Index and Constellation Order Lowering for OFDM With Index Modulation
17 Feb 2020-IEEE Communications Letters (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 24, Iss: 5, pp 1129-1132
TL;DR: The number of symbol carrying sub-carriers and hence the number of used indices can also be lowered along with modulation order lowering, which reduces the aforementioned number of worst case sub-block pairs even further.
Abstract: Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a promising variant of OFDM where indices of symbol carrying sub-carriers also convey information bits besides the complex symbols themselves. Recently, a lower order modulation variant has been proposed for OFDM-IM, where the baseband constellation is lowered with appropriate rotations and index reuse, so as to lower the number of sub-blocks whose pairwise error probability is inversely related to the signal to noise ratio (SNR). In this work, we demonstrate that the number of symbol carrying sub-carriers and hence the number of used indices can also be lowered along with modulation order lowering. This reduces the aforementioned number of worst case sub-block pairs even further. The resulting unused sub-carriers can now be used to enhance the spectral efficiency as well. Numerical results reveal SNR gains up to 5dB for uncoded systems and 2dB for coded systems.
Citations
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TL;DR: In this article , a group-indexed orthogonal frequency division multiplexing index modulation (OFDM-IM) scheme is proposed to achieve a tradeoff between spectral efficiency and bit error rate (BER) performance.
Abstract: In this study, a novel group‐indexed orthogonal frequency division multiplexing index modulation (OFDM‐IM) scheme is proposed to achieve a tradeoff between spectral efficiency (SE) and bit‐error‐rate (BER) performance. In the proposed scheme, the total subcarriers in a group are divided into subgroups, and additional bits are transmitted by subgroup indexing, unlike the conventional OFDM‐IM scheme, which uses index bits to select active subcarriers. With the proposed scheme, the additional degree of freedom provided by the number of active subgroups selected provides a tradeoff between spectral efficiency and BER performance. Decoding is performed in steps to reduce computional complexity in the decoder design. Simulaton results show that the number of active subgroups selected influences the proposed scheme's performance in terms of energy efficiency, spectral efficiency, and BER performance.
2 citations
05 Aug 2021
TL;DR: In this article, the bit error rate performance of a multicarrier system such as the Orthogonal Frequency Division Multiplexing (OFDM) using a particular type of sub carrier index modulation known as Enhanced sub carrier Index Modulation (ESIM) and operating over a non-linear channel with memory is evaluated.
Abstract: Communications systems that use multicarrier modulation techniques are highly sensitive to non-linear distortions due to relatively high values of a peak-to-average power ratio (PAPR). In order to improve the performance of these systems, schemes using sub carrier index modulation techniques are being proposed. This paper presents analytical expressions that allow evaluating the bit error rate performance of a multicarrier system such as the Orthogonal Frequency Division Multiplexing (OFDM) using a particular type of sub carrier index modulation know as Enhanced sub carrier Index Modulation (ESIM) and operating over a non-linear channel with memory. Numerical results obtained for a specific case allow verifying the performance improvement of ESIM-OFDM systems when compared with classic OFDM systems.
01 Jun 2023
TL;DR: In this paper , a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, is proposed to enhance the effectiveness and the reliability of high mobility vehicular networks in intelligent transportation systems.
Abstract: In this paper, a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, is proposed to enhance the effectiveness and the reliability of high mobility vehicular networks in intelligent transportation systems. The SIM-OTFS system adopts a three dimensional index modulation (IM) technique which utilizes the transmit antenna, delay, and Doppler indexes in the space and delay-Doppler domains, respectively, to achieve a higher transmission rate. Considering the characteristics of vehicular networks, we first present the SIM-OTFS system design and the corresponding signal processing. Then, we derive the average bit error rate (ABER) upper bound of the SIM-OTFS system by the union bound theory. Moreover, the diversity, the coding gain, and the complexity of the SIM-OTFS system are further investigated. Numerical results verify the theoretical analysis of the ABER and the diversity of the SIM-OTFS system, which shows the superiority of the SIM-OTFS system in the ABER performance over the multiple-input and multiple-output (MIMO) based OTFS (MIMO-OTFS) system. Meanwhile, the SIM-OTFS system realizes better performance than the spatial modulation (SM) and IM based orthogonal frequency division multiplexing (SM-OFDM-IM) system in high mobility vehicular communication with reasonable complexity sacrifice. Furthermore, the influence of the resolvable multipaths of the channel in vehicular networks on the ABER performance of the SIM-OTFS system is also illustrated.
TL;DR: In this paper , a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, is proposed to enhance the effectiveness and the reliability of high mobility vehicular networks in intelligent transportation systems.
