ROM

ROM :

Computer ROM

·         

      ROM stands for Read Only Memory.

·        Read Only means that the Program and data can only be read from it. Therefore Program and data cannot be written to it.

·        Most Computer contain small amount of ROM to stores programs that enable the computer to boots.

·        It is a non- volatile memory and hence it is referred as a permanent data storage area.

·        Read-only memory (ROM) is a class of storage medium used in computers  
     and other electronic devices.

·        Data stored in ROM cannot be modified, or can be modified only slowly or
     with difficulty, so it is mainly used to distribute firmware

Types of ROM:-

1. Programmable ROM (P-ROM)

·        A P-Rom is a non-volatile memory, it store the program or data permanently.

·        It uses high voltages to permanently destroy or create internal links within the chip.

·        Data can only be written once to the Programmable ROM.

2. Erasable Programmable ROM (EP-ROM)

·        EPROM can be erased by exposure to strong ultraviolet light (typically for 10 minutes or longer).

·        Once the EP-ROM is erased successfully it can be rewritten with a process that again needs higher than usual voltage applied.

3. Electrically Erasable Programmable ROM (EEP-ROM)

·        EEPROM is based on a similar semiconductor structure to EPROM, but allows its entire contents to be electrically erased, and then rewritten electrically, so that they need not be removed from the computer (or camera, MP3 player, etc.).

·        Writing or flashing an EEPROM is much slower (milliseconds per bit) than reading from a ROM or writing to a RAM (nanoseconds in both cases).

BIOS CHIP or BIOS IC

·        It is a type of computer and Laptop ROM.

·        BIOS is a chip located on all motherboard that contain instruction and setup for how your system should boot and how it operate.

·        The BIOS include instruction on how to load basic computer hardware & include a test referred as a POST that verifies the computer needs requirement to boot up properly.

·        If the computer does not pass the POST, you will receive a combination of beep indication what is malfunctioning within the computer.

POST:

·        POST is a test the computer must complete to verify all hardware is working properly before starting the remainder of the boot process.

·        If the computer passes the POST the computer will often return a single beep and if unsuccessful will create a beep code that indicates the error.

Mobile ROM

·        Mobile ROMs are the low level programming (also often called firmware) that contain the operating system and basic applications to make your phone work.

·        This type of memory keeps the saved data even if the device power is off.

·        The ROM forms a part of your internal storage and that part is not Accessible for users to write on and is thus referred to as Read Only Memory.

·        This ROM part of your internal storage is where your Android operating system resides.

·        Also OEM’s add some preinstalled apps in this memory sections which cannot be deleted on users end either.

·        This is the reason why you don’t get full internal memory as advertised on the Box, because a part of it has been used to house O.S. and preinstalled apps.

·        The rest of the internal storage will be used for storing and downloading Apps which will store this.

What is GSM ?

What is GSM?

•  GSM stands for Global System for Mobile Communication.
  
  
• Frequency of GSM is around 900 MHz and 1800 MHz
  
  
•  GSM is digital cellular technology used for transmitting mobile voice and data services.
  
  
• It is a developed by the European Telecommunications Standards Institute (ETSI).
  
• GSM is the only type of cellular service available in Europe and most of the part of the world.
  
  
• It use the TSMA (Time Division Multiple Access) technology because of its digital wireless telephony system.
  
  
•  TDMA has three times the capacity of an analog system using the same number of channels.
  
  
•  GSM digitizes & compresses data, then sends it to the channel with two other streams of user data, each in its own time slot.
  
  
•  The 3GPP developed third-generation (3G) UMTS standards followed by fourth-generation (4G) LTE Advanced standards, which do not form part of the ETSI GSM standard.

What is CDMA?

• CDMA stands for Code Division Multiple Access.
  
  
• Frequency of CDMA is around 800 Mhz
  
  
• Code Division Multiple Access (CDMA) is a sort of multiplexing that facilitates various signals to occupy a single transmission channel.
  
  
• CDMA is an example of multiple access, which is where several transmitters can send information simultaneously over a single communication channel.
  
  
• This allows several users to share a band of frequencies.

Difference between CDMA and GSM mobile phones?

• First, neither GSM nor CDMA is technically better; they ultimately provide the same service and the quality of a network depends on the carrier, not the cellular standard used.
  
