Interference suppression using EM algorithm in OFDM transmissions

Yoda, Naotoshi; Ohtsuki, Tomoaki; Mashino, Jun; Sugiyama, Takatoshi

doi:10.1109/glocom.2014.7037307

Cited by 5 publications

(7 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…7, interferences 1, 2, and 3 superpose on 4 (1 ≤ l ≤ 4, 11 ≤ l ≤ 14, and 21 ≤ l ≤ 24) subcarriers of desired signals, respectively. Each SIR is 3 dB, which corresponds to the assumption in the conventional schemes [15,16]. That is,…”

Section: Simulation Resultsmentioning

confidence: 99%

“…In the scheme, residual powers are averaged in both time and frequency domains to mitigate the variance of them among subcarriers on the same superposed band. Besides, the threshold used to detect superposed bands is updated according to the equation proposed in [16] and superposed band detection is iteratively performed. Although the BER performance is slightly improved compared to that of conventional schemes for large E b /N 0 , and also, the detection rate of superposed bands is made higher by updating the threshold, there are still several points to be improved.…”

Section: Introductionmentioning

confidence: 99%

“…One drawback of the scheme is large computational complexity because of iterative decoding. In [16], EM algorithm is applied to reduce the computational complexity. At the receiver side, first, residual powers are calculated by exploiting hard-decision replica symbols.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Suppression of multiple wideband interferences based on superposition probability

Kakizaki

Shibata

Ohtsuki

et al. 2016

J Wireless Com Network

Self Cite

View full text Add to dashboard Cite

Superposed multicarrier transmission is one of the schemes that achieve efficient use of frequency resources. In the scheme, desired signals are interfered by other systems sharing the same frequency band, which causes unreliable LLR (log-likelihood ratio) setting and leads to degradation of the BER (bit error rate) performance. In many conventional schemes for OFDM (orthogonal frequency division multiplexing) systems, the interference power for each subcarrier is estimated independently. Otherwise, based on the assumption that interferences have the same average power, one interference power is estimated and applied to all subcarriers. However, when there exist multiple wideband interferences with different average power, it is better to detect each interference and estimate each power based on all subcarriers within each superposed band to make it accurate. In this paper, we propose a scheme to suppress multiple wideband interferences based on the probability with which each subcarrier is superposed, referred to as the superposition probability. In the proposed scheme, we derive the PDFs (probability density functions) of residual powers for superposed and non-superposed bands. Based on residual powers and their PDFs, we calculate the superposition probability for each subcarrier. Furthermore, we perform superposed band detection iteratively according to the probabilities and update each estimated interference power. Through simulations, we show that the detection rate of superposed bands is improved by iterating superposed band detection based on superposition probabilities. We also show that the proposed scheme achieves the better BER performance than that of conventional ones.

show abstract

Section: Simulation Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Suppression of multiple wideband interferences based on superposition probability

Kakizaki

Shibata

Ohtsuki

et al. 2016

J Wireless Com Network

Self Cite

View full text Add to dashboard Cite

show abstract

“…When no bit error and no channel estimation error are assumed, p i f (l) is calculated as follows [9].…”

Section: E[·] T Is the Expected Value Note That The Residual Power |mentioning

confidence: 99%

“…(3) where the interference is not taken into account, which leads to the poor performance. To mitigate the impact of interference, the robust LLR was used in [9], which is defined as [7] …”

Section: System Modelmentioning

confidence: 99%

[Invited Paper] Superposed Multicarrier Transmission

Ohtsuki

2018

MTA

Self Cite

View full text Add to dashboard Cite

A superposed multicarrier transmission scheme is known to improve frequency utilization efficiency where several systems share spectrum without any spectrum spreading techniques. In the superposed multicarrier transmission scheme forward error correction (FEC) coding is in general applied so that the effects of interference caused by superposition of spectrum is mitigated by error correction capability. Thus, the superposed multicarrier transmission scheme is effective under cognitive environments where several wireless systems share the same frequency band. The superposed multicarrier transmission scheme is also expected in broadcasting where wireless communications are also used and can be interfered by other wireless systems. In the superposed multicarrier transmission scheme, to reduce the effects of interference by exploiting the capability of FEC, initial log likelihood ratio (LLR) should be set appropriately. Setting LLR correctly requires several information including interference power on each subcarrier, which are not known in general. We have developed several techniques to estimate the information including interference required for the superposed multicarrier transmission scheme. This paper introduces the superposed multicarrier transmission scheme. This paper also introduces some of our techniques proposed for the superposed multicarrier transmission scheme.

show abstract