iPhone 6 Wandering Actions and Optimization

Executive and Suggestions Summary

IOS 8 gadgets try to wander when their associated BSSID indication drops below –70 dBm RSSI. The IOS 8 gadgets then examine out all programs (without 802.11k) or the focus on programs conveyed by their present AP (with 802.11k enabled), and wander to another AP if its indication is 8 dB better (IOS 8 system in effective communication) or 12 dB better (IOS 8 system in idle) than the present AP.

Roaming activities are crucial for VoWifi and business-critical real-time company programs. Effective roaming time is 50 ms. Without 802.11k allowed, dual-band SSIDs, and conventional AP solidity, the overall loss of relationship for an IOS 8 system can achieve 5 a few moments for each wander. With 802.11k allowed, greater AP solidity (AP every 2500 sqft or every 240 sqm), and system developed with 5 GHz, the roaming activities can achieve sub-second.

When developing wi-fi systems for real-time program activities, plan for 5 Megabyte per second per customer and 12 – 14 clients per AP. Make 5 GHz and 802.11k as part of your style requirements for cell mobile phones.

Context

Mid Nov 2014, The apple company assistance released a referrals papers describing how IOS8-based gadgets wander (http://support.apple.com/en-us/HT6463). This website access is based on this referrals papers, but with included lab + actual system dimensions (to differentiate excellent intents from realistic actions in actual world).

The roaming behavior is identical for Refurbished iphone 6, Refurbished iphone 6 plus, Refurbished iphone 5c, Refurbished iphone 5s, iPad Air, and iPad small with retina. The searching behavior also is based on the chipset used in the product. You will see common behavior factors identified by the OS, but also little clock modifications between designs identified by the chipset and its car owner. For example, does the product sensor / probe once or repeatedly per “probe burst”, how many milliseconds between the sensor / probe demands in a given rush, and so on. This papers concentrates on the normal behavior, but the electronic timers proven were calculated on Refurbished iphone 6, using a Broadcom BCM4339 chipset. The behaviour was examined on IOS 8.1.

How Often Does My Refurbished iphone 6 Scan?

When you are NOT associated to any SSID, and your display is off (for example, your cellphone is in your pocket), your cellphone will look into the atmosphere at frequent durations for SSID by delivering sensor / probe demands. The cellphone will examine out more often if you progress (that is, the indication from APs differ, see the When Does My iPhone Roam?, on website 3 area, as the behavior is similar). So let us believe the most severe situation, you are not shifting.

If your mobile details are not available and Place (Settings > Comfort > Place Services) is impaired, your cellphone on the other hand uses its actual MAC deal with and a regionally applied deal with. The idea is to momentarily cover up your actual MAC deal with for privacy reasons. In that place, the product delivers instant sensor / probe demands with the actual MAC deal with. The cellphone then remains quiet for a “random interval” (in the order of 140 seconds), before delivering between one and six probes with a regionally applied deal with, at 135 or 270 second period. The cellphone then remains quiet for another exclusive period (up to 10 minutes) before going returning to the actual MAC deal with and restoring the pattern. The cellphone options a new regionally applied deal with when changing between actual and regionally applied details.

An example of the behavior is proven in the following determine. The horizontally axis symbolizes the catch quantity of second (capture was taken over 8.5 hours, or 30 K seconds). The straight axis symbolizes the period between two successive sensor / probe demands. Nowhere principles are probes using the actual MAC deal with, and the red principles signify probes using a regionally applied deal with. For example, at 5000 second, 322 a few moments after the last sensor / probe demand using a regionally applied deal with, the product delivers a sensor / probe demand using the actual MAC deal with (blue dot at [5000,322]). After 20 milliseconds, the product delivers a second sensor / probe using the actual MAC deal with (point that seems to be at [5000,0], but is in fact at [5000.02, 322.02]). The cellphone then remains quiet for 135 a few moments before delivering a sensor / probe using a regionally applied deal with. The cellphone then delivers two more probes at 135 a few moments period, then two more probes at 270 a few moments period, and remains quiet for 204 a few moments before delivering a sensor / probe with the actual MAC deal with.

Notice that some catch and accident relics incorrectly display regionally applied deal with probes at large durations (beyond 270 seconds).

The regionally applied deal with is not used any longer as soon as you affiliate to a WLAN or if mobile details or Place are allowed. In these instances, the product will examine out your focus on SSID at 90 a few moments period (or the transmitted, if you are not associated), in a form of "maintenance mode". This supposes that the AP indication is constant and display is off (for example, your cellphone is in your wallet while you sit at the shopping center food court).

