HSDPA vs HSUPA
HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access) are 3GPP specifications published to provide recommendations for downlink and uplink of the mobile broadband services. Networks that support both HSDPA and HSUPA are called as HSPA or HSPA+ networks. Both specifications introduced enhancements to the UTRAN (UMTS Terrestrial Radio Access Network) by introducing new channels and modulation methods, so that, more efficient and high speed data communication can be achieved in the air interface.
HSDPA
HSDPA于2002年在3GPP版本5中引入。HSDPA的关键特征是AM（振幅调制）的概念，其中调制格式（QPSK或16-QAM）（QPSK或16-QAM）和有效的代码速率由网络根据系统负载而更改。和渠道条件。HSDPA的开发为每个用户的单个单元格中最多可支持14.4 Mbps。根据HSDPA标准，引入了新的传输通道，称为HS-DSCH（高速下链路共享通道），上行链路控制通道和下行控制通道是UTRAN的主要增强功能。HSDPA根据用户设备和Node-B报告的通道条件选择编码率和调制方法，该方法也称为AMC（自适应调制和编码）方案。除WCDMA网络使用的QPSK（正交相移键合）外，HSDPA还支持在良好的通道条件下数据传输的16QAM（正交振幅调制）。
HSUPA
HSUPAwas introduced with the 3GPP release 6 in year 2004, where Enhanced Dedicated Channel (E-DCH) is used to improve the uplink of the radio interface. Maximum theoretical uplink data rate that can be supported by a single cell as per the HSUPA specification is 5.76Mbps. HSUPA relies on QPSK modulation scheme, which is already specified for WCDMA. It also uses HARQ with incremental redundancy to make retransmissions more effective. HSUPA uses uplink scheduler to control the transmit power to the individual E-DCH users to mitigate the power overload at Node-B. HSUPA also allows self-initiated transmission mode that is called as non-scheduled transmission from UE to support services such as VoIP that need reduced Transmission Time Interval (TTI) and constant bandwidth. E-DCH support both 2ms and 10ms TTI. Introduction of E-DCH in HSUPA standard introduced new five physical layer channels.
What is the difference between HSDPA and HSUPA?
Both HSDPA and HSUPA introduced new functions to the 3G radio access network, which was also known as UTRAN. Some vendors supported the upgrade of WCDMA network into a HSDPA or HSUPA network by software upgrade to the Node-B and to the RNC, while some vendor implementations required hardware changes as well. Both HSDPA and HSUPA use Hybrid Automatic Repeat Request (HARQ) protocol with incremental redundancy to handle re-transmission, and to handle error free data transfer over the air interface.
HSDPA enhances the Downlink of the radio channel, while HSUPA enhances the uplink of the radio channel. HSUPA does not use 16QAM modulation and ARQ protocol for uplink which, is used by HSDPA for downlink. TTI for HSDPA is 2ms in other words re-transmissions as well as changes in modulation method and coding rate will take place every 2ms for HSDPA, whereas with HSUPA TTI is 10ms, also with the option of setting it as 2ms. Unlike HSDPA, HSUPA does not implement AMC. Goal of packet scheduling is completely different between HSDPA and HSUPA. In HSDPA aim of scheduler is to allocate HS-DSCH resources such as time slots and codes between multiple users, while with HSUPA aim of scheduler is to control the overloading of transmit power at Node-B.
Both HSDPA and HSUPA are 3GPP releases that aimed to enhance the downlink and uplink of the radio interface in mobile networks. Even though HSDPA and HSUPA aim at enhancing the opposite sides of the radio link, user experience of speed is inter-dependent on the both links due to request and response behaviour of data communication.
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