GSM (Global System For Mobile Communication)
GSM (Global System For Mobile Communication) is a standard developed by the European Telecommunications Standards Institute to describe the protocols for second-generation digital cellular networks used by mobile devices such as mobile phones and tablets. The idea of GSM was first developed at Bell Laboratories in 1970, and was first deployed in Finland in December 1991.
GSM uses a variation of time division multiple access (TDMA) and is the most widely used among three (CDMA, TDMA & GSM) digital wireless telephony technologies. GSM digitizes and compresses data and then sends it down the channel with two other streams of user data, each in its own time slot. It operates at 850 MHz, 900 MHz, 1800 MHz or 1900 MHz frequency band.
What You Need To Know About GSM
- GSM uses a combination of TDMA and FDMA for effective sharing of the bandwidth i.e with FDMA, the bandwidth is divided into number of channels and with TDMA, these channels are provided with different time slots.
- The GSM network operates in the frequency spectrum of 850 MHz, 900MHz and 1900 MHz.
- In GSM, the efficiency is dependent on the cluster size and number of operators and the efficiency is less than that of CDMA.
- The kind of data being stored in SIM Card makes GSM networks vulnerable to malicious attacks, misuse or hacking even though the network is encrypted.
- A network tower in each GSM cell serves a device located in its area of coverage.
- GSM is the world’s largely used mobile telephony standard. GSM technology is spread in over 190 countries.
- GSM connections are SIM-specific. SIM is an acronym for Subscriber Identity Module and it is in this card where information like mobile number, call plan, data plan, SMS plan etc are stored.
- GSM uses EDGE data transfer technology that has a maximum download speed of 384 kbps which is slower when compared to CDMA.
- GSM is international roaming friendly due to its huge global coverage. There is an interoperability agreement among GSM network providers all over the globe such that users can easily access their existing mobile phone while roaming internationally.
- GSM devices emit continuous wave pulses to operate and therefore, they expose their users to higher level of radiations. They emit about 35 times more radiations on average as compared to CDMA.
- GSM signals are often concentrated in the narrow bandwidth and therefore, signals can be detected easily.
- GSM technology enables transmission of voice and data at the same time.
- The performance of the GSM system is not affected with increase in number of users, because it uses both FDMA and TDMA multiple access methods where each additional users are fixed in different time slots.
- GSM devices are entirely available as unlocked devices and therefore, a user can put any SIM card in it and use that particular network.
- In GSM all the information is stored in the users SIM card and incase the user phone is damaged or the user wants to upgrade it with the same number, all he or she needs to do is to buy a new phone and Swap in the old SIM Card.
CDMA (Code Division Multiple Access)
Code Division Multiple Access (CDMA) is a channel access method used by various radio communication technologies. It is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is commonly used in ultra-high frequency (UFH) cellular telephone systems, bands ranging between 800-MHz and 1900MHz. the CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme referred to as Soft handoff, which minimizes signal breakup as a handset passes from one cell to another.
CDMA employs ADC (analog-to-digital conversion (ADC) in combination with spread spectrum technology. Audio inputs are first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the transmitter frequency.
What You Need To Know About CDMA
- The CDMA is based on spread spectrum technology which makes the optimal use of the available bandwidth. It allows each user to transmit over the entire frequency spectrum all the time.
- The CDMA network operates in the frequency spectrum of 850 MHz, 900MHz, 1800 MHz and 1900 MHz.
- In CDMA, efficiency is maximum due to the fact that CDMA uses a single carrier frequency making the cluster size of a CDMA cell to be one and therefore same frequency can also be use in the adjacent cells.
- In CDMA, there is an encryption standard embedded into the device and all the conversation is encrypted by the device and can be decrypted only with appropriate receiver device. Another, important feature that makes CDMA security tight is the fact that each CDMA device has a unique code that is assigned by the carrier.
- CDMA establishes a physical connection channel and a dedicated code for each device in the network.
- CDMA is limited to a small market compared to GSM and is dominant only in the United States, Japan and Canada.
- CDMA connections are device-specific. All information is stored in the device or modem’s software. Though there are some CDMA devices use Removable User Identity Module (RUIM).
- CDMA has faster data transfer rate when compared to GSM. It uses the EVDO data transfer technology that offers maximum download speeds of 2 mbps.
- International roaming is not easily possible with CDMA, because CDMA’s coverage is only in United States, Japan and Canada.
- CDMA devices do not emit significant continuous wave pulses to operate; therefore they do not expose users to large amounts of radiations.
- CDMA signals cannot be detected easily.
- CDMA technology does not allow transmission of both voice and data at the same time.
- A CDMA system can support unlimited number of users because users are distinguished by their unique code and use the same carrier frequency. However, performance of CDMA is directly proportional to the number of users. As the number of users increase proportionately in CDMA, the performance decreases equally for all the users.
- All CDMA devices are usually locked by the carrier and therefore users can only operate devices approved by the carrier.
