Asynchronous Grant-Free Uplink Transmissions in Multichannel Wireless Networks With Heterogeneous QoS Guarantees

In this paper, we study the problem of providing heterogeneous quality-of-service (QoS) guarantees for asynchronous grant-free uplink transmissions in multichannel wireless networks. The multiple access channel model is the classical collision channel, where partially overlapped packets during the transmissions are assumed to be completely lost. For such a network model, we propose two asynchronous multichannel transmission schedules (AMTS): 1) the EPC-based AMTS and 2) the DS-based AMTS. The EPC-based AMTS is constructed by time-spreading one-dimensional extended prime code (EPC), and the DS-based AMTS is constructed by using difference sets (DS) and finite projective planes. We show for both scheduling algorithms that the maximum delay between two successive successful transmissions of an active device can be upper bounded by a constant when the channel load does not exceed a designed threshold parameter. Moreover, different devices are allowed to have different throughput (rate) guarantees. By conducting extensive simulations, we also show that the overall throughputs of both scheduling algorithms are almost identical to that of the random access protocol, when the number of active devices exceeds the designed threshold parameter.