Tuesday 22 January 2008

3GPP LTE Progressing Nice and Steady

Press release from 3G Americas yesterday, applauds the progress of LTE standardisation over the recent months.

“3G Americas has consistently supported the 3GPP standards for the GSM family of technologies and we applaud the progress of the LTE standard. LTE is a dynamic OFDM-based next generation technology with a great future. 3G Americas is committed to not only today’s global leading standards of GSM, EDGE and UMTS/HSPA but also to the innovation that LTE provides our industry,” stated Chris Pearson, President of 3G Americas.

Pearson added, “With this recent approval, the LTE Terrestrial Radio Access Network technology specifications will be under change control, and included in the forthcoming 3GPP Release 8.”

Meanwhile Martin suggests in his blog that voice will be the real test for LTE networks.

While on mobile Internet devices it might be acceptable to have Skype or some other VoIP technology, smaller handsets who's main purpose is voice service might have a much more difficult time with VoIP. Such devices must also be capable of roaming to 2G and 3G networks when running out of LTE coverage. Especially in 2G networks, VoIP is a no go so voice service must fall back to good old circuit switched telephony. So apart from the question of how VoIP will be done on LTE handsets the much bigger question is how to make the experience seamless over 2G, 3G and LTE.

More about that here.

Tuesday 15 January 2008

80 million mobile WiMAX subcribers (by 2013)

A new report by Juniper Research calculates the number of mobile WIMAX subscribers will exceed 80 million by 2013. The biggest surge in growth, says the research firm, will happen after 2010. Juniper’s projections assume a wide range of attractive devices will be available on the market within three years (at competitive prices), and mobile WiMAX operators will achieve service differentiation from mobile operators.

According to figures from the WiMAX Forum, WiMAX technology had the potential to reach 2.7 billion people before the ITU announcement. That number now rises to over 4 billion.

There are already some interesting announccements regarding WiMAX in the last one month:

Milton Keynes Council has launched what is thought to be the UK's first commercial wireless broadband service using WiMAX technology. ConnectMK, a private company set up by the council to address the issue of poor broadband connectivity across Milton Keynes, has joined forces with Freedom4 to provide residents and businesses in the area with access to WiMAX services.

For those who dont know, Milton Keynes is a relatively newly developed town in Greater London area. When it was being expanded in 1980's, the engineers decided they can save lots of money by having copper plated aluminium cables rather than copper cables for telephone, etc. Their experiment was successful and received lots of applause untill the arrival of ADSL when people realised that these cables cant be used for carrying broadband ;)

Sprint said that the Xohm service will be commercially available in select cities around the United States in the second quarter of 2008.

Sprint was one of a number of vendors at the Consumer Electronics Show with big WiMAX plans. For its part, Sprint said that the Xohm service will be commercially available in select cities around the United States in the second quarter of 2008. The company hopes for a large-scale rollout of its Xohm WiMAX service by the end of the year.

Other CES vendors with WiMAX-related announcements: San Francisco's OQO (an ultra-mobile PC planned for 2008); AsusTek of Taiwan (a variety of WiMAX-embedded devices); and Zyxel (collaborating with Sequans on WiMAX access devices for Xohm's commercial launch).

One of the promises of WiMax, a service Sprint will be providing under the Xohm brand, is that receivers for it can be built into a variety of devices like cameras and Web tablets that usually don't have a built-in Internet connection or rely on Wi-Fi, a short-range technology.

By the way, it seems Sprint is already going through a rough patch:

Now, another round of subscriber losses is expected for the fourth quarter ended Dec. 31 as the firm tightened credit standards for would-be subscribers and failed to price its handsets competitively, said Philip Cusick, an equity research analyst with Bear Stearns in New York.

Shares of Sprint, which have lost more than 25 percent in the past year, closed up 11 cents yesterday at $12.36.

Citing anonymous sources, the Wall Street Journal yesterday reported that Mr. Hesse plans to fire several thousand workers. The company last year fired 5,000. The Journal also disclosed that Mr. Hesse may relocate the company's headquarters to Overland Park, Kan., where 13,000 of the company's 60,000 employees are located.

