Propagation Losses

Antenna and Wave propagation plays a vital role in wireless communication networks. An antenna is an electrical conductor or a system of conductors that radiates/collects (transmits or receives) electromagnetic energy into/from space. An idealized isotropic antenna radiates equally in all directions.

Propagation Mechanisms

Wireless transmissions propagate in three modes. They are −

• Ground-wave propagation
• Sky-wave propagation
• Line-of-sight propagation

Ground wave propagation follows the contour of the earth, while sky wave propagation uses reflection by both earth and ionosphere.

Line of sight propagation requires the transmitting and receiving antennas to be within the line of sight of each other. Depending upon the frequency of the underlying signal, the particular mode of propagation is followed.

Examples of ground wave and sky wave communication are AM radio and international broadcasts such as BBC. Above 30 MHz, neither ground wave nor sky wave propagation operates and the communication is through line of sight.

Transmission Limitations

In this section, we will discuss the various limitations that affect electromagnetic wave transmissions. Let us start with attenuation.

Attenuation

The strength of signal falls with distance over transmission medium. The extent of attenuation is a function of distance, transmission medium, as well as the frequency of the underlying transmission.

Distortion

Since signals at different frequencies attenuate to different extents, a signal comprising of components over a range of frequencies gets distorted, i.e., the shape of the received signal changes.

A standard method of resolving this problem (and recovering the original shape) is to amplify higher frequencies and thus equalize attenuation over a band of frequencies.

Dispersion

Dispersion is the phenomenon of spreading of a burst of electromagnetic energy during propagation. Bursts of data sent in rapid succession tend to merge due to dispersion.

Noise

The most pervasive form of noise is thermal noise, which is often modeled using an additive Gaussian model. Thermal noise is due to thermal agitation of electrons and is uniformly distributed across the frequency spectrum.

Other forms of noise include −

• Inter modulation noise (caused by signals produced at frequencies that are sums or differences of carrier frequencies)

• Crosstalk (interference between two signals)

• Impulse noise (irregular pulses of high energy caused by external electromagnetic disturbances).

While an impulse noise may not have a significant impact on analog data, it has a noticeable effect on digital data, causing burst errors.

Fading

Fading refers to the variation of the signal strength with respect to time/distance and is widely prevalent in wireless transmissions. The most common causes of fading in the wireless environment are multipath propagation and mobility (of objects as well as the communicating devices).

Multipath propagation

In wireless media, signals propagate using three principles, which are reflection, scattering, and diffraction.

• Reflection occurs when the signal encounters a large solid surface, whose size is much larger than the wavelength of the signal, e.g., a solid wall.

• Diffraction occurs when the signal encounters an edge or a corner, whose size is larger than the wavelength of the signal, e.g., an edge of a wall.

• Scattering occurs when the signal encounters small objects of size smaller than the wavelength of the signal.

One consequence of multipath propagation is that multiple copies of a signal propagation along multiple different paths, arrive at any point at different times. So the signal received at a point is not only affected by the inherent noise, distortion, attenuation, and dispersion in the channel but also the interaction of signals propagated along multiple paths.

Delay spread

Suppose we transmit a probing pulse from a location and measure the received signal at the recipient location as a function of time. The signal power of the received signal spreads over time due to multipath propagation.

The delay spread is determined by the density function of the resulting spread of the delay over time. Average delay spread and root mean square delay spread are the two parameters that can be calculated.

Doppler spread

This is a measure of spectral broadening caused by the rate of change of the mobile radio channel. It is caused by either relative motion between the mobile and base station or by the movement of objects in the channel.

When the velocity of the mobile is high, the Doppler spread is high, and the resulting channel variations are faster than that of the baseband signal, this is referred to as fast fading. When channel variations are slower than the baseband signal variations, then the resulting fading is referred to as slow fading.

Terms used in Mobile Communication

MS (Mobile Station)

Mobile station is combination of user's all equipment (mobile phone, SIM, card etc.) and software needed for communication with a GSM network.

Mobile station communicates the information with the user and modifies it to the transmission protocols of the air interface to communicate with the Base Station Subsystem (BSS).

