Is 802.11n too power-hungry for handsets?

Most 802.11n access points draw more power than Power over Ethernet (PoE) can supply, while 802.11a/b/g access points work comfortably with PoE. So 802.11n must be more power consumptive than 11g, right?

The answer is yes, but when you delve into the reasons why you may discover that an 802.11n handset can still have comparable, or better battery life than an 802.11g one.

The big power drain for 802.11n is MIMO, for two reasons. First, MIMO demands a separate radio transmitter for each of its channels. In the Farpoint white paper linked above, testing was done with six transmitters – 3 at 2.4 GHz, 3 at 5GHz. The 11n specification allows up to 4 MIMO channels, and Wi-Fi certification requires at least two. Each of these transmitters burns as much power as the single (or dual in the case of an a/g AP) transmitter in an 11a or 11g access point. A second increase in power demand by 11n comes from the increased processing load not just because of the increased number of channels, and not just because of the increased data throughput, but also because each individual MIMO stream places a heavier processing load than a single 11a or 11g stream.

But the Wi-Fi Alliance (WFA) has waived the MIMO requirements for handsets, allowing 802.11n certification for single-radio devices. So none of these increases in power dissipation needs to apply to handsets.

Single-channel 802.11n still requires more processing than single channel 802.11g, because of advanced features like STBC and LDPC, but STBC and LDPC are amenable to hardware implementation (which reduces their power demand), and these and other advanced features of 802.11n improve “rate at range,” meaning that the transmitter is active for shorter times, and can transmit at lower power.

The net is that Redpine Signals, a pioneer of 11n for handsets, claims that a handset using the Redpine 11n chip actually has better battery life than it would with a competitor’s 11g chip.

Wi-Fi state of the art is a rapidly moving target, and over the past 12 months there have been startling improvements in power efficiency. I have written here about the new Atheros chip, for example. So if the latest 11g handset chips are more power efficient than 11n competitors, it is more a function of their recency than their adherence to 11g.

The benefit of 5 GHz operation is compelling for Voice over Wi-Fi, and it will be hard for handset vendors to promote the decade-old 802.11a over 802.11n. 802.11n is already the Wi-Fi flavor of choice for access points and PC clients, and it soon will be for handsets, too. How soon? It’s hard to say. So far the only chip vendors to announce 11n for handsets are TI, Redpine Signals and Conexant, and Conexant exited the handset Wi-Fi business just two months after it announced this chip. No phone is yet shipping with 802.11n although TI said it was sampling its WiLink 6.0 with 11n in February 2007. The Wi-Fi alliance has not yet published its Handheld profile for 802.11n certification. On the other hand, ABI research in September 2006 predicted that the majority of the 300 million Wi-Fi enabled handsets to ship in 2011 will support 802.11n.

If 802.11n handset shipments fall short of this prediction, it won’t be because of battery life considerations.

Wi-Fi Bluetooth collision

I already wrote about how Bluetooth is specifying Wi-Fi for its high bandwidth transport in a future version. Now there’s another interesting Bluetooth/Wi-Fi juxtaposition.

You may remember that last year Bluetooth subsumed WiBree as an ultra low power consumption variant. Now something analogous is happening in Wi-Fi, where a startup called Ozmo has come up with an ultra low power variation of Wi-Fi, which it is pitching as a substitute for Bluetooth.

Ozmo is not the first to propose this. Nanoradio claims that its implementation of Wi-Fi consumes way less power than Bluetooth, and they have a reference design for a Wi-Fi headset to demo the concept. Atheros has also recently announced a low-power Wi-Fi chip – so low that they claim “near zero” stand-by power consumption.

So Ozmo may not be so radical in its low-power claims, but it also claims low-cost. The Ozmo chip is priced the same as Bluetooth chips, which Ozmo estimates are between 1/4 and 1/3 the cost of Wi-Fi chips.

