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HSDPA

INTRODUCTION

3G HSDPA High Speed Downlink Packet Access is an upgrade to the original

3G UMTS cellular system (3.5G) that provides a much greater download speeds for

data. With more data being transferred across the downlink than the uplink for data-

centric applications, the upgrade to the downlink was seen as a major priority.

Accordingly 3G UMTS HSDPA was introduced into the 3GPP standards as soon as

was reasonably possible, the uplink upgrades following on slightly later.3G UMTS

HSDPA significantly upgrades the download speeds available, bring mobile

broadband to the standards expected by users. With more users than ever using

cellular technology for emails, Internet connectivity and many other applications,

HSDPA provides the performance that is necessary to make this viable for the

majority of users.

When HSDPA will be implemented, it can coexist on the same carrier as the

current Release’99 WCDMA services. This will enable a smooth and cost-efficient

introduction of HSDPA into the existing WCDMA networks. The driving force for

high data rates are greater speed, shorter delays when downloading audio, video and

large files which will be used in PDA’s, smart phones etc. Further a user can

download packet data over HSDPA, while at the same time having a speech call.

HSDPA offers theoretical peak rates of up to 10MBps and in practice more than

2MBps. The technical aspects behind the HSDPA concept include the following:

1. Shared channel transmission

2. Adaptive Modulation and Coding (AMC)

3. Fast Hybrid Automatic Repeat Request (H-ARQ)

4. Fair and fast scheduling at Node B

5. Fast cell site selection (FCSS)

6. Short transmission time interval (TTI)

BM II COLLEGE OF ENGINEERING 1 DEPT. OF ECE

HSDPA

EVOLUTION OF HSDPA

The second generation (2G) of mobile cellular systems has been developed as

a successor of analogue systems (called 1G) and became a commercial success in the

middle 90's. 2G systems cover a certain number of different technologies among

which the most important are: (1) Global System for Mobile Communications (GSM),

the more developed technology in the world, in Europe, in many African, Asian and

Middle-East countries, and also in American countries (USA, Canada and a lot of

South America countries), (2) cdmaOne (also called IS-95), mainly used in the

America and Asia-Pacific regions, (3) IS-136 (TDMA, also called D-AMPS), used in

North and South America and (4) Personal Digital Cellular (PDC), used only in

Japan. These systems offer circuit switched voice and rather limited data rate (e.g. 9.6

Kbps for GSM circuit mode), which nevertheless opened a new market for mobile

data communications through the Short Message Service (SMS).


HSDPA

The demand for higher data rates has led to the development of so-called

"2G+" or "2.5G" systems. For the GSM technology, the first step has been General

Packet Radio Service (GPRS) which offers packet switched transmission at bit rates

of about 40 kb/s by allocating several time slots of a frame to the same data

transmission. The second step for GSM has been Enhanced Data rates for GSM

Evolution (EDGE), which mainly consists in the introduction of the 8-PSK

modulation, multiplying by 3 the on-line date rate compared to GPRS. Indeed, EDGE

is included in the 3G – IMT-2000 family of systems. IS-95 and IS-136 have also

evolved in the same direction. IS-95-HDR implements a packet mode at 144 kb/s

(first step towards CDMA2000), while IS-136 has evolved to an EDGE-GSM-based

system under the name of Universal Wireless Communications 136 (UWC-136).

These technical evolutions aiming to provide more and more efficient data services

have paved the way for the definition of 3G systems.

The ITU has deployed a lot of efforts to define a family of systems, called 3G

systems, which provide high data rate to offer multimedia services. Under the name

International Mobile Telecommunications 2000 (IMT-2000), these systems have been

designed for use in the frequency bands selected by the World Radio Conference

(WRC) in the year 1992. The IMT-2000 family is composed of five systems: (1)

Wideband Code Division Multiple Access (W-CDMA) including TDD and FDD

modes, (2) CDMA 2000 1X, (3) Time Division – Synchronous Code Division

Multiple Access (TD-SCDMA), (4) EDGE (also called UWC-136) and (5) Digital

Enhanced Cordless Telecommunications (DECT).

At the end of the selection phase for IMT-2000, two main families of systems

have emerged, leading to the creation of two groups of standardization (including

operators and manufacturers), namely: (1) 3rd Generation Partnership Project (3GPP),

which developed the W-CDMA standard also called Universal Mobile

Telecommunication System (UMTS) in FDD and TDD modes, and (2) 3GPP2, which

developed the CDMA 2000 standards as an evolution of the IS-95 standards.


HSDPA

The new high speed technology is part of the 3G UMTS evolution. It provides

additional facilities that are added on to t e basic 3GPP UMTS standard. The upgrades

and additional facilities were introduced at successive releases of the 3GPP standard.

Release 4: This release of the 3GPP standard provided for the

efficient use of IP, a facility that was required because the original

Release 99 focused on circuit switched technology. Accordingly this

was a key enabler for 3G HSDPA.

Release 5: This release included the core of HSDPA itself. It provided

for downlink packet support, reduced delays, a raw data rate (i.e.

including payload, protocols, error correction, etc) of 14 Mbps and

gave an overall increase of around three over the 3GPP UMTS Release

99 standard.

Release 6: This included the core of HSUPA with an enhanced uplink

with improved packet data support. This provided reduced delays, an

uplink raw data rate of 5.74 Mbps and it gave an increase capacity of

around twice that offered by the original Release 99 UMTS standard.

