What is TDD and FDD?

TDD stands for Time Division Duplex and FDD stands for Frequency Division Duplex. They are different modes of CDMA. In FDD mode of transmission both the Transmitter and the Receiver transmit simultaneously. This simultaneous transmission is possible because they are both on different frequencies. In TDD mode of operation either Transmitter or Receiver can transmit at one time. This is because they use the same frequency for the transmission.

 Which mode is more common, TDD or FDD?

At present all the major 3G Networks are using FDD mode of operation. As far as i am aware there are no commercial TDD networks at the moment. Recently T-Mobile announced that they wil install TDD Network in Czech Republic. See News Section for more details.

 Can you expand on the FDD mode of operation?

In the FDD mode of operation, the uplink and downlink use separate frequency bands. These carriers have a bandwidth of 5 MHz. Each carrier is divided into 10-ms radio frames, and each frame further into 15 time slots. The frequency allocation consists of one frequency band at 1920-1980 MHz and one at 2110-2170 MHz. These frequency bands are used in FDD mode both by the UE and the Network. The lower frequency band is used for the Uplink (UL) transmission and the upper frequency band is used for the Downlink (DL) transmission. The frequency separation is specified with 190 MHz for the fixed frequency duplex mode and with 134.8MHz to 245.8MHz for the variable frequency duplex mode.

 Can you expand on the TDD mode of operation?

The TDD mode differs from the FDD mode in that both the uplink and the downlink use the same frequency carrier. There are 15 time slots in a radio frame that can be dynamically allocated between uplink and downlink directions. Thus the channel capacity of these links can be different which is very advantageous especially when people are downloading stuff on their mobiles. The chip rate of the normal TDD mode is also 3.84 Mcps, but there exists also a “narrowband” version of TDD known as TD-SCDMA. The carrier bandwidth of TD-SCDMA is 1.6 MHz and the chip rate 1.28 Mcps. TD-SCDMA has been proposed by China and potentially has a large market share in China if implemented.

 What is TDD HCR and TDD LCR?

HCR stands for "High Chip Rate" and is same as 3.84Mcps TDD described above. LCR stands for "Low Chip Rate" ans is the same as TD-SCDMA described above.

 Can you expand on the unequal bandwidth concept in TDD?

The HCR TDD uses 10ms radio frame that is divided into 15 time slots each being able to carry a chip sequence of 2560 complex valued chips. At least one slot has to be reserved for Downlink (DL) transmission to allow for broadcast information and one for Uplink (UL) transmission in order to realize customer’s access to the system. The remaining slots can be arbitrarily distributed to either direction in order to adapt to the asymmetry of requested services. The LCR option, a 10 ms radio frame is divided into two sub-frames of 5 ms duration. Each of the sub-frames contains seven time slots. Transmission bursts fitting into a single slot contain 864 complex valued chips. The first time slot is always used for DL transmission, the latter six can be divided into UL and DL transmission adaptively, starting with the time slots used for UL. Unlike transmission in the HCR mode, the time slots used for LCR transmission in a certain direction have to be grouped together. Between the first two slots in each sub-frame special synchronization and pilot signals are included.

 If FDD is so popular why would people use TDD mode of operation?

Juha Korhonen in his book Introduction to 3G Mobile Communications has summarised the reasons for TDD mode being used. They are:

The main reason for TDD use is spectrum allocation. The spectrum allocated for IMT-2000 is asymmetric, which means that an FDD system cannot use the whole spectrum, as it currently requires symmetric bands. Thus the most obvious solution was to give the symmetric part of the spectrum to FDD systems, and the asymmetric part to TDD systems. The proposed spectrum allocations for UTRAN TDD are 1,900–1,920 MHz and 2,010–2,025 MHz.

Many services provided by the 3G networks will require asymmetric data transfer capacity for the uplink and downlink, where the downlink will demand more bandwidth than the uplink. A typical example of this is a Web-surfing session. Only control commands are sent in the uplink, whereas the downlink may have to transfer hundreds of kilobits of user data per second toward the subscriber. As the TDD capacity is not fixed in the uplink and downlink, it is a more attractive technology for highly asymmetric services. The base station can allocate the time slots dynamically for the uplink or downlink according to current needs.

Another reason for TDD is easier power control. In the TDD mode both the uplink and downlink transmissions use the same frequency; thus, the fast fading characteristics are similar in both directions. The TDD transmitter can predict

the fast fading conditions of the assigned frequency channel based on received signals. This means that closed-loop power control is no longer needed, but only open loop will be sufficient. However, openloop control is based on signal levels, and if the interference level must be known, then this must be reported using signaling.

This “same channel” feature can also be used to simplify antenna diversity. Based on uplink reception quality and level, the network can choose which base station can best handle the downlink transmissions for the MS in question. This means less overall interference.

Since the UE only has to be active (receiving or transmitting) during some of the time slots. There are always some idle slots during a frame and those can be used for measuring other base stations, and systems.

 All the advantages above make TDD look better option than FDD. Why not use only TDD mode? Are there any problems?

The following are the problems that make TDD unpopular:

The main problem is interference from TDD power pulsing. The higher the mobile speed, the shorter the TDD frame so that fast open-loop power control can be used. This short transmission time results in audible interference from pulsed transmissions, both internally in the terminal and with other electronic equipment. Also, the timing requirements for many components are tighter. Both problems can be solved, but the solutions probably require more costly components.

A TDD system is prone to intracell and intercell interference between the uplink and downlink. The basic problem is that in adjacent cells, the same time slot can be allocated for different directions. It may happen that one UE tries to receive on a slot while another UE nearby transmits on the same slot. The transmission can easily block the reception attempt of the first UE. This problem can be prevented if all base stations are synchronized, and they all use the same asymmetry in their transmissions. However, this is costly (time-synchronous base stations), and also limits the usability of the system (fixed asymmetry).

 How is UMTS subscriber differentiated from a GSM subscriber?

UMTS subscriber differentiated from a GSM subscriber based on SIM card. For UMTS and GSM subscriiber the SIM is different. UMTS subscriber uses USIM while GSM one uses SIM.

 Can 2G SIM be used to access 3G Services?

Section 13.1 of 22.101 says: For access to services, provided by PS or CS CN domains, a valid USIM shall be required. Optionally, SIM according to GSM phase 2, GSM phase 2+, 3GPP release 99, 3GPP release 4 specifications may be supported. I guess its upto the network to allow or disallow 2G SIM accessing 3G services.

Last Updated: 27/12/2004 What is 3GPP and how is it related to 3G Wireless?

The 3rd Generation Partnership Project (3GPP) is a collaboration agreement that was established in December 1998. The collaboration agreement brings together a number of telecommunications standards bodies which are known as “Organizational Partners”. The current Organizational Partners are ARIB, CCSA, ETSI, ATIS, TTA, and TTC. Their website is http://www.3gpp.org. 3GPP is in charge of standardising WCDMA technology that is the most popular 3G Wireless standard.

 What are these 3GPP Releases?

Since all the features required cannot be completed simultaneously in one go, it was decided that the 3G mobile will consist of some basic features. After that new functionalities will be added in groups and released. The groups of this new set of functionalities are called releases. Each new Release supports the Old Release plus new set of features. It might also happen that some of the existing functinality was incorrect, it would then be corrected in the new release.

 How many 3GPP releases are there?

The following are 3GPP releases:

RELEASE 99: Functionality frozen in December 99. All 3G mobiles are required to be release 99 compatible or above. Basis of all the existing 3G networks and mobiles available right now. All of Hutchison's networks worldwide are Release 99 compatible.

RELEASE 4: Functionality Frozen in March 99. All new mobiles being designed are based on Release 4.

RELEASE 5: Functionality Frozen in June 2002. RELEASE 6: Functionality to be Frozen by June 2004. RELEASE 7: Not much information available on this one.

 What did Release 99 contain?

Release 99 contained all the basic 3GPP features. This contains a long list that would be incomplete without explanation. Please see the following document for complete Release 99 related information. http://www.3gpp.org/Releases/Rel99-Features-Draft.pdf.

 What is Release 2000?

