More Answers from our Webinar on WiFi Offloading for 3G and 4G Networks

Aricent recently hosted a webinar titled Leveraging 3G/4G WiFi offloading to reduce congestion and increase ROI.The webinar provided exhaustive insights into how Network Equipment Manufacturers can develop highly effective WiFi offloading solution that can help reduce CAPEX and OPEX requirements. They also discussed architectures and functionalities of the various WiFi offloading solutions for technologies such as 3G, LTE, WiMAX and CDMA. Given the huge number of questions asked we were not able to answer every one of them live, so we've addressed others that we didn't get to below.

How does your solution enable seamless roaming between WiFi and 3G/4G/LTE? What type WiFi APs would you propose?

Aricent solution supports ePFD functionality for untrusted Wi-Fi access and also behaves as a Wi-Fi trusted gateway for supporting SaMOG interface. It can use the 3GPP defined mechanism for handover from 3G/4G to WiFi. For WiFi to 3G/4G, the UE needs to send additional trigger over LTE/3G attach indicating handover type so as to support this kind of handover.

Aricent proposes to use the enterprise WiFi Access points that are currently available in market which support Radius interworking as well as support advanced routing functionality including IP in IP tunneling or VLAN support. In addition it should support encryption of tunnels between WiFi access points and WiFi access Controllers as well.

What are some of the unique WiFi deployment strategies for offload solutions that are different from WiFi as it commonly used today?

The unique deployment strategies are as follows:

  1. Common authentication. Currently the WiFi deployments are mainly parallel connections with no common authentication. Using the explained strategies, common authentication can be done for WiFi access and LTE/3G networks.
  2. Common Charging: Common node does the charging and hence common billing can be done for access as well as application usage. This way double charging by the application and access usage can be avoided. Currently since they are disjoint, there is double charging for the users.
  3. Better policy control: Since core network is common, common policy control applications can be used even when connected through WiFi access.
  4. Seamless handover: Most important usage is the seamless handover between WiFi and core network.

How does a seamless UE handover happen from LTE to WiFi network?

For seamless mobility, the UE device needs to first detect that the WiFi signal strength is available. The UE device can detect these through various methods like self-detection of WiFi signals, operator giving SMS or special warning signals, or it can even be manually detected by the subscriber. Once signal is detected, the UE sends trigger to Wi-Fi access points the core network is aware of the tunnels already ongoing in LTE and can thus handover existing tunnels for the user on to the new WiFi interface, by maintaining the same IP address. The bandwidth provided to the user can be upgraded or downgraded depending on the operator policy.

Does a roamed in user access this using an MSRN?

No. The trusted gateway accesses the HSS through AAA proxy. The sessions and IP pipes are through Wi-Fi gateways. HSS and AAA proxy are aware of the position. The MSRN is not required to reach this node.

What solutions are available with Aricent for small cell offloading?

Aricent has solutions which is a single box solution and can behave as Wi-Fi trusted or untrusted gateway with both LTE and 3G handover support for Wi-Fi offloading. For small cell offloading, Aricent has both HNB and HeNB frameworks as well as HNBGW and HeNBGWs. The gateways act as femto gateways which behave as concentrator for multiple HNBs/HeNBs

How does the authentication occur?

The authentication occurs through AAA proxy server which fetches the data from HSS. It is linked to WiFi trusted/untrusted gateways. AKA based authentication is done to authenticate the UE.

Can you comment on QoS support during handover and radio resource management across Wi-Fi and mobile access networks?

While in Wi-Fi access, the Wi-Fi gateways are informed of the QoS from PGW/GGSN. Wi-Fi gateways handle the QoS required for the UE tunnels. Across the WiFi Access points when handover occurs, the Wi-Fi gateways do not change and hence the QoS is maintained.

Can this system be implemented for a WiMAX Network?

Yes, the same system for Wi-Fi handovers can also be maintained for WiMAX networks. In fact, Aricent solution supporting Wi-Fi access and providing offloading from WiMAX networks are already deployed in field.

What is the cost of Wi-Fi offloading from an operator perspective?

The cost for deploying Wi-Fi offloading for operator is very minimal and is mostly a onetime cost. Operators need to deploy the WiFi access points at locations where they need this coverage. No spectrum cost is involved. The WiFi gateways can be collocated with Access controllers or with core networks. The Access points and access controllers are provisioned with pre-shared keys for encryption.

What is the key difference between the loosely coupled and the tightly coupled solution?

The key difference lies in the additional investment needed for enhancing the core network. In tightly coupled solutions the operator has to modify the core network components for supporting WiFi interface as well. In this case the operator may not want additional investments for stabilizing the already stable core networks components.

Can you comment on policy control in terms of when (what conditions) and where the decision to handoff is made?

The policy control for handover can be either at the UE or triggered by the network. The UE devices can detect the signals for Wi-Fi and trigger handover. Or the operator can provision the policy control in core network to detect the higher overload in radio interface and trigger user through signals to request for an offload.

If MSRN is not required, how will the MTC be received?

Terminating triggers would be received to IMS network. It would know the proxy node that the UE is currently registered with. The call would be directed to that. Even the terminating SMS would be triggered to that. Hence the MSRN would not be required.

Is there need for a "client" application?

In case of trusted Wi-Fi gateway, a "client" application is not required as the UE is transparent to the mode of connection. It just needs Wi-Fi access connection.

On other hand for untrusted gateways, a "client' application is required for first using the basic IP for creating IPSec tunnels and then requesting another IP from network. This is the IP that is passed to applications.

Have you resolved the problem of seamless authentication via EAP SSIM/AKA?

Yes. Seamless authentication is currently supported. Same AKA keys are used for authentication through both networks.

Is it seamless? Make-before-break or Break-before-make?

It is make before break and hence it is seamless.

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