Cell Phones Work AMNIMARJESLOW GOVERNMENT 91220017 LOWER HAND SHOOTER LJBUSAF

  

           

                 How Cell Phones Work

From Italy to Greek to Colorado USA  , no matter where you go you'll see someone talking on his or her cell phone. These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace. Depending on the cell phone model, you can:

• Store contact information
• Make task or to-do lists
• Keep track of appointments and set reminders
• Use the built-in calculator for simple math
• Send or receive e-mail
• Get information (news, entertainment, stock quotes) from the Internet
• Play games
• Watch TV
• Send text messages
• Take photos and videos
• Integrate other devices such as PDAs, MP3 players and GPS receivers

You might hear terms like 4G, LTE, GSM and CDMA thrown around and wonder what they refer to. At its most basic, a cell phone is a radio -- an extremely sophisticated radio, but a radio nonetheless. We'll show you what we mean.
 
        

A woman checks messages on her mobile phone. Cell phones have truly taken over the world. See cell

A woman checks messages on her mobile phone. Cell phones have truly taken over the world. See cell phone pictures.

                                        Cell phone electronics basics  

The mobile phone or cell phone as it is often called is equally important to the network in the operation of the complete cellular telecommunications network. Despite the huge numbers that are made, they still cost a significant amount to manufacture, discounts being offered to users as incentives to use a particular network. Their cost is a reflection of the complexity of the mobile phone electronics. They comprise several different areas of electronics, from radio frequency (RF) to signal processing, and general processing.
The design of a cell phone is particularly challenging. They need to offer high levels of performance, while being able to fit into a very small space, and in addition tot his the electronics circuitry needs to consume very little power so that the life between charges can be maintained.

Mobile phone contents

Mobile phones contain a large amount of circuitry, each of which is carefully designed to optimise its performance. The cell phone comprises analogue electronics as well as digital circuits ranging from processors to display and keypad electronics. A mobile phone typically consists of a single board, but within this there are a number of distinct functional areas, but designed to integrate to become a complete mobile phone:

• Radio frequency - receiver and transmitter
• Digital signal processing
• Analogue / digital conversion
• Control processor
• SIM or USIM card
• Power control and battery

Radio frequency elements

The radio frequency section of the mobile phone is one of the crucial areas of the cell phone design. This area of the mobile phone contains all the transmitter and receiver circuits. Normally direct conversion techniques are generally used in the design for the mobile phone receiver.
The signal output from the receiver is applied to what is termed an IQ demodulator. Here the data in the form of "In-phase" and "Quadrature" components is applied to the IQ demodulator and the raw data extracted for further processing by the phone.
On the transmit side one of the key elements of the circuit design is to keep the battery consumption to a minimum. For GSM this is not too much of a problem. The modulation used is Gaussian Minimum Shift Keying. This form of signal does not incorporate amplitude variations and accordingly it does not need linear amplifiers. This is a distinct advantage because non linear RF amplifiers are more efficient than linear RF amplifiers.
Unfortunately EDGE uses eight point phase shift keying (8PSK) and this requires a linear RF amplifier. As linear amplifiers consume considerably more current this is a distinct disadvantage. To overcome this problem the design for the mobile phone is organised so that phase information is added to the signal at an early stage of the transmitter chain, and the amplitude information is added at the final amplifier.

Analogue to Digital Conversion

Another crucial area of any mobile phone design is the circuitry that converts the signals between analogue and digital formats that are used in different areas. The radio frequency sections of the design use analogue techniques, whereas the processing is all digital.
The digital / analogue conversion circuitry enables the voice to be converted either from analogue or to digital a digital format for the send path, but also between digital and analogue for the receive path. It also provides functions such as providing analogue voltages to steer the VCO in the synthesizer as well as monitoring of the battery voltage, especially during charging. It also provides the conversion for the audio signals to and from the microphone and earpiece so that they can interface with the digital signal processing functions.
Another function that may sometimes be included in this area of the mobile phone design or within the DSP is that of the voice codecs. As the voice data needs to be compressed to enable it to be contained within the maximum allowable data rate, the signal needs to be digitally compressed. This is undertaken using what is termed a codec.
There are a number of codec schemes that can be used, all of which are generally supported by the base stations. The first one to be used in GSM was known as LPC-RPE (Linear Prediction Coding - Regular Pulse Excitation). However another scheme known as AMR (Adaptive Multi-Rate) is now widely used as it enables the data rate to be further reduced when conditions permit without impairing the speech quality too much. By reducing the speech data rate, further capacity is freed up on the network.

Digital Signal Processing

The DSP components of the mobile phone design undertake all the signal processing. Processes such as the radio frequency filtering and signal conditioning at the lower frequencies are undertaken by this circuitry. In addition to this, equalisation and correction for multipath effects is undertaken in this area of the design.
Although these processors are traditionally current hungry, the current processors enable the signal processing to be undertaken in a far more power effective manner than if analogue circuits are used.

Control processor

The control processor is at the heart of the design of the phone. It controls all the processes occurring in the phone from the MMI (Man machine interface) which monitors the keypad presses and arranging for the information to be displayed on the screen. It also looks after all the other elements of the MMI including all the menus that can be found on the phone.
Another function of the control processor is to manage the interface with the mobile network base station. The software required for this is known as the protocol stack and it enables the phone to register, make and receive calls, terminate them and also handle the handovers that are needed when the phone moves from one cell to the next. Additionally the software formats the data to be transmitted into the correct format with error correction codes included. Accordingly the load on this processor can be quite high, especially when there are interactions with the network.
The protocols used to interact with the network are becoming increasingly complicated with the progression from 2G to 3G. Along with the increasing number of handset applications the load on the processor is increasing. To combat this, the design for this area of the phone circuitry often uses ARM processors. This enables high levels of processing to be achieved for relatively low levels of current drain.
A further application handled by this area of the design of the mobile phone is the monitoring the state pf the battery and control of the charging. In view of the sophisticated monitoring and control required to ensure that the battery is properly charged and the user can be informed about the level of charge left, this is an important area of the design.

Battery

Battery design and technology has moved on considerably in the last few years. This has enabled mobile phones to operate for much longer. Initially nickel cadmium cells were used, but these migrated to nickel-metal-hydride cells and then to lithium ion cells. With phones becoming smaller and requiring to operate for longer from a single charge, the capacity of the battery is very important, and all the time the performance of these cells is being improved.
Although mobile phones are one of the most commonplace pieces of electronics equipment these days, they are nevertheless complicated inside. An understanding of the mobile phone basics can often be useful when looking at the way a cellular network and cellular technology in general works.


