Wednesday, October 9, 2019

The A - Z Guide Of GSM ARCHITECTURE

In this article, we will briefly go through the Architecture of GSM. The GSM architecture consists of four major interconnected elements which are
 
  1. Mobile Station (MS)
  2. Base Station Subsystem (BSS)
  3. Network Subsystem (NSS)
  4. Operation and Maintenance Center (OMC)
gsm-architecture


1. Mobile Station - Ms

This part of the Gsm network deals directly with users and allow them to initiate their desire request, like making a voice call or sending a short message. Ms consists of two entities Mobile Equipment (ME) and the Subscriber Identity Module (SIM).

Mobile Equipment (ME)

MS is a device used to access the network. It holds a unique number that is permanently attached to it and known as International Mobile Equipment Identity (IMEI). IMEI allows a network to locate its user on the system, which is later used in HLR and VLR databases.

Subscriber Identity Module (SIM)

A small chip also is known as "sim card". Sim card can be plugged in the Mobiel Equipment or also come along with ME. A unique number is known as International Mobile Subscriber Identity (IMSI), also attached to a sim card. Mobile equipment is only an electronic device without a sim card, and it can perform only a few essential functions.

2. Base Station Subsystem - BSS

The BSS is also known as Radio Network because BSS includes all essential nodes and functionalities that connect Mobile Station to the network using air interface. Base Station Subsystem includes Base Transceiver Station (BTS), Base Station Controller (BSC), and Transcoder Sub‐Multiplexer (TCSM).

Base Station Subsystem (BTS)

BTS is responsible for managing the interface between the mobile station and the network. That's why BTS acts as a hub for the entire Network. Transmission of sending and receiving signals are usually done with antennas having 120° sectors. Some of the vital function of the Base Station Subsystem (BTS) are
  • Communicate with both Mobile Station (MS) and Base Station Controller (BSC)
  • Encrypting, Modulating, Encoding, Multiplexing, and feeding RF signals to the antenna.
  • Measures quality and power of the received signal
  • Decrypting, Decoding and equalizing received signals
  • Synchronization of both Time and Frequency
  • Frequency Hoping
  • Transcoding and Rate adaptation

Base Station Controller (BSC)

The primary function of BSC is to control radio resources, especially the base stations (BTS). It also acts as an interface between a base station subsystem (BSC) and a Mobile Switching Centre (MSC). BSC has three primary functions, which include performing handovers or handoffs, controls frequency hopping, and manages radio resources for BTS. A few other tasks are listed below.
  • Provide an interface for MSC to communicate with the mobile station
  • Responsible for the control of transmitted power.
  • Allocating time slot and frequency to MS in its area
  • Determinations of time-delay of signals received from the Mobile station
  • Initiating and terminating calls setups
  • Synchronization of both Time and Frequency
  • Provide an interface for the operations and maintenance center (OMC)
  • Security, alarms, etc

The Transcoders

Basically, Transcoders are part of BSS but sometimes physically located in MSC. Although they are installed in the close of range of  MSC. The primary purpose of transcoders is to save bandwidth and reduce the network in terms of cost. Transcoders compact data to reduce the rate at which data is transmitted. It compresses 64kbps data into 16kbps and vise Versa.

3. Network Subsystem - NSS

Network Switching Subsystem is considered the core of the GSM Network. NSS performs all switching functions and allows other telecommunication networks like Public Switch Network (PSTN), international networks to communicate with GSM users. NSS contains large databases that help in performing switching functions.
NSS include
  • Mobile Switching Center (MSC)
  • Home location register (HLR)
  • Visitor location register (VLR)
  • Authentication Center (AUC)
  • Equipment identity register (EIR)

Mobile Switching Centre (MSC)

MSC is the central component of NSS and is known as the brain of the GSM network. A network usually contains more than once MSC. The primary purpose of MSC is call-switching with other mobile/fixed networks. It also has some additional functions like registration, authentication, handoffs, routing roaming calls, and providing different interfaces.
The summarize important essential function carried out by MSC are

Call processing: controls data/voice call setup, Handoffs, and subscriber validation and location.
Operations and maintenance support: Includes the management of radio resources and database, registration, location updating, traffic metering, and measurement.
Interworking: Provide the interface for PSTN networks, Fix networks, and other supported systems.
Billing: Collecting and processing subscriber billing data.

