
serves as a first-order measurement of CSI feedback overhead. Due to the
partial CSI feedback constraint, conventional IA schemes can not be applied and
hence, we develop a novel IA precoder / decorrelator design and establish new
IA feasibility conditions. Via dynamic feedback profile design, the proposed IA
scheme can also achieve a flexible tradeoff between the degree of freedom (DoF)
requirements for data streams, the antenna resources and the CSI feedback cost.
We show by analysis and simulations that the proposed scheme achieves
substantial reductions of CSI feedback overhead under the same DoF requirement
in MIMO interference networks.Comment: 30 pages, 7 figures, accepted for publication by IEEE transactions on
signal processing in June, 201
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