DEP g Deployment Strategies Migration to establish and exploit high-speed Wireless LAN’s Jan Haagh Senior Product Manager Proxim Wireless LAN Division

Presentation content g Deployment Strategies What is g? Why is co-existence with b an issue? a and b/g differences Need to find the proper balance b only mode g only mode Mix mode of b and g clients Migration to establish and exploit high-speed Wireless LAN’s Today’s enterprise Wireless LAN requirements New WLAN features on the horizon Intelligent Access Points Concept of centralized architecture Positioning of centralized concept and intelligent Access Points Concluding

802.11g Deployment Strategies

What is g? Ratified IEEE standard (as of June 11, 2003) Similar to a Uses same OFDM modulation Supports same data rates: 6, 9, 12, 18, 24, 36, 48 and 54 Mbps Different from a Operates in the 2.4 GHz band, not the 5 GHz band Distance advantage due to propagation difference Far fewer channels available Significant detrimental impact on throughput in dense deployments Requires support for b devices (1, 2, 5.5, and 11 Mbps) Requires support for: Long preamble 20 μs slot times Both of these have significant detrimental impact on throughput

Why is co-existence with b an issue? g operates in exactly the same spectrum/channels as b Inevitably there will be networks with simultaneous.11b/.11g users, or.11b networks in close proximity to.11g networks g b g b

Single Cell Throughput performance 11g is superior due to: Slot time Propagation This is the ideal case and is not real life Multiple channel co-channel interference Interference between different system in same band

Co-channel neighbor cells

Multi Cell Throughput performance

PLCP Header Adding complexity: preamble length Preamble a: OFDM (20 μsec) g: Either long (192 μsec) or short (96 μsec) or OFDM, depending on the mix of traffic on the network b: Either long or short

Adding complexity: slot time Slot time a: 9 μsec g: Either 9 μsec or 20 μsec depending on the mix of traffic on the network b: 20 μsec

Slot time performance impact

802.11b effect on 11g performance

802.11g protection mechanism

Protection mechanism impact

802.11b and g devices deferring for each other g and 11b sharing the medium

Need to find the proper balance Throughput Co-existence OFDM Preamble No RTS/CTS Short Slot Time Long or Short Preambl e RTS/CTS Long Slot Time

802.11b only mode Access Point will always operates with a 20 μsec slot time b clients can only recognize the 20 μsec slot time In this mode the Access Points will be able to respond to clients using either the long or the short preamble The long preamble is only used when a client joins the network that can only use the long preamble bb

802.11g only mode only g modulation (OFDM); restricting associations to g clients Using the short slot time of 9 μsec Preamble that will be relevant is the OFDM preamble No need for a protection mechanism because the traditional medium access mechanisms will manage the sharing of the wireless media The configuration providing the maximum throughput for g devices; no throughput degradations caused by: long slot times b devices protection mechanisms g g

Mix mode of b and g clients Most complex modes: Slot time Preamble RTS/CTS At any b devices, automatically fall back to the use of 20 μs slot times For maximum throughput at slot times of 9 μs when no b devices are detected CTS-only protection mechanism when b clients are present At a mixture of b and g clients, the network will use both long or short preamble gb b

Proxim Proposed Modes b onlyMixed Mode802.11g only Short preamble OFDM preamble No RTS/CTSRTS/CTS with mixed traffic No RTS/CTS 20 μsec slot20 μsec slot with mixed or overlapping traffic 9 μsec slot

Recommended Usage.11b only mode Only.11b clients in the network.11g only mode Only.11g clients in the network Mixed mode Mixed.11b and.11g traffic Using a dual slot Access Point, supporting 11b on one channel and the 11g on another channel

Migration to establish and exploit high-speed Wireless LAN’s How to migrate current architectures to support new features and how to migrate current architectures into new concepts

Today’s enterprise Wireless LAN requirements Administrators and users want integrated voice and data Mobile access to mobile voice and data services Leverage single WLAN infrastructure Wireless users need seamless mobility Transparent roaming within and across subnets Zero-configuration and session persistence Administrators need a secure network Interoperable, integrated, and scalable security Minimal client configuration Administrators need a homogeneous management system Multiple radio technologies, client devices, and user profiles Enterprises need a scalable system Maintain efficiency and manageability as network grows No performance impact with scale

New WLAN features on the horizon IEEE g radio Wi-Fi Protected Access (WPA) security Also known as SSN; Early TKIP implementation Standard is mature IEEE i security AES-CCM encryption (mandatory) 802.1x authentication IEEE e QoS Wireless Multimedia Enhancement (WME) as first out Standard stable Q4-02; (starting to) mature Q2-03

Two directions to support the requirements & new features Maintaining the intelligence in the Access Point Creation of a centralized architecture with the intelligence based in the switch Combination of both possibilities: Appropriate solution for the customer Migration from existing network into a new centralized architecture

Intelligent Access Points Fits perfectly in the decentralized intelligence architecture for enterprises or small and medium venues Single and dual slot Access Points Ease of use for subscriber is key Support for a, b and g Extensive radius AAA support, required for public access Network Management software to manage large networks Secure solutions using VPN, access control, 802.1X, re-keying, WPA and migration to i

An intelligent wireless LAN infrastructure solution which simplifies and reduces the cost of deploying Wireless LANs in the enterprise A self-aware system which delivers enhanced functionality required to support broader and deeper adoption of Wireless LANs, enabling Wireless LANs to grow to thousands of nodes Enhanced security, mobility, manageability, QOS, voice integration Consists of a wireless-enabled switch & (lite) Access Points Advantages over today’s and future intelligent Access Points Supports today’s Access Points Leverages [of] existing technology Open system, not proprietary Concept of centralized architecture

Example of a centralized architecture Wireless Enabled Switch Distribution layer Customer’s Directory Server Network Management System Mobile users Access Layer Wiring Closet Mix of Access Points Access Layer Wiring Closet Campus LAN Wireless Enabled Switch

Positioning of centralized concept and intelligent Access Points General positioning Each solution is best suited to a particular environment and application Primary differentiation is based on scale and economics, not necessarily on features Some customers may have a predisposition to a particular architecture When in doubt, use the traditional Access Points in conjunction with a centralized intelligent switch When an intelligent Access Points  Less than 6 APs  Small area, limited-cell environments  Typical department wise roll-out When a centralized solution  6 APs or greater  Large area, multi-cell environments  Typical corporate IT roll-out

Concluding

802.11g Deployment Strategies.11b only mode Only.11b clients in the network.11g only mode Only.11g clients in the network Mixed mode Mixed.11b and.11g traffic Using a duals slot Access Point, supporting 11b on one channel and the 11g on another channel b only Mixed Mode g only Short preamble OFDM preamble No RTS/CTSRTS/CTS with mixed traffic No RTS/CTS 20 μsec slot20 μsec slot with mixed or overlapping traffic 9 μsec slot

1Maintaining the intelligence in the Access Points 2Centralize the intelligence in the wireless-enabled switch When in doubt, use the traditional Access Points in conjunction with a centralized intelligent switch When an intelligent Access Points  Less than 6 APs  Small area, limited-cell environments  Typical department wise roll-out When a centralized solution  6 APs or greater  Large area, multi-cell environments  Typical corporate IT roll-out Migration to establish and exploit high-speed Wireless LAN’s

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