RE: [WISPA] once again, several of the key...
lol...rather than trying to change the subject Patrick, why not answer Marlon's question? Here it is to refresh your memory. Try to stay on topic. mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. Your answer was to change a setting in the VL radio and to imply problem solved! Yah, right! BTW, I'm not the only one scoffing at your Alvarion manual regurgitation. Twice today alone! Instead focus on the questions being presented. Best, Brad -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Leary Sent: Tuesday, December 26, 2006 3:07 PM To: WISPA General List Subject: RE: [WISPA] once again, several of the key... So "contention window algorithm" is a "glossy advertisement buzz word?" Yeah, I'm sure thems some hot and sexy buzzwords there. Looks to me like that's about as dry and technically desciptive -- i.e. the ANTITHESIS of hype -- as well could do. Brad, if that's a BS "glossy" buzz word, then exactly WHAT, pray tell, should we call such an algorithm? Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brad Belton Sent: Tuesday, December 26, 2006 12:36 PM To: 'WISPA General List' Subject: RE: [WISPA] once again, several of the key... This is a bit misleading and doesn't answer Marlon's question. Entering a "0" value in the VL "contention window algorithm" setting will indeed turn off the VL contention mechanism, but it will do little for the client behind the VL radio trying to pass data. Glossy advertisement buzz words like "contention window algorithm" will not solve the problem Marlon describes. Relocating to a new channel, band and/or polarity is a good start to getting your client back up and running in such an event. Throw in a RX threshold and you'll even have a better chance at keeping that client! Best, Brad -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Leary Sent: Tuesday, December 26, 2006 1:20 PM To: WISPA General List Subject: RE: [WISPA] once again, several of the key... mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. PL: Marlon, "The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not Used..." So one could set the value to 0 and that essentially tuns off the contention mechanism. BTW, regarding ATPC, I think we can all expect ATPC to be mandatory for any new UL frequency. Like it will be for 3650MHz (it was required in the initial R&O). Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance
RE: [WISPA] once again, several of the key...
So "contention window algorithm" is a "glossy advertisement buzz word?" Yeah, I'm sure thems some hot and sexy buzzwords there. Looks to me like that's about as dry and technically desciptive -- i.e. the ANTITHESIS of hype -- as well could do. Brad, if that's a BS "glossy" buzz word, then exactly WHAT, pray tell, should we call such an algorithm? Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brad Belton Sent: Tuesday, December 26, 2006 12:36 PM To: 'WISPA General List' Subject: RE: [WISPA] once again, several of the key... This is a bit misleading and doesn't answer Marlon's question. Entering a "0" value in the VL "contention window algorithm" setting will indeed turn off the VL contention mechanism, but it will do little for the client behind the VL radio trying to pass data. Glossy advertisement buzz words like "contention window algorithm" will not solve the problem Marlon describes. Relocating to a new channel, band and/or polarity is a good start to getting your client back up and running in such an event. Throw in a RX threshold and you'll even have a better chance at keeping that client! Best, Brad -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Leary Sent: Tuesday, December 26, 2006 1:20 PM To: WISPA General List Subject: RE: [WISPA] once again, several of the key... mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. PL: Marlon, "The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not Used..." So one could set the value to 0 and that essentially tuns off the contention mechanism. BTW, regarding ATPC, I think we can all expect ATPC to be mandatory for any new UL frequency. Like it will be for 3650MHz (it was required in the initial R&O). Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should b
RE: [WISPA] once again, several of the key...
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Marlon K. Schafer (509) 982-2181 Sent: Tuesday, December 26, 2006 2:33 PM To: WISPA General List Subject: Re: [WISPA] once again, several of the key... OK, so when we set the value to 0, how does the ap decide who it's going to listen to and when it'll talk? Is this the same as turning the radio into a polling mechanism? Marlon (509) 982-2181 Equipment sales (408) 907-6910 (Vonage)Consulting services 42846865 (icq)And I run my own wisp! [EMAIL PROTECTED] www.odessaoffice.com/wireless www.odessaoffice.com/marlon/cam - Original Message - From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 11:19 AM Subject: RE: [WISPA] once again, several of the key... mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. PL: Marlon, "The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not Used..." So one could set the value to 0 and that essentially tuns off the contention mechanism. BTW, regarding ATPC, I think we can all expect ATPC to be mandatory for any new UL frequency. Like it will be for 3650MHz (it was required in the initial R&O). Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. mks:
RE: [WISPA] once again, several of the key...
