Received Via Email

Airspan Networks comments on draft NBN architecture options paper 10Nov09

Received via email:

We have reviewed the Comms Alliance document (re the first pass proposed architecture for the NBN).

We would like to offer our comments / suggestions from a wireless perspective in good faith and we would welcome feedback. (Happy for you to pass on to the appropriate person(s))

Airspan Comments:

It is interesting to see the assertions that the industry approach is to provide Layer 2 access. Whilst this may be true from the FTTH perspective, this is certainly not the case for cellular networks, and future country wide

networks, which see the benefit of Layer 3 connectivity, which fits in with the growth of the Internet, and devices requiring IP connectivity.

That aside, we believe there is a strong history or Wireless Layer 2 networks (WiMAX 16d and proprietary products for instance). Though it should be noted that typically Mobile WiMAX portfolios are essentially layer 3. Hence one of the first decisions to make regarding the architecture is whether the Wireless Network will be layer 2 or layer 3. There are pros and cons for both options.

Layer 2 Comments:

The Layer 2 example given assumes a standards approach to the Ethernet architecture. This is optimistically based on the WiMAX Standards, although is not the case in practice. In going down the Layer 2 route, there is no requirement to provide an Access Gateway (specifically labelled Wireless GW in the Comms Alliance paper)(which should not be an issue), hence the wireless architecture ideally would utilise a radius client in the BS to ensure co-existence with a suitable AAA Server.

The draft document seems to imply PPP tunnels between the end users and the core network in this scenario. We believe this is a very inflexible approach and doesn’t capitilise on the inbuilt QOS mechanisms in WiMAX. That being, from the perspective of providing QOS for the different services and applications expected to be offered across the network. This is something that is provided through EAP authentication over WiMAX, and ideally solved by selecting a Layer 2 Architecture - the preferred approach.

One con of a Layer 2 approach is it also prevents handover between technologies (which assumes IP continuity), and also makes handover a challenge in the normal deployment. Handover currently assumes an IP architecture.

Layer 3 Comments:

There aren’t really any options shown for wholesale and retail deployments, well not clearly anyway. This seems to suggest that either this is not understood very well ? or, there is simply a favoured approach to the Layer 2 network?.

In one section of the document, there are suggestions that VPN tunnels are required between the retail provider and the end user. This is certainly NOT the case with WiMAX, which provides a very simple method of supporting Retail and Wholesale networks.

The document suggests the connection between the Base Stations and the Wireless Gateway (4.2.1.3) may require specific Ethernet aggregation and transport network. Again, this is not the case with (Mobile) WiMAX, which simply requires IP connectivity between the two. This does not preclude the use of Ethernet backhaul, but this is not a requirement.

In summary, a lot of areas have not yet been assessed, which may tip the balance further.

We would welcome feedback on the above and are happy to provide any further insight / input.

Grant

Grant Stepa

Managing Director (AUS/NZ)

Vice President (Australasia)

Airspan Networks Pty Ltd.

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