Suppose your company needs your help with WMAN project. ZeeTech is a multination

Question

Suppose your company needs your help with WMAN project. ZeeTech is a multinational import-export company. Because ZeeTech has grown in popularity, it now has five offices in Melbourne. ZeeTech is considering implementing a WMAN technology that will link all its offices as well as provide mobile wireless access to the field workers that need to travel between different sites in a city. ZeeTech would install a WMAN in each office and provide its office employees and field workers the tablet computers and mobile phones for better customer service and marketing. For this reason you are asked to perform a comparative study on different WMAN technologies. Your report should briefly describe your chosen technology as well as justify why your chosen technology is most suitable in terms of cost of service, data capacity, service area, speed of installation, and security. Please note, this is a fictional case study and you should assume that all five offices are medium size with 40 employees in each office and around 400 daily customers/clients on average.

Explanation / Answer

Fast communications of network within a city called WMAN, that put up an entire city or other related geographic area and can span up to 50km. WMAN is based on IEEE 802.16 that functioning on Broadband for its wireless metropolitan. WMAN have air interface and a single-carrier scheme intended to activate in the 10-66 GHz spectrum, supports incessantly unreliable transfer levels at many certified frequencies. WMAN opens the door for the creation and Provide high-speed Internet access to business subscribers. It can handle thousands of user stations with prevents collisions and support legacy voice systems, voice over IP, TCP/IP. WMAN offer different applications with different QoS requirements. The technology of WMAN consist of ATM, FDDI, and SMDS.

Components of a wireless MAN generally come in matching pairs because they support fixed wireless connectivity from one point to another. Take a look at the primary components of a wireless MAN.

There are several devices for WMAN. Some are -

Bridges:- This is a device that connects two networks that might use the same or a different data-link layer protocol.

Wireless bridges are generally at each end of a point-to-point link, such as those that interconnect two buildings. A bridge has a wired port that connects to the network and a wireless port that interfaces with a transceiver. The bridge receives packets on one port and retransmits them on another port. A bridge will not start retransmission until it receives a complete packet. Because of this, stations on either side of a bridge can transmit packets simultaneously without causing collisions.

Some bridges retransmit every packet on the opposite port regardless if the packet is heading to a station located on the opposite network. A learning bridge, which is more common, examines the destination address of every packet to determine whether it should forward the packet based on a decision table that the bridge builds over time. This increases efficiency because the bridge will not retransmit a packet if it knows that the destination address is on the same side of the bridge as the sending address. Learning bridges also age address-table entries by deleting addresses that have been inactive for a specified amount of time.

The bridges within the network are transparent to users. Packets are sent through the bridge automatically. In fact, users have no idea that their packets are traversing a link leading to a different location.

Bridges Versus Access Points

Access points connect multiple users wirelessly to each other and to a wired network. Several users equipped with 802.11 NICs might associate with a single access point that connects to an Ethernet network. Each of these users has access to the Ethernet network and to each other. The access point in this case is similar to a bridge device, but the access point interfaces a network to multiple users. A bridge interfaces only other networks.

It's possible to use a wireless bridge indoors. A wireless LAN bridge can interface an Ethernet network directly to a particular access point. This might be necessary if few devices, possibly in a far-reaching part of the facility, are interconnected through Ethernet. A wireless LAN bridge plugs into this Ethernet network and uses the 802.11 protocol to communicate with an access point that is within range. In this manner, a bridge enables the wireless connection of a cluster of users (actually a network) to an access point.

Basic Ethernet-to-Wireless Bridges

An Ethernet-to-wireless bridge connects directly to a single computing device through an Ethernet port and then provides a wireless connection to an access point. This makes it useful when the device, such as a printer, PC, or video game console, has an Ethernet port and no wireless NIC. In some cases, you might have no way of adding a wireless NIC, which makes a basic bridge the only way to go wireless. Printers and video game machines are common examples of this scenario.

Workgroup Bridges

Workgroup bridges are the answer for connecting wireless networks to larger, wired Ethernet networks. A workgroup bridge acts as a wireless client on the wireless network, and then interfaces to a wired network. The wired side connects to an Ethernet switch that connects multiple devices. A workgroup bridge offers more robust and higher-end management and security utilities with higher prices as compared to a basic bridge.

Directional Antennae

The antenna is an important element of a wireless MAN. Unlike other types of wireless networks, most antennae for wireless MANs use directional antennae, mainly because they operate over wider areas.  

