Total 3 Blogs

Created by - Orhan Ergun

MANET: Mobile Ad Hoc Networks

The MANET stands for mobile ad hoc network; in practice, the term generally applies to ad hoc wireless networks of sufficient complexity that some internal routing mechanism is needed to enable full connectivity. The term mesh network is also used for MANETs. MANET nodes communicate by radio signals with a finite range, as in the Figure - 1 below. Each node's radio range is represented by a circle centered about that node. In general, two MANET nodes may be able to communicate only by relaying packets through intermediate nodes, as is the case for nodes A and G in the diagram above. Mobile Ad Hoc networks can use any wireless mechanism In the field, the radio range of each node may not be very circular, due to signal reflection. An additional complication arises when the nodes (or even just obstructions) are moving in real time (hence the “mobile” of MANET); this means that a working route may stop working a short time later. For this reason, routing within MANETs is a good deal more complex than routing in an Ethernet. A switched Ethernet, for example, is required to be loop-free, so there is never a choice among multiple alternative routes. MANETs in general do not support broadcast, unless the forwarding of broadcast messages throughout the MANET is built in to the routing mechanism. MANETs are of theoretical interest, their practical impact has been modest; they are almost unknown, for example, in corporate environments. They appear most useful in emergency situations, rural settings, and settings where the conventional infrastructure network has failed or been disabled. RFC 5820 specifies the needs for OSPF to run on Mobile Ad Hoc Networks. There are many extensions for OSPF such as flooding enhancements, packet structure and so on. Some MANET use cases are depicted below. Figure - 2 Mobile Ad Hoc Networks in military Figure - 3 Mobile Ad Hoc Network in Public Environment

Published - Tue, 26 Nov 2019

Created by - Orhan Ergun

4 Main Design Principles of Mobile Networks

4 Main, Key Design Principles of Mobile Networks – I will explain the 4 key design principles of cellular networks in plain English. In fact I should have said, cell based systems as mobile networks may not be design based on cell based architecture. Let me explain what would be the other deployment option for the mobile network, other than cell based systems and then will highlight the 4 main characteristics of cell based mobile networks. Before, cellular systems designed, mobile network operators used to place their radio transmitters at the tallest buildings in the area which they want to provide a coverage. Single, very high-power transmitters was used to cover very large geographic areas. With the cell based telephone systems, so many  low-power, small coverage area transmitters are used instead of a single, powerful, monolithic transmitter to cover a wide area. This is first design principles of cell based mobile phone networks. Second design principle of cell based systems is frequency reuse. I hared a post on wireless frequency spectrum allocation problem here. Read it as well, if you want to understand the limit and the problems of electromagnetic frequency spectrum. The second design principle which is frequency reuse, takes into account the fact that cellular telephony, like all radio-based services, has been allocated a limited number of frequencies by the regulators. By using geographically small, low-power cells, frequencies can be reused by non-adjacent cells. When usage areas become saturated by excessive usage, cells can be split. This is third design principle of cellular based mobile phone systems. When the network operator realizes that the number of callers refused service because of congestion reaches a critical level, they can split the original cell into two cells, by installing a second site within the same geographical area that uses a different set of non-adjacent frequencies. This has an extended impact; as the cells become smaller, the total number of calls that the aggregate can support increases dramatically. The smaller the cell is the larger the total number of simultaneous callers that can be accommodated. Of course this also causes the cost of deployment to increases exponentially. Fourth and last design principles of cell based phone systems is cell-to-cell handoff, which simply means that the cellular network has the ability to track a call as the user moves across a cell. When the signal strength detected by the current cell is perceived by the system to be weaker than that detected by the cell the user is approaching, the call is handed off to the second cell. Different Cellular Architecture ( 1G,2G,3G,4G) uses different terminology for the device which detects the signal strength and providing the handoff capability. Ideally, the user hears nothing. Cell handoff and other cellular system capabilities are under the central control of a mobile telephone switching office (MTSO, Sometimes called as MSO – Mobile Switching Office or MSC – Mobile Switching Center)