Release 2000 or Release 00 was supposed to be ready by the year 2000 but the things got delayed so much that they decided to scrap it and replace it by Release 4 and Release 5.

 What are Release 4 features?

The following are the features of Release 4:

Evolutions of the Transport in the UTRANo QoS optimisation for AAL2 connections over Iub and Iur interfaces.o Transport bearer modification procedure on Iub, Iur, and Iu (note: this

was previously known as “Migration to modification procedures”). Evolutions of the transport in CN

o IP transport of CN protocol.o FS on transport and control separation in PS domain (this FS will not lead

to any feature). Improvements of Radio Interface - Rel-4 part

o UTRA repeater specificationo DSCH power control improvement in SHO.

Low chip rate TDD option RAB Quality of Service Negotiation over Iu during relocation RAN improvements

o RRM optimization for Iur and Iubo Node B synchronisation for TDDo RAB support enhancement

Transparent End-to-End PS Mobile Streaming Applications Emergency call enhancements – Rel-4 part: for CS based calls Enable bearer independent CS architecture Real time Facsimile MExE Enhancements (the main enhancements are Third MExE classmark for a

new smallfootprint Java platform, support of SDR concepts by software download and Security enhancements)

Tandem Free Operation Transcoder Free Operation ODB (Operator Determined Barring) for Packet Oriented Services Multimedia Messaging Service UICC/(U)SIM enhancements and interworking (U)SIM toolkit enhancements

o USAT local linko UICC API testingo Protocol Standardisation of a SIM Toolkit Interpreter

Advanced Speech Call Items enhancements Reliable QoS for PS domain

More information is available in the following document: http://www.3gpp.org/ftp/tsg_sa/TSG_SA/TSGS_14/Docs/PDF/SP-010724.pdf

 What are Release 5 Features?

The Main Features of Release 5 are:

IMS or IP Based Multimedia Services HSDPA or High Speed Downlink Packet Access Location Services for PS/GPRS IPv6 support Wideband AMR (new 16 kHz codec) End-to-end QoS in the PS domain and GLobal Text Telephony Messaging and Security Enhancements CAMEL Phase 4; new functions such as mid call procedures, interaction with

optimnal routing, etc. Load sharing UTRAN (Radio Network for WCDMA)/GERAN (Radio Network

for GSM/EDGE). WCDMA in 1800/1900 MHaz frequency spectrums Mobile Execution Environment (MExE) support for Java and WAP applications.

 Release 5 does not look like having lot of features.

Release 5 has many more features than the ones that are listed above. A detailed list of features and their explanations are available athttp://www.3gpp.org/Releases/Rel5_features_v_2003_09_09.htm. Also look at http://www.3gamericas.org/pdfs/umtsrel5_beyond_june2004.pdf.

 WHat are Release 6 Features?

The following are main Release 6 Features:

Multicast/Broadcast Multimedia services (MBMS) IMS enhancements for support of conversational services WCDMA/WLAN interworking Speech Recognition Network Sharing Digital Rights Management UE Functionality Split Common Radio Resource Management (UTRAN/GERAN) Radio Optimisation MMS Enhancements Packet Switched Streaming Services

Another significant feature targeted for Rel’6 is the Enhanced Uplink for Dedicated CHannels (EUDCH) feature. As the importance of IP-based services increases, demand to improve the coverage and throughput as well as reduce the delay of the uplink also increases. Applications that could benefit from an enhanced uplink may include services like video clips, multimedia, e-

mail, telematics, gaming, videostreaming etc. The EUDCH feature investigates enhancements that can be applied to UMTS in order to improve the performance on the uplink dedicated transport channels. To enhance uplink performance, features similar to those introduced for HSDPA in the downlink are being considered including:

Adaptive modulation and coding schemes Hybrid ARQ protocols Node B controlled scheduling Physical layer or higher layer signalling mechanisms to support the

enhancements Shorter frame size (TTI) and improved QoS

 What are Release 7 features?

Increasing spectral efficiency of the radio interface is of paramount importance in order to make the most out of the limited suitable spectrum and the operators’ investment in site resources. Multiple-Input multiple-output (MIMO) antenna systems, motivated by an information theoretic consideration, promise a considerable increase in spectral efficiencies. Therefore, support for MIMO systems is one key element considered for evolution of the UMTS radio interface. A large effort is expected to go into the maintenance and enhancement of the considerable new capabilities which have been introduced in the previous two releases. For example, IMS will further be enhanced, e.g. by explicit support for wireline access allowing fixed-mobile convergence. In addition the integration of alternative radio technologies such as WLAN will be considered, e.g. by allowing handover and closer integration with legacy voice services.

 I want to know how to find CR's for a particular 3GPP document?

Please goto http://www.3gpp.org/ftp/Specs/html-info. Scroll to the spec number of interest appended with –CRs.htm and there you will find the original CRs referenced by CR number. E.g, for 25.331http://www.3gpp.org/ftp/Specs/html-info/25331-CRs.htm.

 I have more questions about 3GPP, whom should i ask?

You can look at 3GPP's site for any unanswered questions. The website address is http://www.3gpp.org/faq/faq.htm   .What is 3GPP and how is it related to 3G Wireless?

The 3rd Generation Partnership Project (3GPP) is a collaboration agreement that was established in December 1998. The collaboration agreement brings together a number of telecommunications standards bodies which are known as “Organizational Partners”. The current Organizational Partners are ARIB, CCSA, ETSI, ATIS, TTA, and TTC. Their website is http://www.3gpp.org. 3GPP is in charge of standardising WCDMA technology that is the most popular 3G Wireless standard.

 What are these 3GPP Releases?

Since all the features required cannot be completed simultaneously in one go, it was decided that the 3G mobile will consist of some basic features. After that new functionalities will be added in groups and released. The groups of this new set of functionalities are called releases. Each new Release supports the Old Release plus new set of features. It might also happen that some of the existing functinality was incorrect, it would then be corrected in the new release.

 How many 3GPP releases are there?

The following are 3GPP releases:

RELEASE 99: Functionality frozen in December 99. All 3G mobiles are required to be release 99 compatible or above. Basis of all the existing 3G networks and mobiles available right now. All of Hutchison's networks worldwide are Release 99 compatible.

RELEASE 4: Functionality Frozen in March 99. All new mobiles being designed are based on Release 4.

RELEASE 5: Functionality Frozen in June 2002. RELEASE 6: Functionality to be Frozen by June 2004. RELEASE 7: Not much information available on this one.

 What did Release 99 contain?

Release 99 contained all the basic 3GPP features. This contains a long list that would be incomplete without explanation. Please see the following document for complete Release 99 related information. http://www.3gpp.org/Releases/Rel99-Features-Draft.pdf.

 What is Release 2000?

Release 2000 or Release 00 was supposed to be ready by the year 2000 but the things got delayed so much that they decided to scrap it and replace it by Release 4 and Release 5.

 What are Release 4 features?

The following are the features of Release 4:

Evolutions of the Transport in the UTRANo QoS optimisation for AAL2 connections over Iub and Iur interfaces.o Transport bearer modification procedure on Iub, Iur, and Iu (note: this was

previously known as “Migration to modification procedures”). Evolutions of the transport in CN

o IP transport of CN protocol.o FS on transport and control separation in PS domain (this FS will not lead

to any feature).

Improvements of Radio Interface - Rel-4 parto UTRA repeater specificationo DSCH power control improvement in SHO.

Low chip rate TDD option RAB Quality of Service Negotiation over Iu during relocation RAN improvements

o RRM optimization for Iur and Iubo Node B synchronisation for TDDo RAB support enhancement

Transparent End-to-End PS Mobile Streaming Applications Emergency call enhancements – Rel-4 part: for CS based calls Enable bearer independent CS architecture Real time Facsimile MExE Enhancements (the main enhancements are Third MExE classmark for a

new smallfootprint Java platform, support of SDR concepts by software download and Security enhancements)

Tandem Free Operation Transcoder Free Operation ODB (Operator Determined Barring) for Packet Oriented Services Multimedia Messaging Service UICC/(U)SIM enhancements and interworking (U)SIM toolkit enhancements

o USAT local linko UICC API testingo Protocol Standardisation of a SIM Toolkit Interpreter

Advanced Speech Call Items enhancements Reliable QoS for PS domain

More information is available in the following document: http://www.3gpp.org/ftp/tsg_sa/TSG_SA/TSGS_14/Docs/PDF/SP-010724.pdf

 What are Release 5 Features?