                                           Cellular network basics 

The network forms the heart of any cellular telephone system. The cellular network fulfils many requirements. Not only does the cellular network enable calls to be routed to and from the mobile phones as well as enabling calls to be maintained as the cell phone moves from one cell to another, but it also enables other essential operations such as access to the network, billing, security and much more. To fulfil all these requirements the cellular network comprises many elements, each having its own function to complete.
The most obvious part of the cellular network is the base station. The antennas and the associated equipment often located in a container below are seen dotted around the country, and especially at the side of highways and motorways. However there is more to the network behind this, as the system needs to have elements of central control and it also needs to link in with the PSTN landline system to enable calls to be made to and from the wire based phones, or between networks.
Different cellular standards often take slightly different approaches for the cellular network required. Despite the differences between the different cellular systems, the basic concepts are very similar. Additionally cellular systems such as GSM have a well defined structure, and this means that manufacturers products can be standardised.

Basic cellular network structure

An overall cellular network contains a number of different elements from the base transceiver station (BTS) itself with its antenna back through a base station controller (BSC), and a mobile switching centre (MSC) to the location registers (HLR and VLR) and the link to the public switched telephone network (PSTN). Of the units within the cellular network, the BTS provides the direct communication with the mobile phones. There may be a small number of base stations then linked to a base station controller. This unit acts as a small centre to route calls to the required base station, and it also makes some decisions about which of the base station is best suited to a particular call. The links between the BTS and the BSC may use either land lines of even microwave links. Often the BTS antenna towers also support a small microwave dish antenna used for the link to the BSC. The BSC is often co-located with a BTS.
The BSC interfaces with the mobile switching centre. This makes more widespread choices about the routing of calls and interfaces to the land line based PSTN as well as the HLR and VLR.

Base transceiver station, BTS

The base transceiver station or system, BTS consists of a number of different elements. The first is the electronics section normally located in a container at the base of the antenna tower. This contains the electronics for communicating with the mobile handsets and includes radio frequency amplifiers, radio transceivers, radio frequency combiners, control, communication links to the BSC, and power supplies with back up.
The second part of the BTS is the antenna and the feeder to connect the antenna to the base transceiver station itself. These antennas are visible on top of masts and tall buildings enabling them to cover the required area. Finally there is the interface between the base station and its controller further up the network. This consists of control logic and software as well as the cable link to the controller.
BTSs are set up in a variety of places. In towns and cities the characteristic antennas are often seen on the top of buildings, whereas in the country separate masts are used. It is important that the location, height, and orientation are all correct to ensure the required coverage is achieved. If the antenna is too low or in a poor location, there will be insufficient coverage and there will be a coverage "hole". Conversely if the antenna is too high and directed incorrectly, then the signal will be heard well beyond the boundaries of the cell. This may result in interference with another cell using the same frequencies.
The antennas systems used with base stations often have two sets of receive antennas. These provide what is often termed diversity reception, enabling the best signal to be chosen to minimise the effects of multipath propagation. The receiver antennas are connected to low loss cable that routes the signals down to a multicoupler in the base station container. Here a multicoupler splits the signals out to feed the various receivers required for all the RF channels. Similarly the transmitted signal from the combiner is routed up to the transmitting antenna using low loss cable to ensure the optimum transmitted signal.

Mobile switching centre (MSC)

The MSC is the control centre for the cellular system, coordinating the actions of the BSCs, providing overall control, and acting as the switch and connection into the public telephone network. As such it has a variety of communication links into it which will include fibre optic links as well as some microwave links and some copper wire cables. These enable it to communicate with the BSCs, routing calls to them and controlling them as required. It also contains the Home and Visitor Location Registers, the databases detailing the last known locations of the mobiles. It also contains the facilities for the Authentication Centre, allowing mobiles onto the network. In addition to this it will also contain the facilities to generate the billing information for the individual accounts.
In view of the importance of the MSC, it contains many backup and duplicate circuits to ensure that it does not fail. Obviously backup power systems are an essential element of this to guard against the possibility of a major power failure, because if the MSC became inoperative then the whole network would collapse.
While the cellular network is not seen by the outside world and its operation is a mystery to many, the cellular network is at the very centre of the overall cellular system and the success of the whole end to end system is dependent largely on its performance.

 

                                    Mobile phone network registration  

 

On any cellular telecommunications system the way in which registration and call set-up occur needs to be carefully managed. Not only does the cellular telecommunications network need to provide quick and efficient service for its rightful customers, but it also needs to be able to offer high levels of security for the user and the network.
There are many different cellular telecommunications systems in use around the globe. Older ones are being phased out, and newer cellular systems are being introduced. Accordingly there is no single way in which registration and call set up are managed. However there are some general principles that are used, and these are illustrated here.

Basic requirements

When the mobile phone is turned on it needs to be able to communicate with the cellular telecommunications network. However the phone does not have an allocated channel, time slot or chip code (dependent upon the type of access method used). It is therefore necessary for there to be some methods or allocated means within the cellular telecommunications network, whereby a newly switched on mobile can communicate with the network and set up the standard communication.
Even if a call is not to be made instantly, the network needs to be able to communicate with the mobile to know where it is. In this way the network can route any calls through the relevant base station as the network would be soon overloaded if the notification of an incoming call had to be sent via several base stations.

Cellular registration

There are a variety of tasks that need to be undertaken when a phone is turned on. This can eb seen by the fact that it takes a few seconds from switching the phone on before it is ready for use. Part of this process is the software start-up for the phone, but the majority comes from the registration process with the cellular network. There are several aspects to the regristration. The first is to make contact with the base station, and next the mobile has to register to allow it to have access to and use the network.
In order to make contact with the base station the mobile uses a paging or control channel. The name of this channel, and the exact way in which it works will vary from one cellular standard to the next, but it is a channel that is used that the mobile can access to indicate its presence. The message sent is often called the "attach" message. Once this has been achieved it is necessary for the mobile to register with the cellular network, and to be accepted onto it.

Network elements

It is necessary to have a register or database of users allowed to register with a given network. With mobiles often being able to access the all the channels available in a country, methods of ensuring the mobile registers with the correct network, and to ensure the account is valid are required. Additionally it is required for billing purposes. To achieve this, an entity on the network often known as the Authentication Centre (AuC) is used. The network and the mobile communicate and numbers giving the identity of the subscriber. Here the user information is checked to provide authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call protecting users and network operators from fraud.
Once accepted onto the network two further registers are normally required. These are the Home Location Register (HLR) and the Visitors Location Register (VLR). These two registers are required to keep track of the mobile so that the network knows where it is at any time so that calls can be routed to the correct base station or general area of the network. These registers are used to store the last known location of the mobile. Thus at registration the register is updated and then periodically the mobile updates its position. Even when the mobile is in what is termed its idle mode it will periodically communicate with the network to update its position and status.
When the mobile is switched off it sends a detach message. This informs the network that it is switching off, and enables the network to update the last known position for the mobile.

