GIGABIT WLAN’S

RAGHAVENDER JOGARAJU

WHAT IS GWLAN ?

Gigabit WLAN is a fourth generation system based on high-data-rate Orthogonal Frequency Division Multiplexing(OFDM), Multi Input Multi Output(MIMO) and Efficient MAC protocol techniques

WHY GWLAN ?

Modern Users of the Wireless networks expect the same service and quality from wireless networks as offered by wired networks.

few of the things that a typical user of a wireless network might expect are E-mail, Internet, Voice, Video and Multimedia applications.

2G and 3G technologies are not able to cope with these networks.

802.11n does not completely close the gap, hence we need a Gigabit WLAN.

WiGLAN Architecture• Network Controller

•Allocates channels

•Measures SNR

•Space-Time Diversity

WiGLAN ADAPTER

Appliance

WiGLAN ADAPTER

High Data RateAppliance

WiGLAN ADAPTER

Appliance

WiGLAN ADAPTER

Appliance

Wi

GLAN

ADAPTER

NetworkController

Processor

NGI

Receiver Chain

Receiver Chain

Receiver Chain

Receiver Chain

Transmitter Chain

Transmitter Chain

Transmitter Chain

NetworkServer

DSP

Multi-CarrierAdaptive Rate

QAM

DSPSpace-TimeProcessing

Digital Modulation Digital Space-Time Diversity Processing

Improves channel capacity Replicated Transmit/Receive Chain

Network Controller with Space-Time Diversity

Transmitter Chain

Network Adapter Block Diagram

Network adapter

ApplianceBaseband

Mixed-SignalProcessor

DigitalSignal

Processor

RFTrans.

PREVIOUS WORK

Wireless networking is an important media for computer connectivity, there have been numerous innovations since its introduction through the IEEE 802.11 standard in 1999.

competition and innovation in wireless networking has produced greater capabilities with 802.11a,b and g.

The biggest change in wireless over the past 10yrs has been the availability of the unlicensed wireless spectrum.

Before this, the evolution of wireless technologies was tied to a specific spectrum and specific protocols.

Because of concerns about interference, the transmission of electromagnetic energy was highly regulated.

It has now become possible to connect a radio to a computer that could control signals in new and complicated ways, at rates much greater than ever before.

In the past 10 years the data rate available over unlicensed wireless systems has changed by four orders of magnitude.

WHERE CAN IT BE USED ?

The main application area is the transmission of multimedia content in so-called hot-spots in home scenarios, and in large offices where an enormous data rate back-off is necessary

In order to be able to include a high data rate air-interface into a future heterogeneous mobile communications system, also high mobility applications are covered.

TECHNOLOGIES

Two Technologies that help realize GWLAN are,

1. Multiple Input Multiple Output (MIMO)

2. System-On-a-Package(SOP)

MIMO

MIMO wireless is an emerging cost effective technology that offers substantial leverages in making 1Gbps wireless links a reality.

we can, in principle, meet the 1Gbps data rate requirement if the product of bandwidth (measured in Hz) and spectral efficiency (measured in bps/Hz) equals 10^9.

MIMO wireless constitutes a technological breakthrough that will allow Gbps speeds in NLOS wireless networks.

The performance improvements resulting from the use of MIMO systems are due to,

1. Array gain

2. Diversity gain

3. Spatial Multiplexing Gain

4. Interference Reduction

In general it is not possible to exploit all the leverages of MIMO technology simultaneously due to conflicting demands on the spatial degrees of freedom (number of antennas).

The degree to which these conflicts are resolved depends upon the signaling scheme.

System-On-a-Package

SOP approach for the next-generation wireless solution is a more feasible option than SOC .

Recent development of materials and processes in packaging area makes it possible to bring the concept of SOP into the RF world to meet the stringent needs in wireless communication area.

Wireless devices implementing complex functionality require a large amount of circuitry and consequently, require a large conventional package or MCM real estate.

SOP goes one step beyond Multi Chip Module (MCM) by enhancing overall performances and adding more functionalities.

SOP

SOP is the art of bringing together at the system level ICs and embedded components following a co design philosophy.

The SOP evolution for gigabit wireless applications involves systems, technology and materials consideration.

Research is targeting 3-D high density module technologies for SOP based solutions for wireless communication applications.

ISSUES

1. Integrate unlicensed wireless securely and transparently into existing networking systems

2. Provide the fast handoffs that will be required for continuous mobile connectivity, as cell sizes will continue to decrease

3. Power Consumption.

INTEGRATION WITH EXISTING SYSTEMS

The wireless meshed network must intercommunicate with all the existing legacy systems out there. The interconnections need to be efficient and economically practical.

The meshed network can't require the legacy systems to be extensively modified

So What is the issue?

Several unexpected problems have come up. TCP/IP was originally designed to run over

lossy, highly variable delay networks and still deliver reasonable performance.

The biggest problem for most users of TCP/IP, however, turned out to be that it was not efficient under the load of multiple users (which is what GWLAN would be serving).

What’s the Solution ?

There are two avenues of attack for these types of problems, and both should be followed through in parallel,

1. Modify the existing protocols to be more flexible.

2. Make the wireless mesh network look more like a wired network with predictable delays and minimal losses.

HANDOFF

One of the greatest system design concepts in the evolution of wireless technology is the notion of cellular deployment and the huge reuse of spectrum it provides.

Reusing spectrum every few miles or every few hundred feet provides an essentially unlimited capacity for wireless communications.