The Main Features of Release 5 are:

IMS or IP Based Multimedia Services HSDPA or High Speed Downlink Packet Access Location Services for PS/GPRS IPv6 support Wideband AMR (new 16 kHz codec) End-to-end QoS in the PS domain and GLobal Text Telephony Messaging and Security Enhancements CAMEL Phase 4; new functions such as mid call procedures, interaction with

optimnal routing, etc. Load sharing UTRAN (Radio Network for WCDMA)/GERAN (Radio Network

for GSM/EDGE).

WCDMA in 1800/1900 MHaz frequency spectrums Mobile Execution Environment (MExE) support for Java and WAP applications.

 Release 5 does not look like having lot of features.

Release 5 has many more features than the ones that are listed above. A detailed list of features and their explanations are available athttp://www.3gpp.org/Releases/Rel5_features_v_2003_09_09.htm. Also look at http://www.3gamericas.org/pdfs/umtsrel5_beyond_june2004.pdf.

 WHat are Release 6 Features?

The following are main Release 6 Features:

Multicast/Broadcast Multimedia services (MBMS) IMS enhancements for support of conversational services WCDMA/WLAN interworking Speech Recognition Network Sharing Digital Rights Management UE Functionality Split Common Radio Resource Management (UTRAN/GERAN) Radio Optimisation MMS Enhancements Packet Switched Streaming Services

Another significant feature targeted for Rel’6 is the Enhanced Uplink for Dedicated CHannels (EUDCH) feature. As the importance of IP-based services increases, demand to improve the coverage and throughput as well as reduce the delay of the uplink also increases. Applications that could benefit from an enhanced uplink may include services like video clips, multimedia, e-mail, telematics, gaming, videostreaming etc. The EUDCH feature investigates enhancements that can be applied to UMTS in order to improve the performance on the uplink dedicated transport channels. To enhance uplink performance, features similar to those introduced for HSDPA in the downlink are being considered including:

Adaptive modulation and coding schemes Hybrid ARQ protocols Node B controlled scheduling Physical layer or higher layer signalling mechanisms to support the enhancements Shorter frame size (TTI) and improved QoS

 What are Release 7 features?

Increasing spectral efficiency of the radio interface is of paramount importance in order to make the most out of the limited suitable spectrum and the operators’ investment in site resources. Multiple-Input multiple-output (MIMO) antenna systems, motivated by an information theoretic

consideration, promise a considerable increase in spectral efficiencies. Therefore, support for MIMO systems is one key element considered for evolution of the UMTS radio interface. A large effort is expected to go into the maintenance and enhancement of the considerable new capabilities which have been introduced in the previous two releases. For example, IMS will further be enhanced, e.g. by explicit support for wireline access allowing fixed-mobile convergence. In addition the integration of alternative radio technologies such as WLAN will be considered, e.g. by allowing handover and closer integration with legacy voice services.

 I want to know how to find CR's for a particular 3GPP document?

Please goto http://www.3gpp.org/ftp/Specs/html-info. Scroll to the spec number of interest appended with –CRs.htm and there you will find the original CRs referenced by CR number. E.g, for 25.331http://www.3gpp.org/ftp/Specs/html-info/25331-CRs.htm.

 I have more questions about 3GPP, whom should i ask?

You can look at 3GPP's site for any unanswered questions. The website address is http://www.3gpp.org/faq/faq.htm   .

 What is URA and URA_PCH state?

URA or UTRAN Registration Area is a colection of cells that are used for fast moving UE's in Connected mode when they are not transferring any data. In this case the UE is in CELL_PCH state.

Everytime a fast moving UE in CELL_PCH state changes the cell, a CELL UPDATE needs to be performed to let the UTRAN know of the new position of the UE. This is done because in the connected mode (CELL_PCH), UE is known at cell level rather than UTRAN level as in IDLE state. If too many CELL UPDATES are performed, it defeats the purpose of UE being in CELL_PCH. Hence in this case the UE is put in URA_PCH state. Now the UE will perform CELL UPDATE only when the URA is changed for a UE. The drawback is that when UE needs to be paged the paging area is now extended to many cells belonging to the URA.

Also Note that the CELL_PCH state is actually a subset of the URA_PCH state. It is possible to define overlapping URAs to be used in the URA_PCH state. Thus, the UTRAN operator could define that each cell is a separate URA in addition to other larger URAs. Then the operator could assign small one-cell URAs for slow-moving mobiles, and larger URAs for mobiles with greater mobility. The small URAs could nicely perform the task of the CELL_PCH state. However, it has been decided to keep these states separate.

The URAs can be overlapping or even hierarchical. The same cell may belong to several different URAs, and the UEs in that cell may have been registered to different URAs. SIB 2 contains a list of URA identities indicating which URAs this cell belongs to. This arrangement is done to further reduce the amount of location update signaling because now the UEs moving back and forth in

the boundary area of two URAs do not have to update their URA location information if the boundary cells do belong to both URAs. 

 Every one knows about DRX, but what is DTX, does it has any relationship with downlink rate matching? Contributed by Senthil Kumar

DRX is quite often used and is frequently discussed. But DTX… Rate matching is used to match the amount of data to be transmitted to the available capacity of the different physical channels. It can be done either through puncturing the bits(applicable for both uplink and downlink) if there are too many data for the capacity of the physical channel or through repeating the bits(applicable for uplink) if there is less number of bits when compared to the physical channel capacity.

But for the downlink rate matching, if the number of bits to be transmitted is lower than the maximum allowed bits then DTX indication bits are used to fill up the radio frame. DTX indication bits only indicate when the transmission should be turned off, they are not transmitted.

Unlike uplink where the data rate can be changed every TTI, the downlink data rate is fixed unless changed via higher layer scheduling or through the use of compress mode patterns.

Downlink rate matching is classified on the basis of two approaches.

1. Fixed position for transport channel. Here the decision to puncture or to use DTX bits is specific to a particular transport channel i.e., each transport channel is allocated a specific fixed transmission resource.

2. Flexible position for transport channel. Here the decision on whether to puncture or to use DTX bits is only made once all the data to be transmitted with in a radio frame are assembled. The advantage with this approach is that any spare capacity for one transport channel can be shared with transport channel that require additional capacity.

 If i try to make call using more than one mobile simultaneously to the same network, i am not able to do so. Can the network handle more than one call simultaneously?

There is probably some bug in the network because of which you faced this problem. Generally networks should be able to handle many calls simultaneously. There are some testing devices that allow the network to test this feature as well. Aeroflex TM500 for instance allows upto 32 UE's to simultaneous make calls on a network. 

 If i try to make a call from Mobile A to mobile B and at the same time from Mobile B to Mobile A, none of them rings. I get busy tone on both the phones, why?

When you initiate a call on a mobile, they stop monitoring the paging channel. So if a Paging is sent to the mobile they wont receive it. Hence this behaviour is correct. You will not receive a ringtone on either mobile.

 Why do we need BCCH over FACH and under what scenarios would it become applicable. Is it a handset related feature or a network related activity that comes in place due to service demands?

It is mandatory for UE to support BCCH mapped onto FACH. UE has to read System Information from BCCH mapped on BCH in IDLE, CELL_FACH, CELL_PCH and URA_PCH state. When the System Information gets changed MIB value tag is updated and Paging message is transmitted indicating that System Information has changed. The UE's in IDLE, CELL_PCH and URA_PCH will be able to read the updated System Information. To tell the UE's in CELL_FACH to read the new System Information SYSTEM INFORMATION CHANGE INDICATION message is sent on BCCH mapped to FACH.

