Passive Optical Networks (PONs) are an economically efficient means of providing high bandwidth services to end users because end-points can share the cost and the benefit of fibre optic connection. There is a growing interest in the use of PONs as a bearer for services such as Long Term Evolution (LTE), however work remains to be done to ensure stable, low latency and low packet loss for full duplex Transmission. In this paper we are mostly concerned with the characteristics of the downstream channel so as to further the case for PON sharing. We review typical downstream schedulers used in the industry and propose a three-stage downstream scheduler that assures quality of service, accurately, across Virtual Network Operators (VNOs) in multi-tenant PONs environment. We benchmark our scheduler against other algorithms, obtaining almost ideal scheduling performance.