Power Optimization
Enterprises will likely be disappointed with the power limitations of current Vo-Fi handsets. While cellular phones may enjoy battery lives of three to five days, Vo-Fi handsets are limited to one to two days. Longer spans are available if handset and WLAN infrastructure work together, typically with proprietary extensions.
Cellular handset vendors such as Motorola and Nokia have a distinct engineering advantage--launching dozens of new models per year, many including Wi-Fi in addition to GSM or CDMA capabilities and with manufacturing runs of tens if not hundreds of thousands, these guys have an opportunity with each successive model to "get it right." Pity the enterprise Vo-Fi vendors still selling hardware revision 1.0 at dramatically lower volumes: The Wi-Fi chipsets found in the newest Vo-Fi phones are only second or third generation, and the initial batch of handsets from enterprise Vo-Fi players Cisco, SpectraLink and Vocera were designed three to four years ago, making them dinosaurs when measured in cell-phone-innovation time--think dog years but in reverse.
Chipset manufacturers such as Atheros, Atmel, Broadcom and Texas Instruments are working hard to develop optimized silicon for these small-form-factor devices, but we expect advances to first find their way into consumer versions, until enterprise Vo-Fi vendors more aggressively rev their devices.
There are several factors unique to Vo-Fi handsets that challenge runtime. According to Michael Ward of Trinity Convergence, which develops embedded software for mobile voice and video applications, if the design dictates a DSP (digital signal processor), an additional applications processor is still required to handle such VoIP functionality as the user interface and call control.
It is possible to use an integrated SoC (system on a chip), which combines both the DSP and applications processor into one physical device. In many cases, an applications processor alone can be used to perform all VoIP processing. The benefit of using an SoC or single-application-processor design is the positive effect of lower power draw due to the lower number of components, as well as a smaller overall package for the components, which allows more space to be allocated to a larger battery. Because most Vo-Fi vendors are using chipsets from three to four years ago, SoC support is limited.
WLAN infrastructure vendors have a significant role to play in optimizing power consumption for Vo-Fi handsets. Take simple things like pruning unnecessary broadcast and multicast traffic and performing proxy ARP. The legacy power-save mode, part of the original IEEE 802.11 standard, requires the client to wake up as often as twice per second to listen to the AP's beacon and determine if there's traffic buffered for transmission. In addition, there are client-set intervals to listen for unicast traffic. All this checking in adds up to significant power consumption, even when there's no call in progress.
In one case, simply extending the interval between checks and converting multicast to unicast boosted battery life from 17 hours to more than 100 hours, according to Aruba.
But the greatest power savings are realized when handset and WLAN infrastructure work together. Meru claims it can increase battery life by more than 200 percent if the handset manufacturer uses Meru's sleep-mode drivers. More recently, Aruba announced a comprehensive, aggressive road map toward enterprise fixed-mobile convergence. One element is a plan to provide drivers to Linux-based handsets to optimize interaction with the WLAN infrastructure for battery conservation and roaming performance. Behind the scenes, Cisco has likely undergone the same energy-enhancing tweaking between its own handset and WLAN infrastructure.
Are you detecting a continuation of the proprietary theme here?
The solution in this case is the Wi-Fi Alliance's WMM Power Save standard. WMM Power Save is based on U-APSD (Unscheduled/Unsolicited Automatic Power Save Delivery), which is in turn modeled on some elements within the broader IEEE 802.11e specification.
With WMM Power Save, the application, not the device Wi-Fi driver, dictates how frequently it needs to communicate with the AP. The spec also gives the client flexibility as to the retrieval of buffered frames waiting at the AP; this ensures more timely delivery of packets, reducing both latency and jitter. Rather than wait until the next beacon, every 100 milliseconds or so, the client can send a trigger frame. The second advantage is less signaling overhead to flush buffered frames, which results in more efficient use of available airtime.
