Difference between SDU and PDU

This question keeps propping up in many discussions so here is an explanation for the difference between PDU and SDU.




Going back to the basics, a protocol stack consists of many different individual protocols. Protocols can be simply described as set of rules that allow communication between peer entities or they can also be described as set of rules that facilitate horizontal communication. Now these protocols are arranged in layers as can be seen in the figure above. In the transmitter side, a layer N receives data from layer N+1 and this data is called the SDU or Service Data Unit. This layer will modify the data and convert it into a PDU or a Protocol Data Unit. The peer entity in the receiver is only able to understand this PDU.

In simplest form, this modification by layer N of the layer N+1 SDU contains encapsulation. In encapsulation, the SDU is preserved as it is and an additional header is added by the layer N protocol. The modification can also perform concatenation (where more than one SDU is combined in a single PDU), segmentation (where a SDU can be split so that different parts of it end up in different PDU) and padding (where SDU is so small that filler bits are added in the end to complete the PDU).

In the receiver side, the peer entity receives the PDU from layer N-1 (its actually layer N-1 SDU) and convert it back into SDU(s) and passes it to layer N+1.

The figure above shows an example of RLC SDU and PDU. The SDU's are received from higher layer, which is from PDCP in case of LTE. These SDU's have to be converted to PDU's so they undergo segmentation and concatenation and suitable RLC headers are added to form the RLC PDU's.

First Figure Source: The TCP/IP Guide

Second Figure Source: 3G Evolution - HSPA and LTE for Mobile Broadband, Erik Dahlman et al.

Bankrupt Nortel pays hefty bonuses to executives

Nortel Networks, as it continues to wade through bankruptcy protection, posted a $2.14 billion loss in the fourth quarter and a $5.8 billion loss for all of 2008.

The above news obviously paints picture where the restructuring and job losses will be normal activity at Nortel. However the news which I got to read today and which is not at all normal is that Nortel is going to pay $7.3 million as a bonuses to it’s executives.

This is quite extraordinary for me specially when employees at the bankrupt company were forced to decide between severance pay and their pension plans.

An Ontario Superior Court Judge Geoffrey Morawetz has allowed Nortel Networks Corp. to pay these bonuses to some Canadian senior executives as part of an incentive plan to keep them with the company to drive reorganization as it tries to emerge from bankruptcy protection.Earlier this month, a U.S. court overseeing Nortel's bankruptcy allowed the company to pay $22 million in bonuses the company said it needed to keep 880 employees worldwide.

All the amounts mentioned above do not include any payments to CEO Mike Zafirovski. This becomes quite apparent that whatever compensation Zafirovski receives will come from a separate pot.

It’s reported that under the terms of the key executive incentive plan, the top executives could get cash incentives of 100 per cent to 183 per cent of base salaries where the salaries are thought to in the $1-million U.S. annual range.

These new payments in terms of bonuses has not gone down well and there are vociferous protests specially from a lawyer representing a group of Nortel workers who have been fired but have not received severance pay.

For me this situation is like there is a guy who refuses to pay his debts but then spends £10,000 for a car. These are tough times and it should apply fairly to everybody.

Nortel has offered to give fired employees early access to pension plans and provide medical benefits to retirees under the condition that they drop their claims for severance pay in bankruptcy court.

The telecom equipment giant filed for bankruptcy protection in mid-January and has until May to restructure. Since filing the bankruptcy, Nortel’s revenue declined 15 percent year-over-year in the fourth quarter, down to $2.72 billion.

As a part of restructuring process Nortel may offload some of its major units, including its wireless equipment business, instead of trying to remain a whole company.

Recession is affecting Mobile giants big time.

In November 2008, Nokia cut 600 jobs in Finland, Britain, the United States, and Singapore. According to its final quarter trading statement of last year, Nokia’s operating profits slumped 80% to €492m on the back of a 19 per cent fall in sales to €12.7bn.

