The biggest advantage of wireless mesh networks -- as opposed to wired or fixed wireless networks -- is that they are truly wireless. Most traditional "wireless" access points still need to be wired to the Internet to broadcast their signal. For large wireless networks, Ethernet cables need to be buried in ceilings and walls and throughout public areas.

In a wireless mesh network, only one node needs to be physically wired to a network connection like a DSL Internet modem. That one wired node then shares its Internet connection wirelessly with all other nodes in its vicinity. Those nodes then share the connection wirelessly with the nodes closest to them. The more nodes, the further the connection spreads, creating a wireless "cloud of connectivity" that can serve a small office or a city of millions.

Wireless mesh networks advantages include:

Using fewer wires means it costs less to set up a network, particularly for large areas of coverage.

The more nodes you install, the bigger and faster your wireless network becomes.

They rely on the same WiFi standards (802.11a, b and g) already in place for most wireless networks.

They are convenient where Ethernet wall connections are lacking -- for instance, in outdoor concert venues, warehouses or transportation settings.

They are useful for Non-Line-of-Sight (NLoS) network configurations where wireless signals are intermittently blocked. For example, in an amusement park a Ferris wheel occasionally blocks the signal from a wireless access point. If there are dozens or hundreds of other nodes around, the mesh network will adjust to find a clear signal.

Mesh networks are "self configuring;" the network automatically incorporates a new node into the existing structure without needing any adjustments by a network administrator.

Mesh networks are "self healing," since the network automatically finds the fastest and most reliable paths to send data, even if nodes are blocked or lose their signal.

Wireless mesh configurations allow local networks to run faster, because local packets don't have to travel back to a central server.

Wireless mesh nodes are easy to install and uninstall, making the network extremely adaptable and expandable as more or less coverage is needed.

The Advantages of Wireless Mesh Networks

A wireless mesh network is very similar to a regular wireless network. The only difference between the two is reach. While a wireless network may spread throughout a building or a neighborhood, a wireless mesh network covers a much larger area, such as a city. A wireless mesh network has several advantages over other kinds of networks.

1. Easy to Set Up

o Since a wireless mesh network is simply a bigger wireless network and uses the same protocols and equipment, it is easy to set up and expand a wireless mesh network. The cost of the equipment is lower compared to other networking solutions, and the ease of installation clearly outscores other methods, since there is no need to mount cables around an entire city to obtain a huge network.

Good Coverage

o A wireless mesh network consists of multiple nodes that communicate with each other. If for whatever reason a node is blocked and separated from the network for a while, other nodes in its vicinity cover the respective area and take the load.

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Self-Management

o Once set up, a wireless mesh network can manage its load to avoid clogging a certain network node. If one node becomes very busy, the network traffic is redirected trough other nodes, maintaining a good balance of the network load. The self-management feature, which allows for the system to find the best traffic paths when congestion occurs, provides a system that may experience less failure and downtime.

Speed

o Unlike a traditional network, where a device acts as a server, which handles all data, and requires all data packets to run through it, in a wireless mesh network each node acts as an individual server. This allows for greater speeds for local connection, which run directly from the source to their destination, without needing to pass through a server.

Interconnectivity

o Since wireless mesh networks use the same protocols as regular wireless network, it is easy to establish connectivity between your own local networks and a wireless mesh network. A wireless mesh network can be a good method to connect two local networks, situated in opposite parts of a city, without using the Internet. This way, the data speeds are increased and the chances of a network drop are very low.

Wireless Mesh Networks (WMN)

Mesh is a technology that comes from the optical networking world and has been adapted to the Ethernet market. Mesh is a very smart way to provide resilient networks. Mesh architecture creates the opportunity to change data paths within a second when problems occur. Compared to the older solutions for network resilience, mesh really was a big step forward.

In the Ethernet WAN world mesh has been fully implemented and widely accepted. In the smaller Ethernet LAN world however nobody is using it. The question can be asked, why is everybody discussing (needing) this in the WLAN Ethernet world?

Obviously mesh is mainly related to city-wide (outdoor) Wireless LAN networks and those indoor networks where there are no Ethernet cables available. This immediately explains why mesh has become so popular. Particularly in these networks the radios have to rely on each other to build a successful WAN access, and when one radio fails another has to maintain the path to the WAN. Also the mesh standard is built in such a way that radios are able to find each other easily without any human interference: mesh has its own intelligence!

Disadvantages of WMNs.

