Wireless Communication and Networking by WilliamStallings Chap2Senthil Kanth
Hai I'm Senthilkanth, doing MCA in Mepco Schlenk Engineering College..
The following presentation covers topic called Wireless Communication and Networking
by WilliamStallings for BSc CS, BCA, MSc CS, MCA, ME students.Make use of it.
Wireless Communication and Networking
by WilliamStallings Chapter : 2Transmission Fundamentals
Chapter 2
Electromagnetic Signal
Function of time
Can also be expressed as a function of frequency
Signal consists of components of different frequencies
Time-Domain Concepts
Analog signal - signal intensity varies in a smooth fashion over time
No breaks or discontinuities in the signal
Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level
Periodic signal - analog or digital signal pattern that repeats over time
s(t +T ) = s(t ) -¥< t < +¥
where T is the period of the signal
Time-Domain Concepts
Aperiodic signal - analog or digital signal pattern that doesn't repeat over time
Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts
Frequency (f )
Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
Time-Domain Concepts
Period (T ) - amount of time it takes for one repetition of the signal
T = 1/f
Phase () - measure of the relative position in time within a single period of a signal
Wavelength () - distance occupied by a single cycle of the signal
Or, the distance between two points of corresponding phase of two consecutive cycles
Sine Wave Parameters
General sine wave
s(t ) = A sin(2ft + )
Figure 2.3 shows the effect of varying each of the three parameters
(a) A = 1, f = 1 Hz, = 0; thus T = 1s
(b) Reduced peak amplitude; A=0.5
(c) Increased frequency; f = 2, thus T = ½
(d) Phase shift; = /4 radians (45 degrees)
note: 2 radians = 360° = 1 period
Sine Wave Parameters
Time vs. Distance
When the horizontal axis is time, as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time
With the horizontal axis in space, graphs display the value of a signal at a given point in time as a function of distance
At a particular instant of time, the intensity of the signal varies as a function of distance from the source
Frequency-Domain Concepts
Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency, it’s referred to as the fundamental frequency
Spectrum - range of frequencies that a signal contains
Absolute bandwidth - width of the spectrum of a signal
Effective bandwidth (or just bandwidth) - narrow band of frequencies that most of the signal’s energy is contained in
Frequency-Domain Concepts
Any electromagnetic signal can be shown to consist of a collection of periodic analog signals (sine waves) at different amplitudes, frequencies, and phases
The period of the total signal is equal to the period of the fundamenta
COMPARISON OF BER AND NUMBER OF ERRORS WITH DIFFERENT MODULATION TECHNIQUES I...Sukhvinder Singh Malik
This paper provides analysis of BER and Number of Errors for MIMO-OFDM wireless communication system by using different modulation techniques. Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks, and link reliability. So the performances of the wireless communication systems can be enhanced by using multiple transmit and receive antennas, which is generally referred to as the MIMO technique. Here analysis will be carried out for an OFDM wireless communication system using different modulation techniques and considering the effect and the wireless channel like AWGN, fading. Performance results will be evaluated numerically and graphically using the plots of BER versus SNR and plots of number of errors versus SNR.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Very-Low-Profile Monopole Antennas for Concurrent 2.4- and 5-GHz WLAN Access-...Saou-Wen Su
A very-low-profile, six-antenna MIMO system aimed at operating in the concurrent 2.4 and 5 GHz bands for WLAN access-point applications is proposed. The MIMO system consists mainly of an antenna ground plane and six short-circuited monopole antennas, among which the three antennas are designated for 2.4 and 5 GHz operation respectively. The antennas are set in a sequential, rotating arrangement on the ground plane, and the 2.4 and 5 GHz antennas are facing each other one by one. The results show that well port isolation can be obtained together with good radiation characteristics. With a low profile of 6 mm in height, the proposed design can easily fit into wireless access points or routers and allow the 2.4- and 5-GHz band signals to be simultaneously received and transmitted with no need of external diplexer.
Its exploring the technique for spatially successive interference cancellation and superposition of transmission for upcoming radio communication 5G technology.
Low Noise Amplifier using Darlington Pair At 90nm Technology IJECEIAES
The demand of low noise amplifier (LNA) has been rising in today’s communication system. LNA is the basic building circuit of the receiver section satellite. The design concept demonstrates the design trade off with NF, gain, power consumption. This paper reports on with analysis of wideband LNA. This paper shows the schematic of LNA by using Darlington pair amplifier. This LNA has been fabricated on 90nm CMOS process. This paper is focused on to make comparison of three stage and single stage LNA. Here, the phase mismatch between these patameters is quantitavely analyzed to study the effect on gain and noise figure (NF). In this paper, single stage LNA has shown the 23 dB measured gain, while the three stages LNA has demonstrated 29 dB measured gain. Here, LNA designed using darlington pair shows low NF of 3.3-4.8 dB, which comparable to other reported single stage LNA designs and appreciably low compared to the three stages LNA. Hence, findings from this paper suggest the use of single stage LNA designed using Darlington pair in transceiver satellite applications.
Wireless Communication and Networking by WilliamStallings Chap2Senthil Kanth
Hai I'm Senthilkanth, doing MCA in Mepco Schlenk Engineering College..
The following presentation covers topic called Wireless Communication and Networking
by WilliamStallings for BSc CS, BCA, MSc CS, MCA, ME students.Make use of it.
