introduction to cellular networking and rethinking mobile architectures

Introduction to Cellular Networking and Rethinking

Mobile Architectures

Jatinder Pal Singh EE 392I, Lecture-3

April 13th, 2010

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G

and beyond) Cellular future goals Emerging trends

Alternative wireless access technologiesConvergence

Comparison with Internet and sample scenario studies

Economics of operation From a clean slate

Basics: Structure

Cells Different

Frequencies or Codes

Base Station Fixed transceiver

Mobile Station Distributed transceivers

Downlink

UplinkHandoff

Multiple Access

Basics: Multiple Access Methods

Time

Frequency

Codes

TDMA: Time Division Multiple Access

FDMA: Frequency Division Multiple Access

CMDA: Code Division Multiple Access

Some More Basics Uplink & Downlink separated in

Time: Time Division Duplex (TDD), orFrequency: Frequency Division Duplex (FDD)

Information (voice, data) is digitized and bit streams modulated onto carrier

Modulation, data redundancy (coding), transmission power, data retransmissions (ARQ) adapted to varying wireless channel quality

Spatial attenuation of signalFrequency or codes can be reused (frequency

reuse)

Cellular Technology Evolution

0G: Mobile radio telephones (e.g. MTS) 1G: Analog 2G/3G/4G .. - digital:

GSM/3GPP Family cdmaOne/CDMA2000 Family

GSM

GPRS

EDGE

UMTS, WCDMA

HSPA

cdmaOne/IS-95

CDMA2000 EV-DO

2G

3G

4G LTE

Agenda Basics & Technology Evolution Architecture and Functionality (GSM,

3G and beyond) Cellular future goals Emerging trends




Global System for Mobile communications (GSM)

900/1800 MHz band (US: 850/1900 MHz) For 900 MHz band

Uplink: 890-915Downlink: 935-960

25 MHz bandwidth - 124 carrier frequency channels, spaced 200KHz apart

Time Division Multiplexing for 8 full rate speech channels per frequency channel.

Handset transmission power limited to 2 W in GSM850/900 and 1 W in GSM1800/1900.

Architecture

The Base Station Subsystem (BSS)

Base Transceiver Station BTS - transceivers serve different frequencies.

Frequency hopping by handsets and transceivers

Sectorization using directional antennas Base Station Controller (BSC) controls

several (tens to hundreds) of BTSs allocation of radio channelshandovers between BTSs concentrator of traffic databases with information such as carrier

frequencies, frequency hopping lists, power reduction levels, etc. for each cell site

Network Switching Subsystem (NSS)

This GSM core network manages communication amongst mobile devices & with PSTN

Mobile Switching Center (MSC) : routing of calls and GSM services for users, mobility management, handovers, Gateway MSC – interfaces with PSTN, determines the

visited MSC at which the subscriber being called is currently located

Visited MSC - MSC where a customer is currently located. The Visitor Location Register (VLR) associated with this MSC has subscriber's data.

Anchor MSC - MSC from which handover initiated. Target MSC - MSC toward which a handover should take

place. Home Location Register (HLR): database with all

mobile phone subscriber details

GPRS core network Mobility management, session

management, and transport for IP services

GPRS Tunneling Protocol, GTP allows end users mobility with continued Internet connectivity by transporting user’s data between users’ current SGSN and GGSN

GPRS support nodes (GSN) GGSN - Gateway GPRS Support Node SGSN - Serving GPRS Support Node

GSM Support for Data Services: GPRS

User gets pair of uplink and downlink frequencies.

Multiple users share the same frequency channel with time domain multiplexing.

Packets have constant length corresponding to a GSM time slot.

Downlink uses FCFS packet scheduling Uplink

Slotted ALOHA for reservation inquiries during contention phase

data transferred using dynamic TDMA with FCFS scheduling.

Upto 64 kbps (more for EDGE) downlink per user.

UMTS and 3G technologies (WCDMA & HSPA)

Universal Mobile Telecommunications System (UMTS) – commonly uses WCDMA as the underlying interface

Theoretically supports up to 14 Mbps rates with HSDPA

WCDMA Frequency bands 1885-2025 Mhz (uplink), 2110-2200 Mhz (downlink)US: 1710-1755 MHz and 2110-2155 MHz

W-CDMA has 5 Mhz wide radio channels (CDMA2000 transmits on one or several pairs of 1.25 Mhz radio channels).