Published - Fri, 08 Nov 2019

Created by - Orhan Ergun

Wireless ISPs Spectrum Problem

Wireless ISPs also known as WISP mostly use unlicensed frequency spectrum. Frequency spectrum is the most critical asset for the Mobile and Wireless networks and it is sold in auctions for 100s of millions of dollars. Frequency spectrum is managed by the governments and governments in general, sell frequency spectrum in auctions. And some frequencies are really expensive, I am talking about 100s of millions of dollars. But frequency spectrum is so important ? Why it is a problem with Wireless Internet Service Providers ? What is Wireless Internet Service Provider in the first place ? I explain all these questions during my Telecom Training but I wanted to share below post with you. Below you will find a very nice write up from one of the founding members of the Wireless Internet Service Providers Association (WISPA). Although it is written for the U.S government, situation is the same in every country for the Wireless Internet Service Providers. Congress – Stop Selling Our Airwaves! by John Scrivner Do you have little or no access to broadband (high speed) Internet? Then forward this note to your Congressman to get this fixed. Broadband is something most Americans take for granted. That is unless they live in remote rural areas where cable modems and DSL are rarely available. For rural Americans real access to broadband is limited at best and often is non-existent. Thousands of small companies called WISPs (Wireless Internet Service Providers) have been working for over a decade to bring people broadband in the harder to reach areas of the United States. Thousands of United States WISPs use radio airwaves , also known as spectrum, to transmit broadband through the air from central locations to customers throughout rural parts of America. WISPs are usually started up by a local person with technical knowledge who is an entrepreneur and has decided to take on the effort to bring broadband to their neighborhood, their town or even their whole county. WISPs transmit from existing small towers, water towers, tall building roofs, grain silos, whatever it takes to deliver broadband through the air. They fund their operations using all they have, they borrow against all assets they own, they spend all their savings. There is at least one WISP who was a family farmer and actually “sold the farm” to build the WISP he started in rural Indiana. WISPs are a growing part of our economy employing tens of thousands of Americans to help them serve broadband to rural America. WISPs work against many obstacles to build broadband into areas where the population is so small that a business case would not normally work. By being frugal and doing much of the work themselves WISPs have found a way to make this a thriving business by solving the “digital divide” for their neighbors while earning a good living and often hiring others in their area to help them. There is one obstacle that all WISPs face that is not only preventing millions of Americans from having access to broadband now but is threatening to kill their industry completely. SPECTRUM AUCTIONS ARE KILLING WISPS AND ARE PREVENTING AMERICANS FROM HAVING BROADBAND. There is a dirty little secret hidden in plain sight in the United States. If big businesses were bribing the government to prevent competing small businesses from having access to government owned assets and reserving these assets for themselves one would think we would see people calling to have these people tried for corruption. Instead we are seeing it happening regularly with practically nobody giving it a second thought. It may be a much more formal and open process than bribes but the net effect of Spectrum Auctions is exactly the same. Big Businesses are the only winners of these spectrum auctions and WISPs are left with no access to good spectrum. Spectrum is to a WISP what good land is to a farmer. Without good land a farmer would not be able to deliver much food to market. At this time there is no practical way for a WISP to reach all homes and businesses within what should be the coverage area of their tower locations. The reason is that WISPs have ZERO access to good quality spectrum. WISPs have to use uinlicensed spectrum which has no protections against interference. It is shared by other users of the frequencies. This spectrum is only barely usable for the delivery of broadband when there are trees or other obsructions blocking clear line of sight to the WISP tower locations. Low power restrictions, noise and higher frequencies of the unlicensed spectrum mean that only a portion of potential customers can be served within WISP tower locations. Depsite these limitations WISPs have built their entire business on using these unlicesned frequencies to bring broadband to where it never was before. If WISPs had access to good spectrum then they would be able to build higher quality wireless broadband which would be available to all rural Americans. Plentiful access