Showing posts with label Wireless system. Show all posts
Showing posts with label Wireless system. Show all posts

GSM repeater

We all know that each GSM full form user transmits data burst during a time slot that is assigned to it. The transmission of bursts occurs in a particular format called as in frame as GSM frame.

 1. GSM repeater 900 MHz(voice) - 200m2
  • Suitable for all European 900 MHz providers
  • Low energy consumption
  • Easy to install
  • Indoor coverage up to maximum 200 m2
  • The compact repeater for use at home and offices
  • Supplied with antennas, coaxial cable, and accessories
  • Free of interference
  • Art-Nr. RF E10C
2. GSM repeater 900 MHz(voice) - 300m2
  • Suitable for all European 900 MHz providers
  • Low energy consumption 
  • Easy to install
  • Indoor coverage up to maximum 300 m2
  • The compact repeater for use at home and office
  • Supplied with antennas, coaxial cable, and accessories
  • Free of interference
  • Art-Nr. RF10l - EGSM
3.  GSM band repeater 900+1800 MHz(voice form) - 700m2
  • Suitable for all European 900+1800 MHz providers
  • Low energy consumption 
  • Easy to install
  • Indoor coverage up to maximum 700 m2
  • The compact repeater for use at home and office
  • Supplied with antennas, coaxial cable, and accessories
  • Free of interference
  • Art-Nr. RF ED13-L
4. GSM TRI band repeater 900+1800+800 MHz(voice form) - 2000m2
  • Suitable for all European 900+1800+800 MHz providers
  • Low energy consumption 
  • Indoor coverage up to maximum 2000 m2
  • Compact repeater for use at home and office
  • Easy to install
  • Supplied with antennas, coaxial cable and accessories
  • Free of interference
  • Art-Nr. RF LED20-L
5.  Band GSM repeater all network (3G/4G/LTE internet form) - 2000m2
  • Suitable for all European network
  • Low energy consumption 
  • Easy to install
  • Indoor coverage up to maximum 2000 m2
  • Compact repeater for use at home and office
  • Supplied with antennas, coaxial cable and accessories
  • Free of interference
  • Art-Nr. RF 20-5B

GSM frequency

GSM frequency band listed below :

1.  GSM 850
  • Channel - 128-251
  • Up-link frequency - 824-849 MHz
  • Down-link frequency - 869-894 MHz
2. GSM 1800

  • Channel - 512-885
  • Up-link frequency - 1710-1785 MHz
  • Down-link frequency - 1805-1880 MHz
3 GSM 1900
  • Channel - 512-810
  • Up-link frequency - 1850-1910 MHz
  • Down-link frequency - 1930-1990 MHz
4. GSM 450/480
  • Up-link frequency - 450-458 MHz, 479-486 MHz
  • Down-link frequency - 460-468 MHz, 489-496 MHz

GSM network version

GSM stands for Global system for mobile communication (GSM) is a second generation digital mobile technology system, GSM Provides for the best mobile coverage within countries and across them all over the world.

GSM system used mobile delivered a data speed of 9.6 kb/s. The upgrade pushed up data speed around 48 kb/s.

GSM uses a variation of wireless technology used like time division multiplier access (TDMA) and code division multiple access (CDMA).

GSM operates at either the 900 MHz or much high-frequency band 1800 MHz.

UMTS R4 techniques are preferred as a mobile operator, especially for those with GSM legacy network. This techniques to evolve their existing 2G GSM network. It provides a smooth path to bridge legacy TDM based network to an IP based soft switch network.

The proposed evolution path in UMTS R4 suggests three layers structure solution to seamless coverage UMTS R4 core network with a GSM core network. So can achieve the all IP version and its capable of coverage with EPC and also an IMS.

 GSM networks :
  • T-Mobile
  • AT&T
  • Indigo wireless 
  • Pine cellular
  • TerreStar

GSM definition

GSM stands for Global system for mobile is a world first cellular system to specify as especially digital modulation. It is a second generation system (2G) developed in Europe.