This is a bit misleading and doesn't answer Marlon's question. Entering a "0" value in the VL "contention window algorithm" setting will indeed turn off the VL contention mechanism, but it will do little for the client behind the VL radio trying to pass data. Glossy advertisement buzz words like "contention window algorithm" will not solve the problem Marlon describes. Relocating to a new channel, band and/or polarity is a good start to getting your client back up and running in such an event. Throw in a RX threshold and you'll even have a better chance at keeping that client! Best, Brad -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Leary Sent: Tuesday, December 26, 2006 1:20 PM To: WISPA General List Subject: RE: [WISPA] once again, several of the key... mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. PL: Marlon, "The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not Used..." So one could set the value to 0 and that essentially tuns off the contention mechanism. BTW, regarding ATPC, I think we can all expect ATPC to be mandatory for any new UL frequency. Like it will be for 3650MHz (it was required in the initial R&O). Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. mks: Some of my new wifi gear has the ability to tune for distanc
Re: [WISPA] once again, several of the key...
OK, so when we set the value to 0, how does the ap decide who it's going to listen to and when it'll talk? Is this the same as turning the radio into a polling mechanism? Marlon (509) 982-2181 Equipment sales (408) 907-6910 (Vonage)Consulting services 42846865 (icq)And I run my own wisp! [EMAIL PROTECTED] www.odessaoffice.com/wireless www.odessaoffice.com/marlon/cam - Original Message - From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 11:19 AM Subject: RE: [WISPA] once again, several of the key... mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. PL: Marlon, "The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not Used..." So one could set the value to 0 and that essentially tuns off the contention mechanism. BTW, regarding ATPC, I think we can all expect ATPC to be mandatory for any new UL frequency. Like it will be for 3650MHz (it was required in the initial R&O). Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. mks: Some of my new wifi gear has the ability to tune for distances. It's a great feature and it's amazing how much of a difference it can make. - Low Priority Traffic Minimum Percent feature ensures a selectable certain amount of the t
RE: [WISPA] once again, several of the key...
Marlon, I also just realized you asked what the "Lost Beacon Threshold" setting is about. In standard CSMA/CA radios, the APs will reset if their beacons are not received within a certain window, which can cause havoc on the network. This can happen in high interference environments. With BreezeACCESS VL an operator can set the time value for the "Lost Beacon Threshold." >From the manual: When [an AU] is unable to send beacon frames for a predetermined period of time, such as in the case of interference, the AU resets itself. The Lost Beacons Transmission Threshold parameter represents the number of consecutive lost beacons after which the unit will reset itself. The range for this parameter is 100 - 1000 or 0. When the parameter is set to 0 this feature is disabled, i.e. internal refresh will never be performed. The default value is 218. Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses. -- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
RE: [WISPA] once again, several of the key...
