1.Explain 3G?

=>Third generation (3G) wireless networks will offer faster data transfer rates than current networks. The first generation of wireless (1G) was analog cellular. The second generation (2G) is digital cellular, featuring integrated voice and data communications. So-called 2.5G networks offer incremental speed increases. 3G networks will offer dramatically improved data transfer rates, enabling new

2.What is 3GPP?

=>The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, known as the Organizational Partners. The initial scope of 3GPP was to make a globally applicable third-generation (3G) mobile phone system specification based on evolved Global System for Mobile Communications (GSM) specifications within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). The scope was later enlarged[1] to include the development and maintenance of:3. What is Generic Connection Framework (GCF )

=>GCF was originally defined to rely on the J2ME platform's Connected Limited Device Configuration (CLDC), version 1.0, because the familiar J2SE java.net and java.io APIs were considered too large to fit into the constrained memory available in mobile devices. Today you can find the GCF not only in CLDC-based profiles, such as the Mobile Information Device Profile (MIDP) and the Information Module Profile (IMP), but also in Connected Device Configuration (CDC)-based profiles, such as the Foundation Profile and its relatives the Personal Basis Profile and Personal Profile - and now, with JSR 197, on the J2SE platform as well. You can also find the GCF in an increasing number of optional packages, including those that provide Bluetooth support and access to files and smart cards. A Generic Approach to ConnectivityThe GCF is a straightforward hierarchy of interfaces and classes to create connections (such as HTTP, datagram, or streams) and perform I/O. As the name implies, the GCF provides a generic approach to connectivity. It is generic because it provides a common foundation API for all the basic connection types - for packet-based (data blocks) and stream-based (contiguous or sequence of data) input and output. This generalization is possible through the use of: An interface hierarchy that is extensible A connection factory Standard Uniform Resource Locators (URLs) to indicate the connection types to createThe base CLDC 1.0 GCF is illustrated in Figure 1: Figure 1: The CLDC Generic Connection Framework Interface Hierarchy and Related Classes(Click to Enlarge)

At the top of the interface hierarchy is the Connection interface, the most basic type of connection - all other connection types extend Connection. As you move down the hierarchy, connections become more complex and functional. For packet-based I/O the GCF defines DatagramConnection, and for stream-based I/O InputConnection, OutputConnection, StreamConnection, and ContentConnection. Note how StreamConnection extends both InputConnection and OutputConnection, making it a two-way stream connection. At the bottom of the hierarchy is the ContentConnection, a special type of StreamConnection that provides content-specific information such as data length, content type, and data encoding. Finally, the StreamConnectionNotifier enables an application to wait for incoming stream connections, asynchronously. In addition to the connection hierarchy, the GCF provides the Connector class, which is the connection factory, and the ConnectionNotFoundException that is used to indicate when a connection type can't be created. For packet-based connections, the GCF defines the Datagram interface, which represents a datagram packet. Not defined by the GCF but related to it are InputStream, DataInputStream, OutputStream, and DataOutputStream, familiar to users of the java.io package, for stream-based connections. The GCF is so practical and flexible that it is used across J2ME profiles and optional packages, and now on the J2SE platform as well. The relationship between the base CLDC GCF and the GCF for profiles and platforms is illustrated in Figure 2: Figure 2: Relationships Between Base GCF and GCF for MIDP, FP, and J2SE

MIDP and the Foundation Profile extend the base CLDC 1.0 GCF, while the J2SE version of GCF comes directly from the GCF for Foundation Profile. The GCF - An Extensible Framework for Not-So-Generic ConnectionsThe GCF, which is defined in the javax.microedition.io package, defines a lowest-common-denominator framework - a pretty high-level generalization. It is up to profiles and optional packages to extend the base GCF, and define and provide the actual low-level connection types, and the network and I/O protocol implementations. When we look closely at a typical connection and its related I/O protocol we see that these are not generic. For example, HTTP connections have peculiarities that reflect their request/response nature, while a Bluetooth connection exposes the dynamic (ad hoc) nature of its protocol, and a socket connection exposes low-level networking methods for timeouts and keep-alive options. Fortunately, the GCF is extensible. New connection types, which are defined and standardized via the Java Community Process (JCP), can be added by defining a new Connection subtype and supporting classes, providing a Connector factory class that supports the newly defined connection type, and defining a new URL scheme that identifies the new connection type. Figure 3 illustrates how a particular profile or optional package could extend the GCF: 4. Define FDMA TDMA,CDMA

=>CDMA (Code-Division Multiple Access) refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.=>FDMA (frequency division multiple access) is the division of the frequency band allocated for wireless cellular telephone communication into 30 channels, each of which can carry a voice conversation or, with digital service, carry digital data. FDMA is a basic technology in the analog Advanced Mobile Phone Service (AMPS), the most widely-installed cellular phone system installed in North America. With FDMA, each channel can be assigned to only one user at a time. FDMA is also used in the Total Access Communication System (TACS).=>TDMA (time division multiple access) is a technology used in digital cellular telephone communication that divides each cellular channel into three time slots in order to increase the amount of data that can be carried.

