Thursday, 13 September 2007

IMS Updates

Ericsson and Vodafone launched an IMS network in Czech republic this week. Under an agreement signed earlier this year, Ericsson was responsible for delivery and systems integration of its advanced IMS solution, along with project management, network design and implementation. With Ericsson's IMS solution, Vodafone Czech Republic can offer a wide range of next-generation IP telephony and multimedia services towards both fixed and mobile users. It said IMS is an important step towards fixed-mobile convergence. The international-standards-based technology is highly scalable, takes care of connection control, and ensures service quality as well as network and service security.
Aricent, a full-service, full-spectrum communications Software Company, announced this week that it has joined the IMS Forum, the industry's only forum dedicated to the acceleration of IP Multimedia Subsystem (IMS) application and service interoperability. Aricent has a dedicated IMS practice, with more than 800 person years of experience, offering an extensive portfolio of IMS software services and products. The services range from initial strategy and design, through software implementation to system integration and testing for the entire IMS architecture. These services accelerate time-to-revenue for Aricent clients and reduce their risks when deploying IMS-based solutions. With a comprehensive portfolio of IMS software services and products Aricent enables communications equipment manufacturers, device manufacturers and service providers to significantly reduce their time–to-market and mitigate the risks associated with IMS migration and roll-out.
Meanwhile, The IMS Forum, the industry's only Forum delivering IMS services interoperability verification and certification, announced recently that they have signed an MOU with the International Multimedia Telecommunications Consortium (IMTC), an international alliance of companies working together to improve the customer experience and accelerate market adoption of content delivery and unified communications solutions through interoperability of products and services based on open standards. The IMS Forum focuses on interoperability at the IMS Applications and Services Layer across mobile, fixed and cable broadband networks. The IMTC IMS Activity Group focuses on issues surrounding IMS Client interoperability, development and providing feedback to standards organizations.
Under the terms of the agreement, the IMS Forum and the IMTC will establish both a technical liaison between their Technical Working Groups and a marketing liaison. Through these liaisons the two groups will exchange technical information on IMS specifications, testing and interoperability, share interoperability testing best practices, collaborate on technical documents, and organize and participate in future joint testing events. The marketing liaison between the Marketing Working Groups will allow the organizations to share the results of their joint activities with the industry as well as promote this technology's adoption.

Wednesday, 12 September 2007

On Header Compression

Was doing some digging into pre-ROHC compression techniques and here they are:

Van Jacobson header compression (VJHC) (RFC 1144) is based on delta coding. The differences between two packet headers are referred to as the “delta”. Instead of transmitting the entire header, VJHC transmits only the delta. This approach achieves high compression. On the downside, it introduces vulnerability. If only one delta coded header is corrupted, all the following packets are erroneous. To recover from these errors and re–establish the current base header, VJHC sends all TCP re–transmissions uncompressed. Thus, VJHC does not require any signaling between compressor and decompressor. The disadvantage is the sensitivity to error–prone links. The Van Jacobson compression scheme was developed to increase the performance of IP/TCP flows over low bandwidth links such as PSTN. It does not even support compression of IP/UDP flows since at that time UDP traffic was very low. This scheme uses delta compression, sending only the difference in the value of the changing fields, to minimize the number of bits sent. It achieves compression from 40 bytes to on an average 4 bytes. It relies on the TCP recovery mechanism to recover from errors in the context due to bit errors and residual errors due to packet loss on the link. This scheme is obviously unsuitable for wireless links and multimedia applications.

