Thursday 27 December 2007

Multiuser Cooperative Diversity and Virtual MIMO

MIMO (Multiple Input Multiple Output) by definition requires multiple antenna but it is also possible to use one antenna with Co-operative Diversity to create Cooperative MIMO or Virtual MIMO.

Earlier this year, Nokia Siemens Network reported the following on Virtual MIMO:

Researchers at Nokia Siemens Networks have demonstrated in lab conditions how a virtual Multiple Input Multiple Output (MIMO) technique can be used for the uplink in LTE (Long Term Evolution) networks.

Tests at its labs in Munich, Germany, have shown how, using such an SDMA (Space Division Multiple Access) based technique, two standard mobile devices, each with only one physical transmission antenna, can communicate with a base station simultaneously and on the same radio channel.

On the uplink transmission, data rates of 108Mbit/s were achieved, double the usual speed, while the downlink managed 160Mbit/s.

The researchers say that while MIMO on the downlink primarily generates higher peak data rates for the end user, virtual MIMO on the uplink makes it possible for an operator to increase network capacity and better utilize the available spectrum.

Nokia Siemens also said the technique contributes to one of the crucial prerequisites for the success of LTE by reducing power consumption of LTE based devices to "acceptable levels" even when used for very high data-intensive applications and that this should be achieved at "moderate prices."

The researchers say that with virtual MIMO only one power amplifier and transmission antenna is necessary for each device, contributing to reduced production costs and power needs.

In the LTE test bed, developed and built in collaboration with the Fraunhofer Institute for Telecommunications (Heinrich Hertz Institute), two co-operating end-user devices form a virtual MIMO system in which the antenna elements are distributed over the two devices. The two devices can be supplied simultaneously with data over the same frequency band using space division multiplexing.

The following is an extract from EURASIP Journal onWireless Communications and Networking:

Multihop relaying technology is a promising solution for future cellular and ad hoc wireless communications systems in order to achieve broader coverage and to mitigate wireless channels impairment without the need to use high power at the transmitter.

Recently, a new concept that is being actively studied in multihop-augmented networks is multiuser cooperativediversity, where several terminals forma kind of coalition to assist each other with the transmission of their messages.

In general, cooperative relaying systems have a source node multicasting a message to a number of cooperative relays, which in turn resend a processed version to the intended destination node. The destination node combines the signal received from the relays, possibly also taking into account the source’s original signal.

Cooperative diversity exploits two fundamentals features of wireless medium: its broadcast nature and its ability to achieve diversity through independent channels.

There are three advantages from this:

(1) Diversity. This occurs because different paths are likely to fade independently. The impact of this is expected to be seen in the physical layer, in the design of a receiver that can exploit this diversity.

(2) Beamforming gain. The use of directed beams should improve the capacity on the individual wireless links.The gains may be particularly significant if space-time coding schemes are used.

(3) Interference mitigation. A protocol that takes advantage of the wireless channel and the antennas and receivers available could achieve a substantial gain in system throughput by optimizing the processing done inthe cooperative relays and in the scheduling of retransmissions by the relays so as to minimize mutual interference and facilitate information transmission by cooperation.

Source: Multiuser Cooperative Diversity forWireless Networks by George K. Karagiannidis, Chintha Tellambura, Sayandev Mukherjee and Abraham O. Fapojuwo, Volume 2006, Article ID 17202

There are 3 main types of co-operative diversity which are self-explanatory in the diagram above:

Decode and Forward
  • Simple and adaptable to channel condition (power allocation)
  • If detection in relay node unsuccessful => detrimental for detection in receiver (adaptive algorithm can fix the problem)
  • Receiver need CSI between source and relay for optimum decoding

  • Amplify and Forward
  • Achieve full diversity
  • Performance better than direct transmission and decode-and-forward
  • achieve the capacity when number of relays tend to infinity

  • Coded Cooperation
  • transmit incremental redundancy for partner
  • Automatic manage through code design
  • no feedback required between the source and relay
  • Rely on full decoding at the relay => cannot achieve full diversity!
  • Not scalable to large cooperating groups.
  • Multihop Cellular Networks and ODMA

    While going through September issue of IEEE Communications magazine, I came across Multihop Cellular Networks (MCNs). The concept sounded familiar and another article confirmed my suspicion. MCNs is similar to ODMA for those who remember the early 3GPP specs. ODMA or Opportunity Driven Multiple Access was revolutionary concept but it was too advanced for that time and the chipset (and battery) technology was not that advanced to have it implemented successfully.

