Improving Revenue by System Integration and Cooperative Optimization Reservations & Yield Management Study Group Annual Meeting Berlin April 2002 UNIVERSITY of PADERBORN Georg Kliewer Sven Grothklags Klaus Weber
Slide 2 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Motivation - Planning Processes Fleet Assignment Aircraft Rotation Crew Pairing Crew Rostering Operation Control Network Design Market Modeling Revenue Management
Slide 3 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Agenda Business Process Mathematical Model Optimisation Algorithm Fleet Assignment Problem O&D Revenue Management Current System Integration System Integration Approaches Conclusions
Slide 4 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Fleet Assignment - Business Process Find most Profitable Subfleet Assignment Use a Subfleet that is Feasible for each Leg Use the Existing Fleet and no extra Aircraft Obey Blocktime and Groundtime Constraints Scheduling Activity NetLine Application Fleet Assignment weeklyfully-dated NetLine/Plan NetLine/Sched NetLine/Ops Operations Control Development
Slide 5 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Fleet Assignment - Business Process (cont)
Slide 6 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Strategic Profitability Evaluation Model Strategic-PEM is a forecasting model that measures the network profitability contribution of each schedule scenario The Strategic PEM forecasts are developed on an O&D basis for a representative week for a schedule period Input Data: average revenue for the O&Ds market demand for the O&Ds cost model fleeted schedule Output Data: overall schedule profitability profit information for each leg-subfleet combination
Slide 7 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Strategic Profitability Evaluation Model (cont) Fleet AssignmentProfitability Evaluation Model objective function for fleet assignment assignment Simulated Annealing Market Share Model Connection Builder Spill & Recapture Revenue & Cost Estimation constrained passenger flow prelim. capacity assignment schedule av. revenues market demand itineraries unconstrained demand
Slide 8 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Fleet Assignment - Mathematical Model PAD MUC FRA ground arc ( v-,v ) x l,f y v,v+ v v+ v- flight event leg l x l,f =1 leg l is assigned to subfleet f y v,v+ : aircraft flow on the ground
Slide 9 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Fleet Assignment - Optimisation Algorithm Fleet Assignment fleet schedule restrictions Accept/Reject Generate Neighbor Solution Update Solution final assignment Simulated Annealing Objective Function Profitability Evaluation Model
Slide 10 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Fleet Assignment - Optimisation Algorithm S = initial solution T = warming_up do S new = neighbor solution (S) cost = cost(S new ) - cost(S) if ( cost < 0 or accept( cost,T) ) S = S new until equilibrium T = update(T) until frozen Heuristic solution method based on local search 1 Frozen P Equilibrium
Slide 11 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Fleet Assignment - Results AlgorithmHill-ClimberSimulated Annealing Mixed- Integer Program -solution quality 98,5%99,7%>99,9%
Slide 12 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Agenda Business Process System Overview O&D Control Parameters Fleet Assignment Problem O&D Revenue Management Current System Integration System Integration Approaches Conclusions
Slide 13 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 O&D Revenue Management – Business Process Application NetLine/Plan NetLine/Sched NetLine/Ops NetLine/Price ProfitLine Business Activities Operations Control Pricing Revenue Management Development
Slide 14 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 O&D Revenue Management – System Overview O&D Forecast Engine O&D Optimiser Forecast Interface DB Optimiser Interface DB Inventory GDS... Forecast Building Demand Forecasts Control Parameters Forecasts based on either booking histories or market model and price elasticity model or both e.g. ODIF POS booking limits e.g. fare buckets
Slide 15 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 O&D Revenue Management – O&D Control Parameters EMSR varieties booking class limits per leg / compartment on various granularity levels, e.g. ODIF POS bid prices derived from EMSR curve or approximation fare bucket limits per leg / compartment revenue bucket limits per leg / compartment Dynamic programming bid prices per leg / compartment booking class limits derived from bid prices Parameters to be used by fleet assignment process Reflect demand demand variability estimated fares O&D control parameters depend on type of optimizer
Slide 16 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Agenda Cooperative Approach Fleet Assignment Problem O&D Revenue Management Current System Integration System Integration Approaches Conclusions
Slide 17 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Current System Integration - Cooperative Approach Profitability Evaluation Model Market Share Model Connection Builder Spill & Recapture Revenue & Cost Estimation constrained passenger flow capacity assignment itineraries unconstrained demand Fleet Assignment Accept/Reject Fleet Change on a Leg Sequence Update Solution Simulated Annealing Final Assignment Objective Function 4 5 6
