TD-SCDMA, TDD and FDD

After my posting on TD-SCDMA so many people asked me about what TD-SCDMA is. I am surprised that so many people are not aware of TD-SCDMA. So here is a quick posting on that.

TDD and FDD Mode of Operation

Basically most of the UMTS networks in operation are Frequency Division Duplex (FDD) based. There is also another variant called the Time Division Duplex or TDD. In reality there is more than one variant of TDD, so the normal 5MHz bandwidth TDD is called Wideband TDD of WTDD. There is also another name for WTDD to confuse people, called the High Chip Rate TDD (HCR-TDD). There is another variant of TDD as would have guessed known as the Narrowband TDD (NTDD). NTDD is also known as Low Chip Rate TDD (LCR-TDD) and most popularly its known as TD-SCDMA or Time Division Synchronous CDMA.

"Synchronous" implies that uplink signals are synchronized at the base station receiver, achieved by continuous timing adjustments. This reduces the interference between users of the same timeslot using different codes by improving the orthogonality between the codes, therefore increasing system capacity, at the cost of some hardware complexity in achieving uplink synchronization.

The normal bandwidth of FDD or TDD mode of operation is 5 MHz. This gives a chip rate of 3.84 Mcps (Mega chips per second). The corresponding figure for TD-SCDMA is 1.66 Mhz and 1.28 Mcps.

Assymetric operation in TDD mode

The advantage of TDD over FDD are:

• Does not require paired spectrum because FDD uses different frequencies for UL and DL whereas TDD uses the same frequency hence its more easy to deploy
• Channel charachteristics is the same in both directions due to same band
• You can dynamically change the UL and the DL bandwidth allocation depending on the traffic.
  

The dis-advantage of TDD over FDD are:

• Switching between transmission directions requires time, and the switching transients must be controlled. To avoid corrupted transmission, the uplink and downlink transmissions require a common means of agreeing on transmission direction and allowed time to transmit. Corruption of transmission is avoided by allocating a guard period which allows uncorrupted propagation to counter the propagation delay. Discontinuous transmission may also cause audible interference to audio equipment that does not comply with electromagnetic susceptibility requirements.
• Base stations need to be synchronised with respect to the uplink and downlink transmission times. If neighbouring base stations use different uplink and downlink assignments and share the same channel, then interference may occur between cells. This can increase the complexity of the system and the cost.
• Also it does not support soft/softer handovers

Timing Synchronisation between different terminals

By the way, in Release 7 a new TDD mode of operation with 10 MHz bandwidth (7.86 Mcps) has been added. Unfortunately I dont know much about it.

You can read more about TD-SCDMA in whitepaper 'TD-SCDMA: the Solution for TDD bands'

You can find more information on TD-SCDMA at: http://www.td-forum.org/en/

Scratch Input: Future Input for Mobile Phones

Very interesting...not being able to see past your fingers on smaller devices. That's where "scratch input" comes in. Harrison's prototype uses a digital stethoscope to pick up the sound of scratching on a table or wall. The device attached to the stethoscope, be it a phone, watch or a computer, is programmed to recognise the sounds of different scratch gestures. By tracing a spiral on his desk, Harrison can, for example, turn the volume down on his media player. Ultimately the microphone would be built into the device. Imagine a touch screen watchphone that can be controlled simply by scratching your arm.

You may be interested in reading this article Touch Screens at The Independent here.

Ericsson's Exciter: Conceptual mobile Personal Area Mediator (PAM)

Interesting Video:



If you find this interesting, there is a presentation you can look at here. Unfortunately its in swedish but you can get an idea about which direction things will be going in future.

Huawei becomes a big player in LTE

[Shenzhen, China, 1 September 2009] Huawei, a leader in providing next-generation telecommunications network solutions for operators around the world, today announced that it has been granted 147 Long Term Evolution (LTE) patents by the European Telecommunications Standards Institute (ETSI), representing 12 percent of the total existing 1,272 LTE patents assigned by ETSI as of August 2009. The patents granted were across several key LTE sub-sectors, such as physical-layer air interface, radio resource management and connection management.

Huawei’s robust investment in LTE research and development has accelerated the commercialization of LTE technology. In June 2009, Huawei connected the world’s first LTE mobile broadband internet connection for Teliasonera in Oslo, Norway.

Huawei is an active participant in 91 standardization organizations, with over 100 committee leadership positions. In 2008, Huawei had filed a total of 35,773 patent applications globally.

