The 3GPP 3G UMTS standard has categorised HSDPA UEs or mobile terminals into twelve categories. These different HSDPA categories define the different characteristics including different HSDPA data rates.
The HSDPA UE categories have been implemented to enable the network to accommodate the different levels of UE performance . By having a simple category number, the network is able to provide the UE with data at suitable rate.
HSDPA category definitions
The different categories are outlined in the table below. From this it can be seen that the overall raw data rate and hence the category is determined by a number of elements including the maximum number of HS-DSCH codes, TTI, block size, etc.
It should be remembered that the data rates qoted are for raw data rate - that seen by the user will be less than this because of the error correction, etc.
|HSDPA UE Category Summary|
|HS-DSCH category||Max No of HS-DSCH codes||Min inter-TTI interval||HSDPA data rate (Mbps)||Transport block size||Max no soft bits||Supported mod schemes|
Additional information about the HSDPA categories and data rates table:
- Categories 1-10 support 16QAM (16 quadrature amplitude modulation) as well as QPSK (quadrature phase shift keying). Categories 11 and 12 only support QPSK.
- The maximum number of HS-DSCH codes is the number of multiplexed codes on the high-speed physical downlink shared channel (HS-PDSCH) that receive data.
- The maximum buffer size for hybrid automatic repeat request (H-ARQ) is determined considering signals received prior to resend and resent signals; it is the maximum number of bits in the receive buffer after demodulation.
- The minimum transmission time interval (TTI) is the time interval allocated to the mobile terminal for receiving data. There is a balance between a short TTI for providing adaptivity and while keeping the overhead to a minimum.
The HSDPA UE categories are key to the successful operation of a network carrying HSPA transmissions.
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