Temporary Identities in LTE/SAE - 2: RNTI's

Last year I covered some information on temporary identities but never got a chance to continue on it. Here is one on RNTI's

RNTI or Radio Network Temporary Identifier(s) are used primarily by eNB Physical Layer for scrambling the coded bits in each of the code words to be transmitted on the physical channel. This scrambling process in PHY happens before modulation. There is a sequence followed for scrambling, calculation of which depends on the RNTI(UE specific for channels like PDSCH,PUSCH) and cell specific (for broadcast channels like PBCH). Details could be found in [2].

The following table lists different kinds of RNTI's:

Lets look at some of these in slightly more detail:

P-RNTI (Paging RNTI): To receive paging messages from E-UTRAN, UEs in idle mode monitor the PDCCH channel for P-RNTI value used to indicate paging. If the terminal detects a group identity used for paging (the P-RNTI) when it wakes up, it will process the corresponding downlink paging message transmitted on the PCH.

SI-RNTI (System Information RNTI): The presence of system information on DL-SCH in a subframe is indicated by the transmission of a corresponding PDCCH marked with a special System Information RNTI (SI-RNTI). Similar to the PDCCH providing the scheduling assignment for ‘ normal ’ DL-SCH transmission, this PDCCH also indicates the transport format and physical resource (set of resource blocks) used for the system-information transmission.

M-RNTI (MBMS RNTI): Used in Rel-9 for MCCH Information change notification.

RA-RNTI (Random Access RNTI): The RA-RNTI is used on the PDCCH when Random Access Response (RAR) messages are transmitted. It unambiguously identifies which time-frequency resource was utilized by the UE to transmit the Random Access preamble. If multiple UEs had collided by selecting the same signature in the same preamble time-frequency resource, they would each receive the RAR.

C-RNTI (Cell RNTI): The C-RNTI to be used by a given UE while it is in a particular cell. C-RNTI allocation and details are too complex to explain in the blog so please refer to Nomor newsletter here.

TC-RNTI: When the UE does not have allocated C-RNTI then Temporaru C-RNTI is used. A temporary identity, the TC-RNTI, used for further communication between the terminal and the network. If the communication is successful then TC-RNTI is promoted eventually to C-RNTI in the case of UE not having a C-RNTI.

SPS-C-RNTI (Semi-Persistent Scheduling C-RNTI): For the configuration or reconfiguration of a persistent schedule, RRC signalling indicates the resource allocation interval at which the radio resources are periodically assigned. Specific transmission resource allocations in the frequency domain, and transmission attributes such as the modulation and coding scheme, are signalled using the PDCCH. The actual transmission timing of the PDCCH messages is used as the reference timing to which the resource allocation interval applies. When the PDCCH is used to configure or reconfigure a persistent schedule, it is necessary to distinguish the scheduling messages which apply to a persistent schedule from those used for dynamic scheduling. For this purpose, a special identity is used, known as the Semi-Persistent Scheduling C-RNTI (SPS-C-RNTI), which for each UE is different from C-RNTI used for dynamic scheduling messages. - Source: LTE, The UMTS Long Term Evolution: From Theory to Practice By Stefania Sesia, Issam Toufik, Matthew Baker

TPC-PUCCH-RNTI (Transmit Power Control-Physical Uplink Control Channel-RNTI) and TPC-PUSCH-RNTI (Transmit Power Control-Physical Uplink Shared Channel-RNTI): The power-control message is directed to a group of terminals using an RNTI specific for that group. Each terminal can be allocated two power-control RNTIs, one for PUCCH power control and the other for PUSCH power control. Although the power control RNTIs are common to a group of terminals, each terminal is informed through RRC signaling which bit(s) in the DCI message it should follow.

The following table lists the values that are assigned to different RNTI's in MAC:



[1] 3GPP TS 36.321 - Evolved Universal Terrestrial Radio Access (E-UTRA) Medium Access Control (MAC) protocol specification
[2] 3GPP TS 36.211 - Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation

Takehiro Nakamura on LTE Radio Aspects

In summary:

Release 8 - Minor change requests to it based on March 2009 freeze;
Release 9 - an enhanced version of Release 8 and additional features;
Release 10 (LTE-Advanced) - proposed as an IMT-Advanced and is expected to be approved by December 2010; major differences between LTE and LTE-Advanced

Via: LTE Portal

Google may be the new hate figure in mobile industry

There is this article in The Register which I think is a bit over the top but nevertheless worth reading.

