I am planning to do a project on WIFI offloading using Software Defined Networking. Basically to switch the signals from WIFI to LTE and vice-versa based on the signal strength. Could anybody let me know how i could simulate this and carry out certain experimental tests? I know there is a software called Mininet and i am not sure if we can create base-stations to simulate the experiments. Is it possible to simulate this using Mininet?
Thanks!
You can sett up some link parameters such as bandwidth and latency in mininiet to "emulate" an wireless base station (LTE/WIFI). However, I'm not quite sure how you should emulate signal strength. You could of course write a program with a "node" that moves around on a 3 axis graph where the x,y,z values could give some signal strength value based on output effect multiplied with the vector found in the graph, and when it reaches a threshold have it change to a node (mininet link) that is closer. I.e. change the forwarding tables so your "stream"/tunnel uses another link.
I did an undergraduate thesis on wireless network emulation in Mininet and used Mininet and Ns-3 together using this project. We primarily did validity testing on this platform to determine it's accuracy and limitations (especially at scale). The wireless model is very good until a very clear performance degradation when the CPU usage reaches (100/n)% - where n is the number of available cores on the machine (for a single threaded implementation).
It also has the functionality to set up multiple base stations, although I didn't delve deeply into this beyond initial testing that it works. The main benefits achieved through this tool is the accurate performance degradation due to distance from the source and interference.
A lot of time has past and it seems better ways are available:
ns-3 has LTE features (it seems it got it through LENA)
for mininet-wifi, here, here and here
Related
How can defined topology in Castalia-3.2 for WBAN ?
How can import topology in omnet++ to casalia ?
where the topology defined in default WBAN scenario in Castalia?
with regard
thanks
Topology of a network is an abstraction that shows the structure of the communication links in the network. It's an abstraction because the notion of a link is an abstraction itself. There are no "real" links in a wireless network. The communication is happening in a broadcast medium and there are many parameters that dictate if a packet is received or not, such as the power of transmission, the path loss between transmitter and receiver, noise and interference, and also just luck. Still, the notion of a link could be useful in some circumstances, and some simulators are using it to define simulation scenarios. You might be used to simulators that you can draw nodes and then simply draw lines between them to define their links. This is not how Castalia models a network.
Castalia does not model links between the nodes, it models the channel and radios to get a more realistic communication behaviour.
Topology is often confused with deployment (I confuse them myself sometimes). Deployment is just the placement of nodes on the field. There are multiple ways to define deployment in Castalia, if you wish, but it is not needed in all scenarios (more on this later). People can confuse deployment with topology, because under very simplistic assumptions certain deployments lead to certain topologies. Castalia does not make these assumptions. Study the manual (especially chapter 4) to get a better understanding of Castalia's modeling.
After you have understood the modeling in Castalia, and you still want a specific/custom topology for some reason then you could play with some parameters to achieve your topology at least in a statistical sense. Assuming all nodes use the same radios and the same transmission power, then the path loss between nodes becomes a defining factor of the "quality" of the link between the nodes. In Castalia, you can define the path losses for each and every pair of nodes, using a pathloss map file.
SN.wirelessChannel.pathLossMapFile = "../Parameters/WirelessChannel/BANmodels/pathLossMap.txt"
This tells Castalia to use the specific path losses found in the file instead of computing path losses based on a wireless channel model. The deployment does not matter in this case. At least it does not matter for communication purposes (it might matter for other aspects of the simulation, for example if we are sampling a physical process that depends on location).
In our own simulations with BAN, we have defined a pathloss map based on experimental data, because other available models are not very accurate for BAN. For example the, lognormal shadowing model, which is Castalia's default, is not a good fit for BAN simulations. We did not want to enforce a specific topology, we just wanted a realistic channel model, and defining a pathloss map based on experimental data was the best way.
I have the impression though that when you say topology, you are not only referring to which nodes could communicate with which nodes, but which nodes do communicate with which nodes. This is also a matter of the layers above the radio (MAC and routing). For example it's the MAC and Routing that allow for relay nodes or not.
Note that in Castalia's current implementations of 802.15.6MAC and 802.15.4MAC, relay nodes are not allowed. So you can not create a mesh topology with these default implementations. Only a star topology is supported. If you want something more you'll have to implemented yourself.
I have written and simulated a Verilog code in ISE Project Navigator 2013. this is an RTL model that describes the network-on-chip routers, buffers and links.
which device is better for synthesis and implementation?
How can I get the static and dynamic power consumption, a packet transfer delay, area and the other factors that indicates network performance, using ISE Project Navigator?
The question is very open ended so I will try to provide as general an answer as possible.
Now you have said that you have the code for a NOC Router in ISE. This would imply that you or the designer has a rough idea of the frequency at which the internal logic/system has to operate. The maximum clock tree frequency of your target device and would then be one of the key parameters that you need to check. If your design is running at around 150-200 MHz and is appropriately pipelined (small muxes, not more than 2-3 levels of logic between pipelining stages), then almost any of the currently available device families from both Xilinx and Altera should be suitable.
The next important consideration is of external connectivity. Does your design need high-speed serial connectivity with an external device. If that is true, then you would need to select a device that has high-speed SERDES IPs in-built. That would then limit your choice of devices.
