class 1 umts training

By Eng: Mohammed Eltayib

Email: [email protected]

Dec - 2014

mailto:[email protected]

UMTS Overview

The Universal Mobile Telecommunications System (UMTS) is a third

generation wireless telecommunication system and follows in the footsteps of GSM and

GPRS. Since GSM was standardized in the 1980s, huge progress has been made in many

areas of telecommunication. This allowed system designers at the end of the 1990s to

design a new system that went far beyond the capabilities of GSM and GPRS.

UMTS combines the properties of the circuit-switched voice network with the

properties of the packet-switched data network and offers a multitude of new possibilities

compared to the earlier systems. UMTS was not defined from scratch and reuses a lot of

GSM and GPRS.

UMTS Radio Theory

The Basic Principles of Wireless Communication

I. 3G services

II. Multiple Access Technologies

III. Spectrum Planning

IV. Spreading Technology

V. Coding And Interleave Technology

VI. Modulation

UMTS Radio mechanism

I. UMTS Data transmission Procedure

II. Channel Coding of UMTS

III. Spreading Technology of UMTS

IV. Modulation of UMTS

UMTS Radio Theory


I. 3G servicesII. Multiple Access Technologies




VI. Modulation






3G Services

Data：I. 144 kbps High speed and driving

II. 384 kbps Modest speed and walking

III. 2 Mbps Low speed and indoor

Voice

I. 4.75Kb/s --12.2Kb/s

II. 64kb/s (Video Phone)

Information transmission at variable rate according to bandwidth requirements

Delay requirements of different service

3G Services Radio Transmission Technology Requirements

3G Services


I. 3G services

II. Multiple Access TechnologiesIII. Spectrum Planning



VI. Modulation






UMTS Radio Theory

Multiple Access Technologies

Duplex mode

TDD mode

Uplink and downlink has the same frequency

Adaptable to any frequency band

Suitable for both asymmetric and

symmetric services

TDD ( Time division duplex,

Such as TD-SCDMA)

FDD mode

Uplink and downlink has the different

frequency

Paired frequency bands are needed

Suitable for symmetric services

FDD（ Frequency division duplex, Such as

WCDMA and CDMA2000）


Multiple access technologies enable various users access public

communication line but without interference.

Why Multiple Access?

I. Increased capacity: serve more users

II. Reduced capital requirements since

fewer media can carry the traffic

III. Decreased per-user expense

Types of Transmission Medium:

I. Twisted pair

II. Coaxial cable

III. Fiber optic cable

IV. Air interface (radio signals)

Three methods are frequently used:

I. FDMA

II. TDMA

III. CDMA

Each pair of users enjoys a

dedicated, private circuit

through the transmission

medium, unaware that

theother users exist.

A. Frequency Division Multiple Access means dividing the whole available spectrum

into many single radio channels (transmit/receive carrier pair). Each channel can

transmit one-way voice or control information. Analog cellular system is a typical

example of FDMA structure.

B. Time Division Multiple Access means that the wireless carrier of one bandwidth is

divided into multiple time division channels in terms of time (or called timeslot).

Each user occupies a timeslot and receives/transmits signals within this specified

timeslot. Therefore, it is called time division multiple access. This multiple access

mode is adopted in both digital cellular system and GSM.

C. Code division Multiple Access (CDMA) is a multiple access mode implemented

by Spreading Modulation. Unlike FDMA and TDMA, both of which separate the

user information in terms of time and frequency, CDMA can transmit the

information of multiple users on a channel at the same time. The key is that every

information before transmission should be modulated by different Spreading Code

to broadband signal, then all the signals should be mixed and send. The mixed

signal would be demodulated by different Spreading Code at the different receiver.

Because all the Spreading Code is orthogonal, only the information that was be

demodulated by same Spreading Code can be reverted in mixed signal.


CDMA Application


I. Users are distinguished by scrambling codes and OVSF codes

II. Self-interference system

III. CDMA system is restricted to interference (GSM system is restricted to frequency

resources)


I. 3G services


III.Spectrum PlanningIV. Spreading Technology


VI. Modulation






UMTS Radio Theory

Single Frequency Network

Spectrum Planning

IMT-2000 Spectrum Allocation

Spectrum Planning

3G Spectrum Allocation in Sudan

Spectrum Planning

Allocated Spectrum

Main Operating Frequency Band：FDD mode：1920-1980 MHz / 2110-2170 MHz

TDD mode：1880-1920MHz、2010-2025 MHz


I. 3G services



IV.Spreading TechnologyV. Coding And Interleave Technology

VI. Modulation






UMTS Radio Theory

Spreading Technology

Spread Spectrum Principles:

SHANON Formula

• C = B * log2(1+S/N)

Where:

C is capacity of channel, b/s

B is signal bandwidth, Hz

S is average power for signal, W

N is average power for noise, W

It is the basic principle and theory for spread spectrum communications.