GSM was developed to solve the fragmentation problems of the first generation networks and a developed new technology called 2G network.

GSM is a feature of rich digital wireless technology. It provides subscribers with a high quality digital wireless phone service and clarity also enhanced call security and privacy.

What is spread spectrum

Overview :

Spread spectrum is a one types of techniques it can be used for transmitting radio or telecommunication signal. The increasing demand of wireless communication have faced problems because of limited spectrum capacity and multi-path propagation. These problems can be minimized by spread spectrum communication.

Feature of spread spectrum :
  • Capability of multiple access
  • Resistant to jamming
  • It has the ability to resist multi path propagation 
  • Because of multi-path propagation. It provide  immunity to distortion
  • Higher channel capacity
  • It can not be intercepted by any unauthorized person
Spread spectrum model :

Figure shows the general block diagram of a spread spectrum digital communication system. so not let us talk about one by one block in spread spectrum model in detail.

To shown in figure the input is given to a channel encoder that produces the analog signal with narrow bandwidth at the center frequency.

The the signal is modulated by a spreading code or sequence. The spreading code is generated by pseudo noise or pseudo random number generator. 

Modulation increases the bandwidth of the signal to be transmitted. At the receiver end the digit sequence is used to demodulate the spread signal. The signal is sent to the recover the data.
Spread spectrum model
Advantages of spread spectrum :
  • Reduced cross talk interference
  • Inherent security
  • Hard to detect
  • Longer operating distance
  • Better voice quality 
  • Harder to jam
  • Interception of signal will be difficult
  • Privacy due to pseudo-random code
  • Co-existence
  • Less multi path fading
Processing gain of spread spectrum :

 The processing gain is defined as the factor by which the bandwidth of the message signal is increased.

 Processing gain : N = Bss / B

 Where, 
B = Message signal bandwidth
Bss = Spread spectrum signal bandwidth

 Types of spread spectrum : 
Application of Spread spectrum :
  • Prevent signal jamming
  • Cellular technology
  • Cell phones
  • Global positioning system
  • Wireless local are network security
  • Prevent Interference at specific frequency
  • In obtaining the message signal
You may also check it out difference between DSSS and FHSS

Advantages and disadvantages of frequency hopping spread spectrum

There are some of the advantages of frequency hopping spread spectrum (FH-SS) given below :
  • It has less distance effect.
  • Provide the greatest amount of spreading.
  • The bandwidth of these systems is large.
  • It has a short acquisition time.
  • Best discrimination against multi-path.
  • Very large bandwidth.
  • The synchronization is not greatly dependent on distance.
  • This system can be programmed to avoid some part of the spectrum.
  • It needs complex and costly digital frequency synthesizers are required to be used.
  • It needs error detection.
  • The processing gain is higher than that of a direct sequence spread spectrum.
  • This system is not useful for the range and range rate measurement.
  • The modulation scheme has become obsolete.
Some more advantages of FH/SS compared to DS/SS is given below :
  • FS/SS is less susceptible to be near-far problems than DS/SS.
  • The processing gain is higher than that of system DS/SS.
  • FH/SS can produce signals of wider bandwidth than DS/SS.
  • In FS/SS the problem of a relative power level of co-channel signals is not critical as than DS/SS.
Explore more information:

Advantages and disadvantages of GSM

GSM is a cellular technology used for transmitting mobile voice and data services developed by European Telecommunications standards Institutes to describe the protocols for second generation digital cellular networks. 

 GSM provides standard features like cell phone encryption, data networking, caller ID, call forwarding, call waiting, SMS and conferencing and it can be used in an application like home automation, mobile technology, toll collection, energy conversion etc. GSM has both advantages and disadvantages of which consumers should be aware of. 

