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- Agrell, Erik, 1965, et al.
(author)
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Gray coding for multilevel constellations in Gaussian noise
- 2007
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In: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 53:1, s. 224-235
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Journal article (peer-reviewed)abstract
- The problem of finding the optimal labeling (bit-to-symbol mapping) of multilevel coherent phase shift keying (PSK), pulse amplitude modulation (PAM), and quadrature amplitude modulation (QAM) constellations with respect to minimizing the bit-error probability (BEP) over a Gaussian channel is addressed. We show that using the binary reflected Gray code (BRGC) to label the signal constellation results in the lowest possible BEP for high enough signal energy-to-noise ratios and analyze what is "high enough"in this sense. It turns out that the BRGC is optimal for PSK and PAM systems whenever the target BEP is at most a few percent, which covers most systems of practical interest. New and simple closed-form expressions are presented for the BEP of PSK, PAM, and QAM using the BRGC. © 2007 IEEE.
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| 10. |
- Agrell, Erik, 1965, et al.
(author)
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ML optimal CDMA multiuser receiver
- 1995
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In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 31:18, s. 1554-1555
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Journal article (peer-reviewed)abstract
- A maximum likelihood optimum detector with an asymptotic complexity per user of O(1.5(K)) has been derived for the synchronous DS/CDMA channels. The detector employs a local descent algorithm through the Voronoi regions for the equivalent hypothesis detector.
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| 11. |
- Agrell, Erik, 1965, et al.
(author)
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On the optimality of the binary reflected Gray code
- 2004
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In: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 50:12, s. 3170-3182
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Journal article (peer-reviewed)abstract
- This paper concerns the problem of selecting a binary labeling for the signal constellation in M-PSK, M-PAM, and M-QAM communication systems. Gray labelings are discussed and the original work by Frank Gray is analyzed. As is noted, the number of distinct Gray labelings that result in different bit-error probability grows rapidly with increasing constellation size. By introducing a recursive Gray labeling construction method called expansion, the paper answers the natural question of what labeling, among all possible constellation labelings, will give the lowest possible average probability of bit errors for the considered constellations. Under certain assumptions on the channel, the answer is that the labeling proposed by Gray, the binary reflected Gray code, is the optimal labeling for all three constellations, which has, surprisingly, never been proved before.
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| 12. |
- Agrell, Erik, 1965, et al.
(author)
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The binary reflected Gray code is optimal for M-PSK
- 2004
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In: Proc. IEEE International Symposium on Information Theory, Chicago, Illinois, USA. - 0780382803 ; , s. 164-
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Conference paper (peer-reviewed)abstract
- This paper is concerned with the problem of selecting a binary labeling for the signal constellation in an M-PSK communication system. A good starting point is labelings having the Gray property, but this is not altogether enough, since the number of distinct Gray labelings that result in different bit error probability grows rapidly with increasing constellation size. By introducing a recursive Gray labeling construction method called expansion, the paper answers the natural question of what labeling, among all possible constellation labelings (not only Gray), that will give the lowest possible average probability of bit errors. Under certain assumptions on the channel, the answer is that the labeling originally proposed by Gray, the binary reflected Gray code, is the optimal labeling for M-PSK systems, which has, surprisingly, never been proved before.
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| 14. |
- Berens, Friedbert, et al.
(author)
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Modulation and Coding
- 2000
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In: Third Generation Mobile Communication Systems (Ramjee Prasad, Werner Mohr and Walter Konhäuser editors), chapter 5. - 1580530826
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Book chapter (other academic/artistic)
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- Eriksson, Thomas, 1964, et al.
(author)
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Compression of feedback for adaptive modulation and scheduling
- 2007
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In: IEEE Proceedings. ; 95:12, s. 2314-2321
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Journal article (peer-reviewed)abstract
- For wireless systems with adaptive modulation and/or scheduling, feedback of channel quality information is often necessary. It has been questioned whether the increased system performance is worth the additional feedback rate and the increased algorithm complexity.
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| 21. |
- Eriksson, Thomas, 1964, et al.
(author)
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Compression of Feedback in Adaptive OFDM-Based Systems using Scheduling
- 2007
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In: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 11:11, s. 859-861
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Journal article (peer-reviewed)abstract
- In wirelesscommunication, adaptive modulation and scheduling are promisingtechniques for a substantially increased spectral efficiency. Toachieve the throughput gain, it is necessary to feedback channelquality information. The required feedback rate may beprohibitively high in many applications, and compression of thefeedback information is normally required.In this paper, we propose a novel channel quality feedback scheme tobe used in a wireless OFDM system, based on a data compressionapproach, and show that the channel information can be compressed by afactor of 5-30 with virtually no loss of system throughput.
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| 27. |
- Falahati, Sorour, 1971, et al.
(author)
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EU FP6 IST-2003-507581 WINNER, D2.4 Assessment of adaptive transmission technologies, Feb 2005
- 2005
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Reports (other academic/artistic)abstract
- This document contains a first assessment of adaptive transmission schemes and how these fitto the different WINNER scenarios. It focuses on an adaptation due to the channel properties that mayvary both in time and frequency or, with respect to the selected antennas, in an OFDM-based air interface.Besides the evaluation by analysis, link simulation and multilink simulation, first detailed designs arepresented of adaptive transmission feedback systems for the WINNER FDD and TDD physical layermodes.
