The document discusses High Speed Downlink Packet Access (HSDPA) technology, its architecture, protocols, and performance analysis. HSDPA aims to provide high-speed mobile data services by enhancing the capabilities of existing W-CDMA technology and is particularly beneficial for multimedia applications, boosting data rates and improving user experience. The report also compares HSDPA with similar technologies like WiMAX in terms of coverage, capacity, and security features.

1. High Speed Downlink Packet Access (HSDPA)
Abstract
The title for the report is High Speed Downlink Packet Access (HSDPA). Internet is become apart
of our every day life and mobile users demand for high speed access while they are on the
move. HSDPA can fulfil these demands and offer more services which are broadband related.
The report will analyse and evaluate the HSDPA technology, which include the architecture,
protocols and protocol status. Also the report discuss HSDPA principle operation and the
physical and MAC layer. With Small scale simulation, HSDPA performance and how it handle
different types of traffic and users, will be analyse. Also the report will discuss the outlook
market and how it compete with other similar technologies in the coming years. By the end of
my report I will gain more knowledge and understanding of HSDPA technology and how much
mobile users and business can benefit from it.
Abbreviations
AES Advance Encryption Standard
AMC Adaptive Modulation and Coding
BTS Base Transceiver Station
DCH Dedicated Channel
DES Data Encryption Standard
DTX Discontinuous Transmission
DSL Digital Subscriber Line
FACH Fast Access Channel
GSM Global System for Mobile Communication
UMTS Universal Mobile Telecommunication System
3G Third Generation
WCDMA Wideband code Division Multiple Access
HSDPA High Speed Downlink Packet Access
HSPA High Speed Packet Access
EDGE Enhanced Data Rate for Global Evolution
HS-DSCH High-speed Downlink Shared Channel
VoIP Voice over IP

2. TTI Transmission Time Interval
HARQ Hybrid Automatic Response request
RRM Radio resource Management
SRNC Serving Radio Network Controller
RNC Radio Network Controller
RRC Radio Resource Control
PDCP Packet Data Convergence Protocol
RCL Radio Link Layer
MAC Medium Access Control
RACH Random Access Channel
S-CCPCH Secondary Common Control Physical Channel
HS-DSCH High Speed Downlink Shared Channel
HS-DPCCH High-speed dedicated Physical Control Channel
F-DPCH Fractional Dedicated Physical Channel
HS-PDSCH High-speed physical downlink shared channel
EAPOL Extensible Authentication Protocol over LANs
WEP Wired Equivalent Privacy
EAP Extensible Authentication Protocol
RSNA Robust Security Network Association
QoS Quality of Service
1.0 Introduction
Universal Mobile Telecommunication System (UMTS) is most growing mobile technology in the
recent years. Resulting of that growing of number of services such as mobile TV, Multimedia
and online games video and video streaming, which will demand a high speed data rate.
Current 2.5G and 3G service providers are reporting that a large proportion of usage is due to
data, and the demand for the high speed data rate will increase specially for multimedia
services. Recent Release 99 WCDMA has a maximum of 384 kbps data rate, which will be
increased to 512 kbps and beyond. Then the introduction of High Speed Downlink Packet
Access (HSDPA), which will boost WCDMA speed and performance. HSDPA has better
throughput than WCDMA and it has a higher data rate.

3. HSDPA is defers from W-CDMA, it uses a high-speed downlink shared channel ( HS-DSCH),
which has faster downlink speed, carrying data to mobile phones.
High Speed Downlink Packet Access is mobile communications protocol, based on, and
leveraging technologies from the existing W-CDMA protocol. HSDPA aims to bring high-speed
data communication speeds more inline with those of standard consumer broadband services.
Implementation of HSDPA can be done in the existing UMTS networks and it can work a long
side the 3G networks based on the 3GPP Release 99. there is no need of changing the 3G's core
network as long as it can handle HSDPA traffic.
HSDPA sometimes referred to as 3.5G, will be able to offer theoretical download speeds of
approximately 1.8Mbps, and upload speeds of 384Mbps. higher communication speeds will
soon be possible with advances in technology. Comparable 3G data communications devices.
HSDPA provides a significant increase in high speed mobile communications from its
predecessor.
HSDPA modules can now be easily implemented in mobile computers, using either a PC-Card or
internal mini-card device. So designing the technology into a mobile computer is not difficult for
the manufacturer. The high speed communications of HSDPA allows for a much richer Internet
experience for the mobile user. High speed transmission of Video and voice can be transmitted
at higher speeds with little loss of quality.
This also opens up mobile Voice Over IP (VoIP) to the consumer. Sending Voice over an Internet
connection is certainly cheaper than making a long distance call, and is sure to be the future
method of mobile communications as service providers look to implement these solutions for
their customers.
The mobile workforce (travelling sales people, international business executives) is the obvious
beneficiary of such technologies, but HSDPA can have significant benefits for other users too.
HSDPA provides high speed broadband access foe users and business remote locations who
may not have access to traditional broadband access methods.
HSDPA uses a number of new techniques which provide a good improvement in performance
for mobile users and service providers.
2.0 HSDPA architecture
2.1 Radio resource Management (RRM)
In HSDPA the scheduling control has been moved to BTS and that has overall change in RRM
architecture. SRNC has control of handover, which is simplified in the sense that there is no soft
handover for HSDPA data. Then there is no need to run user data over multiple Iub and Iur

