Traffic Break-Out in LTE

Before we go into details of architecture of traffic breakout, let’s understand some of the terms that come many times when we talk about traffic breakout in LTE. 

Home E-Node B (HeNB):- Home e-NodeB is nothing but a e-NodeB that is optimized to deploy in small coverage area such as library, hospital or for an enterprise. HeNB internally has following components with their specific functions.
(1) HeNB:- Provides LTE coverage to LTE devices, have all functionalities of E-nodeB.
(2)Security Gateway (SeGW):- Helps in establishing security tunnel (IPsec) between HeNB and Core Network.
(3)HeNB Gateway (HeNB-GW):- It is an optional entity. It aggregates traffic from multiple HeNB and helps it to exchange with Core Network (MME and S-GW).

Home E-NodeB use S1-MME interface to interact with MME for Control Plane (i.e. for signalling) and use S1-U to interface with Serving Gateway for User Plane (i.e. For Data).

Home E-NodeB architecture and Deployment scenario

Local PDN Gateway (L-GW): Local PDN Gateways that are used for traffic breakout, it can either be full-fledged PDN Gateways or subset of PDN gateways that are specially designed for breakouts and can have control plane functionality and charging interface. It shall have S5 interface with Serving Gateways.

Local Home Network:  Local Home Network is area that is served with a set of Home E-NodeBs (HeNB) and Local PDN Gateways (L-GW) in a stand-alone architecture (i.e. can server in independently).  Local Home Network ID is an identifier that is used to uniquely identify Local Home Network in PLMN. Generally college campuses, hospitals and enterprises (small area coverage) are served with concept to Local Home Network.

Traffic Break-Out in LTE

Breakout is very simple concept, let’s understand in very simple example of electricity supply, It is beneficial for both house-holds and electricity service provider that either a user shall connect to nearest power station (P-GW) or nearest Transformer (L-GW). Because it shall not reduce Power intensity (QoS) and cost effective. Now let see how Breakout is done in LTE. 

Benefits of Break-out (LIPA & SIPTO)

1-Reduced Network congestion
2-Better quality experience for services (QoS)
3-Optimal utilization of resources and improved revenue
4-Reduces service cost.
5-Breakout is performed without end user intervention so transparently services can be given to subscriber.

Here are the two major architectures for breakout.

Architecture -1:  Breakout at or above RAN; in this breakout, break out point still in core network. I.e. breakout to P-GW nearest to User Location in core network (generally same operator). Major benefits are (1) Reduced number of nodes in core network. (2) Optimal data path shall be chosen. 
Breakout from P-GW "Breakout at or above RAN"

Architecture -2:  Breakout at enterprise IP network, in this breakout, traffic completely by-passes core network. This is achieved with the help of concept of Local Home Network with L-GW and HeNBs comes into picture. Similarly to Architecture-1, If complete data traffic is broken-out then it is a case of LIPA @ L-GW and and if some specific set of data traffic is considered for break-out then it can be case of SIPTO with L-GW
Breakout from L-GW "Breakout at enterprise IP network"
Lets see SIPTO and LIPA in detail.
1) SIPTO [SIPTO (Selected IP Traffic Offload) Function] 
2)LIPA [LOCAL IP Access]

Your Comments /Suggestions and Questions are always welcome,  shall clarify with best of knowledge. So feel free to put Questions.

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