# Analysis of 5G Channel Access for Collaboration with TSN Concluding at a 5G Scheduling Mechanism
## 4 Architecture
### Tsn
#### 4.2.5g  
The fifth generation of mobile communications (5G), standardized by 3 GPP, is expected to satisfy the demand on increasing data rates in the private sector as well as to meet the requirements of further applications in public life and industry. For 5G, the following application profiles are appointed [27]:  
1. eMBB (enhanced Mobile Broadband) for large data rates: * streaming * mass events * VR/AR
2. mMTC (massive Machine Type Communication) for networking a large number of devices with minimal energy resources: * industrial sensor networks * Internet of Things (IoT)
3. uRLLC (ultra Reliable Low Latency Communication) for fail-safe low latency communications for safety-critical applications: * industrial control links * autonomous driving  
In order to support such a wide variety of use cases, 5G has to be highly configurable. Many possibilities for flexible allocation of network resources can be deployed, e.g., Network Function Virtualization (NFV), network slicing, the QoS framework, Bandwidth Parts (BWPs), flexible Subcarrier Spacing (SCS) and frame format, etc.  
A packet entering the 5 GS is mapped via Non-Access Stratum (NAS) packet filters to a specific QoS Flow, which is part of a Protocol Data Unit (PDU) Session. A PDU Session may be of the Ethernet type, i.e., the information contained in the packet's Ethernet header is relied on to determine the forwarding of packets. Entering the Access Stratum (AS), the packets of a QoS Flow are then mapped via AS Mapping Rules to a Data Radio Bearer (DRB). The AS Mapping Rules are configured by the Radio Resource Control (RRC) layer and executed by the Service Data Adaption Protocol (SDAP) layer. A DRB carries all QoS Flows which are to receive the same forwarding treatment over the air interface, and represents a single logical channel to the Medium Access Control (MAC) layer.  
The allocation of physical radio resources to logical channel instances of all UEs is a service provided by the MAC layer to the upper layers. The decision as to how the resources should be divided is performed by the scheduler as part of the MAC layer in the gNodeB (gNB). At every Transmission Time Interval (TTI), resources are divided on a per-UE basis. Several scheduling algorithms can be used in combination with additional mechanisms such as SPS or Configured Grant (CG) to determine the allocation of radio resources to UEs. Within the granted resources for a specific UE, multiple logical channel instances then compete for the channel resources. For every UE, several MAC Service Data Units (SDUs) and MAC control elements (CEs) are assembled to a Transport Block (TB). Every sub-PDU is preceded by a MAC subheader. The sub-PDUs assembled in a TB can be:  
User plane data from DRBs  
Control plane data from Signalling Radio Bearers (SRBs)  
MAC Control Elements  
Padding bits to fill the standardized TB size  
For user plane data, the order in which the logical channels are served is determined by Logical Channel Prioritization (LCP). For this, the RRC layer configures the MAC layer with three parameters per logical channel:  
Priority  
Prioritized bit rate  
Bucket size duration  
The logical channels, which are candidates for resources of a TB, are served in decreasing priority order. If the prioritized bit rate of a logical channel is set to infinity, it obtains as many resources as are needed for the entirety of the queued data. Otherwise, enough resources are allocated to ensure compliance with the prioritized bit rate [28].  
Figure 1 shows an example of a scheduling procedure covering several Radio Bearers for one UE. Here, the Radio Bearer \(RB3\) maps to the logical channel with the lowest priority; it is not served in this TTI, because the TB is completely filled by the PDUs of the other Radio Bearers and a MAC Control Element.