Showing posts with label EPS. Show all posts
Showing posts with label EPS. Show all posts

Thursday, 4 November 2010

Emergency Calls in LTE/SAE Release-9


From a 3GPP presentation by Hannu Hietalahti:

Emergency calls in LTE

Regulatory requirement of emergency calls is supported in Rel-9 for LTE:
1. Detection of emergency numbers in UE
2. Indication and prioritisation of emergency calls
3. Location services, both for routing and user location data for PSAP (Public Safety Answering Point)
4. Callback is possible, but processed as normal call without exceptions

UE matches digits dialledby the user with list of known emergency numbers
1. Emergency number list in the UE is common for CS and PS domain use
2. Default 112 and 911, USIM pre-configuration, downloaded in MM procedure
3. In case of match, the UE shall initiate the call as an emergency call

In IMS emergency calls the UE translates dialled number into emergency service URN
1. Service URN with a top-level service type of "sos" as specified in RFC5031
2. Additionally, sub-service type can be added to indicate emergency category if information on the type of emergency service is known (fire, ambulance, police,…)

P-CSCF (Proxy - Call Session Control Function) must also be prepared to detect emergency call if the UE is not aware of local emergency call
1. This is backup for those cases when the (roaming) UE does not have full information of all local emergency call numbers and initiates a normal call
2. From EPC perspective, it will be a normal PDN connection

Benefit of location information
1. P-CSCF discovers the regionally correct PSAP to take the emergency call
2. PSAP gets information on the precise user location


Related Posts:

Monday, 23 August 2010

Standards Developments in SAE

Tuesday, 17 August 2010

LTE Evolved Packet System Architecture poster from ALU

Interesting poster from ALU on the Evolved Packet System Architecture. Available to download from Slideshare.

Wednesday, 28 July 2010

MSF LTE Interoperability White Paper, Jun 2010

This white paper provides a summary of the MultiService Forum’s (MSF) Global LTE Interoperability event which took place from March 15-30, 2010.

The LTE Interoperability Event is designed to test standards compliance of Evolved Packet Core network scenarios of interest to major Service Providers, and to gauge vendor support for this technology. Building on the success of previous Global MSF Interoperability (GMI) events, the LTE Interoperability event provided the first global “real network” multi-vendor trial of the Evolved Packet Core infrastructure.

Incorporating the Evolved Packet Core defined within the Third Generation Partnership Project (3GPP) Release 8 (R8) standards, the MSF architecture introduced new access tiles to support LTE access and non-3GPP (specifically eHRPD) access to EPC. The IMS core network provided the application layer for which services may be deployed, and the binding of Quality of Service utilizing the Policy and Charging Control (PCC) for the bearer.

The event demonstrated that most of the defined LTE/EPC interfaces were mature and interoperable; however limited backwards compatibility between different implementations of 3GPP Release 8 specifications did create some issues. The fact that 3GPP does not require backward compatibility is a known limitation, but it is important to understand that this is limiting interoperability with commercially available equipment. Service providers will need to factor this into vendor selection.

Highlights of the event included:-
  • Sessions were successfully established via LTE access to EPC, with creation of default and dedicated bearers with appropriate Quality of Service applied.
  • An end-to-end IMS Voice over LTE session was also successfully demonstrated,
  • Access to the EPC via a simulated eHRPD access was successfully tested.
  • Handover between LTE and eHRPD,
  • Roaming was successfully tested.
Though the essential standards are reasonably mature, the implementation of early versions of the standards within several of the available implementations of network nodes highlights the problems that can arise due to non-backwards compatibility between 3GPP releases. It is also clear that early implementations have focused initially on development of LTE access to EPC and that support for legacy access (2G/3G) to EPC is somewhat behind. Events such as the MSF LTE Interoperability event highlight these issues and prove the validity of the MSF approach to achieving multi-vendor interoperability.


This paper is available to download from here.

