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The document discusses Direct Sequence Spread Spectrum (DSSS) and Code Division Multiple Access (CDMA) systems. It explains that DSSS represents each data bit as multiple bits using a spreading code. This spreads the signal across a wider frequency band proportional to the number of bits in the code. As an example, it provides that a 10-bit spreading code would spread the signal across 10 times the bandwidth of a 1-bit code. It then describes how CDMA allows multiplexing of multiple users by assigning each a unique spreading code, and the receiver can isolate the intended user's signal by correlating with their specific code.
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Ch11 spread spectrum
1. Spread spectrum techniques work by spreading data over a wide bandwidth through methods like frequency hopping or direct sequence spreading using a pseudorandom code. This makes the signal harder to intercept or jam.
2. Frequency hopping spreads the signal over different frequencies in a seemingly random pattern synchronized between the transmitter and receiver. Direct sequence spreading represents each data bit as multiple bits set by a pseudorandom code.
3. Code division multiple access (CDMA) allows multiple users to share the same frequency band by assigning each user a unique spreading code. The receiver uses the same code to pick out the desired signal and reject others.
09-SpreadSpectrum.ppt
This document summarizes key aspects of spread spectrum techniques described in Chapter 9 of William Stallings' book "Data and Computer Communications". It discusses two main types of spread spectrum - frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS works by transmitting a signal over a seemingly random series of frequencies, while DSSS represents each data bit with a sequence of bits as defined by a spreading code. Code division multiple access (CDMA) allows multiple users to share the same frequency band by assigning each user a unique spreading code.
spread spectrum technique
This document provides an overview of spread spectrum techniques including frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). It discusses how spread spectrum spreads data over a wide bandwidth to make jamming and interception harder. For FHSS, the signal is broadcast over a seemingly random series of frequencies. For DSSS, each bit is represented by multiple bits in the transmitted signal using a chipping code. Code division multiple access (CDMA) allows multiple users to share the same higher bandwidth with little interference by using orthogonal spreading codes.
CS553_ST7_Ch09-SpreadSpectrum 23.pptx
This document summarizes key points about spread spectrum techniques from William Stallings' Data and Computer Communications textbook. It describes two main types of spread spectrum - frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS works by transmitting a signal over a seemingly random series of frequencies, while DSSS represents each bit with multiple bits using a spreading code. Code division multiple access (CDMA) allows multiple users to share bandwidth using orthogonal spreading codes. Spread spectrum provides benefits like immunity to noise/interference and ability to hide/encrypt signals.
8 spread spectrum
The document discusses different types of spread spectrum techniques used in wireless communications including frequency hopping spread spectrum (FHSS), direct sequence spread spectrum (DSSS), and code division multiple access (CDMA). It explains that spread spectrum works by spreading data over a wider bandwidth through techniques like frequency hopping or spreading each bit into multiple bits, making the signal harder to intercept or jam. The receiver is able to recover the original data by using the same spreading code or sequence as the transmitter.
Lecture spread spectrum
Spread spectrum techniques spread data over a wide bandwidth to make it harder to jam or intercept signals. There are two main types: frequency hopping, where the signal hops between frequencies, and direct sequence, where each bit is represented by multiple bits using a spreading code. Code division multiple access (CDMA) allows multiple users to share the same bandwidth by assigning each user a unique spreading code.
Spread spectrum
Frequency hoping
Signal broadcast over seemingly random series of frequencies
Direct Sequence
Each bit is represented by multiple bits in transmitted signal
Chipping code
Pmit lecture 03_wlan_wireless_network_2016
The document discusses requirements and specifications for wireless local area networks (WLANs). It notes that the IEEE 802 committee develops standards for wired and wireless networking, including 802.11 for WLANs. The document then describes several 802.11 specifications such as 802.11, 802.11a, 802.11b, and 802.11g that define transmission speeds and frequencies for WLANs. It also discusses modulation techniques like BPSK and QPSK used in wireless communications.
Recommended
Ch11 spread spectrum
1. Spread spectrum techniques work by spreading data over a wide bandwidth through methods like frequency hopping or direct sequence spreading using a pseudorandom code. This makes the signal harder to intercept or jam.
