Model 5-1: Simple Call Center

Transcription

1 As you gain experience in modeling, and as your models become bigger, more complex, and more detailed, you might find that you d like to be able to control or model things at a lower level with much details. Call center system provides a central number that customer call for : Technical support Sales Information Order status

2 One phone number for customers to call in to: The central feeds 26 trunk lines, one needed for each call (incoming or outgoing, talking or on hold) If all 26 lines are in use, arriving calls get a busy signal and are lost. Calls arrive with inter-arrivals ~ EXPO (0.857) min. First call arrives at time 0,three incoming call types Initial recording to decide ~ UNIF (0.1, 0.6) min. Tech support (76%), sales (16%), order status (8%)

3 If caller chooses Tech-support calls, a second recording requests asking which of the product type he is using : For product type 1 (25%), 2 (34%), or 3 (41%) Recording/select time ~ UNIF (0.1, 0.5) min There are eight technical support employees to answer tech-support calls: Two for product type 1, three for type 2, three for type 3 Separate FIFO queues for each type Conversation time ~ TRIA (3, 6, 18) min for all product types.

4 Then leaves system, if none of the employees is currently available,the customer is placed in an electronic queue where he is subjected to annoying rock music until support person is available. Sales calls Four sales staff, all have the same skills. One FIFO queue feeding all sales staff Conversation time ~ TRIA (4, 15, 45) min Then leaves system, if none of the sales staff is available the customer is placed in an electronic queue where he is subjected to soothing new -age space music because after all we re hoping for a sale until support person is available. 4

5 Order-status calls All the same Handled automatically by phone system No limit on number in process at a time, except for trunk-line limit. Conversation time ~ TRIA (2, 3, 4) min After conversation, 15% of callers opt to talk to a person Routed to sales staff, conversation lasts an additional TRIA (2, 3, 4) min Sales calls have higher priority (non-preemptive) that means if an order call is in queue waiting and a new arriving sales call enters the sale call will be given priority and answered first.

6 The call Center receives calls from 8am 6pm Must terminate arrival process at 6pm Although the system closes to new arriving calls at 6 pm, all calls that enter the system by that time are answered and served. To 6

7 Arrivals, Direct to Service 1)Create call arrivals Entity type Incoming Call Max Arrivals = MaxCalls, Variable initialized to which means that the arrival process will be terminated after arriving calls

8 Arrivals, Direct to Service -We also define the variable CallsPerArrival and initialize it to a value of 1. -We want to Record the number of attempted call Add 1 to Counter Name Attempted Calls using a record module. 8

9 Arrivals, Direct to Service 2)Entity data module Incoming Call Entity Type already there For Initial Picture, select Picture.Blue Ball 3)Decide module Trunk Line Available? Type = 2-way by Condition Select (logical) Expression for If NR() is number of units of that resource that are busy now MR() is number of units scheduled for the resource Expression : NR(Trunk Line)< MR(Trunk Line)

10 Steps for Decide Module: Define a resource call it trunk line give it capacity 26. Fill the entries for the decide module. 10

11 Decide Module : If False Record rejected call counter, Dispose If True: Seize a unit of Trunk Line Resource Release later 11

12 Arrivals, Direct to Service 12

13 Use the Delay module to account for initial recording time. 13

14 Decide module Determine Call Type Three-sided coin flip Type = N-way by Chance Note that probabilities are entered as percentages (0-100, not 0-1) Last entry is else Direct call to one of tech support, sales, or order-status areas

15 Tech-Support Calls Assign module Change Entity Type for separating out in results Add delay module for Tech Call delay UNIF(0.1,0.5) min

16 Tech-Support Calls Decide module for product type Different three-sided coin flip Direct to appropriate Process module for that product type Process modules for tech-support service Seize-Delay-Release Seize a unit from appropriate multi-unit Resource Use Tech Time defined in Expression data module 16

