PROJECT REPORT Entitled

“LTE Physical Layer Design and Implementation”

Submitted in fulfillment of the requirement For the Degree of

: Presented & Submitted By :

Mr. Mahesh Sukhariya (Roll No. U08EC328) Mr. Rishi Garg (Roll No. U08EC340) Mr. Vikas Aggarwal (Roll No. U08EC364) Mr. Adarsh Pillai (Roll No. U08EC410)

B. TECH. IV (Electronics & Communication) 8th Semester

: Guided By :

Dr. U.D.DalalAssociate Professor, ECED.

(May - 2012)

ELECTRONICS ENGINEERING DEPARTMENTSardarVallabhbhai National Institute of Technology

Surat-395007, Gujarat, INDIA.

ACKNOWLEDGEMENT

We would like to express our greatest gratitude to the people who have helped & supported us

throughout our project. We are grateful to our guide Dr. (Mrs.) U.D.DALAL for her continuous

support for the Project, from initial advice & encouragement to this day. We wish to thank our

parents for their undivided support and our friends who appreciated us for our work & motivated

us and finally to God who made all the things possible.

ABSTRACT

LTE is a standard for wireless data communications technology and an evolution of the GSM/UMTS standards. The goal of LTE is to increase the capacity and speed of wireless data networks using new DSP (Digital Signal Processing) techniques and modulations that were developed in the beginning of the new millennium.

The system supports downlink and uplink peak data rates of 100 Mbps and 50 Mbps respectively with 20 MHz bandwidth. In addition to peak data rate improvements, LTE system provides much higher spectral efficiency .In terms of latency, LTE radio interface and network provides capabilities for less than 10 ms latency for the transmission of a packet from the network to the UE.LTE uses SCFDMA in its uplink.

In SC-FDMA, multiple access among users is made possible by assigning different users, different sets of non-overlapping Fourier-coefficients (sub-carriers). This is achieved at the transmitter by inserting (prior to IFFT) silent Fourier-coefficients (at positions assigned to other users), and removing them on the receiver side after the FFT.

In this project uplink part of the LTE physical layer is implemented using System Vue which is an electronic system-level (ESL) design software. First the various modulation techniques like QPSK, 16-QAM, 64-QAM were successfully implemented and analyzed. Later the LTE uplink physical layer was designed and characteristics of the spectrum were observed for different noise density values in the spectrum analyzer .The throughput and BER was also observed with satisfactory results.

SardarVallabhbhai National Institute of TechnologySurat-395007, Gujarat, INDIA.

ELECTRONICS ENGINEERING DEPARTMENT

This is to certify that the B. Tech. IV (8th Semester)PROJECT REPORT entitled

“LTE Physical Layer Design And Implementation” is presented & submitted by Candidates

Mr. Mahesh Sukhariya, Rishi Garg, Vikas Aggarwal, Adarsh Pillai, bearing Roll Nos.

U08EC328, U08EC340, U08EC364, U08EC410, in the fulfillment of the requirement for the

award of B.Tech. Degree in Electronics & Communication Engineering.

They have successfully and satisfactorily completed their Project Exam in all respect.

We, certify that the work is comprehensive, complete and fit for evaluation.

Dr. U. D. DALAL Prof. N. B. KANIRKAR Dr.S. PATNAIKProject Guide UG In-charge, Head of the Deptt. ECEDAssociate Professor Associate Professor Associate Professor

PROJECT EXAMINERS :

Name Signature with date

1.Asst. Prof. Shweta N. Shah __________________

2.Asst.Prof. Shilpi Gupta __________________

3.Mrs V.P. Bhale __________________

DEPARTMENT SEALMay-2012.

TABLE OF CONTENT

LIST OF FIGURES………………………………………………………………. ii

CHAPTERS

1. INTRODUCTION 1

1.1 Requirements for UMTS Long Term Evolution 2

1.2 Consumer’s Future Requirements 3

1.3 LTE Architecture 5

1.4 Network Architecture 6

1.5 QoS and bearer service architecture 11

1.6 Seamless mobility support 12

2. LTE PHYSICAL LAYER 16

2.1Technology Focus 16

2.2 SCFDMA 19

2.3 Single Carrier Modulation 23

2.4 Subcarrier Mapping 24

2.5 LTE Uplink Physical Channels 26

3. INTRODUCTION TO SYSTEM VUE 38

3.1 Introduction To UI 38

4. LTE Uplink Design 48

4.1 LTE Uplink Transmitter 48

4.2 LTE Uplink Throughput 49

4.3 Blocks used in Simulation using System Vue 50

4.4 BER Analysis 70

RESULT

CONCLUSION

REFERENCES

ACRONYMS

LIST OF FIGURES

SR. NO.

NAME OF THE FIGURE PAGE NO.

1 Fig.1(a) Broadband growth 2005–2012 42 Fig.1(b) Growth of voice and data traffic in WCDMA networks world

wide5

3 Fig .1(c) Network Architecture 74 Fig .1(d) Functional split between eNB and MME/GW 85 Fig .1(e) User Plane Protocol 86 Fig .1(f) Control Plane Protocol 97 Fig .1(g) S1 interfaces user and control planes 108 Fig .1(h) X2 interfaces user and control planes 109 Fig .1(i) EPS bearer service architecture 1110 Fig .1(j) Active Handovers 1311 Fig .1(k) Handover Message Sequence 1512 Fig .2(a)QAM block diagram 17

13 Fig.2(b) Constellation diagram 18

14 Fig. 2(c) BER 1915 Fig. 2(d) Transmitter scheme of SC-FDMA 20

16 Fig .2(e) Uplink slot format 2117 Fig .2(f) OFDM transmitter and receiver 2218 Fig .2(g) SC-FDMA transmitter and receiver 22

19 Fig .2(h) Time domain representation of interleaved SC-FDMA 23

20 Fig. 2(i) Simplified interleaved SC-FDMA transmitter 24

21 Fig .2(j) subcarrier mapping 25

22 Fig.2(k) subcarrier mapping example 26

23 Fig.2(l) PRACH preamble time structure 27

24 Fig.2(m) subcarrier content 29

25 Fig.2(o) non frequency hopping srs 36

26 Fig.2(p) frequency hopping srs 36

27 Fig.2(q)PUSCH structure 37

28 Fig.2(r)PUSCH 37

29 Fig. 3.1(a) SystemVue Getting Started Window 3830 Fig .3.1(b) Setting Source Properties 3931 Fig .3.1(c) Sine Source setup 3932 Fig .3.1(d). SystemVue Design Environment 4033 Fig .3.1(e) Selecting component from Part Selector 40

34 Fig .3.1(f) Setting Source Properties 4135 Fig .3.1(g). Sine Source setup 4136 Fig .3.1(h) Simulation Controller Properties 4237 Fig .3.1(i) SystemVue 4338 Fig .3.1(j). Simulation Dataset 4339 Fig .3.l(k). Adding measurement to Graph 4440 Fig .3.1(l). Graphing Wizard 4441 Fig .3.1(m) spectrum 4542 Fig .3.1(n). Adding Graph from Workspace Tree 4543 Fig .3.1(o) Graphing Wizard 4644 Fig .3.1(p).Spectrum graph 4645 Fig .3.1(q) SystemVue Tile View 4746 Fig .4.1(a) LTE Uplink Transmitter using system vue 4847 Fig .4.2(b) Uplink block diagram using system vue 4948 Fig .4.3(a) random bit generater 5049 Fig .4.3(c) LTE UL Src 5150 Fig .4.3(d). Uplink Transmitter -System Parameters 5151 Fig .4.3(e). Uplink Transmitter-PUSCH parameters 5252 Fig .4.3(f). Uplink Transmitter -RB allocation (PUSCH) parameters 5253 Fig .4.3(g). Uplink Transmitter –PUCCH Parameters 53

54 Fig .4.3(h). Uplink Transmitter PRACH parameters 5355 Fig .4.3(i). Uplink Transmitter SRS parameters 5456 Fig .4.3(j). Uplink transmitter Control info parameters 5457 Fig .4.3(k). Uplink Transmitter Power parameter 5558 Fig .4.3(l). Complex to rectangular converter 5559 Fig .4.3(m). Modulator 5660 Fig .4.3(n). Modulator parameters 5761 Fig .4.3(o) Oscillator 5762 Fig .4.3(p) Spectrum Analyzer 5863 Fig .4.3(q). Spectrum Analyzer Parameters 5864 Fig .4.3(r). Power vs. Frequency graph 5965 Fig .4.3(s). Noise density Block 5966 Fig .4.3(t) Noise density parameters 6067 Fig .4.3(u) Demodulator block 6168 Fig .4.3(v) Demodulator parameters 6169 Fig .4.3(w) Delay block 6170 Fig .4.3 (x) Delay parameters 6271 Fig .4.3(y) LTE UL Receiver 6272 Fig .4.3(z) UL receiver system parameters 6373 Fig .4.3(aa) UL receiver PUSCH parameters 6374 Fig .4.3(bb) UL receiver RB allocation(PUSCH) parameters 6375 Fig .4.3(cc) UL receiver PUCCH Parameters 6476 Fig .4.3(dd) UL receiver PRACH parameters 6577 Fig .4.3(ee) UL Receiver SRS Parameters 6578 Fig .4.3(ff) UL Receiver Control info Parameters 6679 Fig .4.3(gg) UL Receiver Rx algorithm parameters 66

