WiMAX Femtocell System Architecture

So what does it take to build a WiMAX Femtocell solution?

WiMAX Femtocell can be visualized as a scaled down version of WiMAX macro-cell solution. In addition to the capabilities of a WiMAX macro-cell, other required features of a WiMAX Femtocell are the following:

• Spectrum: WFAP operates over licensed spectrum using standard WiMAX wireless air interface and protocol.

• Form factor: WFAP can be standalone (similar to WiFi access points) or integrated with DSL or cable modems.

• Transport: WFAP uses transport network of subscribers’ DSL, FTTH or cable-based broadband connection.

• User Capacity: Since WFAP is deployed inside a building; a WFAP needs to support at least 5-6 subscribers.

• Power Output: With a range of roughly 10 meters, power output should be kept very low, no more than a 2.4 GHz WiFi product.

• Deployment Support: Operating in a licensed spectrum a WFAP may face interference from neighboring base stations (femto or macro). Therefore, a WFAP should have the capabilities to automatically adjust to minimize the interference.

• Local Breakout: A WFAP should optionally support the capability to route incoming or outgoing traffic directly to the destination through the Internet Service Provider (ISP) network. This approach will bypass the WiMAX service provider network, thus offloading WiMAX service provider network and reducing the cost of service to the subscriber.

• Performance: A Femtocell solution should fit as per the WiMAX network architecture defined by the WiMAX forum. The deployment should not limit the number of WFAPs that are able to connect with a designated ASN Gateway unless operator specified. A network deployment should allow different ISPs to connect WFAP with ASN Gateway in the core network.

• Hand-over: A Femtocell solution should allow handovers between WFAP and WiMAX macro cells or with other adjacent WFAPs.

• Security: A Femtocell solution should use a secure channel of communication (for both control plane and data plane) with ASN Gateways in the core network. The core network must authenticate and authorize a WFAP before it starts offering services to MS/SS in its coverage area. A WFAP may authenticate the ASN Gateway with which it gets connected. A WFAP should keep its air interface disabled unless it is authenticated and authorized to start communication with the ASN Gateway in the core network. A Femtocell may support close subscriber group (CSG) database i.e. a list of subscribers allowed to access the WFAP, and its management.

• Accounting: For providing different rate plans to subscribers accessing services through WFAP, a WFAP needs to make sure that it is recognized by the core network.

• Location Information: A WFAP should support location identification procedures with the core network. Location information can then be used for emergency services or location based services.

• Air Interface: A WFAP should provide at least 10 meters of coverage area in a residential set up without any exclusion zone around it.

• Network Synchronization: A WFAP should support mechanism to synchronize with external network to provide services that require strict air interface co-ordination. Some of the services are soft-handovers, support for idle mode paging, and multicast-broadcast (MCBCS) services.

• Quality of Service: A WFAP should support marking of incoming/outgoing packets with appropriate DSCP code, as configured by a service provider. This would allow support for defined service level agreements (SLAs) when the service is delivered through a WFAP.

• Manageability: A WFAP should implement DSL forum’s defined TR069 protocol to allow an operator to remotely manage a WAFP. It must allow an operator to remotely disable/enable the air interface service.

The WiMAX network architecture for femtocell systems is based on the WiMAX basic network reference model that differentiates the functional and business domains of NAPs from those of the network service providers (NSPs). The NAP is a business entity that provides and manages WiMAX radio access infrastructure, while the NSP is the business entity that manages user subscriptions, and provides IP connectivity and WiMAX services to subscribers according to negotiated service level agreements (SLAs) with one or more NAPs. A NAP is deployed as one or more access service networks (ASNs), which are composed of ASN gateways and BSs, while the NSP includes a home agent, authentication, authorization, and accounting (AAA), and other relevant servers and databases.

In a WiMAX network supporting a femtocell, a new business entity called the femto-NSP is introduced, which is responsible for the operation, authentication, and management of WFAPs. The femto-NSP is logically separated from the conventional WiMAX NSPs responsible for MSs’ subscriptions, and it includes femto-AAA and femtocell management/self-organizing network (SON) subsystems.

The femtocell management system is an entity to support operation and maintenance (O&M) features of the WFAP based on TR-069 or DOCSIS standards. Because potentially many femto BSs will be deployed in overlay coverage of macrocell BSs and have to support handover to/from macrocell BSs or neighbor femto BSs, the operating parameters of femto BSs have to be well organized and optimized. Femto BS parameter configuration and network performance, coverage, and capacity optimization can be done in an autonomous fashion by using SON functions. A SON server provides SON functions to measure/analyze performance data, and to fine-tune network attributes in order to achieve optimal performance.

