Abstract
There is an urgent demand for massive machine-type terminals to have access into time-division multiple access (TDMA)-based satellite networks by means of random multiple access (RMA). Several RMA protocols have been proposed by exploiting packet repetitions and interference cancellation to achieve high throughput. In this paper, a framework of non-orthogonal slotted aloha (NOSA) protocol is reported to achieve even higher throughput. With a specifically designed tile-based frame structure, it introduces the intra-tile sparse mapping as a special kind of pre-coded packet repetitions and exploits the joint multi-packet detection to blindly detect superimposed packets. By further employing inter-tile packet repetitions and interference cancellation, the NOSA protocol is able to achieve high throughput with affordable complexity while keeping the same transmission efficiency as and comparable power consumptions to available protocols. Simulation results show that the NOSA prototype has the potential in providing RMA for massive machine-type terminals in practical TDMA-based satellite networks.
Highlights
With the development of Internet-of-Things (IoT) as well as wireless sensor networks, random multiple access (RMA) has represented a promising solution for a massive amount of machine-type communication (MTC) terminals to have access into satellite networks through a shared contention channel [1], [2]
A baseband block diagram of a typical non-orthogonal slotted aloha (NOSA) demodulator is depicted in Fig. 3, in which blocks in dark gray indicates the key ones and blocks in light gray modified ones compared to a Contention Resolution Diversity Slotted Aloha (CRDSA) demodulator
The complexity of preamble detection of NOSA should take into account correlations of those successfully detected replicas in identifying originally collided replicas. As for the latter one, the complexity mainly comes from the maximum likelihood detection (MLD) calculations at function nodes (FN) with the maximum number of connections, which can be expressed as O(LPayQ · 2dmax ), where dmax is defined as the maximum number of connections overall with dmax ≤ dmax, and LPay is used instead of LPkt − LPay since there are at most LPay samples whose FN has a maximum number of connections dmax
Summary
With the development of Internet-of-Things (IoT) as well as wireless sensor networks, random multiple access (RMA) has represented a promising solution for a massive amount of machine-type communication (MTC) terminals to have access into satellite networks through a shared contention channel [1], [2]. A few works attempted to apply LDS-CDMA/SCMA techniques into the RMA transmission in LTE systems [20], [21] by spreading the data of a fixed number of terminals onto subcarriers with randomly selected sparse codes, and a message passing detector (MPD) is utilized to detect superimposed signals Since they rely highly on the LTE system with a fixed number of terminals, there is still a lack of an effective protocol by exploiting LDS-CDMA/SCMA techniques to realizing full RMA in wireless networks, especially in TDMA based satellite networks. By exploiting advantages of both LDS-CDMA/SCMA and CRDSA techniques, we would like to present a novel framework of Non-Orthogonal Slotted Aloha (NOSA) for TDMA based satellite networks.
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