2. Frequency hopping spreads the signal over different frequencies in a seemingly random pattern synchronized between the transmitter and receiver. Direct sequence spreading represents each data bit as multiple bits set by a pseudorandom code.
3. Code division multiple access (CDMA) allows multiple users to share the same frequency band by assigning each user a unique spreading code. The receiver uses the same code to pick out the desired signal and reject others.
09-SpreadSpectrum.ppt
This document summarizes key aspects of spread spectrum techniques described in Chapter 9 of William Stallings' book "Data and Computer Communications". It discusses two main types of spread spectrum - frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS works by transmitting a signal over a seemingly random series of frequencies, while DSSS represents each data bit with a sequence of bits as defined by a spreading code. Code division multiple access (CDMA) allows multiple users to share the same frequency band by assigning each user a unique spreading code.
spread spectrum technique
This document provides an overview of spread spectrum techniques including frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). It discusses how spread spectrum spreads data over a wide bandwidth to make jamming and interception harder. For FHSS, the signal is broadcast over a seemingly random series of frequencies. For DSSS, each bit is represented by multiple bits in the transmitted signal using a chipping code. Code division multiple access (CDMA) allows multiple users to share the same higher bandwidth with little interference by using orthogonal spreading codes.
CS553_ST7_Ch09-SpreadSpectrum 23.pptx
This document summarizes key points about spread spectrum techniques from William Stallings' Data and Computer Communications textbook. It describes two main types of spread spectrum - frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS works by transmitting a signal over a seemingly random series of frequencies, while DSSS represents each bit with multiple bits using a spreading code. Code division multiple access (CDMA) allows multiple users to share bandwidth using orthogonal spreading codes. Spread spectrum provides benefits like immunity to noise/interference and ability to hide/encrypt signals.
8 spread spectrum
The document discusses different types of spread spectrum techniques used in wireless communications including frequency hopping spread spectrum (FHSS), direct sequence spread spectrum (DSSS), and code division multiple access (CDMA). It explains that spread spectrum works by spreading data over a wider bandwidth through techniques like frequency hopping or spreading each bit into multiple bits, making the signal harder to intercept or jam. The receiver is able to recover the original data by using the same spreading code or sequence as the transmitter.
Lecture spread spectrum
Spread spectrum techniques spread data over a wide bandwidth to make it harder to jam or intercept signals. There are two main types: frequency hopping, where the signal hops between frequencies, and direct sequence, where each bit is represented by multiple bits using a spreading code. Code division multiple access (CDMA) allows multiple users to share the same bandwidth by assigning each user a unique spreading code.
Spread spectrum
Frequency hoping
Signal broadcast over seemingly random series of frequencies
Direct Sequence
Each bit is represented by multiple bits in transmitted signal
Chipping code
Pmit lecture 03_wlan_wireless_network_2016
The document discusses requirements and specifications for wireless local area networks (WLANs). It notes that the IEEE 802 committee develops standards for wired and wireless networking, including 802.11 for WLANs. The document then describes several 802.11 specifications such as 802.11, 802.11a, 802.11b, and 802.11g that define transmission speeds and frequencies for WLANs. It also discusses modulation techniques like BPSK and QPSK used in wireless communications.
09 spread spectrum
Spread spectrum techniques spread data signals over a wide bandwidth to make them resistant to jamming and interception. There are two main approaches: frequency hopping spread spectrum (FHSS) rapidly switches a narrowband signal across a wide band of frequencies in a pattern known only to the transmitter and receiver, while direct sequence spread spectrum (DSSS) encodes data bits by adding extra bits using a spreading code before transmission. Code division multiple access (CDMA) allows multiple users to share the same frequency band by using user-specific spreading codes, with the signals combined at the receiver.
Digital communication (DSSS)
(1) Direct-sequence spread spectrum (DSSS) is a modulation technique that spreads transmitted signals across a wider bandwidth than the original information signal by modulating the signal with a pseudorandom noise code. (2) Each information bit is modulated with a sequence of faster chips known by the receiver to reconstruct the original signal. (3) DSSS allows multiple transmitters to share the same channel using different pseudorandom codes, enabling code division multiple access (CDMA) communication.
