Rev. A Revision A of EV-DO makes several additions to the protocol while keeping it completely backwards compatible with Revision 0. These changes included the introduction of several new forward link data rates that increase the maximum burst rate from 2.45 Mbit/s to 3.1 Mbit/s. Also included were protocols that would decrease connection establishment time (called enhanced access channel MAC), the ability for more than one mobile to share the same timeslot (multi-user packets) and the introduction of QoS flags. All of these were put in place to allow for low latency, low bit rate communications such as VoIP.[7] In the United States, Verizon Wireless and Sprint Nextel have migrated 100% of their EV-DO Rev.0 networks to EV-DO Rev. A. [8] The additional forward rates for EV-DO Rev. A are:[9] In addition to the changes on the forward link, the reverse link was enhanced to support higher complexity modulation (and thus higher bit rates). An optional secondary pilot was added, which is activated by the mobile when it tries to achieve enhanced data rates. To combat reverse link congestion and noise rise, the protocol calls for each mobile to be given an interference allowance which is replenished by the network when the reverse link conditions allow it.[9] The reverse link has a maximum rate of 1.8 Mbit/s, but under normal conditions users experience a rate of approximately 500-1000kbit/s but with more latency than cable and dsl. Rev. B EV-DO Rev. B is a multi-carrier evolution of the Rev. A specification. It maintains the capabilities of EV-DO Rev. A, and provides the following enhancements: Higher rates per carrier (up to 4.9 Mbit/s on the downlink per carrier). Typical deployments are expected to include 2 or 3 carriers for a peak rate of 14.7 Mbit/s. Higher rates by bundling multiple channels together enhance the user experience and enables new services such as high definitionvideo streaming. Reduced latency by using statistical multiplexing across channels -enhances the experience for latency sensitive services such as gaming, video telephony, remote console sessions and web browsing. Increased talk-time and standby time Reduced interference from the adjacent sectors especially to users at the edge of the cell signal which improves the rates that can be offered by using Hybrid frequency re-use. Efficient support for services that have asymmetric download and upload requirements (i.e. different data rates required in each direction) such as file transfers, web browsing, and broadband multimedia content delivery.