Robustness at the cost of less compression was introduced by Perkins and Mutka. In “Dependency Removal for Transport Protocol Header Compression over Noisy Channels,” The delta–coding for the adjacent packets has been replaced by a reference frame. Several consecutive packets are aggregated to a frame. The first packet of a frame is sent uncompressed and the following packets use delta coding with respect to the first (uncompressed) packet in the frame. Clearly, the differences to packets at the end of a frame are larger than for those at the beginning. The compression gain is thus limited (and lower than for VJHC). The advantage of this approach is the usage of shorter delta coding ranges. Corrupted packets do not necessarily lead to the loss of synchronization. This is a clear advantage over VJHC.
IP Header Compression (IPHC) provides a number of extensions to VJHC. The most important extensions are support for UDP, IPv6, and additional TCP features (RFC 2507). With the explicit support of UDP come additional features, such as multicast. Nevertheless, support for RTP is still not given which makes the scheme unsuitable for many multimedia applications. Similar to VJHC, IPHC relies on the change of header fields as well as on the derivation of header field contents. The encoding also employs the delta–scheme, transmitting only the changes in the header fields.
The Compressed Real Time Protocol (CRTP) scheme presented in RFC2508 compresses the 40 bytes header of IP to 4 bytes if the UDP checksum is enabled, or to 2 bytes if it is not. This is possible by compressing the RTP/UDP/IP headers together, similar to the VJHC approach. With the characteristics of the RTP protocol, the changes for the RTP header fields become partially predictable. In addition, changes in some fields are constant over long periods of time. Thus, the expected change in these fields can be implied without even transmitting the differences. These implied fields are also referred to as first order changes. They are stored with the general context for each specific connection. The differences within fields that have to be compressed are referred to as second order differences. An example for these are video frame skips. Video frames are generally transmitted every 40 ms. In case a frame cannot be encoded (e.g., due to lack of processing power or because of a slower play-out ratio), the implied time no longer is accurate. Therefore, the new first order is set to the second order and the connection context is updated. CRTP cannot use a repair mechanism as VJHC does because UDP/RTP are unidirectional protocols without retransmissions.
RObust Checksum–based COmpression (ROCCO) is a refinement of CRTP. ROCCO includes a checksum over the original (uncompressed) header in the compressed header. The checksum facilitates local recovery of the synchronization. In addition, ROCCO incorporates compression profiles (tailored for specific applications, e.g., audio or video streaming) and has a code with hints on the change of header fields in the compressed header. These mechanisms improve the header compression performance, especially for highly error–prone links and long round trip times

Tuesday, 11 September 2007

MBMS battle heats up

The MBMS battle has started heating up with new developments and announcements nearly every week.

First of all there was this announcement from ZTE, China

China's ZTE Corp. announced that it has, in collaboration with Qualcomm, successfully completed a Multimedia Broadcast Multicast Service (MBMS) testing based on the 3GPP R6 standard conducted at its Shanghai R&D center last month.

The first testing MBMS inter-operability test (IOT) completed, test results show that 128- and 256Kbps high-speed transmission of MBMS TV programs broadcast and multicast services can be smoothly delivered over cellular networks. The success of MBMS IOT marks the readiness of commercial delivery to the mass market.

"Qualcomm is happy to cooperate with ZTE in conducting the MBMS testing, an area which we believe is part of the core development of ZTE's W-CDMA products," said Frank Meng, president of Qualcomm Greater China. "This is a major contribution in the development of MBMS and we are confident that the results of the testing will help our customers provide more competitive W-CDMA products and solutions moving forward."

Then yesterday, Anite submitted first MBMS Conformance Test which they were able to pass on Nokia NoRM-6 and Qualcomm 7200 UE. Other System Simulator manufacturers are not far behind with Anritsu and R&S also focussing heavily on MBMS test cases development.

Anritsu Protocol Test System (PTS) is shown in the figure above.

At present it seems Nokia and Qualcomm are leading the way on the UE side but in past i have heard about Ericsson and Motorola being MBMS ready soon.

Sunday, 9 September 2007

ROHC, compressing IP headers over air interface

In an All-IP network, when IP packets are transmitted over the air, it would make more sense to strip down the headers as headers could be as big as the data being transmitted and these headers are overhead wasting the precious air resource. To help compress these headers, RObust Header Compression was standardised. Infact ROHC is not the only header compression scheme and i will post a bit more information in my future posts on which scehemes are available and why ROHC is used.

The diagram above shows the basic ROHC principle. It shows that ROHC compresseor is used before the data is sent over the air and decompressor at the receiving end adds the uncompressed headers back to the received packets. As expected, ROHC only works if both the ends have ROHC protocol.

A typical header compression is shown in the diagram above.
More information is available at the 3G4G website.

