Wireless Notes
HubBeamforming Analog Digital Hybrid 5G ImplementationCognitive Radio Dynamic Spectrum Access SensingEdge Computing in Wireless MEC 5G IntegrationMassive MIMO 5G Technology Benefits DeploymentMIMO Systems Spatial Multiplexing Diversity CapacityNetwork Slicing 5G Virtual Networks Use CasesSoftware Defined Radio SDR Architecture ApplicationsAntenna Arrays Phased Arrays and BeamformingAntenna Basics in Wireless CommunicationAntenna Parameters Gain Directivity Beamwidth EfficiencyDipole Antenna Half-Wave Dipole in Wireless CommunicationHorn Antenna Types Working and ApplicationsMicrostrip Patch Antenna Design and ApplicationsMonopole Antenna Quarter-Wave Ground PlaneSmart Antennas MIMO and Massive MIMO SystemsCell Splitting Technique in Cellular NetworksCellular Concept in Mobile CommunicationFrequency Reuse in Cellular NetworksHandoff Techniques in Cellular NetworksCellular Network Planning Coverage Capacity OptimizationRoaming in Cellular NetworksSectoring in Cellular NetworksBandwidth in Wireless CommunicationElectromagnetic Spectrum in Wireless CommunicationFading in Wireless CommunicationFrequency and Wavelength in Wireless CommunicationNoise and Interference in Wireless CommunicationPath Loss in Wireless CommunicationRadio Wave Propagation in Wireless CommunicationSignal Transmission in Wireless CommunicationCellular Network Interview Questions Planning Handoff 5GModulation Interview Questions ASK FSK PSK QAM OFDMWireless Communication Cheatsheet All Formulas Quick ReferenceWireless Communication Interview Questions Top 50 Q&AAdvantages and Disadvantages of Wireless CommunicationApplications of Wireless CommunicationHistory of Wireless CommunicationWhat is Wireless CommunicationWireless vs Wired CommunicationIndustrial IoT IIoT Communication Industry 4.0IoT Case Studies Real-World Implementations Success StoriesIoT Communication Basics Protocols Architecture ConnectivityMQTT Protocol IoT Messaging Publish Subscribe QoSSmart Home Communication Protocols Matter ThreadWireless Sensor Networks WSN Architecture Applications1G Technology First Generation Mobile Communication2G Technology GSM Digital Revolution SMS3G Technology WCDMA HSPA Mobile Broadband4G LTE Technology True Mobile Broadband5G Technology NR Architecture Use CasesBeyond 5G and 6G Future Wireless CommunicationMobile Generation Comparison 1G 2G 3G 4G 5G Complete TableAmplitude Modulation AM in Wireless CommunicationASK Amplitude Shift Keying in Digital CommunicationFrequency Modulation FM in Wireless CommunicationFSK Frequency Shift Keying in Digital CommunicationModulation Techniques Comparison Complete TablePhase Modulation PM in Wireless CommunicationPSK Phase Shift Keying in Digital CommunicationQAM Quadrature Amplitude Modulation Complete GuideQPSK Quadrature Phase Shift Keying ModulationMultiple Access Techniques Comparison FDMA TDMA CDMA OFDMA SDMACDMA Code Division Multiple AccessFDMA Frequency Division Multiple AccessOFDMA Orthogonal Frequency Division Multiple AccessSDMA Space Division Multiple AccessTDMA Time Division Multiple AccessBluetooth LED Control Project BLE Arduino ESP32 AppESP8266 IoT Weather Station WiFi Sensors Cloud DashboardMQTT Smart Home Project Multi-Room Control DashboardWiFi Based Home Automation Project ESP32 MQTT App ControlWireless Sensor Network Project LoRa Multi-Node MonitoringWireless Weather Station Project Multi-Sensor Solar DisplayWireless Communication Formulas and Equations ReferenceFurther Reading and Resources for Wireless CommunicationsWireless Communication Glossary A to Z Terms DefinitionsWireless Standards and Protocols IEEE 3GPP ITU ReferenceCommunication Satellites Types HTS and Satellite InternetGPS System Working Segments Accuracy GNSSSatellite Communication Applications Broadcasting InternetSatellite Communication Basics System Components Link BudgetSatellite Link Design Link Budget C/N Rain FadeSatellite Orbits GEO MEO LEO Types and ComparisonFree Space Propagation Model in Wireless CommunicationMultipath Propagation in Wireless CommunicationRayleigh Fading Model in Wireless CommunicationReflection Refraction Diffraction in Wireless CommunicationRician Fading Model in Wireless CommunicationShadowing Log-Normal Fading in Wireless CommunicationWireless Channel Models Complete OverviewBluetooth Technology Versions BLE ApplicationsInfrared Communication Working Types ApplicationsLoRa and LoRaWAN Long Range IoT CommunicationNFC Near Field Communication Working ApplicationsWiFi Technology IEEE 802.11 Complete GuideWiMAX IEEE 802.16 Technology and Comparison with LTEZigbee Low Power Mesh Network IoT Smart HomeWireless Authentication Techniques PSK 802.1X EAP 5G-AKAWireless Security Best Practices Checklist GuidelinesWEP Wired Equivalent Privacy Why it FailedWireless Attacks Types Methods PreventionWireless Security Basics Threats Principles OverviewWPA and WPA2 TKIP AES-CCMP Enterprise SecurityWPA3 SAE Enhanced WiFi Security Forward Secrecy
Learn FSK Frequency Shift Keying with working principle, BFSK, MFSK, MSK, GFSK, GMSK, bandwidth calculation, BER performance, detection methods, and applications in Bluetooth GSM for engineering students.
