DIFFERENCES IN WIRELESS NETWORKS

1. Channel capacity

Limited spectrum available

Power restrictions

Noise levels

2. Noise and interference have more impact on systems design for wireless systems than on wired systems

3. Before building a wireless system, some sort of frequency allocation (by the Federal Communications Commission in the U.S.) is required.

4. Security is a greater concern in wireless systems than in wired systems since the information may be traveling in free space.

WIRELESS AND MOBILE NETWORKS HAVE TO WORRY ABOUT -

• Network configuration Infrastructure-based

Ad-hoc configuration

• Limitations of devices

Content adaptation to device capabilities

New protocols to handle device limitations

• Bandwidth

• Handoff – type of handoff, handoff implementation, priority, channel assignment

• Error control

WIRELESS AND MOBILE NETWORKS HAVE TO WORRY ABOUT (cont.)-

Mobility management

Addressing and routing issues

Location Tracking –

Broadcasting (paging) to locate a user

Location updating by user after every move

Combination of paging and updating

Ad Hoc Wireless Networks

• Mobile nodes interconnected by multihop communication paths.

• No fixed network or administrative support.

•Topology varies dynamically as mobile nodes join or depart the network or radio links between nodes become unusable.

•Self-creating, self-organizing, and self-administering

Ensuring Effective routing is one of the great challenges for ad hoc networking.Each node must be able to function as routers on demand.

A

B

D

C

Evolution Toward Third Generation Wireless Networks

1-G / 2-G :

Capable of providing voice and low-rate data networks

Air interfaces inadequate for satisfying the high data rates specified by the ITU for IMT-2000.

3-G requirements:

High data rates and QoS metrics

1G(analog) - Advanced Mobile Phone System (AMPS)

Major network deployments in North America, the Asia/Pacific region, and Central and Latin America with other substantial network operations in the Asia/Pacific region.

2G systems –

•GSM ( Predominant standard in Europe and widely deployed throughout the world – largest number of subscribers)

• IS-136

• IS-95 or cdmaOne

•Digital AMPS (DAMPS)

•Personal Digital Cellular (PDC)

GSM, IS-136, and PDC TDMA based systems

IS-95 CDMA

Main standards of North America with other installations in Central and South America and Asia/Pacific regions

Only Japan, but second largest digital subscribers

GSM Evolution

GSM networks will enhance packet data services primarily in three phases. General Packet Radio Services(GPRS) refers to the first phase of GSM network architecture enhancements that allow mobiles to connect to IP or X.25 based networks.

The GSM/GPRS network architecture will further evolve to support Enhanced Data Rates for GSM Evolution (EDGE), which provides significant improvements over GPRS.

Finally, the ETSI/ARIB Wideband CDMA (WCDMA) proposal provides a new air interface for GSM networks - supporting higher data rates meets or exceeds the UMTS/IMT-2000 specifications.

General Packet Radio Services

•Allows GSM mobile subscribers to connect to an IP-based or X.25-based network.

•Two new network elements are introduced with GPRS to the GSM architecture-

Serving GPRS support node (SGSN)

Gateway GPRS support node (GGSN)

The SGSN provides authentication and mobility management.

GGSN provides the interface between the mobile and the IP or X.25 network.

VLR

MSC

SGSN

GGSNBTS

BTS

BTS

BSC

PSTN

IP network

X.25 network

HLR

MH

MH-Mobile Host MSC- Mobile switching center BTS- Base Transceiver station VLR – Visitor location registry BSC-Base Station controller HLR –Home location registry PSTN – Public Switched Telephone network SGSN- Serving GPRS support node GGSN – Gateway GPRS Support node

Enhanced Data Rates for GSM Evolution (EDGE)

EDGE reuses the GSM/GPRS time slot structure

200 kHz carrier and multi-slot operation allow service providers to deploy EDGE transceivers among existing GSM/GPRS transceivers.

Adaptive radio link protocol will be employed to take advantage of the better channel quality.

Note -One of the main differences between GPRS and EDGE is that EDGE will use 8-phase shift keying (8-PSK) modulation, which encodes 3 bits per modulated symbol, as opposed to the 1-bit per symbol GMSK used in existing GSM and GPRS networks.

IS –136 Evolution

IS-136, sometimes referred to as North American TDMA (NA-TDMA), has a two phase migration path

136+

136HS

IS-136+ significantly improves both the voice and data services available using the existing 30 kHz channel bandwidth. Bit rate of 16.2 kbps for a full-rate channel.

Adopting the EDGE standard (see GSM Evolution) for the outdoor component of IS-136HS. The main difference between EDGE deployments in existing IS-136 networks and GSM networks will be spectrum allocation.

IS-95 Evolution

Also referred to as North American CDMA (NA-CDMA), has a two phase migration path:

IS-95B

cdma2000.

IS-95 provides circuit-switched and packet-switched data at rates of 9.6 kbps or 14.4 kbps (depending on the speech coder) using a 1.25 MHz channel bandwidth

GSM -> GPRS -> EDGE -> WCDMA

IS-136 networks -> 136+ -> 136HS(EDGE in outdoor environment)

IS-95 (CDMA) -> IS-95B -> cdma2000

Currently, numerous operators have signed contracts with wireless equipment vendors such as Nokia,Ericsson, Nortel, and Motorola to provide GPRS data services in their existing GSM networks.

EDGE is to be deployed in early 2001

WCDMA and cdma2000 are also undergoing field trials with commercial deployment possibly slated for the 2002 to 2003 time frame.

CURRENT AND EMERGING SYSTEMS/STANDARDS

•Spread Spectrum – Frequency Hopping and Direct Sequence

•Wireless WANs - Metricom, CDPD , ARDIS

•Wireless proprietary LANs – Motorola’s Altair, AT&T’s WaveLAN

•LAN Standards – IEEE 802.11, HIPERLAN

•Wireless ATM

•Mobile IP

QOS AND WIRELESS ACCESS

QoS is a guarantee by the network to satisfy a set of predetermined service performance constraints such as –

•End-to-end delays

•Available Bandwidth

•Probability of packet loss

•Perceived quality

•Cost

QoS guarantees can be attained only with appropriate resource reservation techniques

The most important element is QoS routing.

QoS routing – process of choosing the route to be used by the flow of packets of a logical connection in attaining the associated QoS guarantee.

QoS guarantees are to be kept while topological changes/updates occur.

Exchange of control packets should be given higher priority than data packets in a network designed for QoS.

Difficulty in maintaining QoS guarantees when handling packets of different priorities

Also in heavy traffic situations , guaranteeing QoS for lesser priority traffic may be extremely difficult.

Open area is the development of QoS routing policies , algorithms and protocols for handling user data with multiple priorities.

Similar challenges exist in developing QoS routing schemes supporting multiple service classes.

Security Issues for QoS Routing

The routing protocol should have a robust security policy such that operation integrity is maintained against unintended or deliberate attacks.

Attacks can be in the form of –

Flows making too many invalid requests

Requests for inappropriate allocation of network resources

Attempting to copy or preempt network control functions.

SUMMARY

QoS Management Admission control techniques

Priority to existing user's resource request

Dynamic advance reservation

Adaptive error control techniques

QOS-oriented MAC protocols

Channel borrowing from underloaded regions

Guaranteeing QoS is difficult in wireless networks.More so in mobile and multicast networks.

Mobiware Toolkit :QoS aware middleware for Mobile Multimedia

•Software Intensive ; built on CORBA and Java distributed object technology

•Based on open programmable paradigm to run on mobile devices,wireless access points and mobile-capable switch/routers

•Provides a set of open programmable interfaces and algorithms for adaptive mobile networking