Abstract — Turbo coded Quadrature Amplitude Modulated (original) (raw)
Related papers
2014
Turbo coded Quadrature Amplitude Modulated (QAM) systems have been adopted by standards such as Code Division Multiple Access (CDMA) 2000 and Long Term Evolution (LTE) to achieve high data rates. Although several techniques have been developed to improve the performance of Turbo coded QAM systems, combinations of these techniques to produce hybrids with better performances, have not been fully exploited. This paper investigates the performance of LTE Turbo codes with Joint Source Channel Decoding (JSCD), adaptive Sign Division Ratio (SDR) based scaling and prioritised QAM constellation mapping. JSCD exploits a-priori source statistics at the decoder side and SDR based scaling provides a scale factor for the extrinsic information as well as a stopping criterion. Additionally, prioritised constellation mapping exploits the inherent Unequal Error Protection (UEP) characteristic of the QAM constellation and provides greater protection to the systematic bits of the Turbo encoder. Simulat...
2013
Turbo coded 64-QAM systems have been adopted by standards such as CDMA-2000 and Long Term Evolution (LTE) to achieve high data rates. Although several techniques have been developed to improve the performance of Turbo coded QAM systems, combinations of these techniques to produce hybrids with better performances, have not been fully exploited. This paper proposes a combination of Joint Source Channel Decoding (JSCD), adaptive Sign Division Ratio (SDR) based scaling and prioritised constellation mapping, to improve the performance of Turbo coded 64-QAM. JSCD exploits a-priori source statistics at the decoder side and SDR based scaling provides a scale factor for the extrinsic information as well as a stopping criterion. Additionally, prioritised constellation mapping exploits the inherent Unequal Error Protection (UEP) characteristic of the 64-QAM constellation and provides greater protection to the systematic bits of the Turbo encoder. Simulation results show that at Bit Error Rates...
mapping of turbo coded bits with QAM
Energy efficient communication is a long-standing issue in modern wireless communication systems. With the increase in number of smaller and faster devices, it has become essential to efficiently utilize mobile battery resources. Drastic growth of mobile data traffic, emergence of new applications such as mobile TV demand high data rate which motivated Third Generation Partnership Project (3GPP) to develop Long Term Evolution (LTE). LTE is the most promising technology for 4G mobile communication networks. The goal of LTE is to provide high data transmission rate, scalable bandwidth, low latency, and high-mobility. It also provides superior speed, low latency ,better QoS and packet optimized radio access technology. Quadrature amplitude modulation (QAM) is frequently met in current communication systems. Specific standardized applications use specific variants of QAM. Variants of QAM are used in digital cable television or wireless and cellular technology applications. The 64-QAM is a good compromise between spectral efficiency (6 bit/s/Hz) and performance of bit/frame error rate (B/FER) versus signal to noise ratio (SNR) [1]. 64-QAM gives a symbol error rate of 10-6 for a SNR of about 19 dB for uncoded system. However, using a turbo code, a BER of 10-10 can be obtained at a SNR of 9 dB. The square 64-QAM is the most frequently encountered in applications. For example, in LTE is specified that such modulation techniques with Gray allocation can be used to minimize the BER [2].A specific property of squares QAM modulations with Gray allocation is that the bits of the symbol modulator are not uniform protected. The same non uniform protection characterizes the square 64-QAM modulation. A question arises in the case of a direct coupling between the turbo encoder and the modulator. In this paper analysis is for three locations for the placement of the information and parity bits generated by turbo coding in the symbol modulator. In the first case for both SBTC coding rates, 1/3 and 2/3, the information bit was placed in the best protected position, followed by two parity bits placed in less protected positions. In the second case the information bit is placed on the middle position, so that in the better and less protected positions are placed the parity bits. Finally, in the third case, the information bit appears on the poorly protected position. The results of simulations show a completely different behaviour in the performance of B/FER vs SNR of these allocation variants. Project Stage I Turbo coded bit allocation mode for 64QAM in LTE for improving performance of FER vs SNR DYPCOE Akurdi, Dept. of E&TC, PG(Communication network)1
