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Cellular Phone Forum / General / GSM / September 2003Single chipset supports all major cellular standards
http://www.cellular-news.com/story/9784.shtml >http://www.cellular-news.com/story/9784.shtml I'll bet the licensing fees on that thing will be a bitch. Does this mean we may see cell phones in the future that can handle all modes of coverage in the US? Sometimes fantasy can become reality. paul@wren.cc.kux.edu wrote in article <eak6nv86cato8l03lp57k4rgdgf2fm96qe@4ax.com>: > http://www.cellular-news.com/story/9784.shtml > Does this mean we may see cell phones in the future that can handle all > modes of coverage in the US? Sometimes fantasy can become reality. You mis read the statement. It is for base stations. As from the article. A base station equipped with that technology will be able to support. "GSM, GPRS, EDGE, IS-95 CDMA, WCDMA, cdma2000, and North American TDMA." And it can.......... "process multiple 2G, 2.5G, 3G and future wireless standards at the same time, within the same footprint as today's single-carrier, narrowband architectures." So someone could be using a GSM cell phone, someone else a TDMA and cdma.....(so on and so forth,) on the same tower at the same time. Every phone will be able to operate in it's native mode, no mater what it's native mode is. Now at I think of it, it is about like the idea I had earlier.. Posted on 4/7/2003 by ME(N9WOS) ............................................................................ ... What really puzzles me is why they have to have a dedicated mode for a system. As a person the works with a lot of radio related communications equipment, It boggles my mind why a network would be limited to one digital mode. Every 800meg cell transceiver slot should be occupied with a standard unit. It can work in AMPS TDMA, CDMA, 800meg GSM and any other digital mode That a multi mode DSP reviver and transmitter can be made to run. When a new digital mode comes out for the 800meg band, you just update the firm ware to handle it. Every slot will be able to handle any form of communication on demand. A cell phone that is roaming from another area with a different native digital mode will be able to operate in it's native mode irrelevant of the systems native mode. The cell phone companies need to learn a lesson from the computer industry. There is no need to adopt a standard digital mode. (a computer can interface with all forms of communications channels) There is no need to obsolete old equipment. (An old computer will interface with the web just the same as a new one will.) Everything is upgradeable. (via software, you can increase the computers capiblitys without Changing any hardware.) Everything is backward compatible. If you don't have a V90 modem and you dial in to the service provider, it will default to a legacy mode without any interruption. Your computer is still talking to the same node modem but the node modem can operate in almost any mode. You can dial in with an old 300bps modem and it will connect without a hitch. It works, I have tried :) An old computer can interface the new network. It won't be able to use any of the newer features but It will be able to operate up to it's original design. That is the design basses that should be used for the cellular network. They shouldn't care what types of modes your phone will use. The network can use all of them. ..................................................................... >> Does this mean we may see cell phones in the future that can handle all >> modes of coverage in the US? Sometimes fantasy can become reality. [quoted text clipped - 71 lines] >The network can use all of them. >.................................................................... But you cannot, in general, have different protocols in the same frequency range at the same time. GSM and US-TDMA are narrow-band, time-sliced protocols, and CDMA and WCDMA are wide-band with many users on the same "carrier" frequency at the same time. Furthermore, CDMA (IS-95 and CDMA2000) WCDMA use different bandwidths. The provider with the generic equipment described above would have to partition their frequency allocations among the different protocols (like US Cellular currently does to support both TDMA and CDMA). > But you cannot, in general, have different protocols in the same frequency > range at the same time. GSM and US-TDMA are narrow-band, time-sliced [quoted text clipped - 4 lines] > frequency allocations among the different protocols (like US Cellular > currently does to support both TDMA and CDMA). I know that you can't have two different modes on the same frequency. I never clamed that it was possible, nor did the article. The