Architecture Evolution
Dr. Dionysis Xenakis
National and Kapodistrian University of Athens
Department of Informatics and Telecommunications
SMARTNET Programme – Advanced Network Architectures (M132)
[email protected]
(LTE)
Beware, specs ahead!
E-UTRAN [16]
E-UTRAN includes access network entities enabling UE-to-EPC links [TS 36.300]
eNodeB (eNB), HeNB, HeNB GW, DeNB, Relay Node (RN), MeNB/SeNB (DC), X2-GWs
E-UTRAN functions include (among others)
Header compression and user plane ciphering
MME selection when no routing to an MME can be determined from the information provided by the UE
UL bearer level rate enforcement based on UE-AMBR and MBR via means of uplink scheduling (e.g. by limiting the amount of UL resources granted per UE over time)
DL bearer level rate enforcement based on UE-AMBR
UL and DL bearer level admission control
Transport level packet marking in the uplink, e.g. setting the DiffServ Code Point, based on the QCI of the associated EPS bearer
ECN-based congestion control
eNB functions (described latter)
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
MME
Control node processing the signaling between the UE and the CN
The protocols running between the UE and the CN are known as the Non-Access
Stratum (NAS) protocols
Bearer management, includes the establishment, maintenance and release of the bearers, and is handled by the session management layer in NAS
Connection management, includes the establishment of the connection and security between the network and UE, and is handled by the connection or mobility management layer in the NAS protocol layer
Inter-working with other networks, includes handing over of voice calls to legacy networks
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
MME [16,18]
The Serving GW and the MME may be implemented in one physical node or separated physical nodes.
The protocols running between the UE and the MME a.k.a. Non-Access Stratum (NAS) protocols
MME functions include:
NAS signalling and NAS security, AS Security control
Inter CN node signalling for mobility between 3GPP access networks
Idle mode UE Reachability (including control and execution of paging retransmission), Tracking Area list management (for UE in idle and active mode)
PDN GW and Serving GW selection, MME selection for handovers with MME change, SGSN selection for handovers to 2G or 3G 3GPP access networks
Roaming, Authentication, Bearer management functions including dedicated bearer establishment
Support for PWS (which includes ETWS and CMAS) message transmission;
Optionally performing paging optimisation;
S-GW relocation without UE mobility TS 23.401.
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
S-GW
Handles all user IP packets
Serves as the local mobility anchor for the data bearers when the UE moves between eNodeBs
Retains bearer information when the UE is idle and temporarily buffers DL data while the MME initiates paging of the UE to re-establish the bearers
Performs administrative functions in the visited network, such as collecting information for charging (e.g. volume of data sent to or received from the user)
Serves as the interface/mobility anchor for inter-working with other 3GPP technologies such as GPRS and UMTS
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
S-GW [16,18]
For each UE associated with the EPS, at a given point of time, there is a single Serving GW.
Serving GW functions include [GPRS Tunnelling Protocol (GTP) and Proxy Mobile IPv6 (PIMP)]:
Local Mobility Anchor point for inter-eNB handover, Mobility anchoring for inter-3GPP mobility
E-UTRAN idle mode downlink packet buffering and initiation of network triggered service request procedure
Lawful Interception, Packet routing and forwarding
Transport level packet marking in the uplink and the downlink
Accounting on user and QCI granularity for inter-operator charging
UL and DL charging per UE, PDN, and QCI
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
PDN-GW
Allocates IP addresses to Ues
Performs QoS enforcement for Guaranteed Bit Rate (GBR) bearers
Performs flow-based charging according to rules from the PCRF
Filters downlink user IP packets into the different QoS-based bearers
Serves as the interface/mobility anchor for inter-working with non-3GPP technologies such as CDMA2000 and WiMAX networks
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
PDN-GW [16,18]
PDN GW functions include for both the GTP-based and the PMIP-based S5/S8:
Per-user based packet filtering (by e.g. deep packet inspection)
Lawful Interception
UE IP address allocation
Transport level packet marking in the uplink and the downlink
UL and DL service level charging, gating and rate enforcement
DL rate enforcement based on APN-AMBR
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
SGSN [16]
The main role of the SGSN is inter-working with other previous 3GPP networks
SGSN functions include (TS 23.060):
Inter EPC node signalling for mobility between 2G/3G and E-UTRAN 3GPP access networks;
PDN and Serving GW selection: the selection of S-GW/PDN-GW by the SGSN is as specified for the MME
Handling UE Time Zone as specified for the MME
MME selection for handovers to E-UTRAN 3GPP access network.
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
PCRF [16]
PCRF is the policy and charging control element. PCRF functions are described in more detail in TS 23.203 [6].
