Analog Modulation

Analog modulation: The carrier signal sent in analog radio transmission is simply a continuous electrical signal. It carries no information and is referred to as a CW. Only when the CW is modulated is it called a carrier. Analog modulation is the representation of analog information by an analog signal. There are three types of modulation that can be applied to a analog signal to enable it to carry information. The height of the signal, the frequency of the signal and the relative starting point, or phase of the signal.

Amplitude Modulation (AM): the height of a wave, know as amplitude, can be measured in volts (electrical pressure) .  In Amplitude modulation (AM) the height of the wave is changed in accordance with the height of  another signal, called the modulating signal. AM is very susceptible to interference from outside sources such as lighting , it is general not used for data transmissions.

Screen Shot 2017-08-01 at 7.16.52 pm.png Figure: Amplitude of a signal

Screen Shot 2017-08-01 at 7.16.46 pm.pngFigure: Amplitude modulation(AM)

Frequency Modulation (FM):  In Frequency modulation (FM) , the number of waves that occur during one second undergoes change based on the amplitude  of the modulating signal while the amplitude and the phase of the carrier remain constant.

FM is not as susceptible to interference from outside sources and is most commonly used to broadcast radios programs. An FM carrier has a wider  bandwidth, which allows it to carry Hi-Fi as well as stereophonic signals, with two separate sound channels.

Screen Shot 2017-08-01 at 7.16.29 pm.png

Figure: Frequency modulation (FM)

Phase Modulation: In contrast to AM, which changes the height of the wave, and FM which increase the number of waves per cycle, phase modulation (PM) changes the starting point of the cycle, while the amplitude and frequency of the carrier remain constant. Phase modulation is not generally used to represent analog signals.

A signal composed of sine waves has a phase associated with it. The phase is measured in degrees and one complete wave cycle covers 360 degrees. A phase change is always measured with reference to some other signal.

J. L. Olenewa (2014). Guide to Wireless Communications, ( Third Edition). Boston:CENGAGE Learning

What is an Antenna

Antennas are used to transmitted and receive radio waves. An antenna is a length of copper wire or similar material, with one end free and the other end connected to a receiver or transmitter. When transmitting the radio waves created by the electronic circuit of the transmitter are fed to this antenna. This sets up an electrical pressure (voltage) along the wire, which will cause a small electrical current to flow into the antenna. Because of the current is alternating , it flows back and forth in the antenna at the same frequency as the radio waves,  it creates both a magnetic field and an electrical field around the antenna. This continuous (analog) combination of magnetism and electrical pressure moves away (propagates) from the antenna . The results is an electromagnetic wave(EM wave).

J. L. Olenewa (2014). Guide to Wireless Communications, ( Third Edition). Boston:CENGAGE Learning

Wireless Personal area network

What is a WPAN?

WPAN standards for Wireless personal area network, it consist of a group of short range communication  devices that work from distance from a few inches to 10m  and can on occasion reach up to a distances of 30m.

WPAN are usually designed for  data transmission that do not required high data throughput.

WPAN has 3 advantages;

  • Reduce the  need for cables and wires
  • Do not require much power due low out put transmitting power making battery life last for much longer.
  • Due to distance limitation it has somewhat better security and privacy compared to other wireless technologies.

WPAN technology can consist  but are not limited to the following below types devices

  • portable data exchange devices
  • Home control systems
  • audio head sets
  • industrial control systems
  • home security systems
  • RFID tags
  • inventory and asset tracking

Pyles, J. Carrell, J.L. Tittel, E. (2013). Guide to TCP/IP: IPv6 and IPv4 (Fifth Edition). Boston:CENGAGE Learning

Wireless Signals

The following information is based on my UNI studies on wireless communication systems.

Wireless Signals: All forms of electromagnetic energy- gamma rays, radio waves, even light- travel through space in the forms of waves. These waves are know as electromagnetic waves. They travel at the speed of light :186,000 miles per second (300,000 kilometres).

802.11 use wireless transmission use electromagnetic (EM) waves as the medium, not air or empty space

There are two basic types of waves by which wireless data are sent and received: infrared light and radio waves. Infrared light some of which is invisible, has many characteristics that visible light has , because it is adjacent to visible light on the light spectrum. Yet it is a better medium for data transmissions because it is less susceptible to interference from other sources of visible light.

Each wave length within the spectrum of visible light represents a particular colour. This because  the differing wavelengths of light waves bend at a different angle when passed through a prism. Which in turn produces different colours. The colours that visible light produces are red, orange, yellow, green, blue, indigo, and violet. Visible light is sometime referred to as ROYGBIV.

Infrared wireless systems require that each device have two components: an emitter, which transmits a signal, and a detector, which receives the signal. An emitter is usually a laser diode or a light-emitting diode(LED). Infrared wireless systems send data by the intensity of the light wave. The emitter sends a narrowly focused beam of infrared light.