Cellular roaming

The two registers are required, one for mobiles for which the network is the home network, i.e. the one with whom the contract exists, and the other for visitors. If there was only one register then every time the mobile sent any message to the foreign network, this would need to be relayed back to the home network and this would require international signalling. The approach which is adopted is to send a message back to the HLR when the mobile first enters the new country saying that the mobile is in a different network and that any calls for that mobile should be forwarded to the foreign visited network.
By undergoing a registration procedure when the mobile is turned on, the cellular network is able to communicate correctly with it, provide access for outgoing calls, and also route any incoming calls to it in the most efficient manner. Registration also only allows those mobiles that have permission to access the network to communicate with it. 


                                  Cellular Handover and handoff   

The concept of a cellular phone system is that it has a large number base stations covering a small area (cells), and as a result frequencies are able to be re-used. Cell phone systems also provide mobility. As a result it is a very basic requirement of the system that as the mobile handset moves out of one cell to the next, it must be possible to hand the call over from the base station of the first cell, to that of the next with no discernable disruption to the call. There are two terms for this process: cellular handover is used within Europe, whereas cellular handoff is the term used in North America.
The handover or handoff process is of major importance within any cellular telecommunications network. It is necessary to ensure it can be performed reliably and without disruption to any calls. Failure for it to perform reliably can result in dropped calls, and this is one of the key factors that can lead to customer dissatisfaction, which in turn may lead to them changing to another cellular network provider. Accordingly handover or handoff is one of the key performance indicators monitored so that a robust cellular handover / handoff regime is maintained on the cellular network.

Handover basics

Although the concept of cellular handover or cellular handoff is relatively straightforward, it is not an easy process to implement in reality. The cellular network needs to decide when handover or handoff is necessary, and to which cell. Also when the handover occurs it is necessary to re-route the call to the relevant base station along with changing the communication between the mobile and the base station to a new channel. All of this needs to be undertaken without any noticeable interruption to the call. The process is quite complicated, and in early systems calls were often lost if the process did not work correctly.
Different cellular standards handle hand over / handoff in slightly different ways. Therefore for the sake of an explanation the example of the way that GSM handles handover is given.
There are a number of parameters that need to be known to determine whether a handover is required. The signal strength of the base station with which communication is being made, along with the signal strengths of the surrounding stations. Additionally the availability of channels also needs to be known. The mobile is obviously best suited to monitor the strength of the base stations, but only the cellular network knows the status of channel availability and the network makes the decision about when the handover is to take place and to which channel of which cell.
Accordingly the mobile continually monitors the signal strengths of the base stations it can hear, including the one it is currently using, and it feeds this information back. When the strength of the signal from the base station that the mobile is using starts to fall to a level where action needs to be taken the cellular network looks at the reported strength of the signals from other cells reported by the mobile. It then checks for channel availability, and if one is available it informs this new cell to reserve a channel for the incoming mobile. When ready, the current base station passes the information for the new channel to the mobile, which then makes the change. Once there the mobile sends a message on the new channel to inform the network it has arrived. If this message is successfully sent and received then the network shuts down communication with the mobile on the old channel, freeing it up for other users, and all communication takes place on the new channel.
Under some circumstances such as when one base transceiver station is nearing its capacity, the network may decide to hand some mobiles over to another base transceiver station they are receiving that has more capacity, and in this way reduce the load on the base transceiver station that is nearly running to capacity. In this way access can be opened to the maximum number of users. In fact channel usage and capacity are very important factors in the design of a cellular network.

Types of handover / handoff

With the advent of CDMA systems where the same channels can be used by several mobiles, and where it is possible to adjacent cells or cell sectors to use the same frequency channel there are a number of different types of handover that can be performed:

• Hard handover (hard handoff)
• Soft handover (soft handoff)
• Softer handover (softer handoff)

Although all of these forms of handover or handoff enable the cellular phone to be connected to a different cell or different cell sector, they are performed in slightly different ways and are available under different conditions.

Hard handover

The definition of a hard handover or handoff is one where an existing connection must be broken before the new one is established. One example of hard handover is when frequencies are changed. As the mobile will normally only be able to transmit on one frequency at a time, the connection must be broken before it can move to the new channel where the connection is re-established. This is often termed and inter-frequency hard handover. While this is the most common form of hard handoff, it is not the only one. It is also possible to have intra-frequency hard handovers where the frequency channel remains the same.
Although there is generally a short break in transmission, this is normally short enough not to be noticed by the user.

Soft handover

The new 3G technologies use CDMA where it is possible to have neighbouring cells on the same frequency and this opens the possibility of having a form of handover or handoff where it is not necessary to break the connection. This is called soft handover or soft handoff, and it is defined as a handover where a new connection is established before the old one is released. In UMTS most of the handovers that are performed are intra-frequency soft handovers.

Softer handover

The third type of hand over is termed a softer handover, or handoff. In this instance a new signal is either added to or deleted from the active set of signals. It may also occur when a signal is replaced by a stronger signal from a different sector under the same base station. This type of handover or handoff is available within UMTS as well as CDMA2000.
Cellular handover or cellular handoff are performed by all cellular telecommunications networks, and they are a core element of the whole concept of cellular telecommunications. There are a number of requirements for the process. The first is that it occurs reliably and if it does not, users soon become dissatisfied and choose another network provider in a process known as "churn". However it needs to be accomplished in the most efficient manner. Although softer handoff is the most reliable, it also uses more network capacity. The reason for this is that it is communicating with more than one sector or base station at any given instance. Soft handover is also less efficient than hard handover, but again more reliable as the connection is never lost.
It is therefore necessary for the cellular telecommunications network provider to arrange the network to operate in the most efficient manner, while still providing the most reliable service. 




                       Cellular Telecommunications & Cell Phone Technology  

Key details and essential information about mobile phone or cellular telecommunications technology ranging from the most ercent developments in 5G mobile technology to some of the older established systems including the 2G GSM system that is still widely used.

Most popular cellular telecommunications tutorials

• 3G LTE - Long Term Evolution
• VoLTE
• 5G cellular technology

• 4G LTE Advanced
• LTE Carrier Aggregation

Cellular telecommunications technologies

• 3GPP, 3rd Generation Partnership Project
• 3G HSPA, High Speed Packet Access
• 3G LTE - Long Term Evolution
• 4G LTE Advanced
• 5G cellular system ideas and proposals
• Assisted GPS
• Basic cellular concepts
• IS-95 / cdmaOne technology
• CDMA2000 1X
• CDMA2000 1X EV-DO
• CDMA450
• Cellular conformance testing
• Cellular repeater
• Femtocells basics

• GPRS, General Packet Radio Service
• GSM EDGE
• GSM tutorial and technical overview
• Heterogeneous networks, Hetnet
• i-mode
• Major Mobile Phone Systems
• Mobile phone or cell phone history
• Mobile video
• Network optimisation
• Pacific or Personal Digital Cellular (PDC)
• Self Organising Networks, SON
• UMA - unlicensed mobile access
• UMB, Ultra Mobile Broadband
• UMTS / W-CDMA Tutorial
• Mobile backhaul

Latest news

• Apple launches new iPhone X and other products
• Nokia eases IoT market entry for mobile operators
• G+D Mobile Security offers geo-redundant eSIM Management services
• Metal meets glass with the new IDOL 5
• Nokia to manage TT radio network in Denmark
• Extra Space Storage selects RingCentral Cloud Communications
• More...