4. interferences, even the utilization of the Iur interference can be avoided by performing SRNC
relocation, when the serving HS-DSCH cell under different controlling RNC.
2.2 Protocol architecture
The protocol architecture can be define as user plane part, which handle all user data, and
control plane part.
* Radio Resource Control (RRC) layer handles all the signalling related to configuring the
channels, mobility management, etc.
* PDCP is the Packet Data Convergence Protocol, has as its main functionality header
compression which is not relevant for circuit-switched services.
* Radio Link Layer (RCL) handles the segmentation and retransmission for both user and control
data.
· Medium Access Control (MAC) handles all mapping between the logical channels and the
priorities, as well as selection of the data rates being used.
2.3 Protocol states with HSDPA
* Cell_DCH is the state which is used when active data transmission to and from the terminal on
the DCH or HSDPA is possible.
* Cell_FACH state, which data can be transmitted in this state, using FACH for the downlink and
RACH in the uplink, which means limited data rates these channels do not offer any
performance enhancement features of HSDPA.
* Cell_PCH / URA_PCH state, these states are the most efficient ones from the terminal battery
consumption point of view.
3.0 HSDPA Principles
HSDPA uses a number of new technologies which aiming to increase capacity and throughput
and improve the overall system efficiency.
3.1 HSDPA Technologies
In Release 99 Specifications there are three different methods for downlink packet data
operation:
The FACH is used to carry the signalling when the terminal has moved due to inactivity. It is
operated on its own and depending on the terminal is in. FACH is decoded either continuously
or based on the paging message. For the FACH there neither fast power control nor soft

5. handover. FACH is carried on the secondary common control physical channel (S-CCPCH) with
fixed spreading factor.
The DCH has fixed a spreading factor in the downlink with fixed allocation during the
connection. It can be used for any kind of service. HSDPA is always operated with the DCH
running in parallel.
HSDPA introduced new channels (HS-DSCH) for user data and (HS-SCCH) in the downlink and
(HS-DPCCH) in the uplink. Also in Release 6 specification there is a new channel called fractional
dedicated physical channel (F-DPCH), which cover for operation when all downlink traffic is
carried on the HS-DSCH.
The general HSDPA operation principle is shown in below, where Node B estimates the channel
quality of each active HSDPA user on the basis of the physical layer feedback received in the
uplink. Scheduling and link adaptation are then conducted at a fast pace depending on the
scheduling algorithm and user prioritization scheme.
The other key new technology is physical layer retransmission. The packet is received in the
buffer in the BTS and kept there, if there any packet decoding failure, retransmission
automatically takes place from the base station without RNC involvement.
3.1.1 High-speed downlink shared channel (HS-DSCH)
HS-DSCH is defined as a transport channel which carries the user data in HSDPA. Its has 2 ms
TTI, which help to reduce round trip delay between UE and Node B. this allow a UE to have
minimal steady level of data rate all the time. In the physical layer HS-DSCH is mapped to high-
speed physical downlink shared channel (HS-PDSCH). HS-DSCH has the flowing properties:
* Link adaptation and the use of different coding and modulation.
* Support of higher order modulation.
* User allocation with BTS based scheduling every 2 ms, with fast physical layer signalling.
* Use of physical layer retransmissions and retransmission combining.
* Multimode operation with fixed spreading factor, only SF 16 is used.
* Use of turbo-coding
* No discontinuous transmission (DTX)
3.1.2 Higher Order Modulation
Beside QPSK modulation, HSDPA uses 16QAM modulation which allow 4 bits can be carried per
symbol, instead of 2 bits per symbol with QPSK modulation. This mean with