CDMA
CDMA allows multiple users to share the same channel by assigning each user a unique code. It spreads the user's data signal over a wider bandwidth through multiplication with a pseudo-random code. This allows different signals to be separated at the receiver through correlation with the corresponding code. Major technologies using CDMA include WiFi, Bluetooth, and GPS, which employ techniques like DSSS, FHSS, and long/short codes. Performance of 802.11 networks can be analyzed based on collision probability and throughput calculations under saturated traffic conditions. Later developments expanded CDMA capabilities with techniques like W-CDMA, TD-CDMA, and TD-SCDMA.
09-SpreadSpectrum.ppt
Spread spectrum encoding spreads data over a wide bandwidth to make jamming and interception harder. It uses either frequency hopping or direct sequence approaches. Some advantages of spread spectrum are immunity from noise and multipath distortion, ability to hide or encrypt signals, and allowing multiple users to share bandwidth with little interference. Pseudorandom numbers are used to determine hopping sequences or spreading codes, and must be known to decode the signal. Frequency hopping spreads a signal over different frequencies in sync between transmitter and receiver, while direct sequence represents each bit with multiple bits using a spreading code. Code division multiple access allows multiplexing using spreading codes unique to each user.
09 spread spectrum
Spread spectrum is an important encoding method for wireless communications that spreads analog and digital data over a wide bandwidth using either frequency hopping or direct sequence techniques. Frequency hopping spread spectrum (FHSS) transmits a signal over a seemingly random series of frequencies, making it difficult to jam. Direct sequence spread spectrum (DSSS) represents each data bit with a code sequence, spreading the signal across the frequency band. Code division multiple access (CDMA) allows multiple users to share the same bandwidth by assigning each a unique spreading code.
802.11 technology overview
This document provides an overview of wireless LAN technologies, including infrared, narrowband, and spread spectrum techniques. It describes key aspects of spread spectrum such as direct sequence and frequency hopping transmission methods. Modulation techniques like DBPSK, DQPSK, and CCK are explained. CCK uses complementary codewords to achieve data rates of 5.5 Mbps and 11 Mbps for IEEE 802.11 wireless networks.
Introduction to spred spectrum and CDMA
The document provides an introduction to spread spectrum communication including:
- The origins of spread spectrum dating back to the 1940s and its use in military applications.
- The two main types of spread spectrum techniques: direct-sequence spread spectrum and frequency hopping spread spectrum.
- The advantages of spread spectrum including reduced interference, security, and resistance to jamming.
- Key parameters like processing gain, jamming margin, and PN codes that are used in spread spectrum systems.
- Common PN code generation techniques including maximal length linear feedback shift registers, Gold codes, and Walsh codes.
Spread spectrum techniques
There are four main types of spread spectrum techniques: direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), time hopping spread spectrum (THSS), and hybrid techniques. DSSS uses a pseudo-noise code to spread the bandwidth of digital data. FHSS discretely shifts the carrier frequency in a pattern determined by a code sequence. THSS varies the period and duty cycle of a pulsed RF carrier in a pseudo-random manner. Hybrid techniques combine methods, such as DSSS and FHSS, to leverage advantages from multiple techniques.
Spread Spectrum.ppt
This document discusses spread spectrum techniques for wireless communication. It covers two main types of spread spectrum: frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS transmits signals over different radio frequencies in a pseudorandom sequence. DSSS spreads the signal across a wider bandwidth by combining it with a spreading code. Code division multiple access (CDMA) can allow multiple users to share the same frequency band using unique spreading codes. Pseudorandom noise (PN) sequences are commonly used as spreading codes due to their randomness and unpredictability properties.
Spread spectrum
This document discusses spread spectrum communication techniques. Spread spectrum spreads a narrowband signal over a wide range of frequencies for transmission and then de-spreads it back to the original bandwidth at the receiver. There are two main types: frequency hopping spread spectrum (FHSS) which changes the transmission frequency periodically, and direct sequence spread spectrum (DSSS) which multiplies the data by a pseudo-random code before transmission. Spread spectrum provides benefits like efficient bandwidth utilization, interference rejection, and secure communication.
