Mobile Communication presentation

download Mobile Communication presentation

of 43

description

It is about the various types of mobile communication and how it works!!It can be used as reference by the students pursuing Communication in their engineering.

Transcript of Mobile Communication presentation

  • CELLULAR MOBILE COMMUNICATIONSA cellular mobile communications system provides voice, data and multimedia services.Used large numbers of low power transmitter/receiver (Tx/Rx) known as cell.Cell size depends on subscribers density.Cell can be split into small cell to accommodate growth.

  • CELLA cell is the geographical area covered by a cellular telephone transmitter.A city is divided into small cells.Each cell is equipped with a low-powered radio transmitter/receiver or Radio Base Station (RBS). The cell provided by a RBS can be from one mile to twenty miles in diameter, depending on terrain, transmission power, and capacity demands.The hexagon shape was chosen because it is the most efficient and easily managed system.

  • Clusters

    A cluster is a group of cells. No channels are reused within a cluster. The figure illustrates a seven-cell cluster.

  • CELLULAR SYSTEM COMPONENTS

    Mobile Unit (MU)Radio Base Station (RBS)Mobile Telephone Switching Office (MTSO)Public Switched Telephone Network (PSTN)

  • Mobile Units (MU)

    The mobile unit consists of a control unit and a transceiver that transmits and receives radio transmissions to and from a cell site.

  • Radio Base Station (RBS)

    RBS is the physical location of radio equipment that provides coverage within a cell. A list of hardware located at a cell site includes power sources, interface equipment, radio frequency transmitters and receivers, and antenna systems.

  • Mobile Telephone Switching Office (MTSO)

    The MTSO is the central switch that controls the entire operation of a cellular system.The MTSO is responsible for monitoring the relative signal strength of your cellular phone as reported by each of the cell towers, and switching your conversation to the cell tower which will give you the best possible reception.It houses the mobile switching center (MSC), field monitoring, and relay stations for switching calls from cell sites to PSTN. The MSC controls calls, tracks billing information, and locates cellular subscribers and arranges handoffs.

  • Public Switched Telephone Network (PSTN)

    The worldwide voice telephone network. The PSTN is made up of local networks, the exchange area networks, and the long-haul network that interconnect telephones and other communication devices on a worldwide basis.

  • Radio Base Station (RBS)Radio interface between MSC and MUConsist of antenna, tower or building & equipmentTwo types of radio channelDuplex voice channelsDuplex control channelsSignal coverage from RBS depends onCharacteristic of the terrainHeight of antenna

  • Voice Channels (VC)Voice Channel: A channel used for transmission of voice data from a base station to a cellular phone (forward voice channel) or from a cellular phone to a base station (reverse voice channel)Selected for conversation by MSC during call set upWhen conversation is finished, the channel became free for next conversationMSC kept a list of all voice channels and their status (free, busy, blocked etc)When VC free, the Tx of voice channel unit in RBS is switched OFFWhen VC is selected, the Tx is switched ON

  • Control Channel (CC)Control Channel: A channel used for transmission of digital control information from a base station to a cellular phone (forward control channel) or from a cellular phone to a base station (reverse control channel).The CC is a special frequency that MU & RBS use to talk to one another for things like call set-up and channel changing. MU move from one cell to another will have to tune to new CC of that cell

  • ForwardchannelReversechannel

  • AntennaRBS used 2 types of antenna:DirectionalOmnidirectional

  • Omnidirectional AntennaRadiates or receives equally well in all directions.Also called the "non-directional" antenna because it does not favor any particular direction.Can deliver very long communications distances, but has one drawback which is poor coverage below the antenna.

  • Directional AntennaFocus the RF energy in a particular direction. Can divert the RF energy in a particular direction to farther distances.

  • Cell-phone Codes

    All cell phones have special codes associated with them. These codes are used to identify the phone, the phone's owner and the service provider.Types of codes:Electronic Serial Number (ESN)Mobile Identification Number (MIN)System Identification Code (SID)

  • Electronic Serial Number (ESN) - a unique 32-bit number programmed into the phone when it is manufactured.Mobile Identification Number (MIN) - a 10-digit number derived from cell phone's numberSystem Identification Code (SID) - a unique 5-digit number that is assigned to each carrier by the FCC.ESN is considered a permanent part of the phone, both the MIN and SID codes are programmed into the phone when you purchase a service plan and have the phone activated.

  • PagingPaging: The act of seeking a cellular phone when an incoming call is trying to reach the phone.When MU first power up the phone, it listens for an SID on the control channel. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message.

  • When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its home system.Along with the SID, the phone also transmits a registration request, and the MTSO keeps track of MU phone's location in a database.This way, the MTSO knows which cell MU are in when it wants to ring the phone.