Last year LG had claimed that it has upto 300 patents, not sure if that is still true.

New report on Mobile Broadband Evolution from HSPA to LTE-Advanced

The white paper, HSPA to LTE-Advanced: 3GPP Broadband Evolution to IMT-Advanced (4G), discusses the 3GPP evolution of EDGE, HSPA and LTE, their capabilities and their positions relative to other primary competing technologies and how these technologies fit into the ITU roadmap that leads to IMT-Advanced.

The following are some of the important observations and conclusions of the report:

• HSPA Evolution (HSPA+) provides a strategic performance roadmap advantage for GSM-HSPA operators. Features such as dual-carrier operation, MIMO and higher-order modulation offer operators multiple options for improving their networks, and some of these features are simply network software upgrades.
• Persistent innovation in developing HSPA and HSPA+ is bringing UMTS to its full potential providing mobile broadband to the mass market; in current deployments, HSPA users regularly experience throughput rates well in excess of 1 Mbps under favorable conditions, on both downlinks and uplinks, with 4 Mbps downlink speed commonly being measured. Planned enhancements such as dual-carrier operation will double peak user-achievable throughput rates.
• LTE has become the next-generation platform of choice for GSM-HSPA and CDMA/EV-DO operators.
• The 3GPP OFDMA approach used in LTE matches or exceeds the capabilities of any other OFDMA system providing the most powerful wide area wireless technology ever developed. Peak theoretical downlink rates are 326 Mbps in a 20 MHz channel bandwidth.
• 3GPP has made significant progress investigating how to enhance LTE to meet the requirements of IMT-Advanced in a project called LTE-Advanced.

With a customer base of 4 billion connections today, the GSM family of technologies is available on nearly 800 networks in 219 countries worldwide. Building on this base, UMTS-HSPA – the world’s dominant mobile broadband technology today – has proven to be the most widely deployed and adopted 3G technology of all time, with more than 352 operators in various stages of deployment, including 277 commercial HSPA networks in 116 countries.

The white paper explains the tremendous opportunity afforded to GSM-HSPA operators via the 3GPP roadmap to HSPA+. While OFDMA systems such as LTE and WiMAX have attracted a great amount of attention, evolving HSPA to exploit available radio technologies can significantly enhance its performance capabilities and extend the life of sizable operator HSPA infrastructure investments. Techniques include advanced receivers, MIMO, Continuous Packet Connectivity, Higher-Order Modulation and One Tunnel Architecture, many of which are included in the standardization of 3GPP Release 7 and Release 8.

Depending on the features implemented, HSPA+ can exceed the capabilities of IEEE 802.16e-2005 (Mobile WiMAX Release-1) in the same amount of spectrum. Beyond the peak data rate of 42 Mbps for HSPA+ in Release 8 (with 2X2 MIMO, DL 64 QAM and UL 16 QAM), Release 9 may specify 2X2 MIMO in combination with dual-carrier operation, which would further boost peak theoretical downlink network rates to 84 Mbps. In addition to the increased speeds, HSPA+ also will more than double HSPA capacity and has the potential of reducing latency to below 25 milliseconds.

HSPA and HSPA+ will continue to dominate mobile broadband subscriptions worldwide for the remainder of this decade and well into the next. However, announcements have already begun in support of the next 3GPP evolutionary step, LTE. Trials and deployments of LTE will begin in 2010 by leading operators including AT&T, China Mobile, China Telecom, NTT DoCoMo, Verizon and Vodafone. In fact, today there are more than 2 billion subscriptions represented by combining the total existing customer bases of the more than 100 operators, both GSM and CDMA operators, who have announced indications of their intention to deploy LTE networks.

The deployment of LTE and its coexistence with UMTS-HSPA will be analogous to the deployment of UMTS-HSPA and its coexistence with GSM-EDGE.

Whitepaper available to download here.
Accompanying slide presentation available here.

HSPA+ is everywhere...

EMobile Ltd. , Japan's smallest mobile operator, has deployed HSPA+, also known as HSPA Evolved, in the country's major cities, including Tokyo, Osaka, Yokohama, and Nagoya.

This deployment is based on equipment from Ericsson AB, which supplied the core network and core systems integration services as well as the majority of the radio access network. It builds out the geographical coverage for HSPA+ that EMobile has already established using Huawei Technologies Co. Ltd. equipment in a number of Japan's other cities, including Hokkaido, Sendai, Niigata, Hiroshima, Fukuoka, and Nagasaki.

