The IEEE Benelux joint Chapter on Communications and Vehicular Technology organizes a Distinguished Lecture Tour in Benelux.

A series of talks will be provided by Prof. Wei Yu from University of Toronto on 15, 16 and 19 Oct. 2015, in Luxembourg, Leuven and Delft, respectively.

 

 

Talk in Luxembourg

15 Oct. 2015 at 11h00

Location:

University of Luxembourg, Campus Kirchberg, Room F-213

6, rue Richard Coudenhove-Kalergi

L-1359 Luxembourg-Kirchberg

Title: A Stochastic Analysis of Network MIMO Systems

Abstract: Network MIMO, where base-stations (BSs) cooperatively transmit and receive to/from the users, promises to significantly alleviate the inter-cell interference problem in wireless cellular networks; but its analytical performance characterization is still a difficult open problem. In this talk, we describe a stochastic geometry analysis of a network MIMO system, where the multiple-antenna BSs are distributed according to a Poisson point process and cooperate using zero-forcing beamforming to serve multiple users. We obtain tractable and accurate approximations of the signal power and inter-cluster interference power distributions, and derive a computationally efficient expression for the achievable per-BS ergodic sum rate. The analysis enables us to obtain the optimal number of users to schedule. Further, it allows us to quantify the performance improvement of network MIMO systems as a function of the cooperating cluster size. In particular, due to the zero-forcing penalty across a distributed set of BSs and the inevitable out-of-cluster interference that always exists, the per-BS ergodic sum rate of a network MIMO system does not approach that of an isolated cell even at unrealistically large cluster sizes. Finally, we illustrate the benefit of user-centric clustering for cell-edge users, and remark on a comparison between massive MIMO and network MIMO systems.

Contact person Dr. B. Shankar (Bhavani.Shankar@uni.lu)

Two Talks in Leuven

16 Oct. 2015

15.00-15.45 hrs

KU Leuven, Faculty Club,
Groot Begijnhof 14,
B-3000 Leuven

Title: Cloud Radio Access Networks: System Model, Capacity Analysis, and Optimization Algorithms

Abstract: Cloud radio access network (C-RAN) is an emerging wireless cellular architecture in which the base-stations (BSs) take advantage of high-capacity backhaul links to upload signal processing and computation to a cloud-computing based central processor. The C-RAN architecture offers an enabling platform for the centralized joint encoding and joint decoding of user messages and a capability for intercell interference mitigation across the BSs. In this talk, we address the capacity analysis and optimization technique for C-RAN while specifically taking into account the finite capacity constraint on the backhaul links. In the uplink, the C-RAN architecture can be modeled as a multiple-access relay channel.  We show that a compress-and-forward scheme in which the BSs quantize the received signals and send the quantized signals to the central processor using Wyner–Ziv coding is sum-capacity achieving to within a constant gap. We also propose a successive convex optimization approach for optimizing the quantization noise covariance matrix. In the downlink, the C-RAN architecture can be modeled as a broadcast relay channel. We compare the message-sharing strategy versus compression-based strategy for this setting, and show how compressive sensing and weighted minimum mean-squared error (WMMSE) techniques can be used to solve a network utility maximization problem involving joint user scheduling, BS clustering and beamforming in a user-centric message-sharing C-RAN design.

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16.15-17.00 hrs

Title: Interference Mitigation using Device-to-Device Link

Abstract: In this talk, we consider the use of device-to-device link for cooperative communication in a cellular environment, where a nearby user terminal acts as a relay in enabling both signal enhancement and common interference rejection at the destination. Assuming Gaussian transmission and Gaussian test-channel in the compress-and-forward relaying strategy for a multiple-input multiple-output (MIMO) relay channel with a finite-capacity out-of-band relay-destination link and with arbitrarily correlated noises, we suggest an algorithm for joint optimization of the transmission strategy at the source and compression strategy at the relay. A coordinate ascent approach is employed to iteratively optimize the transmit covariance matrix for reception at both relay and destination, and for optimizing the quantization noise covariance matrix using a simultaneous diagonalization approach. Assuming uniqueness of the optimal solution in iterations, the algorithm converges to a stationary point of the overall problem. We further introduce the concept of antenna pooling, and illustrate that the optimized use of the device-to-device relay link is capable of significantly improving the user throughput in an interfering cellular environment. The relay link can enhance the overall transmission degree-of-freedom by enabling not only joint reception but also interference rejection across the user terminals.

Participation is free of charge but registration is mandatory since places are limited.
Please register by October 12, by  sending name/affiliation to jacqueline.debruyn@esat.kuleuven.be .

Talk in Delft

19 Oct. 2015 at 14h00

Location:

TU Delft, Faculty EEMCS, Room HB17.150,

Mekelweg 4,

NL-2628 CD Delft

Title: Title: A Stochastic Analysis of Network MIMO Systems

Abstract: Network MIMO, where base-stations (BSs) cooperatively transmit and receive to/from the users, promises to significantly alleviate the inter-cell interference problem in wireless cellular networks; but its analytical performance characterization is still a difficult open problem. In this talk, we describe a stochastic geometry analysis of a network MIMO system, where the multiple-antenna BSs are distributed according to a Poisson point process and cooperate using zero-forcing beamforming to serve multiple users. We obtain tractable and accurate approximations of the signal power and inter-cluster interference power distributions, and derive a computationally efficient expression for the achievable per-BS ergodic sum rate. The analysis enables us to obtain the optimal number of users to schedule. Further, it allows us to quantify the performance improvement of network MIMO systems as a function of the cooperating cluster size. In particular, due to the zero-forcing penalty across a distributed set of BSs and the inevitable out-of-cluster interference that always exists, the per-BS ergodic sum rate of a network MIMO system does not approach that of an isolated cell even at unrealistically large cluster sizes. Finally, we illustrate the benefit of user-centric clustering for cell-edge users, and remark on a comparison between massive MIMO and network MIMO systems.

Contact Person: Prof. G. Leus (g.j.t.leus@tudelft.nl)

 

BIOGRAPHY

Professor Wei Yu (S’97-M’02-SM’08-F’14) received the B.A.Sc. degree in Computer Engineering and Mathematics from the University of Waterloo, Waterloo, Ontario, Canada in 1997 and M.S. and Ph.D. degrees in Electrical Engineering from Stanford University, Stanford, CA, in 1998 and 2002, respectively. Since 2002, he has been with the Electrical and Computer Engineering Department at the University of Toronto, Toronto, Ontario, Canada, where he is now Professor and holds a Canada Research Chair (Tier 1) in Information Theory and Wireless Communications. His main research interests include information theory, optimization, wireless communications and broadband access networks.