  
• Second, GSM phones can be unlocked and switch carriers, whereas CDMA phones are locked to a carrier.

GPRS (General Packet Radio Service)

• Extends the GSM network
  
  
• Allows for advanced data service
  
• Use device as Modem
  
  
• Use device as web-browser etc.
  
  
• Data transmission is significantly faster than GSM (up to 54 kbps)

EDGE (Enhanced Data for Global Evolution)

• An extension to the GSM / GPRS networks
  
  
• More than three times faster than GPRS
  
  
• Average download speed of 100 – 130 kbps
• Burst speeds up to 200 kbps
  
  
• Not yet supported on BlackBerry devices
  
  

Evolution of G?

·        G is a generation.

·        Each of these is a different modulation scheme, a different protocol stack, different technology architecture, different radio.

·        Each one is a complete new network & new modem.

1g ?

·        Basic Voice Service.

·        Analog based protocol.

·        Examples include NMT, AMPS, TACS, etc.

2g?

·        Voice Services

·        first digital cellular systems launched early 1990s, offering improved sound quality, better security and higher total capacity.

·        GSM supports circuit-switched data (CSD), allowing users to place dial-up data calls digitally, so that the network's switching station receives actual ones and zeroes rather than the screech of an analog modem.

·        Improved Coverage and Capacity.

·        Examples include GSM, D-AMPS, PDC

3g?

·        Designed for voice and some data consideration(multimedia, text and internet)

·        First mobile broadband.

·        It’s a cellular networks that have data rates of 384kbit/s and more.

·        The UN's International Telecommunications Union IMT-2000 standard requires stationary speeds of 2Mbps and mobile speeds of 384kbps for a "true" 3G.

·        Evdo was marketed as 3G when it was launched, but initially was probably closer to 2.5G and then upgraded to 3G with the EvDO upgraded.

4g?

·        Designed primarily for data

·        LTE and WiMAX are marketed as parts of this generation, even though they fall short of the actual standard.

·        OFDMA, flat architecture, true packet switched
Pure data: voice as VoIP (VoLTE)
Most people say this is LTE & WiMAX, (though some people are waiting for an upgrade to LTE-A, based on a rather silly data rate definition).

·        4.5G term not widely used but some people say that is LTE-A

Differences between HSPA (3.5G) and LTE Advanced (4G)?"

1.      HSPA is encompasses both HSDPA (3GPP Release 5) and HSUPA (3GPP Release 6) technologies. There is also HSPA Evolved (also known as HSPA+ in 3GPP Release 7 and beyond) is an extension for the 3G/UMTS and 4G is a different network

2.     LTE is a complete IP based network while the UMTS is still hybrid IP/voice network. Voice calls in LTE are Voice over IP  while on HSPA they still uses a dedicated channel.

3.     Frequancy bands:

·        the HSPA is a UMTS system and uses the same frequancy, mainly 2100MHz but also 1900, 1800, 900, 850 and more. A complete list is here: UMTS frequency bands.

·        LTE is also using the 1700 and 2600 MHz LTE Frequency bands

4.     Bandwith:

·        W-CDMA uses fixed size 5 MHz chunks of spectrum.

·        LTE is flexible using 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz are standardized.

5.     Data rates:

·        HSPA provides data rates up to 168 Mbps to the mobile device (downlink) and 22 Mbps from the mobile device (uplink).

·        LTE peak download rates is 299.6 Mbps for 4×4 antennas, and 150.8 Mbps for 2×2 antennas with 20 MHz of spectrum. LTE Advanced supports 8×8 antenna configurations with peak download rates of 2,998.6 Mbps in an aggregated 100 MHz channel.

·        LTE Peak upload rates of 75.4 Mbps for a 20 MHz channel in the LTE standard, with up to 1,497.8 Mbps in an LTE Advanced 100 MHz carrier.

6.     Modulation: 

·        HSPA is using a multiple-antenna technique known as MIMO (for "multiple-input and multiple-output") and 64QAM (Quadrature amplitude modulation) modulation. It uses a Wide band CDMA (Universal Mobile Telecommunications System)

·        LTE is using  OFDMA radio-access for the downlink and SC-FDMA on the uplink