Non-Overlapping channels bleed over

I have multiple AP's in an arena enviornment. Now without violating the rule where an AP is assigned a non-overlapping channel, what is best practice if there are neighboring AP's within close proximity of each other and they are assigned the same channel?
For example, in our press level I have 2 AP's both on channel 11, the suite level below has a few more ap's where the signal bleeds over to the press level and even if some were on channel 1, 6, & 11 there would still be conflicting channels. I hope this questions makes sense.

Thanks for the points Rob! Things have been pretty busy the last couple months.
Planning RF fields is a three-dimensional thing, more or less dependent on the construction materials laterally and vertically.
Given that there are only the three channels (for 802.11g), you have no option other than stacking and staggering, like:
level3: 1--6--11--1--6--11--1--6--11
Level2: 6--11--1--6--11--1--6--11--1
Level1: 11--1--6--11--1--6--11--1--6
With the only real variation being the type of antennas you choose, the topology of the spaces, and the power levels of the APs. There's really no other way to do it (using only 802.11g).
NOW, what I'd recommend that you recommend is to add the additional capability for 802.11a. Many/most computer systems have dual band capability, most (Cisco) APs are rigged for dual band.
So light up that 802.11a channel and encourage the folks that can to move up there. It's an easy sell: more bandwidth ("sorta" ...but we're marketing here so outright lies are generally permitted), less interference, and better security (from the aspect of fewer hackers work this band because there's not enough "interesting" stuff on it, etc.).
The benefit to you is that you would have 40 non-overlapping channels ... much easier to plan.
I understand that you have some equipment and users that must remain on 802.11g (try to forbit B if you can, it's making the system slower and reducing your availability), but usually if you offer / encourage those with the capability to move to the better band, they'll take it.
Otherwise, start looking for places where you could say " You know, if I had an antenna with *this* kind of pattern, I could ..." because there probably is an antenna, somewhere, with that radiation pattern.
What you can't get in pattern, you can make up for with barriers, reflectors, etc.
Good Luck
Scott

Similar Messages

Overlapping v's Non-overlapping channels...

I know it is bad practise to have more than one AP within the same cell area using the same channel, but wondered what the effects of this were. For example, if I had an AP in channel 6 and another AP ten yards from it in channel 6 also, what would be the repercussions?
Thinking about it logically, there would be radio collisions. Each AP could potentially try to transmit at the same time causing collisions. Therefore, you would see slow throughput and high error counts on the AP? Also, if a WLAN client transmitted a frame to a user on the wired network, each AP would receive it (regardless of association) and forward the frame on - resulting in the wired client receiving two copies of the same frame (one from each AP)???
Can anyone, explain why it is not good practise to have over-lapping channels (or any useful web links/documents)?
I will continue to use non-overlapping channels, but it would be nice to know why.
Thanks

Hi Darren,
That is a great question. Here are some links that have really good answers;
Channel Deployment Issues for 2.4-GHz 802.11 WLANs
From this doc;
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00802846a2.html#wp134263
Assigning 802.11b Access Point Channels
An important concept to note regarding channel assignments is that the channel actually represents the center frequency that the transceiver within the radio and access point uses (e.g., 2.412 GHz for channel 1 and 2.417 GHz for channel 2). There is only 5 MHz separation between the center frequencies, and an 802.11b signal occupies approximately 30 MHz of the frequency spectrum. The signal falls within about 15 MHz of each side of the center frequency. As a result, an 802.11b signal overlaps with several adjacent channel frequencies. This leaves you with only three channels (channels 1, 6, and 11 for the U.S.) that you can use without causing interference between access points.
From this link;
http://www.wi-fiplanet.com/tutorials/article.php/972261
Channels and international compatibility
Although the statement that channels 1, 6, and 11 are "non-overlapping" is incomplete, the 1, 6, 11 guideline has merit. If transmitters are closer together than channels 1, 6, and 11 (e.g. 1, 4, 7, and 10), overlap between the channels will probably cause unacceptable degradation of signal quality and throughput.
http://en.wikipedia.org/wiki/IEEE_802.11
Hope this helps!
Rob
Please remember to rate helpful posts.........

