Cellular Networks Lecture 6 Paul Flynn Cellular Telephony

Cellular Networks Lecture 6 Paul Flynn

Cellular Telephony Architecture

Very Basic Cellular/PCS Architecture Public Switched Telephone Network Mobility Database Base Station Controller Mobile Switching Center (MSC) Radio Network Base Station (BS) Mobile Station

Duplex Communication - FDD • FDD: Frequency Division Duplex Mobile Terminal M Forward Channel Reverse Channel Base Station B Forward Channel and Reverse Channel use different frequency bands

Access Methods Frequency FDMA Time Frequency TDMA CDMA Time

Clusters • A cluster is a group of cells – No channels are reused within a cluster A seven Cell Cluster

Example - Frequency Spectrum Allocation in U. S. Cellular Radio Service Forward Channel Reverse Channel 991 992 … 1023 1 2 … 799 824 -849 MHz 991 992 … 1023 1 2 … 799 869 -894 MHz Channel Number Reverse Channel 1 <=N <= 799 991 <= N <= 1023 Center Frequency (MHz) 0. 030 N + 825. 0 0. 030(N-1023) + 825. 0 Forward Channel 1 <=N <= 799 0. 030 N + 870. 0 991 <= N <= 1023 0. 030(N-1023) + 870. 0 (Channels 800 -990 are unused) Channel bandwidth is 45 MHz

Frequency Reuse • Only a small number of radio channel frequencies were available for mobile systems – Therefore engineers had to find a way to reuse radio channels to carry more than one conversation at a time – The solution the industry adopted was called frequency reuse. Implemented by restructuring the mobile telephone system architecture into the cellular concept

Frequency Reuse • The concept of frequency reuse is based on assigning to each cell a group of radio channels used within a small geographic area – Cells are assigned a group of channels that is completely different from neighbouring cells – The coverage area of cells is called the footprint and is limited by a boundary so that the same group of channels can be used in cells that are far enough apart

Frequency Reuse • Cells with the same number have the same set of frequencies Frequency Reuse

Frequency Reuse using 7 frequencies allocations f 2 f 7 f 3 f 1 f 6 f 4 f 5 f 2 f 7 f 3 f 1 f 2 f 1 f 6 f 4 f 7 f 3 f 6 f 4 f 5 f 1 f 5 f 6 f 4 f 5 f 7 f 3 Each cell is generally 4 to 8 miles in diameter with a lower lim around 2 miles.

Cell Splitting • Allows urban centres to be split into as many areas as necessary for acceptable service levels in heavy-traffic regions, while larger, less expensive cells can be used to cover remote rural regions

Cellular Concept with Sectors frequency re-use base station

Hand-off • The final obstacle in the development of the cellular network involved the problem created when a mobile subscriber moved from one cell to another during a call

GSM infrastructure MSC, BTS, VLR, HLR, GSGN, GSSN

Compared to a fixed network Transit exchang Gateway MSC Local switches MSC BSC Subscriber stage Fixed phone MS

What’s new? • • • Radio access network Encryption Voice coding Locate a mobile station Identify and authenticate Handle mobility during a call

A bird eye’s view Access Network BTS MSC GMSC databases BSC BSC MS BTS

”Typical” Mobile operator • One to ten MSC per 1 M subscribers • Ten to one hundred BSC per MSC • Thousands of BTS per 1 M subscribers

Base Transceiver Station • Controls the radio link – encryption – error control – signal strength • 1 - 6 duplex carriers, for example: – two layers – 120 o sectors – (6+8)*3 = 42 voice calls • Cost ~ 100 – 200 k$

Base Station Controller • communication with the mobile terminal – – local hand-over voice codecs carrier allocation paging to terminals • talks to the MSC • serves up to 40 BTSs • could be co-located with MSC

Mobile Switching Centre • Mobility management – identifies and authenticates – locates – switches between BSCs – Handover to other MSCs • 64 kbps regular voice channels

Radio Access network A carrier is divided into logical channels control channels CCH traffic channels TCH The first carrier holds 2 controll channels and 6 traffic channels. Additional carriers holds only traffic channels.

