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CDMA (Code Division Multiple Access) and WCDMA (Wideband Code Division Multiple Access) are two widely used wireless transmission facilities in the mobile telecommunications industry. CDMA is a digital cellular technology that uses a spread spectrum in enabling many people access one and the same channel all at once. Every user is assigned a code and the signals from all the users are sent in a manner that the signals having same code at the receiving end is distinguished and separated. WCDMA extends from CDMA and is a 3G technology that provides a faster data connection and capacity as compared to CDMA.
What is CDMA?
CDMA stands for Code Division Multiple Access and serves as a wireless standard applied in the telecommunication industry. It enables several people to work on a single channel by assigning every channel a code. In contrast to FDMA and TDMA, CDMA doesn’t divide the accessible frequencies into a number of channels or time slots respectively, but all users can send signals at once on the same frequency. CDMA uses spread spectrum, lower level modulation of signals, due to this data signal occupies more bandwidth than necessary for transmission. CDMA technology was used in most of the wireless communication systems including the 2G. (eg:-IS-95), 3G (eg:- cdma2000).
Block Diagram of CDMA
Given Below is the Block Diagram of CDMA
.png) CDMA The block diagram of CDMA is as follows:
- Input Signal: The input signal includes types of data such as voice, text, and video.
- Encoder/Decoder: At transmitter, Encoder adds redundancy using convolutional or turbo codes to detect and correct errors. whereas at the receiver decoder reconstructs the original signal by utilizing redundancy added by the encoder to identify and correct errors to ensure data integrity by using methods like Viterbi decoding for convolutional codes and Turbo decoding for turbo codes
- Spreader/De-spreader: At transmitter, the spreader amplifies the encoded signal by using a unique code sequence such as Walsh or PN codes for each user that enables multiple users to share a single frequency channel. At receiver, de-spreader uses same code sequence to correlate with the received signal to narrow down to its original bandwidth and filters out other signals
- Modulator/Demodulator: At transmitter a modulator is used to Superimposition of Input signal on a carrier signal using QPSK and BPSK for effective transmission over a distance whereas at receiver a demodulator is used to extract the information signal from the carrier signal by using techniques like Rake-receivers
- Channel: It is the medium through which the signal travels and may introduce signal degradation factors like noise, fading and interference
- Output Data: The non-erroneous data is transmitted to the required location or application.
What is WCDMA?
WCDMA has wider bandwidth channels and different modulation techniques which produce higher data speed and better network capacity. It has better support for multimedia services and having better spectral efficiency than CDMA 2000, due to this it has been adopted globally. By using High-Speed Packet Access (HSPA) enhancements it offers even higher data transfer rates and reliable connections. WCDMA is important for development of mobile networks since it serves as foundation in the functionalities and enhancement of today’s wireless communications networks.
Block diagram of WCDMA
Given Below is the Block Diagram of WCDMA
.png) WCDMA This block diagram of WCDMA is as follows:
- Input signal: The input signal consists of various forms of digital data, including voice, text, and video.
- Encoder/ Decoder: For encoding and decoding purposes WCDMA uses same techniques as that are used in CDMA
- Spreader/ De-spreader: WCDMA uses spreading techniques such as OVSF (Orthogonal variable spreading factor) codes and scrambling codes and the De-spreader works the same as that in CDMA.
- Modulator/ Demodulator: Advanced modulation techniques used in WCDMA are QPSK, 16- QAM, 64-QAM and demodulation techniques used are enhanced rake receiver to handle fast fading and other channel impairments, adaptive equalization and MMSE (Minimum Mean Square Error) equalizer.
- Pulse Shaper: At transmitter, it uses root-raised cosine filter to determine signal bandwidth and to minimize their ISI, ensures the signal is undistorted during transmission. At receiver it uses same filter to reduce ISI.
- Comparator: The comparator synchronizes the received and decoded signal with the transmitted signal leads to identifying errors and assessing the transmitter’s accuracy.
- Error Counter: It Increments the counter for each error identified by the comparator by providing a measure for signal transmission quality and accuracy.
- Bit Error Rate (BER): The BER is calculated as
BER = Number of erroneous bits received / Total number of bits transmitted
It is used to measure the effectiveness of the communication system and helps to maintain low error rates for higher data integrity.