So, why isn’t everybody using mesh today as its advantages seem to be so appealing? The main reasons why we don’t advise the use of mesh are the negative sides of mesh: bandwidth consumption and lack of interoperability.

Bandwidth (double use):

WLAN has already the disadvantage that almost 50% of the gross data rate has to be used for overhead. These overheads are really important to get stable links and to transmit the data without interruption. To build a mesh network another 50% of the available data-rate has to be reserved

for the fault-back path. As such, radios are sending the same data twice. With the continued rapid growth of bandwidth demand, WMN are unlikely to be able to deliver the speeds required by consumers.

Interoperability:

The IEEE has ratified the 802.11s standard to make a first step into the mesh world. The standard explains how multivendor networks can be built by setting up alternative paths based on Layer 2. It sadly missed the needed mesh-intelligent (layer 3) level, so every mesh vendor is still offering his own proprietary solution.

Disadvantages

The more extensive the network, in terms of scope or of physical area, the greater the investment necessary to build it will be, due, among other considerations, to the amount of cabling and the number of hardware ports it will require. For this reason, such networks are uncommon.

Because every device must be connected to every other device, installation and reconnection are difficult.

The huge bulk of the wiring can often be greater than the available space in the ceiling or under floors can accommodate.

The advantages and disadvantages of wireless sensor networks can be summarizedas follows:Advantages:

1. Network setups can be done without fixed infrastructure.2. Ideal for the non-reachable places such as across the sea,

mountains, rural areas or deep forests.3. Flexible if there is ad hoc situation when additional workstation

is required.4. Implementation cost is cheap.

Disadvantages:

1. Less secure because hackers can enter the access point and get all the information.

2. Lower speed compared to a wired network.3. More complex to configure than a wired network.4. Easily affected by surroundings (walls, microwavea, large

distances due to signal attenuation, etc.).Advantages and disadvantages of mobile ad-hoc networks

ADVANTAGES OF AD HOC NETWORKSThere are many reasons better to use ad hoc than infrastructure.The biggest ad hoc’s strength is its independency from

any infrastructure. Therefore, it is possible to establish an adhoc network in any difficult situations. The following are theadvantages of ad hoc networks.a. No infrastructure and lower cost: There are situations,with which a user of a communication system cannot rely onan infrastructure[1]. Using a service from a infrastructure canbe expensive for specific applications.In an area with very low density, like desert, mountain, orisolated area it is not impossible to establish an Infrastructure.But if we compare how often the people there are using serviceof infrastructure and how many data per day transmitted withcost of installation, maintenance, and repair, it is maybe tooexpensive.Almost the same problem with military network. It is obviouslyvery useless to build an infrastructure in a battlefield.Aside from cost of installation, the enemy can destroy theinfrastructure in short time. A independent from infrastructurenetwork is needed for both cases.b. Mobility (MANET only): In the next generation ofwireless communication systems, there will be a need forthe rapid deployment of independent mobile users[12]. Themost popular examples include military networks, emergency/ rescue operations, disaster effort. In these scenarios we can’t

rely on centralized connectivity. MANETs support nodes’mobility. We can still communicate with our mobile devicesas long as the destination is reachable.c. Decentralized and robust: Another advantage of ad hocnetworks is that they are inherently very robust[4]. Imaginethat for some reason one of the base stations is not working.In this case, all users of that base station will lose connectivityto other networks.In the ad hoc networks you can avoid such problem. If onenode leaves the network or is not working, you can still haveconnectivity to other nodes and maybe you can use these nodesto multi-hop your message to the destination nodes, as longas there is at least one way to desired node.d. Easy to build and spontaneous infrastructure: Malfunctionof a network infrastructure is sometimes not avoidable.It is obviously difficult to repair or replace the malfunctioninfrastructure in short time, while the network’s existence mustbe maintained all-time. Establishing an ad hoc is a good dealin such situation. The network participants can act as ad hocnodes and hop the messages.VI. DISADVANTAGES OF AD HOC NETWORKSThe wireless communication is very famous nowadays,using wireless can make rooms look better, because fewercables are used. The weakness of wireless link impact adhoc. Lower data rate, security, and medium access control arecommon problems in the wireless communications. Ad hocsstrengths cause also some problems. The following are thedisadvanteges of ad hoc networks.a. Higher error rate: Unlike wired transmission, the wirelesstransmission may deal with problem the characteristic ofthe electronic wave. In a free room without obstacle the electronicwave propagate linear indepently from its frequency[1].There is seldom such a situation. The obstacle causes shadowing,reflection, scattering, fading, refraction, diffraction of

