Question

I am to choose the preffered MAC protocol for communication with LEO satellites. I have three to choose from: Dynamic TDMA, WCDMA and OFDM. I need som help on how to approach this. Are there an obvious choice? And what parameters and characteristics abut both LEO and the protocols should i consider in the discussion?

Answer 1

Throughout recent decades, geostationary satellites have been giving space-based correspondence frameworks. They are utilized to give precise overall situating, for example, Global Positioning Systems (GPS), to transmit computerized TV, for military purposes, et cetera. Be that as it may, attributable to their high altitude,geostationary satellites frameworks are not adjusted to constant correspondence systems, for example, communication and Internet associations, which use the Transmission Control Protocol/Internet Protocol (TCP/IP) standard. Without a doubt, high elevation infers high power necessities that are not suited for convenient gadgets, and flag dormancy, which isn't suited for the TCP/IP standard. The advancement of Low Earth Orbit (LEO) satellite systems appears to beat a considerable lot of the issues of geostationary satellite systems and ought to permit genuine worldwide world inclusion if all around planned. Sadly, LEO satellite frameworks have diverse legitimate and mechanical qualities than customary satellite systems. A model will be produced for a superior comprehension of their focal points and restrictions. We will demonstrate that a couple of parameters permit the assurance of the correct position of each satellite in the group of stars, on account of mechanical conditions. This trademark is exceptionally valuable when
endeavoring to pick the best steering methodology. In reality, the fundamental issue in association arranged correspondence is to proficiently course the parcels from the source to the sink. An estimation technique for steering postponements will be produced, and the issues of TCP identified with LEO arrange qualities will be tended to. At long last, it will be demonstrated that the principle consider included dealing with a decent TCP association is the Round Trip Time (RTT). The RTT is the time the framework needs to transmit a parcel from a source to a sink and send back an affirmation to the source

CDMA and TDMA

These are two altogether different techniques use to achieve a similar undertaking, utilize recurrence range considerably more productively than the conventional devoted settled recurrence transmitting framework. The objective is to drastically build the quantity of basically synchronous clients inside a particular bit of radio range. The two strategies achieve this.

CDMA is short for Code-Division Multiple Access, an advanced cell innovation that utilizations spread-range systems. CDMA does not allocate a particular recurrence for every client putting or getting a call. Singular discussions are encoded with a pseudo-irregular computerized grouping plan. The getting hardware must have the capacity to decipher the got motion by being able to reproduce this pseudo-irregular advanced sequencing.

CDMA is really a military innovation initially utilized amid World War II by the English partners to thwart German endeavors at sticking radio transmissions. The partners transmitted distinctive parts of vital data more than a few frequencies, rather than a solitary recurrence, subsequently making it extensively more troublesome for the Germans to get and absorb the entire flag. Since Qualcomm, Inc., made the correspondence chips for CDMA innovation, it approached the ordered data, and once the data wound up accessible to people in general, they turned into the first to market it.

TDMA is short for Time Division Multiple Access, an innovation for conveying computerized remote administration utilizing time-division multiplexing (TDM). TDMA innovation separates a radio recurrence into availabilities and after that apportions these schedule openings to numerous calls. Along these lines, a solitary recurrence can bolster different, synchronous information channels. The getting gear must have the capacity to decipher the got motion by unraveling the got flag and reconstitute it utilizing a similar schedule opening choice calculation as was utilized when it was encoded and transmitted. TDMA is utilized by the GSM advanced cell framework.

Examination factors:

All rf remote frameworks deliver a diminishing sign as the separation between the transmitter and the recipient increment. In the least complex model, free space, the multiplying the separation decreases the got flag level by the square of the proportion of progress in remove. More modern spread demonstrating, which is generally utilized in the business, will uncover that the relationship is significantly more unpredictable than the reverse of the square of the separation. With the utilization of CDMA and TDMA execution estimations show that the corruption can be to the opposite of third or fourth request, making the correct choice of a coveted recipient edge much more critical than with a customary FM two-way radio demonstrating.

For instance, ideally a CDMA telephone may have the capacity to furnish satisfactory administration with a got flag level of - 106 dBm, where a telephone utilizing TDMA mgut require - 99 dBm of got flag level. Nonetheless, it is incorrect to derive that CDMA is dependably the favored innovation, since it can appropriately work with 7 dB less flag. The genuine applications are not great. Building infiltration won't be the same for the two techniques. Having a similar flag level on the two frameworks does NOT imply that the level of reasonableness of execution will be equivalent