GSM: Architecture, Protocols and Services

There is a new book on GSM in the market. Now it makes me wonder that since we are all focussing on 3.6G, 3.75G, 3.9G, 4G, etc., etc. what would be the point of a GSM book?

The following is from the preface of the book:

The GSM family (GSM, GPRS, EDGE) has become one of the most successful technical innovations in history. As of June 2008, more than 2.9 billion subscribers were using GSM, corresponding to a market share of more than 81%, and its story continues, even now, despite the introduction and development of next-generation systems such as IMT-2000 or UMTS (3G) and even systems beyond 3G, dubbed IMT-Advanced.

At the same time, wireless local area networks have substantially expanded the wireless market, sometimes drawing market share from GPRS and 3G (e.g. in public WiFi hotspots), sometimes coexisting (e.g. in UMTS home routers used as a replacement for fixed wire connections). However, these are used typically for low mobility applications. Mobile communication with all of its features and stability has become increasingly important: cellular and GSM technology, plus, of course, lately 3G, GSMs sister technology, so-to-say.

Another impressive trend has emerged since our last edition: the permanent evolution in the handheld market, producing fancy mobile phones with cameras, large memory, MP3 players, Email clients and even satellite navigation. These features enable numerous nonvoice or multimedia applications, from which, of course, only a subset is or will be successful on the market.

In this third edition, we concentrate again on the architecture, protocols and operation of the GSM network and outline and explain the innovations introduced in recent years. The main novelties in this book are the presentation of capacity enhancement methods such as sectorization, the application of adaptive antennas for Spatial Filtering for Interference Reduction (SFIR) and Space Division Multiple Access (SDMA), a detailed introduction to HSCSD and EDGE for higher data rates, and an update of the available GSM services, specifically introducing the Multimedia Messaging Service (MMS).

I think that GSM is going to be the fallback option for most of the new technologies due to its worldwide deployment so now is the time for us to brush up our GSM concepts

Advances in Underwater Wireless Communications

The IEEE Communications Magazine, January 2009, has a interesting section on Underwater Wireless Communications for those who may be interested.

Underwater networks of sensors have the potential to enable unexplored applications and to enhance our ability to observe and predict the ocean. Unmanned or Autonomous Underwater Vehicles (UUVs, AUVs), equipped with underwater sensors, are also envisioned to find application in exploration of natural undersea resources and gathering of scientific data in collaborative monitoring missions. These potential applications will be made viable by enabling communications among underwater devices. UnderWater Acoustic Sensor Networks (UW-ASNs) will consist of sensors and vehicles deployed underwater and networked via acoustic links to perform collaborative monitoring tasks.

The single most killer application for Underwater Wireless Communication would be in disaster prevention. Sensor networks that measure seismic activity from remote locations can provide tsunami warnings to coastal areas, or study the effects of submarine earthquakes (seaquakes).

There are major challenges in the design of underwater acoustic networks that include:

• The available bandwidth is severely limited;
• The underwater channel is impaired because of multipath and fading;
• Propagation delay is five orders of magnitude higher than in Radio Frequency (RF) terrestrial channels, and variable;
• High bit error rates and temporary losses of connectivity (shadow zones) can be experienced;
• Underwater sensors are characterized by high cost because of a small relative number of suppliers (i.e., not much economy of scale);
• Battery power is limited and usually batteries cannot be recharged;
• Underwater sensors are prone to failures because of fouling and corrosion.

There has been intensive research on MAC protocols for ad hoc and wireless terrestrial sensor networks in the last decade. However, due to the different nature of the underwater environment and applications, existing terrestrial MAC solutions are unsuitable for this environment. In fact, channel access control in UW-ASNs poses additional challenges due to the peculiarities of the underwater channel, in particular limited bandwidth, very high and variable propagation delays, high bit error rates, temporary losses of connectivity, channel asymmetry, and extensive time-varying multipath and fading phenomena. Existing MAC solutions are mainly focused on Carrier Sense Multiple Access (CSMA) or Code Division Multiple Access (CDMA). This is because Frequency Division Multiple Access (FDMA) is not suitable for UW-ASN due to the narrow bandwidth in UW-A channels and the vulnerability of limited band systems to fading and multipath. Moreover, Time Division Multiple Access (TDMA) shows a limited bandwidth efficiency because of the long time guards required in the UW-A channel. Furthermore, the variable delay makes it very challenging to realize a precise synchronization, with a common timing reference.

The next challenge is to select a routing protocol from a range of protocols that will work in the best manner with the MAC solution selected.

