Author: Martin

The Nokia N800, WiMAX And Embedded 802.16e Chips

Speculations are growing that Nokia is working on a version of the N800 Internet tablet with a WiMAX chip in addition to Bluetooth and Wifi. This report on Heise News, a reliable German tech website, links Nokia’s plans with the launch of Sprint’s WiMAX network in 2008.

They also link to an interesting data sheet of a WiMAX Module from SyChip, (which they say may or may not be related to the N800 WiMAX development) which contains quite interesting high level details of first generation embedded WiMAX chips. According to the data sheet the WiMAX module is 21.6 x 23.7 x 1.5mm in size and supports 802.16e. The block diagram shows two antenna connectors for MIMO in downlink direction and single stream transmission in uplink direction. Mobile devices communicate with the embedded module either via SDIO or USB.

One of the mysteries around WiMAX to me, still, is how users and devices will be authenticated since I haven’t seen any kind of SIM card specification for WiMAX yet. The data sheet, however, says that the following security mechanisms are supported: EAP-SIM, EAP-AKA, EAP-TLS. While EAP-TLS works with certificates, EAP-SIM was originally specified by 3GPP (UMTS standards body) for Wifi authentication using  the secret keys and subscriber ID contained on a GSM/UMTS SIM card. For details take a look here. Since EAP-SIM has been specified independently from the underlying network technology, it should integrate nicely into WiMAX as well.

This raises the question though what kind of equipment is used on the network side that supports EAP-SIM authentication!? If you have more information, please let me know!

Visual Mailbox – The MMS Killer Application?

Just read on Teltarif today that Vodafone Germany has launched a new product called "Visual Mailbox". Instead of saving voice mail messages on a central server the visual mailbox feature forwards voice mail messages via MMS to the subscriber. MMS is the multimedia cousin of the SMS message and can carry text, pictures and, quite useful for this service in particular, audio files. The advantage: The user does not have to call the voice mail system anymore but listen to voice messages by selecting an MMS message in the incoming messages folder of the mobile phone. Reminds me of the voice mail functionality of the iPhone.

Vodafone Germany offers the service for no additional charge. How nice 🙂

IEEE Wifi And Ethernet Standards Now Available For Free

Nortel and Cisco have decided to use some of their marketing budget for something really useful for engineers, namely to open up the IEEE standards 802 library for free public access. These include the famous Ethernet (802.1,2,3), Wifi (802.11) and WiMAX (802.16) standards. A great help for all doing research in this area. Little downside: Only approved documents are available which excludes hot documents such as the current 802.11n draft.

How Will Users Be Able To Differentiate 11n from 11n?

In the past, things were pretty much clear when it came to Wireless LAN performance. If the box in the shop said it’s an 802.11g device, users could pretty much assume the device would do 54 MBit/s on the physical layer and application layer speed would be around 20 MBit/s. Things are much less clear with the new Draft 802.11n standard, which contains a myriad of options a device may or may not implement.

The standard for example contains three different flavors of MIMO. The most popular one, MIMO spatial multiplexing will be implemented in many devices. But the standard gives devices the option to use 2, 3 or 4 transceivers/antennas. The more receivers, the higher the speed, if of course the receiver has at least as many. O.k. one might be able to sell this story in a fashion like "We do 4×4 MIMO compared to the competition which only does 2×2, so we are twice as fast".

The story doesn’t end there, however. There are two other MIMO modes, namely MIMO beamforming and MIMO STBC (Space Time Block Code) which can significantly enhance range and link stability. It just might turn out that these MIMO modes are just as important for applications such as video streaming to devices that are not close to the Wifi Access Point. Ruckus wireless for example is doing interesting things in this area.

And it certainly doesn’t end here. Draft 802.11n contains further options like multimedia power save (PSMP), shorter OFDM guard intervals, Antenna selection, Maximum Ratio combining, Modulation and Coding Scheme (MCS) feedback, etc. etc. In the end, marketing words on boxes in the electronics store are cheap. Let’s see, how about the Wifi Alliance coming up with something standardized about "enhanced 11n options"? Time will tell.