If you start using your cellphone (actively using the Wi-Fi connection), the product prevents searching, as it uses the AP shining example information details supports to look at the AP indication stage. The Refurbished iphone 6 (with the BCM chipset) still delivers a 'reflex probe" to your SSID every 30 moments. Other designs may have a a little bit different behavior. The IOS 8 element does not ask the product to sensor / probe.

When Does My iPhone Roam?

The Refurbished iphone 6 does not use the accelerometer to find out that you are shifting, and the AP indication needs to examined. It is based completely on the AP alerts to the product to find out if roaming is needed. The limit is –70 dBm. This implies that as lengthy as the AP indication (beacons details frames) is more powerful than –70 dBm, the product does not try to examine on out more definitely or wander.

As soon as the AP RSSI, as read by the product car owner, drops below –70 dBm for more than one second, the product selects that the present AP is useless and selects to wander, which activates checking.

At this aspect, several opportunities exist:

1 You designed your system to use 802.11k. This selection allows the AP to deliver a record of nearby APs to the product upon demand. In that place, the product assessments the best six APs, and tests their programs.

For example, your present AP is on route 36, and the revealed APs are on programs 40 (–68 dBm), 44 (–76 dBm), 48 (–72 dBm), 52 (–78 dBm), 56 (–59 dBm), 60 (–75 dBm), 149 (–74 dBm), 153 (–70 dBm), 157 (–71 dBm) and 161 (–63 dBm). The cellphone discovers that the best six APs are on programs 40, 48, 56, 153, 157 and 161, and delivers sensor / probe demands for the focus on SSID to these programs.

Be cautious, these alerts are revealed as observed by the AP, not as observed by the product. Also, the Refurbished iphone 6 demands the record of next door neighbor APs when coming into the mobile (right after association), not when roaming. So, the record may not be the newest (see the Effect on Your Design, on website 5 area about style recommendations).

2 You did NOT set up your system to use 802.11k. In these instances, the product tests all programs (this can be 11 or 13 programs in 2.4 GHz, and up to 13 programs in 5 GHz). The cellphone tests UNII1, UNII2, and UNII3. The cellphone can also examine UNII2-e, but only passively. The cellphone tests UNII2-e every 6 checking pattern. This is because this group remains safe and secure by 802.11h, and the product has to pay attention passively (no effective scanning) until it listens to an AP. So, discovering APs in UNII2-e can take more than a moment. Even checking the other programs needs time. Anticipate several a few moments for this technique. It requires of course longer if the product is definitely interacting on the AP present route, because the product has to find an period where no details are predicted to leap to the focus on route to examine on out. If the product is not interacting, checking is quicker.

In both situations 1 and 2, the product tests and looks for a better AP to leap to. Realize that the product does not try to keep in the same group, it can leap from 2.4 GHz to 5 GHz or the other way around, even on the same AP. The roaming requirements blogs about the BSSIDs that were recognized (that is, the initial MAC deal with of each stereo providing the focus on SSID name) to the present AP BSSID indication stage. Then, the roaming decision is based on if you are definitely using the Wi-Fi system (traffic to and from the phone) or not (phone is nonproductive or display off, in your pocket). If you are not using the Wi-Fi relationship, the product will only leap if another AP provides a indication really better than the present one. It needs to be at least 12 dB better. If the new AP indication is at least that much better, your cellphone roams. If no recognized stereo has a indication 12 dB or more better than your present AP, the product remains on the present AP, but keeps checking at 90 second durations until it discovers a better BSSID (12 dB better than the present AP BSSID) or until the present AP indication returns above -70 dBm.

If you are using the Wi-Fi relationship, things are more pushing. The cellphone identified that –70 dBm was a inadequate indication and is ready to leap previously. It will wander to a new stereo if the BSSID is 8 dB or more better than the present AP. For example, if your AP stereo indication decreased is to –72 dBm, and the product finds BSSIDs for the same SSID name at - 61 dBm, -63 dBm and -69 dBm. In situation if you are definitely using the Wi-Fi, the product allows to wander to the BSSID at –61 dBm and to the BSSID at –63 dBm. Because, they are 8 dB or more better than the present AP (11 dB and 9 dB better respectively). The cellphone does not wander to the BSSID at –69 dBm, because it is only 3 dB better than the present AP. Having two options, the product selects the BSSID with best indication, and roams to the BSSID at –61 dBm.

