Wireless networks - Lecture 44: 4G issues

Wireless networks - Lecture 44: 4G issues. The main topics covered in this chapter include: 4G overview; achieving a seamless wireless access infrastructure; dynamic address assignment mechanism; heterogeneous wireless networks; mobility management; handoffs and QoS considerations;

Wireless Networks

Lecture 44 4G Issues

Dr Ghalib A Shah

Last Lecture

 Reference Model

 Burst profiles

 Convergence sublayers

 MAC PDU format

 MAC PDU Transmission

 Fragmentation / Packing

 Request/Grant Scheme

 Classes of Uplink service

 Power management/Handoff

4G Overview

 4G mobile communication systems tend to mean different

things to different people:

► for some it is merely a higher-capacity new radio interface,

► while for others it is an inter-working of cellular and wireless LAN

technologies that employs a variant of the Mobile IPv6 mobility management protocol for inter-system handoff.

 There is no doubt that 4G systems will provide higher data

rates Traffic demand estimates suggest that, to

accommodate the foreseen amount of traffic in the 2010 –

2020 timeframe in an economically viable way, 4G mobile

systems must achieve a manifold capacity increase compared

to their predecessors

 There are many wireless network technologies

Cellular networks, Wireless LANs, Wireless

PANs, mobile Wimax, etc.

 4G networks will play a key role for integrating

various network architectures and technologies and achieving a seamless wireless access

infrastructure

 4G provides high-speed, large volume, good

quality, and global coverage to roam between different types of technologies

 It is widely accepted that the individual (wireless and/or

wireline) access networks will interface to core and/or backbone network elements over the IP protocol

 these wireless access networks are expected to have

the following in common:

► A dynamic address assignment mechanism (e.g., DHCP, SLP,

IPv6) that is capable of associating a short-lived or long-lived

IP address to the respective wireless interface at the mobile terminal (e.g., Mobile IP COA association)

► A transparent IP forwarding service that is accessible over the

logical termination of the IP layer at the mobile terminal and one or more gateways

Heterogeneous Wireless Networks

 A mixture of co-existing radio access

technologies.

 Different access technologies (radio interfaces)

and overlapping coverage.

 Different network architectures and protocols

for transport, routing and mobility management.

 Different service demands from mobile users

(low-data rate, high-data rate, voice,

multimedia, etc)

 Different operators in the market.

Evolution of 4G

Heterogeneous  Networks

► Resource coordination to add new users

► Support for multicasting

► Support for quality of service

► Wireless security and authentication

Mobility Management

 Mobility Management

► Location Management: enables system to track

location of mobile terminal (MT)

• Location updates and paging

► Handoff Management: the process by which an MT

keeps its connection when it moves from one point

of attachment (base station or access point) to another

Handoff Management

 Low signalling and processing overhead.

 Minimum packet loss and delay (seamless

HO).

 Guaranteeing QoS during the process and

transfer of context.

 Use of any “triggers” or metrics available to

decide when and where.

 Efficient use of network and MT resources.

Handoff Types

 Homogeneous (Horizontal) Handovers

► Within Single Network (Localized Mobility)

► Limited opportunities

► Mainly use received signal strength (RSS) to decide

handoff

 Heterogeneous (Vertical) Handovers

► Across Different Networks (Global Mobility)

► More Opportunistic

► Handoff metric: RSS, offered bandwidth, price,

power consumption, speed, ……

Vertical handoff process

 Step 1: “System Discovery”

 Step 2: “Handoff Decision”

 Step 3: “Handoff Execution”

Step 1: “System Discovery”

 MT must know which

► wireless networks are reachable

► Periodic beacons from AP

► Signal measurements

► Handoff metrics (network information) gathering:

Bandwidth, cost, delay, SNR, power, etc

► Periodic network scanning

► All interfaces always on

Step 2: “Handoff Decision”

 MT then evaluates the

► Some example policies:

Step 3: “Handoff Execution”

 If MT decides to perform a VHO, it executes

the VHO procedure required to be associated with the new wireless network.

► Packet loss and VHO latency.

 Load balancing between networks.

 QoS guarantees

 Security and Authentication.

Standardization Efforts

 IETF

► Mobility for IPv4 (MIPv4)

► Mobility for IPv6 (MIPv6)

► Mobility for IP: Performance, Signalling and Handoff

Optimization (MIPSHOP)

 IEEE 802.21 Media Independent Handover Group is

working toward the seamless handoffs between IEEE 802.XX family and 3G Cellular

 3GPP and 3GPP2 are working in inter-working with

WLAN as an extension of their radio access networks

► Loosely Coupled Architecture

► Tightly Coupled Architecture

 Tightly coupling

► Provides common charging and billing service

► Provides mobility support using traditional 3G

technology

► Reuses 3G service (e.g., SMS, MMS, etc.)

► Causes large traffic load in 3G core network

 Loosely coupling

► Provides simple integration approach

 Supporting QoS in 4G networks will be a major

challenge due to varying bit rates, channel

characteristics, bandwidth allocation,

fault-tolerance levels, and handoff support among heterogeneous wireless networks

 QoS support can occur at the

► Packet,

► Transaction

► Circuit

► User

 Packet­level QoS  

► applies to jitter, throughput, and error rate

► Network resources such as buffer space and access

protocol are likely influences

 Transaction­level QoS  

► describes both the time it takes to complete a

transaction and the packet loss rate

► Certain transactions may be time sensitive, while

others cannot tolerate any packet loss

 Circuit­level QoS  

► includes call blocking for new as well as existing

calls

► It depends primarily on a network’s ability to

establish and maintain the end-to-end circuit

 User­level QoS  

► depends on user mobility and application type

► The new location may not support the minimum QoS

needed, even with adaptive applications

 Developers need to do much more work to address

end-to-end QoS

► They may need to modify many existing QoS schemes ,

including admission control, dynamic resource reservation, and QoS renegotiation to support 4G users’ diverse QoS

requirements

 A wireless network could make its current QoS

information available to all other wireless networks in either a distributed or centralized fashion so they can effectively use the available network resources

QoS Parameters

► Nominal MSDU size

► Min/mean/max data rate

► Mean/max service interval

► Traffic type (isochronous, asynchronous)

► Burst size

► Traffic class (conversational, streaming, interactive, or background)

► Guaranteed, maximum bit rate

► Maximum SDU size

► SDU/bit error ratio

► Transfer delay

► Traffic priority

► Maximum sustained traffic rate

► Maximum traffic burst

► Minimum reserved traffic rate

► Scheduling type (best-effort, non-real time polling, real-time polling, unsolicited grant)

► Tolerated jitter, maximum latency