please give a Technical Explanation of Slot Cycle Index (not how to adjust it)

[adhood219]

Can someone please explain to me, technically how the Slot Cycle Index works.

My reason behind this, is because on another site someone stated the following:

"Doesn't work. The Slot Cycle is determined almost always by the tower, not the phone. Changing the value on the phone has no effect. It's a good thing too because the 6700's battery life is so short to begin with."

That was in response to me telling someone to adjust their SCI on their phone to receive incoming calls faster.

Thanks

[malatesta]

Can someone please explain to me, technically how the Slot Cycle Index works.

My reason behind this, is because on another site someone stated the following:

"Doesn't work. The Slot Cycle is determined almost always by the tower, not the phone. Changing the value on the phone has no effect. It's a good thing too because the 6700's battery life is so short to begin with."

That was in response to me telling someone to adjust their SCI on their phone to receive incoming calls faster.

Thanks

Guess then everyone who did is just experiencing a placebo effect and don't have a problem anymore? Maybe, but I doubt it

From what I understand, the SCI is the rate at which the phone pings the towers to check for incoming calls. The longer the delay, the more likely to miss a call. So if it's a 5 second delay and a call comes in after you just pinged, it'll be another 4-5 seconds before you get notified.

As far as power consumptin:

a) the 6700 just has a small battery (1350 mah) it actually gets decent battery life (Treo's come with stock 1800 mah)

b) Changing SCI has little to no impact on battery life (source)

Observations:

Changing the SCI to 1 makes almost no difference! Only 1 mA increase!

Changing the SCI to 0 makes very little difference! Only 5 mA increase over default.

Doesn't this make you wonder why the default is 2? Any user would find this phone much better by implementing this hack, which does not greatly effect battery consumption, but greatly increases ringer response time. Too bad many users of this phone will not have the knowledge to change this!

PS Anyone can try this: Change your SCI to the max (7?) and make some phone calls. Then set it at 0 and make some phone calls. Tell us what you find. I bet you'll find a difference. (I love how people say things in posts about it "not making a difference" but then you know, avoid any kind of science to actually test it...). Feel free to tell that guy he's an idiot, btw.

[adhood219]

Another idiot posted this:

Quote:
Originally Posted by adhood219
Guess then everyone who did it is just experiencing a placebo effect and doesn't have a problem anymore? Maybe, but I doubt it

From what I understand, the SCI is the rate at which the phone pings the towers to check for incoming calls. The longer the delay, the more likely to miss a call. So if it's a 5 second delay and a call comes in after you just pinged, it'll be another 4-5 seconds before you get notified.

As far as power consumptin:

a) the 6700 just has a small battery (1350 mah) it actually gets decent battery life (Treo's come with stock 1800 mah)

b) Changing SCI has little to no impact on batter life (source

Observations:

Changing the SCI to 1 makes almost no difference! Only 1 mA increase!

Changing the SCI to 0 makes very little difference! Only 5 mA increase over default.

Doesn't this make you wonder why the default is 2? Any user would find this phone much better by implementing this hack, which does not greatly effect battery consumption, but greatly increases ringer response time. Too bad many users of this phone will not have the knowledge to change this!
[End quote]

Try reading next time. Handsets don't control the SCI, the towers do.
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[malatesta]

Try reading next time. Handsets don't control the SCI, the towers do.
Reply With Quote

Need evidence? I hate when people just "say" things without documentation ask for proof. Damn, just googling around comes up with plenty of evidence.

I mean, if it does nothing, why is it there in the first place? What does changing SCI on the phone do?

Here's some:

(source)

II TECHNICAL QUESTIONS

Q 2.1 In CDMA what is meant by "slot cycle index"?

A 2.1 [Credit: Bill Walker]
On the CDMA Paging Channel (this is the shared channel that all phones
listen to for incoming calls and other control info), time is divided into
"slots". To conserve power, phones that are currently idle only "wake up"
and listen for messages on the Paging Channel during their assigned
slots. The slot cycle index determines how often the phone's slot comes
around. If the slot cycle index is 0, the phone wakes up every 1.28
seconds. If it's one, it wakes up every 2.56 seconds. If it's two, it's
every 5.12 seconds, and so on. The larger the setting, the more power is
conserved, but the longer it takes to page the phone for an incoming
call. You can imagine that if it were set to 10.24 seconds, few callers
would hang on the line long enough for you to answer your phone.

There are two settings that govern this. One is the "preferred slot cycle
index" in the phone, and can be set via service programming. The other is
the "maximum slot cycle index" set in the base station and broadcast in
overhead messages on the Paging Channel. The phone has to use whichever
number is smaller.

More...(source)

What is the phone doing when it's idle?
Short answer: It's actually very busy!

Long answer: It's constantly turning parts of itself on and off; on to perform vital functions and off again to save power so that the battery lasts longer.

By far the most important thing it does is to wake periodically and turn on its receiver briefly to see if it has been paged, which means to find out if there is an incoming call. This happens on what is known as a slot cycle, and the period of the slot cycle is controlled by the cell (for all intents and purposes). Slot cycle indices are numbers from 0 to 7, and for any index the period is 1.28 seconds multiplied by 2^index. In North America, by far the most common slot cycle indices are 1 and 2, which indicates a period of 2.56 seconds or 5.12 seconds respectively. I haven't heard of anyone using anything longer than this, though the specification supports slot cycles of 163.84 seconds.