A femto-NAP implements its infrastructure using one or more femto-ASNs; an ASN is defined as a complete set of network functions needed to provide radio access to a WiMAX femtocell subscriber. The reference model for a the femto-ASN is defined based on some changes to the conventional ASN to address specific needs of WFAPs, which typically reside at customer premises, and are operated and managed remotely by a femtocell operator over third party IP broadband connection. The femto-ASN reference model includes a WFAP connected to a femto-GW serving as the ASN-GW, through a new entity called a security gateway (SeGW). The SeGW provides IP Security (IPsec) tunnels for WFAPs, and is responsible for authentication and authorization of the WFAPs. The WFAP is connected to a femto-ASN gateway (femto-ASN GW) and other functional entities in the network through this IPsec tunnel. The management system is connected to WFAP through Rm for remote configuration, and it will also include the SON server function, to be defined in the next releases of the femto architecture.

The femto-ASN GW is an entity that controls WFAPs, and performs bearer plane routing to the CSN and Internet as well as control plane functions similar to ASN-GW providing the link to the connectivity service network (CSN) and other ASNs with mobility and security support in the control plane and IP forwarding. In addition to common functionalities of the ASN-GW, the femto-ASN GW supports femto-specific functionalities such as closed subscriber group (CSG) subscriber admission control, femtocell handover control, WFAP low-duty mode management, and femtocell interference management.

Image Reference: WiMAX Femtocell: Requirements, Challenges, and Solutions

Focus on TD-LTE by 3G Americas

3G Americas has published an educational white paper titled, "3GPP LTE for TDD Spectrum in the Americas". The report provides a top-level overview on the considerations for deployment of Long Term Evolution (LTE) in Time Division Duplex (TDD) technology spectrum in the Americas and recommends LTE TDD as a mobile broadband solution to utilize valuable TDD spectrum assets in the region.

The white paper explains the technical mechanism in which LTE TDD (also known as TD-LTE) and Time Division Synchronous Code Division Multiple Access (TD-SCDMA), a 3rd Generation Partnership Project (3GPP) third generation technology deployed in China, are smartly designed with the ability to operate together with great harmonization and efficiency. LTE TDD is a natural migration for TD-SCDMA operators. The technical synergy between LTE TDD and TD-SCDMA operators will thus increase the economies of scale for LTE TDD operators throughout the world.

Although operators are making plans for the deployment of LTE Frequency Division Duplex (FDD) technology, the white paper emphasizes that operators, regulators, license holders and investors must strongly consider the significant opportunities behind deployment of LTE in fragmented TDD spectrum as a mobile broadband solution that can serve the communication needs and demands of the marketplace.

Additionally, the report highlights that asmobile broadband is becoming ubiquitous throughout the Americas and the Internet generation is growing more accustomed to having broadband access everywhere, technology usage is exploding and, thus, is putting a tremendous strain on already well-utilized networks and spectrum. 3GPP LTE for TDD Spectrum in the Americas focuses on the LTE ecosystem and how operators are working to meet this increasing demand for mobile broadband services.

The LTE ecosystem supports both FDD and TDD operation, offering operators flexibility to match their existing networks, spectrum and business objectives for mobile broadband and multimedia services. Fifteen paired (for FDD operation) and eight unpaired (for TDD operation) spectrum bands have already been identified by the 3GPP for LTE. This means an operator can introduce LTE in new spectrum bands.

The white paper, 3GPP LTE for TDD Spectrum in the Americas, was written collaboratively by members of 3G Americas and is available for free download on the 3G Americas website at www.3gamericas.org.

The whitepaper is available here.

Updates from GSMA Asia Mobile Congress 09 - Day 2

Summary of interesting facts from the GSMA Mobile Asia Congress 09, Via Tomi Ahonen's, Communities Dominate Brands:

• 55% of Japan has migrated past 3G to 3.5G
• Japanese mobile content industry is worth 14 Billion dollars annually
• 50% of mobile data in Japan is consumed in the home, the peak time for mobile data consumption is between 9 PM and 10 PM; and smartphone users consume 10 times more data than non-smartphone users.
  
• Japan's Softbank will turn off their 2G network already in March of next year, 2010.
• Allen Lew, Singtel's CEO, said that in Singapore almost 50% of smartphone owners are shifting web surfing activity away from PCs.
  