Also when DRAC procedures are applicable, Sib 10 is transmitted over FACH. System Information Block type 10 shall be acquired on the FACH and only by UEs with support for simultaneous reception of one SCCPCH and one DPCH. If System Information Block type 10 is not broadcast in a cell, the DRAC procedures do not apply in this cell. Note that the UE has to be in CELL_DCH to read Sib 10.

SECURITYLast Updated: 16/09/2007

 What kind of Security is present in UMTS networks?

UMTS security consists of two components, Ciphering and Integrity protection.

 Are these mandatory or optional?

Ciphering is optional and Integrity Protection is Mandatory.

 How many algorithms have been defined for Ciphering and Integrity Protection?

Ciphering has two algorithms UEA0 and UEA1 where as Integrity protection has one algorithm UIA1. More algorithms will be defined at a later stage.

 I have heard that if no Ciphering is enabled, the network still treats it as Ciphering is active?

The Ciphering alorithm UEA0 is the same as no ciphering. RANAP standard specifies that:

"The Permitted Encryption Algorithms IE within the Encryption Information IE may contain "no encryption" within an element of its list in order to allow the RNC not to cipher the respective connection. This can be done either by not starting ciphering or by using the UEA0 algorithm. In the absence of the Encryption Information group IE in SECURITY MODE COMMAND message, the RNC shall not start ciphering."

As specified, no ciphering can be interpreted as ciphering with UEA0 algorithm. It is more convinient for the network to treat no ciphering as UEA0 but its upto the designers of the call processing software in RNC.

 Is UEA0 or UEA1 mandatory?

Earlier it was said that UEA0 is mandatory (http://www.3gpp.org/ftp/tsg_sa/WG3_Security/TSGS3_23_Victoria/Docs/PDF/S3-020305.pdf) but in the latest RRC specs it says that both UEA0 and UEA1 are mandatory.

 Which entity in UE or RNC performs Ciphering and Integrity Protection?

Integrity Protection is performed in RRC whereas Ciphering is done in RLC for AM and UM Radio bearers and MAC for TM radio bearers.

 Can different Ciphering algorithms be used for different domains?

RRC specification (25.331) does not restrict this. However RANAP specification (25.413) says that the Ciphering algorithm should be the same for both the domains. The exact text for section 8.18.2 is as follows:

Upon reception of the SECURITY MODE COMMAND message, the UTRAN shall internally select appropriate algorithms, taking into account the UE/UTRAN capabilities. If a signalling connection already exists towards the other core network domain and integrity has been started, the same ciphering and integrity alternatives as being used for that core network domain shall be selected. If a signalling connection already exists towards the other core network domain and the Security Mode Control procedure is ongoing on that core network domain, the same ciphering and integrity alternative shall be selected for the two domains. This means in particular for encryption that if "no encryption" or no Encryption Information IE has been received from the first core network domain and integrity has been started but ciphering has not been started, ciphering shall also not be started for the second core network domain.

 How ciphering is done for different modes of RLC and Why TM mode ciphering is pushed to MAC layer? Contributed by Senthil Kumar

The ciphering function in UMTS is present in MAC or RLC in the UE and UTRAN The parameters to the ciphering algorithm includes, a counter called COUNT-C, the ciphering Key CK, the RB id and the direction(uplink or downlink).

The UM and AM RLC mode ciphering uses the RLC sequence number(SN) which is in the header,since it keeps on changing for every RLC PDU. COUNT-C is a 32 bit counter derived from RLC Hyper Frame Number(HFN) RLC UM COUNT-C = RLC HFN(25 bits) + RLC SN(7 bits) RLC AM COUNT-C = RLC HFN(20 bits) + RLC SN(12 bits) The HFN is incremented once the RLC SN wraps around.

Since for TM RLC, header is not present and hence there is no SN to be used as variable changing parameter. So the TM RLC ciphering is pushed to MAC layer where the CFN is used as a variable changing parameter. RLC TM COUNT-C = MAC HFN(25 bits) + CFN(7 bits) The HFN is incremented when the CFN wraps around. For all the three modes of RLC, the HFN value is initialized to a START value(usually zero) at RRC connection establishment. CK is 128 bits long and there is a separate CK for CS and PS domain. RB id is 4 bits long and parameter direction is one bit long.

 Can you provide a list of documents for further reading on this topic?

Please refer to Security Primer for the references.

 What happens when the Mobile is switched on? How does it find the Scrambling code to camp on? 

When the mobile The synchronization procedure starts with downlink SCH synchronization. The UE knows the SCH primary synchronization code, which is common to all cells. The slot timing of the cell can be obtained by receiving the

primary synchronization channel (P-SCH) and detecting peaks in the output of a filter that is matched to this universal synchronization code. The slot synchronization takes advantage of the fact that the P-SCH is only sent during the first 256 chips of each slot. The whole slot is 2,560 chips long. This is depicted in Figure above. Thus the UE can determine when a slot starts, but it does not know the slot number yet (there are 15 slots in each frame), and thus it does not know where the radio frame boundary may be.

Thereafter the UE correlates the received signal from the secondary synchronization channel (S-SCH) with all secondary synchronization codes (SSC), and identifies the maximum correlation value. The S-SCH is also only sent during the first 256 chips of every slot. One SSC is sent in every time slot. There are 16 different SSCs, and they can form 64 unique secondary SCH sequences. One sequence consists of 15 SSCs, and these sequences are arranged in such a way that in any nonzero cyclic shift less than 15 of any of the 64 sequences is not equivalent to some other sequence. This means that once the UE has identified 15 successive SSCs, it can determine the code group used as well as the frame boundaries (i.e., frame synchronization).

Reference: Introduction to 3G Mobile Communications - Juha Korhonen  

 What is RACH and how does it work?

The Random Access Channel (RACH) is an uplink transport channel. The RACH is always received from the entire cell. The RACH is characterized by a collision risk and by being transmitted using open loop power control. The Random Access Channel (RACH) is typically used for signalling purposes, to register the terminal after power-on to the network or to perform location update after moving from one location area to another or to initiate a call. The structure of the physical RACH for signalling purposes is the same as when using the RACH for user data transmission. 

In UTRA the RACH procedure has the following phases:

The terminal decodes the BCH to find out the available RACH sub-channels and their scrambling codes and signatures.

The terminal selects randomly one of the RACH sub-channels from the group its access class allows it to use. Furthermore, the signature is also selected randomly from among the available signatures.

The downlink power level is measured and the initial RACH power level is set with the proper margin due to the open loop inaccuracy.

A 1 ms RACH preamble is sent with the selected signature. The terminal decodes AICH to see whether the base station has detected the

preamble. In case no AICH is detected, the terminal increases the preamble transmission

power by a step given by the base station, as multiples of 1 dB. The preamble is retransmitted in the next available access slot.

When an AICH transmission is detected from the base station, the terminal transmits the 10 ms or 20 ms message part of the RACH transmission.

The RACH procedure is illustrated in Figure above, where the terminal transmits the preamble until acknowledgement is received on AICH, and then the message part follows. In the case of data transmission on RACH, the spreading factor and thus the data rate may vary; this is indicated with the TFCI on the DPCCH on PRACH. Spreading factors from 256 to 32 have been defined to be possible, thus a single frame on RACH may contain up to 1200 channel symbols which, depending on the channel coding, maps to around 600 or 400 bits. For the maximum number of bits the achievable range is naturally less than what can be achieved with the lowest rates, especially as RACH messages do not use methods such as macro-diversity as in the dedicated channel.

Reference: WCDMA for UMTS: Radio Access for Third Generation Mobile Communications - Harri Holma  

 What is the significance of SFN and CFN?

SFN is the frame number used by the physical layer. CFN is the frame number used by the MAC layer. SFN is independent of the UE contexts, but associated with the Radio Link. CFN is associated with a UE context. The RRC layer maintains the mapping between CFN and various (for each RL) SFNs. 

 What is compressed mode and is it necessary for the UE to support compressed mode?

Compressed mode is needed if the UE needs to perform Inter-Frequency or Inter-RAT measurements. More details on what compressed mode is and how its performed can be seen inCompressed Mode Tutorial.

