Wireless

WIRELESS NETWORKING

Wireless Network Modes
The simplest wireless network consists of two or more PCs communicating directly with each other sans cabling or any other intermediary hardware. More complicated wireless networks use a WAP to centralize wireless communication and bridge wireless network segments to wired network segments. These two different methods are called ad-hoc mode and infrastructure mode.

wireless NIC wireless access point

Ad-hoc Mode
Ad-Hoc mode is sometimes called peer to peer mode, which each wireless node in direct contact with
each other node in a decentralized free for all. This is suited for wireless networks use in small groups


Ad Hoc Mode

Infrastructure Mode
Wireless networks running in infrastructure mode use one or more WAPs to connect the wireless network nodes to a wired network segment, as shown above. A single WAP servicing a given area is called a Basic Service Set (BSS). This service area can be extended by adding more WAPs. This is called, appropriately, an Extended basic Service Set (EBSS).
Wireless networks running in infrastructure mode require more planning and are more complicated to configure than ad-hoc mode networks, but they also give you finer control over how the networks operates. Infrastructure mode is better suited to business networks or networks that need to share dedicated resources like Internet connections and centralized databases. If you plan setting up a wireless network for a large number of PCs, or need to have centralized control over the wireless network, then infrastructure mode is what you need.

Infrastructure Mode

Wireless Networking Security
One of the major complaints against wireless networking is that it offers weak security. In many cases, the only thing you need to do to access a wireless network is walk into a WAP’s coverage area and turn on your wireless device! Further, data packets are floating through the air instead of safely wrapped up inside network cabling. What’s to stop an unscrupulous PC tech with the right equipment from grabbing those packets out of the air and reading that data himself?

Wireless networks use three methods to secure access to the network itself and secure the data that’s’ being transferred. The SSID (network name) parameter ensures that only wireless network devices configured with the same SSID are permitted access to the network. You can tighten security even further by employing MAC filtering, a way of creating a list of machines that are permitted to access the network. Enabling wireless encryption through either Wireless Equivalency Privacy (WEP) or Wi-Fi Protected Access (WPA) ensures that the data packets themselves are secure while in transit

Wireless Networking Security (War Chalking, War Driving and Hot Spots)
Wireless Antennas (Omni Directional vs. Yagi Directional Antennas)
Wireless Channels (mostly use 1, 6 and 11) Beacon advertise wireless presence

SSID
The service set identification (SSID), sometimes called a network name, is a 32bit identification string that's inserted into the header of each data packet processed by a wireless access point. This provides the basic unit of wireless security.

MAC Filtering
MAC filtering, a method that enables you to limit access to your wireless network based on the physical, hard wired addresses of the wireless network adapters you support

WEP
Wireless Equivalency Privacy (WEP) uses a 64bit-128bit encryption algorithm to scramble data packets as sent in a wireless transmission

WPA
WPA addresses the weaknesses of WEP, and acts as a sort of security protocol upgrade to WEP-enabled devices. WPA offers security enhancement such as an encryption key integrity-checking feature and user authentication through the industry-standard Extensible Authentication Protocol (EAP). The use of EAP is a huge security improvement over WEP’s MAC address authentication scheme. After all, MAC addresses are fairly easy to “sniff” out, since they’re transmitted in unencrypted, clear-text format. User names and passwords are encrypted, and therefore much more secure.
Even with these enhancements, WPA is only intended as an interim security solution until the IEEE 802.11i security standard is finalized and implemented.

 

Wireless Networking Standards
To gain better understanding of wireless network technology, let’s take a brief look at the standards they use.

IEEE 802.11-Based Wireless Networking
The IEEE 802.11 wireless Ethernet standard defines methods by which devices may communicate using spread-spectrum radio waves. Spread-spectrum broadcast data in small, discrete chunks over different frequencies available within a certain frequency range. All of the 802.11-based wireless technologies broadcast and receive at 2.4 GHz (with the exception of 802.11a, which uses 5 GHz). The original 802.11 standard has been extended to 802.11a, 802.11b, and 802.11g variations used in Wi-Fi wireless networks, and also hybridized (combined with another wireless communication technology) to form the Shared Wireless Access Protocol (SWAP) used in Home RF networks.

Spread-Spectrum Broadcasting
The 802.11 standard defines two different spread-spectrum broadcasting methods, direct-sequence spread-spectrum (DSSS) and frequency-hopping spread-spectrum (FHSS). DSSS sends data out on different frequencies at the same time, while FHSS sends data on one frequency at a time, constantly shifting (or hopping) frequencies. DSSS uses considerably more bandwidth than FHSS, around 22 MHz as opposed to 1 MHz. DSSS is capable of greater data throughput, but DSSS is also more prone to interference than FHSS. Home RF wireless networks are the only type that uses FHSS; all of the other 802.11-based wireless networking standards use DSSS The newest spread spectrum broadcast today is OFDM Orthogonal Frequency Division Multiplexing.

