LAUSR

The anticipated 1000-fold increase in mobile data traffic over the next decade and the explosion of new services and applications pose great challenges for the current orthogonal multiple access (OMA)-based 4G systems. A promising solution to address these challenges is to shift from the currently predominant OMA to non-orthogonal multiple access (NOMA). This article first introduces the principle of the complexity-constrained capacity-achieving NOMA design. Then a non-orthogonal pattern division multiple access (PDMA) scheme is proposed to meet the exponentially growing demand of mobile users for computing and information application services. The key feature of the PDMA scheme is a joint design of transmitter and receiver, which allows low-complexity successive interference cancellation (SIC)-based multi-user detection with substantially improved performance over conventional OMA schemes. More specifically, the patterns of multiple users are judiciously designed so that the data symbols of different users are of appropriate diversity disparity at the symbol level and power disparity at the resource element level. The appropriate disparity in diversity and power can be effectively exploited by the low-complexity SICbased detector to realize the near-perfect cancellation of multi-user interference. Moreover, the PDMA system parameters can be flexibly adjusted to provide different levels of overload, rendering it suitable to meet the diverse traffic requirements in future 5G systems. Link-level simulations illustrate that PDMA is capable of accommodating a 300 percent overload, while it still enjoys transmission reliability close to conventional OMA schemes. The results demonstrated in this article indicate that PDMA can be a promising multiple access technology with low signaling overhead, low latency, and massive connectivity support for 5G.