Advantages of GSM :
  • More suitable network with robust features.
  • No roaming charges on International calls. 
  • Worldwide connectivity and extensive coverage. 
  • SAIC and DAIC techniques used in GSM provide very high transmission quality. 
  • The phone works based on the SIM card so that it is easy to change the different varieties of phones by users. 
  • GSM signals don't have any deterioration. 
  • Easy to integrate GSM with other wireless technology such as CDMA and LTE.
  • It has the ability to use repeaters. 
  • Because of the pulse nature of transmission talk time is generally high.
Disadvantages of GSM :
  • Bandwidth lag because of multiple users shares the same bandwidth so the transmission can encounter interface. 
  • It can interfere with certain electronics, such as hearing aids that are due to pulse transmission technology. As a result, many locations, such as hospitals, airports and petrol pumps require cell phones to be turned off. 
  • To increase coverage repeaters are required to be installed. 
  • It provided limited data rate capability so for high data rate advanced version of GSM devices are used. 
  • Many of GSM technology is patented by Qualcomm thus license needs to be obtained from them. 
  • Manufacturers are not releasing IS-95 devices due to the lack of a big market so IS-95 is normally installed in the small tower. 
  • GSM has fixed maximum call sites range up to 35 km that is very limited. 
  • There is no end-to-end encryption of user data. 
  • Several incompatibilities within the GSM standards. 
  • Electromagnetic radiation is more with the use of GSM.
  • Macrocells affected by the multipath signal loss.

What is frequency hopping spread spectrum

Frequency hopping spread spectrum is a method of transmitting radio signals by rapidly switching a carrier.  

 In FHSS among many frequency channels using pseudorandom sequence known to both transmitter and receiver. 

 Overview :

 In FHSS the data bits that are transmitted in the different frequency slots are changed by the PN sequence.

 FHSS is often used as a method to allow multiple transmitter and receiver pairs, it can operate in the same space on he same broad channel at the same time.

 In FHSS the data sequence is spread over small frequency slots of the spread spectrum signal.

FHSS is a wireless technology that spreads its signal over rapidly changing frequencies. 

 Advantages and disadvantages :

 The advantages of Frequency hopping spread spectrum given below :
  • It has less distance effect.
  • Provide greatest amount of spreading.
  • The bandwidth of these system is large.
  • It has a short acquisition time.
  • Best discrimination against multi-path.
  • Very large bandwidth.
  • The synchronization is not greatly dependent on distance.
  • It can be programmed to avoid some part of the spectrum.
Disadvantages of Frequency hopping spread spectrum given below :
  • It needs complex and costly digital frequency synthesizers are required to be used.
  • It need error detection.
  • The processing gain is higher than that of direct sequence spread spectrum.
  • It is not useful for range and range rate measurement.
Application :
  • Wireless local area network standard for Wi-Fi.
  • Military communication equipment.
  • Wireless personal area network standard for bluetooth.

Application of direct spread spectrum sequence

  • Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands. 
  • United status GPS technology, European Galileo and Russian GLONASS satellite navigation systems used DS/SS system with a single PN code in conjunction with FDMA and later it is used to achieve CDMA with multiple PN code.  
  • Used in the low probability of intercept signal.
  • It obtain message privacy.
  • Used military and many commercial application.
  • The unique spreading codes support code division multiple access.
  • Support various decision making level.
  • To reject unintentional  interference.
  • To minimize self interference due to the multi-path propagation.
  • It is used in automatic meter reading. 
  • Used in IEEE 802 11b and Zigbee network. 
  • Radio controlled model automotive vehicles. 

Advantages and disadvantages of direct sequence spread spectrum

Advantages of DS/SS :
  • It has best noise and anti-jam performance.
  • Simple hard ware implementation.
  • It support high coverage range due to low SNR requirement at receiver.
  • Do no require high speed fast setting frequency synthesizer.
  • It has best discrimination against multi-path signals.
  • The unidentified receivers find it difficult to detect the direct sequence signals.
  • It can be employed in point to point application at the rate of 11 Mbps.
  • Determination of relative timing between transmitter and receiver. 
Disadvantages of DS/SS :
  • DS/SS has a longer acquisition time.
  • It require wideband channel with small phase distortion.
  • The pseudo noise generator must generate sequence at high rates.
  • Near-far problem.
  • Fast code generator needed.
  • The system is prone to error at lower than frequency hoping spread spectrum.
Explore more information:

What is direct sequence spread spectrum

Direct sequence spread spectrum (DSSS) is spread spectrum modulation technique used in telecommunication to reduce overall signal interface. 