6. higher order modulation we can send more data on a single channel
3.1.3 Fast Link Adaptation
HSDPA uses fast link adaptation to vary the amount of coding error generated by radio channel
coding scheme. This is done by changing and varying the coding and modulation according to
link or channel condition, which will improve data rate and signal quality.
3.1.4 Hybrid Automatic Repeat Request
3.2.1 HS-DSCH coding
HS-DSCH use only turbo-coding. The channel coding chain is simplified and only transport
channel active at a time. An additional new issue is the handling of 16QAM and the resulting
varying number of bits carried by the physical channel even the number of codes used remains
fixed.
3.3 High-speed shared control channel (HS-SCCH)
HS-SCCH carries time-critical signalling information which allows the terminal to demodulate
the correct codes. There are no pilots or power control bits on the HS-SCCH, so the phase
reference is always the same as for the HS-DSCH. HS-SCCH is divided into two parts:
* The first part carries information needed to enable de-spreading of the correct code and
contains the modulation information.
* The second part contains less urgent information, such as which ARQ process is being
transmitted.
3.4 High-speed dedicated physical control channel (HS-DPCCH)
HS-DPCCH carries the uplink feedback information from the terminal to the BTS to enable the
link adaptation and physical layer retransmissions. It has fixed spreading factor of 256 and 2 ms
/ three-slot structure. HS-DPCCH operation has been enhanced in release 6 to improve cell edge
operation.
3.4.1 Fractional DPCH (F-DPCH)
F-DPCH is a stripped-down version of DPCH that handle the power control. The code resource is
time-shared and several users can share the same code space for power control information. It
has some restrictions: not usable with services requiring data to be mapped to the DCH,
feedback-based transmit diversity is not usable.

7. 3.4.2 HS-DSCH Link adaptation
Link adaptation is very dynamic as it operates with 2 ms granularity with the HS-DSCH. It is
based on physical layer CQI being provided by the terminal. By using link adaptation, the
network will gain from the limitation of power control dynamics in the downlink.
3.4.3 Physical layer operation
HSDPA physical layer operation goes through the following steps once one or more users have
been cond as using the HS-DSCH and data start to reach the buffer in the Node B.
* Node B evaluate channel condition, buffer status, time from last transmission, transmission
pending and so forth for each user every 2 ms.
* The Node B identifies the necessary HS-DSCH parameters, including number of codes, 16QAM
usability and terminal capability limitations.
* The Node B starts to transmit the HS-SCCH two slots before the corresponding HS-DSCH TTI.
* The terminal monitors the terminal-specific set of at most four HS-SCCHs given by the
network. Once the terminal has decoded Part 1 from an HS-SCCH, it will start to decode the
remaining parts and will buffer the necessary codes from the HS-DSCH.
* After decoding the HS-SCCH parameters from Part 2, the terminal can determine to which
ARQ process the data belong and whether they need to be combined with data already in the
soft buffer.
* In the Release 6 version, a pre-amble is sent in the ACK/NACK field if the feature is cond to be
used by the network.
* Upon decoding the potentially combined data, the terminal sends in the uplink direction an
ACK/NACK indicator, depending on the outcome of the CRC conducted on the HS-DSCH data.
* If the network continues to transmit data for the same terminal in consecutive TTIs, the
terminal will stay on the same HS-SCCH that was used during the pervious TTI.
* In Release 6, when the data flow end, the terminal sends a post-amble in the ACK/NACK field.
HSDPA basic features
1) Adaptive Coding and Modulation
The principle of ACM is to alter the coding and modulation for transmission according to the
condition of the receiver channel.
2) Hybrid Automatic Repeat Request (HARQ)

