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# 3G Carrier Freqs

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• #68273
Hargeisa
Guest

Hi Friends,
I am working with 2G BSS network, and we are going to 3G system.

in 2G BSS using 900 and 1800(ARFCNs e.g. 1-124 and 512-885) Please can you tell me the equivalent 3G freqs?

Also i heard that 3G uses 5MHz channel bandwidth, what that mean? and how it will be efficient, when we know that 2G channel bandwidth is only 200kHz?

#68274
pix
Guest

hi hargeisa,

band VIII = GSM900
band III = DCS1800

en.wikipedia.org/wiki/UMTS_frequency_bands

you need to define the center frequency of the 5MHz band you want to use. This is explained in the second table of the wikipedia page.
for example, if you need the 5MHz which are at the beginning of the GSM900 band:
in DL GSM900 : 935-960 MHz (ARFCN 1-124)
you have the first 5MHz available:
935-940MHz (ARFCN 1-25)
therefore you need toset the DL center frequency at 937.5 MHz.
the closest available is, using this range “927.4 – 957.6” increment = 0.2 : 937.6 MHz

The code for that frequency is :
5 * ((center freq in MHz) – 340 MHz)
5 * (937.6 – 340) = 2988

which indeed belongs to the Test Set “DL Channel” Range [2937 – 3088]

The UMTS system is more efficient than GSM : every WCDMA site is allocated the full 5MHz. The amount of traffic that can be carried on those 5MHz across a whole network is much more than what you could carry on a GSM network using ARFCN 1-25.

Regards
pix

#68275
Hargeisa
Guest

Thanks very much Mr. PIX

#68276
Somaliland
Guest

plus

Mobile network operators have deployed UMTS-TDD technology in the following bands:

Frequencies (MHz) Channel Number (UARFCN)

1850–1910 9262 – 9538
1900–1920 9512 – 9588
1910–1930 9562 – 9638
1930–1990 9662 – 9938
2010–2025 10062 – 10113
2570–2620 12862 – 13088

#68277
Guest

Hello Experts I need your help

I have noticed from TEMS investigation that there are more numbers of ARFCNs(in case of 2g) as compared to UARFCNs(3G) and EARFCNs(4g) as per operator, my question is that why they are using less number of UARFCNs and EARFCNs as compared to ARFCNs to cover the same coverage area??

#68278
Ahamd
Guest

Hi every one!

Can any one told me about frequency hopping by giving some special example?

kindly help me regarding this concept

Thanks …

#68279
Wallis Dudhnath
Guest

Frequency hopping is linked to CDMA (IS-95) 3G/WCDMA, 4G/LTE(OFDMA), etc..

First of all when compared to TDMA / FDMA, Wideband CDMA (WCDMA) is a power based system that uses the full spectrum bandwidth. WCDMA is based on spread spectrum. With previous modulation schemes the signal was prone to errors, e.g. multipath fading, interference,
co-channel issues, etc..

Frequency Hopping is seen as a way to reduce on the radio errors and to ensure that a level of signal quality is maintained. The way how Frequency Hopping works is that the signal to be
transmitted is mixed with a Pseudo Randam Binary Sequence (PRBS) that is known to the TX and RX. This allows each of the transmitted signals to be spread throughout the defined bandwidth.

The receiver can then extract the signals and create the intelligence. For more information and the mathematics that goes with this area you can look at Direct Sequence Spread Spectrum and Fast Fourier Transformation (FFT).

Note that a good example of CDMA / WCDMA is the “cocktail party”. You are in a noisy party and the background noise is like a Gaussian Bell shaped curve. Despite the noise when somebody mentions
your name you will instantly home in on the discussion even though you are several meters aways and surrounded by noise.

VBR/ Wallis Dudhnath

#68280
LEMAURE
Guest

Hello Ahamd!
following Wallis’ post to first integrate as reason of frequency hopping, functionally you have 2 types of frequency hopping:
– baseband hopping: The frequencies configured on TRX are set in 2 pools called MALIST. MALIST1 will have all the frequencies defined on the cell (including BCCH) and MALIST2 will only have frequencies set on non-BCCH TRX (only on TCH TRX). Now it will be defined per TS, which of the MALIST to use. TS0 of BCCH is always non hopping. all TS0 of nonBCCH TRX will be assigned MALIST2 in other to avoid clashes with BCCH TS position. TS1-7 on all other TRX (including BCCH) will be assigned MALIST 1. From here, any TS using a frequency will be set a new one within his MALIST every frame. MAIO and HSN planning here is not really important as the frequencies should be initially planned as if the system is in non hopping mode.
– synthetised frequency hopping (SFH). it perfectly works when the network is synchronised with very few area of many cells overlapping and the real load factor acceptable (light network). you can choose to perform 1×1 model with the same MALIST used on all cells or 1×3 model with the 3 MALIST created and used on each cell of your site. In one case or another, MAIO and HSN plan are MANDATORY to avoid co and adj interferences. e.g same HSN per site on all cells and avoid reusing the same HSN by potential interferers of these cells.

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