1. Evolution of Mobile Cellular Communication
2.
PAGING SYSTEM
A paging system allows for one-way communication to a large audience. Regardless of the broadcast
source, a one-way paging system lets the speaker provide clear, amplified instructions throughout a
facility. The paging employee speaks a message into a telephone and that message is then broadcast
through a network of speakers. Messages can also be recorded and broadcast at a later time.
Some Benefits and Advantages Of Paging Systems
There are a number of advantages to using a one-way paging system versus other means of mass
communication:
● Emails are often ignored or captured by spam blockers.
● Mass texts depend on a strong, local phone network.
● A paging system is hard-wired into the building's infrastructure, allowing reliable mass
communication.
● A network of speakers ensure that a message is communicated to every area of a building
simultaneously. It's also possible to send pages to specific building "zones" if needed.
● Another key benefit of a paging system is that no dedicated broadcast mechanism is required.
An employee can simply pick up the phone, select the paging system and broadcast to the
entire building.
Some Common Use Cases For Paging Systems
Paging systems can be used to send a variety of messages. The most common example of a paging
system is rapid communication between employees in a retail setting. A department store cashier can
request assistance from another department to answer a customer question. In a similar example, a large
manufacturing facility can page an employee who has an incoming call, but is likely not near a specific
phone.
One of the most important uses for paging is to warn employees of a fire or other emergency. In those
scenarios, there is no more effective means of quickly communicating with your workforce.
HTTPS://WWW.MITEL.COM/FEATURES-BENEFITS/PAGING
SYSTEM#:~:TEXT=A%20PAGING%20SYSTEM%20IS%20HARD,BUILDING%20%22ZONES%22%20IF%20NEEDED.
3. Cordless Telephone System
4. Cellular Telephone System
4. Fundamentals of Cellular System
Cellular network basics
- a summary or tutorial about cellular network basics, detailing the main elements within it BTS, BSC, HLR, VLR, etc.
Cellular / Mobile Telecommunications Basics Includes:
What is cellular communications Concept of cellular system Radio access network, RAN
Base station antenna technology Multiple access techniques Duplex techniques What's
inside a cellphone SIM cards Handover Backhaul
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 center of the overall cellular system and the success of the whole end to end system is
dependent largely on its performance.
5. FDMA
Advantages and Disadvantages of Frequency-division multiple access (FDMA)
Frequency-division multiple access (FDMA) :
Frequency-division multiple access is one among the only multiple access methods. During this method,
the channel bandwidth is subdivided into a variety of sub-channels. This multiple access method used
for voice and data transmission. During this method the general channel bandwidth is being shared by
multiple users, therefore the variety of users can transmit their information simultaneously. The adjacent
frequency bands within the FDMA spectrum are likely to interfere with one another. Therefore, it’s
necessary to incorporate the guard bands between the adjacent frequency bands. No code words and
synchronization are required. Power efficiency reduced using FDMA, it’s an old and proven system and
used for analog signals.
Advantages of FDMA :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Use of efficient numerical codes increases the capacity.
It reduces the worth.
Lowers the inter symbol interference (Equalization isn’t required).
An FDMA system is often easily implemented, system are often configured so, the improvements
in terms of speech encoder and bit rate reduction could even be easily incorporated.
Simple to implement, from a hardware standpoint.
Fairly efficient with a little base population and when traffic is constant.
FDMA includes its applicability to both analog and digital transmission systems, the actual fact
that no special coding is required, the allocation of capacity is simple, no network
synchronization or timing is required, which the baseband signal are often recovered using
simple and cheap receiver equipment.
Reducing the knowledge bit rate and using efficient digital codes can obtain capacity increases.
As FDMA systems use low bit rates (large symbol time) compared to average delay spread, they
reduce the worth, and there is low Inter Symbol Interference (ISI).
There is hardly any equalization required.
Technological advances required for implementation are simple. A system is often configured so
as that improvement in terms of speech coder bit-rate reduction could be readily incorporated.
Disadvantages of FDMA :
1. Due to the simultaneous transmission of a large number of frequencies, there is a possibility of
inter modulation distortion at the transponder.
2. It is suitable only for analog signals.
3. Storage, enhancement of signals is not possible.
4. The large bandwidth requirement for transponders.
5. Guard bands may waste capacity.
6. It requires RF(Radio Frequency) filters to meet stringent adjacent channel rejection
specifications. This may increase the cost of the system.
7. Network planning is cumbersome and time-critical.
8. There is not much flexibility so, need to slowly change already assigned traffic patterns.
9. The carrying capacity of traffic is relatively low.
10. In a general system, because the channels are assigned for a single user, idle channels add to the
spectrum.
