1. Introduction
POTS(Plain Old Telephone Service) is a voice communication service based on the Public Switched Telephone Network (PSTN), utilizing circuit switching technology. It developed at the end of the 19th century and has become a global communication network. Voice over Internet Protocol (VoIP) is an IP-based voice communication technology that digitalizes voice and transmits it via IP networks. VoIP technology originated in the 1970s and, with the popularization of broadband internet, was widely adopted in the late 1990s. It has now become an essential means for enterprise internal communication, remote conferencing, and personal communication. Studying the differences between the two is helpful for enterprises and individuals to choose suitable communication solutions based on requirements such as communication quality, cost, and flexibility. With technological advancements, these two modes are gradually converging, and understanding their development trends is significant for formulating long-term communication strategies. Baudcom, a leading provider of communication solutions, has developed products like the 16 FXO/FXS POTS over Ethernet IP converter to bridge the gap between traditional and IP-based communications.
2. Network Architecture Comparison
POTS: Circuit Switching Architecture
POTS network is based on PSTN and uses circuit switching technology. During a call, a dedicated physical circuit is established between both parties, occupying bandwidth exclusively throughout the connection, even when no voice is transmitted. Its components include telephone terminals, local exchange switches, long-distance switches, signaling networks, and transmission networks. The advantages of this architecture are high call quality and stable latency, while the drawbacks include low resource utilization and poor scalability.
VoIP: Packet Switching Architecture
VoIP adopts packet switching technology, where voice is converted into data packets for transmission over IP networks. Its main components include IP phones/software phones, VoIP gateways (used for interconnection with PSTN), VoIP servers (responsible for call control, authentication, etc.), and IP bearer networks. This architecture boasts high resource utilization and strong scalability, supports multimedia services such as video conferencing. However, the voice quality is more susceptible to network conditions.
Architecture Comparison
|
Features |
POTS |
VoIP |
|
Switching Technology |
Circuit Switching |
Packet Switching |
|
Resource Occupation |
Dedicated Bandwidth |
Shared Bandwidth |
|
Transmission Medium |
Private Lines (Cable/Fiber Optic) |
IP Network (Internet/LAN) |
|
Service Functions |
Basic Voice Calls |
Voice, Video, Instant Messaging, etc. |
|
Scalability |
Low |
High |
|
Cost |
High |
Low |
3. Signal Transmission Mechanism
POTS: Analog Signal Transmission
Sound is converted into continuous analog electrical signals through a microphone and transmitted via copper cables. Signals are susceptible to noise and attenuation, requiring amplification and filtering. The entire transmission remains in analog form, with circuits dedicated to a single call.
VoIP: Digital Signal Transmission
VoIP converts voice into digital signals through analog-to-digital conversion, encoding, and compression (such as G.711, G.729), then encapsulates them into IP packets for transmission. At the receiver end, packets are depacketized and decoded back into sound. This method offers high transmission efficiency and supports multi-function integration but depends on network quality.
Comparison of Transmission Methods
|
Aspect |
POTS |
VoIP |
|
Signal Type |
Continuous Analog Signal |
Discrete Digital Packets |
|
Bandwidth Usage |
Fixed (64kbps per line) |
Compressible (8-64kbps per line) |
|
Anti-Interference |
Poor |
Strong (Error correction) |
|
Function Expansion |
Limited |
Strong (Supports multimedia) |
4. Quality of Service (QoS) Mechanism
POTS QoS
▪ Bandwidth Guarantee: Dedicated circuit ensures stable bandwidth
▪ Low Latency: Signal transmission delay remains fixed
▪ Near-Zero Packet Loss: Circuit switching guarantees data integrity
▪ High Reliability: Supported by professional telecommunication equipment
VoIP QoS
▪ Priority Scheduling: Voice data packets are prioritized for transmission
▪ Jitter Buffer: Mitigates network delay fluctuations
▪ Forward Error Correction: Compensates for packet loss
▪ Adaptive Encoding: Adjusts bit rate according to network conditions
QoS Comparison
|
QoS Indicators |
POTS |
VoIP |
|
Bandwidth Guarantee |
High (Exclusive) |
Medium (Depends on network management) |
|
Latency |
Low and stable |
Highly affected by network |
|
Packet Loss Rate |
Nearly zero |
Possible |
|
Reliability |
Extremely high |
Depends on network quality |
5. Application Scenario Analysis
POTS Applicable Scenes
▪ Emergency Communication
▪ Basic Communication in Remote Areas
▪ Environments with Extremely High Reliability Requirements (such as hospitals, finance)
VoIP Applicable Scenes
▪ Unified Communication for Enterprises (voice, video, instant messaging)
▪ Remote Work and Call Centers
▪ Personal International Long-Distance Communication (such as Skype, WhatsApp)
Scenario Selection Recommendations
▪ For scenarios emphasizing reliability and real-time performance, choose POTS
▪ For scenarios emphasizing cost, flexibility, and functional integration, choose VoIP
6. Development Trends
IP Transformation of POTS
PSTN is evolving towards the next-generation network (NGN) based on IP, and traditional telephone services are gradually being carried over IP networks.
Improvement of VoIP Technology
▪ Codec Optimization (such as Opus)
▪ Enhancement of Transmission Quality through 5G and Edge Computing
▪ Integration of AI for Functions like Smart Noise Reduction and Translation
Integrated Development Trend
In the future, all voice communications will be based on IP technology. The boundaries between POTS and VoIP are gradually blurring, and communication solution choices will focus more on specific needs rather than technological labels.
7. Conclusion
POTS and VoIP have fundamental differences in technology foundation, network architecture, transmission methods, and service quality. POTS is known for high reliability and is suitable for scenarios with stringent quality requirements; VoIP wins in terms of low cost and high flexibility, fitting most modern communication needs. As IP-based networks advance, VoIP has become the mainstream technological direction. Baudcom's 16 FXO/FXS POTS over Ethernet IP converter exemplifies this transition, offering a reliable, cost-efficient solution for integrating traditional voice services into IP networks. Users should weigh their actual needs in terms of reliability, cost, and functionality when making choices.