Another challenge is to select the correct transport layer protocols. A transport-layer protocol is required to achievereliable transport of event features and to perform flow and congestion control. Most existing Transport Control Protocol (TCP) implementations are unsuited for the underwater environment because the flow control functionality relies on window-based mechanisms that require an accurate estimate of the round trip time (RTT).

If you dont have access to IEEE Comms Mag then you can still read one of the papers online here.

Story of two Femto's from opposite end of the world

Verizon (USA) wireless introduced a femtocell product officially and have called it as "mini-cell site". Made by Samsung this will retail at $250+. The big advantage with this is that the phone calls that originate/terminate on "mini-cell site" would be free. The big problem is that this cell only serves voice but not data. So no faster data or any enhanced data services on this one. Maybe that is in the pipeline...

On the other side of the world, in Singapore, Starhub had launched the first "commercial" femtocell service called "Home-zone" back in Nov. It has received positive review in Telecom TV Wireless 3.0 article.

All I had to provide in advance was provide my cable modem MAC address and the phone numbers of the mobiles that would be used in the house (up to four). As soon as theHuaWei femtocell was connected it was recognised by the network it immediately took over from the nearest base station (about 300 metres away) by ‘shaking hands’ with the two mobile phones in our house.

The only noticeable difference was that my handset (a 3GiPhone) showed the StarHub network name and unique cell number. My wife’s phone (an HTC running Windows Mobile) thought it was roaming and only displayed the symbol for that function. I am told that newer Nokia phones actually state they are connected to a Home Zone service. Presumably, as femtocells become more common there will be a standard way of indicating connection. This notification is pretty important as I will explain later.

Previously on one side of the house I had good service to the network, on the other almost none. I found it quite clever that as I walked outside through the doors on either side of the property, the connection switched to the main network. I doubt if this was planned and was most likely coincidental, but it continues to amaze me how clever it is to do that. If the signal was much stronger then the Home Zone service could be subject to abuse. Apart from the differences mentioned above, and just in case I don’t notice the cell ID on my handset, as a call is made a comforting voice lets me know that I am making the call from my Home Zone. I thought this might become annoying but it is comforting to know that I’m connecting via the femtocell and saving my valuable package minutes.

In fact, all calls made from my fixed line (via cable) service, are also free but as my mobile plan comes with a number of free minutes and SMSs included each month, these are not decremented when I connect via the femtocell. Of course, the international segment of my calls are NOT provided free! I spent some time chatting with StarHub’s billing specialists to see how they handled my femtocell or Home Zone calls.

As expected, each call had a unique femtocell identifier and this determined how the call would be handled in the billing system.

It also allows for some creative plans and billing by operators hoping to capture extra market share using femtocell technology.

By the way, if a call is instigated on the Home Zone network and I move outside of the femtocell's range, the call is handed off to the main network but continues to be zero rated. A nice feature I thought. However, calls started on the main network are NOT handed off to thefemtocell, if you happen to already be on a call as you arrive home. That would create quite an interesting billing scenario I suspect.

So, what’s in it for the service provider? Firstly, I am charged a nominal fee of SG$16 (US$11) per month for the use of the femtocell and I suspect that this covers the cost of the unit I was provided with. Considering that I have two digital home services over the cable network also offered by StarHub (a free service if you are also a cable TV customer), then why would I want to pay for the new access method?

Well, I guess I won’t need those two other phone lines any more and will, like many others, use my mobile number as my primary and only contact point in the future. So StarHub loses two lines that earn them no revenue and I get the same free service via my mobile phone and we both win.

Where this does make a big difference is that customers of StarHub’s main competitor, SingTel, who still pay a monthly subscription for their dial up service, may be tempted to swap to StarHub and get the same service via their mobile phone. There will be thousands of permutations of how femtocells can be used for competitive advantage across all markets, but this is just one. This is as ‘sticky’ as it gets!

Of course, I am doing StarHub a great favour as well. If you consider that I pay for my broadband access and that all my home zone calls and data traffic go down that route, I have eased some burden on Starhub's wireless network. If enough people swap to femtocells this could provide a dramatic reduction in 3G/HSPA network traffic.

And when you consider that backhaul costs keep increasing this is great news for operators and should reduce the need for continuously expanding wireless infrastructure.And what about those customers who have poor or marginal coverage in their home or apartment? Femtocells are exactly what they need. As femtocell production numbers increase their cost will also drop and they may be given away free to high ARPU prospects and customers.

Like all new technologies, StarHub discovered some early glitches that have since been remedied. Enterprising early adopters worked out that they could take their femtocell with them and simply plug into a broadband ethernet port anywhere in the world and make calls to Singapore for free on their mobile phones! This has now been corrected and the femtocell must be connected directly to the StarHub network to be recognised.