5. Difference between CDMA and WCDMA

=>CDMA is a spread spectrum multiple access technique. In CDMA a locally generated code runs at a much higher rate than the data to be transmitted. Data for transmission is simply logically XOR (exclusive OR) added with the faster code.

W-CDMA is a wideband spread-spectrum mobile air interface that utilizes the direct-sequence spread spectrum method of asynchronous code division multiple access to achieve higher speeds and support more users compared to the implementation of time division multiplexing (TDMA) used by 2G GSM networks.

6. Difference between 3G and 2G

=>2G is the GSM specification used to enhance the mobile whereas 3G communications is used for mobile users to have communication over voice with added Multimedia Applications with proportionate speed as well..,http://bit.ly/ouNC5C

First, about cellular generations. Having worked in the industry for a while, I have a narrower view what 1G, 2G, 3G, 4G, etc. mean. First 1G service was based on a TDM voice infrastructure -- built around class x switches and 64 kbps slots. It had data, but circuit switched over a 64Kpbs voice bearer.

Second, 2G service had the same switched TDM backbone, but added a true Data Bearer and a digital voice bearer. Data rates were still limited to the max 64kbps of a single time slot.

2.5G added a packet bearer to the mix, still limited to 64kbps slots.

Third generation (3G) changed the backbone slightly to allow a full T1 or E1 or J1 to be consumed by a data sub-scriber, but is still based on an ISDN style backbone. Sure you have packet switched data, but its carried over a traditional TDM backbone. There still a circuit voice backbone and while the data rates are high enough for VoIP, the latency of the data service is to great to base all of the "bearer services" on it, so you still have circuit voice, circuit data and packet data bearers.

7. What is UMTS?

=>Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular technology for networks based on the GSM standard. Developed by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology. UMTS employs wideband code division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators. UMTS specifies a complete network system, covering the radio access network (UMTS Terrestrial Radio Access Network, or UTRAN), the core network (Mobile Application Part, or MAP) and the authentication of users via SIM cards (Subscriber Identity Module).The technology described in UMTS is sometimes also referred to as Freedom of Mobile Multimedia Access (FOMA) or 3GSM.[1]Unlike EDGE (IMT Single-Carrier, based on GSM) and CDMA2000 (IMT Multi-Carrier), UMTS requires new base stations and new frequency allocations

8. Difference between GERAN and UTRAN

9. what is Wcdma technology

=>Support two basic modes: FDD and TDD modesHigh chip rate (3.84 Mcps) and data rates (up to 2 Mbps)Employs coherent detection on uplink and downlink based on the use of pilot symbolsInter-cell asynchronous operationFast adaptive power control in the downlink based on SIRProvision of multirateservicesPacket dataSeamless inter-frequency handoverIntersystem handovers, e.g. between GSM and WCDMASupport for advanced technologies like multiuserdetection (MUD) and smart adaptive antennas

10. 3GPP Specification for every layer

11. Benefit of spreading

WCDMA Spreading

TDD WCDMA uses spreading factors 4 - 512 to spread the base band data over ~5MHz band. Spreading factor in dBs indicates the process gain. Spreading factor 128 = 21 dB process gain). Interference margin is calculated from that:

Interference Margin = Process Gain - (Required SNR + System Losses)1. Required Signal to Noise Ration is typically about 5 dB 2. System losses are defined as losses in receiver path. System losses are typically 4 - 6 dBs

12. Benefit of scrambling

13. What happen when Mobile switch on(Cell Search Procedure)

Cell search procedure

During the cell search, the UE searches for a cell and determines the downlink scrambling code and frame synchronisation of that cell. The cell search is typically carried out in three steps:

Step 1: Slot synchronisation

During the first step of the cell search procedure the UE uses the SCH's primary synchronisation code to acquire slot synchronisation to a cell. This is typically done with a single matched filter (or any similar device) matched to the primary synchronisation code which is common to all cells. The slot timing of the cell can be obtained by detecting peaks in the matched filter output.

Step 2: Frame synchronisation and code-group identification

During the second step of the cell search procedure, the UE uses the SCH's secondary synchronisation code to find frame synchronisation and identify the code group of the cell found in the first step. This is done by correlating the received signal with all possible secondary synchronisation code sequences, and identifying the maximum correlation value. Since the cyclic shifts of the sequences are unique the code group as well as the frame synchronisation is determined.

Step 3: Scrambling-code identification

During the third and last step of the cell search procedure, the UE determines the exact primary scrambling code used by the found cell. The primary scrambling code is typically identified through symbol-by-symbol correlation over the CPICH with all codes within the code group identified in the second step. After the primary scrambling code has been identified, the Primary CCPCH can be detected and the system- and cell specific BCH information can be read.If the UE has received information about which scrambling codes to search for, steps 2 and 3 above can be simplified

3. 4. 5. Structure of synchronization channel6.

The Synchronisation Channel (SCH) is a downlink signal used for cell search. The SCH consists of two sub channels, the Primary and Secondary SCH. The 10 ms radio frames of the Primary and Secondary SCH are divided into 15 slots, each of length 2560 chips. Picture above illustrates the structure of the SCH radio frame.

The Primary SCH consists of a modulated code of length 256 chips, the primary synchronization code (PSC) is transmitted once every slot. The PSC is the same for every cell in the system.

