HSPA - IntroductionHigh Speed Packet Access (HSPA) is an amalgamation of two mobiletelephony protocols, High Speed Downlink Packet Access (HSDPA) andHigh Speed Uplink Packet Access (HSUPA), that extends and improvesthe performance of existing 3G mobile telecommunication networksutilizing the WCDMA protocols. HSPA evolution first introduced downlink counterpart called HSDPA in Release 5. Uplink evolution followed later in Release 6 by the name of HSUPA. HSPA was originally designed for non-real time traffic with high transmission rate requirements.
FEATURES-HSPA improves the end-user experience by:• increasing peak data rates to 14 Mbit/s in the downlink and 5.8 Mbit/s inthe uplink• reducing latency• providing up to five times more system capacity in the downlink and upto twice as much system capacity in the uplink, reducing the productioncost per bit• link adaptation in downlink
TECHNOLOGIES USED-Shared-channel transmission, which results in efficient use of availablecode and power resources in WCDMA.A shorter Transmission Time Interval (TTI) , which reduces round-triptime and improves the tracking of fast channel variations.Link adaptation, which maximizes channel usage and enables the basestation to operate at close to maximum cell power.Fast scheduling, which provides users with the most suitable channelconditions.Fast retransmission and soft-combining, which further increase thecapacity.16QAM and 64QAM , which yields higher bit-rates.MIMO, which exploits antenna diversity to provide furtherimprovements in bit-rates and system capacity.
HSPA PEAK DATA RATES-Downlink Uplink Theoretical up to 14.4 Mbps Theoretical up to 5.76 Mbps Initial capability 1.8 – 3.6 Mbps Initial capability 1.46 Mbps Max Max # of codes Modulation # of codes TTI data rate data rate 2 ms 5 codes QPSK 1.8 Mbps 2 x SF4 1.46 Mbps 10 ms 5 codes 16-QAM 3.6 Mbps 2 x SF2 10 ms 2.0 Mbps 10 codes 16-QAM 7.2 Mbps 2 x SF2 2 ms 2.9 Mbps 2 x SF2 + 15 codes 16-QAM 10.1 Mbps 2 ms 5.76 Mbps 2 x SF4 15 codes 64-QAM 14.4 Mbps
HSDPA In WCDMA 3GPP Release 5, HSDPA adds a new transport channel to WCDMA– the High Speed Downlink Shared Channel (HS-DSCH) – which provides enhanced support for high-performance packet data applications in the downlink. The improved downlink provides up to 14 Mbit/s with significantly reduced latency. Current devices support 7.2 Mbps throughput. In order to support HSDPA features with minimal impact on the existing radio interface protocol architecture, a new MAC sub-layer, MAC-hs, has been introduced. It enables a functional split to be retained between layers and nodes from WCDMA 3GPP Releases 99 and 4.
HSDPA CHANNELSHSDPA scheme introduced three new channel types- User data is sent on High Speed Downlink Shared Channel (HS- DSCH) . Control information is sent on High Speed Common Control Channel (HS-SCCH) . HS-SCCH is sent two slot before HS-DSCH ,to inform the scheduled UE of the incoming transmission on HS-DSCH. High Speed Dedicated Physical Control Channel(HS-DPCCH) carries Channel Quality Indicators (CQIs).
Key Features- Shared Channel and Multi-Code Transmission Higher-order modulation Short Transmission Time Interval (TTI) Fast link adaptation Fast scheduling Fast Hybrid Automatic Repeat reQuest (ARQ)
ADVANTAGES OF HSDPA- The network can employ data schedulers that give higher priority to real-time applications. Employs shorter frame length, thus it can react faster to problems in the radio channel. Provides shorter delays, which enables new applications, such as interactive networked games. It is best for applications with highly variable bandwidth requirements.DISADVANTAGES- Not suitable for applications with low band-width requirements, such as voice.
HSPA+ (Second Phase of HSDPA)The second phase of HSDPA is specified in the 3GPP release7.Provides smooth inter-networking between HSPA and LTE, therebyfacilitating the operation of both technologies.Higher-order modulation can be supported in both uplink(16QAM) and downlink (64QAM).16QAM modulation enables peak data rates of 12 Mbit/s in the uplink,while 64QAM modulation enables peak data rates of 21 Mbit/s in thedownlink.It introduces antenna array technologies such as beamforming andMultiple-input multiple-output communications (MIMO).
DUAL CELL HSDPAPart of 3GPP Release 8.Allows a user to connect to two cells at once, thereby theoreticallydoubling the connection speeds for the user. Can support up to 28 Mbit/s and 42 Mbit/s with a single 5 MHz carrierin Rel7 (MIMO with 16QAM) and Rel8 (64-QAM + MIMO).While in Release 8 DC-HSPDA can only operate on adjacent carriers,Release 9 also allows that the paired cells can operate on twodifferent frequency bands.