As a result, Nokia is cutting another 1,700 jobs around the world, including an undisclosed number in the UK and China. The handset group plans to shed staff across its divisions, including sales and marketing, research and development and its corporate offices. Nokia, which runs UK offices in London, Farnborough and Cambridge, said it was determined to cut costs to weather the recession.

In China, the company has put forward a voluntary resignation plan in February 2009, encouraging employees to resign on a voluntary basis. It was learned that Nokia China would make termination payments to the first 1,000 employees who are willing to resign between March 1 and May 31, 2009. The company says it hopes to reduce human resource costs and avoid involuntary redundancy through this measure. In addition, Nokia is also encouraging its staff to take unpaid leave this year.

Last week, Sony Ericsson plunged the mobile phone industry into crisis , issuing a disastrous profits warning as it revealed that it expected the world to buy 10 per cent fewer handsets this year. This quarter, it is expected to ship about 14 million mobile phones, for sale at, on average, €120 (£113) each. By contrast, it shipped 24.2 million phones at €121 in the previous three months. Sony Ericsson warned that weak demand from consumers, as well as destocking, meant it would lose up to €390m in the first three months of its financial year.

It will be the company's fourth consecutive quarterly loss. The company, which has already announced plans to cut 2,000 staff has so far refused to rule out further job losses. A spokeswoman said 1,000 employees have already left the business, with 1,000 more to follow soon in an attempt to achieve €300m in cost savings by the second-half of this year. However, at the end of January the company announced a further €180m cost-cutting drive, which "will have an additional impact on jobs". The business employs about 500 staff in the UK. One site in Manchester is already earmarked for closure.

Now, Vodafone, the mobile phone giant which is set to post profits of nearly £12bn for the year to March, has scrapped pay rises for all its 10,000 UK staff, ditched bonuses and told its sales reps to keep their cars for longer, as it attempts to trim £1bn from the firm's costs.

Less than one month after Vodafone said it was axing 500 jobs in Britain, a confidential email from Guy Laurence, the chief executive of the firm's UK business, was sent to everyone in Vodafone UK detailing the pay freeze, described by Laurence as a "tough decision to make, but a responsible one".

In the memo, Mr Laurence says: "If we had agreed to a salary rise it would have forced us to increase the number of redundancies in the recent announcement." Vodafone would be "asking company car drivers and those with job requirement cars to keep their cars for longer," he said.

Changes would also be made to "bonus plans for the next financial year", with the incorporation of new targets based on profit shares.

Vodafone said last month that job cuts at the telecoms group were necessary to allow it "to compete more effectively in the UK market". Retail staff were unaffected by the cuts, which largely fell on staff at the firm's Newbury headquarters, with 170 being made redundant.

By the way, According to Telegraph, Motorola, the fifth biggest player, is thought to be on the verge of bankruptcy.

Home e-NodeB Architecture in Release 8

The Architecture of Home e-NodeB's (popularly known as Femtocells) is as shown above.

The E-UTRAN architecture may deploy a Home eNB Gateway (HeNB GW) to allow the S1 interface between the HeNB and the EPC to scale to support a large number of HeNBs. The HeNB GW serves as a concentrator for the C-Plane, specifically the S1-MME interface. The S1-U interface from the HeNB may be terminated at the HeNB GW, or a direct logical U-Plane connection between HeNB and S-GW may be used.

At present there is no support X2 connectivity of HeNBs.

The S1 interface is defined as the interface:

• Between the HeNB GW and the Core Network,
• Between the HeNB and the HeNB GW,
• Between the HeNB and the Core Network,
• Between the eNB and the Core Network.

The HeNB GW appears to the MME as an eNB. The HeNB GW appears to the HeNB as an MME. The S1 interface between the HeNB and the EPC is the same whether the HeNB is connected to the EPC via a HeNB GW or not.

The HeNB GW shall connect to the EPC in a way that inbound and outbound mobility to cells served by the HeNB GW shall not necessarily require inter MME handovers.