80 Fig .4.3(hh) LTE Through put block diagram 6781 Fig .4.3(ii) LTE Throughput parameters 6782 Fig .4.3 (jj) LTE UL AWGN HARQ THROUGHPUT 6883 Fig .4.3 (kk) UL BER Measurement Block Diagram 6884 Fig .4.3(ll) BER properties 6985 Fig .4.3(mm) BER Parameters 6986 Fig .4.4(a) UL BER measurement block diagram 7087 Fig .4.4(b) BER vs. SNR graph 70

LIST OF TABLES

SNO NAME OF TABLE PAGE NO1 2.1. LTE parameters 162 2.2 .Preamble format 273 2.3 .PRACH Preamble format 285 2.5 .UE setting 306 2.6 .channel setting 317 2.7 .PUCCH format type 328 2.8 .Format 34

CHAPTER 1:INTRODUCTION

Long Term Evolution (LTE) is the next step forward in cellular 3G services. Expected in the

2008 time frame, LTE is a 3GPP standard that provides for an uplink speed of up to 50 megabits

per second (Mbps) and a downlink speed of up to 100 Mbps. LTE will bring many technical

benefits to cellular networks. Bandwidth will be scalable from 1.25 MHz to 20 MHz this spectral

efficiency in 3G networks, allowing carriers to provide will suit the needs of different network

operators that have different bandwidth allocations, and also allow operators to provide different

services based on spectrum. LTE is also expected to improve more data and voice services over a

given bandwidth on the channel.

The 3GPP Long Term Evolution (LTE) represents a major advance in cellular technology. LTE

is designed to meet carrier needs for high-speed data and media transport as well as high-

capacity voice support well into the next decade. It encompasses high-speed data, multimedia

unicast and multimedia broadcast services. Although technical specifications are not yet

finalized, significant details are emerging. This report focuses on the LTE physical layer(PHY).

The LTE PHY is a highly efficient means of conveying both data and control information

between an enhanced base station (eNodeB) and mobile user equipment (UE). The LTE PHY

employs some advanced technologies that are new to cellular applications. These include

Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output

(MIMO) data transmission. In addition, the LTE PHY uses Orthogonal Frequency Division

Multiple Access (OFDMA) on the downlink (DL) and Single Carrier – Frequency Division

Multiple Access (SC-FDMA) on the uplink (UL). OFDMA allows data to be directed to or from

multiple users on a subcarrier-by-subcarrier basis for a specified number of symbol periods. Due

to the novelty of these technologies in cellular applications, they are described separately before

delving into a description of the LTE PHY.

Although the LTE specs describe both Frequency Division Duplexing (FDD) and Time Division

Duplexing (TDD) to separate UL and DL traffic, market preferences dictate that the majority of

deployed systems will be FDD. This paper therefore describes LTE FDD systems only.

1.1 Requirements For UMTS Long Term Evolution

LTE is focusing on optimum support of Packet Switched (PS) Services.Main requirements for

the design of an LTE system have been captured in 3GPP TR 25.913 [1] and can be summarized

as follows:

- Data Rate: Peak data rates target 100 Mbps (downlink) and 50 Mbps (uplink) for 20 MHz

spectrum allocation, assuming 2 receive antennas and 1 transmit antenna at the terminal.

- Throughput: Target for downlink average user throughput per MHz is 3-4 times better than

release 6. Target for uplink average user throughput per MHz is 2-3 times better than release 6.

- Spectrum Efficiency: Downlink target is 3-4 times better than release 6. Uplink target is 2-3

times better than release 6.

- Latency: The one-way transit time between a packet being available at the IP layer in either the

UE or radio access network and the availability of this packet at IP layer in the radio access

network/UE shall be less than 5 ms. Also C-plane latency shall be reduced, e.g. to allow fast

transition times of less than 100 ms from camped state to active state.

- Bandwidth: Scalable bandwidths of 5, 10, 15, 20 MHz shall be supported. Also bandwidths

smaller than 5 MHz shall be supported for more flexibility.

- Interworking: Interworking with existing UTRAN/GERAN systems and non-3GPP systems

shall be ensured. Multimode terminals shall support handover to and from UTRAN and GERAN

as well as inter-RAT measurements. Interruption time for handover between E-UTRAN and

UTRAN/GERAN shall be less than 300 ms for real time services and less than 500 ms for non

real time services.

- Multimedia Broadcast Multicast Services (MBMS): MBMS shall be further enhanced and is

then referred to as E-MBMS.

- Costs: Reduced CAPEX and OPEX including backhaul shall be achieved. Cost effective

migration from release 6 UTRA radio interface and architecture shall be possible. Reasonable

system and terminal complexity, cost and power consumption shall be ensured. All the interfaces

specified shall be open for multi-vendor equipment interoperability.

- Mobility: The system should be optimized for low mobile speed (0-15 km/h), but higher

mobile speeds shall be supported as well including high speed train environment as special case.

- Spectrum allocation: Operation in paired (Frequency Division Duplex / FDD mode) and

unpaired spectrum (Time Division Duplex / TDD mode) is possible.

- Co-existence: Co-existence in the same geographical area and collocation with

GERAN/UTRAN shall be ensured. Also, co-existence between operators in adjacent bands as

well as cross-border coexistence is a requirement.

- Quality of Service: End-to-end Quality of Service (QoS) shall be supported. VoIP should be

supported with at least as good radio and backhaul efficiency and latency as voice traffic over the

UMTS circuit switched networks.

- Network synchronization: Time synchronization of different network sites shall not be

mandated.

1.2 Consumer’s Future Requirements

Broadband subscriptions are expected to reach 1.8 billion by 2012. Around two-thirds of these

consumers will use mobile broadband. Mobile data traffic is expected to overtake voice traffic in

2010, which will place high requirements on mobile networks today and in the future. The figure

below shows the broadband growth in the number of subscriptions from year 2005 to 2012 :

Fig 1(a) Broadband growth 2005–2012[2]

There is strong supporting evidence for the take-off of mobile broadband.

First, consumers understand and appreciate the benefits of mobile broadband. Most people

already use mobile phones, and many also connect their notebooks over wireless LANs. The step

towards full mobile broadband is intuitive and simple, especially with LTE that offers ubiquitous

coverage and roaming with existing 2G and 3G networks.

Second, experience from HSPA shows that when operators provide good coverage, service

offerings and terminals, mobile broadband rapidly takes off. Packet data traffic started to exceed

voice traffic during May 2007 as an average world in WCDMA networks (see Figure 1.2). This

is mainly due to the introduction of HSPA in the networks. Recently HSPA data cards and USB

dongles have become very popular. Several operators have seen a four fold increase in data

traffic in just 3 months after they launched HSPA.

Fig 1(b) Growth of voice and data traffic in WCDMA networks world wide[2]

In many cases, mobile broadband can compete with fixed broadband on price, performance,

security and, of course, convenience. Users can spend time using the service rather than setting

up the WLAN connection, worrying about security or losing coverage.

Third, a number of broadband applications are significantly enhanced with mobility. Community

sites, search engines, presence applications and content-sharing sites like YouTube are just a few

examples. With mobility, these applications become significantly more valuable to people. User-

generated content is particularly interesting, because it changes traffic patterns to make the

uplink much more important. The high peak rates and short latency of LTE enable real-time

applications like gaming and IPTV.

1.3 LTE Architecture

The LTE network architecture is designed with the goal of supporting packet-switched traffic

with seamless mobility, quality of service (QoS) and minimal latency. A packet-switched

approach allows for the supporting of all services including voice through packet connections.

The result in a highly simplified flatter architecture with only two types of node namely evolved

Node-B (eNB) and mobility management entity/gateway (MME/GW). This is in contrast to

many more network nodes in the current hierarchical network architecture of the 3G system. One

major change is that the radio network controller (RNC) is eliminated from the data path and its

functions are now incorporated in eNB. Some of the benefits of a single node in the access

network are reduced latency and the distribution of the RNC processing load into multiple eNBs.

The elimination of the RNC in the access network was possible partly because the LTE system

does not support macro-diversity or soft-handoff.

1.4 Network Architecture

All the network interfaces are based on IP protocols. The eNBs are interconnected by means of

an X2 interface and to theMME/GWentity by means of an S1 interface as shown in Figure 1(c).