Control Channels • Broadcast – Frequency correction: to synchronize (FCCH) – Broadcast control: this is me, these are my neighbours (BCCH) • Common control – Paging: to notify a mobile station (PCH) – Random access: for the mobile to request service (RACH) – Access grant: reply with assigned dedicated control channel (AGCH) • Dedicated control – – Standalone dedicated control: used during call set-up, SMS etc (SDCCH) Slow associated control: power, time etc (SACCH) Fast associated control: handover etc, uses the TCH (FACCH) Cell broadcast: cell broadcast

Traffic Channels • Duplex • Error control – Forward Error Correction (FEC) – retransmission (ARQ) • Full rate (TCH/F) – 13 Kbps speech – 9, 6 or 14, 4 Kpbs data • Half rate (TCH/H) – 6, 5 Kbps speech – 7, 2 or 4, 8 Kbps data

Logical channels Hyperframe: 2048 superframes 3 h 28 m Superframe: 26 or 51 multiframes CCH 6. 12 s CCH Multiframe: 26 or 51 TDMA frames CCH TCH 8 time-slot TDMA frame 4. 143 ms

One TDMA frame 148 b 0. 577 ms tail Normal burst 3 tail training 57 b 26 b user data 57 b user data stealing flags Frequency correction burst Synchronization burst Dummy burst Access burst 3 guard 8. 25

Keeping track of a mobile station Location area VLR visiting location register Location area update the VLR with new location area

Moving to a new MSC VLR which LA which MSC ? Location area update the VLR with new location area and new MSC

but also…. HLR home location register VLR update the home location register!

Home Location Register PSTN incomming call where is the mobile? GMSC HLR MSC VLR How do we reach him?

Mobile station numbers PSTN mobile subscriber ISDN number (MSISDN) i. e. the phone number GMSC HLR Mobile Station Roaming Number (MSRN). MSC VLR International Mobile Subscriber Identity Temporary Mobile Subscriber Identity

GPRS Internet Gateway GPRS Support Node GGSN Access Network Packet Control Unit BTS BSC UDP/TCP tunnel Serving GPRS Support Node SGSN MS BTS

Looking to PCS from different Angles PSTN (Telephone Network) Internet Wireless Access Mobile Users -Cell phone users -Cordless phone users Telecom People View Mobile Users -Laptop users -Pocket PC users -Mobile IP, DHCP enabled computers Data Networking People View

Telecom and Data Networking Telecom Interest - Voice Transmission - Frequency Reuse - Handoff Management -Location Tracking -Roaming -Qo. S -GSM, CDMA, Cordless Phones, -GPRS, EDGE Data Networking Interest -Radio Propagation -Link Characteristics -Error Models -Wireless Medium Access (MAC) - Error Control -Data Transmission -Mobile IP (integrating mobile hosts to internet) -Ad-hoc Networks -TCP over Wireless -Service Discovery

Major Mobile Radio Standards Europe Standard Type Year Intro Multiple Access Frequency Band (MHz) Modulation Channe l BW (KHz) ETACS Cellular 1985 FDMA 900 FM 25 NMT-900 Cellular 1986 FDMA 890 -960 FM 12. 5 GSM Cellular/PCS 1990 TDMA 890 -960 GMSK 200 KHz C-450 Cellular 1985 FDMA 450 -465 FM 20 -10 ERMES Paging 1993 FDMA 4 Several 4 -FSK 25 CT 2 Cordless 1989 FDMA 864 -868 GFSK 100 DECT Cordless 1993 TDMA 1880 -1900 GFSK 1728 1993 TDMA 1710 -1880 GMSK 200 DCS-1800 Cordless/PC S

Example - Frequency Spectrum Allocation in U. S. Cellular Radio Service Forward Channel Reverse Channel 991 992 … 1023 1 2 … 799 824 -849 MHz 991 992 … 1023 1 2 … 799 869 -894 MHz Channel Number Reverse Channel 1 <=N <= 799 991 <= N <= 1023 Center Frequency (MHz) 0. 030 N + 825. 0 0. 030(N-1023) + 825. 0 Forward Channel 1 <=N <= 799 0. 030 N + 870. 0 991 <= N <= 1023 0. 030(N-1023) + 870. 0 (Channels 800 -990 are unused) Channel bandwidth is 45 MHz

2 G Technologies cdma. One (IS-95) GSM, DCS-1900 IS-54/IS-136 PDC Uplink Frequencies (MHz) 824 -849 (Cellular) 1850 -1910 (US PCS) 890 -915 MHz (Eurpe) 1850 -1910 (US PCS) 800 MHz, 1500 Mhz (Japan) 1850 -1910 (US PCS) Downlink Frequencies 869 -894 MHz (US Cellular) 1930 -1990 MHz (US PCS) 935 -960 (Europa) 1930 -1990 (US PCS) 869 -894 MHz (Cellular) 1930 -1990 (US PCS) 800 MHz, 1500 MHz (Japan) Deplexing FDD FDD Multiple Access CDMA TDMA Modulation BPSK with Quadrature Spreading GMSK with BT=0. 3 p/4 DQPSK Carrier Seperation 1. 25 MHz 200 KHz 30 KHz (IS-136) (25 KHz PDC) Channel Data Rate 1. 2288 Mchips/sec 270. 833 Kbps 48. 6 Kbps (IS-136) 42 Kbps (PDC) Voice Channels per carrier 64 8 3 Speech Coding CELP at 13 Kbps EVRC at 8 Kbps RPE-LTP at 13 Kbps VSELP at 7. 95 Kbps