Also included within this release was the MBMS, Multimedia

Broadcast Multicast Services providing improved broadcast services,

i.e. Mobile TV.

Release 7: This release of the 3GPP standard included downlink

MIMO operation as well as support for higher order modulation up to

64 QAM in the uplink and 16 QAM in the downlink. However it only

allows for either MIMO or the higher order modulation. It also

introduced protocol enhancements to allow the support for Continuous

Packet Connectivity (CPC).

Release 8: This release of the standard defines dual carrier operation

as well as allowing simultaneous operation of the high order

modulation schemes and MIMO. Further to this, latency is improved to

keep it in line with the requirements for many new applications being

used.


HSDPA

HSDPA PRINCIPLE

HSDPA is based on a combination of technologies. Significant is the

introduction of a new transmission channel for the user data, the High Speed

(Physical) Downlink Shared Channel, HS-(P) DSCH. Multiple users share the air

interface resources available on this channel. An intelligent algorithm in the Node B

decides which subscriber will receive a data packet at which time. This decision is

reported to the subscribers via a parallel signaling channel, the High Speed Shared

Control Channel, HSSCCH. In contrast to UMTS, where a new data packet can be

transmitted at least every 10 ms, with HSDPA data packet transmission can occur

every 2 ms.

Another important innovation is the use of an adaptive modulation and coding

procedure. Every subscriber regularly sends messages regarding the channel quality to

the Node B. Depending on the quality of the mobile radio channel, the Node B selects

a suitable modulation and coding for the data packet that offers satisfactory protection


HSDPA

against transmission errors and that optimizes the use of resources on the air interface.

The Node B can select from the modulation methods QPSK (quadrature phase shift

keying) and 16QAM (quadrature amplitude modulation). While QPSK is already

being used in UMTS release 99, 16QAM provides high data rates specifically for

HSDPA.

In order to achieve robust data transmission, HSDPA uses a HARQ (Hybrid

Automatic Repeat Request) protocol. If a UE receives a data packet with errors, it

requests the data packet again. When repeating the packet transmission, the Node B

can select a different coding version that provides the subscriber with better reception

of the packet (incremental redundancy). This coding version is often referred to as

“redundancy and constellation version” or in short “redundancy version” (RV

version). When a packet has been transmitted to the UE, the Node B has to wait until

an acknowledgement (ACK) or negative acknowledgement (NACK) is received for

this particular packet (so-called stop-and-wait transmission mechanism).. One UE has

to support up to 8 parallel HARQ processes which are equivalent to up to 8

independent HARQ stop-and-wait transmission mechanisms. User feedback about

channel quality as well as packet acknowledgements or negative acknowledgements is

provided in the uplink on the High Speed Dedicated Physical Control Channel, HS-

DPCCH.

KEY HSDPA TECHNOLOGY ENHANCEMENTSHSDPA was designed to increase downlink packet data throughput of UMTS

by means of:

1. Shared channel transmission

2. Adaptive Modulation and Coding (AMC)

3. Fast Hybrid Automatic Repeat Request (H-ARQ)

4. Fair and fast scheduling at Node B

5. Fast cell site selection (FCSS)

6. Short transmission time interval (TTI)


HSDPA

1. SHARED CHANNEL TRANSMISSION

Several new channels are introduced in release 5. A new transport

channel named High-Speed Downlink Shared Channel (HS-DSCH) is the primary

radio bearer. For the associated signaling a channel called high-speed shared control

channel (HS-SCCH) has been added in the downlink and in the uplink the high-speed

dedicated

HS-(P) DSCH Structure

The transport channel HS-DSCH is mapped on one or more physical channels

of type HS-PDSCH. The HS-PDSCH is always spread with spreading factor 16. One

HS-DSCH transport block is transmitted in a transmission time interval (TTI) of 2 ms

(corresponding to 3 timeslots). If UE category allows, HS-DSCH transport blocks can

be scheduled to the UE continuously, i.e. in every TTI. Less complex UEs

corresponding to a lower UE category can only process data received in every second

or even every third TTI. This is described by the so-called inter TTI distance

parameter. An inter TTI distance of 1 equals continuous HS-PDSCH transmission (in

case data is available for transmission). QPSK or 16QAM are available as modulation

scheme on the HS-PDSCH. Figure outlines the structure of the HS-(P) DSCH.

STRUCTURE OF HS-(P) DSCH


HSDPA

HS-SCCH Structure

The HS-SCCH is a fixed rate downlink physical channel, spread with

spreading factor 128. One UE has to monitor up to 4 HS-SCCH channels. The UE is

informed by higher layers at call setup which HS-SCCH channels to monitor. The

HS-SCCH contains scheduling and control information (UE identification, HS-

PDSCH channelization codes, HSPDSCH modulation scheme information, transport

block size information, HARQ process information, redundancy and constellation

version, new data indicator). Figure outlines the HS-SCCH structure:

STRUCTURE OF HS-SCCH

The HS-PDSCH starts 2 timeslots after the start of the corresponding HSSCCH.

HS-DPCCH Structure

The HS-DPCCH is an uplink physical channel used to carry control

information: HARQ ACK/NACK and Channel Quality Information. Figure outlines

the structure of the HS-DPCCH.