primary benefit of the equipment mentioned by the article is that you would no longer requires static partitions, like normal systems do now. If no one is using cdma phones at the time, then you could use the whole band for gsm or tdma calls, or vice versa. You can dynamically partition the bandwidth for what modes are being used the most at that time. If only a few TDMA customers using the phones at that time and one or two amps customers operating, but you have a large influx of cdma customers for some reason, you can leave two or three tdma channels and three amps channels and fill the rest of your spectrum with cdma carriers spaced at normal intervals. If you have only a few cdma customers and a bunch of GSM customers the second day, then you can cut it down to one cdma carrier and fill the rest off the spectrum with gsm carriers at their normal intervals. And you can fit the stray tdma and amps users in the unused space in-between the other blocks. >If only a few TDMA customers using the phones at that time >and one or two amps customers operating, but you [quoted text clipped - 8 lines] >And you can fit the stray tdma and amps users in the unused space >in-between the other blocks. The base station would have to be much more dynamic to meet traffic loads. This would be a nightmare for the carrier owning the cell base station. If the demand was up on the GSM side do you anger the TDMA users by kicking them off that particular frequency segment? Trying also to plan for demand peaks would add to the nightmare! > The base station would have to be much more dynamic to meet traffic > loads. This would be a nightmare for the carrier owning the cell base > station. AKA, a good engineering challenge. :-) > If the demand was up on the GSM side do you anger the TDMA > users by kicking them off that particular frequency segment? That is up to the person that sets up the operating limits of the system. > Trying also to plan for demand peaks would add to the nightmare! The computers can handle that. That is the point of a dynamic system. The computers can allocate space and channels on a real time basses as the loading occurs. There is no need for planning. :-) >> The base station would have to be much more dynamic to meet traffic >> loads. This would be a nightmare for the carrier owning the cell base >> station. > >AKA, a good engineering challenge. :-) Worth the money for the carrier? >> If the demand was up on the GSM side do you anger the TDMA >> users by kicking them off that particular frequency segment? > >That is up to the person that sets up the operating limits of the system. Bad service means that the people you're selling your service to will not pay you nor program their consumer's phones to use your system. >> Trying also to plan for demand peaks would add to the nightmare! > [quoted text clipped - 3 lines] >channels on a real time basses as the loading occurs. >There is no need for planning. :-) So, how does the system get the message down to the consumer's cell phone that the PRL needs to be upgraded dynamically, in real time, just before you make the call? Now, if the base station power amps are over-engineered to handle any RF peak power (expensive) and passband bandwidths (expensive), and all the antennae are tunable (expensive) so that they radiate the pattern you want without a nasty SWR (expensive), AND the mobiles are frequency agile and have the protocol to understand what the base station is trying to tell them, then you've got a system! > So, how does the system get the message down to the consumer's cell > phone that the PRL needs to be upgraded dynamically, in real time, > just before you make the call? It wouldn't have anything to do with the PRL. The system would just be listed in the PRL as a digital system with the proper system ID. The current flux of the system wouldn't affect the PRL. > Now, if the base station power amps are over-engineered to handle any > RF peak power (expensive) Cheaper that a bunch of small amps for each carrier. and passband bandwidths (expensive), and all Standard old broad band, no tune, monolithic amp technology. The monolithic amps in the old 3W analog cell phones can operate across the entire A and B bands with no tuning. And since they are class A, they can amplify multiple carriers at the same time in the pass band with no distortion. As long as the resultant additive peak power is less than the peak capability of the amp. > the antennae are tunable (expensive) so that they radiate the pattern > you want without a nasty SWR (expensive), The last thing you would want is an electrically steered antenna, or point tuned antenna. You want the plain old panel antenna that you aim to get the radiation pattern you