• Jon Fredrik Baksaas, Telenor's President and CEO, spoke about the eco-friendly initiatives they have, such as solar powered cellular network base stations etc, but an interesting tidbit that came out, is that in Europe, Telenor has installed 870,000 household electricity meters that are remote digital meters and operate on the GSM cellular network, in Sweden. As Sweden's population is only about 7 million people that is probably a third of all households.
  
• Rajat Mukarji of Idea (one of India's largest mobile operators), told us of the Indian market, where the average price of a voice minute is 1 cent (US). He Mr Mukarji also said that in India mobile is the first screen, not the fourth screen; and mobile is the first internet connectivity opportunity for most people of India.
• Tony Warren, GM of Regulatory Affairs at Telstra, told that 60% of phones in Australia are 3G already, and over half of mobile data is now non-SMS type of more advanced mobile data. And he said that MMS is experiencing enormous growth, grew 300% in the past year.

You can read the summary of first day here.

Read the complete report here.

LTE = Windows Vista and HSPA = Windows XP

Moray Rumney in Forum Oxford made us aware that 3GPP has published a link on their homepage to address concerns with aspects of LTE deployment covering:

• Support for voice
• Supoort for SMS
• Readiness of IMS
• Support for emergency calling

Dean Bubley, a well known analyst provided the following response:

It takes a very narrow view that "maturity" equals "fully specified". It still maintains that "The voice solution for LTE is IMS VoIP and it is fully specified" and that any other solution is merely a "transition".

In other words, it makes LTE sound unsuitable for those operators which are IP-centric but which do not believe in IMS as a suitable control/service solution.

3GPP is trying to use LTE as a lever to force unwilling operators to adopt IMS. This will fail.

SMS-over-SGs has some serious shortcoming as well as costs, but is probably OK as a short term solution.

I am moving to the view that current LTE is the equivalent of Windows Vista, while HSPA = XP

I think a lot of operators will wait until "Windows 7" becomes available, either LTE Advanced or perhaps Rel 10 LTE.

Very interesting. He has put forward a great analogy of Windows OS that reflects concerns of many of us.

You can follow the complete discussions here.

Updates from GSMA Asia Mobile Congress 09 - Day 1

Summary of interesting facts from the GSMA Mobile Asia Congress 09, Via Tomi Ahonen's, Communities Dominate Brands:

• According to Rob Conway, CEO of the GSM Association, the number of subscribers will grow to 8 Billion (not sure when though).
• China Unicom, China's second largest mobile operator with 142 million subscribers - bigger than AT&T and Sprint put together.
• Bharti Telecom of India has over 110 million subscribers
• According to Manoj Kohli, the CEO of Bharti Telecom, India already 20% of all mobile phone owners have 2 or more subscriptions. He also told us that as India will add 500 million new subscribers by the time frame of 2014-2015. India is currently adding 10 million new mobile subscribers every month. And most revealingly, he said that in India the customers will go from 'no internet' directly to 'mobile internet'.
• According to Wang Jianzhou the Chairman and CEO of China Mobile, the world's biggest mobile operator with over 500 million subscribers, on the Chinese 3G standard of TD-SCDMA, they already have 3G phones being sold that cost about 1,000 Yuan, or about 130 US dollars. The average China Mobile customer spends 1 minute per day on voice calls, but sends on average 3.6 SMS text messages per day.
• According to Yamada-san, the President and CEO of Japan's NTT DoCoMo, on NTT DoCoMo's network, today already 42% of their total revenues come from non-voice data services. NTT DoCoMo is so far in its migration of its customer base from 2G to 3G, they will terminate 2G in March of 2011.
• Yamada-san also told of their new 3G video TV service, they call BeeTV. BeeTV is special in that it is optimized for the small screen, not re-purposed video content from TV and the internet. BeeTV in only six months has achieved 800,000 paying subscribers - who pay 315 Yen per month (about 3 USD).
• Yamada-San's 20 minute presentation also mentioned that NTT DoCoMo's i-Consierge service (yes, think of it as your personal butler, the phone learns your habits and starts to help you with your life, this is like magic) has 2.3 million paying subscribers one year from launch. Their i-Channel idle screen invention is spreading and they have launched it also with their partner in India, Tata, who offer Cricket game updates via the idle screen using i-Channel.
• Japan's mobile advertising market in 2008 was worth 900 million dollars.
• Grameenphone and Huawei won the 'Green Mobile' award for their 'green' network initiatives.