STRUCTURE OF HS-DPCCH


HSDPA

The Channel Quality Information consists of a CQI value. There are different

CQI tables specified for different UE categories, reflecting the level of UE

implementation complexity. The CQI values regularly reported by the UE are

interpreted by the Node B as proposal how to format the HS-(P) DSCH. With this

format, the resulting block error rate of the HS-DSCH is predicted by the UE to be

below 0.1. The higher the CQI value, the more demanding the HS-DSCH

transmission format, i.e. the better the radio link quality has to be.

2. ADAPTIVE MODULATION AND CODING (AMC)

HSDPA uses both the modulation used in WCDMA, namely

Quadrature Phase Shift Keying (QPSK) and under good radio conditions, an advanced

modulation scheme, 16 Quadrature Amplitude Modulation (16 QAM). The benefit of

16 QAM is that four bits of data are transmitted in each radio symbol as opposed to

two with QPSK. 16 QAM increases data throughput, while QPSK is available under

adverse conditions.

Depending on the condition of the radio channel, different levels of forward

error correction (channel coding) can also be employed. For example, a three quarter

coding rate means that three quarters of the bits transmitted are user bits and one

quarter is error correcting bits. The process of selecting and quickly updating the

optimum modulation and coding rate is referred to as fast link adaptation.

QUADRATURE PHASE SHIFT KEYING (QPSK)

Sometimes known as quaternary or quadriphase PSK, 4-PSK, QPSK uses four

points on the constellation diagram, equispaced around a circle. With four phases,

QPSK can encode two bits per symbol, shown in the diagram with Gray coding to

minimize the BER — twice the rate of BPSK. Analysis shows that this may be used

either to double the data rate compared to a BPSK system while maintaining the

bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth

needed. Although QPSK can be viewed as a quaternary modulation, it is easier to see


HSDPA

it as two independently modulated quadrature carriers. With this interpretation, the

even (or odd) bits are used to modulate the in-phase component of the carrier, while

the odd (or even) bits are used to modulate the quadrature-phase component of the

carrier. BPSK is used on both carriers and they can be independently demodulated.

The modulated signal is shown below for a short segment of a random binary data-

stream.

TIMING DIAGRAM OF QPSK

CONSTELLATION DIAGRAM OF QPSK

16- QUADRATURE AMPLITUDE MODULATION (16- QAM)

Data is spit into two channels, I and Q. As with QPSK, each channel can take

on two phases. However, 16-QAM also accommodates two intermediate amplitude


SYMBOL

TRANSMITTED

CARRIER PHASE

00 225°

01 135°

10 315°

11 45°

http://upload.wikimedia.org/wikipedia/commons/b/be/QPSK_timing_diagram.png

HSDPA

values. Two bits are routed to each channel simultaneously. The two bits to each

channel are added, and then applied to the respective channel’s modulator.

CONSTELLATION DIAGRAM OF 16-QAM

Table below shows

the different throughput rates

achieved based on the

modulation, the coding rate,

and the number of HS-DSCH codes in use. Both Convolutional Coding and Turbo

coding are supported but previously only CC has been supported. Note that the peak

rate of 14.4 Mbps occurs with a coding rate of 4/4, 16 QAM and all 15 codes in use.

MODULATION CODING

RATE

THROUGH

PUT WITH 5

CODES

THROUGH

PUT WITH 10

CODES

THROUGH

PUT WITH 15

CODES

QPSK1/4 600kbps 1.2Mbps 1.8 Mbps2/4 1.2Mbps 2.4 Mbps 3.6 Mbps3/4 1.8Mbps 3.6 Mbps 5.4 Mbps


SYMBOL

TRANSMITTED

CARRIER

PHASE

CARRIER

AMPLITUDE0000 225° 0.330001 255° 0.750010 195° 0.75

0011 225° 1.00100 135° 0.330101 105° 0.750110 165° 0.75

0111 135° 1.01000 315° 0.331001 285° 0.751010 345° 0.75

1011 315° 1.01100 45° 0.331101 75° 0.75

1110 15° 0.751111 45° 1.0

HSDPA

16 QAM2/4 2.4Mbps 4.8 Mbps 7.2 Mbps3/4 3.6Mbps 7.2 Mbps 10.7 Mbps4/4 4.8Mbps 9.6 Mbps 14.4 Mbps

3. FAIR AND FAST SCHEDULING AT NODE B

It allows the HS-DSCH channel to take advantage of favorable channel

conditions to make best use of available radio conditions. Each UE periodically

reports on the signal quality to Node B (Base Stations). That information is then used

to decide which users will be sent data on the next 2ms frame and how much data can

be sent to each user.

A first approach for fair scheduling can be Round-Robin method where every

user is served in a sequential manner so all the users get the same average allocation

time. However, the requirement of high scheduling rate along with the large AMC

availability with the HSDPA concept, where the channel is allocated according to the

instantaneous

channel conditions. Another popular packet scheduling is proportional fair packet

scheduling. Here, the order of service is determined by the highest instantaneous

relative channel quality. Since the selection is based on relative conditions, still every

user gets approximately the same amount of allocation time depending on its channel

condition.

