This presentation gives an overview of the ongoing 3GPP Study Item on LTE-WiFi interworking.
This solution relies on the RAN providing relevant information that may be used by a UE to decide:
1. If and when to connect/disconnect to/from an available WLAN
2. Steer one or more data flows from/to 3GPP RAN to/from WLAN
The UE is assumed to receive network selection and traffic steering rules and/or polices either via ANDSF or user preferences or operator provisioning. The solution can be applied in both RCC_IDLE and RRC_CONNECTED modes. More specifically, the figure below, taken from doc R2-132055, illustrates the procedure when UE is idle mode.
- When the UE establishes RRC connection with 3GPP RAN, it transfers interworking capability info to the network
- If the UE has indicated support for WLAN interworking and 3GPP RAN also wants to interwork with WLAN, the latter may provide assistance info to UE via dedicated signalling at the time of RRC connection release.
- In addition, RAN may broadcast System Information which includes assistance info. If UE has valid assistance information provided through dedicated signalling previously, it ignores the related broadcast information.
- UE selects the access network based on information provided by RAN, information obtained from WLAN and rules/policies/preferences.
- As in the previous case, the UE transfers its interworking capability information to RAN at the time of RRC Connection establishment.
- While the UE is connected to RAN, it receives assistance information from RAN through dedicated signalling, if the UE supports WLAN interworking and RAN wants to interwork with WLAN.
- UE selects the access network based on the assistance info provided by RAN, acquired information from WLAN and rules.
In both cases, the assistance information may include the following:
- 3GPP Network load
- Resources allocation for UE
- WLAN thresholds (e.g. RSSI)
- RAN thresholds (e.g. RSRP)
At the recent RAN2 meeting (May 20-24, 2013), the discussions focused mainly on access network selection and traffic steering in 3GPP-WLAN interworking scenarios. The proposed solutions addressed the following cases:
UE is within UTRAN/E-UTRAN coverage, is using 3GPP and goes into WLAN AP coverage
B. UE is within UTRAN/E-UTRAN and WLAN coverage, is using WLAN and goes out of WLAN AP coverage
C. UE is within the coverage area of both, UE using WLAN, all or a subset of the UE’s traffic should be routed via UTRAN/E-UTRAN instead
D. UE is within the coverage area of both, UE using UTRAN/E-UTRAN, all or a subset of the UE’s traffic should be routed via WLAN instead
E. UE using both accesses and should be connected to only one (WLAN or UTRAN/E-UTRAN) or some traffic should be moved to the other access
In broad terms, there are 3 solutions currently being discussed in RAN2:
Solution 1: 3GPP RAN provides UE with information that assists in network selection and traffic steering. This information may be combined with ANDSF rules and/or UE configuration to decide whether to connect to a WLAN, if one is available, and to steer one or more flows to the WiFi link.
Solution 2: 3GPP RAN provides the access network selection parameters, based on which the UE decides when to connect to a WLAN. These parameters may includes thresholds, priorities, rules etc.
Solution 3: UE reports available WLAN(s) based on measurements configured by 3GPP RAN and the decisions related to WLAN selection as well as traffic steering are taken by the network.
In the next post, I will discuss each of these solutions in more detail.