I should also note our support of jumbo packets of 1600 bytes + 4 bytes of CRC. If VLAN is used the length is the same 1600 + 4 bytes. This applies to version 4.0.23 or higher. Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Leary Sent: Tuesday, December 26, 2006 11:48 AM To: WISPA General List Subject: RE: [WISPA] once again, several of the key... Mark, ...also, in terms of your question about packet aggregation, BreezeACCESS VL employs very aggressive concatenation. That is why it delivers over 40,000 packets per second performance of small packets (such as 64k frames). The radio also allows setting the "Maximum Concatenated Frame Size," as well as disabling the concatenation feature. Frame sizes (in software version 4.0 and hardware rev. C or higher) can be aggregated 4032 bytes. As well, you can configure the max number of concatenated frames. Finally, the concatenation process is performed separately by the AU for each subscriber radio. Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Koskenmaki Sent: Tuesday, December 26, 2006 10:57 AM To: WISPA General List Subject: Re: [WISPA] once again, several of the key... Hopefully you understand all of those:) Part of Marlon's issue with the basic 802.11 system is talked about below, but of course, since it's there, the "tuneability" helps, but does not resolve the issue. I beleive Marlon's reference to CSMA / CA is two pronged. While it's true that recieved noise will block transmission, it also blocks reception of ACK packets, meaning a "double" whammy. During periods of high noise or repetitive noise, not only does the AP wait to transmit, it then fails to beleive that the transmission was accepted. After so many of thse failures, it then renegotiates the rate at which it's connected and tries again. While these are not the same process, they do link to each and occur in cascade-type failure. I have seen data on a nearly clear channel suddenly have a 200, 300 or more ms interruption while this "cascade" occurs... repettive noise, rate renegotiations and contention window increases, and ack failures from weak clients all cause all clients to have that momentary communication block. I believe there have been quite a number of interesting means of addressing this, as I recall some products from Trango don't "ack" packets, but instead allows the higher layer controls to ensure data integrity, while some versions seem to have a mechanism to request retransmits. There, of course, are polling type systems, and so on. Each has its perceived strengths and weaknesses. Overall, while what you post below is quite interesting, I doubt that most of us (including me) fully grasp what tuning each of these parameters does "in real life" and why you'd use them and under what circumstances. Thus, I really don't know what effect in real life all this ability to "muck with the works" will have. I have seen real world demonstrations of how differring equipment using the exact same hardware, but different settings for many of those settings performs dramatically different. But not understanding the full picture of what each does, I cannot "estimate" in my mind their worth, nor how much they alleviate the various issues that are part of the nature of 802.11 based systems. I also don't see any mention of packet aggregation or hardware compression, which would be wonderful things to have, and would improve the overall "life" and performance of the system. I believe what most of the respondents have at issue here is really the reliance upon 802.11, which is simply NOT anywhere near "great" when it comes to WISP use. Yes, it appears that you can raise the threshold for ignoring noise, and you can tune the system to better cope with varioius kind of situations - distance, colocated small cells, etc. And then the high inefficiency that 802.11 introduces with it's "ack" mechanism and the large amount of access point time spent doing nothing but passing time, waiting for ACK packets. Please understand, I am neither criticizing nor praising, it just appears to me that people are talking past each other, and that neither I nor at least some of the readers, really understand what real life value these things have. +++ neofast.net - fast internet for North East Oregon and South East Washington email me at mark at neofast dot net 541-969-8200 Direct commercial inquiries to purchasing at neofast dot net ----- Original Message ----
RE: [WISPA] once again, several of the key...
Mark, ...also, in terms of your question about packet aggregation, BreezeACCESS VL employs very aggressive concatenation. That is why it delivers over 40,000 packets per second performance of small packets (such as 64k frames). The radio also allows setting the "Maximum Concatenated Frame Size," as well as disabling the concatenation feature. Frame sizes (in software version 4.0 and hardware rev. C or higher) can be aggregated 4032 bytes. As well, you can configure the max number of concatenated frames. Finally, the concatenation process is performed separately by the AU for each subscriber radio. Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Koskenmaki Sent: Tuesday, December 26, 2006 10:57 AM To: WISPA General List Subject: Re: [WISPA] once again, several of the key... Hopefully you understand all of those:) Part of Marlon's issue with the basic 802.11 system is talked about below, but of course, since it's there, the "tuneability" helps, but does not resolve the issue. I beleive Marlon's reference to CSMA / CA is two pronged. While it's true that recieved noise will block transmission, it also blocks reception of ACK packets, meaning a "double" whammy. During periods of high noise or repetitive noise, not only does the AP wait to transmit, it then fails to beleive that the transmission was accepted. After so many of thse failures, it then renegotiates the rate at which it's connected and tries again. While these are not the same process, they do link to each and occur in cascade-type failure. I have seen data on a nearly