  • The MTSO gets the call, and it tries to find MU. It looks in its database to see which cell MU are in.The MTSO picks a frequency pair that MU phone will use in that cell to take the call.The MTSO communicates with MU phone over the control channel to tell it which frequencies to use, and once MU phone and the tower switch on those frequencies, the call is connected. Now, MU are talking by two-way radio to a friend.

  • As you move toward the edge of your cell, your cell's base station notes that your signal strength is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) sees your phone's signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. This hand off switches your phone to the new cell.

  • Handoff

    Handoff: The process by which the MTSO passes a cellular phone conversation from one radio frequency in one cell to another radio frequency in another. Handoff occurs when the MTSO automatically transfers a call from radio channel to radio channel as a mobile crosses adjacent cells The handoff is performed so quickly that MU usually never notice.

  • During a call, two parties are on one voice channel. When the mobile unit moves out of the coverage area of a given cell site, the reception becomes weak. At this point, the cell site in use requests a handoff. The system switches the call to a stronger-frequency channel in a new site without interrupting the call or alerting the user. The call continues as long as the user is talking, and the user does not notice the handoff at all.

  • Frequency Re-useFrequency Reuse: The process of using the same carrier frequency (channel) in different cells that are geographically separated.A set of cells each operate on different channel in a group to form cluster.A cluster is repeated as many time as necessary to cover wide area.Adjacent cells are not allowed to operate at the same frequency since this causes interference between the cells.

  • Since each cell is designed to use radio frequencies only within its boundaries, the same frequencies can be reused in other cells not far away with little potential for interference.Cells are assigned a group of channels that is completely different from neighboring cells.

  • Cell Splitting

    Cell Splitting - The process of creating more coverage and capacity in a wireless system by splitting/divide a single cell into smaller cells.As a service area becomes full of users, this approach is used to split a single area into smaller ones. In this way, urban centers can be split into as many areas as necessary to provide acceptable service levels in heavy-traffic regions, while larger, less expensive cells can be used to cover remote rural regions

  • Signal-to-noise Ratio (SNR)Signal-to-noise ratio (SNR or S/N) is defined as the ratio of a signal power to the noise power.Measured in decibels (dB)SNR shows how much stronger/weaker the desired signal compared to unwanted noise.A higher value indicates less background noise.

  • Making a CallWhen a cellular user makes a call from a cellular phone, radio signals are transmitted to the cell site. The cell site alerts the MTSO switching station. The MTSO provides an open channel ( frequency ) and connects the call to the PSTN. The PSTN put the call through to the number to be reached. This process takes the same amount of time that it takes to make a call from a land line phone.

  • Receiving a CallA call placed to a cellular phone may come from either a land line phone or another cellular phone. Whichever the source, the MTSO is notified that a call has been placed to a specific cellular telephone number. At this point, the MTSO searches for the correct cellular phone by sending out data over the radio waves. Cellular phones that are in standby mode ( i.e., turned on but not being used in a call ) continuously scan the radio waves being transmitted by the MSTO.

  • If a phone " hears " its telephone number, it sends back a signal that informs the closest cell site of its Electronic Serial Number ( ESN ) and its telephone number ( Mobile Identification Number or MIN ). The cell site passes this information to the MTSO, where the ESN and MIN are verified and a channel ( frequency ) is assigned for the call. The cellular phone receives the message directing it to tune to the correct voice channel. The cell site makes the voice channel available, and the call is completed.

  • Call TerminationIf the land-based phone ends the call, the MTSO issues a release order. The phone responds by sending about two seconds of supervisory tone. If the mobile unit ends the call, it simply sends about two seconds of supervisory tone. In either case, the phone then turns off the transmitter, tunes to the strongest paging channel, and returns to the idle state, listening for a page.

  • WAPWireless Application Protocol (WAP) is an open international standard for applications that use wireless communication. Its main use is to enable access to the Internet from a mobile phone or PDA.In 1997, Nokia, Motorola, Ericsson and Phone.com came together to create the WAP because they believed that a universal standard is critical to the successful implementation of wireless Internet.A mini-browser is an integral part of WAP enabled phones.

  • WAP strips all but graphics for display on small screens, such as mobile phones. A WAP browser provides all of the basic services of a computer based web browser but simplified to operate within the restrictions of a mobile phone, such as its smaller view screen.WAP sites are websites written in WML (Wireless Markup Language) and accessed via the WAP browser.WAP allows mobile users to check Email by mobile phone, tracking of stock market prices, sports results, news headlines and music downloads

  • Amazon web in InternetAmazon web WAP