Abstract: In this paper, a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, is proposed to enhance the effectiveness and the reliability of high mobility vehicular networks in intelligent transportation systems. The SIM-OTFS system adopts a three dimensional index modulation (IM) technique which utilizes the transmit antenna, delay, and Doppler indexes in the space and delay-Doppler domains, respectively, to achieve a higher transmission rate. Considering the characteristics of vehicular networks, we first present the SIM-OTFS system design and the corresponding signal processing. Then, we derive the average bit error rate (ABER) upper bound of the SIM-OTFS system by the union bound theory. Moreover, the diversity, the coding gain, and the complexity of the SIM-OTFS system are further investigated. Numerical results verify the theoretical analysis of the ABER and the diversity of the SIM-OTFS system, which shows the superiority of the SIM-OTFS system in the ABER performance over the multiple-input and multiple-output (MIMO) based OTFS (MIMO-OTFS) system. Meanwhile, the SIM-OTFS system realizes better performance than the spatial modulation (SM) and IM based orthogonal frequency division multiplexing (SM-OFDM-IM) system in high mobility vehicular communication with reasonable complexity sacrifice. Furthermore, the influence of the resolvable multipaths of the channel in vehicular networks on the ABER performance of the SIM-OTFS system is also illustrated.
References
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TL;DR: It is shown via computer simulations that the proposed OFDM with index modulation scheme achieves significantly better error performance than classical OFDM due to the information bits carried in the spatial domain by the indices of OFDM subcarriers.
Abstract: In this paper, a novel orthogonal frequency division multiplexing (OFDM) scheme, called OFDM with index modulation (OFDM-IM), is proposed for operation over frequency-selective and rapidly time-varying fading channels In this scheme, the information is conveyed not only by M-ary signal constellations as in classical OFDM, but also by the indices of the subcarriers, which are activated according to the incoming bit stream Different low complexity transceiver structures based on maximum likelihood detection or log-likelihood ratio calculation are proposed and a theoretical error performance analysis is provided for the new scheme operating under ideal channel conditions Then, the proposed scheme is adapted to realistic channel conditions such as imperfect channel state information and very high mobility cases by modifying the receiver structure The approximate pairwise error probability of OFDM-IM is derived under channel estimation errors For the mobility case, several interference unaware/aware detection methods are proposed for the new scheme It is shown via computer simulations that the proposed scheme achieves significantly better error performance than classical OFDM due to the information bits carried by the indices of OFDM subcarriers under both ideal and realistic channel conditions
752 citations
01 Dec 2012
TL;DR: It is shown via computer simulations that the proposed OFDM with index modulation achieves significantly better error performance than classical OFDM due to the information bits carried by the indices of OFDM subcarriers under both ideal and realistic channel conditions.
Abstract: In this paper, a novel orthogonal frequency division multiplexing (OFDM) scheme, which is called OFDM with index modulation (OFDM-IM), is proposed for frequency-selective fading channels. In this scheme, inspiring from the recently introduced spatial modulation concept for multiple-input multiple-output (MIMO) channels, the information is conveyed not only by M-ary signal constellations as in classical OFDM, but also by the indices of the subcarriers, which are activated according to the incoming bit stream. Different transceiver structures are proposed and a theoretical error performance analysis is provided for the new scheme. It is shown via computer simulations that the proposed scheme achieves significantly better error performance than classical OFDM due to the information bits carried in the spatial domain by the indices of OFDM subcarriers.
574 citations
"Index and Constellation Order Lower..." refers background or methods in this paper
...First, the system model of conventional OFDM-IM [1] is detailed and later, the lower order constellation aided scheme of [8], denoted LO-OFDM-IM hereafter, will be reviewed....
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...Owing to its superior bit error rate (BER) performance over conventional OFDM systems [1], several variants have been proposed for index modulation aided OFDM, which address different aspects like spectral efficiency, BER performance and Peak-to-Average Power Ratio (PAPR)....
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...In total, gp = g(p1 + p2) bits are conveyed by the OFDM-IM system [1]....
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...k ) bits select k sub-carriers from the n, while the second sub-stream of p2 = k log2 M bits modulate the chosen k sub-carriers with a complex constellation of cardinality M [1]....
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..., the probability of the ML detector decoding x̂loi when xloi was transmitted, is given by [1], [8]...
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TL;DR: Monte Carlo simulations on BER corroborate the analyses and show that the proposed schemes appear as promising multi-carrier transmission alternatives by outperforming the existing OFDM-IM counterparts.
