High speed downlink packet access

1. High-Speed Downlink Packet
Access
Pankaj Khodifad

2. Introduction
• High-Speed Downlink Packet Access (HSDPA, also
known as High-Speed Data Packet Access) is 3G
(third generation) mobile telephony communications
protocol in the High-Speed Packet Access (HSPA)
family
• Current speed is 42 Mbps(downlink), it can be
increased 337 Mbps with HSPA+ 3GPP standards

3. HS DSCH
For HSDPA new HS DSCH channel is added
which is implemented by three new physical layer
channel
1. HS-SCCH
2. HS-DPCCH
3. HS-PDSCH

4. HS-HCCH
• The High Speed-Shared Control Channel (HS-SCCH)
informs the user that data will be sent on the HS-
DSCH, 2 slots ahead

5. HS-DPCCH
• The Uplink High Speed-Dedicated Physical Control
Channel (HS-DPCCH) carries acknowledgment
information and current channel quality indicator
(CQI) of the user
• This value is then used by the base station to calculate
how much data to send to the user devices on the next
transmission

6. HS-PDSCH
• The High Speed- Physical Downlink Shared Channel
(HS-PDSCH) is the channel mapped to the above HS-
DSCH transport channel that carries actual user data

8. HARQ
• Data is transmitted together with error correction bits.
So minor errors can thus be corrected without
retransmission
• If retransmission is needed, the user device saves the
packet and later combines it with retransmitted packet
to recover the error-free packet