    The best place to understand ODMA is in 3GPP TR 25.924. Also see this.

    So what exactly is multihop cellular network (MCN)?

    To quote from IEEE Communications Magazine (Sep 07):

    MCN incorporates the flexibility of ad hoc networking, while preserving the benefits of using an infrastructure.

    The salient feature of MCN is that communications are not restricted to single hop; multihop transmissions are allowed.

    The advantages of using MCN include capacity enhancement, coverage extension, network scalability, and power reduction. However, there are still a number of open research issues that need to be solved in order to provide efficient and effective multihop transmissions in cellular networks in the future.

    From another article in the same issue:

    Existing architectures and protocols proposed for MCNs are very diverse and different in several aspects. Relay Stations (RSs) can be preinstalled by network operators or simply be other idle MHs who are not transmitting their own data. Also, depending on how radio resources are allocated for routing paths of active connections, different protocols at the medium access control and routing layers can be designed. Radio resources forMobile Hosts (MHs) at different hops may be allocated in timedivision duplex (TDD) or frequency-divisionduplex (FDD) mode. Frequency bands other than the cellular frequency band may be used for relaying. Finally, advanced techniques using cooperative diversity can be employed to enhance network performance compared to simple relaying schemes.

    Wednesday 19 December 2007

    Triple-play, Quad-play and now Penta-Play?

    We know that Triple-play consists of:
    • Phone/Voice (based on VoIP),
    • Internet and
    • Television (generally IPTV)

    and Quad-play also includes:

    • Mobile

    So now when i hear people mentioning Penta-play, i cant think of what is this 5th thing in Penta-play? They dont seem to mention anything. Does anyone know?

    Tuesday 18 December 2007

    CAMEL and IMS

    CAMEL is to CS domain what IMS is to IP domain. Since we are all moving towards IMS, eventually CAMEL would become obsolete. Another important thing with IMS is that it is access independent and defined for wireless as well as wireline technologies.

    IMS will take some time to be implemented and in the meantime CAMEL and IMS will co-exist. In the meantime operators may use CAMEL to control IMS to take advantage of the technology they have heavily invested in and have tested for some years.

    CAMEL control of IP multimedia calls forms a bridge between the CS mobile network and the IP multimedia network. The IMS is the IP-based communication system for mobile networks. Although IMS, which was introduced in 3GPP release Rel-5, is specified for the mobile network,
    it may also be used for wireline networks. In fact, the nature of IMS facilitates arbitrary access methods to be used.

    Some Useful Specs as follows:

    • 22.228: Service requirements for the IMS
    • 22.250: IP multimedia subsystem group management
    • 22.340: IP multimedia subsystem messaging
    • 23.228: IP multimedia subsystem
    • 23.278: CAMEL – IP multimedia system interworking
    • 24.228: Signalling flows for the IP multimedia call control based on session initiation protocol and session description protocol (discontinued after Rel-5)
    • 24.229: Internet protocol multimedia call control protocol based on session initiation protocol and session description protocol
    • 29.228: IP multimedia subsystem Cx and Dx interfaces; signalling flows and message contents
    • 29.229: Cx and Dx interfaces based on the diameter protocol; protocol details
    • 29.278: CAMEL application part specification for IP multimedia subsystems

    Further Reading: CAMEL: Intelligent Networks for the GSM, GPRS and UMTS Network by Rogier Noldus

    Friday 14 December 2007

    NTT DoCoMo's F801i Kids Phone

    TOKYO, JAPAN, December 10, 2007 --- NTT DoCoMo, Inc. and its eight regional subsidiaries announced today that the FOMA™ F801i, a new child-friendly 3G mobile phone loaded with special features for the safety and convenience of children, will go on sale December 20.

