Exact and approximated expressions of the log-likelihood ratio for 16-QAM signals

Allpress, S.; Luschi, C.; Felix, Stephan B.

doi:10.1109/acssc.2004.1399245

Cited by 35 publications

(30 citation statements)

References 5 publications

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“…For MLSD, results for both CS (all bit flips available) and PD are given. For LE, soft information is generated using (17) in [29]. Observe that PD gives a slight loss relative to CS.…”

Section: Performancementioning

confidence: 99%

A Novel Multistage Group Detection Technique and Applications

Bottomley

Wang

2010

IEEE Trans. Wireless Commun.

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In this letter, a multistage group detection (MSGD) approach to nonlinear equalization is proposed. At each stage, symbols are divided into groups, and maximum-likelihood detection (MLD) within the group is performed. The MLD process identifies a number of promising group values. It is constrained to only consider candidate symbol values identified in the previous stage. Groups are formed by combining groups from the previous stage. For example, symbols are detected one at a time, then two at a time, then four at a time, and so on. The last stage is a form of constrained maximum-likelihood sequence detection (MLSD). The overall demodulation process can be viewed as approximate MLSD, and results show that near-MLSD performance is possible with reasonable complexity. While the High Speed Downlink Packet Access (HSDPA) cellular system is used as an example, the approach can be applied other situations, including the Long Term Evolution (LTE) uplink and MIMO.Index Terms-Intersymbol interference, equalization, maximum likelihood detection, CDMA, MIMO systems.

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“…For MLSD, results for both CS (all bit flips available) and PD are given. For LE, soft information is generated using (17) in [29]. Observe that PD gives a slight loss relative to CS.…”

Section: Performancementioning

confidence: 99%

A Novel Multistage Group Detection Technique and Applications

Bottomley

Wang

2010

IEEE Trans. Wireless Commun.

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“…The calculation of LLR for the proposed system is inspired by work in [3] that discusses the exact and approximate expressions of the LLR for a 16-QAM signal.…”

Section: Log-likelihood Ratio Calculationmentioning

confidence: 99%

Soft output detector for parity bit selected CDMA system

Mirzaee

D’Amours

2009

2009 11th Canadian Workshop on Information Theory

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This paper investigates the performance of the Parity Bit selected Code Division Multiple Access (PB-CDMA) system when a soft output detector based on Log Likelihood Ratio (LLR) calculation is employed. In this system, information bits are convolutionally encoded prior to being used in the parity bit selected Direct Sequence Spread Spectrum (DS-SS) system. Reliability of the detected bits in the receiver is calculated in the form of LLRs and then used as the input of a soft input Viterbi decoder. The performance of the proposed system is compared to conventional coded spread spectrum systems where no parity bit selected spreading sequence is used. Numerical results show that the proposed system can be used to improve the capacity of a Code Division Multiple Access (CDMA) system in terms of the number of simultaneously transmitting users.Index Terms-Spread spectrum communication, CDMA, error control coding, log likelihood ratio.

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“…In this Letter, we propose a simplified soft-decision demapping algorithm. The proposed algorithm can reduce the computation complexity compared with the conventional soft-decision method [1][2][3]. Compared with the MAX method, the proposed algorithm can reduce the hardware resources required by about 81%.…”

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confidence: 92%

“…Introduction: In conventional wireless communication systems, the log likelihood ratio (LLR) method has been used as a soft decision technique for the iterative coding scheme, soft input soft output (SISO) [1]. However, this method has problems in terms of its hardware complexity and power consumption, owing to the complicated operations involved.…”

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confidence: 99%

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Simplified soft-decision demapping algorithm for digital video broadcasting system

2010

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A simplified soft-decision demapping algorithm for digital video broadcasting via satellite, second generation (DVB-S2), is presented. The proposed algorithm can reduce the computational complexity required to compute the log likelihood ratio values between the received noisy symbol and possible constellation points compared to conventional algorithms. The simulation results show that the proposed algorithm has negligible performance degradation compared with conventional algorithms. Compared with the maximum algorithm, the proposed algorithm can reduce the hardware resources required by about 81%.Introduction: In conventional wireless communication systems, the log likelihood ratio (LLR) method has been used as a soft decision technique for the iterative coding scheme, soft input soft output (SISO) [1]. However, this method has problems in terms of its hardware complexity and power consumption, owing to the complicated operations involved. To overcome these problems, various soft decision techniques have been proposed [2,3]. The maximum (MAX) method can reduce the number of exponential and logarithm functions as compared to the LLR method. Hence, its hardware complexity is lower than that of the LLR method. The Euclidean method can reduce the number of multiplications of the channel estimation value. However, this method requires square and square root operations, thereby increasing the hardware complexity compared with the MAX method. In addition, the bit error rate (BER) performance is deteriorated compared to the LLR and MAX methods. In this Letter, we propose a simplified soft-decision demapping algorithm. The proposed algorithm can reduce the computation complexity compared with the conventional soft-decision method [1][2][3]. Compared with the MAX method, the proposed algorithm can reduce the hardware resources required by about 81%.

show abstract

Exact and approximated expressions of the log-likelihood ratio for 16-QAM signals

Cited by 35 publications

References 5 publications

A Novel Multistage Group Detection Technique and Applications

A Novel Multistage Group Detection Technique and Applications

Soft output detector for parity bit selected CDMA system

Simplified soft-decision demapping algorithm for digital video broadcasting system

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