clear channel suddenly have a 200, 300 or more ms interruption while this "cascade" occurs... repettive noise, rate renegotiations and contention window increases, and ack failures from weak clients all cause all clients to have that momentary communication block. I believe there have been quite a number of interesting means of addressing this, as I recall some products from Trango don't "ack" packets, but instead allows the higher layer controls to ensure data integrity, while some versions seem to have a mechanism to request retransmits. There, of course, are polling type systems, and so on. Each has its perceived strengths and weaknesses. Overall, while what you post below is quite interesting, I doubt that most of us (including me) fully grasp what tuning each of these parameters does "in real life" and why you'd use them and under what circumstances. Thus, I really don't know what effect in real life all this ability to "muck with the works" will have. I have seen real world demonstrations of how differring equipment using the exact same hardware, but different settings for many of those settings performs dramatically different. But not understanding the full picture of what each does, I cannot "estimate" in my mind their worth, nor how much they alleviate the various issues that are part of the nature of 802.11 based systems. I also don't see any mention of packet aggregation or hardware compression, which would be wonderful things to have, and would improve the overall "life" and performance of the system. I believe what most of the respondents have at issue here is really the reliance upon 802.11, which is simply NOT anywhere near "great" when it comes to WISP use. Yes, it appears that you can raise the threshold for ignoring noise, and you can tune the system to better cope with varioius kind of situations - distance, colocated small cells, etc. And then the high inefficiency that 802.11 introduces with it's "ack" mechanism and the large amount of access point time spent doing nothing but passing time, waiting for ACK packets. Please understand, I am neither criticizing nor praising, it just appears to me that people are talking past each other, and that neither I nor at least some of the readers, really understand what real life value these things have. +++ neofast.net - fast internet for North East Oregon and South East Washington email me at mark at neofast dot net 541-969-8200 Direct commercial inquiries to purchasing at neofast dot net ----- Original Message ----- From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 10:20 AM Subject: [WISPA] once again, several of the key... > ...features that make VL NOT a basic CSMA/CA product. > > - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS > VL system uses a special mechanism based on detecting the presence of a > carrier signal and analyzing the information contained in the > transmissions of the AU to estimate the activity of
RE: [WISPA] once again, several of the key...
...by the way, also, along with being able to set values in VL for max number of retries, etc., only unicast packets are retransmitted if not acknowledged. Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Koskenmaki Sent: Tuesday, December 26, 2006 10:57 AM To: WISPA General List Subject: Re: [WISPA] once again, several of the key... Hopefully you understand all of those:) Part of Marlon's issue with the basic 802.11 system is talked about below, but of course, since it's there, the "tuneability" helps, but does not resolve the issue. I beleive Marlon's reference to CSMA / CA is two pronged. While it's true that recieved noise will block transmission, it also blocks reception of ACK packets, meaning a "double" whammy. During periods of high noise or repetitive noise, not only does the AP wait to transmit, it then fails to beleive that the transmission was accepted. After so many of thse failures, it then renegotiates the rate at which it's connected and tries again. While these are not the same process, they do link to each and occur in cascade-type failure. I have seen data on a nearly clear channel suddenly have a 200, 300 or more ms interruption while this "cascade" occurs... repettive noise, rate renegotiations and contention window increases, and ack failures from weak clients all cause all clients to have that momentary communication block. I believe there have been quite a number of interesting means of addressing this, as I recall some products from Trango don't "ack" packets, but instead allows the higher layer controls to ensure data integrity, while some versions seem to have a mechanism to request retransmits. There, of course, are polling type systems, and so on. Each has its perceived strengths and weaknesses. Overall, while what you post below is quite interesting, I doubt that most of us (including me) fully grasp what tuning each of these parameters does "in real life" and why you'd use them and under what circumstances. Thus, I really don't know what effect in real life all this ability to "muck with the works" will have. I have seen real world demonstrations of how differring equipment using the exact same hardware, but different settings for many of those settings performs dramatically different. But not understanding the full picture of what each does, I cannot "estimate" in my mind their worth, nor how much they alleviate the various issues that are part of the nature of 802.11 based systems. I also don't see any mention of packet aggregation or hardware compression, which would be wonderful things to have, and would improve the overall "life" and performance of the system. I believe what most of the respondents have at issue here is really the reliance upon 802.11, which is simply NOT anywhere near "great" when it comes to WISP use. Yes, it appears that you can raise the threshold for ignoring noise, and you can tune the system to better cope with varioius kind of situations - distance, colocated small cells, etc. And then the high inefficiency that 802.11 