In FSK, the carrier's frequency is changed to represent digital data (0 and 1). One frequency (f1) is used for Bit 1 and another frequency (f2) is used for Bit 0.
🎯 What is FSK?
FSK is the digital version of Frequency Modulation. Different frequencies are assigned to different digital bits.
| │ Digital Data | │ 1 │ 0 │ 1 │ 1 │ 0 │ 0 │ 1 │ │ |
| │ FSK Signal | │ |
| │ Bit 1 | Frequency f1 (higher) │ |
| │ Bit 0 | Frequency f2 (lower) │ |
⚙️ Working Principle
Mathematical Expression:
┌──────────────────────────────────────────────────────┐
│ │
│ Binary FSK: │
│ │
│ s(t) = { Ac × cos(2πf1×t) for bit 1 (mark) │
│ { Ac × cos(2πf2×t) for bit 0 (space) │
│ │
│ Where: │
│ f1 = fc + Δf (frequency for bit 1) │
│ f2 = fc - Δf (frequency for bit 0) │
│ Δf = Frequency deviation │
│ fc = Center frequency │
│ │
└──────────────────────────────────────────────────────┘
FSK Generation:
Data = 1 ──▶ Switch ──▶ Oscillator f1 ─┐
│ ├──▶ FSK Output
Data = 0 ──▶ Switch ──▶ Oscillator f2 ─┘
Or using VCO (Voltage Controlled Oscillator):
Digital Data ──▶ [VCO] ──▶ FSK Signal
(0V = f2, V1 = f1)
📊 Types of FSK
1. Binary FSK (BFSK)
- 2 frequencies: f1 and f2
- 1 bit per symbol
- Simple, widely used
2. M-FSK (M-ary FSK)
- M different frequencies
- log₂(M) bits per symbol
- More bandwidth needed, better BER per bit
3. MSK (Minimum Shift Keying)
- Special BFSK with minimum frequency separation
- Δf = 1/(4Tb) → modulation index h = 0.5
- Continuous phase (no abrupt phase jumps)
- Better spectral efficiency than standard FSK
- Used in: GSM (GMSK variant)
4. GFSK (Gaussian FSK)
- FSK with Gaussian pulse shaping
- Reduces bandwidth (smooth transitions)
- Used in: Bluetooth, DECT, Zigbee
5. CPFSK (Continuous Phase FSK)
- Phase continuous at bit transitions
- Better spectral properties
- MSK is a special case of CPFSK
| │ Standard FSK | Phase discontinuity at transitions │ |
| │ CPFSK/MSK | Smooth phase transitions │ |
| │ GFSK | Gaussian filtered, extra smooth │ |
📡 Bandwidth
| │ BFSK Bandwidth | │ |
| │ Where | │ |
| │ Modulation Index | h = 2Δf/Rb = 2Δf×Tb │ |
| │ MSK | h = 0.5, BW ≈ 1.5 × Rb │ |
| │ GFSK | BW < MSK (depends on BT product) │ |
| FSK Type | Bandwidth | Spectral Efficiency |
|---|---|---|
| Wide-deviation FSK | 2Δf + 2Rb | Low |
| Narrow-deviation FSK | ≈ 2Rb | Moderate |
| MSK | 1.5 × Rb | Good |
| GFSK (BT=0.5) | ≈ 1.0 × Rb | Better |
📉 BER Performance
| Coherent BFSK | BER = (1/2) × erfc(√(Eb/2N₀)) |
| Non-coherent BFSK | BER = (1/2) × exp(-Eb/2N₀) |
| Coherent BFSK | Eb/N₀ ≈ 13.5 dB |
| Non-coherent BFSK | Eb/N₀ ≈ 14.2 dB |
| Compare | BPSK needs only 10.5 dB (3 dB better) |
The BER performance of FSK is better than ASK (constant amplitude = better against noise) but worse than PSK.
