1,513 research outputs found
Single-Symbol ML Decodable Distributed STBCs for Partially-Coherent Cooperative Networks
Space-time block codes (STBCs) that are single-symbol decodable (SSD) in a
co-located multiple antenna setting need not be SSD in a distributed
cooperative communication setting. A relay network with N relays and a single
source-destination pair is called a partially-coherent relay channel (PCRC) if
the destination has perfect channel state information (CSI) of all the channels
and the relays have only the phase information of the source-to-relay channels.
In this paper, first, a new set of necessary and sufficient conditions for a
STBC to be SSD for co-located multiple antenna communication is obtained. Then,
this is extended to a set of necessary and sufficient conditions for a
distributed STBC (DSTBC) to be SSD for a PCRC, by identifying the additional
conditions. Using this, several SSD DSTBCs for PCRC are identified among the
known classes of STBCs. It is proved that even if a SSD STBC for a co-located
MIMO channel does not satisfy the additional conditions for the code to be SSD
for a PCRC, single-symbol decoding of it in a PCRC gives full-diversity and
only coding gain is lost. It is shown that when a DSTBC is SSD for a PCRC, then
arbitrary coordinate interleaving of the in-phase and quadrature-phase
components of the variables does not disturb its SSD property for PCRC.
Finally, it is shown that the possibility of {\em channel phase compensation}
operation at the relay nodes using partial CSI at the relays increases the
possible rate of SSD DSTBCs from when the relays do not have CSI
to 1/2, which is independent of N
High Rate Single-Symbol Decodable Precoded DSTBCs for Cooperative Networks
Distributed Orthogonal Space-Time Block Codes (DOSTBCs) achieving full
diversity order and single-symbol ML decodability have been introduced recently
for cooperative networks and an upper-bound on the maximal rate of such codes
along with code constructions has been presented. In this report, we introduce
a new class of Distributed STBCs called Semi-orthogonal Precoded Distributed
Single-Symbol Decodable STBCs (S-PDSSDC) wherein, the source performs
co-ordinate interleaving of information symbols appropriately before
transmitting it to all the relays. It is shown that DOSTBCs are a special case
of S-PDSSDCs. A special class of S-PDSSDCs having diagonal covariance matrix at
the destination is studied and an upper bound on the maximal rate of such codes
is derived. The bounds obtained are approximately twice larger than that of the
DOSTBCs. A systematic construction of S-PDSSDCs is presented when the number of
relays . The constructed codes are shown to achieve the upper-bound
on the rate when is of the form 0 modulo 4 or 3 modulo 4. For the rest of
the values of , the constructed codes are shown to have rates higher than
that of DOSTBCs. It is also shown that S-PDSSDCs cannot be constructed with any
form of linear processing at the relays when the source doesn't perform
co-ordinate interleaving of the information symbols.Comment: A technical report of DRDO-IISc Programme on Advanced Research in
Mathematical Engineerin
Observation of the Presuperfluid Regime in a Two-Dimensional Bose Gas
In complementary images of coordinate-space and momentum-space density in a
trapped 2D Bose gas, we observe the emergence of pre-superfluid behavior. As
phase-space density increases toward degenerate values, we observe a
gradual divergence of the compressibility from the value predicted by
a bare-atom model, . grows to 1.7 before
reaches the value for which we observe the sudden emergence of a spike
at in momentum space. Momentum-space images are acquired by means of a 2D
focusing technique. Our data represent the first observation of non-meanfield
physics in the pre-superfluid but degenerate 2D Bose gas.Comment: Replace with the version appeared in PR
Made-to-measure galaxy models - III Modelling with Milky Way observations
We demonstrate how the Syer & Tremaine made-to-measure method of stellar
dynamical modelling can be adapted to model a rotating galactic bar. We
validate our made-to-measure changes using observations constructed from the
existing Shen et al. (2010) N-body model of the Milky Way bar, together with
kinematic observations of the Milky Way bulge and bar taken by the Bulge Radial
Velocity Assay (BRAVA). Our results for a combined determination of the bar
angle and bar pattern speed (~30 degrees and ~40 km/s/kpc) are consistent with
those determined by the N-body model. Whilst the made-to-measure techniques we
have developed are applied using a particular N-body model and observational
data set, they are in fact general and could be applied to other Milky Way
modelling scenarios utilising different N-body models and data sets.
Additionally, we use the exercise as a vehicle for illustrating how N-body and
made-to-measure methods might be combined into a more effective method.Comment: Accepted for publication, 10 pages, 7 figure
Modulation Diversity for Spatial Modulation Using Complex Interleaved Orthogonal Design
In this paper, we propose modulation diversity techniques for Spatial
Modulation (SM) system using Complex Interleaved Orthogonal Design (CIOD) meant
for two transmit antennas. Specifically, we show that by using the CIOD for two
transmit antenna system, the standard SM scheme, where only one transmit
antenna is activated in any symbol duration, can achieve a transmit diversity
order of two. We show with our simulation results that the proposed schemes
offer transmit diversity order of two, and hence, give a better Symbol Error
Rate performance than the SM scheme with transmit diversity order of one.Comment: 7 page
Multidimensional Index Modulation for 5G and Beyond Wireless Networks
This study examines the flexible utilization of existing IM techniques in a
comprehensive manner to satisfy the challenging and diverse requirements of 5G
and beyond services. After spatial modulation (SM), which transmits information
bits through antenna indices, application of IM to orthogonal frequency
division multiplexing (OFDM) subcarriers has opened the door for the extension
of IM into different dimensions, such as radio frequency (RF) mirrors, time
slots, codes, and dispersion matrices. Recent studies have introduced the
concept of multidimensional IM by various combinations of one-dimensional IM
techniques to provide higher spectral efficiency (SE) and better bit error rate
(BER) performance at the expense of higher transmitter (Tx) and receiver (Rx)
complexity. Despite the ongoing research on the design of new IM techniques and
their implementation challenges, proper use of the available IM techniques to
address different requirements of 5G and beyond networks is an open research
area in the literature. For this reason, we first provide the dimensional-based
categorization of available IM domains and review the existing IM types
regarding this categorization. Then, we develop a framework that investigates
the efficient utilization of these techniques and establishes a link between
the IM schemes and 5G services, namely enhanced mobile broadband (eMBB),
massive machine-type communications (mMTC), and ultra-reliable low-latency
communication (URLLC). Additionally, this work defines key performance
indicators (KPIs) to quantify the advantages and disadvantages of IM techniques
in time, frequency, space, and code dimensions. Finally, future recommendations
are given regarding the design of flexible IM-based communication systems for
5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible
publicatio
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