Guidance of Capacity Calculation in EV-DO Rev.A

1HUAWEI TECHNOLOGIES CO., LTD.
Calculation formula of EVDO capacity
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HUAWEI TECHNOLOGIES CO., LTD.
Subs per Sector = Throughput per Sector / User Speed / EAP
Throughput per Sector
User Speed
Equivalent active percentage (EAP) = (Subs DRF) x (Packet DRF)
EAP is an important parameter to scale the engrossed network resource by Subscribers
Subs DRF
The Number of users occupy the total users in BH
The recommend value is 15~25%. If accurate value is needed, the value can be get after calculating from existing network.
Packet DRF
The percentage of average downloading time comparing with the total time for per user
The recommend value is 15~25%. If there have subscribers, the value can be get after calculating from existing network.
For detail formula and illustration, refer to third part
Definition
Instance of FA calculation
Background
For instance: The total subscribers are 2k. And in the BH of 19:00~20:00, there are 500 subscribers online.
The calculation of FA capacity
Suppose the Packet DRF is 20%
To ensure the rate up to 300kbps per user, the FA calculation is:
= Throughput per Sector / User Speed / (Subs DRF x Packet DRF)
= 1.5Mbps / 300kbps / (500/2000 x 20%)
= 1.5Mbps / 300kbps / (25% x 20%)
= 100
Instance
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Definition of basic conception
PPP Session
After user open an account in the system, one session will be assigned. One Session delegates one connection.
The duration of one session
Packet Call
The data call caused by discontinuous service request in PPP Session
Basic Packet
BHCA (Busy Hour Call Attempt)
BHCA = ( Busy Hour Call attempt ) / (Subscriber Number)
BHE (Busy Hour Erlang)
CDR (Call Data Rate)
CDR = (Throughput) / (Holding time)
BHT (Busy Hour Throughput)
Four hierarchy EV-DO service model
Packet Call
PPP Session
PPP Session
Packet Call
Packet Call
PPP Session
Basic Packet
Basic Packet
Basic Packet
Basic Packet
Basic Packet
Basic Packet
Basic Packet
Dormant Timer
Illustration of DO data service traffic model(1)
One PPP Session means once dial-up access.
One PPP Session is constituted by many Packet Calls. Each Packet Call is composed by several Basic Packets.
The relationship between PPP Session and Packet Call
The data downloading or uploading are not always happen when user is on-line
The users’ status will switch to Dormant after a cycle (20s by default) of no data flowing. At this time one Packet Call is completed and the resource will be released to other users, but the PPP Session is not over.
When there is data flowing, the new Packet Call starting and the status of the user switch to Active again with new allocated resource.
The relation between Packet Call and Basic Packet
The data exchange is not happen all along the PPP Session
Although there is no data transfer during the intermission, it need time to judge whether to switch the status to Dormant. The data will be encapsulated into Basic Packet according to the different data rate in the Packet Call every time. And these packets are actually the data transfer process.
For example :Download traffic and frequency are different between web browsing and download big files. When browse webpage the Basic Packet may be multi-packet rate of 38.4kbps including characters or pictures. But in the other hand, when downloading a big file, there may be only one big packet in rate of 2457.6kbps is continuing transferred.
The Basic Packet rate is the real rate that users can realize.
The Model parameters and attributes
The latitudinal title refers to the 4 main parameters impacting the EVDO Service
The longitudinal title refers to the 5 attribute of the 4 main parameters
Parameters
Subscriber
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The calculation of FA capacity based on specified data rate
EAP = Subscriber DRF x PPP Session DRF x Packet Call DRF
Subscriber DRF = Online Subs on Busy Hour / Total Subs
PPP Session DRF= Packet Call Holding Time /PPP Session Holding Time
Packet Call DRF= Basic Packet Holding Time / Packet Call Holding Time
We can get the result based on above formula:
PPP Session DRF * Packet CALL DRF
= Basic Packet Holding Time /PPP Session Holding Time
=(Packet Call Throughput / Basic Packet CDR)/PPP Session Holding Time
=Packet Call Throughput /(Basic Packet Throughput / Basic Packet Holding Time)/ PPP Session Holding Time
= Basic Packet Holding Time/ PPP Session Holding Time
= Basic Packet Holding Time/ (Counter Period* PPP Session Number)
Definition
Illustration of parameters
Throughput per Sector, restricted by the bandwidth of EVDO, the average value is1500kbps
User Speed is the respected ratefor instance300kbps
Only DRF can impact the capacity of FA at the fixed throughput per sector and rate of 300kbps
DRF (Dormant Reduction Factor)
Subscriber DRF= Online Subs on Busy Hour / Total Subs. Online Subs on Busy Hour can be queried in Max Times of PPP Dormancy on PCF
PPP Session DRF * Packet CALL DRF
= Basic Packet Holding Time / (Counter Period * PPP Session Number)
Counter Period is the traffic cycle;
PPP Session Number is the active users in the statistical period
Because we can not know the exact time of PPP Session Holding Time, we only can suppose that all the active uses are connectted during the statistical period.
Basic Packet Holding Time = Basic Packet Number * Basic Packet Payload / Raw speed
Basic Packet Number can be get from the Stat.
The relationship among Basic Packet Number and Basic Packet Payload and Raw speed showed in the next table
Relation of Basic Packet Number, Basic Packet Payload, Raw speed
Adjustment of traffic model
With the increasing of the user, If the tariff strategy is not change, the habit of customer will not change too. So, theoretically, the DRF will not change.
