Metropolitan Area Network (MAN) Definition

Metropolitan Area Network (MAN) Definition - Metropolitan Area Network (MAN) is a network in a city with high speed data transfer which connects various locations such as campuses, offices, administration, and so on. Here are the characteristics of the MAN namely: 

Covers an area of between 5 and 50 km range. MAN includes many urban areas.

A Metropolitan Area Network (such as WAN) is generally not owned by a single organization. MAN, his link and communication equipment, are generally owned by a consortium of the user or by the network service providers who sell services to users.

Metropolitan Area Network often acts as a high-speed network to allow sharing of regional resources. It is also often used to provide a shared connection to other networks by using the link to the WAN.

Metropolitan Area Network larger and usually wear the same technology as LAN.

Only have one or two cables and has no switching elements, which serves to set the packet through multiple output cable. The existence of switching elements makes the design becomes simpler.

Metropolitan Area Network itself is defined as a network that covers a city (Computer networks, ANDREW ST, page 117). At first the series Metropolitan Area Network is connected by using the LAN cable to connect to the office of the other branches that were located a few KM, with the presence of the WIMAX internet users are increasingly interested in large-scale Wireless MAN.

Equipment pre-WiMAX (IEEE 802.16) is a device designed specifically for wireless MAN skala, examples of this equipment are Redline AN-50 AN-30, Alva ion Link Blaster.

Wireless MAN can play at multiple frequencies, namely frequency of 900 MHz, 1.5 GHz, 2 GHz, 2.5 GHz, 3.3 GHz, and 5.8 GHz. And now in Indonesia which allowed the government to be used by the general public is the 2.4GHz frequency which is then subdivided into several channels.

Here the author presents the frequency distribution of the image used in the air:

(Image taken from the e book "CCNA: Cisco Certified Network Associate Study Guide six Edition" page 706)

In this moment I assume we are using the IEEE 802.11b wireless networking to design large-scale MAN (Metropolitan Area Network) using 2.4GHz frequency.

The frequency list of channels that can be used at a frequency of 2.4GHz
Channel Frequency Channel Frequency
1 2,412 2,447 GHz 8 GHz
2 2,417 2,452 9 GHz GHz
3 2,422 2,457 GHz 10 GHz
4 2,427 2,462 GHz 11 GHz
5 2,432 2,467 GHz 12 GHz
6. 2,437 2,472 GHz 13 GHz
7. 2,442 2,477 GHz 14 GHz

Each country has different rules depending on the use of the channel above, For example, for some areas in the United States, can only use the channel 1 to channel 11, Europe as using the channels 1 to 13, while Japan alone has a high technological level just playing on channel 14,

Wifi that is labeled for use Modulation 802.11b Direct Sequence Spread Spectrum (DSSS), it would appear that the wide spectrum of 22MHz for each station radiating.
22MHz
2401MHz 2412MHz 2423MHz
Can be seen above the channel will be widened down 11MHz and will widen 11MHz up to a total spectrum drawn is 22MHz, it is certainly going to take two channels above and 2 channel underneath so the channel in use as much as 5 channels, so if you want to build this network there it helps you free up / do not use 2 channels and 2 channels under the above of the channel you use to be free of interference.

Non-Overlapping Channel Set
Non-overlapping Channel is a channel that is estimated to have a set of sets / separation frequency and can be used together in the same time without interference; non-overlapping channels are working on RF link.

Pictured above is the result of spectrum measurement using a spectrum analyzer? In the picture seems clear canals that are used with the same time i.e. channel 1, channel 6 and channel 11 which is located at a frequency of 2412MHz, 2437MHz and 2462MHz.

In this picture interference does not occur (seen from the absence of the line piece between the frequencies of the frequency with which other frequencies).

Basically we could not only berpatok at 3 channels freakiest that, we can also use the 4 channels simultaneously at the same time, this can be done if the target area coverage more broadly so that it takes 4 different channels.

2412MHz 2432MHz 2452MHz
2472MHz

Channel 5 2432MHz
Channel 9 2452MHz
Channel 13 2472MHz

Use of this Channel 4 was able to reach a wider area, but there will be little interference on each channel, you can watch the above scheme, seen chunks of lines in each diagram indicates channel interference.

DISTANCE TRANSMISSION WLAN
In figure above describes the ability of Transmit / Receive transmit power and / Receiver a set perelatan Wireless limitations Effective Isotropic Radiated Power (EIRP) Only 30-36 so we only have a limited range.

Legally beam antenna which permitted is 36 dBmW, so that when you use a 24dBi antenna you only use the power of about 15dBm / 30 mW only.

In general, existing WLAN equipment market have between 15-20 dBm transmit power (30-100mW), with limited power this resulted jangkauanpun distance is limited.

The points above illustrates the range of radio transmissions for a particular type antenna. This design will be used as reference for modeling sell dijaringan Wireless Metropolitan Area Network. In Tiori Access Point with antenna Omnidirectoral will cover some areas with a coverage area of about 4 to 5 km.