If no BSSID is recognized at 8 dB better than the present AP, the product remains on the present AP, but keeps checking at 90 a few moments durations (one sensor / probe demand followed by a second sensor / probe demand 10 nanosecond later) until it discovers a better BSSID (12 dB better than the present AP BSSID) or until the present AP indication returns above –70 dBm. The following chart reveals this behavior with an Refurbished iphone 6 on a dynamic Wi-Fi relationship, managed far from its AP (signal at around –75 dBm) without different AP to leap to.

Enabling 802.11k

Roaming with an IOS 8 system is more effective if you apply 802.11k than if you do not apply 802.11k. This is because the checking time is smaller with 802.11k. In the following example, an iPhone was transferred to and fro between two APs. The APs were far enough from each other that the iPhone would combination the –70 dBm advantage while shifting from one AP to the other.

Both APs had the same SSID allowed, available on both 2.4 GHz and 5 GHz. Energy was set to 3 on 5 GHz, and 5 on 2.4 GHz, making the 2.4 GHz mobile about only 30% greater than the 5 GHz mobile.

Without 802.11k allowed, roaming periods are lengthy. Moving to and fro 3 periods between APs display several roams (more than the predicted six roams). This is because the iPhone leaps from 5 GHz to 2.4 Ghz, then returning to 5 when getting near the next AP. The common roaming time (time between the last bundle recognized to or from the product on one AP and the first bundle to or from the product on the next AP) was near to 5 a few moments. This implies, generally, your cellphone drops its relationship (no communication) for near to 5 a few moments when roaming.

With 802.11k allowed, the frequent roaming time is down to about 1 second. These activities can be improved to achieve sub-second with counsel below.

Configuring the Band

Enabling 802.11k improves roaming efficiency, but does NOT restrict the iPhone to one group. Automatically, 802.11k provides details about nearby APs only on the consumer group. In other terms, if your iPhone is associated to the BSSID on 5 GHz, the AP will provide details about nearby APs in the 5 GHz group, not in the 2.4 GHz group. But this does not mean that the iPhone will remain on the 5 GHz group.

When an SSID is available on both groups at "good indication level" (more than -70 dBm RSSI), the iPhone will affiliate in concern to the 5 GHz stereo. However, at equivalent AP power, at any reason for the mobile, the 2.4 GHz indication is generally about 7 dB more than the 5 GHz indication. This distinction is due to common technical variations in aerial features for each group, and similarly impacts most clients. It is not due to the doorway.

The outcome is that when the iPhone is associated to the 5 GHz stereo, it goes away and gets to the –70 dBm border for 5 GHz, the indication from the same AP in 2.4 GHz is generally recognized as –63 dBm. This is a theoretical distinction. In actual area deployments, the statistic precision is commonly 4 dB. This implies, if the AP indication is –63 dBm, the consumer will review a indication that can be anything between –67 dBm and –59 dBm, based upon on the consumer actual place in space and RF modifications.

When it affiliates to the doorway, at frequent durations during the relationship, the product demands a record of nearby APs from the AP, using 802.11k action supports. As the product is associated to 5 GHz, the AP only provides next door neighbor BSSIDs in 5 GHz. When the iPhone gets to the –70 dBm border on 5 GHz, it uses the 802.11k next door neighbor record to only look at 5 GHz programs described in the record. However, the iPhone also tests 2.4 GHz, without a record to work from. Two situations can occur:

1 The cellphone discovers a nearby BSSID on 5 GHz at excellent indication stage (8 dB better than the first AP if the product is definitely communicating), and possibly a nearby AP on 2.4 GHz at excellent indication stage. In that place, the product roams to the BSSID on 5 GHz (the cellphone likes 5 GHz when provided the choice).

2 The cellphone discovers a nearby BSSID on 5 GHz, but its indication is not 8 dB better than the present AP (because the overlap between tissues is little, or because the product reviews a lower indication because of recognition imprecision). The cellphone also discovers a nearby BSSID on 2.4 GHz. Because of the mixture of "signal generally 7 dB greater in 2.4 GHz", and "4 dB indication statistic imprecision", the product is likely to see the 2.4 GHz BSSID as a better applicant than the 5 GHz BSSID, inducing the product to wander from 5 GHz to 2.4 GHz. When shifting nearer to the next AP, during the next examine out pattern, the product may see the 5 GHz BSSID as "good", and leap returning to the best group, 5 GHz. This trend produces additional roams with potential interaction interruptions.

