adhoc hierarchical networks

[netuser786]

Hi,
i am a beginner in networking area. during the study of adhoc networks, i have a question. if i have a 2 level hierarchical network, with N nodes where N is a large no. and x regions or groups, then what should be the best value for x. Should it be large or small. Also, if the nodes are large in number, is 2 level hierarchy beneficial?

Any help is appreciated

 

[RadiclDreamer]

I would like to help you, but your post is very difficult to understand. Can you rephrase what you are asking?

 

[netuser786]

hi,
i mean that if i have an adhoc network which has 2 level hierarchy, which means that there would be N nodes divided into x groups or regions. the complexity in this case would be x.O(N/x). If N is a very large number, then keeping x a constant would not improve the asymptotic notation, so i think that x should be a function of N, for example x=N/constant. Is this the best we can do, or we can have x that can further improve the asymptotic notation? that is why i asked the best value of x.
Another question i have is that if we consider the hierarchy 2-level as a function of x and N is it beneficial or having a greater hierarchy (3,4,5-level) is better?

I hope that clarifies my question.

 

[ScottMac]

Hi,
i am a beginner in networking area. during the study of adhoc networks, i have a question. if i have a 2 level hierarchical network, with N nodes where N is a large no. and x regions or groups, then what should be the best value for x. Should it be large or small. Also, if the nodes are large in number, is 2 level hierarchy beneficial?

Any help is appreciated

AdHoc networks of more than two nodes ALWAYS suck and should be avoided in all but the most extreme of dire situations.

If your instructor doesn't like that answer, YOU tell 'em why.

 

[netuser786]

hi,
If adhoc networks are not beneficial if more than 2 nodes, then which networks are used in such scenarios?

 

[netuser786]

AdHoc networks of more than two nodes ALWAYS suck and should be avoided in all but the most extreme of dire situations.

Then which networks are used in such scenarios, where wireless mobile networks with large number of nodes are required.

 

[Ghiedo27]

Your limiting resource in this situation is the unlicensed frequency band. Ad hoc wireless networks are still going to cause significant interference with one another and you won't have the access point to control the talking stick. Dropping the access point doesn't give you extra channels. You do, however, increase the man hours it takes to configure and maintain your network along with a significant drop in reliability.

In reality, once the number of hosts passes a certain number (which is variable based on host density) it's simply cheaper, easier, more secure, and faster to manage a wired infrastructure.

You could configure multiple wireless APs using different frequency bands across both the 2.4 and 5ghz ranges. Depending on the location you could tune your AP power output and swap antennas to optimize coverage. This would be a huge pain in the rear end and inferior to a wired install in every way. But if you had, had, had to use wireless I would approach it from that angle (i.e. most use of unlicensed freq spectrum with access point infrastructure).

 

[ScottMac]

Then which networks are used in such scenarios, where wireless mobile networks with large number of nodes are required.

Networks that would implement an Access Point, which assumes the role of traffic manager. However "large" is an ambiguous and misleading term without knowing the area of coverage, and the number of access points, as well as the spectrum (2.4 vs 5GHz).

A "busy" one-AP network might only have five hosts associated with it ... or it might have as many as twenty or so (per Cisco recommendations, last time I looked). How much traffic each host / application generates is the key. Closer hosts get more throughput then the more distant hosts.

802.11 B, G, or N makes a huge difference too.

You're still on shared bandwidth, for all of the clients to see all of the other clients, they have to be on the same channel. The necessary handshakes and permission signaling all take time, and any control signaling means that there's no "real" data passing.

While not exactly line of sight (the signal can bounce around some) signal quality between all nodes will widely vary, and that tends to put the hosts into a more data protective mode, which further slows the traffic / transmission rate. Also, APs (or their antennas) tend to be mounted high for better RF visibility. Hosts usually aren't, reducing the acceptable link distance and / or the data rate.

As mentioned previously, it's a gut-wrenching nightmare to administer. For the time wasted in administration (time is money), you could have easily used an infrastructure system.

Aside from a quick, temporary two or three person file sharing or gaming session, AdHoc sucks. Sux Deluxe.

It sucks in pretty much any way that a network can suck, and then some. Wireless is, at best, a convenience that is helpful in a limited constellation of circumstances. It isn't intended to replace wired LANs, and probably won't for "a while."