The information of the user communicates with the MS through a microphone and speaker for the speech, keyboard and display for short messaging and wire and cable connection for other data terminals.

In GSM, MS consists of four main components:

• Mobile Termination (MT)
• Terminal Equipment (ME)
• Terminal Adapter (MA)
• Subscriber Identity Module (SIM)

Base Station (BS)

• A Base station transmits and receives user data in the cellular network to customer phones and cellular devices. It is connected to an antenna (or multiple antennas).
• BS is a fixed point of communication for customer cellular phones on a carrier network.
• BSs (Base stations) are company specific. However one single site may host multiple base stations from competing telecommunication companies.
• Different types of base stations can be setup according to the coverage required, as follows:
  • Macrocells
  • Picocells

Subscriber Identity Module (SIM)

It is a smart card which stores data for GSM cellular telephone subscriber. It is also called portable memory chip. Data stored by the SIM includes user identity, location and phone number, network authorization data, contact lists, personal security keys and stored text messages. Security features contains authentication and encryption to protect data and prevent eavesdropping.

Base Transceiver Station (BTS)

The BTS is used for data transmission between the mobile phone and the base station. It has a equipment for encryption and decryption of communications, spectrum filtering equipment, antenna and transceivers (TRX).

A Base Transceiver Station consists of the following:

• Antennas that relays radio messages
• Transceivers
• Duplexers
• Amplifiers

Mobile Switching Center (MSC)

It is a telephone exchange that is actually used to make the connection between mobile users within the network, from mobile users to the public switched network (PSTN) and from mobile users to other mobile networks.

MSC is the hardware part of wireless switch. It also provides support for registration and maintenance of the connection with the mobile stations.

Base Station Controller (BSC)

BSC is used to control a group of Base Transceiver Stations. It is used for the allocation of radio resources to a mobile call and for the handovers that are made between base stations (BS) under their control. Other handovers are controlled by the MSC.

Channels

Channel is a range of frequency allotted to particular service or systems.

Carrier

Carrier is a company to which your mobile device connects to, such as Idea, Airtel, BSNL, Vodafone etc.

Transceiver

Transceiver is a device capable to perform simultaneously transmitting and receiving radio signals.

Gateway

It a network point that acts as an entrance to another network.

GSM

GSM is called Global System for Mobile Communication. It is a standard to describe protocols for digital cellular networks used by mobile phones.

Bluetooth

A Bluetooth technology is a high speed low powered wireless technology link that is designed to connect phones or other portable equipment together. It is a specification (IEEE 802.15.1) for the use of low power radio communications to link phones, computers and other network devices over short distance without wires. Wireless signals transmitted with Bluetooth cover short distances, typically up to 30 feet (10 meters).

It is achieved by embedded low cost transceivers into the devices. It supports on the frequency band of 2.45GHz and can support upto 721KBps along with three voice channels. This frequency band has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM).rd-compatible with 1.0 devices.

Bluetooth can connect up to “eight devices” simultaneously and each device offers a unique 48 bit address from the IEEE 802 standard with the connections being made point to point or multipoint.

History Of Bluetooth

Bluetooth wireless technology was named after a Danish Viking and King, Harald  Blatand; his last name means “Bluetooth” in English. He is credited with uniting Denmark and Norway, just as Bluetooth wireless technology is credited with uniting two disparate devices.

The Bluetooth technology emerged from the task undertaken by Ericsson Mobile Communications in 1994 to find alternative to the use of cables for communication between mobile phones and other devices. In 1998, the companies Ericsson, IBM, Nokia and Toshiba formed the Bluetooth Special Interest Group (SIG) which published the 1^st version in 1999.

The first version was 1.2 standard with a data rate speed of 1Mbps. The second version was 2.0+EDR with a data rate speed of 3Mbps. The third was 3.0+HS with speed of 24 Mbps. The latest version is 4.0.