Compressed Mode is performed in Uplink(UL) as well as in Downlink(DL). Uplink compressed mode must be used if the frequency to be measured is close to the uplink frequency used by the UTRAN air interface (i.e., frequencies in TDD mode/GSM 1800/1900 band). Otherwise interfrequency interference may affect the results. Downlink compressed mode is not necessary if the UE has dual receivers. In that case one receiver can perform interfrequency measurements while the other handles the normal reception. Note however, that double receivers in the UE do not remove the need for uplink compressed mode. If the uplink frequency is close enough to the downlink frequency to be measured, then compressed mode must be employed in the uplink to prevent interfrequency interference.

Reference: Introduction to 3G Mobile Communications - Juha Korhonen  

 Why is secondary scrambling code needed?

For each primary scrambling code there is a set of 16 secondary scrambling codes. They can be employed while transmitting channels that do not need to be received by everyone in the cell. They should be used sparingly because channels transmitted with secondary scrambling codes are not orthogonal to channels that use the primary scrambling code. One possible application could be in sectored cells, where separate sectors do not have to be orthogonal to each other.

The secondary downlink scrambling codes can be applied with the exception of those common channels that need to be heard in the whole cell and/or prior to the initial registration. Only one scrambling code should be generally used per cell or sector to maintain the orthogonality between different downlink code channels. With adaptive antennas the beams provide additional spatial isolation and the orthogonality between different code channels is less important. However, in all cases the best strategy is still to keep as many users as possible under a single scrambling code to minimise downlink interference. If a secondary scrambling code needs to be introduced in the cell, then only those users not fitting under the primary scrambling code should use the secondary code. The biggest loss in orthogonality occurs when the users are shared evenly between two different scrambling codes.

 How does PLMN Selection take place in UMTS?

The UE normally operates on its home PLMN (HPLMN) or equivalent home PLMN (EHPLMN). However a visited PLMN (VPLMN) may be selected, e.g., if the MS loses coverage. There are two modes for PLMN selection:

1. Automatic mode: This mode utilizes a list of PLMNs in priority order. The highest priority PLMN which is available and allowable is selected.

2. Manual mode: Here the MS indicates to the user which PLMNs are available. Only when the user makes a manual selection does the MS try to obtain normal service on the VPLMN.

There are two cases:

International Roaming: This is where the MS receives service on a PLMN of a different country than that of the HPLMN.

National Roaming: This is where the MS receives service from a PLMN of the same country as that of the HPLMN, either anywhere or on a regional basis. The MS makes a periodic search for the HPLMN while national roaming.

To prevent repeated attempts to have roaming service on a not allowed LA, when the MS is informed that an LA is forbidden, the LA is added to a list of "forbidden LAs for roaming" which is stored in the MS. This list is deleted when the MS is switched off or when the SIM is removed. Such area restrictions are always valid for complete location areas independent of possible subdivision into GPRS routing areas. The structure of the routing area identifier (3GPP TS 23.003) supports area restriction on LA basis.

If a "No Suitable Cells In Location Area" message is received by an MS, that location area is added to the list of "forbidden LAs for roaming" which is stored in the MS. The MS shall then search for a suitable cell in the same PLMN but belonging to an LA which is not in the "forbidden LAs for roaming" list.

If a "PLMN not allowed" message is received by an MS in response to an LR request from a VPLMN, that VPLMN is added to a list of "forbidden PLMNs" in the SIM and thereafter that VPLMN will not be accessed by the MS when in automatic mode. A PLMN is removed from the "forbidden PLMNs" list if, after a subsequent manual selection of that PLMN, there is a successful LR. This list is retained when the MS is switched off or the SIM is removed. The HPLMN (if the EHPLMN list is not present or is empty) or an EHPLMN (if the EHPLMN list is present) shall not be stored on the list of "forbidden PLMNs".

In A/Gb mode, an ME not supporting SoLSA may consider a cell with the escape PLMN code (see 3GPP TS 23.073) to be a part of a PLMN belonging to the list of "forbidden PLMNs".

Optionally the ME may store in its memory an extension of the "forbidden PLMNs" list. The contents of the extension of the list shall be deleted when the MS is switched off or the SIM is removed.

If a "GPRS services not allowed in this PLMN" message is received by an MS in response to an GPRS attach, GPRS detach or routing area update request from a VPLMN, that VPLMN is added to a list of "forbidden PLMNs for GPRS service" which is stored in the MS and thereafter that VPLMN will not be accessed by the MS for GPRS service when in automatic mode. This list is deleted when the MS is switched off or when the SIM is removed. A PLMN is removed from the list of "forbidden PLMNs for GPRS service" if, after a subsequent manual selection of that PLMN, there is a successful GPRS attach. The maximum number of possible entries in this list is implementation dependant, but must be at least one entry. The HPLMN (if the EHPLMN list is not present or is empty) or an EHPLMN (if the EHPLMN list is present) shall not be stored on the list of "forbidden PLMNs for GPRS service".

In the UE, the AS shall report available PLMNs to the NAS on request from the NAS or autonomously.

UE shall maintain a list of allowed PLMN types. The allowed PLMN type can be GSM-MAP only, ANSI-41 only or both. During PLMN selection, based on the list of allowed PLMN types and a list of PLMN identities in priority order, the particular PLMN may be selected either automatically or manually. Each PLMN in the list of PLMN identities can be identified by either 'PLMN identity' (GSM-MAP) or 'SID'. In the system information on the broadcast channel, the UE can receive a 'PLMN identity' (GSM-MAP) or a 'SID' or a 'PLMN identity' (GSM-MAP) and a 'SID', in a given cell. For a given cell, the UE might receive several 'PLMN identities' from the system information on the broadcast channel. The result of the PLMN selection is an identifier of the selected PLMN, the choice being based on the allowed PLMN types, UE capability or other factors. This identifier is one of either 'PLMN identity' for GSM-MAP type of PLMNs or 'SID' for ANSI-41 type of PLMNs.

On request of the NAS the AS should perform a search for available PLMNs and report them to NAS.

The UE shall scan all RF channels in the UTRA bands according to its capabilities to find available PLMNs. On each carrier, the UE shall search for the strongest cell and read its system information, in order to find out which PLMN the cell belongs to. If

the UE can read one or several PLMN identities in the strongest cell, each found PLMN shall be reported to the NAS as a high quality PLMN (but without the RSCP value), provided that the following high quality criterion is fulfilled:

1. For an FDD cell, the measured primary CPICH RSCP value shall be greater than or equal to -95 dBm.

2. For a TDD cell, the measured P-CCPCH RSCP shall be greater than or equal to -84 dBm.

Found PLMNs that do not satisfy the high quality criterion, but for which the UE has been able to read the PLMN identities are reported to the NAS together with the CPICH RSCP value for UTRA FDD cells and P-CCPCH RSCP for UTRA TDD cells. The quality measure reported by the UE to NAS shall be the same for each PLMN found in one cell.

The search for PLMNs on the rest of the carriers may be stopped on request of the NAS. The UE may optimise this search by using stored information of carrier frequencies and optionally also information on cell parameters, e.g. scrambling codes, from previously received measurement control information elements.

Once the UE has selected a PLMN, the cell selection procedure shall be performed in order to select a suitable cell of that PLMN to camp on.

References: 3GPP TS 23.122: Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode 3GPP TS 25.304: UE Procedures in Idle Mode and Procedures for Cell Reselection in Connected Mode. Introduction to 3G Mobile Communications - Juha Korhonen  

 How does the initial UE Cell Selection takes place?

The initial cell-selection procedure is used in case there is no information on the current environment stored in the UE. However, normally the UE starts the cell selection with a stored information cell-selection procedure. The UE may have stored the necessary information of the cell it was previously camped on, such as frequency and scrambling code. The UE may first try to synchronize into that cell, and if it fails, it may trigger the initial cell selection.

The purpose of the initial cell-selection procedure is to find a cell, not necessarily the best cell, but a usable cell, for the UE to camp on after power-on. In the UTRAN, the number of carrier frequencies is quite small. One operator typically operates only on

two or three frequency carriers. In the first phase of UMTS in Europe, the frequency allocation for UMTS-FDD is 2 × 60 MHz (uplink/downlink), which means that there can be, at most, only 12 carrier frequencies of 5-MHz bandwidth each. These carriers are then divided between up to six operators. Each carrier will only support one operator. This obviously forces the operators to coordinate their networkplanning activities near national borders because the same frequency can be used by different operators in adjacent countries.