    Building on the popular FOMA SA800i model that DoCoMo released in March 2006, the F801i offers many new or improved child-friendly features for security, theft/loss prevention, ease of use and more.

    In an emergency, the child can quickly switch on the phone's 100-decibel alarm, which produces two types of noise alternately. When the alarm is activated, the phone also emits a bright light (high-intensity LED) that is easily visible to people in the surrounding area.

    The phone can be set to automatically notify loved ones when the alarm is activated, and provide the handset's current location as well. Computer-generated phone calls can be placed to up to three registered numbers and messages can be sent to registered individuals who subscribe to the i-mode™ location service called imadoco search™.
    In addition, the child can discreetly message their location to a registered imadoco search user by simply pushing a button on the side of the phone.

    If the phone's power is switched off, a presetting can enable the handset to automatically turn back on (in as little as five minutes) and message the incident and the phone's location to a registered DoCoMo phone.

    An amulet-style remote controller worn by the child can be used to make a misplaced phone beep if within a range of about 10 meters (may vary with usage environment). If the user moves even farther from the handset, the phone can automatically lock (requires presetting). If the handset remains out of the amulet's range for more than five minutes, a message can be sent automatically to a registered DoCoMo phone.

    The F801i is ergonomically designed for easy use by small hands, and its waterproof body can withstand accidental immersion (up to 30 minutes at one-meter depth) or concentrated water sprays.

    The phone's soft-rectangle shape and round speaker grille enclosed by a ring-shape LED were conceived by renowned designer Kashiwa Sato to symbolize safety, peace of mind, creativity and the future.

    DoCoMo, as part of its corporate social responsibility program, provides education on the proper use of mobile phones by children. The Mobile Phone Safety Program involves workshops for students from elementary through high school, as well as for parents. DoCoMo has conducted more than 3,600 workshops for some 540,000 people throughout Japan since 2004. This program, along with services for site-access restriction, location information, etc., form a broad framework within which DoCoMo works to provide parents and their children with a safe and secure environment for using mobile phones.
    More Photos of the phone can be found at Akhiabara News website.

    Thursday 13 December 2007

    In 4G we trust

    So we have this again, LTE is being referred to as 4G. Firstly, this is not really news because i mentioned this in September. Check the post here. Also Verizon is not the first operator to commit to LTE future. AT&T has said the same before them. Regarding the terminology i said earlier that LTE is 3.9G, see here. But 4G sounds better than 3.9G and will confuse ordinary people less so...

    Anyway, an article titled "3G bad; 4G better be better" came to my attention:

    Not surprisingly, tech-savvy young adults are frustrated by the speed and connectivity limitations of 3G networks and expect both better speed and more reliable connectivity when 4G arrives, according to focus groups in the U.S. and Japan queried by Nortel and the consultant firm CSMG ADVENTIS.

    “There was uniform dissatisfaction with today’s UMTS or 3G networks, whether that was because the feeds just weren’t good enough, the applications that they were running, like video, just weren’t good enough.
    They look forward in the next generation of technologies to something that can deliver their expectations for these applications in ways that are easy, friendly and useful,” said Scott Wickware, vice president of wireless networks for Nortel.

    Wickware said that the focus groups, based in New York City, Seattle and Washington, D.C. in the U.S. and Tokyo and Osaka in Japan, had similar unhappy feelings about their 3G wireless services.

    “We expected the Japanese to have a different perspective on this because they’re perceived to be the most tech-savvy nation on the planet, but 25-year-old businesspeople in both countries seem to want the same thing,” Wickware said.

    Not coincidentally, what they want is what Nortel has been preaching: “this hyper-trend called mega-connectivity that says everything that could be connected to the network and would be beneficial to the network will be connected to the network,” Wickware said. “We couldn’t have scripted it any better because the feedback came back almost universally saying the same thing.”