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| 28. |
- Falahati, Sorour, 1971, et al.
(author)
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Future improvements to wideband CDMA
- 1999
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In: Proceedings Radiovetenskap och Kommunikation, Karlskona, Sweden. ; , s. 470-475
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Conference paper (peer-reviewed)
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| 32. |
- Frenger, Pål, 1968, et al.
(author)
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Code-spread CDMA using low-rate convolutional codes
- 1998
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In: Proceedings IEEE International Symposium on Spread Spectrum Techniques and Applications, Sun City, South Africa. - : Institute of Electrical and Electronics Engineers (IEEE). ; 48:1, s. 374-378
-
Conference paper (peer-reviewed)abstract
- In code division multiple-access (CDMA) systems, maximum total throughput assuming a matched filter receiver can be obtained by spreading with low-rate error control codes. Previously, orthogonal, bi-orthogonal and super-orthogonal codes have been proposed for this purpose. We present in this paper a family of rate-compatible low-rate convolutional codes with maximum free distance. The performance of these codes for spectrum spreading in a CDMA system is evaluated and shown to outperform that of orthogonal and super-orthogonal codes as well as conventionally coded and spread systems. We also show that the proposed low rate codes will give simple encoder and decoder implementations. With these codes, any rate 1/n, n⩽512, are obtained for constraint lengths up to 11, resulting in a more flexible and powerful scheme than those previously proposed.
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| 35. |
- Frenger, Pål, 1968, et al.
(author)
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Combined coding and spreading in CDMA systems using maximum free distance convolutional codes
- 1998
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In: Proceedings IEEE Vehicular Technology Conference, Ottawa, Canada. ; 3, s. 2497-2501
-
Conference paper (peer-reviewed)abstract
- In CDMA systems maximum theoretical performance can be obtained by spreading with low-rate error control codes. Previously, orthogonal and superorthogonal codes have been proposed for this purpose. We present a family of rate-compatible low-rate convolutional codes with maximum free distance. The performance of these codes for spectrum spreading in a CDMA system is evaluated and shown to outperform that of orthogonal and superorthogonal codes as well as conventional coding/spreading schemes. We also show that our low-rate codes will give simple encoder and decoder implementation. With these codes any 1/n rate can be obtained regardless of the constraint length, resulting in a more flexible and powerful scheme than those proposed up to now.
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| 38. |
- Frenger, Pål, 1968, et al.
(author)
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Evaluation of coded CDMA with interference cancellation
- 1999
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In: Proceedings IEEE Vehicular Technology Conference, Houston, Texas. ; , s. 642-647
-
Conference paper (peer-reviewed)abstract
- The performance of an asynchronous CDMA system (up-link) employing very low-rate maximum free distance codes for combined coding and spreading is analyzed when successive or parallel interference cancellation is applied. An analytical approach to the evaluation of the bit error rate is presented and shown to give results close to simulations. Our results show that the code-spread system outperforms the conventionally coded and spread system. Without interference cancellation the single-user bound is never reached (except for one user). With two stages of parallel interference cancellation, a code-spread system with a load only slightly less than 1 bit/chip can obtain a bit error rate very close to that of a single-user system.
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| 39. |
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| 40. |
- Frenger, Pål, 1968, et al.
(author)
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Performance of CDMA systems with low-rate coding and interference cancellation
- 1999
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In: Proceedings FRAMES Workshop, Delft, The Netherlands. ; , s. 212-217
-
Conference paper (peer-reviewed)abstract
- ABSTRACT The performance of a CDMA system employ-ing very low-rate maximum free distance codes for com-bined coding and spreading is analyzed when successive o r parallel interference cancellation is applied. An analytical approach to the evaluation of the bit error rate is presented and shown to give results close to simulations. Our results show that the code spread system outperforms the conven-tionally spread system. Without interference cancellation the single-user bound is never reached except for one user. With two stages of parallel interference cancellation, a code-spread system with a load only slightly less than 1 bittchip obtains a bit error rate very close to that of a single user system with signal-to-noise ratio per information bit of 4 dB. Keywords| CDMA, low-rate convolutional codes, orthog-onal codes, successive i n terference cancellation, parallel in-terference cancellation, rate-compatible, maximum free dis-tance.
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| 44. |
- Gil Jiménez, Victor P., et al.
(author)
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Methods for Compression of Feedback in Adaptive Multi-carrier 4G Schemes
- 2008
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In: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 47:1, s. 101-112
-
Journal article (peer-reviewed)abstract
- In this paper, several algorithms for compressing the feedback of channel quality information are presented and analyzed. These algorithms are developed for a proposed adaptive modulation scheme for future multi-carrier 4G mobile systems. These strategies compress the feedback data and, used together with opportunistic scheduling, drastically reduce the feedback data rate. Thus the adaptive modulation schemes become more suitable and efficient to be implemented in future mobile systems, increasing data throughput and overall system performance.
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