Non-overlapping channels - 802.11a/n - need clarification

There seems to conflicting or inconclusive information the topics below. I have just been readying various docs using google searches. I am hoping to get some solid answers.
1) What channels for 802.11a are really non-overlapping? 8 or 12? I have read in some sources that it is 12 but the last 4 are for outdoor use(?).
2) in regards to 802.11a, channels 149 - 165 are considered for outdoor use so indoor availability is only 8 channels, correct?
3) What would be the non-overlapping channels for 802.11n? Indoor use only.
4) What happens when an 802.11n/a device and a traditional 802.11a device connect to the same network?
Thank you,

Hi Jacob,
Following diagram should helps you (Ref source )
Referencing this & if you look at your 4 queries you can find the proper answer. Here is my response
1) What channels for 802.11a are really non-overlapping? 8 or 12? I have read in some sources that it is 12 but the last 4 are for outdoor use(?).
As you can see, excluding UNII-2 extended there are 12 non overlapping channels (13 including CH165), depends on the different country regulations you can use those for indoor/outdoor deployments.
2) in regards to 802.11a, channels 149 - 165 are considered for outdoor use so indoor availability is only 8 channels, correct?
It depend on the courntry regulation. I think in US you can use that band(UNII-3) for both indoor/outdoor deployments. So in that case 12 CH availabel excluding UNII-2 extend band.
3) What would be the non-overlapping channels for 802.11n? Indoor use only.
802.11n in this band, you can aggregate two 20MHz channel, (effective 40MHz bandwidth). You can see 6 non-overlapping channels available with 40MHz width in those bands (80MHz & 160MHz option shown in the above diagram applicable to 802.11ac standard)
4) What happens when an 802.11n/a device and a traditional 802.11a device connect to the same network
802.11n device will communicate with 40MHz (if configured on you wireless network & client support channel bonding) & normal 802.11a client will connect using 20MHz channel without any CH bonding or aggregation
If that answers to your query pls mark this thread as "Answered"
HTH
Rasika
**** Pls rate all useful responses ****

Overlapping Channels Query

Hi,
I'm troubleshooting a wireless issue at one of our sites and had a query about the current setup. I've attached a diagram of the AP locations and the channels that are in use.
I notice that there are a few neighbouring APs using the same (overlapping) channel and wondered if this is of any concern. Wireless is not my speciality, but as far as I understand it, neighbouring APs are supposed to use non-overlapping channels.
For Info;
APs 2-3,9 -10, and 26 use omni-directional antennas
APs 4-8, 11-15, use directional antennas facing out of the building.
All APs are autonomous and use the same SSID
Should the channels be reconfigured so there are no overlapping channels?
Thanks,
Paul

Hi,
When working with wireless on the 2.4ghz we need to make sure that you distribut the 3 non overlapping channels between all your access points so that the access points with the same channel are the further apart and on the 5ghz we do not need to worry about this becasue all the channels are non overlapping vrs the 2.4ghz that the only non overlapping channels are 1-6-11.
Also we need to keep in mind that other access points close to you from another company will create interfirence to yours and yours to them the only way to fix this is distribut the non overlapping channels between your access points and the close access points.

Overlapping channels

Folks,
I have installed about 10 access-points in a company. Everything seems to be working fine, except fast roaming. I had a question about overlapping channels. Since the access-points have G radios, i presume that you can have 8 overlapping channels as appose to B radios which only have 3 overlapping channels. Am i right on this?
Also, would the access-points automatically select non overlapping channels so that they do not interfere with the adject AP frequency, or do i have to set that up manually??
Any advice would be highly appreciated!!!
Thanks

I think you are confusing G radio with A. G operates in the same frequenzy as B does (2,4Ghz) so you still have the same overlapping channels support.
That is 3. A radio however has the possibility of 8 channels and uses the 5Ghz spectrum.
Regarding the automatic. The AP searches for the least congested channel during startup. I´m not sure but I think they try to choose noneoverlapping channels. So in order to load-balance with overlapping channels you´d need to manually set them. However Cisco reccomends that you manually set the channels. That way you may always be sure it stays the same.
regards. Kristjan Edvardsson CCNP Wireless Lan support specialist.