the wave. These propagation may lead to transmitted packetsbeing garbled and thus received in error.b. Lower data rate: One of biggest Problem of ad hocnetworks is reduced data rates. The characteristic of wave,which is used for wireless communication, prevents wirelesscommunication to transmit data better than wired communication.A higher frequency can transmit more data, but then itis more vulnerable to interference and performs well in shortrange.c. Dynamic topology and scalability: Because ad hoc networksdo not allow the same kinds of aggregation techniquesthat are available to standard Internet routing protocols, theyare vulnerable to scalability problem[6].Since the MANET’s nodes are mobile, the routing changesas the nodes move. Current connectivity Information must tobe propagated to all network’s participant. Control messageshave to sent around the network frequently. The increasednumber of control messages burdens the available bandwidth.Therefore, the ad hoc protocols are typically designed toreduce the number of control messages, such as by keepingthe current information.A good algorithm for ad hoc networks must be able toevaluate and compare networks’ relative scalability in the faceof increased number of nodes and nodes mobility. It is veryimportant to know how many control message is required. Sowe can control bandwidth’s usage.d. Security: Due to dynamic distributed infrastructure-lessnature and lack of centralized monitoring points, the ad hoc

networks are vulnerable to various kinds of attacks[13]. Unlikewired channel, the wireless channel is accessible to bothlegitimate network users and malicious attacker. Therefore,the ad hoc networks are susceptible to attacks ranging frompassive attacks such as eavesdropping to active attack suchas interfering[14]. Especially for MANET, limited power

consumption and computation capabilities, due to energylimitation, causes incapability to execute computation-heavyalgorithms like public key algorithms.Passive attack means, that the attacker does not send anymessage. The attacker just listens the channel, therefore, it isalmost impossible to detect this attack. In contrast, the activeattacks modifies, deletes the packets, injects packets to invaliddestination. Active attack can be detected.There are numerous security problem issues in the ad hocnetworks. The following are some of the security problem ofIEEE 802.11.1) Eavesdropping (passive), a non-legitimate listening intoa transmission between two nodes.2) Traffic analysis (passive), the attacker monitoring thetransmission for patterns of communication.3) Masquerading (active), the attacker pretends to authorizeduser of a system in order to gain access to it or togain access to it or to gain greater privileges than theyare authorized for.4) Replay (active), the attacker spies transmissions andretransmits message as the legitimate user5) Message modification (active), the attacker alters aoriginal message by deleting, adding to, modifying it.6) Denial-of-service or interruption (active), the attackerprevents or prohibits the normal use or management ofcommunications facilities.e. Energy limitation (MANET only): A MANET networkallows mobile nodes to communicate in the absence of afixed infrastructure. Therefore, they operate with on batterypower. Because of these limitation, they must have algorithmswhich are energy-efficient as well as operating with limitedprocessing and memory resources[15]. The usage of availablebandwidth will be limited because nodes may not be able tosacrifice the energy consumed by operating at full link speed.It is also very annoying, while receiving data from someone

with PDA, the battery is almost depleted. Repeating thetransfer process after recharging is necessary. Therefore aMANET is not suitable for a permanent network

Wireless ad hoc networks are collections of wireless nodes,that communicate directly over a common wireless channel.The nodes are equipped with wireless transceiver. They don’tneed any additional infrastructure, such as base station orwired access point, etc. Therefore, each node doesn’t onlyplays the role of an end system, but also acts as a router, thatsends packets to desired nodes.The ad hoc are expected to do assignments, which theinfrastructure can’t do. Ad hoc networks are mostly used bymilitary, rescue mission team, taxi driver. Their works can’trely on a infrastructure’s network. As an illustrative example,imagine firefighters put out hazardous fire in a big forest.They have to communicate each other, but establishing ainfrastructure or cabling in such area is impossible or tooexpensive.The main problems in ad hoc networks are routing andcharacteristic of wireless communication. In infrastructure’s

networks a node can communicate with all nodes in the samecell. In ad hoc a node can communicate only with nodes inits area. this node can communicate with other nodes, but arouting algorithm is necessary. Unlike wired communication,wireless networks have transmission problem with data transmissionsuch as, possibility of asymmetric connections andhigher interferences.