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Monday, June 30, 2008

Is Internet offload the next bottleneck for mobile broadband?

This article about H3G Austria implementing a "direct tunnel" for data caught my eye today. It fits into an emerging theme I've been seeing about the need to offload mobile data traffic from transiting core network elements unnecessarily. Given that some stats suggest that 95% of all 3G data is going to/from the Internet, it makes sense to "dump" as much of it straight onto a connection to the web rather than routing it through expensive (and capacity-limited) core nodes like SGSNs that add no value.

I heard much the same story about femtocells last week, and I've also heard it mentioned about UMA-type WiFi services, sometimes called "Split tunnel architecture". It makes particular sense for roaming data traffic from PCs, for which there is zero value in backhauling via the home network (and especially for H3G, which doesn't charge data roaming fees to on-net customers).

Now in theory, much of this capability to provide a "flattened" IP network architecture should arrive with LTE, and more specifically its counterpart the Evolved Packet Core (EPC, formerly SAE, System Architecture Evolution). But given the timelines, it makes sense for the more data-centric operators to move ahead sooner.

I have a strong suspicion that offload / direct or split tunnel / (assorted other similar terms) will become the next "big thing" after the current backhaul bottleneck is fixed for mobile broadband operators. There will probably be a few different architectures, which I guess will dovetail with specific operator instances of local (femto/WiFi) radio offload, and macro transport connectivity (owned / 3rd-party).


Steve said...

I think this makes the most sense when the consumer is paying a flat rate for data/packet access.

In this case, it's likely faster to go to the internet direct rather than through the GSN (subscriber wins) and the operator still gets paid (operator wins).

David said...

I believe the original article you refer to about the direct tunnel approach is simply part of the 3GPP standard - an optimisation added for 3G compared to the original 2G GPRS. The benefit is simply that data traffic goes directly from RNC to GGSN, thus reducing the cost and complexity of the SGSN. It also improves performance by not having two tunnels terminated on the SGSN.

So yes its helpful and useful - it will reduce the cost of SGSNs - but its not a major breakthrough.

As you've indicated, offloading data closer to the cellsite (e.g. as ip.access have demonstrated with their femtocell) is a much greater benefit. However, it reduces the operators visibility and control (including for billing purposes).

For example, some of the DPI capabilities being tried out are colocated at the GGSN and so would not see any data offloaded prior to that. Traffic shaping based on subscription levels would therefore be difficult to implement (the cellsite/RNC has no knowledge of the subscriber profile).

Therefore I'd agree with Steve's comment that this has to be for flat rate/best effort data which doesn't require traffic shaping.

There may still be some concerns about abuse/overload if the operator really loses all control over data volume and prioritisation of traffic on a cell. Not really a problem for femtocells, but might be for public areas.

john said...

All femto vendors will offer local data offload. Regulatory/billing issues will be a problem for all

The interesting issue is why spend on an EPC core when you have direct tunnel in a GPRS core. There are three new untested logical boxes in an EPC core (MME, SGW, PGW) two of them on the data plane (SGW, PGW)- admittedly they can be co-located.

Moreover for a 2G/3G/HSPA/HSPA+/UMA phone or femto you need to go via an SGSN to get to the EPC core. So we are now talking about 4 logical boxes

In a GPRS core supporting direct tunnel there are only two well understood boxes (SGSN and GGSSN) and only one box in the data plane (GGSN)

The protocols between EPC boxes are not more useful/efficient than those between GPRS boxes unless you want a core that supports WiMAX/WLAN also but single packet core for 3GPP(2G/3G/HSPA/HSPA+/UMA/femto/LTE), WLAN, WiMAX etc will be a stretch

So given it will take forever to have large numbers of LTE phones and the EPC core is not any better for 2G/3G/HSPA/HSPA+/UMA phones and femtos why should an operator replace their xGSNs with an EPC any time soon?

Anjan said...

There is a 3GPP approved standard called I-WLAN that is similar to UMA but targets the data offload market and allows seamless mobility between Wifi and 3G networks. You can get more information at www.intellinet-tech.com.