The S1 interface supports a many-to-many relationship between MME/GW and eNBs.

The functional split between eNB and MME/GW is shown in Figure 1(d). Two logical gateway

entities namely the serving gateway (S-GW) and the packet data network gateway (P-GW) are

defined. The S-GW acts as a local mobility anchor forwarding and receiving packets to and from

the eNB[3] serving the UE. The P-GW interfaces with external packet data networks (PDNs)

such as the Internet and the IMS. The P-GW also performs several IP functions such as address

allocation, policy enforcement, packet filtering and routing.

The MME is a signaling only entity and hence user IP packets do not go through MME.An

advantage of a separate network entity for signaling is that the network capacity for signaling

and traffic can grow independently. The main functions of MME are idle-mode UE reachability

including the control and execution of paging retransmission, tracking area list management,

roaming, authentication, authorization, P-GW/S-GW selection, bearer management including

dedicated bearer establishment, security negotiations and NAS signaling, etc.

Evolved Node-B implements Node-B functions as well as protocols traditionally implemented in

RNC. The main functions of eNB are header compression, ciphering and reliable delivery of

packets. On the control side, eNB incorporates functions such as admission control and radio

resource management. Some of the benefits of a single node in the access network are reduced

latency and the distribution of RNC processing load into multiple eNBs.

Fig 1(c) Network Architecture[4]

Fig 1(d) Functional split between eNB and MME/GW[4].

The user plane protocol stack is given in Figure 1(e).We note that packet data convergence

Protocol (PDCP) and radio link control (RLC) layers traditionally terminated in RNC on

Fig 1(e) User Plane Protocol[4]

Fig 1(f) Control Plane Protocol[4]

The network side is now terminated in eNB. The functions performed by these layers are

Described in Section 1.5.

Figure 1(f) shows the control plane protocol stack. We note that RRC functionality traditionally

implemented in RNC is now incorporated into eNB. The RLC and MAC layers perform the same

functions as they do for the user plane. The functions performed by the RRC include system

information broadcast, paging, radio bearer control, RRC connection management, mobility

functions and UE measurement reporting and control. The non-access stratum (NAS) protocol

terminated in the MME on the network side and at the UE on the terminal side performs

functions such as EPS (evolved packet system) bearer management, authentication and security

control, etc.

The S1 and X2 interface protocol stacks are shown in Figures 1(g) and 1(h) respectively. We

note that similar protocols are used on these two interfaces. The S1 user plane interface (S1-U) is

defined between the eNB and the S-GW. The S1-U interface uses GTP-U (GPRS tunneling

protocol – user data tunneling) on UDP/IPtransport and provides non-guaranteed delivery of user

plane PDUs between the eNB and the S-GW. The GTP-U is a relatively simple IP based

tunneling protocol that permits many tunnels between each set of end points. The S1 control

plane interface (S1-MME) is defined as being between the eNB and the MME.

Similar to the user plane, the transport network layer is built on IP transport and for the reliable

transport of signaling messages SCTP (stream control transmission protocol) is used on top of

IP.

Fig 1(g) S1 interfaces user and control planes[4].

Fig 1(h) X2 interfaces user and control planes[4].

The SCTP protocol operates analogously to TCP ensuring reliable, in-sequence transport of

messages with congestion control. The application layer signaling protocols are referred to as S1

application protocol (S1-AP) and X2 application protocol (X2-AP) for S1 and X2 interface

control planes respectively.

1.5 QoS And Bearer Service Architecture

Applications such as VoIP, web browsing, video telephony and video streaming have special

QoS needs. Therefore, an important feature of any all-packet network is the provision of a QoS

mechanism to enable differentiation of packet flows based on QoS requirements. In EPS, QoS

flows called EPS bearers are established between the UE and the P-GW as shown in Figure 1(i).

A radio bearer transports the packets of an EPS bearer between a UE and an eNB. Each IP flow

(e.g. VoIP) is associated with a different EPS bearer and the network can prioritize traffic

accordingly.

Fig 1(i) EPS bearer service architecture[4].

When receiving an IP packet from the Internet, P-GW performs packet classification based on

certain predefined parameters and sends it an appropriate EPS bearer. Based on the EPS bearer,

eNB maps packets to the appropriate radio QoS bearer. There is one-to-one mapping between an

EPS bearer and a radio bearer.

1.6 Seamless mobility support

An important feature of a mobile wireless system such as LTE is support for seamless mobility

across eNBs and across MME/GWs. Fast and seamless handovers (HO) is particularly important

for delay-sensitive services such as VoIP. The handovers occur more frequently across eNBs

than across core networks because the area covered by MME/GW serving a large number of

eNBs is generally much larger than the area covered by a single eNB. The signaling on X2

interface between eNBs is used for handover preparation. The S-GW acts as anchor for inter-

eNB handovers.

In the LTE system, the network relies on the UE to detect the neighboring cells for handovers

and therefore no neighbor cell information is signaled from the network. For the search and

measurement of inter-frequency neighboring cells, only the carrier frequencies need to be

indicated. An example of active handover in an RRC CONNECTED state is shown in Figure 1(j)

where a UE moves from the coverage area of the source eNB (eNB1) to the coverage area of the

target eNB (eNB2). The handovers in the RRC CONNECTED state are network controlled and

assisted by the UE. The UE sends a radio measurement report to the source eNB1 indicating that

the signal quality on eNB2 is better than the signal quality on eNB1. As preparation for

handover, the source eNB1 sends the coupling information and the UE context to the target

eNB2 (HO request) on the X2 interface. The target eNB2 may perform admission control

dependent on the received EPS bearer QoS information. The target eNB configures the required

resources according to the received EPS bearer QoS information and reserves a C-RNTI (cell

radio network temporary identifier) and optionally a RACH preamble.

The C-RNTI provides a unique UE identification at the cell level identifying the RRC

connection. When eNB2 signals to eNB1 that it is ready to perform the handover via HO

Response message, eNB1 commands the UE (HO command) to change the radio bearer to eNB2.

Fig 1(j) Active Handovers[4].

The UE receives the HO command with the necessary parameters (i.e. new C-RNTI, optionally

dedicated RACH preamble, possible expiry time of the dedicated RACH preamble, etc.) and is

commanded by the source eNB to perform the HO. The UE does not need to delay the handover

execution for delivering the HARQ/ARQ responses to source eNB.

After receiving the HO command, the UE performs synchronization to the target eNB and

accesses the target cell via the random access channel (RACH) following a contention-free

procedure if a dedicated RACH preamble was allocated in the HO command or following a

contention-based procedure if no dedicated preamble was allocated. The network responds with

uplink resource allocation and timing advance to be applied by the UE. When the UE has

successfully accessed the target cell, the UE sends the HO confirm message (C-RNTI) along

with an uplink buffer status report indicating that the handover procedure is completed for the

UE. After receiving the HO confirm message, the target eNB sends a path switch message to the

MME to inform that the UE has changed cell. The MME sends a user plane update message to

the S-GW. The S-GW switches the downlink data path to the target eNB and sends one or more

“end marker” packets on the old path to the source eNB and then releases any user-plane/TNL

resources towards the source eNB. Then S-GW sends a user plane update response message to

the MME. Then the MME confirms the path switch message from the target eNB with the path

switch response message. After the path switch response message is received from the MME, the

target eNB informs success of HO to the source eNB by sending release resource message to the

source eNB and triggers the release of resources. On receiving the release resource message, the

source eNB can release radio and C-plane related resources associated with the UE context.

During handover preparation U-plane tunnels can be established between the source eNB and the

target eNB. There is one tunnel established for uplink data forwarding and another one for

downlink data forwarding for each EPS bearer for which data forwarding is applied. During

handover execution, user data can be forwarded from the source eNB to the target eNB.

Forwarding of downlink user data from the source to the target eNB should take place in order as

long as packets are received at the source eNB or the source eNB buffer is exhausted.

For mobility management in the RRC IDLE state, concept of tracking area (TA) is introduced. A

tracking area generally covers multiple eNBs . The tracking area identity (TAI) information

indicating which TA an eNB belongs to is broadcast as part of system information. A UE can

detect change of tracking area when it receives a different TAI than in its current cell. The UE

updates the MME with its new TA information as it moves across TAs. When P-GW receives

data for a UE, it buffers the packets and queries the MME for the UE’s location. Then the MME

will page the UE in its most current TA. A UE can be registered in multiple TAs simultaneously.

This enables power saving at the UE under conditions of high mobility because it does not need

to constantly update its location with the MME. This feature also minimizes load on TA

boundaries.