(TV remote is an example of this type of device)

Infrared wireless transmission can be either directed or diffused. A directed transmission requires that the emitter and detector be directly aimed at one another( line of sight).

A diffused transmission relies on reflected light. With diffused transmission the emitters have a wide focus beam instead of a narrow beam.

Infrared  wireless systems have several advantages. Infrared light neither interferes with other types of communications signals(such’s as radio waves) nor is it affected by other signals. Expect light.

Infrared wireless light does not penetrate wall, the signals are kept inside a room, this makes it impossible for someone else to listen in on the transmission signal.

Infrared wireless systems have several serious limitations

Lack of mobility: directed infrared wireless systems use a line of sight principle, which makes it difficult for users because the alignment between the emitter and the detector would have to be continually adjusted.

Range: limited range of coverage. Directed infrared systems required line of sight and cannot have anything place in-between the infrared beam, which means they need to place close together to ensure that nothing obstructs there path, due to the angle of deflection, diffused infrared can cover a ranged of 50feet(15m), and because diffused infrared requires  a reflection point, it can only be used indoors.

Speed: limitation of speed, diffused infrared can send data a maximum speeds of only 4Mbps. This is because of the wide angles of the beam lose energy as it reflects. The loss of energy results in a weakening of the signal. The weak signal cannot be transmitted over long distance, nor does it have sufficient energy to maintain a high transmission speed, resulting in a lower data rate.

Because of the limitation, infrared wireless systems are generally used in specialised applications, such as data transfers between computers, digital cameras, handheld data collection devices, PDAs, electronic books and other similar mobile devices.

Radio waves provide the most common and effective means of wireless communications today. Radio waves travel the space or air similar to that of  electromagnetic wave, electromagnetic waves that travel in this fashion is called radio wave(radiotelephony). When an electric current passes through wire, it creates a magnetic field in the space around the wire. As this magnetic field radiates, it creates radio waves. Radio waves like light and heat waves, are electromagnetic waves, they move outward , usually in all directions from the source.

Unlike infrared light and heat radio waves are free from some of there limitations, radio waves can travel great distances and penetrate most solid objects.

Analogue and digital data are transmitted over radio waves. An analogy signal is one in which the intensity of the waves( voltage or amplitude) varies and is broadcast continuously.

Digital signal consists of discrete or separate pulses, as opposed to an analogy signal, which continuous. A digital signal has numerous starts and stops throughout the signal.

To transmit a digital signal over an analog medium, it requires a device know as a modem(MOdulator/DEmodulator) is to be used. A modem takes the distinct digital signals from a computer and encodes them into continuous analog signal for transmission over analog phone lines. The process of encoding the digital signals(bits) onto an analog wave is called modulation. The modem at the receiving end of the connection then reversers the process by decoding the analog signal into its original digital signal

Wavelength: is the distance between any point in one wave cycle and the same point in the next cycle

Frequency: is the number of time a cycle( which composed of one top (positive) and one bottom(negative peak) occurs within one second.  Frequencies are measured by the amount of cycles per second. The term hertz(Hz) is used instead of cycles per second.

Radio transmitter send what is know as a carrier signal. This is a continuous wave(CW) of constant amplitude(measured in volts) and frequency. The up and down movement of the  wave is call an oscillation signal or sine wave.

A CW by itself carries no useful information. Only after it is modulated does it contain some kind of information which is then called a carrier signal or carrier wave.

J. L. Olenewa (2014). Guide to Wireless Communications, ( Third Edition). Boston:CENGAGE Learning

Time to Live IPv4 and Hop limit IPv6

The Time to Live field is required in an IP Packet so that a Router( Layer 3 Network device) knows  how long the packet has been in the network for  and if it should discard it due to exceeding its limit, which can be a value between 1 and 255.

In Ipv4 the 8 bit field is called Time to Live , but for IPv6 its is called Hop Limit field as it was often referred to in IPv4, both the TTL and Hop limit  achieve the same results which is to stop a packet looping the network by decrementing their value by 1 after each hop with a maximum value of 255

TCP/IP vs OSI model

TCP/IP being the first of the models, is the foundation model from which Internet is based on. Into days world it is extremely unlikely to find a network that is not running TCP/IP.

TCP/IP  consisting of the 4 layers, Network, Internet, Transport and Applications.

  •  Network interface (layer 1):  physical components of network connectivity between the network and the IP protocol.
  •  Internet (layer 2): Contains all functionality that manages the movement of data between two network devices over a routed network.
  •  Host-to-host (layer 3): Manages the flow of traffic between two hosts or devices, ensuring that data arrives at the application on the host for which it is targeted.
  •  Application (layer 4): Acts as final endpoints at either end of a communication session between two network host.