The Secondary SCH consists of repeatedly transmitting a length 15 sequence of modulated codes of length 256 chips, the Secondary Synchronisation Codes (SSC), transmitted in parallel with the Primary SCH. The SSC is denoted csi,k in figure 20, where i = 0, 1, , 63 is the number of the scrambling code group, and k = 0, 1, , 14 is the slot number. Each SSC is chosen from a set of 16 different codes of length 256. This sequence on the Secondary SCH indicates which of the code groups the cell's downlink scrambling code belongs to.

Summary of the process:Channel Synchronisation acquired Note

PrimarySCH Chip, Slot, SymbolSynchronisation 256 chipsThe same in all cells

Secondary SCH Frame Synchronisation,Code Group (one of 64) 15-code sequence of secondary synchronisation codes.There are 16 secondary synchronisation codes.There are 64 S-SCH sequences corresponding to the 64 scrambling code groups256 chips, different for different cells and slot intervals

Common Pilot CH Scrambling code(one of 8) To find the primary scrambling code from common pilot CH

PCCPCH *) Super Frame Synchronisation,BCCH info Fixed 30 kbps channel27 kbps ratespreading factor 256

SCCPCH **) Carries FACH and PCH channelsVariable bit rate

7. *) Primary Common Control Physical Channel**) Secondary Common Control Physical Channel

Further reading: 3GPP TS 25.211 25.213

14. Mode of operations of RLC

Radio Interface Architecture

Larger pieces of data are not suitable to be sent over the air interface where bit faults are common. Smaller pieces can be individually retransmitted Retransmissions on higher Protocol level take too long time. Therefore it is better to have the retransmission as close to the biggest trouble source (i.e. The radio interface)RLC main functionalities Segmentation and reassembly. Concatenation. Padding. Transfer of user data. Error correction. In-sequence delivery of upper layer PDUs. Duplicate detection. Flow control. Sequence number check. Protocol error detection and recovery. Ciphering. SDU discard. Out of sequence SDU delivery. Duplicate avoidance and reorderingData flow between layersData flow for transparent RLC

Data flow for non-transparent RLC

15. Functions of RRC LayerRadio Resource ControlThe Radio Resource Control (RRC) protocol belongs to the UMTS WCDMA protocol stack and handles the control plane signalling of Layer 3 between the UEs (User Equipment) and the UTRAN. It includes: Functions for connection establishment and release, Broadcast of system information, Radio bearer establishment/reconfiguration and release, RRC connection mobility procedures, Paging notification and release, Outer loop power control.

16. Functions of different MAC entities.

MAC-b is the MAC entity that handles the following transport channels: 1. broadcast channel (BCH) MAC-c/sh/m, is the MAC entity that handles the following transport channels: 1. paging channel (PCH) 2. forward access channel (FACH) 3. random access channel (RACH) 4. downlink shared channel (DSCH). The DSCH exists only in TDD mode. 5. uplink shared channel (USCH)MAC-d is the MAC entity that handles the following transport channels: 1. dedicated transport channel (DCH) MAC-hs is the MAC entity that handles the following transport channels: 1. high speed downlink shared channel (HS-DSCH

MAC-m is the MAC entity that handles the following transport channels: 1. forward access channel (FACH). MAC-e/es are the MAC entities that handle the following transport channels: 1. enhanced dedicated transport channel (E-DCH

17. Information of all the system informationSystem information comes in System Information Blocks (SIB) (which itself is part of RRC SYSTEM INFORMATION message). SIBs can be segmented or segments can be packed in one message. One SIB cater to particular type of information like SIB type 4 will have Cell identity, Cell selection and re-selection information etc. There are 18 types of SIBs ( 1 till 7 and 11 till 18 - 8/9/10 are not applicable to R5). SIBs are broadcast regularly, but with different repetition rate. System information is actually organised as tree with Master Information Black (MIB) as root. MIB contain references to SIB and (1 or 2) Scheduling blocks (SB). Scheduling blocks contain references to other SIBs as shown below:

Why do we need Scheduling blocks ? Once UE has camped on a network and read all required system information, it may not be needed to read this information again and again. In fact, for registered UEs, any change in system information is indicated by network in paging message or RRC SYSTEM INFORMATION CHANGE INDICATION message sent on S-CCPCH/FACH channel (depending on RRC state). This way, UE power is saved. In addition, by having tree structure and scheduling blocks for system information, UE need not listen to P-CCPCH, but can (sleep and) listen to (changed or required) SIB at scheduled time. This way, further power saving is achieved. As MIB is the root, MIB is scheduled at fixed intervals. During cell search, UE must first look for MIB and then proceed accordingly. In next article we will continue with RRC states. References: UMTS by Sanchez and Thioune, and WCDMA for UMTS by Holma and Toskala.

18. Channels and its mapping with different layersUTRA Channels

UTRA FDD radio interface has logical channels, which are mapped to transport channels, which are again mapped to physical channels. Logical to Transport channel conversion happens in Medium Access Control (MAC) layer, which is a lower sublayer in Data Link Layer (Layer 2).