Wireless Communication and Networking
by WilliamStallings Chapter : 2Transmission Fundamentals
Chapter 2
Electromagnetic Signal
Function of time
Can also be expressed as a function of frequency
Signal consists of components of different frequencies
Time-Domain Concepts
Analog signal - signal intensity varies in a smooth fashion over time
No breaks or discontinuities in the signal
Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level
Periodic signal - analog or digital signal pattern that repeats over time
s(t +T ) = s(t ) -¥< t < +¥
where T is the period of the signal
Time-Domain Concepts
Aperiodic signal - analog or digital signal pattern that doesn't repeat over time
Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts
Frequency (f )
Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
Time-Domain Concepts
Period (T ) - amount of time it takes for one repetition of the signal
T = 1/f
Phase () - measure of the relative position in time within a single period of a signal
Wavelength () - distance occupied by a single cycle of the signal
Or, the distance between two points of corresponding phase of two consecutive cycles
Sine Wave Parameters
General sine wave
s(t ) = A sin(2ft + )
Figure 2.3 shows the effect of varying each of the three parameters
(a) A = 1, f = 1 Hz, = 0; thus T = 1s
(b) Reduced peak amplitude; A=0.5
(c) Increased frequency; f = 2, thus T = ½
(d) Phase shift; = /4 radians (45 degrees)
note: 2 radians = 360° = 1 period
Sine Wave Parameters
Time vs. Distance
When the horizontal axis is time, as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time
With the horizontal axis in space, graphs display the value of a signal at a given point in time as a function of distance
At a particular instant of time, the intensity of the signal varies as a function of distance from the source
Frequency-Domain Concepts
Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency, it’s referred to as the fundamental frequency
Spectrum - range of frequencies that a signal contains
Absolute bandwidth - width of the spectrum of a signal
Effective bandwidth (or just bandwidth) - narrow band of frequencies that most of the signal’s energy is contained in
Frequency-Domain Concepts
Any electromagnetic signal can be shown to consist of a collection of periodic analog signals (sine waves) at different amplitudes, frequencies, and phases
The period of the total signal is equal to the period of the fundamenta
COMPARISON OF BER AND NUMBER OF ERRORS WITH DIFFERENT MODULATION TECHNIQUES I...Sukhvinder Singh Malik
This paper provides analysis of BER and Number of Errors for MIMO-OFDM wireless communication system by using different modulation techniques. Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks, and link reliability. So the performances of the wireless communication systems can be enhanced by using multiple transmit and receive antennas, which is generally referred to as the MIMO technique. Here analysis will be carried out for an OFDM wireless communication system using different modulation techniques and considering the effect and the wireless channel like AWGN, fading. Performance results will be evaluated numerically and graphically using the plots of BER versus SNR and plots of number of errors versus SNR.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Very-Low-Profile Monopole Antennas for Concurrent 2.4- and 5-GHz WLAN Access-...Saou-Wen Su
A very-low-profile, six-antenna MIMO system aimed at operating in the concurrent 2.4 and 5 GHz bands for WLAN access-point applications is proposed. The MIMO system consists mainly of an antenna ground plane and six short-circuited monopole antennas, among which the three antennas are designated for 2.4 and 5 GHz operation respectively. The antennas are set in a sequential, rotating arrangement on the ground plane, and the 2.4 and 5 GHz antennas are facing each other one by one. The results show that well port isolation can be obtained together with good radiation characteristics. With a low profile of 6 mm in height, the proposed design can easily fit into wireless access points or routers and allow the 2.4- and 5-GHz band signals to be simultaneously received and transmitted with no need of external diplexer.
Its exploring the technique for spatially successive interference cancellation and superposition of transmission for upcoming radio communication 5G technology.
Low Noise Amplifier using Darlington Pair At 90nm Technology IJECEIAES
The demand of low noise amplifier (LNA) has been rising in today’s communication system. LNA is the basic building circuit of the receiver section satellite. The design concept demonstrates the design trade off with NF, gain, power consumption. This paper reports on with analysis of wideband LNA. This paper shows the schematic of LNA by using Darlington pair amplifier. This LNA has been fabricated on 90nm CMOS process. This paper is focused on to make comparison of three stage and single stage LNA. Here, the phase mismatch between these patameters is quantitavely analyzed to study the effect on gain and noise figure (NF). In this paper, single stage LNA has shown the 23 dB measured gain, while the three stages LNA has demonstrated 29 dB measured gain. Here, LNA designed using darlington pair shows low NF of 3.3-4.8 dB, which comparable to other reported single stage LNA designs and appreciably low compared to the three stages LNA. Hence, findings from this paper suggest the use of single stage LNA designed using Darlington pair in transceiver satellite applications.
Příspěvek pro odborný seminář Zabezpečení dokumentů konaný 20.4.2010 v Praze. Představení řešení zabezpečení dokumentů Oracle Information Rights Management (IRM).
Příspěvek pro odborný seminář Zabezpečení dokumentů konaný 10.12.2009 v Oracle Partner Studio v Praze. Představení řešení zabezpečení dokumentů Oracle Information Rights Management (IRM).
Příspěvek pro odborný seminár Správa a zabezpečenie dokumentov konaný 27.10.2009 v Bratislavě. Představení řešení správy obsahu organizace (dokumentů, archiválií, webových prezentací a multimédií) Oracle Universal Content Management (UCM).
Příspěvek pro odborný seminár Správa a zabezpečenie dokumentov konaný 27.10.2009. Představení řešení zabezpečení dokumentů Oracle Information Rights Management (IRM).
Příspěvek pro 5. ročník konference Svět IT Security 2009 (s podtitulem „Vytvořme si bezpečnou budoucnost“) konané 6.10.2009 v rámci akce INVEX FORUM 2009. Představení řešení zabezpečení dokumentů Oracle Information Rights Management (IRM), a to včetně praktické ukázky z pohledu koncového uživatele prostřednictvím aplikace Oracle IRM Desktop.