Simulation of Direct Sequence Spread Spectrum for Wireless Communication Syst...
In this work, a simulation model for Direct Sequence Spread Spectrum (DSSS) scheme for wireless communication systems has been proposed. Unlike the case of a single frequency carrier, the modulated signal in DSSS occupies a much wider bandwidth in order to reduce the possible interferences with narrow band communication signals. In telecommunications, DSSS is a spread spectrum modulation technique used to reduce overall signal interference. The spreading of this signal makes the resulting wideband channel more noisy, allowing for greater resistance to unintentional and intentional interference. Y.V.S Durga Prasad | K. Venkateswarlu"Simulation of Direct Sequence Spread Spectrum for Wireless Communication Systems using Simulink" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14118.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/14118/simulation-of-direct-sequence-spread-spectrum-for-wireless-communication-systems-using-simulink/yvs-durga-prasad
Topic: Spread Spectrum
These slides cover a topic on Spread spectrum in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
Mimo
This document discusses multiple-input multiple-output (MIMO) systems. It begins by outlining the motivations and aspirations for developing MIMO systems, including achieving high data rates near 1 gigabit/second while maintaining quality of service. It then provides an overview of MIMO system modeling and capacity studies. Key topics covered include diversity versus spatial multiplexing design criteria, example architectures, MIMO with orthogonal frequency-division multiplexing, and networking applications involving MAC protocols.
Spread spectrum
Spread spectrum is a technique used in communication systems to spread the bandwidth of the transmitted signal, making it more resistant to interference and harder to intercept. There are three main types of spread spectrum: direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), and time hopping spread spectrum (THSS). DSSS spreads the signal by multiplying it with a pseudo-random code before transmission. FHSS rapidly switches the carrier frequency according to a pseudo-random sequence. THSS transmits signal bursts in pseudo-random time slots within a frame. Spread spectrum provides advantages like interference rejection, multipath immunity, multiple access, and secure communication.
Mimo
This document discusses multiple-input multiple-output (MIMO) systems, including their motivations and capabilities. MIMO systems use multiple antennas at both the transmitter and receiver to achieve high data rates approaching 1 Gbps while maintaining quality of service. The document covers MIMO channel models and capacity, design criteria like diversity and spatial multiplexing, practical architectures like V-BLAST and Alamouti's scheme, and applications to networking including MIMO-OFDM and MIMO MAC protocols.
multiplexing
This document discusses different multiplexing techniques used in data and computer communications, including frequency division multiplexing (FDM), wavelength division multiplexing (WDM), time division multiplexing (TDM), statistical TDM, and their applications. It also covers digital carrier systems, synchronous optical network (SONET), asynchronous digital subscriber line (ADSL), discrete multitone (DMT) modulation, and cable modem operations.
Mimo
This document discusses multiple-input multiple-output (MIMO) systems. It begins by outlining the motivations and aspirations for developing MIMO, including achieving high data rates near 1 Gbps while maintaining quality of service. It then covers MIMO system modeling and capacity studies. Different MIMO designs are presented that aim to achieve spatial multiplexing gain or diversity gain. Practical MIMO systems and architectures like V-BLAST are described. Networking applications of MIMO including MAC protocols are also discussed.
Cdma and 3 g
The document discusses CDMA and 3G spread spectrum technology. It describes how CDMA uses direct sequence spread spectrum to allow multiple users to access the same frequency band simultaneously. It explains the key elements of spread spectrum communication including using a chip rate that is faster than the data rate, synchronization at the receiver, and using pseudo-random codes. It provides details on IS-95 CDMA including channel structures, call processing, and authentication.
Spread Spectrum.pptx
Spread spectrum technology works to mitigate problems caused by frequency dependent fading and interference by spreading narrowband signals across a broader frequency band. It has two main alternatives: direct sequence spread spectrum (DSSS) which uses a pseudo-random code to spread user data, and frequency hopping spread spectrum (FHSS) which rapidly switches a carrier among various frequencies according to a code. FHSS can operate in either a slow or fast hopping mode, with fast hopping providing greater immunity to interference but at increased complexity.
