Modified CI and Modulation Order Replacement for Enhancing OFDM-IM Performance
06 Jun 2019-IEEE Journal of Selected Topics in Signal Processing (IEEE)-Vol. 13, Iss: 6, pp 1286-1300
TL;DR: A novel coordinate interleaving scheme is incorporated on the OFDM-IM system, where instead of the conventional application of CI to the data symbols alone, it is applied to the entire sub-block containing data symbols and zero-padded sub-carriers.
Abstract: Recently, a lower order modulation aided bit error rate reduction scheme was proposed for orthogonal frequency division multiplexing with index modulation (OFDM-IM). Here, the key idea was to replace the conventional modulation order in OFDM-IM with a lower order modulation and its rotated versions. In this paper, we incorporate on the aforementioned system, a novel coordinate interleaving (CI) scheme, where instead of the conventional application of CI to the data symbols alone, it is applied to the entire sub-block containing data symbols and zero-padded sub-carriers. Also, we replace the conventional modulation order in OFDM-IM with a higher order signal constellation. This leads to an increase in the number of symbol selecting bits and a subsequent decrease in the number of index combinations required for mapping. Next, the resulting excess inactive sub-carriers are used to carry more copies of the same data symbols in order to provide diversity. Finally, this modulation order replacement scheme is extended to the in-phase quadrature variant of OFDM-IM. Numerical results indicate that up to 7-dB transmit power gains over OFDM-IM and also over the existing lower order constellation aided scheme can be accrued.
Citations
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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.
4 citations
Cites background or methods from "Modified CI and Modulation Order Re..."
...As explained in [8], LO-OFDM-IM can outperform conventional OFDM-IM because it can lower the number of subblocks whose pair-wise error probability (PEP) falls as 1/SNR [8], [9]....
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...In fact, for k ≥ 2, the ratio of number of sub-block pairs whose PEP falls inversely with SNR in OFDM-IM, α, to the corresponding term in LO-OFDM-IM, αLO is given by (see Theorem 1 in [9])....
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TL;DR: In this article , the error performance of uncoded OFDM-IM and OFDM under barrage jamming (BJ) and partial band jamming attacks was examined and an upper bound for the average bit error probability under AJ attack was derived.
Abstract: Orthogonal frequency division multiplexing (OFDM) with index modulation (IM), OFDM-IM, is considered as a potential enabling technology for 5G and beyond wireless networks due to its advantages compared to OFDM. This paper firstly examines and compares the error performance of uncoded OFDM-IM and OFDM under barrage jamming (BJ) and partial band jamming (PBJ) attacks. In addition, we propose a novel arbitrary jamming (AJ) model and extend our analysis to this attack. We demonstrate that uncoded OFDM-IM is more resistant against jamming attacks when compared to uncoded OFDM. In the OFDM-IM system, we derive an upper bound for the average bit error probability under AJ attack to verify our simulation results. The achievable rate of OFDM-IM under jamming attack is also investigated. We then apply low-density parity-check (LDPC) coding to further enhance the strength of the system under a heavy jamming attack. The optimum log-likelihood ratios for the OFDM-IM system in the case of jamming attack are calculated. We compare and analyze the bit error rate (BER) performances of LDPC coded OFDM and OFDM-IM for different jamming types, code rates, code block lengths, and code decoding algorithms through extensive computer simulations. At high code rates under jamming attack, we prove that the coded OFDM-IM has BER performance superiority. Moreover, we demonstrate that coded OFDM-IM is more resistant against imperfect channel state information than coded OFDM under BJ. We also compare the performances of LDPC coded OFDM-IM and the higher-order OFDM-IM (HO-OFDM-IM), an enhanced version of OFDM-IM.
TL;DR: In this article , the error performance of uncoded OFDM-IM and OFDM under barrage jamming and partial band jamming attacks was examined and an upper bound for the average bit error probability under an arbitrary jamming attack was derived.
Abstract: Orthogonal frequency division multiplexing (OFDM) with index modulation (IM), OFDM-IM, is considered as a potential enabling technology for 5G and beyond wireless networks due to its advantages compared to OFDM. This paper firstly examines and compares the error performance of uncoded OFDM-IM and OFDM under barrage jamming (BJ) and partial band jamming (PBJ) attacks. In addition, we propose a novel arbitrary jamming (AJ) model and extend our analysis to this attack. We demonstrate that uncoded OFDM-IM is more resistant against jamming attacks when compared to uncoded OFDM. In the OFDM-IM system, we derive an upper bound for the average bit error probability under AJ attack to verify our simulation results. The achievable rate of OFDM-IM under jamming attack is also investigated. We then apply low-density parity-check (LDPC) coding to further enhance the strength of the system under a heavy jamming attack. The optimum log-likelihood ratios for the OFDM-IM system in the case of jamming attack are calculated. We compare and analyze the bit error rate (BER) performances of LDPC coded OFDM and OFDM-IM for different jamming types, code rates, code block lengths, and code decoding algorithms through extensive computer simulations. At high code rates under jamming attack, we prove that the coded OFDM-IM has BER performance superiority. Moreover, we demonstrate that coded OFDM-IM is more resistant against imperfect channel state information than coded OFDM under BJ. We also compare the performances of LDPC coded OFDM-IM and the higher-order OFDM-IM (HO-OFDM-IM), an enhanced version of OFDM-IM.