Pure SQL to partition date-time occurrences into non-overlapping windows?

i've a question that so far, i've never been able to solve via a pure SQL option.
it's hard to explain in words, but it's something like this:
given a set of date-time, i would like to partition the data into non-overlapping windows of 30 minutes each.
the data is supposed to be partitioned into windows of 30 minutes, meaning when the data is within 30 minutes of the first occurrence, only the first occurrence will be returned. in the next second after the 30th minute, the record will be considered as the start of a new window and is also returned. so those data that occurs within the window period are suppressed. the first occurrence is not necessarily occurring on the 00th minute, so the window start will never be constant.
run the below query to look at the dummy data.
SELECT     'A' AS ID
          , TRUNC(SYSDATE) + 7 / 24 + 1 *(ROWNUM - 1) / 1440 AS datetime
      FROM DUAL
CONNECT BY ROWNUM <= 50
UNION ALL
SELECT     'A' AS ID
          , TRUNC(SYSDATE) + 9 / 24 + 8 / 1440 + 1 *(ROWNUM - 1) / 1440 AS datetime
      FROM DUAL
CONNECT BY ROWNUM <= 35
UNION ALL
SELECT     'B' AS ID
          , TRUNC(SYSDATE) + 7 / 24 + 5 *(ROWNUM - 1) / 1440 AS datetime
      FROM DUAL
CONNECT BY ROWNUM <= 15this is supposed to be the output.
ID     DATETIME
A     5/19/2010 07:00:00
A     5/19/2010 07:30:00
A     5/19/2010 09:08:00
A     5/19/2010 09:38:00
B     5/19/2010 07:00:00
B     5/19/2010 07:30:00
B     5/19/2010 08:00:00so far, i'm using a PL/SQL to pipe the records. but i would like to know if this is achievable via SQL or not.
i've tried looking at analytics, width_bucket, ntile and alll options i can think of, but i just can't solve this at all.

hey Bob,
your answer is most definitely correct and does what i want. i've verified it again my data set and it returns the results as required!
you've definitely proven me wrong. i was always under the impression that this wasn't possible. thanks!
just a small note:
i need the windows to be binned by seconds, so have changed the numtodsinterval to raw numbers.
WITH t AS
     (SELECT 'A' AS ID
            , TRUNC(SYSDATE) +(6.75 / 24) AS datetime
        FROM DUAL
      UNION ALL
      SELECT 'A' AS ID
            , TRUNC(SYSDATE) +(6.75 / 24) AS datetime
        FROM DUAL
      UNION ALL
      SELECT     'A' AS ID
                , TRUNC(SYSDATE) + 7 / 24 + 1 *(ROWNUM - 1) / 1440 AS datetime
            FROM DUAL
      CONNECT BY ROWNUM <= 50
      UNION ALL
      SELECT     'A' AS ID
                , TRUNC(SYSDATE) + 9 / 24 + 8 / 1440 + 1 *(ROWNUM - 1) / 1440 AS datetime
            FROM DUAL
      CONNECT BY ROWNUM <= 35
      UNION ALL
      SELECT     'B' AS ID
                , TRUNC(SYSDATE) + 7 / 24 + 5 *(ROWNUM - 1) / 1440 AS datetime
            FROM DUAL
      CONNECT BY ROWNUM <= 15)
    ,a AS
     (SELECT ID
            ,datetime
            ,LAG(datetime) OVER(PARTITION BY ID ORDER BY datetime) AS prevtime
            ,LAST_VALUE(datetime) OVER(PARTITION BY ID ORDER BY datetime RANGE BETWEEN CURRENT ROW AND 30 / 1440 + 1 / 86400 FOLLOWING) AS interval_end
        FROM t)
    ,b AS
     (SELECT ID
            ,datetime
            ,LEAD(datetime) OVER(PARTITION BY ID ORDER BY datetime) AS nexttime
        FROM t)
    ,ab AS
     (SELECT a.ID
            ,a.datetime
            ,a.prevtime
               ,a.interval_end
               ,b.datetime as b_datetime
            ,b.nexttime
        FROM a JOIN b ON(a.ID = b.ID
                         AND a.interval_end = b.datetime)
SELECT     ID
          ,datetime
      FROM ab
START WITH prevtime IS NULL
CONNECT BY ID = PRIOR ID
       AND datetime = PRIOR nexttime
ORDER BY ID
          ,datetime;this most definitely proves that i'm still not sure of how to use hierarchy queries.
Edited by: casey on May 20, 2010 11:20 AM

