OS X WiFi Latency Problem Identified?

SUMMARY: Keeping the MacBook's wireless adapter "busy" with traffic seems to prevent it from entering a "micro-sleep" state; This "micro-sleep" can result in highly variable ping latencies which are often improperly interpreted as a "bad" WiFi connection.

BACKGROUND
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Many have complained about sub-standard WiFi performance on their recent MacBook / MacBook Pros. Many have cited inconsistant ping latency as the "smoking gun" which makes their case. Unfortunately, ping, and the default timing of each ping counter this theory.

ICMP (of which ping is a part) is one of the first traffic classes that a modern TCP/IP stack will purposely drop as various resources become limited. It's therefore counterintuitive that INCREASING the amount of traffic on a wireless connection would DECREASE the overall network latency.

The default timing of one packet per second means that Mac OS actively uses the NIC for 0.002s out of every 1 second in realtime. ( time ping -c 1 some_LAN_ip ). In the remaining 0.998 seconds, when possible, the MacBook's aggressive power saving algorithms will put the wireless adapter into a "micro-sleep" state. In this state, processing a ping reply is rightly delayed until the next time the adapter wakes up.

By keeping the adapter "awake" with traffic, in this case by sending 10 pings per second, the OS replies to the ping replies without delay as they come in, resulting in a streak of improved latency. The variable latency returns shortly after adapter activity returns to one ping /sec.

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