Digital Communication 4
This document discusses bandwidth utilization and multiplexing techniques. It begins by explaining that bandwidth is a precious commodity in communication and that bandwidth utilization aims to make wise use of available bandwidth. It then discusses various multiplexing techniques including frequency-division multiplexing (FDM), time-division multiplexing (TDM), and wavelength-division multiplexing (WDM). For each technique, it provides examples and applications. It also covers digital carrier systems like T1, T2, T3 and discusses the North American digital multiplexing hierarchy.
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09 spread spectrum
Spread spectrum techniques spread data signals over a wide bandwidth to make them resistant to jamming and interception. There are two main approaches: frequency hopping spread spectrum (FHSS) rapidly switches a narrowband signal across a wide band of frequencies in a pattern known only to the transmitter and receiver, while direct sequence spread spectrum (DSSS) encodes data bits by adding extra bits using a spreading code before transmission. Code division multiple access (CDMA) allows multiple users to share the same frequency band by using user-specific spreading codes, with the signals combined at the receiver.
Digital communication (DSSS)
(1) Direct-sequence spread spectrum (DSSS) is a modulation technique that spreads transmitted signals across a wider bandwidth than the original information signal by modulating the signal with a pseudorandom noise code. (2) Each information bit is modulated with a sequence of faster chips known by the receiver to reconstruct the original signal. (3) DSSS allows multiple transmitters to share the same channel using different pseudorandom codes, enabling code division multiple access (CDMA) communication.
CDMA
CDMA allows multiple users to share the same channel by assigning each user a unique code. It spreads the user's data signal over a wider bandwidth through multiplication with a pseudo-random code. This allows different signals to be separated at the receiver through correlation with the corresponding code. Major technologies using CDMA include WiFi, Bluetooth, and GPS, which employ techniques like DSSS, FHSS, and long/short codes. Performance of 802.11 networks can be analyzed based on collision probability and throughput calculations under saturated traffic conditions. Later developments expanded CDMA capabilities with techniques like W-CDMA, TD-CDMA, and TD-SCDMA.
09-SpreadSpectrum.ppt
Spread spectrum encoding spreads data over a wide bandwidth to make jamming and interception harder. It uses either frequency hopping or direct sequence approaches. Some advantages of spread spectrum are immunity from noise and multipath distortion, ability to hide or encrypt signals, and allowing multiple users to share bandwidth with little interference. Pseudorandom numbers are used to determine hopping sequences or spreading codes, and must be known to decode the signal. Frequency hopping spreads a signal over different frequencies in sync between transmitter and receiver, while direct sequence represents each bit with multiple bits using a spreading code. Code division multiple access allows multiplexing using spreading codes unique to each user.
09 spread spectrum
Spread spectrum is an important encoding method for wireless communications that spreads analog and digital data over a wide bandwidth using either frequency hopping or direct sequence techniques. Frequency hopping spread spectrum (FHSS) transmits a signal over a seemingly random series of frequencies, making it difficult to jam. Direct sequence spread spectrum (DSSS) represents each data bit with a code sequence, spreading the signal across the frequency band. Code division multiple access (CDMA) allows multiple users to share the same bandwidth by assigning each a unique spreading code.
802.11 technology overview
This document provides an overview of wireless LAN technologies, including infrared, narrowband, and spread spectrum techniques. It describes key aspects of spread spectrum such as direct sequence and frequency hopping transmission methods. Modulation techniques like DBPSK, DQPSK, and CCK are explained. CCK uses complementary codewords to achieve data rates of 5.5 Mbps and 11 Mbps for IEEE 802.11 wireless networks.
Introduction to spred spectrum and CDMA
The document provides an introduction to spread spectrum communication including:
- The origins of spread spectrum dating back to the 1940s and its use in military applications.
- The two main types of spread spectrum techniques: direct-sequence spread spectrum and frequency hopping spread spectrum.
- The advantages of spread spectrum including reduced interference, security, and resistance to jamming.