Possible to make non-HD channel switch to HD channel? (like 7 to 507)

Hey, just got Fios installed this week and am liking it so far.
Quick question... I had Cablevision before this, and they had it set up so that if you put on an non-HD channel using an HD set top box, it automatically switched to the HD version of that channel.
Is there any way to make this happen with Fios? So like... if I put on 7, it would automtically change to 507.
Thanks in advance for any help.
Solved!
Go to Solution.

Welcome to FiOS, and welcome to the forums!
Unfortunately no. But if you will take the time to set up a Favorites list, if you haven't already done so, then you can at least somewhat minimize accidentally surfing to the SD channel by mistake. If you are interested in setting up a Favorites list, here is a link to a thread which should help you get started:
http://forums.verizon.com/t5/FiOS-TV-Technical-Assistance/Exploiting-FiOS-TV-Favorites/td-p/9935
With my Favorites list I have all of the HD channels I care about included, and only those SD channels I am interested in that are not duplicated by HD channels. And I must admit, it is pretty rare that I ever watch any SD channel any more.....
Justin
Verizon FiOS TV, Internet, and phone
QIP6416-P1, IMG 1.7.1, Build 09.97
Keller, TX 76248

Groups having non-overlapping intervals

Hi there,
I need help on some mind boggling overlap problem, or perhaps non-overlap problem.
Having the sample data below, I need to put together subcodes in groups having non-overlapping
intervals [MIN_VAL;MAX_VAL[
I have this table:
SQL>create table t (product   varchar2(1) not null
2                 ,subcode   number(1)   not null, constraint subcode_chk check (subcode >= 0)
3                 ,min_val   number(2)   not null, constraint min_val_chk check (min_val >= 0)
4                 ,max_val   number(2)   not null, constraint max_val_chk check (max_val >= 0)
5                 ,constraint t_pk primary key (product, subcode)
6                 ,constraint t_val_chk check (min_val < max_val));
Table created.
SQL>
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 0, 0, 99);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 1, 0, 99);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 2, 18, 67);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 3, 20, 65);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 4, 0, 99);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 5, 45, 60);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 6, 20, 40);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 7, 0, 99);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 8, 60, 65);
1 row created.
SQL>insert into t (product, subcode, min_val, max_val) values ('A', 9, 0, 99);
1 row created.
SQL>commit
2 /
Commit complete.
SQL>
SQL> select product, subcode, min_val, max_val
2      from t
3     where product = 'A'
4 order by product, subcode;
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL
A                0          0         99
A                1          0         99
A                2         18         67
A                3         20         65
A                4          0         99
A                5         45         60
A                6         20         40
A                7          0         99
A                8         60         65
A                9          0         99
10 rows selected.
SQL>The records of interest are subcodes 5,6,8 since they in certain cases can be considered as one subcode.
It is OK, that MAX_VAL of one record = MIN_VAL of other record. The main thing is that the subcodes
within a group are mutual disclosing on MIN_VAL, MAX_VAL.
SQL> select product, subcode, min_val, max_val
2      from t
3     where product = 'A'
4       and subcode in (5,6,8)
5 order by min_val;
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL
A                6         20         40
A                5         45         60
A                8         60         65
SQL>I have started out by trying to solve it using lag/lead analytical functions, but without luck.
Next, I've come up with this hierarchial query, but I don't quite understand it myself, and that bothers me!
SQL>    select distinct -- This, distinct, bothers me!
2                      product
3                     ,subcode
4                     ,min_val
5                     ,max_val
6 --                   ,connect_by_isleaf
7 --                   ,connect_by_root subcode
8        from t
9       where connect_by_isleaf = 1 -- Why does this help me?
10 start with -- This, start with, seems "clumpsy"
11            min_val in ( select min_val
12                            from t
13                        group by product, subcode, min_val)
14 connect by nocycle -- This, nocycle, really bothers me!
15                     min_val > prior min_val
16                 and max_val <= prior max_val
17                 and product = prior product
18                 and subcode <> prior subcode
19    order by product
20            ,subcode
21            ,min_val
22            ,max_val;
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL
A                5         45         60
A                6         20         40
A                8         60         65
SQL>Currently I'm struggling with just identifying the three subcodes. In the perfect world this would be better output
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL   GROUP_FLAG
A                0          0         99
A                1          0         99
A                2         18         67
A                3         20         65
