With OptimizAir, the Wi-Fi radio chip is no longer a passive provider of access: it can enforce pre-provisioned rules, based on a range of criteria, to restrict clients to a window of transmit time. "You can adjust this time bucket' in real time to deliver specified throughput" for each client, Weiss says.
How this capability will be applied is unclear, because it hinges on what the service provider priorities are, and their assessment of how to optimize the wireless experience for their customers.
Weiss thinks that these providers are likely to use the new OptimizAir capability to create two or more SSIDs for a given Wi-Fi access point and, within each SSID, a "hierarchy" of client devices. One SSID might be reserved for home automation sensors, another for the provider's Wi-Fi enabled set top box, another for a public Wi-Fi hotspots. Initially, the airtime/throughput tradeoff could be "set in stone" with specific allocations for each SSID. That could be expanded to specific allocations for different classes of devices.
"I envision that the time is divided evenly," Weiss says. "This alone will take you a long way. Today, the strong clients are killing the clients farther away. Sometimes it's vice versa. It's never balanced out and this balances it out."
The concept of airtime fairness in Wi-Fi is not new, as Weiss acknowledges. WLAN vendors have focused on it as a way to improve client performance. The idea is to collect more information about, and from, Wi-Fi clients, and then use an array of techniques and clever tricks to let the network exercise more control over the vagaries of client wireless behaviors. In some cases this has meant shifting clients from one frequency to another, or to a less loaded access point.
Aerohive, Aruba, Cisco, Meru and Motorola, to name just a few all offer some form of airtime management, as Network World's Wireless Alert blogger, Joanie Wexler noted in a 2009 blogpost.
"[T]hey dynamically determine the exact amount of airtime each client is consuming in microseconds," she wrote. "They then adjust the number of opportunities each client gets to transmit, using algorithms that account for each client's characteristics, such as current throughput, distance from the AP and even 802.11n's comparative efficiencies such as packet aggregation and 40MHz channels. The primary goal is to ensure that the slowest client doesn't set the pace for all clients on the network and monopolize the air."
Broadcom promotes "airtime fairness" as a feature of its enterprise-focused, 802.11ac BCM43460 system-on-chip, first announced in early 2012 for release in the second half of that year.
Celeno's OptimizAir 2.0 firmware is sampling with customers now.
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