Cellular IoT EPS
optimization provides improved support of small data transfers. The IoT devices
mostly use Machine-Type-Communication (MTC), and they have a broad spectrum of
capabilities with varied devices. The numbers of MTC devices are growing
rapidly and using the existing LTE technology for transmitting data of these
IoT devices would lead to a network overload. Though the user data transmitted
is small, amount of signaling remains the same.
Stratum (NAS) is a set of protocols in the Evolved Packet System. The NAS is
used to convey non-radio signaling between the User Equipment (UE) and the
Mobility Management Entity (MME) for LTE/E-UTRAN access.
The Access Stratum
(AS) is the functional layer below NAS, working between the UE and radio
network. It is responsible for transporting data over wireless connection and
managing radio resources.
A new interface
named S11-U interface is introduced as a part of control plane CIoT EPS
optimization for small data transmission between the MME and S-GW. It is based
on the existing GTP-U architecture. It is a GTPv1 user plane interface and
carries small data sent and received over NAS between MME and S-GW.
The SGi interface
exists between the PDN gateway and the packet data network. The PDN can be an
operator's external public or private packet data network or an intra-operator
packet data network.
Important: This feature is license controlled. Contact your Cisco account
representative for information on how to obtain a license.
The Cellular IoT
EPS optimizations are categorized as follows:
can be used:
User Plane CIoT
EPS Optimization - transports user data passing through the user plane
CIoT EPS Optimization - transports user data or SMS messages passing through
MME. This is done by encapsulating them in NAS, reducing the total number of
control plane messages when handling a short data transaction.
Separately: If the UE or the network supports one of them.
In Parallel: If the UE
or the network supports both. If both the Control Plane and User Plane CIoT EPS
optimizations are supported for a UE, the PDN connections that use only control
plane CIoT optimizations are handled through the Control Plane CIoT EPS
optimizations. For example, the MME that has included the "control plane only
indicator" in the ESM request will be handled by the control plane CIoT EPS
All other PDN
connections are handled using Control Plane or User Plane CIoT EPS
optimizations. In addition, the Control Plane CIoT optimization can be used to
support PDN connections to an SCEF.
The regular S1-U
data transfer is used independently to support PDN connections to P-GW. All the
SGi PDN connections of a UE either use S11-U or S1-U interface at any point in
time. Support for SGi based delivery of Non-IP data is used by any UE, that is,
it is independent of support for the User Plane CIoT EPS Optimization and the
Control Plane CIoT EPS Optimization.
provides control plane CIoT optimization support by establishing S11-U PDN
connection and other applicable procedures for the S11-U interface.
S11u data support was not present for S-GW.
S11u data support is now present for S-GW.
Customer: Data can now be sent from S-GW to MME over the S11u tunnel.