Design Article
How Bluetooth, UWB, and 802.11 stack up on power consumption
Gadi Shor, CTO, Wisair
4/15/2008 7:05 AM EDT
By 2013, analysts predict that one in every three mobile phones sold will be a smartphone. Entertainment-based mobile devices are also on the rise with the digital still camera (DSC) household penetration rate expected to reach 80% by 2010 in the United States alone.
Wireless technologies such as Bluetooth, Ultra-wideband (UWB) and WLAN, all make this wireless data transfer viable today, yet each has its own obstacles which makes its use in the mobile market challenging. Additionally, due to the inherent nature of each of these technologies, some may be better suited than others in applications requiring, for example, a high bandwidth or a wide operating range.
In the case of the mobile market, one of the main requirements is long battery life. Therefore, one key factor that must be evaluated when determining which technology to implement in a mobile device design is power consumption.
Throughput is also an important factor as it contributes to the technology's overall power consumption. Choosing the right wireless technology is crucial to developing an optimal, commercially-viable mobile device.
Understanding power consumption
At the end of the trip, the consumer returns home only to find that the camera has a mere 5% of its battery power left, making it impossible to transfer the camera's content to another device, such as a desktop computer.
During typical camera usage, this is exactly the type of capability that today's consumer demands.
Given this scenario, it is easy to see why low power consumption and high throughput are so critical. Standby power and active power consumption (e.g., in a cellular phone the power attributed to talk time, or in this case, attributed to data transfer) must therefore be reduced in order to increase battery life.
Consequently, today's designers require implementation of a wireless technology which supports multiple low power modes, regardless of whether the device's active power is on or it is in standby mode.
Throughput (e.g., power per Mbit of data) also plays a critical role here because even if a protocol's active power is high, it may ultimately exhibit the lowest total power energy consumption, and therefore provide the best power efficiency, if it transfers data extremely fast.
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Santhoff
4/17/2008 1:02 PM EDT
UWB does indeed have the lowest power consumption of any wireless technology available today at the PHY Layer. What is meant by at the "PHY Layer" is the actual radiated Radio Frequency energy used to close a link budget. What the article does not say in the case of the WiMedia implementation is the huge complexity and associated power consumption inherent in both the Transmitter and Receiver design of WiMedia devices. The Transmitter requires a 6 bit DAC at 1+ GHz to generate the OFDM symbol and the Receiver requires two (For I/Q RF) ADC's using 4 to 6 bits at 1+ GHz to process the received RF. These by themselves are highly power consumptive now add the digital baseband processing to feed and process the DAC and two ADC's and you really start getting into some power. (We haven't even talked about the FEC processing yet) Bottom line, UWB over the air PHY interface is the lowest power wireless technology available today. HOWEVER, I am not aware of ANY WiMedia implementation that is less than 2 Watts which is a long way from the claimed 250mW.
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