Unfortunately, of the 25 devices currently listed on the Wi-Fi Alliance's Web site as supporting WMM Power Save, only one is a Vo-Fi-capable phone, and it's from a relatively unknown vendor, MediaTek.
The standard has been out since December 2005, but no enterprise Vo-Fi vendor has a shipping product that takes advantage of it. SpectraLink told us it will support WMM Power Save and shared that, behind the scenes, it's working on interoperability testing with WLAN infrastructure vendors.
Cisco's newest handset, the 7921G, supports 12 hours of talk time or 100 hours of standby. And SpectraLink, with its NetLink 8000 series, offers a choice of batteries, topping out at 160 hours. Apparently Vo-Fi vendors understand the need to stay juiced.
Vocera will likely remain status quo until they release devices based on a new hardware platform. Hitachi plans to make U-APSD part of its next software release but may not undergo Wi-Fi Alliance certification. Cisco's newest phone supports U-APSD, and hopefully when the device is released, it will also be WMM-PS-certified.
While each platform is always optimized at the hardware layer for the best balance between power and performance, enterprise Vo-Fi vendors need to work a little quicker to take advantage of relevant standards that address real problems.
Pace Setters
Four vertical markets--retail, health care, manufacturing and supply chain--are taking the lead in Vo-Fi use; they've ironed out implementation kinks and provide models for developing a Vo-Fi infrastructure. The common denominator: A significant number of mobile employees who need ready access to others within, and sometimes outside, the enterprise.
Early on, many verticals deployed proprietary radio systems from the likes of SpectraLink, Engenius and others. Although an improvement over wired systems, these radio deployments locked companies in. Complete forklift upgrades were required to replace aging systems. That changed with the advent of Wi-Fi for data access and inventory; once a WLAN was in place, adding Vo-Fi made sense.
Take health care: In the emergency room, immediate access to nurses and doctors can make a life-or-death difference. Rather than using a delayed pager or call an external cell phone, members of the health team can use in-house systems to make contact immediately. When supply-chain or retail employees need to verify inventory for a customer, prepare an order or load a truck, Vo-Fi can provide affordable voice connectivity in locations where cellular coverage is poor and lots of intrasite communication occurs.
If the WLAN infrastructure is ignored as a sunk cost for regular data support, the $300 to $600 price per single-mode Vo-Fi handset is not unreasonable compared with the $250 to $750 tab for today's digital and IP desk sets. Of course, a mobile worker also may have his own or a shared desk set, but the companies that we spoke with consistently said that productivity increases offset those costs.
List prices for single-mode phones range from $300 to $600 each, with accessories, supporting infrastructure and extended warranties extra. SpectraLink introduced a new line of single-mode phones with the NetLink 8000 series but told us it intends to continue marketing its hardy e340 device with a SIP load, and push the price down into the sub-$300 range, to attract the small-business market.
Dual-mode phones are higher, $500 to $700, and prices will likely stay somewhat stable as dual-mode smartphones, which incorporate multiple radios, continue to develop into multimedia computing devices.
Despite the price gap, both Disruptive Analysis and Infonetics Research say sales of dual-mode phones will soon overtake sales of simpler single-mode devices. Infonetics predicts that by 2009, 91 percent of handset revenue will come from dual-mode.
List prices for single-mode phones range from $300 to $600 each, with accessories, supporting infrastructure and extended warranties extra. SpectraLink introduced a new line of single-mode phones with the NetLink 8000 series but told us it intends to continue marketing its hardy e340 device with a SIP load, and push the price down into the sub-$300 range, to attract the small-business market.
Dual-mode phones are higher, $500 to $700, and prices will likely stay somewhat stable as dual-mode smartphones, which incorporate multiple radios, continue to develop into multimedia computing devices.
Despite the price gap, both Disruptive Analysis and Infonetics Research say sales of dual-mode phones will soon overtake sales of simpler single-mode devices. Infonetics predicts that by 2009, 91 percent of handset revenue will come from dual-mode.
