Friday, 26 March 2010

E-UTRAN Mobility Drivers and Limitations

Many years back, when things used to be simple, I wrote a tutorial about Handovers in UMTS. It would be very difficult to write a similarly simple tutorial for LTE. Things are a bit complicated because there are many different conditions in which handovers can take place.

It was also easier to visualise the Intra-frequency and Inter-frequency handovers in UMTS and you can probably do the same to some extent in LTE but with things getting more complicated and carrier aggregation, classifying handovers in these categories may be difficult.

3GPP TS 36.300 has an informative Annex E which details the scenarios in which handovers and cell change can/will take place.

It is best to go and see Annex E in detail. Here is a bit of summary from there:

Intra-frequency mobility: intra-frequency mobility is the most fundamental, indispensable, and frequent scenario. With the frequency reuse being one in E-UTRAN, applying any driver other than the “best radio condition” to intra-frequency mobility control incur increased interference and hence degraded performance.

Inter-frequency mobility: as in UTRAN, an operator may have multiple carriers/bands for E-UTRAN working in parallel. The use of these frequency layers may be diverse. For example, some of these frequency layers may utilise the same eNB sites and antenna locations (i.e., co-located configuration), whereas some may be used to form a hierarchical cell structure (HCS), or even be used for private networks. Some frequency layers may provide MBMS services, while some may not. Moreover, E-UTRAN carriers/bands may be extended in the future to increase capacity.

Inter-RAT mobility: the aspects that need to be considered for inter-RAT are similar to those for inter-frequency. For mobility solutions to be complete with the inter-RAT drivers, relevant updates would be necessary on the legacy (UTRAN/GERAN) specifications. This will add to the limitations, which are evidently more effective in inter-RAT.

The drivers for mobility control are:

Best radio condition: The primary purpose of cell reselection, regardless of intra-frequency, inter-frequency, or inter-RAT, is to ensure that the UE camps on/connects to the best cell in terms of radio condition, e.g., path loss, received reference symbol power, or received reference symbol Es/I0. The UE should support measurements to suffice this aspect.

Camp load balancing: This is to distribute idle state UEs among the available bands/carriers/RATs, such that upon activation, the traffic loading of the bands/carriers/RATs would be balanced. At least the path loss difference between different bands should be compensated to avoid UEs concentrating to a certain frequency layer.

Traffic load balancing: This is to balance the loading of active state UEs, using redirection for example. In E-UTRAN, traffic load balancing is essential because of the shared channel nature. That is, the user throughput decreases as the number of active UEs in the cell increases, and the loading directly impacts on the user perception.

UE capability: As E-UTRAN bands/carriers may be extended in the future, UEs having different band capabilities may coexist within a network. It is also likely that roaming UEs have different band capabilities. Overlaying different RATs adds to this variety.

Hierarchical cell structures: As in UTRAN, hierarchical cell structures (HCS) may be utilised in E-UTRAN to cover for example, indoors and hot spots efficiently. It is possible that E-UTRAN is initially deployed only at hot spots, in which case this driver becomes essential for inter-RAT, not just for inter-frequency. Another use case would be to deploy a large umbrella cell to cover a vast area without having to deploy a number of regular cells, while providing capacity by the regular cells on another frequency.

Network sharing: At the edge of a shared portion of a network, it will be necessary to direct UEs belonging to different PLMNs to different target cells.

Private networks/home cells: Cells that are part of a sub-network should prioritise the camping on that sub-network. UEs that do not belong to private sub-networks should not attempt to camp or access them.

Subscription based mobility control: This mobility driver aims to limit the inter-RAT mobility for certain UEs, e.g., based on subscription or other operator policies.

Service based mobility control: An operator may have different policies in allocating frequencies to certain services. For example, the operator may concentrate VoIP UEs to a certain frequency layer or RAT (e.g., UTRAN or GERAN), if evaluations prove this effective. UEs requiring higher data rates may better be served on a frequency layer or RAT (e.g., E-UTRAN) having a larger bandwidth. The operator may also want to accommodate premium services on a certain frequency layer or RAT, that has better coverage or larger bandwidth.

MBMS: For Release-9, no new mobility procedures compared to Release-8 are included specifically for MBMS. In future releases the following should be considered. As MBMS services may be provided only in certain frequency layers, it may be beneficial/necessary to control inter-frequency/RAT mobility depending on whether the UE receives a particular MBMS service or not. For MBMS scenarios only, UE based service dependent cell reselection might be considered acceptable. This aspect also depends on the UE capability for simultaneous reception of MBMS and unicast.