And finally the rest:

Airspan Announces 5 GHz WiMAX Deployments in Ukraine

Alcatel-Lucent opens WiMAX interoperability testing center in Taiwan

Kirkland, Wash.-based Clearwire, founded in 2003, is building a nationwide high-speed wireless network based on WiMax technology. Under the agreement, Clearwire would offer Google's email and calendar applications to its customers. In the future, Clearwire also plans to offer Google's search tools.

Chrysler to put WiMax into its cars

Axtel (Mexico) selects Motorola for WiMAX deployment

Alvarion and Bridgewater Team for Joint WiMAX Deployment in Angola

Friday 11 January 2008

I-HSPA: HSPA+ by another name

Nokia refers to HSPA+ by the name I-HSPA or Internet-HSPA.

According to their whitepaper:
  • 3G operators who have deployed I-HSPA have flat network architecture similar to LTE/SAE in place, and can thus cost-efficiently introduce LTE/SAE.
  • 3G operators with a deployed WCDMA/HSPA network can migrate
    directly to LTE/SAE. Migrating to the flat network architecture of
    Internet High Speed Packet Access (I-HSPA) may also be beneficial
    because it accommodates LTE/SAE’s flat IP-based network architecture while supporting legacy WCDMA/HSPA handsets. The operator can thus enjoy the transport and network scaling benefits immediately and easily upgrade the network to LTE/SAE later.
  • Greenfield and CDMA operators can introduce LTE/SAE networks
    directly or follow one of the above paths. GSM/EDGE may be a good choice for strategies more immediately focused on voice centric business. Operators opting to take the I-HSPA path can capitalize on the ecosystem of HSPA terminals, benefit from the flat architecture today, and quickly optimize mobile broadband performance.

Heard of MobileFi?

A new book title came to my attention, "Wimax/Mobilefi". I hadnt heard of MobileFi before so i did a bit of digging up and here are the details.

MobileFi is also known as Mobile-Fi or Mobile Broadband Wireless Access (MBWA) and is better known as IEEE 802.20

IEEE 802.20, also referred to as Mobile-Fi, is optimized for IP and roaming in high-speed mobile environments. This standard is poised to fully mobilize IP, opening up major new data markets beyond the more circuit-centric 2.5G and 3G cellular standards. The Mobile Broadband Wireless Access (MBWA) Working Group was established as IEEE 802.20 in December 2002. Its main mission is to develop the specification for an efficient packet-based air interface optimized for the transport of IP-based services. The goal is to enable global deployment of low-cost, ubiquitous, interoperable, and always-on multivendor mobile broadband wireless access networks. IEEE 802.20 has designed a new physical layer (Layer 1 protocol) and MAC/link layer (Layer 2 protocol) around IP packet Layer 3. It can operate in licensed bands below 3.5GHz, with cell ranges of 9 miles (15 km) or more. IEEE 802.20 can operate at speeds of up to 155 mph (250 kph).

Unlike WiMAX, which was incubated inside IEEE 802.16 family and evolved from earlier 802.16 technologies, 802.20 [5] or Mobile-Fi was designed from ground up as a technology to support high-mobility services. It aims to support mobility as high as 250 km/h and a peak rate of up to 260 Mbps in the licensed spectrum below 3.5 GHz. Th e enabling technologies are also OFDM, MIMO, and beam-forming. The draft standard is still under the IEEE standardization process.

Both WiMAX and 802.20 use OFDM-MIMO, which is emerging as the main technology for future cellular packet data networks, including 3GPP long-term evolution and 3GPP2 air interface evolution as well.
While the data rate and range of Mobile-Fi are only half those of Mobile WiMax, Mobile-Fi is inherently more mobile. It has an astonishing latency of just 10 milliseconds (500 milliseconds is standard for 3G communications) and can maintain integrity at speeds as high as 155 mph (250 kph), compared to just 60 mph (100 kph) for WiMax. Because it uses more common spectrumlicensed bands up to 3.5GHzit also offers global mobility, handoff, and roaming support. Whereas Mobile WiMax is looking at the mobile user walking around with a PDA or laptop, Mobile-Fi addresses high-speed mobility issues. One key difference is the manner in which the two standards are deployed. One assumption is that the carriers are going to deploy Mobile WiMax in their existing (802.16a) footprint as opposed to deploying a more widespread footprint, like a cellular network. Because Mobile-Fi is aimed at more ubiquitous coverage, a larger footprint will be required.