HSDPA allows networks based on UMTS to have higher data rates on downlink(1.8. 3.6, 7.2, 14.0 Mbps via AMC, and HARQ, fast packet scheduling.

Next Generation Mobile Networks

Next Generation Mobile Networks (NGMN) Ltd. - Consortium with partnership of major mobile operators

Recommendations without specific technology prescriptions

Target to establish performance targets, recommendations and deployment scenarios for future wide-area mobile broadband network packet switched core

The architecture intended to provide a smooth migration of existing 2G/3G networks towards an IP network that is cost competitive and has broadband performance.

NGMN: Beyond 3G Video telephony and multimedia conferencing, IM,

video streaming – among high drivers for NGMN Essential System recommendations

Seamless mobility across all bearers with service continuity through a min of 120 km/h

Peak uplink data rates 30-50 Mbps Peak > 100Mbps downlink Latency core < 10ms, RAN <10ms, <30ms e2e QoS based global roaming Broadcast, multicast, and unicast services to subscribers

of all environments Real time, conversational and streaming in PS across all

required bearers Cost per MB : as close to DSL as possible

NGMN Envisioned System Architecture

Alternative fixed wireless and MAN standards

WiMAX, the Worldwide Interoperability for Microwave Access based on IEEE 802.16 standard

Last-mile broadband access, backhaul for cellular networks, Internet Services

802.16d Fixed WiMAX, 802.16e - Mobile WiMAX.

Licensed spectrum profiles: 2.3GHz, 2.5GHz and 3.5GHz. US mostly around 2.5 GHz, assigned primarily to Sprint Nextel, Clearwire.

Convergence Heterogeneous access technologies Multi-mode access devices

Dual mode phones (WiFi, 2.5/3G), UMA

Heterogeneous Services Cellular Internet access and Internet based

voice/video access Challenges

Time variant heterogeneous network characteristics

Heterogeneous applications with different utilitiesSystem design and networking challenges

Cellular Networks and Internet

Cellular Networks Internet

VoiceData

Packet Switched

Controlled Semi-Organic

Good Poor

Incipient Service

Technology

Evolution

Mobility Support

Circuit Switched Analog

Circuit Switched Digital

C.S. Voice + P.S. Data

New Services Operator initiated or partnered

Third party/ independent (largely)

Cellular Networks and Internet

Cellular Networks Internet

Data rates for supporting broadband services

Insufficient as of present

Relatively high

Cost per MB of data

HigherLower

QoS at edges Good Support (voice vs. data)

Mostly absent

Internet : Sample scenario – Residential Broadband access

Internet

BRASDSLAM

Home WiFi Router

QoS: Wireless hop (802.11e?), PPPoE, IP QoS (Diffserv) and translation mechanisms

Mobility Options: MIP - high-barrier, delay performance, incremental patch rather than clean solution?

Cellular Scenario

Better QoS, scheduling

Better Mobility within the cellular network

Integrated voice/data Authentication

Downside is excessive edge network delays, costs of network deployment.

The Economics 3G spectrum licensing and migration cost Telecom equipment vendors – economics

of operation, meeting bids vs. system upgrades for technical innovation

Stiff competition for fixed and mobile segments of operators, drive towards services.

Interesting and sometimes conflicting dynamics for both fixed and mobile operators.

From a Clean Slate Greater intelligence at edges of networks, eventually leading

to just network elements of different sizes and capabilities Functional homogeneity in network elements in terms of

storage/caching, processing, networking capability. Such network element should likely be multi-homed connected with heterogeneous technologies

(including p2p, delay tolerant), have intelligence for resource allocation, QoS have interaction capability with other network elements

(including user devices), support mobility, handoffs have ability to recognize needs of existing and new applications

(HDTV, phone, streaming video) be plug and play

Interfacing of applications/services (QoS specs) with underlying serving networks for fast and easy deployment.

Heterogeneity in access technologies amongst user carried devices honored and accepted by the network elements.

Options for operators Sharing the spectrum/infrastructure

costs? New service models to forestall cost

of upgrades Good opportunity for fixed and mobile

carriers to take initiative.

introduction to cellular networking and rethinking mobile architectures

Documents

anchor msc msc

target msc msc

visited msc

center msc

carrier frequency channels

gateway msc interfaces

frequency hopping lists

mobile devices