wlan evolution

Evolution of WLAN Systems

Kourosh Parsa Senior Wireless Systems Engineer Ortronics/Legrand 7 June 2006

Copyright 2006 Ortronics/Legrand, All rights reserved

Ortronics/Legrand 125 Eugene O'Neill Drive New London, CT 06320 (860) 445-3800 www.ortronics.com


Introduction We are experiencing a global wireless gold rush. Introduction of third-generation wireless

technologies as well as the proliferation of 802.11-base WLAN systems represents two major

global trends in this gold rush.

One of the major elements of the next generation wireless (next generation wireless refers to

various technologies for 3G, WiFi, WiMax, etc) systems capabilities is global seamless service.

Cognitive Radios, Software Defined Radios, and multi-mode devices play a significant role in the

future of wireless systems.

Dense deployment with a centralized architecture and thin access points is an example of agile

infrastructure in the WLAN domain seamless global service provision concept. Connectivity to IP

networks, wire line-wireless integration, seamless service provision and high traffic density

(Mbps/er lang/square feet) are a few major components of such an evolution.

While 802.11e enables the introduction of real time services into WLAN systems and the future

802.11n introduces speeds higher than 100 Mbps, the combination of a centralized architecture

and dense deployment pushes the limit to a point where the user experiences a QoS (Quality of

Service) similar to that of a wired connection.

WLAN Evolution As the world rapidly adopts 802.11 a/b/g, standards organizations are moving towards more

advanced versions for the wireless LAN application. The evolution of the Wireless LAN as an

integral part of the future global seamless wireless service is not limited to the air interface. The

evolution spans the architecture and seamless integration of wire line and wireless services;

particularly with the introduction of real-times services such as Voice over WLAN (VoWLAN) and

Video over WLAN and the seamless integration of wire line and wireless services.

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Centralized Architecture and IP Connectivity Dense deployment in the enterprise environment has necessitated the introduction of thin Access

Points controlled by a central wireless controller which acts as the gateway to the WAN as well as

the wired LAN (Figures 1-3). This architecture is called a centralized architecture. Installations

where the number of Access Points exceeds 2 or 3 (Figure 1), the centralized approach is far more

cost effective when compared to a similar dense deployment. The Wireless Controller functions as

a gateway to the LAN.

Centralized versus de-centralized approaches in dense WLAN deployments

Install Wi-Jack APs1 2 Install / configureController(s)

WebWebMgmtMgmt

DATA CENTER

DISTRIBUTIONCORE

ACCESS OPS CENTER

EMPLOYEE

GUEST

VOICE

IOS IOS

ACSACS

NMSNMS

Figure 1: Centralized Versus Decentralized Architecture

Seamless Wireless Wire Line Integration Another component of WLAN evolution is the seamless integration of the WLAN system with the

existing Structured Cabling System (SCS) which enables seamless wireless wire line service

provision. This contributes to the concept of seamless service provision in the enterprise domain.

The user experiences the same level of QoS as it moves from the wired to the wireless network

and vice versa. A central enabling component for a seamless service provision is the ability to

provide wire-line like data rates in the wireless domain. This is accomplished by dense deployment

where the Mbps/user/square foot approaches the fixed wire networks capability (Figure 2).

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Thin AP: compatible to existing infrastructureseamless wired/wireless integration

No change to the existingwired infrastructure

Figure 2: Seamless Wireless and Wire Line Integration

Higher Speeds and Throughput First generation WLAN systems operated at 2 Mbps. 802.11b introduced a five-fold increase in the

maximum transmission speed featuring 11 Mbps. 802.11 a/g extended this further to 54 Mbps.

Innovations such as MIMO and beam forming in the air interface pave the way for speeds higher

than 100 Mbps and more reliable wireless links. The 802.11n standard is targeted for ratification in

late 2006 or early 2007. In all of these cases, the actual throughput seen by a single user is less

than 54 Mbps. Factors such as channel utilization, traffic intensity, number of users in the system,

as well as the signaling/coding overhead contribute to a lower throughput than the maximum

transmission speed.

Dense Deployment The dense deployment strategy enabled by centralized architecture and thin access points yields

high wireless reliability and the highest traffic density per user per square feet at low cost (Figure 3). The thin access points could serve extremely small areas when configured at the lowest transmission power. As such, the throughput offered to a single user could reach the maximum

possible throughput per Access Point.

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Thin APs and centralized architecture enable dense deployment: Approaching wire line QoS

Highest Mbps/ Erlang/ user/ square feet

Lobby Cafeteria

Conference Rooms

Offices/Cubicles

Figure 3: Example of Dense Deployment Planning

Support for Real Time Services Another element in the evolution of WLAN systems is the ability to provide Voice over WLAN as

well as other real time services over a truly packet switched air interface. The finalization of

802.11e in recent months is another significant step in that direction. 802.11 systems had been

originally designed to support non-real time traffic with no guarantee on the Quality of Service.

802.11e is standardization of methods to support real time traffic over the 802.11 systems.

Competition EV-DO (Evolution-Data Optimized) and HSDPA (High Speed Downlink Packet Access) promise

high data rate speeds of close to 500 Kbps- 1 Mbps per user in the downlink direction. The speed

and throughput uplink direction will be limited in both technologies due to inherent limitations. The

above speeds are quite useful in the mobile environment; however, they fall short of user

expectations in the enterprise environment since the users expect speeds similar to the wire line.

WiMAX is another potential contender for the indoor environment. However, this technology has

been designed and optimized for the outdoor environment and long ranges. WiMAX could turn into

a disruptive technology for the 3G and 3.5G market, but it is not comparable to Wi2.5 Support for

real time services.

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Evolution of WLAN Systems Another element in the evolution of WLAN systems is the ability to provide Voice over WLAN as

well as other real time services over a truly packet switched air interface. The finalization of

802.11e in recent months is another significant step in that direction.

Conclusion Price is a key driver in technology choice. As the world pushes towards third generation mobile

systems and WLAN systems proliferate rapidly, we see the elements of the next generation

wireless systems emerging in small scales. A good example of such is a centralized architecture

based dense deployment where the wireless users experience approaches that of the wire line

user. The future is about scrambling to introduce global seamless service. The push towards higher

speeds, innovative technologies such as MIMO, beam forming, SDR, Cognitive Radios, and OFDM

(Orthogonal Frequency Division Modulation) is all about provision of more spectrum efficient and

therefore more economical systems. In the unlicensed domain, spectrum is not costly and as such

the overall cost of WLAN deployment is not high. Furthermore, the future is here in this domain; the

users are already experiencing the wire line QoS through their wireless system and connectivity

with dense deployment.

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