Month: April 2006

Muni Wifi: How many Access Points are necessary to cover a city?

There’s not a single day in which I do not read about Municipal Wifi on a web site or blog. However, most do not say how many access points are required for city wide coverage and how that compares to cellular networks that offer similar services. Maybe I can add some numbers here.

Dailywireless has recently featured an interesting article on Muni Wireless in Annapolis and San Francisco. In this article they state that about 25 access points are required per square mile. If you do the maths you end up with one access point about every 300 meters. That sounds realistic as I can imagine that communication between access points over 300 meters without directional antennas in the open is possible. Communication between the nodes is required for the meshed network architecture most Muni Wifi projects use in order to minimize the number of fixed line Internet connections required.

25 doesn’t sound like a lot at first. However, a square mile is not much either. The article goes on to say that San Fransisco’s Muni Wifi network will cover 54 square miles. With 25 access points per square mile as described in the blog above, 1.350 access points need to be distributed in an area of 7.5 x 7.5 miles.

Let’s compare this number to the number of cellular towers of a UMTS/HSDPA or CDMA/1xEV-DO network required for the same area: Let’s say such a network operator aims for reasonable indoor coverage (which by the way the Wifi Muni network can not do with an access point every 300m). In such a configuration, the cell radius would be about one mile. This gives you a coverage area of a single base station of around three square miles, or 3 times 25 = 75 wireless LAN access points. 75 that’s quite a ratio. For a 54 square mile area, this would result in 18 cellular sites vs 1.350 wireless lan access points. I know, a wireless lan access point is a lot cheaper than a cellular base station but it has to be a lot cheaper to make up for this. (Note: Since my initial posting I changed this paragraph twice to take the good information given in the comments below into account. Thanks for posting!)

Looks like these numbers are no fiction. Take a look at this article about the Wifi Network in Taipei. It says they will (or already have?) distribute(d) 10.000 Wifi access points in the city. Quite a challenge!

From a consumer perspective I hope there will be enough competition to have a positive effect on prices.

What can we learn from Japanese FOMA phones?

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Over the last few days, I’ve had an interesting discussion with Denis of Wapreview on mobile phone experiences during his recent trip to Japan. There are a number of very interesting links in the blog entry as well, including one to download the English manual of the NEC N902i, which seems to be a quite popular phone in Japan. I had a look through the manual to see what kind of functionality it offers that I haven’t seen so far on phones in Europe or in the U.S. and found a number of quite interesting features.

Camera with stabilization: The built in 4 mega pixel camera has an auto focus, digital (only) zoom, and a stabilization/anti shake feature.

Lock phone: In case your phone gets stolen you can lock the phone from a payphone or any other phone. This is done by calling the phone a certain number of times within a certain time frame. I wonder why I haven’t seen this one before, it’s so simple to implement. Does NEC hold a patent on this one and it’s unaffordable to license it?

Bar Code Reader: A hot topic in the blogsphere. It looks like in Japan this is already used very much in everyday life. Bar codes (one and two dimensional) are scanned with the camera and can contain contact addresses and phone numbers to be put into the phone book, eMail addresses and URLs that can be bookmarked or used to go directly to a page. Wap review mentions that these bar codes are at many places in Japan these days, including posters and business cards. I wonder how long it takes for this to become popular in Europe and elsewhere!? A typical critical mass problem.

Remote Monitoring: Incoming video calls from pre-programmed numbers can be accepted automatically (auto answer).

Change between Voice and Video Call: A call can be started as a
voice call and upgraded to a video call later on (by the calling party
only). An interesting feature, I don’t think other UMTS networks and
phones support this today!?

Mobile Wallet (FeliCa): A chip on the back of the phone can be used for contact less micro payment, e.g. for train tickets. The chip also communicates with the phone where an application can used to see transaction / current balance, etc.  The chip can also be used to receive text information like for example phone book entries or coupons in conjunction with the application on the mobile phone.

Text Scanner: The camera can be used to make pictures of business cards, URLs, mail addresses and free memos. Once the picture is taken the phone scans the picture and extracts the information for the phone book, the browser etc. Cool for business cards without a 2 dimensional bar code 🙂

Speech output of Text: The phone can read eMails to the user (I wonder how that sounds like)

So Nokia’s, Motorola’s and Sony-Ericsson’s of this world, it’s time to play catch up ! (and to open your pockets for license payments?)

Wireless Broadband in Rural Austria

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While UMTS operators are starting to upgrade their networks for high speed Internet access (HSDPA) it seems the competition is already a step ahead in some areas. During a walk in the countryside in Austria (to be exact: Gaspoltshofen, 3000 inhabitants, about 60 km from Linz) I saw an interesting antenna tower on a hill (see pictures). Turns out that the antenna belongs to Flashnet, a local company providing fast wireless Internet access to the local population.