How Bluetooth Works:

Bluetooth Network consists of a Personal Area Network or a piconet which contains a minimum of 2 to maximum of 8 bluetooth peer devices- Usually a single master and upto 7 slaves. A master is the device which initiates communication with other devices. The master device governs the communications link and traffic between itself and the slave devices associated with it. A slave device is the device that responds to the master device. Slave devices are required to synchronize their transmit/receive timing with that of the masters. In addition, transmissions by slave devices are governed by the master device (i.e., the master device dictates when a slave device may transmit). Specifically, a slave may only begin its transmissions in a time slot immediately following the time slot in which it was addressed by the master, or in a time slot explicitly reserved for use by the slave device.

The frequency hopping sequence is defined by the Bluetooth device address (BD_ADDR) of the master device.  The master device first sends a radio signal asking for response from the particular slave devices within the range of addresses. The slaves respond and synchronize their hop frequency as well as clock with that of the master device.

Scatternets are created when a device becomes an active member of more than one piconet. Essentially, the adjoining device shares its time slots among the different piconets.

Bluetooth Specifications:

• Core Specifications : It  defines the Bluetooth protocol stack and the requirements for testing and qualification of Bluetooth-based products.
• The profiles specification:  It defines usage models that provide detailed information about how to use the Bluetooth protocol for various types of applications.

 The core specification consists of 5 layers:

• Radio: Radio specifies the requirements for radio transmission – including frequency, modulation, and power characteristics – for a Bluetooth transceiver.
• Baseband Layer: It defines physical and logical channels and link types (voice or data); specifies various packet formats, transmit and receive timing, channel control, and the mechanism for frequency hopping (hop selection) and device addressing.It specifies point to point or point to multipoint links. The length of a packet can range from 68 bits (shortened access code) to a maximum of 3071 bits.
• LMP- Link Manager Protocol (LMP): defines the procedures for link set up and ongoing link management.
• Logical Link Control and Adaptation Protocol (L2CAP): is responsible for adapting upper-layer protocols to the baseband layer.
•  Service Discovery Protocol (SDP): – allows a Bluetooth device to query other Bluetooth devices for device information, services provided, and the characteristics of those services.

The 1^st three layers comprise the Bluetooth module whereas the last two layers make up the host. The interfacing between these two logical groups is called Host Controller Interface.

Advantages of Bluetooth Technology:

• It removes the problem of radio interference by using a technique called Speed Frequency Hopping.  This technique utilizes 79 channels of particular frequency band, with each device accessing the channel for only 625 microseconds, i.e. the device must toggle between transmitting and receiving data from one time slot to another. This implies the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. This ensures that the interference won’t take place as each transmitter will be on different frequencies.
• The power consumption of the chip (consisting of transceiver) is low, at about 0.3mW, which makes it possible for least utilization of battery life.
• It guarantees security at bit level. The authentication is controlled using a 128bit key.
• It is possible to use Bluetooth for both transferring of data and verbal communication as Bluetooth can support data channels of up to 3 similar voice channels.
• It overcomes the constraints of line of sight and one to one communication as in other mode of wireless communications like infrared.

Bluetooth Applications:

Cordless Desktop: All (or most) of the peripheral devices (e.g., mouse, keyboard, printer, speakers, etc.) are connected to the PC cordlessly.

Ultimate headset: It can be used to allow one headset to be used with myriad devices, including telephones, portable computers, stereos, etc.

Automatic synchronization: This usage model makes use of the hidden computing paradigm, which focuses on applications in which devices automatically carry out certain tasks on behalf of the user without user intervention or awareness.

Multimedia Transfer:- Exchanging of multimedia data like songs, videos, pictures can be transferred among devices using Bluetooth.

 

 

Internet

The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices.

Types of Internet Connections

Modern technology has come a long way, especially in the last few years. There is a lot that we can do that seemed impossible just a decade or two, like instantly connecting with people all over the world, and your options for doing so are growing every day. Internet service is one of those quickly evolving industries, and it can be hard to determine what kind of service you may need or what is available to you. Clarus Broadband wants you to have access to amazing high-speed internet no matter where you live, which is why we have made it our mission to bring internet service to the communities that need it most. Keep reading to learn more about all the different kinds of internet connections out there, and explore our site today to learn what you can do to bring lightning fast internet service to your hometown!

