Introduction Radio and Core Networks

2 Agenda Introduction to telecommunication Introduction to Core network Primary functions of CN Introduction to Radio network Examples

3 Introduction to Telecommunication What is telecommunication ? Wireless communication How mobile phone works? What are the components involved while making call or SMS Multiple access schemes

4 Telecommunication

5 What is Wireless ? The word wireless is dictionary defined “having no wires ”. In networking terminology, wireless is the term used to describe any computer network where there is no physical wired connection between sender and receiver, but rather the network is connected by radio waves and or microwaves to maintain communications. Wireless networking utilizes specific equipment such as NICs and Routers in place of wires (copper or optical fiber).

6 History Of Wireless – : Dr. Loomis demonstrates wireless – 1876: Graham Bell get US patient for improvement in Telegraphy – 1887: Heinrich Hertz discovers Electromagnetic waves – 1927: Bell develops French phone with transceivers –WW II: Extensive use in RADAR, Walkie talkie, etc.. – 1946: First commercial mobile telephone service – 1960’s: Nokia, Ericson, NTT started radio telephone production – 1971: Intel produces first Microprocessor (4004) – 1978: First Commercial cellular telephone system at Bahrain – 1983: TI and Lucent produce digital signal processor (DSP) on IC – 1980’s: Cell telephony spreads in Nordic circle, Japan, West Europe – 1982: Global System for Mobile communication (GSM) formed – 1994: Qualcomm Proposes Spread Spectrum (IS-95)

7 Challenges to Wireless Communication Bandwidth : -- All signals that are transmitted consist of multiple frequencies. The range of frequencies a signal occupies is called the bandwidth of the signal. -- The bandwidth is measured in terms of Hertz (Hz). User Mobility : -- it has to be able to seamlessly transfer a customer from one base station to another while using the service -- it has to keep track of the location of its customers, to handle incoming calls. Attenuation Noise Signalling Standards Advanced Services High Throughput

8 Challenges to Wireless Communication conti... Attenuation : -- reduction in signal strength commonly occurring while transmitting analog or digital signals over long distances. Noise Signalling Advanced Services High Throughput

9 Mobile phone

10 Network Components MS – Mobile station BTS – Base Transceiver Station BSC – Base Station Controller MSC – Mobile Switching Center HLR – Home location Register VLR – Visitor Location Register PSTN – Public Switched Telephone Network IWF – Interworking Function

11 The Multiple Access Problem The base stations need to serve many mobile terminals at the same time (both downlink and uplink) All mobiles in the cell need to transmit to the base station Interference among different senders and receivers So we need multiple access scheme

12 Multiple Access Schemes Three orthogonal Schemes: Frequency Division Multiple Access (FDMA) Time Division Multiple Access (TDMA) Code Division Multiple Access (CDMA)

13 Frequency Division Multiple Access Each mobile is assigned a separate frequency channel for the duration of the call Sufficient guard band is required to prevent adjacent channel interference Usually, mobile terminals will have one downlink frequency band and one uplink frequency band Different cellular network protocols use different frequencies Frequency is a precious and scare resource. We are running out of it – Cognitive radio frequency

14 Time Division Multiple Access Time is divided into slots and only one mobile terminal transmits during each slot – Like during the lecture, only one can talk, but others may take the floor in turn Each user is given a specific slot. No competition in cellular network – Unlike Carrier Sensing Multiple Access (CSMA) in WiFi Guard time – signal transmitted by mobile terminals at different locations do no arrive at the base station at the same time

15 Code Division Multiple Access Use of orthogonal codes to separate different transmissions Each symbol of bit is transmitted as a larger number of bits using the user specific code – Spreading – Bandwidth occupied by the signal is much larger than the information transmission rate – But all users use the same frequency band together Orthogonal among users

16 Core network Introduction Central part of a telecommunication network. Provides various services to customers who are connected by the access network. Main functions is to route telephone calls across the PSTN.

Primary functions ‏Aggregation Authentication Call Control/Switching Charging Service Invocation Gateways

Aggregation The highest level of aggregation in a service provider network. The next level in the hierarchy under the core nodes is the distribution networks and then the edge networks.‏

Authentication To decide whether the user requesting a service from the telecom network is authorized to do so within this network or not.‏

Call Control/Switching It decides the future course of call based on the call signaling processing. Example : switching functionality may decide based on the "called number" that the call be routed towards a subscriber within this operator's network or with number portability more prevalent to another operator's network.‏

Charging It handles the collation and processing of charging data generated by various network nodes.‏ Two types -- prepaid charging -- postpaid charging

Service Invocation Service invocation may happen based on some explicit action (e.g. call transfer) by user or implicitly (call waiting).‏

Gateways Gateways shall be present in the core network to access other networks. Gateway functionality is dependent on the type of network it interfaces with.‏

Example ‏

Radio network Two types of radio networks -- One- to-many broadcast network -- Two way radio network

One to many broadcast network Used for public information and mass media entertainment.

Two way radio network Used for public safety and public services such as police, fire, taxicabs, and delivery services.

List of radio networks in INDIA All India Radio (AIR) Vividh Bharati Radio City (91.1) Big FM (92.7) Radio One (94.3) Radio Mirchi (98.3) Red FM (93.5) Suryan FM (93.5) Hi FM (106.4) chaska (95.0)

Overview Evolved hardware technologies + Improved network bandwidth = Entertainment apps on mobile

Summary Communication over a distance by cable, telegraph, telephone, or broadcasting. "digital telecommunication has much to recommend it“ Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor. Functions of core network Different types of radio networks

Discussion Points What is bandwidth ? Wireless Challenges Types of access schemes Core network functions Radio network types

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