Private mobile radio

• Private mobile radio, PMR, systems overview
• MPT1327 trunking system

• TETRA private mobile radio tutorial
• Project 25, P25 (APCO-25)
• DMR digital mobile radio
• dPMR digital professional / private, mobile radio
• NXDN land mobile radio

Analysis and case studies from industry experts

• Cellular Base Station Installation & Maintenance Challenges
• Data Driven Networks: managing mobile’s digital transformation
• Mobile World Congress 2017, MWC17 – trends, news, releases
• Realizing the Promise of 5G: utilizing the technologies
• Dirty fibre and poor QoS – are operators about to trip on the first 5G hurdle?
• Mobile Network Metrics - what they mean
• Service assurance in virtualised networks
• 4G, 5G & IoT Predictions for 2016
• How LTE is the enabling technology for new automotive systems
• Virtualised VoLTE gives operators the power of innovation 

                                     5G Mobile Wireless Technology  


With the 4G telecommunications systems now starting to be deployed, eyes are looking towards the development of 5th generation or 5G technology and services.
Although the deployment of any wireless or cellular system takes many years, development of the 5G technology systems is being investigated. The new 5G technologies will need to be chosen developed and perfected to enable timely and reliable deployment.
The new 5th generation, 5G technology for cellular systems will probably start to come to fruition around 2020 with deployment following on afterwards.

5G mobile systems status

The current status of the 5G technology for cellular systems is very much in the early development stages. Very many companies are looking into the technologies that could be used to become part of the system. In addition to this a number of universities have set up 5G research units focussed on developing the technologies for 5G
In addition to this the standards bodies, particularly 3GPP are aware of the development but are not actively planning the 5G systems yet.
Many of the technologies to be used for 5G will start to appear in the systems used for 4G and then as the new 5G cellular system starts to formulate in a more concrete manner, they will be incorporated into the new 5G cellular system.
The major issue with 5G technology is that there is such an enormously wide variation in the requirements: superfast downloads to small data requirements for IoT than any one system will not be able to meet these needs. Accordingly a layer approach is likely to be adopted. As one commentator stated: 5G is not just a mobile technology. It is ubiquitous access to high & low data rate services.

5G cellular systems overview

As the different generations of cellular telecommunications have evolved, each one has brought its own improvements. The same will be true of 5G technology.

• First generation, 1G:   These phones were analogue and were the first mobile or cellular phones to be used. Although revolutionary in their time they offered very low levels of spectrum efficiency and security.
• Second generation, 2G:   These were based around digital technology and offered much better spectrum efficiency, security and new features such as text messages and low data rate communications.
• Third generation, 3G:   The aim of this technology was to provide high speed data. The original technology was enhanced to allow data up to 14 Mbps and more.
• Fourth generation, 4G:   This was an all-IP based technology capable of providing data rates up to 1 Gbps.

Any new 5th generation, 5G cellular technology needs to provide significant gains over previous systems to provide an adequate business case for mobile operators to invest in any new system.
Facilities that might be seen with 5G technology include far better levels of connectivity and coverage. The term World Wide Wireless Web, or WWWW is being coined for this.
For 5G technology to be able to achieve this, new methods of connecting will be required as one of the main drawbacks with previous generations is lack of coverage, dropped calls and low performance at cell edges. 5G technology will need to address this.

5G specifications

Although the standards bodies have not yet defined the parameters needed to meet a 5G performance level yet, other organisations have set their own aims, that may eventually influence the final specifications.
Typical parameters for a 5G standard may include:

Suggested 5G Wireless Performance
Parameter	Suggested Performance
Network capacity	10 000 times capacity of current network
Peak data rate	10 Gbps
Cell edge data rate	100 Mbps
Latency	< 1 ms

These are some of the ideas being put forwards for a 5G standard, but they are not accepted by any official bodies yet.

Current research

There are several key areas that are being investigated by research organisations. These include:

• Millimetre-Wave technologies:   Using frequencies much higher in the frequency spectrum opens up more spectrum and also provides the possibility of having much wide channel bandwidth - possibly 1 - 2 GHz. However this poses new challenges for handset development where maximum frequencies of around 2 GHz and bandwidths of 10 - 20 MHz are currently in use. For 5G, frequencies of above 50GHz are being considered and this will present some real challenges in terms of the circuit design, the technology, and also the way the system is used as these frequencies do not travel as far and are absorbed almost completely by obstacles. Read more about 5G millimetre wave links
• Future PHY / MAC:   The new physical layer and MAC presents many new interesting possibilities in a number of areas:
  • Waveforms:   One key area of interest is that of the new waveforms that may be seen. OFDM has been used very successfully in 4G LTE as well as a number of other high data rate systems, but it does have some limitations in some circumstances. Formats being proposed include: GFDM, Generalised Frequency Division Multiplexing, as well as FBMC, Filter Bank Multi-Carrier, UFMC, Universal Filtered MultiCarrier. Each has its own advantages and limitations and it is possible that adaptive schemes may be employed, utilising different waveforms adaptively for the 5G mobile systems as the requirements dictate. This provides considerably more flexibility for 5G mobile communications. Read more about 5G waveforms
  • Multiple Access Schemes:   Again a variety of new access schemes are being investigated for 5G technology. Techniques including OFDMA, SCMA, NOMA, PDMA, MUSA and IDMA have all been mentioned. Read more about 5G multiple access schemes
  • Modulation:   Whilst PSK and QAM have provided excellent performance in terms of spectral efficiency, resilience and capacity, the major drawback is that of a high peak to average power ratio. Modulation schemes like APSK could provide advantages in some circumstances. Read more about 5G modulation schemes
• Duplex methods:   There are several candidate forms of duplex that are being considered. Currently systems use either frequency division duplex, FDD or time division duplex, TDD. New possibilities are opening up for 5G including flexible duplex, where the time or frequencies allocated are variable according toth e load in either direction or a new scheme called division free duplex or single channel full duplex. This scheme for 5G would enable simultaneous transmission and reception on the same channel. Read more about 5G full duplex
• Massive MIMO:   Although MIMO is being used in many applications from LTE to Wi-Fi, etc, the numbers of antennas is fairly limited -. Using microwave frequencies opens up the possibility of using many tens of antennas on a single equipment becomes a real possibility because of the antenna sizes and spacings in terms of a wavelength.
• Dense networks   Reducing the size of cells provides a much more overall effective use of the available spectrum. Techniques to ensure that small cells in the macro-network and deployed as femtocells can operate satisfactorily are required.