want. They already sell them that will operate across the entire transmit or receive portions of the A and B band with no tuning required by the installers. They have a useable SWR across the entire bandwidth. > AND the mobiles are > frequency agile There is no more agility needed by that system than what is used today. as long as the phone can operate on any cellular channel or pcs channel, it is perfectly suited for the application. >and have the protocol to understand what the base > station is trying to tell them, then you've got a system! The base station will talk to them with their normal protocol. There is no need for you to have any new multimode protocol. Most phones don't support any cross cdma/gsm "or the like". so there is no need for a new protocol. the phone just thinks it's talking to a native gsm or cdma system. >> So, how does the system get the message down to the consumer's cell >> phone that the PRL needs to be upgraded dynamically, in real time, [quoted text clipped - 19 lines] >As long as the resultant additive peak power is less than the peak >capability of the amp. So, we're talking a massive retro-fit, and a stringent amp design so that there's no intermod! >> the antennae are tunable (expensive) so that they radiate the pattern >> you want without a nasty SWR (expensive), > >The last thing you would want is an electrically steered antenna, >or point tuned antenna. Ah, but you were talking about using frequencies from multiple bands, hence the need for complex antennae systems. >You want the plain old panel antenna that you aim to >get the radiation pattern you want. >They already sell them that will operate across the entire >transmit or receive portions of the A and B band with no >tuning required by the installers. >They have a useable SWR across the entire bandwidth. I'm not talking about just A & B, I'm talking about non-800 MHz bands. >> AND the mobiles are >> frequency agile [quoted text clipped - 11 lines] >so there is no need for a new protocol. >the phone just thinks it's talking to a native gsm or cdma system. So you're really talking about a "hobbled" system that only supports specific services at specific frequency slots in the 800 MHz bands. This will be terrible for serving subscribers using different services, especially for a spectrum deficient carrier. > Ah, but you were talking about using frequencies from multiple bands, > hence the need for complex antennae systems. Uuuu......no I was talking about multiple frequencies from one large band. Up to 70Mhz wide. > >You want the plain old panel antenna that you aim to > >get the radiation pattern you want. [quoted text clipped - 4 lines] > > I'm not talking about just A & B, I'm talking about non-800 MHz bands. I am talking about the A and B system AND the PCS bands. They also sell PCS panel antennas that cover the entire PCS spectrum with no tuning or setup required by the installer. > So you're really talking about a "hobbled" system that only supports > specific services at specific frequency slots in the 800 MHz bands. > This will be terrible for serving subscribers using different > services, especially for a spectrum deficient carrier. Hobbling stuff together makes a great learning experience. I have learned a lot from home brewing electronic stuff. :-) >Now, if the base station power amps are over-engineered to handle any >RF peak power (expensive) No, just the peak power needed by the system that needs the highest peak power. Controlling it down from there is cheap. > and passband bandwidths (expensive) Again, only the bandwidth needed by the system needing the highest bandwidth. A wideband amplifier can amplify a narrow signal. >and all the antennae are tunable (expensive) We're either talking about an 800 MHz system or a 1900 MHz system, right? Antennas for either system cover the entire band. >so that they radiate the pattern you want without a nasty SWR (expensive) SWR and pattern aren't really related. >AND the mobiles are frequency agile Any cell phone can hop frequency. >and have the protocol to understand what the base >station is trying to tell them Bingo! And that, supposedly, is the new chip set. I know I'm getting on in years so I may have overlooked something obvious. Feel free to point it out. >>Now, if the base station power amps are over-engineered to handle any >>RF peak power (expensive) [quoted text clipped - 15 lines] > >SWR and pattern aren't really related. They can affect each other! >>AND the mobiles are frequency agile > >Any cell phone can hop frequency. The mobile should hop 800, 1900, 700, 450 Mhz, 1500, and 1700 MHz. (I'm talking world-phone, here) >>and have the protocol to understand what the base >>station is trying to tell them > >Bingo! And that, supposedly, is the new chip set. The new chipset is for the base. I think for what I really want for the mobile, the eventual best solution is software defined radio. > >Bingo! And that, supposedly, is the new chip set. > > The new chipset is for the base. > > I think for what I really want for the mobile, the eventual best > solution is software defined radio. Now that is pushing it. The chipset they have for the base is a software defined radio. But.... They can only implement it with a super conducting chip being driven by gigabit Ethernet with multiple PC's producing carriers to mix into the final broad band output to the antenna. It takes about 1Ghz worth of computing power to produce one GSM carrier. When the day comes that you can have a super conducting chip on you cell phone, running 12Ghz plus, then you are talking. >> >Bingo! And that, supposedly, is the new chip set. >> [quoted text clipped - 14 lines] >When the day comes that you can have a super conducting chip >on you cell phone, running 12Ghz plus, then you are talking. I don't think it'll need to be a superconductor. It will, with current technology, chew up alot of power, indeed. Give it 5 years. Meanwhile, the GSM1x handsets are starting to come out, and Qualcomm has some GSM/cdma2000 1x/cdma20001x EV-DO chipsets. So, aside from the tuning, we're starting to "get there". Stripline antenna, anyone? > The computers can handle that. > That is the point of a dynamic system. > The computers can allocate space and > channels on a real time basses as the loading occurs. > There is no need for planning. :-) Hmmmmmmmmm......... That gives me an idea for a network forecast. Something that you could get from the 611 menu. ...................................... Welcome to the N9 dynamic cellular network. Current network weather for the day of September 27. 12.5 megahertz currently in use. 2.5 megahertz currently available. 5 megahertz unallocated. Operating spectrum is as follows. 3 CDMA carriers. 152 TDMA carriers 33 GSM carriers 8 analog carriers. There has been 3 unsuccessful calls and 21 dropped calls within the last hour. To go back to the main menu, hit 1, Or hit end to finish the call at any time. ..................................................... Kinda makes me think of the solar forecast on WWV. :-) >> The computers can handle that. >> That is the point of a dynamic system. [quoted text clipped - 25 lines] >To go back to the main menu, hit 1, >Or hit end to finish the call at any time. Good thought! >..................................................... >Kinda makes me think of the solar forecast on WWV. :-) The Boulder K Index at 03 UT was 2.... > I know that you can't have two different modes on the same frequency. > I never clamed that it was possible, nor did the article. Actually, you can. GSM and CDMA can share the same frequencies, but one will cause *noise* with the other, effectively reducing bandwidth. CDMA could compensate, but I am not sure how well GSM could. I think such a scheme would work best when the majority of calls are CDMA with only the occassional call being GSM or another carrier type that appears as noise to CDMA. Tom Veldhouse > > But you cannot, in general, have different protocols in the same frequency > > range at the same time. GSM and US-TDMA are narrow-band, time-sliced [quoted text clipped - 30 lines] > And you can fit the stray tdma and amps users in the unused space > in-between the other blocks. Frequency re-use conflicts will, unfortunately, nip your idea in the bud. Your multi-mode BTS proposal is a noble one, but you are forgeting an exceedingly important fundamental of cellular radiotelephony: frequency re-use, more specifically the constraints, or lack thereof, imposed by frequency re-use. CDMA, as a code-division air-interface, is not subject to frequency re-use limits. CDMA utilizes a frequency re-use pattern of N=1. CDMA carrier channels utilizing the same 1.2288 MHz spectrum are deployed at all cells/sectors. Thus, in a hypothetical 10 MHz block of spectrum, the entire 10 MHz, minus any guardbands, would be available for CDMA carrier deployment at each & every sector/cell. AMPS, IS-136 TDMA, & GSM, as frequency-division (underlying time-division in the case of TDMA & GSM) air-interfaces, most certainly are arrested by frequency re-use concerns. In said hypothetical 10 MHz block of spectrum, anywhere from perhaps 238 KHz per sector, for a tri-sectorized AMPS network at a frequency re-use pattern of N=7*3, to perhaps 416 KHz per sector, for a tri-sectorized TDMA network at a frequency re-use of N=4*3, to perhaps 555 KHz per sector, for a tri-sectorized GSM network at a frequency re-use of N=3*3, would be available for deployment at