The OSI model was  developed some 10 years later to compete with the TCP/IP. OSI Networking model is still used todays as an excellent tool to describe and explain network communication.

The OSI model  is broken down into 7 layers that are used to describe a specific aspect of network communications.

  • Physical (layer 1): Provides access to the cable electrical signals ones and zeros.
  • Data Link (layer 2): Provides Physical addressing, ensures data is error free.
  • Network (Layer 3): Provides “logical” addressing, finds best path a destination .
  • Transport (layer 4): determines “how” the data is sent, defines well-know services(ports).
  • Session (layer 5) : Starts and ends sessions, logically keeps sessions separate.
  • Presentation (layer 6): Takes data and formats into a generic language understandable by applications.
  • Application (layer 7): Interfaces with applications -provides access to Apps.


TCP/IP in my opinion is the most widely know out of the two Network models , but  when working with and describing networks, especially when relating to fault finding I always refer to the OSI network model, as I believe breaking  everything down into individual layers helps describe and isolate specific faults.


Pyles, J. Carrell, J.L. Tittel, E. (2013). Guide to TCP/IP: IPv6 and IPv4 (Fifth Edition). Boston:CENGAGE Learning

Cioara, J.(2008). CCNA Mega Guide: CCNA (640-802).

The Pro’s and Cons of utilizing IPv6 in today’s network Architecture design.

In todays world the need for devices connectivity  continues  to grow rapidly, As I look around my house, I count over 25 devices that require an IP Address and internet connection, Long gone are the days of just having the one desktop computer in the household.

The need for more IP Address was the driving  force behind the implementation of IPv6.


-IPv6 provides 3.4×10^38 IPv6 address  .

-Broadcast are no longer used as IPv6 uses multicast to communicated with multiple host simultaneously reducing network bandwidth requirements.

-NAT/PAT no longer needed:  The IPv6 Address space is so large that is has removed the need to use NAT/PAT making  routing  more efficient.

-Address assignment features:  includes stateless auto configuration and DHCP for dynamic address assignment.

-Aggregation: makes for much easier aggregation of IP address blocks, making for more efficient routing on the internet .

-Mobility support built in: Devices can retain there IPv6 address and not lose current Application sessions whilst moving around an internetwork.

-IPSEC:  requires that all IPv6 devices be able to support IPsec.

-Routing efficiency : IPv6 reduces the size of routing tables making routing more efficient.

No requirement for to perform Subnetting.


-Learning an new format of IP Addressing ,it took forever for me to understand IPv4.

-Checking equipment for IPv6 Compatibility before purchasing and implementation .

-Learning IPv6 command line on Routers and switches.

The Pro’s of using IPv6  certainly out number the Cons however even with this Companies are not rushing out to implement IPv6 within there organisations .


Wallace, K. (2015). CCNP Routing and Switching Route 300-101 Official Cert Guide. Indianapolis: Cisco Press

Pyles, J. Carrell, J.L. Tittel, E. (2013). Guide to TCP/IP: IPv6 and IPv4 (Fifth Edition). Boston:CENGAGE Learning

Wireless Site Survey (EDC)

The following below every day carrier (EDC) items are what I have on me every day at work (as at Oct 2017)

This is my go to kit for all my wireless surveys and fault finding

Engineering laptop:Surface Pro 4-Core i5, 8gigs of ram, 256HDD

Wireless site survey kit contained inside a Pelican 1030 case(Refer to Figure 1 & 2:)

  • 3x USB NIC300  (suggest label with the Mac-address )
  • 2x Metageek DBX
  • 1x Riverbed AirPCAP NX
  • 2x USB cables for DBX
  • 32gb USB- contains Network software applications and drivers

Storage pouch:(refer to figure 3)

  • Alfa networks  802.11b/g /n adapater
  • Alfa networks  802.11ac adapter
  • Antennas for AirCap NX and Alfa cards
  • USB 2 dongle
  • USB 3 dongle
  • RJ45 adapters
  • USB to Ethernet adapters
  • USB 3 cables
  • USB 2 cables
  • USB male to female cable

Screen Shot 2017-07-27 at 7.26.37 pm.pngScreen Shot 2017-07-27 at 7.27.32 pm.png

Frequency Bands

Frequency Bands

Extremely low (ELF)                        3Hz – 30Hz

Super Low (SLF)                               30Hz – 300Hz

Ultra Low (ULF)                                300Hz – 3000Hz (3KHZ)

Very Low (VLF)                                 3KHz – 30KHz

Low (LF)                                             30KHz – 300KHz

Medium (MF)                                  300KHz – 3000KHz (3MHz)

High (HF)                                           3MHz – 30MHz

Very High (VHF)                               30MHz – 300MHz

Ultra High (ULF)                               300MHz – 3000MHz (3GHz)

Super High (SHF)                             3GHz – 30GHz

Extremely High (EHF)                     30GHz – 300GHz