introduces with it's "ack" mechanism and the large amount of access point time spent doing nothing but passing time, waiting for ACK packets. Please understand, I am neither criticizing nor praising, it just appears to me that people are talking past each other, and that neither I nor at least some of the readers, really understand what real life value these things have. +++ neofast.net - fast internet for North East Oregon and South East Washington email me at mark at neofast dot net 541-969-8200 Direct commercial inquiries to purchasing at neofast dot net - Original Message ----- From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 10:20 AM Subject: [WISPA] once again, several of the key... > ...features that make VL NOT a basic CSMA/CA product. > > - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS > VL system uses a special mechanism based on detecting the presence of a > carrier signal and analyzing the information contained in the > transmissions of the AU to estimate the activity of other SUs served by > the AU.) The available values are 0, 7, 15, 31, 63, 127, 255, 511 and > 1023. A value of 0 means that the contention window algorithm is not > used and that the unit will attempt to access the medium immediately > after a time equal to DIFS. The default min. value is 15. The default > maximum is 1023. > > - Cell Distance Mode feature: The higher the distance of an SU from the > AU that is serving it, the high
RE: [WISPA] once again, several of the key...
Mark, yes that is true with basic CSMA/CA, but VL, again, allows adjustments of parameters to prevent what you fear. For example, the ack time is first based on the Max Cell Distance setting you set, so the radio knows to expect, so to speak, an ack from each station within a very specific time and it knows the ack from each station will be different (it 'learns' that info). So if the ack does not come when expected, the radio will attempt a retrans, but it will not "cascade" as you fear. Why, because you are able to set the maximum number of retries. Not only can you do that, but you can set different values for that retry number for high priority versus low priority traffic. Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Koskenmaki Sent: Tuesday, December 26, 2006 10:57 AM To: WISPA General List Subject: Re: [WISPA] once again, several of the key... Hopefully you understand all of those:) Part of Marlon's issue with the basic 802.11 system is talked about below, but of course, since it's there, the "tuneability" helps, but does not resolve the issue. I beleive Marlon's reference to CSMA / CA is two pronged. While it's true that recieved noise will block transmission, it also blocks reception of ACK packets, meaning a "double" whammy. During periods of high noise or repetitive noise, not only does the AP wait to transmit, it then fails to beleive that the transmission was accepted. After so many of thse failures, it then renegotiates the rate at which it's connected and tries again. While these are not the same process, they do link to each and occur in cascade-type failure. I have seen data on a nearly clear channel suddenly have a 200, 300 or more ms interruption while this "cascade" occurs... repettive noise, rate renegotiations and contention window increases, and ack failures from weak clients all cause all clients to have that momentary communication block. I believe there have been quite a number of interesting means of addressing this, as I recall some products from Trango don't "ack" packets, but instead allows the higher layer controls to ensure data integrity, while some versions seem to have a mechanism to request retransmits. There, of course, are polling type systems, and so on. Each has its perceived strengths and weaknesses. Overall, while what you post below is quite interesting, I doubt that most of us (including me) fully grasp what tuning each of these parameters does "in real life" and why you'd use them and under what circumstances. Thus, I really don't know what effect in real life all this ability to "muck with the works" will have. I have seen real world demonstrations of how differring equipment using the exact same hardware, but different settings for many of those settings performs dramatically different. But not understanding the full picture of what each does, I cannot "estimate" in my mind their worth, nor how much they alleviate the various issues that are part of the nature of 802.11 based systems. I also don't see any mention of packet aggregation or hardware compression, which would be wonderful things to have, and would improve the overall "life" and performance of the system. I believe what most of the respondents have at issue here is really the reliance upon 802.11, which is simply NOT anywhere near "great" when it comes to WISP use. Yes, it appears that you can raise the threshold for ignoring noise, and you can tune the system to better cope with varioius kind of situations - distance, colocated small cells, etc. And then the high inefficiency that 802.11 introduces with it's "ack" mechanism and the large amount of access point time spent doing nothing but passing time, waiting for ACK packets. Please understand, I am neither criticizing nor praising, it just appears to me that people are talking past each other, and that neither I nor at least some of the readers, really understand what real life value these things have. +++ neofast.net - fast internet for North East Oregon and South East Washington email me at mark at neofast dot net 541-969-8200 Direct commercial inquiries to purchasing at neofast dot net - Original Message - From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 10:20 AM Subject: [WISPA] once again, several of the key... > ...features that make VL NOT a basic CSMA/CA product. > > - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS > VL system uses a special mechanism based on detecting the presence of a > carrier signal and analyzing
RE: [WISPA] once again, several of the key...
mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. PL: Marlon, "The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not Used..." So one could set the value to 0 and that essentially tuns off the contention mechanism. BTW, regarding ATPC, I think we can all expect ATPC to be mandatory for any new UL frequency. Like it will be for 3650MHz (it was required in the initial R&O). Patrick Leary AVP WISP Markets Alvarion, Inc. o: 650.314.2628 c: 760.580.0080 Vonage: 650.641.1243 [EMAIL PROTECTED] mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. mks: Some of my new wifi gear has the ability to tune for distances. It's a great feature and it's amazing how much of a difference it can make. - Low Priority Traffic Minimum Percent feature ensures a selectable certain amount of the traffic is reserved to low priority packets to prevent starvation of low priority traffic when there is a high demand for high priority traffic. mks: Cool. - Layer-2 traffic prioritization based on IEEE 802.1p and layer-3 traffic prioritization based on either IP ToS Precedence (RFC791) or DSCP (RFC2474). It also supports traffic prioritization based on UDP and/or TCP port ranges. In addition, it may use the optional Wireless Link Prioritization (WLP) feature to fully support delay sensitive applications, enabling Multimedia Application Prioritization (MAP) for high performance voice and video. (MAP can increase VoIP capacity by as much as 500%) mks: That's good. As long as we have clear air for the transmit cycle.. - Auto o
Re: [WISPA] once again, several of the key...
Hopefully you understand all of those:) Part of Marlon's issue with the basic 802.11 system is talked about below, but of course, since it's there, the "tuneability" helps, but does not resolve the issue. I beleive Marlon's reference to CSMA / CA is two pronged. While it's true that recieved noise will block transmission, it also blocks reception of ACK packets, meaning a "double" whammy. During periods of high noise or repetitive noise, not only does the AP wait to transmit, it then fails to beleive that the transmission was accepted. After so many of thse failures, it then renegotiates the rate at which it's connected and tries again. While these are not the same process, they do link to each and occur in cascade-type failure. I have seen data on a nearly clear channel suddenly have a 200, 300 or more ms interruption while this "cascade" occurs... repettive noise, rate renegotiations and contention window increases, and ack failures from weak clients all cause all clients to have that momentary communication block. I believe there have been quite a number of interesting means of addressing this, as I recall some products from Trango don't "ack" packets, but instead allows the higher layer controls to ensure data integrity, while some versions seem to have a mechanism to request retransmits. There, of course, are polling type systems, and so on. Each has its perceived strengths and weaknesses. Overall, while what you post below is quite interesting, I doubt that most of us (including me) fully grasp what tuning each of these parameters does "in real life" and why you'd use them and under what circumstances. Thus, I really don't know what effect in real life all this ability to "muck with the works" will have. I have seen real world demonstrations of how differring equipment using the exact same hardware, but different settings for many of those settings performs dramatically different. But not understanding the full picture of what each does, I cannot "estimate" in my mind their worth, nor how much they alleviate the various issues that are part of the nature of 802.11 based systems. I also don't see any mention of packet aggregation or hardware compression, which would be wonderful things to have, and would improve the overall "life" and performance of the system. I believe what most of the respondents have at issue here is really the reliance upon 802.11, which is simply NOT anywhere near "great" when it comes to WISP use. Yes, it appears that you can raise the threshold for ignoring noise, and you can tune the system to better cope with varioius kind of situations - distance, colocated small cells, etc. And then the high inefficiency that 802.11 introduces with it's "ack" mechanism and the large amount of access point time spent doing nothing but passing time, waiting for ACK packets. Please understand, I am neither criticizing nor praising, it just appears to me that people are talking past each other, and that neither I nor at least some of the readers, really understand what real life value these things have. +++ neofast.net - fast internet for North East Oregon and South East Washington email me at mark at neofast dot net 541-969-8200 Direct commercial inquiries to purchasing at neofast dot net - Original Message ----- From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 