Abstract: Orthogonal frequency division multiplexing with index modulation (OFDM-IM) performs transmission by considering two modes over OFDM subcarriers, which are the null and the conventional $M$ -ary signal constellation The spectral efficiency (SE) of the system, however, is limited, since the null mode itself does not carry any information and the number of subcarrier activation patterns increases combinatorially In this paper, a novel IM scheme, called multiple-mode OFDM-IM (MM-OFDM-IM), is proposed for OFDM systems to improve the SE by conveying information through multiple distinguishable modes and their full permutations A practical and efficient mode selection strategy, which is constrained on the phase shift keying/quadrature amplitude modulation constellations, is designed Two efficient detectors that provide different tradeoffs between the error performance and detection complexity are also proposed The principle of MM-OFDM-IM is further extended to the in-phase and quadrature components of OFDM signals, and the method of generating multiple modes from the $M$ -ary pulse amplitude modulation constellation for this modified scheme is also introduced Bit error rate (BER) analyses are provided for the proposed schemes Monte Carlo simulations on BER corroborate the analyses and show that the proposed schemes appear as promising multi-carrier transmission alternatives by outperforming the existing OFDM-IM counterparts
252 citations
TL;DR: A dual-mode OFDM technique is proposed, which is combined with index modulation and enhances the attainable throughput of conventional index-modulation-based OFDM and achieves a considerably better BER performance than other OFDM systems using index modulation, while imposing the same or lower computational complexity.
Abstract: Index modulation has become a promising technique in the context of orthogonal frequency division multiplexing (OFDM), whereby the specific activation of the frequency domain subcarriers is used for implicitly conveying extra information, hence improving the achievable throughput at a given bit error ratio (BER) performance. In this paper, a dual-mode OFDM technique (DM-OFDM) is proposed, which is combined with index modulation and enhances the attainable throughput of conventional index-modulation-based OFDM. In particular, the subcarriers are divided into several subblocks, and in each subblock, all the subcarriers are partitioned into two groups, modulated by a pair of distinguishable modem-mode constellations, respectively. Hence, the information bits are conveyed not only by the classic constellation symbols, but also implicitly by the specific activated subcarrier indices, representing the subcarriers’ constellation mode. At the receiver, a maximum likelihood (ML) detector and a reduced-complexity near optimal log-likelihood ratio-based detector are invoked for demodulation. The minimum distance between the different legitimate realizations of the OFDM subblocks is calculated for characterizing the performance of DM-OFDM. Then, the associated theoretical analysis based on the pairwise error probability is carried out for estimating the BER of DM-OFDM. Furthermore, the simulation results confirm that at a given throughput, DM-OFDM achieves a considerably better BER performance than other OFDM systems using index modulation, while imposing the same or lower computational complexity. The results also demonstrate that the performance of the proposed low-complexity detector is indistinguishable from that of the ML detector, provided that the system’s signal to noise ratio is sufficiently high.
245 citations
"Index and Constellation Order Lower..." refers background or methods in this paper
...Furthermore, as the number of active indices are reduced, the consequent unused sub-carriers can be used to increase the amount of information conveyed, using an approach similar to Dual-Mode OFDM-IM of [3]....
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...Dual-mode OFDM-IM [3] utilizes the remaining (n − k) sub-carriers of OFDM-IM to convey more information bits via a distinguishable constellation....
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...Dual-Mode OFDM-IM [3] increases the number of bits conveyed by utilizing the inherent unused or silent sub-carriers of OFDM-IM to carry symbols from a different constellation....
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...Similar SNR gains are achieved over Dual-Mode OFDM-IM of [3] with same spectral efficiency of 2....
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...Bits conveyed per sub-block is p1 + p2 + (n − k) log2 Md with Md being the order of signal constellation that modulated the (n − k) sub-carriers [3]....
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23 Jun 2014
TL;DR: Both theoretical analysis and simulation results are presented to show that the proposed OFDM with interleaved sucarrier-index modulation (OFDM-ISIM) can achieve better system performance than conventional OFDM-IM and OfDM with low-order modulation schemes such as binary phase shift keying, quadrature phase shiftkeying and 16 quadratures amplitude modulation.
Abstract: Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a recently developed technique which modulates part of the information bits using the indices of OFDM subcarriers. In this letter, a simple and efficient subcarrier-level interleaving scheme is introduced to improve the performance of conventional OFDM-IM through enlarging the Euclidean distances among the modulated symbols. Both theoretical analysis and simulation results are presented to show that the proposed OFDM with interleaved sucarrier-index modulation (OFDM-ISIM) can achieve better system performance than conventional OFDM-IM and OFDM with low-order modulation schemes such as binary phase shift keying, quadrature phase shift keying and 16 quadrature amplitude modulation.
233 citations
"Index and Constellation Order Lower..." refers background or methods in this paper
...The modulated and interleaved [2] sub-carriers undergo IFFT operation followed by cyclic prefix (CP) appending and parallel to serial conversion before they are converted to waveforms and transmitted [1]....
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...For instance, block level interleaving of [2] improves the BER performance of OFDM-IM, especially when the channel is correlated....
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