Wednesday, 5 September 2007

Back to work

Had been enjoying the sun in sunny Istanbul for a week now and back to work to find over 200 mails in my different Inboxes. Will take some time for me to get back to the routine.
By the way, the photo is taken just outside Blue Mosque (known as Sultanahmet).

Wednesday, 29 August 2007

More on Continuous Packet Connectivity (CPC)

Just realised that CPC is becoming more important with the Network Operators and UE manufacturers because it can allow more UE's to be ready for transmitting data. In my earlier post i had given some details about CPC.

Before i could begin writing some more details on CPC, i came across Martin's Blog which have excellent information on this topic. So i have listed them down here:

Continuous Packet Connectivity (CPC) Is Not Sexy - Part 1

Continuous Packet Connectivity (CPC) Is Not Sexy - Part 2

Continuous Packet Connectivity (CPC) Is Not Sexy - Part 3

There might be a part 3 coming soon, which will make life simpler for people like . Any additional information in form of comments most welcome.

Added on the 14th of Jan 2009.
Part 3 has now added to the same post...

Monday, 27 August 2007

WiMAX on display

Vodafone has deployed WiMAX technology in Malta. The island (population 400,000) is one of Vodafone's smallest markets.

The supplier of the network, Airspan, announced in June that Vodafone Malta had deployed its HiperMAX 80216d 'fixed' WiMAX base stations and CPE to offer bundled mobile, fixed voice, and data services to residential and business customers. Since that announcement was made, Vodafone has joined the lead industry organisation promoting and steering WiMAX development, the WiMAX Forum.

According to Pyramid research, "Vodafone, owing to its scale, is an agent of change in the operator community and we expect others to follow its trajectory. With operators present in different markets and looking for new revenue sources, there is no 'one-size-fits-all' technology, but the wrong technology can set an operator back years."

The research firm adds that "in catering to the needs of different markets and customer segments, operator networks will comprise diverse access technologies, each optimised for certain geographies, demographics, and services. For the WiMAX champions this is good news; for LTE backers it is a strong warning that should lead to increased R&D budgets for the next few years—in both camps.

In other news, Samsung Electronics will demonstrate the next generation telecommunications technologies at its annual international forum, which will shed light on what they call as global 4G technologies and gadgets.

This year’s Samsung 4G Forum will draw more than 130 influential industry leaders and service providers from 26 countries. It will mark the first time that all three candidate 4G technology _ IEEE 802.16m (Mobile WiMAX), 3GPP2 Ultra Mobile Broadband (UMB) and 3GPP Long Term Evolution (LTE) _ will be seen with each other.Each of the 4G technologies has a head cheerleader, with Intel supporting WiMAX, Ericsson touting LTE and Qualcomm preferring UMB. IEEE 802.16m WiMAX, UMB and LTE are expected to be initially implemented in 2010.

I think for companies like Samsung to break into new markets, its very important to use the term 4G. Lets hope that they all succeed.

Saturday, 25 August 2007

Mobile TV via Satellite

A heading of news article yesterday read: "European mobile operators are looking for economic ways of launching broadcast mobile TV services directly to handsets". This made me wonder, if there is a strong case for Mobile TV via Satellite?

Couple of days back, 3 Italia reported that it had 719,000 people using its DVB-H service by August 22, which is about 9.4 percent of its 7.68 million customer base reports Dow Jones in Italian. The figure is a good sign—at the beginning of June it was 600,000 and back in March it was 250,000, or about 3.7 percent of the subscriber base. So this proves that some people are using Mobile TV if available.

The only popular satellite Mobile TV i am aware of being used practically (please correct me if you know more) is the S-DMB being used in Korea.

According to a report in Moconews, currently some 7 million people in S. Korea are watching mobile TV--that equates to one in every seven residents of the country--but none of the operators offering DMB services has yet to make any money. Each of the six terrestrial DMB operators has piled up an accumulated loss of between $22 million and $33 million. The only mobile TV operator that charges for its service is SK Telecom-owned TU Media, which offers its DMB service over a satellite-based system (S-DMB). It has 1.2 million paid subscribers, but TU says it needs at least 2.5 million to break even in operation. That’s before it can even start to recoup its $435 million investment in satellites and networks.

