Enhancing information freshness for coordinated direct and relay transmission

This paper investigates the information freshnessof relay-aided status updating in coordinated direct and relaytransmission (CDRT) for the first time. Information freshness ismeasured by age of information (AoI), defined as the time elapsedsince the generation of the last successfully received updatepacket. In CDRT, one sensor communicates directly with thereceiver while another sensor requires the assistance of a decode-and-forward relay. Conventional CDRT is achieved via timedivision multiple access (TDMA) or non-orthogonal multiple ac-cess (NOMA). Interestingly, our experiments on software-definedradios (SDR) indicate that in error-prone wireless networks,TDMA-CDRT and NOMA-CDRT are not superior to each otherin terms of peak AoI in all signal-to-noise ratio (SNR) regimes. Specifically, the direct sensor prefers NOMA-CDRT while therelay-aided sensor prefers TDMA-CDRT, leading to a dilemmain optimizing the peak AoI of the system. To this end, we put fortha hybrid CDRT scheme that combines TDMA and NOMA. TheSDR experimental results show that the hybrid CDRT schemenot only balances the peak AoI of the direct and relay-aidedsensors, but also achieves better information freshness for thewhole CDRT system. KCI Citation Count: 0