4. FAST HYBRID AUTOMATIC REPEAT REQUEST (H-ARQ)

Some data will inevitably be corrupted in transit to the device and will have to

be retransmitted. With HSDPA, data retransmission may be handled “locally” by the

base-station improving response times compared to earlier UMTS networks (where

only the more distant RNC could manage data retransmissions). HSDPA employs a

“stop and wait hybrid automatic repeat request” (SAW HARQ) retransmission


HSDPA

protocol between the base-station and the user device. With HARQ, each device

checks the integrity of its received data in each relevant HS-DSCH TTI. If the data is

correct, the device returns an “ACK” (acknowledging receipt of correct data) signal,

in which case the base-station can move on to the next set of data. If the data is not

successfully received, the device transmits an “NACK” (negative acknowledgement)

and the base-station retransmits the corresponding data. With “soft combining” at the

user device, the earlier set(s) of corrupted data can be combined with subsequently

retransmitted data to increase the likelihood of correctly decoding valid data.

The AMC uses an appropriate modulation and coding scheme according to the

channel conditions. Even after AMC, we may land up with errors in the received

packets due to the fact that the channel may vary during the packet is on the fly. An

automatic repeat request (ARQ) scheme can be used to recover from these link

adaptation errors. When the transmitted packet is received erroneous then the receiver

requests the transmitter for the retransmission of that erroneous packet. The basic

technique is to use the energy of the previously transmitted signal along with the new

retransmitted signal to decode the block. There are two main schemes for H-ARQ,

Chase combining and Incremental redundancy.

Chase Combining involves the retransmission of the same data packet which

was received with errors. Once the retransmission is received, the receiver combines

the soft values of the original signal and the retransmitted signal weighted by the SNR

prior to decode the data packet. It is advantageous as each transmission and

retransmission can be decoded individually (self-decodable), time diversity gain, may

be path diversity gain. The main disadvantage is transmission of the entire packet

again, which is wastage of bandwidth.


HSDPA

CHASE COMBINING SCHEME

Incremental Redundancy is used to get maximum performance out of the

available bandwidth. Here the retransmitted block consists of only the correction data

to the original data that carries no actual information (Redundancy). The additional

redundant information is sent incrementally when the first, second retransmissions are

received with errors. It is advantageous as it reduces the effective data throughput/

bandwidth of a user and using this for another user. The main disadvantages are the

systematic bits are only sent in the first transmission and not with the retransmission

which makes the retransmissions non-self decodable. So, if the first transmission is

lost due to large fading effects there is no chance of recovering from this situation.


HSDPA

INCREMENTAL REDUNDANCY

Although the HSDPA standard supports both chase combining and

incremental redundancy, it has been shown that incremental redundancy performs

almost always better than chase combining, at the cost of increased complexity,

though.

5. FAST CELL SITE SELECTION (FCSS)

HSDPA does not use soft handover. This is because the AMC, H-ARQ and

fast packet scheduling are techniques that require a constant one-to-one connection

between the HSDPA mobile terminal and the BS. Thus hard handover, in which the

destination BS is selected each time the cell changes, is needed. Since the only traffic

supported by HSDPA is delay-tolerant data traffic soft handover is also not as

necessary as when dealing with voice traffic.

6. SHORTER TRANSMISSION TIMEThe shorter time interval enables higher speed transmission in the physical

layer, so that the system will be more reactive to changing link conditions and can

reallocate capacity to users quicker.


HSDPA

HSDPA ARCHITECTURE

The protocol structure for HSDPA is outlined in figure. Compared to UMTS

release 99, significant functionality has been moved to the Node B in release 5. Thus,

new MAC-hs (Medium Access Control– high speed) protocol entity has been

introduced in the Node B. It is responsible for flow control, scheduling and priority

handling of data, control of HARQ processes and selection of appropriate transport

formats and resources. The MAC-hs entity is terminated on the UE side.

HSDPA PROTOCOL ARCHITECTURE

Within the Radio Resource Control (RRC) protocol, existing messages for

bearer setup, reconfiguration and release were modified to support HSDSCH. New

information elements were introduced, e.g. to inform the UE about the HS-SCCH set

to monitor and about the measurement cycle for the CQI reporting.

Mobility for HSDPA is based on existing release 99 handover procedures. For

the HS-PDSCH no macro diversity is applied, i.e. a specific HSPDSCH is transmitted

in a single cell only.


HSDPA

PERFORMANCE OF HSDPA

The performance of each technology is determined by a number of constraints,

including the throughput, the latency etc.

The throughput is the data rate of the standard. The theoretical maximum

throughput is the throughput rate available to a single connection under ideal

circumstances. These speeds may not be achieved regularly in typical usage. The

typical throughput is what users have experienced most of the time when well-within

the usable range to the base station. This value is not known for the newest

experimental standards. Note that these figures cannot be used to predict the

performance of any given standard in any given environment, but rather as

benchmarks against which actual experience might be compared.

The latency is the time taken for the smallest packet to travel between the user

terminal and base station. Just as important as throughput is network latency, defined

as the round-trip time it takes data to traverse the network. Each successive data

technology from GPRS forward reduces latency, with HSDPA networks having

latency as low as 70 milliseconds. HSUPA brings latency down even further, as will

3GPP LTE. Ongoing improvements in each technology mean all these values will go

down as vendors and operators fine tune their systems. Figure shows the latency of

different 3GPP technologies.