While the issues mentioned above drive E-UTRAN towards “aggressive” mobility control, the limiting factors also have to be considered:

UE battery saving: The mobility solution should not consume excessive UE battery, e.g., due to measurements, measurement reporting, broadcast signalling reception, or TA update signalling.
Network signalling/processing load: The mobility solution should not cause excessive network signalling/processing load. This includes over-the-air signalling, S1/X2 signalling, and processing load at network nodes. Unnecessary handovers and cell reselections should be avoided, and PCH and broadcast signalling, as well as dedicated signallings, should be limited.

U-plane interruption and data loss: U-plane interruption and data loss caused by the mobility solution should be limited.

OAM complexity: The mobility solution should not demand excessive efforts in operating/maintaining a network. For example, when a new eNB is added or an existing eNB fails, the mobility solution should not incur excessive efforts to set up or modify the parameters.

More details available in Annex E of 3GPP TS 36.300

Thursday, 25 March 2010

Home Relays for LTE-Advanced

If you look at the Home eNodeB (Femtocell) architecture, the HeNB is connected to its gateway which in turn is connected to MME/S-GW. There is a considerable amount of technology investment in this approach. The HeNB consists of complete protocol stack, the HeNB-GW is an expensive piece of equipment and there is lots of other things including the management software, etc.

Now in LTE-A, there is a concept of Relays which we have talked about. The Relays do not contain the complete stack (generally just L1 and L2). If capacity is not an issue but coverage, then we may be able to use Home Relays.

The backhaul for Femtocell is Internet whereas for Relay its generally the same Radio resources within the cell. I guess the main thing for Relay is the requirement of reasonably good channel (Line of sight maybe). Home Relays can use the Internet connection but rather than connection terminating in some kind of gateway, it can terminate at the actual eNB.

There are already many advanced antenna techniques that can handle the transmission and reception without much interference and maybe the SON algorithms may need some additional improvements.

The main thing is that if this technology becomes reality then it may cost less than $50 per Home relay and would become really a commonplace.

Tuesday, 23 March 2010

Femtocells for Beginners

Good beginner level primer for Femtocells is available at Radio-Electronics website. It covers important topics like architecture, interference, security and health issues. Wort a read if you are a newbie to the Femto domain. Click here.

Monday, 22 March 2010

Speech for Mobile to become big industry

Its interesting that its not only Google that experimenting with Voice Recognition and Voice search but a whole lot of other players. Earlier I blogged about Real time Speech Translation and another one was the Voicemail search. Google's search App also allows to search using voice rather than by entering text.

SpeechTek Europe 2010 is a new conference that promises to make everyone aware of the new Speech Technologies and their application in Mobile and other domains.

Produced by the publishers of the industry’s best-read magazine, Speech Technology, SpeechTEK Europe is the sister of the highly successful New York annual event series and aims to capitalise on the wealth of speech innovators based here in Europe.

The conference has been developed by a Steering Committee which comprises some of the industry’s most respected thought leaders. Here they share their insights into the future for speech technologies, how they are developing, and where they will be used.

Loquendo’s Vice President of International Sales, Rosanna Duce, predicts that voice control will be a major growth area in the next five years:

One important emerging speech technology is undoubtedly the voice control of all kinds of devices, for example, PDAs, mobile phones, DVD players.” She comments, “These technologies are currently being expanded and upgraded to allow all functions to be accessed using voice, thus eliminating the need to use a keyboard. Consumer demand seems to suggest that the option to dictate text messages will be a major source of growth in this area, as will be the reading of incoming messages by a TTS application bundled with the phone/PDA.”

Nava Shaked, CEO of Business Technologies, agrees,

The combination of voice search engines, internet and mobile is a real opportunity for speech technology growth and influence. This includes the introduction of previously unseen applications for voice user interface and transcription. The combination of voice and video is also promising and will be inevitable in our interaction with multimedia.”

James Larson, the Conference Chair, supports these views,

Multimodal applications on mobile devices will enable customers to not only speak and listen, but to also read and type and use additional modes in interaction. These apps will be easy to learn, easy to use, and much more natural than current voice-only apps or GUI-only apps. They will always be available, and customers can use them wherever they are, not just at their desktop or in their car.” He concludes, “Multimodal applications on mobile devices will dramatically change how we interact with appliances - TV, radio, environmental control - with the internet, and with other people.”

The SpeechTEK Europe conference programme explores these trends and the implications for the industry as a whole. Real world applications and case studies are a particular feature of the event, so delegates can see for themselves how speech is working in a variety of different environments, how to select and implement the technology, and how to evaluate its performance.

The full SpeechTEK Europe programme is available at: along with registration information, details of registration savings, and free entry exhibition tickets.

Friday, 19 March 2010

IPv6 transition in cellular networks gaining momentum

IPv6 is good and we all know that. I has been talked for years but practically it hasnt found much success. Verizon made some noise last year but I am not sure of the conclusion.