The Atheros and Nanoradio chips are full implementations of Wi-Fi; Ozmo’s is, according to this EETimes article, a “stripped down” version. This may mean that it is a non-standard version, in which case it would need a new certification program from the Wi-Fi Alliance – not a major obstacle, I presume, in view of Intel’s strong support for Ozmo.

So why would anybody want a version of Wi-Fi to substitute for Bluetooth, when we already have Bluetooth? Well, while most phones come with Bluetooth these days, in the PC world Wi-Fi is far more common than Bluetooth. So for peripherals designed exclusively for PCs, like mice and keyboards, Wi-Fi makes more sense than Bluetooth simply on the grounds of out-of-the-box compatibility. Add the technical benefits, like coexistence (Bluetooth and Wi-Fi tend to step on each others’ toes) and superior performance (Ozmo claims double the battery life in similar applications to Bluetooth), and it seems like a no-brainer.

The factors that could cause it to fail are ease of use and price. The setup of the peripherals with the PC must be completely automatic, and the operation of the devices must be flawless. Peripheral manufacturers must produce Wi-Fi versions of all their wireless products, and price them the same as their Bluetooth versions. The Wi-Fi drivers on the PC side will have to be modified in order to permit the PC Wi-Fi to communicate simultaneously with access points and peripherals. This is being done anyway by Intel, in a project called “Cliffside.”

All these impediments are mitigated considerably by Intel’s involvement. Intel makes most of the Wi-Fi chips in PCs, and presumably these chips will support the Ozmo products. With this assurance, peripheral manufacturers will feel comfortable going ahead with Ozmo-powered products.

Agito and Cisco Motion

Agito Networks was in the news recently as a part of Cisco’s Motion announcement. I have mentioned Agito a couple of times before in this blog. Like DiVitas it offers PBX-agnostic enterprise-based fixed-mobile convergence.

One of Agito’s unique technical claims is that it employs location based technology as one of the factors to determine the handover between Wi-Fi and Cellular (and vice versa).

The RoamAnywhere Mobility Router adds the element of location awareness to solve the challenging problem of routing between multiple networks.

From the Agito website

The Mobile Intelligent Roaming component of Cisco’s new Mobility Services Engine (MSE) also uses location as one of the factors (the other are signal strength and signal quality) to determine when to hand off between networks. This incorporation of location awareness into the MSE’s handover recommendation appears to weaken Agito’s claim to uniqueness in this respect, so why is Agito so enthusiastic about the MSE?

The MSE boils down an assortment of metrics related to handover decision-making to a simple binary message – link-up or link-down – which it sends to a third party eFMC controller like the Agito RoamAnywhere Mobility Router. The message is a recommendation, not a command, but since the MSE sends just this binary event, rather than any of the metrics that go into it, Cisco seems to be claiming responsibility for the decision about when to hand over.

Rather than simply obeying the link-up or link-down event by changing networks, the Agito mobility router takes these events as triggers to run its own handover-decision algorithm, using metrics gathered by the handset. This makes sense for several reasons. First, the Agito location determination mechanism is more precise for this particular application, since it knows when it is going through a doorway, whereas the Cisco location mechanism has a more general idea about the perimeter of the building. Second, the entire Agito handover-decision algorithm has to be maintained regardless of how good the MSE is at making the decision, because in many places there is no MSE (at home, in public areas, in buildings with non-Cisco networks and in buildings with Cisco networks lacking an MSE).

So Agito views the information from the MSE as a mere additional factor for its handover decision-making, rather than a substitute. On the other hand, Cisco’s marketing program around the MSE is a huge benefit to Agito.

Even though this part of the MSE will not be released until later this year, Agito’s Mobility Router works fine without it; the Cisco Motion announcement has led to a burst of interest in Agito from Cisco’s channel partners. According to Cisco, it has 65% share of enterprise Wi-Fi infrastructure, so Pej Roshan, Agito’s V.P. of marketing, anticipates that the relationship will “slingshot us to the next level of sales and customers.”