LATENCY OF DIFFERENT TECHNOLOGIES


HSDPA

Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the

information rate that can be transmitted over a given bandwidth in a specific

communication system. It is a measure of how efficiently a limited frequency

spectrum is utilized by the physical layer protocol, and sometimes by the media

access control (the channel access protocol).

NET BIT RATE PER

FREQUENCY

CHANNEL (Mbps)

BANDWIDTH PER

FREQUENCY

CHANNEL (MHz)

SPECTRAL

EFFICIENCY

(bps/Hz/site)GSM 0.013 0.2 0.17EDGE 0.384 0.2 0.33WCDMA 0.384 5 0.51HSDPA 14.4 5 2.88LTE 326.4 20 16.32

COMPARISON WITH WCDMA (R’99)

3GPP’s Release 99 specified the first UMTS 3G network. The technology

used in R’99 systems is called W-CDMA. HSDPA is a high speed data enhancement

to WCDMA systems like EDGE was for GSM/GPRS and will most often be deployed

with an R’99 system. That is WCDMA is used for voice and HSDPA for data on the

same network, they will thus have to share bandwidth and power. HSDPA is evolved

from and backward compatible with Release 99 WCDMA systems.

WCDMA (R’99) HSDPAModulation Scheme QPSK QPSK, 16- QAMDownlink Multiple

Access

CDMA CDMA- TDMA

Uplink Multiple Access CDMA CDMADuplex Method FDD FDDChannel Bandwidth 5 MHz 5MHzFrame Size 10 ms 2 msCoding CC CC, TurboDownlink Peak Data

Rate

384 Kbps 14.4 Mbps

COMPARISON WITH COMPETING TECHNOLOGIES


HSDPA

Competing wireless technologies with HSDPA are Mobile WiMAX (IEE

802.16e) and 1X EvDo in CDMA 2000.

COMPARISON WITH MOBILE WIMAX AND EV- DO

HSDPA and Mobile WiMAX are high speed mobile technologies with

different backgrounds. HSDPA is a data enhancement for a voice-centric 3GPP

system while WiMAX is data-centric broadband technology that has an added feature

of mobility. Many operators around the world have invested in R’99 UMTS networks.

For them

HSDPA offers a significant service upgrade and an opportunity to accelerate the

Return of Investment. HSDPA networks are already widely deployed and handsets

have been on the market since 2006. For Mobile WiMAX it is necessary to build new

networks, and the manufacturing of handsets has been quite complicated and required

a totally new set of chips and platforms. EvDo is standardized by 3rd Generation

Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has

been adopted by many mobile phone service providers around the world – particularly

those previously employing CDMA networks. It is also used on the Globalstar

satellite phone network

Despite their different background there are several technical features that the

three technologies have in common. Those include Adaptive Modulation and Coding

(AMC), Hybrid ARQ and Fast Scheduling.

In OFDMA systems users are allocated different portions of the channel where

as in CDMA each user transmits over the entire channel. This means that in OFDMA

there is no multiple access interference (MAI) between multiple users. In CDMA

orthogonal spreading codes are used to avoid MAI but due to the uplink

synchronization issues, asynchronous CDMA is used in the uplink in most practical

CDMA systems and there will be interference and reduced spectral efficiency. As

only a portion of the channel is occupied by the WiMAX signals frequency selective


HSDPA

scheduling can be used to choose sub channels with the best condition at each time

and hence improve QoS. For smart antenna technologies the processing complexity

scales with the channel bandwidth. Since in CDMA the signals occupy the entire

bandwidth this becomes quite a problem when used in broadband wireless channels

and limits the options of using advanced Antenna Technology. OFDMA on the other

hand is well suited for these technologies. Mobile WiMAX will most commonly use

TDD while HSDPA generally uses FDD. FDD is more efficient than TDD in the case

of symmetric traffic but TDD allow for asymmetric traffic and as the downlink traffic

is usually much heavier than the uplink traffic, asymmetric traffic can be very

practical. TDD requires system-wide frame synchronization to counter interference

issues and the discontinuous transmissions reduce the average power. On the

other hand TDD assures channel reciprocity and thus better supports link adaptation,

MIMO and other advanced antenna technologies.

The 60% longer radius of HSDPA gave it an advantage in economic feasibility

while 70% higher throughput for Mobile WiMAX did not give any economic

advantage. The performance of HSPA and Mobile WiMAX technologies is

comparable: Mobile WiMAX does not offer any technology advantage over HSPA.

Both technologies offer similar peak data rates, spectral efficiency and network

complexity. However, Mobile WiMAX requires more sites to offer the same coverage

and capacity as HPSA.

EvDo is standardized by 3rd Generation Partnership Project 2 (3GPP2) as part

of the CDMA2000 family of standards and has been adopted by many mobile phone

service providers around the world – particularly those previously employing CDMA

networks. It is also used on the Globalstar satellite phone network. EV-DO uses many

of the same techniques for optimizing spectral efficiency as HSPA, including higher

order modulation, efficient scheduling, turbo-coding, and adaptive modulation and

coding. For these reasons, it achieves spectral efficiency that is virtually the same as

HSPA. The 1x technologies operate in the 1.25 MHz radio channels, compared to the

5 MHz channels UMTS uses. This result in lower theoretical peak rates, but average

throughputs for high level of network loading is similar. Under low to medium-load


HSDPA

conditions, because of the lower peak achievable data rates, EV-DO or EVDO Rev A

achieves a lower typical performance level than HSPA. Operators have quoted 400 to

700 kilobits per second (kbps) typical downlink throughput for EV-DO Rev 035 and

between 600 kbps and 1.4 Mbps for EV-DO Rev A.36.

