Addressing the Challenges of Wireless Convergence
Addressing the Challenges of Wireless Convergence
By: Gavin Stone
Jan. 1, 2000 12:00 AM
Developing multimode (or even dual-mode) products is far from being an easy task. For a product to have any hope of success in a marketplace that is as competitive as the wireless industry, there are many challenges that need to be addressed simultaneously. Both near- and long-term strategies are necessary.
The wireless industry is driven by network operators trying to generate as much revenue as possible from consumers by providing them with services they can't do without. Services like mobile voice and messaging have become commonplace while more advanced services like mobile e-mail, video, and gaming have yet to attain "indispensable" status. As the next generation of wireless mobile networks becomes a reality, these new services will be made available only in areas likely to generate maximum return on investment for the carrier.
Blanket coverage is an expensive exercise, especially when most of your revenue-generating consumers are concentrated into specific areas. For 3G Wireless Wide Area Networks (WWANs) like WCDMA, the most attractive coverage areas are metropolitan regions, and for Wireless Local Area Networks (WLANs) like 802.11, these coverage areas include places like airports, coffee shops, hotels, and conference centers.
Additionally, most of the network operators who are currently implementing 3G and/or WLAN networks have existing 2G/2.5G networks like GSM/GPRS. These networks already have extensive coverage areas and offer voice and limited data services to a wide base of consumers.
Each of these wireless communication technologies has different access speeds, coverage areas, and subscription fees, and could well require the user to maintain multiple accounts to utilize the services. Mobile users wanting to make use of the most appropriate services are currently required to carry multiple mobile radio access devices or to choose only one wireless access technology with limited coverage or data-rate capability. These solutions provide a less than optimum user/service experience. Based on this, the corresponding expected uptake of "integrated" services offered in such an ad hoc manner will be limited to niche markets at best.
Next-generation wireless mobile devices need to be capable of using multiple WWAN and WLAN technologies to access services, information, and content. These terminals must be able to dynamically select the most appropriate access technology (or technologies) depending on the application.
An example of such a wireless mobile device is one that is able to operate on GSM/GPRS, WCDMA, and 802.11 networks. This would enable the consumer to have high-speed/local-area connectivity indoors (802.11), medium-speed/wide-area connectivity outdoors (WCDMA), and low-speed/wide-area connectivity outside of metropolitan regions (GSM/GPRS) as shown in Figure 1.
It also enables applications to select the lowest cost access method (least-cost routing) depending on the required Quality of Service (QoS). The uptake of products with these integrated capabilities is expected to be significantly enhanced.
The development costs associated with creating a completely new product are extremely high, especially when integrating multiples of these wireless access technologies into the same handheld mobile device. Add to this the significant development risk and the extensive development time associated with such a complex integration, and the challenge is compounded even further.
Problems such as high power consumption (reduced battery life) and increased interference also have to be solved before a multimode converged solution can be successful. Currently the power budget for single-mode 802.11 implementations is more than double that which handheld mobile devices can handle and still maintain a satisfactory battery life and adequate communication range. Thus, to include 802.11 into a battery-constrained mobile device would require a significant decrease in power consumption by at least 50%. This does not even take into account multimode scenarios that would require more than one access technology to be in operation concurrently.
So, you can see that developing multi-mode (or even dual-mode) products is far from being an easy task. For a product to have any hope of success in a marketplace that is as competitive as the wireless industry, these challenges (and others) need to be addressed simultaneously.
Addressing the Challenges
The integration of a new, highly complex technology like WCDMA with an existing GSM/GPRS solution at the silicon level, results in a new, even more complex and totally unproven single-chip solution. Because of the complexity of such a tightly integrated solution, the development time and cost, not to mention testing on the various networks, are also factors that could result in the product being uncompetitive.
Already, network operators are claiming handset shortages and reliability as one of the major factors delaying the rollout of 3G networks, and handset manufacturers are attributing this shortage to the lack of market-ready dual-mode chipset solutions.
When looking at a converged cellular and WLAN solution, the prospect of chip level integration becomes even more daunting. "The convergence of WLAN and cellular capabilities into a single device will provide a significant challenge at the chip level," says Navin Sabharwal, director of residential & networking technologies at Allied Business Intelligence. Physical chip size, yield, and integration complexity are just a few of the issues that need to be addressed.
A simpler approach is needed in the near-term to ensure that the products consumers want are brought to market quickly and remain affordable. This low-cost, low-risk approach is far less complex and calls for integration at the product level and not at the silicon level. In other words, reuse the existing 2G/2.5G chip, develop a new 3G chip designed to connect to the 2G/2.5G chip, and provide a two-chip dual-mode solution. The challenge here is to develop the new 3G chip in such a way that it is able to connect to a variety of different 2G/2.5G chips.
This innovative approach limits development time and production costs by leveraging a proven GSM/GPRS chipset without the need for redesign. Development risk is also minimized by reducing the amount of integration required and by validating the new WCDMA chipset prior to integration. In this way, a mobile device using a two-chip dual-mode GSM/GPRS and WCDMA solution, based on an existing GSM/GPRS chipset, can be brought to market quickly and cost effectively with the least amount of risk and reduced need for network testing.
Although somewhat more complicated, this "add-on" approach can also be used to create a multimode chipset solution that integrates WWAN and WLAN technologies. Once again, the WCDMA and 802.11 chipsets are designed to connect to the existing GSM/GPRS chipset (see Figure 2).
However, the method of integration is not the biggest problem to be dealt with when incorporating 802.11 into a handheld mobile device. Navin Sabharwal agrees: "Only by dramatically lowering the power consumption of 802.11 solutions will it become feasible to add WLAN functionality to mobile devices such as PDAs and cellphones." Significant power consumption, interference, and range issues need to be overcome prior to integration.
Currently, some manufacturers are reducing transmission power of 802.11 solutions, and thus sacrificing a considerable amount of range, so as to fit within the power budget of a handheld mobile device. An emerging technology called Space-Time Processing (STP) utilizes multiple antennas and advanced signal processing to cancel interference, extend range, and reduce the required transmission power of the mobile device. STP can extend the range by up to four times when four antennas are used and can cancel interference from cordless phones, microwave ovens, and other 802.11 users. This results in a considerable reduction in required transmission power and enables the 802.11 solution to be integrated into a multimode handheld mobile device.
This solution is specifically designed for the near term by simultaneously addressing all of the challenges to produce a viable multimode converged product. As these new 3G and WLAN technologies become more mature and are proven, the cost and risk of silicon-level integration becomes less and will become the optimum method. For the time being, product level integration will remain as a highly attractive and very flexible alternative.
Creating converged wireless products is not, and will never be, a simple undertaking. The challenges facing the product manufacturer are many and varied. By addressing these convergence challenges with a low-risk, low-cost approach and by having both near-term and long-term strategies, product manufacturers give themselves the best chance of success in the highly competitive wireless industry.
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