Japan is a market with a reputation for being first with new technology, but HSPA+ has been passed over, most notably by market leader NTT DoCoMo Inc., which has focused on moving to Long-Term Evolution (LTE) as fast as possible.

The No. 2 player, KDDI Corp. , is similarly pushing toward LTE, although from a CDMA base that takes HSPA out of the equation, while Softbank Mobile Corp. is known to have run HSPA+ lab trials and has also said it will move to LTE when it gets the necessary spectrum.

EMobile is by far the smallest of Japan's operators, with just 1.67 million subscribers at the end of the second quarter, compared to DoCoMo's 54.86 million, KDDI's 31 million, and Softbank's 20.96 million customers, according to Wireless Intelligence .

You can check out the HSPA+ features in Rel-7 and Rel-8 here.

Zapp, mobile operator of Romania, has launched the first stage of its HSPA+, the upgraded mobile broadband service in the capital city of Bucharest. With this service, the subscribers can enjoy peak download speeds of 21.6Mbps, while upload speeds will increase by up to 15 times, from 384Kbps to 5.8Mbps. According to a report, Zapp contracted Chinese firm ZTE to deploy the network, which will run parallel to the cellco’s second phase 3G rollout, expanding its UMTS services to 63 cities nationwide.


O2 Germany is currently running a friendly user test in Munich where O2 Germany's technology partner is Huawei. Beside being O2's network partner for the overall HSPA-network upgrade, Huawei is also O2 Germany's major vendor for UMTS sticks and therefore O2 Germany is using Huawei equipment for the HSPA+ test as well. The used Huawei E182E stick is a slide-out USB stick, supporting quadband GSM/GPRS/EDGE as well as quadband UMTS/HSDPA up to 21.6 Mbps and HSUPA up to 5.76 Mbps. Furthermore the stick is MIMO ready.

Spanish mobile network operator Vodafone Spain has announced it will begin deploying HSPA+ technology across its network in the autumn of 2009. The cellco says the upgrade will allow its infrastructure to achieve theoretical download speeds of up to 21.6Mbps, while uplink speeds would increase to up to 5.7Mbps. Initially Vodafone expects to launch the increased speeds in seven unnamed ‘major’ cities, with further expansion to follow. In addition, Francisco Roman, president and CEO of Vodafone Spain, has announced that the operator plans to further extend its provision of ADSL services across the country, although it has not given any specifics for areas it plans to extend its reach to.

­Swiss network operator, Swisscom says that it is deploying a HSPA+ (HSPA Evolution) upgrade, with the first areas completed in time for the ITU Telecom World 2009 in Geneva. The upgrade will offer a peak rate data transfer rate of 28.8 Mbps - although the more realistic average is no higher than 8Mbps. The network has launched a HSPA 14.4Mbps service at the beginning of this year.

Chunghwa Telecom, the Taiwanese mobile operator has reportedly selected Nokia Siemens Networks (NSN) to upgrade its wireless infrastructure with HSPA+ technology. The operator intends to launch its HSPA+ and 3G services by 2010, boosting mobile broadband download speeds to up to 21Mbps. Initially, devices able to utilise the HSPA+ service will include data network cards, USB dongles and wireless modules before it is extended to cover smartphones, netbooks and notebooks.

ZTE Corp has completed the interoperability test (IOT) of its 3GPP R7-based HSPA+ MIMO (multiple-input multiple-output) solution, conducted in conjunction with mainstream terminal chip platform manufacturers, in July 2009.

The MIMO solution, realized with its SDR-based next-generation base station, has reached a theoretical speed limit of 28.8Mbps in both cable connection and wireless environment tests. The trials included data download services for UDP (User Datagram Protocol) and FTP (File Transfer Protocol), as well as various IOT item tests.

All the test results indicated stable and fast data download performance. The successful IOT testing confirms that ZTE's MIMO solution is now ready for large-scale commercial deployment worldwide.

Improved LTE backhaul via Alcatel-Lucent's 10G GPON

“The PON vendor landscape got interesting in the fourth quarter of 2008, with Alcatel-Lucent, Motorola, and Tellabs each grabbing 10% of worldwide revenue share, behind perennial leader Mitsubishi and the now number-two player, Fiberhome. In the fast-growing GPON segment, front-runner Alcatel-Lucent is being seriously challenged by Motorola, which increased its quarterly GPON revenue share 5 points in 4Q08. Meanwhile, the EPON segment, long dominated by Mitsubishi and Hitachi, is seeing some action as Sumitomo, Fiberhome, and Dasan Networks all moved up.” - Jeff Heynen, Directing Analyst, Broadband and Video, Infonetics Research

I have blogged a bit about GPON and Backhaul before. Click on the links if you havent seen the posts before.