The European Space Agency (ESA) has joined the DVB-H party by funding development of technologies for broadcasting TV to mobiles via satellite. ESA has called its standard DVB-SH (Digital Video Broadcast - Satellite, Handheld) and envisages using satellites to send out video at 2GHz to 4GHz (S-Band). Terrestrial repeaters would be used to give indoor coverage. Eutelsat has commissioned a new satellite to be launched in 2009, with the intention of broadcasting DVB-SHb - though it's hedging its bets by claiming it's for multimedia distribution rather than any specific technology or application. Much of the technology needed by DVB-SH doesn't yet exist, so the ESA will be issuing invitations to tender (ITT) for companies that want to have a go at developing them. First up will be a mobile chipset capable of receiving and decoding DVB-SH version b signals. The ITT is due to be published in the next few months.

Finally i found a good report on BetaNews detailing the pros and cons of Satellite Mobile TV:

It's an ambitious idea, and it's not nearly a done deal. But yesterday, a proposal was introduced before the European Parliament for a timetable by which the EU would select a few choice service providers, for the precious and narrow spectrum it will be making available for the entire continent. It will require the consent and cooperation of all 27 member states - something the EU rarely gets even with less ambitious proposals.

Here's what it means: Last February, the EU established two small chunks of radio spectrum - 1980-2010 MHz and 2170-2200 MHz - as reserve space for future MSS broadcasting. Under normal EU law, member states would each have the right to select their own service providers for satellite TV and radio service for their respective countries. In fact, if the EU were to change its mind now and do nothing, that's what EU states would do next.

But there's two big problems: First of all, no single EU country is very big, geographically speaking, compared to the whole of Europe. A satellite signal covers a very broad portion of the Earth, so any service provider licensed for, say, France could probably have its signal picked up in southern Finland. Simply put, the laws of physics dictate a wide coverage area that technology cannot circumvent...unless every mobile TV receiver in Europe were custom-built for each member country. (If you're thinking like a manufacturer of DVD consoles, you might not be too opposed to trying that.)

Even if France's signal and England's and Bulgaria's and all the others could be picked up everywhere else - which, if you think about it, will be the case anyway - Bulgaria's service provider wouldn't want its signal overlapping England's. And that leads us to the second big problem: There's not enough MSS spectrum available in the 2 GHz band to go around.

So the European Union is stepping in, or at least attempting to. But in order for member states to allow it to do so, it has to formally present its case to those states for why it has the authority to do so. Imagine if, under a different style of US constitution, in order for the federal government to make its case for regulating the public airwaves, it had to get all 50 states' consent to giving up their own rights to do so individually.
Thus a large part of the EU proposal yesterday explains - as it must do under European law - why it's claiming the authority to propose a national selection process for MSS providers.

For its claim to qualify as valid, it has to meet two tests under the EU constitution. First, the claim must meet the Subsidiarity Principle: essentially, that the nature of the job at hand means it can be performed better by the EU than by all the 27 states acting independently. In other words, the EU has to prove it can do the job not because it's better at these sorts of things, but because the problem at hand makes a single body better suited to the task.

Here is where the EU has physics on its side: Satellite signals cover broad territory, and states' boundaries do not. "Selection and issuance of rights over the same spectrum to different satellite operators in different Member States would prevent satellites from covering their natural footprint," the EU proposal reads, "which by nature covers a large number of countries; it would risk fragmenting the satellite communications market and eliminate the natural advantage of satellites compared to other modes of communication. The mobile character of the services involved also means that citizens travelling in the EU should benefit from the availability of such services throughout the EU."

Second, the EU's case must meet the Proportionality Principle. This means it can't claim more authority than it needs to do the job...and once the job is done, it steps out of the way. In other words, it can't appoint a permanent commission like the FCC.

In making that part of the case, the EU goes on, "The proposal will create a mechanism for coordinating the selection and definition of certain conditions to be attached to rights of use of spectrum. It will not touch upon the right of Member States to grant the authorizations to use the spectrum or to attach specific conditions applying to the provision of services in areas which are not harmonized. Member States will be closely involved in elaborating the details of the selection procedure."

