---
title: "Bluetooth network topology"
subject: "Instrumentation II"
chapter: 5
key: "semester_5/instrumentation_ii:bt-topology"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/bt-topology
site: BCT Engineering
---

# Bluetooth network topology

Instrumentation II · Chapter 5: Data Acquisition And Transmission

- Asked in: 2073 Chaitra, 4 marks; 2071 Chaitra, 4 marks; 2070 Asar, 2 marks; 2069 Chaitra, 4 marks; 2068 Chaitra, 3 marks; 2079 Baisakh, 4 marks; 2076 Asoj, 4 marks; 2075 Asoj, 3 marks; 2075 Chaitra, 4 marks (asked 9 times)
- Video: [piconet and scatternet in bluetooth in hindi](https://www.youtube.com/watch?v=d139X3tEq_w) — Perfect Computer Engineer
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/bt-topology
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-5

## Question

Explain the Bluetooth network topology (piconet and scatternet) with diagrams.

## Short answer

A piconet has one master and up to seven active slaves; the master controls timing and frequency hopping. A scatternet links multiple piconets via a bridge device that participates in more than one piconet, extending range and device count.

## Answer

**Bluetooth** is a short-range wireless standard in the 2.4 GHz ISM band. Devices form ad hoc networks with two topologies: the piconet and the scatternet.

#### Piconet
A piconet is a network of one **master** and up to **seven active slaves** (8 active devices, with up to 255 more devices parked). The master sets the frequency-hopping sequence and the clock, and all slaves synchronise to it. Communication is master-slave and time division duplex (625 us slots): the master transmits in even slots, and a slave answers in the following odd slot only when addressed. Slaves cannot talk directly to each other; all data goes through the master.
```text
            S1
            |
     S3 --- M --- S2          M = master
            |                 S = active slave
            S4
```
Each piconet uses its own hopping sequence (derived from the master's address), so several piconets can coexist in the same area.

#### Scatternet
A scatternet is formed when two or more piconets overlap and are connected by a **bridge device** (a device that is a member of more than one piconet). The bridge may be a slave in both piconets, or a master in one and a slave in the other. It shares its time between the piconets, since it can be active in only one at a time. This extends the range and the number of devices beyond 8.
```text
   S1   S2        S5   S6
    \   /          \   /
     M1 ---- B ---- M2
    /   \          /   \
   S3   S4        S7   S8

   piconet 1        piconet 2        B = bridge (slave in both)
```
A device cannot be the master of two piconets at once. Scatternets allow flexible, larger networks such as sensor and logger networks.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How many active slaves can one master have in a piconet?
   A. Up to 3
   B. Up to 15
   C. Unlimited
   D. Up to 7
   Answer: D. A piconet has one master and up to seven active slaves, with more devices parked. (Key point: Piconet size)

2. How do two slaves in a piconet exchange data?
   A. Through the master, since slaves cannot talk directly
   B. Directly with each other
   C. Using their own hopping sequence
   D. Through the bridge only
   Answer: A. All traffic goes via the master, which polls slaves in a TDD slot scheme. (Key point: Master-slave communication)

3. What forms a scatternet?
   A. One master with eight slaves
   B. A single device with parked slaves
   C. Overlapping piconets connected by a bridge device
   D. Two masters in one piconet
   Answer: C. A bridge device that is a member of more than one piconet links them, extending range and device count. (Key point: Scatternet)

4. How does a bridge device operate between two piconets?
   A. It is active in both at the same time
   B. It time-shares, active in only one piconet at a time, and cannot be master of both
   C. It is master of both piconets
   D. It uses the same hopping sequence for both
   Answer: B. A device cannot be master of two piconets; it switches between them by time sharing. (Key point: Bridge behaviour)

## Related in Instrumentation II

- [Data logger with Bluetooth scatternet](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Abt-datalogger-scatternet) — Instrumentation II, chapter 5