3G Mobile Networks (Packet Domain)

Agenda

• Introduction to Mobile Networks• UMTS Network• Mobility management procedures• Session management procedures• Evolution to 4G networks

Basic Working of Mobile Networks

• The user-equipment is a radio device, analogous to a traditional radio

• But it has to both transmit and receive!• The network radio transceivers shouldn’t be

too far. • A cellular model is used, enabling both

proximity of towers and re-use of frequencies

Cellular structure

Network Evolution

1 G

Analog i

n nature

2 G

Introducti

on of GPRS.

Addition of

new network

elements to

support

Data

2.5 G

Digitized

3 G

Radio te

chnology

overhau

l to

support

more bw per user

Complete radio + netw

ork

overhau

l to su

pport more bw per

user

4 G

Comparison of Available Band-width

Technology Downlink speedsGPRS (2.5G) 60-80 kbpsEDGE (2.75G) 236 kbpsUMTS (3G) 7.2 MbpsHSPA+ (3.5G) 21 MbpsLTE (4G) 50 - 100 Mbps

• Figures are theoretical speeds• Refer to the respective standards for the

actual possible speeds

Available TechnologiesGeneration Family Available Standards

1G AMPS familty AMPS, N-AMPS, TACS, ETACS

Other NMT, HiCAP, Mobitex, DataTAC

2G GSM family GSM, CSD

3gpp2 family cdmaOne (IS-95), Ansi-J-STD

AMPS familty D-AMPS

Other CDPS, iDEN, PDC, PHS

2.5G GSM family HSCSD, GPRS, EDGE

3gpp2 family CDMA2000 1X

Other WiDEN

3G 3gpp family UMTS, WCDMA-FDD, WCDMA-TDD

3gpp2 family CDMA 2000 1X-Ev-DO Release 0

3.5G 3gpp family HSPA, HSPA+

3gpp2 family CDMA 2000 1X-Ev-DO Release A

4G 3gpp family LTE

IEEE family WiMAX-Advanced

UMTS Network

Some important nodes in the network

Packet Data Network

• UMTS helps to make a Mobile Station (MS) participate in any network which employs datagram management protocol – Eg: IP networks, X.25 networks

• Could be internet, private networks of corporate companies or the operator’s private networks

• To participate in the packet network, the MS needs a PDN address. This could either be statically allocated or dynamically allocated to the MS.

Network HierarchyPLMN

LA LA

RA RA RA RA

Cell Cell Cell Cell Cell Cell Cell Cell

• PLMN is identified by a 3 digit MCC and a 2/3 digit MNC• LA is a number between (1-65535)• RA is a number between (1-255)• Cellid is a number between (1-65535)• Every country is assigned a MCC by the International

Telecommunication body. The national authorities further split their nation into different regions and spectrums and issue unique MNC for each of them. These are usually auctioned.

• The operators further split the PLMN into LA/RA and cell themselves based on their network designing.

Mobile Station

• Every subscriber is identified by a IMSI which is a 15 digit number. IMSI embeds the mcc/mnc of the operator followed by the subscriber identification digits

• The IMEI identifies the equipment/hand-set.

MS/UEME(IMEI)

USIM(IMSI)

IMSIMCC MNC MSIN

• There are broadly 2 main categories of procedures performed by the network and MS– Mobility management: This involves tracking the

movement of the MS and being able to contact the MS wherever it presently is.

– Session Management: This involves enabling the packet network participation of the MS via the UMTS network.

Mobility Management

• Connection between MS and the Network

• Based on the connectivity with network, the ms is either in one DETACHED, IDLE or CONNECTED state

Channels available

• System broad-cast channel• Paging-channels• Random access channels• Fast-Access channels• Dedicated channelsIn Detached state, the mobile listens to nothingIn IDLE, it listens to broad-cast and pagingIn CONNECTED, it listens to broad-cast + its dedicated

channels

Initial Connection

• The network broadcasts ‘system information’ consisting of the plmn, cell-id in broad-cast channels

• The ms listens to these broad-casts and knows what networks are available.

• It does a PLMN-selection, then cell-selection and then does an Attach with the network.

Attach Procedure

Change of location

Soft-handover

Periodic Update

• Triggered by Source-RNC rather than ms itself.• Usually happens when ms moves while in

connected state.

• Usually radio resources are released immediately.• The ms runs a timer, at expiry of which it updates

the current sgsn of its presence. The sgsn runs a timer slightly larger to detect loss of ms

Detach

Session Management

• The overall aim of the network is to offer the MS a participation in a packet-network!

• Each packet-network is identified by a Access Point Name (APN)

• The MS tells the network which APN it wants to be a part of. Each Apn is available by a GGSN.

• The architecture is such that the SGSN manages the mobility while GGSN manages the session. This way the reach ability of the ms to the other elements of the packet data network is ensured.

Activation

Deactivation

Downlink data for IDLE MS

Large picture

4G Evolution• The SGSN is a bottle neck for it is in both Controlling path and

Data path• Further connections between nodes are based on SS7

protocols, while IP based protocols have proven to me more easier to manage and are easily scalable

• On the radio side, OFDM has been shown to be more efficient.

• Voice can be now carried over reliably on a packet-network. So there is no need to have a separate CS-domain.

The 4G network incorporates the above and many more changes.

A 4G Network

Further study…

• http://en.wikipedia.org/wiki/Cellular_network• http://en.wikipedia.org/wiki/UMTS• http://www.umtsworld.com/• TS: 23.060 (off 3gpp)

http://3gpp.org/ftp/Specs/html-info/23060.htm