Home Location Register (HLR)

HLR is a permanent storage database that includes subscriber information like service profile, activity status, and location information. When a user by a new SIM, their data is stored in HLR. It contains IMSI, MSISDN, Service subscription information (prepaid/postpaid), Billing information, roaming restrictions, supplementary services, etc.

Visitor Location Registrar (VLR)

The primary purpose of the VLR database is to reduce signaling between MSC and HLR, thus putting a less burden on HLR. VLR temporary store information of the visiting subscriber. VLR includes the following information
  • Temporary mobile subscriber identity (TMSI)
  • Location area identity (LAI)
  • Mobile Station Roaming Number (MSRN)
  • Cell Phone status

Authentication Center (AUC)

AUC performs an authentication function to protects against intruders in the air interface.
Generally associated with HLR required to access and update subscriber data continuously.
The authentication process will habitually process begins whenever a user initializes any process in the system. AUC uses authentication keys and algorithms like (SRES, RAND, KC, ETC) to provide extra security.

Equipment identity register (EIR)

The Equipment Identity Register consists of IMEIs data distributed in three list
White List:  List of IMEIs that are allowed to use the network without any trouble.
Gray List: This list consists of IMEIs that have received a warning message for using faulty software or equipment. Such IMEIs can be possibly get banned at any time.
Black List: IMEIs that are banned for illegal activity or for some other reason. Such IMEIs are not allowed to use network resources. The primary purpose of creating these lists is to deal with fraudulent, stolen, and banned devices. 

4. Operations and maintenance center (OMC)

Nowadays, networks are getting more complex; that is why they require more attention because no one wants a system that has up and downs. Operation and Maintenance Centre (OMC) is used to make sure that the network runs smoothly. OMC performs four primary operations which is
  • Network Monitoring
  • Network Measurement
  • Network Development
  • Fault management
OMC will generate alarms in case of error or fault is detected. Some errors (software related) are fixed automatically, and others would require a visit. OMC collects data for analysis, which plays a vital role in network optimization.

Reference Book: 
1. Mishra, Ajay R.-Fundamentals of network planning and optimization 2G_3G_4G _ evolution to 5G-Wiley (2018)
2. Sauter, Martin "From GSM to LTE‐Advanced Pro and 5G"
3. Gottapu Sasibhushana Rao "Mobile CellularCommunication"

Tuesday, October 8, 2019

Handoffs or Handover process in cellular communication

What are Handoffs or Handover

In cellular communication, the coverage is divided into many cells, and the base station was installed to provide coverage to the cells. Users in the coverage area served by the specified base station by providing a specific channel. A question comes in mind that.

What will happen if a user on a call leaves the coverage area and moves to another cell served by another base station?

Or

The quality of established a link between Mobile Station and Base station decreasing continuously.

In such a situation, a technique is used to transfer a call from one cell to another cell served by another base station. So we can define Handover as
The switching of an ongoing call to a different channel or cell (base station) is known as handover or handoff.
Handovers-Handoffs-in-telecommunication

Why handoff and what parameters required for successful handoff?

Suppose you are on a call with the boss or client receiving necessary instruction while traveling in a subway, and your call gets disconnected, or you start receiving disturbing noise. Ah damn, no one wants such a network, and you will decide to move another network. Usually, this happens when distances between the mobile station and the base station are not quite enough to receive the threshold signal. That's why handover gains attraction of network engineers. Some primary reason is listed below

  1. If signals between the mobile station and base station go down from threshold value, then handoff is required.
  2. It will allow the mobile station to continue voice calls while moving in a high-speed vehicle.
  3. Less call drop and congestion rate, which increases network performance.