Link: http://www.theregister.co.uk/2010/01/08/google_nexus_partner_friendly/

Technologies and Standards for TD-SCDMA Evolutions to IMT-Advanced

Picture Source: http://www.itu.int/dms_pub/itu-t/oth/21/05/T21050000010003PDFE.pdf

This is a summary of a paper from IEEE Communications Magazine, Dec 2009 issue titled "Technologies and Standards for TD-SCDMA Evolutions to IMT-Advanced" by Mugen Peng and Wenbo Wang of Beijing University of Posts and Telecommunications with my own comments and understanding.

As I have blogged about in the past that China Mobile has launched TD-SCDMA network in China and the main focus to to iron out the basic problems before moving onto the evolved TD-SCDMA network. Couple of device manufacturers have already started working on the TD-HSPA devices. Couple of months back, 3G Americas published a whitepaper giving overview and emphasising the advantages of TDD flavour of LTE as compared to FDD. The next milestone is the IMT-Advanced that is under discussion at the moment and China has already proposed TD-LTE-Advanced which would be compatible with the TD-SCDMA technology.

For anyone who does not know the difference between TDD, FDD and TD-SCDMA please see this blog.

The TD-SCDMA technology has been standardised quite a while back but the rollout has been slow. The commercial TD-SCDMA network was rolled out in 2009 and more and more device manufacturers are getting interested in the technology. This could be due to the fact that China Mobile has a customer base of over 500 million subscribers. As of July 2009 over 100 device manufacturers were working on TD-SCDMA technology.

The big problem with TD-SCDMA (as in the case of R99 3G) is that the practical data rate is 350kbps max. This can definitely not provide a broadband experience. To increase the data rates there are two different approaches. First is the Short Term Evolution (STE) and the other is Long Term Evolution (LTE).

The first phase of evolution as can be seen in the picture above is the TD-STE. This consists of single carrier and multi-carrier TD-HSDPA/TD-HSUPA (TD-HSPA), TD-MBMS and TD-HSPA+.

The LTE part is known as TD-LTE. There is a definite evolution path specified from TD-SCDMA to TD-LTE and hence TD-LTE is widely supported by the TD-SCDMA technology device manufacturers and operators. The target of TD-LTE is to enhance the capabilities of coverage, service provision, and mobility support of TD-SCDMA. To save investment and make full use of the network infrastructure available, the design of TD-LTE takes into account the features of TD-SCDMA, and keeps TD-LTE backward compatible with TD-SCDMA and TD-STE systems to ensure smooth migration.

The final phase of evolution is the 4G technology or IMT-Advanced and the TD-SCDMA candidate for TD-LTE+ is TD-LTE-Advanced. Some mature techniques related to the TD-SCDMA characteristics, such as beamforming (BF), dynamic channel allocation, and uplink synchronization, will be creatively incorporated in the TD-LTE+ system.

Some academic proposals were also made like the one available here on the future evolution of TD-SCDMA but they lacked the industry requirements and are just useful for theoretical research.

The standards of TD-SCDMA and its evolution systems are supervised by 3GPP in Europe and by CCSA (Chinese Cellular Standards Association) in China. In March 2001 3GPP fulfilled TD-SCDMA low chip rate (LCR) standardization in Release 4 (R4). The improved R4 and Release 5 (R5) specifications have added some promising functions including HSDPA, synchronization procedures, terminal location (angle of arrival [AOA]-aided location), and so on.

When the industry standardizations supervised by CCSA are focusing on the integration of R4 and R5, the N-frequency TD-SCDMA and the extension of HSDPA from single- to multicarrier are presented. Meanwhile, some networking techniques, such as N-frequency, polarized smart antenna, and a new networking configuration with baseband unit plus remote radio unit (BBU+RRU), are present in the commercial application of TD-SCDMA.

TD-SCDMA STE

For the first evolution phase of TD-SCDMA, three alternative solutions are considered. The first one is compatible with WCDMA STE, which is based on HSDPA/HSUPA technology. The second is to provide MBMS service via the compatible multicast broadcast single-frequency network (MBSFN) technique or the new union time-slot network (UTN) technique. The last is HSPA+ to achieve similar performance as LTE.

On a single carrier, TD-HSDPA can reach a peak rate of 2.8 Mb/s for each carrier when the

ratio of upstream and downstream time slots is 1:5. The theoretical peak transmission rate of a three-carrier HSDPA system with 16-quadrature amplitude modulation (QAM) is up to 8.4 Mb/s.