802.11n update

There’s some FUD around 802.11n. A comment on this blog wonders how long it will be before it is ratified, and calls it a “pipe dream.”

So I was pleased to hear an aside from a Cisco executive in the webinar about the new Cisco Mobility vision. A participant asked Brett Galloway if delays in the ratification of 802.11n are holding back deployment. He responded:

We don’t see it. Technology adoption is a cycle. Late adopters are more conservative. Large numbers of 11n clients are shipping. The driver is Wi-Fi Alliance Draft N certification. There is comprehensive agreement around the ecosystem for interoperability testing using the WFA testbed. Cisco announced recently that it had shipped 50,000 11n access points.

The critical point here is that a final 802.11n specification is not needed for successful deployment. The main thing you want from a Wi-Fi device is that it is interoperable with all the others, and that’s what the Wi-Fi Alliance Draft N certification delivers – at least to the same extent that 11g devices are interoperable.

While 50,000 is a trivial number in the context of Wi-Fi access points, remember this is just enterprise-grade APs, and doesn’t include anything from Cisco’s Linksys division. When the litigation goes away and the final specification is published, all the access points out there are likely to be upgradable with a download. So go ahead and enjoy the benefits of 11n like so many other people are doing.

Intel returns to the smartphone business in late 2009

The Intel Atom is aimed at Internet tablets, Mobile Internet Devices and Ultra-mobile PCs (or whatever the nom de jour is), but not at phones. I don’t think Intel has formally announced its return to the phone processor business yet, but Paul Otellini has been talking about it for a while now, so it seems overdue to make it official. That’s what the Financial Times did today with the headline “Intel to re-enter mobile market.” Otellini said the same thing to the New York Times on Sunday as well. Of course it has been expected ever since the first Atom announcement, and it may not really qualify as news, but here it is: “A second generation version of the chip, expected in late 2009, will be aimed at smart phones.”

As you know, the Atom is Intel’s prospective ARM-killer, but Intel will have some very heavy sledding to do to achieve this goal. The first obstacle is size and complexity. The Intel Architecture instruction set is much more complicated than the ARM, with decades of legacy dross gunking it up. The core proposition of IA for handsets is that IA is compatible with all the PC software and websites out there, so none of the legacy stuff can be left out. Intel has two factors working in its favor for this issue: first, a lot of the little-used functionality of IA can be implemented in microcode, which takes minimal die space. Second, Intel leads the world in process technology, and as it moves to the 32 nm and below nodes, vast numbers of transistors can be fitted into tiny chips. This shrinkage, and advances in power management technology, may enable the next generation of Atom to get into the same ballpark as ARM for battery life.

The second obstacle is incumbency. There are vastly more ARM processors out running in the world than there are Intel Architecture processors. The ARM is the processor used by effectively all phones and smart phones, and there are even more ARMs in other embedded applications. While Intel can point to a huge independent software developer community for IA, with a rich array of third party developer support, so can ARM for its architecture. And it’s not clear that the Atom will have a significant performance advantage over the ARM. ARM is not standing still on its architecture, delivering faster, lower power chips in step with Moore’s law just like Intel.

The incumbency issue also has a political aspect. Handset manufacturers are disinclined to hand Intel the kind of architectural franchise that it has in the PC world, so the Atom will have to have a compelling, essential advantage over the ARM in order to displace it in any but niche applications. Intel hopes that “the real Internet” is that advantage, but the iPhone has demonstrated that the real Internet can run very nicely on an ARM-based phone. In any case, within three years more smart phones will be shipping than PCs, and the other handset manufacturers will probably have caught up with Apple on the browser front, so it is possible that more Internet browsing will be being done with ARMs than IA chips.

The third obstacle is business model. To satisfy the stock market, Intel requires aggregate gross margins around 60%. This will be very tough to achieve in the mass-market for handset processors, because the margins on competing ARMs are much lower.

Good background on the Atom can be found in this EETimes article, this Beyond3d article, and this one by my colleague Linley Gwenapp.