In non-roaming scenario, there is only a single PCRF in the HPLMN associated with one UE's IP-CAN session.
In a roaming scenario with local breakout of traffic there may be two PCRFs associated with one UE's IP-CAN session:
H-PCRF that resides within the H-PLMN, V-PCRF that resides within the V-PLMN
Policy control decision-making
Controlling the flow-based charging functionalities in the Policy Control Enforcement Function (PCEF) which resides in the PDN-GW
QoS authorisation (QoS class identifier and bit rates) that decides how a certain data flow will be treated in the PCEF and ensures that this is in accordance with the user’s subscription profile
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
HSS [17]
HSS is a database that contains user-related and subscriber-related information
EPS-subscribed QoS profile, access restrictions for roaming, information about the PDNs to which the user can connect (in the form of Access Point Name –APN-, or a PDN Address)
Dynamic information such as the identity of the MME to which the user is currently attached or registered
Provides support functions in mobility management, call and session setup, user authentication and access authorization
May integrate the Authentication Centre (AuC) which generates the vectors for authentication and security keys
Is based on the pre-3GPP Release 4 - Home Location Register (HLR) and Authentication Centre (AuC)
SGi Gx
Operator's IP Services (e.g. IMS, PSS etc.) S10
UE LTE-Uu
E-UTRAN
S11
Serving S5 Gateway
PDN Gateway S1-U
S4
Network Interfaces – Reference Points
S1-MME: Reference point for the control plane protocol between E-UTRAN and MME
S1-U: Reference point between E-UTRAN and Serving GW for the per bearer user plane tunnelling and inter eNodeB path switching during handover
S3: Enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state. Can be used intra-PLMN or inter-PLMN (e.g. in the case of Inter- PLMN HO)
S4: Provides related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW. If Direct Tunnel is not established, it provides the user plane
tunnelling
S5: Provides user plane tunnelling and tunnel management between Serving GW and PDN GW. Used for Serving GW relocation due to UE mobility and if the Serving GW needs to
connect to a non-collocated PDN GW for the required PDN connectivity
S6a: Enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS
Gx: Provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW
SGi S12
PCRF Gx
Operator's IP Services (e.g. IMS, PSS etc.)
Rx S10
UE LTE-Uu
E-UTRAN
MME S11
Serving S5 Gateway
PDN Gateway S1-U
S4
Network Interfaces – Reference Points
S8: Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5.
S9: Provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function.
S10: Reference point between MMEs for MME relocation and MME to MME information transfer. Can be used intra-PLMN or inter-PLMN (e.g. in the case of Inter-PLMN HO).
S11: Reference point between MME and Serving GW.
S12: Reference point between UTRAN and Serving GW for user plane tunnelling when Direct Tunnel is established. It is based on the Iu-u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and GGSN. Usage of S12 is an operator configuration option.
S13: Enables UE identity check procedure between MME and EIR.
SGi: Reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. Corresponds to Gi for 3GPP accesses.
Rx: Resides between the AF and the PCRF in the TS 23.203 [6].
SGi S12
PCRF Gx
Operator's IP Services (e.g. IMS, PSS etc.)
Rx S10
UE LTE-Uu
E-UTRAN
MME S11
Serving S5 Gateway
PDN Gateway S1-U
S4
Interfaces - Reference
Points
Specs ahead!
