Thanks much. I love it when you talk technical! Sorry, couldn't help it...
No really, the devil is always in the details in these things. This is just the detail I was looking for. After I digest I hope I may send questions your way off-list. Still hoping operators using other brands will share what bw management algorithms they may have built-in. thanks again, Rich ----- Original Message ----- From: Patrick Leary To: WISPA General List Sent: Wednesday, January 24, 2007 6:23 PM Subject: RE: [WISPA] Advanced Bandwidth Management Rich, --- Here is the detail from the manual. I have first cut & pasted the "graceful degradation" math detail: Graceful Degradation Limit (AU only) Sets the limit on using the graceful degradation algorithm. In cases of over demand, the performance of all SUs is degraded proportionally to their CIR (IR=(100%-k%) x CIR). The graceful degradation algorithm is used as long as k ≤ K, where K is the Graceful Degradation Limit. Beyond this point the simple "brute force" algorithm is used. The Graceful Degradation Limit should be raised in proportion to the demand in the cell. The higher the expected demand in a cell, the higher the value of the Graceful Degradation Limit. Higher demand can be expected in cases of significant over subscription and/or in deployments where a high number of subscribers are in locations without proper communication with the AU at the highest data rate. The available values range from 0 to 70 (%). --- And here is the whole bit about how the mechanism works 4.2.6.6.2 MIR and CIR Parameters The CIR (Committed Information Rate) specifies the minimum data rate guaranteed to the relevant subscriber. The MIR (Maximum Information Rate) value specifies the maximum data rate available for burst transmissions, provided such bandwidth is available. Under normal conditions, the actual Information Rate (IR) is between the applicable CIR and MIR values, based on the following formula: IR=CIR+K(MIR - CIR). In this formula K is between 0 and 1 and is determined dynamically by the AU according to overall demand in the cell and the prevailing conditions that influence the performance of the wireless link. In some situations the minimum rate (CIR) cannot be provided. This may result from high demand and poor wireless link conditions and/or high demand in over-subscribed cells. When this occurs, the actual information rate is lower than the CIR. The simple solution for managing the information rate in such cases can result in an unfair allocation of resources, as subscribers with a higher CIR actually receive an IR lower than the CIR designated for subscribers in a lower CIR bracket. A special algorithm for graceful degradation is incorporated into the AU, ensuring that the degradation of performance for each individual Subscriber Unit is proportional to its CIR. The MIR/CIR algorithm uses buffers to control the flow of data. To balance the performance over time, a special Burst Duration algorithm is employed to enable higher transmission rates after a period of inactivity. If no data is received from the Ethernet port during the last N seconds, the unit is allowed to transmit N times its CIR value without any delay. For example, after a period of inactivity of 0.5 seconds, a unit with CIR = 128 Kbps can transmit up to 128 Kbits x 0.5 = 64 Kbits without any delay. 4.2.6.6.2.1 MIR: Downlink (SU only) Sets the Maximum Information Rate of the downlink from the AU to the SU. The MIR value cannot be lower than the corresponding CIR value. Available values range and default value are shown inTable 4-12. The actual value will be the entered value rounded to the nearest multiple of 128 (N*128). 4.2.6.6.2.2 MIR: Uplink (SU only) Sets the Maximum Information Rate of the up-link from the SU to the AU. The MIR value cannot be lower than the corresponding CIR value. Available values range and default value are shown in Table 4-12. The actual value will be the entered value rounded to the nearest multiple of 128 (N*128). 4.2.6.6.2.3 CIR: Downlink (SU only) Sets the Committed Information Rate of the downlink from the AU to the SU. The CIR value cannot be higher than the corresponding MIR value. Available values range and default value are shown inTable 4-13. The actual value will be the entered value rounded to the nearest multiple of 128 (N*128). 4.2.6.6.2.4 CIR: Uplink (SU only) Sets the Committed Information Rate of the uplink from the SU to the AU. The CIR value cannot be higher than the corresponding MIR value. Available values range and default value are shown in Table 4-13. The actual value will be the entered value rounded to the nearest multiple of 128 (N*128). Table 4-12: MIR Ranges and Defaults MIR Uplink MIR Downlink Unit Type Range (Kbps) Default (Kbps) Range (Kbps) Default (Kbps) SU-3 128-2,048 2,048 128-3,072 3,072 SU-6 128-4,096 4,096 128-6,016 6,016 SU-54 128-53,888 32,896 128-53,888 32,896 Table 4-13: CIR Ranges and Defaults CIR Uplink and Downlink Unit Type Range (Kbps) Default (Kbps) SU-3 0-2,048 0 SU-6 0-4,096 0 SU-54 0-45,056 0 4.2.6.6.2.5 Maximum Burst Duration (SU and AU) Sets the maximum time for accumulating burst transmission rights according to the Burst Duration algorithm. Available values range from 0 to 2000 milliseconds). The default value is 5 (milliseconds), enabling a maximum burst of (0.005 X CIR) Kbps after a period of inactivity of 5 milliseconds or more. 4.2.6.6.2.6 Maximum Delay (SU only) Sets the maximum permitted delay in the buffers system. As certain applications are very sensitive to delay, if relatively high delays are permitted, these applications may suffer from poor performance due to data accumulation in the buffers from other applications, such as FTP. The Maximum Delay parameter limits the number of available buffers. Data that is delayed more than the permitted maximum delay is discarded. If the SU supports applications that are very sensitive to delay, the value of the Maximum Delay should be decreased. Valid values range from 300 to 10000 milliseconds. The default value is 5000 (milliseconds). 4.2.6.6.2.7 Graceful Degradation Limit (AU only) Sets the limit on using the graceful degradation algorithm. In cases of over demand, the performance of all SUs is degraded proportionally to their CIR (IR=(100%-k%) x CIR). The graceful degradation algorithm is used as long as k ≤ K, where K is the Graceful Degradation Limit. Beyond this point the simple "brute force" algorithm is used. The Graceful Degradation Limit should be raised in proportion to the demand in the cell. The higher the expected demand in a cell, the higher the value of the Graceful Degradation Limit. Higher demand can be expected in cases of significant over subscription and/or in deployments where a high number of subscribers are in locations without proper communication with the AU at the highest data rate. The available values range from 0 to 70 (%). The default value is 70 (%). 4.2.6.6.2.8 MIR Only Option (AU only) When the MIR Only Option is enabled, it forces the MIR/CIR algorithm to use MIR values only. The MIR/CIR algorithm determines the actual information rate for each of the supported SUs under changing conditions of demand, based on the configured CIR and MIR values. When the MIR Only Option is enabled, the MIR/CIR algorithm is overridden and forced to operate with MIR values only. For example, the AU attempts to enable all SUs to transmit/receive information at the specified MIR value. When enabled, the graceful degradation algorithm, which is a part of the CIR/MIR algorithm, is also disabled. The default is Enable. 4.2.6.6.2.9 Show MIR/CIR Parameters Displays the current values of the MIR and ---- 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 Rich Comroe Sent: Wednesday, January 24, 2007 4:01 PM To: WISPA General List Subject: Re: [WISPA] Advanced Bandwidth Management Fascinating. I only spoke of leaky bucket because that's practically a match to what Jason originally described to the list (and I happen to know of radios that have this algorithm internally programmed -- happens to be Canopy). But I presume there are other algorithms programmed to different manufacturer's radios. Patrick, is it possible to share details of the Alvarion implemented 4th gen algorithm you spoke of? ************************************************************************************ 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/ -- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