10:20 AM Subject: [WISPA] once again, several of the key... > ...features that make VL NOT a basic CSMA/CA product. > > - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS > VL system uses a special mechanism based on detecting the presence of a > carrier signal and analyzing the information contained in the > transmissions of the AU to estimate the activity of other SUs served by > the AU.) The available values are 0, 7, 15, 31, 63, 127, 255, 511 and > 1023. A value of 0 means that the contention window algorithm is not > used and that the unit will attempt to access the medium immediately > after a time equal to DIFS. The default min. value is 15. The default > maximum is 1023. > > - Cell Distance Mode feature: The higher the distance of an SU from the > AU that is serving it, the higher the time it takes for messages sent by > one of them to reach the other. To ensure appropriate services to all > SUs regardless of their distance from the AU while maintaining a high > overall performance level, two parameters should be adapted to the > distances of SUs from the serving AU: The time that a unit waits for a > response message before retransmission (ACK timeout) should take into > account the round trip propagation delay between the AU and the SU (The > one-w
Re: [WISPA] once again, several of the key...
- Original Message - From: "Patrick Leary" <[EMAIL PROTECTED]> To: "WISPA General List" Sent: Tuesday, December 26, 2006 10:20 AM Subject: [WISPA] once again, several of the key... ...features that make VL NOT a basic CSMA/CA product. - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS VL system uses a special mechanism based on detecting the presence of a carrier signal and analyzing the information contained in the transmissions of the AU to estimate the activity of other SUs served by the AU.) The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not used and that the unit will attempt to access the medium immediately after a time equal to DIFS. The default min. value is 15. The default maximum is 1023. mks: And what happens when we have someone light up a Wmux type system that's ALWAYS on? The time value won't make a difference since there will NEVER be totally clear air. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. mks: Some of my new wifi gear has the ability to tune for distances. It's a great feature and it's amazing how much of a difference it can make. - Low Priority Traffic Minimum Percent feature ensures a selectable certain amount of the traffic is reserved to low priority packets to prevent starvation of low priority traffic when there is a high demand for high priority traffic. mks: Cool. - Layer-2 traffic prioritization based on IEEE 802.1p and layer-3 traffic prioritization based on either IP ToS Precedence (RFC791) or DSCP (RFC2474). It also supports traffic prioritization based on UDP and/or TCP port ranges. In addition, it may use the optional Wireless Link Prioritization (WLP) feature to fully support delay sensitive applications, enabling Multimedia Application Prioritization (MAP)
RE: [WISPA] once again, several of the key...
Hello Patrick, With all due respect I don't think anyone here doubts the Alvarion VL is not simply a plain vanilla CSMA product. However, unfortunately the end result is the same when deployed in a RF hostile environment. All the items you list below while impressive are of little use in RF hostile environments. Believe me I wish this wasn't the case as I'd love to make use of some of the many nifty VL features. Unfortunately until VL makes the turn and offers the tools required in today's unlicensed fixed wireless world it is best suited for bursty, best effort applications. The VL can scream in the right environment, but unfortunately the days of friendly RF and clean unlicensed airways are long gone in many markets and disappearing quickly in the rural markets as well. As unlicensed users we require greater flexibility out of the products we purchase not less flexibility. Best, Brad -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Leary Sent: Tuesday, December 26, 2006 12:21 PM To: WISPA General List Subject: [WISPA] once again, several of the key... ...features that make VL NOT a basic CSMA/CA product. - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS VL system uses a special mechanism based on detecting the presence of a carrier signal and analyzing the information contained in the transmissions of the AU to estimate the activity of other SUs served by the AU.) The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not used and that the unit will attempt to access the medium immediately after a time equal to DIFS. The default min. value is 15. The default maximum is 1023. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. - Low Priority Traffic Minimum Percent feature ensures a selectable certain a
[WISPA] once again, several of the key...
