Introduction To Telecom Networks: Fixed/Wireless Networks

Explore the nuts and bolts of the internet by examining network edge devices, where clients (browsers on phones or computers) connect to servers in data centers, hosting applications as hosts.

Explain how the access network ties to the core network through the access router, and how Internet service providers form interconnected networks to create a network of networks.

Explore the complexity of internet and computer networks, including hosts, routers, wireless and wired media, optical fiber, protocols, hardware, and software, and learn how the layered approach organizes this complexity.

Explore how air travel illustrates layered service system from ticketing to baggage, gate, and routing. Each layer delivers a service and relies on layer below, enabling modularity and change transparency.

Receives packets from the data link layer, adds synchronization bits, and converts them into a physical signal via modulation for wireless, wired, or optical fiber media to reach next node.

The data link layer sits above the physical layer, forms frames by adding header to network packets, provides flow and error control, and Ethernet switches forward frames by mac addresses.

Explore how application layer protocols function as processes to provide services, such as FTP for file download, HTTP for web browsing, and RTP for multimedia calls, over TCP and UDP.

Explore the legacy telecom network architecture, where circuit-switched voice uses ss7 signaling and SDH multiplexing over DWDM optical fiber, while data travels as IP over ATM or Ethernet.

Describe how subnetworks form an IP network, connect via mac-addressed layer two switches and Wi-Fi routers, and enable end-to-end delivery through TCP and sockets.

Explore the differences between IP version four and IP version six, focusing on address sizes (32-bit vs 128-bit) and the dotted decimal notation used for IPv4.

Learn how routers perform routing and forwarding, using a local forwarding table to direct IP packets to the correct interface based on destination addresses via a routing algorithm.

Learn how IP addresses are assigned in a data network, private or public, as hosts connect via a local area network with an ethernet switch to a router.

Understand how a host connects to the data network via wired and wifi interfaces, each sending and receiving packets and possessing a 32-bit IPv4 address in dotted decimal notation.

Explain how subnets form isolated networks with a common 24-bit prefix and an eight-bit host part, and that devices on the same subnet communicate without a router.

Explore how ICANN assigns a block of IP addresses to an ISP, divides them with /20 and /23 subnet masks for eight organizations, and allocates remaining bits to hosts.

Explore how classless inter-domain routing (CIDR) subdivides networks into subnets by increasing the subnet part and mask, enabling efficient IP address allocation and route aggregation.

Voice over IP (VoIP) technology uses packet switching over IP networks to deliver low-cost voice calls, video and data services, and reduced bandwidth on the Internet through advanced audio compression.

The media gateway connects the soft switch to the PSTN, converting 64 kbps voice into IP packets using codecs like g.729, g.711, and g.722, transported via RTP.

Describe the media gateway controller (MGC) as the call controller directing media gateways for setup and teardown, coordinating with announcement server and application servers via SIP to deliver value-added services.

Identify separation of media and call control, with media gateways handling media near source and sink. Use centralized media gateway controllers to manage signaling across gateways, enabling rapid feature additions.

Learn how megaco, a media gateway control protocol, enables media gateway controller to connect voice channels to rtp streams, select codecs, and manage terminations with add, modify, subtract, and notify.

Explains the Megaco (H.248) call flow with a media gateway controller coordinating two gateways, detailing notify, modify, and add requests to establish a bi-directional RTP path and dial tone.

Explore how session initiation protocol enables inter-mgc signaling between media gateways, carrying session description protocol details, IP addresses, port numbers, codecs, and bandwidth for RTP streams.

Explain class four and class five softswitches, where class four routes VoIP via protocol conversion and transcoding, while class five connects end users and provides IVR and prepaid calling.

Explore the IP multimedia subsystem (IMS) architecture, an open, non-proprietary framework enabling voice over IP and IP-based multimedia services across fixed and wireless networks with seamless mobility.

Explore IMS features and its layered architecture enabling scalability and flexibility via application servers. IMS is access agnostic, open, backward-compatible, supporting DSL, Wi-Fi, mobile networks, and PSTN interfaces.

Examine the IMS architecture across three layers: the application layer with service logic on application servers, the control layer managing sessions, and the transport layer connecting end devices.

Examine the ims control layer and its call session control function. Learn how the hss stores user profiles and keys for authentication and authorization.

Explore how call session control functions route SIP messages in the IMS network, focusing on the proxy CSCF as the contact, routing requests, blocking floods, and enabling QoS for calls.