Představení řešení zabezpečení dokumentů Oracle Information Rights Management (IRM). Příspěvek pro 2. den odborné konference IIR Nové výzvy CIO konané 1.-2.12.2009 v hotelu Diplomat v Praze.
The global coverage of the 2.4 GHz ISM band has ensured its visibility among device vendors. In addition to the rapid increase of devices to be deployed, the number of RF technologies and protocols sharing this band has also increased.
Of course, it is important that all devices operate well and within the regulation of the band, but even then, the chances of RF interference between devices in the band are considerable (see Figure 1).
This interference can lead to packet loss, increased power consumption, and degraded network performance. The key to maintaining good coexistence with other devices in the band is robustness in terms of interference.
A frequency shortcut scheme and good selectivity for this application can ensure that this coexistence is achieved.
Fundamental of Radio Frequency communications.pptginanjaradi2
Fundamentals of Radio Frequency (RF) communications encompass the principles and techniques used to transmit and receive information wirelessly using electromagnetic waves within the radio frequency spectrum. Here's a breakdown of the key components:
1. **Electromagnetic Spectrum**: RF communications utilize a portion of the electromagnetic spectrum. This spectrum ranges from low frequencies used for power transmission to high frequencies used in technologies like microwaves and beyond. RF typically occupies the frequency range from about 3 kHz to 300 GHz.
2. **Modulation**: Modulation is the process of impressing information onto a radio wave by varying one or more of its properties such as amplitude, frequency, or phase. Common modulation techniques include Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
3. **Transmitters**: Transmitters generate radio frequency signals carrying the information to be transmitted. They typically consist of an oscillator to produce the carrier frequency, modulation circuitry to impress the information onto the carrier, and amplifiers to boost the signal for transmission.
4. **Receivers**: Receivers capture radio frequency signals, extract the desired information, and convert it into a usable form. Receivers include components such as antennas to capture the incoming signal, amplifiers to boost weak signals, demodulators to extract the information from the carrier, and filters to remove unwanted noise and interference.
5. **Antennas**: Antennas are crucial components for both transmitting and receiving RF signals. They convert electrical signals into electromagnetic waves for transmission and vice versa for reception. Antennas come in various designs optimized for different applications, such as dipole antennas, patch antennas, and parabolic antennas.
6. **Propagation**: RF signals propagate through the atmosphere, and their behavior is influenced by factors such as frequency, distance, terrain, and environmental conditions. Understanding propagation characteristics is essential for designing efficient communication systems.
7. **Propagation Models**: Propagation models describe how RF signals propagate in different environments. These models help engineers predict signal strength, coverage areas, and potential sources of interference. Common models include free-space path loss, multipath fading, and terrain-based models.
8. **Spectrum Management**: Since the radio frequency spectrum is a finite and shared resource, its allocation and usage are regulated by government agencies such as the Federal Communications Commission (FCC) in the United States. Spectrum management involves allocating frequency bands to different users, enforcing regulations to prevent interference, and promoting efficient spectrum utilization.
9. **Applications**: RF communications find applications in various fields, including broadcasting, telecommunications, wireless networking.
This work presents a rectangular of microstrip ultra wideband patch antenna for worldwide interoperability for microwave access (Wi-Max) and wireless local area network (WLAN) with a dual band-notched feature. The planned an antenna consists the rectangular of patch antenna with the largely deficient of ground structure. Through inserting slots in the radiating patch, dual notch characteristics may be produced. The suggested antenna is 20×30×1.6 mm3 in volume. The first notch, made by slots operating at the first notch, produced by slots running at 3.5 GHz, for Wi-Max (from 3.3-3.7 GHz), while of a second, created by slots operating at 5.5 GHz, for WLAN (from 5.1-5.8 GHz). An antenna covers the whole ultra-wideband frequency range (3.1-10.6 GHz). Computer simulation technology (CST) 2021 simulation software used for simulate proposed of antenna. A simulated antenna’s emission pattern is almost omnidirectional, and the recommended antenna’s gain is approximately constant over the ultra-wideband (UWB) spectrum, excluding notch areas.
Indoor Radio Propagation Model Analysis Wireless Node Distance and Free Space...IJERA Editor
Ultra wide bandwidth (UWB) signals are commonly defined as signals that have a large relative bandwidth
(bandwidth divided by the carrier frequency) or a large absolute bandwidth. Typical indoor environments contain
multiple walls and obstacles consisting of different materials. The RF ultra wideband (UWB) system is a
promising technology for indoor localisation owing to its high bandwidth that permits mitigation of the multipath
identification problem. The work proposed in this paper identifies exact position of transmitter and receiver
wireless nodes, calculates free space path loss and distance between two nodes by considering frequency
bandwidth using 2-point and 3-point Gaussian filter. Also in the paper three types of indoor radio propagation
models are analyzed at ultra wideband frequency range and results are compared to select best suitable model for
setting up indoor wireless connectivity and nodes in typical office, business and college environments and
WPAN applications.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
The Effects of Interferenceon the Transmission and Coverage in High Buildings IJERA Editor
Wireless communication is one of the most rapidly developing technologies in recent time, with wonderful
services and products emerging together. These developments present huge challenges for communication
engineers, as the demand for increased wireless capacity grow fast. Re-using the limited available spectrum will
results a critical issue that affects the system performance, which is co-channel interference. This issue will
limits the uplink coverage and capacity of the wireless system. It is needed to come up with such method of
interference cancellation. We will investigate the transmission in multiple floors building by deploying
femtocell based distributed antenna that connected at each entire floor, the signal will be processed by jointing
all femto base stations for all cells in the building. We will try to introduce a solution to the arising problem of
co-channel interference from frequency reuse, by measuring and analyzing the gain when deploying interference
cancellation at each base station.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A trade-off design of microstrip broadband power amplifier for UHF applications IJECEIAES
In this paper, the design of a Broadband Power Amplifier for UHF applications is presented. The proposed BPA is based on ATF13876 Agilent active device. The biasing and matching networks both are implemented by using microstrip transmission lines. The input and output matching circuits are designed by combining two broadband matching techniques: a binomial multi-section quarter wave impedance transformer and an approximate transformation of previously designed lumped elements. The proposed BPA shows excellent performances in terms of impedance matching, power gain and unconditionally stability over the operating bandwidth ranging from 1.2 GHz to 3.3 GHz. At 2.2 GHz, the large signal simulation shows a saturated output power of 18.875 dBm with an output 1-dB compression point of 6.5 dBm of input level and a maximum PAE of 36.26%.
