- This topic has 13 replies, 1 voice, and was last updated 14 years, 4 months ago by navdeep Singh.
31st August 2007 at 07:19 #49020AshokGuest
I am Core Network Person . I would like to know the fundamentals of Spetrum Allocation etc . I confused that a per the GSM standards , if the Uplink & downlink frequencies are fixed to be 890-915 Mhz & 935-960 Mhz then how does the rdaio frequency of Airtel can be different from Hutch . Also how does CDMA Operator frequency are different from GSM ? How does the frequency bands get allocated Frirnds, please tell me the basics of how does spectrum gets allocated & what is the recnt fuss about all operators asking for more spectrum .
This would be really helpful for me31st August 2007 at 07:28 #49021pixGuest
the frequency band defined for GSM is 890-915 Mhz & 935-960 Mhz (so 25MHz of bandwidth in UL and 25 in DL). It means that a GSM communication, by definition, should use a frequency within this range.
One GSM communication uses 200kHz in UL and 200kHz in downlink (and actually, this little slice of frequencies can be used by 8 communications at the same time !!). Therefore a GSM channel = 200kHz.
Who is in charge of these 2x25MHz ? It is the government.
Who wants to use them ? The operators.
So the government must share this band among different operators. One operator can receive for instance 2x8MHz of the GSM900 band.
These 8MHz = 8000/200 = 40 GSM channels.
I guess you know about frequency reuse ? A site can have 3 cells, using 4 TRX each. Each TRX must use one channel (it is a “non hopping” example). So this site uses 12 channels.
How many sites can you plan with 40 channels ? Not much… what happen is that the channels will be reused, far enough as to avoid interference with the other sites using the same channels.
But you understand the concept : with only 40 channels, it is very complicated to put site 3×4. You are limited in terms of capacity, in order to keep a “good” frequency reuse.
But the problem is gone if you receive more bandwidth 🙂 That’s what all the fuss is about.
Regards,5th September 2007 at 06:20 #49022AshokGuest
Hello Mr Pix,
Thanks for your reply. So, what I can say is that if suppose as of now Hutch has been give 2X8Mhz by Govt, as your example & that gives it a limitation in terms of setting up more Sites with maximum TRXs per sector. So, now it would need to get more share , let us say 2X6 Mhz more but thne this comes to be 2X14 mHz for Hutch only. But we have only 2X25 MHz channels only as per GSM specs . Now if just 2X25 Mhz is to be divided anmongts so many operators obviously not many operators would be having sufficeint spectrum. Is there any plans to increase the overall available spectrum of 2X25 MHz ?
Also I have some more queries :
01. Whatever spectrum is allocated to Hutch , say 2X8 MHz then the same is to eb used by Hutch in all Circles or it can be different circle wise ?
02. We alos hear about Defence being told to vacate some spectrum. Are they also using out of the GSM 2X25 Mhz spectrum only ? If not, then how does tehir vacating affect the GSM spectrum avauialbility .
Please excuse me for being naive but I told you that I am a Core Network Person & I really do not know mcuh about Access side.
Please help me on these .
Anybody else also having some good inputs on this topic is requested to please share that .
Ashok6th September 2007 at 10:54 #49023Navdeep SinghGuest
ur queries about spectrum in diffrent area.yes it is totally restricted by the govt. for diffrent places.only applicable commercial spectrum for diffrent areas u can use with permission of WPC after clearance of SACFA.
regarding ur second query. defence purpose used spectrum can be vacated but it can be given after permitted by WPC only.
WPC is a wireless protection committee of india having diffrent authorities as member like all forces,prasar bharti,BCI.and others containing more than 12 members by the govt.6th September 2007 at 15:07 #49024PixGuest
I’ll try to help you as much as you need, your questions can help others as well. But one thing first : Don’t call me mister, i’m neither that old, nor that formal 🙂
2×25 MHz is not enough as soon as you have more than 2 operators ! What is the solution… use another frequency band. That is the reason why another band, in the 1800 MHz, can be used.
2×75 MHz are available. Plenty enough for 5 or 6 operators.
For your other questions, Navdeep gave you the answers already.
The government can decide to allocate certain frequencies to operator A in one region, and the same frequencies to another operator B in another region. It all depends on your government choices. They can do whatever they want.
Regards,17th October 2007 at 07:15 #49025ashokGuest
Hi Navdeep & Pix,
Thanks for claering my doubts .
I will get back again if I have some doubts6th November 2007 at 11:48 #49026baburaoGuest
for allocating frequency band let us take the example of up link.
Avalable range is 890-915.
Govt can allocate like this:
Hutch: 1800-1805(1800MHz Band)6th November 2007 at 17:03 #49027VKGuest
If we better talk in terms of ARFCN, it would be more technical & easy to understand!6th November 2007 at 20:42 #49028JoshuaGuest
Please, i would like to know little bit about the basic knowledge of frequency reuse in gsm12th November 2007 at 06:44 #49029ajayGuest
wht is re-use of frequency12th November 2007 at 09:01 #49030pixGuest
there is a limited amount of frequencies. In GSM for instance, there are only 124 channels.
Each operator can receive 40 channels for instance.
In this situation, it means that 40 TRX can be activated “on air” without risks of interference. But if you want to cover a whole country, you need much more than 40 TRX’s ! Therefore you need to reuse your 40 frequencies available : several TRX’s must use identical frequencies. And in order to avoid interference, you must ensure that two TRX’s with same frequencies will not overlap their coverage, because that would generate interference.
The goal of frequency planning is to perform the best mapping of frequencies, that is, to find the best reuse pattern.30th January 2008 at 09:57 #49031AmitGuest
Still the question remains unasnwered. What is this fuss about Defence forces not vacating spectrum for use by GSM operators. Can somebody pls explain in detail the spectrum allocation principle used in India5th February 2008 at 07:01 #49032anoopmGuest
As i want to Know about the total working of the BTS,mainly the call routine when dialed or received.From ur previous messages i had to know about the allocation of the band.So from that please explain me about the 2X25 MHz band,means what this 2 and 25 means for.
I am curiosly waiting for the reply.9th April 2008 at 03:42 #49033navdeep SinghGuest
Hi amit & Anoopm
ur queries we have already answered please see 6th september ,2007 on board note of Pix and mine ,where your queries have complete answer.wpc is the controlling authority of spectrum allocation.defence is using spectrum according to guidlines of wpc.