- Key parameters like processing gain, jamming margin, and PN codes that are used in spread spectrum systems.
- Common PN code generation techniques including maximal length linear feedback shift registers, Gold codes, and Walsh codes.
Spread spectrum techniques
There are four main types of spread spectrum techniques: direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), time hopping spread spectrum (THSS), and hybrid techniques. DSSS uses a pseudo-noise code to spread the bandwidth of digital data. FHSS discretely shifts the carrier frequency in a pattern determined by a code sequence. THSS varies the period and duty cycle of a pulsed RF carrier in a pseudo-random manner. Hybrid techniques combine methods, such as DSSS and FHSS, to leverage advantages from multiple techniques.
Spread Spectrum.ppt
This document discusses spread spectrum techniques for wireless communication. It covers two main types of spread spectrum: frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS transmits signals over different radio frequencies in a pseudorandom sequence. DSSS spreads the signal across a wider bandwidth by combining it with a spreading code. Code division multiple access (CDMA) can allow multiple users to share the same frequency band using unique spreading codes. Pseudorandom noise (PN) sequences are commonly used as spreading codes due to their randomness and unpredictability properties.
Spread spectrum
This document discusses spread spectrum communication techniques. Spread spectrum spreads a narrowband signal over a wide range of frequencies for transmission and then de-spreads it back to the original bandwidth at the receiver. There are two main types: frequency hopping spread spectrum (FHSS) which changes the transmission frequency periodically, and direct sequence spread spectrum (DSSS) which multiplies the data by a pseudo-random code before transmission. Spread spectrum provides benefits like efficient bandwidth utilization, interference rejection, and secure communication.
Simulation of Direct Sequence Spread Spectrum for Wireless Communication Syst...
In this work, a simulation model for Direct Sequence Spread Spectrum (DSSS) scheme for wireless communication systems has been proposed. Unlike the case of a single frequency carrier, the modulated signal in DSSS occupies a much wider bandwidth in order to reduce the possible interferences with narrow band communication signals. In telecommunications, DSSS is a spread spectrum modulation technique used to reduce overall signal interference. The spreading of this signal makes the resulting wideband channel more noisy, allowing for greater resistance to unintentional and intentional interference. Y.V.S Durga Prasad | K. Venkateswarlu"Simulation of Direct Sequence Spread Spectrum for Wireless Communication Systems using Simulink" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14118.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/14118/simulation-of-direct-sequence-spread-spectrum-for-wireless-communication-systems-using-simulink/yvs-durga-prasad
Topic: Spread Spectrum
These slides cover a topic on Spread spectrum in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
Mimo
This document discusses multiple-input multiple-output (MIMO) systems. It begins by outlining the motivations and aspirations for developing MIMO systems, including achieving high data rates near 1 gigabit/second while maintaining quality of service. It then provides an overview of MIMO system modeling and capacity studies. Key topics covered include diversity versus spatial multiplexing design criteria, example architectures, MIMO with orthogonal frequency-division multiplexing, and networking applications involving MAC protocols.
Spread spectrum
Spread spectrum is a technique used in communication systems to spread the bandwidth of the transmitted signal, making it more resistant to interference and harder to intercept. There are three main types of spread spectrum: direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), and time hopping spread spectrum (THSS). DSSS spreads the signal by multiplying it with a pseudo-random code before transmission. FHSS rapidly switches the carrier frequency according to a pseudo-random sequence. THSS transmits signal bursts in pseudo-random time slots within a frame. Spread spectrum provides advantages like interference rejection, multipath immunity, multiple access, and secure communication.
Mimo
This document discusses multiple-input multiple-output (MIMO) systems, including their motivations and capabilities. MIMO systems use multiple antennas at both the transmitter and receiver to achieve high data rates approaching 1 Gbps while maintaining quality of service. The document covers MIMO channel models and capacity, design criteria like diversity and spatial multiplexing, practical architectures like V-BLAST and Alamouti's scheme, and applications to networking including MIMO-OFDM and MIMO MAC protocols.
multiplexing
This document discusses different multiplexing techniques used in data and computer communications, including frequency division multiplexing (FDM), wavelength division multiplexing (WDM), time division multiplexing (TDM), statistical TDM, and their applications. It also covers digital carrier systems, synchronous optical network (SONET), asynchronous digital subscriber line (ADSL), discrete multitone (DMT) modulation, and cable modem operations.
