Everyone knows that although LTE and NB-IoT are in the same breath, LTE's design goals are high-rate and high-volume traffic, while NB-IoT is born for the "intermittent transmission of small data in the Internet of Things," and both are in the opposite direction. Therefore, the LTE core network EPS is no longer adapted to NB-IoT applications and needs to be optimized.
In order to improve the transmission efficiency of small data in the NB-IoT system, the 3GPP SA2 working group began researching the CIoT EPS optimization framework in July 2015 and proposed that the CIoT EPS must support four major functions:
1 support ultra-low power Internet of things terminals
2 supports a large number of IoT devices connected to each cell
3Support narrowband spectrum wireless access technology
4 Support Internet of Things Enhanced Coverage
It also simplifies the functions and cuts out four functions of LTE EPS:
1 does not provide emergency call service
2 does not support traffic offload, such as local lP access (LIPA) and selective IP traffic offload
3On EPS connection management, only reselection in IDLE mode is supported, and handover in CONNECTED mode is not supported
4 does not support the establishment of GBR bearers and dedicated bearers
Finally, 3GPP proposed two optimization schemes: C-Plane CIoT EPS optimization and U-Plane CIoT EPS optimization. For IoT terminals, the "Control Plane Optimization Transmission Plan" must be supported, and "User Plane Optimization Transmission Plan" can be optionally supported.
Control plane optimization transmission scheme
The control plane optimizes the transmission scheme so that small data packets can be transmitted on the control plane. The data is encapsulated on the control plane signaling message in the format of a non-access stratum protocol data unit (NAS PDU). The concept is similar to that of a shopping mall if the consumer Buy only a small amount of goods and checkout via the designated fast-track.
This scheme can reduce the signaling overhead of the control plane when transmitting data, thus helping to reduce terminal power consumption and reduce the use frequency band.
As shown in the above figure, the control plane optimization transmission scheme supports IP data and non-IP data transmission. The transmission path can be divided into two: 1 transmitted to the P-GW through the S-GW and then transmitted to the application server (CIoT Services); 2 through the SCEF. (Service Capability Exposure Function) is connected to the application server. This path only supports non-IP data transmission.
According to the transmission path and whether to support IP data transmission, it can be divided into three transmission modes:
Transmission path 1 (IP data transmission)
The transmission path is from the S-GW to the P-GW to the application server, and the NB-IoT can be rapidly deployed using the existing IP communication technology. The disadvantage is that the security is low and the SCEF is not passed, and the telecom operator still plays the role of a pipe.
Transmission path 1 (non-IP data transmission)
The transmission path is still from the S-GW to the P-GW to the application server. However, since there is no IP address to transmit the data packet, the ID of the NB-IoT terminal and the IP address of the AS and the port number must be on the P-GW. Correspondence relation, can transmit the data packet correctly on the interface of SGi, this kind of method is called UDP/IP Point-to-Point (PtP) Tunneling Technology. The parameters of the tunnel, that is, the destination IP address and the UDP port number, need to be configured on the P-GW in advance. For the data transmitted between the NB-IoT terminal and the AS, the P-GW is a transparent transmission node.
This method is safe and power-efficient, but it requires the development of new point-to-point tunneling technologies.
Transmission path 2 (non-IP data transmission)
That is, Non-IP data is transmitted through SCEF. This path only supports non-IP data transmission and belongs to Non-IP proprietary solution. This method has many advantages, such as high security and power saving, and operators can create new business value. However, new SCEF network element nodes need to be developed and new API technologies need to be developed.
SCEF
SCEF is a newly added node of NB-IoT. It provides services to AS through API interfaces, instead of directly sending data, making telecommunication operators no longer just pipes, but can safely open service capabilities to third-party service providers. Realize big data analysis on the Internet of Things to create new business value.
The SCEF architecture is shown in the figure above. For security reasons, the SCEF is placed in the trust domain of the operator and passed through the OMA (Open Mobile Alliance), GSMA (Groupe Speciale Mobile Association), or other standards organizations (Standardisation). Bodies, SDOs) API access services. At the same time, SCEF APIs support many different types, such as DIAMETER, RESTful APIs and XML over HTTP, making SCEF more flexible for different networks. Network Entity refers to HSS, MME, P-GW, PCRF or network nodes related to billing and security.