Ranking (best to worst BER): BPSK > Coherent BFSK > Non-coherent BFSK > ASK
🔍 FSK Detection Methods
1. Coherent Detection
- Uses local oscillator synchronized with carrier
- Better performance (lower BER)
- More complex receiver
2. Non-Coherent Detection
- No phase synchronization needed
- Slightly worse BER (0.7 dB penalty)
- Simpler receiver
- Used in most practical FSK systems
3. Discriminator Detection
- Frequency-to-voltage converter
- Simple analog approach
- Used in legacy FM/FSK receivers
✅ Advantages & Disadvantages
Advantages:
- Constant amplitude → immune to amplitude fading/noise
- Simple non-coherent detection possible
- Better BER than ASK
- Good performance in fading channels
- Easy to implement with VCO
Disadvantages:
- Larger bandwidth than PSK (needs 2 frequencies + gap)
- Lower spectral efficiency than PSK/QAM
- BER worse than PSK for same Eb/N₀
- For M-FSK: bandwidth grows linearly with M
🌐 Applications
| Application | FSK Variant | Why? |
|---|---|---|
| Bluetooth | GFSK | Low power, simple, narrow BW |
| Zigbee (868 MHz) | BFSK | Simple IoT devices |
| DECT cordless phones | GFSK | Good quality, simple |
| Caller ID | BFSK (Bell 202) | Simple modem standard |
| Pagers | BFSK/4-FSK | Non-coherent, simple RX |
| LoRa | CSS (chirp spread) | Long range variant |
| Old dial-up modems | FSK | Simple, reliable |
| GSM | GMSK (Gaussian MSK) | Spectral efficiency + constant envelope |
📝 Summary
| Parameter | BFSK |
|---|---|
| Frequencies | 2 (f1 for 1, f2 for 0) |
| Amplitude | Constant |
| Bandwidth | 2(Δf + Rb) |
| BER (coherent) | (1/2)erfc(√(Eb/2N₀)) |
| vs ASK | Better (constant amplitude) |
| vs PSK | Worse (needs more BW) |
| Best for | Fading channels, simple receivers, IoT |
| Modern use | Bluetooth (GFSK), GSM (GMSK), Zigbee |
❓ FAQ
Q: Why does Bluetooth use GFSK instead of PSK? A: Bluetooth is designed for low-power, low-cost devices. GFSK has a constant envelope (efficient power amplifier), simple non-coherent detection is possible, and for short-range it works well enough.
Q: Why is GMSK used in GSM? A: GMSK has a constant envelope (power efficient), good spectral containment (Gaussian filter), and MSK's smooth phase ensures low out-of-band emissions. 3G/4G/5G use OFDM+QAM for higher data rates.
Q: FSK mein Δf kitna rakhein? A: Minimum Δf for orthogonality = 1/(2Tb) (coherent) ya 1/Tb (non-coherent). MSK uses exactly Δf = 1/(4Tb) which is the minimum for non-coherent while maintaining good properties.
Exam Focus
Revise definitions, diagrams, examples, and short-answer points for FSK Frequency Shift Keying in Digital Communication.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this Wireless Communications topic.
Search Terms
wireless-communications, wireless communications, wireless, communications, modulation, techniques, fsk, fsk frequency shift keying in digital communication
Related Wireless Communications Topics
Continue learning this concept
Modulation TechniquesAmplitude Modulation AM in Wireless CommunicationLearn Amplitude Modulation AM from basics with working principle, modulation index, AM spectrum bandwidth, power calculation, DSB SSB VSB types, advantages disadvantages, and applications explained for engineering students.Modulation TechniquesASK Amplitude Shift Keying in Digital CommunicationLearn ASK Amplitude Shift Keying with working principle, OOK on-off keying, M-ASK, bandwidth calculation, BER performance, constellation diagram, advantages disadvantages, and applications for engineering students.Modulation TechniquesFrequency Modulation FM in Wireless CommunicationLearn Frequency Modulation FM with working principle, CarsonModulation TechniquesModulation Techniques Comparison Complete TableComplete comparison of all modulation techniques AM FM PM ASK FSK PSK QPSK QAM with performance metrics, bandwidth efficiency, power efficiency, BER, applications, and selection criteria for engineering students.Modulation TechniquesPhase Modulation PM in Wireless CommunicationLearn Phase Modulation PM with working principle, mathematical representation, relationship with FM, modulation index, PM generation methods, and applications in digital PSK systems explained for engineering students.Modulation TechniquesPSK Phase Shift Keying in Digital CommunicationLearn PSK Phase Shift Keying with BPSK working, constellation diagram, coherent detection, BER performance, DPSK differential, comparison with ASK FSK, and applications in GPS satellite WiFi for engineering students.