    The feedback also indicated that users did not necessarily want a single multi-use device but preferred multiple devices connected to the network.
    “They don’t want just the mobile phone connected to the network or their PC, they want their camera, their MP3 player, their vehicle, they want everything. I think the trending is a single or dual-purpose device is what a lot of people want,” he said.

    Overall, he said, respondents are looking for more from future network services.

    “We asked them a wide variety of questions about what they wanted from 4G. We didn’t define 4G for them and lead them down the path to see what they had to say, but left it pretty wide open so we were getting top-of-mind stuff that wasn’t influenced by our views,” he said.

    Long time back i remember being so happy with Dial up Internet Connection but now i am not too happy with my 8M broadband. So i suppose the same goes for other technologies.

    Wednesday 12 December 2007

    FMC: The long wait

    FMC might take some time to roll out because nobody wants to fix something thats not broken.

    According to this old (and relevant) article:

    Despite the hype, heavy adoption isn’t expected until the next decade, analysts say. Dragging it down is carrier reluctance to market FMC services and tepid demand among cash-strapped U. S. companies still trialing products from established vendors and newcomers.

    “Why would [carriers] want to do anything to disrupt the nature of the return that they’re getting in tariffed services?” asks Robert Rosenberg, president of Insight Research, referring to wireline and wireless carriers such as Verizon and AT&T, which continue to see growing wireless revenue and fat profit margins of 40% to 45% every quarter. “Naturally, they are much happier to take your minutes of use and apply them to cell phones. Same would [be true for] a tariffed voice service. There’s really no incentive for them to rock that boat.”

    Both wireline service providers and cellular providers lose revenue when calls are moved off of their respective networks and onto the enterprise’s wireless LAN (WLAN). They lose additional revenue if the off-site traffic is routed to another enterprise network, Insight notes.

    A recent article on this topic says:

    It sounds like a simple concept, but FMC requires lots of technical stitching on the part of the carrier or vendor to smooth out the seams between the wired and unwired worlds. FMC melds several disparate infrastructures - such as TDM and packet VoIP, IP data, Wi-Fi and various flavors of cellular - into one. There are multiple instantiations of FMC from which an enterprise can choose, which makes the right FMC decision more difficult.

    But once the networks are stitched and the decisions about whether to opt for a carrier managed service or enterprise-centric FMC implementation are made, the benefits are manifold, industry experts say. They include the ability to be reached through one phone number wherever you are - at your desk, around campus, roaming about or at home - as well as reduced enterprise telecom costs by, for example, bypassing international mobile roaming charges when making cross-border calls.

    Enterprises also can save on telecom costs. In addition to bypassing international roaming charges, businesses can tame their out-of-control cellular bills by selecting one or two service providers or vendors to include cellular as a component of an overall FMC or unified communications package, Mathias says.

    As i said in the start, nobody is going to make a move on FMC till someone starts shouting and others start listening to him.

    Now, according to a report by The Yankee Group, one of the positives that FMC brings to the table—its cost-savings by moving mobile minutes off wireless and onto wireline devices— does not outweigh the trepidation of enterprise IT professionals and decision makers.

    “We see it as something that will hit eventually but in the short term probably not,” said Brian Kotlyar, research associate with The Yankee Group and author of the report, “Productivity is the Prettier Face of FMC.”

    Twenty-nine percent of the 302 IT decision makers surveyed for the report considered FMC a nice technology to have but not a critical application on their networking road map. Even more daunting, there is an adoption rate of less than 2 percent for the concept, the report said, so things aren’t taking off in that space even while it might be viewed as a positive.

    Finally some stats to put everything in perspective:

    Though FMC registers barely a blip on the radar screen, there will be 92 million FMC subscribers worldwide by 2011 and FMC revenue will amount to $28 billion by that time, representing 3% of overall mobile subscriptions globally, according to market research firm Informa Telecoms and Media. The firm says the United States will lead the way with 33.2 million subscribers.