Logical Channels:Broadcast Control Channel (BCCH), Downlink (DL)Paging Control Channel (PCCH), DLDedicated Control Channel (DCCH), UL/DLCommon Control Channel (CCCH), UL/DLDedicated Traffic Channel (DTCH), UL/DLCommon Traffic Channel (CTCH), Unidirectional (one to many)

Transport Channels:Dedicated Transport Channel (DCH), UL/DL, mapped to DCCH and DTCHBroadcast Channel (BCH), DL, mapped to BCCHForward Access Channel (FACH), DL, mapped to BCCH, CCCH, CTCH, DCCH and DTCHPaging Channel (PCH), DL, mapped to PCCHRandom Access Channel (RACH), UL, mapped to CCCH, DCCH and DTCHUplink Common Packet Channel (CPCH), UL, mapped to DCCH and DTCHDownlink Shared Channel (DSCH), DL, mapped to DCCH and DTCH

Physical Channels:Primary Common Control Physical Channel (PCCPCH), mapped to BCHSecondary Common Control Physical Channel (SCCPCH), mapped to FACH, PCHPhysical Random Access Channel (PRACH), mapped to RACHDedicated Physical Data Channel (DPDCH), mapped to DCHDedicated Physical Control Channel (DPCCH), mapped to DCHPhysical Downlink Shared Channel (PDSCH), mapped to DSCHPhysical Common Packet Channel (PCPCH), mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision Detection/Channel Assignment Indication Channel (CD/CA-ICH)

19. What is channel20. Role and architecture of RNC21. How scrambling code is calculated

Calculating Downlink Scramble CodesThe N7600A Signal Studio software implements scrambling codes for downlink channels in compliance with 3GPP W-CDMA specifications. This is done through the use of Scramble Code, Scramble Type, and Scramble Offset fields in the downlink channel parameter selection table. These fields are linked so that an entry to any field affects the actual scramble code.

The Primary Scrambling Code for all channels is set in the downlink carrier parameter selection table.

To better understand the relationship, please refer to the following formula.n = (16 x i) + k + mn = scramble codeRange: 0 to 511

i = scramble code field inputPrimary Range: 0 to 511Secondary Range: 0 to 511

k = scramble offset field inputRange: 0 to 15

m = scramble type field inputStandard: adds 0Right Alternate: adds16384Left Alternate: adds 8192

The Scramble Code field has two sets: primary and secondary, each with a field range of 0 through 511. The primary and secondary sets are determined by the Scramble Offset field. If the Scramble Offset field is zero, then the scramble code is in the primary set. Any non-zero entry enables the secondary set. The Scramble Offset field has a range of 0 through 15.The Scramble Type field has three modes: Standard, Right Alternate, and Left Alternate. The standard scramble type has a value of zero and does not contribute to the scramble code. Selecting the right alternate adds 16384 to the actual scramble code, whereas the left alternate adds 8192.Scramble Codes with Standard Scramble TypeA primary scramble code is the product of the Scramble Code field entry and 16. Therefore, the primary scramble code set contains all multiples of 16 from 0 through 8176.A secondary scramble code is the sum of the non-zero Scramble Offset field entry and the primary scramble code. The secondary scramble code set uses the numbers in between the multiples of 16.Thus, all numbers from 0 through 8191 are available for scramble codes when using the standard scramble type. Refer to the following for examples of scramble codes generated with the primary and secondary sets:n = (16 x i) + k + mn = scramble code

i = scramble code field input

k = scramble offset field input

m = scramble type field input

Primary SetSecondary Set

i = 6i = 8

k = 0k = 7

m = 0m = 0

n = 96n = 135

Scramble Codes with Right and Left Alternate Scramble TypesRecalling that right alternate adds 16384 to the scramble code and left alternate adds 8192, refer to the following examples of scramble codes generated with the right alternate and left alternate scramble types:n = (16 x i) + k + mn = scramble code

i = scramble code field input

k = scramble offset field input

m = scramble type field input

Primary Set + Left AlternateSecondary Set + Right Alternate

i = 6i = 8

k = 0k = 7

m = 8192m = 16384

n = 8288n = 16519

22. What are signaling radio bearer and there specific uses

Signalling Radio Bearer (SRB) ParametersLast updated: January 15, 2009A Signalling Radio Bearer (SRB) is a radio bearer that carries DCCH signalling data. An SRB is used during connection establishment to establish the Radio Access Bearers (RABs) and then also to deliver signalling while on the connection (for example, to perform a handover, reconfiguration or release).The test set supports three SRBs: 3.4k DCCH - see 3GPP TS 34.108 6.10.2.4.1.2 13.6k DCCH - see 3GPP TS 34.108 6.10.2.4.1.3 2.2k DCCH - this signalling radio bearer has the following properties: 2.2k DCCH SRB Properties

Transport Channel Parameters:

TrCH TypeDCH (DCCH)

TB size100

TF 00 x 100

TF 11 x 100

TTI (ms)40

Coding TypeConv, 1/3

CRC12 bit

Downlink Physical Channel:

DTX Positionn/a

TFCIused

Slot Structure5

SF256

Uplink Physical Channel:

