Types of mobile or cellular sets
Mobile phone service providers are offering various services to the customers. Due to different uses of mobile phones, nowadays people are using different types of mobile phone sets. Based on the structural aspects and multipurpose use of the mobile phone, mobile or cellular phone sets can be divided into several categories. namely --
(i) Basic Mobile Phones
(ii) Camera mobile phones
(iii) Music or MP-3/MP-4 mobile phones
(iv) Video mobile phones
(v) Smart mobile phone
(vi) PDA or Note mobile phone
Types of mobile phone technology: The current mobile phone technology can be mainly divided into two categories, namely--
(i) GSM = Global System for Mobile Communication, technology and
(ii) CDMA (CDMA Code Division Multiple Access) technology.
GSM
It was first named Group Special Mobile (GSM) in 1982, then the definition of the name was changed to Global System for Mobile Communication (GSM). The third generation version of GSM technology is standardized by the Universal Mobile Telecommunication System (UMTS). Grameenphone, Robi, Banglalink, Teletalk and Airtel are using GSM technology in Bangladesh.
GSM is a channel access method combining FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access). The total number of channels of FDMA is 124 and each channel is 200 kHz. 25 MHz is allocated for both 935-960 MHz uplink and 935-960 MHz downlink. Dual separation is 45 MHz. TDMA is used in 200 KHz channels but TDMA is developed for 8 time dure systems to become a frame.
CDMA
The full name of CDMA is Code Division Multiple Access. CDMA is the second generation mobile standard. CDMA is different from TDM (Time Division Multiplexing) and higher quality frequency. The customer service capacity of such systems is much higher than other cellular systems. CDMA uses higher frequency bands for voice and data applications.
GSM network
Features of GSM Mobile Technology:
- Roaming is available in European countries. In many other countries this service is available for a fee.
- Easy use of SIM card.
- Frequency Hopping Advantage: Automatically jumps to lower frequencies.
- ISDN can be connected through RA box.
- High quality continuous transmission.
- Provides GPRS and EDGE facilities. The transmission power can be controlled.
There are basically four types of frequencies used in GSM. They are denoted by GSM 400, GSM 900, GSM1800, GSM 1900.
Components of GSM Network: GSM mainly consists of following four systems. They are--
(i) Mobile stations
(ii) Base Station Sub-system
(iii) Network and Switching Sub-Systems
(iv) Operation sub-system.
Functions of GSM: There are some important functions of GSM
(i) Call Dialing
(ii) Call Restriction Service
(iii) Bluetooth
(iv) Call Holding
(v) Mobile Fax Service
(vi) Connection of computer with mobile phone
(vii) Close User Group Services etc.
Advantages of GSM Network: Some of the significant advantages of GSM are-
(i) GSM network operates in different frequency ranges.
(ii) Transmission quality and system capacity are high and qualitative.
(iii) Roaming agreements between mobile network operators allow anyone from anywhere in the world to use their mobile phone under GSM coverage.
(iv) Loss and attenuation of signal is very less.
(v) It has the facility of using a Subscriber Identification Module (SIM).
(vi) Third Generation-3G enabled.
(vii) Provision of GPRS and EDGE facilities.
(viii) Secure data encryption.
Disadvantages of GSM Network: Some of the significant disadvantages of GSM are-
(i) GSM network system is very complex.
(ii) Power consumption is relatively high.
(iv) Call drops at low frequency.
(v) In case of certain electronics (eg pagers, hearing aids etc.) causing interference in transmission.
(vi) Data transmission rate is relatively low.
CDMA Network: In the CDMA system, radio waves are divided into several carrier channels. Here individual codes are given for each customer and this code is spread across the entire carrier. It is 1.25MHz wide
CDMA is generally divided into three categories, viz
(i) Frequency-Hope CDMA
(ii) Direct Sequence CDMA
(iii) Multi Carrier CDMA
Features of CDMA:
(i) Voice coding method.
(ii) Data transmission rate is high.
(iii) Controlling energy.
(iv) Low power consumption.
(v) The carriers into which radio waves are divided act as channels.
(vi) Information can be sent simultaneously from multiple transmitters or sending stations through a single communication.
Advantages of CDMA:
(i) Transmission quality is high and qualitative.
(ii) Low power consumption.
(iii) Safety is relatively high.
(iv) The cell size of the network is relatively large.
(v) Each customer has a different code
(vi) Network works even with relatively low signal.
(vii) Data transmission rate is relatively high
(viii) E-mail exchange facility available.
(ix) Availability of images, graphics, audio, video (xi) Availability of shares.
(x) SMS has benefits.
Disadvantages of CDMA:
(i) Its use and popularity is relatively low.
(ii) As the number of users increases, the quality of data transmission decreases.
(iii) Not available on all handsets.
(iv) No international roaming facility.
(v) It has not yet developed into a complete and established network.
(vi) Signal is very weak in metropolitan areas.
Uses of CDMA:
(i) CDMA 2000 technology is used as the standard for the Global Star satellite phone network.
(ii) Used in Wi-Fi technology.
(iii) Used in blow-tooth.
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