Difference Between CDMA and WCDMA
Given Below is the Difference between CDMA and WCDMA
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Parameters
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CDMA
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WCDMA
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Generation
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Used in 2G and 3G standards
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Used in 3G standards
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Technology origin
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Based on IS-95 standards
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Based on UMTS standards
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Bandwidth
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Uses narrowband of 1.25MHz
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uses wideband of 5MHz
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Data Rates
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Has lower data rates up to 384 kbps
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Has Higher data rates up to 2Mbps
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Modulation
Techniques
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Uses BPSK and QPSK
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Uses QPSK, 16-QAM, 64-QAM
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Frame Length
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Variable frame lengths used such as 5ms, 10ms, 15ms, 20ms
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Standard Frame length of 10ms is used
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Power Control
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Has power control at 800Hz
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Has faster power control at 1500Hz
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Chip rate
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Has a chip rate of 1.2288 Mcps
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Has a higher chip rate of 3.84 Mcps
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Network Capacity
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Lower network capacity
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higher network capacity
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Channelization methods
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Fixed length walsh codes used
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OVSF codes used
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Advantages of CDMA and WCDMA
Advantages of CDMA
- Increased capacity and spectral efficiency due to simultaneous sharing of frequency bands.
- Enhanced security through unique codes for each user that prevents eavesdropping.
- Improved call quality and reliability especially in challenging signal conditions.
- Seamless connectivity due to soft handoff between cell sites.
- Flexible deployment methods across various frequency bands for optimized coverage.
Advantages of WCDMA
- Higher data rates and capacity due to wider bandwidth channels and advanced modulation techniques.
- Spectral efficiency and network performance is enhanced for better utilization of resources.
- Support for multimedia applications such as video streaming and online gaming with improved quality.
- Seamless handover between cells for uninterrupted connectivity during mobility.
- Global standard for 3G networks which ensures interoperability and roaming across different regions.
Disadvantages of CDMA and WCDMA
Disadvantages of CDMA
- Higher complexity and infrastructure costs compared to simpler technologies.
- Limited device compatibility and potential interoperability issues with other systems.
- Spectral efficiency may be lower compared to newer technologies like LTE.
- Susceptibility to interference that impacts performance in crowded spectrum environments.
- Data speeds may be constrained compared to technologies optimized for high-speed data.
Disadvantages of WCDMA
- Higher deployment and maintenance costs compared to older technologies.
- Limited compatibility with devices designed for other cellular technologies.
- Spectral efficiency still may lag behind newer technologies like LTE or 5G.
- Vulnerable to interference that impacts the performance in crowded spectrum environments.
- Data speeds may not match those of technologies that are optimized for high-speed data.
Applications of CDMA and WCDMA
Applications of CDMA
- Used in cell phones for providing voice and data services to millions of users worldwide.
- Supports various data services such as texting, web browsing, and sending multimedia.
- It uses machine-to-machine (M2M) communication for remote monitoring and telemetry.
- Beneficial mainly for police, fire and ambulance services as it guarantees no communication failure during calamities.
- Ideal for IOT such as smart meters and home automation.
Applications of WCDMA
- Used in Mobile telephony for providing voice and data services with faster speeds and better quality.
- It Supports video streaming, online gaming, and mobile internet browsing.
- Used in IoT devices for wide coverage and remote monitoring.
- Essential for public safety and emergency services which ensures reliable communication during crises.
- Facilitating machine to machine connections for various purposes such as asset tracking and telemetry.
Conclusion
This article aims at making the following comparison in attempt to present CDMA and WCDMA as distinct entities. CDMA is utilized in 2G and 3G network which provide good spectrum and good voice capacity but at slow data rates and less globally deployed. WCDMA is an improvement on 3G that uses a larger bandwidth to support the higher data rate so as to increase its capacity through standardization globally and to incorporate the support of multimedia services and roaming internationally. Collectively, these technologies formed the basis for 4G LTE and 5G.
Frequently Asked Questions on CDMA vs WCDMA – FAQ’s
What is main difference between CDMA and WCDMA?
CDMA uses a 1.25 MHz channel for communication whereas WCDMA uses a wider 5 MHz channel that allows for higher data speeds and better multimedia support
Will CDMA phones be able to work on WCDMA networks?
No, CDMA phones cannot work on WCDMA networks unless they are multimode devices that support both technologies
Why was there a need to develop WCDMA ?
WCDMA was developed to provide higher data rates and improved network capacity by providing advanced mobile services like video streaming and faster internet access
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