Next Generation (NextG)Wireless Networks

7/2/2004

Farid Farahmand

Outline

Description of wireless networks Wireless network evolution Wireless key technologies Current researches

Wireless Networks

Motivated by people-on-the-go PCs availability, Internet usage, Mobile

life Aimed is to establish wide-area voice

data communications Includes mobile systems (cellular

telecommunication systems)

Wireless Network Evolution First generation (1G): Analog voice systems

No standardization Second Generation (2G): Digital voice systems

Currently deployed systems CDMA, GSM (Global System for Mobile communication), PDC

(Japan) D-AMPS (Digital Advanced Mobile Phone System) PCS Systems

Second Generation – advanced (2.5G): Combining voice and data communications Providing enhanced data rate Two basic technologies:

GSM-based (high baud rate) GPRS (General Packet Radio Service)

Utilizes voice time slots to send packet traffic An overlay over the existing voice system

Should really be called 2.1G!! Any standards?

Wireless Network Evolution Third Generation (3G): Digital voice and

data communications Developing a more general mobile network

Handling Internet access, email, messaging, multimedia

Access to any services (voice, video, data, etc.) Requires high quality transmission

Forth Generation (4G): All-IP mobile networks Ubiquitous wireless communications Transparent to any services Integrating multinetworks

Third Generation (3G) Two basic proposals to handle voice and data

Ericsson: Universal Mobile Telecommunications systems (UMTS) Compatible with European GSM Backed by ETSI and Japan

Qualcom: CDM2000 Not compatible with GSM (cannot hand off called to GSM-based cells) Compatible for IS-95 (supported by U.S)

3G Standards 1999 UMTS took over and an agreement was made over setting some

standards A revolutionary technology with unlimited potential or not so great?

Major competing technologies Bluethood Wireless LAN (IEEE 802.x standards) – also known as WiFi

Short range wireless communications Highly utilized and very popular: offices, airports, coffee shops, universities

and schools Two basic modes of operations:

Ad-hoc networking: computers send data to one another Access point:: sending data to the base station

Forth Generation Wireless Networks Otherwise known as NextG, Beyond 3G, 4G, and more! Motivation

Providing all available services to highly mobile people (anytime anywhere) Use your wireless device anywhere for listening to music, shopping (m-commerce) ,

downloading (file transfer), watching video (live streaming) Multiple applications (talk and use Internet services at the same time)

Objectives Total convergence of the wireless mobile and wireless access communications

(developing a broadband wireless network) Ubiquitous wireless communications and services

Integration of multi-networks using IP technology Similar technology to the wired Internet where users are freed from their local

networks All-IP based wireless networks

Not just IP end-to-end but over-the-air packet switching Supporting native wireless IP mode Highly integrated High bandwidth / high-speed wireless

Highly compatible with wired network infrastructures ATM, IP, ATM

4G Technology Challenges

Supporting heterogeneous multitude of systems Includes multiple networks:

Cellular telecommunication systems Digital video broadband Digital audio broadband Wireless LAB, Bluethood-based networks

Open communication network: infrastructure independent which can access to any services and applications (now and in the future!)

Complete compatibility between wireless and wired networks through gateways Supporting statistical multiplexing of heterogeneous data over-the-air

Latency, noisy environment, unpredictable discontinuities and loss, etc. High-speed wireless transmission over the air

High performance physical layer 20Mbps (2G: 28Kbps, 3G: 2Mbps)

Scarce bandwidth availability Efficient frequency spectrum utilization Efficient hand off Dynamic bandwidth allocation Advanced digital transmission technology (modulation, low power devices, etc.)

4G Key Issues - Research Areas

IP Addressing Mobile IPv6 protocol provides unbroken connectivity between mobile nodes

Architecture Horizontal communications between different access technologies using gateways Including local-area access technology (3G only covers wide-area packet switched

cellular technology) Hand off

Fast hand off due to high-speed transmission High reliability

QoS framework Interoperability between wireless and wired networks QoS classes: Conversational (most delay sensitive), streaming, interactive,

background (least delay sensitive) Fair bandwidth allocation Class-based QoS over the air

4G Key Issues - Research Areas

Security and billing Essential in e-commerce More than just authentication and encryption (as in 3G) End-to-end security mechanisms between the Internet server (wired) and the

mobile terminal No translation and decomposition of the data at the gateways

Usage fee Volume based or time-based?

TCP performance in wireless / mobile communications Research shows unmodified standard TCP is not well aligned with cellular

boundaries New protocols have been developed: Snoop, Split connections, other end-to-

end protocol families Using Snoop agent the exchange of TCP packets and ACKs are monitored and

performs local retransmissions as needed (OBS-like!) Split-connections deals with wireless and wired network inconsistencies (gateways,

translations, etc.) Two separate connections between fixed and mobile hosts

End-to-end protocols deal with retransmission timeout causing the TCP window to shrink too often

QoS-enabled MAC Protocol- Scheduling Problem

Mac protocols: Wirelines: FIFO, Generalized Processor Sharing (GPS) Wireless: Random Access Protocols

Voice-based MAC protocols don’t work well for multimedia applications No packet ordering is supported, no fair packet loss sharing

Multimedia traffic exhibit highly bursty traffic rates Each class of traffic has a QoS requirement and traffic rate characteristics A new MAC protocol with fair packet loss sharing scheduling for 4G is proposed

Assumes time-division/code-division multiple access wireless system with IP transmission Objective (conflicting):

support as many users as possible (high channel utilization), dropped packets between all users are shared fairly

Basic Idea: Allocate minimum amount of resources to satisfy the QoS requirements Maximize the total number of scheduled packets

How to calculate the number of packets dropped: Give enough BW to meet the QoS guaranteed level, drop the rest Maximize the number of packets sent: bin-packing problem

Blocks BinsPack

IP Pkts Time Slots

Class-based QoS over Air Interface in 4G

Basic characteristics: Flexible (support various services) Effective (easy negotiation mechanism to handle QoS over air)

Basic Idea: Check congestion over the air When congestion occurs, users with lower QoS have to back off

their transmission rate The extent of the back off depends on the class it belongs to

Basic problem is possible under-utilization Supports any number of QoS classes based on the specified

resource assignment for each class

WirelessInternet Bkbone

QoS Over Air