Third Generation Wireless Modeling in Urban EnvironmentEECJOURNAL
The global mobile communication is fast growing in industry. This paper recommends appropriate settings to evaluate the performance of wireless mobile system deploying third generation networks in an urban environment. To meet this aim, a case Study of Sulaimanyia city is considered for this study by establishing suitable radio channel models. The work presents a statistical channel model, where fixed and nomadic analysis services are considered in the simulated radio coverage scenario. The cartographic dataset had been collected, and Matlab Software was used for showing the analysis and simulation results. Statistical channel models are derived that combine standard parameters such as separation distance, operating frequency and terminal height with more advanced and innovative parameters such as distance dependent shadowing and LOS probability.
Similar to Link budjet radio and spread spectrum theory (20)
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
2. 2-2
This is the lowest possible noise level for a system with a
given physical temperature. For most applications,
temperature is typically assumed to be room temperature
(290K). Equations 1 and 2 demonstrate that RF power and
bandwidth can be traded off to achieve a given performance
level (as defined by BER).
Range and Path Loss
Another key consideration is the issue of range. As radio
waves propagate in free space, power falls off as the square
of range. For a doubling of range, power reaching a receiver
antenna is reduced by a factor of four. This effect is due to
the spreading of the radio waves as they propagate, and can
be calculated by:
where:
D = the distance between receiver and transmitter
λ = free space wavelength = c/f
c = speed of light (3 x 108 m/s)
f = frequency (Hz)
Equation 3 above describes line-of-sight, or free space
propagation. Because of building obstructions such as walls
and ceilings, propagation losses indoors can be significantly
higher. This occurs because of a combination of attenuation by
walls and ceilings, and blockage due to equipment, furniture,
and even people. For example, a “2 x 4” wood stud wall with
sheetrock on both sides results in about 6dB loss per wall.
Experience has shown that line-of-sight propagation holds only
for about the first 20 feet. Beyond 20 feet, propagation losses
indoors increase at up to 30dB per 100 feet (see Figure 1) in
dense office environments. This is a good “rule-of-thumb”, in
that it is conservative (it overstates path loss in most cases).
Actual propagation losses may vary significantly depending on
building construction and layout.
R
Multipath and Fade Margin
Multipath occurs when waves emitted by the transmitter
travel along a different path and interfere destructively with
waves travelling on a direct line-of-sight path. This is
sometimes referred to as signal fading. This phenomenon
occurs because waves travelling along different paths may
be completely out of phase when they reach the antenna,
thereby canceling each other.
Since signal cancellation is almost never complete, one
method of overcoming this problem is to transmit more
power. In an indoor environment, multipath is almost always
present and tends to be dynamic (constantly varying).
Severe fading due to multipath can result in a signal
reduction of more than 30dB. It is therefore essential to
provide adequate link margin to overcome this loss when
designing a wireless system. Failure to do so will adversely
affect reliability.
The amount of extra RF power radiated to overcome this
phenomenon is referred to as fade margin. The exact
amount of fade margin required depends on the desired
reliability of the link, but a good rule-of-thumb is 20dB to
30dB.
One method of mitigating the effects of multipath is antenna
diversity. Since the cancellation of radio waves is geometry
dependent, use of two (or more) antennas separated by at least
half of a wavelength can drastically mitigate this problem. On
acquisition of a signal, the receiver checks each antenna and
simply selects the antenna with the best signal quality. This
reduces, but does not eliminate, the required link margin that
would otherwise be needed for a system which does not
employ diversity. The downside is this approach requires more
antennas and a more complicated receiver design.
Another method of dealing with the multipath problem is via
the use of an adaptive channel equalizer. Adaptive
equalization can be used with or without antenna diversity.
(EQ.3)L = 20 log10 (4π D / λ)
FIGURE 1. ESTIMATED INDOOR PROPAGATION LOSSES AT
2.4GHz
130
120
110
100
90
80
70
60
50
20 40 60 80 100 120 140 160 180 200 220 240
RANGE (FT)
PATHLOSS(dB)
FREE SPACE
INDOOR
FIGURE 2. MULTIPATH
MULTIPATH SIGNAL #2
BUILDING
STRUCTURE
DIRECT PATH SIGNAL
M
ULTIPATH
SIG
NAL
#1
OFFICE
FURNITURE
TX
RX
Application Note 9804
3. 2-3
After the signal is received and digitized, it is fed through a
series of adaptive delay stages which are summed together
via feedback loops. This technique is particularly effective in
slowly changing environments such as transmission over
telephone lines, but is more difficult to implement in rapidly
changing environments like factory floors, offices and homes
where transmitters and receivers are moving in relation to
each other. The main drawback is the impact on system cost
and complexity. Adaptive equalizers can be expensive to
implement for broadband data links.