The functions supported by the HeNB shall be the same as those supported by an eNB (with the possible exception of NNSF - NAS Node Selection Function) and the procedures run between a HeNB and the EPC shall be the same as those between an eNB and the EPC.

The HeNB hosts the same functions as an eNB, with the following additional specifications in case of connection to the HeNB GW:

• Discovery of a suitable Serving HeNB GW
• A HeNB shall only connect to a single HeNB GW at one time, namely no S1 Flex function shall be used at the HeNB in case of connection to the HeNB GW.
• If the HeNB is connected to a HeNB GW, it will not simultaneously connect to another HeNB GW, or another MME.
• The TAC and PLMN ID used by the HeNB shall also be supported by the HeNB GW.
• When the HeNB connects to a HeNB GW, selection of an MME at UE attachment is hosted by the HeNB GW instead of the HeNB;
• HeNBs may be deployed without network planning. A HeNB may be moved from one geographical area to another and therefore it may need to connect to different HeNB GWs depending on its location.

The HeNB GW hosts the following functions:

• Relaying UE-associated S1 application part messages between the MME serving the UE and the HeNB serving the UE;
• Terminating non-UE associated S1 application part procedures towards the HeNB and towards the MME. Note that when a HeNB GW is deployed, non-UE associated procedures shall be run between HeNBs and the HeNB GW and between the HeNB GW and the MME.
• Optionally terminating S1-U interface with the HeNB and with the SGW.
• Supporting TAC and PLMN ID used by the HeNB

In addition the MME hosts the following functions:

• Access control for UEs that are members of Closed Subscriber Groups (CSG).

Mechanisms for filtering of paging messages, in order to avoid paging message distribution to HeNBs belonging to CSGs where the UE is not registered, is FFS.

Source: 3GPP TS 36.300 - E-UTRA and E-UTRAN Overall description; Stage 2 (Release 8)

LTE: MIB and SIB transmission

One very interesting change that has been done is that in LTE the system information is not all transmitted on the same channel unlike UMTS/HSPA. Logically all BCH info is mapped on BCCH. On the transport channel side, the information is mapped either on BCH or DL-SCH. (DL-SCH = Downlink Shared Channel). Ofcourse they map onto different physical channels as can be seen in the diagram.

Once the UE has achieved synchronisation, it will read the MIB to camp on the cell. In LTE, MIB contains very limited information. It contains information about the cell bandwidth, some information about PHICH (Physical HARQ Indicator Channel) and the SFN.

The SIB's as I mentioned are transmitted on DL-SCH mapped on PDSCH. To receive information about SIB's the UE needs information about PHICH which is read from the MIB.

The BCH channel has a TTI of 40ms (which is quite a lot for LTE, if you think about it). Also it has very small transport block size and protected with 1/3 convolutional code and 16bit CRC.

All these help to keep the overhead in LTE system to minimum.

QR Codes expected to become big in the US

Quick-response (QR) codes are well-entrenched in Japan, where consumers routinely use their cellphones to check e-mail, download movie trailers, navigate Tokyo's labyrinthine streets, pay water bills, buy Cokes from high-tech vending machines, download e-coupons and even have their fortunes told.

They also use their phones to scan QR codes on magazine and outdoor ads. The digital codes are read by the phones' cameras and redirect them to designated mobile sites.

Northwest Airlines, for instance, has used QR codes on large outdoor posters in high-traffic areas in downtown Tokyo to send e-certificates for travel deals and award frequent-flyer bonus miles through its WorldPerks program. The campaign was created by Mindshare's Tokyo office.

Nestle used the technology to launch a canned drink called Nescafe Shake. A QR code on promotional materials led cellphone users to a mobile site where they could download two 15-minute films created by WPP's JWT, Tokyo. Users could also download the films' original music as songs or ringtones.

QR codes have moved beyond Japan into other Asian markets, including China. The latest generation of QR technology lets marketers and retailers fine-tune their messages, making the experience more personal.