Just to recap, IPv4 was introduced back in 1982 and IPv6 work started since 1995. IPV4 uses 32 bit (4 bytes) addresses while IPV6 uses 128 bit (16 bytes) addresses. Theoretically we would now have 2^96 times more addresses than in case of IPv4.

Most of network infrastructure manufacturers have their equipment ready for IPv6 as some of the handset manufacturers. The main driver being that someday soon IPv4 addresses would be exhausted (Internet Assigned Numbers Authority will run out of IPv4 addresses in September of 2011, based on current projections) and their equipment would be ready to provide IPv6 addresses without any problems.

Recently, IETF-3GPP Workshop on IPv6 in cellular networks was held in San Francisco, USA on 1 - 2 March, 2010. There are lots of interesting presentations available here for people who want to dig a bit deeper. The concluding report that summarises the presentations and discussions are available here. Here is a brief summary from one of the reports (with links at the end):

  • Scenarios for IPv6 migration were discussed based on 3GPP Technical Report 23.975
    • The discussion focused on validating the scenarios
  • General IPv6 transition and deployment guidelines were outlined based on input from IETF
  • Solutions for migration and v4-v6 co-existence were presented
    • Solutions included existing RFCs and working group items but also proposals in Internet Drafts
    • Gap analysis wrt transition scenarios was discussed

Conclusions on scenarios
  • Scenarios 1 and 3 based on dual-stack and IPv6-only deployments were generally recognized as valid
  • Scenario 2 was also recognized as valid, addressing two separate problems related to insufficient RFC1918 space and subscriber identification
  • Scenario 4 did not receive wide support from the workshop, largely because it was felt that it addressed a problem already solved by other scenarios
  • Variants of some of these scenarios were brought up during the discussions, conclusions were not reached on these
    • These may need further discussion

Conclusions on solutions
  • It was recognized that necessary support in the network and devices is already available to “switch on” IPv6 in 3GPP networks
    • Some networks reported running dual stack
    • Some networks reported running IPv6-only now
  • Solutions enhancing existing mechanisms for dual stack deployments and new solutions for IPv6-only deployments drew wide support
    • Gateway-initiated Dual Stack Lite
    • Stateful IPv4/IPv6 translation
Next steps: 3GPP
  • IETF and 3GPP are expected to focus further work based on the conclusions of the workshop
    • Note that the workshop itself does not have the mandate to make formal decisions
  • 3GPP is expected to identify possible normative specification impacts, if any, of the preferred solutions
  • A need was identified to provide more operational guidelines about IPv6 deployment to 3GPP operators
    • The best location for these guidelines is FFS (e.g. 3GPP TR 23.975, GSMA, etc)
Next steps: IETF
  • IETF and 3GPP are expected to focus further work based on the conclusions of the workshop
    • Note that the workshop itself does not have the mandate to make formal decisions
  • IETF is encouraged to continue working on stateless and stateful IPv4/IPv6 translation mechanisms
    • These mechanisms are being worked on in IETF BEHAVE group
  • IETF is also encouraged to consider new solutions that are not yet working group items
    • Gateway Initiated DS Lite
    • Per-interface NAT44 bindings addressing IPv4 address shortage
  • Note that the workshop has not set any timelines

Further reading:

Thursday, 18 March 2010

The size of Mobile Market (Amazing Pic)

Click on the photograph to view the larger version. I assume, its self explanatory.

Mobile Apps market to grow to '$17.5bn by 2012'

A study done for Getjar, the world's second biggest app store, said the market will grow to $17.5bn (£12bn) in the next two years.

The study claimed downloads would climb from 7bn last year to 50bn by 2012 - a 92% year-on-year increase.

It found there had been a gold rush with the number of app stores rising from four before 2008 to 48 today.

The study also suggests Apple's domination of the market could be challenged.

The report titled, 'Sizing up the Global Mobile Apps Market' by Chetan Sharma is available to download here.

Some more interesting stats from the report as follows:
  • The overall mobile apps downloads are expected to increase from over 7 billion in 2009 to almost 50 billion by 2012 growing at the rate of 92% CAGR
  • The revenue from mobile apps which includes both paid downloads and revenue from advertising and virtual goods is expected to increase from $4.1 billion in 2009 to $17.5 billion by 2012 at the rate of 62% CAGR.
  • The overall global subscriptions base is expected to exceed 5 billion by the end of 2010 with over 27% of them being data subscribers
  • Non-carrier appstores jumped from a mere 8 to 38 last year
  • In 2009, advertising contributed almost 12% to the overall apps revenue.
  • The price range of applications in various stores can vary from $0.99 to $999.

Wednesday, 17 March 2010

Ringtones to help you in your daily life..

I am sure you must have heard of Music being used to torture terrorists or hardened crminals. Now you can have complete different use of music or ringtones in this case.