The suggestions is to restrict the SSID to 5 GHz if possible. When doing so, ensure that the overlap between your tissues allows permanently roaming circumstances from the product viewpoint. This implies, at the purpose where the first AP indication gets to –70 dBm, the next AP indication should be –62 dBm or better. This results in developing your mobile advantage at about –66 dBm or better. Establishing your mobile advantage at better indication allows for better activities. This prevents the 4 dB statistic imprecision to outcome in circumstances where the product gets to what it finds as the –70 dBm advantage, somewhere where the product does not identify the next AP at –62 dBm yet.

If your style indicates enabling the SSID on both the 2.4 GHz and 5 GHz receivers, let the 'dual band' option of 802.11k, thus enabling the AP to review nearby AP both in 2.4 GHz and 5 GHz. This helps the product to rate up its next AP finding time. However, keep in thoughts that this technique will outcome in more frequent roams, as the product is likely to wander from 5 GHz to 2.4 GHz first, then returning to 5 GHz as the iPhone goes nearer to the next AP.

If your style indicates enabling the SSID on both the 2.4 GHz and 5 GHz receivers, 802.11k is allowed, and if the overlap between the 5 GHz tissues is acceptable (cell at –66 dBm or better, no protection holes between cells), allow BandSelect. This selection allows the APs to obstruct their reactions in 2.4 GHz, thus enabling a longer period for the product to identify the SSID in 5 GHz and wander, before getting an answer in 2.4 GHz.

Tuning Your Network Design for IOS 8 Wandering Performances

Designing your system to provide maximum roaming circumstances to IOS 8 gadgets indicates developing several conditions:

1 Make your system for 802.11a. Set the SSID to 802.11a-only, and allow 802.11k to enhance next AP finding time.

2 Make RF circumstances coordinate the IOS 8 system reasoning. When your system gets to a spot in the mobile where the AP indication drops below –70 dBm, the next AP should be observed at –62 dBm or better. Therefore applying a top rated system, with one AP for every 2500 sqft (250 sqm) area generally. The AP power should be set to a value much like IOS 8 gadgets frequent power for the 5 GHz group. A the best value is 10 to 11 dBm for systems focused at mobile phones (tablets have greater transfer power capabilities), or power 3 for the A regulating sector. The IOS 8 roaming reasoning indicates developing a mobile advantage at advanced stage than normal VoWiFI recommendations.

3 As much as possible, try to style roaming routes that are efficient. In the following example, APs sit tactically to take advantage of the atmosphere and create AP community in accordance with the roaming direction. When the Refurbished iphone 6 goes from place A to place B, APs 1 and 2 can be observed. However, AP A does not listen to AP 3. As a impact, when the Refurbished iphone 6 demands a record of others who live nearby from AP 1, AP 1 provides AP 2 details, but not AP 3. This allows the Refurbished iphone 6 to only get a restricted record of programs to examine on out, and to discover AP 2 easily. These circumstances cannot always be designed, but try to style your system so that the IOS 8 system always learn from its present AP the route of the next AP people are likely to affiliate to while roaming. If possible, restrict the number of APs that can be been told by each AP, so that each AP “802.11k neighborhood” only contains APs that are on the roaming direction.

By developing these circumstances, you can significantly reduce the roaming duration of an IOS 8 system. In the following example, APs were placed as per the example above, and the Refurbished iphone 6 was shifted from the top left area (position A) to the base right area of the area, and back again. The roaming periods are around 50 milliseconds (counted as wait from the last structure from the Refurbished iphone 6 on one route, to the first structure from the Refurbished iphone 6 on the next route, after checking and reassociation to the next AP). 50 milliseconds roaming periods are appropriate for real-time programs.

However, this example system was designed with IOS 8 roaming in thoughts. Unless you are applying a new system, you may not be able to style these perfect circumstances. In every case, keep in thoughts that the IOS 8 roaming requirements reasoning may be described as follows: "associate to 5 GHz if you can. Live there until the indication gets bad, and then turn to another BSSID if it is really better". This type of requirements, generally classified as "generation 2" (partly sticky), is commonly developed for non-real-time programs, with a roaming regularity predicted to be low. It is not developed for real-time programs and frequent roaming. Building your mobile style as suggested above will increase the roaming activities. However, these activities are unlikely to associate those of gadgets applying creation 3 to creation 5 roaming methods, unless you can follow totally counsel above. Do not suggest to your people to use IOS 8 for business-critical real-time programs if frequent roaming is predicted, and if the system was not enhanced particularly to provide efficient roaming activities.