Different types of antennae have different vertical and horizontal beamwidths. An omnidirectional antenna has a horizontal beamwidth of 360 degrees and a vertical beamwidth that ranges from 7 to 80 degrees. A semidirectional antenna might have a vertical beamwidth of 20 degrees and a horizontal beamwidth of 50 degrees. Generally, the narrower the beamwidth, the longer the range when transmit power is kept constant.

Semidirectional Antennae

There are several different types of antennae that have semidirectional radiation patterns. A directional patch antenna will have at least double the range as compared to an omnidirectional antenna.

Semidirectional antennae effectively increase the signal's amplitude referred to as gain by approximately 10 times. Their use is mostly for extending wireless LANs to cover a larger area.

Highly Directional Antennae

A highly directional antenna has an extremely narrow beamwidth, with long radiation patterns and corresponding range. To achieve this degree of directivity, you need to use dish antennae that focus the radio energy mostly in one direction. These types of antennae are expensive compared to omni- and semidirectional antennae; however, the costs may be feasible if the solution requires long range.

Many of the higher-gain directional antennae use a parabolic dish to focus the radio frequency (RF) power in one direction. A parabolic dish, for example, has a narrower horizontal and vertical beamwidth of 4 to 25 degrees. This extreme focusing of the RF power increases range significantly.

A problem, however, is that the dish antennae are subject to damage from weather because of excessive wind loading, especially if the antenna is not mounted correctly. As a result, highly directional grids that have plenty of holes in the dish are generally safer to deploy.

In addition, both semidirectional and highly directional antennae require a clear line of sight between both ends of the system. In some cases, RF signals can pass through trees and some buildings, but infrared requires an unobstructed path. RF and infrared signals also experience periodic attenuation due to obstructions moving across the path of the signal, such as passing trains and automobiles. Planning wireless MANs is difficult in city environments because of buildings that block the path between the ends of the system.

Effect of Polarization

Antenna polarization is the physical orientation of the antenna along a horizontal or vertical plane. vertical polarization, which is the most common for wireless LANs, occurs when the antenna is perpendicular to the Earth. Parallel polarization applies to an antenna that is parallel to the Earth.

To maximize the transfer of RF energy from the transmitter to the receiver antenna, both antennae should have the same polarization. If one antenna has vertical polarization and the other has horizontal polarization, no transfer of power or communications will occur.

So WLAN required a lot of hardware and high cost hardware. This required high service cost.

WLAN spread in large area (in Km) so the traveling maintenance also increase the cost. Speed is Highly dependent on a lot of things like weather , climate.

You have an increasing choice of options for authentication and encryption, from several emerging technologies to VPNs. Depending on the size of your enterprise and the level of risk WLAN opens up.

Basic 802.11 security deters casual eavesdropping. In most WLAN products, however, these security features are disabled by default. Disabled means the WLAN operates in "open system" mode--any station can join because they know the network's Service Set Identifier (SSID).

The 802.11 standard's security is composed of authentication and encryption. When shared-key authentication is enabled, stations can associate with the AP only if they have a 40- or 128-bit key known to both parties. When Wired Equivalent Privacy (WEP) is enabled, the same key is fed into the RC4 cipher to encrypt data frames. Only stations that possess the shared key can join the WLAN, but the same key decrypts frames transmitted by other stations. If your policy requires authentication of individual stations, or confidentiality beyond the air link, you must adopt other measures.

The perils awaiting unprotected WLANs are many. Wireless traffic is easily recorded. Passive eavesdroppers can gather proprietary information, logins, passwords, intranet server addresses, and valid network and station addresses. Intruders can steal Internet bandwidth, transmit spam, or use your network as a springboard to attack others. They can capture and modify traffic to masquerade as you, with financial or legal consequences. Even a low-tech attacker can disrupt your business by launching wireless packet floods against your APs, nearby servers, next-hop wired network or Internet uplink.

In short, early adopters have been lucky. The cost of downtime and cleanup can be an order of magnitude greater than the cost of prevention.

In this case you can impliment WLAN,(your requirement is each office and provide its office employees and field workers the tablet computers and mobile phones for better customer service and marketing ) but the cast is high, service and security is not guaranteed because Passive eavesdroppers can gather proprietary information, logins, passwords, intranet server addresses, and valid network and station addresses. Intruders can steal Internet bandwidth, transmit spam, or use your network as a springboard to attack others.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.