C-SGN
The C-SGN, the CIoT Serving Gateway Node, is a new node introduced in the control plane optimization transmission scheme. The node is a combination of the LTE EPS control plane node MME, the user plane node S-GW, and the P-GW minimization function. A single logical entity, C-SGN function, can also be deployed in the MME of the live network EPS.
HLCom
In the control plane optimization transmission scheme, an HLCom mechanism, that is, Optimization to support High Latency Communication, may be introduced. This mechanism caches downlink data in the S-GW. Since the NB-IoT terminal intermittently receives data through technologies such as PSM and eDRX to achieve power saving, when the NB-IoT terminal is in a dormant state, the S-GW buffers the downlink data until the terminal is awakened. The cached data is sent to the terminal.
User plane optimization transmission scheme
The data transmission is carried on the user plane in the same way as the LTE EPS. However, the optimization scheme introduces two new states of Suspend and Resume at the RRC layer to adapt to the intermittent transmission characteristics of the Internet of Things data. - IoT terminals, eNBs, and MMEs store connection information to quickly restore and reestablish connections, simplify signaling procedures, and improve transmission efficiency.
After such an optimization, the bearer can be established on an as-needed basis, thereby reducing terminal power consumption and supporting single-cell large-scale IoT device connections. In addition to supporting existing EPS functions, this solution can also support the transmission of non-IP data through the P-GW.
RRC Suspend Process
As shown in the above figure, the process is activated by the eNB to release the RRC connection between the NB-IoT terminal and the eNB and the S1-U bearer between the eNB and the S-GW.
Steps (1) and (2):
The eNB sends a UE Context Suspend Request, and initiates release of bearer information related to the NB-IoT terminal to the S-GW through the MME.
Step (3):
The S-GW releases the S1-U bearer associated with the NB-IoT terminal. Specifically, the S-GW only releases the eNB address and the downstream tunnel endpoint identifier (TEID) and continues to store other information.
Steps (4) and (5):
After completing the S1-U bearer release at the S-GW, the eNB receives the UE Context Suspend Response notification through the MME.
Steps (6) and (7):
The eNB stores Access Stratum (AS) information, S1-AP connection information, and bearer information of the NB-IoT terminal and sends an RRC Connection Suspend message to the NB-IoT terminal.
Step (8):
The MME stores the S1-AP connection information and bearer information for the NB-IoT terminal and enters the IDLE state.
Step (9):
After receiving the RRC Connection Suspend message from the eNB, the NB-IoT terminal stores the AS information and IDLE state.
RRC Resume process
As shown in the above figure, the process reestablishes (resets) the RRC connection between the NB-IoT UE in the Suspend state and the eNB, and the released S1-U bearer between the eNB and the S-GW. The Resume process is initiated and activated by the NB-IoT.
Steps (1) and (2):
The connection to the network is first restored using the AS information stored by the RRC Suspend process.
Step (3):
At this time, the eNB performs a security check on the NB-IoT terminal and provides the restored NB-IoT terminal with the restored radio bearer list, and synchronizes the EPS bearer status between the NB-IoT UE and the eNB.
Step (4):
The eNB sends a UE Context Resume Request to the MME to notify that its connection with the NB-IoT terminal has been safely restored.
Steps (5) and (6):
After receiving the recovery notification from the eNB, the MME restores the S1-AP connection information and bearer information of the NB-IoT terminal, enters the CONNECTED state, and sends a UE Context Resume Response message (including S-GW address and S1-AP connection information to the eNB). ).
Step (7):
Now the NB-IoT terminal can send uplink data to the S-GW.
Steps (8) and (9):
The MME sends the eNB address and the downlink TEID to the S-GW through the Modify Bearer Request message to reestablish the downlink S1-U bearer between the NB-IoT terminal and the S-GW.
Steps (10) and (11):
The S-GW sends a Modify Bearer Response message to the MME and then begins to transmit downlink data.
It is worth mentioning that, when the S-GW receives the downlink data and the NB-IoT terminal is in the Suspend state, the S-GW buffers the data packet and initializes the Downlink Data Notification process between the S-GW and the MME. The MME then pages the NB-IoT terminal, thereby initiating the activation connection Resume procedure through the NB-IoT terminal.
Wireless Vacuum Cleaner,Best Wireless Vacuum Cleaner,Wireless Car Vacuum Cleaner,Best Vacuum Cleaner Wireless
Ningbo ATAP Electric Appliance Co.,Ltd , https://www.atap-airfryer.com