Spread spectrum systems are fairly robust in the presence
of multipath. Direct Sequence Spread Spectrum (DSSS)
systems will reject reflected signals which are significantly
delayed relative to the direct path or strongest signal. This is
the same property which allows multiple users to share the
same bandwidth in Code Diversity Multiple Access (CDMA)
systems. Frequency Hopping Spread Systems (FHSS) also
exhibit some degree of immunity to multipath. Because a
FHSS transmitter is continuously changing frequencies, it
will always hop to some frequencies which experience little
or no multipath loss. In a severe fading environment,
throughput of an FHSS system will be reduced, but it is
unlikely that the link will be lost completely. The performance
of DSSS systems in the presence of multipath is described
further in a separate section below.
Modulation Technique
Modulation technique is a key consideration. This is the
method by which the analog or digital information is
converted to signals at RF frequencies suitable for
transmission. Selection of modulation method determines
system bandwidth, power efficiency, sensitivity, and
complexity. Most of us are familiar with Amplitude
Modulation (AM) and Frequency Modulation (FM) because
of their widespread use in commercial radio. Phase
Modulation is another important technique. It is used in
applications such as Global Position System (GPS)
receivers and some cellular telephone networks.
For the purposes of link budget analysis, the most important
aspect of a given modulation technique is the Signal-to-
Noise Ratio (SNR) necessary for a receiver to achieve a
specified level of reliability in terms of BER. A graph of Eb/No
vs BER is shown in Figure 4. Eb/No is a measure of the
required energy per bit relative to the noise power. Note that
Eb/No is independent of the system data rate. In order to
convert from Eb/No to SNR, the data rate and system
bandwidth must be taken into account as shown below:
where:
Eb = Energy required per bit of information
No= thermal noise in 1Hz of bandwidth
R = system data rate
BT= system bandwidth
Spread Spectrum Radios
The term “spread spectrum” simply means that the energy
radiated by the transmitter is spread out over a wider amount
of the RF spectrum than would otherwise be used. By
spreading out the energy, it is far less likely that two users
sharing the same spectrum will interfere with each other.
This is an important consideration in an unlicensed band,
which why the regulatory authorities imposed spread
spectrum requirements on radios which transmit over -1dBm
(about 0.75mW) in the following bands:
FIGURE 3. ADAPTIVE EQUALIZER
∑
W1 W2 W3 W4 Wn
Z-1 Z-1 Z-1 Z-1
DIGITAL EQUALIZER OUT
DIGITIZED
BASEBAND
INPUT
TABLE 1. TYPICAL BANDWIDTHS FOR VARIOUS DIGITAL
MODULATION METHODS
MODULATION METHOD
TYPICAL BANDWIDTH
(NULL-TO-NULL)
QPSK, DQPSK 1.0 x Bit Rate
MSK 1.5 x Bit Rate
BPSK, DBPSK, OFSK 2.0 x Bit Rate
FIGURE 4. PROBABILITY OF BIT ERROR FOR COMMON
MODULATION METHODS
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Eb/No (dB)
1.0E-01
1.0E-02
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-07
BE
INCOHERENT OOK, OFSK
COHERENT OOK, OFSK
DBPSK, DQPSK
MSK, PSK
(EQ.4)SNR = (Eb/No) * (R/BT)
Application Note 9804
4. 2-4
In the U.S., these bands are collectively designated as
Industry, Science, and Medicine (ISM) bands. Operation in
these bands with approved devices does not require an FCC
license. By waiving licensing requirements, these bands
have been made generally accessible to virtually anyone.
This is mainly why the ISM bands are so important for
commercial and consumer applications.
As mentioned above, radios employing spread spectrum
methods are allowed to radiated up to 1.0W (30dBm) of RF
energy, as compared to less than 1mW for non-spread
radios. There are two common types of spread spectrum
systems. The easiest to understand is Frequency Hopped
Spread Spectrum (FHSS). In this method, the carrier
frequency hops from channel to channel in some pre-
arranged sequence. The receiver is programmed to hop in
sequence with the transmitter. If one channel is jammed, the
data is simply retransmitted when the transmitter hops to a
clear channel. The major drawback to FHSS is limited data
rate. In the 2.4GHz band, FCC regulations require that the
maximum occupied bandwidth for any single channel is
1MHz. This effectively limits the data rate through this type
of system to about 1Mbps.
By contrast, Direct Sequence Spread Spectrum (DSSS)
systems in the ISM bands provide much higher data rates.
DSSS systems do not jump from frequency to frequency.
Instead, the transmitter actually spreads the energy out over
a wider portion of the RF spectrum. This can be
accomplished by combining the data stream with a much
higher rate Pseudo Random Numerical (PRN) sequence via
an XOR function. The result is a digital stream at the same
rate as the PRN. When the RF carrier is modulated by the
higher speed digital stream, the result is a spreading of the
RF energy.
The individual 1’s and 0’s that make up the PRN are called
“chips”. They are distinct from the “bits” in the data stream
because chips are predetermined by the PRN sequence and
hence, contain no information. The ratio of the chip rate (C)
to the data rate (R) is called processing gain. In the PRISM
radio, this ratio is selectable. It can be set to 11, 13, 15, or 16
chips/bit. The IEEE 802.11 Standard specifies an 11 chip PN
sequence (Barker code), which will be used for this example.
