I. INTRODUCTION
In today’s world there is an increasing demand for wireless connectivity. But with the present technology there is an inefficient use of the available. A large part of the spectrum is underutilised as shown in Fig 1. Due to the inefficient use of spectrum by the current spectrum allocation methods there is a need for developing new methods which aids in efficient use of available spectrum.
One alternative solution to this is the use of alternate technology. Cognitive radio (CR) is an available option. Cognitive radio concept was introduced by Mitoala [2]. CR in general can be defined as the usage of licensed spectrum by an unlicensed user when the former is not using it. This is called as spectrum hole. CR uses these for transmission of data/voice [3]. CR as defined by Haykin is:
“Cognitive radio is an intelligent wireless communication system that is aware of its surrounding environment (i.e., outside world), and uses the methodology of understanding by- building to learn from the environment and adapt its internal states to statistical variations in the incoming RF stimuli by making corresponding changes in certain operating parameters (e.g., transmit-power, carrier-frequency, and modulation strategy) in real-time, with two primary objectives in mind: highly reliable communication whenever and wherever needed; efficient utilization of the radio spectrum.” [4]
To clearly understand the concept of CR systems a background on software defined radio (SDR). Traditional radio systems which is oriented around hardware limits cross functionality and physical intervention is needed for modification. This reduces the flexibility and increases the cost of implementation and operation. An alternative to this is softwar...
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...CR-BS environment.
5) PS-MS ↔ PS-BS: This link being bi-directional at all times is a connection between MS and BS which has to be done in one hop. PR-BS being the master has the function of communication coordination in its cell coverage area and also providing access to PR-MS to backbone network.
6) PS-MS ↔ CR-MS: This is needed for enabling interoperability between systems of different kind. Here CR-MS will become a part of PS by reconfiguring itself.
7) PS-MS ↔ CR-BS: This link also serves the same purpose as that between PS-MS↔CR-MS. Additionally if CR-BS has the capability of running the protocol of PS, access service to PR-MS can be provided through it.
8) PS-MS ↔ PS-MS: This link may be useful as ad-hoc network for wireless connection. This is present in PS. Here, if both the nodes are given CR capability, this link will mirror that of between CR-MS↔CR-MS.
a. Systems: Personnel Readiness Management (PRM), Personnel Information Management (PIM), Personnel Accounting and Strength Reporting (PASR), Unit Manning Roster (UMR), Electronic Military Personnel Office (eMILPO), Defense Theater Accounting System (DTAS), Interactive Personnel Electronic Records Management System (iPERMS).
Star topology networks require more cabling than bus, but the tradeoff comes in the form of a more solid network topology. A break in the network media will only affect a single node, since every node has a dedicated connection to the central device; a hub or switch. This also makes the central device a Single Point of Failure (SPOF). Redundant or failover switches are often used to eliminate the SPOF in a star LAN.
6) Michele Zorzi, “Wireless Sensor and networks: Recent trends and Research Issues’’, University of Padova, Italy, IEEE communication society, Poland, April 28-30, 2008.
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Simultaneous communication, also known as Sim-com is a form of communication process that utilizes both signs and sound. Quite often Sim-com has been referred to as a sign supported speech; these signs are usually in English in order to ensure that there is fluency in the language. In this, it is noted that some other non-verbal cues like the use of finger spelling and visual aids which rhyme to the spoken language can be used. Simultaneous communication has always been known to be a form of communication that is intended to help people who have hearing problems (deaf) understand what is being said. In this, it is realized that over the years, Sim-com has been able to utilize other systems of communication like seeing essential English. Sim-com has proven its advantageous use in both the deaf and hearing people because it presents both the spoken language and also the non-verbal. Simultaneous language is not only used by the deaf, but also used when communicating with students at the preschool level. This is important because these children tend not to understand verbal communication fully (Beginnings, 2014).
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Analog communication employs continuous transmission of an electromagnetic wave form that varies in frequency and amplitude.
Spectrum Decision Making calls for reconfiguration for the channel and protocol required for constantly adapting to mobile changing environments and adjustment of output power or even alteration of transmission parameters (such as modulation formats (e.g. low to high order QAM), variable symbol rates, different channel coding schemes) and characteristics by the Cognitive radio devices. CR should be able to use multiple antennas for interference knolling, capacity increase or range extension.
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main advantage of FM broadcasting is of it is static free. But the drawback to
As wireless communication and multimedia applications are increasing at a rapid pace and there is need to meet the requirements a better standard for communication is developed titled LTE. With the release of various versions over the years shows a continuous enhancement in the framework standard. This paper discusses about the advent of LTE into the mobile and wireless communication universer and the need for it. The various features and technical aspects are also discussed. With features such as closed subscriber group, self-organising networks, location services, enhancement cell ID and Multimedia Broadcast services this is a standard which pretty much became the norm. Technologies such as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output(MIMO) which were instrumental in the evolution to the LTE-Advanced are also discussed.
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