CMC ICT3207 Call Flow

Associate Professor

Dept. of Electrical and Electronic Engineering

Dr.

Mohammad

J

unaebur

R

ashid (

JR

)

ICT3207: Cellular and Mobile Communication (3.0 Cr)

Course Teacher

Bangladesh University of Professionals

Lecture 21

Channel assignment

• The total number of available channels can be divided into sets (subgroups) depending on

the sectorization of the cell configuration: the 120°-sector system, the 60°-sector system, and

the 45°-sector system.

• A seven-cell system usually uses three 120° sectors per cell, with the total number of

channel sets being 21. In certain locations and special situations, the sector angle can be

reduced (narrowed) in order to assign more channels in one sector without increasing neighboring-channel interference.

• Sectorization serves the same purpose as the channel-borrowing scheme in delaying cell

splitting. In addition, channel coordination to avoid cochannel interference is much easier in sectorization than in cell splitting. Given the same number of channels, trunking efficiency

decreases in Sectorization.

Lecture 21

Channel assignment

• Omni-cells: If a K = 7 frequency-reuse pattern is used, the frequency sets assigned in each

cell can be followed by the frequency-management chart (shown in Fig. 8.1).

• However, terrain is seldom flat; therefore, K = 12 is sometimes needed for reducing

cochannel interference.

• For K = 12, the channel-reuse distance is D = 6R, or the cochannel reduction factor q = 6.

• Sectorized cells: There are three basic types.

1. The 120°-sector cell is used for both transmitting and receiving sectorization. Each sector

has an assigned a number of frequencies. Changing sectors during a call requires

handoffs.

2. The 60°-sector cell is used for both transmitting and receiving sectorization. Changing

Lecture 21

Channel assignment

3. The 120°- or 60°-sector cell is used for receiving sectorization only. In this case, the

transmitting antenna is omni-directional.

- The number of channels in this cell is not subdivided for each sector. Therefore, no handoffs are required when changing sectors.

-_{This receiving-sectorization- only configuration decrease interference or increase the D/R}

ratio

- _{It also allows for a more accurate, decision regarding handing off the calls to neighboring}

Lecture 21

Security in GSM

• Security services

- Access control/authentication

a) User - SIM (Subscriber Identity Module): secret PIN (personal identification number)

b) SIM - network: challenge response method -Confidentiality

Voice and signaling encrypted on the wireless link (after successful authentication)

- Anonymity

Temporary identity TMSI (Temporary Mobile Subscriber Identity)

Newly assigned at each new location update (LUP)

Lecture 21

Security in GSM

• Three algorithms specified in GSM

- A3 for authentication (“secret”, open interface)

- A5 for encryption (standardized)

Lecture 21

Lecture 21

Location registration

• MS has to register with the network to get communication services • Registration is required for a change of network

• MS has to report to current network with its IMSI and receive new TMSI by executing

Location Registration process.

• The TMSI is stored in SIM, so that even after power on or off, there is only normal

Location Update.

• If the MS recognizes by reading the LAI broadcast on BCCH that it is in new LA, it

performs Location Update to update the HLR records.

• Location update procedure could also be performed periodically, independent of the MS

movement.

• The difference in Location Registration and Location Update is that in location update the

Lecture 21

Lecture 21

Lecture 21

Lecture 21

Lecture 21

Data services in GSM

• Data transmission standardized with only 9.6 kbit/s - Advanced coding allows 14.4 kbit/s

- Not enough for Internet and multimedia applications

• HSCSD (High-Speed Circuit Switched Data)

- Mainly software update on MS and MSC to split a traffic stream into several streams.