Min Spreading Factor256

DPCCH slot format0

TFCIused

During connection establishment, an RRC Connection Setup procedure establishes the SRB. The SRB is then used to send all subsequent signalling to start the desired service and establish the radio bearers for the service (see Call Processing Ladder Diagrams ). Establishment of the radio bearers is achieved using an RB Setup procedure. The RB Setup procedure configures how both the DCCH and DTCH will be carried on the radio bearers.The RB Setup may specify a different DCCH RLC block size from the DCCH RLC block size that was being used when only an SRB was present. For example, the DCCH RLC block size for the default 3.4k DCCH SRB is 144 bits, but all RMCs (Reference Measurement Channels) call for a DCCH RLC block size of 96 bits. If the RB Setup specifies a change in the DCCH RLC block size from the stand-alone SRB configuration, the UE and network must change the DCCH RLC block size and then perform an RLC Re-establishment procedure to reset the RLC buffers. If your UE does not support changing the DCCH RLC block size during connection setup, you must establish the call using an SRB with a DCCH RLC block size that is equal to the DCCH RLC block size defined for the service you wish to establish.SRB DCCH RLC Block Size

SRBDCCH RLC Block Size

2.2k DCCH96 bits

3.4k DCCH144 bits

13.6k DCCH144 bits

RAB DCCH RLC Block Size

RABDCCH RLC Block Size

All RMCs (Reference Measurement Channels)See Radio Bearer Test Mode and Packet Switched Data 96 bits

All PS Data RABs (Radio Access Bearers)See Packet Switched Data 144 bits

All CS RABsSee Circuit Switched Data Service 144 bits

All AMR Radio Access BearersSee AMR Setup 144 bits

If your UE supports changing RLC block size during connection setup, but does not support the RLC Re-establishment procedure, you must either use an SRB that matches your desired service as explained above, or set RLC Reestablish to Off .To set the channelization code for the signalling radio bearers, see Downlink Channel Codes .Manual operation: Select SRB Parameters ( F12 on Call Parms 2 of 3 ).SRB Configuration ControlSome UEs can only move to an RMC at the RB Setup phase of the connection if they were assigned to a 2.2k DCCH SRB (i.e. some UEs do not support changing the DCCH RLC block size during connection setup). These same UEs would require a 3.4k DCCH SRB be assigned before establishing any other service type, such as AMR Radio Access Bearer, CS data or PS data. The SRB Configuration Control = Auto setting can be used to automatically change which SRB the UE is assigned based on the anticipated service.If SRB Configuration Control is set to Auto , the test set assigns the UE to a 2.2k DCCH SRB if call status is Paging and Paging Service Type is set to RB Test Mode . Otherwise, the test set assigns the UE to a 3.4k SRB.If SRB Configuration Control is set to Manual , the test set assigns the UE to the SRB specified by the Manual SRB Configuration setting.Note, if your UE does not support changing RLC block size during connection setup and you wish to establish a 64k UL / 384k DL RMC (3GPP TS 25.101 A.2.2 and A.3.4) connection, you must set SRB Configuration Control to Manual and set Manual SRB Configuration to 2.2k DCCH . The Auto setting for SRB Configuration Control does not account for this particular channel configuration.GPIB command: CALL[:CELL]:SRBearer:CCHannel:DEDicated:DRATe[:MANual] Manual SRB ConfigurationWhen SRB Configuration Control is set to Manual , this parameter determines what SRB the test set establishes with the UE.GPIB command: CALL[:CELL]:SRBearer:CCHannel:DEDicated:DRATe[:MANual] Operating Considerations These settings cannot be changed during Active Cell operation. Instead, use the Cell Off operating mode when changing these settings. Attempting to change these settings while in Active Cell operating mode results in an error issued and the test set will reject the change. See CALL:OPERating to select operating modes. Related Topics

23. Contents of Measurement control

24. Explain all seven Measurement reports

25. Differences between Rel99and HSDPA/HSUPAThe Universal Mobil Telecommunications System (also known as UMTS) is a third generation (or 3G) telecommunications technology for mobile electronics. The most common form of UMTS makes use of W-CDMA (Wideband Code Division Multiple Access, which is an air interface standard that is a compulsory feature of any mobile telecommunications device of the 3G network). However, the system makes use of TD-CDMA (Time Division CDMA) and TD-SCDMA (Time Division Synchronous CDMA). UMTS is a complete network system. As such, it also covers the radio access network, the core network, and the authentication of users using the USIM cards (or Subscriber Identity Module).High Speed Downlink Packet Access (also known as HSDPA) is also part of the 3G network; however, it is of an enhanced nature. It is a protocol that is used in mobile telephony communications in the High Speed Packet Access family a combination of the HSDPA and HSUPA (High Speed Uplink Packet Access) that extends and improves the performance of those WCDMA protocols that are currently in existence. As such, those networks that are part of the UMTS are capable of reaching higher data transfer speeds and capacities.UMTS requires the use of new base stations, as well as new frequency allocations. Despite these restrictions, however, UMTS is closely related to GSM (that is Global System for Mobile Communications, the most popular standard for mobile communication technology), and builds upon the concepts of GSM most UTMS handsets support GSM in order to allow dual mode operation without any issues.For HSDPA to function properly, a new transport layer channel had to be created (High Speed Downlink Shard Channel, or HS-DSCH) and added to the W-CDMA specification. By introducing three new physical layer channels (HS-SCCH, HS-DPCCH, and HS-PDSCH), the HSDPA network is capable of informing the user that the desired data will be sent, acknowledging information and current channel quality, and calculating how much data to send to any device the user uses in the next transmission, respectively. UMTS has a theoretical maximum data transfer of 21 Mbits/s (in the HSDPA form). However, for those currently using UMTS handsets, an expected transfer rate of 384 kbit/s and 7.2 Mbit/s is a more accurate expectation for R99 handsets and HSDPA handsets, respectively. Most HSDPA technology shows a theoretical transfer rate of 1.8, 3.6, 7.2, and 14.0 Mbit/s. However, there are further speed increases with the availability of the HSPA+ (providing speeds of up to 42 Mbit/s on the downlink, and 84 Mbit/s with the Release 9).