User information bits are spread over a wide bandwidth by multiplying high speed

spread code(chip)

Spread signal bandwidth W wider than original signal bandwidth Rb





White noise refers to a statistical model for signals and signal sources, rather than to any specific signal

Spreading Mode


Direct sequence spread spectrum (DS-SS）Base band data is spread by multiplication of pseudo-noise sequence and base-band

pulse, the pseudo-noise sequence generated by the pseudo-noise generator

BER subject to Multiple Access Interference and near-far effect

Power control can overcome the near-far effect, but it is limited by power detection

accuracy

WCDMA uses DS_SS

Frequency hopping spread spectrum FH-SS）Data is transmitted in the random channel by the carrier frequency hopping

Before FH again, data is transmitted using traditional narrowband modulation

No near-far effect

DS-SS communication system


A technology of transmission after spreading signal spectrum.


Spread Spectrum Principles


Spread Spectrum Principles

Any Code Channel can be extracted from the received composite signal by

using the “right” orthogonal code

Energy for transmitting signal can be lower than interference and noise

Direct spread technique


Concept of Orthogonal Code

Orthogonal: the result

of multiplying and

sum is 0

Example of orthogonal code

Sketch map of Spreading and Despreading

Example of orthogonal code

Spreading Communication Characteristics

I. High anti-multi-path-interference capability

II. Anti-sudden-pulse

III. High security

IV. Lower transmitting power

V. Easy to implement large-capacity Multiple Access Communication

VI. Occupied frequency band is wide

VII.Complex realization


I. 3G services




V. Coding And Interleave TechnologyVI. Modulation






UMTS Radio Theory

Purpose of Channel Coding

Coding And Interleave Technology

By adding redundant information in the original data stream,

receivers can detect and correct the error signal, and improve data

transmission rates.

Effect:

1. Enhance the correlation among symbols so as to recover the signal when

interference occurs

2. Provides better error correction at receiver, but brings increment of the delay

Principle of Channel Codingv:-


I. Error-correcting ability obtains by adding redundancy in the original data

II. Convolutional coding and Turbo coding （1/2，1/3）are widely applied.

III. Increase noneffective load and transmission time

IV. Suitable to correct few non-continuous errors

Example of ½ Convolutional Coding

Channel coding Types

WCDMA Channel Coding


During the transmission, there are many interferences and fading. To guarantee

reliable transmission, system should overcome these influence through the channel

coding which includes convolution and interleaving.

The first is convolution that is used for anti-interference. Through the technology,

many redundant bits will be inserted in original information. When error code is

caused by interference, the redundant bits can be used to recover the original

information.

In WCDMA network, both Convolution code and Turbo code are used.

Convolution code applies to voice service while Turbo code applies to high rate

data service.

Principle of Interleave Technology


In channel coding , there is another technology named interleaving. Communications over

radio channel are characterized by fast fading that can cause large numbers of consecutive

errors. Most coding schemes perform better on random data errors than on blocks of errors.

By interleaving the data, no two adjacent bits are transmitted near to each other, and the

data errors are randomized.

Note: - Interleaving period is 10,20,40 and 80 ms

Principle of Interleave Technology


Advantage:

Interleave is to change the sequence of data to random the unexpected errors

Advance the correcting validity

Disadvantage:

Increase the processing delay

Especially, Several independent random errors may intertwined for the unexpected

error.

Encoding and Interleaving



I. 3G services





VI.Modulation






UMTS Radio Theory

Definition:-

Modulation is the process where the amplitude, frequency, or phase of an electronic

or optical signal carrier is changed in order to transmit information.

Using symbol stand for one or more bits to improve communication effectiveness

Classification:-

Analog Modulation (AM, FM & PM)

Digital Modulation (ASK, FSK & PSK)

Modulation


I. 3G services





VI. Modulation


I. UMTS Data transmission process ProcedureII. Channel Coding of UMTS



UMTS Radio Theory

UMTS Data transmission process Procedure


WCDMA Source Coding

Source coding can increase the transmitting efficiency.

1. AMR (Adaptive Multi-Rate) Speech

A integrated speech codec with 8 source rates.

The AMR bit rates can be controlled by the RAN

depending on the system load and

Quality of the speech connections.

2. Video Phone Service

H.324 is used for VP Service in CS domain.

Includes: video codec, speech codec, data protocols,

multiplexing and etc.