As we learn above about the importance of handover, network engineers need to take care of specific parameters to implement a handoff system. That includes

  1. Availability of Channels.
  2. The base station must have information about the signal strength of the connected mobile station.
  3. Signal Strength of nearby base stations.

Process of Handoff/handover

Handoff or handover has different types, and each individual is somehow different from each other. Handover takes place after verifying specific parameters, and it cannot be done in one or two steps. The below-described method is the general format of handover.
Proper-Handover-process-in-telecommunication
  1. Mobile Station monitors signal strength regularly of the adjacent base station.
  2. Its keep updating connected base station about receive signal strength.
  3. In case of signals drop and reach to a minimum acceptable level, then MS acknowledge base station.
  4. Base station checks channel availability and also inform nearby base station about new incoming Ms.
  5. The old base station sends MS information to a new base station.
  6. When a new base station receives MS detail than the old base station free channel for other users.
  7. Now the mobile station is served by the new base station.
Reference Book:
Theodore S Rappaport "Wireless Communications- Principles And Practice"
Gottapu Sasibhushana Rao "Mobile Cellular Communication"

Friday, September 27, 2019

Why -48 volt used in Telecom Equipments?

"Why -48 volt used in telecom equipment?"
Many people asked this valuable but straightforward question on different platforms. Also, an interviewer can ask you this simple question. So it is better to make yourself ready for such types of problems. I have done a little research and gather all the information I found you can see below.
ethernet cable
Ethernet cable
Top 5 Reason Behind -48 volt used in Telecom Equipments
  1. As per Columb's law, like charges repel each and we know that Lighting or Thunders is 95% negatively charged and 5% positive. In this way, we have the chance to save telecommunication devices from heavenly light by using negative voltage.
  2. The positive voltage causes more corrosion in the metal than the negative energy. ( What is corrosion? Corrosion is a natural process that gradually destroys metals through chemical or electrochemical reactions with their environment. )
  3. To avoid leakage currents to ground generated by moisture do not electroplate away the copper in the wires.
  4. +48 voltage offers more fluctuation as compared to -48 voltage.
  5. A negative voltage is considered safer for the human body as compared to positive voltage while working in the field.
That's for all of you other reason then that please don't forget comment below ... Love

Wednesday, May 22, 2019

What is means by GSM BURST and its types

GSM BURST

As we know the GSM network uses the time slot to transmit information and Burst is a type of information that contains in particular time slots of GSM network. Bursts are designed to fit in these time slots to transmit information. GSM consist of five bursts which are
  1. Normal Burst 
  2. Synchronization Burst 
  3. Frequency Correction Burst 
  4. Access Burst
  5. Dummy Burst

1. Normal Burst

Gsm-Normal-Burst
Gsm Normal Burst

Typical burst contains 114 bit of valuable information and divided into two groups 57 bits each. These bits contain signaling and user data.
Stealing flag helps to indicate special events like Handovers etc. It also helps to verify that whether the block contains data or is stolen.
Tail bits found at the start and end of data. It is used as a guard time. Tail bit are three (3) in number and set to zero and placed at the beginning and at the end of a burst.
The Guard Period (GP) helps to avoid overlapping with other bursts that may carry some additional information. The length of the Guard Period is 8.25 bits.
The training sequence has a length of 26 bits and is used to synchronizes the receivers, hence this effects multipath propagation. The Training sequence helps in adapting the receiver parameters to the current path propagation.

2. Synchronization Burst:

GSM-Synchronization-Burst
GSM Synchronization Burst

As its name suggests, this burst is used to synchronize Mobile Station
and BTS using a synchronization channel (SCH). The function of both Tail and Guard bit the same as to mention above in Normal Burst.
Coded Data tells about TDMA frame number.
The training sequence tells about the base station number.
Mobile Station at first demodulates synchronization burst. That's why the length is 64 bits. It helps to avoid Larger multipath delay spreads.