Read more: Difference Between UMTS and HSDPA | Difference Between | UMTS vs HSDPA http://www.differencebetween.net/technology/difference-between-umts-and-hsdpa/#ixzz1gxNYMaHC

26. What is Initial Direct Transfer

27. Explain the contents of Radio Bearer Reconfiguration. specify Dynamic and semi static part of Radio Bearer Reconfiguration28. Explain soft , softer and Hard HandoverTypes of Handover(s) Before we start discussing the handovers in detail we would like to list all of them for convenience of the reader 1. Softer Handover 2. Soft Handover 3. Intra-frequency hard handover 4. Inter-frequency hard handover 5. SRNS Relocation 6. Combined Hard handover and SRNS Relocation 7. Inter-RAT hard handover

Softer Handover

Fig 1: Softer Handover Strictly speaking softer handover is not really a handover. In this case the UE combines more than one radio link to improve the reception quality. On the other hand the Node B combines the data from more than one cell to obtain good quality data from the UE. [1] Specifies the maximum number of Radio Links that a UE can simultaneously support as 8. In practice this would be limited to 4 as it is very difficult to make the receiver with 8 fingers. Generally speaking when RRC connection is established, it would always be established on one cell. The network initiates Intra-Frequency measurements to check if there are any other cells the UE can connect simultaneously to improve the quality of the data being transferred between the RNC and the UE. If a suitable cell is found then Active Set Update procedure is initiated. Using this Active Set Update message, the network adds or deletes more than one radio link to the UE. The only requirement is that from the start till the end of this Active Set Update procedure, one Radio Link should remain common. Soft Handover

Fig 2: Soft Handover Soft Handover is the same as softer handover but in this case the cells belong to more than one node B. In this case the combining is done in the RNC. It is possible to simultaneously have soft and softer handovers.

Fig 3: Soft Handover with Iur connection A more complicated soft handover would include a cell that belongs to a Node B in different RNC. In this case an Iur connection is established with the drift RNC (RNC 2) and the data would be transferred to the Serving RNC (RNC 1) via Iur connection. In a typical UMTS system, the UE is in soft/softer handover around 50% of the time. One of the very important requirements for the soft/softer handover is that the frames from different cells should be within 50ms of each other or this would not work. The last thing one needs to remember is that the soft/softer handover is initiated from the RNC and the core network is not involved in this procedure. Hard Handover Hard handover occurs when the radio links for UE change and there are no radio links that are common before the procedure is initiated and after the procedure is completed. There are two types of hard handover. First is Intra-frequency hard handover and the second is Inter-frequency hard handover. Intra-frequency hard handover will not occur for the FDD system. It would happen in TDD system. In this case the code spreading/scrambling code for UE will change but the frequency remains the same. Inter-frequency hard handover generally occurs when hierarchical cells are present. In this case the frequency at which the UE is working changes. This happens when the current cell is congested, etc. Have a look at the Inter-Frequency Measurement primer for more information. Hard handover procedure can be initiated by the network or by the UE. Generally it would be initiated by the network using one of the Radio Bearer Control messages. In case of UE initiated, it would happen if the UE performs a Cell Update procedure and that Cell Update reaches the RNC on a different frequency. The Core Network is not involved in this procedure. SRNS Relocation SRNS Relocation procedure is not strictly speaking a handover procedure but it can be used in combination with the handover procedure. A simple SRNS Relocation can be explained with the help of figures present in [9].

Fig 4: Data flow before SRNS Relocation procedure ([9], Fig 37)

Fig 5: Data flow after SRNS Relocation procedure ([9], Fig 38)The UE is active on a cell that belongs to a different RNC (than the one on which call was initiated) and a different MSC/SGSN. This arrangement causes unnecessary signalling between two RNC's. Hence the relocation procedure is initiated. In this, the CN negotiated the relocation procedure between the two RNS's. Once the procedure is completed the connection towards the old domain is released as shown in Fig. 5. The relocation procedures will generally be used for UE in Packet Switched mode. This procedure is time consuming and is not really suitable for real time services. Combined Hard handover and SRNS Relocation

Fig 6: Before Combined hard handover and SRNS Relocation Procedure([9], Fig. 40)