Other 5G concepts

There are many new concepts that are being investigated and developed for the new 5th generation mobile system. Some of these include:

• Pervasive networks :   This technology being considered for 5G cellular systems is where a user can concurrently be connected to several wireless access technologies and seamlessly move between them.
• Group cooperative relay:   This is a technique that is being considered to make the high data rates available over a wider area of the cell. Currently data rates fall towards the cell edge where interference levels are higher and signal levels lower.
• Cognitive radio technology:   If cognitive radio technology was used for 5th generation, 5G cellular systems, then it would enable the user equipment / handset to look at the radio landscape in which it is located and choose the optimum radio access network, modulation scheme and other parameters to configure itself to gain the best connection and optimum performance.
• Wireless mesh networking and dynamic ad-hoc networking:   With the variety of different access schemes it will be possible to link to others nearby to provide ad-hoc wireless networks for much speedier data flows.
• Smart antennas:   Another major element of any 5G cellular system will be that of smart antennas. Using these it will be possible to alter the beam direction to enable more direct communications and limit interference and increase overall cell capacity.

There are many new techniques and technologies that will be used in the new 5G cellular or mobile telecommunications system. These new 5G technologies are still being developed and the overall standards have not yet be defined. However as the required technologies develop, they will be incorporated into the new system which will be defined by the standards bodies over the coming years. 

5G Timescales & Timeline

No formal dates have been set yet for the development of 5G, but a number of companies and organisations have set their own 5G timelines so they can plan ahead.
There are many elements to the overall 5G timeline - everything from the investigation and development of new technologies, to the standardisation process, and the release of spectrum needed to support 5G.
Accordingly the various elements in the 5G timeline need to be closely managed and all the elements brought together to enable the system to be launched in the required timescale.

Frequency spectrum

One major enabler for 5G will be the release of frequency spectrum and this needs to be managed on a global scale to ensure commonality and also the reduction of interference between services, especially those operating globally. This process is managed under the auspices of the International Telecommunications Union, ITU.
To manage the process of spectrum allocations, large international meetings called the World Radio Conference, WRC are held every four years. There is one in 2015, another in 2019, and this is followed four years later by one in 2023..
A summary of the WRC dates and timeline is:

• 2015 - WRC15:   In this World Radio Conference, the main focus for mobile telecommunications is for providing additional frequency spectrum for 4G services. Work is not yet sufficiently advanced for determining allocations for 5G.
• 2019 - WRC19:   By this date, it is anticipated that work on 5G will have advanced sufficiently, and this will have allowed adequate work to be undertaken to determine the spectrum requirements for 5G. More will be required at frequencies below 5GHz, but additional spectrum is anticipated for frequencies above 5GHz as well. It is within this timeframe that 5G allocations will be discussed.
  
  Although the earliest deployments for 5G may occur around 2020, these will be comparatively limited and its use not as wide as it is anticipated to be later. Accordingly the dates for spectrum release for 5G will progressively occur as 5G deployments increase and the bandwidth requirements grow.
• 2023 - WRC23 :   Work towards WRC23 will only commence properly once WRC19 has taken place. However many will be looking towards this timeframe for further allocations for 5G and beyond.

Technology investigation timescales

One of the key elements in the early stages of 5G is the development of the basic technology. This started shortly after the first deployments of 4G.
Although the timeline for the research phase can only be broadly bounded and work will be ongoing even after the system enters service, it is anticipated that the basic research and investigations will need to be complete by around 2016 to enable this to feed into the standardisation process.

Standardisation process timelines

Standardisation is a key element of the 5G process. The timescales and dates of this activity are key to the successful deployment of 5G. It also involves several agencies including 3GPP, ETSI, NGMN, IEEE, and the like.
Possibly one of the key authorities is 3GPP. Their standards are used for the definition of the cellular standard, but with 5G being an aggregation of technologies, it is likely to require a number of standards institutions to work together.
The submission for the IMT 2020 are to follow the following dates and deadlines:

• Initial technology submission date:
• Deadline: Jun. 2019
• Detailed specification submission date
• Deadline: Oct. 2020

One of the key elements of the 5G developments themselves is the work on the radio access network, RAN. It is anticipated that the discussions on the RAN could be started around December 2015.
It is anticipated that the bulk of the requirements will be agreed in the first 6 months of the RAN discussion to guide the work in the working groups.

5G useful life timescale

It is generally estimated that the timescale for the first 5G networks will be around 2020, although there is pressure for some operators to launch much earlier.
However the useful lifetime for 5G is likely to be long. As it is aimed at providing general connectivity, and for IoT and M2M communications many of these applications will need to remain in place for many years. Utility meters, for example remain in place for many years, and the utility companies will not take kindly to having to replace their meters more frequently to follow the cellular technologies. Accordingly the useful life timescale for 5G is anticipated to remain in use until at least 2040.

5G Requirements for the next generation Mobile Wireless System

In order to ensure that the correct 5G wireless system is developed, it is necessary to collect and agree the requirements of the system.
By collecting the requirements, it is possible to understand the needs and design the 5G wireless system to meet the requirements, and in that way fulfil the needs.
By agreeing the requirements, all parties can work towards developing the same system and develop work-arounds where their own particular needs may not be sufficiently met.
Care has to be taken that the 5G requirements are carefully collected and analysed so that the best system is achieved. Otherwise it could result in a system that is not usable.

5G technology requirements

In recent years there have been several views about the ultimate form that 5G wireless technology should take. There have been two views of what 5G wireless technology should be:

• Hyper connected view:   This view of the requirements for 5G wireless systems aims to take the existing technologies including 2G, 3G, 4G, Wi-Fi and other relevant wireless systems to provide higher coverage and availability, along with more dense networks. Apart from having requirements to provide traditional services, a key differentiator would be to enable new services like Machine to Machine, M2M applications along with additional Internet of Things, IoT applications. This set of 5G requirements could require a new radio technology to enable low power, low throughput field devices with long battery lifetimes of ten years or more.
• Next generation radio-access technology:   This view of the 5G requirements takes the more technology driven view and sets specifications for data rates, latency and other key parameters. These requirements for 5G would enable a clear demarcation to be made between 4G or other services and the new 5G wireless system.

In order to meet the industry and user needs, it is necessary to accommodate all requirements within the definition process, ensuring that the final definition meets the majority of users needs without becoming so demanding that any system cannot succeed.