“Well . . . I can definitely feel a bit of adrenalin,” says Yukari Sendo, savouring the mobile phone ringtone like a fine wine, “but it really doesn’t make me want to do any housework.”
She flicks through a menu of alternative tunes and settles on one that offers to improve her skin tone through the power of alpha-waves.

Ms Sendo and her friend Ayaka Wakabayashi are among an army of young Japanese drawn to the allure of “therapeutic ringtones” — a genre of melodies that promises to ease a range of day-to-day gripes, from chronic insomnia to a rotten hangover.

Japan is no stranger to bizarre phone fads but the popularity of the ringtones is perhaps surprising given the flimsiness of the science behind them.

Much of the tones’ credibility rests in the solid reputation of Matsumi Suzuki, the head of the Japan Ringing Tone Laboratory, an eight-year-old subsidiary of the Japan Acoustic Laboratory.

Mr Suzuki’s adventures in the realm of mood-altering ringtones follow a career at the National Research Institute of Police Science, where he made award-winning advances in the field of voiceprints. One of his proudest achievements was the development of a synthetic mosquito noise that is inaudible to Japan’s over-60s but supposedly discourages teenagers from “congregating in parks at midnight”.

A spokesman for Index, the giant Japanese mobile phone content provider that sells Mr Suzuki’s ringtones, explains that while there is a shortage of actual experimentation, “the number of downloads suggests the ringtones must be working to a certain extent”. Index’s other innovations include an iPhone application that translates your dog’s bark; the “Bowlingual” automatic canine interpreter draws on an database of woofs from dozens of species.
The first therapeutic tone, a high-energy rhythm, tested for The Times by Ms Sendo and Ms Wakabayashi, was supposed to provide a sudden burst of impetus to sluggardly housewives. Yukari and Ayaka had their doubts.

The tone that is said to improve skin mixes a burst of electro-Schubert with woodland noises such as birdsong and streams. “I suppose it might subconsciously make you think of washing your face, and that is good for the skin,” said Ayaka. “At least, it would certainly send you towards the bathroom.”

Ms Sendo and Ms Wakabayashi were marginally more impressed by the sleep-inducing and sleep-preventing tones, suspiciously akin to a lullaby and a dance track. The one with most practical use, they concluded, was the tone that scares away crows — the sinister jungle ravens that terrorise the dawn streets of Tokyo by pecking at bags of rubbish.

Mr Suzuki’s latest ringtone has been timed to coincide with the Japanese hay fever season. The Ohana Sukkiri Melody emits a series of sounds at different frequencies “so that people can choose the sound that resonates most to their sinus and causes pollen lodged there to fall from the nasal cavity”.

Index admitted that it had not conducted any research on how great a pollen deluge would be induced by the ringtone but said that it was “generally understood” that resonance would help hayfever sufferers if they brought the phone close to their noses.

When it came to testing the hangover chaser ringtone, Yukari and Ayaka were relieved from experimental duties. This popular application works through what Index describes as a careful selection of “pulse-melodies” chosen for their astonishing atunement to the body’s “medical rhythms”. Testers concluded that a fried breakfast, though less portable, still had the edge.

Tuesday, 16 March 2010

How to avoid network choking in the future?

If you are looking for an answer to this question then you wont find an answer to that here. Probably no one really knows a complete answer to this question right now. A simple answer would be to have a mix of the Macro cells, Micro cells and Femtocells with some way to offload some more traffic via WiFi.

Earlier this month Skype announced that its client would be able to work on most Symbian phones. I have used the Skype client on phones from '3' and they work great. Skype is even available on iPhones and they were downloaded 1 million times in the first couple of days. Now a big chunk of operator profits come from long distance calls and calls when abroad. If we all start using our phones with Skype, its going to bite into the operators profits. That means they will have to recover this profit from us by another way.

Skype on phones will be used in always on mode, meaning that the networks will get loaded and get congested. A simple solution is to have Femtocells at home that can offload the traffic on Internet. These background apps do cause a considerable amount of traffic and recently an Operator blamed the apps for its network woes.

Femtocells have been targeted generally at the residential market with developments going on for Business users as well. Another smaller Picocells and Microcells are also easily and cheaply available nowadays. With the Ad-Hoc deployment of all these smaller cells, Self Organising Networks (SON) may have a big role to play.

What happens where there are multiple networks present in the same place via these smaller cells? Can the back-haul not get congested because of these multiple networks which may be lying Idle most of the time? How would these impact other services that we use on our PC's?

These questions can be easily answered if a single Microcell/Picocell/Femtocell was able to work for Multiple Networks. Practically this may not be possible right now because each network has a different Authentication and Security arrangement.

At least we can start thinking and working on these problems while we still have time. When its too late, we may have to come up with workarounds. These workarounds only cause more headache in the longer term.