A                4          0         99
A                5         45         60            1
A                6         20         40            1
A                7          0         99
A                8         60         65            1
A                9          0         99Or even better, if using herarchial query:
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL   ROOT_SUBCODE
A                0          0         99              0
A                1          0         99              1
A                2         18         67              2
A                3         20         65              3
A                4          0         99              4
A                5         45         60              6
A                6         20         40              6
A                7          0         99              7
A                8         60         65              6
A                9          0         99              9Any help and inspiration would be much appreciated. But please don't get offended if I don't follow up the next 12-14 hrs.
Regards
Peter
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64biEdited by: Peter on May 19, 2009 12:52 PM
- Changed line 15 in hierarchial query

Brillant as always, Frank. Ten points and mange tak for you.
(1) What is your concept of "group" in this problem? In what sense do subcodes 5, 6 and 8 form a group? Is it that they share the quality of not overlapping with some other row with the same product? That is, will there be at most two groups per product: rows that overlap with every other row, and rows that don't?By group I mean, that when isolated from other subcodes, a group does not overlap. For product A, I have 10 different subcodes. In certain situations I'm allowed to consider 5,6 and 8 as one, since they don't overlap. In general the data presented results in 8 groups, 7 groups having 1 subcode, 1 group having 3 subcodes.
(2) What you mean by "mutually disclosing"? Is it that the min_val to max_val ranges do not overlap?Yes. They are however allowed to be equal.
As to your query. Seems you're right, it might actually be that "simple". I changed slightly, allowing >= and <=
SQL> SELECT m.*,
2         CASE
3            WHEN
4            EXISTS (
5                     SELECT NULL
6                     FROM    t
7                     WHERE   product = m.product
8                     AND     (       min_val >= m.max_val
9                             OR      max_val <= m.min_val
10                             )
11                   )
12         THEN 1 END group_flag
13    FROM t m;
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL GROUP_FLAG
A                0          0         99
A                1          0         99
A                2         18         67
A                3         20         65
A                4          0         99
A                5         45         60          1
A                6         20         40          1
A                7          0         99
A                8         60         65          1
A                9          0         99
10 rows selected.
SQL>
This assumes that min_val <= max_val on each row.Your assumption is perfectly correct, as expessed in check constraint on table t.
>
The rest of this message concerns the CONNECT BY query you posted, in case you want to understand it better.
When I run the CONNECT BY query you posted, I get these results:
P    SUBCODE    MIN_VAL    MAX_VAL
A          0          0         99
A          1          0         99
A          4          0         99
A          5         45         60
A          6         20         40
A          7          0         99
A          8         60         65
A          9          0         99
Ouch, my bad. Somehow I posted the wrong query. I have edited line 15 from
15                    min_val >= prior min_valinto
15                    min_val > prior min_val
The START WITH clause includes all rows: you might as well not have a START WITH clause:
10 start with -- This, start with, seems "clumpsy"
11            min_val in ( select min_val
12                            from t
13                        group by product, subcode, min_val)
That's great, somehow I was misled to believe that wew should always have a START WITH.
Thank you for your remainding comments on hierarchial query. I'll definitely have to play around with it to fully understand. With the edit mentioned, and
without a START WITH it now looks as,
SQL> select distinct -- This, distinct, bothers me!
2                       product
3                      ,subcode
4                      ,min_val
5                      ,max_val
6         from t
7        where connect_by_isleaf = 1 -- Why does this help me?
8   connect by nocycle -- This, nocycle, really bothers me!
9                      min_val > prior min_val
10                  and max_val <= prior max_val
11                  and product = prior product
12                  and subcode <> prior subcode -- Not necessary
13     order by product
14             ,subcode
15             ,min_val
16             ,max_val;
PRODUCT    SUBCODE    MIN_VAL    MAX_VAL
A                5         45         60
A                6         20         40
A                8         60         65
3 rows selected.
SQL>One final question. In your solution with EXISTS, you use < and >. In my rewritten example I use <= and >=. It seems that it still works, even without a condition on subcode != m.subcode in the subquery.
Maybe I'm too tired by now, but why is that? - just don't get it
Regards
Peter

