Code-expanded Random Access (CeRA) is a promising technique for supporting mMTC in cellular IoT networks. However, its potentiality is limited by code ambiguity, which results from the inference of a larger number of codewords than those actually transmitted. In this letter, we propose a random access scheme to alleviate this problem by allowing devices to select the preambles to be transmitted considering a q-ary code with maximum average distance. Moreover, a CeRA decoding approach based on hypergraphs is proposed and an analytical model is derived. Numerical results show that the proposed scheme significantly increases the probability of successful channel access as well as resource utilization.

翻译：代码扩展随机存取(CeRA)是支持移动式IoT网络中移动式MMTC的一个很有希望的技术,但其潜力受到代码模糊性的限制,而代码模糊性是由比实际传送的代码字数多得多的推论造成的。在本信中,我们提出了一个随机存取计划来缓解这一问题,允许设备选择要传送的序言,同时考虑最大平均距离的q-ary代码。此外,还提出了一个基于高空图的CeRA解码方法,并产生了一个分析模型。数字结果表明,拟议的计划大大增加了成功访问频道和资源利用的可能性。