Quality of service (QoS) provisioning is critical to real-time applications such as VOIP and IPTV, but has not been resolved in multihop networks such as mesh and ad hoc networks. For multiple access in ubiquitous networks, energy efficiency is of the single most important design goal, and can be supported through power save and power control techniques. In this paper, we propose a class of MAC protocols based on binary countdown for strong differentiation capability and energy efficiency. A unique advantage for this class of protocols is that the collision rate can be significantly reduced or virtually eliminated. This collision rate issue is often ignored in QoS MAC and sensor MAC protocol designs, but is in fact indispensable for QoS and energy-efficient MAC since service quality will be otherwise considerably degraded due to exponentially increased backoff delay, and energy will be wasted unnecessarily.