--- title: "Queuing system usefulness and types" subject: "Simulation and Modeling" chapter: 4 key: "semester_8/simulation_and_modeling:queuing-types-usefulness" source: https://www.bctengineer.com/q/semester_8/simulation_and_modeling/queuing-types-usefulness site: BCT Engineering --- # Queuing system usefulness and types Simulation and Modeling · Chapter 4: Queuing system - Asked in: 2069 Bhadra (old course), 2+2+6 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/simulation_and_modeling/queuing-types-usefulness - Whole chapter: https://www.bctengineer.com/md/semester_8/simulation_and_modeling/chapter-4 ## Question What is a queuing system? How is it useful for simulation? Explain the different types of queuing system with example. ## Short answer A queuing system consists of customers arriving, waiting in line, receiving service, and leaving. It is useful for simulation because many real systems are queues, simulation allows studying performance measures without disturbing the system, and it handles complex distributions where exact formulas fail. Types include single-server single-queue, multi-server single-queue, multi-server multi-queue, tandem queues, network of queues, and finite/infinite population or capacity. ## Answer #### Queuing system A **queuing system** is a system in which customers arrive for a service, wait in a line when the server is busy, receive service and leave. Examples are a bank counter, a petrol pump and a CPU with waiting processes. It consists of an arrival process, a queue, one or more servers and a queue discipline. #### Usefulness for simulation - Many real systems (banks, networks, factories, hospitals) are queues, so a queuing model gives a ready framework for building their simulation models. - Simulation of a queue shows how waiting time, queue length, idle time and utilisation change when the arrival rate, number of servers or service time changes, without disturbing the real system. - When arrival or service times follow complex distributions, or the queue has limited capacity or priorities, exact formulas often do not exist, and simulation is the practical method. - Results are used to decide staffing, buffer sizes and number of machines, and to compare alternatives cheaply before spending money. - Simple formulas such as M/M/1 results can be used to verify the simulation model. #### Types of queuing systems | Type | Description | Example | |---|---|---| | Single server, single queue | One queue, one server | Small shop with one cashier | | Multiple servers, single queue | One common line feeds several servers | Bank with a common line and several tellers | | Multiple servers, multiple queues | Each server has its own line | Supermarket checkout lanes, toll gates | | Series (tandem) queues | Customer passes through servers one after another | Assembly line, passport office with several counters | | Network of queues | Customers move between several service centres, possibly back again | Computer network, hospital departments | | Finite or infinite population | Source is limited (machines to repair) or very large | Machine repair shop vs public at a bank | | Finite or infinite capacity | Waiting room limited (customers lost when full) or unlimited | Telephone exchange lines vs a long road queue | Systems can also be classified by discipline: FIFO (ticket counter), LIFO (stack of plates), priority (emergency ward) and random service. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is simulation used when queues have limited capacity or priorities? A. Exact formulas do not exist for such complex cases B. Formulas are always exact for them C. Simulation is cheaper than doing nothing D. Priorities cannot be modelled by any method Answer: A. Complex distributions, limited capacity or priorities have no exact formulas, so simulation is practical. (Key point: Usefulness) 2. How can M/M/1 formulas help a simulation study? A. To generate arrival times B. To verify the simulation model C. To replace the clock D. To choose the programming language Answer: B. Simple results give a check on the simulation output. (Key point: Verification) 3. Which example fits multiple servers with multiple queues? A. A bank with one common line to several tellers B. A small shop with one cashier C. Supermarket checkout lanes or toll gates D. A passport office with counters one after another Answer: C. Each server having its own line is the multiple-queue type. (Key point: Types of queues) 4. What are series (tandem) queues? A. All customers wait in one common line for one server B. Servers have separate lines and customers never move C. Customers leave without any service D. The customer passes through servers one after another, e.g. an assembly line Answer: D. In tandem systems service stages are in series. 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