...features that make VL NOT a basic CSMA/CA product. - Configurable Minimum and Maximum Contention Windows: The BreezeACCESS VL system uses a special mechanism based on detecting the presence of a carrier signal and analyzing the information contained in the transmissions of the AU to estimate the activity of other SUs served by the AU.) The available values are 0, 7, 15, 31, 63, 127, 255, 511 and 1023. A value of 0 means that the contention window algorithm is not used and that the unit will attempt to access the medium immediately after a time equal to DIFS. The default min. value is 15. The default maximum is 1023. - Cell Distance Mode feature: The higher the distance of an SU from the AU that is serving it, the higher the time it takes for messages sent by one of them to reach the other. To ensure appropriate services to all SUs regardless of their distance from the AU while maintaining a high overall performance level, two parameters should be adapted to the distances of SUs from the serving AU: The time that a unit waits for a response message before retransmission (ACK timeout) should take into account the round trip propagation delay between the AU and the SU (The one-way propagation delay at 5 GHz is 3.3 microseconds per km/5 microseconds per mile.). The higher the distance from the AU of the SU served by it, the higher the ACK timeout should be. The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or 20+Distance (miles)*2*5. To ensure fairness in the contention back-off algorithm between SUs located at different distances from the AU, the size of the time slot should also take into account the one-way propagation delay. The size of the time slot of all units in the cell should be proportional to the distance from the AU of the farthest SU served by it. The Cell Distance Mode parameter in the AU defines the method of computing distances. When set to Manual, the Maximum Cell Distance parameter should be configured with the estimated distance of the farthest SU served by the AU. When set to Automatic, the AU uses a special algorithm to estimate its distance from each of the SUs it serves, determine which SU is located the farthest and use the estimated distance of the farthest SU as the maximum cell distance. The value of the maximum cell distance parameter (either computed or configured manually) is transmitted in the beacon messages to all SUs served by the AU, and is used by all units to calculate the size of the time slot, that must be the same for all units in the same sector. When the Per SU Distance Learning option is enabled, the AU uses the re-association message to send to each SU its estimated distance from the AU. The per-SU distance is used to calculate the ACK timeout to be used by the SU. When the Per SU Distance Learning option is disabled (or if it cannot be used because the SU uses a previous SW version that does not support this feature), the SU will use the maximum cell distance to calculate the ACK timeout. The AU always uses the maximum cell distance to calculate the ACK timeout. It should be noted that if the size of the time slot used by all units is adapted to the distance of the farthest unit, then no unit will have an advantage when competing for services. However, this reduces the overall achievable throughput of the cell. In certain situations, the operator may decide to improve the overall throughput by reducing the slot size below the value required for full fairness. This means that when there is competition for bandwidth, the back-off algorithm will give an advantage to SUs that are located closer to the AU. The Cell Distance Parameters menu includes the following parameters: fairness factor, per SU distance learning, show cell distance parameters. - Low Priority Traffic Minimum Percent feature ensures a selectable certain amount of the traffic is reserved to low priority packets to prevent starvation of low priority traffic when there is a high demand for high priority traffic. - Layer-2 traffic prioritization based on IEEE 802.1p and layer-3 traffic prioritization based on either IP ToS Precedence (RFC791) or DSCP (RFC2474). It also supports traffic prioritization based on UDP and/or TCP port ranges. In addition, it may use the optional Wireless Link Prioritization (WLP) feature to fully support delay sensitive applications, enabling Multimedia Application Prioritization (MAP) for high performance voice and video. (MAP can increase VoIP capacity by as much as 500%) - Auto or configurable maximum cell distance - Automatic distance learning: Per SU Distance Learning mechanism controlled by the AU enables each SU to adapt its Acknowledge timeout to its actual distance from the AU, minimizing delays in the wireless link. - Configurable threshold for lost beacon watchdog - Intelligent ATPC (The algorithm is controlled by the AU that calculates for each received frame the average SNR at which it receives transmissions from the specific SU. The average cal
