Linksys WRT54G-TM manual What is ISM band?, What is Spread Spectrum?

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Wireless-G Broadband Router

maintain contact with the wireless network even when not actually transmitting data. Achieving these functions simultaneously requires a dynamic RF networking technology that links access points and nodes. In such a system, the user’s end node undertakes a search for the best possible access to the system. First, it evaluates such factors as signal strength and quality, as well as the message load currently being carried by each access point and the distance of each access point to the wired backbone. Based on that information, the node next selects the right access point and registers its address. Communications between end node and host computer can then be transmitted up and down the backbone.

As the user moves on, the end node’s RF transmitter regularly checks the system to determine whether it is in touch with the original access point or whether it should seek a new one. When a node no longer receives acknowledgment from its original access point, it undertakes a new search. Upon finding a new access point, it then re-registers, and the communication process continues.

What is ISM band?

The FCC and their counterparts outside of the U.S. have set aside bandwidth for unlicensed use in the ISM (Industrial, Scientific and Medical) band. Spectrum in the vicinity of 2.4 GHz, in particular, is being made available worldwide. This presents a truly revolutionary opportunity to place convenient high-speed wireless capabilities in the hands of users around the globe.

What is Spread Spectrum?

Spread Spectrum technology is a wideband radio frequency technique developed by the military for use in reliable, secure, mission-critical communications systems. It is designed to trade off bandwidth efficiency for reliability, integrity, and security. In other words, more bandwidth is consumed than in the case of narrowband transmission, but the trade-off produces a signal that is, in effect, louder and thus easier to detect, provided that the receiver knows the parameters of the spread-spectrum signal being broadcast. If a receiver is not tuned to the right frequency, a spread-spectrum signal looks like background noise. There are two main alternatives, Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).

What is DSSS? What is FHSS? And what are their differences?

Frequency-Hopping Spread-Spectrum (FHSS) uses a narrowband carrier that changes frequency in a pattern that is known to both transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical channel. To an unintended receiver, FHSS appears to be short-duration impulse noise. Direct-Sequence Spread- Spectrum (DSSS) generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The longer the chip, the greater the probability that the original data can be recovered. Even if one or more bits in the chip are damaged during transmission, statistical techniques embedded in the radio can recover the original data without the need for retransmission. To an unintended receiver, DSSS appears as low power wideband noise and is rejected (ignored) by most narrowband receivers.

Appendix A: Troubleshooting

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Frequently Asked Questions

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Contents 802 GHz .11g Wireless- G Word definition Copyright and TrademarksTable of Contents Appendix C Upgrading Firmware Appendix D Windows Help Appendix a TroubleshootingAppendix B Wireless Security Router’s Back Panel List of Figures23 Wireless Tab Wireless MAC Filter Wireless-G Broadband Router Welcome IntroductionWhat’s in this User Guide? Wireless-G Broadband Router Network Topology Planning Your Wireless NetworkAd-Hoc versus Infrastructure Mode Ssid service set identifier your wireless network’s namePlanning Your Wireless Network Network Layout Back Panel Getting to Know the Wireless-G Broadband RouterDMZ Front PanelOverview Connecting the Wireless-G Broadband RouterConnecting Your Network Devices Connecting Another Router Hardware Installation for Connection to Another RouterConnecting Your Network Devices Password Screen Configuring the Wireless-G Broadband RouterInternet Setup Setup Tab Basic SetupPPPoE Connection Type Optional Settings Router IP 12 Setup Tab Ddns Setup Tab Ddns13 Setup Tab MAC Address Clone Setup Tab MAC Address Clone14 Setup Tab Advanced Routing Gateway Setup Tab Advanced RoutingWireless Tab Basic Wireless Settings 17 Wireless Tab Wireless Security WPA Personal Wireless Tab Wireless Security20 Wireless Tab Wireless Security WPA2 Enterprise 21 Wireless Tab Wireless Security Radius 23 Wireless Tab Wireless MAC Filter Wireless Tab Wireless MAC FilterSetting Wireless Tab Advanced Wireless SettingsWireless-G Broadband Router Security Tab VPN Passthrough Security Tab FirewallTo create an Internet Access policy Access Restrictions Tab Internet AccessTo create an Inbound Traffic policy 33 Applications and Gaming Tab Port Range Forward Applications and Gaming Tab Port Range ForwardPort Triggering Applications & Gaming Tab Port TriggeringApplications and Gaming Tab QoS Applications and Gaming Tab DMZApplication Port Priority Administration Tab Log Administration Tab Management39 Administration Tab Diagnostics Administration Tab DiagnosticsAdministration Tab Config Management Administration Tab Factory DefaultsAdministration Tab Firmware Upgrade 45 Status Tab Router Status Tab Router46 Status Tab Local Network Status Tab Local Network48 Status Tab Wireless Status Tab WirelessNeed to set a static IP address on a PC Appendix a TroubleshootingCommon Problems and Solutions Wireless-G Broadband Router Wireless-G Broadband Router Application Start and End Protocol IP Address Enabled Can’t get the Internet game, server, or application to work Firmware upgrade failed, and/or the Power LED is flashing To start over, I need to set the Router to factory defaultNeed to upgrade the firmware My DSL service’s PPPoE is always disconnecting Is IPSec Pass-Through supported by the Router? Frequently Asked QuestionsPower LED keeps flashing Where is the Router installed on the network?Does the Router support ICQ send file? What is Network Address Translation and what is it used for?How can I block corrupted FTP downloads? What is the Ieee 802.11b standard? What is DMZ Hosting?What are the advanced features of the Router? What is the Ieee 802.11g standard?What is infrastructure mode? What Ieee 802.11g features are supported?What Ieee 802.11b features are supported? What is ad-hoc mode?What is DSSS? What is FHSS? And what are their differences? What is ISM band?What is Spread Spectrum? How do I resolve issues with signal loss? What is WEP?What is a MAC Address? How do I reset the Router?Security Threats Facing Wireless Networks Appendix B Wireless SecuritySecurity Precautions Appendix B Wireless Security Wireless-G Broadband Router Appendix C Upgrading Firmware TCP/IP Appendix D Windows HelpWindows 2000 or XP Instructions Windows 98SE or Me InstructionsFigure E-4 MAC Address Filter List For the Router’s Web-based UtilityAppendix F Glossary Wireless-G Broadband Router Wireless-G Broadband Router Wireless-G Broadband Router Wireless-G Broadband Router Wireless-G Broadband Router Wireless-G Broadband Router WRT54G Appendix G SpecificationsOperating Temp Limited Warranty Appendix H Warranty InformationFCC Statement Appendix I Regulatory InformationWireless-G Broadband Router Wireless-G Broadband Router Wireless-G Broadband Router Wireless-G Broadband Router Dual-Band Wireless Access Point Appendix J Contact Information
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