AMR is compatible with current mobile communication system (GSM,

IS-95, PDC and so on), thus, it will make multi-mode terminal design easier.


I. 3G services





VI. Modulation


I. UMTS Data transmission process Procedure

II. Channel Coding of UMTSIII. Spreading Technology of UMTS


UMTS Radio Theory

Convolutional Code

Channel Coding of UMTS

Mainly used in the voice channel and control signal channel

Coding rate is ½ and 1/3.

Characteristics of Convolutional code:-

Easy decode

Short delay

Generally use the Viterbi Algorithm

Channel bit error rate is10 -3 magnitude

Suitable to realtime service

e.g. speech and video service.

Channel Coding of UMTS

Turbo Code

Used in Data service channel

Code Rate is 1/3

Can be implemented in the transmission for large block and long delay services

Turbo coding structure is based on two or more weak error control code

combinations. The information bits are interleaved in the two Encoder, and generate

two information flow. At last, this information can be multiplexed and punctured

Decoding needs cycle iterative calculation

Characteristics of Turbo Codes

Complex decoding

Use the LOG-MAP arithmetic

Channel bit error rate is 10－6 magnitude

Very suitable to non-realtime package service which is BER sensitive & delay

insensitive, e.g. WWW, FTP, E_mail, multimedia transmission


I. 3G services





VI. Modulation




III.Spreading Technology of UMTSIV. Modulation of UMTS

UMTS Radio Theory

Spreading Technology of UMTS

Spreading Process of UMTS

Spreading can increase the capability of overcoming interference.

Bit, Symbol, Chip

Bit : data after source coding

Symbol: data after channel coding and interleaving

Chip: data after spreading

Process Gain

Process gain differs for each service.

If the service bit rate is greater, the process gain is smaller, UE needs more power

for this service, then the coverage of this service will be smaller, vice versa.

For common services, the bit rate of voice call is 12.2kbps, the bit rate of

video phone is 64kbps, and the highest packet service bit rate is 384kbps(R99). After

the spreading, the chip rate of different service all become 3.84Mcps.


Correlation

Correlation measures similarity between any two arbitrary signal, on other

hand determine the Identical and Orthogonal signals

Correlation is used to measure similarity of any two arbitrary signals. It is

computed by multiplying the two signals and then summing (integrating) the

result over a defined time windows. The two signals in figure (a) are identical and

therefore their correlation is 1 or 100 percent. In figure (b) , however, the two

signals are uncorrelated, and therefore knowing one of them does not provide any

information on the other.

Figure (a)

Figure (b)

Correlation

Cross Correlation: related to the multi-user interference characteristic

Auto Correlation: related to the multi-path interference characteristic

Orthogonal Code Usage - Coding

De-CodingCoding


Channelization Code

OVSF Code (Orthogonal Variable Spreading Factor)

SF = chip rate / symbol rate

High data rates → low SF code

Low data rates → high SF code

Orthogonal codes are easily generated by starting with a seed of 1, repeating the 1

horizontally and vertically, and then complementing the -1 diagonally. This process is to

be continued with the newly generated block until the desired codes with the proper

length are generated. Sequences created in this way are referred as “Walsh” code.

Spreading code uses OVSF code, for keeping the orthogonality of different subscriber

physical channels. OVSF can be defined as the code tree illustrated in the following

diagram.

Spreading code is defined as Cch SF, k,, where, SF is the spreading factor of the code,

and k is the sequence of code, 0≤k≤SF-1. Each level definition length of code tree is SF

spreading code, and the left most value of each spreading code character is corresponding

to the chip which is transmitted earliest.


Channelization Code

WCDMA Channelization Code

For uplink, Channelization code ( OVSF code ) is used to separate different physical

channels of one connection

For downlink, Channelization code ( OVSF code ) is used to separate different

connections in a cell

Purpose of Channelization Code

For voice service (AMR), downlink SF is 128, it means there are 128 voice services

maximum can be supported in one WCDMA carrier;

For Video Phone (64k packet data) service, downlink SF is 32, it means there are 32

voice services maximum can be supported in one WCDMA carrier.

WCDMA Scrambling Code – Gold Sequence

Scrambling codes Properties

38 400 chip long sequences

Repeated every 10 ms

Coming from Pseudo Noise sequences

For uplink, Scrambling code (Gold sequence) is used to separate different connection

For downlink, Scrambling code (Gold sequence) is used to separate different cell

Scrambling code sequence Generator

I. Gold sequence is made by two m sequence.

II. m sequence is generate by a series of shift-registers, and the period is 2n-1, here n

is the length of the shift-registers.


