Page 284 - 5G Basics - Core Network Aspects

1 Core network aspects

The keywords "is not recommended" indicate a requirement which is not recommended but which is not
specifically prohibited. Thus, conformance with this specification can still be claimed even if this requirement
is present.
The keywords "can optionally" indicate an optional requirement which is permissible, without implying any
sense of being recommended. This term is not intended to imply that the vendor's implementation must
provide the option and the feature can be optionally enabled by the network operator/service provider.
Rather, it means the vendor may optionally provide the feature and still claim conformance with the
specification.

6 Scenarios and requirements

6.1 Scenarios

6.1.1 Access discovery scenario
When coverage of multiple access technologies is available, it is important for terminals to have the capability
to discover and select the available and/or desired network(s).
Use case 1: heterogeneous access discovery

Alice arrived at a foreign airport that has ubiquitous wideband code division multiple access (W-CDMA)
network coverage everywhere and Wi-Fi only at certain places. Whether she was using the W-CDMA service
or not, Alice is able to discover the Wi-Fi network when she moves into the range covered by an access point
(AP). The W-CDMA Node B to which Alice has attached might also discover the presence of the Wi-Fi AP.

Use case 2: independent owner discovery
Alice leaves the airport and arrives at her hotel. When she checks in, she finds there are three different
service set identifiers (SSIDs) (i.e., names of the Wi-Fi networks): the first is provided by a local operator, the
second is owned by the hotel and the third comes from a personal device (such as an Android AP). Alice's
mobile device would identify the owners for each access by private/enterprise/home operator/visit operator,
etc. The network might also recognize Alice's role, e.g., whether she is a roaming subscriber, a customer of
the hotel or only a guest.

Use case 3: different access status discovery
Alice purchases a rate card and accesses Wi-Fi provided by a visited operator. She then enters a café. The
café allows its customers to enjoy free Wi-Fi from the same operator but using a different SSID. Therefore,
Alice's terminal is informed that there is an additional Wi-Fi access that is different from hers in price or
current traffic load, quality of service (QoS), security, available internet/IPv4/IPv6, etc. The network is also
able to assess whether she needs to reselect her current access.

6.1.2 Access selection scenario
Since multi-connection may benefit users to obtain better quality of experience (QoE) and benefit operators
to balance traffic loads and increase network performance and reliability, mobile devices or the network may
initiate access selection to cover certain requirements. The access selection scenario is detailed below:
Use Case 1: Valid access selection

Alice's handset discovered an SSID launched by a high-power AP. However, Alice was too far from the AP to
allow her handset's reply to return to the AP. Thus, the AP was unavailable to Alice. Subsequently, her
handset deleted the SSID of the AP from her handset's SSID list.

Use Case 2: Dynamic access reselection
Alice is on a moving bus. She is listening to music online via Wi-Fi. Her device is using SSID1 to access AP1.
After a while, the bus, travelling to another place, forces Alice's device to disconnect from AP1. Two minutes
later, the bus enters the coverage area of the same SSID1, but under AP2. Her device accesses AP2

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