Coexistence Of Contention-Based General Authorized Access Networks In 3.5 Ghz Cbrs Band

The opening up of the 3550-3700 MHz band in the US for Citizen's Broadband Radio Service (CBRS) represents a new opportunity for deploying spectrum-sharing cellular networks. The three-tier structure of the CBRS sharing regime with different interference protection constraints per tier imposes a coexistence challenge for networks based on Long-Term Evolution (LTE). As a result, contention-based channel access mechanisms can be incorporated into LTE networks as a method of sharing frequency channels assigned by the Spectrum Access System (SAS). In this work, we examine the design and implications of contention-based channel access for the lowest CBRS tier that comprises opportunistic users known as General Authorized Access (GAA) devices. In particular, we assess the suitability of Listen-Before-Talk (LBT) for GAA channel access. Performance evaluations for an outdoor deployment scenario show that LBT-based coexistence is effective for low-power GAA users or symmetric power situations, while a combination of LBT and channel allocation is preferred for asymmetric power situations with a mix of low and high-power GAA transmitters.