The aim of this paper is to characterize the impact of non-orthogonal multiple access (NOMA) on the age of information (AoI) of grant-free transmission. In particular, a low-complexity form of NOMA, termed NOMA-assisted random access, is applied to grant-free transmission in order to illustrate the two benefits of NOMA for AoI reduction, namely increasing channel access and reducing user collisions. Closed-form analytical expressions for the AoI achieved by NOMA assisted grant-free transmission are obtained, and asymptotic studies are carried out to demonstrate that the use of the simplest form of NOMA is already sufficient to reduce the AoI of orthogonal multiple access (OMA) by more than 40%. In addition, the developed analytical expressions are also shown to be useful for optimizing the users' transmission attempt probabilities, which are key parameters for grant-free transmission.

翻译：本文的目的是说明非横向多重存取(NOMA)对无赠款传输(AoI)信息年龄的影响,特别是将低复杂性的NOMA(称为NOMA协助随机存取)用于无赠款传输,以说明NOMA对减少AoI的两种好处,即增加频道存取和减少用户碰撞。获得NOMA协助的无赠款传输(NOMA)实现的AoI的封闭式分析表达方式,并进行非抽取性研究,以证明使用最简单的NOMA形式已经足以将无赠款多重存取(OMA)的AoI减少40%以上。此外,已开发的分析表达方式还有助于优化用户的传输尝试概率,这是无赠款传输的关键参数。