    As a consequence, sales of dual-mode handsets will increase to 5% of global handset sales by 2011, Informa expects. Eighty-five percent of these sales will be to consumers adopting FMC services for convenience and cost benefits, although a "significant proportion of revenues" will be from enterprises adopting FMC as part of a unified communications strategy for more effective business interactions, the firm says.

    So is anyone doing something on FMC?

    If you want to read further:

    ZTE now shows off 2Mbps TD-HSDPA

    ZTE Corporation a leading global provider of telecommunications equipment and network solutions, showcased its 2M TD-HSDPA high-speed wireless downloading technology solution in line with the company’s theme of “Talking to the Future” at the GSMA Mobile Asia Congress 2007 held from 12th to 14th November 2007 at The Venetian® Macau. The GSMA Mobile Asia Congress (formerly 3GSM World Congress Asia) is the sister event of the Mobile World Congress in Barcelona, and is attended by mobile professionals and innovators from across Asia and around the world.

    With its 2M TD-HSDPA technology solution, ZTE clearly shows its vision to further enhance the TD-SCDMA concept and make it a part of consumers’ mobile wireless communication experience. ZTE’s 2M TD-HSDPA technology provides user endpoint’s downstream data rate as high as 2M, allowing users to enjoy smooth high-definition movies online, download documents in bulk, as well as experience many top-line multimedia functions. 2M speed rate is best achieved on 1.6M broadband single carrier, while 20Mbps can be achieved on multi-HSDPA carriers.

    HSDPA is a large volume mobile multimedia service 3G technology for GSM-based mobile phones developed by mobile operators to bring true broadband speed wirelessly. It incorporates AMC (Adaptive Modulation and Coding), HARQ (Hybrid Automatic Repeat reQuest), RRM (radio resource management) and MIMO (Multiple-Input Multiple-Out-put) technologies, all of which significantly improve downstream data rate.

    “ZTE’s 2M TD-HSDPA showcase at GSMA Mobile Asia Congress Macau builds the momentum of our successful presence in PT/Wireless & Networks Expo Comm in Beijing, China last month,” says Mr. Liang Ming, International Marketing Director of TD-SCDMA products, ZTE Corporation. “As the first provider to showcase TD-MBMS mobile TV solution, we further solidify our remarkable capability in TD area with this solution. As a run-up to the forthcoming Beijing Olympics, ZTE is setting the stage as among the pioneers in providing users in the country with extraordinary TD-SCDMA wireless solutions.”

    Tuesday 11 December 2007

    Lets talk Femtocell

    Femtocell is back on agenda with activity from the Femtoforum. Femto Forum has formed four specific working groups to study the subject (femtocell progress) from multiple angles.

    The working groups include
  • over-the-air radio and physical layer issues;
  • networks and interoperability;
  • regulatory issues;
  • market issues.

    Each area is receiving support from both vendors and operators including such heavyweights as Rogers Wireless, UTStarcom, Motorola, NEC and Nokia Siemens Networks.

    Since the Forum is not a standards-setting body, it’s biggest goal is to “make sure that we can speed up the standards and that they’re appropriate and actually span across the different air interfaces, including the WiMAX area and the 3GPP and 3GPP2 interfaces,” said Simon Saunders, the Forum’s chairman. “Where there are commonalities, that helps to drive economies of scale.” Since the “absolutely core focus” for femtocells is the residential environment, “it’s very important to make all the pieces work together so the femto works well with the DSL or cable infrastructure behind it,” said Saunders.

    Meanwhile, IDATE (a consulting firm specialising in Femtocells) expects to see the femtocell market developing rapidly over the following years. While a lack of agreed standards and outstanding technical issues will inhibit major rollouts in 2008, network integration issues are likely to be solved by 2009.Coupled with cost reductions this should lead to a ramp up in volumes in 2009/2010. IDATE believes 10 million UMTS femtocells will be shipped in 2010, rising to 18 million in 2011.

