This document defines the radio (RF)@ Physical Layer (PHY)@ Medium Access Control (MAC)@ and Layer 3 (L3) specifications for the HC-SDMA (High Capacity - Spatial Division Multiple Access) protocol. This specification does not address functionality at the service and application layers. Typical deployments are expected to use a standardized data networking access paradigm@ such as L2TP and PPP. Purpose HC-SDMA provides wide-area broadband wireless data-connectivity for fixed@ portable@ and mobile computing devices and appliances that may or may not be handheld. The protocol is designed to be implemented with antenna array techniques to substantially improve the RF coverage@ capacity@ and performance of the system. Specifically@ the HC-SDMA protocol: ? Specifies base station (BS) radio frequency characteristics such as output power levels@ transmit frequencies and timing error@ pulse shaping@ in-band and out-of-band spurious emissions@ receiver sensitivity and selectivity. ? Specifies user terminal (UT) radio frequency characteristics such as output power levels@ transmit frequency and timing error@ pulse shaping@ in-band and out-of-band spurious emissions@ receiver sensitivity and selectivity. ? Defines associated frame structures for the various burst types including standard uplink and downlink traffic@ paging and broadcast burst types. ? Specifies the modulation@ forward error correction@ interleaving and scrambling for various burst types. ? Describes the various logical channels (broadcast@ paging@ random access@ configuration and traffic channels) and their roles in establishing communication over the radio link. ? Specifies procedures for error recovery and retry. ? Describes Layer 3 (L3) mechanisms for creating and controlling logical connections (sessions) between user terminal and base station including registration@ stream start@ power control@ handover@ link adaptation@ stream closure. ? Describes L3 mechanisms for user terminal authentication and secure transmission of on the uplink and downlink data links.