Read the complete blog here.

Motorola believes in TD-LTE

According to Fierce Broadband Wireless:

Motorola is being very strategic about the contracts it goes after, said Bruce Brda, senior vice president and general manager of the vendor's wireless networks business, in an interview with FierceBroadbandWireless.

"We are not trying to go head to head in every part of the globe. We've been selective in our engagements, focusing on the customers that we think we have a higher advantage with," Brda said. "Our initial thrust is in places in Asia where we have a significant competitive advantage." That's why it won an LTE contract with Japan's KDDI, he said, despite the fact 10 vendors in all competed for that business.

Motorola's other sweet spot is the TDD (unpaired spectrum) version of LTE, otherwise known as TD-LTE, a technology China Mobile is keen on deploying. Brda believes that Motorola's OFDM experience with WiMAX coupled with its TDD experience, again with WiMAX, will give Motorola an advantage in China.

TD-LTE, in fact, won't be a niche market, Brda said. "With the demand for data that exists around the world, it will be a solution set that solves the equation, not just FDD, but a series of solutions, and TD-LTE will play in increasingly large role, maybe coexisting in the same network as FDD LTE."

Brda noted that Motorola is talking to a number of European operators that envision TD-LTE and FDD LTE coexisting. "You could have one set of services carried over the TDD network and another set going over FDD," he said. "It's would create a more efficient use of the network, but I also think more and more TDD spectrum is going to be available. It's been kind of ignored around most of the world, but it's much easier to find un unpaired block of spectrum than a paired block."

Another aspect that has been largely ignored is the fact that experience in mobile WiMAX is highly transferable to the LTE world. Motorola, which has constructed about 20 WiMAX networks, and Samsung are now the two major vendors that have stuck with the mobile WiMAX game to a high degree. Many vendors such as Alcatel-Lucent, Ericsson and Nokia Siemens Networks either shunned mobile WiMAX or significantly scaled back on their efforts in favor of LTE.

Picture source: ChinaByte

The Secret world of WiMAX Femtocell

We have talked of WiMAX femtocells before and since I have mostly been focussing on 3GPP standardised Femtocell, I thought it is wise to focus on WiMAX femtocell and learn more about its terminology and implementation. Whenever possible, I will draw comparisons with the 3GPP femtos and try to provide more insight if I can.

Surprisingly I found it difficult to find the information on WiMAX femtocells. I am sure its not because no one is interested in the technology but its more because of the standards not being available in public domain. An old article on Think Femtocell informs us of the initial players of WiMAX femtocells. I havent tried digging in who is doing what in the WiMAX femtocell world, so if you are aware of potential players, feel free to highlight them via comments.

In WiMAX terminology, femtocells are known as femto base stations (BSs) or WiMAX femto access points (WFAPs). They are intended to serve the same purpose as the 3GPP femtocell that I have mentioned time and again. WiMAX as a technology is intended for data and voice can be an OTT application. In a way its a disadvantage for this technology but can be considered as an advantage as it doesnt have the baggage of old Circuit Switched system.

Another thing that I should clarify here is that WiMAX is intended to operate in licensed spectrum and so are the WFAPs. All femtocells start playing important role when high data rates are required and when the operating frequencies are high. Higher frequencies means lower penetration inside homes and the signal inside the offices can be easily enhanced with femtocells (or for that matter picocells in big buildings).

The WiMAX Forum has commenced the development of femtocell standards in two phases. The first phase is based on IEEE 802.16-2009 (aka 802.16Rev2) and system profile Release 1.0 or Release 1.5, so no change in the air interface standard or legacy MS is required to enable basic femtocell deployments. Some optional software upgradable enhancements in the MS may be used to enable additional femtocell functionalities only for such femto-aware MSs. The network framework to support femtocells in phase 1 is being developed in the WiMAX Forum as part of Network Working Group (NWG) release 1.6. The complete end-to-end femtocell specifications are expected to be finalized by the end of 2009. The second phase of WiMAX femtocell development, which brings additional functionalities and more optimal performance, will be introduced in system profile and network Release 2 based on the 802.16m air interface. The evolution to phase 2, which is expected to be completed by 2011–2012, enables enhanced femtocell systems with 802.16m MSs’ advanced functionalities while continuing the support of phase 1 legacy MSs with basic functionalities. Femtocells are expected to play an important role in terms of cost-effective delivery of new services, such as multimedia, gaming, social networking, and other demanding applications with the high quality of service (QoS) level expected by users in an indoor environment. However, femtocells are in an early stage of development and have some technical challenges to overcome.

