The HC-SDMA interface operates on a similar premise as
cellular phones, with hand-offs between HC-SDMA cells repeatedly providing the user with a seamless wireless
Internet access even when moving at the speed of a car or train. The standard's proposed benefits: • IP roaming & handoff (at more than 1 Mbit/s) • New MAC and PHY with IP and adaptive antennas • Optimized for full mobility up to vehicular speeds of 250 km/h • Operates in Licensed Bands (below 3.5 GHz) • Uses Packet Architecture • Low Latency Some technical details were: • Bandwidths of 5, 10, and 20 MHz. • Peak data rates of 80 Mbit/s. • Spectral efficiency above 1 bit/sec/Hz using
multiple input/multiple output technology (MIMO). • Layered frequency hopping allocates OFDM carriers to near, middle, and far-away handsets, improving SNR (works best for SISO handsets.) • Supports low-bit rates efficiently, carrying up to 100 phone calls per MHz. • Hybrid ARQ with up to 6 transmissions and several choices for interleaving. • Basic slot period of 913 microseconds carrying 8 OFDM symbols. • One of the first standards to support both TDM (FL, RL) and separate-frequency (FL, RL) deployments. The protocol: • specifies base station and client device RF characteristics, including output power levels, transmit frequencies 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; and • specifies procedures for error recovery and retry. The protocol also supports
Layer 3 (L3) mechanisms for creating and controlling logical connections (sessions) between client device and base including registration, stream start, power control, handover, link adaptation, and stream closure, as well as L3 mechanisms for client device authentication and
secure transmission on the data links. Currently deployed iBurst systems allow connectivity up to 2 Mbit/s for each subscriber equipment. Apparently there will be future firmware upgrade possibilities to increase these speeds up to 5 Mbit/s, consistent with HC-SDMA protocol. == History ==