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The long awaited Wi-Fi/cellular handset and VoIP over WLAN system from the partnership of Motorola, Avaya and Proxim will launch in September, but will require enterprises to invest in 802.11a systems.

Article courtesy of ARCchart Limited

Mandating 802.11a may be a double-edged sword. o­n the o­ne hand, in the enterprise market that the trio is targeting with its voice over Wi-Fi development, 802.11a will certainly produce better performance, since it runs in 5GHz spectrum and therefore is less susceptible to interference, latency and packet dropping problems that arise in the overcrowded 2.4GHz band.

On the other hand, it will compel organizations to upgrade their WLANs, and so may slow uptake in companies where VoWLAN does not have an urgent business case, by adding to the required capital investment and disruption – especially as ‘a’ systems do not interoperate with older ‘b’-only networks.

Also, by providing o­nly o­ne network option, the Motorola group is backing a technology that some observers believe is dead in the water. Although ‘a’ has generally been accepted as being more suitable to enterprise use than the other fast option, 802.11g – because of its lower interference levels and the higher real world speeds it achieves through having 21 non-overlapping channels - the latter has been adopted enthusiastically. It provides an easy migration from ‘b’, and a fairly cheap o­ne, since fewer access points are required than with ‘a’, so that its momentum may now be unstoppable.

However, there is now a range of dual-radio a/g equipment o­n the market and the high quality of service requirements of voice or video over WLAN could well create a new surge of interest in ‘a’. At a recent mobile enterprise summit in London, several integrators said they were recommending customers to implement dual WLANs – a viable option given the relatively low cost of equipment – with ‘g’ being used for data and either ‘b’ or ‘a’ for voice. With ‘a’, a heavy voice user could allocate several channels to voice and so ensure that the system did not fail because of poor performance and therefore low user support – a very real risk in some early deployments.

A more compelling option for 802.11a is via products that have multiple radios or multiple channels in a single box, such as products powered by Engim’s chipset. In that model, because each access point could have several hundred Mbps of actual throughput through bonded or standalone channels, it would be worth deploying the denser installation required by 802.11a. 802.11b and g have substantial limits o­n total system speed because of their staggered and overlapping channels.

Proxim claims that o­nly ‘a’ is well suited to enterprise class voice applications because it has 21 non-overlapping channels rather than a staggered channel scheme like ‘g’, and so can support about 25 VoIP calls at a time from o­ne access point. It points out that savings o­n cellphone bills should cover the cost of upgrading to 802.11a within a few months.

Motorola launched its first Wi-Fi/cellular handset, the Windows-based MPx100, in February, but this was targeted at operators, while the Avaya/Proxim system will be sold through enterprise channels. The giant claims that the so-called ‘Enterprise Phone’ will have a lightweight battery that will provide talk time of 10-12 hours and standby time of 24 hours, not too far from high end cellphones in terms of battery efficiency, o­ne of the key user criteria when adopting handsets.

New chipsets are helping to improve the battery life and Motorola is thought to be using silicon from Texas Instruments. Broadcom and Philips started the trend towards low power, often single-chip implementations of 802.11b, with a sharp eye o­n the handset market, last autumn and have been followed into the space by TI, Atheros and Conexant, with TI – predictably, given its power in the phone market – taking the technological high ground in dual-mode handsets.

In March, it came up with a roadmap that showed it determined to dominate the dual-mode platform and so far it is working with both the majors that have already launched Wi-F-/cellular devices, Nokia and Motorola. Its 802.11g/b and 802.11a/g/b offerings, also launched in March, are the first of the highly compact Wi-Fi chipsets o­n the market to support 802.11g and be targeted at phones. (Atheros, which was the first to launch a single-chip solution supporting ‘g’, says it has no plans to target handsets.)

The two-chip TI product builds o­n the company’s recent work o­n shrinking down the components to achieve chipsets compact and power efficient enough to be viable for phones. It is working o­n a single-chip solution for the future based o­n its ground breaking Digital RF architecture, which it outlined at February’s International Solid State Circuits conference.

The chipset is designed to be used with TI’s OMAP application processors, GSM, GPRS, CDMA and EDGE chipsets and single-chip Bluetooth solution. Architecture innovations in the TNETW1250 such as o­n-chip power management, reuse of cellular clock frequencies, and low pin-count host interfaces were included to eliminate barriers for integration of WLAN into cellular handset designs.

As important as battery life to a successful voice over WLAN strategy will be hand-off and Motorola says it has developed, with Proxim and Avaya, new techniques to hand off the call between a WLAN and a cellular network, although there are no details as yet.

The full system from the trio will work with Proxim switches and will provide the functions of a wired corporate desktop phone o­n a mobile handset, working through an Avaya PBX and able to handle four incoming lines. Features such as forwarding calls and conferencing will use ‘soft buttons’ that mimic the functions of buttons o­n a desktop telephone, which could be entirely replaced by the new system.

The main Proxim contribution to the system will be based o­n the Orinoco Switching System it launched earlier this year, as a challenge to the Wi-Fi switch start-ups. The system is optimized for VoWLan and promises to support seamless hand-off between subnets and between cellular and Wi-Fi connections, as well as load balancing and fast authentication, all features essential for voice quality of service.

It can operate as a standalone 802.11 product, but can also be deployed as a voice-optimized add-on for conventional switched networks.

Key to voice over WLAN uptake in the enterprise will be the 802.11e quality of service extension to the Wi-Fi standard, and a more distant specification for fast hand-off. Proxim has been involved in both developments and says it will support as much of the standards as is possible until they are fully ratified, and will also incorporate 802.11i security when that specification is finalized.