8. When receiver can not decode data because of data error, HARQ main job is retransmitting the
data.
3) The Active time Space Priority (TSP)
TSP manage and control packets in the buffer of base station.
3.0 HSDPA Performance
HSDPA has a high data rate of 10 Mbit/s in normal 5 MHz channel, also its fast switching
capability (2 ms) increases trunking efficiency for high data rate packet service. HSDPA high
order modulation can be used to increase user throughput and improve cell capacity. Also fast
packet scheduling gives a high cell capacity and maintain required QoS.
There are several factors that effect HSDPA performance and here some of them:
* Network algorithms, specific algorithms such as MAC-hs packet scheduler, HS-DSCH link
adaptation, HS-SCCH power control and HSDPA transmission resource allocation.
* UE detector performance and capability, such as peak data rate, number of HS-PDSCH
channel codes, number of transmit and receive antennas, and baseband receiver algorithms.
* Traffic and quality of service (QoS), such as number of active users, and their corresponding
QoS requirements.
* Channel condition which include the environment of the cell itself, time dispersion, own cell
interference and other cell inference.
3.1 Single-user Performance
QPSK (Quarter phase shift keying) modulation is used when is only one HS-PDSCH code is used,
so there is less power required per user bit and the result is low data rate. Other factors that
effect single-user performance are transmission, processing delays and the Channel Quality
Indicator (CQI). Indoor user with microcell in use, channel quality will be good and so the data
rate, because of less time dispersion and interference. In the other hand, outdoor user using
macro cell, and because of high time dispersion and other cell interference, peak data rate is
limited. Data coverage is low because there is no switching gain in single user situation, but
overall cell capacity has a gain from soft handover.
3.2 Multiple-user Performance
The use of fast packet scheduling, in multiple user environments, has a great effect on the cell
throughput and the required QoS by the end user. The throughput gain directly related to the
number of users using the same HS-DSCH channel and the interference ratio. Note that when

9. the of users increase, per user throughput decreases because HS-DSCH capacity is shared
between users.
HSDPA uses different types of scheduling methods and here are some of them;
* Round robin and fair packet scheduler; this method dose not take count of channel condition
and schedule users the best instantaneous channel quality.
* Proportional fair algorithm which offers an attractive trade off between user fairness and cell
capacity, and used when users have good instantaneous channel condition. The method
improve user and cell throughput [1].
4 HSDPA vs. WiMax
4.1 Coverage and bit rates
WiMAX range coverage can reach up to 50 km, with bandwidth up to 70 Mbit/s, but the actual
bandwidth is lower than the above and still subject to debate. WiBro has a data rate up to 30
Mbit/s, which gives users downlink data rate up to 18 Mbit/s and 6 Mbit/s on the uplink. But
signal is getting weaker when distance between UE and BTS is large, because the signal over
noise ratio is decrease quicker as distance increase. Also WiMAX BTS's can communicate with
each other even without line of sight.
In HSDPA system, downlink bandwidth can reach up to 14.4 Mbps at distance less than 1km,
and 384 kbit/s on the uplink, but bandwidth drop as distance increase, same as in WiMAX
system. but users can transmit data even with very low bandwidth.
4.2 Capacity
HSDPA technology is design for simultaneous users, lots users can share channels and
bandwidth. If number of users increase, the system can still cope but with low data rate.
WiMAX can only operate with few dozens of users and the network can not cope when number
of users increase.
4.3 Multimedia capability
For both HSDPA and WiMAX, there is similarities in multimedia capability and capacity and both
have QoS multimedia applications.
4.4 Security features
HSDPA authenticate users through their SIM card which include two way challenge, encryption
of signalling traffic, use of two way authentication of 3G network and encryption on radio link.
and does not have any other security feature. Data encoding for different users, typical of all

10. CDMA standards, works better than any cryptographic algorithm, but not if an intruder is in a
base station or somehow gets its channels code. WiMAX supports modern cryptographic
algorithms, such as AES and DES. It uses X.509 certificate and EAP. It will certainly please
corporate users, who want to keep their data in secret.
Mobile WiMAX
HSDPA
Date of introduction
2008-9
2006-7
Downlink data rate (max)
23 Mbit/s
14.4 Mbit/s
Uplink data rate (max)
4 Mbit/s
384 kbit/s
Latency
50 ms
100 ms
Security
Certificate or EAP
SIM-based security
Spectrum
2.3 GHz, new at 2.5 GHz
3G 2 GHz, new at 2.5 GHz
Service set-up time
50 ms
2 sec reducing to 0.6 esc