any given sector/cell. Subsequently, the specific 238 KHz or 416 KHz or 555 KHz spectrum block, or more accurately aggregation of interleaved FDMA channels, respectively, could not be re-used for another 21 or 12 or nine sectors, respectively. Therefore, to institute your proposed multi-mode BTS in a sectorized cellular network, all air-interfaces, if dynamically-deployed from a static spectrum pool, would be forced to conform to the lowest common denominator in terms of frequency re-use. Assuming AMPS could be omitted, the re-use contraints of IS-136 TDMA would be the limiting factor. In said 416 KHz per sector, a dynamic mix of up to 13 TDMA or two GSM physical channels could be deployed. CDMA, at 1.25 MHz per carrier, would be impossible in the 416 KHz divisions created in only 10 MHz of total spectrum. If the spectrum ante were upped to a contiguous block of 20 MHz, as would be the case w/ either Cellular A or B licenses (as only 20 of 25 MHz is contiguous for each of both the A-side & B-side), CDMA would still irrealizable, at yet only 833 KHz per sector, in a dynamically-assigned multi-mode TDMA, GSM, & CDMA BTS. If the spectrum allowance were elevated yet again to 30 MHz, as would be the case w/ PCS A, PCS B, or PCS C licenses, then the inclusion of one CDMA carrier might finally become viable, just barely, as the per sector bandwith allotment would increase to 1.248 MHz. Even so, such would require that CDMA operate in a frequency-division manner, in keeping w/ the prescribed FDMA re-use imployed, such that soft/softer-handoff would be impossible. Each CDMA handoff, whether inter-cell or inter-sector, would have to be an inter-frequency hard-handoff, something that CDMA can be called upon to accomplish, but is also a great subversion of one of the superior strengths of the CDMA air-interface. In a multi-mode network, while perhaps not perfectly efficient, it is far more practical to statically partition spectrum to each desired air-interface, as has been done countless times over the years w/ networks utilizing AMPS/TDMA, AMPS/CDMA, AMPS/TDMA/CDMA, AMPS/TDMA/GSM, et al. For inclusion of CDMA, a dedicated partition of at least 1.25 MHz coincident at every cell/sector might be the only operable solution, which would largely defeat the purpose of the contemplated multi-mode dynamism. However, for FDMA air-interfaces like IS-136 TDMA or GSM, flexible channel-allocation technologies are currently being used to dynamically optimize frequency re-use patterns according to spatial network loading w/in a single air-interface. So, while it would open a Pandora's box of immense complexity, perhaps in the future such allocation technologies could be expanded to incorporate interface-allocation into the mix. Andrew -- Andrew Shepherd cinema@ku.edu cinema@sprintpcs.com http://www.ku.edu/home/cinema/ You are thinking in terms of a static cellular system. where channels have to be arranged in blocks for The band pass networks and everything to work. those factors are not relevant in this system. A major point of the system is it has a 75Mhz bandwidth DSP based IF. You can cover both A and B cellular bands with a single receiver and Transmitter. You can place a carrier at any frequency in the pass band. You can receive any frequency in the pass band. And you can operate as many channels of any type that you want. Every sector will have that capability. You are not stuck with one level of reuse. You can change the reuse layout as you shift your modes of operation. You could lay out the channels in every sector, in any way you want. You are not stuck with assigning channel blocks per each sector. You could have one cdma carrier operating on the top end of the band. with a frequency reuse of 1=N You could aggregate the 720Khz below that into 24 TDMA channels at any pattern, for a reuse of 4*3, Or two channels per sector. (ie) Sector, channel 1 1 and 2 2 3 and 4 ,,,,,,,,,,,,,,,,,,,,,,,,,,, Or 1 1 and 12 2 2 and 13 ,,,,,,,,,,,,,,,,,,,,,,,,,, so on and so forth. And aggregate below that for any GSM channels at any reuse you want at that time. You wouldn't even need to have the same mode of operation for a frequency range across the network. If you have a small group of people running GSM around one cell, then assign A few GSM channels to handle them at that cell, but you can use the same frequency for CDMA across the rest of the network. The other towers that are operating a 1.2 meg cdma channel won't bug the GSM users at that tower because the GSM phones can't hear the other towers. If there was enough GSM or TDMA usage at one point and the channels were being used lightly in the rest of the system, You could assign most of the bandwidth to the one sector that sees the