Single-carrier TD-HSUPA can achieve different throughput rates if the configurations and parameters are varied, including the number of occupied time slots, the modulation, and the transport block size in bytes. Considering the complexity of a terminal with several carriers in TD-HSUPA, multicarrier is configured in the Node B, while only one carrier is employed in the terminal.

In Rel-7 based TD-HSPA+, In order to match the performance of orthogonal frequency-division multiple access (OFDMA)-based TD-LTE systems, some advanced techniques are utilized, such as multiple-input multiple-output (MIMO), polarized BF, higher modulation and coding schemes (64-QAM is available), adaptive fast scheduling, multicarrier techniques, and so on. Theoretically, 64-QAM can improve performance by a factor of 1.5 compared to the current 16-QAM; for single-carrier the peak rate reaches 4.2 Mb/s, and three-carrier up to 12.6 Mb/s.

For the MIMO technique, double transmit antenna array (D-TxAA), based on the pre-coding method at the transmitter, has been employed in frequency-division duplex (FDD)-HSPA+ systems, while selective per antenna rate control (S-PARC), motivated by the Shannon capacity limit for an open loop MIMO link, has been applied in TD-HSPA+ systems.

TD-SCDMA LTE

The TD-SCDMA LTE program was kicked off in November 2004, and the LTE demand report was approved in June 2005. The LTE specified for TD_SCDMA evolution is named TD-LTE.

LTE systems are supposed to work in both FDD and TDD modes. LTE TDD and FDD modes have been greatly harmonized in the sense that both modes share the same underlying framework, including radio access schemes OFDMA in downlink and SC-FDMA in uplink, basic subframe formats, configuration protocols, and so on.

TD-LTE trials have already started last year with some positive results.

TD-SCDMA LTE+

IMT-Advanced can be regarded as a B3G/4G standard, and the current TD-SCDMA standard migrating to IMT-Advanced can be regarded as a thorough revolution. TD-LTE advanced (TD-LTE+) is a good match with the TD-SCDMA revolution to IMT-Advanced.

It is predicted that the future TD-SCDMA revolution technology will support data rates up to approximately 100 Mb/s for high mobility and up to approximately 1 Gb/s for low mobility such as nomadic/local wireless access.

Recently, some advanced techniques have been presented for TD-LTE+ in China, ranging from the system architecture to the radio processing techniques, such as multi-user (MU)-BF, wireless relaying, and carrier aggregation (CA).

For MU-BF see the paper proposed by Huawei, CHina Mobile and CATT here (http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_55b/Docs/R1-090133.zip).

For Wireless Relaying see the ZTE paper here (http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_56b/Docs/R1-091423.zip).

To achieve higher performance and target peak data rates, LTE+ systems should support bandwidth greater than 20 MHz (e.g., up to 100 MHz). Consequently, the requirements for TD-LTE+ include support for larger transmission bandwidths than in TD-LTE. Moreover, there should be backward compatibility so that a TD-LTE user can work in TD-LTE+ networks. CA is a concept that can provide bandwidth scalability while maintaining backward compatibility with TD-LTE through any of the constituent carriers, where multiple component carriers are aggregated to the desired TD-LTE+ system bandwidth. A TD-LTE R8 terminal can receive one of these component carriers, while an TD-LTE+ terminal can simultaneously access multiple component carriers. Compared to other approaches, CA does not require extensive changes to the TD-LTE physical layer structure and simplifies reuse of existing implementations. For more on Carrier Aggregation see CATT, LGE and Motorola paper here (http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_56b/Docs/R1-091655.zip).

Finally, there are some interesting developments happening in the TD-SCDMA market with bigger players getting interested. Once a critical mass is reached in the number of subscribers as well as the manufacturers I wouldnt be surprised if this technology is exported beyond the Chinese borders. With clear and defined evolution path this could be a win-win situation for everyone.

Morgan Stanley's 'The Mobile Internet Report'

A bit old but may be interesting for people who are interested in Stats. Back in Dec. Morgan Stanley released a report titled 'The Mobile Internet Report' which is probably one of the biggest collection of mobile Stats.

According to Tomi Ahonen:

The report while they call it a 'mobile internet' report - is in fact, a report on smartphone based use of browser data services. It is very US centric, but is global, and it is far too obsessed about the iPhone. And it disappoints me, that while the report writers are very aware of simpler technologies, even when they discuss the Emerging World, they obsess about 3G, which will not be a meaningful part of the internet experience in places like Africa for most of the next decade..

But it does discuss SMS to some degree, and briefly mentions MMS and 'non 3G' internet such as in China (ie WAP). It is also very good making analysis of Japan's mobile internet (including i-Mode before 3G). Totally worth downloading and reading.