[svn] 4323: Bug: LCDS-544 - Scenario where two components have seperate channel sets with overlapping channels not working .

Revision: 4323
Author: [email protected]
Date: 2008-12-15 19:23:10 -0800 (Mon, 15 Dec 2008)
Log Message:
Bug: LCDS-544 - Scenario where two components have seperate channel sets with overlapping channels not working.
QA: Yes
Doc: No
Checkintests Pass: Yes
Details:
* Hunting to a new channel within a channelset never triggered a disconnect from the previous channel(s). This isn't a problem in general, but does becomes a problem when an app defines two distinct channelsets containing at least one shared channel at the head of the list. In this case, the first channelset hunts past it and connects on a later channel. But when the second channelset hunts through (triggering a connect fault when it hits that initial shared channel that can't connect), the fault is processed by the first channelset as well (incorrectly).
Ticket Links:
http://bugs.adobe.com/jira/browse/LCDS-544
Modified Paths:
flex/sdk/trunk/frameworks/projects/rpc/src/mx/messaging/ChannelSet.as

Running the script by python2 solves it for me:
su - mythtv -c "nice -n 19 python2 /usr/bin/tv_grab_nl_py --output ~/listings.xml"
Best regards,
Cedric

Aironet 1250 Overlapping Channels

Hi,
In my LAN, I have always been used an Aironet 1250 for internal use and always work fine. Now, I added a 3com AP but both AP are not correct. When I turned off the AIRONET 1250, the 3COM AP settings works fine. When both are turn on, the 3COM AP loses connectivity all the time.
I have heard about the overlapping channels in 802.11b/g networks.
Someone could tell me what I could do for solving this?
Note: Due to restrictions on my security lan, I could not use two SSID(using vlans) on my aironet 1250. This will be the best scenario, but it was not possible.
Thanks in Advance,
Fernando

yes. The Aironet 1250 connects to a DHCP server in the range 10.150.x.x and the 3com AP connects to a range 192.168.1.x. The DHCP servers are in different places and there is no any possibility that they could overlap one and another.
But I realized that the problem must be between the two access point because the 3 com AP got an IP Address from the range 10.150.x.x(it sounds crazyness but its true). Offcourse, soon the 3COM AP loses the connection.
Tks you very much,
Fernando