Fig

1(k) Handover Message Sequence[4]

CHAPTER 2:LTE PHYSICAL LAYER

2.1 Technology Focus

Modern digital modulation techniques and multiple access techniques are basic building blocks

of the physical (or radio) interface of all digital communication systems. Techniques such as

OFDM, OFDMA, SOFDMA, SC-FDMA, DMT, MIMO and BLAST, CPM modulations (e.g.,

GMSK), CDMA and adaptive modulation and coding methods e.g., Nyquist Signaling, QPSK,

QAM and GMSK, and the optimum receivers for these modulations are very important parts of

the implementation of modern communications systems, especially for broadband wireless

communications. These concepts are being utilized in new mobile and broadband wireless

systems, including 4G-LTE, Mobile Wi-Max (IEEE 802.16), Wi-Fi (IEEE 802.11) and the new 

IMT-Advanced (4G) systems, as well as in xDSL systems, to greatly improve both bandwidth

and power efficiency.

Table 2.1 LTE parameters

Quadrature amplitude modulation (QAM) is both an analog and a digital modulation scheme

used in LTE System. Like all modulation schemes, QAM conveys data by changing some aspect

of a carrier signal, or the carrier wave, (usually a sinusoid) in response to a data signal. In the

case of QAM, the amplitude of two waves, 90 degrees out-of-phase with each other (in

quadrature) are changed (modulated or keyed) to represent the data signal. Amplitude

modulating two carriers in quadrature can be equivalently viewed as both amplitude modulating

and phase modulating a single carrier.

For a given available bandwidth, QAM enables data transmission at twice the rate of standard

pulse amplitude modulation (PAM) without any de-gradation in the bit error ratio (BER).

QAM block diagram

Figure 2(a) QAM Block Diagram[3]

• XI(t)=in phase

• XQ(t)=quadrature

• QAM signal=XI(t)cos(wct) +XQ(t)sin(wct)

There are various versions of QAM used for different applications. In digital

telecommunications the data are usually binary, the number of points in the grid is usually a

power of 2 (2, 4, 8 ...). Since QAM is usually square, some of these are rare—the most common

forms are 16-QAM, 64-QAM and 256-QAM. By moving to a higher-order constellation, it is

possible to transmit more bits per symbol. However, if the mean energy of the constellation is to

remain the same (by way of making a fair comparison), the points must be closer together and

are thus more susceptible to noise and other corruption; this results in a higher bit error rate and

so higher-order QAM can deliver more data less reliably than lower-order QAM, for constant

mean constellation energy.

Figure2(b) Constellation Diagram[3]

A constellation diagram is a representation of a signal modulated by a digital modulation scheme

such as QAM. It displays the signal as a two-dimensional scatter diagram in the complex plane at

symbol sampling instants. The real and imaginary axes are often called the in phase, or I-axis and

the quadrature, or Q-axis.

While higher order modulation rates are able to offer much faster data rates and higher levels of

spectral efficiency for the radio communications system, this comes at a price. The higher order

modulation schemes are considerably less resilient to noise and interference. 64-QAM and 256-

QAM are often used in digital cable television and cable modem applications

Figure 2(c) BER[3]

In SC- FDMA we use 64 QAM in which we are sending 6 bits per symbol .Fig shows that as we

go from QPSK to 256 QAM C/N is increasing.

2.2 SC-FDMA

The uplink transmission scheme is based on single-carrier FDMA, more specifically

DFTSOFDM. The uplink sub-carrier spacing Δf = 15 kHz. There are two cyclic-prefix lengths

defined: normal cyclic prefix and extended cyclic prefix corresponding to seven and six SC-

FDMA symbols per slot.

Fig 2(d) Transmitter scheme of SC-FDMA[5]

The sub-carriers are grouped into sets of 12 consecutive sub-carriers, corresponding to the uplink

resource blocks. 12 consecutive sub-carriers in one slot correspond to one uplink resource block

– the same as in the downlink – which is depicted in Figure. In the frequency domain, the

maximum number of resource blocks, NRB, can range from NRB-min = 6 to NRB-max = [110].

Each element in the resource grid is called a resource element and is uniquely defined by the

index pair (k, l) in a slot where k and l are the indices in the frequency (subcarrier) and time

domain (symbol), respectively.

SC-FDMA is a new multiple access technique that utilizes single carrier modulation, DFT spread

orthogonal frequency multiplexing, and frequency domain equalization. It has a

Similar structure and performance as OFDM.

Fig

2(e) Uplink slot format[5]

SC-FDMA is currently adopted as the uplink Multiple access schemes for 3GPP LTE.

Transmitter and receiver structure for SC-FDMA OFDM are given in Figures. It is evident from

the figures that SC-FDMA transceiver has similar structure as a typical OFDM system except the

addition of a new DFT block before subcarrier mapping. Hence, SC-FDMA can be considered as

an OFDM system with a DFT mapper.

Fig 2(f) OFDM transmitter and receiver[5]

Fig 2(g) SC-FDMA transmitter and receiver[5]

The main difference between OFDM and SC-FDMA transmitter is the DFT mapper. After

Mapping data bits into modulation symbols, the transmitter groups the modulation symbols

Into a block of N symbols. An N-point DFT transforms these symbols in time domain into

Frequency domain. The frequency domain samples are then mapped to a subset of M subcarriers

where M is typically greater than N. Similar to OFDM, an M-point IFFT is used to generate the

time-domain samples of these subcarriers, which is followed by cyclic prefix,

Parallel to serial converter, DAC and RF subsystems.

Each data symbol is DFT transformed before mapping to subcarriers, hence the SC-FDMA

Is called DFT-precoded OFDM. In a standard OFDM, each data symbol is carried on a separate

subcarrier. In SC-FDMA, multiple subcarriers carry each data symbol due to mapping of the

symbols’ frequency domain samples to subcarriers. As each data symbol is spread over multiple

subcarriers, SC-FDMA offers spreading gain or frequency diversity gain in a frequency selective

channel. Thus, SC-FDMA can be viewed as frequency-spread OFDM or DFT-spread OFDM.

2.3 Single Carrier Modulation

Based on SC-FDMA’s structure, the reasons for some of its names, such as DFT-precoded

OFDM or DFT-spread OFDM, are clear. But for the use of ‘Single Carrier’ in its name,

SCFDMA, is not as obvious and is often the reason why is not explained, unlike the standard

OFDM where the each data symbol is carried by the individual subcarriers, the SC-FDMA

transmitter carries data symbols over a group of subcarriers transmitted simultaneously. In other

words, the group of subcarriers that carry each data symbol can be viewed as one frequency band

carrying data sequentially in a standard FDMA. For some of the subcarrier mappings, the time

domain representation of the IFFT output, as shown in Figures below, will give more insight on

the SC-FDMA signal. It can be mathematically shown that the SC-FDMA baseband time domain

samples after IDFT or IFFT is the original data symbol set repeated in time domain over the

symbol period.

Fig 2(h) Time domain representation of interleaved SC-FDMA

Fig 2(i) Simplified interleaved SC-FDMA transmitter

2.4 Subcarrier Mapping

DFT output of the data symbols is mapped to a subset of subcarriers, a process called Subcarrier

mapping. The subcarrier mapping assigns DFT output complex values as the Amplitudes of

some of the selected subcarriers. Subcarrier mapping can be classified into Two types: localized

mapping and distributed mapping. In localized mapping, the DFT Outputs are mapped to a

subset of consecutive sub-carriers thereby confining them to only a Fraction of the system

bandwidth. In distributed mapping, the DFT outputs of the input data Are assigned to subcarriers

over the entire bandwidth non-continuously, resulting in zero Amplitude for the remaining

subcarriers. A special case of distributed SC-FDMA is called Interleaved SC-FDMA, where the

occupied subcarriers are equally spaced over the entire Bandwidth. Figure is a general picture of

localized and distributed mapping.

Fig

2(j) Subcarrier Mapping[5]

An example of subcarrier mapping is shown below. This example assumes three users Sharing

12 subcarriers. Each user has a block of four data symbols to transmit at a time. The DFT output

of the data block has four complex frequency domain samples, which are mapped over 12

subcarriers using different mapping schemes.

SC-FDMA inherently offers frequency diversity gain over the standard OFDM, as all.

Information data is spread over multiple subcarriers by the DFT mapper. However, the

Distributed SC-FDMA is more robust with respect to frequency selective fading and offers

Additional frequency diversity gain, since the information is spread across the entire system

Bandwidth. Localized SC-FDMA in combination with channel-dependant scheduling can

potentially offer multi-user diversity in frequency selective channel conditions.

Fig

2(k) Subcarrier mapping example[5]

2.5 LTE Uplink Physical Channels

PRACH

The PRACH transmission (the PRACH preamble) is an OFDM-based signal, but it is generated

using a different structure from other uplink transmission; most notably it uses narrower

subcarrier spacing and therefore is not orthogonal to the PUSCH, PUCCH and SRS, therefore

those channels will suffer from some interference from the PRACH. However, the subcarrier

spacing used by the PRACH is an integer submultiple of the spacing used for the other channels

and therefore the PUSCH, PUCCH and SRS do not interfere on the PRACH.

