Posted on

Low power 802.11n sampling from Redpine

Redpine Signals has announced that it is sampling a low power 802.11n chip suitable for cell phones. A reference design was certified in January, making it the first handset-grade 802.11n chip to market.

One of the major benefits of 802.11n is MIMO, so you might think that since a handset is unlikely to have multiple antennas, 802.11n isn’t going to help much. Actually, it will make an enormous difference in reliability and range, and consequently throughput. I wrote before about the array of improvements incorporated in 11n. The one of greatest interest in this context is Space-Time Block Coding (STBC).

The WFA website shows 90 Access Points (APs) certified for 802.11n, but STBC is optional in 11n, not mandatory, and not all the AP chipsets support it. The main makers of AP chipsets are Atheros, Broadcom and Marvell. None of these have mentioned STBC until recently. But now Broadcom says it is in the BCM4322, which is set to ship in the first quarter of 2008, and Marvell says it is in the TopDog 11n-450, which is scheduled to ship in 2Q 2008.

This Techworld article has a good discussion of the current state of enterprise 11n access points, noting that multi-radio APs are currently too power-hungry to be powered over Ethernet (PoE).

Posted on

Dual mode phone trends – Update

In May 2007 I showed a chart of dual-mode phone certifications by time. Certifications have continued to grow since then, as the updated graph below shows. These numbers are pretty raw, for example six certifications in November 2006 were for variations on a Motorola phone first certified in October. If you go back and look at the previous chart you will also notice discrepancies in the number of certifications for any particular month. These are presumably because of revisions at the WFA website.
Dual mode phone trends
From 2006 to 2007 smartphone certifications were essentially flat, going from 33 to 36, while feature phone certifications went from 11 to 21. These add up to 44 dual mode phone certifications in 2006 and 57 in 2007.

Posted on

Open wireless handsets and networks for America?

I have previously written about OpenMoko. It seems now that it was the drop before the deluge. Google’s Android appears to have gained good traction with Sprint and T-Mobile joining the Open Handset Alliance, with Dell rumored (update) to be planning an Android-based phone, and with Verizon expressing lukewarm support. Nokia has for some time sponsored open source handset software through Maemo.org, but this week it upped the ante with its acquisition of TrollTech. Trolltech is responsible for Qtopia, a semi-open source platform used in Linux-based phones. That makes four credible Linux-based mobile phone software platforms. Update: Make that five – the LiMo Foundation is a consortium of carriers (including NTT DoCoMo and Vodafone), phone makers (including Samsung, Motorola and LG) and others “dedicated to creating the first truly open, hardware-independent, Linux-based operating system for mobile devices.”

But a phone doesn’t have to be open-source to be an open application platform, and this category is just as vigorous, but better established. Nokia’s Symbian phones have always been open to an extent – there are over 2 million developers registered in Nokia’s developer organization, Forum Nokia. Then we have Microsoft. Microsoft claims that sales of Windows Mobile phones are set to double year-on-year, to 20 million units. Windows Mobile provides a sufficiently open application environment that applications like Skype run on it. The iPhone is not yet officially an open application environment, but there is still a healthy slate of applications from third parties for those with the stomach to take the unofficial route. This is scheduled to change in February when the open-ness goes official with the release of Apple’s SDK for the iPhone. So that’s three major open application environments for smart phones.

2008 is also the year that Wi-Fi phones will come into their own. The dam broke with the iPhone. Wi-Fi on the iPhone raises the bar for all the other smart phones, making Wi-Fi a baseline checklist item for the next generation of smart phones. Previously mobile network operators were fearful that Wi-Fi in a phone would divert traffic from their data networks. This fear led, for example, to AT&T’s removal of Wi-Fi from their version of the Nokia E61. But there is now new evidence. At last week’s IT Expo East I heard an unsubstantiated report that 60% of wireless data usage in December was by 2% of the phones: iPhones. If this is even partly true, it would demonstrate that a web-friendly phone will drive traffic on the cellular data network even when it has Wi-Fi.

Posted on

Tango FMC for enterprises

Tango Networks was founded in 2005 and fully funded by February of 2007. It is one of several startups addressing the enterprise FMC market, integrating with the corporate PBX, but it claims a unique twist in that it also integrates closely with service provider infrastructure.