5G requirements summary

By accounting for the majority of needs, the following set of 5G requirements is gaining industry acceptance.

• 1-10Gbps connections to end points in the field (i.e. not theoretical maximum)
• 1 millisecond end-to-end round trip delay - latency
• 1000x bandwidth per unit area
• 10-100x number of connected devices
• Perception of) 99.999% availability
• Perception of 100% coverage
• 90% reduction in network energy usage
• Up to ten year battery life for low power, machine-type devices

One of the key issues with the 5G requirements is that there are many different interested parties involved, each wanting their own needs to be met by the new 5G wireless system. This leads to the fact that not all the requirements form a coherent list. No one technology is going to be able to meet all the needs together.
As a result of these widely varying requirements for 5G, many anticipate that the new wireless system will be a umbrella that enables a number of different radio access networks to operate together, each meeting a set of needs. As very high data download and ultra low latency requirements do not easily sit with low data rate and long battery life times, it is likely that different radio access networks will be needed for each of these requirements.
Accordingly it is likely that various combinations of a subset of the overall list of requirements will be supported when and where it matters for the 5G wireless system.
.

5G Waveforms  

Although OFDM has been a great success and still has many advantages, there are many ideas for new 5G waveforms that could bring additional advantages to the new cellular system under certain conditions and circumstances. No single waveform provides all the advantages and answers that are needed.
As a result many anticipate that the final outcome for 5G waveforms may include an adaptive solution - using the optimum waveform for any given situation.
Now that 5G is being investigated, there is an excellent opportunity to consider the optimum waveforms for the 5G system that will be used until at least 2040.

5G waveform background

Orthogonal frequency division multiplexing has been an excellent waveform choice for 4G. It provides excellent spectrum efficiency, it can be processed and handled with the processing levels achievable in current mobile handsets, and it operates well with high data rate stream occupying wide bandwidths. It operates well in situations where there is selective fading.
However with the advances in processing capabilities that will be available by 2020 when 5G is expected to have its first launches means that other waveforms can be considered.
There are several advantages to the use of new waveforms for 5G. OFDM requires the use of a cyclic prefix and this occupies space within the data streams. There are also other advantages that can be introduced by using one of a variety of new waveforms for 5G.
One of the key requirements is the availability of processing power. Although Moore's Law in its basic form is running to the limits of device feature sizes and further advances in miniaturisation are unlikely for a while, other techniques are being developed that mean the spirit of Moore's Law is able to continue and processing capability will increase. As such new 5G waveforms that require additional processing power, but are able to provide additional advantages are still viable.

5G waveform requirements

The potential applications for 5G including high speed video downloads, gaming, car-to-car / car-to-infrastructure communications, general cellular communications, IoT / M2M communications and the like, all place requirements on the form of 5G waveform scheme that can provide the required performance.
Some of the key requirements that need to be supported by the modulation scheme and overall waveform include:

• Capable of handling high data rate wide bandwidth signals
• Able to provide low latency transmissions for long and short data bursts, i.e. very short Transmission Tine Intervals, TTIs, are needed.
• Capable of fast switching between uplink and downlink for TDD systems that are likely to be used.
• Enable the possibility of energy efficient communications by minimising the on-times for low data rate devices.

These are a few of the requirements that are needed for 5G waveforms to support the facilities that are needed.

Candidate 5G waveforms

There are several new 5G waveform formats that are being considered. These include:

• FBMC, Filter Bank Multi-Carrier:   FBMC has gained a high degree of interest as a potential 5G waveform candidate. This waveform scheme provides many advantages.
  
  In many ways FBMC has many similarities to CP-OFDM, OFDM using a cyclic prefix which is used as the 4G waveform. Instead of filtering the whole band as in the case of OFDM, FBMC filters each sub-carrier individually. FBMC does not have a cyclic prefix and as a result it is able to provide a very high level of spectral efficiency.
  
  The subcarrier filters are very narrow and require long filter time constants. Typically the time constant is four times that of the basic multicarrier symbol length and as a result, single symbols overlap in time. To achieve orthogonality, offset-QAM is used as the modulation scheme, so FBMC is not orthogonal with respect to the complex plane.
• UFMC, Universal Filtered MultiCarrier:   This 5G waveform can be considered as an enhancement of CP-OFDM. It differs from FBMC in that instead of filtering each subcarrier individually, UFMC splits the signal into a number of sub-bands which it then filters.
  
  UFMC does not have to use a cyclic prefix, although one can be used to improve the inter-symbol interference protection.
• GFDM, Generalised Frequency Division Multiplexing:   GFDM is a flexible multi-carrier transmission technique which bears many similarities to OFDM. The main difference is that the carriers are not orthogonal to each other. GFDM provides better control of the out-of-band emissions and the reduces the peak to average power ratio, PAPR. Both of these issues are the major drawbacks of OFDM technology.
• Filtered OFDM, f-OFDM   As the name, f-OFDM indicates, this form of OFDM uses filtering to provide its unique characteristics. Using f-OFDM, the bandwidth available for the channel on which the signal is to be transmitted is split up into several sub-bands. Different types of services are accommodated in different sub-bands with the most suitable waveform and numerology. This enables a much better utilisation of the spectrum for the variety of services to be carried.

In addition to these waveforms, and number of other waveforms are also being considered for use with 5G

5G Modulation Schemes

The modulation schemes used for 5G will have a major impact on performance.
Whilst there are requirements to ensure that the data rates needed can be carried and the 5G modulation schemes performance issues including peak to average power ratio, spectral efficiency, and performance in the presence of interference and noise need to be included in any decisions made.

Peak to average power ratio, PAPR

The peak to average power ratio is one aspect of performance that needs to be considered for any 5G modulation scheme.
The peak to average ratio has a major impact on the efficiency of the power amplifiers. For 2G GSM, the signal level was constant and as a result it was possible to run the final RF amplifier in compression to obtain a high level of efficiency and maximise the battery life.
With the advent of 3G, then its HSPA enhancements and then 4G, the modulation schemes and waveforms have meant that the signals have become progressively more 'peaky' with higher levels of peak to average power ratio. This has meant that the final RF amplifiers cannot be run in compression and as the PAPR has increased, so the efficiency of the RF amplifiers has fallen and this is one factor that has shortened battery life.
The opportunity now arises to utilise 5G modulation schemes that can reduce the PAPR and thereby improve efficiency.

Spectral efficiency

One of the key issues with any form of 5G modulation scheme is the spectral efficiency. With spectrum being at a premium, especially in frequencies below 3 GHz, it is essential that any modulation scheme adopted for 5G is able to provide a high level of spectral efficiency.
There is often a balance between higher orders of modulation like 64 QAM as opposed to 16 QAM for example and noise performance. Thus higher order modulation schemes tend to be only sued when there is a good signal to noise ratio.
Accordingly any 5G modulation scheme will need to accommodate high levels of performance under a variety of conditions.