The specifications do not accurately dictate how the initial cellselection procedure should be implemented; it is left for the UE manufacturers to decide. Most of the functionality, however, has to be in the physical layer, and the RRC layer has only a management role. The initial cell-selection procedure is performed on one carrier frequency at a time until a suitable cell is found. In principle the process includes the following:

1. Search for primary synchronization channels (P-SCHs);2. Once such a channel is found, acquire time-slot synchronization from it;3. Acquire frame synchronization from the corresponding S-SCH;4. Acquire the primary scrambling code from the corresponding CPICH;5. Decode system information from the cell to check whether it is a suitable cell

for camping (i.e., it contains the right PLMN code and access to it is allowed).

All P-SCHs have the same fixed primary synchronization code. The search procedure should yield a set of P-SCHs in the area. Because the P-SCH is only transmitted during the first 256 chips of each time slot, the beginning of its transmission also indicates the start of a time slot in the corresponding cell.

In the second phase of the process, the received signal is correlated with all possible secondary synchronization code (S-SCH) words on the S-SCH. There are 16 different SSCs, and these can be combined into 64 different code words, each with a length of 15 SSCs. Once the right code word is found, this gives the UE the frame synchronization and the code group identity, which indicates eight possible primary scrambling codes for the control channels.

The third phase of the procedure consists of finding the right primary scrambling code for this cell. Each candidate cell’s primary scrambling code (there are eight of them as shown in the second phase) is applied, in turn, to the common pilot channel (CPICH) of that cell. Because the CPICH carries a predefined bit/symbol sequence, the UE knows when it has found the correct primary scrambling code. The resolved primary scrambling code can then be used to detect the CCPCH, which carries the BCH, which contains the system information the UE is seeking. There are various ways to optimize this procedure to make it quicker. Note that phase five actually contains

another major procedure, PLMN (i.e., the operator) selection. PLMN is identified by a PLMN code, a number that is transmitted on the BCCH channel of that network. A UE tries to find its home PLMN, the operator it has a contract with. In principle, a UE should first scan through all UTRAN frequencies until a good PLMN is found, and then start an initial cell-selection process on that frequency.

Note that one frequency can only be used by one operator (except in areas near country borders). However, while looking for the right PLMN code, the UE has already obtained all the necessary information for camping on a suitable cell, and no new scanning procedure is necessary once the correct PLMN is found. The situation is different if the UE is roaming abroad, and the home PLMN is not found. In that case RRC has to report all available PLMNs to NAS and wait for its selection decision, which can be either automatic or manual (user selection). This is time consuming, and many readers may have noticed this phenomenon when arriving at an airport in a new country and switching their GSM phones on. It may take a very long time before the phone registers to a network, especially if the phone is a multimode model with several frequency bands to scan.

The initial cell-selection process is repeated as many times as necessary until the first suitable cell is found for camping. Once the UE has managed to camp on a cell, it decodes the system information from it, including the neighbor cell list. This information can be used to help the UE find the best cell to camp onto. Note that the initial cell-selection procedure only found a cell to camp on (the first possible cell). It is possible that this cell will not be the best possible cell. For example, there could have been other frequencies including better cells for this particular UE that had not yet been scanned.

The neighbor cell list immediately tells the UE which frequencies and neighbor cells should be checked while the best possible cell is being searched for. The list includes additional information that can be used to optimize the cell-synchronization procedure, information such as the primary scrambling codes and timing information (optional, relative to the serving cell). With this information it should be possible to quickly descramble the CPICH from a neighbor cell.

From the CPICH it is possible to calculate the received chip energy to- noise ratio (Rx Ec/No) for this cell. This measurement is acquired for each neighbor cell in the list. Based on this information, the UE can determine whether there are better cells available. From a possible candidate cell, the UE must decode the system information to check that it is not barred for access.

If the neighbor cell list contains cells from another RAT—for example, GSM cells—and the serving cell quality level is worse than the Ssearch parameter, then the GSM cells must be taken into consideration in the cell reselection procedure.

 What does the Mobility Management (MM) layer do?

The main function of the Mobility Management sublayer is to support the mobility of user terminals, such as informing the network of its present location and providing user identity confidentiality. A further function of the MM sublayer is to provide connection management services to the different entities of the upper Connection Management (CM) sublayer.

 Sometimes MM is referred to as GMM; are they the same?

MM sub-layer consists of two types of procedures; MM procedures for non-GPRS services and GMM procedures for GPRS services. The G in GMM stands for GPRS.

 What are MM Procedures?

Depending on how they can be initiated, three types of MM procedures can be distinguished:

1. MM common procedures: A MM common procedure can always be initiated whilst a RR connection exists. The procedures belonging to this type are: Initiated by the network:

o TMSI reallocation procedure;o authentication procedure;o identification procedure;o MM information procedure;o abort procedure.

However, abort procedure is used only if an MM connection is being established or has already been established i.e. not during MM specific procedures or during IMSI detach procedure, see subclause 4.3.5.

Initiated by the mobile station:

o IMSI detach procedure (with the exceptions specified in subclause 4.3.4).

2. MM specific procedures: A MM specific procedure can only be initiated if no other MM specific procedure is running or no MM connection exists. The procedures belonging to this type are:

o normal location updating procedure;o periodic updating procedure;o IMSI attach procedure.

3. MM connection management procedures: These procedures are used to establish, maintain and release a MM connection between the mobile station and the network, over which an entity of the upper CM layer can exchange information with its peer. A MM connection establishment can only be performed if no MM specific procedure is running. More than one MM connection may be active at the same time.

 What are GMM procedures?

Depending on how they can be initiated, two types of GMM procedures can be distinguished:

1. GMM common procedures: In Iu mode, a GMM common procedure can always be initiated whilst a PS signalling connection exists.

The procedures belonging to this type are:

Initiated by the network when a GMM context has been established:

o P-TMSI (re-) allocation;o GPRS authentication and ciphering;o GPRS identification;o GPRS information.

2. GMM specific procedures: Initiated by the network and used to detach the IMSI in the network for GPRS services and/or non-GPRS services and to release a GMM context:

o GPRS detach.

Initiated by the MS and used to attach or detach the IMSI in the network for GPRS services and/or non-GPRS services and to establish or release a GMM context:

o GPRS attach and combined GPRS attach;o GPRS detach and combined GPRS detach.

Initiated by the MS when a GMM context has been established:

o normal routing area updating and combined routing area updating;o periodic routing area updating.

In UMTS, initiated by the MS and used to establish a secure connection to the network and/or to request the resource reservation for sending data:

o Service Request.

 Do i need to have RR (RRC) connection to perform Mobility Management functions?

Yes. If you do not have a RR connection than you need to establish one to perform MM functions. You cannot perform any MM/GMM procedures without RRC conection.

 How is MM signalling done?

After RRC connection has been setup, the direct transfer messages are used to perform MM signalling. Look at the tutorial on message sequence for Registration for details. It could be seen that after RRC connection has been setup

High Speed Downlink Packet Access (HSDPA) FAQ

By Zahid Ghadialy (zahidtg@yahoo.com)

Last Updated: 07/02/2010

QUESTIONS What does HSDPA stand for? So what exactly is HSDPA? Interesting! Is HSDPA part of 3G or will it be part of 4G? Why not similarly have HSUPA where U stands for uplink? Are HSDPA networks rolled out and can i buy HSDPA capable phones? Can existing 3G Networks be upgraded to support HSDPA with new Software release? What could be the possible uses of HSDPA? How did 3GPP manage to increase the speed of DL to over 10Mbps? Is HSDPA applicable for CS and PS RABs both? Is HSDPA applicable in CELL_FACH or CELL_DCH or both the UE states. Can you give comparison of HSDPA in FDD & TDD Mode? Where can i find basic tutorial on HSDPA? I would like to follow all HSDPA related News, which is the best place to look for? 

