Spread Spectrum

28
May 28-June1, 2001 R. Z. Ziemer, Colorado Springs, CO 1 Spread spectrum

description

Garima MaaM, Mobile Com

Transcript of Spread Spectrum

Page 1: 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

Page 2: 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

Page 3: Spread Spectrum

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

Page 4: Spread Spectrum

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

Page 5: 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

Page 6: Spread Spectrum

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

Page 7: Spread Spectrum

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

Page 8: Spread Spectrum

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

Page 9: Spread Spectrum

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

Page 10: Spread Spectrum

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

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Frequency Hopping Spread Spectrum (FHSS)

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Frequency selection in FHSS

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FHSS cycles

Frequency Hopping Spread Spectrum

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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

Page 11: Spread Spectrum

May 28-June1 2001 R Z Ziemer Colorado Springs CO 11

Direct Sequence Spread Spectrum Example

Direct Sequence Spread SpectrumTransmission Technique

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Direct Sequence Spread Spectrum Transmitter

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Direct Sequence Spread Spectrum Receiver

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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)

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Frequency selection in FHSS

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FHSS cycles

Frequency Hopping Spread Spectrum

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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

Page 12: Spread Spectrum

Direct Sequence Spread SpectrumTransmission Technique

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Direct Sequence Spread Spectrum Transmitter

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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

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Frequency Hopping Spread Spectrum (FHSS)

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Frequency selection in FHSS

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FHSS cycles

Frequency Hopping Spread Spectrum

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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

Page 13: Spread Spectrum

May 28-June1 2001 R Z Ziemer Colorado Springs CO 13

Direct Sequence Spread Spectrum Transmitter

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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

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Frequency Hopping Spread Spectrum (FHSS)

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Frequency selection in FHSS

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FHSS cycles

Frequency Hopping Spread Spectrum

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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

Page 14: Spread Spectrum

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

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Frequency Hopping Spread Spectrum (FHSS)

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Frequency selection in FHSS

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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

Page 15: Spread Spectrum

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)

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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

Page 16: Spread Spectrum

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

Page 17: Spread Spectrum

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

Page 18: Spread Spectrum

May 28-June1 2001 R Z Ziemer Colorado Springs CO 18

Frequency Hopping Spread Spectrum (FHSS)

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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

Page 19: Spread Spectrum

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

Page 20: Spread Spectrum

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

Page 21: Spread Spectrum

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

Page 22: 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

Page 23: Spread Spectrum

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

Page 24: Spread Spectrum

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

Page 25: Spread Spectrum

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

Page 26: Spread Spectrum

DS-CDMA

Figure The Principle of DS-CDMA

Page 27: Spread Spectrum