The spread spectrum wireless focuses on what 3 unlicensed bands?

900 MHz, 2.4 GHz, and 5 GHz

What are the different kinds of wireless networks that can be deployed?

- Personal-area network (PAN)

- LAN

- Metropolitan-area network (MAN)

- WAN 

What are the frequency and speeds for the following IEEE standards in wireless technology?

 

- 802.11a

- 802.11b

- 802.11g 

How does CSMA/CD work in wireless communication compared to wired communication?

In a wired network, when 2 stations transmit simultaneously, the wire voltage is raised, signifying a collision. But on a wireless network, the station knows its transmission was successful only if it receives an acknowledgement. The absence of the positive acknowledgement implies a collision.

What are the different physical (PHY) components of 802.11?

The PHY components are MAC (L2), Physical Layer Convergence Procedure (PLCP, L1 and L2), and the Physical Medium Dependent (PMD, L1)

How are the PHY sublayers used in wireless communication?

The PHY continues to use the MAC portion while replacing the LLC with the PLCP. The PLCP provides a common interface to the MAC sublayer and is more unique in that it transends into the physical layer too. The PLCP creates frames from the MAC layer PDUs by adding the correct header mapped on the PMD's selected modulation.

How many channels are nonoverlapping in the United States?

There are 11 channels available in the US, and only 3 of these channels are nonoverlapping (1, 6, and 11)

What are Cisco's two WLAN architectures?

Autonomous and Lightweight. Autonomous APs were once called thick, fat, or decentralized, and lightweight APs were called thin or centralized.

What is the difference between autonomous and lightweight APs?

Autonomous APs have local configurations requiring local management, which might make consistent configurations difficult and add to the cost of network management. A lightweight AP receives control and configutation from a WLAN controller to which it is associated. The lightweight wireless LAN controllers communication with the APs over any L2 or L3 infrastructure using Lightweight Access Point Protocol (LWAPP)

What is the Adaptive Wireless Path (AWP) protocol used for in a wireless network?

The AWP protocol enables each AP to identify its neighbors and intelligently choose the optimal path to the wired network by calculating the cost of each path in terms of signal strength and the number of hops required to get to a controller.

What are the different Basic Service Sets (BSS) modes in a WLAN design?

- Independent mode - Also known as ad hoc mode, is a peer-to-peer network where mobile clients connect directly without an intermediate AP. This is called an Independent BSS (IBSS).

 

- Infrastructure mode -  Adds greater diversity and control for larger environments by incorporating APs, which are used to provide stations with communication.

What is an extended serice area (ESA)?

An extended service area (ESA) is when any number of cells can be added to extend the range if a single cell does not provide enough coverage. It is recommended that the ESA cells have 10 to 15 percent overlap to allow remote users to roam without losing RF connections.

When a wireless root bridge is used, what devices are supported by default?

- Non-root bridges - Typically, considered the remote side of the bridge connection

- Wireless client cards -  PC cards, PCI card and user connections

- WGB - A bridge that can directly connect wired devices

- Repeater - An AP that helps extend the reachability 

What are the benefits of a good microcell architecture?

- Seamless roaming - Roaming across APs allows users to maintain connection while moving around a facility or campus environment

 

- Power management - Managing the audio results in better battery life for portable devices.

 

-  Dynamic load balancing - Users can be dynamically distributed among APs to increase the throughput of each user.

 

- Fault tolerance - WLAN backbones can be provided with the use of APs with overlapping coverage cells. 

What are some natural causes that can impact radio waves/RF?

- Reflection - Occurs when RF bounces off objects (such as metal or glass surfaces)

 

- Refraction - Occurs when RF passes through objects and changes direction (such as glass surfaces)

 

- Absorption - Occurs when RF is absorbed by an object (such as a wall or furniture)

 

- Scattering - Occurs when an RF wave strikes an uneven surface and is reflected in many directions.

 

- Diffraction - Occurs when an RF wave strikes sharp edges, which bends the signal 

What unit of measurement is used to specify the power levels for wireless?

The power levels for wireless are in milliwatts, whereas the power levels for radio stations are in megawatts

What is the formula used in WLANs to calculate power?

Transmit Power (dBm)= 10 * log[Transmit Power (mW)]

What are the different categorizes of antennas in regards to radiant energy?

- Omnidirectional - The most widely used today but not always the best solution. The shape of the radient energy is a doughnut-shaped pattern

 

- Semidirectional - Offer the ability to direct and apply gain to the signal. The shape of the radient energy is a cowbell-shaped pattern

 

- Highly directional - Intended for highly directed signals that must travel a long distance. The shape of the radient energy is a telescope pattern 

What are the center frequencies for all the available channels?

Channel 1 starts with 2412, and for every channel after that, the center frequency increases by 5. For example, channel 2 is 2417, channel 3 is 2422, etc.

What are some key points to remember when first setting up the microcells for a WLAN?

- It is recommended that neighboring cells not be placed on nieghboring frequencies.

 

- Seven users per AP with no conference rooms provides 4.5 Mbps per user

 

- Seven users plus one conference room (10 users), which equals to 17 total users, provides 1.8 Mbps per user. 

When is a non-root bridge able to communicate with another non-root bridge?

A non-root bridge communicates with another non-root bridge as long as one of the non-root bridges has a root bridge in its uplink.

What are the five interconnecting elements of the Cisco Unified Wireless Network?

- Client devices

- Mobility platform

- Network unification

- World-class network management

- Unified advanced services 

Explain how the split-mac architecture works on wireless devices.

The split-mac architecture allows the splitting of 802.11 protocols between the AP and the WLAN controller. The AP handling the real-time portions of the 802.11 protocols is split from the WLAN controller that handles those items that are not time sensitive.

At which layer does an AP attempt to connect to a WLC?

A Cisco AP will first attempt to associate using L2. If that fails, it will then attempt an association at L3. It alternates back and forth until a controller can be found.

What are the different types of interfaces that can be configured on a WLC?

- Management

- AP-manager

- Virtual

- Service-port

- Dynamic 

Describe the function of the management interface on a WLC.

The maangement interface is the default interface for in-band management of the controller and connectivity to enterprise services such as AAA servers.

Describe the AP-manager interface on a WLC.

A controller has one or more AP-manager interfaces, which are used for all L3 communication between the controller and lightweight APs after the APs have joined the controller. The static AP-manager interface must be assigned to distribution system port 1 and must have a unique IP address.

Describe the virtual interface on a WLC.

The virtual interface is used to support mobility management, DHCP relay, and embedded L3 security such as guest web authentication and VPN termination.

Describe the service-port interface on a WLC.

The service-port interface controls communication through and is statically mapped by the system to the service port. It enables you to manage the controller directly or through a dedicated operating system network which can ensure service access during network downtime.

Describe a dynamic interface on a WLC.

Dynamic interfaces are created by users and designed to be analogous to VLANs for WLAN clients. Each dynamic interface is individually configured and allows separate communication streams to exist on any or all of a controller's distribution system ports.