| 1. |
- van de Beek, Jaap, et al.
(författare)
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A conceptual study of OFDM-based multiple access schemes : Part 4: Tracking of time and frequency offset
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper is part of a conceptual study of a multiuser OFDM system. In previous reports we have examined requirements for the air interface and presented uncoded performance (in terms of bit error rate) for the uplink of such systems. In this report we adopt the user allocation structure from the previous parts of the study and examine the role of channel coding. We present performance simulations that illustrate the effects of a convolutional code exploiting channel diversity, and channel estimator performance exploiting the channel correlation.
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| 2. |
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| 3. |
- van de Beek, Jan-Jaap, et al.
(författare)
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A time and frequency synchronization scheme for multiuser OFDM
- 1999
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Ingår i: IEEE Journal on Selected Areas in Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8716 .- 1558-0008. ; 17:11, s. 1900-1914
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Tidskriftsartikel (refereegranskat)abstract
- We present a multiuser synchronization scheme for tracking the mobile's uplink time and frequency offsets. It uses the redundancy introduced by the cyclic prefix and does not need additional pilots. We show performance results of an orthogonal frequency division multiplexing (OFDM)-based radio interface based on universal mobile telecommunication system (UMTS) parameters. For a UMTS-typical mobile channel environment, the performance of a coherent system employing the scheme is virtually indistinguishable from the performance of a perfectly synchronized system. In a differentially modulated system, synchronization errors decrease the system performance by about 0.7 dB compared to a perfectly synchronized system. Index Terms - Communication system, delay estimation, frequency estimation, multicarrier, multiuser system, orthogonal frequency division multiplexing (OFDM), synchronization, universal mobile telecommunication system (UMTS).
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| 4. |
- van de Beek, Jaap, et al.
(författare)
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Synchronization of a TDMA-OFDM frequency hopping system
- 1998
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Ingår i: Pathway to a global wireless revolution. - Piscataway, NJ : IEEE Communications Society. - 0780343204 ; , s. 1290-1294
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a Time Division Multiple Access-Orthogonal Frequency Division Multiplexing (TDMA-OFDM)-based radio interface proposal for the Universal Mobile Telecommunication System (UMTS). We focus on synchronization and present an implementable algorithm for the tracking of the mobiles' time and frequency offsets at the base station in the uplink. This algorithm is based on recently developed estimation methods that use redundancy introduced by the cyclic prefix. A modified Maximum Likelihood (ML) estimator for the Additive White Gaussian Noise (AWGN) channel is used to meet both implementational requirements and performance requirements for frequency-selective fading multiuser environments. Simulation results for a typical UMTS mobile channel environment show that the uncoded symbol error rate of a coherently modulated system using our synchronization scheme is virtually indistinguishable from that of a system with no time and frequency offset.
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| 5. |
- van de Beek, Jaap, et al.
(författare)
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A conceptual study of OFDM-based multiple access schemes : Part 2: Channel estimation in the uplink
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper deals with the design of channel estimators in the uplink of an OFDM based multi-user system. First, we propose a user allocation scheme that is based on the aim to use the correlation of the radio channel for channel estimation purposes. Further, we present the linear MMSE channel estimator based on a few pilot tones. We present an error analysis that proves valuable in the evaluation of linear channel estimators under mismatch. Finally, we present some results on the design of linear channel estimators and pilot patterns, showing by means of examplesthe importance of careful pilot positioning.
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| 6. |
- van de Beek, Jaap, et al.
(författare)
-
A conceptual study of OFDM-based multiple access schemes : Part 3: Performance evaluation of a coded system
- 1996
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper is part of a conceptual study of a multiuser OFDM system. In previous reports we have examined requirements for the air interface and presented uncoded performance (in terms of bit error rate) for the uplink of such systems. In this report we adopt the user allocation structure from the previous parts of the study and examine the role of channel coding. We present performance simulations that illustrate the effects of a convolutional code exploiting channel diversity, and channel estimator performance exploiting the channel correlation.
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| 7. |
- van de Beek, Jaap, et al.
(författare)
-
Channel estimation in the uplink of an OFDM system
- 1996
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Ingår i: Proceedings of Nordic Radio Symposium. ; , s. 32-35
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the design of linear pilot based channel estimators in the uplink of an OFDM-based multiuser system, We evaluate such estimators and pilot patterns, showing by means of examples the importance of careful pilot positioning.
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| 8. |
- Wahlqvist, Mats, et al.
(författare)
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A conceptual study of OFDM-based multiple access schemes : Part 1: Air interface requirements
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The multimedia era has started. The migration of computer (packet oriented) and telephony (circuit switched) networks in combination with an explosive development of new services, creates a mass market for public broadband communication. There are no reasons foreseen why these kinds of services should not go mobile. Future customers will not treat a mobile access differently than a fixed access to the network. The different types of services together with the demand of broadband mobile communication requires a new air interface. Limitations in the existing systems (flexibility and bit-rate) gives that they are not serious competitirs.
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| 9. |
- Wahlqvist, Mattias, et al.
(författare)
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Description of Telias OFDM based proposal
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document gives an overview of Telias OFDM based proposal for UTRA and should be cinsidered as an input to the OFDM concept group within SMG 2. The document describes the fundamental frame structure, principles of the detection, modulation, coding and synchronization. Further, the channel structure, the resource management and handover principles are outlined
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