- Bundling of several time-slots to get higher AIUR (Air Interface User Rate) (e.g., 57.6

kbit/s using 4 slots, 14.4 each)

- Advantage: ready to use, constant quality, simple

Lecture 21

Data services in GSM

• GPRS (General Packet Radio Service)

- Packet switching

- Using free slots only if data packets ready to send (e.g., 50 kbit/s using 4 slots temporarily)

- Standardization 1998, introduction 2001

- Advantage: one step towards UMTS, more flexible -Disadvantage: more investment needed (new hardware)

• GPRS network elements

- GSN (GPRS Support Nodes): GGSN and SGSN

- GGSN (Gateway GSN)

Interworking unit between GPRS and PDN (Packet Data Network)

- SGSN (Serving GSN)

Lecture 21

Benefits of SMS

• At a minimum, SMS benefits include the following:

- Delivery of notifications and alerts - Guaranteed message delivery

- Reliable, low-cost communication mechanism for concise information - Ability to screen messages and return calls in a selective way

-Increased subscriber productivity

• More sophisticated functionality provides the following enhanced subscriber benefits:

- Delivery of messages to multiple subscribers at a time

- Ability to receive diverse information - E-mail generation

Lecture 21

GMS SMS

• Can contain up to 140 octets, or 160 char.

• To allow messages longer than 160 char.

- SMS concatenation

- SMS compression

• SDCCH signaling channel • Two type of GSM SMS

Lecture 21

Lecture 21

Frequency management

• Second Generation Mobile Service (2G):

-According to NFAP, spectrum of 900 MHz & 1800 MHz bands are allocated for Second

Generation Mobile Service (2G).

• 3G/4G/LTE service: According to ITU Radio Regulation, 450-470, 703-748/ 758-803,

825-845/870-890, 890-915/935-960, 1710-1785/1805-1880, 1920-1980/2110-2170,

2500-2570/ 2620-2690 and 3400-3500/3500-3600 MHz frequency band have been reserved for International Mobile Telecommunication (IMT) in the NFAP of Bangladesh

• In order to provide 4G services, assignment of frequency from 700 MHz

Lecture 21

Frequency management

• ISP: uses spectrum from 3.5 GHz, 5.2 GHz, 5.6 GHz and 2.3 GHz band

• Terrestrial Broadcasting: Only Bangladesh Television (BTV) is being transmitted using

terrestrial television broadcasting technology. BTV is using 174-230 MHz spectrum in

VHF band for this transmission.

• Satellite Television Broadcasting: Satellite television channels have been assigned 6, 9 or

12 MHz uplink frequency from 5.85-6.425 GHz band.

• FM Radio Broadcasting: According to NFAP, spectrum from 87.5 MHz to 108 MHz is

reserved for FM Radio broadcasting.

• As per NFAP of Bangladesh, 108 MHz to 117.975 MHz and 118 to 136 MHz spectrum

are generally used for Aeronautical radio service.

Lecture 21

Frequency management

Spectrum

Band Spectrum Range(MHz) Total Spectrum Mobile BWA ISP PSTN Total

450 MHz 450-460/460-470 20 MHz

700 MHz 703-748/758-803 90 MHz 6+6 12

800 MHz 825-845/870-890 40 MHz 15+15 2.52+2.52 35.04

900 MHz 890-915/935-960 50 MHz 25+25

1800 MHz 1710-1785/1805-1885 150 MHz 52+52 7.4+7.4 118.8

1880 MHz 1800 - 1900 20 MHz

1900 MHz 1900-1910/1980-1990 20 MHz 2.6+2.6 5.2 2000 MHz 2010-2025 15 MHz

2100 MHz 1920-1980/2110-2170 120 MHz 35+35 70

2300 MHz 2300 - 2400 100 MHz 35 35

2500 MHz 2500-2690 190 MHz 75 75

3500 MHz 3400-3500/3500-3600 200 MHz 191 191

Lecture 21

Lecture 21

Frequency management

Spectrum Usage Fees

Formula:

STU The Spectrum Tariff Unit, currently set at 70 taka;

CF The Contribution Factor, varies according to the subscriber base of the operator (more subscribers, higher the CF)

BW The assigned bandwidth in MHz;

AF The Area Factor ( surface area of Bangladesh, 147570 sq km)

Lecture 21

Frequency management

Spectrum Acquisition Fees

Mobile Operators

Year Price / MHZ

(Core Tk) US$ MnPrice in Sold Freq (MHZ) Total Income (Crore Taka) Acquisition Method

2005 22.33 2.82 15 335 License Transfer of to Airtel

2008 80 10.25 12 960 Commission Meeting

2011 150 19.23 49.8 7470 Renewal of 2G Spectrum

2012 163.24 21 25 4081 3G Auction