Countries and companies often seek to control the market by developing standards they hope will dominate the global scene. The United States has led the way with IEEE standards, and the European Union's ETSI standards are their counterparts. The work of standards consensus is ongoing, uncertain, and difficult to predict. Mobile operators, who are generally friendly to Mobile WiMax, see Mobile-Fi as a competing standard that could make their 3G licenses worth rather less than they paid for them. The fact that Intel is behind WiMax is a strong force and will undoubtedly push the WiMax standards forward.

Mobile-Fi will have to overcome several hurdles. First among them is the fact that it can be used only in licensed bands below 3.5GHz. Another is that Mobile-Fi trails the Mobile WiMax standards process by a couple years. Another hurdle is whether there is indeed a large requirement for 155 mph (250 kph) handoff. In addition, we do not know what effect Mobile WiMax being nationalized in Korea will have. And, very importantly, cellular companies may not be willing to undercut their 3G service. Certainly, we can assume that the US$100 billion investment in 3G spectrum by the European mobile carriers alone might be weighed against a workable Mobile-Fi standard. With the possibility of proprietary systems (e.g., WiBro, Flash-OFDM) being in place a number of years before Mobile-Fi is standardized, the likelihood is that by then, Mobile WiMax will be backward compatible with WiMax fixed services. Licensed or unlicensed, Mobile-Fi will not be ubiquitous, and WiMax probably will.

Further Reading:
* Book: Wimax/Mobilefi
* Official IEEE 802.20 website

Friday 4 January 2008

HSPA Data Rates Calculation

People often get lost while calculating the data rates for HSDPA, HSUPA or HSPA+

Note: HSPA+ is better known as eHSPA or HSPAe where e stands for evolution or evolved

Most people are aware that the theoretical maximum for HSDPA is 14.4Mbps, so lets see how we reach 14.4Mbps:

In UMTS, in each slot the maximum number of bits transmitted is 2560. The correct term to use is chips rather than bits. If you want to know where this 2560 comes from or why chips then please refer 3GPP TS 25.211

There are 15 slots per 10ms frame so since the TTI for HSDPA is 2ms, there will be 3 slots. So there will be a total of 7680 chips.

QPSK has 2 bits per symbol = 7680 * 2 chips for 2ms = 15360 chips/2ms = 15360 * 1000 /2 chips per second

Now the SF is fixed at 16
= (15360 * 1000) / (2 * 16)
= 480 Kbps

Terminal that uses 15 QPSK codes will get 480 * 15 = 7.2Mbps

On other hand 16 QAM will have 4 bits per symbol so the rate would be 7.2 * 2 = 14.4Mbps

In HSPA+ we will also have 64QAM which has 6 bits per symbol (2^6 = 64) so the max rate would be 7.2 * 3 = 21.6Mbps.
The figure above is self explanatory and shows the data rate in case of eHSPA.

Thursday 3 January 2008

Ericsson Networks to launch MBMS in March 2008

Ericsson Networks last month successfully completed IOT (Inter-operability Testing) with EMP (Ericsson Mobile Platforms ... Handset people) and LG.

The plan is to have early launch systems in March 2008 followed by full deployment in September 2008. The only limiting factor might be the handsets which are not ready yet and have many problems that need to be sorted out.

According to CIO, Australians might be the first to get their hands on MBMS networks.

From what I have seen, Nokia is much ahead of its rivals in the MBMS game but they are keeping mum on this topic ... atleast for the moment. Sure it will be an interesting 2008.

Happy New Year

Its still not too late ... HAPPY New Year to everyone.

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?