Now a few key highlights. The total mobile data industry for 2009 worth... 284 Billion dollars. Wow. Morgan Stanley says it grew 20% this year (while the global economy shrunk 5%). For those who were looking for regional splits of phone market shares or smartphone market shares - this report has them. It says that the modern smartphone is equivalent to a desktop PC 8 years ago in performance. Haha, fave topic of mine - they also say that for internet content consumption - the mobile is 'better' in at least four areas (but not in every case). These 4 are email, VoIP, news and social networking. And they tell us that the value of paid digital content on mobile phones is 4x as big as the value of paid digital content on the PC internet.

And yes, hundreds of more data points, stats and tons of good graphs to help explain. Totally worth downloading, reading and quoting. Enjoy

You can download the report from here.

3.9G (LTE) to 4G

Yesterday I blogged about the LTE-Advanced workshop. There are loads of documents that a lot of you will probably find it useful. You can also check the latest whitepapers and presentations on the 3g4g website here.

Last month Nomor published a whitepaper titled 'The way of LTE towards 4G'. The paper is good summary of the progress in standardisation. The following is summary from that paper with regards to LTE-A standardisation:

3GPP already agreed on the schedule for Release 10 where LTE Advanced will be standardized with:

• functional freeze in December 2010

• ASN.1 freeze in March/June 2011

In practice this means that the Physical Layer specification will have to be completed around September 2010, which leaves just about 9 months time. The protocol, interface and test

specification are to be completed by December 2010.

According to the major LTE-A functional enhancements, the following work items have been approved for Release 10:

• Carrier aggregation for LTE

• Enhanced downlink multiple antenna transmission for LTE

• Uplink multiple antenna transmission for LTE

• Latency reductions for LTE

A presentation introducing LTE-A technologies has been published early this year in [4].

The work on Cooperative Multipoint Transmission (CoMP) is still part of the downlink multiple

antenna work item. It is stated that the standardization impact of downlink CoMP will be assessed and a decision will be done in March 2010 if downlink CoMP will be standardized as part of this work item.

LTE Advanced will be fully built on the existing LTE specification Release 10 and not be defined as a new specification series. Stage 2 (architecture and functional description) will for instance be added to TS 36.300 in Release 10.

Please keep in mind that there are a large number of other work items within Release 10. Remarkably 3GPP also approved a Work Item on LTE Advanced Relays to improve coverage and improve cell edge throughput. The Work Item was supported by key operators.

You can read the complete paper here.

3GPP IMT-Advanced Workshop in Beijing

3GPP technical experts have attended the recent IMT-Advanced workshop, in Beijing, China, hosted by the China MIIT Institute of Communication Standards Research (CATR) and China Mobile.

The workshop was chaired by the 3GPP TSG RAN chairman, Takehiro Nakamura, with the first day given over to 3GPP RAN working group presentations and the second to the twelve IMT-Advanced evaluation groups.

3GPP Presentations:

• LTE technologies (Takehiro Nakamura: TSG-RAN Chair, NTT DOCOMO)
• Physical layer aspects (Matthew Baker: RAN WG1 Chair, Alcatel-Lucent)
• Layer 2 and 3 aspects (Magnus Lindström: RAN WG2, Ericsson)
• RAN architecture aspects (Dino Flore: RAN WG3 Chair, Qualcomm)
• RF aspects (Takaharu Nakamura: RAN WG4 Chair, Fujitsu)
• 3GPP Self evaluation methodology and results (Tetsushi Abe: RAN WG1 Vice-Chair, NTT DOCOMO)

Status reports from the IMT-Advanced Independent Evaluation Groups (IEG):

• ARIB
• ATIS WTSC Evaluation Group
• CEG
• ChEG (Part I) (Part II)
• ETSI
• REG
• TCOE India
• TR 45 (Presentation not available)
• TTA PG707
• WFEG
• WINNER+ (Part I)(Part II

You can view the agenda of the workshop here.

You can also check all the documents directly here.

LOL, Hitler upset for LTE does not have CS domain

LTE Release-8 UE Categories table

I had posted a table earlier about the LTE UE Categories here. Just came across the 3GPP official UE Categories table today as shown in the picture above.

It would be very interesting to see a device supporting 4x4 MIMO later that can be useful in transferring high amounts of data.

Interesting Presentation on Mobile Social Networking in Japan

Japan Mobile SNS Study 2010

View more presentations from yaromir.

If you have any comments or questions, leave it at the authors blog here.