5G modulation schemes

3G and 4G have used modulation schemes including PSK and QAM. These schemes provide excellent spectral efficiency and have enabled the very high data rates to be carried but fall short in terms of their peak to average power ratio.
To overcome the PAPR issue, one option being considered for a 5G modulation scheme is APSK or amplitude Phase Shift Keying.
However in view of the fact that amplitude components of a signal are more subject to noise, which is substantially amplitude based, it is likely that any overall 5G modulation scheme will be adaptive, enabling the system to switch to the most optimum for of modulation for the given situation.

Note on APSK - Amplitude & Phase Shift Keying:

Amplitude and Phase-Shift Keying, APSK, is a digital modulation scheme that uses both the amplitude and the phase changes to modulate the radio frequency carrier. It has the advantage that the constellation diagram can be adjusted to optimise the signal, particaulrly in terms of reducing peak to average power ratios.

Whilst APSK may provide many advantages in terms of reducing the PAPR, it is not the complete answer and may be used as one option in an overall adaptive modulation scheme 

5G Multiple Access Schemes  


One key element of any cellular communications system is the multiple access technology that is used.
As a result the 5G multiple access schemes are being carefully considered and researched to ensure that the optimum technique or techniques are adopted.
There are several candidate 5G multiple access schemes that are in the running. Each has its own advantages and disadvantages and as a result, no single technique is likely to meet all the requirements.

5G multiple access schemes

There are several candidate systems that are being considered as the 5G multiple access scheme. They include a variety of different ideas.

• Orthogonal frequency division multiple access, OFDMA:   OFDMA has been widely used and very successful for 4G and could be used as a 5G multiple access scheme. However it does require the use of OFDM and requiring orthogonality between carriers and the use of a cyclic prefix has some drawbacks. As a result other multiple access schemes are being investigated.
• Sparse Code Multiple Access, SCMA:   SCMA is another idea being considered as a 5G multiple access scheme and it is effectively a combination of OFDMA and CDMA. Normally with OFDMA a carrier or carriers is allocated to a given user. However if each carrier has a spreading code added to it, then it would be able to transmit data to or from multiple users. This technique has been developed to use what are termed sparse code and in this way significant numbers of users can be added while maintaining the spectral efficiency levels.   Read more about Sparse Code Multiple Access, SCMA
• Non-orthogonal multiple access, NOMA:   NOMA is one of the techniques being considered as a 5G multiple access scheme. NOMA superposes multiple users in the power domain, using cancellation techniques to remove the more powerful signal. NOMA could use orthogonal frequency division multiple access, OFDMA or the discrete Fourier transform, DFT-spread OFDM. .   Read more about Non-Orthogonal Multiple Access, NOMA

There are several multiple access schemes that could be used with 5G. The one or ones used will be chosen as a result of the standardisation process which is currently onging.




       

                     How WAP Works 

 

NEXT PAGE  

Wireless Internet can be built into your cell phone or received through a wireless card. See more internet connection pictures.

Cameron Spencer/Getty Images

You and millions of other people around the world use the Internet every day -- to communicate with others, follow the stock market, keep up with the news, check the weather, make travel plans, conduct business, shop, entertain yourself and learn. Staying connected has become so important that it's hard to get away from your computer and your Internet connection because you might miss an e-mail message, an update on your stock or some news you need to know. With your business or your personal life growing more dependent on electronic communication over the Internet, you might be ready to take the next step and get a device that allows you to access the Internet on the go.
That's where wireless Internet comes in. You've probably seen news or advertising about cell phones and PDAs that let you receive and send e-mail. This seems a logical next step, but there are some questions that come up when you think about going mobile with the Internet. Will you still be able to surf the Web? How fast will you be able to get the information you need? You might have heard of the Wireless Application Protocol (WAP) and wonder how it works. Learn just what WAP is, why it is needed and what devices use it. 

The Cellular Explosion

    

Probably the most important factor in the birth of wireless Internet has been the proliferation of digital cell phones in the last few years. The expanding network of digital cellular and personal communication services (PCS) has created a solid foundation for wireless Internet services. It is estimated that there are more than 50 million Web-enabled cell phones in use. In 1997, Nokia, Motorola, Ericsson and Phone.com came together to create the WAP because they believed that a universal standard is critical to the successful implementation of wireless Internet. Since then, more than 350 companies have joined them in the WAP Forum.
Making a Web site accessible through a wireless device is quite a challenge. So far, only a small portion of the more than a billion Web sites provide any wireless Internet content. As the use of WAP-enabled devices grows, you can expect that many more Web sites will be interested in creating wireless content

WAP is designed to work on any of the existing wireless services, using standards such as:

• Short Message Service (SMS)
• High-Speed Circuit-Switched Data (CSD)
• General Packet Radio Service (GPRS)
• Unstructured Supplementary Services Data (USSD)    

Wireless Markup Language

      

WAP uses Wireless Markup Language (WML), which includes the Handheld Device Markup Language (HDML) developed by Phone.com.
WML can also trace its roots to eXtensible Markup Language (XML). A markup language is a way of adding information to your content that tells the device receiving the content what to do with it. The best known markup language is Hypertext Markup Language (HTML). Unlike HTML, WML is considered a meta language. Basically, this means that in addition to providing predefined tags, WML lets you design your own markup language components. WAP also allows the use of standard Internet protocols such as UDP, IP and XML. 

There are three main reasons why wireless Internet needs the Wireless Application Protocol:

• Transfer speed
• Size and readability
• Navigation

Most cell phones and Web-enabled PDAs have data transfer rates of 14.4 Kbps or less. Compare this to a typical 56 Kbps modem, a cable modem or a DSL connection. Most Web pages today are full of graphics that would take an unbearably long time to download at 14.4 Kbps. Wireless Internet content is typically text-based in order to solve this problem.
The relatively small size of the LCD on a cell phone or PDA presents another challenge. Most Web pages are designed for a resolution of 640x480 pixels, which is fine if you are reading on a desktop or a laptop. The page simply does not fit on a wireless device's display, which might be 150x150 pixels. Also, the majority of wireless devices use monochrome screens. Pages are harder to read when font and background colors become similar shades of gray.
Navigation is another issue. You make your way through a Web page with points and clicks using a mouse; but if you are using a wireless device, you often use one hand to scroll keys.
WAP takes each of these limitations into account and provides a way to work with a typical wireless device

Wireless Application Protocol 


Here's what happens when you access a Web site using a WAP-enabled device:

• You turn on the device and open the minibrowser.
• The device sends out a radio signal, searching for service.
• A connection is made with your service provider.
• You select a Web site that you wish to view.
• A request is sent to a gateway server using WAP.
• The gateway server retrieves the information via HTTP from the Web site.
• The gateway server encodes the HTTP data as WML.
• The WML-encoded data is sent to your device.
• You see the wireless Internet version of the Web page you selected.

