# Directional Paging for 5G Communications Based on Partitioned User ID
## 2 Related Work
### Paging Broadcast by the Network  
When in idle mode, the UE performs TA update procedures to notify its location in the network database to the Mobility Management Entity (MME). The paging mechanism is instigated at the MME of the tracking area, and subsequently, the paging message is notified to all eNBs in the TA. Hence, the paging messages are broadcasted in the configured POs for all the cells associated with the last updated TA [10]. Paging procedures along with TA update incur more than 33% of the total signaling load that is managed by the MME in the legacy LTE networks [11]. With the expected increase in the number of mobile subscribers in the near future, the efficient operation of the MME becomes even more crucial. The mmWave beam-formed communication (fundamental to the 5G system) would further accentuate network overheads due to complications of paging broadcast in the directional paradigm. Though several research works with a focus on paging overhead optimization are available, they are based on LTE or MTCommunications [11; 13; 14; 15; 16; 17; 18; 19; 20; 21]. In [11], paging areas are assigned using mobility models to reduce signaling traffic in LTE. Rule-based artificial intelligence is proposed in [13], while multilevel graph partitioning is promoted in [14] for intelligent paging and TA optimization. In view of the dense and nested deployment of small cells, a local anchor-based location management scheme for HetNets is presented in [15]. For efficient MTC/IoT DRX, novel methods like quick sleeping, group paging and re-synchronization are being researched [18; 19; 20]. DRX in connected state for 5G is discussed in [7; 22; 23], and the tracking area management framework for 5G networks is presented in [24]. However, the effect of limited paging resources in the directional air interface is not yet comprehensively studied.  
In a directional 5G system, the same paging message needs to be transmitted over all the beams for each cell in the TA. However, the limitation and complexity of antenna modules at the gNB are deterrents to the simultaneous transmission [8] in the cell. The paging transmission takes place over different time slots, resulting in increased resource requirement. The related work in [25] has  
Figure 2: Paging frame (PF) and paging occasion (PO) in a legacy network.  
already shown the overwhelming rise in resources for directional paging in 5G communications in comparison to the legacy LTE networks. Table 1 highlights that the system capacity requirement is substantially high for directional paging in 5G compared to LTE at the 80-MHz bandwidth [25]. In [25], the UE informs about its beam to the gNB by uploading an indication for reducing paging resources. An extension of this work is presented in [10], where the effect of the proposed indication on the energy savings of the UE is evaluated. In [10], the resource savings at the network is achieved at the cost of the increase in energy expenditure at the UE. The increase in energy expense at the UE motivated us to propose the PIDP mechanism, an alternate paging scheme for directional 5G communications. Table 2 summarizes a brief survey of the latest research works in the related fields.