Dial-Up

At the inception of the internet, dial-up was your only possible connection. Your computer dials a phone number to give you access to the World Wide Web, which comes with some obvious problems. The biggest issue for most has been the fact that you can’t make or receive phone calls while someone is using the computer. Many adults today can probably remember being pulled away from the keyboard so their parents could use the phone. Such a problem probably would never even occur to most kids now, and that’s because many have moved away from dial-up internet. It may be cheap, but it is slow and ineffective.

If you are a resident of rural Texas, dial-up may be one of the few internet service connections available to you, which is why Clarus Broadband is working so hard with local communities in Belton, Copperas Cove, Gatesville, and more to give you better options. Learn how you can become a champion and bring better internet service to your town today!

Satellite

Satellite internet is another option often available where broadband – which we will discuss in a moment – is not, which means it is another one of the more common connection types used in rural areas. As you might expect, satellite internet offers your computer a connection by communicating with a satellite orbiting Earth. It requires a satellite dish with a clear line-of-sight, which is just one drawback. Another major problem you may face? The signal from your satellite dish has to travel a long way – thousands of miles – which is why the connection can be delayed when compared to broadband. It can provide high-speed internet, but it’s not a great option for online gaming or video streaming, because you share bandwidth with other people in the area.

Broadband

The term “broadband” is shorthand for “broad bandwidth,” and it offers significantly better high-speed connections than dial-up. However, you should know that the word “broadband” is often used to describe a wide variety of internet connection types, and not always in a way that is technically correct. For our purposes in this article, we are going to use it in its more general sense and then explain more specific connection types that may be categorized under “broadband”, correctly or incorrectly.

DSL

DSL stands for “digital subscriber line” and in its simplest form, it can be explained as a better, more high-tech version of dial-up internet. It still uses phone lines to connect, but it uses two lines and leaves room for you to continue to make and receive calls. It is a significantly faster and higher quality internet connection when compared to dial-up.

Cable

Rather than phone lines, cable internet operates over – you guessed it – cable TV lines. Cable internet offers greater bandwidth than DSL, and therefore faster access. Speed can depend on how you use your access, however, and whether you are uploading or downloading any files.

Wireless

The abbreviation “WiFi” has almost become synonymous with “internet” these days, but it refers to a specific kind of internet connection that utilizes radio frequencies rather than phone or cable lines. It’s always on, and it can be access from anywhere within network range. It’s one of the fastest options on the market.

Fiber Optics

When you want the best of the best internet connections, you want fiber optics. Fiber optics have tapped into an innovative and relatively new way to transmit signals using light conveyed through cables made of a special, flexible plastic or glass. Nothing in the universe travels as fast as light, which is one of the reasons why fiber optics offers such blisteringly fast internet speeds. It’s a great option for houses with multiple devices in use and the speed of your connection is unaffected by your neighbors’ internet use, which is not something many other types of internet service can claim.

 

Wireless Technology Trends:

Wireless technology plays a key role in today’s communications, and new forms of it will become central to emerging technologies including robots, drones, self-driving vehicles and new medical devices over the next five years. Gartner, Inc. has identified the top 10 wireless technology trends for enterprise architecture (EA) and technology innovation leaders.

“Business and IT leaders need to be aware of these technologies and trends now,” said Nick Jones, distinguished research vice president at Gartner. “Many areas of wireless innovation will involve immature technologies, such as 5G and millimeter wave, and may require skills that organizations currently don’t possess. EA and technology innovation leaders seeking to drive innovation and technology transformation should identify and pilot innovative and emerging wireless technologies to determine their potential and create an adoption roadmap.”

The top 10 wireless technology trends are:

1. Wi-Fi

Wi-Fi has been around a long time and will remain the primary high-performance networking technology for homes and offices through 2024. Beyond simple communications, Wi-Fi will find new roles — for example, in radar systems or as a component in two-factor authentication systems.