Image Reference: WiMAX Femtocells Whitepaper - Aricent

Content Reference: WiMAX Femtocell: Requirements, Challenges, and Solutions

Global LTE Commitments, November 09

Click on the picture to enlarge it.

Source: GSACOM

Bangladesh: Learn English on your Mobile

More than 300,000 people in Bangladesh, one of Asia’s poorest but fastest-growing economies, have rushed to sign up to learn English over their mobile phones, threatening to swamp the service even before its official launch on Friday.

The project, which costs users less than the price of a cup of tea for each three-minute lesson, is being run by the BBC World Service Trust, the international charity arm of the broadcaster. Part of a UK government initiative to help develop English skills in Bangladesh, it marks the first time that mobile phones have been used as an educational tool on this scale.

Since mobile-phone services began in Bangladesh just over a decade ago, more than 50.4m Bangladeshis have acquired phone connections, including many in remote rural areas. This far outnumbers the 4m who have internet access.

English is increasingly seen as a key to economic mobility. An estimated 6.2m Bangladeshis work overseas and hundreds of thousands of others want to follow in their steps. However, English is also important for securing jobs at home, where about 71 per cent of employers look for workers with “communicative English”.

Through its Janala service, the BBC offers 250 audio and SMS lessons at different levels. Each lesson is a three-minute phone call, costing about 3 taka (2.6p).

One basic lesson involves listening to and repeating simple dialogue like: “What do you do?” “I work in IT, what about you?” “I’m a student.” “That’s nice.” Another is devoted to differentiating vowel sounds like those in ship and sheep or leaf and live.

All six mobile phone operators in Bangladesh have agreed to cut the cost of calls to the service by 50 per cent to make it more affordable. Ms Chamberlain said the project team was in talks with the mobile phone companies to increase capacity to cope with the unexpectedly high demand.

The launch of the service comes just weeks after Grameenphone, the country’s largest mobile phone operator, held Bangladesh’s largest IPO, raising $71m from retail investors in the largest offering ever held in the country.

The language lessons are mainly targeting 18 to 24-year-olds, who typically had five or more years of formal education, but whose training in English had been weak. The target market is people living on less than 10,000 taka ($145, €97, £87) a month, who would struggle to pay for formal English lessons.

The relatively low cost of mobile handsets and connection charges has led to an explosion in their use and an estimated 50 million people now have access to phones.

Now users will be able to listen via their phones to weekly bilingual ­English language lessons and receive lessons by text as part of a low-cost service. Lessons are available at four levels, ranging from basic conver­sation skills, to support with sounds that Bangladeshis find difficult to pronounce, and the higher-level vocabulary of English language news media.

New lessons will be available each week with older lessons accessible from an archive. Learners can also ­assess their skills by doing audio quizzes and tests delivered by text message.

The trust says that it has negotiated reductions on standard mobile tariffs of up to 75% to make the service affordable to users with limited incomes.

Allan Freedman, country director for BBC World Service Trust Bangladesh, said: “Young people across Bangladesh have told us they consider learning English as a path to better jobs and opportunities. Our project is about meeting that demand and helping millions of people access English learning tools for the first time.

“It’s arguably the most exciting use of English to improve the lives of ­people in the developing world today.”

The Janala lessons will also be available via the internet on a ­website designed to develop both English-­language and web-user skills, in a country where computer use has been severely restricted by high costs and lack of electricity in rural areas.

Janala will also be promoted via a weekly television programme, BBC Buzz, produced by the World Service Trust, which started broadcasting last month. The show features stories aimed at younger viewers and covers topics such as careers, politics, fashion and music.

It includes the English language learning exploits of a cartoon character called Rinku. Viewers can receive follow-up lessons via mobile phone that build on language points raised by Rinku and have a say on future ­episodes.

eMBMS: Naughty after 11pm ;)

I have blogged about MBMS in past about how it didn't take off even though it was a promising technology. Now you may probably be aware that eMBMS is part of Release-9. I heard some interest in this feature.

The expectation is that the demand for data drops off later in the night after around 10pm. The operators may start some channels say after 11pm because the network will have lots of spare capacity that could be used for television channels. You could have late night movies, sports channels and adult channels.

An advantage of going eMBMS way would mean that even if you are roaming, you can have pay per view kind of approach as long as the other network is Release-9 compliant.

Interesting idea, not sure if it will take off.