References
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Book•
01 Jan 2005TL;DR: This book covers the fundamental principles of space-time coding for wireless communications over multiple-input multiple-output (MIMO) channels, and sets out practical coding methods for achieving the performance improvements predicted by the theory.
Abstract: This book covers the fundamental principles of space-time coding for wireless communications over multiple-input multiple-output (MIMO) channels, and sets out practical coding methods for achieving the performance improvements predicted by the theory. The theory and practice sections can be used independently of each other. Written by one of the inventors of space-time block coding, this volume is ideal for a graduate student familiar with the basics of digital communications, and for engineers implementing the theory in real systems.
872 citations
"Modified CI and Modulation Order Re..." refers background in this paper
..., the probability of the event where detector erroneously declare x̂ when x was transmitted, given the channel vector h, is given by [3], [35]:...
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...It is evident from [3], [35] that the unconditional pairwise error probability (UPEP),...
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...Thus, it is possible to define diversity order as min rank(A) similar to that in [35]....
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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
"Modified CI and Modulation Order Re..." refers background or methods in this paper
...g) is as given below [3]...
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...Therefore the number of bits that determine the symbols to be carried on the selected subcarriers, p2 = k log2 M [3], and g(p1 + p2) bits are conveyed in total....
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...Therefore only 2 ′′ 1 index combinations are required in bits to index mapping in contrast with 21 of conventional OFDM-IM [3]....
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...select the same index combination of [1,3], and yet, the sym-...
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...Index modulation in general is a communication technique where information bits are conveyed not only through the basic units of the communication system like antennas, sub-carriers, or RF mirrors, but also by the means in which a set of them are selected [3], [4]....
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TL;DR: Three forms of IM are investigated: spatial modulation, channel modulation and orthogonal frequency division multiplexing (OFDM) with IM, which consider the transmit antennas of a multiple-input multiple-output system, the radio frequency mirrors mounted at a transmit antenna and the subcarriers of an OFDM system for IM techniques, respectively.
Abstract: What is index modulation (IM)? This is an interesting question that we have started to hear more and more frequently over the past few years. The aim of this paper is to answer this question in a comprehensive manner by covering not only the basic principles and emerging variants of IM, but also reviewing the most recent as well as promising advances in this field toward the application scenarios foreseen in next-generation wireless networks. More specifically, we investigate three forms of IM: spatial modulation, channel modulation and orthogonal frequency division multiplexing (OFDM) with IM, which consider the transmit antennas of a multiple-input multiple-output system, the radio frequency mirrors (parasitic elements) mounted at a transmit antenna and the subcarriers of an OFDM system for IM techniques, respectively. We present the up-to-date advances in these three promising frontiers and discuss possible future research directions for IM-based schemes toward low-complexity, spectrum- and energy-efficient next-generation wireless networks.
676 citations
"Modified CI and Modulation Order Re..." refers background in this paper
...Let them be {[1, 2], [1, 3], [1, 4], [2, 4]}....
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...For instance, if the selected indices are [1, 2] and symbols on these are s1, s2, the unused combination [5, 6] also carries [s1, s2] and so does [7, 8]....
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...select the same index combination of [1,3], and yet, the sym-...
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...ORTHOGONAL frequency division multiplexing with index modulation (OFDM-IM) belongs to a broad category of communication strategies known as index modulation [1], [2]....
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...If the chosen index combination is [1, 2], sub-carriers 1, 5, 7 carry the same symbol s1....
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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
"Modified CI and Modulation Order Re..." refers background or methods in this paper
...In each sub-block,k sub-carriers are selected and modulated according to the incoming bit stream [3]....
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...Therefore the number of bits that determine the symbols to be carried on the selected subcarriers, p2 = k log2 M [3], and g(p1 + p2) bits are conveyed in total....
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...Therefore only 2 ′′ 1 index combinations are required in bits to index mapping in contrast with 21 of conventional OFDM-IM [3]....
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...Let them be {[1, 2], [1, 3], [1, 4], [2, 4]}....
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...2921520 and modulated from the available sub-carriers which are divided into a number of sub-blocks [3]....
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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