Fig 7: After Combined hard handover and SRNS Relocation Procedure([9], Fig. 41)The combined procedure is a combination of hard handover and SRNS Relocation. Fig. 6 and 7 explain the procedure. Inter-RAT hard handover When UE reaches end of coverage area for UMTS services, it can handover to a 2G service like GSM (if the UE supports multiple RAT). Inter-RAT handover procedure can be initiated in variety of ways. RNS might send a Handover From UTRAN command explicitly telling the UE to move to a different RAT or the UE might select a cell that belongs to a different RAT or the Network may ask UE to perform Cell Change Order from UTRAN. Inter-RAT hard handover using Handover from UTRAN command can be performed when there are no RAB's or when there is atleast one CS domain RAB. The state of the UE is CELL_DCH. Inter-RAT hard handover using Cell change order from UTRAN can be performed when UE is either in CELL_DCH or CELL_FACH state. The only requirement is that there should be atleast a PS signalling connection and no CS signalling connection.

29. What is Compressed mode and why it is requiredCompressed mode, also known as the Slotted Mode, is needed when making measurements on another frequency (inter-frequency) or on a different radio technology (inter-RAT). In the Compressed Mode the transmission and reception are stopped for a short time and the measurements are performed on other frequency or RAT in that time. After the time is over the transmission and reception resumes. To make sure that the data is not lost, the data is compressed in the frame making empty space where measurements can be performed. Compressed mode is not necessary. If the UE has a second receiver it can make measurements on that receiver while continuing with the transmission/reception on the first receiver. This does not happen in practise as the cost would go up. The UE capabilities define whether a UE requires compressed mode in order to monitor cells on other FDD frequencies and on other modes and radio access technologies. UE capabilities indicate the need for compressed mode separately for the uplink and downlink and for each mode, radio access technology and frequency band. A UE shall support compressed mode for all cases for which the UE indicates that compressed mode is required. A UE does not need to support compressed mode for cases for which the UE indicates that compressed mode is not required. For these cases, the UE shall support an alternative means of making the measurements. The UE shall support one single measurement purpose for one transmission gap pattern sequence. The measurement purpose of the transmission gap pattern sequence is signalled by higher layers.

The figure above gives an idea of how the frame is compressed for performing measurements. In compressed frames, TGL slots from Nfirst to Nlast are not used for transmission of data. As illustrated in figure, the instantaneous transmit power is increased in the compressed frame in order to keep the quality (BER, FER, etc.) unaffected by the reduced processing gain. The amount of power increase depends on the transmission time reduction method. What frames are compressed, are decided by the network. When in compressed mode, compressed frames can occur periodically, as illustrated in figure, or requested on demand. The rate and type of compressed frames is variable and depends on the environment and the measurement requirements. Parameterisation of the compressed mode [3] In response to a request from higher layers, the UTRAN shall signal to the UE the compressed mode parameters. A transmission gap pattern sequence consists of consecutive occurrences of transmission gap pattern 1, where transmission gap pattern 1 consists of one or two transmission gaps. See figure below.

