108,465 research outputs found
Generalized Spatial Modulation in Indoor Wireless Visible Light Communication
In this paper, we investigate the performance of generalized spatial
modulation (GSM) in indoor wireless visible light communication (VLC) systems.
GSM uses light emitting diodes (LED), but activates only of them at
a given time. Spatial modulation and spatial multiplexing are special cases of
GSM with and , respectively. We first derive an analytical
upper bound on the bit error rate (BER) for maximum likelihood (ML) detection
of GSM in VLC systems. Analysis and simulation results show that the derived
upper bound is very tight at medium to high signal-to-noise ratios (SNR). The
channel gains and channel correlations influence the GSM performance such that
the best BER is achieved at an optimum LED spacing. Also, for a fixed
transmission efficiency, the performance of GSM in VLC improves as the
half-power semi-angle of the LEDs is decreased. We then compare the performance
of GSM in VLC systems with those of other MIMO schemes such as spatial
multiplexing (SMP), space shift keying (SSK), generalized space shift keying
(GSSK), and spatial modulation (SM). Analysis and simulation results show that
GSM in VLC outperforms the other considered MIMO schemes at moderate to high
SNRs; for example, for 8 bits per channel use, GSM outperforms SMP and GSSK by
about 21 dB, and SM by about 10 dB at BER
On the Capacity and Performance of Generalized Spatial Modulation
Generalized spatial modulation (GSM) uses antenna elements but fewer
radio frequency (RF) chains () at the transmitter. Spatial modulation and
spatial multiplexing are special cases of GSM with and ,
respectively. In GSM, apart from conveying information bits through
modulation symbols, information bits are also conveyed through the indices of
the active transmit antennas. In this paper, we derive lower and upper
bounds on the the capacity of a ()-GSM MIMO system, where is the
number of receive antennas. Further, we propose a computationally efficient GSM
encoding (i.e., bits-to-signal mapping) method and a message passing based
low-complexity detection algorithm suited for large-scale GSM-MIMO systems.Comment: Expanded version of the IEEE Communications Letters pape
Generalized Spatial Modulation in Large-Scale Multiuser MIMO Systems
Generalized spatial modulation (GSM) uses transmit antenna elements but
fewer transmit radio frequency (RF) chains, . Spatial modulation (SM)
and spatial multiplexing are special cases of GSM with and
, respectively. In GSM, in addition to conveying information bits
through conventional modulation symbols (for example, QAM), the
indices of the active transmit antennas also convey information bits.
In this paper, we investigate {\em GSM for large-scale multiuser MIMO
communications on the uplink}. Our contributions in this paper include: ()
an average bit error probability (ABEP) analysis for maximum-likelihood
detection in multiuser GSM-MIMO on the uplink, where we derive an upper bound
on the ABEP, and () low-complexity algorithms for GSM-MIMO signal detection
and channel estimation at the base station receiver based on message passing.
The analytical upper bounds on the ABEP are found to be tight at moderate to
high signal-to-noise ratios (SNR). The proposed receiver algorithms are found
to scale very well in complexity while achieving near-optimal performance in
large dimensions. Simulation results show that, for the same spectral
efficiency, multiuser GSM-MIMO can outperform multiuser SM-MIMO as well as
conventional multiuser MIMO, by about 2 to 9 dB at a bit error rate of
. Such SNR gains in GSM-MIMO compared to SM-MIMO and conventional MIMO
can be attributed to the fact that, because of a larger number of spatial index
bits, GSM-MIMO can use a lower-order QAM alphabet which is more power
efficient.Comment: IEEE Trans. on Wireless Communications, accepte
Intellectual Property Rights, Strategic Technology Agreements and Market Structure, The Case of GSM
This paper investigates the role of intellectual property rights (IPRs) in shaping the GSM industry. Thisindustry is an example of a high-tech industry in which standards play a large role. In the process ofdesigning the GSM standard, a lot of attention has been given to IPRs, mainly to avoid a situation inwhich a single IPR holder could hamper or even totally block the development of the standard.Nevertheless, the ultimate GSM standard contains a large amount of so-called ‘essential IPRs’, i.e., IPRswithout which the implementation of GSM products is impossible.The paper starts with a general discussion of the development of GSM, and the role of firm strategy andIPRs in this process. Next, we present a database on the essential IPRs in the GSM standard. This databasehas been compiled on the basis of international patent statistics, and the data that manufacturers havesupplied to ETSI, the European standardization body responsible for defining the GSM standard. We usethis database to assess the dynamic IPR position of firms in the original GSM standard and its subsequentdevelopment.economics of technology ;
Eavesdropping on GSM: state-of-affairs
In the almost 20 years since GSM was deployed several security problems have
been found, both in the protocols and in the - originally secret -
cryptography. However, practical exploits of these weaknesses are complicated
because of all the signal processing involved and have not been seen much
outside of their use by law enforcement agencies.
This could change due to recently developed open-source equipment and
software that can capture and digitize signals from the GSM frequencies. This
might make practical attacks against GSM much simpler to perform.
Indeed, several claims have recently appeared in the media on successfully
eavesdropping on GSM. When looking at these claims in depth the conclusion is
often that more is claimed than what they are actually capable of. However, it
is undeniable that these claims herald the possibilities to eavesdrop on GSM
using publicly available equipment.
This paper evaluates the claims and practical possibilities when it comes to
eavesdropping on GSM, using relatively cheap hardware and open source
initiatives which have generated many headlines over the past year. The basis
of the paper is extensive experiments with the USRP (Universal Software Radio
Peripheral) and software projects for this hardware.Comment: 5th Benelux Workshop on Information and System Security (WISSec
2010), November 201
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