03802_05_FqHopping

LZU 108 5958 Uae Rev A 1

03813-LZU 108 5958 Uae Rev A Slide 1 (22)

Frequency Hopping


Frequency Hopping

A

A

A

Burst 1

Burst 2

Burst 3

Frequency 1

Frequency 2

Frequency 3

Burst 4

HFS



Effect on the Air Interface

• Interference averaging– Gain depends on transceiver distribution

and frequency• Frequency diversity

– Gain depends on number of frequenciesand the bandwidth


Frequency Hopping



C/I Distributions

C/I

MS

dist

ribut

ion

FHOP

FHOP+BTSPC

FHOP+BTSPC+DTX

Nothing

Acceptable C/Ino FHOP

Acceptable C/IFHOP


Achievements

• More uniform speech quality• A more dependable and predictable radio environment• Increased capacity (tighter frequency re-use enabled)



Performance of Frequency Hopping• Hopping on many frequencies gives better

frequency diversity and interference averaging.However the relative benefit by adding yetanother frequency will diminish.

• Hopping over a wide band decreases thecorrelation between the fading dips of differentfrequencies thus improving the frequencydiversity.

• A high traffic load will reduce the gain ofinterference averaging.

• Usage of DTX and dynamic power control willincrease the gain of interference averaging.


A Higher RxQual Can Be Tolerated

Maximum RxQual providing acceptable speech quality

(approx.)No frequency hoppingNo DTX 4.5

Frequency hoppingNo DTX 5-6



• Cyclic sequence (HSN = 0)... , f4, f1, f2, f3, f4, f1, f2, f3, f4, f1, f2, ...

• A cyclic sequence is the best sequence for combatingconsecutive fading dips.

Hopping Sequences - Cyclic and Random


• Random sequences (HSN = 1 - 63)... , f1, f4, f4, f3, f1, f2, f4, f1, f3, f3, f2, ...

• The period of a (pseudo) random sequence is 6 minutes long.

• Random sequences give better interference averaging (if the network is planned using frequency groups.)

• Different random sequences (different HSNs) should be assigned to nearby cells having the same frequencies.



Orthogonal Sequences

• The transmitters in a channel group never use thesame frequency simultaneously.

... , f1, f4, f4, f3, f1, f2, f4, f1, f3, f3, f2,

...

... , f2, f1, f1, f4, f2, f3, f1, f2, f4, f4, f3,

...

... , f3, f2, f2, f1, f3, f4, f2, f3, f1, f1, f4,

...

... , f4, f3, f3, f2, f4, f1, f3, f4, f2, f2, f1,

...


Two Hopping Modes

• Baseband hopping (FHOP = BB)

• Synthesizer hopping (FHOP = SY)



Baseband HoppingcontrollerTRX1

controllerTRX2

controllerTRX3

controllerTRX4

combiner

bus for routing of bursts

transmitterf0

transmitterf1

transmitterf2

transmitterf3

filter

• Baseband hopping : Each transmitter transmits on a fixed frequency.The bursts from the transceiver controller are routed to the differenttransmitters by a bus.

+ A narrow-band filter combiner can be used. To this combiner it ispossible to connect up to 6 TRX:s without more than 3dB combinerloss.

- It is impossible to hop on more frequencies than there are TX:s.


Synthesizer hopping

• Synthesizer hopping: The transmitters change frequency for every burst.

+ It is possible to hop on more frequencies than there are transmitters.

- Hybrid combiners must be used. When connecting many transmitters theloss will be big.

TRX1

controllerTRX2

controllerTRX3

controllerTRX4

controller

transmitterf1 fn...transmitterf1 fn...transmitterf1 fn...

transmitterf1 fn...

combinerhybrid

combinerhybrid



Co Filling at Baseband Hopping

• 30 TCH:s and hopping on the BCCH frequency.

controllerTRX1

controllerTRX2

controllerTRX3

controllerTRX4

combiner

bus for routing of bursts

transmitterf0

transmitterf1

transmitterf2

transmitterf3

filter

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7BCCHf0

f1f2f3

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

TCHTCH

TCH TCHTCHTCH

TCHTCHTCHTCH

TCHTCHTCHTCH

TCHTCHTCHTCH

TCHTCHTCHTCH

TCHTCHTCHTCH

TCH

TCHTCH

SDCCHTCH


• 22 TCHs and hopping on BCCH frequency.

• One transmitter acting only as Co filler.

• All traffic bursts that are to be sent on Co are routed to Co transmitter.

TSTS0 TS1 TS2 TS3 TS4 TS5 TS6 7

TCHTCH

BCCH

TCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

SDCCH

fn

...

f0f1f2f3

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

Co Filling at Synthesizer Hopping With an Extra Transmitter

TRX1

transmitter

controller

TRX2 controller

TRX3 controller

f0f0

f0

f0

f0


combinerhybrid

combinerhybrid



• 23 TCHs and hopping on BCCH frequency• One transmitter acting only as Co filler and one “BCCH controller”

makes it possible to use one more TCH compared to the prior case.• All traffic bursts that are to be sent on Co are routed to this

transmitter.


TCHTCHTCH

BCCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCH

SDCCH

fn

...

f0f1f2f3

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

Co Filling at Synthesizer Hopping With an Extra Transmitter and BCCH Controller

TRX1transmitter

controllerTRX2

controllerTRX3

controllerTRX4

f0f0

f0

f0

BCCHcontroller f0

transmitterf1 fn...

transmitterf1 fn...

transmitterf1 fn...

combinerhybrid

combinerhybrid


Co Filling at Synthesizer Hopping With Two Channel Groups

• 30 TCHs and a non-hopping BCCH frequency.

• If utilization of hardware is more important than it is to hop on theBCCH frequency.

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0

fillingc0


fn

...

f0f1f2f3 TCH

TCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

TCHTCHTCH

SDCCH

BCCH TCH TCH TCH TCHTCH TCH TCH

TRX1

controllerTRX2

controllerTRX3

controllerTRX4

controller


transmitterf1 fn...

combinerhybrid

combinerhybrid



Parameter Summary

• HOP is the switch for tuning frequency hopping on or off, defined per channel group. HOP defines whether all channels except the broadcast channel hop ( HOP = ON), all traffic channels hop (i.e. all channels except the broadcast channels and the SDCCHs (HOP = TCH), or no channels at all hop (HOP = OFF).

• HSN is the hopping sequence number, defined per CHGR. This parameter specifies which hopping sequence to be used. All timeslots in one channel group are configured with the same HSN. HSN = 0 yields a cyclic sequence. HSN = 1 to 63 yields pseudo-random sequences.


Parameters

• FHOP selects which hopping method to be used, baseband (FHOP = BB) or synthesizer ( FHOP = SY) hopping. It is defined per TG.

• COMB specifies which combiner type that has been connected, a wide-band hybrid combiner (COMB = HYB) or a narrow-band filter combiner (COMB = FLT). It is defined per TG. If a filter combiner is connected, only basebandhopping can be used.



Parameters

• MAIO is a parameter that will allow the operator to specify a list of up to 32 MAIO values, in the order in which they are to be allocated to a channel group. This parameter can also be set to DEFAULT, which removes the manual MAIO list in favour for the default MAIO list.


Value Ranges and Default ValuesParameter name

Default value

Recommended value

Value range Unit

MAIO Default - 0-31 or Default

-

HOP OFF ON OFF, TCH,ON -

HSN - Use the same HSN for synchronized co-sited cells

0-63 -

FHOP - SY BB, SY -

COMB - HYB HYB, FLT -

03802_05_FqHopping

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