17 Tech-Support Calls 17

18 Sales Calls Assign module change Entity Type Process module Seize-Delay-Release Seize a unit of Sales Resource Sales calls priority over order-status calls that seek a person? Queue data module, Process Sales Call.Queue Type = Lowest Attribute Value Attribute Name = Sales Call Priority Undefined for sales calls, so has value 0... will set to 1 for order-status calls that seek a person, putting sales calls ahead in the queue

19 Sales Calls 19

20 Order-Status Calls Assign module change Entity Type Delay Use Decide Module No sales person required (15%) go directly to system-exit logic If Sales person required: Assign module set Sales Call Priority Attribute to 1 so these will have lower priority than real sales calls

21 Order-Status Calls Seize module for a unit of Sales resource Define Queue Name = Process Sales Call.Queue shared with sales calls Process module does not allow for specifying a shared queue, so can t use here Delay for conversation with sales person TRIA(2,3,4) minutes. Release the unit of Sales resource using release module. 21

22 Order-Status Calls 22

23 System Exit All calls of all types come here when finished Release module release the unit of Trunk Line resource seized upstream Record module increment Completed Calls counter Dispose of call

24 Final Model 5-1 c re a te c a l l a rri v a l s 0 Re c o rd Attem pted Call 0 Tr ue Se i z e Tru n k L i n e Tru n k L i n e Av a i la b l e? Initial rec ording De l a y 0 False Calls Arrive Record Rjec ted Ca l ls Di s p o s e Re j e c te d Ca l l s 0 As s i g n T e c h n i c a l Ca l l e n ti ty ty p e Technic al Call Recording Delay Determ ine Produc t Ty p e Proc es s Produc t T y p e 1 T e c h Ca l l De te rm i n e Ca l l Ty p e Else Else Proc es s Produc t T y p e 2 T e c h Ca l l Tech Support Calls 0 Proc es s Produc t T y p e 3 T e c h Ca l l 0 As s i g n Sa l e Ca l l En ti ty T y p e Sales Calls Pro c e s s Sa l e Ca l l 0 Releas e Trunk L i n e Re c o rd Com pleted Calls Di s p o s e o f c a l l e n ti ty 0 As s i g n Ord e r Sta tu s e n ti ty T y p e delay for order s ta tu s c a ll 0 No s a l e s p e rs o n Tr ue re q u i re d? 0 False Se t o rd e r Sta tu s Ca l l Pri o ri ty Order Status Calls Ca l l s i e z e s Sales person order s tatus c o n v e rs a ti o n wi th s ales person o rd e r s ta u s c a l l s releas es s ales person 24

25 Arrival-Cutoff Logic In our model we indicated that the system closes to new calls after 6 pm, but all calls that entered the system before that time are answered and processed. This means that we allow calls to enter the system from 8 am to 6 pm,a total of 600 minutes need to shutoff the arrivals after 600 minutes. making sure just one is created Time Between Arrivals = min

26 Arrival-Cutoff Logic Assign module to set Variable MaxCalls to 1(shutting off our arrival stream) Also after 600 minutes Arena schedules the next creation as long as the Max Arrivals is not reached.so as time 600 is approached,there will be a last illegal call. To cut off this illegal call also set in Assign module CallsPerArrival to 0 26

27 Arrival-Cutoff Logic 27

28 Run > Setup Replication Parameters tab (other tabs as usual) Base Time Units = Minutes Replication Length = Infinite (the default) Terminating Condition field: TNOW >= && Total WIP == 0 Arena clock Variable Greater than or equal to 600 minutes, (6pm) Base Time Units Logical and Variable we maintained in model Equality test for zero It s 6pm or later and there are no calls in the system.

29 Run > Setup Terminating Time frame of interest for each replication Terminating specific starting, stopping conditions (this model)stopping conditions could be of several forms fixed time, count, condition. 29

30 Output performance measures As a point of interest will be counting the Number of calls attempted, rejected(busy signals), and completed By call type total time in system Resource utilization of personnel, trunk lines..

31 Viewing Reports of Model 5-1 (one replication) Number of calls attempted, rejected(busy signals), and completed:

32 Viewing Reports of Model 5-1 By call type total time in system Resource utilization of personnel, trunk lines.. 32