Characteristic of Scrambling code

There are 224 Uplink Scrambling Codes, they are used to distinguish different users

in one cell.

There are 218 -1 Downlink Scrambling Codes, used to distinguish different cells

Scrambling codes usually used are the first 8192 codes, which are code 0，1

，……，8191. They are divided into 512 aggregations each aggregation has 1

primary scrambling code (PSC) and 15 secondary scrambling codes (SSC).

The 512 primary scrambling codes are divided further into 64 primary

scrambling code groups , with 8 primary scrambling codes in each group.


Numbering rule for Downlink Scrambling Codes

WCDMA Code Functions

Channelization code :

for separation of physical channels in the uplink and separation of users

in the downlink

Scrambling code :

for separation of users/terminals in the uplink and cells/sectors in the

downlink.

Spreading code & scrambling code

Cch：spread code

Relative to service rate，extended to 3.84Mchips/s

A kind of orthogonal code

Cscrambling：scrambling code

Have no effect on signal bandwidth

Downlink for identifier cell，uplink identifier terminal

A pseudo-random sequence

Code Multiplexing

Downlink Transmission on a Cell Level

Code Multiplexing

Uplink Transmission on a Cell Level

Spreading and Despreading


Spreading and Despreading


During the process of receiving the expected correct signal that belongs to the

subscriber, complete synchronous despreading codes are adopted for the despreading

operation. After obtaining the despreading data, the correlation receiver integrates the

resulting products, then get the integration data.

Signals of other subscribers using different spreading codes are actually the interference

signals to the first subscriber. In this case, multiply the signals and the despreading code of

the first subscriber to get the despreading signal, and then perform integration. Finally, an

interference signal with a signal value fluctuating along with 0 will be got. It can be

viewed that the signal amplitude of the subscriber increases by 8 times than that of the

other interference systems in average. That is to say, the correlation detection increases the

expected subscriber signal by the multiple of spreading factor value within the

interference of CDMA system. This effect is called “Processing Gain”, and it is the basic

characteristic of the spreading system. Elementarily, this kind of correlation receivers are

adopted for the BTS and UE in theWCDMA system. Because the existence of multi-path

propagation and multi receiving antennas, multiple correlation receivers are necessary for

retrieving the signal energy from all the paths or antennas. And the collection of these

correlation receivers forms the CDMA RAKE receiver.

Processing Gain


PG=Wc/Rb (Where Wc : Chip rate , Rb : Service bit rate)

Transmitter/receiver can obtain gain after spread/despread

The narrower original signal bandwidth, the larger Pg , the better

The higher PG, the more anti-interference capability system has.

Relation between Eb/N0 and PG



I. 3G services





VI. Modulation





IV.Modulation of UMTS

UMTS Radio Theory

Modulation Overview

Modulation of UMTS

Modulation Overview

Modulation of UMTS

QPSK: Quadrature Phase Shift Keying . Phase shift keying in which four

different phase angles are used.

Modulation Overview

Modulation of UMTS

Modulation Methods in UMTS

BPSK (Binary Phase Shift Keying) in Uplink channles

QPSK (Quadrature Phase Shift Keying) in Downlink channels

16QAM (16-state Quadrature Amplitude Modulation) in HSDPA

Demodulation

Modulation of UMTS

QPSK Constellation Diagram

Principle of RAKE Receiver

RAKE receiver help to overcome on the multi-path fading and enhance the

receive performance of the system

When WCDMA systems were designed for cellular systems, the inherent wide bandwidth signals with their orthogonal

Walsh functions were natural for implementing a RAKE receiver. InWCDMA system, the bandwidth is wider than the

coherence bandwidth of the cellular. Thus, when the multi-path components are resolved in the receiver, the signals from

each tap on the delay line are uncorrelated with each other. The receiver can then combine themusing any of the combining

schemes. The WCDMA system then uses the multi-path characteristics of the channel to its advantage to improve the

operation of the system.

I. The RAKE receiver take advantage of multi-path diversity

II. The RAKE receiver processes the received signal

Identify the time delay positions at which significant energy arrives

Allocate correlation receivers (RAKE fingers) to those peaks

Within each Rake finger, track the fast-changing phase and amplitude values

Adjust the phase, remove the values originating from fast-fading

Combine the demodulated and phase-adjusted symbols across all active fingers

Present them to the decoder for further processing

III. This processing is called Maximal Ratio Combining

Principle of RAKE Receiver

WCDMA Signal Demodulation process

Many Thanks

Question Time

class 1 umts training

Documents

multiple access technologiesa

channel coding of umtsiii

technology of umtsiv

new system

data network

g servicesii

spectrum planningiv

frequency bandsuitable