On the fact that not all regions in terms of six points on the above can receive wireless coverage, this is because the shape of the radiation from the antenna are oval, so that in terms of the sixth there will be a vacant area is often called the Blank spot.

Besides other factors which it is possible to inhibit the signal beam is form the texture of the area range. If the area is hilly or many high buildings, the beam will be retarded.

Orange color in the image above is the area of wireless coverage
Design Metropolitan Area Network (MAN) Based on the three non-overlapping channels
Omnidirectionsl Access Point

In the section we use the model range hexagonal involving 3 different channels are channel 1 (2412MHz), Channel 6 (2437MHz) and channel 11 (2462MHz).

Because it only uses 3 channel then simple logic to avoid interference with the formulation that different channels on each sell adjacent, this logic is poured on the structure shown above in which each channel of different colored and no different channels.

With the above channel arrangement is expected to reach the area / city covering an area of 35x35 km without interference. Assume we sell only if one can accommodate 10-30 nodestation / cafe then you can imagine this can include wireless minimum of at least 70 nodestation / wanet.

Sectoral Access Point
Furthermore, we use a technique Sectoral Access point, with three different types of channels are of course using different access points. In the case of these three types of access points are placed in the same Tower with an estimated coverage of 120 degrees at each access point. It is estimated that if there is no obstacle that means access point can reach 6 hinggga 8 Km at each access point.

Can be seen above, a tower placed one corner tapat sell, it is intended to save the use of the tower.

Traficc network density depends on the traffic on the network, this is why the total WiFi every sell is limited ie ranging in the 10- 30 nodestation. Keep in mind actually computers connected kejaringan total amount is greater than the Wifi nodes in the network.

Looked over the suckler wireless using the principle of sectoral, Similarly, the composition of the omnidirectional, susunaan also uses 3 different channels too, can be seen with different colors on the composition of the cell, range of colors (in this case frequency) apart, so that interference will not occur.

Reach region of the arrangement is similar to that omnidirectional 35x35 square km, but not the same thing with the number of nodes that can be reached on this arrangement, this arrangement can cover 9 with 9x30 sell 270 node or nodes.

Design Metropolitan Area Network (MAN) with 4 Non-Overlapping Channel
Using 4 different channels are characteristic of this cell arrangement, the arrangement does not use the form of the reach sell-six terms as the previous discussion, but has been using the square-four. Because the rectangular shape of each antenna does not cover 120 derejat again, but 90 degrees only.

Similarly, the sectoral composition, the tower is placed at an angle to sell, but certainly in terms of the arrangement is not used as the sixth region of the coverage because it uses 4 channels on one tower. Channel used in this arrangement is channel 2412 MHz, 2432 MHz channel, channel 2452 MHz, and 2472 MHz channel.

Because using the 4 channel that is different but still within the range of 2412 MHz to 2477MHz so in this arrangement there will be less interference. The distance is the same range as the distance range of the previous arrangement that is 6 to 8 km, but with a different configuration.

You can see, if structured as above, the range of areas that can be reached will be much greater than before, with only 3 pieces tower (each tower mounted 4 different channels) is able to cover the 3x4 or twelve sell.

Seeing this course will also betambah node number, the number of computers that can be served also increases but does not increase the number of towers, of course with the addition of a frequency channel into 4 types of different channels.

Incorporating Connection Point to Point (P2P)
By khasus using tower we needed a lot of connections between each tower, the connection is often known as POINT to POINT, One requirement is point to point connection, the connection is obliged to work on the same frequency and working in the region. Point- to-point connections typically use Omni antenna and sectoral (so mixes),
Channel used on:
1. Three non - overlapping channels
Channel 3 is at a frequency of 2422MHz
Channel 8 is at a frequency of 2447MHz
Four non-overlapping channels
Channel 3 is at a frequency of 2422MHz
Channel 7 is at a frequency of 2442MHz
Channel 11 is at a frequency of 2462MHz
P2P P2P
In the picture above is an example of using sambuangan Point to point and point to multi-point.

Metropolitan Area Network advantages:
a. The server can serve as the central office of branch office data center.
b. Real-Time Transactions (data on a central server is updated at that moment, for example ATM Bank unluk national territory)
c. Communication between the office can use e-mail, chat and Video Conference (VICON).

Metropolitan Area Network (MAN) loss:
a. Operational costs expensive.
b. Installation of infrastructure is not easy.

c. Complicated in case of network trouble (trouble shoot network)

Metropolitan Area Network is a network that covers a city. At first the series MAN connected using LAN cable to connect to the office of the other branches that were located a few KM, with the presence of the WIMAX internet users are increasingly interested in large-scale Wireless MAN. Equipment pre-WiMAX (IEEE 802.16) is a device designed specifically for large-scale wireless Metropolitan Area Network.