PRACH preamble time structure

The PRACH preamble consists of a cyclic prefix, useful part of the sequence and then a guard

period which is simply an unused portion of time up to the end of the last subframe occupied by

the PRACH:

Fig2(l)

PRACH preamble time structure[6]

This guard period allows for timing uncertainty due to the UE to eNodeB distance the size of the

guard period determines the cell radius, as any propagation delay exceeding the guard time

would cause the random access preamble to overlap the following subframe at the eNodeB

receiver.The use of an OFDM transmission with cyclic prefix allows for an efficient frequency

domain based receiver in the eNodeB to perform PRACH detection

PRACH formats

There five PRACH preamble formats which have different lengths for the cyclic prefix, useful

part of the symbol, and guard period:

Table 2.2 preamble format[7]

Note that Preamble Format 4 is only applicable for TDD in special subframes (subframe 1 or 6)

and with Special Subframe Configuration

Formats 2 and 3 have two repetitions of the nominal PRACH sequence which provides more

total transmit energy and therefore allows for detection at lower SNRs. Also, Format 1 versus 0

and Format 3 versus 2 have a longer guard period, allowing for a larger cell size. The downside

is that when the cyclic prefix time, sequence time and guard period are totaled up, some of the

formats require multiple subframes for transmission:

Table 2.3 PRACH Preamble format[7]

Preamble format Number of subframes

0 1

1 2

2 2

3 3

4 1

The penalty for using multiple subframes is a reduction in the capacity for normal uplink

transmission.

PRACH preamble frequency structure

As already mentioned, the PRACH uses a narrower subcarrier spacing that normal uplink

transmission, specifically 1250Hz for Formats 0-3 and 7500Hz for Format 4. The ratio of the

normal uplink subcarrier spacing to PRACH subcarrier spacing, , is  =12 for Formats 0-3

and  =2 for Format 4.

The PRACH is designed to fit in the same bandwidth as 6 RBs of normal uplink transmission i.e.

72 subcarriers at 15000Hz spacing = 1.08MHz. This makes it easy to schedule gaps in normal

uplink transmission to allow for PRACH opportunities.

Therefore there are   subcarriers for the PRACH, specifically 864 for Formats 0-3 and 144 for

Format 4. As will be explained in the following subsection, the PRACH transmission for

Formats 0-3 uses 839 active subcarriers, and for Format 4 uses 139 active subcarriers; the

number of active subcarriers is denoted .

As with normal uplink SC-FDMA transmission there is a half subcarrier (7500Hz) shift, which

for the PRACH is a  /2 subcarrier shift. A further subcarrier offset   (7 for Formats 0-3 and 2

for Format 4) centers the PRACH transmission within the 1.08MHz bandwidth:

Table 2.4 Preamble format with details[7]

Preamble format

0-3 13 839 12

4 3 139 2

PRACH subcarrier content

The actual PRACH transmission is an OFDM-based reconstruction of a Zadoff-Chu sequence in

the time domain; the OFDM modulator is used to position the Zadoff-Chu sequence in the

frequency domain i.e. to place the 6RBs of PRACH transmission in the 6 consecutive RBs

starting from some particular physical resource block (denoted   in the standard). If the

output of the OFDM modulator in the time domain is to be a Zadoff-Chu sequence, then the

input to the OFDM modulator must be a Zadoff-Chu sequence in the frequency domain.

Therefore the active subcarriers, which total in number, are set to the values of an  -point

DFT of an  -sample Zadoff-Chu sequence.

Fig

2(m) Subcarrier Content[6]

UE specific settings includes the fields:

Table 2.5 UE settings[7]

Although the parameters Format and ConfigIdx are both described as optional, at least one of

these parameters must be specified.

PRBSet will either be empty, indicating that the PRACH is not present, or will contain 6

consecutive Physical Resource Block numbers, indicating the frequency domain location of the

PRACH. Note that the PRACH uses a different SC-FDMA symbol construction from the other

channels (PUCCH, PUSCH and SRS) and therefore the PRBSet indicates the frequency range

(180kHz per RB) that the PRACH occupies, it does not occupy the set of 12 subcarriers in each

RB in the same fashion as other channels. The PRACH occupies a bandwidth approximately

equal to 1.08MHz = 6RBs. Specifically the PRACH will be generated in any subframe for FDD,

and for TDD the PRACH will be generated only in special subframes for Preamble Format 4,

and in uplink subframes for Preamble Format 0-3,

Table 2.6 channel settings[6]

Field Description

Field Description

Format Optional. Preamble format (0...4) (default absent)

SeqIdx Optional. Logical root sequence index

(RACH_ROOT_SEQUENCE) (0...837) (default 0)

ConfigIdx Optional. PRACH Configuration Index (prach-

ConfigurationIndex) (0...63) (default absent)

PreambleIdx Optional. Scalar preamble index within cell (ra-

PreambleIndex) (0...63) (default 0)

CyclicShiftIdx Optional. Cyclic shift configuration index

(zeroCorrelationZoneConfig, yields N_CS) (0...15) (default 0)

HighSpeed Optional. High Speed flag (highSpeedFlag, 1=Restricted Set,

0=Unrestricted Set) (0...1) (default 0)

TimingOffset Optional. PRACH timing offset in microseconds (default 0.0)

FreqIdx Only required for 'TDD' duplex mode.

Optional. Frequency resource index (f_RA) (0...5) (default 0)

FreqOffset Only required for 'TDD' duplex mode.

Optional. PRACH Frequency Offset (n_PRBoffset) (0...94)

(default 0)

provided there are consecutive uplink subframes for the chosen TDD configuration starting from

the current subframe.

PUCCH(Physical Uplink Control Channel)

Uplink Control Information on PUCCH Format 1, 1a, 1b

Format 1 uplink control information (UCI) contains scheduling requests and acknowledgement

responses or retransmission requests (ACK and NACK). The various PUCCH Format 1

messages used are identified by the type of control information they carry and the number of

control bits they require per subframe. The table below shows the three format 1 types as well as

their modulation scheme and the number of information bits they use:

Table 2.7 PUCCH Format types[7]

PUCCH Format Modulation Scheme No. of bits per sub

frame

Type of control

information

1 N/A N/A Scheduling Request

1a BPSK 1 HARQ ACK (1 bit)

1b QPSK 2 HARQ ACK (2 bits)

The bandwidth available during one subframe of a single resource block exceeds that needed for

the control signalling information of a single user terminal. To make efficient use of the available

resources, the resource block can be shared by multiple user terminals. Even though the same RB

is used for the PUCCH Formats 1, 1a and 1b there is no possibility of intra-cell interference if

different cyclic shifts of the same base reference sequence are used. Moreover, for PUCCH

Formats 1, 1a and 1b an extra degree of freedom is provided by applying an orthogonal cover

code.

Format 1

A request for uplink resources can be made by means of the random access channel, however

due to the probability of collisions during high intensity periods an alternative method is

provided using the PUCCH Format 1.

Each UE in the cell is assigned a specific resource index mapping, a resource which can be used

every n-th frame in order to transmit a scheduling request. Therefore if PUCCH energy is

detected the eNodeB will identify it as a scheduling request from the corresponding UE. Since

each UE will have a specific resource allocated there is no probability of a collision. However

the number of available PUCCH resources is reduced.

Format 1a/b

For transmission of the hybrid-ARQ acknowledgement, the HARQ ACK bit(s) are used to

generate a BPSK/QPSK symbol – depending on the number of codewords present. The

modulated symbol is then used to generate the signal to be transmitted in each of the two

PUCCH slots.

Channel coding for UCI HARQ-ACK

The HARQ acknowledgement bits are received from higher layers and depending on the number

of code words present consists of 1- or 2-information bit(s). A positive acknowledgement (ACK)

is encoded as a binary ‘1’ while a negative acknowledgement (NACK) is encoded as a binary

‘0’. The HARQ-ACK bits are then processed as required by the PUCCH.

Channel coding for UCI scheduling request

The scheduling request indication is received from higher layers. 0 information bits are used to

request resources to transmit UL-SCH, however the eNodeB knows when to expect a scheduling

request from each UE within the cell. Therefore if PUCCH energy is detected the eNodeB will

identify it as a scheduling request from the corresponding UE.

Uplink Control Information on PUCCH Format 2

The types of PUCCH Format2 used and their function are listed in the table below along with the

number of bits and modulation scheme used:

Table 2.8 Format 2[7]

PUCCH

format

Modulation

scheme

Number of bits per

sub frame

Type of control

information

2 QPSK 20Channel status

reports

2aQPSK +

BPSK21

Channel status

reports and HARQ-

ACK (1-bit)

2bQPSK +

BPSK22

Channel status

reports and HARQ-

ACK (2-bit)

The processing chain for PUCCH Format 2 includes the following:

Fig2(n) PUCCH[6]

Scrambling: The transport codeword is bit-wise multiplied with an orthogonal sequence and a

UE-specific scrambling sequence to create a sequence of symbols for each codeword.

