271 research outputs found
Evaluation of cross-layer reliability mechanisms for satellite digital multimedia broadcast
This paper presents a study of some reliability mechanisms which may be put at work in the context of Satellite Digital Multimedia Broadcasting (SDMB) to mobile devices such as handheld phones. These mechanisms include error correcting codes, interleaving at the physical layer, erasure codes at
intermediate layers and error concealment on the video decoder. The evaluation is made on a realistic satellite channel and takes into account practical constraints such as the maximum zapping time and the user mobility at several speeds. The evaluation is done by simulating different scenarii with complete protocol stacks. The simulations indicate that, under the assumptions taken here, the scenario using highly compressed video protected by erasure codes at intermediate layers seems to be the best solution
on this kind of channel
Efficient Error Control for Scalable Media Transmission over 3G Broadcast Networks
Abstract. Broadcast and mobile phone technologies have now combined to provide wireless multimedia services. 3GPP2 has introduced the Broadcast and Multicast Services (BCMCS) architecture in a 3G wireless network. BCMCS are capable of supplying multimedia content, which requires successive frames to arrive within a specific time interval. We analyze the execution time of Reed-Solomon decoding, which is the MAC-layer forward error correction scheme used in cdma2000 1xEV-DO BCMCS, under different air channel conditions. The results show that the time constraints of MPEG-4 cannot be guaranteed by Reed-Solomon decoding when the packet loss rate (PLR) is high, due to its long computation time on current hardware. To alleviate this problem, we propose three error control schemes. Our static scheme bypasses Reed-Solomon decoding at the mobile node to satisfy the MPEG-4 time constraint when the PLR exceeds a given boundary. Our second, dynamic scheme corrects errors in a best-effort manner within the time constraint, instead of giving up altogether when the PLR is high. The third, video-aware dynamic scheme fixes errors in a similar way to the dynamic scheme, but in a priority-driven manner which improves the quality of the final video. Extensive simulation results show the effectiveness of our schemes compared to the original FEC scheme
Power control for WCDMA
This project tries to introduce itself in the physical implementations that make
possible the denominated third generation mobile technology. As well as to
know the technology kind that makes possible, for example, a video-call in real
time.
During this project, the different phases passed from the election of WCDMA
like the access method for UMTS will appear. Its coexistence with previous
network GSM will be analyzed, where the compatibility between systems has
been one of the most important aspects in the development of WCDMA, the
involved standardization organisms in the process, as well as the different
protocols that make the mobile communications within a network UTRAN
possible. Special emphasis during the study of the great contribution that has
offered WCDMA with respect to the control of power of the existing signals will
be made.
The future lines that are considered in the present, and other comment that
already are in their last phase of development in the field of the mobile
technology.
UMTS through WCDMA can be summarized like a revolution of the air
interface accompanied by a revolution in the network of their architecture
Spectrum Policy and Management
This project provides an examination of the FCC’s policies towards spectrum reallocation. The project examines the National Broadband Plan and how the FCC has approached the goals described within it. The demand for broadband communications has increased dramatically in recent years and has resulted in a predicted spectrum deficit in the near future. In addition to a number of spectrum auctions and their winners the project examines how the redistribution of spectrum impacts the broadband community. The project also provides an examination of spectrum reallocation and policy in other countries, to provide a broader view of spectrum policy. Finally the project examines new spectrum technologies and spectrum usage policies to further examine how the US’s spectrum policies should evolve
Wireless communications in the new millennium and third generation wireless networks
At the end of the 20 century, and at the beginning of this one, wireless communications are making large advances. The new technologies are on the way to provide a high-speed, high-quality information exchange between handheld terminals, and information repositories. The so called 2,5 generation networks, using the techniques like the HSCSD1, GPRS2, EDGE3, and the 3r generation wireless systems will help the wireless world to reach those goals. In this thesis I will start from the first and second-generation wireless networks, and then look into the 2,5 generation and 3rd generation wireless communications more in detail. The latest advances in the wireless world are the main focus of this paper although a short history of wireless communications is also given. The various aspects related to 3rd generation systems will be explored in this thesis, for example the air interface discussions, its time scale, its elements like the mobile equipment, software and security, USLM4, services that will be offered, etc. In addition, the technical factors and key technologies that are likely to shape the wireless network environment of the future will be explored. This part is expected to help us to see beyond the 3rd generation