I am a researcher and i would like some references to read more on HSDPA. 

 What does HSDPA stand for?

HSDPA stands for High Speed Downlink Packet Access

 So what exactly is HSDPA?

HSDPA is an enhancement to the 3G technology through which you can increase the DL data rates from 384Kbps (theoretically 2Mbps) to 10Mbps (theoretically 14Mbps). Here Kbps stands for Kilo bits per second and Mbps stands for Mega bits per second. HSDPA delivers higher capacity through improved spectral effeciancy, which provides higher data rates, shorter response times and better Qos (Quality of Service).

 Interesting! Is HSDPA part of 3G or will it be part of 4G?

HSDPA is part of 3G but people also refer to it as 3.5G. More details here.

 Why not similarly have HSUPA where U stands for uplink?

There is already a HSUPA. More details available in HSUPA FAQ here.

 Are HSDPA networks rolled out and can i buy HSDPA capable phones?

In most of the countries, HSDPA networks have already been rolled out and HSDPA phones are already available. You can find the latest status of HSDPA capable networks in different countries on the GSMA website here.

 Can existing 3G Networks be upgraded to support HSDPA with new Software release?

In theory they can be but it might not always be the case. According to The Register HSDPA is a power-hungry technology, and many of the base stations out there aren’t up to the job. The key piece of technology is the power amplifier, which has to be a full power, 45-watt model, to handle the extra data output. Having said that, most of the new newly designed RNC and Node B's are now capable of handling not just an upgrade from 3H to HSDPA and HSPA+ but also to LTE.

 What could be the possible uses of HSDPA?

The same use as that of Broadband connections at home. It would be possible to watch extremely good quality real time Videos, download complete song tracks in less than a minute. Do real time video conferencing with more than one user using very high quality video. Eventually the wireless operators plan that instead of having wired broadband at home, people will move to wireless broadband. The list is non exhaustive.

 How did 3GPP manage to increase the speed of DL speed to over 10Mbps?

To increase the data rates a new channel called HS-DSCH (High speed downlink shared channel) was defined. This was somewhat similar to the DSCH defined in the release 99 specs. This channel maps to HS-PDSCH (high speed physical downlink shared channel). To support this data channel a control channel HS-SCCH (High speed shared control channels). The HS-DSCH is transmitted over the entire cell or over only part of the cell using e.g. beam-forming antennas.

The increased data rates are supported through the introduction of Fast and Complex channel-control mechanisms based on a short fixed packet TTI (transmission time interval), AMC (adaptive modulation and coding) and L1 HARQ (layer1 hybrid automatic repeat request).

 Is HSDPA applicable for CS and PS RABs both?

In release 5 HSDPA is only applicable for PS streaming/interactive/background RABs. In release 6, HSDPA will be used for Signalling Radio Bearers as well.

 Is HSDPA applicable in CELL_FACH or CELL_DCH or both the UE states.

HSDPA is only applicable to CELL_DCH state.

 Can you give comparison of HSDPA in FDD & TDD Mode?

With respect to TDD FDD

Uplink Uses HS-SICH (Shared Information Channel ) to send Ack/Nack & CQ I to Node-B

Uses an associated uplink dedicated control channel (DPCCH-HS) to send Ack/Nack, CQI to Node-B.

DownLink It consists of associated Dedicated Physical Channels and shared Control Channels(HS-SCCHs)

It consists of one or several HS-PDSCHs along with associated DPCH combined with several shared Physicl control Channels(HS-SCCHs)

Spreading Factor HS-DSCH uses fixed SF =16. HS-DSCH uses fixed SF=16 e or SF=1

Terminal Complexity Uses Joint Detection Uses RAKE reciever

Transmit Time Interval It uses 10 ms It uses 2ms

Timing Releationships It needs minimum 5 slots between HS- SCCH and start of Corresponding HS-DSCH TTI

It needs 2 slots between HS- SCCH and start of Corresponding HS-DSCH TTI

Closed Loop Power Calculates Closed loop Power Control on HS-SCCH by estimating BLER using HCSN (HS-SCCH Cyclic Sequence Number)

Not Applicable

Measurement Report of CQI

It is associated with each HS-SCCH transmission

It is configured by higher layer signalling

Information On Downlink

TFRI carries Resource Allocation

(21- Bit), Modualtion (1- Bit) and Transport block size(9- Bit)

TFRI carries Channelisastion Codes(7- Bit), Modulation Scheme(1- Bit) and Transport block size(6-Bit)

 Where can i find basic tutorial on HSDPA?

Please see the following Tutorial.

 I would like to follow all HSDPA related News, which is the best place to look for?

 What is handover and how does it work?

You can learn more about Handover principles and concepts in the Handover Tutorial. Alternatively you can also read Soft Handover Tutorial if you are only interested in learning about Soft/Softer handover. 

 What is Blind Handover and how does it work?

If the mobile phone is leaving a UMTS cell and it cannot find a new UMTS cell then the base station can hand over an appropriately equipped mobile phone to a cell in another system. These intersystem handovers are highly complex because two technically disparate systems must be combined with each other. Basically, there are two handover options from WCDMA to GSM:

In the case of blind handover, the base station simply transmits the mobile phone with all relevant parameters to the new cell. The mobile phone changes “blindly” to the GSM cell, i.e. it has not yet received any information about the timing there. It will first contact the transmitted BCCH channel, where it tries to achieve the frequency and time synchronization within 800 ms. Next, it will switch to the handed-over physical voice channel, where it will carry out the same sequence as with the non-synchronized intercell handover.

For the second type of handover from WCDMA to GSM, the compressed mode is used within the WCDMA cell; in this mode, transmission and reception gaps occur

during the transmission between base station and mobile phone. During these gaps, the mobile phone can measure and analyze the nearby GSM cells. For this purpose, the base station, similar to the GSM system, provides a neighbour cell list, and the mobile phone transfers the measurement results to the base station. The actual handover in the compressed mode is basically analogous to blind handover.

There is, of course, an intersystem handover from GSM to WCDMA. A special neighbour cell list for WCDMA cells was established in GSM to support this handover.

Reference: Handover scenarios in GSM systems - R&S 

 I have a small query related to IRAT HO.I just need to know what we can do to control the number of IRAT HO from 3G to 2G in some particular cells if they are at border and non border? I know that we can change some RNC parameters to change the GSM threshold,but more interested to know about Cell Level Parameters and the cells which are in the middle of a city. Give me some thoughts and idea? I want to reduce the number of IRAT HO from 3G to 2G at some of my downtown cells!!! - Arun Verma in Yahoo Groups: UMTS

Answered by Kamal Vij in Yahoo Groups: UMTS

As u might be well aware of , in UMTS UE always tries to do Intra-freq. HO. And to trigger an Inter Freq and Inter RAT there are several triggers /threshold criteria which must be fulfiulled.

For example, theCPICH EcNo coverage is very "BAD", CPICH RSCP coverage is "BAD", the UE is using very "HIGH" transmission power and is close to saturation, DL transmission power for that particular radio link is very "HIGH" and so on...

The words "BAD" and "HIGH " are defined by cell level thresholds. I cant write more precisely because it goes beyond the privacy agreements with my customer.

Please try to look for the Parameters which define Inter System THRESHOLDS .

For example , consider CPICH EcNo.

Genrally -8 is very good coverage, -12 is ok, and -15 EcNO is just close to the coverage hole.

Att -13 u may start Inter RAT. If u allow the mobiles to survive in 3G even if the coverage is -14 dB (almost close to coverage hole), u can save a lot of Inter RAT handovers.

LTE REF

3GPP LTE/SAE (Long Term Evolution / Service Architecture Evolution)

BLOG ENTRIES 

 Blog entries on LTE/SAE 

 Blog Entries on Release 9 

 Blog Entries on Release 8 

 Blog entries on LTE Technical topics 

 Blog Entries on LTE Voice and SMS Issues  

LTE/SAE FREQUENTLY ASKED QUESTIONS 

 Frequently Asked Questions (FAQ) 

LTE/SAE WHITEPAPERS/TUTORIALS 

 LTE Release 9 Technology Introduction, White paper, Rhode&Schwarz, Dec. 2011 

 LTE Transmission Modes and Beamforming, White paper, Rhode&Schwarz, Oct.