GSM Speech Signal Processing

GSM and CDMA Coverage Map Worldwide

Evolution

1 G TECHNOLOGY 1 G refers to the first generation of wireless telephone technology, mobile telecommunications which was first introduced in 1980 s and completed in early 1990 s. It's Speed was upto 2. 4 kbps. It allows the voice calls in 1 country. 1 G network use Analog Signal. AMPS was first launched in USA in 1 G mobile systems.

DRAWBACKS OF 1 G Poor Voice Quality Poor Battery Life Large Phone Size No Security Limited Capacity Poor Handoff Reliability 1 G Wireless System

2 G TECHNOLOGY 2 G technology refers to the 2 nd generation which is based on GSM. It was launched in Finland in the year 1991. 2 G network use digital signals. It’s data speed was upto 64 kbps. Features Includes: It enables services such as text messages, picture messages and MMS (multi media message). It provides better quality and capacity.

DRAWBACKS OF 2 G requires strong digital signals to help mobile phones work. If there is no network coverage in any specific area , digital signals would weak. These systems are unable to handle complex data such as Videos. 2 G Wireless System

3 G TECHNOLOGY 3 G technology refer to third generation which was introduced in year 2000 s. Data Transmission speed increased from 144 kbps- 2 Mbps. Typically called Smart Phones and features increased its bandwidth and data transfer rates to accommodate web-based applications and audio and video files.

FEATURES OF 3 G TECHNOLOGY Providing Faster Communication Send/Receive Large Email Messages High Speed Web / More Security Video Conferencing / 3 D Gaming TV Streaming/ Mobile TV/ Phone Calls Large Capacities and Broadband Capabilities 11 sec – 1. 5 min. time to download a 3 min Mp 3 song.

DRAWBACKS OF 3 G TECHNOLOGY Expensive fees for 3 G Licenses Services It was challenge to build the infrastructure for 3 G High Bandwidth Requirement Expensive 3 G Phones. Large Cell Phones

4 G TECHNOLOGY (Anytime , Anywhere)

4 G TECHNOLOGY (Anytime , Anywhere) 4 G technology refer to or short name of fourth Generation which was started from late 2000 s. Capable of providing 100 Mbps – 1 Gbps speed. One of the basic term used to describe 4 G is MAGIC: Mobile Multimedia Anytime Anywhere Global Mobility Support Integrated Wireless Solution Customized Personal Services Also known as Mobile Broadband Everywhere.

Countries Have 4 -G Except for the Scandinavian Countries (Northern Europe that includes Denmark and two of the nations of Scandinavian , Norway and Sweden. ), a few countries have started the 4 G commercially. In the US, Sprint Nextel and Others Germany , Spain, China , Japan and England are also using the 4 G services and mobiles.

WIRLESS MODELS OF 3 G & 4 G 3 G WIRELESS SYSTEM 4 G WIRELESS SYSTEM

5 G TECHNOLOGY 5 G technology refer to short name of fifth Generation which was started from late 2010 s. Complete wireless communication with almost no limitations. It is highly supportable to WWWW (Wireless World Wide Web).

BENEFITS OF 5 G TECHNOLOGY High Speed, High Capacity 5 G technology providing large broadcasting of data in Gbps. Multi - Media Newspapers, watch T. V programs with the clarity as to that of an HD Quality. Faster data transmission that of the previous generations. Large Phone Memory, Dialing Speed, clarity in Audio/Video. Support interactive multimedia , voice, streaming video, Internet and other 5 G is More Effective and More Attractive.

EVOLUTION OF 1 G TO 5 G TECHNOLOGY

WIRELESS APPLICATIONS Wireless applications are those which we use free space as the transmission medium & do not involve cabling like fibre or copper cables.

WIRELESS SERVICES Wireless solution for: Business and Industry Schools , Colleges Doctors , Pilots Police and Vehicles etc.

CONCLUSION All totally the best way to help all users is to use 5 G as the next wireless system and in totally it is safety and secure for public, this the need that demands the solution. Today’s wired society is going wireless and if it has problem, 5 G is answer. 5 G technology is going to give tough competition to Computers and Laptops. It will be available in the market 2020 at affordable cost with more reliability than previous mobiles.