During this year's Broadband World Forum Europe, Alcatel-Lucent not only shows that it masters next-generation wireline and wireless access. The company also highlights that Long Term Evolution (LTE) and next-generation passive optical networking (PON) technologies converge seamlessly for a smooth delivery of the most demanding, high-speed broadband services.

The live demonstration in Alcatel-Lucent's Paris demo center shows LTE's capability to deal with multiple concurrent video streams and fast channel change - and is complemented by a high-capacity 10G GPON backhaul solution for future-safe backhaul via fiber.

Alcatel-Lucent is at the forefront of developing cutting-edge technologies long before they are standardized. Even though the 10G GPON standards are still being ratified, Alcatel-Lucent shows it is ready - when needed - to meet the request for higher capacities in its customers' access networks.

Alcatel-Lucent is engaged in over 95 FTTH projects around the world, over 80 of which are with GPON (as-of Q2, 2009). In Gartner's latest FTTH Magic Quadrant assessment, Alcatel-Lucent was positioned in the leaders quadrant for the fiber-to-the-home space.

Alcatel-Lucent is also opening up details of its optical management and control interfaces (OMCIs) in a bid to help create a true multi-vendor gigabit passive optical networking (GPON) infrastructure.

Announced at this year's Broadband World Forum Europe in Paris, the first version of the OMCI Interoperability Implementer's Guide is aimed at helping other optical network terminal vendors integrate their hardware with Alcatel-Lucent's.

TD-SCDMA: Where are we

Interesting things are going on in the Chinese market.

A new mobile phone platform has been launched by China Mobile for it's TD-SCDMA 3G mobile phone network. In fact, it’s the first ever mobile phone operating system designed by a 3G mobile phone operator and is called Ophone. The OPhone is a linux-based terminal software platform for mobile internet.

In conjunction with the announcement for the Ophone, China Mobile announced a number of Ophone compatible handsets from Samsung, Lenovo, Phillips and Dell.

China Mobile stated that by introducing the Ophone operating system, significant savings will be made on TD-SCDMA handset design and development.

"Dopod CEO Dennis Chen said the Qilin handset is the first result of China Mobile's $7 million in subsidies to encourage TD-SCDMA handset development. Dopod has expanded investment in manpower and funding towards TD-SCDMA R&D and will release numerous high-end TD-SDCMA (sic) handsets next year."

The HTC Qilin has some pretty good genes: WM 6.5, 600MHz TI OMAP processor, 3.6" WVGA screen, GPS, 5MP camera, and CMMB Mobile TV and is apparently based on HTC's Whitestone design. The TD-SCDMA standard is China's home-grown 3G standard, which means that the Qilin won't have access to 3G networks outside of China. Having said that, HTC and China Mobile have just signed an MOU to partner up in R&D, market research, and product development, so the Qilin will be just the first in a series of handsets HTC will develop for China Mobile.

The Qilin is slated for release in December, which puts it just in time for runup to the Chinese New Year holidays.



China Mobile and LG have recently showcased the GW880, LG’s first smartphone to use the Android-based OMS (Open Mobile System) platform.

Featuring GSM and TD-SCDMA connectivity, the LG GW880 will be available via the largest Chinese mobile carrier later this year, for a price that was not announced.

The smartphone is a high-end one, as it comes with a 3.5 inch WVGA touchscreen display, 5MP camera with flash, Mobile TV, 512MB ROM and 256MB RAM.

We’re probably not going to see the LG GW880 outside China, but that’s OK, since LG is surely preparing some Android phones for other markets.

China Mobile saw its number of TD-SCDMA subscribers increase by 129,000 to 1.088 million in July. The first batch of handsets were released in May.

Nearly one half billion people subscribed to China Mobile cellular services last month, but the giant's efforts to promote a Chinese 3G standard have made little headway. The world's largest carrier grew to 498 million mobile subscribers last month, a number larger than the populations of the U.S. or the European Union. The number of subscribers using their mobile phones to play games, download music and surf the Internet also rose during the first half of the year, China Mobile said Thursday. But growth was slow for TD-SCDMA, a domestic 3G mobile standard that the government tapped China Mobile to market. Subscribers surpassed 1 million in July, continuing a slow climb upward from the launch of TD-SCDMA services in January.