Mimo
This document discusses multiple-input multiple-output (MIMO) systems. It begins by outlining the motivations and aspirations for developing MIMO, including achieving high data rates near 1 Gbps while maintaining quality of service. It then covers MIMO system modeling and capacity studies. Different MIMO designs are presented that aim to achieve spatial multiplexing gain or diversity gain. Practical MIMO systems and architectures like V-BLAST are described. Networking applications of MIMO including MAC protocols are also discussed.
Cdma and 3 g
The document discusses CDMA and 3G spread spectrum technology. It describes how CDMA uses direct sequence spread spectrum to allow multiple users to access the same frequency band simultaneously. It explains the key elements of spread spectrum communication including using a chip rate that is faster than the data rate, synchronization at the receiver, and using pseudo-random codes. It provides details on IS-95 CDMA including channel structures, call processing, and authentication.
Spread Spectrum.pptx
Spread spectrum technology works to mitigate problems caused by frequency dependent fading and interference by spreading narrowband signals across a broader frequency band. It has two main alternatives: direct sequence spread spectrum (DSSS) which uses a pseudo-random code to spread user data, and frequency hopping spread spectrum (FHSS) which rapidly switches a carrier among various frequencies according to a code. FHSS can operate in either a slow or fast hopping mode, with fast hopping providing greater immunity to interference but at increased complexity.
Digital Communication 4
This document discusses bandwidth utilization and multiplexing techniques. It begins by explaining that bandwidth is a precious commodity in communication and that bandwidth utilization aims to make wise use of available bandwidth. It then discusses various multiplexing techniques including frequency-division multiplexing (FDM), time-division multiplexing (TDM), and wavelength-division multiplexing (WDM). For each technique, it provides examples and applications. It also covers digital carrier systems like T1, T2, T3 and discusses the North American digital multiplexing hierarchy.
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- 1. Topic: Direct Sequence Spread Spectrum (DSSS) Name: Naval Kishor Sharma Subject: CDMA SYSTEMS Roll no: 20MTECE008 Class: M.Tech (ECE) 3rd Sem
- 2. Direct Sequence Spread Spectrum (DSSS) • Each bit represented by multiple bits using spreading code • Spreading code spreads signal across wider frequency band — In proportion to number of bits used — 10 bit spreading code spreads signal across 10 times bandwidth of 1 bit code • One method: — Combine input with spreading code using XOR — Input bit 1 inverts spreading code bit — Input zero bit doesn’t alter spreading code bit — Data rate equal to original spreading code • Performance similar to FHSS
- 3. Direct Sequence Spread Spectrum Example
- 4. Direct Sequence Spread Spectrum Transmitter
- 5. Direct Sequence Spread Spectrum Transmitter
- 6. Direct Sequence Spread Spectrum Using BPSK Example
- 8. Code Division Multiple Access (CDMA) • Multiplexing Technique used with spread spectrum • Start with data signal rate D — Called bit data rate • Break each bit into k chips according to fixed pattern specific to each user — User’s code • New channel has chip data rate kD chips per second • E.g. k=6, three users (A,B,C) communicating with base receiver R • Code for A = <1,-1,-1,1,-1,1> • Code for B = <1,1,-1,-1,1,1> • Code for C = <1,1,-1,1,1,-1>
- 9. CDMA Example
- 10. CDMA Explanation • Consider A communicating with base • Base knows A’s code • Assume communication already synchronized • A wants to send a 1 — Send chip pattern <1,-1,-1,1,-1,1> • A’s code • A wants to send 0 — Send chip[ pattern <-1,1,1,-1,1,-1> • Complement of A’s code • Decoder ignores other sources when using A’s code to decode — Orthogonal codes
- 11. CDMA for DSSS • n users each using different orthogonal PN sequence • Modulate each users data stream —Using BPSK • Multiply by spreading code of user
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