Isolated E-UTRAN operation for public safety

Updated 24.5.2016

Resiliency and service availability can be enhanced in terrestrial public safety LTE network based on capability called 'Isolated E-UTRAN Operation for Public Safety (IOPS)'. IOPS enables local services in case backhaul connection to centralized macro core is lost. IOPS assumes that local EPC function is co-sited with eNodeB. Local EPC can serve also multiple eNodeBs. Local EPC includes at least HSS, MME, SGW and PGW functions.

The figure below depicts an example of shared RAN, which is serving both PS users and commercial subscribers. There are separate PLMN identities for commercial customers (PLMN 'A')  and PS customers (PLMN 'PPDR') and there are also separate core networks. In normal condition commercial and PS subscribers are attached to their own centralized core networks and all data connectivity and communication services are provided by the centralized core networks. The lower part of figure depicts a transmission failure in backhaul. In that case eNodeBs can activate IOPS mode and offer local services. However IOPS services are available only for PS UEs that have subscription for IOPS mode including access class 11 or 15.

The fall-back procedure is illustrated in the next figure. Public safety UEs are normally attached to centralized EPC and there can be also UEs in active state when the backhaul connection is lost. Any RRC connected UEs are released and the eNodeB establishes S1 connection to local EPC. IOPS mode is indicated by broadcasting an 'IOPS' PLMN ID for which PS UE has a separate USIM application. The IOPS PLMN is marked in system information broadcast as reserved for operator use, which means that access classes 0-9 and 12-14 behave as if the cell status is "barred" (See 36.304).  

Because the minimum functionality of local EPC provides only IP connectivity service, it may be necessary to include also other functions for efficient isolated communication. Mission critical push to talk (MCPTT) is definitely important application for PS users. Also some broadband data applications can be considered for IOPS. For example real time video for situational awareness is typical application enabled by LTE.

IOPS is specified initially in 3GPP release 13 (23.401 Annex K) and it is optional in any public safety LTE network. 

Comments

  1. AnonymousJune 6, 2016 at 5:29 AM

    Hi
    Thanks for you post.
    I have a few questions which I hope you can help clarify.

    1.
    Can I assume that the spectrum assignment for the commercial PLMN 'A' and PLMN 'PPDR' are the same, within the same LTE bands? For example the same 20MHz block in LTE B28? If not the same, wouldn't it be a interference/IMD problem? How is the radio resources/scheduler between the two EPC being coordinated with the eNodeB?

    2. How would the EPC tasks between local and Macro EPC be coordinated? Would both the EPC simultaneously handle EPC tasks (e.g. handover/call flow) or only one at a time? how is this being managed?
    Is it typical for a commercial carrier to have more then 1 EPC being setup? I have heard that for a reasonable size carrier, Singapore for example, only one EPC is required. Not sure for the larger carriers like AT&T in the USA. Comments?

    ReplyDelete
  2. Mika AaltoJune 6, 2016 at 10:36 PM

    1. Yes, same carrier can be shared. Either all radio resources are allocated/scheduled according to bearer QoS parameters (QCI, ARP, MBR/GBR) between all subscribers or then eNB vendor has a solution to virtually split the carrier capacity between PLMNs. Alternatively it is also possible that both PLMNs have own carriers (e.g. 2 separate 10 MHz carriers at B28).

    2. Local EPC for IOPS is serving only PPDR subscribers when macro EPC is not reachable. Local EPC is not serving, if macro EPC is available.
    Commercial carriers have typically multiple EPC sites for geo-redundancy (in case of major core network disaster). In very large countries there are multiple EPC sites to keep also e2e latency in reasonable level.

    ReplyDelete
  3. Kit KilgourJuly 11, 2016 at 7:16 PM

    Thanks again for the post. Looking at the specs, it seems that the PLMN PPDR EPC shown in the top figure may not need to exist in that shared network scenario. i.e. the IOPS eNodeB need only start broadcast the IOPS PLMN ID once it detects that the S1 link to macro core is lost

    ReplyDelete
    Replies
    1. Mika AaltoJuly 11, 2016 at 7:39 PM

      The upper figure is showing shared access with separate core networks for commercial and public safety users. So, both macro core networks are active. Local EPC is serving only public safety users in isolated mode. I assume here that backhaul is lost to both core networks.