China Mobile Communications Corp. aims to have as many as 80 million users of its homegrown third-generation mobile technology within two years of its initial rollout, Minister of Industry and Information Technology Li Yizhong said. Speaking at a news briefing, Li acknowledged the domestic standard isn't as developed as its more mature international rivals, but said he is confident in its commercial development.

Youtube Clip on Dangers of driving while texting

The film tells the story of a fictional 17-year-old girl, Cassie Cowan (nickname COW), who is distracted by her mobile for a few seconds while driving with two friends.

COW – a "nice girl from a nice valleys family" – causes a devastating crash which kills her friends and another couple. The impact and its aftermath is portrayed in vivid, harrowing and bloody detail.

One girl's face hits the windscreen with sickening force. A child in the car COW crashes into asks: "When will mummy and daddy wake up?" while a baby strapped into a child seat stares unblinking and may be dead.

Actually, police had intended to commission a different film – on joyriding. But when they spoke to pupils at Tredegar comprehensive, the youngsters told them that texting while driving was a much more important issue for them.

With a budget of £10,000, film-maker Peter Watkins-Hughes was asked to write and direct the film. Local people donated props including the cars that are smashed up and the locations while Watkins-Hughes and his cast gave their time.

A 30-minute version of the film is due to be shown for the first time this autumn but Watkins-Hughes put a four-minute clip of it on YouTube (entitled COW test 001) to show it to a friend. For weeks the clip remained unnoticed by anyone but the friend and a few crew members.

Then suddenly it began to attract hits. It was copied on to other sites, attracted attention around the world and within a couple of weeks became one of the most popular viral videos. Today it was still ninth on one global viral video chart. Clips about Oasis and Jay-Z were at first and second place.

Watkins-Hughes said it felt like being in an Ealing comedy when a small Welsh community had suddenly attracted worldwide attention.

The "weirdest" moment for him was when his explanation, "We've gone for grim reality", was a quote of the day on the Time website.

Watkins-Hughes said he thought it was so powerful because the violence of the crash was shown but the film then "lingered" on the human price – the baby, the child asking about his mother and father. And the screams of COW, who survives the crash.

The film has struck such a chord in the US where the danger of texting while driving is a big issue because it is not illegal in all states. The trend in America has been to try to get the anti-texting message across more gently through humour or playing on the emotions but not showing violence.

However, one survey in the US found that 80% of people who had seen the Gwent film were less likely to text while driving than before.

In the UK, the road safety charity Brake, having been asked to watch the clip by the Guardian, praised the film-makers and said it was important to show the reality of road crashes.

Farmers worldwide being helped by Mobile Phones Technology

Airtel has entered into a strategic tie-up with IFFCO (Indian Farmers Fertilisers Cooperative) for providing agriculture and allied information to farmers through mobile phones. The facility was formally launched by the Chief Operating Officer (Andhra Pradesh) of Bharti Airtel Limited, Rajnish Kaul, at a function at Anakapalle town, about 40 km from here on Tuesday.

Addressing a media conference on the occasion, he said that the unique facility would benefit over 10 lakh IFFCO society members of rural Andhra Pradesh by giving them access to vital information. The farmer members would be given five free voice messages on farming techniques, weather forecasts, dairy farming, animal husbandry, fertilizer availability and rural health initiatives.

Mr. Kaul said the farmers could also call a dedicated free helpline to get answers from a qualified veterinarian to their specific queries regarding the health of their animals. He said that SIM cards would be provided at subsidised rates and lifetime activation would be done for a mere Rs.47. Calls between the members would be charged at 50 paise a minute. The SIMs would be compatible with any mobile handsets and farmers could buy the handsets of their choice depending on their purchasing power. He said the facility was launched about six months ago in various districts of the State and there were already 65,000 connections.

Question Box provides a service in India and Uganda. In India, phone boxes are installed in slums and villages that connect users to operators that will answer questions. In Uganda, users can call in from any mobile phone and ask their questions. The operators have access to a repository of previously asked questions (and their answers), and they can also occasionally consult the Internet. A special search engine and database were also built specifically for the project.

Another initiative, Avaaj Otalo, provides an audio community forum for farmers in rural Gujarat, India. Working with an organization that produced a popular radio program, Otalo provides a call-in number where farmers can exchange questions and answers. Users are also able to listen to archives of the radio program.