Tango has a box plugged into the MNO’s call control infrastructure talking directly to another Tango box that plugs into the corporate PBX. These boxes are named Abrazo-C (carrier) and Abrazo-E (enterprise). Abrazo is the Spanish for embrace, reinforcing the concept of the carrier side and the enterprise side being tightly connected. This balanced architecture enables Tango to offer a rich feature set while maintaining versatile.

One of the aspects of this versatility is that they aren’t fixated on dual mode phones. Tango works with any cell phone, and hands off between the corporate desk phone and the cell phone in response to the user punching in a star code on their phone keypad. This method of input also gives the user complete access to all the features of the corporate PBX over the cellular network. But Tango acknowledges that star codes are not the most user friendly of interfaces, so they do provide an “ultra thin client” for those phones that support third party software.

Requiring a box in the carrier network helps with things like caller ID manipulation and number translation (like 4 digit dialing to PBX extensions from your cell phone). On the other hand it limits Tango’s ability to sell directly to enterprises. The primary customer for all sales has to be a carrier. Marketing efforts directed to end users serve only to provide pull through.

Offering a box on the enterprise premises addresses the major concern of businesses evaluating VCC and other carrier centric FMC solutions: businesses don’t want to lose control of their voice network. By leaving the enterprise side of the system under the control of the corporate IT department, Tango resembles the PBX model of business voice more closely than the never popular Centrex model.

Posted on

How does 802.11n get to 600Mbps?

802.11n incorporates all earlier amendments to 802.11, including the MAC enhancements in 802.11e for QoS and power savings.

The design goal of the 802.11n amendment is “HT” for High Throughput. The throughput it claims is high indeed: up to 600 Mbps in raw bit-rate. Let’s start with the maximum throughput of 802.11g (54 Mbps), and see what techniques 802.11n applies to boost it to 600 Mbps:

1. More subcarriers: 802.11g has 48 OFDM data subcarriers. 802.11n increases this number to 52, thereby boosting throughput from 54Mbps to 58.5 Mbps.

2. FEC: 802.11g has a maximum FEC (Forward Error Correction) coding rate of 3/4. 802.11n squeezes some redundancy out of this with a 5/6 coding rate, boosting the link rate from 58.5 Mbps to 65 Mbps.

3. Guard Interval: 802.11a has Guard Interval between transmissions of 800ns. 802.11n has an option to reduce this to 400ns, which boosts the throughput from 65 Mbps to 72.2 Mbps.

4. MIMO: thanks to the magical effect of spatial multiplexing, provided there are sufficient multi-path reflections, the throughput of a system goes up linearly with each extra antenna at both ends. Two antennas at each end double the throughput, three antennas at each end triple it, and four quadruple it. The maximum number of antennas in the receive and transmit arrays specified by 802.11n is four. This allows four simultaneous 72.2 Mbps streams, yielding a total throughput of 288.9 Mbps.

5. 40 MHz channels: all previous versions of 802.11 have a channel bandwidth of 20MHz. 802.11n has an optional mode (controversial and not usable in many circumstances) where the channel bandwidth is 40 MHz. While the channel bandwidth is doubled, the number of data subcarriers is slightly more than doubled, going from 52 to 108. This yields a total channel throughput of 150 Mbps. So again combining four channels with MIMO, we get 600 Mbps.

Lower MAC overhead
But raw throughput is not a very informative number.

The 11a/g link rate is 54 Mbps, but the higher layer throughput is only 26 Mbps; the MAC overhead is over 50%! In 11n when the link rate is 65 Mbps, the higher layer throughput is about 50 Mbps; the MAC overhead is down to 25%.

Bear mind that these numbers are the absolute top speed you can get out of the system. 802.11n has numerous modulation schemes to fall back to when the conditions are less than perfect, which is most of the time.

But to minimize these fall-backs, 11n contains additional improvements to make the effective throughput as high as possible under all circumstances. These improvements are described in the following paragraphs.