Will France Get A (Hopefuly More Agressive) Fourth 3G Operator?

Today I saw reports for example here and here that Illiad has brought forward the necessary papers to get the fourth and final batch of France’s 3G licenses in the 2.1GHz UMTS band before the deadline expired yesterday.

Illiad is the mother company of ADSL Internet provider "Free", certainly one of the most aggressive players in the French ADSL market. That gives me some hope that in case their bid is accepted and they are ready to go for it there might finally be reason for hope that competition could finally arrive in the French 3G market. Also, Free might have more of an Internet and IP angle than the local 3G incumbents so they might be more inclined to finally let customers use their network for Internet services for an attractive price rather than to let base stations sit around only producing hot air.

According to the report of Les Echos linked above the stock market was not quite happy to hear that Illiad has put their name in the hat. They see mobile as a risk rather than an opportunity. Short sighted bunch…

Need an 802.11n Beacon Frame?

Standards are well and good but usually contain a zillion options nobody ever implements. The 802.11 ‘draft-n’ standard is no exception. To find out which options different vendors have actually implemented, the best thing to do is to trace the beacon frames of ‘draft-n’ access points. A couple of months ago I described how to trace WLAN frames here.

If you are looking for beacon frames traced by other people to compare functionalities with your own ‘draft-n’ access point at home, take a look here. The beacon frame traced by ‘swordfish’ seems to be from a Linksys access point, judging from the first three bytes of the MAC address which identifies the manufacturer of the device. So here are the main ‘draft-n’ features this access point supports taken from the ‘HT Capability‘ (HT = high throughput) parameter (element ID 45):

  • 20 MHz and 40 MHz channel operation support
  • Greenfield mode support, i.e. protection mechanisms used to allow 802.11b and 11g devices to be part of the network can be switched off.
  • the access point has two independent transmitters and supports 2 spatial MIMO streams.
  • All of the other gazillion options such as short guard interval, STBC diversity, beamforming, MIMO power save, advanced coding, MCS feedback, antenna selection, etc. etc. are not supported.

The current mode of operation according to the ‘HT Information‘ parameter (element ID 61) erroneously called ‘Additional HT Capability’ in the trace):

  • The access point currently operates in 20 MHz mode only (either set by user or due to other networks using the same channel)
  • The access point runs in greenfield mode, i.e. only 11n devices have joined the network

Also interesting to see that the size of beacon frames has dramatically increased. Current 11g access points send beacon frames with a length of around 110 bytes. This ‘draft-n’ beacon frame has a length of 228 bytes!

Draft 802.11n Devices Must Implement 802.11e QoS

It’s good to see that both the IEEE 802.11n draft Standard and the Wifi-Alliance certification program require that future draft 802.11n Wifi devices also have to support the 802.11e QoS standard, sometimes also referred to as Wireless Multimedia (WMM).

WMM introduces Quality of Service for the Wifi Air Interface which means certain traffic flows can be prioritized over others. This is important for example when high bandwidth streaming and several phone calls are to be carried over the same wireless access point simultaneously.

By requiring QoS support from 802.11n devices I think this functionality has a real chance to become widespread in a relatively short amount of time which would probably not have happened otherwise.

Sources:

  • The 802.11n draft standard which confirms this in several paragraphs, like for example in a quite simple and not very easy to understand statement in chapter 5.2.8: "An HT STA is also a QoS STA"

For further information on WMM and how applications can use the functionality take a look at this previous blog entry.

How To Top-Up A Vodafone Prepaid SIM for Websessions

A final piece of information for users of Vodafone Germany Prepaid SIMs for Websessions has so far been missing: How to top-up without scratch cards that can only be bought in Germany!?