Cisco’s Motion Announcement

Cisco’s Motion announcement on May 28th was huge for enterprise mobility. It defined some new terms which we will be hearing a lot: “Cisco Motion,” “Mobility Services Architecture” and “Mobility Services Engine.” Cisco Motion is the name of the “vision.” The Mobility Services Engine 3350 is a $20,000 appliance that embodies the Mobility Services Architecture, which is a part of Cisco’s Service Oriented Network Architecture.

Cisco has published a lot of useful information about these new products. A good place to start is the launch webinar, which includes an informative Powerpoint presentation. The Mobility Services Architecture is described in a white paper. There are two press releases: a conventional press release consisting of written words, and a “social media release” consisting of links to YouTube clips and podcasts.

What we’re doing here is abstracting the network control element of the architecture and the services and application integration piece. This reflects what we have been talking about for the last 2 plus years around the Services Oriented Network Architecture. It’s about how we can drive new capabilities into the network, that can be married up with a host of different applications and turned into a solution for our customers. It’s not just applications running over the network. Increasingly with this architecture, it is about applications running “with” the network.

Ben Gibson, Senior Director Mobility Solutions, Cisco Systems

Cisco describes the MSE as a “platform for partnering,” the idea being that it exposes network-level information through an open application programming interface (API) to applications delivered by independent software vendors (ISVs).

Adding wirelessness to the IP world generates network-layer information that can be useful to applications, notably information about the location of known devices, and the intrusion of unknown devices. The MSE orders that information and presents it through the API.

Cisco Motion also addresses some downsides of mobility. Adding mobility to the IT world brings a lot of new headaches:

  • There are multiple network types (currently cellular and Wi-Fi, later WiMAX)
  • There is a profusion of new device types (currently smart phones) which must be managed and tracked
  • There is a wave of innovation in consumer applications. Employees are demanding these applications in the enterprise environment.
  • Mobility also complicates compliance with data confidentiality regulations like PCI and HIPAA.

So far Cisco has identified four categories of application that can run on the MSE: Context-Aware applications, Wireless Intrusion Prevention Systems, Client Management and Intelligent Roaming.

Context Aware Applications
“Context Aware applications” seems to be Cisco’s term for applications that do asset tracking. Cisco is partnering with ISVs in both horizontal and vertical markets. These ISVs are OAT, Intellidot, Aeroscout, Pango/Innerwireless and Airetrak. The Context-Aware software is scheduled to ship in June 2008.

Adaptive Wireless Intrusion Prevention Systems

Overlay wireless intrusion prevention systems add devices to monitor wireless traffic looking for rogue access points and clients. The innovation here appears to be that the MSE exposes information from the access points and wireless controllers that eliminates the need for these overlay devices. IPS software running on the MSE can substitute for the overlay IPS, while yielding equivalent depth of reporting and features. A further benefit of running the IPS over the MSE API is that the same software will be able to handle future wireless networks in addition to Wi-Fi. The Adaptive WIPS software is scheduled to ship in the second half of 2008.

Mobile Intelligent Roaming

This is enterprise Fixed-Mobile Convergence. The MSE isn’t a mobility controller; it issues an event up through the API when it determines that the Wi-Fi network needs to hand the call off to the cellular network. This event is handled by mobility controller software from an ISV. Cisco’s launch partners for this are Nokia for phones, and Agito on the mobility controller side. The Mobile Intelligent Roaming software is scheduled to ship in the second half of 2008.

Secure Client Manager

This works with Cisco’s 802.1X and CCX products. Cisco estimates that 80% of IT’s wireless and mobility effort goes to client troubleshooting and security provisioning. The Secure Client Manager will help mitigate this problem for the imminent wave of mobile devices. The Secure Client Manager is scheduled to ship in the first half of 2009.

Unified Wireless Network Software

Cisco Motion requires a new software load for the access points and WLAN controllers: the Cisco Unified Wireless Network Software Release 5.1, which shipped in May 2008.