The 802.11 Standard
Devices that use the original 802.11 (with no letter) standard are a rarity these days. You’re most likely to find them in service on some brave early adopter’s network.
The original 802.11 standard was hampered by both slow speeds (2 Mbps maximum) and limited range (about 150 feet). However, 802.11 employed some of the same features that are in use in the current wireless standards. 802.11 uses the same 2.4 GHz broadcast range, and security is provided by the use of industry-standard WEP and WAP encryption.

802.11a
Despite the “a” designation for this extension to the 802.11 standard, 802.11a was actually developed after 802.11b. 802.11a differs from the other 802.11-based standards in significant ways. Foremost is that it operates in a different frequency range, 5 GHz. This means that devices that use this standard are less prone to interference from other devices that use the same frequency range. 802.11a also offers considerably greater throughput than 802.11 and 802.11b at speeds up to 54 Mbps, though its actual throughput is no more than 25 Mbps in normal traffic conditions. While it’s theoretical range tops out at about 150 feet, in a typical office environment, its maximum range will be slower. Despite the superior speed of 802.11a, it it is not’t widely adopted in the PC world.

802.11b
802.11b is practically ubiquitous in wireless networking. The 802.11b standards supports data throughput up to 11 Mbps (with actual throughput averaging 4 to 6 Mbps)-on par with older wired 10BaseT networks- and a maximum range of 300 feet under ideal conditions. In a typical office environment, its maximum range will be lower.
802.11b networks can be secured through the use of WEP and WPA encryption. The main downsize to using 802.11b is, in fact, that it’s most widely used standard. The 2.4 GHz frequency is already a crowded place, so you’re likely to run into interference from other wireless devices.

802.11g
The latest-and-greatest version of 802.11g offers data transfer speeds equivalent to 802.11a, up to 54 Mbps, with the wider 300-foot range of 802.11b. More importantly, 802.11g is backwards-compatible with 802.11b, meaning that the same 802.11g WAP can service both 802.11b and 802.11g wireless nodes.

802.11 Chart

802.11n (MIMO) Multiple Input/Multiple Output (Found on some wireless networks today)

Infrared Wireless Networking
Wireless networking using infrared technology is largely overlooked these days, probably due to explosion of interest in the newer and faster wireless standards. This is a shame, because infrared provides an easy way to transfer data, often without the need to purchase or install any additional hardware or software on your PCs.

Infrared Data Association Standard
Communication through infrared devices is enabled via the Infrared Data Association (IrDA) protocol. The IrDA protocol stack is widely supported industry standard, and has been included in all versions of Windows since Windows 95.
Speed-and range wise, infrared isn’t very impressive. Infrared devices are capable of transferring data up to 4 Mbps. Not too shabby, but hardly stellar. The maximum distance between infrared devices is 1 meter.

Infrared links are direct line-of-sight, and are susceptible to interference.
Infrared devices operate at half-duplex, meaning that while one is talking, the other is listening-they can’t talk and listen at the same time. IrDA has a mode that emulates full-duplex communication, but it’s really half-duplex.

Security-wise, the IrDA protocol offers exactly nothing in the way of encryption or authentication. Infrared’s main security feature is the fact that you have to be literally within arm’s reach to establish a link.
Clearly, infrared is not the best solution for a dedicated network connection, but for a quick file transfer or print job without getting your hands dirty, it’ll do in a pinch.

Bluetooth
Bluetooth wireless technology (named for 9th century Danish king Harald Bluetooth) is designed to create small wireless Personal Area Networks (PANs) that link PCs to peripheral devices such as PDAs and printers, scanners, web cams, input devices like keyboards, joystick and mice, and even consumer electronics like cell phones, head sets, home stereos, televisions, home security systems, and so on.


Bluetooth Operation Modes

Master/Slave Scheme in which one master device can control up to seven active slave devices

Bluetooth Communication

Bluetooth devices go to four stages to find each other and start talking.

Discovery Service – Broadcast it’s MAC address as well as what type of device it is
Name Discovery – Device identifies itself by a friendly name such as Motorola headsets
Association – Bonding, Pairing or Joining the device officially joins your Bluetooth network
Service Discovery – Device tells what kind of service or profile it provides

Bluetooth services

Bluetooth is not designed to be a full-function networking solution, nor is it meant to compete with either Wi-Fi or HomeRF. If anything, Bluetooth is poised to replace infrared as a means to connect PCs to peripherals.

The IEEE organization has made Bluetooth the basis for its forthcoming 802.15 standard for wireless PANs. Bluetooth uses the FHSS spread-spectrum broadcasting method, switching between any of the 79 frequencies available in the 2.45 GHz range. Bluetooth hops frequencies some 1,600 times per second, making it highly resistant to interference. Some high-powered Bluetooth devices have throughput speed of a whopping 2 Mbps and a maximum range of up to 300 feet, but these are uncommon.

special thanks to linksys, belkin, dlink, microsoft, jabra, motorola