The codes have improved, too. A Hong Kong-based company called MyClick Media has pioneered image-recognition mobile marketing in North Asia. Instead of photographing bar codes, users click on logos, objects and images selected by marketers. The photos grant users one-click access to mobile-based internet content, services, rewards and gifts via e-mail, text and multimedia messaging service.

Since the technology is limited to high-end phones and requires a software download, MyClick hasn't been a success for mass-market campaigns. But marketers such as Coca-Cola and Adidas have scored points with consumers in smaller promotions such as sporting events. China Mobile used MyClick to encourage subscribers to share good wishes for athletes during the Olympic Games last year in Beijing.

Not long back, I blogged about Bar Coded train tickets on mobiles. They now seem to be catching on in USA as well.

When Peter Shipman, a franchise owner of the Qdoba casual Mexican restaurant chain, was launching his third outlet in the college town of Ann Arbor, Mich., he needed a way to draw students to the new location -- and he wanted to speak their technological parlance. So he bought ads in the campus newspaper and posted promotional posters, each with a code kids could scan with their phones to get a mobile coupon for a buy-one-get-one-free burrito.

The campaign, which ran on technology from a company called Jagtag, netted a 52% redemption rate with about 400 scans* , roughly 1% of the total target student population.

For Qdoba, it was a digital version of clipping coupons. But these codes -- known as 2-D barcodes, since they're scanned both horizontally and vertically -- can also deliver product reviews, video demos or any other tool a marketer has in its digital arsenal. They can also help marketers track static ads and product performance in retail channels: Did the print ad get more scans in the men's lifestyle glossy or the outdoor-enthusiast magazine?

Qdoba joins small but growing group of marketers warming to the long-promised technology. In fact, among three vendors working to make this a reality -- Scanbuy, Jagtag and Clic2C -- there are at least 15 initiatives involving national brands in the retail, fashion, food and beverage categories that should hit next quarter.

Nike 6.0, the action-sports division of the footwear maker, recently deployed 2-D barcodes at several sporting events it sponsored late last year, delivering content about Nike athletes to fans who sent in images of Jagtag codes. While Nike won't disclose campaign metrics, Butch Bannon, a business-development exec at its promotional-marketing agency, TAOW Productions, said Nike will look at other ways of integrating 2-D barcodes in future venues.

Microsoft will be slapping 2-D barcodes on the next round of packaging for its Xbox games, said Larry Harris, CEO of Ansible, which worked with Microsoft on a 2-D-barcode campaign to promote an enterprise server.

This kind of one-to-one exchange between brand and consumer is already well-entrenched in Japan, where they're known as QR codes and where readers come preinstalled on about 70% of all mobile phones. But stateside only a few brands have flirted with the technology, mostly because consumers don't want to bother downloading the applications required to read the codes. Plus, there are no standards for 2-D barcodes in the U.S., meaning the codes employed in one-off campaigns are proprietary, and each require their own reader and decoder.

Jagtag is trying to solve that problem by making it easier for consumers. Rather than downloading an application, they take a picture of Jagtag's 2-D barcode and send it to a short code, and Jagtag sends back a URL, coupon or other media via multimedia messaging service.

But analysts and Jagtag competitors agree that for 2-D barcodes to gain any meaningful traction, the code reader must come preloaded on cellphones -- and only the wireless carriers can make happen, as they dictate the specs to handset makers.

Jonathan Bulkeley, CEO of Scanbuy, a Jagtag competitor, said he expects his code reader to be preinstalled on 10 to 12 handsets sold by Sprint and Alltel, which Verizon has acquired, by this spring. But consider there are 250 different handsets in the U.S., and they run on several different operating systems. That's a long way to go.

The wireless carriers are slowly coming onboard as they look to transactions and commerce to help drive revenue. Scanbuy has been chasing AT&T and Verizon for at least 18 months; late last year, it got Sprint to approve its application, so users can download it on 40 handsets sold by the carrier. The No. 3 U.S. carrier began promoting Scanbuy's application on its website late last year. Jagtag's service works with AT&T and Verizon. "Carriers need to figure out how to make money on navigation, transaction and advertising," Mr. Bulkeley said. "On mobile, consumers are going to go directly to what they're interested in, not go search for it."

