Small Cell Backhaul

Resilient backhaul options for enterprise small cells

ResilienceEnterprise small cells require some form of IP broadband connection back into the mobile operator core. But what if it fails? The consequences to ongoing business activity could be significant. Several options are available, depending on the level of protection against outage required.

Shared or combined backhaul for multiple operators

Where service from multiple network operators is provided onsite, it’s not unusual that each has their own dedicated backhaul. This is particularly true for the larger DAS installations, where each operator is responsible for providing their own basestations.

It can often be true for shared macrocell tower sites or in-building small cells, where each operator may insist on their own dedicated backhaul connection in order to guarantee end-to-end control and quality assurance.

In urban areas, wireless mesh backhaul, which can be designed with multiple alternative routes and fibre interconnects to cope with any individual relay node failure, are another potential option.

Clearly, there are cost savings to be had. Some operators are happy to share backhaul links from cell towers – indeed some tower companies provide that as part of their service. This is equally feasible for in-building deployments, but is more variable because the industry is still at a nascent stage.

Shared access to Enterprise Internet broadband

Many Enterprise IT departments already operate their own high capacity broadband internet connections – sometimes with considerably more spare capacity that would be needed for an Enterprise small cell solution.

We’ve heard of examples where mobile operators are relenting from their initial stance of requiring dedicated links and agreeing to interconnect through existing high speed services onsite. This doesn’t necessarily mean sharing the internal IT infrastructure – that’s a separate decision – and the connection may be made outside the corporate IT firewall. There’s also the question of whether a guaranteed minimum datarate can be assured, to avoid service disruption during busy periods elsewhere on the corporate net.

Re-using an existing Internet backhaul can greatly reduce the deployment timescale, especially in locations where installation lead times for new fibre connections can be many months or more. One option is to use this for an initial launch period, until dedicated backhaul becomes available.

Multiple diverse backhaul routes

Outage of an in-building data network can seriously disrupt business activity.  This could be from an external hack, a rogue employee or a system outage. IDC estimate the average cost of a mission critical application failure can be up to $1M per hour.

One argument for installing separate independent small cells and backhaul for each of the mobile operators would be that if any one failed, you’d still be able to use the others. However this seems an expensive choice and there may still be common points of failure (such as the cable routing through the same telco central office).

An alternative approach is to ensure there are at least two independent backhaul routes. These could involve:

  • -       separate physical cables/fibres (some campuses and large industrial areas have connections located at opposite ends).
  • -       separate technology (wired/fibre and wireless/microwave).
  • -       Separate fixed network providers (Cable TV/Fixed Telco)

Falling back to cellular

Another possibility would be to fallback by relaying standard LTE from a nearby outdoor macro or microcell. It’s unlikely this would provide full service bandwidth or low latency, but might keep the voice calls and basic data services up and running.

I’ve seen several products intended for residential fixed broadband use, which combine relatively slow copper DSL with high speed LTE on demand. These are more intended to provide a boost of high speed when occasionally required, but have a side-effect of improving network resilience. There are also several off-air DAS solutions that could be melded with small cells for this purpose. It wouldn’t even need to be duplicated for multiple operators if a shared backhaul internet connection is bundled and piped as an encrypted stream through any single one.

Looking to the sky

But what if all physical and nearby wireless connections fail?

Persistent Telecom in the US provides access to satellite backhaul for an in-building solution. They claim to have a guaranteed reserved capacity available which would cater for major outages for their clients – clearly it’s not much help if the backup links become overloaded in the event of a major incident. This should allow buildings with their own generators to continue functioning even through major regional electrical blackouts.

Any of the choices above will need to be considered alongside aspects of:

  • -       what level of resilience and redundancy is required
  • -       who pays for installation/setup and ongoing costs
  • -       who actively monitors and manages the backhaul links
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