to good quality spectrum would also mean that prices would lower as more people per tower would be buying the service which would allow for a better return on investment for each tower built. Spectrum Auctions happen now because Congress tells the FCC they have to sell off the all-important spectrum licenses at auction as opposed to allowing WISPs and others to pay for licenses with monthly fees or register them for free if they prove they are serving the public good with broadband. Congress and the FCC tell the public that auctions are good because they raise billions of dollars in auction revenues. If Spectrum Auctions are so good for America then why do we still have large areas where services are not available after 20 years of selling off spectrum to the highest bidder? Why are we selling off the airwaves to the highest bidders and then turning around and giving away tax money for people to build broadband (aka broadband stimulus and USDA grants)? I have a novel idea for Congress and the FCC. Stop selling off the airwaves to big business and stop paying us to build broadband. Let’s just cut to the chase and get the spectrum out to the people who need it. Let’s stop pretending that selling off spectrum is the in America’s best interest. It is quite the opposite. On the surface raising money from spectrum acutions looks like the government is being responsible but auctions are causing great harm. To put this into perspective please imagine for a moment that a US “Farm and Crop Commission” (FCC for short) suddenly held property rights to all farm ground outside of the big cities in the United States. The only exceptions would be ground that was rocky or otherwise was not capable of real agriculture. Now imagine that Congress tells the FCC that the only access to this ground by family farmers or anyone else would be to buy it at auction. Now imagine that only a small portion of all the farm ground is made available at auction once every 5 to 10 years. Now imagine that the smallest parcel of ground would be millions of acres in 12 county wide sized blocks of ground with no ability to buy smaller parcels. Next the FCC sets minimum auction price for a parcel of the ground at $5 Million dollars. There would be ZERO chance of a single farmer having access to even 1 acre of good quality farm ground in this scenario. How many family farmers do you think would survive trying to grow crops on the few rocky outcroppings on hillsides with no property rights of any kind? How much do you think food would cost if there were only 5 mega-farmers in the United States who grew all the food? Do you think we could get enough food to live if we only had 5 farmers who held a monopoly position on the only farm ground available to be farmed in the United States? To a WISP and to all American citizens, spectrum is just like farm land and broadband is just like food. This is a travesty. I think once you really read the FCC / farm land metaphor above and understand what is going on then you will understand why the number one obstacle to Americans having access to cheap and plentiful broadband across the entire country is that WISPs (aka your broadband family farmers) are being deinied access to good quality spectrum under reasonable terms. WISPs do not expect a free ride. WISPs will pay good money for access to good spectrum. WISPs will pay license fees over time or raise enough money to buy a license for each tower as they build these locations. What we CANNOT do is pay millions or billions of dollars for access to good quality spectrum and try to compete at these spectrum auctions with the likes of at&t, Verzon, Sprint, etc.. We will lose every time in that scenario. So we need Congress to act now today. We need them to tell the FCC to give us access to unused spectrum now. The auctions need to end now. The way to simulate the economy and give everyone broadband is one simple solution and it does not cost us a penny. We need to make spectrum available for broadband use in the US for free. Once a WISP, cable company, phone company, municipality or other organization uses this spectrum to serve up broadband to a significant portion of an area the FCC needs to grant an exclusive license to the entitiy serving the broadband at that location. Think of it as homesteading. In the past the US needed to grow into the land westward so they allowed people free access to land if they settled it and lived on it and made it their own. That is how we quickly expanded our great country. We need to do the same thing now with broadband. We need to let people homestead the spectrum to grow our access to broadband. Spectrum Homesteading will do just that. Congress – we plead with you now – stop auctioning off our spectrum and let us homestead it now. Pass a Spectrum Homesteading Act and let the free market flourish in building broadband access to 100{ea8372c0850978052e20c0d53be15bc420c794e9b9b32f0ee9dfe0056552e01e} of Americans without a single penny of government subsidies.

Published - Fri, 08 Nov 2019