At the receiver, the pseudo random code is used to
“de-spread” the received data. In the PRISM chip set, this is
accomplished by means of a matched filter at baseband. It is
during this process that the matched filter rejects unwanted
interference because it is uncorrelated with the PRN. By
careful selection of the PRN sequence, the matched filter
provides an additional benefit. It can reject multipath signals
which are delayed relative to the main signal by more than
one chip period, or about 44ns. In this manner, it provides
some of the benefits of the adaptive equalizer shown in
Figure 3, though its operation and implementation are much
simpler.
TABLE 2. WORLD WIDE UNLICENSED FREQUENCY
ALLOCATION RF POWER LIMITS
BAND
FCC REGS
(US)
ETSI
(EUROPE)
MPT
(JAPAN)
902 - 928MHz <1000mW N/A N/A
2400 - 2483.4MHz <1000mW <100mW N/A
2471 - 2497MHz N/A N/A <10mW/MHz
5725 - 5875MHz <1000mW <100mW N/A
FIGURE 5. FHSS SPECTRUM UTILIZATION
t-5 t-2 t0 t-1 t-4 t-3
2.400GHz 2.483GHz
FIGURE 6. COMBINING PRN SEQUENCE AND DATA
DATA
OUT
PRN
1-BIT
PERIOD
11 CHIPS
11 CHIPS 1-BIT
11-BIT BARKER CODE (PRN):
1 0 1 1 1 0 1 0 0 0
01000101111011101000
(EQ.5)Processing Gain = 10log10(C/R) = 10.4dB
FIGURE 7A. TRANSMITTER BASEBAND SIGNAL BEFORE
SPREADING
FIGURE 7B. TRANSMITTER BASEBAND SIGNAL AFTER
SPREADING
Application Note 9804
5. 2-5
If viewed on a spectrum analyzer, the de-spreading process
would cause the received spectrum to decrease in width by
a factor of 11:1, while at the same time causing the peak in
the spectrum to increase in amplitude by the same amount.
This is why this effect is called processing gain.
Example 1: Wireless Link to Dial-Up Modem
As an example, consider a data link intended to provide a
wireless link between a laptop computer and a dial-up
modem in a home environment as shown in Figure 10. In
order to support a throughput of 28.8kbps, the link should be
designed for about 40kbps. The additional data rate is
needed to accommodate framing, overhead, checksums
which may be required for the wireless link.
Example 1: Requirements
Required data rate = 40kbps
(28.8kbps plus framing, overhead, and checksum)
Range =5 meters
Desired BER =10-6
Example 1: FCC and ETSI Regulations
For unlicensed systems not employing spread spectrum
techniques, RF power is limited to -1.25dBm, or about
0.75mW. For details on RF power limitations, refer to FCC
Regulations 15.247 and 15.249. If spreading is employed,
RF power can be increased to 1W (U.S. operations). For
Europe, ETSI regulations (ETSI 300, 328) limit RF power for
spread spectrum radios to 20dBm, or 100mW. Spreading is
therefore attractive because it allows for transmission of up
to 1000 times more RF power.
Example 1: So, Should Spread Spectrum
Techniques Be Used In This Case?
Spread spectrum offers some interference rejection
properties, but it also entails higher complexity. Therefore,
the application should first be evaluated to determine if it can
be reliably serviced by a low power, non-spread spectrum
radio. If not, then spread spectrum high power radios should
be considered.
FIGURE 8. MATCHED FILTER CORRELATOR
Z-1
2N
Z-1
6
Z-1
5
Z-1
4
Z-1
3
Z-1
2
Z-1
1
∑
R1 R2 R3 RN N = 16
SYMBOL PERIOD
CHIP
PERIOD
CORRELATION SCORE
A/D
SAMPLE
CLOCK
PARALLEL PN
REGISTER LOAD
RX DATA
FROM ADCs
2X CHIP CLOCK
11-BIT BARKER CODE EXAMPLE:
+1 -1 +1 +1 -1 +1 +1 +1 -1 -1 -1
FIGURE 9A. RECEIVER BASEBAND SIGNAL BEFORE
MATCHED FILTER CORRELATOR
FIGURE 9B. RECEIVER BASEBAND SIGNAL AFTER
MATCHED FILTER CORRELATOR
FIGURE 10. EXAMPLE 1: WIRELESS LINK TO MODEM
RF
XCVR
28.8KBPS
MODEM
PHONE
LINE
LAPTOP
PC
RF
XCVR
Application Note 9804
6. 2-6
Example 1: Frequency Selection
There are several bands available for unlicensed operation
(see Table 2). As described previously, in the Multipath and
Fade Margin section, the higher the frequency, the higher
the propagation loss. Therefore, a lower frequency is better
in terms of propagation loss. It is generally less expensive to
build radios at lower frequencies. Other considerations
include available bandwidth and regulatory limitations. The
available bands are 900MHz, 2.4GHz, and 5.725GHz. The
easy choice is 900MHz, but this band is getting crowded with
things like cordless phones. For such a short link, 900MHz is
still a good choice.
Example 1: Modulation Technique
There are lots of choices here. The Intersil PRISM radio chip
set uses Phase Shift Keying (PSK) modulation, but some of
the motivating factors behind this choice are not applicable
in this instance. A simpler method is Frequency Shift Keying
(FSK). FSK is actually a form of Frequency Modulation (FM),
which has been around for a long time. With FSK, two
separate frequencies are chosen, one frequency
representing a logical “zero”, the other representing logical
“one”. Data is transmitted by switching between the two
frequencies.