The interrogating call session control function uses the HSS to verify registration and assigns an S-CSCF when needed, then routes calls by locating the device's S-CSCF via the I-CSCF.

Explore the protocols used in IMS, including SIP for establishing and terminating calls, Diameter for authentication and billing, and RTP for voice and video streams.

Explore how the session initiation protocol (SIP) enables creating, modifying, and terminating sessions by exchanging SIP packets carrying SDP to negotiate IP addresses, ports, codecs, and bandwidth.

SIP uses a client-server model where a SIP user agent client sends requests to a server, which responds, with invite to establish a session, acknowledgment, by, cancel, register, and options.

Explain sip call setup in ims networks: invite with sdp offer negotiates codecs and ip/port, followed by 183 session progress with sdp answer, 180 ringing, 200 ok, and bearer establishment.

Clarify uplink as mobile-to-base station communication and downlink as base-station-to-mobile communication, using base transceiver systems that transmit and receive simultaneously.

Explore the overall 4G EPS architecture, identifying data links (solid) and signaling links (dashed), the access network of enodebs, and the core network of gateways, nodes, and routers.

The mobility management entity authenticates and registers user equipment with the 4g core network, assigns temporary identifiers, maintains ue context, and handles serving gateway, tracking areas, and handovers.

Describe how the packet data network gateway assigns IP addresses, connects the 4G core to the internet, performs deep packet inspection, and anchors handovers for interception by law enforcement agencies.

Orchestrates bearer allocation for voice calls through the PCF, deciding when to add eps bearers. Formulates qos and charging rules, including throttling in bad channel conditions.

Explore the policy and charging enforcement function (PCF) in the gateway, enforcing QoS on bearers and charging data flows by volume and traffic type, with static or PCF-supplied rules.

Understand how the home subscriber server functions as a central database in 4g networks, managing user registration, authentication with security keys, services, QoS, roaming restrictions, and call routing.

Explain how VoLTE uses IMS to carry voice as IP packets over LTE, eliminating circuit-switched voice and interfacing with PSTN for IMS-based calls.

Examine how the IP multimedia subsystem enables VoLTE using SIP signaling for call setup between the gateway and IMS, with Diameter handling authentication, authorization, and billing over the KCS interface.

Explore how legacy 4g architecture deployed physical network functions as separate hardware nodes, driving high cost, bulk, and poor scalability due to proprietary hardware and non recyclable components.

Physical network functions evolved into virtual network functions deployed as software on off-the-shelf hardware. ETSI introduced network function virtualization in 2012, and by 2014 operators virtualized 4G core networks.

Learn how hypervisors transform commercial off-the-shelf hardware into multiple virtual servers, enabling virtualized network functions like gateway and serving gateway to run as software on shared hardware.

Leverage virtualization to create virtual network functions, like gateways, in seconds, scale resources easily, upgrade via software, and clone for redundancy, all while lowering cost with commercial off-the-shelf servers.

Explore the ETSI NFV architecture, detailing the NFV infrastructure with cots hardware, the virtualization layer, and the network management and orchestration function that manages virtual resources and network functions.

Explore traditional IP networks by examining routers with separate control and data planes, routing algorithms, and forwarding tables that determine end-to-end packet paths based on the destination IP.

Learn how STN and NFV enable programmable, centralized control of virtual routers and firewalls in the telco cloud, delivering agile networks and reduced hardware costs.

Explain how a passive optical network operates within an optical fiber access network, detailing OLTs, ONUs, and splitters that connect homes to triple-play services, voice, data, and video.

Passive optical splitters connect in series to divide the incoming light into three signals, and the linked fiber cables form the optical distribution network.

PON networks use a point-to-multipoint architecture with a single feeder fiber and OLT transceiver, while passive splitters near users require no power, reducing costs and delivering gigabit data rates.

Compare xdsl and pon technologies, noting dslam with copper pair for 2–20 mbps over 3.5–5 km, while pon uses fiber up to 40 km via olt in fttc, fttb, ftth.

Explain how GPON uses single-mode fiber and wavelength division multiplexing to carry downstream 1490 nm, upstream 1310 nm, and video 1550 nm on the same fiber.

GPON downstream data uses a three-slot time-division multiplexing frame, broadcast by a splitter and encrypted with AES using different keys so each destination decrypts only its time-slot data.

Describe how upstream data from multiple ONUs is sent to the OLT in allocated time slots, combined by a splitter into a TDMA frame, with timing to prevent collisions.