The following parameters characterise a transmission gap pattern: TGSN (Transmission Gap Starting Slot Number): A transmission gap pattern begins in a radio frame, henceforward called first radio frame of the transmission gap pattern, containing at least one transmission gap slot. TGSN is the slot number of the first transmission gap slot within the first radio frame of the transmission gap pattern; TGL1 (Transmission Gap Length 1): This is the duration of the first transmission gap within the transmission gap pattern, expressed in number of slots; TGL2 (Transmission Gap Length 2): This is the duration of the second transmission gap within the transmission gap pattern, expressed in number of slots. If this parameter is not explicitly set by higher layers, then TGL2 = TGL1; TGD (Transmission Gap start Distance): This is the duration between the starting slots of two consecutive transmission gaps within a transmission gap pattern, expressed in number of slots. The resulting position of the second transmission gap within its radio frame(s) shall comply with the limitations of [1]. If this parameter is not set by higher layers, then there is only one transmission gap in the transmission gap pattern; TGPL1 (Transmission Gap Pattern Length): This is the duration of transmission gap pattern 1, expressed in number of frames; The following parameters control the transmission gap pattern sequence start and repetition: TGPRC (Transmission Gap Pattern Repetition Count): This is the number of transmission gap patterns within the transmission gap pattern sequence; TGCFN (Transmission Gap Connection Frame Number): This is the CFN of the first radio frame of the first pattern 1 within the transmission gap pattern sequence. In addition to the parameters defining the positions of transmission gaps, each transmission gap pattern sequence is characterised by: UL/DL compressed mode selection: This parameter specifies whether compressed mode is used in UL only, DL only or both UL and DL; UL compressed mode method: The methods for generating the uplink compressed mode gap are spreading factor division by two or higher layer scheduling and are described in [1]; DL compressed mode method: The methods for generating the downlink compressed mode gap are spreading factor division by two or higher layer scheduling and are described in [1]; downlink frame type: This parameter defines if frame structure type 'A' or 'B' shall be used in downlink compressed mode. The frame structures are defined in [1]; scrambling code change: This parameter indicates whether the alternative scrambling code is used for compressed mode method 'SF/2'. Alternative scrambling codes are described in [4]; RPP: Recovery Period Power control mode specifies the uplink power control algorithm applied during recovery period after each transmission gap in compressed mode. RPP can take 2 values (0 or 1). The different power control modes are described in [5]; ITP: Initial Transmit Power mode selects the uplink power control method to calculate the initial transmit power after the gap. ITP can take two values (0 or 1) and is described in [5]. The UE shall support simultaneous compressed mode pattern sequences which can be used for different measurements. The following measurement purposes can be signalled from higher layers: FDD TDD GSM carrier RSSI measurement Initial BSIC identification BSIC re-confirmation. The UE shall support one compressed mode pattern sequence for each measurement purpose while operating in FDD mode, assuming the UE needs compressed mode to perform the respective measurement. In case the UE supports several of the measurement purposes, it shall support in parallel one compressed mode pattern sequence for each supported measurement purpose where the UE needs compressed mode to perform the measurement. The capability of the UE to operate in compressed mode in uplink and downlink is given from the UE capabilities. The GSM measurements Initial BSIC identification and BSIC re-confirmation are defined in [6]. Higher layers will ensure that the compressed mode gaps do not overlap and are not scheduled to overlap the same frame. The behaviour when an overlap occurs is described in [7]. UE is not required to support two compressed mode gaps in a frame. In all cases, higher layers have control of individual UE parameters. Any pattern sequence can be stopped on higher layers' command. The parameters TGSN, TGL1, TGL2, TGD, TGPL1, TGPRC and TGCFN shall all be integers. Different Methods of Frame Compression There are three different methods through which the frame compression can be achieved Puncturing: The symbol rate can be reduced by puncturing the data bits. This method is practical only for short TGLs. This is because there is an upper limit to the amount of data that can be punctured and then receovered at the other end. The advantage is that it is a simple method and there is no need to change the speading code as in the other method. This method has been removed from the latest version of the specifications. Changing the Spreading Factor (SF): In this method the frame in which compression is to be carried out, SF is reduced by 2 so the same amount of data can be transmitted in half the time and the remaining time measurements can be done. This is the most popular method used in practice as its very straightforward. Higher Layer scheduling: The higher layers are aware of the compressed mode schedule, so they could lower the data rate in the frame measurements need to be done thus avoiding the need for new spreading factor and new channelisation codes. Higher layers sets restrictions so that only a subset of the allowed TFCs are used in a compressed frame. The maximum number of bits that will be delivered to the physical layer during the compressed radio frame is then known and a transmission gap can be generated. Note that in the downlink, the TFCI field is expanded on the expense of the data fields and this shall be taken into account by higher layers when setting the restrictions on the TFCs. Compressed mode by higher layer scheduling shall not be used with fixed starting positions of the TrCHs in the radio frame.

Frame structure in the uplink [1] The frame structure for uplink compressed frames is illustrated in figure below:

Frame structure types in the downlink [1] There are two different types of frame structures defined for downlink compressed frames. Type A maximises the transmission gap length and type B is optimised for power control. The frame structure type A or B is set by higher layers independent from the downlink slot format type A or B. With frame structure of type A, the pilot field of the last slot in the transmission gap is transmitted. Transmission is turned off during the rest of the transmission gap (figure a). In case the length of the pilot field is 2 bits and STTD is used on the radio link, the pilot bits in the last slot of the transmission gap shall be STTD encoded assuming DTX indicators as the two last bits in the Data2 field. With frame structure of type B, the TPC field of the first slot in the transmission gap and the pilot field of the last slot in the transmission gap is transmitted. Transmission is turned off during the rest of the transmission gap (figure b). In case the length of the pilot field is 2 bits and STTD is used on the radio link, the pilot bits in the last slot of the transmission gap shall be STTD encoded assuming DTX indicators as the two last bits of the Data2 field. Similarly, the TPC bits in the first slot of the transmission gap shall be STTD encoded assuming DTX indicators as the two last bits in the Data1 field.

(a) Frame structure type A

(b) Frame structure type B

Transmission gap position [1]

(a) Transmission gap position

(b) Transmission gap positions with different Nfirst

Transmission gaps can be placed at different positions as shown in figures a and b (above) for each purpose such as interfrequency power measurement, acquisition of control channel of other system/carrier, and actual handover operation. When using single frame method, the transmission gap is located within the compressed frame depending on the transmission gap length (TGL) as shown in figure a(1). When using double frame method, the transmission gap is located on the center of two connected frames as shown in figure a(2). Parameters of the transmission gap positions are calculated as follows. TGL is the number of consecutive idle slots during the compressed mode transmission gap: TGL = 3, 4, 5, 7, 10,14 Nfirst specifies the starting slot of the consecutive idle slots, Nfirst = 0,1,2,3,,14. Nlast shows the number of the final idle slot and is calculated as follows; If Nfirst + TGL 15, then Nlast = Nfirst + TGL 1 ( in the same frame ), If Nfirst + TGL > 15, then Nlast = (Nfirst + TGL 1) mod 15 ( in the next frame ). When the transmission gap spans two consecutive radio frames, Nfirst and TGL must be chosen so that at least 8 slots in each radio frame are transmitted.

30. Explain HARQ and how it is different from ARQ