On Hybrid MAC Approaches within MC-CDMA Systems for the use in Wireless Industrial Communications

Abstract:
Wireless Industrial Communication Systems are currently a hot research topic and are in the focus of both industry and academia, as new manufacturing scenarios with higher mobility and flexibility demands arise. These scenarios form the vision of the fourth industrial revolution, which is referred to as "Industry 4.0" in Germany. Although Wireless Systems are recognized as an attractive alternative to Wire-line Systems in terms of flexibility and costs, there’s still some effort necessary to get competitive with wire-line systems in terms of robustness and latency. Multi-Carrier Spread Spectrum (MC-SS) systems, combining multi-carrier (OFDM) techniques and spread spectrum techniques, are known to offer high spectral efficiency, robustness and flexibility and are therefore a promising candidate for a wireless industrial communication system. These MC-SS systems are usually used with a CDMA part consisting of standard Hadamard spreading sequences. In this paper, we will present two Hybrid MAC concepts aiming to efficiently, i.e. without unintentionally increasing the spreading factor, combine robust transmission fulfilling real-time requirements as well as transmission with best-effort traffic, which has lower robustness requirements but could use higher throughput. We will investigate overloaded code sets as well as an approach using CSMA as multiplexing technique in a MC-CDMA system. Furthermore we will compare the performance of these approaches with a simulation.