Thursday, 18 June 2009

LTE QCI and End-to-end bearer QoS in EPC



Gary Leonard, Director Mobile Solutions, IP Division, Alcatel-Lucent in a presentation at the LTE World Summit

Friday, 12 June 2009

GPRS Roaming eXchange (GRX) for LTE/EPS Networks


The GSM Association (GSMA) has came to the realization that GPRS roaming based on bilateral relationships between individual GPRS operators is incredibly complex and expensive to maintain, in particular if the number of roaming partners is high. In fact, each operator will have to have N(N - 1) dedicated links to other operators (given that N is the global numbers of operators for which roaming should be supported). The GSMA has therefore recommended the use of a GPRS Roaming eXchange (GRX) for the Inter-PLMN GPRS roaming scenario.

The GRX is built on a private or public IP backbone and transports GPRS roaming traffic via the GTP between the visited and the home PLMN (Figure above). A GRX service provider has a network consisting of a set of routers and the links connecting to the GPRS networks. Moreover, the GRX network will have links connecting to other GRX nodes to support GRX peering between networks.

The GRX service provider acts as a hub, therefore allowing a GPRS operator to interconnect with each roaming partner without the need for any dedicated connections. This allows faster implementation of new roaming relations, faster time to market for new operators, and better scalability since an operator can start with low-capacity connections to the GRX and upgrade them depending on the bandwidth and quality requirements of the traffic. Other benefits of GRX are as follows:

Support of QoS: This aspect that will be very important for the GPRS services and, in particular, for the transition to 3G systems.

Security: The interconnection between the home operator and the visited operator uses the private GRX networks, hence does not require the overhead of maintaining expensive IPSEC tunnels over the public Internet.

DNS support: Through GRX it is possible to support a worldwide ".gprs" DNS root, where the various GRX operators will collaborate in managing the root and each operator's DNS servers will be connected to such roots to provide translation of DNS names specific to one operator.

In conclusion, GRX is introduced for GPRS roaming to facilitate the network operators for the interconnection between networks to support roaming and will play a very important role for the transition to third-generation systems.

In the LTE World Summit, Alex Sinclair, Chief Technology Officer, GSMA mentioned about the important role GRX will play in the LTE networks. The figure below are his views on GRX.





Diagram and Initial text Reference: IP in Wireless Networks By Basavaraj Patil, et al.

More information on GRX is available in GSM Association IR.34 document.

Sunday, 31 May 2009

CS Services over EPS study in Release 9

One of the Release-9 items is "Study on Circuit Switched (CS) domain services over evolved Packet Switched (EPS) access" which is described in 3GPP TR 23.879.

Martin Sauter has already done some analysis on this topic so I would advice anyone interested to read it on his blog here.

Wednesday, 27 May 2009

Service Specific Access Control (SSAC) in 3GPP Release 9


In an emergency situation, like Earthquake or Tsunami, degradation of quality of service may be experienced. Degradation in service availability and performance can be accepted in such situations, but mechanisms are desirable to minimize such degradation and maximize the efficiency of the remaining resources.

When Domain Specific Access Control (DSAC) mechanism was introduced for UMTS, the original motivation was to enable PS service continuation during congestion in CS Nodes in the case of major disaster like an Earthquake or a Tsunami.

In fact, the use case of DSAC in real UMTS deployment situation has been to apply access control separately on different types of services, such as voice and other packet-switched services.

For example, people’s psychological behaviour is to make a voice call in emergency situations and it is not likely to change. Hence, a mechanism will be needed to separately restrict voice calls and other services.

As EPS is a PS-Domain only system, DSAC access control does not apply.

The SSAC Technical Report (see Reference) identifies specific features useful when the network is subjected to decreased capacity and functionality. Considering the characteristics of voice and non-voice calls in EPS, requirements of the SSAC could be to restrict the voice calls and non-voice calls separately.

For a normal paid service there are QoS requirements. The provider can choose to shut down the service if the requirements cannot be met. In an emergency situation the most important thing is to keep communication channels uninterrupted, therefore the provider should preferably allow for a best effort (degradation of) service in preference to shutting the service down. During an emergency situation there should be a possibility for the service provider also to grant services, give extended credit to subscribers with accounts running empty. Under some circumstances (e.g. the terrorist attack in London on the 7 of July in 2005), overload access control may be invoked giving access only to authorities or a predefined set of users. It is up to national authorities to define and implement such schemes.

Reference: 3GPP TR 22.986 - Study on Service Specific Access Control