Anza Frequency Hopping Sept 09

7/26/2019 Anza Frequency Hopping Sept 09

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Frequency Hopping

Techniques

Anza RabbaniRF Planning


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Baseband Hopping Synthesizer Hopping Current Frequency Hopping Technique used in Telenor Pakistan

Overview


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Frequency hopping in the base stations can be implemented in either of

two ways :

Baseband hopping or Synthesizer hopping technique


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BASEBAND HOPPING


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Each transmitter operates on a fixed frequency so that a dedicated TRX is needed for each frequency.

Use combiner which has up to 16 inputs, makes the combiner possible to use many TRXs without having to connect several combiners in cascade, but calls can be dropped, if a single TRX fails.

Uses as many transmitter as frequencies in the hopping sequence.

Possible to use many transceivers with one combiner.


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Routing of bursts from the TRX to the transmitter atbaseband hopping


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Each frame of eight timeslots is input to a different RFU and so to a different frequency. In this way the transceivers do not need to retune to different frequencies, but each channel effectively hops over the available frequencies.

Digital Radio Codec and Control Radio Frequency Unit


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TRX 1

TRX 2

TRX 3

TRX 4

Bursts routing at baseband hopping

TRX n


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Example of

Baseband

Hopping

Suppose that a base station containing four TRXs so only four frequencies can be defined at cell 1 as:

TRX1 . 75 (BCCH)TRX2 . 78 (TCH)TRX3 . 81 (TCH)TRX4 84 (TCH)

84

81

78

75

CELL 1

CELL 3

CELL 2

BCCH

TCH


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Channel Configuration for Four Transceivers and BasebandFrequency Hopping


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Three Hopping Frequency Sets (HFS) are defined: HFS1 = {f0} HFS2 ={f1,f2,f3} HFS3 ={f0,f1,f2,f3}


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Synthesizer Hopping


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TRX output changes the frequency at each burst.

The bursts are sent straight on forward and not routed by the bus.

Each transmitter operates on a number of frequencies which are arranged in the form of list.

Transmitter can use use large number of available frequencies.

Number of Transmitters can be less than the number of frequencies.

Applied on all traffic and signaling channels, except for the broadcast common control channel (BCCH), which must transmit on a fixed

frequency in order to make possible correct RXLEV measurements.


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Routing of bursts from the TRX to the transmitter at synthesizer hopping


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With Synthesizer Hopping, each RFU within a transceiver retunes to a different frequency transmitting a frame.

Digital Radio Codec and Control Radio Frequency Unit


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Dropped call reduction.

Increase of the received mean level. Possibility of using tighter schemes (like 1/3) providing higher capacity. No degradation of audio quality.

Improvement on System Performance


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Current Frequency Hopping Technique used in Telenor Pakistan


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In Telenor the Synthesizer Hopping Technique is used for interference averaging.

Using synthesizer Hopping, Fractional load calculation is important while creating MAList which represents the list of hopping frequencies.Fractional load can be calculated as

Fractional load = no. of TRXs

no. of

frequencies

Better averaging of interference can be achieved by assigning more hopping frequencies to a cell.


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Each TRX in Synthesizer Hopping is assigned a set of hopping frequencies MAList, a Mobile Allocation Index Offset (MAIO) and a Hopping Sequence Number (HSN) and MAIO step.

Different MALists are used in the network depending on frequency band, number of radios and quality


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Frequency Range 900 Islamabad

RegionFrequency Range 900 AJK

Region

For Islamabad 6379ARFCN range is used for BCCH.

For AJK Region 7790ARFCN range is used

for BCCH.BCCH is non hopping.


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Frequency Range 1800 Islamabad

Region

Frequency Range 1800 AJK

Region

MALIST:

1. 100 [587, 588, .,626]2. 105 [587, 588, .,618]


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The MAI states which

frequency has

to

be

used

for

each burst


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HSN ( H opping S equence N umber ): The HSN is used to choose the hopping sequence,values can be 0 to 63. Value 0 defines cyclic hopping, all other values generate a random sequence.

MAIO ( M obile A llocation I ndex O ffset): Defines the starting frequency the transmission will start on within the hopping sequence. The value can be 0 to N1 where N is the number of allocated frequencies.

FN ( F rame N umber O ffset): This number counts the TDMA framesFN_MAX.

Same HSN and the same FN but different MAIO never use the same frequency at the same time.


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Example Assigning MAIO to 3 sector site TRXs


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N = 6, HSN = 3, MAIO = 2

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N = 6, HSN = 3, MAIO = 4

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MAIO=2

MAIO=4

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Anza Frequency Hopping Sept 09