Early femtocells also had difficulty with the hand-off to and from external cells and with automatically varying signal power as the handsets came closer to the femtocell. Working closely with the equipment vendor StarHub has ironed out most issues and the latest femtocells appear to be efficient and reliable.

Operators like StarHub see this technology as a complementary and an effective tool to attract and maintain customers ahead of their competitors. They also see femtocells as an avenue to push promotions and offers to customers over the air, and they may become quite a weapon in capturing key customers in one very tough market. If all their customers have the same experience as me, femtocells will be a big winner.

LTE Status: Jan 09 updates

According to this news, Verizon Wireless says that the Next-Gen 'LTE' Wireless Network Still On Track For 2010 Launch:

Despite a tanking economy and a potential delay getting access to the spectrum Verizon bought in last year's FCC auction, the telco says it's still on track to roll out its next-generation wireless network next year.

On the company's earnings call today, Verizon COO Denny Strigl said he's still hoping LTE will be commercially available in the first half of 2010, with in-house testing to begin later this year.

Meanwhile in Sweden, Swedish telecommunications operator TeliaSonera has signed contracts towards the launch of an 4G high-speed wireless network in 2010, saying it aims to be one of the first with an LTE network up and running.

TeliaSonera said on Thursday it had signed up Ericsson to construct its initial Stockholm LTE (the Long Term Evolution of 3G) network, and Huawei for the initial Oslo network. Both equipment makers said it was their first commercial LTE contract.

The telco said it is still evaluating suppliers for further LTE networks across Sweden and its other markets.

No cancer risk due to phones but maybe due to the masts

One of the recent studies dispelled the myth that phones can cause melanoma or eye cancer:

Regular mobile phone use does not appear to increase a person's risk of getting a type of cancer called melanoma of the eye, German researchers said on Tuesday.

The study involving about 1,600 people detected no link between the time a person spent using a cell phone over about a decade and their chances of developing melanoma of the eye, they wrote in the Journal of the National Cancer Institute.

The findings contradicted an earlier, smaller study by the same researchers that had raised concern about such a link.

Melanoma is an aggressive form of cancer that can spread quickly. It arises in cells that produce the pigment called melanin that gives skin its color. The eyes also have cells that produce melanin. Melanoma of the eye is rare. The condition also is called uveal melanoma.

The issue of whether long-term use of cell phones can cause cancer, in particular brain tumors, has been a hot topic, but most studies examining the matter have found no such association.

In the other news, Barack Obama has turned to a Midland anti-mobile phone mast campaigner to help the fight against cancer.

Eileen O’Connor, as a founder member of the Radiation Research Trust, has led the battle against the relentless growth of mobile phone masts and technology for the past seven years.

And now the US President’s cancer panel, set up by Obama to research the possible links with both nuclear and electro-magnetic radiation, has asked Eileen for her views on the issue.
The trust has supported widespread research into the possible dangers of mobile and wireless radiation and campaigns for the technology to be made safer.

Eileen said: “Obama’s panel has launched an information gathering exercise and I was invited to provide evidence. While I am not building up my hopes, I am delighted the issue is being taken seriously by the President.

“President Obama recently said science is about ensuring that facts and evidence are never twisted or obscured by politics or ideology.

“It’s about listening to what our scientists have to say, even when it’s inconvenient and I welcome this approach.”

The evidence gathered by the panel will be considered in drawing up advice to the new President on measures needed to be taken to improve the health of Americans.

Any steps taken are likely to be considered around the world.

Eileen first suspected a link between mobile phone masts and cancer when the arrival of a mast in her home village of Wishaw, near Sutton Coldfield coincided with a cluster of cancer cases, including her own.

The campaign hit the headlines in 2003 when the mast was pulled down in the middle of the night and residents blockaded the site to stop it being replaced.

The Radiation Research Trust funds and draws together scientific research from around the world and lobbies government to adopt a more cautious approach to mobile technology.

A key theory is that it is the electromagnetic radiation frequency, and not intensity or power of the signal, which can cause the damage. It is also thought that some people are more sensitive to the effects than others.

Mobile Backhaul Networks and their Load

These are self explanatory slides on Mobile Network Backhaul presented by Professor Steve Ferguson, Head of Market Strategy, Product Area Broadband Networks, Ericsson in the LTE World Summit last year.

Commercially Viable Video over Wireless Broadband

(Click on the diagram for full sized image)

Continuing the LTE World Summit theme, Paul Steinberg, Fellow and Chief Architect - Telecommunications Wireless Infrastructure, Motorola spoke on 'Video Impact and Opportunity on a LTE Network'.

