EXPERIMENT NO 3

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BE(EXTC) SEM VIII (RCOE) Page 1

Name : ________________________________________

Branch : Electronics & Telecommunication (SEM VIII)

Subject : Wireless Network

Experiment No: 03

Title : To Estimate SINR of HSDPA.

Date :

Subject In-Charge Sign

:

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EXPERIMENT NO: 03

AIM

: To Estimate SINR of HSDPA.

APPARATUS

: MATLAB 7

THEORY:

High-Speed Downlink Packet Access (HSDPA)

HSDPA is based on the same set of technologies as high data rate (HDR) to improve spectral

efficiency for data services such as shared downlink packet data channel and high peak data rates

using high-order modulation and adaptive modulation and coding, hybrid ARQ (HARQ)

retransmission schemes, fast scheduling and shorter frame sizes.

HSDPA marks a similar boost for WCDMA that EDGE does for GSM. It provides a two-fold

increase in air interface capacity and a ﬁve-fold increase in data speeds in the downlink direction.

HSDPA also shortens the round-trip time between the network and terminals and reduces

variance in downlink transmission delay.

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BE(EXTC) SEM VIII (RCOE) Page 3 The improvements in performance are achieved by:

 Bringing some key functions, such as scheduling of data packet transmission and

processing of retransmissions (in case of transmission errors) into the base station — that

is, closer to the air interface.

 Using a short frame length to further accelerate packet scheduling for transmission.

 Employing incremental redundancy for minimizing the air-interface load caused by

retransmissions.

 Adopting a new transport channel type, known as high-speed downlink shared channel

(HS-DSCH) to facilitate air interface channel sharing between several users.

 Adapting the modulation and coding scheme according to the quality of the radio link.

The primary objective behind HSDPA is to provide a cost-effective, high-bandwidth, low-delay,

packet-oriented service within UMTS. Backward compatibility is critical, so the HSDPA

architecture adheres to an evolutionary philosophy. From an architectural perspective, HSDPA is

a straightforward enhancement of the UMTS Release ’99 (R99) architecture, with the addition of

a repetition/scheduling entity within the Node B that resides below the R99 media-access control

(MAC) layer. From a cellular-network perspective, all R99 techniques can be supported in a

network supporting HSDPA, since HSDPA mobile terminals (UEs) are designed to coexist with

R99 UEs. HSDPA is particularly suited to extremely asymmetrical data services, which require

signiﬁcantly higher data rates for the transmission from the network to the UE, than they do for

the transmission from the UE to the network.

HSDPA introduces enablers for the high-speed transmission at the physical layer like the use of a

shorter transmission time interval (TTI) (2 ms), and the use of adaptive modulation and coding.

HS-DPCCH is used to carry the acknowledgment signals to Node B for each block. It is also

used to indicate channel quality (CQI) used for adaptive modulation and coding. HS-DSCH uses

2 ms TTI to reduce trip time, to increase the granularity in the scheduling process, and to track

the time varying radio channel better.

The basic operational principles behind HSDPA are relatively simple. The RNC routes data

packets destined for a particular UE to the appropriate Node B. Node B takes the data packets

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BE(EXTC) SEM VIII (RCOE) Page 4 user’s priority and estimated channel operating environment with an appropriately chosen coding

and modulation scheme (that is, 16-QAM vs. QPSK). The UE is responsible for acknowledging

receipt of the data packet and providing Node B with information regarding channel condition,

power control, and so on. Once it sends the data packet to the UE, Node B waits for an

acknowledgment. If it does not receive one within a prescribed time, it assumes that the data

packet was lost and retransmits it.

HSDPA continuously strives, with some modest constraints, to give the maximal bandwidth to

the user with the best channel conditions. The data rates achievable with HSDPA are more than

adequate for supporting multimedia streaming services. (refer to Table).

Although conceptually simple, HSDPA’s implementation within the context of a Node B does

raise some architectural issues for the designer. In a typical network deployment, the Node B

radio cabinet sits in proximity to the radio tower and the power cabinet. For indoor deployments

the radio cabinet may be a simple rack, while in outdoor deployments it may be an

environmental-control unit. The guts of the radio cabinet are an antenna interface section (ﬁlters,

power ampliﬁers, and the like), core processing chassis (RF transceivers, combiner, high

performance channel cards, network interface and system controller card, timing card,

back-plane, and so on), plus mechatronics (power supply, fans, cables, etc.) and other miscellaneous

elements. The core processing chassis is the cornerstone of Node B and bears most of the cost. It

contains the RF transceiver, combiner, network interface and system controller, timing card,

channel card and backplane. Of the core processing chassis elements, only the channel card

needs to be modiﬁed to support HSDPA.