Non-Overlapping Rings

Do you know of a function or series of functions that I can use to create non-overlapping rings around a table of points? Non-overlapping rings are circular buffers around points. Areas of overlap are removed where rings cross.
The link below is a non-overlapping rings example:
http://www.mappinganalytics.com/map/images/radius-map.jpg
If you do not have a function, what would be the logic for creating such a function? Any guidance would be welcome.
Thanks
Edited by: user11121688 on Jun 24, 2010 8:47 AM

Hi,
Sorry I misunderstood your non-overlapping ring definition . The boundaries of the rings are straight lines from the intersection points.
the following is my suggestion :
First figure out which buffers intersect. Using the sdo_distance between two points and the buffer distance (radius)
should do (distance < radius means intersecting!). Each buffer can have a set of intersecting buffers.
Then for each intersecting pair (buffer_i, buffer_j), find out the pairwise non-overlapping ring for each buffer.
Assume that buffer_i has the center c_i and , buffer_j has the center, c_j
If a buffer has no intersecting buffer,
its pairwise non-overlapping ring is itself.
else
use the exterior rings (as linestring) of each buffer and find out their intersections points, i_1 and i_2.
You might want to take care of some exception cases like buffers are touching (1 intersection pt cases)
or the same (same point cases).
Construct a 3-pt polygon t_j (c_j,i_1,i_2).
The pairwise non-overlapping ring for buffer_i w.r.t. buffer_j is sdo_difference(buffer_i,t_j, tolernace).
Find out all pairwise non-overlapping rings for buffer_i with all other intersecting buffers.
We have a set of pair-wise non-overlapping ring for buffer_i.
Find out the intersection for all such buffers and we have the aggregate non-overlapping ring for buffer_i.
For a buffer without any pairwise non-overlapping ring, its aggregate non-overlapping ring is itself.
Follow the same approach for all other buffers to find out all aggregate non-overlapping rings.
This approach should be applicable to both geodetic and projected coordinate systems.
hope it helps!
jack

ITouch stereo channels bleeding

I have a problem with my iTouch's output jack's stereo channels bleeding into each other. I currently use a 1st gen iPod for playing backing tracks for a band. It works perfectly. I have mp3 tracks that have the click panned hard left and the backing track panned hard right. No problems. So I got the iTouch to do the same. The tracks bleed into each other during playing, which cannot happen when using them as backing tracks. I've had 2 itouchs now (a 2nd gen and now a 4th gen) and both are doing it. Anyone had this problem? Thanks.

You could try bouncing the tracks down in another format, some times WAV files don't bleed.
In settings on the Touch there may be a stereo enhancer function that is turned on, try turning that off.

Left/Right Channel Bleed? Discrete Separation Possible?

I have a need to playback stereo music files with discrete L & R channels on both iTunes and iPod devices. When I output these files from ProTools, the left and right channels are discrete. However, when I play them back from iTunes, listening to just the left or right channels alone reveals bleed from between the channels, which is unacceptable. The only work-around I have fund is to pull out an old portable CD player and hook it directly to the amp. The same CD in iTunes simply does not produce discrete tracks out of the Mac or once converted to MP3s, the iPod.
Is there some setting that must be adjusted to prevent this cross-over bleed in iTunes and in particular, the iPod? Or are these devices incapable of producing discrete L/R channel separation?

Bump

Connecting to non-secure listener port over TCPS

Hi,
I am trying to connect to non-SSL port over TCPS.
When I use tnsping, it hangs.
When I do an OCIServerAttach, it hangs.
Client is 10.2
And Database server is 9.2 and higher..
Any way I can find out why this is happening??
-Harsha

Maybe I'm not getting the point, but when you do not use SSL on this port, why do you want to use TCPS. Wouldn't TPC be a better choice?
cu
Andreas