These projects differ in that Question Box avoids having to process users' questions by adding a human listener in the loop; Avaaj Otalo avoids processing by organizing their collection of audio prompts with into a menu. Both programs, however, have yet to deal with the problem of cost because they subsidize the service for users. Otalo operates with a toll-free number and Question Box provides the phones to call from in India. In Uganda, Grameen Community Knowledge Workers provides the mobile phones.

It's easy to see why the fishermen of the southern Indian state of Kerala captured the attention of a Harvard economist when they began using mobile phones a few years ago to track prices in the markets where they sold their catch of the day. Observing how these devices can be used to promote economic growth, Robert Jensen wrote in a 2007 paper titled, "The Visible Hand(set): Mobile Phones and Market Performance in South Indian Fisheries -- The Micro and Mackerel Economics of Information," that "before mobile phones, deciding which [market] would offer the best price was sheer guesswork." With mobile phones, however, suddenly it became an information-based decision. What's more, noted Jensen (who is currently at Brown University in Rhode Island), "it's not a zero-sum trade-off." The fishermen's customers benefitted from lower prices and greater choice, and there was less waste since the fishermen could easily identify the villages that would have the greatest demand for their fish each day.

Now Jensen's "visible handset" is reaching further into rural India. Following a nationwide launch this summer of Nokia Life Tools (NLT), India's farmers can use their mobile phones to access tailored information to help them grow, harvest and sell their crops and manage their livestock. "There is no reason why farmers should not be as successful as fishermen," says Ravi Bapna, associate professor of information systems at the Carlson School of Management in Minnesota and executive director of the Centre for Information Technology and the Networked Economy at Hyderabad-based Indian School of Business (ISB).

Consider Ravindra Shinde, a farmer in Magardhokada, a village in the Nagpur district of Maharashtra. When he recently harvested 125 quintal (a quintal is 100 kilograms) of soybeans and was about to take the crop to market, the price was $32 a quintal. But then he received a message on his handset that soybean production in the U.S. and Argentina had fallen, so he held back and later sold his crop for $48 a quintal.

IN the early 1990s, I was engaged in an empirical research work relating to the nexus between mobile phone and poverty in rural Bangladesh. However, friends used to tease me and raise their eyebrows on hearing about the project and my interest at that time. This was to be expected in the early 1990s when, not to speak of the poor, even the "solvent" could not afford to have a mobile set. It was treated as a "luxury" item, only to be monopolised by the moneyed people.

My research findings on village pay phones of the Grameen Bank at that time -- and as published in international journals in subsequent years -- clearly showed that mobile phones could help the poor escape "rural penalty" (a la H. Hudson), defined as poverty mainly due to distance, poor connectivity and asymmetric information. However, as of today, about 40 percent of the rural households in Bangladesh are reported to have access to mobile phones and roughly one-fourth of the users are poor. Rickshaw pullers, fishermen, traders all use it to minimise information asymmetry and quicken communication between two points.

About a decade later, I was invited to comment on two research papers showing the impacts of mobile phones on farmers and traders in Africa.

The first paper was by Megumi Muto and Takashi Yamano, both representing JICA and Foundation for Advanced Studies on International Development (FASID). They drew upon panel data of rural Uganda where banana producers could reduce marketing costs and raise income with expansion of mobile phone coverage. The message is that the expansion of mobile networks increased market participation and sales of the perishable product, banana. More importantly, small producers and farmers in remote areas gained the most.

As information flow increases due to the expanded mobile phone coverage, the cost of crop marketing is expected to decrease, particularly in remote areas where potential marketing gains from the increased information flow is large. We indeed find that the network expansion has a larger impact in market participation in areas farther away from the district centers than in closer areas.

The second paper was presented by Jenny C. Aker of the University of California, Berkeley, on the impact of mobile phones on price dispersion of grains in Niger. Using a sequential searching model, the researcher observed that cell phones increased traders' reservation sales price and the number of markets over which they searched. This reduces price dispersion across markets. To be specific, grain price dispersion reduced by 6-7 percent and reduced intra-annual price variation by 10 percent.

What is important, and as revealed in both papers, is that every farmer need not possess a set. It could be the community, producers' organisations and others from where the price information could spread, either as a "public good" or as a "private good." A participant from the audience in that seminar informed us that in his village in Africa, a mobile phone is hung from the branch of a tree and interested persons could use it on payment of a fee. Second, even with access to mobile phones, full gains might not be reaped as farmers might need more information. The role of public authority and media in this respect is very important. Again, producers' organisations could form an information forum of their own to be more effective at bargaining than individual initiatives.