11. Table: Comparison of WiMAX and HSDPA (BT Technology Journal [6])
5 Market Outlook for HSDPA
Internet market is growing rapidly, in recent years, specially mobile broadband, which provide
internet for users either on the move or in remote areas where they can not get access to
traditional broadband access. In 2009, more than 250 HSDPA networks went online providing
broadband services across the globe, with speed up to 42Mbit/s. the number of broadband
subscribers are increasing rapidly, and by end of year 2013 the total subscribers will be more
than 30% of whole mobile users.
The implementation of HSDPA does not require building a new network infrastructure, it can be
done with existing 3G network with better coverage and very effective and efficient use of
bandwidth. So rolling out HSDPA services can done quickly and cost effectively driven by users
demand for such service.
PC card are the first HSDPA device, it can be slotted into desktop or laptop giving users high
speed internet broadband connection. Then it moved on to USB modems, and now laptop and
mobile phones come with built in HSDPA capability. Also HSDPA service can be provided
through landline Ethernet and Wi-Fi.
5.1 UK Market
The introduction of mobile broadband services is enabled by HSDPA technology in 3G mobile
networks, that enables laptop uses to access the Internet on the move at speeds of up to 1.8
Mbit/s, similar to ADSL and cable modem broadband services. Vodafone was the first UK
Mobile Operator to lunch HSDPA service in 2006, which offer subscriber mobile broadband with
speed up 2Mbps and monthly fee of £45, with maximum usage of one Gbyte per month. Now
all operators in the UK are offering HSDPA service with average price of £10 to £15 a month and
maximum download of 2 Gbyte. That mean subscribers are paying average of £0.025 per Mb.
Also some operators are offering free WiFi usage.
Now, Vodafone offering mobile broadband with maximum speed of 8Mb, and working in
upgrading its network to maximum speed of 14.4 Mb. This will make Vodafone the first
operator to offer highest downlink speed, but in real life this speed will never be true. Other UK
operators are offering a lower speed, T Mobile offering mobile broadband with speed up to
4.5Mbp/s, O2, Orange and Three are offering speed of up 3.6Mbp/s and they are still working
to upgrade their network to accommodate speed of 7Mbp/s.
5.2 International Market
HSDPA can be implemented on 3G networks and there no need for building new infrastructure,
this make of rolling out HSDPA a head of its competitor. Number of subscribers are reach the 1

12. Billion in commercial HSPA enabled networks, with number of 204 HSDPA operator in 89
countries, has been reported. With 35 networks in APAC region, 61 networks in Western
Europe, 34 networks in Eastern Europe, 16 networks in the USA and Caribbean and 20 networks
in Middle East and Africa [7].
6 Conclusion
HSDPA is the new generation in the mobile broadband technology, which has a higher data rate
and faster internet access. HSDPA dose not require building a new networks and it can be
implemented on the existing 3G networks. Mobile operators still working hard and promise
their customers to upgrade their networks to top maximum downlink speed of 14.4Mbit/s,
while keeping their prices down. But HSDPA facing a big competition from similar technologies
such as WiMAX, which offer maximum downlink speed up to 23Mbit/s. HSDPA has a good
mobility, voice and data from cellular platform.
7 References
1 Harri Holma and Antti Toskala, WCDMA for UMTS: HSPA Evolution and LTE, fourth edition,
Wiley 2007
2 Harri Holma and Antti Toskala, HSDPA/HSUPA for UMTS: High Speed Radio Access for Mobile
Communications, Wiley 2006
3 Byeong Gi Lee and Sunghyun, “Broadband Wireless Access and Local Networks: Mobile
WiMAX and WiFi, Artech House 2008
4 Nokia HSDPA Solution, [online], visited on 28/2/10, available at
http://nds2.ir.nokia.com/NOKIA_COM_1/About_Nokia/Press/WhitePapers/pdf_files/HSDPA
5 WCDMA and WLAN for 3G and beyond, [online], visited on 1/3/10, available at
http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp
%2Fstamp.jsp%3Ftp%3D%26arnumber%3D998520%26isnumber%3D21543&authDecision=-203
6 N Johnston and H Aghvami, comparing WiMAX and HSDPA, a guide to the technology, BT
Technology Journal, Vol. 25 No. 2 April 2007.
7 HSPA is Global system of choice for mobile broadband, GSA survey, [online], visted on 3/3/10,
available at
http://www.mobileeurope.co.uk/news_wire/113504/GSA_survey_said_to_confirm_HSPA_as_g
lobal_system_of_choice_for_mobile_broadband.html