2. 5G Cellular

5G cellular systems are starting to be deployed in 2019 and 2020. The complete rollout will take five to eight years. In some cases, the technology may supplement Wi-Fi, as it is more cost-effective for high-speed data networking in large sites, such as ports, airports and factories. “5G is still immature, and initially, most network operators will focus on selling high-speed broadband. However, the 5G standard is evolving and future iterations will improve 5G in areas such as the Internet of things(IoT) and low-latency applications,” Mr. Jones added.

3. Vehicle-to-Everything (V2X) Wireless

Both conventional and self-driving card will need to communicate with each other, as well as with road infrastructure. This will be enabled by V2X wireless systems. In addition to exchanging information and status data, V2X can provide a multitude of other services, such as safety capabilities, navigation support and infotainment.

“V2X will eventually become a legal requirement for all new vehicles. But even before this happens, we expect to see some vehicles incorporating the necessary protocols,” said Mr. Jones. “However, those V2X systems that use cellular will need a 5G network to achieve their full potential.”

4. Long-Range Wireless Power

First-generation wireless power systems have not delivered the revolutionary user experience that manufacturers had hoped for. In terms of the user experience, the need to place devices on a specific charger point is only slightly better than charging via cable. However, several new technologies can charge devices at ranges of up to one meter or over a table or desk surface.

“Long-range wireless power could eventually eliminate power cables from desktop devices such as laptops, monitors and even kitchen appliances. This will allow for completely new designs of work and living spaces,” Mr. Jones said.

5. Low-Power Wide-Area (LPWA) Networks

LPWA networks provide low-bandwidth connectivity for IoT applications in a power-efficient way to support things that need a long battery life. They typically cover very large areas, such as cities or even entire countries. Current LPWA technologies include Narrowband IoT (NB-IoT), Long Term Evolution for Machines (LTE-M), LoRa and Sigfox. The modules are relatively inexpensive, so IoT manufacturers can use them to enable small, low-cost, battery-powered devices such as sensors and trackers.

6. Wireless Sensing

The absorption and reflection of wireless signals can be used for sensing purposes. Wireless sensing technology can be used, for example, as an indoor radar system for robots and drones. Virtual Assistants can also use radar tracking to improve their performance when multiple people are speaking in the same room.

“Sensor data is the fuel of the IoT. Accordingly, new sensor technologies enable innovative types of applications and services,” Mr. Jones said. “Systems including wireless sensing will be integrated in a multitude of use cases, ranging from medical diagnostics to object recognition and smart home interaction.”

7. Enhanced Wireless Location Tracking

A key trend in the wireless domain is for wireless communication systems to sense the locations of devices connected to them. High-precision tracking to around one-meter accuracy will be enabled by the forthcoming IEEE 802.11az standard and is intended to be a feature of future 5G standards.

“Location is a key data point needed in various business areas, such as consumer marketing, supply chain and the IoT. For example, high-precision location tracking is essential for applications involving indoor robots and drones,” said Mr. Jones.

8. Millimeter Wave Wireless

Millimeter wave wireless technology operates at frequencies in the range of 30 to 300 gigahertz, with wavelengths in the range of 1 to 10 millimeters. The technology can be used by wireless systems such as Wi-Fi and 5G for short-range, high-bandwidth communications (for example, 4K and 8K video streaming).

9. Backscatter Networking

Backscatter networking technology can send data with very low power consumption. This feature makes it ideal for small networked devices. It will be particularly important in applications where an area is already saturated with wireless signals and there is a need for relatively simple IoT devices, such as sensors in smart homes and offices.

10. Software-Defined Radio (SDR)

SDR shifts the majority of the signal processing in a radio system away from chips and into software. This enables the radio to support more frequencies and protocols. The technology has been available for many years, but has never taken off as it is more expensive than dedicated chips. However, Gartner expects SDR to grow in popularity as new protocols emerge. As older protocols are rarely retired, SDR will enable a device to support legacy protocols, with new protocols simply being enabled via software upgrade.

 

Wireless Communication

:

Wireless Communication is the fastest growing and most vibrant technological areas in the communication field. Wireless Communication is a method of transmitting information from one point to other, without using any connection like wires, cables or any physical medium.

