propitious,
re: paired (unpaired) frequencies.
<< Eric writes that minimum for cdma2000 is 2.5mhz (Why is that, Eric, I thought it was 1.25mhz; is it that two bands are minimum?) and 10mhz for wCDMA ( I thought it was 5mhz -- again why double). >>
If you happened to listen to Oliver Valente's interview with SoundView earlier this week you may have heard him say at 21:00 "cdma 1x can be upgraded in 2.5 MHz increments ... where WCDMA has to be deployed in minimum of 10 MHz increments".
Evidently engineer feels that I am wrong (and by extension seemingly so is Oliver as well):
"Eric is wrong. It is 1.2288 Mhz spreading for CDMA2000 hence the 1.25 Mhz bandwidth and 3.884 Mhz spreading for WCDMA, hence with much more sloppy guardbands, 5 Mhz.
Won't be the first time I've been wrong ...
... regardless, I'll explain why I answered the way I did, and hopefully engineer will comment back to explain to all of us the error of my ways, since we are all here to learn.
Typically cellular or PCS data transmission takes place using separate transmit and receive frequencies and regulators generally license spectrum with this in mind. In the US in the PCS bands (where PCS is licensed) 1850-1910 MHz is licensed for mobile to base transmission and 1930-1990 MHz for base to mobile.
Based on what Oliver stated I'm assuming that Sprint PCS plans to use "about" 1.25 MHz for transmit and "about" 1.25 MHz for receive, although there may be more to this than meets the eye, and that is what I am hopeful engineer will respond to.
In UMTS UTRA Frequency Division Duplex (FDD aka WCDMA) operations require paired uplink and downlink spectrum segments. The radio access scheme is direct-sequence CDMA with information spread over a bandwidth of "about" 5 MHz with a chip rate of 3.84 Mcps. As a consequence for a UMTS carrier using FDD an allocation of paired frequencies is necessary (minimum "about" 10 MHz) and depending on what spectrum is available and what cell structure is deployed more will be required.
UMTS forum offers these guidelines on allocation for FDD and TDD:
* 2 x 5 MHz will allow a single layer only; a hierarchical cell structure is not feasible in this case
* 2 x 10 MHz gives room for a two-layer structure, e.g. a macro cell layer together with either a micro cell layer or picocell
* 2 x 15 MHz allows the deployment of a complete hierarchical cell structure where the traffic demand is high or a mix of layers such as one macro cell and two micro cells
* 2 x 20 MHz allows increased flexibility and additional capacity.
In addition to the allocation of paired frequencies an operator may need an allocation of unpaired frequencies for Time Division Duplex (TDD) operation, in particular for low mobility applications indoors.
* 5 MHz may be required in order to give satisfactory capacity for asymmetric traffic
* 10 MHz would give more flexibility and additional capacity for asymmetric traffic
Based on the assumptions made, the UMTS Forum recommends 2x15 MHz (paired) + 5 MHz (unpaired) as the preferred minimum spectrum requirement per public UMTS operator in the initial phase. The allocation of unpaired spectrum is foreseen to handle asymmetric traffic in an optimized way. However, depending on country specific situations, other spectrum allocations per operator may be more appropriate.
At the current time and regardless how IMT-2000 3G licenses have been awarded (auction, beauty contest) specific spectrum allocation differs country to country and even within a country and in some cases their is additional spectrum set aside in the IMT-2000 core band (or the bands extended be WRC-2000) that nay be licensed at a later date.
In Japan DoCoMo is currently licensed for 1920-1940 MHz uplink & 2110-2130 MHz downlink, J-Phone is licensed for 1940-1960 MHz uplink & 2130-2150 MHz downlink and KDDI is licensed for 1960-1980 MHz uplink 2150-2170 MHz downlink.
In South Korea SK Telecom is licensed for 1940-1960 MHz, KT ICOM for 1960-1980 MHz, and 1920-1940MHz.
In the UK Vodafone is licensed for 2x15+ 5 MHz, 3 carriers are licensed for 2x10+ 5MHz, and 1 for 2x15 MHz.
In Germany 5 licenses were awarded for 2x10+ 5 MHz and 1 was awarded for 2x10 MHz.
Etc ...
Regardless of the specific spectrum awarded the minimum bandwidth used by any carrier using FDD will be 2 x 5 MHz and that is what AWS plans to initially deploy since it will still be supporting IS-136 (supplemented by GSM/GPRS and/or EDGE).
Most appreciative of Ramsey passing on engineer's comments and I'm in total agreement with the last sentence of same.
- Eric - |
