CODEWITHSUNDEEP
androidnetwork-programmingwifi
Ranjith
Ranjith

Reputation: 181

android wifi network latency galaxy s2

i am trying to estimate network delay between two android devices connected over WiFi to synchronize clocks. but the network delay is varying a lot from 2ms to 1024ms. sometimes i gets delay value which varies between 2-10ms for continuous 100 readings. but sometimes values ranges between 2ms to 1024ms for continuous 100 readings like 2, 100, 570, 640, 2, 5, 150.

I am using socket timestamps to determine the exact receive and send time of the packet. my setup uses one laptop as wifi access point and two mobile phones. There is not much load on the network. my question is why is it varies less sometime and why it varies so much sometimes.

How to make it vary less. am i missing any configuration on android. Give me some possible reasons for this kind of behavior...

Upvotes: 0

Views: 845

Answers (2)

Ranjith
Ranjith

Reputation: 181

Solved this problem by using WIFI_MODE_FULL_HIGH_PERF. After acquiring this lock, i have observed constant network delays.

http://developer.android.com/reference/android/net/wifi/WifiManager.html#WIFI_MODE_FULL_HIGH_PERF

Upvotes: 1

SomeWittyUsername
SomeWittyUsername

Reputation: 18368

Unlike wired links, wireless links are affected from a lot of different factors. You can get stable results only in a sterile environment without electromagnetic or mechanical interferences.

Most latency fluctuations are a direct result of RF collisions. WiFi networks implement the CSMA/CA protocol to deal with the collisions. In general it detects whether there is any activity in the air and postpones the transmission if it's noisy.

You can try to minimize the external influences but still this doesn't guarantee anything:

  • Perform WiFi scan and see what channels are the noisiest. Choose the less occupied for our link. Remember, there are overlaps between various channels, so moving to a different channel won't necessary remove all the noises. See here about channels overlapping and how to choose a channel: http://en.wikipedia.org/wiki/List_of_WLAN_channels .

  • Remove mechanical obstacles from your environment.

  • Increase the transmission (Tx) power of your devices from their SW configuration.

  • Check the Quality of Service (QoS) configuration of your devices, some tweaking there might yield improvements.

Upvotes: 3

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