A good choice of modulation would therefore be FSK. The
separation of two frequencies relative to the bit rate is called
modulation index (h).
h = frequency separation / bit rate
= ∆f / R
A modulation index of 1 (h = 1) is a good choice for a low
cost application, unless there are restrictions on bandwidth.
When h = 1, the frequencies are said to be orthogonal. This
form of modulation is called Orthogonal FSK, or OFSK.
Choosing h = 1 results in a simple but fairly robust receiver
design. In this case, the frequencies would be separated by
40kHz.
Example 1: System Bandwidth and Noise Floor
In general, the modulation technique dictates the required
system bandwidth (or visa versa, depending on design
constraints). For FSK modulation and h = 1, the bandwidth is
typically about 2 times the data rate (see Table 1), or 80kHz.
We therefore can compute the noise power:
= 1.38 x 10-23 J/K x 290K x 80,000 s-1
= 2.4 x 10-13mW
= -126dBm
This figure represents a theoretical noise floor for an ideal
receiver. A real receiver noise floor will always be higher, due
to noise and losses in the receiver itself. Noise Figure (NF) is
a measure of the amount of noise added by the receiver
itself. A typical number for a low cost receiver would be
about 15dB. This number must be added to the thermal
noise to determine the receiver noise floor:
= -111dBm
Example 1: Receiver Sensitivity
The first step in performing the link budget is determining the
required signal strength at the receiver input. This is referred
to as receiver sensitivity (Prx). As described previously, this
is a function of the Modulation Technique and the desired
BER. A graph of Eb/No vs BER is shown in Figure 2. For the
case at hand, the modulation technique is OFSK. For 10-6
BER:
= 26.3 * (40kbps / 80kHz)
= 11dB
= -111dBm + 11dB
= -100dBm
Example 1: Link Calculation
Propagation loss (Lfs) can be computed as:
= 20 x log10(4 * pi * 5 meters/0.33 meters)
= 46dB
Note: lambda is the free space wavelength at the carrier
frequency
λ = c/f
= 3 x 108ms-1/900MHz
= 0.33 meters
Finally, some assumption must be made about transmit and
receive antenna gain values. For a simple dipole antenna,
an assumption of 0dB gain is reasonable. This number will
be taken for the gain of both the transmit antenna gain
(Gtx)and receive antenna gain (Grx). Now, the required
transmitter power (Ptx) can be computed:
= -100dBm - 0dB - 0dB + 46dB + 30dB
= -24dBm
Example 1: Conclusions
This exercise shows that the wireless modem link can be
reliably served by an OFSK radio operating at 900MHz using
as little as -24dBm transmit power. FCC regulations permit
(EQ.6)N = kTB
(EQ.7)Receiver Noise Floor = -126dBm + 15dB
(EQ.8)Eb/No = 14.2dB = 26.3
(EQ.9)SNR = (Eb/No) * (R/BT)
(EQ. 10)Prx = Receiver Noise Floor + SNR
(EQ. 11)Lfs = 20 x log10(4 * pi * D/lambda)
(EQ. 12)Ptx = Prx - Gtx - Grx + Lfs + Fade Margin
Application Note 9804
7. 2-7
transmission of up to -1.25dBm in the unlicensed bands
without requiring spread spectrum modulation. However, as
mentioned above, the 900MHz band is becoming crowded.
This is particularly true for consumer application due to the
proliferation of cordless telephones. If this is considered a
major problem, the above analysis can easily be re-
evaluated assuming a carrier frequency in other unlicensed
bands such as 2.4GHz, or even 5GHz.
In addition to the analysis of the radio link itself, there are
other considerations beyond those mentioned here. These
include the suitability of the modem protocol to packet mode
transmission, synchronization of data rates, etc. The
foregoing discussion focused on the link analysis and is by
no means exhaustive. It is intended to illustrate top level
trades involving data rate, range, and choice of modulation.
Example 2: Wireless USB - An Ideal
Application for PRISM
Having shown that PRISM is not the optimal choice for a
short-haul, low bit rate wireless link such as the wireless
modem described above, a more suitable application will
now be explored. Universal Serial Bus (USB) is rapidly
replacing the serial port on personal computers. USB
provides high speed flexible interconnectivity between a PC
and its peripherals. Despite its flexibility, USB has a range
limitation of 5 meters.
USB has two modes of signaling. The full speed signaling
rate is 12Mbps, while the low rate is 1.5Mbps. The low speed
rate is designed to support devices such as mice and
keyboards. However, a radio capable of providing 1.5Mbps
throughput could be used in a wireless hub application,
though it could not support the full hi-speed rate of 12Mbps.
A wireless hub could support bulk transfers, and possibly
isochronous applications such as wireless audio and
MPEG1 video if rate buffering were available at the transmit
side of the link.
In this example, a wireless digital link capable of 1.5Mbps
throughput at up to 100 feet indoors is desired. As in the
previous example, a somewhat higher data rate will be
required in order to accommodate framing, overhead, and
checksum for the wireless link. Typically, throughput is about
70% to 75% of peak data rate. Therefore, the required data
rate for the wireless link is roughly 2Mbps.
Example 2: Requirements
Data Rate = 2Mbps (1.408Mbps + framing, overhead,
checksum)
Range = 30 meters indoors (100 feet)
Desired BER = 10-6
Example 2: Should I Use a Spread Spectrum
Radio?
In the previous example, spreading was not required.
