621 research outputs found
The interplay between standardization and technological change: A study on wireless technologies, technological trajectories, and essential patent claims
In many technology fields, standardization is the primary method of achieving alignment between actors. Especially if strong network effects and increasing returns are present, the market often ends up with a single standard that dominates the technical direction, activities and search heuristics, for at least one full technology generation. Although literature has addressed such decision processes quite extensively, relatively little attention has been paid to the way in which standards affect - and are affected by - technological change. Building upon the concepts of technological regimes and trajectories (Dosi, 1982), and on the methodology proposed by (Hummon & Doreian, 1989) to empirically investigate such trajectories, this papers aims to study the interplay between standardisation and technological change. We conclude that the empirically derived technological trajectories very well match the standardisation activities and the main technological challenges derived from the engineering literature. Moreover, we also observe that the Hummon & Doreian methodology can indeed reveal technological discontinuities. To the best of our knowledge, this has not been the case in earlier studies using this technology, and refutes concerns that this methodology has a (too) strong bias towards incremental, continuous technological paths. Finally, we compare the set of patents in the most important technological trajectories to the set of so-called essential patent claims at standards bodies, and conclude that there is no significant relationship. This confirms earlier arguments that essential patents are not necessarily βimportantβ patents in a technical sense.technological trajectories, standardization, innovation
ADAPTIVE CODING TECHNIQUES TO IMPROVE BER IN OFDM SYSTEM
Adaptive modulation and diversity combining represent very important adaptive solutions for the future generations of communication systems. In order to improve the performance and the efficiency of wireless communication systems these two techniques have been recently used jointly in new schemes named joint adaptive modulation and diversity combining .The highest spectral efficiency with the lowest possible combining complexity, given the fading channel conditions and the required error rate performance. Increase the spectral efficiency with a slight increase in the average number of combined path for the low signal to noise ratio (SNR) range while maintaining compliance with the bit error rate (BER)
A hybrid optical-wireless network for decimetre-level terrestrial positioning
Global navigation satellite systems (GNSS) are widely used for navigation and
time distribution, features indispensable for critical infrastructure such as
mobile communication networks, as well as emerging technologies like automated
driving and sustainable energy grids. While GNSS can provide centimetre-level
precision, GNSS receivers are prone to many-metre errors due to multipath
propagation and obstructed view of the sky, which occur especially in urban
areas where accurate positioning is needed most. Moreover, the vulnerabilities
of GNSS, combined with the lack of a back-up system, pose a severe risk to
GNSS-dependent technologies. Here, we demonstrate a terrestrial positioning
system which is independent of GNSS and offers superior performance through a
constellation of radio transmitters, connected and time-synchronised at the
sub-nanosecond level through a fibre-optic Ethernet network. Employing optical
and wireless transmission schemes similar to those encountered in mobile
communication networks, and exploiting spectrally efficient virtual wideband
signals, the detrimental effects of multipath propagation are mitigated, thus
enabling robust decimetre-level positioning and sub-nanosecond timing in a
multipath-prone outdoor environment. This work provides a glimpse of a future
in which telecommunication networks provide not only connectivity, but also
GNSS-independent timing and positioning services with unprecedented accuracy
and reliability.Comment: 38 pages, 9 figures, 3 table
A Link Quality Model for Generalised Frequency Division Multiplexing
5G systems aim to achieve extremely high data rates, low end-to-end latency
and ultra-low power consumption. Recently, there has been considerable interest
in the design of 5G physical layer waveforms. One important candidate is
Generalised Frequency Division Multiplexing (GFDM). In order to evaluate its
performance and features, system-level studies should be undertaken in a range
of scenarios. These studies, however, require highly complex computations if
they are performed using bit-level simulators. In this paper, the Mutual
Information (MI) based link quality model (PHY abstraction), which has been
regularly used to implement system-level studies for Orthogonal Frequency
Division Multiplexing (OFDM), is applied to GFDM. The performance of the GFDM
waveform using this model and the bit-level simulation performance is measured
using different channel types. Moreover, a system-level study for a GFDM based
LTE-A system in a realistic scenario, using both a bit-level simulator and this
abstraction model, has been studied and compared. The results reveal the
accuracy of this model using realistic channel data. Based on these results,
the PHY abstraction technique can be applied to evaluate the performance of
GFDM based systems in an effective manner with low complexity. The maximum
difference in the Packet Error Rate (PER) and throughput results in the
abstraction case compared to bit-level simulation does not exceed 4% whilst
offering a simulation time saving reduction of around 62,000 times.Comment: 5 pages, 8 figures, accepted in VTC- spring 201
Multiuser MIMO-OFDM for Next-Generation Wireless Systems
This overview portrays the 40-year evolution of orthogonal frequency division multiplexing (OFDM) research. The amelioration of powerful multicarrier OFDM arrangements with multiple-input multiple-output (MIMO) systems has numerous benefits, which are detailed in this treatise. We continue by highlighting the limitations of conventional detection and channel estimation techniques designed for multiuser MIMO OFDM systems in the so-called rank-deficient scenarios, where the number of users supported or the number of transmit antennas employed exceeds the number of receiver antennas. This is often encountered in practice, unless we limit the number of users granted access in the base stationβs or radio portβs coverage area. Following a historical perspective on the associated design problems and their state-of-the-art solutions, the second half of this treatise details a range of classic multiuser detectors (MUDs) designed for MIMO-OFDM systems and characterizes their achievable performance. A further section aims for identifying novel cutting-edge genetic algorithm (GA)-aided detector solutions, which have found numerous applications in wireless communications in recent years. In an effort to stimulate the cross pollination of ideas across the machine learning, optimization, signal processing, and wireless communications research communities, we will review the broadly applicable principles of various GA-assisted optimization techniques, which were recently proposed also for employment inmultiuser MIMO OFDM. In order to stimulate new research, we demonstrate that the family of GA-aided MUDs is capable of achieving a near-optimum performance at the cost of a significantly lower computational complexity than that imposed by their optimum maximum-likelihood (ML) MUD aided counterparts. The paper is concluded by outlining a range of future research options that may find their way into next-generation wireless systems
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