concentration point until the peak passes. (ie) 7Mhz aggregated into tdma carriers for one sector and aggregate The rest into tdma channels for the rest of the system in the area. > (ie) > 7Mhz aggregated into tdma carriers for one sector and aggregate > The rest into tdma channels for the rest of the system in the area. And there is nothing that says that the channel system has to be contiguous. You know those big CDMA channels, and that guard band between them. That is many fine Khz of spectrum going to waste. I am sure you could plant one or two TDMA carriers in the CDMA guard band without causing any cross mode interference. Stick the narrow band channels in where ever you have guard bands or where you have any left over space. (ie) The last few Khz that is left over above the last CDMA channel that is too small to hold another CDMA channel. > > (ie) > > 7Mhz aggregated into tdma carriers for one sector and aggregate [quoted text clipped - 11 lines] > (ie) The last few Khz that is left over above the last CDMA channel > that is too small to hold another CDMA channel. So how much guard band are we talking about? 1.2500 - 1.2288 = 0.0212 MHz or 21.2 KHz That's the gap between two IS-95 CSMA carriers edges. Not enough for one AMPS channel (30 KHz, three ID-136 timeslots) or one GSM channel (200 KHz, eight timeslots). Between a band edge and a carrier edge would be half that, 10.6 KHz. There isn't enough room, unless we're willing to accept some interference. If I have made a error, let me know gently. John C. N4BKN > So how much guard band are we talking about? > 1.2500 - 1.2288 = 0.0212 MHz or 21.2 KHz [quoted text clipped - 6 lines] > There isn't enough room, unless we're willing to accept some > interference. The spreading sequence and data correction should tolerate some fringe signals without loss of data. And it will just show up as white noise to the TDMA carrier. And it will be so much lower than the signal level of the TDMA carrier that the TDMA carrier won't notice. Technically, a CDMA signal should be able to tolerate a narrow band signal or two within it's pasband without any problem. Remember the whole ruckus in the ham community about sharing ham bands with spread spectrum modes. Having two tdma signals right in the middle of the 1.2meg pas band should only raise the noise floor for the CDMA channel a few DB and the tdma signals won't even notice a DB raise in noise floor. CDMA gets that off it's military heritage. It is it's one true distinct capability. But that capability is never utilized with the cellular application. My opinion is direct sequence SS TDMA would be a better interface tech than the chipping method that cdma uses. The code spreading sequence doesn't gain anything that you can't get with other interlacing methods besides the secure communications junk which is no longer secure when the spreading sequences are public knowledge. Go figure????? > My opinion is direct sequence SS TDMA would be a better interface tech > than the chipping method that cdma uses. Nick that.............. Just go with a non spread high bandwidth QPSK TDMA. Who needs any spreading sequence. :-) >> So how much guard band are we talking about? >> 1.2500 - 1.2288 = 0.0212 MHz or 21.2 KHz [quoted text clipped - 24 lines] >It is it's one true distinct capability. >But that capability is never utilized with the cellular application. The answer is that isn't quite that simple. Todays CDMA activities are very toleratant of sharing space and rising noise floor , because the chipping to data rate provides a processing gain on the order of 1000. In other words a narrow interefering signal can only damage a tiny portion of the data, because the data is spread so widely. However when you go broad band applications that people are proposing for use with WCDMA, and instead of 10,000 bit per second channel, you want a 2 million bit per second channel, the gain from the chipping to data rate is suddenly more like 2-3, and at that ratio, the system is a whole lot less tolerant of raising the noise floor. > The answer is that isn't quite that simple. Todays CDMA activities are > very toleratant of sharing space and rising noise floor , because the [quoted text clipped - 8 lines] > rate is suddenly more like 2-3, and at that ratio, the system is a > whole lot less tolerant of raising the noise floor. The bandwidth verses power is the primary factor. A 10kbps signal is still 20Khz of actual bandwidth no matter how much the CDMA spreading process spreads it. A 100mw 10Kbps CDMA signal has the same range as A 100mw 10kbps 20Khz wide signal. If you take a 1Mbps (2Mhz wide) signal and spread it across 5Mhz of spectrum. You will need a lot higher power to spread across the larger 2Mhz