Fast MCS feedback – rate selection.
Existing equipment finds it hard to track rapid changes in the channel. Say you walk through the shadow of a pole in the building. The rate may go from 50 to 6 to 50 mbps in one step. It’s hard for conventional systems to track this, because they adapt based on transmit errors. With delay sensitive data like voice you have to be very conservative, so adapting up is much slower than down. 11n adds explicit per-packet feedback, recommending the transmission speed for the next packet. This is called Fast MCS (Modulation and Coding Scheme) Feedback.

LDPC (Low Density Partity Check) coding
LDPC is a super duper Forward Error Correction mechanism. Although it is almost 50 years old, it is the most effective error correcting code developed to date; it nears the theoretical limit of efficiency. It was little used until recently because of its high compute requirement. An interesting by-product of its antiquity is that it is relatively free of patent issues.

Transmit beam-forming
The term beam-forming conjures up images of a laser-like beam of radio waves pointing exactly at the client device, but it doesn’t really work like that. If you look at a fine-resolution map of signal intensity in a room covered by a Wi-Fi access point, it looks like the surface of a pond disturbed by a gust of wind – it is a patchwork of bumps and dips in signal intensity, some as small as a few cubic inches in volume. Transmit beam-forming adjusts the phase and transmit power at the various antennas to move one of the maxima of signal intensity to where the client device is.

STBC
In a phone the chances are that there will only be one Wi-Fi antenna, so there will be only one spatial channel. Even so, the MIMO technique of STBC (Space-Time Block Coding) enables the handset to take advantage of the multiple antennas on the Access Point to improve range, both rate-at-range and limiting range.

Incidentally, to receive 802.11n certification by the Wi-Fi Alliance, all devices must have two or more antennas except handsets which can optionally have a single antenna. Several considerations went into allowing this concession to handsets, mainly size and power constraints. STBC is particularly useful to handsets. It yields the robustness of MIMO without a second radio, which saves all the power the second radio would burn. This power saving is compounded with another: because of the greater rate-at-range the radio is on for less time while transmitting a given quantity of data. STBC is optional in 802.11n, though it should always be implemented for systems that support 802.11n handsets.

Hardware assistance
Many of these features impose a considerable compute load. LDPC and STBC fall into this category. This is an issue for handsets, since computation costs battery life. Fortunately these features are amenable to hardware implementation. With dedicated hardware the computation happens rapidly and with little cost in power.

Posted on

CSR pitches better sound quality, battery life in Bluetooth headsets

CSR announced their Bluecore 6 chip today. It will ship in production volumes in January 2008. CSR claims a more robust connection – with increased transmit power and receive sensitivity. CSR also claims a breakthrough in sound quality, achieved by going from a Continuous Variable Slope Delta (CVSD) codec to Adaptive Differential Pulse Code Modulation (ADPCM). This enables packet retransmission and a halving of transmission bandwidth. The reduced bandwidth requirement results in a reduction in power consumption, and the ADPCM codec yields a MOS of 4.14 compared with a maximum of 2.41 for CVSD.

This is a welcome change, but doesn’t really go far enough. What’s needed is a wideband codec like AMR-WB to yield better-than-toll quality sound. While this would be redundant in a regular cell phone – ADPCM is more than adequate to carry a signal that has been encoded in GSM – it would make a huge difference in dual-mode phones carrying Voice over Wi-Fi.

Posted on

Femtocells, FMC, Wi-Fi

There’s an interesting article on femtocells in EETimes. It mentions the Femto Forum. It is a thoughtful look at the prospects for femtocells, a welcome counterbalance to the hype. The most telling quote is from the CTO of Ubiquisys:

We—that is, the femtocell ecosystem—probably have a two-year window to make our mark, ensure we come up with standard interfaces, and, above all, avoid fragmentation.

The two year comment is about beating Wi-Fi dual mode phones to the punch. But currently the primary driver for Wi-Fi in cell phones is feature inflation in high-end handsets, not FMC. In other words, there are really two dynamics driving Wi-Fi into handsets, FMC is the minor one and feature inflation is the major one; femtocells don’t affect the latter.