 Direct sequence spread spectrum (DSSS) is one type of channel access method is better known as direct sequence CDMA. This is mainly used in IEEE 802.11b and also used  Zigbee technology. 

 Overview : 
  • The term DS/SS stands for direct sequence spread spectrum
  • In this method, the pseudo-random code is used when the signal can be detected at the receiver end. If avoid unauthorized signal access.
  • The DS/SS is affected by the near-far problem. This problem occurs because of the unequal power that is received by the user.
  • It is a very sensitive technology.
  • Many users can be used in the same band with a better signal to noise ratio. 
  • DS/SS is used point to point scenario.
  • The DS/SS signal spectrum is spread over a wide band while the PSD is small, Hence, it is simple to hide the signal within the noise floor.
  • DS/SS delivers capacity of about 11 Mbps.
Advantages of  DS/SS :
  • It has the best noise and antijam performance.
  • Simple hardware implementation.
  • It supports high coverage range due to low SNR requirement at receiver.
  • Do not require high-speed fast setting frequency synthesizer.
  • It has the best discrimination against multi-path signals.
  • The unidentified receivers find it difficult to detect the direct sequence type of signals.
  • It can be employed in point to point the application at the rate of 11 Mbps.
Disadvantages of DS/SS :
  • DS/SS has a longer acquisition time.
  • It requires a wideband channel with small phase distortion.
  • The pseudo noise generator must generate a sequence at high rates.
  • Near-far problem.
  • Fast code generator needed.
  • The system is prone to error at lower compared to FH/SS.
Application of DSSS :

 The application of direct spread spectrum analysis is listed below.
  • DSSS is used in the low probability of intercept signal.
  • It obtains message privacy.
  • It is used military and much commercial application.
  • It can support the unique spreading codes support code division multiple access.
  • Support various decision-making level.
  • To reject unintentional interference.
  • To minimize self-interference due to the multi-path propagation.
Explore more information:

Feature of WiFi

Wi-Fi stands for Wireless fidelity is an alternative to wired technology that is commonly used for connecting devices in wireless mode. There is numerous application of Wi-Fi in different areas because of some useful feature of Wi-Fi. So now let us check the features of Wi-Fi one by one below :

 Features of Wi-Fi :
  • While using Wi-Fi there is no limitation
  • Faster and secure
  • Unmatched mobility
  • Fortress technology
  • No need for cabling
  • Secure interment connection for feature
  • It's convenient and everywhere
  • It is a scalable and robust system
  • Great power consumption
  • The easy way of network installation
  • The configuration of the device is very easy
  • If we are nearer to Wi-Fi hotspot  network then you will automatically connect internet 

Application of GSM

  • Home automation.
  • Mobile telephony.
  • Automatic meter reading.
  • Toll collection.
  • A user can control in case of forgetting to do so while leaving for some other place.
  • Value-added services.
  • Fleet management.
  • Energy Conversion.
  • Personal communication using GSM.
  • Irrigation system.
  • It will also help to control while attending the other work.
  • It is used to improve the security of our home and office.
  • Office automation.
  • Remote sensing and also for monitoring of electrical fault in a pump or motor.
Some application while combining with GSM techniques including  W-CDMA, LTE, EGGE :
  • Measuring multi-standard radio base station.
  • Including EDGE evolution with GSM to change in radio interface.
  • Machine to machine communication is about integrated real-time data from remote assets with a business process to gain more business advantages.