11. Frequency planning is time-consuming.
12. Required multi-channel receivers that are expensive.
13. The highest bit rate per channel is fixed and small.
14. Hardware involves narrowband filters, which cannot be realized in VLSI.
6. TDMA
Advantages and disadvantages of TDMA
TDMA full form is Time Division Multiple Access uses time instead of frequency. It is used to facilitate
channel sharing without interference. Different user shares the same time slot of the complete time
available. Each user to allocate a time slot in which the user can access the channel and in each slot, only
one user is allowed to transmit or receive.
TDMA was more used by Europe, Japan, and Asian countries, whereas CDMA is widely used in North and
South America. But nowadays both technologies are very popular throughout the world.
Advantages of TDMA :
●
●
●
●
●
●
●
●
●
●
●
TDMA can easily adapt to the transmission of data as well as voice communication.
It has the ability to carry 64 kbps to 120 Mbps of data rates.
No interference from simultaneous transmission.
TDMA is the cost-effective technology to convert an analogue system to digital.
Share a single carrier frequency with multiple users
Mobile assisted handoff possible
TDMA provides the user with extended battery life since transmitting the only portion of the
time during conversations
Flexible bit rate
No frequency guard band required
No need of a precise narrowband filter
TDMA separates users according to time ensures that there will be no interference from the
simultaneous transmission.
●
●
●
●
TDMA allows the operator to do services like fax, voiceband data, SMS as well as applications
such as multimedia and video conferencing.
TDMA offers substantial savings in base-station equipment, space, and maintenance, an
important factor as cell sizes grow ever smaller.
Dual-band 800/1900 MHz.
It is the only technology that offers an efficient utilization of hierarchal cell structures like pico,
micro, and macro.
Disadvantages of TDMA :
●
●
●
●
●
●
●
●
●
In TDMA each user has a predefined time slot so that users roaming from one cell to another are
not allotted a time slot. Thus, if all the time slots in the next cell are already occupied, a cell
might well be disconnected. In the same way, if all the time slots in the cell in which a user
happens to be in are already occupied, a user will not receive a dial tone.
It is subjected to multipath distortion. A signal coming from a tower and receive to handset
might come from any one of several directions so on the road signal bounced off several
different buildings before arriving which can cause interference.
Network and spectrum planning is intensive.
Too few users result in ideal channels rural versus urban environment.
High synchronization overhead.
Frequency/slot allocation is to be complex in TDMA.
Equalization was necessary for high data rates.
Demands high peak power on the uplink in transient mode.
Signal processing is required for matched filtering and correlation detection.
7. CDMA advantages and disadvantages
The term CDMA full from is Code Division Multiple Access. It is one type of cellular technology
in which two main system Base system and mobile subscriber or users. It allows multiple
transmitters to transmit information over a single channel simultaneously. CDMA system works
based on spread spectrum concept. This article gives information about the advantages and
disadvantages of CDMA to know more about CDMA technology.
Advantages of CDMA :
●
●
●
●
●
●
●
●
CDMA channel is not easily decodable hence it offers increases cellular communication
securities
Call quality is better with more consistent sound as compared to GSM
Less interference due to hand off features reduces call dropping
Gives better coverage and needs few antenna sites and also consumes less power
Increase user capacity because of more users per MHz of bandwidth than any other
system so that it has 4 to 5 times capacity than GSM
Better multipath performance
The frequency reuse plan is easier to manage
Smaller phones
●
●
●
●
●
●
●
●
●
●
●
●
●
Greatest spectrum efficiency
Low power requirement
Increase efficiency as it can serve more users
High voice quality as well as signal quality
Flexible allocation of resources
Operate at a very low power level
CDMA does not require any synchronization
It has many numbers of users can share in the same bandwidth
Efficient practical utilization of fixed frequency spectrum
No sense of handoff when changing cells
Easy to add many numbers of users
Increase user resources
Impossible for hackers to decipher the code sent
Disadvantages of CDMA :
●
●
●
●
●
●
●
●
●
●
Time synchronization is required
It can't offer international roaming, a large GSM advantage
The CDMA system performance degrades with an increase in the number of users
A network of CDMA is not mature because it is relatively new with GSM
In while we are using CDMA, code length can be carefully selected, because it can
induce delay
When the number of users increases, the overall quality of service decreases.
Self-jamming problem
The near-far problem arises when we are using CDMA techniques
Higher cost due to the greater equipment
Reduce capacity because gradual transfer increases the use of radio resources