So if femtocells overcome their numerous challenges, FMC services for consumers will come mainly through femtocells. Femtocells will not impact Wi-Fi attach rate much, since Wi-Fi is becoming a checklist feature on high end phones. How useful the Wi-Fi in these handsets will be depends on how successful the phone makers are at keeping them open.

Posted on

T-Mobile launches FMC nationally in USA

***Update: I went to the T-Mobile store this morning and signed up. The service here in Dallas is $10 per month, not $20 as reported by Reuters. The store manager also told me that people with poor cellular reception at home can use the UMA service at no additional monthly charge, but that this usage is treated the same way as cellular usage – in other words, it counts against your cellular minutes.***

***Update 2: Here are some details on the T-Mobile launch campaign. ***

Reuters reported this morning that T-Mobile is rolling out FMC service nationally.

Subscribers would pay an extra fee of up to $19.99 per line or $29.99 for five lines on top of regular monthly cellular bills for unlimited calls in a subscriber’s home or the nearly 8,500 places T-Mobile runs Wi-Fi, like Starbucks coffee shops.

This pricing model seems ambitious, compared to what it is competing with. T-Mobile’s MyFaves 300 plan gives you unlimited minutes nights and weekends and unlimited minutes to a list of five people that you choose. So the 300 minutes are consumed during the day, calling to people whom you call infrequently. For $20 more you can bump this to 1,000 minutes. Alternatively, you can spend that $20 on the FMC service. It seems like the FMC service would only be a better deal for people who are home all day (or at Starbucks), who want to talk a lot to people beyond their five most frequently called. MyFaves 1000 would be a better deal for people who want to talk to a large variety of people during the day when they are not at home, for example in the car or out of range of a Starbucks – like at work, for example.

So who are these people that this “HotSpot@Home” service is aimed at? Surely there can’t be many. Why doesn’t T-Mobile use this technology to gain more customers, by giving it away free to subscribers? This would appeal to all the people who have poor reception at home, who would feel bilked by having to pay extra just for acceptable quality of service there (Hey! They do! See the update above). Another way to increase customer appeal would be to go with a wideband codec for Wi-Fi calls, guaranteeing CD-quality sound to Wi-Fi on-network calls. Or why not do both? This would provide a viral motivation to complement MyFaves, it would be unique among US carriers, it would improve retention, and it would bring new subscribers to start exploiting all that spectrum that T-Mobile picked up in the AWS auction in September 2006.

Posted on

Apple to let outsiders create programs for iPhone???

Reuters carried a story yesterday from the Apple World-Wide Developer Conference in San Francisco. The headline is “Apple to let outsiders create programs for iPhone,” and the story says “Apple Inc. will allow independent developers to write applications for its upcoming iPhone by tapping into the device’s built-in Web browser.” The story was presumably based on Apple’s press release on the topic.

This sounds exciting, so why did Apple stock lose $4.30 on the day? Well, the market focused on the glass-half-empty. Apple didn’t open the iPhone up to third party developers in the way that most developers want. The comment that squelched the crowd was “there’s no SDK!” The official version, what Jobs, Forstall and the press release said beyond that, is too scant and ambiguous to draw a clear idea of how well developers will be able to exploit the iPhone as a platform. Here’s a link to the video of the Jobs keynote. The iPhone developer part starts at time index 1:14. Ryan Block of Engadget was there live-blogging the Jobs keynote. His transcription and commentary:

Jobs: “We have been trying to come up with a solution to expand the capabilities of the iPhone so developers can write great apps for it, but keep the iPhone secure. And we’ve come up with a very. Sweet. Solution. Let me tell you about it. An innovative new way to create applications for mobile devices… it’s all based on the fact that we have the full Safari engine in the iPhone. And so you can write amazing Web 2.0 and AJAX apps that look and behave exactly like apps on the iPhone, and these apps can integrate perfectly with iPhone services. They can make a call, check email, look up a location on Gmaps… don’t worry about distribution, just put ’em on an internet server. They’re easy to update, just update it on your server. They’re secure, and they run securely sandboxed on the iPhone. And guess what, there’s no SDK you need! You’ve got everything you need if you can write modern web apps…”
Block: “Weeeeeaaaak.”
Scott Forstall, VP of iPhone software: “Your applications can take advantage of the built-in native services.”
Block: “He’s in the iPhone — no new apps up on screen, the same 11 as before — sorry iPhone fans!”
Forstall: “We built a custom corporate address book app to use our internal LDAP… it actually took less than one person-month to do this. It’s under 600 lines of code to do the whole thing.”
Block: “Shows up the vCards as they look in the built-in contact app. Not too shabby!”