    In another report the prediction is that there can be between 20 and 40 million users by end of 2012.

    An article in (sorry for subscribers only) argues that for Femtocells to be successful, Voice is not enough:

    The business case for femtocells involves a voice-only strategy, the potential for large incremental revenues is questionable, while an approach that positions femtocells as a platform for delivering multimedia services to the home will yield greater financial benefits.

    "One of the big advantages of deploying femtocells is the ability to offer good coverage and data speeds close to those of fixed-line access, in the very place where people are most likely to want them: in the home," Heath says. "Consequently, operators should be looking at services which fit these criteria, rather than simply offering cheap mobile voice minutes."

    He added that in Finland, where mobile subscribers enjoy good indoor coverage, traffic from fixed to mobile networks shifted 10 per cent in 2006 - the most ever for the country in one year. That migration proves, he said, that once mobile usage is perceived as being affordable, even though it might still be more expensive than fixed, people will adopt it.

    "Therefore, operators might not need to go as far as offering cheaper voice calls," Heath said. "Instead, they should look at carefully segmenting their customer base and target customers with little or no indoor coverage."

    Tal Givoly, chief scientist at Amdocs said the introduction of femtocells was not a big step forward in terms of technology or the ability to deliver new services. He said that many operators were actually aiming to deliver Telco 2.0 and become "purveyors of the digital lifestyle" but that femtocells were essentially a Telco 1.0 play and would not help operators achieve that objective. "First cases would have to be increased customer loyalty rather than substantially revised new services," he said.

    Mobile TV is one service that operators are eager to roll out and for which femtocells could be seen as a disruptive technology that saves operators a great deal of capex and opex. Heath said that DVB-H requires operators to invest a considerable amount in new infrastructure, requiring as it does a lot of new transmitters. He added that the development of a range of killer applications, including mobile TV, video and audio services, would significantly broaden the consumer appeal of femtocell services.

    As the market progresses toward triple- and quadruple-play offerings, consumers will most likely expect high-quality mobile TV, video and audio services, which will be difficult to deliver using 3G macrocell networks. Heath said that deploying femtocells could substantially reduce the investment necessary and achieve significant capacity and cost savings.

    Heath also says that although many network operators are offering mobile broadband services at attractive prices, they can do so only while 3G networks are relatively underused. "Without femtocells, they could soon run into QoS problems as mass take-up occurs," he said.

    Finally, if you want an alternative view to these analysis then you may want to read this report from Analysis.

    Femtocells, while likely to provide great benefits for mobile subscribers and improved in-building service for mobile operators are not a technological end game. On the contrary, the femtos, which improve in-building mobile connectivity, carry considerable commercial risk, according to a report, “Femtocells in the Consumer Market: business case and marketing plan,” published by Analysys.
  • Wednesday 5 December 2007

    UTRAN Network Sharing

    This is a new feature that the network operators are getting more interested in. The problem is that the Network side is more prepared than the handset side which still has some way to go.

    The possibility of sharing part or all of the network by two or more separated commercial entities was not considered in the initial specification work of 3GPP. However, as e.g. a result of partnerships, the need for two or more operators to share common network infrastructure has become an economically desirable goal. Meanwhile, changes to public network operating licence conditions make such sharing possible from a regulatory point of view.

    Some work has already been carried out in this area with the definition of the equivalent PLMN concept and partly with the introduction of Iu-Flex, but there is still the need to consolidate these activities under a coherent work plan.

    Network sharing is in a way similar to what is done by MVNO's who use the host network to offer services. In network sharing case the other operator would not generally be a MVNO and probably the equipment would belong to both of the operators along with the cost and revenue earned. This is easily possible if the network is not overloaded (as in case of 3 UK) but if its a long time existing operator (like Vodafone) than they may not have enough spare capacity to allow someone else to share their infrastructure.

    3GPP Specs for further reference:
    3GPP TS 23.251 - Network Sharing; Architecture and functional description
    3GPP TR 22.951 - Service aspects and requirements for network sharing