Multicast Scheduling and Resource Allocation Algorithms for OFDMA-Based Systems: A Survey
Multicasting is emerging as an enabling technology
for multimedia transmissions over wireless networks to support several groups of users with flexible quality of service (QoS)requirements. Although multicast has huge potential to push the limits of next generation communication systems; it is however one of the most challenging issues currently being addressed. In this survey, we explain multicast group formation and various
forms of group rate determination approaches. We also provide a systematic review of recent channel-aware multicast scheduling and resource allocation (MSRA) techniques proposed for downlink multicast services in OFDMA based systems. We study these enabling algorithms, evaluate their core characteristics, limitations and classify them using multidimensional matrix. We cohesively review the algorithms in terms of their throughput maximization, fairness considerations, performance complexities,
multi-antenna support, optimality and simplifying assumptions. We discuss existing standards employing multicasting and further highlight some potential research opportunities in multicast systems
Technologies of Mobile Communication
Long-Term Evolution (LTE) is a new technology recently specified by 3GPP-Third Generation Partnership Project on the way towards fourth-generation mobile. This thesis presents the main technical features of this technology as well as its performances in terms of peak bit rate and average cell throughput, among others. LTE entails a big technological improvement as compared with the previous 3G standards. 1 However, this thesis also demonstrates that LTE performances do not fulfill the technical requirements established by ITU-R to classify one radio access technology as a member of the IMT-Advanced family of standards. Thus, this thesis describes the procedure followed by 3GPP to address these challenging requirements. Through the design and optimization of new radio access techniques and a further evolution of the system, 3GPP is laying down the foundations of the future LTE-Advanced standard, the 3GPP candidate for 4G
The use of BGAN to implement a robust tsunami early warning system
A tsunami is a series of waves created when a body of water, such as an ocean, is rapidly displaced probably by an oceanic earthquake. The effects of a tsunami for the population can be devastating due to the immense volumes of water and energy involved.The EU-funded Distant Early Warning System (DEWS) project is currently implementing a reference model for a national and regional warning dissemination system of possible hazards or disasters, especially in the prevention of tsunamis. In DEWS several universities and companies are participating specially coming from Europe and from the three countries of interest Sri Lanka, Indonesia and Thailand.The Department of Communications and Networking of the Helsinki University of Technology (TKK) is a consortium member of the DEWS project working on the development of the communications architecture between the different Emergency Centres, first responders and general public.In this thesis report we present the implementation of a backup satellite communications system between DEWS centres and governmental authorities in order to enable the warning dissemination in case the terrestrial communication structures are disrupted due to the hazard effects.The backup communications structure would employ the BGAN Inmarsat service for the date transmission. BGAN ensures the coverage in almost global earth area and support mobility on its terminals, offering adequate characteristics for an emergency communications system. To that end, we design and describe this communications architecture and discuss its performance in the possible scenarios based on simulations
Wireless communication, identification and sensing technologies enabling integrated logistics: a study in the harbor environment
In the last decade, integrated logistics has become an important challenge in
the development of wireless communication, identification and sensing
technology, due to the growing complexity of logistics processes and the
increasing demand for adapting systems to new requirements. The advancement of
wireless technology provides a wide range of options for the maritime container
terminals. Electronic devices employed in container terminals reduce the manual
effort, facilitating timely information flow and enhancing control and quality
of service and decision made. In this paper, we examine the technology that can
be used to support integration in harbor's logistics. In the literature, most
systems have been developed to address specific needs of particular harbors,
but a systematic study is missing. The purpose is to provide an overview to the
reader about which technology of integrated logistics can be implemented and
what remains to be addressed in the future
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