2011 

 LTE Whitepaper, Santosh Kumar Dornal, Oct. 2009 

 3GPP Long Term Evolution: System Overview, Product Development, and Test Challenges, Agilent, Sep. 2009 

 Cell search and cell selection in UMTS LTE, Application Note, Rhode&Schwarz, Sep. 2009 

 The LTE Link-Layer Design, Ericsson/IEEE, April 09 

 Introduction to Evolved Packet Core, Alcatel-Lucent, March 09 

 Mobile Broadband Evolution: the roadmap from HSPA to LTE, UMTS Forum, Feb.09 

 3GPP Release 8 and beyond, HSPA+, SAE/LTE and LTE-Advanced, 3G Americas, Feb. 09 

 Evolving IP-IP Gateways to Multi-Access Convergence Gateways, Aricent, Dec. 08 

 Long Term Evolution Protocol Overview, Freescale, Oct. 08 

 3GPP Release 7 to Release 8: HSPA and LTE/SAE, 3G Americas, June 08 

 Key features of the LTE radio interface, Ericsson, May 08 

 Overview of LTE Air-Interface, Motorola, Oct. 07 

 The Evolution of Rel-7 to Rel-8—HSPA and SAE/LTE, 3G Americas, July 2007 

 Long Term Evolution (LTE): A Technical Overview, Motorola, June 2007 

 UMTS Long Term Evolution (LTE) Technology Introduction, Rhode&Schwarz, Mar. 2007  

 The 3G Long-Term Evolution – Radio Interface Concepts and Performance Evaluation, Ericsson, Feb. 2006 

LTE PRESENTATIONS 

 Key drivers for LTE success: Services Evolution, 3GPP, Sep. 2011  

  3GPP LTE Channels and MAC Layer, Event Helix, Mar. 2009  

 LTE Release 8 and beyond, Qualcomm, Feb. 2009 

 LTE: What, Where, and When, Qasara, Jan. 2009 

 Long Term Evolution and Enhanced Packet Core, Alcatel Lucent, Oct. 2008 

 3GPP LTE, Intel, May 2008 

 Technical Overview of 3GPP LTE, Hyung Myung, May. 08 

 LTE – Long-Term Evolution, Ericsson, Dec. 07 

 3G Long Term Evolution, Ericsson, Mar. 07 

 3GPP’s Long Term Evolution and System Architecture Evolution projects, 3GPP, Dec. 06 

 3GPP Long-Term Evolution / System Architecture Evolution Overview, Alcatel, Nov. 06 

 3GPP LTE & 3GPP2 LTE Standardisation, Samsung, June 06 

 Long-Term 3G Evolution – Radio Access, Ericsson, Nov. 05 

 3G long-term evolution, Ericsson, Oct. 05 

SAE PRESENTATIONS 

 Standardisation and Developments within SAE, 3GPP, Oct. 2011  

 3GPP Core Network migration towards the Evolved Packet Core, 3GPP, Sep. 2011 

 Evolution of the 3GPP Network Architecture,(the Evolved Packet Core - EPC),

3GPP, May 2011 

 SAE – The Core Network for LTE, Ericsson, Apr. 2008 

RELEASE 8/9 PRESENTATIONS 

 Examining the 3GPP Release 8 Standards:What still needs to be done?, 3GPP, May 09 

 Exploring 3GPP Rel9, 3GPP, May 09 

MIMO 

 MIMO Transmission schemes for LTE and HSPA Networks, 3G Americas, June 09 

 Introduction to MIMO and Ten Things You Should Know, Agilent, Mar. 09 

 Making MIMO Measurements, Agilent, Mar. 09 

 LTE: MIMO Techniques in 3GPP-LTE, Freescale, Nov. 08 

 MIMO-LTE: A relevant Step towards 4G, Aug. 07, MimoOn 

SC-FDMA 

 White Paper: De-mystifying Single Carrier FDMA The New LTE Uplink, Agilent, Apr. 08 

 Presentation: SC-FDMA –the new LTE uplink explained, Agilent, Mar. 08 

SECURITY 

 Presentation: 3GPP LTE Security Aspects, 3GPP, May 2011 

 Presentation: Security in 3GPP, Jan 2011 

 White Paper: Security in the LTE-SAE Network, Agilent, July 2009 

 Presentation: 3GPP Security: LTE/SAE and Home (e)NB, ETSI, May. 2009 

VOLTE / VOICE ISSUES IN LTE 

 White Paper: Voice and SMS in LTE, Rohde & Schwarz, May 2011 

 Voice over LTE, Ericsson, Dec. 2010 

 Voice in an LTE Network, Iain Sharp, Nortel, Oct. 2009 

VOLGA 

 White Paper: Voice over LTE via Generic Access, Martin Sauter, Aug. 09 

 Voice over LTE, T-Mobile International and VoLGA Forum, May 09 

 Why mobile operators are looking to the 3GPP GAN standard to deliver core telephony and SMS services over LTE, Kineto, Mar 2009, 

SELF-ORGANIZING NETWORKS (SON) 

 Latest Blog entries on SON 

 Self-Optimising Networks: The Benefits of SON in LTE, 4G Americas, July 2011 

 The Benefits of SON in LTE, 3G Americas, Dec. 2009 

 Self Organizing Network - “NEC's proposals for next-generation radio network management”, NEC, Feb. 2009 

 Self-Organizing Networks (SON) in 3GPP Long Term Evolution, Nomor Research, May 2008 

RESEARCH AND THESIS 

 Proof of Concept Implementation of UMTS LTE, Lulea University, Nov. 07 

LTE/SAE SIGNALLING 

 LTE UE Registration Signaling 

 LTE Mobile Originated PS Call Signalling example 

 3GPP LTE UE Conformance Tests Description and Logs 

LTE TRIALS 

 An Update from the LTE/SAE Trial Initiative, LSTI Forum, May 09 

 Latest Results from the LSTI, Feb 2009 

GELTE 

 GSM, EDGE & LTE Interworking – What is GELTE?, 3GPP, Sep. 2011 

LTE AND WIMAX 

 LTE vs. WiMAX: 4th generation telecommunication networks, Berlin Institute of Technology, Jan. 2011 

 LTE and WiMAX - Where did we come from and where are we going?, Alcatel-Lucent, Jan. 2009 

 LTE and WiMAX Comparison at a Glance, WiMax Forum, Oct. 2008 

 LTE vs. WiMAX: Complementing or Competing?, Agilent, Oct. 2008 

 Trends in Mobile Network Architectures, Siemens, Nov. 2006 

LTE INTEROPERABILITY 

 Coexistence of GSM, HSPA and LTE, 4G Americas, May 2011 

 CDMA2000/ LTE Interoperability, Alcatel-Lucent, April 09 

VIDEO TUTORIALS 

 Rohde & Schwarz LTE Basics Webinar 

 LTE Radio Access - Physical Layer - IEEE Comsoc 

 Multiple Input Multiple Output (MIMO) 

 LTE Master and System Information Block Recovery  

 Overview of GTP 

 EPS Architecture 

LTE TECHNICAL STUFF (Layer 1 - Layer 3) 

 LTE Radio Physical Layer, 3GPP, May 2011 

 Radio Access Network Architecture and Protocols, 3GPP, May 2011 

 3GPP LTE Channels and MAC Layer, Event Helix, Nov. 2009 

 3GPP LTE Radio Link Control (RLC) Sub Layer, Event Helix, Nov. 2009 

DICTIONARY / ABBREVIATIONS 

 LTE: A Pocket Dictionary of Acronyms 

 List of Acronyms - Agilent 

EXTERNAL LINKS 

 3GPP UTRA-UTRAN Long Term Evolution (LTE) and 3GPP System Architecture Evolution (SAE) 

RELATED LINKS 

 LTE-Advanced (IMT-Advanced) 

TRAINING 

 eXplanoTech - Explaining Technology