WiMAX features

A wireless broadband solution that offers various features with a lot of flexibility in terms of potential service offering is WiMAX technology.
  • WiMAX support multipath.
  • IT provide up to 50 km of service area range.
  • WiMAX uses OFDM technology.
  • WiMAX support TDD and FDD.
  • WiMAX offer modulation and error correction.
  • Adaptive modulation enables while using WiMAX system to optimize the throughput based on the propagation conditions.
  • Very scalable bandwidth and high-speed data rate.
  • Flexible and dynamic per-user resource allocation.
  • Support for advanced antenna techniques.
  • Support for mobility.
  • Portable internet usage.
  • Quality of service support.
  • It is IP based architecture.
  • WiMAX is always best connected.

WiMAX architecture

As we know that the WiMAX system consists of two major parts: Main part is to be (i) A WiMAX base station (ii) And a WiMAX receiver.

 Let us take a look at the WiMAX architecture to shown in the figure.

 A WiMAX base station :

 WiMAX base station is very similar to accessing a wireless access point in a Wi-Fi network, but the coverage is greater than to another network.

WiMAX base station can provide a very large area up to a radius of around 6 miles. A WiMAX base station(BS) consists of indoor electronics and as we know that WiMAX tower similar look like to a cell phone tower.

Each base station(BS) can provide wireless coverage over an area called a cell. The WiMAX base station can also use a multiple antennas point in a different direction. This area covered by one antenna signal called sector.

The uplink and also a downlink channel are shared among the many subscriber stations in a given sector. WiMAX can also have support bursty data and also provide high-quality telephone and high volume multimedia.

The uplink and also for downlink channels are divided into slots of equal size. A WiMAX frame takes multiple slots. Different frame takes a different number of slots. The downlink channel easy to subdivide into connection as only the base station sends on that channel.

A WiMAX receiver : 

A WiMAX receiver side may have a separate antenna or could be a stand-alone box or a PCMCIA card present in your laptop or any other device. It is called as customer premise equipment (CPE).

In most of the cases, a simple plug and play terminal, similar to a DSL modem provides connectivity as shown in the figure given below.

For customer located several kilometers from the WiMAX base station, a self-install outdoor. The antenna may be required to improve transmission quality. 

For customer requesting a voice in addition to broadband services, specific CPE will allow the connection of standard or VoIP phones device.
WiMAX architecture

WiMAX standard

We all know that the WiMAX system has been supporting IEEE 802.16, This standard is called IEEE  called 802.16, it was associated with 802.16a / REV d / e standard.

 These standards were issued by IEEE standard 802.16 into the subgroup called  (802.16a/REV d/e) standard that originally covered the Wireless local loop (WLL) technologies with radio spectrum from 10 to 66 GHz. Recently were extended below 10 GHz.

 In the year of January 2003, the approved IEEE standard 802.16a as an amendment to IEEE  standard 802.16 defining line of sight capability.

 In the year of 2004, the IEEE 802.16 standard Revd was introduced to support basically indoor customer premises equipment through additional radio capabilities like antenna beamforming and OFDM sub channeling.

 In the year of 2005, an IEEE standard 802.16e variant was developed for supporting mobility device.

 Following are the details of various IEEE 802.16 standard related to WiMAX system listed below.

1. 802.16
  • Spectrum - 10-66 GHz
  • Configuration  - Line of sight
  • Mobility - Fixed
  • Channel bandwidth - 20,25 MHz
  • Typical cell radius - 1-3 miles
  • Modulation - QPSK-16 QAM 64 QAM
  • Completion  - December 2001
2. 802.16a
  • Spectrum - 2-11 GHz
  • Configuration  - Non-Line of sight
  • Mobility - Fixed
  • Channel bandwidth - Selectable, 1.25-20 MHz
  • Typical cell radius - 3-5 miles
  • Modulation - total number of 256 subscribers, OFDM using QPSK, 16 QAM, 64 QAM, 256-QAM
  • Completion - January 2003
3. 802.16e
  • Spectrum - <6 GHz
  • Configuration  - Non-Line of sight
  • Mobility - Fixed
  • Channel bandwidth - 5 MHz planned
  • Typical cell radius - 1-3 miles
  • Modulation - total number of 256 subscribers, OFDM using QPSK16, QAM, 64 QAM, 256-QAM
  • Completion - 2nd half of 2005

GSM handover

Definition of handover : 

 Handover is the process of transferring a mobile station from one channel to another channel side.