The receiver consumes quite a lot of power. relatively speaking, and the purpose of the slot cycle is to permit the phone to keep the receiver turned off most of the time. This is vital to extend battery life. When the phone first registers with a cell, the cell and phone determine which paging channel the phone will use (if there is more than one) and what phase of the slot cycle that phone will use. Thereafter, the phone wakes periodically, turns its receiver on briefly to see if it has an incoming call or if there is other traffic from the cell it must respond to, and if there is nothing then it shuts the receiver down again and waits until the next slot time.

When an incoming call arrives at the cell for a given phone, the phone system generates the sound of a phone ringing as a comfort tone back to the caller, and the cell waits until the slot time for the phone. When it comes around, the cell sends a message to the phone telling it that there is an incoming call. This causes the phone to waken and set up the call, and to begin to ring.

If the phone doesn't respond to the page, the cell may try again on the next slot.

The advantage of a longer slot cycle is that the phone spends a lower percentage of the time with its receiver on and thus the battery will last longer. It also means there is more capacity on the paging channel. The advantage of a shorter slot cycle is that the phone gets more chances to receive the page, and will receive the page sooner.

When the cell system needs to send out that page, it obviously needs to know where to broadcast it. The cell system as a whole will be divided into zones, and when a phone is paged, every sector of every cell in the zone it's in will carry the page. This means that no matter where the phone is located in that zone, it will receive the page. When the phone moves from one zone to another, it registers again, which permits the cell to know where it is located. The size and layout of the zones is another tradeoff: if the zones are large, the traffic channels will carry a great deal of redundant paging information and can become overloaded, but the phone doesn't have to perform zone-based registration very often as it moves around, which means its battery will last longer. On the other hand, if the zones are small then the paging channels are used more efficiently but the phone will need to register more often and thus will use more battery power.

You may have noticed that when you turn your phone off it takes several seconds for it to actually shut down. That's because it is sending a message to the cell to tell the cell that the phone is going offline. However, the phone can go down unexpectedly without having the chance to send this to the cell (for instance, the battery could be popped from the phone unexpectedly while the phone is operating, which is generally not recommended), and in that case the phone would be offline but the cell wouldn't know it. That would then mean that the cell would try to handle an incoming call for that phone by paging it even though the phone was off, and it generally means that the cell's database would be loaded with entries for phones which aren't available. As a long term recovery for that, the phone is required in most systems to do timer-based registration, which means that every ten or twenty minutes it turns its transmitter on to let the cell know that it's still there. If the cell misses a couple of these registrations in a row, it decides that the phone has gone offline and removes it from the database of "phones which are currently turned on".

Under some circumstances, the cell system can directly challenge the phone for a registration. This happens on the paging channel at the slot, and when the phone receives this message, it turns its transmitter on and sends a registration immediately.

If there is pending voice mail for the phone, the phone will be told on a slot to alert its user of this fact.

All of these registration messages sent by the phone are nearly identical, and they simply identify the phone and contain a few other important pieces of information about it. Despite how it sounds, they (deliberately) don't happen very often and (deliberately) represent a negligible impact on standby time. But they are necessary for the phone system as a whole to work properly.

Of course, the phone is also updating its display to show the current date and time and signal strength and amount of energy remaining in the battery, and perhaps other things depending on the phone model.

That "idle" phone is plenty busy!

Here's a whole thread at those "crazies" at Howard Forums.

It IS true that the tower's SCI can over-ride the phones...but, a lot of companies set it low (SCI 1) like Verizon and presumably Sprint does too.

[WarDogg]

____________

[wezx]

"Another idiot posted this:"


WOW...harsh.

[malatesta]

Wardogg/Wezx,

Just to clear things up, this looks worse than it is: I'm for the first time, having a debate with someone by proxy , so the OP is *not*calling me an idiot (well, I don't think so at least) but this guy in another forum is responding to me via the OP who I'm assuming copy/pasted my explanation into that forum.

i think that is what is going on...

now where is that emoticon for this situation...ahh yes

[GroundNPound]

In case anyone is wondering here is the thread explaining how to change your SCI:

http://www.smartphoneforums.com/foru...66-post15.html

[adhood219]

Sorry malatesta, I wasn't calling you an idiot. I was referring to the individual on the other forum who posted this:

"Try reading next time. Handsets don't control the SCI, the towers do.
Reply With Quote"

Yes I did copy/paste your explanation. It was a very good explanation. Couldn't have written it better myself.

[malatesta]

Sorry malatesta, I wasn't calling you an idiot. I was referring to the individual on the other forum who posted this:

"Try reading next time. Handsets don't control the SCI, the towers do.
Reply With Quote"

Yes I did copy/paste your explanation. It was a very good explanation. Couldn't have written it better myself.

, no problem that's what I figured was happening.

It is a complicated issue and defiintely the tower setting can play a role but the bottom line is this: the towers seem to have a lower SCI than our phones do (by default) and hence why we notice an improvement OR it's basically whoever (the phone or the base station) has the lowest SCI, that is used. Plus, people with nokias and other phones do this as well, so it's just not a 6700 phenomenon.

Either way, power consumption is minimal and I can't see the harm in doing it.