But actually, with the increasing of the user, the Basic Packet allocation mechanism will change, the fact is that the Call DRF will increase along with the increasing of users. So generally we need to assume a bigger number for the number of Packet Call DRF to match the change of the theoretic capacity with the increasing of users
After getting the result of the three DRF, we should correct the value of Packet Call DRF according to the developing trend of recent network to adjust the value of Subscriber DRF and PPP Session DRF.
The theoretic traffic model:
Get the theoretic capacity value based on the existing network’s traffic model
The capacity, founded on the before formula, is called theoretical traffic model
Traffic model for operation
Used to guide how to operate and launching numbers based on the recent development of subscribers.
Definition
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Instance of capacity calculation in TN EVDO
Calculate one week’s billing record in BH, get the number of users and the data of PPP Session
Total launching number this month: Total Subs = 200
On-line user in BH this month: Online Subs on Busy Hour = Max Times of PPP Dormancy on PCF = 40
Total number of PPP Session
Total PPP Session Holding Time = Counter Time = 1800*7*2*40 Seconds
Note: 1800:the cycle of traffic Stat.; 7: 7 days of 1week; 2:each day 2“half an hour”;
40: total number of users
Total Basic Packet Action Time= 79243 Seconds
To ensure the rate of 2000kbps, input the above value to the formula:
Subscriber DRF = 40 / 200 = 20%
Basic Packet Action Time/PPP Session Holding Time=79243/1800/7/2/40=7.86%
EAP = Subscriber DRF x PPP Session DRF x Packet Call DRF = 20% * 7.86% = 1.57%
Subs per sector = Throughput per Sector / User Speed / EAP = 1500 / 300 / 1.57% = 318
The theoretic value calculated per sector base on the existing network is 318 users
Instance
Instance of one carrier’s capacity calculation
The DRF value adjusts to the below according to the user development trend
Subscriber DRF = 20%
1/5 user are on-line through EVDO network during BH
The DRF will decreasing with the increasing of users, because of the competition of getting the forward timeslot. One may cannot transfer without timeslot. Generally we need to assume a bigger number for the number of Packet Call DRF to match the change of the theoretic capacity
PPP Session DRF * Packet Call DRF = 20%
The equivalent activated rate in BH is: 20%
The final operate-guide traffic model
EAP = 20% * 20% = 4%
Conclusion
Instance
Please open the Excel file attached
Instance
CDR Type
Subscriber DRF = Online Subs on Busy Hour / Total Provisioned Subs
PPP Session DRF x Packet Call DRF
20%
PPP Session DRF x Packet Call DRF=Basic Packet Holding Time/ Counter Period/ PPP Session Number
EAP
4%
Users/Sector.Carrier
Concurrent Downloading Users Number
5
the number of users that supported at highest transmission flux simultaneously per FA
Provisionable Subscribers
125
The maximum of users can supported in one FA, this is a theoretic value. This number,Packet Call DRF and capacity will change with increasing of users.
Holding Time per PPP Session On Busy Hour
720
Seconds/Session
The time of one PPP connection per one hour in BH
Throughput per PPP Session On Busy Hour
136.070963206
kbs/Session
Concurrent Online Users
Users On Busy Hours
Subscriber DRF
0.2
Seconds/Session
The duration that one PPP connection cost per hour in BH
Total Days
25200
Seconds/Session
Suppose there are PPP connections in the statistical period. There will be warp if Stat. in the idel time.
FTCH 1228.8k 1Slot Sent Packet Count
3599242
Packet
1874328
Packet
13547
Packet
1024779
Packet
1717688
Packet
1221348
Packet
77007
Packet
4753673
Packet
894056
Packet
27030
Packet
4372749
Packet
4112206
Packet
285697
Packet
2328946
Packet
53913919488
Bite
79243.8272173762
second
theoretic traffic model
Subscriber DRF = Online Subs on Busy Hour / Total Provisioned Subs
PPP Session DRF x Packet Call DRF
7.86149%
PPP Session DRF x Packet Call DRF=Basic Packet Holding Time/ Counter Period/ PPP Session Number
EAP
1.57230%
Concurrent Downloading Users Number
5
the number of users that supported at highest transmission flux simultaneously per FA
Provisionable Subscribers
318.0058420307
The maximum of users can supported in one FA, this is a theoretic value. This number,Packet Call DRF and capacity will change with increasing of users.
Holding Time per PPP Session On Busy Hour
283.0136686335
Throughput per PPP Session On Busy Hour
53.4860312381
kbs/Session
SubsbyTime
Time
Subscribers
0.211029711
1053
users
28
days
Subscriber DRF
222.2142857143
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SubsbyTime
Time
Subscribers
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DRF definition
Packet Call DRF = Basic Packet Holding Time / Packet Call Holding Time
PPP Session DRF= Packet Call Holding Time / PPP Session Holding Time
CDR definition
Basic Packet CDR = Basic Packet Throughput / Basic Packet Holding Time
Packet Call CDR = Packet Call Throughput / Packet Call Holding Time
PPP Session CDR = PPP Session Throughput / PPP Session Holding Time
Packet Call Throughput = Basic Packet Throughput = PPP Session Throughput
Formula
Basic Packet CDR = Packet Call Throughput / Basic Packet Holding Time
PPP Session CDR = Packet Call Throughput / PPP Session Holding Time
Then
Basic Packet Holding Time = Packet Call Throughput / Basic Packet CDR
Packet Call Holding Time = Packet Call Throughput / Packet Call CDR
PPP Session Holding Time = Packet Call Throughput / PPP Session CDR
Result
Packet Call DRF = Basic Packet Holding Time / Packet Call Holding Time
= Packet Call CDR / Basic Packet CDR
PPP Session DRF= Packet Call Holding Time / PPP Session Holding Time
= PPP Session CDR / Packet Call CDR
Reference

Documents

Guidance of Capacity Calculation in EV-DO Rev.A