IPHOBAC's advanced photonic technologies: Up to 12.5 Gbit/s @ 60 GHz

With much of the mobile world yet to migrate to 3G mobile communications, let alone 4G, European researchers are already working on a new technology able to deliver data wirelessly up to 12.5Gb/s.

The technology – known as ‘millimetre (mm)-wave’ or microwave photonics – has commercial applications not just in telecommunications (access and in-house networks) but also in instrumentation, radar, security, radio astronomy and other fields.

Despite the quantum leap in performance made possible by combining the latest radio and optics technologies to produce mm-wave components, it will probably only be a few years before there are real benefits for the average EU citizen.

This is thanks to research and development work being done by the EU-funded project IPHOBAC, which brings together partners from both academia and industry with the aim of developing a new class of components and systems for mm-wave applications.

The mm-wave band is the extremely high frequency part of the radio spectrum, from 30 to 300 gigahertz (GHz), and it gets it name from having a wavelength of one to 10mm. Until now, the band has been largely undeveloped, so the new technology makes available for exploitation more of the scarce and much-in-demand spectrum.

It recently unveiled a tiny component, a transmitter able to transmit a continuous signal not only through the entire mm-wave band but beyond. Its full range is 30 to 325GHz and even higher frequency operation is now under investigation. The first component worldwide able to deliver that range of performance, it will be used in both communications and radar systems. Other components developed by the project include 110GHz modulators, 110GHz photodetectors, 300GHz dual-mode lasers, 60GHz mode-locked lasers, and 60GHz transceivers.

Project coordinator Andreas Stöhr says millimetre-wave photonics is a truly disruptive technology for high frequency applications. “It offers unique capabilities such as ultra-wide tunability and low-phase noise which are not possible with competing technologies, such as electronics,” he says.

What this will mean in practical terms is not only ultra-fast wireless data transfer over telecommunications networks, but also a whole range of new applications.


One of these, a 60GHz Photonic Wireless System, was demonstrated at the ICT 2008 exhibition in Lyon and was voted into the Top Ten Best exhibits. The system allows wireless connectivity in full high definition (HD) between devices in the home, such as a set-top box, TV, PC, and mobile devices. It is the first home area network to demonstrate the speeds necessary for full wireless HD of up to 3Gb/s.

The system can also be used to provide multi-camera coverage of live events in HD. “There is no time to compress the signal as the director needs to see live feed from every camera to decide which picture to use, and ours is the only technology which can deliver fast enough data rates to transmit uncompressed HD video/audio signals,” says Stöhr.

The same technology has been demonstrated for access telecom networks and has delivered world record data rates of up to 12.5Gb/s over short- to medium-range wireless spans, or 1500 times the speed of upcoming 4G mobile networks.

One way in which the technology can be deployed in the relatively short term, according to Stöhr, is wirelessly supporting very fast broadband to remote areas. “You can have your fibre in the ground delivering 10Gb/s but we can deliver this by air to remote areas where there is no fibre or to bridge gaps in fibre networks,” he says.

The project is also developing systems for space applications, working with the European Space Agency. Stöhr said he could not reveal details as this has not yet been made public, save to say the systems will operate in the 100GHz band and are needed immediately.

There are various ongoing co-operation projects with industry to commercialise the components and systems, and some components are already at a pre-commercial stage and are being sold in limited numbers. There are also ongoing talks with some of the biggest names in telecommunications, including Siemens, Ericsson, Thales Communications and Malaysia Telecom.

“In just a few years time everybody will be able to see the results of the IPHOBAC project in telecommunications, in the home, in radio astronomy and in space. It is a completely new technology which will be used in many applications even medical ones where mm-wave devices to detect skin cancer are under investigation,” says Stöhr.

You can see their demo here.

LTE is really going for it

In my blog last week I tried to present some arguments which lead to the belief that LTE might take us out from the current recession.

