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Transcript of Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 1
Spread spectrum
I History of Spread Spectrum
II Spread Spectrum System Model
III Spread Spectrum Classification
IV Spread Spectrum Techniques
Outline
History of Spread Spectrum
Spread Spectrum was actually invented by 1940s Hollywood actress Hedy Lamarr(1913-2000)
An Austrian refugee in 1940 at the age of 26 she devised together with music composer George Antheil a system to stop enemy detection and jamming of radio controlled torpedoes by hopping around a set of frequencies in a random fashion
She was granted a patent in 1942 (US pat 2292387) but considered it her contribution to the war effort and never profited
Techniques known since 1940s and used in military communication systems since 1950s
ldquoSpreadrdquo radio signal over a wide frequency range
Several magnitudes higher than minimum requirement
Gained popularity by the needs of military communication
Proved resistant against hostile jammers
Ratio of information bandwidth and spreading bandwidth is identified as spreading gain or processing gain
Processing gain does not combat white Noise
Introduction to Spread Spectrum
Offers the following applications
1048713 able to deal with multi-path
1048713 multiple access due to different spreading sequences
1048713 spreading sequence design is very important for performance
1048713 low probability of interception
1048713 privacy
1048713 anti-jam capabilities
Spread Spectrum Applications
InterferencePrevents interference at specific frequenciesEg other radio users electrical systems
MilitaryPrevents signal jammingScrambling of lsquosecretrsquo messages
Wireless LAN securityPrevents lsquoeavesdroppingrsquo of wireless linksPrevents lsquohackingrsquo into wireless LANs
CDMA (Code Division Multiple Access)Multiple separate channels in same medium using different spreading codes
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
I History of Spread Spectrum
II Spread Spectrum System Model
III Spread Spectrum Classification
IV Spread Spectrum Techniques
Outline
History of Spread Spectrum
Spread Spectrum was actually invented by 1940s Hollywood actress Hedy Lamarr(1913-2000)
An Austrian refugee in 1940 at the age of 26 she devised together with music composer George Antheil a system to stop enemy detection and jamming of radio controlled torpedoes by hopping around a set of frequencies in a random fashion
She was granted a patent in 1942 (US pat 2292387) but considered it her contribution to the war effort and never profited
Techniques known since 1940s and used in military communication systems since 1950s
ldquoSpreadrdquo radio signal over a wide frequency range
Several magnitudes higher than minimum requirement
Gained popularity by the needs of military communication
Proved resistant against hostile jammers
Ratio of information bandwidth and spreading bandwidth is identified as spreading gain or processing gain
Processing gain does not combat white Noise
Introduction to Spread Spectrum
Offers the following applications
1048713 able to deal with multi-path
1048713 multiple access due to different spreading sequences
1048713 spreading sequence design is very important for performance
1048713 low probability of interception
1048713 privacy
1048713 anti-jam capabilities
Spread Spectrum Applications
InterferencePrevents interference at specific frequenciesEg other radio users electrical systems
MilitaryPrevents signal jammingScrambling of lsquosecretrsquo messages
Wireless LAN securityPrevents lsquoeavesdroppingrsquo of wireless linksPrevents lsquohackingrsquo into wireless LANs
CDMA (Code Division Multiple Access)Multiple separate channels in same medium using different spreading codes
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
History of Spread Spectrum
Spread Spectrum was actually invented by 1940s Hollywood actress Hedy Lamarr(1913-2000)
An Austrian refugee in 1940 at the age of 26 she devised together with music composer George Antheil a system to stop enemy detection and jamming of radio controlled torpedoes by hopping around a set of frequencies in a random fashion
She was granted a patent in 1942 (US pat 2292387) but considered it her contribution to the war effort and never profited
Techniques known since 1940s and used in military communication systems since 1950s
ldquoSpreadrdquo radio signal over a wide frequency range
Several magnitudes higher than minimum requirement
Gained popularity by the needs of military communication
Proved resistant against hostile jammers
Ratio of information bandwidth and spreading bandwidth is identified as spreading gain or processing gain
Processing gain does not combat white Noise
Introduction to Spread Spectrum
Offers the following applications
1048713 able to deal with multi-path
1048713 multiple access due to different spreading sequences
1048713 spreading sequence design is very important for performance
1048713 low probability of interception
1048713 privacy
1048713 anti-jam capabilities
Spread Spectrum Applications
InterferencePrevents interference at specific frequenciesEg other radio users electrical systems
MilitaryPrevents signal jammingScrambling of lsquosecretrsquo messages
Wireless LAN securityPrevents lsquoeavesdroppingrsquo of wireless linksPrevents lsquohackingrsquo into wireless LANs
CDMA (Code Division Multiple Access)Multiple separate channels in same medium using different spreading codes
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
ldquoSpreadrdquo radio signal over a wide frequency range
Several magnitudes higher than minimum requirement
Gained popularity by the needs of military communication
Proved resistant against hostile jammers