The typical UMTS channel card comprises a general-purpose processor that handles the

miscellaneous control tasks, a pool of digital signal processor (DSP) resources to handle

symbol-rate processing and chip-symbol-rate assist functions, and a pool of specialized ASIC (application

speciﬁc integrated circuit) devices to handle intensive chip-rate operations such as spreading,

scrambling, modulation, rake receiving, and preamble detection.

To support HSDPA, two changes must be made to the channel card. First, the downlink chip-rate

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BE(EXTC) SEM VIII (RCOE) Page 5 formats associated with HSDPA. In addition, the downlink symbol-rate processing section must

be modiﬁed to support HSDPA extensions.

HSDPA UE categories

HSDPA will require investments to the R99/R4 UMTS (WCDMA) network and will affect radio

network hardware and software, core network software, and transmission network hardware. It

can be deployed using small upgrades, not required for all base stations and radio network

controllers. HSDPA does not require a completely new network structure and protects the current

investments made to the network.

In HSDPA, all users’ traffic is carried on an HS-DSCH. The HSDPA requires a different

approach for dimensioning network resources. The most critical dimensioning input is the

average throughput expected from the HS-DSCH. The amount of throughput that an HS-DSCH

can carry depends on many variables, the most important being its power allocation. Because

HSDPA is an add-on feature to existing BTSs of WCDMA, a ﬁxed amount of power is allocated

for use by the HS-DSCH. The designer’s target during the dimensioning phase is to specify the

exact amount of that power. HSDPA power should be sufficient to meet expected throughput

demand. On the other hand, enough power should be reserved for all dedicated channel (DCH)

traffic in WCDMA. For a mixed R99 and HSDPA HSDSCH power should be around 4 to 7 W,

whereas for a dedicated HSDPA carrier the power should be 10 to 12 W, assuming that the

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BE(EXTC) SEM VIII (RCOE) Page 6 HSDPA can enable a wider coverage than R99 due to adaptive modulation, coding, and fast

scheduling in the base station. In HSDPA, throughput is not a single concept. It consists of

average cell throughput for a single user, minimum throughput at the cell edge for a single user,

and average user throughput. The average cell throughput and minimum throughput at the cell

edge for a single user are not dependent on the number of simultaneous HSDPA users in the cell.

These are commonly used to set the dimensioning target for HSDPA coverage. HSDPA

throughput depends directly on radio channel conditions. It changes rapidly all the time due to

fast fading of the radio channel (BS uses a link adaptation procedure). The achieved throughput

is different in every transmission time interval (TTI) of 2 ms. Average throughput can be

estimated if the average signal-to interference-plus-noise ratio (SINR) is known. Since HSDPA

is to be overlaid on the WCDMA network, the objective of the HSDPA link budget is to estimate

the maximum data rate achievable in the downlink at the cell edge, assuming that coverage is

uplink limited. Table gives a sample HSDPA link budget. The HSDPA peak data rate

calculations are based on the following parameters:

 Path loss as calculated by the HSDPA link budget

 Percent of BTS power allocated to HSDPA data users

 Scheduler margin: For HSDPA, the adaptive modulation and coding (AMC) combination

allows different operating points to be selected based on initial transmission power. It is

therefore possible to use either a more conservative approach that uses more power but

results in fewer retransmissions, or a more aggressive strategy that uses less power but

results in more retransmissions.

 Orthogonality factor: This accounts for non-orthogonal interference received by the

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BE(EXTC) SEM VIII (RCOE) Page 7 HSDPA SINR Calculation

The use of Eb/No in link budget requires the knowledge of bit rate or number of codes. Since bit

rate and number of codes change every TTI (2 ms) in the HSDPA, we use average SINRinstead

of Eb/No in link budget calculations. The average SINR does not depend on bit rate or number of

codes of HSDPA and can be calculated when HSDPA power, BS total power, orthogonality, and

G factor are known.

SINR = SF

DSCH

=

where

SFDSCH = spreading factor of DSCH; ﬁxed at 16

(Ptx) DSCH = transmit power of the DSCH

(Ptx) = Total base station power, including HS-PDSCH and HS-SCCH

= downlink orthogonality factor

G = geometry factor

PROGRAM:

max_tx_power=5.5;

total_basestation_power=18;

downlink_orthogonality_factor=0.2; geometry_factor=0.363;

spreading_factor=16;

SINR=(max_tx_power/(total_basestation_power*

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RESULT:

max_tx_power = 5.5000

total_basestation_power = 18

downlink_orthogonality_factor = 0.2000

geometry_factor = 0.3630 spreading_factor = 16 SINR = 1.3753