a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)
controls media access and avoids (rather than detect) collisions
Mesh topology
- This topology is rarely used because of the significant cost and work involved in having network components directly connected to every other component.
- If a break occurs in a segment of cable, traffic can still be rerouted using the other cables.
- It is common for partial topologies to be deployed. This balances cost and the need for redundancy.
Ad hoc Topology
- Uses a physical mesh topology with a logical bus topology
- Is cheap and easy to set up.
- Cannot handle a large number of hosts.
- Requires special modifications to reach wired networks.
Infrastructure Topology
- The network uses a physical star topology with a logical bus topology
- You can easily add hosts without increasing administrative efforts.
- The access point (AP) can be connected to a wired network easily, allowing clients to access both wired and wireless hosts.
- The placement and configuration of APs require planning to implement effectively
Transmission mediums
- speeds are affected by distance, obstructions (such as walls), and interference
- you can either achieve the maximum distance or the maximum speed, but not both
Wireless Network
- all devices on the network operate at the legacy speed
Bluetooth
an open wireless technology standard for transmitting fixed and mobile electronic device data over short distances
IR
the use of wireless technology in devices or systems that convey data through infrared radiation
RFID (radio frequency identification)
is a form of wireless communication that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency portion of the electromagnetic spectrum to uniquely identify an object, animal or person
802.11a
Released after 802.11b, 802.11a has greater theoretical throughput and a greater coverage area.
802.11b
Implemented as a standard in 1999. This standard provides 22 separate channels in the 2.4 GHz band. It can operate at speeds up to 11Mbps at a range of up to 50 meters.
802.11g
Also used the 2.4 GHz band, is a reasonable upgrade path from 802.11b The main advantages are the throughput (54 Mbps) that it supported 802.11b transmissions.
802.11n
provided 600 Mbps throughput over greater distances. This higher speed allowed voice and video communications to be supported.
-is backward compatible with 802.11g, 802.11b, and 802.11a.
802.11ac
- provides well over 6 Gbps on the 5 GHz band,
- access points can handle multiple data streams on the same frequency
- often dual-band, meaning they can operate on the 2.4 GHz or 5GHz bands eliminating any compatibility issues with legacy equipment.
2.4GHz
- unallocated, unlicensed band free for any purpose
- . Wi-Fi routers, some cordless telephones, and Bluetooth all operate on this frequency, creating the opportunity for interference between devices
- cell phones and AM radio signals do not operate on this range.
5.0GHz
-unregulated band which is seeing a lot of use in the wireless networking environment
-
Speed and distance requirements - 802.11a
Frequency- 5 GHz
Rated Throughput- 54 Mbps
Range- 100 m
Speed and distance requirements - 802.11b
Frequency- 2.4 GHz
Rated Throughput- 11 Mbps
Range-50 m
Speed and distance requirements -802.11g
Frequency- 2.4 GHz
Rated Throughput- 54 Mbps
Range- 100 m
Speed and distance requirements- 802.11n
Frequency- 2.4 or 5 GHz
Rated Throughput- 600 Mbps
Range: Indoor – 70 m Outdoor- 250m
Speed and distance requirements- 802.11ac
Frequency- 5 GHz
Rated Throughput- 1.3 Gbps - 6.93 Gbps
Range: Indoor – 70 m Outdoor – 250m
Bluetooth
Frequency- 2.4 GHz
Rated Throughput- 3 Mbps
Range- 10 m @ 2.5 mW
Channel bandwidth
Channels have a bandwidth of 22MHz. As a result, channels 1, 6, and 11 are commonly used to avoid overlap. These non-overlapping channels are 5MHz apart from the next closest non-overlapping channel.
Channel bonding
combines two non-overlapping 20 MHz channels into a single 40 MHz channel, resulting in slightly more than double the bandwidth.