It looks like they are using Wireless LAN as technology and directional antennas which are installed on the rooftops of their customers houses. Prices are quite interesting, €30.- a month for 2 gigabyte data traffic and 1 MBit/s up- and downlink. Their website also provides a map of the coverage area and they say on their website that they are now serving over 1000 customers in the area. Too bad that they don’t specify how many sites they use to cover the area.

Great stuff!!!

Audible on S60 revisited

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Back in January I expressed my frustration with the Audible player for S60 that would only download audio content over the air (via GPRS, UMTS, etc.) but would not play audio content that I’ve already downloaded to my PC and from there to the phone. Well, it looks like it was worth writing the blog entry because Bruno Santos kindly enough left me a message with a solution:

The audible player for Series 60 can only decode category 2 and 3 files but not the highest quality category 4 encoding with which (of course) I’ve downloaded all my audio files to the PC. After downloading one of my audio books again with category 3 encoding to the PC and then to the mobile phone, the audible player just asked once to connected to the Internet to verify that I have the rights to listen to the content. Since then no more costly connections to the Internet. The player works fine even if used over several hours at a time. Thanks very much Bruno, your tip will save me a lot of work (see blog entry from back in January).

Wireless VoIP Demystified – Part 4: Skype

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This blog entry is part four in my mini series of looking at the different Voice over IP systems (VoIP) that can be used over wireless networks such as UMTS or CDMA 1xEV-DO. Part 1 focused on UMA, part 2 on SIP, part 3 on IMS, and this part will take a look on the use of Skype over wireless.

UMA, SIP and IMS are all centralized systems. That means that they use a centralized server which is responsible for authenticating users, for establishing connections between users for voice, video, instant messaging or any other kind of media transfer, and also for billing. Skype uses a fundamentally different architecture as it does not rely on a centralized server for most of these tasks. Skype is a Peer to Peer network in which end points of the network help out each other to establish and maintain a connection.

A peer to peer network has a number of advantages over a centralized approach:

  • Centralized servers are costly to buy, maintain and operate. The more people use the service the bigger the server has to become. In a peer to peer network such as Skype, however, signaling load at a central point does not increase in the same way as in centralized systems.
  • Individual peers help out each other to establish a connection. This is especially important as many users are behind firewalls or network address translation (NAT) routers typically used at home. Thus, they can not communicate directly with each other. Skype peers that have no such restrictions help out peers that do and forward traffic between such users. This is the main reason why Skype is so easy to set up on PCs and other devices compared to other technologies like for example SIP. For those of you who would like to find out more about Skype, here’s a link to an analysis of how Skype works which has been published by Philippe Biondi and Fabrice Desclaux of EADS.

While most other VoIP systems use legacy voice codecs to transport the media stream over IP, Skype uses its own resource efficient codecs which which on top even have a superior voice quality. Thus, Skype works quite well over UMTS and I use it on a regular basis when traveling. It should also work quite well over EV-DO as well, as bandwidth is also sufficient. Personally I’ve never tried so this is just a speculation.

Many operators (carriers) are scared of Skype and other VoIP systems as they are afraid that such services will decrease their revenue on traditional voice minutes. I think there is no such risk in the near future as there is still a PC required to run Skype over a wireless link. However there are first signs that Skype is also moving to mobile devices. A beta client for Windows Mobile is already available and a non official beta of Skype on a Nokia S60 6680 has also been spotted by the author (see picture above). So operators should hurry up and develop strategies to integrate such innovative applications into their concepts. Some have already done so, like for example E-Plus in Germany. They even offer a UMTS flatrate together with the Skype software and a headset. An interesting first step, certainly not made too soon as new devices such as the Nokia N80 with built in WLAN will spur the interest of a wider audience to cheap VoIP over wireless.

At this point I close my wireless VoIP mini series for now. Four different VoIP systems, four different basic ideas and four ways for every one in the industry and of course the users to benefit. I think it will still take several years before Wireless VoIP becomes mainstream but the first signs are already here.

AOL joins Google to adapt pages for mobiles

AOL is about to start competing with Google and others in the mobile space. This includes adapting pages for mobile viewing with an automatic re-rendering service.

"AOL Wireless Director of Emerging Technologies Raine Bergstrom told BetaNews […] "We’re not just re-rendering, but reorganizing as well," he explained. Bergstrom said most, if not all pages will initially be rendered using the automatic system, and would change based on necessity. [….] "One size does not fit all" ". Here’s the full article.

While I have put my thoughts on the positive sides of such technology in one of my recent blog entries, a lot of other people don’t like it at all. Looks like the front widens…