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Sunday, 20 November 2016

WiFi & LTE Convergence at RAN level using 3GPP LIMONET standards.

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This is in coninuation, rather to say,  to supplement  my earlier blog on WiFi offload or rightly saying WiFi & LTE convergence. putting down some excerpt from that     .......""

What is of interest....

Wi-Fi is not there for hand off or to say in popular term offload. It could be leveraged as associated network. An associated data path to LTE network by converging at RAN or IP-RAN through a Local PGW and keeping the common EPC core. This convergence is possible if S1AP will be terminated at this Local PGW and MME is kept transparent to converged Local network. EPC/PGW while creating the bearer, based on IPCAN session (contains the policy), will provide the information, based on policy, which will help Local PGW to distinguish and forward the data flow.

Wi-Fi and cellular could be converged at radio access level and Wi-Fi can be used an associated data channel for the mobile access. This feasibility is well accepted now and companies like Qualcomm have more obsessed approches. Qualcomm is pursuing the aggregation at radio link level with a point of convergence at PDCP layer (

On the convergence of two at RAN, the small cell forum is also putting its attention through research and industry surveys. Its recent whitepaper, feb 2016, titled "Industry perspectives, trusted WLAN architectures and deployment considerations for integrated Small-Cell Wi-Fi (ISW) networks" SCF states at section 2.0 Integrated small cell Wi-Fi (ISW) networks..... "other interesting alternatives are possible, namely integration in the SC-APs (i.e. RAN-based integration) and/or in SC-gateways (i.e. GW-based integration). Here, the Integration function resides at the edge, possibly in an integrated ISW-AP. RAN-based integration of licensed/unlicensed access is now being addressed by 3GPP release 13, including approaches for RAN based integration of Wi-Fi and LTE.

Finally, architectures that integrate Wi-Fi and SCs at the gateway level are possible. For example, the SC-GW (i.e. H(e)NB-GW) as well as Wi-Fi GW (i.e. ePDG and/or TWAG/TWAP) may be realized together, along with associated integration functions. At the time of writing, these architectures are still in consideration and development."

So that's the future.....

This could be done at network level, where you need not to go all the way to PGW at EPC but having a local PGW at RAN/IP-RAN network. The advantage it will bring is the common EPC for both cellular and Wi-Fi networks i.e. no need for the transfer of PDN connectivity context like an inter-RAT scenarios. Only thing is that the solution is not for any kind of Wi-Fi device but it is for cellular device equipped with Wi-Fi as we need cellular for all the service control level functionality.

Service delivery is well controlled through the 3GPP PCC architecture that define PCRF, PCEF (PGW) and Application server (AS) level interaction and coordination also referred to as IPCAN session. In EPC we need bearer to carry the traffic for specific service. This bearer traffic is delivered to RAN to reach to end devices over air interfaces or radio channels. EPC provide all the necessary information as QoS parameter for specific bearer to RAN for required radio channel capacity. The interface between EPC and RAN is S1 (S1-AP for control path and S1-U for data path).

Instead of having direct interface between eNB and EPC if we keep a Local PGW node (L-PGW) to interface with EPC and provide convergence of Wi-Fi network at this L-PGW . A replica of this PCC architecture can be implemented at this L-PGW level which will decide to deliver the service at Wi-Fi of Cellular radio. This will definitely need the modification on RAN and EPC interfaces like s1AP and NAS etc. as L-PGW has to coordinate with MME.

There is nothing to scratch to get go, the provisions of such nature framework and already there with 3GPP, like for LIMONET ( We can leverage this for convergence of the two networks at local network level with a common core. The Standards for LIPA specific work at 3GPP (23.859) provide the data path connectivity compressed till local network, although the signaling for that remain intact like a normal PDN connectivity. This could be taken in principle for the convergence of two networks at local network level.

We believe strongly that Service provider can create yielding business case around a associated Wi-Fi network. The convergence at RAN and at network layer level would be a pure software solution with existing infrastructure and can be a ready to move solution. Other specific approaches will be requiring necessary ecosystem around for their success.

We are actively seeking the support and sponsors to extend our POC work. We need support from service provider and OEMs for widen-out our POC development. Please feel free to contact us for detail and discussion.

Note : We are strongly pursuing on our believe on next gen network with a central theme of "Homogeneous connectivity through heterogeneous networks" the solution for Wi-Fi convergence to cellular is inclined to this theme. We believe technology like MEC is going to give a master boost to our center theme.