Or Why Use Multiband Even If You Do Not Need More Capacity
The art of bundling multiple carriers in different bands has gained popularity in the last couple of years. This allows operators and service providers to combine the strengths of microwave backhaul (range and availability) with the merits of millimeter wave backhaul. E band, in particular, opens the door to the multi-Gbps wireless backhaul era.
The most common use case for multiband, as you probably know (being a dedicated follower of this blog), is the ability to enhance the capacity of an existing link using E band. This can be done without compromising on service availability, even when it comes to a reach of 5-10 km, a distance in which the availability of an E-band link does not meet the 99.999% (or even the 99.9%, for that matter) target.
This is achieved by utilizing a layer-1 carrier aggregation mechanism that combines the E-band and microwave backhaul carriers into a single link.
But what if you do not need more capacity? What if you are happy with your current 1Gbps capacity, achieved by an 18GHz band 56MHz channel with XPIC? Could you simply ignore multiband?
Well, there might be other challenges for which multiband can assist you.
Let's discuss spectrum costs, for instance. In some countries, E-band spectrum fees could be as much as 100-times lower than 18GHz band cost, compared on a per MHz basis.
So even if the E-band carrier requires more spectrum, as it uses lower modulations, it will still cost 10-times less when compared on a per Mbps basis.
This is why higher microwave backhaul bands (e.g. 38GHz and 42GHz) tend to see strong migration towards E band, wherever E-band regulation opens and the E-band spectrum costs are, indeed, significantly lower.
The thing is, however, the typical range of a 38GHz or a 42GHz link could be easily covered by E band. This is not the case when it comes to lower bands, such as 18GHz, or even 23GHz.
So we cannot replace those links with an E-band link. But we sure can reduce the spectrum costs utilizing E band with multiband technology.
Let’s take a case in which we have (and are happy with) a 1Gbps link at 18GHz, using a chunk of 56MHz. We can reduce costs by switching from 56MHz to 28MHz (achieving 500Mbps with 99.999% availability), saving half of the spectrum costs (assuming a linear cost structure).
To return to a full 1Gbps capacity (plus some change, even), we can now use an E-band carrier, combined with the existing (yet shrunk down) microwave link, with multiband.
True, the availability of the E-band half of the link will not meet the 99.999% target; however, we can trust the multiband mechanism to allow the required availability for any of the services running over the link.
Cost-wise, assuming the price per Mbps is 1/10 of the cost in the microwave band, we have savings of 45% of the link’s spectrum costs. Calculating such savings across your entire network may accumulate to a very significant amount.
To learn more, read our Technical Brief: Multiband Solution for High Capacity and Reach Wireless Backhaul