3. Frequency Correction Burst

Frequency-Correction-Burst
Frequency Correction Burst

The most simple format of all the bursts is used for the frequency correction burst, which is transmitted only in the frequency correction channel (FCCH).
All 148 bits are coded with zeros and frequency, which is a pure sine wave (GMSK modulator Produce sine wave) is transmitted that enables mobile to synchronize its frequency with the master frequency.
Frequency correction burst appears on frequency correction channel.

4. Random Access Burst:

Random-Access-Burst
Random Access Burst
Random Access Burst has a unique format as compared to others because of its special task. When first switched on, A mobile station (MS) uses the access burst for initial access to a BTS. The first job is to synchronize itself with BTS in frequency and time using synchronization burst.
Burst has a length of 88 bits plus 68.25 guard bits. The access burst length is set large because to make it possible, that access burst appears at the BTS. It can be increased more by adding a guard band of 68.25.

5. Dummy Burst:

GSM-Dummy-Burst
GSM Dummy Burst
Dummy burst contains no user data information. Dummy is used to fill out idle time slots on the channel when a user is not sending any data. Dummy burst sent by the base station on the base channel. When a mobile station is turned on, it easily discovers the base channel. The pseudo-random bit sequence is used to avoid accidental confusion with frequency correction burst.

Thursday, March 7, 2019

4 Things you need to Improve Coverage and Capacity in cellular system

The improvement in wireless technology increased the number of cellular users to a massive level. This results in more wireless services, but the number of channels assigned to a cell is not enough to support the user in some areas like cities, which are usually more populated.

To overcome this problem, cellular design techniques are needed like cell splitting, Sectoring, Microcell, and Repeaters for range extension to support the required number of users in such areas. However, these techniques increase the number of Base Station and sometimes also increased the number of the cluster in the coverage area.
  1. Cell Splitting 
  2. Sectoring
  3. Microcell Zone concept
  4. Repeaters

1. Cell Splitting 

This technique is used to divide a Congested cell into a smaller cell or microcell, each with its own base station. To do this, we need to lower the antenna's height and transmitting power. I know a question will arise in your mind that

How can cell splitting increase improve coverage and capacity in a cellular system?

The answer is cell splitting increases the number of times that channels are reused.

How?

New cells of a shorter radius were installed between the existing cells. Where each cell has its own base station installed on the corner of the cell that increases the number of channels per unit area.

Now let’s make it more clear using an example. Take a look at the below image, imagine if the radius of each cell was cut in half. This will increase the number of cells approximately four times the original cell number, and it will also increase the number of clusters that increase the number of capacity and channels. Remember that while adding a smaller cell, also take care frequency reuse plan.
Cell-splitting-concept-in-cellular-communication-Micro-zone
Micro-zone cell concept 

Transmitting Power for new cell


As we know that the size of the new cells is smaller, so the transmitting power also will be reduced. The power of the original cell will be cut in half as a cell divided by half. You can find the transmitted power of the original cell by examining the received power (Pr) at original cell boundaries. It will help to maintain the frequency reuse plan.

Practical Scenario of cell splitting


The practical scenario of cell splitting is a bit different, then it is mention above, or you read somewhere on the internet. All cells cannot be split at the same time because a cell in real life is not of the same size. Even it is hard for network engineers to find the real estate of the cell to split it further. That is why network engineers take too careful to keep the distance between co-channel. Also increasing base station in a region increase the ratio of handover, which is usually controlled using an umbrella approach.

A question arises can we use one large power for all newly define microcell?

The answer is simply No.

Why?

When smaller transmit power is used, then many parts in the larger cell will remain left Pockets. And in the second case, when a lager transmits power is used, then some channel in a cell will be challenging to separate from their co-channels. In such a scenario, a channel of old divide into two groups. One group served a smaller cell, and the second group is used by the larger cell for handoff purposes. The process of cell splitting continues when required more channels, and one stage comes that all coverage areas will be served by smaller cells.

2. Sectoring

Unlike cell splitting, Sectoring is another way to increase both capacity and coverage of the cellular system. Sectoring does not require changing cell size, but it will reduce the number of clusters. As the number of clusters decreases, the frequency reuse factor will increase.