- In CDMA, the carrier loads all the information into the phone’s software and incase the phone is damaged or the user wants to upgrade to a new phone with same number, he or she will have request the carrier to unlock the phone, get the serial number and other important codes and install them in the new phone.
Difference Between GSM And CDMA In Tabular Form
|BASIS OF COMPARISON||GSM (Global System For Mobile Communication)||CDMA (Code Division Multiple Access)|
|Spectrum||It is based on Wedge spectrum; it uses a combination of TDMA and FDMA for effective sharing of the bandwidth.||It is based on spread spectrum technology which makes the optimal use of the available bandwidth.|
|Frequency||The network operates in the frequency spectrum of 850 MHz, 900MHz and 1900 MHz.||The network operates in the frequency spectrum of 850 MHz, 900MHz, 1800 MHz and 1900 MHz.|
|Efficiency||The efficiency is dependent on the cluster size and number of operators and the efficiency is less than that of CDMA.||Efficiency is maximum due to the fact that CDMA uses a single carrier frequency making the cluster size of a CDMA cell to be one and therefore same frequency can also be use in the adjacent cells.|
|Risk||The kind of data being stored in SIM Card makes GSM networks vulnerable to malicious attacks, misuse or hacking even though the network is encrypted.||There is an encryption standard embedded into the device and all the conversation is encrypted by the device and can be decrypted only with appropriate receiver device.|
|Network||A network tower in each GSM cell serves a device located in its area of coverage.||It establishes a physical connection channel and a dedicated code for each device in the network.|
|Coverage||GSM is the world’s largely used mobile telephony standard.||It is limited to a small market. It dominant only in the United States, Japan and Canada.|
|SIM Cards||SIM card is required for the working of GSM device.||Devices do not use SIM cards, but rather rely on ESNs (Electronic serial numbers)|
|Data Transfer Technology||GSM uses EDGE data transfer technology.||It uses the EVDO data transfer technology that offers maximum download speeds of 2 mbps.|
|Signals||GSM signals are concentrated in the narrow bandwidth hence easily detectable.||The signals cannot be detected easily in CDMA.|
|International Roaming||GSM is international roaming friendly due to its huge global coverage.||International roaming is not easily possible with CDMA.|
|Flexibility||GSM devices are entirely available as unlocked devices and therefore, a user can put any SIM card in it and use that particular network.||All CDMA devices are usually locked by the carrier and therefore users can only operate devices approved by the carrier.|
|Countries Of Dominance||GSM technology is spread in over 190 countries.||It is dominant only in the United States, Japan and Canada.|
|Connections||GSM connections are SIM-specific.||CDMA connections are device-specific.|
|Radiations||They expose their users to higher level of radiations.||They do not expose users to large amounts of radiations.|
|Data Transfer Rates||GSM has slower data rates when compared to CDMA.||CDMA has faster data transfer rate when compared to GSM.|
Advantages Of GSM
- It is easy to interoperate GSM with other wireless technology based devices such as CDMA, LTE etc
- GSM provides improved spectrum efficiency.
- International roaming is supported by GSM.
- GSM networks store all customer information on removable SIM cards. As such, customers can easily swap phones or networks by putting in another SIM or putting their SIM card in another device.
- Advanced versions of GSM with higher number of antennas will provide high speed download and upload of data.
- High-quality voice calls
Disadvantages Of GSM
- In order to increase the coverage repeaters are required to be installed.
- Many GSM technologies are patented by Qualcomm and hence operation license is required to be obtained from them.
- GSM provides limited data rate capability, for higher data rate GSM advanced version devices are used.
- GSM uses pulse based burst transmission technology and hence it interferes with certain electronics. In this regard, airplanes, petrol bunks and hospitals discourage the use of GSM based devices.
Advantages Of CDMA
- During the handover between the cells, due to soft handoff feature initially connection is being established with new cell and hence it reduces the chances of call drop or disconnection.
- CDMA covers larger areas with fewer towers
- It is impossible for hackers to decipher the code sent
- Operates at very low power level.
- Call quality is better with more consistent sound as compared to GSM.
- Supports unlimited number of users
- There is efficient utilization of fixed frequency spectrum
- Large signal bandwidth reduces multipath fading.
- Rake receivers can be used to improve signal reception.
- CDMA technology is compatible with other cellular technologies such as GSM/LTE.
- The CDMA is nominally 1.23 MHZ wide
- CDMA is robust against fading and noisy environment.
- CDMA does not require any synchronization.
Disadvantages Of CDMA
- Precision code synchronization is required to recover the original baseband signal.
- When the number of users increase, the overall quality of service decreases.
- International roaming is significantly not possible.
- Self jamming is common in CDMA system due to loss of orthogonality of PN codes or spreading sequences of different subscribers.
- CDMA system is more complicated.
- Limited number of devices uses CDMA, at present the majority mobile companies use GSM technology.
- Gradual transfer increases the use of radio resources and may reduce capacity.
- A large code length can induce delay or may cause interference. In this regard, the code length must be carefully selected.