The technology choices
Fibre is inevitably the preferred choice for mobile backhaul when available, but small cells present a very different challenge to macrocells. It's usually not practical or affordable to take fibre to the lamppost and wireless backhaul will be the only viable option in most outdoor urban environments.
Conventional wireless backhaul systems based on PTP and PTMP architectures are available, but these are not sufficiently robust, flexible or cost-effective to handle the complexities of deployment down at street level.
NLOS solutions in the sub-6 GHz bands typically use a PTMP architecture. The equipment is relatively small, cheap and easy to deploy, but offers lower capacity and requires licensed spectrum that's in short supply. This will lead to performance issues and higher levels of interference as small cell density increases.
LOS microwave solutions using a PTMP architecture operate in licensed, area-based spectrum that's widely available in most markets. The equipment is larger and two to three units are typically required per lamppost, which is not desirable from a planning perspective. The star topology requires LOS links back to a hub site, which offers less flexibility during deployment as locations may not always be available. Installation is slow as each link must be manually aligned by specialist telecom engineers. And systems are not easy to scale, with re-planning and re-alignment required for existing nodes when new ones are added.
LOS microwave solutions using a PTP architecture operate in licensed spectrum that must be obtained on a cumbersome link-by-link basis. They offer relatively high capacity, but units are larger and two or three typically required per lamppost, which raises concerns with planning officers. Installation is slow with precise, manual alignment for each link. The systems are difficult and costly to scale with re-planning and re-alignment required for existing nodes when new ones are added.
LOS solutions in the V/E millimetre bands (60 GHz and 80 GHz) typically use PTP links. They offer higher capacity and unlicensed spectrum is readily available in most markets. But the equipment is larger with multiple radios required per lamppost, which is often unacceptable to urban planners. Deployment is relatively slow and expensive because of the requirement for radio planning and precise alignment, as well as relays for NLOS links. And the need to re-plan, re-visit and re-align existing sites when new nodes are added makes it costly and impractical for the organic nature of small cell network growth.
Metnet has been developed to overcome the trade-offs other systems impose. It currently operates at 26 and 28 GHz in licensed, area-based spectrum that's widely available in most markets. The small form factor and only one unit per lamppost easily satisfies urban planning requirements. The node's unique self-organising capability and wide 270-degree field of view enables plug-and-play installation in under 15 minutes, with no need for radio planning or manual alignment. A unique multipoint-to-multipoint architecture with self-healing links offers higher availability and resilience. And the system is easy to scale as existing nodes will automatically re-organise and re-align as new ones are added.