Modulation mapper : The scrambled codeword undergoes QPSK, 16QAM or 64QAM

modulation to generate complex valued symbols. This choice provides the flexibility to allow the

scheme to maximize the data transmitted depending on the channel conditions.

Resource element mapper: The final stage in the PUSCH processing is to map the symbols to the

allocated physical resource elements. The symbols are mapped in increasing order beginning

with subcarriers, then SC-FDMA symbols. Below is an example of the order of mapping the

output of the precoding stage to the allocated resource blocks.

Sounding Reference Signals (SRS)

The SRS is used by the base station to estimate the quality of the uplink channel for large

bandwidths outside the assigned span to a specific UE. This measurement cannot be obtained

with the DRS since these are always associated to the PUSCH or PUCCH and limited to the UE

allocated bandwidth. Unlike the DRS associated with the physical uplink control and shared

channels the SRS is not necessarily transmitted together with any physical channel. If the SRS is

transmitted with a physical channel then it may stretch over a larger frequency band. The

information provided by the estimates is used to schedule uplink transmissions on resource

blocks of good quality.

SRS can be transmitted as often as every second subframe (2 ms) or as infrequent as every

16th frame (160ms). The SRS are transmitted on the last symbol of the subframe.

Figures 1 and 2 illustrate the two methods of transmitting the SRS:

In wideband mode one single transmission of the SRS covers the bandwidth of interest.

The channel quality estimate is obtained within a single SC-FDMA symbol. However,

under poor channel conditions (deep fade, high path loss) this can result in a poor channel

estimate.

In frequency hopping mode the SRS transmission is split into a series of narrowband

transmissions that will cover the whole bandwidth region of interest; this is the preferred

method under poor channel conditions.

Fig 2(o) Non-frequency hopping SRS[6]

Fig 2(p) Frequency hopping SRS[6]

To avoid overlap of SRS and PUSCH transmissions from different terminals within a cell, all

UEs in the cell are aware in what subframes the SRS may be transmitted by any terminal. In

these frames the last symbol, which the SRS is transmitted on, is not used for PUSCH by any UE

in the cell.

 Physical Uplink Shared Channel (PUSCH)

Resources for the PUSCH are allocated on a sub-frame basis by the UL scheduler. Subcarriers

are allocated in multiples of 12 (PRBs) and may be hopped from sub-frame to sub-frame. The

PUSCH may employ QPSK, 16QAM or 64QAM modulation.

Fig2(q) PUSCH structure[6]

The Physical Uplink Shared Channel (PUSCH) carries uplink shared channel data and control

information. The processing chain for the PUSCH includes scrambling, modulation mapping,

precoding, resource element mapping and Single Carrier – Frequency Division Multiple Access

(SC-FDMA) modulation; this is illustrated by the following processing chain:

Fig 2(r) PUSCH[6]

CHAPTER 3 INTRODUCTION TO SYSTEM VUE

3.1 Introduction to UI

The SystemVue design environment consists of menus, windows, toolbars, and standard editing

options. It is easily integrated with other programs, and you can use it to view multiple

projects,schematics , and simulations at the same time.

SystemVue Getting Started Window

When you first start SystemVue you can select a “blank” template from the “getting started”

dialog. Once the “blank” template is open you will see a window like the one below.

Fig 3.1(a) SystemVue Getting Started Window [10]

Fig 3.1(b) Setting Source Properties [10]

4. Add a generic “Sink” to the schematic. The sink can be found the same way we found the Sine

source. Connect the Sink to the Sine source as show below.

Fig3.1(c) Sine Source setup [10]

Fig3.1(d). SystemVue Design Environment [10]

Build a basic Sine Source and display waveform

1. Find Sine Gen source on Parts Selector (use “Filter By”) using Algorithm Design library

Selecting component from Part Selector

2. Place Source in schematic by left mouse click on source and then left clicking on Schematic.

3. Double click on Sine Gen to open source properties dialog, set frequency as 1 KHz

Fig3.1(e) Selecting component from Part Selector [10]

Fig 3.1(f) Setting Source Properties [10]

4. Add a generic “Sink” to the schematic. The sink can be found the same way we found the Sine

source. Connect the Sink to the Sine source as show below.

Fig 3.1(g). Sine Source setup [10]

5. Examine the Workspace tree before running the simulation. Note that we only have a

“Design1” schematic and a Design1 Analysis in the workspace tree. The “Design1 Analysis”

should be red, indicating a simulation has not been run and there are no simulation results.

6. Double click on the “Design1 Analysis” and set the simulation properties as shown in Fig.

Enter System Sample Rate=10KHz, Number of Samples=256

Fig 3.1(h) Simulation Controller Properties [10]

7. Run Simulation. This can be accomplished by either left mouse clicking on the tool bar “Run

Analysis” button as shown in Fig3.1(f) or by right clicking on the “Design1 Analysis” item on

the workspace tree and select Calculate Now.

Fig 3.1(i) SystemVue [10]

8. The simulation should have now completed without error and workspace tree should now

show a new item for “Design1_Data”. This is the simulation dataset.

9. Open and view the data in the dataset. This is accomplished by double left mouse clicking on

the “Design1_Data” item in the workspace tree then left mouse clicking on the dataset variable

you want to display (should be S2, which is the name of the sink added in the earlier step. If your

sink has a different name then this is the name that will be displayed in the dataset). This should

bring open the dataset table as shown in Fig3.1(h)

Fig3.1(j) Simulation Dataset [10]

10. We can now add the data to a graph by right mouse clicking on the dataset variable we want

to plot, then selecting “Add to Graph” then “New Graph” as per Fig3.1(i) below

Fig3.1(k) Adding measurement to Graph [10]

11. This will now bring open the graphing wizard, left mouse click on the “Time” series type on

the left and “S2” data variable on the right . After clicking the “OK” button twice you should see

the graph . This is just way of plotting data graph in SystemVue. Let’s understand other way of

adding graph for results plot by plotting Spectrum of the S2 sink data.

12. Right click on main folder under Workspace Tree and select Add->Add Graph

Fig3.1(l) Graphing Wizard [10]

Fig 3.1(m) spectrum [10]

Fig3.1(n) Adding Graph from Workspace Tree [10]

Fig3.1(o) Graphing Wizard [10]

13. Select Series Type = Spectrum and select S2 from Select Data. Click OK twice to see

Spectrum graph

Fig 3.1(p) Spectrum graph[10]

Let’s wrap up this exercise by tiling the windows by going to Window->Tile Horizontal so that

we can see all the windows as shown below.

Fig 3.1(q) SystemVue Tile View[10]

CHAPTER 4 :LTE UPLINK DESIGN

4.1 LTE Uplink Transmitter

Fig 4.1(a) LTE Uplink Transmitter Simulation Using System Vue[10]

This  demonstrates a spectrum of an LTE uplink transmitter. The spectrum measurement is

performed using the Spectrum Analyzer part.

The resulting spectrum is shown in the LTE_UL_Tx_Spectrum Measurements graph.

4.2 LTE UL Throughput

Fig 4.2(a) Uplink block diagram for throughput measurement[10]

4.3 Blocks Used In Simulation Using System Vue

1. Random Bit Generator

Fig 4.3(a) Random Bit Generator[10]

This model generates a random bit sequence, in which the probability of a 0 bit is “Prob Of Zero”

and the probability of a 1 bit is “1 – Prob Of Zero.” It includes options such as bit rate, sample

rate, initial delay and burst mode.

Fig4.3(b) Bits parameters[10][6]

2. LTE Uplink Src

This sub network generates LTE uplink baseband signal. LTE uplink transmission is based on

SC-FDMA.

Fig 4.3(c) LTE Uplink Src[10][6]

Screen Shots Showing the parameters used in the simulation

Fig 4.3(d) Uplink Transmitter -System Parameters[10][6]

Fig4(e) LTE_UL_Src_System Parameters

Src_pusch parameters

Fig 4.3(e) Uplink Transmitter-PUSCH parameters[10][7]

Fig 4.3(f) Uplink Transmitter -RB allocation (PUSCH) parameters[10][6]

Fig 4.3(g) Uplink Transmitter –PUCCH Parameters[10][7]

Fig 4.3(h) Uplink Transmitter PRACH parameters[10][8]

Src prach parameters

Fig 4.3(i) Uplink Transmitter SRS parameters[10][6]

Fig 4.3(j)Uplink transmitter Control info parameters[10][6]

Src_control info parameters

Fig 4.3(k) Uplink Transmitter Power parameter [10][6]

3. Complex To Rectangular Converter

The CxToRect model converts input complex values to output real and imaginary values

Fig 4.3(l) Complex to rectangular converter[10]

The CxToRect model converts input complex values to output real and imaginary values

4. Modulator

Fig 4.3(m) Modulator[10]

The Modulator model implements a modulator that can perform amplitude, phase, frequency,

or I/Q modulation. This model reads one sample from its inputs and writes one sample to its

outputs. The LO input(3) is optional. When not connected, an internal LO signal is used at

the frequency FCarrier. When the external LO input is used, it must be a complex envelope

signal with characterization frequency greater than zero. If use with a real signal is needed,

then the LO input to this model can be preceded with an EnvFcChange model that will re-

characterize a real signal to its representation at a specified frequency. The LO input can

include power, phase, and noise variations in the LO signal.

