1. Next Generation (NextG) Wireless Networks
7/2/2004
Farid Farahmand

2. Outline Description of wireless networks Wireless network evolution
Wireless key technologies
Current researches

3. 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)

4. 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?

5. Wireless Network Evolution
Third Generation (3G): Digital voice and data communications
Developing a more general mobile network
Handling Internet access, , 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

6. 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

7. 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

8. 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.)

9. 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

10. 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

11. QoS-enabled MAC Protocol- Scheduling Problem
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
Pack
Blocks
Bins
IP Pkts
Time Slots

12. 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
QoS Over Air
Wireless
Internet
Bkbone