However, there are a couple of major differences with this
example. The data rate is much higher and the range is a
farther. Therefore, due to FCC restrictions on transmitted
power for non-spread spectrum transmitters in the
unlicensed bands, the non-spread OFSK radio described in
Example 1 above will not be capable of meeting this far more
stringent application. By contrast, Intersil’s PRISM radio was
designed specifically for such demanding applications. It
employs spread spectrum techniques and can radiate up to
1W of RF power according to FCC regulations (FCC
15.247).
Example 2: Frequency Selection
As described previously, there are several bands allocated
for unlicensed operation. There is spectrum at 902-928MHz.
However, this band is getting pretty crowded. Another
consideration is the limited bandwidth. There is only 26MHz
in this band. A better choice would be the 2.400 - 2.483GHz.
There is less radio traffic in this band (although there is
potential interference from microwave ovens), and the total
available bandwidth is 83MHz. In addition, this frequency
band is approved for unlicensed operation in the U.S.,
Europe, and Japan.
Example 2: Modulation Technique
PRISM utilizes Differential Binary Phase Shift Keyed
(DBPSK) modulation to transmit data at up to 1Mbps, and
Differential Quadrature Phase Shift Keyed (DQPSK)
modulation to transmit data up to 2Mbps. The main
advantage of DQPSK is spectral efficiency. The null-to-null
bandwidth for a DQPSK radio is about the same as the data
rate (R).
RF
RECEIVER
RF
RECEIVER
DESKTOP
PC
USB
RF
TRANSMITTER
WIRELESS
USB HUB
LEFT SPEAKER RIGHT SPEAKER
FIGURE 11. WIRELESS USB LINK
Application Note 9804
8. 2-8
All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification.
Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time with-
out notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see web site http://www.intersil.com
Example 2: System Bandwidth and Noise Floor
For 2Mbps, the occupied bandwidth of a PRISM transmitter
would be 22MHz due to spreading. Due to the 11:1 ratio
between the chip rate (C) and the data rate (R), the radio is
transmitting 22Mcps. This results in an occupied bandwidth
of 22MHz (see Figure 7). However, after the de-spreading at
the receiver, the bandwidth at baseband would be restored
to 2MHz (see Figure 8). It is important to note that although
PRISM is a spread spectrum radio, the noise floor is
computed using the de-spread bandwidth:
= 1.38 x 10-23 J/K x 290K x 2,000,000 s-1
= 4 x 10-12mW
= -113dBm
PRISM has a receiver noise figure of 7dB. The receiver
noise floor is then:
= -104dBm
From Figure 1, the free space path loss at 100 feet for indoor
propagation may be determined. This value is 80dB. DQPSK is
an efficient modulation technique. The required Eb/No to
achieve a 10-6 BER is 11dB. The required signal-to-noise ratio
(SNR) and receiver sensitivity (Prx) can now be determined:
= 12.7 * (2Mbps / 2.0MHz)
= 11dB
= -104dBm + 11dB
= -93dBm
One of the characteristics of Direct Sequence Spread
Spectrum (DSSS) radios such as PRISM is reduction in the
effects of multipath. If the indirect signal is delayed by more
than a chip period, it will appear to the receiver as
uncorrelated random noise, and will not cancel the direct
signal. Therefore, an allocation of 30dB is an even more
conservative assumption for fade margin. Transmit and
receive antenna gain are unchanged from the previous
example (0dB). Using this data, the link budget may now be
recalculated:
= -93dBm - 0dB - 0dB + 80dB + 30dB
= 17dBm
FCC regulations permit DSSS systems to transmit up to 1W
(or 30dBm). The PRISM Radio chip set provides +18dBm
radiated power, which is ideal for this application. In addition,
the DSSS waveform provides an additional 10dB of rejection
of potential jammers, such as microwave ovens, arc welders,
and other industrial machinery.
Example 2: Conclusions
PRISM is an ideal solution for high bit rate (up to 2Mbps)
mobile data transmission. In addition to its robust waveform, it
features IEEE 802.11 compliant operation. It has a Carrier
Sense Multiple Access collision avoidance feature which
allows multiple users to share the same RF channel. The
programmable synthesizer allows for the collocation of several
channels to accommodate even more users. The highly
integrated chip set provides a complete Antenna-to-Bits
solution.
References
For Intersil documents available on the internet, see web site
www.intersil.com/
Intersil AnswerFAX (321) 724-7800.
[1] Modern Communications Systems, Couch, Leon W.,
Prentice-Hall, Inc., Englewood Cliffs, NJ, 1995. (ISBN
0-02-325286-3)
[2] Digital Communications Systems, Peebles, Peyton Z.,
Prentice-Hall, Inc., Englewood Cliffs, NJ, 1987. (ISBN
0-13-211970-6)
[3] Mobile Cellular Telecommunications Systems, Lee, Will-
iam C. Y., McGraw-Hill, New York, NY, 1989 (ISBN 0-
07-037030-3)
[4] Digital Communications, Proakis, John G., Second Edi-
tion, McGraw-Hill, New York, NY, 1989 (ISBN 0-07-
050937-9)
[5] Spread Spectrum Systems, Dixon, Robert C., Third Edi-
tion, John Wiley & Sons, New York, NY, 1994 (ISBN 0-
471-59342-7)
(EQ. 13)Noise = kTB
(EQ. 14)Rx Noise Floor = -111dBm + 7dB
(EQ. 15)Eb/No = 11dB = 12.7
(EQ. 16)SNR = (Eb/No) * (R/BT)
(EQ. 17)Prx = Receiver Noise Floor + SNR
(EQ. 18)Ptx = Prx - Gtx - Grx + Lfs + Fade Margin
Application Note 9804