bandwidth. If you use TDMA, you can cut the TX time down to around 1/1000 of a second at a rate of around 10 times a second. For a total TX time of 1/100 of a second. Of course, the peak TX power during that time will be around 10W. :-) But you will still have 100mw average. Granted, it wouldn't be hand held friendly. During low usage, one phone could pretty much use the entire 1Mbps channel. Who needs 3G? :-) You could stack a couple carriers on the band with the chipping sequence rotated a few notches. And since the signal is still Spread spectrum like CDMA, you can use rake receivers to add reflected signals and signals from multiple towers. > You are thinking in terms of a static cellular system. > where channels have to be arranged in blocks for > The band pass networks and everything to work. > those factors are not relevant in this system. Actually, no, I hypothesized just such an amorphous beast at the conclusion of my previous post: "...for FDMA air-interfaces like IS-136 TDMA or GSM, flexible channel-allocation technologies are currently being used to dynamically optimize frequency re-use patterns according to spatial network loading w/in a single air-interface. So, while it would open a Pandora's box of immense complexity, perhaps in the future such allocation technologies could be expanded to incorporate interface-allocation into the mix." However, a bare minimum level of air-interface stability, equivalent to at least one permanently deployed channel per air-interface at each cell/sector, must be maintained. Pilots & control channels simply cannot be ephemerally flitting in & out as the system dynamically optimizes its interface equilibrium. For the sake of idle mobiles & system acquisition, at least one CDMA pilot & sync pair plus one GSM BCCH plus one IS-136 TDMA DCCH must be statically deployed at a known invariable frequency at each cell/sector to serve as a beacon for mobiles. For example, in a hypothetical 10 MHz block of spectrum, a coincident 1.25 MHz would have to be dedicated at every cell/sector for a single consistent CDMA carrier. For the FDMA interfaces, a frequency re-use pattern of N=4*3 would be assumed for the beacon "place-holder" channels. Thus, w/in each given re-use cluster, 2.4 MHz (200 KHz * 12) & 360 KHz (30 KHz * 12) must be reserved at every sector/cell for GSM & IS-136 TDMA control channels, respectively, for a total (CDMA + GSM + TDMA) aggregation of 4.01 MHz. Thus, only 990 KHz paired would be remaining out of 5 MHz paired in each cellular cluster for flexible interface-allocation. The situation improves significantly, however, w/ licensed bandwidths of 20 MHz or 30 MHz, as the dynamic interface-allocation spectrum pool would rise to a maximum of 5.99 MHz or 10.99 MHz, respectively. All of the above, of course, assumes a great deal of presupposition that is typically not the case in wireless network deployment, creating numerous potential conflicts, notably the interleaved rather than contiguous nature of FDMA spatial re-use (e.g. sector #1: channels 1, 11, 21, etc.; sector #2: channels 2, 12, 22, etc.), MACA (mobile-assisted channel-allocation) across multiple fluctuating air-interfaces, and GSM SFH (slow frequency-hopping). Solve those problems and you may have something... Andrew -- Andrew Shepherd cinema@ku.edu cinema@sprintpcs.com http://www.ku.edu/home/cinema/ > However, a bare minimum level of air-interface stability, equivalent > to at least one permanently deployed channel per air-interface at each [quoted text clipped - 5 lines] > invariable frequency at each cell/sector to serve as a beacon for > mobiles. I understand that the beacon/pilot channels will be hard on available spectrum. But the DCCH doesn't have to be static for TDMA. A TDMA phone scans all the channels for a DCCH. You could put the DCCH at any channel in the network and it will find it. If the DCCH drops and moves, the phones will have to find it again. Once the phone loses the signal, it will assume it has went out of rang and will search for it's neighbors first then go into scan mode again. It wouldn't require any change in tdma phone setting or firm ware. That is normal operation The cdma one channel is assumed. I am not very familiar with GSM so I won't comment on it. one thing I wonder is if there is any command in the TDMA, GSM or CDMA architecture to forcefully tell the phone on the pilot channel to go to another pilot channel. That way you could start a new DCCH or BCCH and send the phones to it from the old pilot channel and then close the old pilot channel. That would eliminated the need for the phone to look for it again and eliminate any dropped calls while they are doing so. > For example, in a hypothetical 10 MHz block of spectrum, a