Handoff is the transition for any given user of signal transmission from one base station to a geographically adjacent base station as the user moves around

The smaller the cell size, the larger the communication capacity per unit area. This imposes huge pressure for very high-speed, short-distance radios.

Thus, as cell size naturally shrinks, the available data rate increases.

The Problem

Since a GWLAN gives very high data rates we need to use more number of cells.

The main limiting factor is the ability to provide fast handoffs over cells sized a few hundred feet in diameter.

Typical vehicle speeds of a hundred feet per second mean switching cells every few seconds.

So We need a mechanism that takes care of these fast handoffs.

For that we will need faster processors .Standards bodies today are defining the

interfaces required to make the faster handoff’s possible .

POWER CONSUMPTION

The need to reduce power consumption is one of the most challenging and interesting topics in wireless engineering.

We require complicated physical solutions before any real system can be implemented

Today's cellphone solutions have made huge strides in conserving battery power, which has been achieved with fixed Throughput.

The next challenge for GWLAN is to keep this trend intact while increasing the throughput by several orders of magnitude

One method of decreasing power consumption is to bring the radios closer together or, in other words, to create a ubiquitous mesh network .

To bring radios closer together, they must become exponentially cheaper, as the number required increases (at best) by the square of the ratio of decrease in their average separation .

There is also a great push to increase the power density of batteries or other power-storage devices for reasons of portability.

GWLAN’S should always strive to minimize power consumption, because the loss of one node would mean loss of a whole lot of Data.

OTHER ISSUES

ADCDIRTY RFMIMO TechniquesMAC

ADC

Given today’s analog-to-digital

conversion technology and its only moderate evolution speed over the last decades, a digitization bandwidth of 100 MHz appears to be a reasonable assumption for GWLAN

But For this a spectral efficiency of at least 10 bit/s/Hz will be required.

Dirty RF

In view of the high system bandwidth requirements for Gigabit Wireless, carrier frequencies can be expected to be significantly higher in the future.

In combination with decreasing supply voltages and high SNR requirements for MIMO techniques, non-linear effects in the RF front-end (e.g., phase-noise, clock jitter, non-linear amplifiers) will have a strong impact on system performance making RF an issue.

Appropriate analog predistortion as well as digital compensation techniques have to be developed in order to compensate the error effects.

MIMO Techniques

The use of multiple antenna techniques is a prerequisite to achieving a spectral efficiency of at least 10 bits/s/Hz within reasonable SNR limits.

The main design challenges that have to be addressed to make the inclusion of MIMO techniques possible are channel estimation and base band signal processing complexity.

MAC

In today’s WLAN systems, the reception of a packet is usually confirmed by an acknowledgement message of no more than 14 bytes.

The transmission of such very short messages,over a conventional MAC is highly inefficient, due to minimum burst sizes and additional overhead (e.g., for authentication,request to send, clear to send, channel estimation,etc.).

It is obvious that, if we follow the conventional approach, achieving a payload rate of 1 Gbit/s could require data rates of as much as 2 Gbit/s “over the air” which is neither feasible nor reasonable.

SO ARE WE THERE ?

If WiMAX -- an extension of Wi-Fi's reach -- is still more than a year from full use, Gi-Fi is a glimmer in the eyes of wireless enthusiasts.

Regardless of the time it might take Gi-Fi to gain wide use, its promoters argue Gi-Fi has a tangible purpose and could find a willing market.

OTHER ADVANTAGES OF GWLAN’S

Lower Deployment and Production Costs.

Indoor/Outdoor mobility.Availability .Security comparable to Wired Networks.

CONCLUSION

If the success of Wi-Fi and the imminent wide usage of WiMAX is any indication, Gi-Fi potentially can bring wireless broadband to the enterprise in an entirely new way.

References

Paving the Way for Gigabit Networking

By Jean-Pierre Ebert, Eckhard Grass, Ralf Irmer, Rolf Kraemer, and Gerhard Fettweis,Karl Strom, Günther Tränkle, Walter Wirnitzer, Reimund Witmann, Hans-Jürgen Reumerman, Egon Schulz, Martin Weckerle, Peter Egner, and Ulrich Barth

An Overview of MIMO Communications - A Key to Gigabit Wireless

A. J. Paulraj, D. Gore, R. U. Nabar, and H. B¨olcskei The Future of WLAN

ACM Queue vol. 1, no. 3 - May 2003 by Michael W. Ritter, Mobility network systems

Gigabit Wireless: System-on-a-Package Technology

RAO R. TUMMALA, FELLOW, IEEE AND JOY LASKAR, SENIOR MEMBER, IEEE http://www.wigwam-project.de/

Challenges and Opportunities in Broadband and Wireless Communication Designs

Jan M. Rabaey1, Miodrag Potkonjak2, Farinaz Koushanfar3, Suet-Fei Li1,TimTuan11 EECS Department, University of California, Berkeley, CA 94720 {2 CS, 3 EE} Departments, University of California, Los Angeles, CA 90095

http://www.theregister.co.uk/2004/11/19/gigabit_wi-fi_promised/ System Concept for 1 Gbit/sand Beyond

Tutorial IEEE 802 Plenary, Vancouver, November 2005

Gerhard Fettweis Vodafone Chair Mobile Communications Systems

TechnischeUniversitätDresden, Germany WIGWAM-A Wireless Gigabit System with Advanced Multimedia Support

Gerhard Fettweis, Tim Hentschel, Ernesto Zimmermann, Technische Universität Dresden, Germany