Generally, in a communication system, information is transmitted from transmitter to receiver that are placed over a limited distance. With the help of Wireless Communication, the transmitter and receiver can be placed anywhere between few meters (like a T.V. Remote Control) to few thousand kilometres (Satellite Communication).

We live in a World of communication and Wireless Communication, in particular is a key part of our lives. Some of the commonly used Wireless Communication Systems in our day – to – day life are: Mobile Phones, GPS Receivers, Remote Controls, Bluetooth Audio and Wi-Fi etc.

What is Wireless Communication?

Communication Systems can be Wired or Wireless and the medium used for communication can be Guided or Unguided. In Wired Communication, the medium is a physical path like Co-axial Cables, Twisted Pair Cables and Optical Fiber Links etc. which guides the signal to propagate from one point to other.

Such type of medium is called Guided Medium. On the other hand, Wireless Communication doesn’t require any physical medium but propagates the signal through space. Since, space only allows for signal transmission without any guidance, the medium used in Wireless Communication is called Unguided Medium.

If there is no physical medium, then how does wireless communication transmit signals? Even though there are no cables used in wireless communication, the transmission and reception of signals is accomplished with Antennas.

Antennas are electrical devices that transform the electrical signals to radio signals in the form of Electromagnetic (EM) Waves and vice versa. These Electromagnetic Waves propagates through space. Hence, both transmitter and receiver consists of an antenna.

What is Electromagnetic Wave?

Electromagnetic Waves carry the electromagnetic energy of electromagnetic field through space. Electromagnetic Waves include Gamma Rays (γ – Rays), X – Rays, Ultraviolet Rays, Visible Light, Infrared Rays, Microwave Rays and Radio Waves. Electromagnetic Waves (usually Radio Waves) are used in wireless communication to carry the signals.

An Electromagnetic Wave consists of both electric and magnetic fields in the form of time varying sinusoidal waves. Both these fields are oscillating perpendicular to each other and the direction of propagation of the Electromagnetic Wave is again perpendicular to both these fields.

Advantages of Wireless Communication

There are numerous advantage of Wireless Communication Technology, Wireless Networking and Wireless Systems over Wired Communication like Cost, Mobility, Ease of Installation, and Reliability etc.

Cost

The cost of installing wires, cables and other infrastructure is eliminated in wireless communication and hence lowering the overall cost of the system compared to wired communication system. Installing wired network in building, digging up the Earth to lay the cables and running those wires across the streets is extremely difficult, costly and time consuming job.

In historical buildings, drilling holes for cables is not a best idea as it destroys the integrity and importance of the building. Also, in older buildings with no dedicated lines for communication, wireless communication like Wi-Fi or Wireless LAN is the only option.

Mobility

As mentioned earlier, mobility is the main advantage of wireless communication system. It offers the freedom to move around while still connected to network.

Ease of Installation

The setup and installation of wireless communication network’s equipment and infrastructure is very easy as we need not worry about the hassle of cables. Also, the time required to setup a wireless system like a Wi-Fi network for example, is very less when compared to setting up a full cabled network.

Reliability

Since there are no cables and wires involved in wireless communication, there is no chance of communication failure due to damage of these cables which may be caused by environmental conditions, cable splice and natural diminution of metallic conductors.

Disaster Recovery

In case of accidents due to fire, floods or other disasters, the loss of communication infrastructure in wireless communication system can be minimal.

Disadvantages of Wireless Communication

Even though wireless communication has a number of advantages over wired communication, there are a few disadvantages as well. The most concerning disadvantages are Interference, Security and Health.

Interference

Wireless Communication systems use open space as the medium for transmitting signals. As a result, there is a huge chance that radio signals from one wireless communication system or network might interfere with other signals.

The best example is Bluetooth and Wi-Fi (WLAN). Both these technologies use the 2.4GHz frequency for communication and when both of these devices are active at the same time, there is a chance of interference.

Security

One of the main concerns of wireless communication is Security of the data. Since the signals are transmitted in open space, it is possible that an intruder can intercept the signals and copy sensitive information.

Health Concerns

Continuous exposure to any type of radiation can be hazardous. Even though the levels of RF energy that can cause the damage are not accurately established, it is advised to avoid RF radiation to the maximum.

