Exploring the Non-Overlapping Visibility Regions in XL-MIMO Random Access and Scheduling

NOMA-Based Random Access in mMTC XL-MIMO

“…3. Similarly, as [13], [15], we consider a simplified bipartite graph model in XL-MIMO, the array is divided into B subarrays (SAs), each composed by a fixed number of M b = M/B antennas, ensuring the minimum antennas elements (M b ≥ 50), to achieve the inherent properties of massive MIMO [22]. Each SA is equipped with a remote processing unit (RPU) that performs channel estimate, SIC, and resource allocation in a distributed manner, these RPUs are connected to a coordinating central processing unit (CPU), and decoded signals in RPU are sent to CPU to be combined in an equal gain combiner (EGC), where each branch has the same weight, integrated to the BS.…”

“…Let M denote the set of all BS SAs and V k ⊂ M the subset of SAs visible to the k-th UE. To compose the mathematical modeling, we assume that the subset V k is generated at random, where each SA is visible with probability P b by UE k, like in [13], [15]. This probability simulates the influence of random obstacles and scatterers in the environment that interact with the signals transmitted by/to the UEs, resulting in VRs.…”

“…Since each SA visibility follows a Bernoulli distribution with success probability P b , it is crucial to note that when an antenna is visible to a user, it indicates that the user may transmit/receive signals to/from this antenna with a nonzero channel gain [15]. We assume an overcrowded scenario where K iUEs (K ≫ M ) are randomly distributed within a square cell with maximum distance d max and minimum distance d min , respectively, as in Fig.…”

“…Similarly as [13], [15], we adopt the average large scale fading for the k-th user at the b-th SA, β…”

“…Recently, XL-MIMO systems have received a lot of research interest. Recent papers analyse RA improvements in linear receiver schemes [13]- [15], appropriate channel models [12], channel estimation algorithms [16], non-linear receiver schemes [17], and efficient RA schemes in XL-MIMO [18]- [20].…”