Another factor to consider is interface to external SDRAM or RLDRAM. If your design needs to interface with such external devices, then you need to pick a device that has support either through a softcore or a Megafunction (Altera) or a hard IP block.
Finally you need to look at your logic utilization. You want to chose a device that is just big enough to satisfy your requirements, unless your design is part of a bigger project and there are modules that would be designed later and would sit alongside your NOC. You would have to make a rough guess of the number of LEs/LUTs that your design would need and pick a device 50% bigger than that. You can then run a trial synthesis run and check if your estimates are okay. If they are, and your device is less than 50% utilized, you could go in to a smaller device as need be.
There are also a few other considerations such as number of IOs, presence of a PLL/Clock manager that may affect your choice of device
I'm making an application for a running competition on a fixed track. I'm investigating what systems could be used and tough of using a stick containing a GPS/DGPS module and a Zigbee enabled chip to communicate the location to a server.
I've researched the subject (on the internet) but I was wondering if anyone has some practical advice/experience with using a Zigbee mesh/star topology in a dynamic environment wich could apply to this use case. I'm also very interested in using a mesh topology where the data is transmitted (hopping) trough the different Zigbee modules to the server.
Runners are holding a stick; run around the track and than pass the stick on to the next team member.
I am not particularly clear about your goal. But I'd like to say a few things.
First, using GPS/DGPS to measure which team reaches the finish line is inaccurate. Raw GPS data is horrible in accuracy (varying in 1 - 10 meters, well, around that), also the sampling rate of a GPS module is low (say once a second?) How do you determine exactly which team reaches the finish line first?
Second, to use a mobile ZigBee chip to communicate in real-time is hard. I assume your stick has a ZigBee end device. When it is moving (which in your case is pretty fast), it must dynamically find and associate with new parent routers, which takes time and depending on the wireless environment, it might involve several retries. So you will imagine a packet is only successfully delivered to the other end after 100ms or even a second. This might not be a problem if your stick records the exact time when a team reaches the finish line. Since you have a GPS module in the stick so there is no problem in getting very accurate time.
I do already have an answer but am wondering if there's a any better way. The problem is: I have a set of clients on a relatively slow WiFi network. Each client has a distance to the access point (AP), which determines how fast that client-to-AP link will run. Shorter links run faster than longer links.
My goal is to have each node calculate the length of its own link (and that of all nodes in the network). Nodes can talk to each other, but always via the AP, of course. Knowing the distances between nodes and the AP lets us optimize the network simply by moving the worst nodes closer to the access point.
Use round trip time as http://www.tkn.tu-berlin.de/fileadmin/fg112/Papers/hoene_paper2.pdf suggest.
Read Wi-Fi signal strength and use formulas to calculate it as How to calculate distance from Wifi router using Signal Strength? suggest.
What would be the best way to triangulate a wireless network passively. Are there tools available? Algorithms? Libraries?
My goal would be to create a relative map of various objects that sends or receive signals using signal strength (DB's), signal/noise ratio, signal phase, etc. from a few location points. With enough sampling, i'm guessing it would be possible to create a good 2d/3d map.
I'm searching for stuff in any language / platform.
Some keywords: wi-fi site survey, visualization, coverage, location, positioning
Thinking about using kismet to gather the data and then process it. Maybe Free Space Path Loss for RF in the 2.4Ghz range to calculate a relative distance. And optionally try to use RF obstacle attenuation estimation values (based on some user input) to give better estimates. Then use trilateration to generate possible relative coordinates.
You can't use the GPS technique because the timing is nothing like accurate enough.
The best you can do is Trilateration based on the signal strength from each base station and assume that range is proportional to signal.
You will probably need to force a connection to each base station in turn in order to measure the signal strength.
Interesting question. Initial thoughts were using output from something like the WiSpy spectrum analyzer. I like the idea of using a directional antenna. Looks like some research (may) be underway.
Instead of trilateration you could use bilinear interpolation. This is said to be better for non-linear distance vs. signal strength data like wifi in an urban environment would be. http://courses.cit.cornell.edu/ee476/FinalProjects/s2007/ayl26_ym82/ayl26_ym82/index.htm has the background math and the what I assume is AVR C for doing it with magnetic field sensors.
Using signal strength to judge distance could easily be thrown off by differences in materials blocking line-of-sight to each of the sampling points. It would probably be better to do the sampling with a directional antenna, and from each sampling point, find the bearing that maximizes signal strength to each device you want to locate. With this technique, you can use only two or three sampling locations, depending on the accuracy with which you can estimate the bearings.
Ars Technica has an article about this, citing the Fraunhofer Institute and Skyhooks Wireless. This technology is built into every iPhone and iPad.
Actually I think you should try using an algorithm like the GPS one (wikipedia).. of course you can simplify it according to your need, for example:
you need to install on every item that should broadcast its position (the navigation signal) an application that actually does it
you should use a different channel for every single item to be sure not to generate collisions (it depends also on how much you broadcast the signal)
so if you place at least 4 broadcasters you can triangulate on every client to allow it to calculate its position. Naturally the bcasters should be as much similar as possible in response..
by the way these are just ideas..