Ratio of information bandwidth and spreading bandwidth is identified as spreading gain or processing gain
Processing gain does not combat white Noise
Introduction to Spread Spectrum
Offers the following applications
1048713 able to deal with multi-path
1048713 multiple access due to different spreading sequences
1048713 spreading sequence design is very important for performance
1048713 low probability of interception
1048713 privacy
1048713 anti-jam capabilities
Spread Spectrum Applications
InterferencePrevents interference at specific frequenciesEg other radio users electrical systems
MilitaryPrevents signal jammingScrambling of lsquosecretrsquo messages
Wireless LAN securityPrevents lsquoeavesdroppingrsquo of wireless linksPrevents lsquohackingrsquo into wireless LANs
CDMA (Code Division Multiple Access)Multiple separate channels in same medium using different spreading codes
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Offers the following applications
1048713 able to deal with multi-path
1048713 multiple access due to different spreading sequences
1048713 spreading sequence design is very important for performance
1048713 low probability of interception
1048713 privacy
1048713 anti-jam capabilities
Spread Spectrum Applications
InterferencePrevents interference at specific frequenciesEg other radio users electrical systems
MilitaryPrevents signal jammingScrambling of lsquosecretrsquo messages
Wireless LAN securityPrevents lsquoeavesdroppingrsquo of wireless linksPrevents lsquohackingrsquo into wireless LANs
CDMA (Code Division Multiple Access)Multiple separate channels in same medium using different spreading codes
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Spread Spectrum Applications
InterferencePrevents interference at specific frequenciesEg other radio users electrical systems
MilitaryPrevents signal jammingScrambling of lsquosecretrsquo messages
Wireless LAN securityPrevents lsquoeavesdroppingrsquo of wireless linksPrevents lsquohackingrsquo into wireless LANs
CDMA (Code Division Multiple Access)Multiple separate channels in same medium using different spreading codes
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
System ModelSpread Spectrum Transmission
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Spread Spectrum Criteria
A communication system is considered a spread spectrum system if it satisfies the following two criteria
Bandwidth of the spread spectrum signal has to be greater than the information bandwidth (This is also true for frequency and pulse code modulation)
The spreading sequence has to be independent from the information Thus no possibility to calculate the information if the sequence is known and vice versa
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Spread Spectrum Classification
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Direct Sequence Spread Spectrum
Information signal is directly modulated (multiplicated) bya spreading sequences (see next slide)
Spreading sequence consists of chips each with aduration of tchip
A set of chips represent a bit the exact number of chipsper bit equals the spreading gain
Near far effect
Require continuous bandwidth
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 11
Direct Sequence Spread Spectrum Example
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Direct Sequence Spread SpectrumTransmission Technique
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 13
Direct Sequence Spread Spectrum Transmitter
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 14
Direct Sequence Spread Spectrum Receiver
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 15
Direct Sequence Spread Spectrum Using BPSK Example
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 16
ApproximateSpectrum of DSSS Signal
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
The information signal is transmitted on different frequenciesTime is divided in slotsEach slot the frequency is changedThe change of the frequency is referred to as slow if more thanone bit is transmitted on one frequency and as fast if one bit istransmitted over multiple frequenciesThe frequencies are chosen based on the spreading sequences
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 18
Frequency Hopping Spread Spectrum (FHSS)
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 19
Frequency selection in FHSS
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 20
FHSS cycles
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Frequency Hopping Spread Spectrum
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
May 28-June1 2001 R Z Ziemer Colorado Springs CO 22
Bandwidth sharing
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Time Hopping Spread Spectrum
Time divided into frames each TF longEach frame is divided in slotsEach wireless terminal send in exactly one of these slots perframe regarding the spreading sequenceNo near far effect
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
Comparison of different Spread SpectrumTechniques
SS Technique advantage disadvantage
Direct Sequence 1048713best behavior in multi path rejection
1048713no synchronization1048713simple implementation1048713difficult to detect
1048713near far effect1048713coherent bandwidth
FrequencyHopper
1048713no need for coherent bandwidth1048713less affected by the near
far effect
1048713complex hardware1048713error correction needed
Time Hopper 1048713high bandwidth efficiency
1048713less complex hardware1048713less affected by the
near far effect
1048713error correction needed
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
The Idea
In MCM we split the data in to different streams and transmit using separate Sub Carriers
DS-CDMA
Figure The Principle of DS-CDMA
DS-CDMA
Figure The Principle of DS-CDMA