To make this possible, the relative interface should be reduced without affecting the transmitted power. One way to minimize the co-channel interface effectively is to replace Omni-directional antennas into directional antennas. The replaced directional antenna will radiate in its own specified sector, which results in less interference as compared to Omni-directional antennas.

So we can define sector as
The technique used to increase system capacity and decrease co-channel interference by using a directional antenna is known as sectoring.


How many Sectors does a cell have?


Usually, cells are divided into three sectors (120 or 60 degrees). You can see the image below as an example where a cell is divided into three (3) and six (6) sectors.
Cell-sectors-in-cellular-system
Cell Sector

Remember that in sectoring, channels are dedicated to the specified sector and used within a particular sector. Now let’s understand it with an example. Take a look at the below image, you will find a cell label “5” at the center of the picture. It also has 3 co-channel on both left and right side center cell label “5”. Now you can see only two sectors radiate in the direction of the center cell. So this means out of 6 sectors, the center cell will experience interference on the forward link from only two left side sectors. In a practical scenario, interference can be further improved by down-tilting the antennas.
Cell-Sectoring-concept-in-cellular-system
Cell Sectoring concept in a cellular system

To summarise, sectoring improves coverage and capacity in a cellular system by radiating in a specific direction using directional antennas and reducing the number of clusters. However, sectoring increases the number of antennas.

The Draw Backs of Sectoring


Sectoring also has drawbacks, which include an increasing number of the antenna. Furthermore, decreasing coverage area in sectoring will increase the number of handoffs. This increases the burden on the Mobile Switching Center. However, handoffs are not the real problem because several modern base stations are allowed to control handovers in a cell from one sector to another without interrupting MSC.

The major problem is the loss of traffic due to decreased trunking efficiency. Sectoring uses more than one antenna and has a dedicated specific number of channels. This breaks up results, reducing trunking efficiency.

3. Microcell Zone Approach

This is another pretty awesome technique used to increase capacity and improve coverage of the cellular system. As we learn, sectoring increase the number of handoffs, which puts an extra burden on MSC. The microcell zone technique is then presented to overcome the handoffs issue. This approach is based on a microcell for seven cell reuse.

In this proposed scheme, the cell is made from the combination of many zones and the single base station. Typically 3 zones are used, which shown in the below image.
Microzone-cell-concept-in-cellullar-system
Microzone cell concept in cellullar system

These zones are connected to a single base station through Co-axial cable, Optical fiber, and a Microwave link. Mobile users received the strongest signal within the cell. Antennas in the microcell are installed at the outer edge of the cell.

Handoffs are avoided by switching channels between zone sites. This means whenever a user moves from one zone to another zone within the cell, the user receives the same channel. Co-channel is reduced by replacing a large central base station to the small, lower-powered transmitter on the edge of the cell. The reduction of interference also increased capacity, and trunking efficiency is not affected in the microcell.

4. Repeaters

In many cases, a large building, mountains, or any other obstacle makes it hard for the service provider to provide coverage efficiently in such areas. For the solution of such problems, a device is used known as a repeater.
Repeater Concept in Cellular system
Two users connected using a repeater

A repeater is actually a bidirectional radio transmitter. This means that it send and receive simultaneously from a particular base station. A repeater can be installed anywhere accordingly because of its size. When the repeater received a signal from the base station, it amplifies and radiates in the required coverage area.

Remember that noise and interference in the original signal also radiate along with the newly generated signals.

Note that the repeater does not add capacity to the system. It is only the way to provide coverage to the area block by obstacles. It is also used to provide inside the buildings.

