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.

Real-time wireless communications such as motion controls of vehicles and machines have been attractive in recent years, in which latency and reliability are of significant importance. A new orthogonal frequency-division multiplexing (OFDM)-based uplink multiple access system called subcarrier hopping multiple access (SHMA) can achieve high reliability due to both coding gain and frequency diversity gain without increasing decoding delay by combining super-orthogonal convolutional codes (SOCC) with subcarrier hopping. In order to improve the spectral efficiency, multiple users should share the same set of subcarriers together with multiuser detection and decoding (MUD) at the receiver to mitigate multiple access interference. In this work, we focus on two representative MUD schemes, i.e., super-trellis decoding (STD) and successive interference cancellation (SIC), and develop approximate bit error rate expressions when each MUD scheme is employed. Through the comparison with simulation results, we demonstrate that our analysis is useful for predicting the behavior of MUD. Also shown is the effectiveness of our proposed hopping design in fully achieving frequency diversity gain over static fading channels.

We consider a new uplink multiple access system based on orthogonal frequency-division multiplexing (OFDM), subcarrier hopping, and super-orthogonal convolutional codes (SOCC) that can achieve high coding gain and frequency diversity without sacrificing latency. Such a system is of significant importance for future wireless communications targeting motion controls of machines and vehicles. In order to improve the spectral usage, multiple users should share the same subcarriers with multiuser detection and decoding (MUD) at the receiver. In this work, we focus on super-trellis decoding (STD) and successive interference cancellation (SIC) in the framework of our proposed multiple access system. Through the extensive analysis based on simulations, we reveal that 1) properly designed SIC can achieve almost the same performance as the optimum STD with much lower complexity than the STD, and 2) our proposed system with SIC can outperform the conventional orthogonal frequency-division multiple access (OFDMA) with twice as much spectrum efficiency as OFDMA. The major drawback of SIC is its increased latency as the number of the users increases. Therefore, we also propose an alternative multiple access approach based on STD that can achieve optimum performance and low latency.

We consider a new orthogonal frequency-division multiplexing (OFDM)-based uplink multiple access system called subcarrier hopping multiple access (SHMA) targeting real-time wireless communications such as motion controls of vehicles and machines. By applying the super-orthogonal convolutional codes (SOCC) as a channel code with subcarrier hopping, it can achieve reliable communications due to the frequency diversity and coding gain without increasing decoding latency. In this work, we attempt to evaluate its system level performance according to the specifications and channel models of the IEEE 802.11n standard, aiming at its use for WiFi compatible environment. In particular, the frame error rate (FER) performance comparison reveals that the proposed SHMA can achieve higher reliability than the IEEE 802.11n standard at the cost of reduced data rate, which is still suitable for the purpose of motion control applications. The proposed SHMA system exploits Golay sequences as the outputs of SOCC in order to suppress the peak power of OFDM signals. We also evaluate the gain provided by this low peak power property taking into account the power amplifier (PA) efficiency. Finally, we address how these gains contribute to the enhancement of the transmission range over the conventional WiFi standard for a given amount of average power at the transmitter.

Bit-interleaved coded modulation (BICM), together with orthogonal frequency-division multiplexing (OFDM) signaling, has found its application in many recent wireless standards. BICM-OFDM systems are able to simplify the design of coding and modulation with various information rates for link adaptation. Furthermore, they provide robustness against frequency-selective fading channels. The combination of BICM-OFDM and convolutional code turns out to be attractive as it allows for low complexity and low latency decoding architecture at the receiver. It has been known that the performance of convolutionally coded BICM-OFDM systems depends on the bit interleaver structure, but little attention has been paid for its theoretical performance analysis. In this paper, we develop a novel theoretical expression for approximate BER of convolutionally coded BICM-OFDM that can be used for evaluating the performance of a given bit interleaver structure, and propose a design guideline for its optimization. Numerical comparisons between the optimized interleaver that satisfies our guideline and other random and structured interleavers demonstrate the validity of our design criterion.

This paper proposes a new physical layer architecture for uplink multiple access based on orthogonal frequency division multiplexing (OFDM). It achieves low peak-to-average power ratio (PAPR) and high reliability with low computational complexity at both the transmitter and receiver, targeting low-latency communications such as transmission of control information in machine-to-machine (M2M) and device-to-device (D2D) communications. Our approach is based on the judicious combination of subcarrier hopping and super-orthogonal convolutional codes (SOCC) for achieving high coding gain and frequency diversity, together with Golay complementary sequences for low PAPR signaling. By introducing non-orthogonal multiple access where the subcarriers of different users are partially overlapped, the overall bandwidth efficiency can be improved. Furthermore, the low PAPR nature improves the power efficiency and thus enhances the transmission range. Employing the successive interference cancellation at the receiver further mitigates the resulting multiple access interference.

Bit-interleaved coded modulation (BICM) has found its application in various wireless communication systems due to its simplicity in the design of coding and modulation. In particular, the BICM combined with convolutional coding has been adopted by several recent standards due to its low complexity and low latency at the decoder side. The performance of the convolutionally coded BICM depends not only on the constraint length of the code but also significantly on the structure of the bit interleavers introduced mainly for the purpose of dispersing the correlated bits. To date, however, theoretical analysis of the performance that well captures its dependence on the interleaver structures has not been presented in conjunction with the convolutionally coded BICM due to its complexity in precise analysis. In this paper, we derive a tight approximate BER expression over AWGN channels to evaluate its performance for a given bit interleaver structure, and present a design guideline for an optimal interleaver structure with its performance over fading channels in mind.

Bit-interleaved coded modulation (BICM) system combined with orthogonal frequency-division multiplexing (OFDM) has been adopted in many recent wireless standards, where the random interleaver is commonly assumed due to its simplicity of analysis for BICM. On the other hand, the recent results have shown that BICM using convolutional code without any interleaving shows better performance than that with bit interleaving over an AWGN channel without fading. Nevertheless, the interleaver design suitable for BICM with convolutional code over general fading channels has not been well studied. In this paper, we propose an approach for optimizing conventional block interleavers in the framework of BICM-OFDM and demonstrate its effectiveness over frequency-selective Rayleigh and Ricean fading channels.