coincident > 1.25 MHz would have to be dedicated at every cell/sector for a single > consistent CDMA carrier. Yeap. >For the FDMA interfaces, a frequency re-use > pattern of N=4*3 would be assumed for the beacon "place-holder" > channels. Thus, w/in each given re-use cluster, 2.4 MHz (200 KHz * > 12) & 360 KHz (30 KHz * 12) must be reserved at every sector/cell for > GSM & IS-136 TDMA control channels, respectively, for a total (CDMA + > GSM + TDMA) aggregation of 4.01 MHz. That is the main problem, a way to reduce the base line spectrum required. Of course, that is one that any cellular/pcs provider wished they could answer. The TDMA control channels are relatively small at 360 or so Khz. The CDMA channel is fine because it carries traffic. But the GSM channels is a problem. They would not be a problem during high usage, but during low GSM usage, it would be nice if there was a way to compact the pilot channels to a bare minimum. One thing that comes to mind is to reduce the aggregation of the cells for the channel spacing to reduce the number of channels needed. (ie) Transmit the same GSM pilot on all three sectors of a tower. aggregate the channels on the towers to provide a total channel requirement of (guestimates....)4 then you would reduce the GSM requirement down to 800Khz, with each pilot channel covering three sectors. You can't transmit the same pilot channel on two adjacent towers because of the mixing effect. Hmm.... something to think about.....:-) And if a person had the A or B cell band and one or so PCS licenses, then you would have plenty of workable space. :-) > Transmit the same GSM pilot on all three sectors of a tower. > aggregate the channels on the towers to provide a total channel requirement > of (guestimates....)4 then you would reduce the GSM requirement down > to 800Khz, with each pilot channel covering three sectors. > You can't transmit the same pilot channel on two adjacent towers > because of the mixing effect. Duuu..... that is what the tower in Nashville already does. It transmits the same TDMA DCCH and analog pilot on all three sectors. So, if you did that at low tdma usage, you could get the tdma usage down to 4 channels or 120 khz plus 1.2meg for cdma and 800k for gsm would leave you with 2.12Mhz of minimum usage. > So, if you did that at low tdma usage, you could get the > tdma usage down to 4 channels or 120 khz > plus 1.2meg for cdma and 800k for gsm would leave you > with 2.12Mhz of minimum usage. A big problem I see is when you throw WCDMA into the mix, with it's 5Mhz bandwidth, everything goes out the window. > > Transmit the same GSM pilot on all three sectors of a tower. > > aggregate the channels on the towers to provide a total channel [quoted text clipped - 11 lines] > plus 1.2meg for cdma and 800k for gsm would leave you > with 2.12Mhz of minimum usage. Yes, your train of thought seems promising. By deploying the GSM BCCHs at a re-use of N=4 omnidirectional, the dedicated GSM spectrum requirement is reduced from 2.4 MHz to only 800 KHz w/in the re-use cluster. Minimum capacity would be seven full-rate timeslots per cell, as timeslot zero would be the static BCCH. And the robust GMSK modulation should be able to manage any decrease in link margin due to the tighter N=4 re-use, which provides a consistent one cell diameter offset between like cells in adjacent clusters. As for IS-136 TDMA, retain the N=4*3 sectorized re-use, which can create an additional half cell diameter separation between like cells in adjacent clusters. Primarily, pi/4-OQPSK, requiring a greater link margin than GSM, is not so immune to lowered C/I from tighter re-use. And minimum TDMA capacity would only be two full-rate channels per cell, as the timeslot 1+3 pair would be reserved for the DCCH. On the other hand, if N=4*3 re-use were employed for IS-136, the capacity per cell would be six full-rate timeslots, essentially equivalent to the GSM capacity, while the spectrum requirement would still only be 360 KHz, again almost exactly comparable to the GSM spectrum outlay. Andrew -- Andrew Shepherd cinema@ku.edu cinema@sprintpcs.com http://www.ku.edu/home/cinema/ > Does this mean we may see cell phones in the future that can handle all > modes of coverage in the US? Sometimes fantasy can become reality. [quoted text clipped - 4 lines] > > [posted via phonescoop.com] If that is the case, roaming would certainly be *interesting*. Tom Veldhouse I can't even imagine the possible billing issues. > > Does this mean we may see cell phones in the future that can handle all > > modes of coverage in the US? Sometimes fantasy can become reality. [quoted text clipped - 8 lines] > > Tom Veldhouse |
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