To create wireless Internet content, a Web site creates special text-only or low-graphics versions of the site. The data is sent in HTTP form by a Web server to a WAP gateway. This system includes the WAP encoder, script compiler and protocol adapters to convert the HTTP information to WML. The gateway then sends the converted data to the WAP client on your wireless device.


  WAP protocol stack 

What happens between the gateway and the client relies on features of different parts of the WAP protocol stack. Let's take a look at each part of the stack:

• WAE - The Wireless Application Environment holds the tools that wireless Internet content developers use. These include WML and WMLScript, which is a scripting language used in conjunction with WML. It functions much like Javascript.
• WSP - The Wireless Session Protocol determines whether a session between the device and the network will be connection-oriented or connectionless. What this is basically talking about is whether or not the device needs to talk back and forth with the network during a session. In a connection-oriented session, data is passed both ways between the device and the network; WSP then sends the packet to the Wireless Transaction Protocol layer (see below). If the session is connectionless, commonly used when information is being broadcast or streamed from the network to the device, then WSP redirects the packet to the Wireless Datagram Protocol layer (see below).
• WTP - The Wireless Transaction Protocol acts like a traffic cop, keeping the data flowing in a logical and smooth manner. It also determines how to classify each transaction request: Reliable two-way Reliable one-way Unreliable one-way The WSP and WTP layers correspond to Hypertext Transfer Protocol (HTTP) in the TCP/IP protocol suite.
• WTLS - Wireless Transport Layer Security provides many of the same security features found in the Transport Layer Security (TLS) part of TCP/IP. It checks data integrity, provides encryption and performs client and server authentication.
• WDP - The Wireless Datagram Protocol works in conjunction with the network carrier layer (see below). WDP makes it easy to adapt WAP to a variety of bearers because all that needs to change is the information maintained at this level.
• Network carriers - Also called bearers, these can be any of the existing technologies that wireless providers use, as long as information is provided at the WDP level to interface WAP with the bearer.

Once the information is received by the WAP client, it is passed to the minibrowser. This is a tiny application built into the wireless device that provides the interface between the user and the wireless Internet.
The minibrowser does not offer anything more than basic navigation. Wireless Internet is still a long way from being a true alternative to the normal Internet. It is really positioned right now for people who need the ability to connect no matter where they are. The WAP Forum is continually working on the specifications of the WAP standard to ensure that it evolves in a timely and useful manner. 

by Shelley Danzy POSTED Sep 12, 2017

---

Robocalls aren't new, but now scammers are illegally disguising their identities under familiar-looking numbers to get people to pick up their phones for these recorded messages. Oscar Wong/Getty Images

Your phone rings. It's a local number, but it's not one you know, so there are a few seconds when your thumb seesaws between tapping the answer and ignore icons. But it could be a potential job interviewer or a food delivery driver, so you answer the call with a hesitant "hello." Alas, you roll your eyes when you hear a mechanical voice say, "Great news! You've won!"
It's easy to ignore 800-numbers, but it's tricky when your area code pops up and even trickier when a recognizable prefix displays. These dreaded prerecorded, auto-dialed telemarketing robocalls with local numbers are dubbed "neighbor-spoofing" calls.
If you're getting these calls, you're not alone. It's estimated that U.S. phone users received 2.4 billion monthly robocalls in 2016, even if they added their number to the 14-year-old National Do Not Call Registry. Along with telemarketing solicitations, robocalls ring No. 1 among consumer complaints to the Federal Communications Commission. 

So what's all the buzz about? Familiarity. A spoofing service can insert a fake ID instead of the caller's real number, often using Voice over Internet Protocol (VoIP) software, which transmits calls via the internet. We tend to let our guard down when we see phone numbers that appear to originate close to our local area. When a call comes in with the same area code and first three digits as ours, we're more inclined to answer.
The problem is, these misleading robocalls are illegal under the Truth in Caller ID Act, which prohibits spoofing "with the intent to defraud, cause harm, or wrongly obtain anything of value." Often, people and companies spoofing robocalls hide their identity because they're committing fraud. Although the FCC requires telemarketers to have consumers' written or oral consent to receive robocalls, people share their phone numbers in so many places — like social media profiles and contest entries — that it's easy for telemarketers to get hold of them.
However, phone companies do offer robocall-blocking services. And the telecom industry is trying to prevent, detect and filter these fraudulent robocalls with the Industry Robocall Strike Force, formed in 2016. In 2017, the FCC even proposed an $82 million fine against a health insurance telemarketer who made millions of illegally spoofed robocalls. So, even though telemarketers are sure to employ more schemes to get people's personal information and money — like ringless voicemail — it's good to know people still have options to protect their privacy and avoid scammers. 



     

  
  Telephone Headgear  illustration

Acompact, inexpensive and low component count telecom head- set can be constructed using two readily available transistors and a few other electronic components. This circuit is very useful for hands-free operation of EPABX and pager communication. Since the circuit draws very little current, it is ideal for parallel operation with electronic telephone set. Working of the circuit is simple and straightforward. Resistor R1 and an ordinary neon glow- lamp forms a complete visual ringer circuit. This simple arrangement does not require a DC blocking capacitor because, under idle conditions, the telephone line voltage is insufficient to ionise the neon gas and thus the lamp does not light. Only when the ring signal is being received, it flashes at the ringing rate to indicate an incoming call. The bridge rectifier using diodes D1 through D4 acts as a polarity guard which protects the electronic circuit from any changes in the telephone line polarity. Zener diode D5 at the output of this bridge rectifier is used for additional circuit protection. Section comprising transistor T1, resistors R2, R3 and zener diode D6 forms a constant voltage regulator that provides a low voltage output of about 5 volts. Dial tone and speech signals from exchange are coupled to the receiving sound amplifier stage built around transistors T2 and related parts, i.e. resistors R7, R6 and capacitor C5. Amplified signals from collector of transistor T2 are connected to dynamic receiver RT-200 (used as earpiece) via capacitor C7. A condenser microphone, connected as shown in the circuit, is used as transmitter. Audio signals developed across the microphone are coupled to the base of transistor T1 via capacitor C3. Resistor R4 determines the DC bias required for the microphone. After amplification by transistor T1, the audio signals are coupled to the telephone lines via the diode bridge. The whole circuit can be wired on a very small PCB and housed in a medium size headphone, as shown in the illustration. For better results at low line currents, value of resistor R2 may be reduced after testing

      

 






      =========AMNIMARJESLOW GOVERNMENT  17 LOW  SHOOTER=========