Takeover rumors run at full 'Sprint'

4 ants on iDEN? Are they running a simplex TX/RX. I have been in a few Nextel shelters but they were all omni sites. Running 3 iDen panels and 1 CDMA seems odd to me. Is the CDMA ant dual pole or quad pole? All the Nextel towers are 3 ants up here to include their new builds.

 

I know about soft handoffs being the mainstay of CDMA, but I thought CDMA could handle hard handoffs as required as well. For example, when travelling between switches or even SIDS so long as the backhaul system is set up to handle the handoff. I even thought CDMA could handle channel changes (that's a hard hand-off, too, correct?) within a switch if demand/load calls for it. If GSM indeed is the only platform that can handle 800/1900 handoffs well, then that would seem to give the GSM carriers a big advantage with managing their network and optimizing coverage with the 2 bands.

Anyone else care comment on this? It is something I would like to better understand.

 

I did alittle looking around in the cell sites at different states. I was able to find the 3 panel Nextel setup in alot of different states. Nextel sector sites up here before sprint were a 3 panel (except high cap sites) There are a few new Sprint/Nextel with this setup, maybe these were already planned builds and they only built them out as iDen. I just thought of another point.

Is Sprint overlaying CDMA where they have mom and pop PCS companies using their name? Up here a company named IPCS is doing a pretty good job of putting Sprints name to same. I dont see why Sprint couldnt as long as the CDMA alpha tag says NEXTEL. From talking to the Nextel techs I have run into they have started to integrate CDMA, perhaps only high traffic areas.

Far as handoffs GSM does handle Dual band handoffs. We are running both 850 and 1900. Dual band or commonly known as a Hyperband handoff is alot slower than a single band and is more prone to dropped calls.

The biggest problem is the signal from 1900 will degrade so fast that it cant hand off to 850 fast enough before you drop.

 

I think Verizon runs both 850 and 1900 but I dont know if they have dual band handoffs. Next time I run into one of their techs I will ask.

 

Depends on how many radios are installed on a sector. All the radios are combined then duplexed so potentially each antenna could be transmitting on one sector and up to three of the antennas are shared back for the diversity receive.

An omni site is really no different but it will only have one rack of radios versus three. The duplexing and diversity receive is handled basically the same.

 

It can be done but it's a hard handoff. You won't simply bounce back and forth between 850 and 1900 but you can be sent from one to the other if you were going from a 1900 only site to a 850 only site.

 

Thanks - I appreciate it.

 

Undestood. I have no idea if it would be possible (I m\am not an industry insider), but it would be nice if in an overalyed the system was set up so that during a call, during a call, let's say the call is presently being handled on 1900, that the communication sequence between the phone and the tower included information on the "standby" 800 MHz channel to switch to if needed. Normally, the phone and tower would monitor received signal strength during the call and if it got below a threshold (call not yet dropped), either the phone or tower could then request/command a switch to the 800 MHz standby channel. Even in a sudden 1900 MHz signal loss scenario, with a 800 MHz standby channel already pre-identified, perhaps the call could continue or be very quickly reesatblished on 800 without it dropping.

In the reverse situation, where the call is on 800, but the user enters strong 1900 signal area, the phone would need to be able to monitor 1900 signal strength while simultenously conducting a 800 MHz call, in order to request a switch back to 1900 if appropriate.

All of this would be done with the higher objectives of maximizing geographical reach of the network (deploying 800 and using it when needed), and keeping that 800 MHz free to serve that very purpose by captilizing on the strenghts and capacity offered by 1900 channels whenever cals can be sucessfully carried on that band..

I understand such a concept may not be part of CDMA protocols or handset capabilities now (especially the ability to monitor 2 frequencies at opne time), but could it be?

 

Larry, Sprint has been adding towers a lot here on both sides. Sprint in rural Sussex county (lowest portion of DE) on Nextel towers. Nextel has been added in my area and up north, more for capacity I'm guessing. Nextel has DE blanketed. All Synergy sites that I've seen, has been changing from 2pps Sprint to Nextel 3pps and 1 Sprint pps, with Nextel being downtilted, just like in your picture.

 

CDMA2000 does do hard hand off like states elsewhere in this thread, but it takes quite a bit more leg work to make it a "smooth" handoff. Even after fine tuning there is usually some problems. GSM does have an advantage if you will with being able to handoff from 850 to 1900, and even going from one GSM carrier to another the handoff works well. But CDMA's soft handoff is definately an advantage in the core of a carriers network. CDMA soft handoff helps in supporting calls and shedding traffic onto less busy sectors. IMO GSM has its advantage with the HHO, and CDMA has its advantage w/soft handoff.

 

CDMA does do channel changes mid call if ncessary will it not? For example I usually see channel 350 and 375 here in the Atlanta area. I wonder if the network ever switches me from one to the other during a call. Is a frequency change considered a type of hard handoff?

 

[edit] Nextel U.S. operations interfere with police and fire radios
Nextel's systems in U.S. cities have been linked to significant interference problems affecting municipal government trunked and conventional 800 MHz two-way radio systems. These problems are costly to address and technically difficult to resolve.

Federal Communications Commission precedent calls for the party causing interference to solve the problem. The interference stems from Nextel's buy-out of private analog FM two-way radio systems. To expand capacity of their digital iDEN systems the company purchased private commercial two-way systems from small companies in cities nationwide. After purchase the analog equipment was removed and replaced with Nextel's digital trunked system transmitters or "EBTS." In some cases these new transmitters were configured in ways that caused interference to existing systems–including police and fire systems. This interference is difficult to filter out because the original spectrum plan for the 800 MHz band interleaved business, public safety, and commercial mobile radio systems on adjacent channels.