This system can be defined as a mechanism to hand over the mobile device to the neighboring cell.

Basically, handover is a core element that can be planned and deployed cellular system based network. It must be efficiently done using different strategies.

In the handover process, if the mobile device moves out the range of one cell, a different base station provides it with a use of the stronger signal.

In this process, if the channel of the base station is busy then the nearby base station can provide service to the device.

 Types of handover :

There are two types of handover :
  1. Hard Handover
  2. Soft Handover
1. Hard handover :
In hard handover, the radio link must be dropped for a small amount of time before it can be taken over by another base station.

So the call process not from only one base station (BS) to another base station but from current transmits to receiver frequency pair to another frequency pair. A break in call transmission is called as a call drop.

In general, the handover occurs in a very few milliseconds. The GSM system performs hard handovers.

2. Soft handover :
While in soft handover indicates an MS full form is a mobile station at the boundary of two adjacent cells does not call drop because of handover in the boundary region. 

 A mobile can be connected easily to several base station (BS full form) is base stations simultaneously. The 3D CDMA support soft handover.

Features of Bluetooth

Bluetooth technology is an open standard that provides an ad-hoc way for connecting devices in the 10 m range. Bluetooth in the 2.4 GHz band and uses a frequency hopping TDD method for each radio channel. Now let us check it out features of Bluetooth to know more details about Bluetooth. 
  • Better IOT
  • Quick data transfer
  • Better audio quality
  • Easy transport 
  • Greater flexibility
  • Available everywhere
  • Up to eight devices can be a network in the piconet
  • The device does not need to be a point at each other, as a signal is OMNI directional 
  • Increases numbers of advertising packets
  • Provide location-based services
  • Government  worldwide regular it, so it is possible to utilize the same standards wherever one travel
  • Sending the information between the two devices which are close to each other

Bluetooth architecture

Bluetooth architecture defines two types of structure :
  1. Piconet
  2. Scatternet
1. Piconet 
  • Eight devices are connected in a Bluetooth network called as a piconet, so the piconet has up to eight active nodes 
  • One of them acts as a master and others act as slaves.
  • In piconet communication between the primary and secondary can be one to one or one to many forms. 
  • All communication is done between master and slave. slave-slave or master-master communication is not possible
2. Scatternet
  • A scatternet is formed when two more piconets connect through a bridge node. 
  • It is combining various piconet.
  • In scattered addition to be seven active slaves, there can be up to 255 parked nodes in the net that can only respond to a beacon signal from the master.
  • The slaves are also dumb devices that do the task that the master tells them to do.
  • Mater controlling the clock and it is determining in which slave gets to communicate in which time slot.
  • All the communication is between the master and slave and but not between the slaves.
Bluetooth architecture

Bluetooth frame structure

Access code: It identifies the master so that slaves within the radio range of two masters can tell which is traffic for them. It is a 72-bit field, that contains synchronization bits.

Header: The 54-bit header contains an 18-bit header that is repeated 3 times for a total of 54 bits. It allows the receiver to remind all three copies of each beat and reject the ones that do not have a majority.

Address field: The address field in the header identifies which of the eight devices the frame is intended for.

Types field: Types field identifies whether it is an ACL, SCO, pull or null frame types, the types of error correction used in the data field and how many slots long the frame is

Flow bit: It is used for primitive types of flow control and is asserted by the slave when its buffer is full and cannot receive any more data.

ACK bit: ACK bit is used to piggyback an acknowledgment onto a frame

Sequence bit: It is used to number the frame to detect re-transmission in a stop and wait for a protocol. It is followed by an 8-bit checksum.

Bluetooth frame structure
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