E-UTRAN consists of a flat architecture mainly of eNBs
HeNB, HeNB GW, DeNB, Relay Node (RN), MeNB/SeNB (DC), X2-GWs
No centralized intelligent controller (vs. BSC, or MCS)
Speeds up the connection set-up and reduces the time required for a handover
Can be critical real time data session
eNB provides the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE
eNBs are interconnected with each other by means of the X2 interface
eNBs are also connected by means of the S1 interface to the EPC
S1-MME interface to the MME (Mobility Management Entity)
S1-U interface to the Serving Gateway (S-GW)
The S1 interface supports a many-to-many relation between MMEs / Serving Gateways and eNBs
Protocols running between eNBs and UEs are known as the Access Stratum (AS) protocols
eNB functions (Rel. 12)
Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in uplink, downlink and sidelink (scheduling)
IP header compression and encryption of user data stream
Selection of an MME at UE attachment when no routing to an MME can be determined from the information provided by the UE
Routing of User Plane data towards Serving Gateway
Scheduling and transmission of paging messages (MME)
Scheduling and transmission of broadcast information (MME or O&M)
Measurement / reporting configuration for mobility and scheduling
Scheduling and transmission of Public Warning System (which includes ETWS and CMAS) messages (MME)
CSG handling
Transport level packet marking in the uplink
S-GW relocation without UE mobility - TS 23.401
SIPTO@LN handling
Optionally registering with the X2 GW (if used)
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1 S1
S1 S1
X2 X2 X2
E-UTRAN
Functionality
The PHY offers data transport services to higher layers. The access to the PHY services is through the use of a transport channel via the MAC sub-layer. The PHY performs the following functions in order to provide the data transport service:
Error detection on the transport channel and indication to higher layers
FEC encoding/decoding of the transport channel
Hybrid ARQ soft-combining
Rate matching of the coded transport channel to physical channels
Mapping of the coded transport channel onto physical channels
Power weighting of physical channels
Modulation and demodulation of physical channels
Frequency and time synchronisation
Radio characteristics measurements and indication to higher layers
Multiple Input Multiple Output (MIMO) antenna processing
Transmit Diversity (TX diversity)
Beamforming RF processing
[1] https://www.ccontrols.net/en/applications/internet-of-things-iot/wireless-networks/
[2] Syed Junaid Nawaz, Shree Krishna Sharma, Babar Mansoor, Mohmammad N. Patwary, and Noor M. Khan, “Non-Coherent and Backscatter Communications:
Enabling Ultra-Massive Connectivity in the Era Beyond 5G”, arXiV preprint, v2, 2020, [online]: https://arxiv.org/abs/2005.10937 [3] https://en.wikipedia.org/wiki/Stochastic_geometry_models_of_wireless_networks
[4] A. Kitana, I. Traore, I. Woungang, “Impact Study of a Mobile Botnet over LTE Networks”, Journal of Internet Services and Information Security, 2016
[5] https://docstore.mik.ua/univercd/cc/td/doc/product/wireless/moblwrls/cmx/mmg_sg/cmxgsm.htm
[6] S. Kanchi, S. Sandilya, D. Bhosale, A. Pitkar and M. Gondhalekar, "Overview of LTE-A technology," 2013 IEEE Global High Tech Congress on Electronics, Shenzhen, 2013, pp. 195-200, doi: 10.1109/GHTCE.2013.6767272.
[7] https://www.slideshare.net/3G4GLtd/an-introduction-to-macrocells-small-cells [8] https://en.wikipedia.org/wiki/Stochastic_geometry_models_of_wireless_networks
[9] H. S. Dhillon, R. K. Ganti, F. Baccelli and J. G. Andrews, "Modeling and Analysis of K-Tier Downlink Heterogeneous Cellular Networks," in IEEE Journal on Selected Areas in Communications, vol. 30, no. 3, pp. 550-560, April 2012, doi: 10.1109/JSAC.2012.120405.
[10] https://www.banaao.co.in/2g-vs-3g-vs-4g-vs-5g/
[11] https://medium.com/5g-nr/5g-service-based-architecture-sba-47900b0ded0a [12] https://www.3gpp.org/about-3gpp
[13] https://www.3gpp.org/technologies/keywords-acronyms/100-the-evolved-packet-core
[14] https://www.cambridgewireless.co.uk/media/uploads/files/RadioAI_18.9.18-Ublox-Sylvia-Lu.pdf [15] https://www.rantcell.com/comparison-of-2g-3g-4g-5g.html
[16] 3GPP TS 23.401, “General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access”, V12.11.0, March 2016
[17] https://www.3gpp.org/technologies/keywords-acronyms/100-the-evolved-packet-core
[18] 3GPP TS 36.300, “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN);”, V12.10.0, June 2016
[19] 3GPP TS 36.402, “Services provided by the physical layer (Release 12)”, V12.8.0, Sept 2016.
[20] https://www.3gpp.org/technologies/keywords-acronyms/97-lte-advanced
[21] 3GPP TS 36.786, “Vehicle-to-Everything (V2X) services based on LTE; User Equipment (UE) radio transmission and reception (Release 14)”, V14.0.0, Mar. 2017
[22] https://www.cablefree.net/wirelesstechnology/4glte/overview-of-lte-3gpp-releases/
[23] https://www.ericsson.com/en/reports-and-papers/ericsson-technology-review/articles/5g-nr-evolution [24] K. Lee, J. Lee, and Y. Yi, “Mobile Data Offloading : How Much Can WiFi Deliver?,” Proc. 6th Int. Conf. ACM Conex., vol. 21, iss. 2, Nov. 2010, p. 36.
[25] 3GPP TR 36.902 V9.3.1, “Self-configuring and self-optimizing network (SON) use cases and solutions (Release 9)”, March 2011
[26] 3GPP TS 32.500 V12.1.0, “Self-Organizing Networks (SON); Concepts and requirements (Release 12)”, Dec
