| 1. |
- Alvarado, Alex, 1982, et al.
(författare)
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Exploiting UEP in QAM-based BICM: Interleaver and Code Design
- 2010
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 58:2, s. 500-510
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we formally analyze the interleaver and code design for QAM-based BICM transmissions using the binary reflected Gray code. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds the optimum design of interleaver and code is found, and numerical results for representative configurations are presented. When the new design is used, the improvements may reach 2 dB, and they are obtained without any increase on the transceiver's complexity. We also introduce the concept of generalized optimum distance spectrum convolutional codes, which are the optimum codes for QAM-based BICM transmissions.
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| 2. |
- Alvarado, Alex, 1982, et al.
(författare)
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On BICM-ID with Multiple Interleavers
- 2010
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 14:9, s. 785-787
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we study the performance of BICM-ID with multiple interleavers (BICM-ID-M) in terms of bit-error rate (BER), and show that BICM-ID-M is well-suited to exploit the unequal error protection (UEP) caused by the binary labeling. We show that BICM-ID-M should always be the preferred alternative for BICM-ID and that the gains obtained appear even for the simplest configuration (0.5-0.75 dB for a BER of 10-7). It is found that conventional design paradigms such as maximizing the free distance of the code should be modified.
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| 3. |
- Alvarado, Alex, 1982, et al.
(författare)
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On the Capacity of BICM with QAM Constellations
- 2009
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Ingår i: Proceedings International Wireless Communications and Mobile Computing Conference, IWCMC'09, Leipzig, Germany [Invited]. - New York, NY, USA : ACM. - 9781605585697 ; , s. 573-579
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Konferensbidrag (refereegranskat)abstract
- In this tutorial paper we analyze the capacity of bit-interleaved coded modulation (BICM) with quadrature amplitude modulation (QAM) constellations, and we pay special attention to different bit-to-symbol labeling strategies. The relation between the BICM capacity and the capacity of other CM schemes such as trellis coded modulation (TCM) and multilevel codes (MLC) is analyzed. Motivated by the fact that for BICM with some particular labelings, the same Eb/No maps to more than one BICM capacity value, we study the relation between the capacity and Eb/No. In particular, we present some analytical results on this relation, and we also give an intuitive explanation for the somehow contradictory behavior of these curves.
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| 4. |
- Alvarado, Alex, 1982, et al.
(författare)
-
On the Design of Interleavers for BICM Transmission
- 2008
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Ingår i: Proceedings European Wireless Conference 2008, EW2008, Prague, Czech Republic. - 9783800731022
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Konferensbidrag (refereegranskat)abstract
- In this paper we design interleavers for bit-interleaved coded modulation (BICM) based on popular convolutional codes and quadrature amplitude modulation with Gray mapping. We analyze the so-called modular interleavers where the outputs of the convolutional encoder are appropriately matched with the input bits of the modulator. To quantify the achievable improvements we develop bounds on the coded BER using themultidimensional weight distribution spectrum of a code together with an equivalent QAM channel model. Based on these bounds, we show that the assignment of the encoder's output to the bit positions in the symbol significantly affects the system performance. The analytical developments are contrasted with numerical simulations. The improvements obtained through the proposed approach do not change the receiver's complexity and, depending on the system's parameters (rate, modulation, code's memory), they may be up to 1.7 dB!
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| 5. |
- Alvarado, Alex, 1982, et al.
(författare)
-
Unequal Error Protection in BICM with QAM Constellations: Interleaver and Code Design
- 2009
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781424434350
-
Konferensbidrag (refereegranskat)abstract
- In this paper we present a general methodology for the interleaver and code design for QAM-based BICM transmissions. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds, the optimum design of interleaver and code is presented. The improvements obtained reached 2~dB for the analyzed cases, and are obtained without complexity increase. Although previous works noted the influence of the interleaver design and the UEP, to the best of our knowledge, this paper is the first to analyze formally this problem for BICM transmissions.
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| 6. |
- Haghighi, Kasra, 1978, et al.
(författare)
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Wideband Sequential Spectrum Sensing with Varying Thresholds
- 2010
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Ingår i: Proceedings IEEE Global Communications Conference, Wireless Communications Symposium, Miami, Florida, USA. - 9781424456383
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Konferensbidrag (refereegranskat)abstract
- In this contribution, time varying threshold sequentialdetectors are employed for energy detection-based spectrumsensing in low-SNR regimes. Sequential detection is proven to befaster (on average) than any other multi-sample detector for a setof given probabilities of detection and false-alarm. In this report,exact performance of a sequential detector for spectrum sensingis analyzed using the direct method. The theoretical resultspresented herein are verified with Monte-Carlo simulations. Itis shown that for a SNR of −10 dB, among tests with Wald andtriangular thresholds with similar probabilities of mis-detectionand false-alarm, triangular performs 54% faster in terms ofmaximum detection time (90 percentile).
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| 7. |
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| 8. |
- Wessman, Matts-Ola, 1972, et al.
(författare)
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Frequency Diversity Performance of Coded Multiband-OFDM Systems on IEEE UWB Channels
- 2004
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Ingår i: Proceedings IEEE Vehicular Technology Conference Fall, Los Angeles, California, USA. - 1090-3038. - 0780385217 ; 2, s. 1197-1201
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Konferensbidrag (refereegranskat)abstract
- This paper investigates how convolutional and Reed-Solomon codes can be used to improve the performance of multiband-OFDM by utilizing the inherent frequency diversity of the new IEEE 802.15 UWB channel models. A normalized amplitude autocovariance function of the Fourier transform of the channel impulse response is defined. Then the average coherence bandwidths of CM1, CM2, CM3, and CM4 are estimated to be 31.6, 16.3, 11.0, 5.8 MHz, respectively. Using the central limit theorem, we can expect that the performance of an uncoded OFDM system on CM1-CM4 without shadowing is the same as in a Rayleigh fading channel with uniformly distributed phase. The performance of a convolutional code with rate 1/2 and constraint length 7 on CM2-CM4 without shadowing are up to 0.4 dB worse than that of on an uncorrelated Rayleigh fading channel. The loss for CM1 is around 1 dB. A block interleaver with 32 rows and 24 columns was used. This result is also valid for a convolutional code with rate 1/4 and constraint length 7. For code rates around 2/3, the performance of a punctured convolutional code with soft-decision decoding is much better than that of the Reed-Solomon codes with with 6, 7, and 8 bits per symbol and hard-decision decoding.
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| 9. |
- Wessman, Matts-Ola, 1972, et al.
(författare)
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Performance of Coded Single-Band Carrier-Based DS-SS Systems on IEEE 802.15.3a UWB Channels
- 2005
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Ingår i: Proceedings IEEE International Conference on Ultra-Wideband, Zürich, Switzerland. - 078039397X ; , s. 152-157
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Konferensbidrag (refereegranskat)abstract
- A set of physical layer specifications is provided for a single-band system. The system fulfills the FCC regulations on UWB devices and the physical layer requirements from IEEE 802.15.3a. It gives reliable communication, i.e., a 90th-percentile PER equal to 8% for 1024 payload bytes, at 110 Mbps with a transmitter-receiver separation of up to 10 meters on the IEEE 802.15.3a channel model CM4. 205 Mbps at 6.7 meters on CM4 and 513 Mbps at 3.8 meters on CM2 are also achieved. The system uses the spectrum 3.1-4.9 GHz, a chip-spaced Rake combiner with 60 fingers, a sliding window channel estimator, and a sampling rate of 1540 Msamples/s.
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