      Delete
  4. JamesSeptember 16, 2016 at 4:57 PM

    Not sure what authentication/cryptographic protection is used within IOPS - any idea?

    ReplyDelete
    Replies
    1. Mika AaltoSeptember 16, 2016 at 5:11 PM

      Standard 3GPP mutual authentication, key generation and air interface ciphering & integrity protection. Standards support SNOW 3G, AES and ZUC ciphering.

      Delete
  5. Mika AaltoSeptember 16, 2016 at 5:11 PM

    This comment has been removed by the author.

    ReplyDelete
  6. Pedro TrigueiraFebruary 14, 2017 at 5:15 PM

    Hi Mika,

    Would it be any difference in IOPS behaviour on commercial network in respect to the type of agreement with PPDR - light MVNO (apn), full MVNO (dedicated core) or RAN sharing ?!
    Tks

    ReplyDelete
    Replies
    1. Mika AaltoFebruary 15, 2017 at 8:41 PM

      Standards compliant IOPS requires specific PLMN ID to be used in IOPS mode. In that sense no difference.

      Delete
  7. Pedro TrigueiraFebruary 20, 2017 at 6:59 PM

    Hi Mika,

    Are you aware if mobility procedures (HO) are applicable in IOPS (i.e. backhaul not available but inter-site connectivity exists...) ?!

    ReplyDelete
    Replies
    1. Mika AaltoFebruary 20, 2017 at 7:36 PM

      Yes, HOs are supported between neigboring cells of IOPS eNB or neighboring eNBs, if served by same local EPC.

      Delete
  8. epcquoteFebruary 24, 2017 at 5:32 PM

    This comment has been removed by a blog administrator.

    ReplyDelete

Post a Comment

Popular posts from this blog

Mission Critical Push To Talk and EPS bearers

Image
Mission critical push to talk architecture defines several reference points and uses multiple protocols over different EPS bearers. 23.179 specifies that UE connets to MCPTT specific APN in order to use MCPTT service. It is defined that SIP signaling uses QCI 69 bearer. Additionally HTTP is used for signaling. 23.179 defines also that QCI 8 or better is used for HTTP messaging. Voice media is transmitted over secure RTP either using unicast GBR QCI65 bearer or optionally in multicasting downlink media over MBMS GBR QCI65 bearer. Same bearer (unicast or multicast) is used also floor control. Following figure depicts how these MCPTT reference points can be mapped to unicast and multicast bearers. Although the 23.179 states that SIP and HTTP can be mapped to different unicast bearers that have different QoS, it can be also interpreted that QCI69 is better than QCI8 and therefore it should be possible to carry both SIP and HTTP signalling over the default QCI69 bearer. After LT...
Read more

APNs in MCPTT smartphone

Image
LTE smartphones provide mobile broadband connection to Internet. The prerequisite is that the UE has correct settings, which depend on the mobile operator. Nowadays device vendors and operators have made the use of mobile data so easy that usually users do not need to do any manual configuration. Each smartphone has an internet APN (Access Point Name) configuration, which matches with the operator's network configuration. In general certain APN configuration allows UE to connect (when included in subscription) to certain IP network called packet data network (PDN). So, smartphones know operator's internet APN setting, which enables UE to connect to Internet. Operators have also other APNs and respective PDNs, which offer operator specific services. Some of those services are standardized. On old, still existing service is MMS (Multimedia Messaging Service). MMS is supported by all smartphones and probably automatically configured in all devices and networks. The question is...
Read more

Public Safety prioritization

Image
LTE QoS and prioritization for mission critical communication Public safety (PS) users have the most stringent requirements for network & service accessibility and service quality. Various mechanisms can be used to fulfill these requirements in different network conditions. Those mechanisms must be able to differentiate both users and applications based on certain priorities.  PS users can have different priority levels, which can also change dynamically. For example paramedic engaged in emergency mission has a higher priority than policemen on a lunch break. LTE networks can be shared serving both PS users and commercial subscriber with same resources (e.g. same carriers), in which case there is also a need to prioritize PS users over regular subscribers. Key reason for adopting LTE for mission critical communication is of course broadband capability for data applications. At the same time LTE certainly supports also voice calls (both group calls & one-to-one ca...
Read more