Fig 4.3(n) Modulator parameters[10][7]

5. Oscillator

Fig 4.3(o) Oscillator[10]

Oscillator generates an RF (complex envelope) defined by its carrier frequency and with optional

thermal noise and phase noise. The frequency, power, and phase of the first tone are defined by

the Frequency, Power and Phase parameters, respectively.

6. Spectrum Analyzer

Fig 4.3(p) Spectrum Analyzer[10]

The Spectrum Analyzer model can be used to measure the spectrum of a real baseband or a

complex envelope signal.

Fig 4.3(q) Spectrum Analyzer Parameters[10][7]

Spectrum analyzer results

Fig

4.3(r) Power vs. Frequency graph[10]

7. Noise Density

Fig 4.3(s) Noise density Block[10]

This model adds noise to the input signal. At every execution, it reads 1 sample from the

input and writes 1 sample to the output. If NDensityType is set to Constant noise density,

then the noise added is white Gaussian.The noise density is specified in the NDensity

parameter. Although the units for this parameter are power units the value is interpreted as

power spectral density, that is, power per frequency unit (Hz).The total noise power added to

the input signal is NDensity × BW

1. This model adds noise to the input signal.

2. At every execution, it reads 1 sample from the input and writes 1 sample to the output.

3. If NDensityType is set to Constant noise density, then the noise added is white Gaussian.

The noise density is specified in the NDensity parameter. Although the units for this

parameter are power units the value is interpreted as power spectral density, that is, power

per frequency unit(Hz).The total noise power added to the input signal is: NDensity × BW

Fig 4.3(t) Noise density parameters[10][7]

8. Demodulator

Fig 4.3(u) Demodulator block[10]

The Demodulator model implements a coherent demodulator that can be used to perform

amplitude, phase, frequency, or I/Q demodulation.

This model reads one sample from its input and writes one sample to its outputs. The input

signal must be a complex envelope signal with characterization frequency greater than zero.

Real input signals will result in a simulation error. If use with a real signal is needed, then the

input to this model can be preceded with an EnvFcChange model that will recharacterize a real

signal to its representation at a specified frequency.

Fig4.3(v) Demodulator parameters[10][8]

9. Delay

Fig 4.3(w) Delay block[10]

1. The Delay model introduces a delay of N samples to the input signal.

2. For every input, there is one output.

Fig 4.3(x) Delay parameters[10][9]

10. UL Receiver

Fig 4.3(y) LTE UL Receiver[10]

This subnetwork constructs 3GPP LTE uplink baseband receiver .In this receiver, the data type

in most input/output ports are matrix which should be column vector (i.e the matrix size should

be N × 1,N is the size of vector)

Fig 4.3(z)UL receiver system parameters[10][9]

Fig 4.3(aa) UL receiver PUSCH parameters[10][9]

Fig 4.3(bb) UL receiver RB allocation(PUSCH) parameters[10][9]

Fig 4.3(cc)UL receiver PUCCH Parameters[10][9]

Fig 4.3(dd) UL receiver PRACH parameters[10][8]

Fig 4.3(ee) UL receiver SRS parameters[10][8]

Fig 4.3(ee) UL receiver

Fig 4.3(ff) UL Receiver Control info Parameters[10][9]

Uplink receiver control info parameters

Fig 4.3(gg) UL Receiver Rx algorithm parameters[10][8]

11. LTE Throughput

Fig 4.3(hh) LTE Through put block diagram[10][9]

This model performs the averaged closed-loop HARQ throughput over subframes from

Subframe#SubframeStart to Subframe#SubframeStop for both PDSCH and PUSCH.

Fig 4.3(ii) LTE Throughput parameters[10][9]

Throughput vs SNR

Fig 4.3(jj) LTE UL AWGN HARQ THROUGHPUT[10][9]

RED:1/3 TURBOCODING QPSK,GREEN:3/4 TURBOCODING 16 QAM,BLUE:5/6 TURBO CODING 64 QAM

12. BER Block

Fig 4.3(kk) BER Block[10]

The BER_FER model can be used to measure the BER (bit error rate) and FER (frame error rate)

of a system. In some systems, FER is referred to as PER (packet error rate) or BLER (block error

rate). The input signals to the reference (REF) and test (TEST) inputs must be bit streams. The

bit streams must be synchronized, otherwise the BER/FER estimates are wrong.

Fig 4.3(ll) BER Parameters[10][9]

Fig 4.3(ll) BER properties

Fig 4.3(mm) BER Parameters[10][8]

4.4 BER Analysis

4.4 LTE UL BER Measurement

Fig 4.4(a)UL BER Measurement Block Diagram[10]

BER vs SNR

Fig 4.4(b) BER vs. SNR graph[10]

RED: QPSK,GREEN:16 QAM,BLUE: 64 QAM

OBSERVATIONS AND RESULT

QPSK and 16 QAM

In this project uplink part of the LTE physical layer is implemented using System Vue . First the

modulation techniques QPSK and 16 QAM was implemented and its constellation diagrams

were obtained. The pattern of the input bits sent and the output bits received after demodulation

were found to be the same. Thus QPSK and 16 QAM was successfully implemented and its

results were analyzed.

Uplink Spectrum

The LTE uplink physical layer was designed and characteristics of the spectrum were observed

for different noise density values in the spectrum analyzer . A plot of Power vs. Frequency was

obtained and maximum power of -10 dbm was found at the carrier frequency of 2GHz.

Uplink Throughput

The throughput for the LTE Uplink physical layer was observed using the LTE Throughput

block . A graph was plotted between throughput and SNR .The SNR was found to be maximum

for 64 QAM and minimum for QPSK.

For QPSK: A throughput of 27 bits/sec was obtained for an SNR of 0.2 db. The throughput was

found to be increasing with increase in SNR.A maximum throughput of 90 bits/sec was obtained

for an SNR value of 1db.

For 16 QAM: A throughput of 50bits/sec was obtained for an SNR of 10db.The throughput was

found to be increasing for increase in SNR. A maximum throughput of 100bits/sec was obtained

for an SNR value of 14db.

For 64 QAM: A throughput of 51bits/sec was obtained for an SNR of 21db. In this case also the

throughput was found to be increasing with increase in SNR. A maximum throughput of

100bits/sec was obtained for an SNR of 23.6 db.

Uplink BER

Then the Uplink BER was found using the BER block found in System Vue software. A graph

between BER and SNR was plotted for QPSK,16 QAM and 64 QAM.

For QPSK: A BER of .12 was obtained for an SNR of .24 db. The BER was found to be

decreasing with increase in SNR. A very low BER value of 1e-6 was found for an SNR value

of .48db.

For 16 QAM: A BER of .091 was obtained for an SNR of 9.7db. The BER was found to be

decreasing with increase in SNR.A minimum BER value of 1e-9 was obtained for an SNR value

of 13.5db.

For 64 QAM: A BER value of .003 was obtained for an SNR value of 21.1db. The BER was

found to be decreasing with increase in SNR.A minimum BER value of 6e-5 was obtained for an

SNR value of 24db.

CONCLUSION

LTE supports downlink and uplink peak data rates of 100 Mbps and 50 Mbps respectively with

20 MHz bandwidth. The uplink coverage is based on SCFDMA that promises increased uplink

coverage due to low peak to average power ratio relative to OFDMA.

SystemVue which is a focused electronic design automation (EDA) environment for electronic

system-level (ESL) design was used for implementing the design.

The constellation diagrams obtained for both QPSK and QAM were matching with the expected

results. The input bits transmitted were received successfully .

The Uplink physical layer was simulated and various parameters such as the Spectrum,

Throughput and BER was analyzed .When we go from QPSK to 16 QAM to 64 QAM, the

throughput increases and BER decreases with increase in SNR as shown in figure Fig 4.3jj and

Fig 4.4(b) respectively.

This project can be further extended by carrying out simulations for LTE advanced by

incorporating MIMO into the present design. The various parameters like data rate throughput,

BER, Transmission power etc can be calculated for LTE advanced. Furthermore the analyzer can

be used for the physical analysis of the signals for the given parameters .

