Reliable VoIP

QoS metrics are important, and several companies have products that measure packet loss, jitter, latency and so on. But you can have perfect QoS, and your VoIP system can still be defective for all sorts of reasons.

I spoke with Gurmeet Lamba, VP of Engineering, at Clarus Systems at the Internet Telephony Expo this week. He said that even if a VoIP system is perfectly configured on installation, it can decay over time to the point of unusability. Routers go down and are brought up again with minor misconfigurations; moves, adds and changes accumulate bad settings and policy violations.

VoIP systems are rarely configured perfectly even on installation. For example, IP phones have built-in switches so you can plug your PC into your desk phone. Those ports are unlocked by default. But some phones are installed in public areas like lobbies. It’s easy for installers to forget to lock those ports, so anybody sitting in the lobby can plug their laptop into the LAN. There are numerous common errors of this kind. Clarus has an interesting product that actively and passively tests for them; it monitors policy compliance and triggers alarms on policy violations.

Clarus uses CTI to do active testing of your VoIP system, looking for badly configured devices and network bottlenecks. Currently it works only on Cisco voice networks, but Clarus plans to support other manufacturers.

Clarus started out focusing on automated testing of latency, jitter and packet loss for IP phone systems. It went on to add help desk support with remote control of handsets, and the ability to roll back phone settings to known good configurations.

The next step was to add “Business Information,” certifying deployment configurations, and helping to manage ongoing operations with change management and vulnerability reports. Clarus’ most recent announcement added passive monitoring based on a policy-based rules engine.

Clarus claims to have tested over 350 thousand endpoints to date. It has partners that offer network monitoring services.

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.

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.

iPhone activation experience

I sat down with my iPhone and my MacBook, turned on the iPhone and tapped on the screen where it said “Activate iPhone.” The screen went black. Not a good sign.
Then I remembered that the iPhone needs to be plugged in to the PC physically to activate it. This is weird, because one of the things I like best about my MacBook is the way I can just put my Mororola Razr on the desk near it and download photos without any fuss.
So I plugged in the iPhone to the USB and fired up iTunes to do the activation.
Some of the questions were intrusive. It forced me to enter my social security number, also a credit card number for iTunes. I would have preferred to wait until I was ready to buy something from iTunes before giving it credit card info.
The minimum billing I could find was $59.99 a month plus a $36 activation fee for an obligatory 2 years.
This is a $1,536 commitment; add in the $600 for the phone and this toy costs over $2,000.
iTunes showed me my new phone number, and the phone screen said:
“Waiting for AT&T activation. This may take some time.”
This sounded ominous, but within a minute the phone said it was activated.
I made a phone call. Sounded OK.

OpenMoko ships Neo 1973

Lost in the iPhone brouhaha was a June 27th announcement about a phone that may turn out to be more revolutionary:

In our factory in China, 400 Neos are waiting… Starting July 9th, we will launch and start taking orders.

400 units sounds laughable compared to the iPhone’s initial run of 6 million. But it is the seed of something that could turn out to be insanely great. Steve Jobs will remember that the initial production run of the Apple I was only 220 units.

The Neo 1973 looks somewhat similar to the iPhone. It has a similar multi-touch screen that has twice the resolution (640×480) of the iPhone, though it is physically smaller.

What is revolutionary is the software business model. The iPhone isn’t even technically a Smart Phone, since it doesn’t support third party applications. The Neo 1973 is Linux-based, it is open source, and you are welcome to modify it to suit your needs.

This is huge for small, vertically oriented ISVs all over the world. While Motorola and other phone makers have already delivered Linux phones, they are notoriously secretive about the APIs, and make it almost impossible to develop tightly integrated applications. With the Neo 1973, ISVs will finally be free to customize a phone for a particular application or vertical market.

The first version shipping in early July will not support Wi-Fi. A revision in October will. This will be a breakthrough device, selling only to enthusiasts and early adopters in 2007, but gaining sales through 2008 as more applications are developed, and as hardware improvements (like faster CPU, larger screen, 802.11n, NFC, more memory, improved battery life, thinner) are made.

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!”

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 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.

Reuters says FMC “years off”

Reuters ran a story today from the FMC World Congress in Amsterdam.
The article cites very weak consumer uptake leading to the cancellation of T-Mobile’s T-One service in Germany, and weak uptake also at Neuf Cegetel. It seems strangely unbalanced, since it doesn’t mention T-Mobile’s imminent national rollout of FMC in the USA, the BT/Vodafone Fusion service and the FT/Orange Unik service. There are several other UMA deployments that would have made the outlook seem less gloomy.
The T-Mobile service was survived in Germany by T-Com’s similar service, Telekom-Vorteil, a “fixed/Wi-Fi” service that routes wireline calls over Wi-Fi, so you can use a Wi-Fi phone or the Wi-Fi of your dual mode phone to pick up calls on your home number when you are at home. This is not UMA based, and drops the call when you move out of Wi-Fi range. People like it.

Dual mode phone trends

Here is a chart of the number of dual mode phones certified for Wi-Fi each month starting in 2004, compiled from data found on the Wi-Fi Alliance website. There is a suggestion of a trend over the first few months of 2007, but of course it’s too early to call the entry of FMC into the trough of disillusionment. In the first three months of 2007 there were 14 certifications, versus 8 in the first three months of 2006. That’s a healthy 75% year on year increase. When you look at it on a quarterly scale, the first calendar quarter of 2007 is the second best ever, beaten only by the twenty certifications in the fourth quarter of 2006. But broken down by month it looks like certifications are sliding. There has only been one so far in May.
Wi-Fi certifcations of dual mode phones

Nokia’s WiMAX “Phone”

Reuters picked up on one little sentence buried in a Nokia press release entitled “Nokia Demonstrates Leadership in Technologies for Internet on Mobile Devices at Web 2.0 Expo.” The relevant paragraph, in its entirety, reads:

“Nokia Shows Commitment to WiMAX as Web 2.0 Enabler

“Nokia is dedicating significant research, development and intellectual property to WiMAX and supports efforts in making it a global broadband standard. The combination of WiMAX broadband technology and Web 2.0 services offers people an enriched high-speed Internet experience free from the desktop PC. Nokia plans to bring its first WiMAX enabled mobile device to market in early 2008.”

With no apparent evidence, the headline of the Reuter’s story mentioned the word “phone,” and the Internet echo chamber commenced to spawn dozens of stories saying that Nokia is going to release a WiMAX phone in 2008. Actually it looks more as though they are talking about an Internet Tablet like their N800, which is much less exciting.

A Nokia phone based on WiMAX would either have to have a regular cellular radio for the voice channel, or it would use WiMAX for voice. A phone that uses WiMAX for voice would most likely be aimed at a wireless Internet provider that doesn’t have a cellular network, for example ClearWire in the USA. This would put a date on their anticipated entry into mobile voice over WiMAX to compete with the incumbent cellular operators.

But that’s not what the press release says.