Super-orthogonal Convolutional Codes Research Articles

A New Uplink Multiple Access Based on OFDM With Low PAPR, Low Latency, and High Reliability

This paper proposes a new physical layer architecture based on orthogonal frequency-division multiplexing (OFDM) for uplink multiple access. It aims at high reliability with fixed decoder latency targeting emergent low-latency wireless applications, such as transmission of control information in machine-to-machine (M2M) and device-to-device (D2D) communications. Our proposed system is based on the judicious combination of subcarrier hopping and super-orthogonal convolutional codes for achieving high coding gain and frequency diversity, together with Golay complementary sequences for low peak-to-average power ratio (PAPR) signaling. The low PAPR nature improves the power efficiency at a power amplifier (PA) and thus contributes to the transmission range enhancement. Furthermore, by introducing non-orthogonality among users through the assignment of the same set of subcarriers to multiple users, the overall spectral efficiency can be improved. In order to suppress multiple access interference caused by the non-orthogonal overlap of users, multiuser detection (MUD) is employed. Theoretical expressions of approximate bit error rate for the proposed system with MUD are also developed. Numerical results reveal that our proposed system achieves higher reliability and higher spectral efficiency than the conventional orthogonal frequency-division multiple access (OFDMA)-based system.

Repeat-punctured superorthogonal convolutional turbo codes on AWGN and flat Rayleigh fading channels

Repeat-punctured turbo codes, an extension of the conventional turbo-coding scheme, has shown a significant increase in bit-error rate performance at moderate to high signal-to-noise ratios for short frame lengths. Superorthogonal convolutional turbo codes (SCTC) makes use of superorthogonal signals to improve the performance of the conventional turbo codes and a coding scheme that applies the repeat-punctured technique into SCTC has shown to perform better. We investigated two new low-rate coding schemes, repeat-punctured superorthogonal convolutional turbo codes (RPSCTC) and dual-repeat-punctured superorthogonal convolutional turbo codes (DRPSCTC), that make use of superorthogonal signaling, together with repetition and puncturing, to improve the performance of SCTC for reliable and effective communications. Simulation results in the additive white Gaussian noise (AWGN) channel and the frequency non-selective Rayleigh fading channel are presented together with analytical bounds of bit error probabilities, derived from transfer function bounding techniques. From the simulation results and the analytical bounds presented, it is evident that RPSCTC and DRPSCTC offer a more superior performance than SCTC in the AWGN channel, as well as in flat Rayleigh non-line-of-sight fading channels. The distance spectrum is also presented for the new schemes and accounts for the performance improvement rendered in simulations. It is important to note that the improved performance that SCTC, and consequently RPSCTC and DRPSCTC, exhibit is achieved at the expense of bandwidth expansion and complexity and would be ideal for power-limited satellite communication links or interference-limited systems.

Repeat-punctured superorthogonal convolutional turbo codes on AWGN and flat Rayleigh fading channels

Repeat-punctured turbo codes, an extension of the conventional turbo-coding scheme, has shown a significant increase in bit-error rate performance at moderate to high signal-to-noise ratios for short frame lengths. Superorthogonal convolutional turbo codes (SCTC) makes use of superorthogonal signals to improve the performance of the conventional turbo codes and a coding scheme that applies the repeat-punctured technique into SCTC has shown to perform better. We investigated two new low-rate coding schemes, repeat-punctured superorthogonal convolutional turbo codes (RPSCTC) and dual-repeat-punctured superorthogonal convolutional turbo codes (DRPSCTC), that make use of superorthogonal signaling, together with repetition and puncturing, to improve the performance of SCTC for reliable and effective communications. Simulation results in the additive white Gaussian noise (AWGN) channel and the frequency non-selective Rayleigh fading channel are presented together with analytical bounds of bit error probabilities, derived from transfer function bounding techniques. From the simulation results and the analytical bounds presented, it is evident that RPSCTC and DRPSCTC offer a more superior performance than SCTC in the AWGN channel, as well as in flat Rayleigh non-line-of-sight fading channels. The distance spectrum is also presented for the new schemes and accounts for the performance improvement rendered in simulations. It is important to note that the improved performance that SCTC, and consequently RPSCTC and DRPSCTC, exhibit is achieved at the expense of bandwidth expansion and complexity and would be ideal for power-limited satellite communication links or interference-limited systems.

Repeat-punctured superorthogonal convolutional turbo codes on awgn channels

The performance of turbo codes has been shown to be near the theoretical limit in the additive while Gaussian noise channel. By using orthogonal signaling, which allows for bandwidth expansion, the performance of the turbo coding scheme can be improved even further. Since this is a low-rate code, the code is mainly suitable for spread-spectrum modulation applications. In classical turbo codes the frame length is set equal to the interleaver size, however, the codeword distance spectrum of turbo codes improves with an increasing interleaver size. It has been reported that by using repetition and puncturing the performance of turbo codes can be improved. Repeat-Punctured Turbo Codes has shown a significant increase in performance at moderate to high signal-to-noise ratios. In this paper, we study the use of orthogonal signaling and parallel concatenation together with repetition and puncturing to improve the performance of superorthogonal convolutional turbo codes for reliable and effective communications. Simulation results for the additive white Gaussian noise channel are presented together with analytical upper bounds, which have been derived using transfer function bounding techniques.

A Combined Coding and Modulation to Support Both Coherent and Non-coherent Ultra-Wideband Receivers

This letter proposes a simple combined coding and modulation based on super-orthogonal convolutional codes (SOCs) in order to support both coherent and non-coherent ultra-wideband (UWB) receivers. In the proposed scheme, the coherent receivers obtain a coding gain as large as the SOC while simultaneously supporting non-coherent receivers. In addition, their performance can be freely adapted by changing the encoder constraint length and the number of PPM slots according to its application. Thus, the proposal enables a more flexible system design for low data-rate UWB systems.

Performance of Super-Orthogonal Convolutional Coding for Ultra-Wideband Systems in Multipath and Multiuser Channels

This paper investigates the application of super-orthogonal convolutional codes (SOCC) to a direct-sequence based ultra- wideband (DS-UWB) system under a realistic environment including inter-symbol interference (ISI) and multiuser interference (MUI). The effect of MUI and ISI on the performance of SOCC is analyzed by using both maximum ratio combining (MRC) RAKE receiver and minimum mean-squared error (MMSE) RAKE receiver followed by matched filter receiver. The analysis shows that in the case of employing simple MRC-RAKE receiver, the performance of SOCC is ffected by MUI and ISI because of the short length of the spreading sequence. In order to combat MUI and ISI, a code-hopping scheme is proposed in conjunction with SOCC. The results show that SOCC scheme outperforms the higher-rate conventional convolutional coded scheme for multipath and multiple access channels. Furthermore, the use of MMSE-RAKE receiver to suppress interference is analyzed and the subsequent increase of the system capacity is observed.

Very low rate trellis/Reed-Muller (TRM) codes

This paper considers a technique for very low rate channel coding. The main application for such codes is in spread-spectrum systems where significant bandwidth spreading is possible. New, very low rate binary channel codes based on a combination of a trellis code with a first-order Reed-Muller block code (trellis/Reed-Muller (TRM) codes) are presented. The construction technique for TRM codes, which is considered in this paper, is related to Kerdock (1972) codes. It is shown that these TRM codes provide a better tradeoff between rate and gain than other existing very low rate codes, such as the orthogonal or superorthogonal convolutional codes, and the IS-95 uplink code. Due to their improved performance, TRM codes can significantly increase the bandwidth efficiency of spread-spectrum multiple-access systems.