Here is where critics say the EU's case may fall apart. In order to win the authority to drive the MSS adoption process, the EU is limiting itself to driving the selection process for prospective service providers. Once that job is done, it's leaving it up to member states to apportion per-country licenses to those companies, for channels which the EU would already have selected as well.

On the one hand, it doesn't make sense. In order to sell its plan, the EU is leaving open the option for member states to deny licenses. But assuming a state does so, how could it block the reception of a signal from a service provider whose license was denied? That might take a technological solution...which brings up the whole "per-country" manufacturing option for MSS receivers again.

On the other hand, only such a hare-brained scheme might just work, because member states don't want to be perceived by their citizens as ceding any part of their authority to a federal institution. Giving them the right to say "no" could be a kind of ceremonial concession, not unlike the establishment of a constitutional monarchy where the monarch is essentially a face on a coin - which is a state of affairs not unfamiliar to member states.

"Since industry so far could not agree on a single standard for mobile TV, commercial launches of mobile TV are delayed," reads a statement from the EU's central authority in Brussels last month. "Europe's competitors, most notably from Asia, have made significant progress - partly due to state intervention - and Europe risks losing its competitive edge unless sufficient momentum is achieved. This is why there is a need to develop a 'blueprint' for mobile TV in Europe."

Is UMB the same as LTE

Recently i have come across press releases trying to sell UMB (Ultra Mobile Broadband) as 4G technology. This is the same as trying to sell LTE and mobile -WiMAX as a 4G technology.

IMT has taken a clever approach and instead of calling the successor of 3G as 4G, they are calling it IMT-Advanced.

The main requirements for 4G are as follows:

  • Peak data rate of 100Mbps for high mobility applications such as mobile access
  • Approx. 1Gbps for low mobility applications such as nomadic/local wireless access

Doing some digging on the UMB topic, i realised that it is the same as LTE but an evolution from CDMA2000. This is being standardised by 3GPP2.

Some of the key features (and comparing it with LTE) includes:

  • It used OFDMA based air interface (same as LTE)
  • It supports FDD (LTE supports FDD and TDD and a combination of them so i am not sure if UMB only supports FDD)
  • Scalable b/w of 1.25MHz to 20MHz (same as LTE)
  • MIMO and Beamforming (Same as LTE but UMB also supports 4x4 antennas whereas LTE supports 2x2)
  • Data speeds upto 275Mbps in DL and 75Mbps in UL (LTE has 144Mbps in DL and 57Mbps in UL but that is because of 2x2 MIMO)

Since the term 4G is already being abused so much, one option is to let people use 4G as they wish and then when IMT-Advanced is available, start calling it 5G. What do you think?

Tuesday, 21 August 2007


Sprint (US) is getting ready to unleash a WiMAX network unto the masses. The quirky news is that they've decided to name it XOHM. The 4G high-speed data network will be based on WiMAX technology, and they plan on sharing the network with Clearwire.

By the end of 2008, the XOHM (pronounced "zoam"... sort of like a zoom-roam hybrid) network will be able to reach 100 million people. If everything goes according to plan, this number will expand to 125 million by the end of 2010. The initial building of the infrastructure will cost Sprint about $2.5 billion.

The first cities to experience XOHM will be Chicago, Baltimore, and Washington when they get their hands on the soft launch at the end of this year. The full commercial WiMAX launch is scheduled for "the first half of 2008."
In another announcement, Sprint Nextel Corp., the third largest US wireless service firm, has announced plans to spend nearly $5 billion by the end of 2010 on a new network based on the emerging high-speed wireless technology known as WiMax, Reuters reported. The company said that it expects spending on the network through the end of 2008 to be at the low end of its previously announced estimates due to its agreement to connect its network with Clearwire Corp., a small wireless service provider. Sprint said it expects to spend $2.5 billion on the network through the end of 2008 compared with its earlier estimate of $2.5 billion to $3 billion. Sprint expects to reach a potential 100 million customers in that time, with the company providing coverage to 70 million people and Clearwire covering 30 million people.
To read the Press release for XOHM click here.
Official XOHM Website here.