One challenge for EV-DO operators is that they cannot dynamically allocate

their entire spectral resources between voice and high-speed data functions. The EV-

DO channel is not available for circuit-switched voice, and the 1xRTT channels offer

only medium speed data. In the current stage of the market, where data only

constitutes a small percentage of total network traffic, this is not a key issue. But as

data usage expands, this limitation will cause suboptimal use of radio resources.

Another limitation of using a separate channel for EV-DO data services is that it

currently prevents users from engaging in simultaneous voice and high-speed data

services, whereas this is possible with UMTS and HSPA. Many users enjoy having a

tethered data connection from their laptop—by using Bluetooth, for example—and

being able to initiate and receive phone calls while maintaining their data sessions.

HSDPA Mobile WiMAX EV-DOBase Standard WCDMA IEEE 802.16e CDMA 2000

Duplex Method FDD TDD FDD

Downlink Multiple

Access

CDMA-TDMA OFDMA TDM

Uplink Multiple Access CDMA OFDMA CDMA

Frequency 900MHz/1.8/2.1GHz 2.3/2.5/3.5GHz 450/850/900Mhz/1.8G

HzChannel Bandwidth 5MHz Scalable: 5, 7,8.75,

10MHz

1.25MHz

Frame Size DL= 2ms, UL =10ms 5ms DL=1.67ms, UL=6.67ms

Modulation Downlink QPSK, 16-QAM QPSK, 16-QAM,64-

QAM

QPSK, 8-PSK, 16-QAM

Modulation Uplink BPSK, QPSK QPSK, 16-QAM BPSK,QPSK, 8-PSK

Coding CC, Turbo CC, Turbo CC, Turbo

Downlink Peak Data

Rate

14.4Mbps 46Mbps 2.45Mbps

Uplink Peak Data Rate 2.3Mbps 46Mbps 0.15Mbps

Scheduling Fast scheduling in DL Fast scheduling in DL,

UL

Fast scheduling in DL


HSDPA

H-ARQ Chase Combining Chase Combining Incremental

RedundancyHandoff Network Initiated Hard

Handoff

Network Optimized

Hard Handoff

Virtual Soft

HandoffCoverage 3 Miles <2 Miles >3 Miles

Mobility High Low/ Mid High

CURRENT DEPLOYMENT OF HSDPA

HSDPA (High Speed Downlink Packet Access) is an upgrade to

UMTS/WCDMA. HSDPA increases the download speeds by up to 3.5 times, initially

delivering typical user data rates of 550 to 800 kbps. Improvements to the downlink,

through HSDPA, were the first upgrade steps available to operators seeking to deploy

mobile broadband services as a part of 3GPP Release 5. HSDPA speeds are ideal for

bandwidth-intensive applications, such as large file transfers, streaming multimedia

and fast Web browsing. HSDPA also offers latency as low as 70 to 100 milliseconds

(ms) making it ideal for real-time applications such as interactive gaming and delay-

sensitive business applications such as Virtual Private Networks.

High Speed Downlink Packet Access is predominately a software upgrade to

Release 99 of the UMTS standard. HSDPA has been commercially available since

December 2005, when Cingular Wireless – now AT&T – launched the world's first

large scale HSDPA service. There are more than 300 HSDPA networks commercially

deployed or in various stages of deployment in more than 115 countries (May 2009).

International roaming is available as the technology falls back on UMTS, EDGE and

GPRS for the continuation of voice and data services. Sony Ericsson Z-50, K850i,

W910iare some HSDPA supported handsets available in markets. In November 2003,

Motorola became the first vendor to demonstrate HSDPA on a commercially

available UMTS base station at its Swindon, UK facility. HSDPA supported Motorola

handsets are RAZRZ8 and RAZRV9. Nokia N95, E51, E90, 6120Clasic are some

HSDPA supported handsets from Nokia which can provide a maximum downlink

speed of 3.6Mbps.HSDPA devices also include 39 wireless routers, 61 laptops and

100 devices for laptop connectivity (USB modems etc). The number of HSDPA

networks, devices and subscribers is constantly growing. For example


HSDPA

WCDMA/HSDPA was responsible for 75% of the mobile subscription growth in

Western Europe in 2007. In India MTNL DOLPHIN has started 3G Services under

the brand name of 3G Jadoo where Jadoo means Magic in Hindi. While BSNL has

launched 3G HSDPA services with speed up to 2 Mbit/s at 12 Indian Cities on

27.02.2009. The BSNL’s Commercial 3G service are available now in Amabala,

Agara, Dehardun, Jammu, Jaipur, Jalandhar, Lacknow, Shimla, Patna, Ranchi, Haldia

and Durgapur. They are collaborating with Nokia, Sony and Samsung for offering 3G

capable mobile handsets along with packages in the market.

HSDPA usually requires only new software and base station channel cards,

instead of necessitating the replacement of major pieces of infrastructure from UMTS

and does not require additional spectrum for deployment. As a result, UMTS

operators can deploy HSDPA quickly and cost-effectively. In fact, most operators that

deploy 3G UMTS are deploying an HSDPA-ready network.