After the current Mobile world congress the vibes coming out are very much in favour of LTE. It looks like an LTE onslaught. I must admit that the recent development in the LTE sector ahs really pushed the technology closer to the reality. These developments have really given a kick to the WiMax camp as well and one can see the nervousness in the WiMax camp.
Following are some of the recent LTE onslaught as I might say:

• Motorola, Nokia Siemens Networks and Ericsson have already made LTE announcements.
• Motorola introduced its LTE base stations,
• Nokia announced a new version of its Flexi Multiradio base station that expands the technologies supported by the NSN line to cover GSM/EDGE, WCDMA/HSPA and LTE in a single unit.
• Ericsson introduced an evolved packet core portfolio for LTE networks so that HSPA operators can gracefully migrate to LTE.

Things are a really spicing up in the market especially with the operators already started playing mind games in terms of whom to choose their vendors for the LTE devices.

Just last week there was a report where it said that Verizon Wireless and Nokia are reportedly planning a partnership that might be an exclusive deal to create an "iconic" device to run on Verizon's Long Term Evolution (LTE) network.

Although not sure how true the above report is but it still was buzzing news. There is no doubt that whenever the announcement will come from Verizon regarding the very vendors it is choosing, it will be a surprise to everyone.

Just remember the last year where the industry was really struggling to put a strong hold on LTE. I still remember very well, last year all the talks were for WiMax and the Vodafone Group CEO Arun Sarin urged the vendor community to step up efforts on the LTE standard since WiMAX was ahead in its development. WiMAX may still be ahead this year, but LTE certainly has the momentum behind it.

Certainly WiMax and the news related to it will be around but what interests me is how some of the companies are now making LTE as their priority as the future broadband technology. It’s unbelievable that those companies who were once heavily pushing WiMAX have now jumped into the LTE market.

Wireless 20/20, for instance, used to be WiMAX 20/20, but now its on the LTE bandwagon.

It’s already reported that 26 operators have committed to Long Term Evolution (LTE) technology out of which ten network operators are ready to launch their networks by 2010

Other companies have made some good progress in WiMAX, announcing new innovative products; still others appear to be threatened by the onslaught of LTE, trying to dub LTE as just another Long Term Excuse.

£300/min: The cost of mobile broadband while roaming

Trying to keep his young son entertained in the evenings on a skiing holiday, Will Pierce decided to download a few episodes of their favourite TV shows.

He had assumed that he could use his £25 Vodafone data card - which gives him access to mobile broadband while overseas - without incurring any unexpected costs.

But when he returned from the five-day break in Meribel, he was sent a phone bill for nearly £21,716.

Mr Pierce and his son Louis, eight, had gone for a 'boys' holiday' with another father and his son, also eight.

The group rented an apartment, but it did not have any English-language TV channels. With the boys too young to spend evenings out in the resort, Mr Pierce was anxious to keep them entertained.

So over the course of the stay he downloaded several shows - mostly Top Gear for the boys and Kavanagh QC for the grown-ups - on to his laptop computer using the data card.

He was charged according to the number of megabytes used, meaning one show lasting less than 18 minutes cost him £5,132 - almost £300 a minute. Downloading the same size file in the UK would not have cost Mr Pierce anything under most broadband tariffs.

Mr Pierce did not deal directly with Vodafone, instead addressing his complaint to DRD Communication Services, the European network operator.

DRD agreed to waive its fees, bringing the bill down to £16,500, but Vodafone initially insisted that the usage was 'valid' and refused to back down.

However, a spokesman for Vodafone said yesterday that the company would waive the full amount.

She added: 'Such bills are exceptionally rare and we have an investigation under way.'

Next Generation “Sixth Sense” game-changing wearable tech

TED has this very interesting concept from Pattie Maes’ lab at MIT, spearheaded by Pranav Mistry. It’s a wearable device with a projector that paves the way for profound interaction with our environment. Imagine “Minority Report” and then some...


Its just matter of time after this concept becomes reality for it to be available in mobiles, etc.