The image above conveys loads of information and I found it very interesting so I have shared it with everyone. The main message of the presentation was:

• Mobile Video is Real & LTE Enables Commercially Viable Wireless Video
• Technical Innovations Improve the Viability of Mobile Video Delivery
• Video Encoding / LTE Air Interface / Devices / Network Architecture
• Operators Can Leverage Video as Differentiator to Monetize LTE Networks

LTE Femtocells Killer App: Wireless HDD

Just read this article:

Security appears to be all washed up, as USB sticks with sensitive data are being left regularly in pockets when workers take their clothes to be cleaned at laundrettes.

According to a survey from Credant Technologies, who claims that 9,000 USB sticks have been forgotten and left in pockets of clothes taken to dry cleaners. These figures were obtained from phone interviews with 500 dry cleaners across the UK, who found an average of two USB keys per year. Extrapolating this to the 4,500 dry cleaners in the UK leads to the 9,000 figure.

Data sticks are most frequently found in city centres and commuter areas with one proprietor in the City of London finding 80 memory sticks in 2008 alone.

Back in the LTE world summit last year, one of the things I mentioned was, that once LTE Femtocells are available we may be able to create innovative and groundbreaking applications to run on it. I was aware of some people suggesting that the broadband providers may throttle the backhaul traffic on the Femto but I was assured by one person from Sweden (or Finland ... cant recall for sure) that in the Nordics there is already upto 100Mbps speeds available and most of the people use P2P networks thereby consistently loading the ISP's. He did not think that there will be a problem.

One of the applications I suggested was a wireless Hard Disk Drive (HDD) or maybe a better term would be mobile USB (MUSB). The following slides are extracted from my presentation as I am being a bit lazy (and busy) to put them here.

As always, I am happy to receive feedback, comments, criticisms, etc, etc.

Recipe to design Killer Applications

Back in the LTE world summit, I presented recipe for designing killer mobile applications. I have listed them out here but feel free to suggest some more things or to correct me.

Recipe to design killer applications:

• Something new everyday
• E.g., News
• Available instantly whenever needed
• E.g., Youtube or similar VOD services
• Challenging or Entertaining
• E.g., Games, Music, etc.
• Something that can reduce cost
• E.g., VoIP services like Skype
• Keeping in touch
• E.g., Facebook, MSN messenger, etc.
• Something to help in everyday life
• E.g.,GPS, Maps, LBS, etc.
• Purchase whatever and whenever you like
• E.g., E-bay or Amazon

You may notice that I have not listed Email and browsing above because they fit multiple categories. Can you add to the list?

HSPA+ arriving soon from Vodafone and TIM

Telecom Italia Mobile (TIM) says it will be offering mobile data packages with peak download speeds of 21Mbps by mid-2009, rising to 28Mbps by year-end. The services, based on HSPA+ technology, will initially work via PC datacards using Qualcomm chipsets, CellularNews reports. Ericsson will supply equipment for the network upgrade.

Vodafone has trialled the Release 7 version HSPA+ mobile broadband technology in its Spanish network, and has achieved actual peak data download rates of up to 16Mbits/s.

The field trail of the HSPA+ 64QAM technology was done in conjunction with chip supplier Qualcomm Inc. and network gear provider Ericsson, following convincing results in laboratory tests.

Vodafone now plans to trial mobile broadband data connections with peak rates of up to 21Mbits/s early in 2009 using HSPA+ MIMO functionality.

The operator says the technology would be capable of video downloads at more than 13Mbits/s in good conditions and an average of more than 4 Mbits/s across a full range of typical cell locations, including urban environments.

If the trials prove a success, Vodafone plans to make this technology available in selected commercial networks.

HSPA+ technology is the next evolutionary step in the (3G) HSPA roadmap and increases performance through the use of the more powerful 64QAM modulation technique. Download performance is also improved through the use of multiple antennae (MIMO) technology on both base stations and data devices.

The operator is also working with several device vendors on the testing and validation of these devices ready for commercial availability.

Other major operators known to be conducting trials of HSPA+ technology include 3 and Australian company Telstra.

Telecoms equipment supplier Huawei has revealed that it will be showing off the world’s first commercial HSPA+ modem at the upcoming Mobile World Congress event, taking place in Barcelona next month.

Huawei’s connection to the Vodafone trials is unknown, but The Link has done a bit of detective work and observes that Vodafone released a statement early last year announcing partnerships with Huawei (amongst others) to develop the service. Huawei’s commercial HSPA+ stick could therefore be the first glance of Vodafone’s upcoming service, unless of course another network has quietly beaten it to the punch.

No release date or price has been revealed, but it does sound like HSPA+ will be arriving a lot sooner than we’d first thought. Mobile World Congress is taking place from the 16th – 19th February.