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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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- 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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- 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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- 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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- 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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