How do I AI config for SCXI multiple non-contiguous channels

I need to configure a measurement of with multiple groups of thermocouple channels.
Using LV 5.1.1 (could use 6, but I am supporting lots of code built with 5.1.1), DAQ 6.8.1 (can up to 6.9.1 if it matters), PXI-6052E, SCXI-1102, SCXI-1303 (or TC-2095).(using SCXI addressing).
The problem occurs when I try to configure multiple scan lists with gaps between channels.
(see LV DAQ SCXI example SCXI-1102/1127/1101 Thermocouple)
example channel list:
ob1 ! sc1 ! md1 ! cjtemp
ob1 ! sc1 ! md1 ! 0:3
ob1 ! sc1 ! md1 ! 5:9
This gives an error: -10370 in AI Group Config.
Likewise if I use an individual channel in each address string. like:
...md1 ! 0
...md1 ! 1
...md1 ! 3
But, I can skip channels betwe
en cjtemp and the first channel of the next scanlist without error.
Also, I can add scan lists for other modules, like:
...md1 ! 0:3
...md1 ! 4:8
...md3 ! 12:14
without error!
What I really want to do is to do AI Config first for all channels, then start, then loop on AI Read and some processing & storage.
When I loop through the channel address lists (strings with contiguous channel sets e.g. 3:6) I get the same task # for all config calls. Then when I loop through the AI Start's for each , I get an error -10609 in AI Clock Config.
The thing is that I cannot necessarily have all contiguous channels, and I don't want to go through a sequence of {AIConfig, AIStart, AIRead, AI CLear} for each scanlist each time through. That takes too much time and resources.
Eventually I want to configure multiple non-contiguous scanlists in multiple SCXI modules.
But, for right now I need to do this for one SCXI module.
Anyone have any ideas?
How can I approach this.
Thanks
Dave

Dave
Check the following link into the NI Knowledgebase (if you haven't already)
which I think explains your situation.
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/02a55e1f39
e8bd15862567e700577877?OpenDocument
Bottom line is you will not be able to skip channels on any SCXI module
other than the SCXI-1112. You will need to include the channels in your scan
list then discard the data later.
Either that or as the Knowledgebase suggests, use Virtual Channels. You can
then miss channels out in the scan list as you require. They actually get
scanned but NI-DAQ discards the data for you.
Ian Bell
NI UK
"Dave Karon" wrote in message
news:[email protected]...
> I need to configure a measurement of with multiple groups of
> thermocouple channels.
> Using LV 5.1.1 (could use 6, but I am supporting lots of code built
> with 5.1.1), DAQ 6.8.1 (can up to 6.9.1 if it matters), PXI-6052E,
> SCXI-1102, SCXI-1303 (or TC-2095).(using SCXI addressing).
>
> The problem occurs when I try to configure multiple scan lists with
> gaps between channels.
> (see LV DAQ SCXI example SCXI-1102/1127/1101 Thermocouple)
> example channel list:
> ob1 ! sc1 ! md1 ! cjtemp
> ob1 ! sc1 ! md1 ! 0:3
> ob1 ! sc1 ! md1 ! 5:9
> This gives an error: -10370 in AI Group Config.
> Likewise if I use an individual channel in each address string. like:
> ..md1 ! 0
> ..md1 ! 1
> ..md1 ! 3
>
> But, I can skip channels between cjtemp and the first channel of the
> next scanlist without error.
> Also, I can add scan lists for other modules, like:
> ..md1 ! 0:3
> ..md1 ! 4:8
> ..md3 ! 12:14
> without error!
>
> What I really want to do is to do AI Config first for all channels,
> then start, then loop on AI Read and some processing & storage.
> When I loop through the channel address lists (strings with contiguous
> channel sets e.g. 3:6) I get the same task # for all config calls.
> Then when I loop through the AI Start's for each , I get an error
> -10609 in AI Clock Config.
>
> The thing is that I cannot necessarily have all contiguous channels,
> and I don't want to go through a sequence of {AIConfig, AIStart,
> AIRead, AI CLear} for each scanlist each time through. That takes too
> much time and resources.
>
> Eventually I want to configure multiple non-contiguous scanlists in
> multiple SCXI modules.
> But, for right now I need to do this for one SCXI module.
>
> Anyone have any ideas?
> How can I approach this.
> Thanks
> Dave

Non-Overlapping channels bleed over

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