Reference Book:
1) Wireless Communications- Principles and Practice by Theodore S Rappaport
2) Mobile Cellular Communication Gottapu Sasibhushana Rao

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Thursday, February 28, 2019

How channel are assigned to users in cellular System

Channel Assignment Strategies

As a communication student or network engineer, you must know that the radio spectrum is not enough to support the required cellular user. For this reason, a different technique like FDMA, TDMA, OFDMA, are adapted for efficient reuse of frequency having minimum interference. Channel created using these techniques also need to be assigned in proper manners. For this reason, a group of channels is allocated to each individual base station. Many methods are adapted to attach the given channel to users because it has a significant impact on network performance. Even as I said, this also helps in the reduction of co-channel interference. The channels assignment method is either fix or dynamic.
Channel-Assignment-Techniques
Channel Assignment Methods

Also Read:
 

1. Fixed Channel Assignment

Using this technique, a set of voice channels is allocated to a cell. The user gets a channel when a call attempt is made. A user is always serving with unused channels. In case all channels are busy then the call attempt is blocked, and the user needs to wait until the channel gets free. This means blocking probability in fixed channel assignment is high, which degrades the network performance.

2. Borrowed Channel Assignment

This is the modified version of the fixed channel technique. In this approach, a channel is acquired from the near base station when all channels are busy. Later this channel is returned back to the original base station when the call is ended. The borrowing process is supervised by a Mobile switching center (MSC) while taking care of the frequency Reuse plan.

3. Dynamic Channel Assignment

In a dynamic channel assignment technique, no channel is permanently allocated to a cell. Each time MSC allocates channels whenever a base station receives a call request. MSC takes care of specific parameters like frequency reuse distance and cost during channel assignment processing to avoid co-channel interference and decreased the ratio of call blocking. In the dynamic channel, the allocation channel is only assigned if that channel is not used in the current cell. Also, MSC makes sure that the channel is not used within a restricted area because to avoid co-channel interference. This results in a decreasing call blocking ratio and increase the capacity of the cellular system. However, Dynamic channel allocation puts some load on MSC because this technique requires real-time data simultaneously like channel occupancy, traffic distribution, and RSSI (radio signal strength indication). Also, this information requires space to store data.

Wednesday, February 27, 2019

Multiple Access Techniques in communication: FDMA, TDMA, CDMA

Multiple access techniques:

In a communication system, it is unrealistic and impossible to provide a single line to every separate user on the network. So what do we need to do? The answer is multiple access techniques. To overcome these problems, different types of methods implemented to share a single limited band or channel into various users.

In communication, Multiplexing Techniques used to allow many users to share together a finite amount of radio spectrum. Multiple access techniques are based on multiplexing techniques. It will also reduce the cost and complexity of the network. E.g., Old telephone system uses FDMA to allow multiple calls on the single line.

Also Read:

Communication channels can be a wireless spectrum, or cable connections are of a higher price. Different varieties of channels adapted to the mobile communication system, e.g., like time slots into frequency bands, frequency channels, and clear codes.
Basic Communication access techniques are
  1. FDMA
  2. WDMA
  3. OFDMA
  4. TDMA
  5. CDMA
  6. SSMA
  7. SDMA
  8. PDMA

1) FDMA (Frequency Division Multiple Access)

It is based on Frequency Division Multiplexing (FDM). It is the operation of splitting a single channel or bandwidth into several bands of frequency. In this channel access scheme, every user gets a separate sub-band of frequency like in FM radio. In this system, the user transmits data onto different frequencies at the same time.

It enables many users to transmit at the same time but using different frequency channels. It is necessary to keep the channel wider, to accept the signal spectra of the conveyance to propagate. FDMA is less complicated than TDMA, and it implemented in the narrowband system.
The most comprehensive cable system is approximately placed in every home, hotel, and restaurant, which provides a hundred live TV channels through only one coaxial cable( 4 MHz - 1 GHz). This bandwidth divides into many small wide bands to carry different channels. E.g., At the first one, the TV station requires a single 6-MHz band.

2) WDMA (Wavelength Division Multiple Access )

Based on wavelength division multiplexing (WDM) uses in fiber optic communication. At the multiplexer side, multiple lights combine into a single light source, and at the de-multiplexer, the light source converted again into various sources.
Wave-division-multiple-access-techniques
WDM working Principle

Using FDMA, the bandwidth of an Optical fiber can be subdivided. Different data source gets a different light frequency(referred to Wavelength, λ) to transmit. The FDMA technique in Optical Fiber is known as WDMA.

