UTRA-TDD HCR, an acronym for UMTS Terrestrial Radio Access(UTRA)-Time Division Duplex(TDD) High Chip Rate(HCR), is a 3GPP standardized channel access method based on a combination of TDMA and CDMA (known as TD-CDMA).
In GSM/UMTS, the various UTRA standards are air interfaces, and are also (but not exclusively) referred to as "access modes".
Unlike TD-CDMA (UTRA-TDD 3.84 Mcps High Chip Rate, UTRA-TDD HCR) which complements W-CDMA (UTRA-FDD), it is suitable for both micro and macro cells.
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UMTS-TDD's air interfaces that use the TD-CDMA channel access technique are standardized as UTRA-TDD HCR, which uses increments of 5 MHz of spectrum, each slice divided into 10ms frames containing fifteen time slots (1500 per second).