Here’s a link to an online service here that allows to top-up German prepaid SIM cards. The pages itself are in German but pretty easy to figure out for non natives as well. To top-up a Vodafone SIM card, select "Vodafone CallNow", create an account by typing in your eMail address, specifiy the SIM card’s phone number, select the amount to top-up and enter your credit card details. After a minute the selected amount is on the SIM card and can then be used for WebSessions. All quite straight forward and works well.

Any 5 GHz 802.11n Devices Out There Except For The Airport Extreme?

Just saw an article in a German computer magazine testing a number of different pre-802.11n access points and related client adapters. Performance was around 50 MBit/s which is not a lot considering the test here and here showed performance in the range of about 100 MBit/s on the application layer.

What also struck me was that all the top 3 access points were 2.4 GHz only products. So looks like except for the Apple Airport Extreme we have to wait for a while before other 5 GHz pre-802.11n products make it to the market!?

The top three candidates where:

If anyone knows a pre-802.11n Access Point for 5 GHz except for Apple’s access point, please let me know!

Review: Wireless Communications – The Future

Williamwebb0470033126
I have to admit I had William Webb’s latest book „Wireless Communications – The Future“ at home for a couple of months before I finally came around to read it back to back. A mistake, as it turned out, to wait that long. As title suggests, the book deals with the future of wireless telecommunications, over a period of the next 20 years.

Webb, working for Ofcom and a newly appointed fellow of the Royal Academy of Engineers draws an interesting picture of how he sees wireless technology evolving. His drastic conclusion is that fourth generation wireless will not make it off the ground. His main reasons for this are that he sees no need for systems that go beyond what’s possible in terms of data rates with 3.5G and the evolution these systems will undergo in the future. Note that he also counts LTE and similar technologies as 3G+ technologies. The second main reason at arriving at his conclusion is that today’s wireless technologies are already close to natural boundaries in terms of available frequency bands and efficiency. In short he sees continuous evolution of existing wireless systems rather than a new radio technology beyond OFDM revolutionizing wireless telecommunication in the next two decades.

Throughout the book the author discusses his own predictions such as how fixed and wireless networks will converge, industry inflection points where current vertical wireless vs. fixed network operator / content provider silos break up and new business models are required around horizontal structures with companies dealing with the network, companies dealing with the service and companies dealing with the applications on top. Also, Mr. Webb has invited a number of outstanding industry members to share their visions of the wireless future and discusses how these views integrate with his visions.

For every statement I agree with in the book there is at least another prediction which I vehemently disagree with. But I guess that’s just natural when trying to predict the future. Here are some statements which I found of particular interest and fully agree with:

  • “The concept of lengthening time between generations of cellular technology being bridged through evolution of standards is now becoming increasingly accepted. This has the implications that moving to a new generation is not as urgent a need as it has been in the past […]”
  • “Some [DSL] users […] are unlikely to achieve data rates above 1 MBit/s [in the future] unless there is a substantial infrastructure upgrade”
  • “… a new service or product might take anything between four and ten years to reach mass adoption…”
  • “Once almost all users have access almost everywhere to average data rates of several hundred megabits per second in active periods, their senses are no longer able to make use of more data and higher data rates become irrelevant” (Simon Saunders)
  • “Some data measured by a large European ISP on their broadband customer base in 2005 showed that 50% of their customers were shipping less than 600 Mbytes per month” (Stephen Temple)
  • “Video calls will become increasingly attractive as the ‘Metcalfe rule’ applies…”
  • “The extent to which these services actually emerge will be set by industry structure and the ‘boldness’ of the strategies deployed by the key players”
  • “Users will have found that the combination of 3G with its falling costs and improving data rates, and nomadic W-LAN coverage when static provides the best combination of cost and utility.”

These quotes are just the tip of the iceberg and although I do not agree with everything in the book I can say it is a real page turner and well worth a read. I learnt a great deal, I scribbled a lot of notes into the book so I can compare in 5 or 10 years from now and the book has definitely inspired a lot of new thoughts.

For those who are interested here’s a link to book’s page on the publisher’s website.