CDMA 95, also known as IS-95 (Interim Standard 95), is the first generation (1G) CDMA-based digital cellular technology that was developed and standardized by the Telecommunications Industry Association (TIA). It laid the foundation for later CDMA-based standards such as CDMA2000. CDMA 95 introduced several system features that were instrumental in shaping the landscape of digital cellular communication. Let’s delve into the details of the key features of the CDMA 95 system:
1. Code Division Multiple Access (CDMA) Technology:
- Spread Spectrum Technique:
- CDMA 95 utilizes spread spectrum modulation, where each user’s signal is spread over a wide frequency band using a unique spreading code.
- This allows multiple users to share the same frequency band simultaneously without mutual interference.
2. Digital Voice Transmission:
- CDMA 95 marked the transition from analog to digital voice transmission in cellular networks.
- Digital voice encoding techniques, such as Variable Rate Vocoder (VRV) and Selectable Mode Vocoder (SMV), were introduced to efficiently compress and transmit voice signals.
3. Soft Handoff:
- CDMA 95 introduced the concept of soft handoff, allowing mobile devices to communicate with multiple base stations simultaneously during a handover.
- Soft handoff enhances call quality and reduces the likelihood of call drops during transitions between cells.
4. Forward and Reverse Channels:
- CDMA 95 utilizes separate forward and reverse channels for communication between the mobile device and the base station.
- Forward channels are used for transmitting data from the base station to the mobile device, while reverse channels handle data transmission from the mobile device to the base station.
5. Power Control:
- CDMA 95 incorporates power control mechanisms to adjust the transmission power of mobile devices based on signal strength.
- Power control helps in optimizing network capacity, minimizing interference, and conserving battery life in mobile devices.
6. Voice and Data Integration:
- CDMA 95 supports both voice and data services on the same network.
- This integration allows users to make voice calls and access data services, such as Short Message Service (SMS), on a single digital network.
7. Wireless Data Services:
- CDMA 95 facilitated the provision of wireless data services, enabling mobile users to access basic data services, including messaging and limited internet connectivity.
8. Rate Set Options:
- CDMA 95 introduced multiple rate sets to accommodate varying data rate requirements.
- Different rate sets allowed the adaptation of data transmission based on user needs and network conditions.
9. Spectral Efficiency:
- CDMA 95 offered improved spectral efficiency compared to analog cellular technologies.
- The use of spread spectrum modulation and advanced digital encoding contributed to the efficient use of available frequency spectrum.
10. Call Processing and Network Management: – CDMA 95 defined call processing procedures and network management protocols. – It established the foundation for efficient call setup, teardown, and network optimization.
11. Handset and Infrastructure Compatibility: – CDMA 95 standards facilitated compatibility between handsets and network infrastructure from different manufacturers. – This interoperability was crucial for the growth and development of the CDMA ecosystem.
12. Global Adoption: – CDMA 95 gained international acceptance and was adopted by operators in various countries, contributing to the global evolution of digital cellular networks.
In summary, CDMA 95 introduced a range of pioneering features in the realm of digital cellular communication. The utilization of CDMA technology, soft handoff, digital voice transmission, power control, and the integration of voice and data services were among the key innovations that set the stage for subsequent generations of CDMA-based standards. The legacy of CDMA 95 is evident in the evolution of CDMA technologies, including CDMA2000, which built upon the foundational features introduced by IS-95.