A Review on Adaptive Modulation and Turbo Coding in LTE
2016
The LTE standard uses three different modulation schemes to adapt to various channel conditions in order to improve achievable data rates. These modulation schemes are the QPSK, 16-QAM and 64-QAM. This paper presents an overview of a LTE digital communication system Simulink model, designed in order to study the effects of the QPSK, 16-QAM and 64-QAM modulation schemes on the BER performance with an AWGN channel model. Different subsystems within the transmitter and receiver blocks are implemented in Simulink. It is noted that the LTE system uses Turbo channel coding and bit level scrambling to offer reliable and secure services to the users. Depending on the assumed channel condition (clear, medium clear or noisy), the 64QAM, 16-QAM or QPSK modulation scheme, on the transmitter side; as well as the corresponding demodulation scheme, on the receiver side; are automatically selected. Based on the recovered data bits, the obtained bit error rates are analysed, compared and
Application and standardization of turbo codes in third-generation high-speed wireless data services
IEEE Transactions on Vehicular Technology, 2000
This paper addresses the application of turbo codes for third-generation wireless services. It describes the specific characteristics of high-rate data applications in third-generation wide-band code-division multiple-access (CDMA) systems that make turbo codes superior to convolutional codes. In particular, it shows the positive effect of fast power control employed in these systems on the relative performance of turbo codes with respect to convolutional codes. It also shows how turbo and convolutional codes behave differently when the figure of merit is changed to frame error rate from bit error rate for high-speed data services. Furthermore, it describes in detail how and why the standardized turbo code has been selected in the presence of other candidates, which were also based on iterative decoding. Details of turbo interleaving and trellis termination as specified in the standards are explained. Performance of turbo codes under wide-band CDMA operating conditions are presented. The suitability of turbo codes for low-rate data applications is discussed. Finally, it is shown that the performance loss as a result of internal decoder parameter quantization is negligible.
2021
One of the most often-used stopping criteria is the cross-entropy stopping criterion (CESC). The CESC can stop turbo decoder iterations early by calculating mutual information improvements while maintaining bit error rate (BER) performance. Most research on iterative turbo decoding stopping criteria has utilised low-modulation methods, such as binary phase-shift keying. However, a high-speed network requires high modulation to transfer data at high speeds. Hence, a high modulation technique needs to be integrated into the CESC to match its speed. Therefore, the present paper investigated and analysed the effects of the CESC and quadrature amplitude modulation (QAM) on iterative turbo decoding. Three thresholds were simulated and tested under four situations: different code rates, different QAM formats, different code generators, and different frame sizes. The results revealed that in most situations, the use of CESC is suitable only when the signal-to-noise ratio (SNR) is high. This...
Bit Error Rate Performance of Third Generation Turbo Codes
2005
After the invention of Turbo Codes (TCs) many coding theorist and researchers further tried to improve the performance of these codes. Now the performance of Turbo Codes is becoming closer to the Shannon's limit. The performance of turbo codes depends on its architectural component and the architecture of TCs is application dependent. So the researchers are trying to develop the standard architecture of TCs for specific application so that its performance becomes optimum. In this paper we analyze the performance, in terms of bit error rate (BER) vs. bit energy to noise spectral ratio (E b /N o ) of Turbo Codes that are using in Third Generation Partnership Project standard (Universal Mobile Telephone Systems-UMTS) . This paper focuses on the effect of the variation of the architectural components of UMTS TCs on its performance. In particular code rate, frame size i.e., length of information bits, number of decoding iteration and channel models variations of Turbo Codes are taken into account in studying the performance of Turbo Codes. These effects are shown in the performance curve (BER vs. E b /N 0 ) of the UMTS standard turbo codes.