Basic Elements of a Wireless Communication System

A typical Wireless Communication System can be divided into three elements: the Transmitter, the Channel and the Receiver.

The Transmission Path

A typical transmission path of a Wireless Communication System consists of Encoder, Encryption, Modulation and Multiplexing. The signal from the source is passed through a Source Encoder, which converts the signal in to a suitable form for applying signal processing techniques.

The redundant information from signal is removed in this process in order to maximise the utilization of resources. This signal is then encrypted using an Encryption Standard so that the signal and the information is secured and doesn’t allow any unauthorised access.

Channel Encoding is a technique that is applied to the signal to reduce the impairments like noise, interference, etc. During this process, a small amount of redundancy is introduced to the signal so that it becomes robust against noise. Then the signal is modulated using a suitable Modulation Technique (like PSK, FSK and QPSK etc.) , so that the signal can be easily transmitted using antenna.

The modulated signal is then multiplexed with other signals using different Multiplexing Techniques like Time Division Multiplexing (TDM) or Frequency Division Multiplexing (FDM) to share the valuable bandwidth.

The Channel

The channel in Wireless Communication indicates the medium of transmission of the signal i.e. open space. A wireless channel is unpredictable and also highly variable and random in nature. A channel maybe subject to interference, distortion, noise, scattering etc. and the result is that the received signal may be filled with errors.

The Reception Path

The job of the Receiver is to collect the signal from the channel and reproduce it as the source signal. The reception path of a Wireless Communication System comprises of Demultiplexing , Demodulation, Channel Decoding, Decryption and Source Decoding. From the components of the reception path it is clear that the task of the receiver is just the inverse to that of transmitter.

The signal from the channel is received by the Demultiplexer and is separated from other signals. The individual signals are demodulated using appropriate Demodulation Techniques and the original message signal is recovered. The redundant bits from the message are removed using the Channel Decoder.

Since the message is encrypted, Decryption of the signal removes the security and turns it into simple sequence of bits. Finally, this signal is given to the Source Decoder to get back the original transmitted message or signal.

Types of Wireless Communication Systems

Today, people need Mobile Phones for many things like talking, internet, multimedia etc. All these services must be made available to the user on the go i.e. while the user is mobile. With the help of these wireless communication services, we can transfer voice, data, videos, images etc.

Wireless Communication Systems also provide different services like video conferencing, cellular telephone, paging, TV, Radio etc. Due to the need for variety of communication services, different types of Wireless Communication Systems are developed. Some of the important Wireless Communication Systems available today are:

• Television and Radio Broadcasting
• Satellite Communication
• Radar
• Mobile Telephone System (Cellular Communication)
• Global Positioning System (GPS)
• Infrared Communication
• WLAN (Wi-Fi)
• Bluetooth
• Paging
• Cordless Phones
• Radio Frequency Identification (RFID)

There are many other system with each being useful for different applications. Wireless Communication systems can be again classified as Simplex, Half Duplex and Full Duplex. Simplex communication is one way communication. An example is Radio broadcast system.

Half Duplex is two way communication but not simultaneous one. An example is walkie – talkie (civilian band radio). Full Duplex is also two way communication and it is a simultaneous one. Best example for full duplex is mobile phones.

The devices used for Wireless Communication may vary from one service to other and they may have different size, shape, data throughput and cost. The area covered by a Wireless Communication system is also an important factor. The wireless networks may be limited to a building, an office campus, a city, a small regional area (greater than a city) or might have global coverage.

 

Microprocessor

The microprocessor is the central unit of a computer system that performs arithmetic and logic operations, which generally include adding, subtracting, transferring numbers from one area to another, and comparing two numbers. It's often known simply as a processor, a central processing unit, or as a logic chip. It's essentially the engine or the brain of the computer that goes into motion when the computer is switched on. It's a programmable, multipurpose device that incorporates the functions of a CPU (central processing unit) on a single IC (integrated circuit).

