Mode of Digital Transmission PDF

**Mode of Digital Transmission** **Parallel Transmission** ''n'' wires are used to send ''n'' bits at one time. It is faster than serial, more expensive, limited to short distance. **Serial Transmission** One bit follows another, so only one communication channel is required. Cost is l...

**Mode of Digital Transmission** **Parallel Transmission** ''n'' wires are used to send ''n'' bits at one time. It is faster than serial, more expensive, limited to short distance. **Serial Transmission** One bit follows another, so only one communication channel is required. Cost is less compared to parallel. **Asynchronous Transmission** Data is sent one byte at a time. Each string of bits attached with ''Start'' bit at the beginning and ''Stop'' at its end. It is not used when great amount of data sent. **Synchronous Transmission** Instead of using STOP and START byte, here Sync byte are used. This bits are synchronize internal clocks in sending and receiving devices, so they are in time with each other. No gap between data. **Differences** \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--  **Data Transmission Mode** Transmission modes refers to the direction of information flow between two devices. There are three types of transmission modes. **Simplex Transmission :**Data can travel in only one direction (i.e. television broadcast) **Half Duplex Transmission :** Data can travel in only Both direction but only one at the a time (i.e. walkie-talkies) **Full Duplex Transmission :** Data can travel in only Both directions simultaneously. (i.e. two or more computers connected to a network device such as switch). ***Physical Topology***  **MESH Topology** **\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--** Every device has a dedicated point-to-point link to every other devices **Dedicated** Link carries traffic only between the two devices it connects A fully connected mesh network has n(n-1)/2 physical channels to link n devices Every device on the network must have n-1 input/output (I/O) ports **Advantage** Less traffic, robust, secure, easy to maintain **Disadvantage** Need more resource (cable and ports), expensive **STAR Topology** \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- Each device has a dedicated point-to-point link only to a central controller, usually called a hub. No direct traffic and link between devices **Advantages** Less expensive Easy to install and reconfigure Robustness **Disadvantage** Single point of failure **BUS Topology** \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- A multipoint topology All devices are linked through a *backbone* cable Nodes are connected to the bus cable by drop lines and taps. Drop line A connection running between the device and the main cable Tap A connector that either splices into the main cable or punctures the sheathing of a cable to create a contact with the metallic core ** Advantage:** Ease of installation  **Disadvantages:** Difficult reconnection and fault isolation Broken or fault of the bus cable stops all transmission **RING Topology** \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- Each device is dedicated point-to-point connection only with the two devices on either side of it A signal is passed along the ring in the direction, from device to device, until it reaches its destination Each device in the ring incorporates a repeater **Advantages** Relatively easy to install and reconfigure Fault isolation is simplified **Disadvantage** Unidirectional traffic **Tree Topology** \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- Tree topologies integrate multiple topologies together Example: Tree topology integrates multiple star topologies together onto a bus **Advantages**: Point-to-point wiring for individual segments. Supported by several hardware and software venders. **Disadvantages**: Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies. **Networks** Different types of networks have different allowable distances between connected devices **Categories of networks** \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- A network is a linking of a group of computers to communicate with each other and share software and hardware resources via the cables and interfaces that connect the computers and peripherals. ** Define Local Area Networks (LANs)** \- A network serving a home, building or campus is considered a Local Area Network (LAN)  **Define Wide Area Networks (WANs)** \- LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN) ** Define the Internet** The internet is defined as a global mesh of interconnected networks  Describe network representations  **Transmission Media** **Transmission medium** Anything that can carry information from a source to a destination Several names : channels, link, circuit and media **Types of Transmission media** Guided (wired) media Twisted pair cable Coaxial cable Fiber optic cable Unguided (wireless) media Free space