| 1. |
- Eriksson, Magnus, et al.
(författare)
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Packet-by-packet Radio Resource Management by means of Dynamic Single Frequency Networks
- 2000
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Konferensbidrag (refereegranskat)abstract
- By combining a cellular system with the terrestrial digital video broadcasting system (DVB-T), wide-area asymmetric Internet access can be achieved, with a downlink peak bit rate of 10-20Mbps. In this paper, we study dynamic resource management on a packet-by-packet basis for this broadband downlink. A model for best-effort traffic is proposed, which simplifies the evaluation of maximum throughput and fairness. Dynamic Single Frequency Networks (DSFN) are evaluated, which exploits the macrodiversity capability of the OFDM modulation scheme. The transmitters are divided into single frequency networks (SFNs), i.e. groups of transmitters that send the same information at the same channel frequency simultaneously. An algorithm changes the SFN grouping from timeslot to timeslot, and schedules the packets. DSFN is a way of introducing timeslots and Dynamic Channel Allocation into DVB-T, without keying of the transmitter power. Thus, receiver and transmitter circuits existing on the market today can be used, and only software modifications are required. A spectrum efficiency of 0.45 bit/s/Hz/site is achieved with omni-directional antennas under certain conditions. This is a capacity improvement of 170% in comparison to a Fixed Channel Allocation solution with static handover.
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| 2. |
- Jennehag, Ulf, et al.
(författare)
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Numerical modeling of transmission errors and video quality of MPEG-2
- 2001
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Ingår i: Signal processing. Image communication. - 0923-5965 .- 1879-2677. ; 16:8, s. 817-825
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Tidskriftsartikel (refereegranskat)abstract
- To efficiently combat the signal loss of MPEG-2 transmission over unreliable networks, priority encoding transmission, unequal packet loss protection and priority dropping techniques have been studied in many papers. Those studies are based on the qualitative analysis of different importance of signals, without quantitative investigation of signal loss effect on video quality. In this paper, MPEG-2 packet loss effect on video quality is quantitatively investigated, a temporal layered signal model is described and evaluated, a quality measure for reconstructed pictures called macroblock impairment ratio is suggested and defined. The investigation and the model are specified for MPEG-2, but the principles and the methods are suitable for any layered video. These are useful for the development of efficient schemes and protocols for packet video transmission over unreliable networks.
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| 9. |
- Xu, Youshi
(författare)
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A concatenated random error and burst erasure decoding scheme for random noise and burst fading or interference channels
- 1997
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Ingår i: Proceedings of IEEE International Symposium on Information Theory, 29 June-4 July 1997 , Ulm, Germany. - New York : IEEE. ; , s. 466-
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Konferensbidrag (refereegranskat)abstract
- A concatenated random error correction and burst erasure recovering code scheme is proposed. This will significantly improve the performance of communication systems in some applications. This proposal is based on an efficient erasure decoding algorithm for binary block codes and an efficient application in the presence of fading or interference.
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| 10. |
- Xu, Youshi
(författare)
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A modified Euclidean algorithm and the VLSI implementation
- 1996
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Ingår i: 8th Mediterranean Electrotechnical Conference, 1996. MELECON '96., Bari, Italy, 13-16 May 1996. Vol. 3. ; , s. 1324-1327
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Konferensbidrag (refereegranskat)abstract
- The extended Euclidean algorithm is important in algebraic and symbolic computations, in error correcting codes, in code division multiple access and, in cryptology. We propose a modified algorithm and a recursive implementation. Both the time and space complexity of the implementation is better than conventional ones. The regular and modular construction implies that it can be implemented on VLSI chips. The implementation can be used in decoding BCH codes, RS codes and Goppa codes. A throughput of hundreds of megabits per second is achievable.
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| 13. |
- Xu, Youshi
(författare)
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Efficient integration of voice and data services in wireless local area networks
- 2000
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Ingår i: EEE Vehicular Technology Conference. - : IEEE conference proceedings. ; , s. 1395-1399
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Konferensbidrag (refereegranskat)abstract
- We propose a new scheme of mixing speech information, network control message and data information with different priority in PRMA. This proposed PRMA can be viewed as a combined protocol of voice-only PRMA for voice terminals, carrier sense (CS)-slotted ALOHA for network control and CS-TDMA for data terminals. A mechanism for the sensing of hidden transmitting terminals is described. The integrated control packets and data packets do not have any influence on voice transmission. Simulation results show that the delay of network control packets and the channel throughput can be significantly improved, compared to all the other integrated PRMA protocols. This protocol distributes major control to the terminals, which may be extremely useful and important in the future.
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| 14. |
- Xu, Youshi, et al.
(författare)
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On the utilization of voice-unused resource for data transmission in PRMA systems
- 1998
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Ingår i: IEEE 1998 International Conference on Universal Personal Communications, Florence, It., Oct 05-09, 1998. ICUPC '98. Vol. 2. - : IEEE. ; , s. 1043-1047
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Konferensbidrag (refereegranskat)abstract
- In the paper voice-unused resource in a voice-only PRMA system is analyzed. A mechanism for the detection of voice-unused resource is proposed. How to use the voice-unused resource for data transmission is proposed. Therefore, the voice subsystem is totally a voice-only PRMA system, and the existence of data transmission just improves the channel utilization efficiency, without any influence on the performance of voice communications. Simulation results show that a significant amount of data traffic can be supported by the voice-unused resource.
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| 17. |
- Xu, Youshi, et al.
(författare)
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Variable shortened-and-punctured Reed-Solomon codes for packet loss protection
- 2002
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Ingår i: IEEE Transactions On Broadcasting. - 0018-9316 .- 1557-9611. ; 48:3, s. 237-245
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, techniques of Reed-Solomon (RS) codes to recover lost packets in digital video/audio broadcasting and packet switched network communications are reviewed. Usually, different RS codes and their corresponding encoders/decoders are designed and utilized to meet different requirements for different systems and applications. We incorporate these techniques into a variable RS code and present an encoding and decoding algorithm suitable for the variable RS code. A mother RS code can be used to produce a variety of RS codes and the same encoder/decoder can be used for all the derivative codes with adding/detecting zeros, removing a part of parity symbols, and adding erasures. A VLSI implementation for erasure decoding of the proposed variable RS code is described and the achievable performance is quantitatively analyzed. A typical example shows that the signal processing speed is up to 2.5 Gbits/second and the processing delay is less than one millisecond, when integrating the decoder on a single chip. Therefore, the proposed algorithm and the encoder/decoder can universally be utilized for different applications with various requirements, such as transmission data rate, packet length, packet loss protection capacity, as well as layered protection and adaptive redundancy protection in DVB/DAB broadcasting, Internet and mobile Internet communications.
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