Working

A microprocessor accepts binary data as input, processes that data, and then provides output based on the instructions stored in the memory. The data is processed using the microprocessor's ALU (arithmetical and logical unit), control unit, and a register array. The register array processes the data via a number of registers that act as temporary fast access memory locations. The flow of instructions and data through the system is managed by the control unit.

Benefits of a Microprocessor

But computer systems aren't the only devices that use microprocessors. Everything from smartphones to household appliances to cars use microprocessors these days. Here are a few reasons why microprocessors are so widely used:

• They don't cost a lot - Due to their use of IC technology, microprocessors don't cost much to produce. This means that the use of microprocessors can greatly reduce the cost of the system it's used in.
  
  
• They are fast - The technology used to produce modern microprocessors has allowed them to operate at incredibly high speeds--today's microprocessors can execute millions of instructions per second.
  
  
• They consume little power - Power consumption is much lower than other types of processors since microprocessors are manufactured using metal oxide semiconductor technology. This makes devices equipped with microprocessors much more energy efficient.
  
  
• They are portable - Due to how small microprocessors are and that they don't consume a lot of power, devices using microprocessors can be designed to be portable (like smartphones).
  
  
• They are reliable - Because semiconductor technology is used in the production of microprocessors, their failure rate is extremely low.
  
  
• They are versatile - The same microprocessor chip can be used for numerous applications as long as the programming is changed, making it incredibly versatile.

Categories of Microprocessors

Microprocessors can be classified in different categories, as follows:.

Based on Word Length

Microprocessors can be based on the number of bits the processor's internal data bus or the number of bits that it can process at a time (which is known as the word length). Based on its word length, a microprocessor can be classified as 8-bit, 16-bit, 32-bit, and 64-bit.

 

Reduced Instruction Set Computer (RISC)

RISC microprocessors are more general use than those that have a more specific set of instructions. The execution of instructions in a processor requires a special circuit to load and process data. Because RISC microprocessors have fewer instructions, they have simpler circuits, which means they operate faster. Additionally, RISC microprocessors have more registers, use more RAM, and use a fixed number of clock cycles to execute one instruction.

 

Complex Instruction Set Computer

CISC microprocessors are the opposite of RISC microprocessors. Their purpose is to reduce the number of instructions for each program. The number of cycles per instruction is ignored. Because complex instructions are made directly into the hardware, CISC microprocessors are more complex and slower. CISC microprocessors use little RAM, have more transistors, have fewer registers, have numerous clock cycles for each instruction, and have a variety of addressing modes.

 

Special Purpose Processors

Some microprocessors are built to perform specific functions. For example, coprocessors are used in combination with a main processor, while a transputer is a transistor computer: a microprocessor that has its own local memory.

Evolution of Microprocessors

We can categorize the microprocessor according to the generations or according to the size of the microprocessor:

First Generation (4 - bit Microprocessors)

The first generation microprocessors were introduced in the year 1971-1972 by Intel Corporation. It was named Intel 4004 since it was a 4-bit processor.

It was a processor on a single chip. It could perform simple arithmetic and logical operations such as addition, subtraction, Boolean OR and Boolean AND.

I had a control unit capable of performing control functions like fetching an instruction from storage memory, decoding it, and then generating control pulses to execute it.

Second Generation (8 - bit Microprocessor)

The second generation microprocessors were introduced in 1973 again by Intel. It was a first 8 - bit microprocessor which could perform arithmetic and logic operations on 8-bit words. It was Intel 8008, and another improved version was Intel 8088.

Third Generation (16 - bit Microprocessor)

The third generation microprocessors, introduced in 1978 were represented by Intel's 8086, Zilog Z800 and 80286, which were 16 - bit processors with a performance like minicomputers.

Fourth Generation (32 - bit Microprocessors)

Several different companies introduced the 32-bit microprocessors, but the most popular one is the Intel 80386.

Fifth Generation (64 - bit Microprocessors)

From 1995 to now we are in the fifth generation. After 80856, Intel came out with a new processor namely Pentium processor followed by Pentium Pro CPU, which allows multiple CPUs in a single system to achieve multiprocessing.

Other improved 64-bit processors are Celeron, Dual, Quad, Octa Core processors.