The Web 2.0/AJAX model is great for AT&T, because this model requires continuous interaction with the server, so you will be burning up your data minutes. Except, I hope, when you are at home or at work and can use the Wi-Fi connection.

This is, as Block says, weak compared to loading real OSX applications on the phone. How weak depends on what Steve Jobs means by “the full Safari engine.” Apple’s Safari FAQ page says “All versions of Safari support Netscape-style plug-ins.” This undoubtedly applies to the iPhone version of Safari, since Steve Jobs has been toying with the idea of including Flash. The published Safari plugin SDK isn’t any use to iPhone developers, since the CPU is an ARM. So if Apple doesn’t publish an iPhone SDK, even the Safari plugin support is moot to third parties, except those working closely with Apple, like Google. One obvious Google plugin that would reduce the sting of no SDK would be Google Gears, which lets you run server-based applications off-line. The usual example is Google’s complete suite of Office applications.

From the overall context it appears that there is a JavaScript API to control some elements of the iPhone subsystem. That could be cool, depending how capable the API is. As for documentation of the API, a check of the Apple Developer website doesn’t reveal anything of that nature yet. There was a session at WWDC called “Developing Web Sites for iPhone,” which may have had some related information.

Blog reaction has been hysterical (but when has it ever not been?) Jesus Diaz of Gizmodo says No iPhone SDK Means No Killer iPhone Apps. One interesting tidbit in his piece concerns the degree of integration with the the iPhone’s services. Here’s what he says about clicking on a phone number in the browser to place a call:

This is nothing new, however. We knew this from the very beginning because iPhone’s Safari was already doing it. It’s called auto-detection of phone numbers and addresses: you click on a phone or address in your web page and it gets passed by Safari to the operating system, which calls the number or shows the address in the Google Maps app.

I certainly hope this isn’t the extent of it. If so, this guy is right. Nothing special here at all.

We live in hope, though. Steve Jobs was accurate in saying that Web 2.0/AJAX programming is the hot new thing, and that highly capable applications (especially enterprise applications) are being built like this. Users don’t care how software is written, they just want it to perform a useful function in a responsive and considerate way. If the API is rich enough, popular opinion will follow the trail that Ryan Block blazed, from “Weeeeeaaaak” to “Not too shabby!”

Posted on

Dual mode phones taking off?

Instat came out yesterday with a report entitled “Portable Connectivity Driving Wi-Fi Chipset Market.”
The report says:

Although dual-mode cellular/Wi-Fi handsets represented only 3% of total shipments in 2006, this category will be the breakout market segment in 2007, and will reach 20% of the total Wi-Fi chipset market in 2009.

A look at the database of smartphones and PDAs at pdadb.net reveals that of 343 phones listed, 192 have Wi-Fi; of the 96 phones released since December 2006, 76 have Wi-Fi. This confirms Instat’s opinion at the top end of the phone market.

Although the smartphone market is small relative to the overall cell phone market (4% in US, 9% in Europe according to Telephia), it is still big. With well over a billion cell phones being sold in 2007, the number of smartphones will be of the order of 100 million. In another report, Instat predicts about 400 million Wi-Fi chipsets to be sold in 2009. So the 20% number seems quite doable with smart phones alone.

If FMC takes off, Wi-Fi will also become common in non-smartphones, and the volume of Wi-Fi chip sales will be even higher. But mobile network operators remain tentative about FMC; rapid widespread rollout is not happening yet. Consumers rightly see little value in FMC the way that it is currently being sold to them. FMC is more likely to be led by enterprises deploying smart phones using third party applications to extend their PBX. The mobile and fixed operators have the power to thwart this use of their networks, and some will. But the benefits of this model to enterprises are clear and compelling, so it will eventually prevail.