For out door use, the 60 GHz band is seeing growing interest in providing backhaul for small cells. However for outdoor 60 GHz backhaul a phase array antenna system is a necessary ingredient to meet to cost, size and reliability needs of the market. Blu Wireless is developing a backhaul system using electronically steerable antennas for a customer deployment in the second half of 2016.
A key challenge at 60 GHz is how to overcome the additional signal losses due to oxygen absorption. If transmit powers and antenna gains were equal, at 60 GHz the received signal would be 1000x weaker than a Wi-Fi signal. To address this challenge, millimetre wave systems need electronically steered high gain antennas to track users as they move within the network.
The problem is that electronically steerable antennas or phase array systems will violate EU CEPT REC(09)01 rules. According to Mark Barret Chief Marking Officer at Blu Wireless Technology the problem stems from how the EU regulations specify EiRP.
ETSI EN 302 217 specifies an EiRP limit of 55 dBmi but limits maximum conducted power to +10 dBm and the minimum antenna gain to +30 dBi.
In the USA, under FCC Part 15.255 the EiRP limit is specified at +40 dBmi. However, it allows a trade-off of conducted power up to 27 dBm with antenna gain as long as EiRP does not exceed +40 dBmi. Further, the FCC allows outdoor link operation between fixed points to use an even higher EIRP of up to +82 dBmi.
By allowing a more flexible trade-off between gain and power the USA enables the use of lower cost active phased array antennas for 60 GHz wireless backhaul. For companies that want to deploy 60 GHz networks for operation in Europe the current regulations require the use of mechanically steered high gain antennas since the antenna gain must exceed +30 dBi and conducted power must be under +10 dBm).