Besides MIMO performance, chipset size and power requirements are important.

In mobile WiMAX, initial user devices will be laptops and handhelds such as smartphones and PDAs. These devices require Wave 2 chipsets that have minimal power consumption and are physically small. Those requirements are different from a fixed WiMAX (802.16d) environment, where most user devices are gateways that sit on a desk and plugged into a wall outlet.

Consequently, the mobile WiMAX chipsets must be developed from the ground up for a mobile environment where footprint, cost and power consumption are critical. The BCS200 is the first Wave 2 chipset and has a small footprint suitable for handheld devices. It has lower power consumption than Wave 1 despite the improvement in performance and features. Small footprint and power consumption are key in the eyes of service providers who cannot afford to launch mobile WiMAX devices that are bulky and have short battery lives.

Chipset size, cost and power consumption aren't the only factors that determine a device vendor's ability to bring competitive products to market. Another consideration is the chipset's ability to support multiple bands and channel bandwidths with a single compact design.

For example, the BCS200 features a direct-conversion radio (DCR), which eliminates the need for surface acoustic wave (SAW) filters. This design allows manufacturers to develop a single 802.16e product SKU that can be applied into multiple mobile markets, each of which has different mobile WiMAX spectrum bands. With the BCS200, device makers can provide the same hardware design for use in any of the four primary mobile WiMAX bands — 2.3 GHz, 2.5 GHz, 3.3 GHz and 3.5 GHz — operating with variable channel bandwidths from 5 MHz to 10 MHz, all enabled through software. Figure 4 shows the block diagram for a mobile WiMAX Wave 2 modem with multiband, multichannel direct-conversion radio.

By comparison, 802.16e chipsets that use SAW filters limit device vendors' options. That's because SAW filters for different bands and bandwidths have different footprints. Hence, if a device maker plans to switch to a different type of SAW filter to enter another market with different requirements, then it has to redesign its board to accommodate the new footprint. Not being able to provide a single, software-defined radio solution renders the device vendor's position uncompetitive, in addition to the added cost and time to market.

The flexibility of the BCS200's DCR, on the other hand, enables global mobile WiMAX roaming by allowing a device that works at 2.5 GHz frequency and 10 MHz channel bandwidth in one operator's network to switch seamlessly to 2.3 GHz and 8.75 MHz channel bandwidth in another operator's network, which is key for service providers who target enterprises and international business travelers. Considering that those users will be mobile WiMAX's early adopters and the most coveted, lucrative customers over the long term, 802.16e devices that can accommodate their global roaming needs will be particularly attractive in the eyes of service providers.

Eliminating SAW filters has side benefits. For example, it reduces the chipset's component count and its bill of materials (BOM).

Furthermore, mobile WiMAX is likely to mimic cellular with respect to integrated baseband and RF functions. Having benefited handset makers, this trend will quickly play out in mobile WiMAX arena, too.

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