Slide 18 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Current System Integration - Cooperative Approach (cont) Strategic PEM + Fleet AssignmentNetLine/Plan Tactical PEM + Fleet AssignmentNetLine/Sched fully-dated schedule Basic O&D Fleet Assignment Approximative revenue estimation Fast evaluation loop: essential for Simulated Annealing even faster with internal feedback by passenger flow model State
Slide 19 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Agenda Internal Feedback External Feedback by O&D Revenue Management System System View Fleet Assignment Problem O&D Revenue Management Current System Integration System Integration Approaches Conclusions
Slide 20 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 System Integration – Internal Feedback Fleet Assignment Profitability Evaluation Model Accept/Reject Passenger Flow LP-Model Dual Variables for Legs Fleet Change on a Leg Sequence Update Solution Final Assignment Simulated Annealing Market Share Model Connection Builder Spill & Recapture Revenue & Cost Estimation passenger flow capacity assignment itineraries unconstrained demand Objective Function 4 5
Slide 21 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Profitability Evaluation Model System Integration – External Feedback by O&D RMS Fleet Assignment Accept/Reject Fleet Change on a Leg Sequence Update Solution Simulated Annealing Final Assignment O&D Revenue Management O&D Forecast Engine O&D Optimiser O&D Forecasts O&D Control Parameters Revenue Estimation Objective Function Capacity Assignment Market Share Model Connection Builder Spill & Recapture Cost Estimation passenger flow capacity assignment itineraries unconstrained demand
Slide 22 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 System Integration – System Details Iterative Proration (ProBP) O&D Revenue Management O&D Forecast Engine O&D Optimiser O&D Forecasts Capacity Assignment ODIF POS buckets O&D Control Parameters
Slide 23 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 System Integration – System Details (cont) O&D Revenue Management O&D Forecast Engine O&D Optimiser O&D Forecasts O&D Control Parameters Revenue Estimation Capacity Assignment Estimated revenue = sum of EMSR values
Slide 24 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 System Integration – System Details (cont) O&D Revenue Management O&D Forecast Engine O&D Optimiser O&D Forecasts Capacity Assignment O&D Control Parameters Dynamic Bid Price (DynBP) models revenue management as multistage decision process Bid price matrix per compartment time to departure vacant seats R t-1 (x) = max[f i + R t (x-1), R t (x)] = max [uf i + R t (x-u)] u {0, 1} R t-1 (x) = R t (x) t t-1 x x-1 R t-1 (x) = f i + R t (x-1)
Slide 25 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 System Integration – System Details (cont) C Increase current optimization point Decrease remaining capacity next optimization point C-1 C-2 tt-1t-2 time to deptarture Bid price matrix per compartment O&D Revenue Management O&D Forecast Engine O&D Optimiser O&D Forecasts O&D Control Parameters Revenue Estimation Capacity Assignment Estimated revenue = sum of bid prices
Slide 26 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 System Integration – Discussion two loop system revenue estimation loop fleet assignment loop significant runtime differences coordination of loops capacity dependency of revenue management optimization runtime! Approximation? partly overlapping system functions (market model, OD-Forecast) redundancy, requires further integration forecast uncertainty and actual fares taken into account simple interfaces between fleet assigner and revenue management system more accurate revenue estimation StateChallenges
Slide 27 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 O&D Revenue Management System Current System Integration Fleet Assignment Problem Agenda System Integration Approaches Conclusions
Slide 28 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 applied in Fleet Assignment Systems of... Conclusions - Fleet Assignment in Practice Simulated Annealing-based Fleet Assignment Optimization substantial part of commercial Fleet Assignment tool Cooperative Approach Integrated Approaches prototype
Slide 29 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Conclusions - Summary Integration of Fleet Assignment and Revenue Management can improve overall revenue Facets of the fleet assignment problem introduced: business, mathematics, simulated annealing Substantial part: Profitability Evaluation Model (PEM) Revenue management system introduced: particularly important for integration: control parameters Current state of integration: Cooperative Approach with PEM (without integration of RMS) - successfully used by three airlines System integration prototype: based on internal passenger flow model (deterministic LP) based on external link to O&D RMS: EMSR-based, dynamic programming good better almost perfect
Slide 30 Grothklags, Kliewer, Weber: Improving Revenue by System Integration and Co-operative Optimization AGIFORS Reservations & Yield Management Study Group Annual Meeting 2002 Conclusions - Ongoing Work, Outlook Ongoing tests of system integration prototype Market Model used in FA is also used in Pricing further Integration possible Integration of the Passenger Flow Model in Fleet Assignment optimization approach for enhanced O&D Fleet Assignment Usage in short-term → pre-implementation phase: booking dependent (demand driven) fleet assignment
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