Access Access Restriction Restriction

6.5.2

Access Access RestrictionRestriction

Naturally, the eNB should only allow access for a single subscriber (or Naturally, the eNB should only allow access for a single subscriber (or group of subscribers) while all other

group of subscribers) while all other subscribers must be barred from usingsubscribers must be barred from using it. The cell served by the home eNB is referred to as a Closed Subscriber it. The cell served by the home eNB is referred to as a Closed Subscriber Group (CSG) cell. As the term suggests, only a UE from a specific user Group (CSG) cell. As the term suggests, only a UE from a specific user group should be allowed access to that cell.

group should be allowed access to that cell.

This access restriction is needed because some backhaul links for this type This access restriction is needed because some backhaul links for this type of deployment are not considered to provide adequate QoS to support a of deployment are not considered to provide adequate QoS to support a large numbers of UEs. There may also be regulatory issues with sharing large numbers of UEs. There may also be regulatory issues with sharing the backhaul link/eNB access in that location. Finally, the backhaul link  the backhaul link/eNB access in that location. Finally, the backhaul link  may be owned by or paid for by the subscriber and he/she may not be too may be owned by or paid for by the subscriber and he/she may not be too happy to share the link with others!

happy to share the link with others!

The user group associated with a specific home eNB needs to be updated, The user group associated with a specific home eNB needs to be updated, under the supervision of the network operator, by the subscriber which is under the supervision of the network operator, by the subscriber which is registered as the owner of the home eNB. When a subscriber is added to registered as the owner of the home eNB. When a subscriber is added to the user group by the registered owner the UE of the subscriber should be the user group by the registered owner the UE of the subscriber should be able to (almost) immediately camp on the cell of the home eNB and then able to (almost) immediately camp on the cell of the home eNB and then acquire service through the home eNB. This is especially important in the acquire service through the home eNB. This is especially important in the

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the network, i.e. there is no macro-layer coverage available.is no macro-layer coverage available.

A UE should not camp on or access a CSG cell if it is not part of the user A UE should not camp on or access a CSG cell if it is not part of the user group that is allowed to access that CSG cell. The exact mechanisms for group that is allowed to access that CSG cell. The exact mechanisms for this is currently still under investigation.

this is currently still under investigation.

6.5.3

Mobility

6.5.3

Mobility

The home eNB/CSG cells are part of the network of the operator, and The home eNB/CSG cells are part of the network of the operator, and therefore the design needs to support mobility of UEs between the macro- therefore the design needs to support mobility of UEs between the macro- layer network and the home eNB/CSG cells. This is true for both Idle state layer network and the home eNB/CSG cells. This is true for both Idle state behaviour (cell re-selection) and Connected state behaviour (handover). behaviour (cell re-selection) and Connected state behaviour (handover). The home eNBs will be deployed in order

The home eNBs will be deployed in order to improve network coverage, toto improve network coverage, to improve network capacity and to offer differentiated billing

improve network capacity and to offer differentiated billing models. As themodels. As the user billing could be dependent on whether the UE is using the home eNB user billing could be dependent on whether the UE is using the home eNB or not it is important that the UE, when it is in range, automatically camps or not it is important that the UE, when it is in range, automatically camps on the home eNB. This can be done by setting broadcasted re-selection on the home eNB. This can be done by setting broadcasted re-selection parameters in such a way that the UE will

parameters in such a way that the UE will always prioritize the CSG cell.always prioritize the CSG cell. It is also important that UEs camped on the home eNB do not cause It is also important that UEs camped on the home eNB do not cause excessive signalling load or processing load if/when the UEs moves excessive signalling load or processing load if/when the UEs moves frequently between the macro-layer network and the home eNB (e.g. frequently between the macro-layer network and the home eNB (e.g. excessive Tracking Area update signalling should be avoided). A possible excessive Tracking Area update signalling should be avoided). A possible solution to this is to, during automated initialization, make sure the home solution to this is to, during automated initialization, make sure the home eNB belongs to the

eNB belongs to the same Tracking Area as the surrounding macro eNBs.same Tracking Area as the surrounding macro eNBs. As discussed above the home eNBs will have an associated user group As discussed above the home eNBs will have an associated user group defining which UEs can access the home eNB. The handover procedure defining which UEs can access the home eNB. The handover procedure needs to take the user group of the Target home eNB into account when needs to take the user group of the Target home eNB into account when deciding whether to handover a UE to a specific home eNB.

deciding whether to handover a UE to a specific home eNB.

As the number of home eNBs in the network will become large the As the number of home eNBs in the network will become large the proportion of measurements made by a UE which could be wasted may proportion of measurements made by a UE which could be wasted may become large, to the point where it affects the mobility performance of the become large, to the point where it affects the mobility performance of the UE/system as well as draining the battery of the UE. It is therefore UE/system as well as draining the battery of the UE. It is therefore necessary for the UE to, somehow, be able to avoid unnecessary necessary for the UE to, somehow, be able to avoid unnecessary measurements of home eNBs where it does not belong to the user group. measurements of home eNBs where it does not belong to the user group. It should be noted that, due to the expected high number of home eNBs It should be noted that, due to the expected high number of home eNBs and the nature of their deployment, it would not be practical to change the and the nature of their deployment, it would not be practical to change the configuration for the mobility procedures (measurements, handover etc) in configuration for the mobility procedures (measurements, handover etc) in the macro layer nodes whenever a home

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6.5.4

Security

6.5.4

Security

The operator’s network must be protected from cases where the user (or The operator’s network must be protected from cases where the user (or someone else) is ‘tampering’ with the home eNB in an un-desired manner. someone else) is ‘tampering’ with the home eNB in an un-desired manner. Thus, the implementation of the home eNB must

Thus, the implementation of the home eNB must offer appropriate securityoffer appropriate security protecting home eNB users and the connected network from security protecting home eNB users and the connected network from security threats arising from accessing the backhaul link or internal interfaces (or threats arising from accessing the backhaul link or internal interfaces (or configuration data) within the home eNB.

configuration data) within the home eNB.

To protect both the operator and the eNB owner it is desirable that mutual To protect both the operator and the eNB owner it is desirable that mutual authentication, between home eNB and network, and establishment of a authentication, between home eNB and network, and establishment of a secure connection with a Security Gateway (SeGW) is part of the home secure connection with a Security Gateway (SeGW) is part of the home eNB initialization process. The exact security mechanism to be used and eNB initialization process. The exact security mechanism to be used and the location of the SeGW function is not

the location of the SeGW function is not yet decided.yet decided. Furthermore, since the home eNB will be a small,

Furthermore, since the home eNB will be a small, easily portable, device iteasily portable, device it is desirable for the operator that the home eNB recognises when it is is desirable for the operator that the home eNB recognises when it is operated in a different country to the HPLMN and, as a result, deactivates operated in a different country to the HPLMN and, as a result, deactivates itself. Such a function can be important for charging reasons.

itself. Such a function can be important for charging reasons.