4) OFDMA (orthogonal frequency division multiplexing)

It is based on orthogonal frequency division multiplexing (OFDM) uses in the 4G mobile communication system. It is the process of accommodating many users in an assigned bandwidth using the OFDM modulation technique. OFDM Split given channel into multiple separate narrow-band channels at different bands to neglect interference and cross-talk occurrence.

5) TDMA (Time Division Multiple Access)

In this channel access scheme, every user gets a separate time slot to transmit data onto a standard frequency band. It allows users to send information or data using the same frequency band but different times slots.
TDMA-Frame-Structure
TDMA frame structure

In digital systems, we have no place for continuous transmission because the users never use the assigned bandwidth all the time. TDMA is based on Time Division Multiplexing and uses in Global System for Mobile Communication (GSM).

The primary purpose of introducing TDMA technology is to gain capacity over the FDMA system by providing one band or frequency channel to multiple users. In TDMA, we add time slots in frequency band/channel so that many users can use a single band/frequency.

Digital Bits transmitted in a specified time slot on a given frequency channel. Every user gets one or more than one-time slot per frame, and the entire bandwidth is available to use for a finite period as long as needed. For both transmission and reception, TDMA uses a different time slot.
TDMA slot must be synchronized. It uses the lower number of channels, that why interference can neglect.

6) Space-division multiple access (SDMA)

Space-division multiple access (SDMA) transmits different information in different physical areas. Examples include simple cellular radio systems and more advanced mobile systems that use directional antennas and power modulation to refine spatial transmission patterns.

7) Power-division multiple access (PDMA)

The power-division multiple access (PDMA) scheme is used to provide power to the users according to their needs. PDMA sets variable power transmission between the user in order to share the available power on the channel. For example, SCPC modems on a satellite transponder, where users get on-demand power.

References Book:
1. Frenzel, Louis E., Principles of Electronic Communication Systems, 3rd Edition, McGraw Hill, 2008.
2. Skylar, Bernard, Digital Communications, 2nd Edition, Prentice-Hall, 2001.
3. https://en.wikipedia.org/wiki/Channel_access_method

Introduction to Generation in mobile Communication 2G, 3G, 4G, 5G

Generation in Mobile Communication

In our daily life, Everyday, we face new technology which provides latest and better performance. Now a day 4G and 5G are most trends in the telecommunication system. In this article, we will learn about the generation of mobile communication.
Generation-in-mobile-communication-2G-2.5G-3G-4G-5G
Generation in mobile communication

The first generation 1G

The first generation of mobile network technology was the first analog network.  It was a completely analog system uses Frequency Division Multiplexing Techniques-FDM, and only voice call was supported. The first generation of mobile networks has no support for SMS and the Internet. The first generation does not use encryption techniques; that why information carried by the first generation is not secured.


A telephone call was the only way of communication to transmit the message to the other person. Because of low-frequency bandwidth and it used to take lots of energy to send data to far distance and also signal would get disturbed while reaching to the particular recipient.

Mobile phones were big and thick in size due to bigger antennas. Also, mobile phones had a lower battery life because data transmission used to take lots of energy. After 10 long years of 1G technology, 2G was launched.

Second Generation or 2G

2G or Second Generation is considered the most famous and influential in the communication world. It is also called the Global system of mobile communication (GSM).

In the era of the second generation, digital-based technology introduced that uses Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). It brings new technology like short message service (SMS) and E-mails.

Moreover, this development use in another technique like 2.5G or GPRS technology, which results in increased speed of data up to 144 kbps. After some, a new technology comes in the front line that is known as EDGE. That brings up new services like the multimedia message and Wireless Internet WAP. The speed improves to one Mbps.

Third generation 3G

A UMTS base supported technology which provides higher speed up to 2 Mbps or slightly exceeds. Due to the third generation, a new service has added, such as a video call.