HSDPA technology significantly improves the UMTS downlink performance

through techniques, such as adaptive modulation and coding, hybrid ARQ (HARQ)

and fast scheduling. On the receiving side, initial HSDPA User Equipment (UE)

solutions were based on single antenna CDMA rake receiver structures, similar to

Release 99 UMTS receiver structures. The corresponding minimum performance

requirement for HSDPA rake receivers was specified in Release 5. While the single

antenna rake receivers worked very well for conventional UMTS and met initial

system needs for HSDPA, advanced receiving technologies were later used to achieve

even higher HSDPA throughputs. To achieve this goal, 3GPP studied two applicable

techniques (receive diversity and advanced receiver architectures) as well as their

minimum performance improvement and has specified them in Release 6.

HSDPA also benefits operators by making more efficient use of spectrum, up

to three times more capacity than UMTS. This efficiency means that operators can

easily and cost-effectively accommodate more users and services without having to

buy additional spectrum just to keep up with growth. That efficiency also reduces

operators' overhead costs, and thus, makes them better able to price their services at a

point that is competitive yet profitable.


HSDPA

HSDPA is backward-compatible with UMTS, EDGE and GPRS. This design

benefits customers when they travel to areas that have not yet been upgraded to

HSDPA, as their HSDPA-enabled handsets and modems will still provide fast packet-

data connections. This design also benefits operators and application developers

because applications designed for UMTS also run on HSDPA networks and devices.

HSDPA benefits from the scope and scale of the GSM ecosystem of vendors.

Vendors currently offer more than 1,300 models of HSPA/HSDPA devices at a

variety of price points. Besides handsets and PC card modems, HSPA/HSDPA is also

embedded in many laptops from major vendors such as Acer, Dell, Fujitsu Siemens,

HP, Lenovo and Panasonic. Embedded modems are particularly attractive to

enterprises because CIOs and IT managers do not have to worry about whether a

particular modem is compatible with a particular laptop model. Devices also are

available at most GSM frequencies, enabling global roaming.

DEPLOYMENT CHALLENGES: INDIAN FACTS

Since there is no copper laid out in rural India, DSL is not an option to deliver

high bandwidth services. Given the existing and potential coverage realized by GSM/

GPRS cellular systems, the incremental cost of implementing HSDPA should be

much lower than that of setting up any other Greenfield wireless network. WiMAX

could be a challenger, but its maturity is currently much lower than HSDPA.

India has seen a rapid increase in wireless coverage. GSM and CDMA are the

competing technologies. As of July 2009, the wireless penetration at 59.83 million is

significantly higher than landline penetration, which is at 47.17 million. The monthly

cellular additions are getting closer to 3 million/month, with GSM technology base

having a higher subscriber base accounting for about 80%. GSM coverage enables

quick and easy HSDPA access. As can be seen, the range of HSDPA is severely

limited to around 2Km cells, as compared the current GSM/GPRS systems that have

range that is one order of magnitude higher. This could mean that the current


HSDPA

GSM/GPRS infrastructure is largely insufficient for HSDPA coverage, and significant

additional capex may be required to deploy HSDPA into rural areas. The entire cost

benefit gains of HSDPA due to its higher capacity could thus be offset due to the cost

increase due to lower range.

Increasing the range of HSDPA is a key research problem that determines its

success for rural India. Lower frequencies reach further. Lower rate transmissions can

span a higher range.

RELEASES BEYOND HSDPA

Work is now staring on developing the standards for High Speed Uplink

Packet Access (HSUPA) to improve the data rates on the 3G W-CDMA mobile or cell

phone standard. With the cellular telecommunications standards established and work

progressing to introduce the equipment for High Speed Downlink Packet Access

(HSDPA), the standards are now starting to be developed to enable the uplink from

the mobile handset or User Equipment (UE) to the base station (Node B) to be able to

handle data at similar speeds. This is known as HSUPA and it will enable new

features including full video conferencing to be introduced. 3G HSPA of High Speed

packet Access is the combination of two technologies. 3G HSPA is widely deployed

and providing significantly increased data transfer rates required for the variety of

data applications including mobile broadband for Internet connectivity now being

used by mobile users. As 3G UMTS HSPA is normally a relatively straightforward

upgrade based around a software change, its incorporation involves a relatively low

cost upgrade. As the use of 3G HSPA is able to increase the efficiency of the overall

network, reducing the cost per bit, then it is often a very cost effective upgrade.

Evolved HSPA provides HSPA data rates up to 42 Mbit/s on the downlink and

22 Mbit/s on the uplink with MIMO technologies and higher order modulation.

MIMO on CDMA based systems acts like virtual sectors to give extra capacity closer

to the mast. The 42Mbit/s and 22Mbit/s represent theoretical peak sector speeds. The

actual peak speed for a user closer to the mast may be about 14Mbit/s. As of August


HSDPA

2009, there are 10 HSPA+ networks running in the world at 21Mbit/s and the first

28Mbit/s network has been completed in Italy. The first to launch was Telstra in

Australia in late 2008, with Australia-wide access in February 2009 with speeds up to

21Mbit/sec.

