Wifi guide pdf

The access point transmits a wireless signal over a short distance. It typically covers around feet. When a WiFi enabled device such as a Pocket PC encounters a hotspot, the device can then connect to that network wirelessly. Most hotspots are located in places that are readily accessible to the public such as airports, coffee shops, hotels, book stores, and campus environments.

The The largest public WiFi networks are provided by private internet service providers ISPs ; they charge a fee to the users who want to access the internet. Hotspots are increasingly developing around the world. Even select McDonald's restaurants now feature WiFi hotspot access. Any notebook computer with integrated wireless, a wireless adapter attached to the motherboard by the manufacturer, or a wireless adapter such as a PCMCIA card can access a wireless network.

Some Hotspots require WEP key to connect, which is considered as private and secure. As for open connections, anyone with a WiFi card can have access to that hotspot. It defines an over-the-air interface between a wireless client and a base station or between two wireless clients. Note that IEEE WiFi systems are the half duplex shared media configurations, where all stations transmit and receive on the same radio channel. The fundamental problem of a radio system is that a station cannot hear while it is sending, and hence it is impossible to detect a collision.

Because of this, the developers of the All transmissions are acknowledged, so if a station does not receive an acknowledgement, it assumes a collision occurred and retries after a random waiting interval.

The incidence of collisions will increase as the traffic increases or in situations where mobile stations cannot hear each other. The enhanced part is that EDCA will define eight levels of access priority to the shared wireless channel. Like the original DCF, the EDCA access is a contention-based protocol that employs a set of waiting intervals and back-off timers designed to avoid collisions.

However, with DCF all stations use the same values and hence have the same priority for transmitting on the channel. With EDCA, each of the different access priorities is assigned a different range of waiting intervals and back-off counters. Transmissions with higher access priority are assigned shorter intervals.

The standard also includes a packet-bursting mode that allows an access point or a mobile station to reserve the channel and send 3- to 5-packets in a sequence. In WSM, the access point periodically broadcasts a control message that forces all stations to treat the channel as busy and not attempt to transmit.

During that period, the access point polls each station that is defined for time sensitive service. To use the WSM option, devices need to send a traffic profile describing bandwidth, latency, and jitter requirements. If the access point does not have sufficient resources to meet the traffic profile, it will return a busy signal. Security has been one of the major deficiencies in WiFi, though better encryption systems are now becoming available.

Encryption is optional in WiFi, and three different techniques have been defined. This is a new standard from the WiFi Alliance that uses the 40 or bit WEP key, but it changes the key on each packet. The IEEE is finalized the The WiFi Alliance designate products that comply with the The picture has become somewhat confused as service providers started using WiFi to deliver services for which it was not originally designed.

This is an idea of selling an Internet access service using wireless LAN technology and a shared Internet connection in a public location designated as a hot spot.

From a technical standpoint, access to the service is limited based on the transmission range of the WLAN technology. You have to be in the hot spot i. From a business standpoint, users either subscribe to a particular carrier's service for a monthly fee or access the service on a demand basis at a fee per hour.

While the monthly fee basis is most cost effective, there are few intercarrier access arrangements, so you have to be in a hot spot operated by your carrier in order to access your service. To address the limited range, vendors like Mesh Networks and Tropos Networks have developed mesh network capabilities using WiFi's radio technology.

The idea of a radio mesh network is that messages can be relayed through a number of access points to a central network control station. These networks can typically support mobility as connections are handed off from access point to access point as the mobile station moves.

Some municipalities are using WiFi mesh networks to support public safety applications i. In an OFDM modulation system, the available radio band is divided into a number of sub-channels and some of the bits are sent on each. Some of the transmitted information is redundant, so the receiver does not have to receive all of the sub-carriers to reconstruct the information.

And if you are like me if you work with this technology for a living and want to pick up some pieces of technology that you were not aware of, this book is for you. You may also like. First, when he writes on a topic he covers the given topic in-depth. Easy and economical hands-on projects allow readers to boost power with a variety of common household items, which make this book a true standout. Amazon Advertising Find, attract, and engage customers. The unique FAQ-index feature allows readers to zero in on precisely what they need to know without plowing through unrelated text.

Working with Wi-Fi now reminds me of the Crazy Years of personal computing, back in the 70s and 80s when anything was possible and the suits were still trying to figure out how to put it all back in the bottle.

The discussion of attennas is really first rate. The Wi-Fi industry is really confusing with so many standards In this book, legendary tech teacher, wireless expert, and best-selling author Jeff Duntemann explains how to make Wi-Fi really work. The first part of the book is an introduction to Wi-Fi and its applications. Many technical figures clarify difficult concepts, with abundant Web driive-by to further information.

The fourth part deals with extending the range of your laptop and some of the secrets behind wardriving. The gain is higher than my Tin Can Bandwidth Expander see Chapter 15 but the beam width is also much narrower, and I think this is an antenna for fixed-point applications like bridging networks between houses. Cisco is buying Linksys!

Shopbop Designer Fashion Brands. From the Publisher We are really pleased to be publishing this expertly written hands-on guide by legendary tech writer, Jeff Duntemann. Paraglyph Press- Computers — pages. He is a great writer of tech stuff. A start-up called Vivato has announced an interesting technology that greatly expands the range of Wi-Fi hotspots.

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