3G improves as time spend, and new technology takes a step in like 3.5G and 3.7G. 3.5G technology involves HSDPA and HSUPA.

HSUPA provides data rate for uplink is 5.76 Mbit/s.

HSDPA achieve peak data rates of 14.0 Mbit/.

After 3.5G then 3.75G step in which can be named as HSPA+ technology. Due to this technology, the speed gain increases to 42.2 and 22 Mbit/s for download and upload, respectively. This just makes technology impressive. It makes the communication system more reliable and efficient.

The drawback of the third generation is that two costly and the highest consumption of energy.

Fourth Generation 4G

The fourth-generation or 4G is based on the standards of LTE and WiMAX, which offers speeds of up to 173 Mbps. 4G has been developed to reach 225 Mbps using new standards LTE-A, which enables you to download a movie at 800 MB in less than half a minute.

The fifth-generation 5G

This is upcoming technology and still under test condition and might be released commercially in 2020. 5G will offer 1Gbps internet speed.

Tuesday, February 26, 2019

What is LIFI technology and how it work?

Light of Fidelity (LIFI)

The LIFI Stand of “Light of Fidelity.” It was first discovered by German physicist “Harald Haas” from the University of Edinburgh. It was announced in 2011 and was considered the best innovation of the year. LIFI emits visible light rays to communicate with user computer and devices. It is based on the type of LED lamps.
LI-FI-technology-and-how-it-working-principle

How LIFI Work

The working principle of LIFI is the same as Fiber Optic Communications, where light travels in the form of Pulses through the fiber. Here is the same scenario that data will move in the form of light pulses (Binary Number), but the Optical medium will not require. It does not use radio wave-like Wi-Fi. It uses LED light for data transmission purposes. A photodetector device is necessary to decode light on the receiving side.

You can still use the internet while light decreases to some limits that it cannot be observed by eyes. But it will result in decreasing internet speed.

The speed of Lifi is 100 times greater than Wifi. The researchers measured speed for Lifi 10 Gbps while Wifi provides 100 Mbps. Wow, imagine data transfer with such speed. You can still use the internet while light decreases to some limits that it cannot be observed by eyes. But it will result in decreasing internet speed. Lifi uses the regular light bulb as a router to transmit its information. Lifi provides the same speed all the time as compare to Wifi because it depends on light, and Wifi uses radio waves that do not remain stable all the time.

The Advantages of LIFI

1) Safety

One of the main benefits of LIFI over wifi is that its area of the internet is limited to the field of light. This becomes harder for a hacker to reach your network. In the case of WIFI, radio waves spread all around and hard to control, this becomes easier for a hacker to spy on your network.

2) Speed

LIFI provide 100 times better the wifi because LIFI uses the frequency of waves is 1000 time greater than the frequency of radio wave uses by WIFI. It's mean that you can play online HD videos and high-quality Graphic games, etc.

3) Costs

Lifi does not need any specialized equipment that costs you a lot. Because it does not require significant infrastructure or larger towers etc.

4) Restricted Areas

In some sensitive areas like hospitals, airplanes, factories, people are restricted from the use of the internet because radio waves can cause damage. LIFI technology solves this problem and allows us to use the internet in such sensitive areas without causing any damage.

The Disadvantages of LIFI

1) Range

Now let start discussing the weakness of LIFI. One of the main drawbacks is Range. LIFI cannot penetrate walls, so if you are outside of the room, you will not access the internet.

Keep in mind that not only walls interrupt the signal, you should also care about everything that stops passing LED bulb light through it. That way, we will short of range using LIFI.

2) Another Light Source

The second disadvantage of LIFI is another light source. If you placing LIFI in such a place where light can reach from outside or within a room, so there is a chance of interference.

3) Late Night User

The last disadvantage is especially for Gammer and late-night internet users. They will not enjoy the internet at night because by dimming the lights will reduce the internet speed. That's why you should keep a bright full brighter to access the fast internet.