TAS: an Evolution in Wireless Communication Performance

A modern-day smart wireless device is equipped with a multitude of radios employing 4G, 5G, Wi-Fi, and Bluetooth technologies, and each radio uses multiple antennas covering a wide variety of frequency bands to ensure the high user experience expectation of modern-day users. To meet these high user expectations, product design engineers have taken great care to maximize the transmit power of these radios to ensure that the Netflix movie or YouTube video you’re streaming on your smart wireless device won't be slowed or interrupted by a poor wireless signal.

Regulatory bodies of various countries and regions worldwide have set SAR criteria that all portable (i.e., used with 20cm of the human body) wireless devices must meet to protect users from exposure to excessive electromagnetic energies generated by these devices.

 

With a portable wireless device having multiple radios that transmit at maximum power for an extended period of time, however, the SAR level could easily exceed the regulatory limit, given the direct correlation between the SAR level and transmit output power level. To address this challenge, radio chipset manufacturers have developed what is called the time-averaged SAR (TAS) algorithm to intelligently manage transmit power across multiple radio antennas. This guarantees that the level of SAR will remain within the regulatory limit over the specified time period, while still allowing the device to maintain an optimal over-the-air transmission performance. 

 

Here is an illustration of a comparison between a wireless device employing a TAS algorithm and one that does not employ a TAS algorithm:
The advantages of employing the TAS algorithm: Power consumption is optimized for longer battery life. Exposure is kept under the SAR limit while a network connection can still be maintained. Products applicable:  smartphones, tablets, laptops, smart watches, hotspots, etc.
As illustrated in the chart on the left, in the absence of the TAS algorithm, once the radio transmits at maximum output power for an extended period of time, the call must be terminated to comply with the SAR limit.  As illustrated in the chart on the right, with the algorithm enabled, the radio would transmit at maximum output power for a specified period of time, but instead of dropping the call to comply with the SAR limit, the power is reduced to a level that allows the call to continue while still meeting the SAR limit.

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Understanding TAS Using an Analogy
Explaination	Using personal expenses as an example, assuming you have a monthly budget of $900 Daily spend limit (dotted green line): $30 Actual daily spend (red line): over $30 on some days and under $30 on some days Average daily spend (blue line): Under $30 for the entire month.	Applying this concept to TAS Regulatory SAR limit = daily spend limit (dotted green line) Peak SAR = actual daily spend (red line) SAR with TAS = average daily spend (blue line)

 

SGS Taiwan boasts the most complete TAS verification scope out of all the labs in Taiwan:

Wireless Technology	Chipset Provider	Algorithm Name	Version Differences	Status
WWAN	Qualcomm	Smart Transmit		Approved
		Smart Transmit™ 2.0	Power backoff	Approved
		Smart Transmit™ 3.0	Antenna group for EFS v19+	Approved
		Smart Transmit™ 4.0	Satellite Messaging (QSM) for EFS v20+	Approved
	Mediatek	Time Average SAR (TA-SAR)		Approved
		Time Average SAR (TA-SAR) 2.0	Antenna group, NTN, 3TX exposure switch	Approved
		Time Average PD (TA-PD)		Approved
		Time Average PD (TA-PD) 2.0	ECI change, Multi_SPLSR FR1+FR2 switch	Approved
	Intel	Time Average SAR (TA-SAR)		Approved
WLAN	Qualcomm	FastConnect™ WIFI TAS		Approved
	Mediatek	Time-average Tech 1.0WL		Approved
		Time-average Tech 2.0WL	TER for Wi-Fi & BT simultaneous transmit	Approved
	Realtek	Time Average SAR Control 1.0		Approved
	Intel	Time Average SAR		Approved

 

If you want to know more about IOT-NTN or certification requirements, please contact us:

📧  twwireless.MKT@sgs.com  ☎ (02) 2299-3279 # 1530 / 1522 / 1567