LTE (Long Term Evolution) is the last step toward the 4th generation of radio

technologies designed to increase the capacity and speed of mobile telephone

networks. Where the current generation of mobile telecommunication networks are

collectively known as 3G (for "third generation"), LTE is marketed as and called 4G

insinuating that it's the "fourth generation". The LTE specification provides downlink

peak rates of at least 100 Mbps, an uplink of at least 50 Mbit/s and RAN round-trip

times of less than 10ms. LTE supports scalable carrier bandwidths, from 20 MHz

down to 1.4 MHz and supports both Frequency Division Duplexing and Time

Division Duplexing.

CONCLUSION

The HSDPA concept facilitates peak data rates exceeding 2 Mbps and

theoretically reaching 10 Mbps. The cell throughput gain over previous releases has

been evaluated to be in the order of 50-100% or more, which is highly dependent on

factors such as the radio environment and the service provision strategy of the

network operator. Practical HSDPA user bit rates even in large macro cells can be

similar to broadband home DSL lines. As HSDPA enables more bits to be transferred

with the same radio frequency, it also enables lower cost per bit than Release'99 based

WCDMA. The H-ARQ technique which is best suited in HSDPA would be partial

incremental redundancy. Performance of partial IR is in between chase combining and

IR. Further evolution of HSDPA peak data rates can be achieved with multiple-input

multiple-output (MIMO) antenna techniques of 3GPP Rel.'6. No changes are required

to the networks except increased capacity within the infrastructure to support the

higher bandwidth.

REFERENCES


HSDPA

1. 3rd Generation Partnership Project (3GPP). Available at:

http://www.3gpp.org/

2. 3rd Generation Partnership Project 2 (3GPP2). Available at:

http://www.3gpp2.org/

3. Global Mobile Suppliers Association (GSA). Available at:

http://www.gsacom.com

4. WiMAX Forum, http://www.wimaxforum.org/

5. P. Rysavy, 3G Americas. Mobile Broadband: EDGE, HSPA and LTE.

Available at: www.3gamericas.org/English/Technology_Center/WhitePapers/

6. Comparison of Mobile WiMAX and HSDPA: Kolbrun Johanna Runarsdottir

7. Wikipedia contributors, "UMTS frequency bands,"

http://en.wikipedia.org/w/index.php?

title=UMTS_frequency_bands&oldid=186921008

8. High-Speed Downlink Packet Access - Wikipedia, the free encyclopedia

http://en.wikipedia.org/w/HSDPA/

GLOSSARY OF TERMS

1xEV-DO One Carrier Evolved, Data Optimized

1xEV-DV One Carrier Evolved, Data Voice

2G Second Generation

3G Third Generation

3GPP 3G Partnership Project

3GPP2 3G Partnership Project 2

4G Fourth Generation

ACK Acknowledgement

ADSL Asynchronous Digital Subscriber Line

AMC Adaptive Modulation and Coding

ARQ Automatic Repeat Request

BTS Base Station

CDMA Code Division Multiple Access

DPCH Dedicated Physical Channel


http://www.3gpp.org/

http://en.wikipedia.org/w/HSDPA/

http://en.wikipedia.org/w/index.php?title=UMTS_frequency_bands&oldid=186921008

http://en.wikipedia.org/w/index.php?title=UMTS_frequency_bands&oldid=186921008

http://www.3gamericas.org/English/Technology_Center/WhitePapers/

http://www.wimaxforum.org/

http://www.gsacom.com/

http://www.3gpp2.org/

HSDPA

DL Downlink

EDGE Enhanced Data Rates for GSM Evolution

E-UTRAN Enhanced UMTS Terrestrial Radio Access Network

FDD Frequency Division Multiplex

FP Frame Protocol

GPRS General Packet Radio Service

GSM Global System for Mobile communication

GSMA GSM Association

HLR Home Location Register

HO Handover, Handoff

HSDPA High Speed Downlink Packet Access

HSPA High Speed Packet Access

HSUPA High Speed Uplink Packet Access

H-ARQ Hybrid- ARQ

ITU International Telecommunication Union

IEEE Institute of Electrical and Electronic Engineers

LAN Local Area Network

LTE Long Term Evolution

MAC Media Access Control

MAC-hs Medium Access Control – high speed

MIMO Multiple Input Multiple Output

MMS Multimedia Message Service

MS Mobile Station

MSC Mobile Switching Centre

NACK Negative Acknowledgement

OFDMA Orthogonal Frequency Division Multiple Access

PER Packet Error Rate

PHY Physical layer

PSTN Public Switched Telephone Network

QAM Quadrature Amplitude Modulation

QoS Quality of Service

QPSK Quadrature Phase Key Shifting

RAN Radio Access Network


HSDPA

RF Radio Frequency

RL Reverse Link (also Radio Link)

RNC Radio Network Controller

SGSN Serving GPRS Support Node

SIM Subscriber Identification Module

SIMO Single Input Multiple Output

SMS Short Message Service

SNR Signal-to-Noise Ratio

TDD Time Division Duplex

TDMA Time Division Multiple Access

TTI Transmission Time Interval

UE User Equipment

UL Uplink

UMTS Universal Mobile Telephony System

UTRAN UMTS Terrestrial Radio Access Network

VoIP Voice over IP

VPN Virtual Private Network

WCDMA Wideband CDMA

WiFi Wireless Fidelity

WAP Wireless Application Protocol

WiBro Wireless Broadband

WiMAX Worldwide Interoperability for Microwave Access


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