REFERENCES

[1] 3GPP TSG RAN TR 25.848 v4.0.0, Physical Layer Aspects of TRA High Speed

Downlink Packet Access,July 2008

[2] IEEE Std 802.16e-2005, Air Interface for Fixed and Mobile Broadband Wireless Access

Systems,2009

[3] 3GPP TSG RAN TR 25.913 v7.3.0, Requirements for Evolved Universal Terrestrial

Radio Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN),2008

[4] Upena Dalal,”Wideband Modulation Techniques” in Wireless Communication, Second

Edition, Oxford University Press, Delhi, India, 2009

[5] Hyung G. Myung ,Junsung Lim and david J.Goodman,”Single Carrier FDMA for uplink

wireless Transmission” IEEE paper,Sept 2006

[6] 3GPP TS 36.211 V8.9.0,”Physical channels and modulations”,December 2009

[7] 3GPP TS 36.213 V8.8.0,”Physical Layer Procedures”,September 2009

[8] 3GPP TS 36.101 V8.6.0 , “User Equipment radio transmission and reception,September

2009

[9]TR 25.814 “ Physical layer aspects for evolved universal Terrestrial radio

access ,V7.0.0,June,2006

[10] System Vue 2011 Electronic Design Software

ACRONYMS

LTE: Long term evolution

UE: User Equipment

MME: Mobile Management Entity

eNB : E-UTRAN Node B

PDCP: Packet Data Convergence Protocol

RLC: Radio Link Control

RRC: Radio Resource Control

MAC: Medium Access Control

E-UTRAN: Evolved Universal Terrestrial Radio Access Network

PDU: Protocol Data Unit

PCCH: Paging Control Channel

PCH: Paging Channel

PDN: Packet Data Network

P-GW: PDN Gateway

QPSK: Quadrature Phase-Shift Keying

OFDM: Orthogonal Frequency Division Multiplexing

SC-FDMA: Single-Carrier Frequency Division Multiple Access

SCFDM: Single-Carrier Frequency Division Multiplexing

ISI: Inter-Symbol Interference

CP: Cyclic Prefix

PAPR: Peak-to-Average Power Ratio

IFFT: Inverse Fast Fourier Transform

DFT: Discrete Fourier Transform

FFT: Fast Fourier Transform

TDD: Time Duplex Division

FDD: Frequency Duplex Division

QPSK Modulation and Demodulation

Fig 3.2(a) Qpsk block

Fig a) QPSK block [10]

Fig b) Bits[10]

APPENDIX

Fig c) QPSK symbol mapping[10]

Fig d) Bits QPSK[10]

Fig e) Constellation QPSK [10]

Fig f) QPSK demapper block diagram [10]

Fig g) Qpsk demapper[10]

Fig h) bits after demapping[10]

16 QAM Modulation

Fig i) Bits[10]

Fig j) 16 QAM mapper output [10]

Fig k) 16 qam block diagram [10]

Fig l) Bits graph

Fig m) 1000 Bits spectrum

Fig n) Qam mapper output

Fig o) 16 Qam Spectrum[10]

Fig p) 16 QAM Constellation[10]

QPSK BER Analysis

Step1: QPSK Baseband Source Design

Using the knowledge designers have gained till now, arrange following blocks on the schematic

from Algorithm Design library for baseband QPSK signal generation. In this case schematic

name was modified to be QPSK Source instead of default Design1.

Fig

q) Baseband QPSK signal generation [10]

Fig r) Simulation Controller Settings[10]

Run simulation and add a graph on the workspace tree. For results, select Series Type =

Constellation and select sink name (e.g. S1 as per Fig1) and change X and Y-axis to be Min=-1.2

and Max=1.2

Fig s). Plotting QPSK Constellation Fig t) Graph Properties [10]

Once done, Constellation graph as below should be visible:

Fig u). QPSK Constellation Graph[10]

Step2: QPSK Modulator Design

Basic building blocks of a QPSK modulator can be arranged as below from Algorithm Design

library.

Fig v). QPSK Modulator Design[10]

Root Raised Cosine Filter:

Place Filter Design component from library and set the following properties in the Filter

Designers window:

Response Type = Lowpass

Sample Rate= Sample_Rate (internal variable where SVue reads the sample rate from Simulation

Controller)

RollOff=0.35

Square Root=YES

Interpolation=8

IQ Modulator:

Set the Frequency = 70E6 Hz

Amp Sensitivity= sqrt(2) (This will provide 13dBm power at the modulator output)

Fig w) Filter Designer Window with Filter Response Graphs [10]

Finished QPSK modulator should look as below with all blocks integrated.

Fig x) QPSK Modulator Design [10]

Simulation Controller:

Simulation controller for QPSK modulator can be set as per fig below

Fig y) data flow [10]

Simulation Results:

Run simulation and plot Spectrum of QPSK Modulator .

Fig z). QPSK IF Spectrum [10]

Step3: QPSK Demodulator

Similar to modulator design, use following blocks to design QPSK demodulator in SystemVue.

RRC filter to modified to have Interpolation=1 and set Decimation=8 (same no. as used in QPSK

modulator), rest of the properties of the filter will be kept same as in modulator design part.

Fig aa). QPSK Demod Design [10]

Step4: AWGN Channel

Place AddNDensity component from Algorithm Design and we can define few equations to set

the Noise Density of the AWGN Channel based on Eb/No so that we can sweep the value in

order to compute BER later. Using Equations utility in SystemVue type the equations below to

calculate the NDensity which can be then used in AWGN block on the system level design

Fig bb). AWGN Channel Component [10]

Step5: QPSK System Design

With all these individual blocks already designed end-2-end system can be designed as shown below:

Fig cc). QPSK System Design Schematic [10]

Simulation Controller:

Setup the simulation controller as below and run simulation to plot Transmitter and Receiver

spectrum to observe the data.

Fig dd). Transmitter Spectrum Fig ee). Receiver Input Spectrum (after AWGN)

Understanding BER:

In digital transmission, the bit error rate or bit error ratio (BER) is the number of received bits

that have been altered due to noise, interference and distortion, divided by the total number of

transferred bits during a studied time interval. BER is a unitless performance measure, often

expressed as a percentage number.

As an example, assume this transmitted bit sequence:

0 1 1 0 0 0 1 0 1 1,

And,

following is the received bit sequence:

0 0 1 0 1 0 1 0 0 1,

The BER is in this case is 3 incorrect bits (underlined) divided by 10 transferred bits, resulting in a

BER of 0.3 or 30%.

The bit error probability pe is the expectation value of the BER. The BER can be considered as an

approximate estimate of the bit error probability. This estimate is accurate for a long studied time

interval and a high number of bit errors.

In a noisy channel, the BER is often expressed as a function of the normalized carrier-to-noise ratio

measure denoted Eb/N0, (energy per bit to noise power spectral density ratio), or Es/N0 (energy per

modulation symbol to noise spectral density).

For example, in the case of QPSK modulation and AWGN channel, the BER as function of the

Eb/N0 is given by: BER = 1 / 2erfc(Eb / N0).

Designers usually plot the BER curves to describe the functionality of a digital communication

system. In optical communication, BER (dB) vs. Received Power (dBm) is usually used; while in

wireless communication, BER (dB) vs. SNR (dB) is used.

Fig ff) BER [10]

Step6: BER Simulation for QPSK System

For proper BER simulation, reference and test signals have to time synchronized. SystemVue

offers Cross Correlation function to find out the delay between the 2 signals and we can use the

same in our design. In order to find delay using Cross Correlation function in ADS we can use 2

sinks: 1st sink after Gray Encoder block and 2nd one after QPSK Demapper as shown below

Simulation controller is setup pretty much like previous step. Run simulation to plot the Cross

Correlation as shown below by selecting Series Type = Cross Correlatio

Fig gg) QPSK System Setup for Cross Correlation

Fig

hh). Setting up Cross Correlation Fig ii). Cross Correlation graph [10]

From the cross correlation graph we can calculate the delay required to synchronize the reference

Tx and receiver test data. Ideally, the cross correlation peak should appear at the simulation

sample (8191 in our case) else the difference between correlation peak and no of simulation

samples outlines the delay required to synchronize the data.

Delay required = No. of Simulation samples – Cross Correlation Peak

Based on our simulation, we can find delay as below:

Delay required = 8191-8175 = 16

Fig jj). QPSK BER Schematic with Delay block Fig kk)Cross Correlation Graph [10]

In order to synchronize delay between Tx_Ref and Rx_Test, insert Delay component with 16

samples delay as shown. Run the simulation to ensure cross correlation peak appears at 8191

which is equal to simulation sample.

As we can observe the “Ref” and “Test” are now synchronized properly hence we can perform

BER analysis. Insert BER sink onto schematic and connect Ref and Test pins to transmitter bit

sequence and receiver output respectively as shown below

Fig ll). QPSK BER Schematic with Delay and BER Sink [10]

Double click on the BER sink and change the StartStopOption=Samples as shown below

Fig mm) BER Sink Properties [10]