1,485 research outputs found
Uplink capacity of a variable density cellular system with multicell processing
In this work we investigate the information theoretic capacity of the uplink of a cellular system. Assuming centralised processing for all base stations, we consider a power-law path loss model along with variable cell size (variable density of Base Stations) and we formulate an average path-loss approximation. Considering a realistic Rician flat fading environment, the analytical result for the per-cell capacity is derived for a large number of users distributed over each cell. We extend this general approach to model the uplink of sectorized cellular system. To this end, we assume that the user terminals are served by perfectly directional receiver antennas, dividing the cell coverage area into perfectly non-interfering sectors. We show how the capacity is increased (due to degrees of freedom gain) in comparison to the single receiving antenna system and we investigate the asymptotic behaviour when the number of sectors grows large. We further extend the analysis to find the capacity when the multiple antennas used for each Base Station are omnidirectional and uncorrelated (power gain on top of degrees of freedom gain). We validate the numerical solutions with Monte Carlo simulations for random fading realizations and we interpret the results for the real-world systems
Free Probability based Capacity Calculation of Multiantenna Gaussian Fading Channels with Cochannel Interference
During the last decade, it has been well understood that communication over
multiple antennas can increase linearly the multiplexing capacity gain and
provide large spectral efficiency improvements. However, the majority of
studies in this area were carried out ignoring cochannel interference. Only a
small number of investigations have considered cochannel interference, but even
therein simple channel models were employed, assuming identically distributed
fading coefficients. In this paper, a generic model for a multi-antenna channel
is presented incorporating four impairments, namely additive white Gaussian
noise, flat fading, path loss and cochannel interference. Both point-to-point
and multiple-access MIMO channels are considered, including the case of
cooperating Base Station clusters. The asymptotic capacity limit of this
channel is calculated based on an asymptotic free probability approach which
exploits the additive and multiplicative free convolution in the R- and
S-transform domain respectively, as well as properties of the eta and Stieltjes
transform. Numerical results are utilized to verify the accuracy of the derived
closed-form expressions and evaluate the effect of the cochannel interference.Comment: 16 pages, 4 figures, 1 tabl
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
On Achievable Rate Region of Multiple Coordinated Multiple Access Channels
Coordination between two or more multiple access channel (MAC) receivers can enlarge the achievable rate region of the whole system. This paper focuses on coordination by sharing the codebooks of the users between the receivers of MACs. We first define the achievable rate region of the time invariant multiple coordinated MAC (MCMAC) and subsequently derive its achievable rate region. We later express the achievable rate region in terms of the dominating points. We base our numerical analysis on the two-user two-receiver Gaussian coordinated MAC and make comparison with the interference channel, full cooperation and the individual MAC performance analysis. It is observed that this approach though suboptimal is less complex in comparison with full cooperation and that the MCMAC rate region is at least equal to the rate region of the uncoordinated approach. Over several channel states, the rate region of MCMAC exceeds that of the uncoordinated approach
Cellular Systems with Full-Duplex Amplify-and-Forward Relaying and Cooperative Base-Stations
In this paper the benefits provided by multi-cell processing of signals
transmitted by mobile terminals which are received via dedicated relay
terminals (RTs) are assessed. Unlike previous works, each RT is assumed here to
be capable of full-duplex operation and receives the transmission of adjacent
relay terminals. Focusing on intra-cell TDMA and non-fading channels, a
simplified uplink cellular model introduced by Wyner is considered. This
framework facilitates analytical derivation of the per-cell sum-rate of
multi-cell and conventional single-cell receivers. In particular, the analysis
is based on the observation that the signal received at the base stations can
be interpreted as the outcome of a two-dimensional linear time invariant
system. Numerical results are provided as well in order to provide further
insight into the performance benefits of multi-cell processing with relaying.Comment: To appear in the Proc. of the 2007 IEEE International Symposium on
Information Theor
Cooperative Multi-Cell Networks: Impact of Limited-Capacity Backhaul and Inter-Users Links
Cooperative technology is expected to have a great impact on the performance
of cellular or, more generally, infrastructure networks. Both multicell
processing (cooperation among base stations) and relaying (cooperation at the
user level) are currently being investigated. In this presentation, recent
results regarding the performance of multicell processing and user cooperation
under the assumption of limited-capacity interbase station and inter-user
links, respectively, are reviewed. The survey focuses on related results
derived for non-fading uplink and downlink channels of simple cellular system
models. The analytical treatment, facilitated by these simple setups, enhances
the insight into the limitations imposed by limited-capacity constraints on the
gains achievable by cooperative techniques
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