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Programme |
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Day 1/1 (Date: |
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09:00 Welcome Trevor Gill, Head of Networks,
Vodafone Group R&D, and Walter Tuttlebee, Chief
Executive, Mobile Welcome
and introduction to the proceedings with an outline of the original
objectives of the project. |
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Dr Muhammad A Imran, Research Fellow from Abstract--In the information-theoretic literature, the Wyner’s model has been the starting point for studying the capacity limits of cellular systems. Wyner’s simple infinite cellular model was adopted and extended by researchers in order to incorporate flat fading environments and power-law path loss models. However, the majority of these extensions have preserved a fundamental assumption of Wyner’s model, namely the co-location of User Terminals (UTs). In this talk, we present our work that alleviate this assumption and assumes a variable density cellular system with user distribution. The model under investigation is a cellular system where power-law path loss and Rayleigh flat fading is present. The presented results are interpreted in the context of practical cellular systems using appropriate figures of merit. |
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10:15 Evaluating
Capacity of MIMO Cellular Systems Dr Alister Burr, Professor from Abtract--In MIMO cellular systems it is
important to take into account the directional characteristics of interference,
since receive antenna arrays can perform spatial filtering and hence
significantly reduce the effect of such interference by exploiting its
direction. Moreover adaptive, or closed loop MIMO transmissions can
also provide directional transmission, and hence not only increase gain to
the wanted receiver but also reduce interference to other users. Note, however, that it is not straightforward to
evaluate the user capacity of cellular systems, even when simplifying
assumptions are made about radio propagation. Previous approaches have tended
either to use analytical methods which make further simplifying assumptions
which limit applicability, or are based on simulation of a large number of
users over a number of cells, and hence are extremely computationally
complex. These issues are further complicated by the use of MIMO, and
especially by adaptive MIMO. Hence the presentation will first discuss the
benefits available from MIMO with spatial filtering and adaptive MIMO. It
will then consider the system capacity evaluation problem for cellular
systems in general, describing the principle of reduced complexity simulation
methods, and finally discuss how these might be extended to spatially
filtered and adaptive MIMO systems. |
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11:00 Coffee break |
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Dr Gerhard Fettweis, Professor
from Abtract--Recently, multi-cell joint transmission and
joint detection schemes have been identified as promising features of next
generation mobile communications systems, as they enable to actively exploit
inter-cell interference rather than treating it as noise. Both for uplink and
downlink, concrete algorithms have been proposed, and strong increases in
spectral efficiency and system fairness have been predicted. Besides posing
strong requirements towards the time and frequency synchronization of
communicating entities, one essential problem connected to multi-cell
cooperative signal processing is the large extent of backhaul required
between base stations. In this presentation, we will observe the capacity
limits of both uplink and downlink transmissions in small toy scenarios, if
only limited cooperation between base stations is possible. The presentation
will reveal that different forms of cooperation (in terms of the kind of
information that is exchanged over the backhaul) are possible, and that a
practical system should ideally switch between these cooperation schemes
according to the current channel realization. |
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12:00 Encoding/Decoding
Strategies and Achievable Rates for Cooperative Multiple Access Channels Dr Onur Kaya, Assistant Professor
from Abstract--The wireless medium
brings along its unique challenges such as fading and multiuser interference,
which make the analysis of communication systems more complicated. On the other
hand, the same challenging properties of such systems are what give rise to
the concepts such as diversity, over-heard information, etc., which can be
carefully exploited to the advantage of the network capacity. In this talk, we will explore
some recent results the achievable rates of cooperative multiple access
channels (MAC). We will focus on power control for the two-user cooperative
MAC, and show that it automatically dictates optimum transmit and relay
strategies, thereby yielding a cross-layer type of solution. Then, we will
present novel block Markov based adaptive encoding and decoding strategies,
and the associated rate regions, for the three-user cooperative MAC with
channel state information. This type of channel is of particular importance
not only because it provides increased diversity to all participating users,
but also because it contains as special cases the multiple relay channel and
the multiple access relay channel, and may be viewed as a simple building
block of wireless ad-hoc networks. |
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12:45 Remote Presentation: Wireless: From
Networks to Systems Dr Panganamala Kumar, Professor from Abstract We
address issues ranging from wireless networks, to sensor networks, and
networked control. We begin by addressing the question of what should be the
architecture of wireless networks. Then turning to sensor networks, we
address the issue of how information should be processed in-network within
such systems. Finally, we turn to the issue of abstractions and architectures
for networked control. (Joint work
with many graduate students). |
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13:30 Lunch break |
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14:30 Remote
Presentation: Capacity Scaling in Arbitrary Wireless Networks Dr Piyush Gupta, Researcher from Abstract--
Recently, there has been considerable interest in multi-hop wireless
networks. Example scenarios are hybrid networks consisting of a mix of base
stations, relays, pico-/femto-cells, peer-to-peer users, etc., automated
transportation networks, and in defense environments. An important issue is
how the per-user throughput scales in such networks with the number of users? In this
talk, we will first review some recently proposed multi-user cooperation
schemes for achieving optimal throughput scaling in random wireless networks
(i.e., users are located uniformly at random in a given region). These schemes are, however, strongly
dependent on the uniform random placement of users -- they do not work well
when users are arbitrarily located, which will often be the case in general
networks. We will then discuss new cooperation schemes that also work
efficiently for near-arbitrary user locations. The talk is based on joint work with U. Niesen and D. Shah, MIT. |
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15:15 Remote Presentation: Recent
Progress on the Interference Channel Dr David Tse, Professor from Abstract
One approach to mitigating interference in wireless systems is through
infrastructure cooperation: base stations cooperate to jointly decode and
transmit signals to the mobile users, thus converting interference into
useful signals. Here we explore an alternative framework where there is no
cooperation between either the transmitters or the receivers. This is more
practical in cellular systems where there is no centralized processing and in
peer-to-peer wireless networks with completely decentralized processing. The
information theoretic model for this communication scenario is the
interference channel. Recently there has been significant progress on our
information theoretic understanding of this channel. Two key ideas emerged:
partial interference cancellation and interference alignment. In this talk we
discuss these ideas. |
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16:00 Coffee break |
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16:15 Panel
discussion All |
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18:00 End
of Workshop |
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19:30 Dinner |