To resolve these problems, Nextel and the Federal Communications Commission developed a plan, approved by the FCC in August of 2004 [1] to relocate systems on certain 800 MHz frequencies to elsewhere in the 800 MHz band in order to reduce the potential for interference. Specifically, systems on the 806-809/851-854 MHz band will initially swap with Nextel frequencies in the 809-814/854-859 MHz band, leaving Nextel the only user in 806-809/851-854 MHz. Then the Nextel use of the 806-809/851-854 MHz band will be swapped with the national public safety use of the 821-824/866-869 MHz band, leaving Nextel with contiguous spectrum in 817-824/862-869 MHz and the business and public safety users in contiguous spectrum at 806-817/851-862 MHz. The use of contiguous spectrum allows for simple filters to be installed to protect the public safety radio systems from interference, which is currently impossible under the existing channelization of the 800 MHz band. Nextel is paying for much of the cost of this reconfiguration, but in compensation for "lost" 800 MHz spectrum is receiving spectrum in the 2 GHz band at 1910-1915/1990-1995 MHz. The 2 GHz spectrum is near the existing Sprint PCS allocations and can be used to expand the number of channels available for that service, without needing to bid for that additional capacity in a spectrum auction

 

From reading the above article and some of the stuff I found on the FCC website it looks like Nextel will keep its 800. The new 800 is all grouped together which is better for all. The existing 800 interferes with public radio and 850 A band in some cases. They are also picking up some new 1900 which in some cases is co-located with some of Sprints 1900 licenses.

 

Most of the lower 800 MHz is what Sprint has to give up 801-824 MHz
The upper 800 MHz licenses they will keep.
Most likely Sprint will have to continue iDEN not CDMA on the upper 800 MHz because it would takes about 16 continuous SMR blocks just to do just 1 CDMA2000 spread. If any provider has 1 SMR license with 16 blocks or they only have 15 the spread would not work.

 

I am just happy Nextel is keeping some 800 freqs. If you look at the New spread they are just below 850 A band UL and DL freq. This 800 freq problem has been a thorn in the side of out industry for long enough. I dont think the FCC should have allowed Public Safety or Business Land Mobile to use the 800 band. The VHF and UHF bands are more suited for that use. My state police migrated their radios over to 800 a couple of years ago knowing the 800band would probably have problems.

 

But how long will it be before there are any phones that have been designed/tested/FCC arproved to be used on the 1910-1915/1990-1995 spectrum? All the existing devices do not include those channels.

 

Sprint will end up with 817-824 (mobile) and 862-869 (base station) in most markets. In the Southeast, there will be more bandwidth, I think because of Southernlinc.

www.800ta.org

 

I have validated twice in the past few days that my phone will transistion from channel 375 to channel 350 while in the middle of a call. I put the phone in debug mode and called voicemail to observe this. It does this at the same location on my daily commute. I noticed no detectable handoff, and I have been on regular calls in this area in the past, so I would have to say it handles the hard handoff without any issues.

 

Larry - is a NID a subset within a SID?

 

Switching between channels depending on network/sector load is something CDMA can do without a problem. I observe this a lot actually.

 

You can do some call loading on GSM but not as advanced as CDMA offloading calls on to other sectors or towers. The setup is call a Concentric Cell. You have a dual band 1900/850 both freqs are in the same cabinet. You have a inner and outer zone. Normal the 1900 is at a lower power and the inner zone and the 850 is the outer. The 1900 is defaulted to be the first to accept the call or handoff because the 850 will load up alot faster due to the better blanket of coverage. Both zones can perform a hard handoff to each other if necessary, I.E going in a building the 1900 will handoff to the 850. I wish they would implement the CDMA call sharing on GSM.

 

CelloneTech - this "Concentric Cell" 850/1900 arrangement you describe is EXACTLY what I have been trying to communicate/advocate to this forum for years, precisely due to 850 MHz advantages for reach and building penetration, coupled with capacity on the 1900 band. Do you know if any CDMA carrier has implemented such an arrangement?

You mention the call sharing (i.e. multiple tower) capabilties of CDMA. While this no doubt offers advantages in its own way, I still would like to see a Concentric Cell concept applied to CDMA; what a tremendous coverage boost that would seem to afford for all but the highest density environments where 1900 towers are already so closely spaced (due to capacity issues) as to render moot issues around 1900 mhz signal propagation weaknesses.

 

That's good. I wonder could this be applied to a concentric cell arrangement like Cellonetech describes?

 

From talking to friends that work with CDMA, CDMA is tricky to get to perform a hyperband handoff i.e 850 to 1.9. I guess you can play with parameters to force it to do a hard hand off.

I look at my documents on WCDMA and WCDMA will hand off to 850/1.9 and GSM of both freqs.

I have a concentric cell on a rooftop one cabinet is 1900 and the other 850. The 850 takes triple the calls. The gamma sector does about 50,000 calls for 850 and the 1900 about a third of that. We have actually done quite a few concentric omni sites as well.

 

This is fascinating.

I'm not an industry insider so I do not know what gamma sector is. Can you elaborate?

For an ongoing call how does the system and/or handset decide when a handoff between frequencies is warranted? What parameters are assessed to make this decision and who (handset or base station) makes it?

 

there is basically 2 type of tower configs. 1st is the omni site which is seen in mostly rural areas, the antennas are round fiberglass rods. Then there are sectorized sites that use panel antennas. There are both a Bi-sector site that has 2 sectors, usually used to cover up and down highways. And there is the tri-sector which is the most common and provides 360 degree coverage. The most common names for a three sector is Alpha (true north 0degrees) Beta (south east 120 degrees) and Gamma (south west 240)

Some companies have different names for the sectors. Some call it x,y,z (nortel) A,B,C (Nokia) and 1,2,3 these are just a few I have seen.